Inhalation Exposure of Organophosphate Pesticides by Vegetable Growers in the Bang-Rieng Subdistrict in Thailand
This study investigated inhalation exposure to organophosphate pesticides (OPPs) and evaluated the associated health risks to vegetable growers living in the Bang-Rieng agricultural community. Air samples were collected by using personal sampling pumps with sorbent tubes placed in the vegetable growers' breathing zone. Samples were collected during both wet and dry seasons. Residues of organophosphate pesticides, that is, chlorpyrifos, dicrotofos, and profenofos, were analyzed from 33 vegetable growers and 17 reference subjects. Results showed that median concentrations of OPPs in air in farm areas were in the range of 0.022–0.056 mg/ and air in nonfarm areas in the range of <0.0016–<0.005 mg/. The concentration of the three pesticides in the vegetable growers was significantly higher than that of the references during both seasons. The results also indicate that the vegetable growers may be at risk for acute adverse effects via the inhalation of chlorpyrifos and dicrotofos during pesticide application, mixing, loading, and spraying. It is suggested that authorities and the community should implement appropriate strategies concerning risk reduction and risk management.
Thailand exports a large amount of agricultural products to the world market every year. The agricultural labor force makes up about 55.7% of the Thai population. Most of this workforce’s income is generated through sales of farm products such as rice, fruit, cassava, and para-rubber . To minimize crop damage and to increase land productivity, the use of pesticides has become more essential. The import of pesticides has increased considerably from approximately 4,000 tons in 1962 to 37,039 tons in 2001. The burden of pesticides, as applied for crop protection, may affect environmental quality and human health .
Due to the ease of purchase and the high effectiveness in pest control, farmers are applying pesticides in large quantities. Since the ban of organochlorine pesticides in Thailand, the most widely used pesticide has become organophosphate pesticides (OPPs). OPPs are very effective in the eradication of insects and they are not as persistent in the environment as organochlorine pesticides. However, OPPs can cause acute adverse human health effects. At certain doses, OPPs have adverse effects on insects and humans. OPPs inhibit acetylcholinesterase enzymes (AChEs) at nerve ending that result in a build up of acetylcholine (Ach). Ach is an important neurotransmitter. When it accumulates at a synapse due to jamming of information the passing of messages between nerve cells is prevented. Adverse effects from OPP exposure include pulmonary edema, cyanosis, muscle spasms, muscle weakness, blurred vision, respiratory difficulty and possibly death due to respiratory failure . The severity of the health effects varies with exposure dose and duration.
The Bang-Rieng subdistrict is a large agricultural area in Songkhla Province, Southern Thailand. The farmers in this area grow a variety of vegetables. The Bang-Rieng community can be divided into two regions based on the patterns of agricultural practices: intensive and integrated pest management (IPM). Intensive agriculture refers to a commercial agriculture system that relies on a large market. As part of intensive practices, farmers mainly use pesticides for pest control. IPM, on the other hand, focuses on reducing pesticide use through alternative techniques such as biological control, crop rotation, or netted crop growing.
This study focuses on intensive agricultural areas due to intensive pesticide use in Thailand. The intensive agricultural region within the Bang Reing community consists of approximately 891 rai (143 ) of vegetable farm area, including 92 households (information obtained from the GIS survey by the Faculty of Natural Resources, Prince of Songkhla University, 2004). The reference areas are 7-8 km away from the farm areas, within the same subdistrict. The reference areas consist of 1,056 rai (169 ) including 96 households (information obtained from database of Bang Reing subdistrict, 2004)
Farmers in the Bang-Rieng community are directly and indirectly exposed to OPP residues either by inhalation during mixing, loading, or application of pesticides; by ingestion through artesian well water; or by dermal exposure from contact with soil residues, pesticide residues on plants, or while handling pesticides. This study will focus on the inhalation route of organophosphate pesticides that is chlorpyrifos, dicrotophos, and profenofos because they are the most popular and widely used in Bang Reing agricultural area. Inhalation exposure results in the individual breathing in dilute pesticide, that is, absorbed through the surface of the lung. Chemicals then enter the blood stream and are distributed to the rest of the body .
2. Methods and Materials
This study was approved by the Ethical Review Committee for Research Involving Human Subjects and/or Use of Animals in Research, Health Science Group of Faculties, Colleges and Institutes, Chulalongkorn University, Thailand under document no. 097/2006. All participants signed a consent form prior to participation in this study.
Thirty-three vegetable growers were selected as the study group. Vegetable growers were asked to participate in this study based on the farmers organophosphate pesticide use. The reference, or control, groups were made up of seventeen workers who collect latex from rubber tree plants and do not work with pesticides. The reference area was chosen based on interviews and background data. Since they live in the same subdistrict as the vegetable growers, this study will also investigate whether the reference group has inhalation exposure at work to the specific pesticides used by the vegetable growers (Figure 1). A survey was also administered by the study investigator to obtain information on subject age, body weight, and spray time.
2.1. Air Sampling
Altogether, 100 air samples were collected; 50 air samples were collected during the dry season (April–June 2006) and 50 during the wet season (September–October 2006). Each season, 33 air samples were collected from vegetable farm areas and 17 air samples were collected from the reference areas. Each subject provided two air samples. The air samples were treated as independent because of difference in sample collection time and weather conditions. Air samples were collected by using personal sampling pumps with sorbent tubes (OVS-2 tube: 13 mm quartz filter; XAD-2 140/270 mg). The personal sampling pump was set and calibrated with a flow rate of 1 L/min. The sorbent tube was placed in the subjects’ breathing zone and the personal pump was worn around the waist. The personal pump evacuates the air through the solid sorbent tube. Personal air samples were collected while vegetable growers mixed and loaded the pesticides outdoors and while walking and spraying the pesticides in the farm area. The average time of sample collection was 27.6 minutes or 0.46 hours (range 10.2–54 minutes or 0.17–0.9 hours). After the growers finished spraying, the exposure time of vegetable growers was recorded from the timer on the personal pump. The vegetable growers only sprayed pesticides once a day, usually during the morning hours from 5:00 AM–8:00 AM when the winds are calm. Two to three samples were collected per day. Pesticides are not sprayed when it is raining so samples were not collected on rainy days. The personnel pump was calibrated using a rotameter in the lab everyday before sample collection. The sampling method for measuring the pesticide air concentration followed the NIOSH manual of analytical methods, number 5600 [5, 6].
The plastic cap and polytetrafluoroethylene (PTPE) retainer ring of the sorbent tube was removed for analyses. The quartz filter and front XAD-2 section was transferred to a 4 mL vial and the short polyurethane foam plug along with back-up XAD-2 section was transferred to a separate 4-mL vial. Desorbing solvent (2 mL of acetone/toluene solution: 1/9) was added to each vial and let to stand for 30 minutes. The sample was then extracted in an ultrasonic bath for 30 minutes and concentrated by evaporation with nitrogen gas and reconstituted with of desorbing solvent for gas chromatography with flame photo detector (GC/FPD) analysis. An Agilent 6890 GC/FPD was used for quantification of OPP compounds. The retention times of dicrotofos, chlorpyrifos, and profenofos were 13.924, 16.917, and 20.255 minutes, respectively.
After collecting air samples from the vegetable growers, air samples were collected from the reference subjects during latex collection from the rubber plants. Sampling conditions and collection methods for the reference subjects were the same as for the vegetable growers. The sampling duration determined for the vegetable growers was also used for nonapplicators, 27.6 minutes.
2.2. Quality Control
A calibration curve using the external mixed standards of chlorpyrifos, dicrotophos, and profenofos was created for each compound to be quantified at concentrations of 1, 2, 4, 8, and 10 g/mL. Calibration standards were run before samples were injected and all measurements were performed in the ranges of linearity found for each compound. The limit of method detections (MDLs) for chlorpyrifos, dicrotophos, and profenofos were 0.0016, 0.005, and 0.003 , respectively. The validation data showed quantitative recoveries at 2 ppm of the three standards mixed (chlorpyrifos, dicrotophos, and profenofos). Percent recoveries of spiked samples with chlorpyrifos, dicrotophos, and profenofos in OVS-2 air sample tubes were in the range of 96–110, 102–104, and 96–106%, respectively.
2.3. Air Inhalation Exposure Assessment
Air inhalation exposure was calculated by the following algorithm :
where ADD is Average Daily Dose for air inhalation (mg/kg/day), is concentration of pesticides in air (mg/), IR is inhalation rate (/day), (for vegetable growers average breathing rate = 1.472 /day, calculated from breathing rate in heavy activity and multiply by 0.46 hr/day for average spraying pesticide period of vegetable farmers. For reference group breathing rate and breathing time use as same as vegetable growers = 1.472 /day) BW = body weight (kg) (65kg; average body weight of vegetable growers).
2.4. Risk Characterization
Based on toxicology criteria and potential for exposure, the Health Effects Division (HED) of the US Environmental Protection Agency has conducted inhalation exposure assessments for occupational handlers. Noncancer inhalation health risk estimates are expressed in terms of the Margin of Exposure (MOE). The margin of exposure (MOE) is used to convey Noncancer health risks. The MOE is the relationship of the pesticides no adverse observable adverse effects level (NOAEL), or the lowest adverse observable effects level (LOAEL), to the pesticides approximate level of exposure. The MOE is compared to the pesticides uncertainty factor; an MOE greater than the uncertainty factor reflects a possible health concern .
The NOAELs of chlorpyrifos for inhalation in acute effect was 0.1 mg/kgday . Dicrotophos LOAELs for inhalation acute effects was 0.5 mg/kgday . Profenofos LOAELs for inhalation acute effects was 9.7 mg/kg/day
LOAEL can be substituted for NOAEL in (2), but then it is desirable to have a larger MOE.
2.5. Statistical Analyses
This is a cross-sectional study design. Data was analyzed using SPSS 16.0. Descriptive statistics were used to describe and summarize the data. Tests of normality were also checked. Since the air samples produced a skewed distribution, the Mann Whitney-U test was used to compare the two study groups (vegetable growers versus reference) and seasons (dry versus wet).
The vegetable grower and reference groups had similar distributions of gender, age, and weight. The surveys showed that 32 males and 1 female made up the vegetable growers with an average age of 39 years and an average weight of 65 kg. The reference group, or control group, consisted of 16 males and 1 female. The average age of the reference group was 40 years, and the average weight of the reference group was 65 kg. The vegetable growers average spray time was 0.46 hrs/day (ranging 0.17–0.9 hrs/day).
