bluuebunny/crossref_metadata_2025 huggingface dataset:
Worldwide trend of atmospheric mercury since 1995
Authors: Slemr F. , Brunke E.-G. , Ebinghaus R. , Kuss J.
Published: May 2011

Abstract. Concern about the adverse effects of mercury on human health and ecosystems has led to tightening emission controls since the mid 1980s. But the resulting mercury emissions reductions in many parts of the world are believed to be offset or even surpassed by the increasing emissions in rapidly industrializing countries. Consequently, concentrations of atmospheric mercury are expected to remain roughly constant. Here we show that the worldwide atmospheric mercury concentrations have decreased by about 20 to 38 % since 1996 as indicated by long-term monitoring at stations in the Southern and Northern Hemispheres combined with intermittent measurements of latitudinal distribution over the Atlantic Ocean. The total reduction of the atmospheric mercury burden of this magnitude within 14 years is unusually large among most atmospheric trace gases and is at odds with the current mercury emission inventories with nearly constant anthropogenic emissions over this period. This suggests a major shift in the biogeochemical cycle of mercury including oceans and soil reservoirs. Decreasing reemissions from the legacy of historical mercury emissions are the most likely explanation for this decline since the hypothesis of an accelerated oxidation rate of elemental mercury in the atmosphere is not supported by the observed trends of other trace gases. Acidification of oceans, climate change, excess nutrient input and pollution may also contribute by their impact on the biogeochemistry of ocean and soils. Consequently, models of the atmospheric mercury cycle have to include soil and ocean mercury pools and their dynamics to be able to make projections of future trends.
Impacts of future climate change and effects of biogenic emissions on surface ozone and particulate matter concentrations in the United States
Authors: Lam Y. F. , Fu J. S. , Wu S. , Mickley L. J.
Published: May 2011

Abstract. Simulations of present and future average regional ozone and PM2.5 concentrations over the United States were performed to investigate the potential impacts of global climate change and emissions on regional air quality using CMAQ. Various emissions and climate conditions with different biogenic emissions and domain resolutions were implemented to study the sensitivity of future air quality trends from the impacts of changing biogenic emissions. A comparison of GEOS-Chem and CMAQ was performed to investigate the effect of downscaling on the prediction of future air quality trends. For ozone, the impacts of global climate change are relatively smaller when compared to the impacts of anticipated future emissions reduction, except for the Northeast area, where increasing biogenic emissions due to climate change have stronger positive effects (increases) to the regional ozone air quality. The combination effect from both climate change and emission reductions leads to approximately a 10 % or 5 ppbv decrease of the maximum daily average eight-hour ozone (MDA8) over the Eastern United States. For PM2.5, the impacts of global climate change have shown insignificant effect, where as the impacts of anticipated future emissions reduction account for the majority of overall PM2.5 reductions. The annual average 24-h PM2.5 of the future-year condition was found to be about 40 % lower than the one from the present-year condition, of which 60 % of its overall reductions are contributed to by the decrease of SO4 and NO3 particulate matters. Changing the biogenic emissions model increases the MDA8 ozone by about 5–10 % or 3–5 ppbv in the Northeast area. Conversely, it reduces the annual average PM2.5 by 5 % or 1.0 μg m−3 in the Southeast region.
Cloud-system resolving model simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment
Authors: Morrison H. , Grabowski W. W.
Published: May 2011