Chlorpyrifos, dicrotophos, and profenofos were found in all the vegetable grower’s air samples. Figure 2 shows the medians and distributions of all three pesticides. Results showed that median concentrations of OPPs in farm area air samples were in the range of 0.022–0.056 mg/. All reference area samples were below the analytic limit of detection, for all three sampled pesticides. The concentrations of chlorpyrifos, dicrotophos, and profenofos were significantly higher in the farm areas compared to the reference areas, during both the wet and dry seasons (Mann Whitney-U (MWU) Test; MWU,). Figure 3 shows in the farm areas, there was no difference in chlorpyrifos, dicrotophos and profenofos concentrations between the dry and the wet seasons (MWU, ,. 469, and .160, resp.).
The chlorpyrifos concentrations of all samples in short-term exposure during both the wet and dry seasons did not exceed Recommended Exposure Limit (REL) of chlorpyrifos = 0.6 mg/ as recommended by the American Conference of Governmental Industrial Hygienist (ACGIH) . The profenofos concentrations of all samples in short-term exposure during both the wet and dry seasons did not exceed. Occupational Exposure Limit (OEL) of profenofos = 3 mg/ as suggestion by Syngenta Crop Protection, Inc . But the 3% of all samples was found dicrotophos concentrations in short-term exposure during both the wet and dry exceed Permission exposure limits (PELs) = 0.25 mg/as recommended by the National Institute for Occupational Safety and Health .
3.1. Dose and Risk Characterization
The Margin of Exposure (MOE) is a ratio of the No Observed Adverse Effects Level (NOAEL) of chlorpyrifos, the Lowest Observed Adverse Effects Level (LOAEL) of dicrotophos, and profenofos to exposure dose. For chlorpyrifos, the US EPA has set an MOE of 100 as the US EPA MOE approach that has shown to be adequate protection for workers (US EPA, 1999) . The MOE for dicrotophos is 1000 and 300 for profenofos (US EPA, 1999) [10, 11].
The estimated inhalation dose for chlorpyrifos, dicrotophos, and profenofos are presented in Table 1. To compare dose with effect level was presented as MOE in Table 2. Table 2 shows that 39% of vegetable grower’s air samples had chlorpyrifos levels below the US EPA MOE approach and 87% of the samples had dicrotophos levels below the US EPA MOE approach. None of MOE of profenophos was below the US EPA MOE approach. The MOEs of chlorpyrifos, dicrotophos, and profenofos are not a concern in the reference area since measurable levels were not detected in these areas.
4. Discussion and Conclusions
This is a study of 33 vegetable farmers in Bang-Rieng, Thailand. Vegetable growers do not wear proper protective. It was found that 39% and 87% of vegetable growers are at risk of inhalation exposures to chlorpyrifos and dicrotophos organophosphate insecticides that exceeded EPA recommended, respectively. Whereas no vegetable growers had risk concern inhalation exposure to profenofos organophosphate insecticides that exceeded EPA recommended.
The US investigated agricultural (various PPE or engineering controls) inhalation exposure to chlorpyrifos and dicrotophos. It was found that for 16% (9 of 56 scenarios) of chlorpyrofos exposure  and 8% (2 of 24 scenarios) of dicrotophos exposure exceeded EPA recommendations . No agricultural worker (individual wearing long pants, a long-sleeve shirt, shoes and socks, no gloves. and no respirator) had inhalation exposure to profenofos organophosphate insecticides that exceeded EPA recommendations .
The result found that a higher percent of agricultural workers in Thailand were exposed to organophosphate pesticides (including chlorpyrifos and dicrotophos) than US agricultural workers. This is due to the fact that US agricultural workers wear the appropriate PPE and have better engineering control. The vegetable growers should be required to wear protective masks when working with pesticides and educated on the proper use of pesticides. Administrative changes such as rotating workers and scheduling application times differently may help lower the risk of exposure as well.
Data analysis also showed that the vegetable growers were exposed to a higher level of organophosphate (0.022–0.056 mg/) than the reference group (0.0016–0.005 mg/m3). Three percent of the samples showed that short-term exposure to dicrotophos during both the wet and dry seasons exceeded the permissible exposure limits (PELs) of 0.25 mg/m3 as recommended by the National Institute for Occupational Safety and Health. Whereas chlorpyrifos and profenofos did not exceed the short time exposure Recommended Exposure Limit (REL) or the Occupational Exposure Limit (OEL).
Comparisons of pesticide exposure to previous studies in Thailand found that the chlorpyrifos exposure of 33 vegetable growers (0.0016–0.4537 mg/m3) in the vegetable farm area was slightly less than the chlorpyrifos exposure of 31 rice farmers in the rice fields (ranging from 0.0216–0.5500 mg/m3). This may be a result of the amount of pesticides used on vegetable farms (vegetable growers farm area: 0.8 hectare) being less than rice farms (rice farmer area: 1.6–3.2 hectare) .
The comparison of pesticide concentrations with ACGIH/NIOSH guidelines and the MOE, analysis found that some of the dicrotophos samples (chlorpyrifos: 3% exceeded REL and 87% exceeded MOE) exceeded the fixed values. It was also found that profenofos (profenofos: 0% exceeded OEL and 0% exceeded MOE) did not exceed the fixed values. The incident rates of chlorpyrifos showed that 39% of the samples exceeded the MOE. The incident rates of the MOE may be more than PEL, REL or OEL because the EPA derived a margin of exposure (MOE) from the dermal no-observed-adverse-effect level (NOAEL; mg/kg/day).
The NOAEL relied on animal studies and human studies (if applicable). The uncertainty factor (UF) accounts for the uncertainty involved in extrapolating animal data for human health. The uncertain factor for occupational exposure, MOE(chlorpyrifos) 100 (i.e., 10 interspecies and 10 intraspecies variability, do not exceed HED’s level concern) and MOE 300 (profenofos) or 1000 (dicrotophos) (i.e., 10 interspecies and 10 intraspecies variability, do not exceed HED’s level concern the addition 3-to 10-fold cushion between NOAEL and LOAEL) . The uncertainty factors derived from combination with actual data and surrogate data (for professional judgment). This is one sources of uncertainty that may not represent the exposure scenario being analyzed. However, EPA set uncertainty factors as high potential safety factors. So using the MOE and EPA to enforce standards, it may reduce pesticide exposure.
The Occupational Safety and Health Act (OSHA) ensure a safe and healthy work environment. This is accomplished by setting occupational safety and health standards and by providing research, information, and training in the field of occupational safety and health . The ACGIH limits are based on the risk of cholinesterase inhibition associated with exposure to chlorpyrifos and dicrotophos [17, 18]. The workers are viewed as generally healthier than the general population and having chosen to face certain risks and be compensated for this risk through payment of wages, but neither assumption is necessarily correct.
From the reasons above the degree of pesticide exposure with ACGIH/NIOSH guidelines and the MOE analysis was different. Congress has forbidden OSHA from conducting inspection at farms that employ 10 or fewer persons, leaving EPA as the only agency with meaningful enforcement authority in many situations . Each vegetable farm in Thailand consists of fewer persons. So Thailand should enforce pesticide use by the EPA MOE since the EPA sets as high potential safety factor.
Even though it is important to estimate inhalation exposure, it is not enough to estimate occupational exposure. Measuring inhalation exposure alone may underestimate each subject’s true dose because of the known propensity for dermal exposure of these three agents and the high probability of skin exposure during mixing and backpack-spray application. The potential for systematic toxicity can be observed following dermal exposure. Therefore, ACGIH set short-term exposure levels (STELs) of chlorpyrifos with skin notations. The skin notation indicates that the cutaneous route of exposure (including mucous membrane and eye) contributes to the overall exposure. In addition, OSHA set a PEL for dicrotophos with skin notations as well. Even though this research did not focus on dermal exposure, it is recommended that dermal exposure be investigated in future studies. Dermal exposure is a concern in Thailand since Thai farmers do not wear appropriate personal protective equipment during the loading, mixing, and spraying of pesticides.
This study is a preliminary aggregate risk assessment (of all pesticides used on farms) of inhalation exposure among farmers in Thailand. The information obtained from this study is useful for risk management and risk communication in the Bang-Rieng agricultural community. It also provides baseline information for local and national government to make decisions relevant to farmer health. Individual health risk assessments were also reported to each vegetable grower who was also provided guidance on protection from pesticide exposure.
This study was supported by the National Center of Excellence for Environmental and Hazardous Waste Management (NCE-EHWM), Chulalongkorn University and partially funded by the 90th Anniversary of Chulalongkorn University Fund.
Agricultural Extension Department, Agriculture data of Thailand, June 2007, http://www.doae.go.th/stat/statt.htm.
W. Siriwong, Organochlorine pesticide residues in aquatic ecosystem and health risk assessment of local agricultural community, Ph.D. dissertation, Graduated School Chulalongkorn University, Bangkok, Thailand, 2006.
US EPA, Recognition and Management of Pesticide Poisoning, Office of Pesticide Program, US Environmental Protection Agency, Washington, DC, USA, 1999.
National Association of state Department of agriculture Research Foundation (NASDAF), National Pesticide Application Certification: Core Manual, NASDAF, Washington, DC, USA, 2008.
National Institute of Occupational Safety and Health (NIOSH), NIOSH Manual of Analytical Methods (NMAM) 5600: Organophosphorus Pesticides, NIOSH, 4th edition, 1994.
V. Jirachaiyabhas, P. Visuthismajarn, P. Hore, and G. M. Robson, “Organophosphate pesticide exposures of traditional and integrated pest management farmers from working air conditions: a case study in Thailand,” International Journal of Occupational and Environmental Health, vol. 10, pp. 289–295, 2004.View at: Google Scholar
National Research Council of the National Academies, Science and Decisions Advancing Risk Assessment, National Academic Press, Washington, DC, USA, 2009.
US Environmental Protection Agency (US EPA), “Human Health Risk Assessment Chlorpyrifos,” Office of Pesticide Program, Health Effect Division (7509c), 2000, http://www.epa.gov/scipoly/sap/meetings/2008/september/hed_ra.pdf.View at: Google Scholar
US Environmental Protection Agency (US EPA), “Dicrotophos: HED preliminary risk assessment for the Re-registration Eligibility Decision (RED) document,” HED DOC 013817, US EPA, Office of Pesticide Programs Special Docket for Pesticide Re-registration Risk Assessments (DVD Set), Washington, DC, USA, 1999.View at: Google Scholar
R. P. Ryan, C. Terry, and S. S. Leffingwell, Toxicity Desk Reference: The Toxic & Medical Monitoring Index, vol. 1, Taylor & Francis, Philadelphia, Pa, USA, 5th edition, 2000.
Syngenta Crop Protection, Inc., Material safety datasheet, 2006, http://www.syngentacropprotection.com/pdf/msds/03_100239292006.pdf.
P. Kongtip, T. Tingsa, W. Yoosook, and S. Chantanakul, “Health risk assessment and biomarkers of chlorpyrifos in rice farmers,” Journal of Health Research, vol. 23, no. 1, pp. 23–29, 2009.View at: Google Scholar
Reference Agency for Toxic Substance & Disease, Public Health Assessment Guidance Manual, Lewis, Boca Raton, Fla, USA, 1992.
“Occupational Safety and Health Guideline for chlorpyrifos,” 1995, http://www.cdc.gov/niosh/docs/81-123/pdfs/0137.pdf.View at: Google Scholar
“Occupational Safety and Health Guideline for dicrotophos,” 1995, http://origin.cdc.gov/niosh/docs/81-123/pdfs/0203.pdf.View at: Google Scholar
A. M. Finkel and P. B. Ryan, “Risk in the workplace,” in Risk Assessment for Environmental Health, M. G. Robson and W. A. Toscano, Eds., John Wiley & Sons, San Francisco, Calif, USA, 2007.View at: Google Scholar


Brazilian Journal of Oral Sciences, Vol. 7, No. 25, Apr-Jun, 2007, pp. 1555-1558
Influence of light-curing units on the flexural strength and flexural modulus of different resin composites
William Cunha Brandt1; Leandro Cardoso2; Rafael Ratto de Moraes1; Lourenço Correr-Sobrinho3; Mário Alexandre Coelho Sinhoreti3
1 DDS, MS, Graduate Student Department of Restorative Dentistry, Dental Materials Division, Piracicaba Dental School, University of Campinas, Brazil
Received for publication: June 25, 2008 Accepted: July 18, 2008
Code Number: os08017
Aim: This study aimed to evaluate the flexural strength and flexural modulus of different resin composites (MasterFill, Opallis, Z250, Supreme) after photoactivation with quartz-tungsten-halogen (QTH - XL2500) or light-emitting diode (LED - Radii and Ultrablue Is) light-curing units (LCUs).
Key words: Composite resin, light, physical properties, polymers, photoactivation.
The ultimate goal of dental restorative materials is to replace the biological and functional properties of healthy tooth structures, with physical and esthetic properties matching those of natural teeth. Since their introduction about 40 years ago, restorative resin composites have proven to be successful1, and it is expected that their use for restoring both anterior and posterior teeth will continue to increase. Although considerable improvements have been made in the properties of these materials over the last decade2, Brazilian formulations are increasingly available, but little is know about their performance. For this reason, studies evaluating their properties are warranted.
Likewise composites, several light-curing units (LCUs) are available, each one having specific characteristics of light emission, such as irradiance level and spectral emission range and peak. Although quartz-tungsten-halogen (QTH) LCUs are the most traditional ones, blue light-emitting diodes (LEDs) are increasingly popular among clinicians. These LCUs emit a narrow spectrum of wavelengths that is better correlated with the spectral absorbance of camphorquinone (CQ), the most commonly used photoinitiator in dental composites3.
In comparison to LEDs, QTH LCUs also present some drawbacks that may interfere with their long-term exposure efficiency, such as high heat generation within the quartz bulb, degradation of filters over the course of time, and relatively overall short efficient working life span4-5. However, although some studies describe similar curing efficiency for QTH and LED units, the actual efficiency of LEDs still needs further evaluation. Therefore, the aims of this study were to evaluate the light characteristics (irradiance level and spectral emission) of LED and QTH LCUs, and to investigate their influence on flexural strength and flexural modulus of different resin composites. The tested null-hypothesis was that no significant differences in strength and modulus would be observed regardless of the LCU or resin composite.
Material and Methods
Four commercial hybrid resin composites, shade A3, were evaluated: MasterFill (Biodinâmica, Ibiporã, PR, Brazil), Opallis (FGM, Joinville, SC, Brazil), Filtek Z250 and Filtek Supreme (3M ESPE, St. Paul, MN, USA). Materials’ compositions are shown in Table 1.
Three LCUs were investigated: XL2500 QTH (XL - 3M ESPE), UltraBlue Is LED (UB - DMC, São Carlos, SP, Brazil) and Radii LED (RD - SDI, Victoria, Australia). The LCUs were connected to a voltage stabilizer and the output power (mW) of each unit was measured with a digital power meter (Ophir Optronics Inc., Danvers, MA, USA). The diameter of each light guide tip (cm) was measured with a digital caliper (Mitutoyo, Tokyo, Japan) accurate to 0.01 mm. Irradiance (mW/cm2) was computed as the ratio of the output power by the area of the light guide. Additionally, the spectral distribution of each LCU was obtained using a computer-controlled spectrometer (USB2000; Ocean Optics, Dunedin, FL, USA).
Flexural strength test was conducted in accordance with the ISO4049 standard specifications6. Five rectangular barshaped specimens (25 x 2 x 2 mm) were prepared for each material-unit combination by placing the composites into a stainless steel mold held between two glass microscopic slides. After light-activation procedures, the specimens were removed from the mold and stored in distilled water at 37°C in the dark. After 24 h, the height and width of the specimens were measured with a digital caliper (Mitutoyo) and the samples were subjected to a three-point bending test in a mechanical testing machine (DL500; EMIC, São José dos Pinhais, PR, Brazil), at a crosshead speed of 0.5 mm/min until failure. Flexural strength (FS) was determined as follows:
FS = 3Pf L / 2WH2
where Pf is the measured maximum load (N) at the time of specimen fracture, L is the distance between the supports on the tension surface (20 mm), W is the mean specimen width, and H is the mean height of the specimen between the tension and compression surfaces. Data were submitted to two-way ANOVA and Tukey’s test (p<0.05).
A chart plotter recorded the stress-deformation profile during the flexural test. Flexural modulus (FM) was calculated from the linear-elastic range, between bending force and specimen displacement before fracture, as follows:
FM = (DF / Dy) x (L3 / 4WH3)
where DF / Dy is the change in force (DF) per unit change in deflection of the center of the specimen (Dy). Data were submitted to two-way ANOVA and Tukey’s test (p<0.05).
Table 2 presents the light characteristics for each LCU. Figure 1 shows a comparison for the spectrum of wavelengths. For XL, a spectrum concentrated in the 400-520 nm wavelength range was observed. For RD and UB, the spectrum was concentrated in the 430-530 and 420520 nm range, respectively.
Results for flexural strength are shown in Table 3. The factor ‘LCU’ was not significant (p=0.179), while the factor ‘material’ (p<0.001) and the interaction unitmaterial (p=0.018) were significant. For XL, Opallis showed significantly lower flexural strength than the other composites (p<0.001), which were similar to each other (pe”0.947). Correspondingly, for RD, Z250 and Supreme were similar between them (p=0.554), while MasterFill was similar only to Supreme (p=0.119); Opallis showed significantly lower strength than Z250 and Supreme (pd”0.004), but similar to MasterFill (p=0.565). On the other hand, for UB, all composites presented similar results (pe”0.349). When comparing the different LCUs for each material, no significant differences were observed for MasterFill (pe”0.269) and Opallis (pe”0.091). For Z250 and Supreme, RD showed the highest flexural strength values, which were similar to XL (pe”0.31), but significantly higher than UB (pd”0.041); XL and UB presented similar results (pe”0.176).
Results for flexural modulus are shown in Table 4. The factors ‘material’ and ‘LCU’ were significant (p<0.001), but not their interaction (p=0.165). For XL and UB, Z250 and Supreme showed significantly higher values than both MasterFill and Opallis (pd”0.012), which performed similar (pe”0.147). For RD, Z250 and Supreme presented similar results (p=0.072), and both presented significantly higher modulus than MasterFill and Opallis (p<0.001), which were similar (p=0.677). When comparing the different LCUs for each material, no significant differences were detected for Opallis (pe”0.194). For MasterFill and Z250, XL and RD were similar (pe”0.155), and so were RD and UB (pe”0.295), but XL yielded significantly higher modulus than UB (pd”0.04). For Supreme, XL and RD were similar (p=0.992), generating significantly higher modulus than UB (pd”0.004).
Flexural strength is a measure of composite strength: the higher the value, the stronger the material. The ISO4049 standard6 classifies dental polymer-based restorative materials into 2 types: Type I materials are those claimed by the manufacturers to be suitable for restorations involving occlusal surfaces, while Type II are all other polymer-based restorative materials. The minimum flexural strength requirement for Type I materials is 80 MPa6-7 . The results of this study showed that all composites presented flexural strength higher than 80 MPa, except for Opallis photoactivated with QTH. Indeed, Opallis showed the lowest strength values among all tested composites, regardless of the LCU. Therefore, the nullhypothesis is rejected. The probable explanation for this result may rely on the fact that the composites tested in this study present distinct compositions, and differences in filler load and type, organic matrix components, and even surface treatments of the particles, may affect the mechanical behavior of the materials.
On the other hand, flexural modulus describes stiffness, a measure of material’s resistance to deformation under load. There are debates on how much modulus resin composites should possess8. Class V cervical cavities, for example, demand a low modulus restorative material to flex with the tooth. A relatively high modulus, on the other hand, is expected for posterior restorations to withstand the occlusal forces and preserve the adhesive interface. Theoretically, the ideal value would be similar to that of dental structures, so the restorative would have similar deformation to the surrounding tooth under loading. However, when compared to the modulus of human enamel (84 GPa)9, resin composites have much lower values; in comparison to human dentin (14 GPa)9-10, some composites may present similar values.
In the present study, Z250 and Supreme generally presented higher modulus than the other tested composites. This result might be related to differences in resin formulation or inorganic load among the materials, which strongly affect the properties of the dental composites. Opallis and MasterFill possess irregular glass particles, while the other composites possess spherical ceramic particles that present higher strength and improve the packing of the inorganic fillers, enhancing the properties of the composite. Composites made with irregular particles could have lower flexural strength and modulus than those made with spherical fillers due to the fact that the stress concentration around the fillers would be expected to be greater for materials loaded with irregular-shaped particles11 .
The LCUs produced different results among the resin composites. In general, RD and XL generated higher values for strength and modulus. This is probably explained by the fact that these LCUs presented higher irradiance than UB. The amount of light energy delivered to the specimens might affect the conversion of double bonds which, in turn, might interfere with the development of mechanical properties. Moreover, a photo-polymerization initiated at low light level is generally associated with relatively few centers of polymer growth, possibly resulting in a more linear final polymer structure, with lower network strength. On the other hand, irradiance at high levels produces a multitude of growth centers and leads to the formation of densely cross-linked polymers12-13, which might also explain the results observed for RD and XL.
In addition to irradiance, the polymerization potential by photoactivation is also dependent on the correlation between the light spectrum emitted by the LCU and spectrum of absorption of the photoinitiator14-15. Therefore, one could expect better results for RD, since the peak of emission for this LCU was centered on the absorption peak of CQ, as shown in Figure 1. Nonetheless, similar results for flexural strength and modulus were detected for both RD and XL, irrespective of the resin composite. This result might be attributed to the fact that both LCUs presented high and similar irradiance values, which might have accounted for their similar results16 .
The present results have clinical implications, since both flexural strength and flexural modulus were found to be dependent on the material and LCU tested. The Brazilian resin composites generally presented poorer properties as compared with the other composites tested, while highintensity LCUs generated polymers with enhanced strength and modulus. Notwithstanding, the results of the present study should be restricted to the conditions tested here. Further studies evaluating different resin composites and curing devices are necessary.
The authors are grateful to the Dental School of the Federal University of Pelotas, RS, Brazil, for the access to its facilities, and to Biodinâmica and FGM for donating the materials used in the study.
© Copyright 2008 - Piracicaba Dental School - UNICAMP São Paulo - Brazil
The following images related to this document are available:
Photo images[os08017t4.jpg] [os08017t3.jpg] [os08017f1.jpg] [os08017t1.jpg] [os08017t2.jpg]