Abstract. This paper presents results from 240-member ensemble simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment. Simulations using a two-dimensional cloud system-resolving model are run with pristine, polluted, or highly polluted aerosol conditions and large-scale forcing from a 6-day period of active monsoon conditions during the 2006 Tropical Warm Pool – International Cloud Experiment (TWP-ICE). Domain-mean surface precipitation is insensitive to aerosols primarily because the large-scale forcing is prescribed and dominates the water and static energy budgets. The spread of the top-of-atmosphere (TOA) shortwave and longwave radiative fluxes among different ensemble members for the same aerosol loading is surprisingly large, exceeding 25 W m−2 even when averaged over the 6-day period. This variability is caused by random fluctuations in the strength and timing of individual deep convective events. The ensemble approach demonstrates a small weakening of convection averaged over the 6-day period in the polluted simulations compared to pristine. Despite this weakening, the cloud top heights and anvil ice mixing ratios are higher in polluted conditions. This occurs because of the larger concentrations of cloud droplets that freeze, leading directly to higher ice particle concentrations, smaller ice particle sizes, and smaller fall velocities compared to simulations with pristine aerosols. Weaker convection in polluted conditions is a direct result of the changes in anvil ice characteristics and subsequent upper-tropospheric radiative heating and weaker tropospheric destabilization. Such a conclusion offers a different interpretation of recent satellite observations of tropical deep convection in pristine and polluted environments compared to the hypothesis of aerosol-induced convective invigoration. Sensitivity tests using the ensemble approach with modified microphysical parameters or domain configuration (horizontal gridlength, domain size) produce results that are similar to baseline, although there are quantitative differences in estimates of aerosol impacts on TOA radiative fluxes.
Analysis of ΔO2/ΔCO2 ratios for the pollution events observed at Hateruma Island, Japan
Authors: Minejima C. , Kubo M. , Tohjima Y. , Yamagishi H. , Koyama Y. , Maksyutov S. , Kita K. , Mukai H.
Published: May 2011

Abstract. In-situ observations of atmospheric CO2 and O2 concentrations at Hateruma Island (HAT, 24° N, 124° E) often show synoptic scale pollution events when air masses are transported from East Asian source regions. We calculate the regression slopes (-ΔO2/ΔCO2 molar ratios) of the correlation plots between O2 and CO2 for selected pollution events observed between October 2006 and December 2008. The observed -ΔO2/ΔCO2 ratios vary from 1.0 to 1.7. Categorizing the air mass origins for the pollution events by using back trajectory analysis, we find that there is a significant difference in the average -ΔO2/ΔCO2 ratios between events from China (1.14±0.12, n = 25) and Japan/Korea (1.37±0.15, n = 16). These values are comparable to the -O2:CO2 molar exchange ratios, which are estimated from the national fossil fuel inventories from CDIAC. Simulations using a particle dispersion model reveal that the pollution events at HAT are predominantly CO2 emissions from the combustion of fossil fuels in East Asian countries, which is consistent with the above observational results. Although the average value of the model-predicted -ΔO2/ΔCO2 ratios for Japan/Korea origin is underestimated in comparison with the observation, that for China origin agree well with the observation. The sensitivity experiment suggests that the -ΔO2/ΔCO2 ratio at HAT reflects about 90% of the change in the -O2:CO2 exchange ratio for the fossil carbon emissions from China.
Application of infrared remote sensing to constrain in-situ estimates of ice crystal particle size during SPartICus
Authors: Cooper S. J. , Garrett T. J.
Published: May 2011

Abstract. In a prior paper (Cooper and Garrett, 2010), an infrared remote sensing technique was developed that quantifies the effective radius re of ice crystals in cirrus clouds. By accounting for a broad range of expected inversion uncertainties, this retrieval scheme isolates those radiometric signatures that can only occur if the cirrus has nominally "small" values of re below 20 μm. The method is applicable only for specific cloud and atmospheric conditions. However, it can be particularly useful in constraining in-situ estimates of cirrus cloud re obtained from aircraft. Recent studies suggest that airborne measurements may be compromised by the shattering of ice crystals on airborne instrument inlets, so robust, independent confirmation of these measurements is needed. Here, we expand the Cooper and Garrett (2010) retrieval scheme to identify ice clouds that are likely to have "large" values of re greater than 20 μm. Using MODIS observations, we then compare assessments of cirrus cloud re with in-situ measurements obtained during three test cases from the 2010 SpartICus campaign. In general, there is good agreement between retrievals and in-situ measurements for a "small" and "large" crystal case. For a more ambiguously "small" re case, the 2D-S cloud probe indicates values of re that are slightly larger than expected from infrared retrievals, possibly indicating a slight bias in the 2D-S results towards large particles. There is no evidence to support that an FSSP-100 with unmodified inlets produces measurements of re in cirrus that are strongly biased low, as has been claimed.
Climate indicators for Italy: calculation and dissemination
Authors: Desiato F. , Fioravanti G. , Fraschetti P. , Perconti W. , Toreti A.
Published: May 2011

Abstract. In Italy, meteorological data necessary and useful for climate studies are collected, processed and archived by a wide range of national and regional institutions. As a result, the density of the stations, the length and frequency of the observations, the quality control procedures and the database structure vary from one dataset to another. In order to maximize the use of those data for climate knowledge and climate change assessments, a computerized system for the collection, quality control, calculation, regular update and rapid dissemination of climate indicators was developed. The products publicly available through a dedicated web site are described, as well as an example of climate trends estimates over Italy, based on the application of statistical models on climate indicators from quality-checked and homogenised time series.
Quantifying methane emissions from rice paddies in Northeast China by integrating remote sensing mapping with a biogeochemical model
Authors: Zhang Y. , Wang Y. Y. , Su S. L. , Li C. S.
Published: May 2011

Abstract. The Sanjiang Plain located in Northeastern China is one of the major rice producing regions in the country. However, differing from the majority rice regions in Southern China, the Sanjinag Plain possesses a much cooler climate. Could the rice paddies in this domain be an important source of global methane? To answer this question, methane (CH4) emissions from the region were calculated by integrating remote sensing mapping with a process-based biogeochemistry model, Denitrification and Decomposition or DNDC. To quantify regional CH4 emissions from the plain, the model was first tested against a two-year dataset of CH4 fluxes measured at a typical rice field within the domain. A sensitivity test was conducted to find out the most sensitive factors affecting CH4 emissions in the region. Based on the understanding gained from the validation and sensitivity tests, a geographic information system (GIS) database was constructed to hold the spatially differentiated input information to drive DNDC for its regional simulations. The GIS database included a rice map derived from the Landsat TM images acquired in 2006, which provided crucial information about the spatial distribution of the rice fields within the domain of 10.93 million ha. The modeled results showed that the total 1.44 million ha of rice paddies in the plain emitted 0.48–0.58 Tg CH4-C in 2006 with spatially differentiated annual emission rates ranging between 38.6–943.9 kg CH4-C ha−1, which are comparable with that observed in Southern China. The modeled data indicated that the high SOC contents, long crop season and high rice biomass enhanced CH4 production in the cool paddies. The modeled results proved that the northern wetland agroecosystems could make important contributions to global greenhouse gas inventory.
Air-sea CO2 fluxes on the Bering Sea shelf
Authors: Bates N. R. , Mathis J. T. , Jeffries M. A.
Published: May 2011

Abstract. There have been few previous studies of surface seawater CO2 partial pressure (pCO2) variability and air-sea CO2 gas exchange rates for the Bering Sea shelf. In 2008, spring and summertime observations were collected in the Bering Sea shelf as part of the Bering Sea Ecological Study (BEST). Our results indicate that the Bering Sea shelf was close to neutral in terms of CO2 sink-source status in springtime due to relatively small air-sea CO2 gradients (i.e., ΔpCO2 and sea-ice cover. However, by summertime, very low seawater pCO2 values were observed and much of the Bering Sea shelf became strongly undersaturated with respect to atmospheric CO2 concentrations. Thus the Bering Sea shelf transitions seasonally from mostly neutral conditions to a strong oceanic sink for atmospheric CO2 particularly in the "green belt" region of the Bering Sea where there are high rates of phytoplankton primary production (PP)and net community production (NCP). Ocean biological processes dominate the seasonal drawdown of seawater pCO2 for large areas of the Bering Sea shelf, with the effect partly countered by seasonal warming. In small areas of the Bering Sea shelf south of the Pribilof Islands and in the SE Bering Sea, seasonal warming is the dominant influence on seawater pCO2, shifting localized areas of the shelf from minor/neutral CO2 sink status to neutral/minor CO2 source status, in contrast to much of the Bering Sea shelf. Overall, we compute that the Bering Sea shelf CO2 sink in 2008 was 157 ± 35 Tg C yr−1 (Tg = 1012 g C) and thus a strong sink for CO2.
Responses of CH4 uptake to the experimental N and P additions in an old-growth tropical forest, Southern China
Authors: Zhang T. , Zhu W. , Mo J. , Liu L. , Dong S.
Published: May 2011