There are several types of lithium batteries, but the three most common types are:
- Lithium-ion (Li-ion) batteries: Li-ion batteries are the most common type of lithium battery used in consumer electronics, such as smartphones and laptops. They are lightweight, have a high energy density, and can be recharged many times.
- Lithium polymer (LiPo) batteries: LiPo batteries are similar to Li-ion batteries but are packaged in a flexible pouch rather than a hard casing. They are commonly used in small devices such as drones, remote-controlled toys, and portable power banks.
- Lithium iron phosphate (LiFePO4) batteries: LiFePO4 batteries are a type of lithium-ion battery that uses an iron phosphate cathode instead of a cobalt or nickel-based cathode. They are known for their long lifespan, high power output, and safety. They are commonly used in applications such as electric vehicles, solar power systems, and backup power systems.
Each type of lithium battery has its own set of advantages and disadvantages, and choosing the right type of battery depends on the specific needs of the application.


Organocatalytic Enantioselective Construction of Conformationally Stable C(sp2)–C(sp3) Atropisomers
journal contributionposted on 06.01.2022, 22:33 authored by Giulio Bertuzzi, Vasco Corti, Joseph A. Izzo, Sebastijan Ričko, Nicolaj Inunnguaq Jessen, Karl Anker Jørgensen
Nonbiaryl atropisomers are molecules defined by a stereogenic axis featuring at least one nonarene moiety. Among these, scaffolds bearing a conformationally stable C(sp2)–C(sp3) stereogenic axis have been observed in natural compounds; however, their enantioselective synthesis remains almost completely unexplored. Herein we disclose a new class of chiral C(sp2)–C(sp3) atropisomers obtained with high levels of stereoselectivity (up to 99% ee) by means of an organocatalytic asymmetric methodology. Multiple molecular motifs could be embedded in this class of C(sp2)–C(sp3) atropisomers, showing a broad and general protocol. Experimental data provide strong evidence of the conformational stability of the C(sp2)–C(sp3) stereogenic axis (up to t1/225 °C >1000 y) in the obtained compounds and show kinetic control over this rare stereogenic element. This, coupled with density functional theory calculations, suggests that the observed stereoselectivity arises from a Curtin–Hammett scenario establishing an equilibrium of intermediates. Furthermore, the experimental investigation led to evidence of the operating principle of central-to-axial chirality conversions.
Read the peer-reviewed publication
stereogenic axis featuringshow kinetic controlrare stereogenic elementorganocatalytic enantioselective constructionorganocatalytic asymmetric methodologyexperimental investigation ledconformationally stable caxial chirality conversionssup >°</ supc ( spc </ supobserved stereoselectivity arisesscaffolds bearingoperating principleobtained compoundsnatural compoundsmolecules definedhigh levelsgeneral protocolconformational stability>< sub


Copper Aluminum Trans-Busbar
Author:Frank Time:2023-05-05Single - Double – Sided Copper - Aluminum Composite Transition Sheet Busbar
With the rapid development of lithium battery automobile industry, the problem of PACK connection of lithium battery is becoming more and more prominent. Many buses to the vehicle battery pack thousands of groups, of monomer battery anode material of aluminum foil and copper foil, is how to realize the lithium battery pack is safe, reliable, light weight, simple string, and the connection is the bottleneck restricting the development of lithium battery car technology.
Signi Aluminium Company has developed two kinds of copper - aluminum composite materials connected by independent innovation.Copper - aluminum composite base column material and copper - aluminum composite transition film.Column base material, and 10 mm aluminium plate with 3 mm copper composite made of copper aluminum composite column material, complete copper cathode copper set associative, and aluminum and aluminum plate, forming two electrodes are exposed aluminum battery pack can be done with the normal laser welding process connection; Connecting sheet material: a copper strip with 10mm in the middle of the aluminum plate, copper strip through copper rivets and internal copper set, and the aluminum plates on both sides of the aluminum plate are connected in parallel with each other.
Composite strength: = 12N/mm;
Compound rate: 100%;
Shear strength: >= 35Mpa;
Tensile strength: 90-130mpa;
Extension rate: <= 35%;
Dc resistivity: < = 0.0245 Ω. Mm2/m;
Product features :
high conductivity, high mechanical strength, good reliability, low density and cost saving, high composite strength, metallurgical combination of copper and aluminum, no contact resistance between copper and aluminum, stable and reliable quality.
Product size : customized according to user demand.
Technical parameters : composite strength: greater than 100MPa;
|Weight Display in Common Specification|
1) Proportion of Copper/Aluminum is 2:8 and the proportion could be adjusted by customer's demand.
2) Single and double side copper clading are available.
3) Consistency of thickness is stable and very suitable for mass stampling production.
4) Resistance to corrosion and high temperature (500degree c without separation).
5) With good stability, excellent deep drawability and tensile properties, it can even bear 90°bend without separation.
6) With an electrical conductivity of 98% or more, it can completely replace pure copper by saving cost64% under same volume.
7) The dimension can be produce as requested.
Signi Aluminium Co., LTD. has independently developed and produced the material for the production of copper and aluminum, which is widely used in the transformer, reactor and other electrical industry, effectively replacing the traditional flash welding and brazing process.


|Exploring conceptual frameworks of models of atomic structures and periodic variations, chemical bonding, and molecular shape and polarity: a comparison of undergraduate general chemistry students with high and low levels of content knowledge
Barrow, Lloyd H.
Institute of Education
|The purpose of the study was to explore students' conceptual frameworks of models of atomic structure and periodic variations, chemical bonding, and molecular shape and polarity, and how these conceptual frameworks influence their quality of explanations and ability to shift among chemical representations. This study employed a purposeful sampling technique and used three diagnostic instruments for conceptual understanding to determine the students' level of content knowledge of the related concepts. Six student interviews were analyzed to portray students' conceptual frameworks in high and low content knowledge (HCK and LCK, respectively) groups. The study's major findings revealed that moving from a high toward a low level of content knowledge, the quality of students' explanations declined, as did their ability to reconcile new information to their existing knowledge frameworks. Three essential concepts - models of atomic structure, effective core charge and principles of electrostatic force, and quantum mechanics descriptions - were identified that may explain students' failure to learn the necessary aspects of molecular geometry and polarity. This study provides empirical evidence of how students' content knowledge influences their understanding about molecular polarity. The findings have implications for college chemistry education with respect to teaching concepts about molecular polarity.
|CHEMISTRY EDUCATION RESEARCH AND PRACTICE
|Appears in Collections:
Files in This Item:
If it is a zip file, please download the file and unzip it, then open index.html in a browser to view the full text content.


Mercury contamination from historical gold mines represents a potential risk to human health and the environment. This fact sheet provides background information on the use of mercury in historical gold mining and processing operations in California, with emphasis on historical hydraulic mining areas.
During the trituration process, the surface layer of the silver-tin alloy dissolves in the liquid mercury and the reaction causes new phases to be formed. These new solid phases cause solidification of …
Copper mining. Chemical reactions. - SchoolScience. Part of an interactive on-line booklet about copper mining explaining the chemical reactions used to purify copper. page 4: Chemical reactions : At this stage of the process, the chemical reactions begin.
silver mining chemical reaction Silver, chemical reactions during mining silver - CRUSHER is a What chemical reaction happens when you put copper into silver ... get price Chemical Reactions In Mining by Michaela …
Silver Mining Chemical Reaction - montaz-nabytku. chemical reactions during mining silver. This page is provide professional chemical reactions during mining silver information for you. Mining - Wikipedia. Mining in the Philippines began around 1000 BC. The early Filipinos worked various mines of gold, silver, copper and iron.
Silver is a chemical element with symbol Ag (from the Latin argentum, derived from the Proto-Indo-European h₂erǵ: "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal.
Feb 06, 2016· chemical process of mining silver offers 1031 chemicals used in coal mining products. About 5% of these are paper chemicals, 4% are electronics chemicals, and 1% are polymer. A wide variety of chemicals used in coal mining options are available to you, such as free samples.
silver smelting chemical reaction. Smelting - Wikipedia, the free encyclopedia. ... Recovering Silver, Refining Silver, silver extraction,and Silver mining. ... If a chemical reaction is stopped to fill Nitric acid added. A metallic .... 1.3 Smelting Gold. Read more. Chemical Reactions - Chemwiki.
chemical reactions during mining silver . Chemistry for Kids Elements Silver Ducksters- chemical reactions during mining silver Kids learn about the element silver and its chemistry including atomic weight atom uses sources name and discovery It will not react with air or water It will tarnish Most of the silver mined in the United States is from the Silver Royal
chemical reactions during mining silver. Silver Chemicool Show more, including: Heats, Energies, Oxidation, Reactions, Compounds,, Silver and lead often appear together in nature, for example in the mineral, Silver's chemical symbol, Ag, is an abbreviation of the Latin .
Silver Chemistry Encyclopedia Water ProteinsSilver is a precious or smelting methods Silver is used in the manufacture of Localised Argyria : Chemical Nature of the Silver.Chemical reactions, also called chemical Take as an example the smelting of Here is an example of a single replacement reaction : silver nitrate solution.
Silver metal is a good catalyst for oxidation reactions; in fact it is somewhat too good for most purposes, as finely divided silver tends to result in complete oxidation of organic substances to carbon dioxide and water, and hence coarser-grained silver tends to be used instead.
Two key types of chemical reactions are oxidation and reduction. ... Oxidation is the loss of electrons during a reaction by a molecule, atom or ion. Oxidation occurs when the oxidation state of a molecule, atom or ion is increased. The opposite process ... Silver metal whiskers grow onto the copper wire, while copper ions are released into the ...
Gold cyanidation (also known as the cyanide process or the MacArthur-Forrest process) is a hydrometallurgical technique for extracting gold from low-grade ore by converting the gold to a water-soluble coordination complex.
A chemical reaction is a process that is usually characterized by a chemical change in which the starting materials (reactants) are different from the products. Chemical reactions tend to involve the motion of electrons, leading to the formation and breaking of chemical bonds.There are several different types of chemical reactions and more than one way of classifying them.
Silver distributed widely in the rat following ingestion of silver chloride (in the presence of sodium thiosulfate) and silver nitrate in drinking water (at 88.9 mg silver/kg/day for silver nitrate) ... .
Silver is a chemical element with symbol Ag ... in catalysis of chemical reactions, as a colorant in stained glass and in specialised confectionery. Its compounds are used in ... Peru, Bolivia and Mexico have been mining silver since 1546, and are still major world producers.
Smelting is a process of applying heat to ore in order to extract out a base metal.It is a form of extractive metallurgy.It is used to extract many metals from their ores, including silver, iron, copper, and other base metals.Smelting uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal base behind.
This includes the mining of coal, copper, gold, silver, zinc, lead, and uranium. The mineral pyrite, more commonly known as "fool's gold," is iron disulfide (FeS 2 ). Pyrite is one of the most important sulfides found in the waste rock of mines.
Sulfuric acid is a toxic chemical used in copper mining. It is also a byproduct of many kinds of mining, mixing with water and heavy metals to form acid mine drainage. Sulfuric acid smells like rotten eggs.
Cyanide is used in the process of separating the gold and silver particles from the ore. These reactions are used to safely (or as safely as possible) remove the particles from the ore. The cyanide mixes with the ground up ore and gold/silver and the cyanide easily reacts and separates the two.
Silver mining in North America dates back to the eighteenth century. ... resonant, moldable, malleable, and possesses the highest thermal and electric conductivity of any substance. The chemical symbol for silver ... it does react with sulfur, which is always present in the air, even in trace amounts. The reaction causes silver to tarnish ...
Electrolysis uses a direct electric current to create a chemical reaction. This process is used to produce pure copper metal in the final stage of copper extraction from ores after being removed from the …
Alloys of gold with silver or copper are used to make gold coins and goldware, and alloys with platinum or palladium are also used in jewelry. The content of gold alloys is expressed in 24ths, called karats ; a 12-karat gold alloy is 50 percent gold, and 24-karat gold is pure.
Gold processing, preparation of the ore for use in various products. For thousands of years the word gold has connoted something of beauty or value. These images are derived from two properties of gold, its colour and its chemical stability.


Soap made with salt has always fascinated me, but I have never tried to make it. Today that will change!
There are two ways to make soap with salt. The first way is to simply add salt to the soap batter for a scrubby bar. This works well using fine sea salt, and the bars have a long life in the shower. I’ve purchased some from friends and enjoyed them very much.
The other way to make salt soap is to make a salt brine. You add salt to the hot lye solution and stir it well to dissolve the salt. You don’t want to go over a 20% salt solution. This is known as Soleseife soap. (“Soleseife” is German for “brine water.”) You’ll often find Soleseife soaps featured in spas for their nourishing and hydrating effects on the skin. Soleseife bars are not scrubby; they are hard, smooth bars.
I opted to go with the brine soap for my first salt soap attempt. I used our usual 6-5-4-1 formula for the oils, choosing Grapeseed Oil as my luxury oil. I’ll scent my soap in Awapuhi Seaberry, a clean and fresh scent that is one of our most popular.
Join me in the workroom to make some Soleseife Soap!
What You’ll Need
6 ounces Soybean Oil
5 ounces Coconut Oil
4 ounces Olive Oil
1 ounce Grapeseed Oil
2.21 ounces lye (8% superfat)
2.21 ounces salt
10 ounces water
Before you get started, get prepared to soap safely. Long sleeves, gloves, eye protection, and close-toed shoes are a must. If you have never made cold process soap before, we’re glad you’re here! Please check out this blog post, which is the first in a series on beginning soapmaking.
Weigh all the oils into a microwave-safe container; set aside.
Weigh the fragrance oil into a small glass container; set aside.
Weigh the lye into a small glass container.
Weigh the salt.
Weigh the distilled water. I use a stainless steel pitcher for my lye solution.
Slowly add the lye to the liquid, stirring. Do this in a well-ventilated area. As soon as all the lye has dissolved, and while the lye solution is still hot, add the salt to the lye solution. Stir well until salt has dissolved. (The salt did not completely dissolve in my lye solution, so I poured through a sieve to catch the undissolved salt when adding the lye solution to the oils.) Check the temperature of the lye solution; set aside to cool.
Pop the oils into the microwave to melt, using 30-second increments. When oils are completely melted, check the temperature, and set the oils aside to cool.
Here is your break to clean up your work space, set out the mold you will use, visit the rest room. Once the oils and the lye mixture are within 10 degrees of each other and have cooled to about 90-100 degrees F, you’re ready to make soap.
When your oils and lye solution have reached the proper temperature, carefully pour the lye solution into the oils through a fine sieve to catch any undissolved salt. Whisk to combine, being careful not to splash.
Add the fragrance oil, whisking to combine. At this point, your soap batter will already have reached a noticeable trace. Keep whisking until the batter is emulsified. You can check for emulsification by dipping a metal spoon into the soap batter and looking at the back of the spoon to see if the oils do not separate.
Once the soap batter has reached emulsion, carefully pour it into cavity molds and set aside to harden. Using cavity molds for any salt soap is recommended because it hardens so quickly, cutting a loaf of soap may be impossible.
I was amazed that this soap was not super hard the next day when I unmolded it. It was firm enough that it came out of the paw print mold whole, but it was still a bit soft around the edges. It will need to cure for a while before it’s okay to use. I’m sure that is because I used a lot of water in the soap batter.


Polyhomologation and ATRP: A Perfect Partnership toward Unique Polyethylene-Based Architectures
KAUST DepartmentChemical Science Program
KAUST Catalysis Center (KCC)
Office of the VP
Physical Science and Engineering (PSE) Division
Polymer Synthesis Laboratory
Permanent link to this recordhttp://hdl.handle.net/10754/630555
MetadataShow full item record
AbstractThe recent developments in organoborane initiated C1 polymerization (chain grows by one atom at a time) of ylides opens unique horizons towards well-defined/perfectly linear polymethylenes (equivalent to polyethylenes, PE). On the other hand, atom transfer radical polymerization (ATRP) is an excellent and powerful controlled/living polymerization for polar monomers such as (meth)acrylates and styrenes. In this Chapter the partnership of these two living polymerizations towards the synthesis of well-defined PE (perfectly linear)-based block copolymers, with unprecedented macromolecular architectures, is presented. Some ideas about new ylide monomers are also discussed.
CitationWang D, Zhang Z, Zhang H, Gnanou Y, Hadjichristidis N (2018) Polyhomologation and ATRP: A Perfect Partnership toward Unique Polyethylene-Based Architectures. Reversible Deactivation Radical Polymerization: Materials and Applications: 1–24. Available: http://dx.doi.org/10.1021/bk-2018-1285.ch001.
SponsorsResearch reported in this publication was supported by the King Abdullah University of Science and Technology (KAUST).
PublisherAmerican Chemical Society (ACS)


|ZFIN ID: ZDB-PUB-160613-1|
Fatty liver disease induced by perfluorooctane sulfonate: Novel insight from transcriptome analysis
Fai Tse, W.K., Li, J.W., Kwan Tse, A.C., Chan, T.F., Hin Ho, J.C., Sun Wu, R.S., Chu Wong, C.K., Lai, K.P.
|Source:||Chemosphere 159: 166-177 (Journal)|
|Keywords:||Environmental pollutant, Hepatotoxicity, Perfluorooctane sulfonate, Transcriptome, Zebrafish|
|PubMed:||27289203 Full text @ Chemosphere|
Fai Tse, W.K., Li, J.W., Kwan Tse, A.C., Chan, T.F., Hin Ho, J.C., Sun Wu, R.S., Chu Wong, C.K., Lai, K.P. (2016) Fatty liver disease induced by perfluorooctane sulfonate: Novel insight from transcriptome analysis. Chemosphere. 159:166-177.
ABSTRACTPerfluorooctane sulfonate (PFOS), a hepato-toxicant and potential non-genotoxic carcinogen, was widely used in industrial and commercial products. Recent studies have revealed the ubiquitous occurrence of PFOS in the environment and in humans worldwide. The widespread contamination of PFOS in human serum raised concerns about its long-term toxic effects and its potential risks to human health. Using fatty liver mutant foie gras (fgr(-/-))/transport protein particle complex 11 (trappc11(-/-)) and PFOS-exposed wild-type zebrafish embryos as the study model, together with RNA sequencing and comparative transcriptomic analysis, we identified 499 and 1414 differential expressed genes (DEGs) in PFOS-exposed wild-type and trappc11 mutant zebrafish, respectively. Also, the gene ontology analysis on common deregulated genes was found to be associated with different metabolic processes such as the carbohydrate metabolic process, glycerol ether metabolic process, mannose biosynthetic process, de novo' (Guanosine diphosphate) GDP-l-fucose biosynthetic process, GDP-mannose metabolic process and galactose metabolic process. Ingenuity Pathway Analysis further highlighted that these deregulated gene clusters are closely related to hepatitis, inflammation, fibrosis and cirrhosis of liver cells, suggesting that PFOS can cause liver pathogenesis and non-alcoholic fatty liver disease in zebrafish. The transcriptomic alterations revealed may serve as biomarkers for the hepatotoxic effect of PFOS.


Thermal expansion and Gruneisen parameters in some Pr–Ni–Si compounds
In this study, the thermal expansion and Gruneisen parameter of polycrystalline “Pr5Ni2Si3” and “Pr15Ni7Si10” were investigated over the temperature range of 5–300 K. Calculations of the phonon contribution to thermal expansion were made, which allowed the magnetic contribution to thermal expansion to be calculated from the difference between the total thermal expansion and the phonon contribution. This resulted in a temperature-dependent magnetic contribution to thermal expansion that varied with the magnetic ordering of the material. The results show two magnetic transitions in each compound, the higher temperature transition corresponding to the Curie temperature and the lower temperature transition resulting from a spin reorientation.
Copyright 2005 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
The following article appeared in Journal of Applied Physics 97 (2005): 10M313 and may be found at http://dx.doi.org/10.1063/1.1855196.


Every bottle of nutrients you see at Cultivate is going to have an NPK label.
These letters stand for Nitrogen (N), Phosphorus (P) and Potassium (K) and they are essential to the healthy development of your plants. If your plant is missing any of these elements, it will not survive.
Each element serves its purpose in plant development, from initial growth through the final stages of flowering. This makes nitrogen the most essential element during early growth, and phosphorus and potassium later on.
But really, all three work in unison throughout the entire growth process to produce a strong healthy plant. That's why it's important to know the importance of every single one!
What is Phosphorus?
Phosphorus is a chemical element with the atomic number 15. It’s highly reactive and is found in ATP, DNA, RNA, phospholipids, and the Earth’s crust. In other words, it can be found in all life!
Behind nitrogen, phosphorus is considered the second most essential nutrient because of its responsibility for managing biological functions like helping plants capture and store energy from the sun during photosynthesis. Phosphorus converts ADP (adenosine diphosphate) into ATP (adenosine triphosphate), a chemical found in all living things that stores and transfers energy.
ATP provides the energy to drive many different processes and biochemical reactions from seedling growth to harvest. Without phosphorus, there is no ATP.
Is That a Phosphorus Deficiency?
When your plant is young, a phosphorus deficiency can be hard to catch. A phosphorus deficiency will be shown through less growth during the early stages of vegetative growth.
Smaller leaves, stems, and shorter overall plants compared to others at the same stage of development is a good sign that your plant could be missing phosphorus. If a deficiency occurs in a later stage of growth, it can be easier to spot.
The early stages of phosphorus deficiency in more mature plants typically expresses itself through the leaves. They will turn a purplish-red hue, which should be noticeably different from the natural color of your plants.
If you can catch the deficiency here and stop it, then you can avoid a lot of trouble down the road. However if you don't notice it right away it can develop into a much more noticeable problem, turning from purplish-red to dark brown as your leaves start to die.
Fixing a Phosphorus Deficiency
The problem a lot of growers face with NPK deficiencies is that they can look pretty similar. This can bring in a little bit of guesswork on the part of the grower, which is always uncomfortable when you're dealing with your plants!
Because the deficiency could be phosphorus, or nitrogen, or potassium, it's best to test out just a couple plants instead of the whole garden. For example, if you have six plants, and all of them look they might have a phosphorus deficiency, give just two plants a phosphorus supplement to see if anything changes.
If you notice positive results, then you can incorporate the supplement into the rest of your plants. The reason we do this is in case the deficiency is from something other than phosphorus. If phosphorus turns out not to be the problem, giving all of your plants extra phosphorus can lead to nutrient lockout of other nutrients.
If you want to be sure which deficiency you have before you start giving it supplements, check out our article figuring out nutrient deficiencies.
Just the P in NPK
It's important to remember that even though phosphorus is essential to plant growth, it is only one part of the three-part NPK formula that your plants need. Nitrogen and potassium are just as essential as phosphorus and you should monitor how much of each your plant is receiving constantly.
Stay tuned for more breakdowns on nitrogen and potassium to get the full scope of how important these three elements truly are!


|Aug23-08, 10:16 PM||#1|
heating gases at constant pressure or constant volume?
if i was to heat a gas [any gas] by 10 degrees celcius, using the smallest amount of heat energy, would i be better off heating the gas at constant pressure or constant volume. i think constant pressure, however i dont know how to justify my answer...
|Aug23-08, 11:40 PM||#2|
You'll want to look for the specific heat capacity of an ideal gas at constant volume and at constant pressure, and compare them. The smaller heat capacity means it takes less heat to raise the temperature of the gas by a chosen amount.
|gases, heat energy, pressure, volume|
|Similar Threads for: heating gases at constant pressure or constant volume?|
|work- constant pressure, changing volume||Introductory Physics Homework||2|
|Thermodynamics: Amount of work required to increase pressure at constant volume||Introductory Physics Homework||6|
|Time for heating to equilibrium with constant heat flux||Introductory Physics Homework||1|
|Isobaric process, Cv and constant volume?||Introductory Physics Homework||0|
|Constant Volume/Ideal Gas||Introductory Physics Homework||1|


Japan is desperate for Kazatomprom to accelerate the rare earth joint ventures it launched this year with Sumitomo and Toshiba.
Japan looks to Central Asia for rare earth supply
This month a team of executives from Kazatomprom, the Kazakh state company that is the world's biggest uranium producer, were invited to the economy ministry in Tokyo.
The ministry was not interested in discussing fuel supplies for its nuclear power plants. It wanted to talk about rare earth metals.
For almost a month China, which is responsible for more than 93 per cent of rare earth metals production, has imposed a de facto embargo on exports of the metals to Japan, the world's biggest user.
As a result, Japan is desperate for Kazatomprom to accelerate the rare earth joint ventures it launched this year with Sumitomo and Toshiba.
Once an obscure corner of the mining industry, rare-earth metals - 17 elements from the middle of the periodic table - are increasingly essential for making computer screens, hybrid cars, superconductors and even the iPod.
The leading hybrid car, the Toyota Prius, relies on a rare earth magnet made partly from neodymium.
The lure for the Japanese in Kazakhstan is a plant once so secret it was known only by the codename "2A".
The core of the former Soviet Union's nuclear weapons programme, the Ulba Metallurgical Plant developed skills in rare metals and rare elements - particularly in beryllium, tantalum and niobium - that are still unmatched more than 20 years on.
Even today it is one of only three plants in the world capable of making finished strips of beryllium and it has advanced capabilities for making super-conducting cables.
"The Cold War had some advantages," said an official at Kazatomprom who asked not to be identified. "Ulba had the best research and development in the Soviet era. The people there are still experts, they haven't stopped."
Sumitomo of Japan has already opened an office next door to Ulba for its joint venture with Kazatomprom, called the Summit Atom Rare Earth Company.
It is working on a feasibility study and a pilot plant to produce rare earth compounds and products, sourcing the raw material from tailings, or waste material piles, of Kazakhstan's uranium industry.
But the joint venture is still waiting for the final go-ahead from the Kazakh authorities.
Toshiba signed a memorandum of understanding with Kazatomprom in June and a joint venture is due to be established by the end of this year.
The urgency is increasing. China has yet to fully end the embargo, which was never official. Chinese customs officials have simply blocked all rare earth shipments to Japan in what looks like punishment for Japan's intransigence in its dispute over the uninhabited Senkaku Islands.
At the same time, China is cranking up tariffs and reducing export quotas. After cutting export quotas this year by 40 per cent, Beijing is planning a further 30 per cent decrease next year.
The result is that rare earth metal prices are soaring, with most more than doubling in the past few months alone. With demand expected to increase about 12 per cent a year, rising from 124,000 tonnes annually today to 170,000 tonnes in the next three years, the pressure on prices and supplies is not expected to relent.


Free Delivery in (GAUTENG ONLY)
* Durable marble pool plaster
* Applied to new or renovated pools
* Trowel-on application
* Over 40 years proven experience
* Extensive colour range
* Superior quality
A 6mm thick smooth plaster, recommended for the interior plastering of walls and floors of swimming pools, which becomes a very hard integral part of the pool structure. Not for use above the water level.
Q: Why should I use PoolCrete instead of other pool plasters?
A: Cemcrete only makes use of top quality marble dust and the world’s best white cement. This ensures that our product will not change colour, as some products on the market do. Market research indicates that there are products on the market where the cement becomes yellow, blue and even grey in a short space of time. Cemcrete has manufactured PoolCrete since 1973 and have been at the forefront in solving the industry’s issues related to the chemical staining of pool plasters, due to our commitment and research within this market.
Q: What is the lifespan of PoolCrete?
A: PoolCrete, correctly applied, can last anything between 15 and 20 years. PoolCrete is by far the most durable pool finish in its range, however the secret to longevity is correct water balance and maintenance.
Q: After installing PoolCrete, how should I maintain my pool?
A: It is important to follow the PoolCrete Start-up Guide when filling your newly finished pool, however your experienced contractor should guide you through the process. When maintaining your pool with chemicals, always follow the manufacturer’s instructions when adding them to your pool.
Q: What chemicals can I use in my PoolCrete pool?
A: The use of traditional chlorine, sodium bicarbonate, acid and stabilizers in your swimming pool are permitted. Other chemicals should be used in consultation with the relevant manufacturers and skilled pool practitioners. Avoid using chemicals that contain copper sulphate and herbicides.
There is a variety of other chemicals on the market and one should use them in consultation with the relevant manufacturer & skilled pool practitioners for their correct use. Special care should be taken when using copper sulphate & herbicide containing pool care products are possible staining can occur
DUE TO THE NATURE OF THIS PRODUCT PLEASE ENSURE YOU ORDER THE CORRECT QUANTITY AND COLOUR AS NO RETURNS OR REFUNDS CAN BE PROCESSED AFTER DELIVERY.


MPY - Mils per Year
The term "MPY" describes the corrosion rate of a metallic surface. This is interesting for pipes or piping systems. The formula is used to calculate the material or weight loss of a metal when corroding. You will find detailed information here: https://www.merusonline.com/mpy-mils-per-year/.
MIC - Microbiologically Induced Corrosion
"MIC" describes all corrosion caused by microbiological organisms such as bacteria. Some of these produce acids which harm metallic surfaces. If the microbes or bacteria settle in a so-called biofilm their influence even intensifies at this spot.
SRB - Sulfur Reducing Bacteria
SRB are Bacteria which live in the deep sea mostly around so-called "Black Smokers". They are anaerobe and can destabilize steel in pipelines or processing machines. If you are interested in further information please see this page: https://www.merusonline.com/srb-sulfur-reducing-bacteria/.
COC - Cycle of Concentration
"COC" is a term used to describe a phenomenon in the cooling water. In an open cooling water system, the water constantly evaporates and fresh water is added. Substances as limescale, which have been solved remain in the cooling loop. Their concentration in the cooling water increases gradually. If the amount of foreign substances exceeds a certain level, the water has to be exchanged completely and the cooling loop is cleaned. The Cycle of Concentration can be used to define how often the water in the cooling loop can be pumped around before a blowdown is needed.
When writing about "Downstream Applications" we usually refer to Refineries and the Petrochemical Industry.
The applications we describe around the "Midstream Sector" include Trunk Lines and Crude Oil Terminals.
Our Upstream Applications include Wells, Flow Lines, the Gathering Station as well as Separation Plants.
Corrosion can be an issue where water is in contact with metal pipes. The topic is also interesting for the Oil and Gas business as the water contained in crude can be sufficient to cause corrosion in the pipelines. It harms the surface of the pipes and can erode the substance.
Open Cooling Water System
In an open cooling water system there is a certain type of exchange between cooling water and the environment. Either with the ambient air, as evaporation is used for cooling or by adding fresh, cool water to the system. Adding new water while used water evaporates Leads to a Cycle of Concentration as formerly solved substances remain in the system.
Closed Cooling Water System
In a closed cooling water system, the cooling water circulates without contact with the environment. It is cooled by a chiller or heat exchanger. These systems are used, where very low temperatures are needed or for very risky processes where the cooling must not be disturbed. Before entering the cooling loop the water is purified, therefore the risk for scaling or fouling is reduced. Nevertheless, corrosion can be an issue if the water is stagnating.


Additional Investigations Concerning the Hydration of Magnesium Oxide in the Waste Isolation Pilot Plant
Nathalia L. Chadwick and Anna C. Snider
Sandia National Laboratories1
Carlsbad Programs Group
Carlsbad, NM 88220
WIPP is a U.S. Department of Energy repository for the disposal of defense-related, transuranic waste. The repository is located in southeast New Mexico at a depth of 655 m in the Salado Formation, a Permian bedded salt formation. MgO is currently being emplaced in the repository to reduce actinide solubilities by consuming CO2 produced by possible microbial activity, buffering the repository at about pH 9, and by consuming water. Magnesium oxide (MgO) is the only engineered barrier that is recognized as such for the WIPP by the U.S. Environmental Protection Agency. Premier Chemicals is presently the supplier of MgO to the WIPP project.
Initial results from our inundated hydration experiments indicate that Premier MgO does not appear to be fully hydrated and some sets of data are irreproducible. To address these issues additional experiments have been initiated with different conditions, such as grain size, different MgO lots, etc., to ascertain the determining factors involved. Sets of experiments, containing 5 g of Premier MgO in 100 mL solutions, are placed in ovens at varying temperatures and shaken frequently. The pH is measured and weight loss on ignition (LOI) is calculated on the samples. The new data will aid in the interpretation of the complex MgO hydration system.
Acknowledgement: This research is funded by WIPP administrated by the Department of Energy.
1. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energys National Nuclear Security Administration under Contract DE-AC04-94AL85000.


ScIDre is a company based in Dresden, Germany. Scientific Instrument Dresden is a globally acting technology enterprise, which is a partner of the Leibniz Institute for Solid State and Materials research Dresden.
ScIDre GmbH is considered to be a professional in fundamental research and natural sciences. Therefore, the main business area of the company is the development of unrivaled scientific equipment with unique features, based on the requests and requirements of scientists. Any kind of customized solution could be made on request. The company transfers it's technologies from from the Leibniz Institute. But this doesn't mean that own know-how are unacceptable. The main point of cooperation with ScIDre is creating customer-specific versions of already created engineering activities. Transparent licensing and cooperation agreements are the advantages company offers. Among products of the company we can find: - Crystal Growth Systems: floating zone, bridgman, czochralski and flux growth. Each system has an ability to work at pressures at up to 150 bar with different gases and mixtures in the growth chamber. - Special Process Furnaces: Ultra-clean rod preparation, High pressure oxygen syntering and Aggressive Media Treatment. - Scientific equipment: Phase transition microscope, Ultra-clean argon preparation, cold isostatic press - Vacuum & Cryo-Technologies: Linear Manipulator, liquid helium pump. It is necessary to emphasize that company offers such services as Design & Calculations, software development, job order production and exploitation of ideas. More information on a website of the company.
Business Type: Nanotextile » | Biotechnology » | Electrotechnics » |
Share with friends:
Next companies in category


Objective: The objective of this experiment is to use acid-base extraction techniques to separate a mixture of organic compounds based on acidity and/or basicity. After the three compounds are separated we will recover them into their salt forms and then purify them by recrystallization and identify them by their melting points.
Extraction of Carboxylic Acid
A pre-weighed (0.315g) mixture of Carboxylic acid, a phenol, and neutral substance was placed into a reaction tube (tube 1). tert-Butyl methyl ether (2ml) was added to the tube and the solid mixture was dissolved. Next, 1 ml of saturated NaHCO3 solution was added to the tube and the contents were mixed separating the contents into three layers. Once this was completed the bottom layer was transferred to tube 2 using a pipette. Once in tube 2 the contents were washed with approximately 0.2 ml of ether and then the ether layer was discarded.
Extraction of Phenol
After the extraction of the Carboxylic acid, two tubes will be present one with the extracted Carboxylic acid and the other being Tube 1’ which is now a mixture of the Phenol, neutral substance, ether, and NaHCO3. Before moving on with the extraction the tube is washed with approximately 0.2 ml NaHCO3 to make sure all the Carboxylic acid has been extracted. To tube 1 (1 ml) 3M NaOH is added to separate the Phenol from the neutral substance. The bottom layer is then pipetted to a new tube (tube 3). 0.15 ml of H2O is added to tube 1’’ and the lower layer is added to tube 3. Tube 3 is washed with 0.2 ml ether and the ether layer is disposed of. The washing ensures that tube 3 is strictly phenol. Recovery of the neutral substance
Tube 1’’ is washed with saturated NaCl (0.3 ml) and the aqueous layer is discarded. To make sure all the water is removed CaCl2 drying pellets are added and the solution is transferred to a pre-weighed tube (tube 4). Tube 1’’ is rinsed 2-3 times with ether and the rinsing is placed into tube 4. Tube 4 is...
Please join StudyMode to read the full document


Nowadays cell phones are ubiquitous. Everyone has one and everyone uses it all the time. But have you ever thought about what goes into making a cell phone — more specifically, the precious minerals and metals that are used to produce it? Cell phones are made with a host of rare materials that are often mined in countries all over the world. So, what’s really in your cell phone? Here are the minerals and metals that you carry with you every day.
Copper is one of the oldest mined metals in the world. It’s been used for over 10,000 years. A reddish-brown color that’s malleable compared to other metals, copper is used in the circuitry of phones because it’s good at conducting electricity. It’s also the most important element used in the electronics of the phone overall since it makes the connectors and wires. Most copper is found in porphyry copper deposits in the large chunks of molten rock that make up the Earth’s crust. Chile is the world’s top copper producer, mining 28 percent of this precious metal.
Lithium is the soft, light metal that gives cell phones their charge. It’s used in the rechargeable lithium ion that give phone batteries their power and density, as well as helping them to charge faster and last longer. Unlike other metals, lithium is not found in an elemental state. Instead, it’s extracted from lithium rocks and from lithium chloride salts. Like copper, Chile is the largest lithium producer in the world. The country extracts most of the precious metal from the Atacama Salt Flat. Argentina produces the second most lithium in the world.
More on Cell Phones:
Smartphone addiction is real. One woman puts hers down for a week to see what happens.
Endless buzzes and dings can burden our minds and even influence important decision-making — but researchers are searching for solutions.
Silica is an element found in quartz. It’s used to make the chips and microprocessors in your cell phone. Silica is also found in the Earth’s crust. The type of silica used to make cell phone chips is an ultra-refined and inherently delicate form of silicon dioxide particles. These important silica sand deposits are found in places like Queensland, Australia, as well as Mid-Atlantic states in the U.S., like North Carolina and Virginia.
Germanium is used to make the semiconductors in cell phones. This silvery white, brittle element is commonly used in a host of electrical devices. The rare mineral is found in rock deposits of germanite and argyrodite, as well as in zinc ore. The U.S. does have germanite, but we still rely heavily on China, which produces more than 70 percent of the mineral in places like the Yunnan Province. Inner Mongolia is also known to produce the mineral.
Bauxite is the main source of the mineral gallium which is used to produce the LED backlighting that make our phones shine bright in the night. Most of the world’s bauxite is found in tropical and subtropical regions of the world. The largest “blanket deposits” are found in places like West Africa, South America, Australia and India. Australia is the world’s biggest producer of the mineral. Miners extract the material from surface and underground deposits and the mineral gallium is a byproduct of the process.
Potassium comes from an element called orthoclase and it’s used to make the touch screen on your cell phone. It comes from a potassium salt called sylvite that’s found in places like Canada, Russia and Belarus. Cell phone screens are treated with potassium salts at the end to add durability so that they survive all the drops and destruction that we put them through daily.
These are just a few of the many precious minerals and metals used to make the cell phones we depend on every day. No matter where it’s made, producers depend on materials from at least a dozen countries or more for your phone to shine bright, conduct electricity, hold a charge, record a message, take a picture and so many other functions that we take for granted.


One of the most popular materials for the production of bone implants is ultra high molecular weight polyethylene (UHMWPE). Scientists of NUST “MISiS” have been engaged in the development of biomimetic (repeating the real structure of bone implants) scaffolds (structures that become implants after implantation) for several years. Particular attention is paid to simulating the porosity of the bone core, so that after the implant is installed, the patient’s bone tissue cells can divide and “sprout” into the implant. Previously, the team achieved this architecture of samples by 3D-modeling and printing the “negative” of the bone, followed by filling the mold with polymer.
A new development of scientists is a biomimetic scaffold from UHMWPE, the structure of which is copied from the structure of a real mammalian bone. Initially, experiments were carried out with fragments of cow bones. The bone marrow was removed using hydrogen peroxide, then the bone was filled with polyethersulfone to form a “negative” internal structure. Then, the resulting “negative” was washed with hydrochloric acid, filled with UHMWPE powder, and thermal pressing occurred. Finally, the sample was immersed in N-methylpyrrolidone — it completely dissolved the polyethersulfone “negative”, leaving only the porous UHMWPE, which has a structure that mimics the original bone structure.
“A characteristic feature of the spongy part of the bone is anisotropy – elongated pores along the length of the bone, ellipsoidal in the section. It is impossible to completely repeat this on a 3D printer because of the high viscosity of the UHMWPE melt, ”says Inna Bulygina, an employee of the Center for Composite Materials of NUST“ MISiS ”and the main author of the development. – When we used as a “negative” bone with lengths of the major and minor pore axes ~ 770 μm and 470 μm, respectively, we obtained polymer pores with axis lengths of ~ 700 μm and 500 μm. That is, the shape of the pores turned out to be ellipsoidal at the cut, as close to natural as possible. ”
Scientists from the Technical University of Dortmund assessed the topography of the sample, and thanks to specialists from the NMIC named after N.N. Blokhin were tested in vitro.
The experiments performed on incubation of the implant with multipotent mesenchymal stromal cells proved their 75% proliferation after 48 hours.
Next, scientists plan to test various combinations of materials for the manufacture of implants with a spongy core and hard shell. According to the researchers, the most promising niche for the potential implementation of the development is veterinary medicine.
The technology has already been patented, an article on the development published in the journal Polymer Degradation and Stability.