Abstract. It is well established that tropical forest ecosystems are often limited by phosphorus (P) availability, and elevated atmospheric nitrogen (N) deposition may further enhance such P limitation. However, it is uncertain whether P availability would affect soil fluxes of greenhouse gases, such as methane (CH4) uptake, and how P interacts with N deposition. We examine the effects of N and P additions on soil CH4 uptake in an N saturated old-growth tropical forest in Southern China to test the following hypotheses: (1) P addition would increase CH4 uptake; (2) N addition would decrease CH4 uptake; and (3) P addition would mitigate the inhibitive effect of N addition on soil CH4 uptake. Four treatments were conducted at the following levels from February 2007 to October 2009: control, N-addition (15 g N m−2 yr−1), P-addition (15 g P m−2 yr−1), and NP-addition (15 g N m−2 yr−1 plus 15 g P m−2 yr−1). Static chamber and gas chromatography techniques were used to quantify soil CH4 uptake every month throughout the study period. Average CH4 uptake rate was 31.2 ± 1.1 μg CH4-C m−2 h−1 in the control plots. The mean CH4 uptake rate in the N-addition plots was 23.6 ± 0.9 μg CH4-C m−2 h−1, significantly lower than that in the controls. P-addition however, significantly increased CH4 uptake by 24 % (38.8 ± 1.3 μg CH4-C m−2 h−1), whereas NP-addition (33.6 ± 1.0 μg CH4-C m−2 h−1) was not statistically different from the control. Our results suggest that increased P availability may enhance soil mathanotrophic activity and potentially mitigate the inhibitive effect of N deposition on CH4 uptake in tropical forests. Phosphorus and nitrogen treatments also significantly changed the fluxes of greenhouse gases N2O and CO2, altering the net global warming potential (GWP) of this tropical forest located in a high-N deposition zone of Southern China.
Remote sensing of size structure of phytoplankton communities using optical properties of the Chukchi and Bering Sea shelf region
Authors: Fujiwara A. , Hirawake T. , Suzuki K. , Saitoh S.-I.
Published: May 2011

Abstract. Recent ocean warming and subsequent sea ice decline resulting from climate change could affect the northward shift of the ecosystem structure in the Chukchi Sea and Bering Sea shelf region. The size structure of phytoplankton communities provides an index of trophic levels that is crucial to understanding the mechanisms underlying such ecosystem changes and their implications for the future. This study proposes a new ocean color algorithm for deriving this characteristic by using the region's optical properties. The size derivation model (SDM) estimates the phytoplankton size index FL on the basis of size-fractionated chlorophyll-a (chl-a) using the light absorption coefficient of phytoplankton, aph(λ), and the backscattering coefficient of suspended particles including algae, bbp(λ). FL was defined as the ratio of algal biomass attributed to cells larger than 5 μm to the total. It was expressed by a multiple regression model using the aph(λ) ratio, aph(488)/aph(555), which varies with phytoplankton pigment composition, and the spectral slope of bbp(λ), γ, which is an index of the mean suspended particle size. A validation study demonstrated that the SDM successfully derived an FL value of 69 % within an error range of ± 20 % for unknown data. The spatial distributions of FL for the cold August of 2006 and the warm August of 2007 were compared to examine application of the SDM to satellite remote sensing. The results suggested that phytoplankton size was responsive to changes in sea surface temperature. Further analysis of satellite-derived FL values and other environmental factors can advance our understanding of ecosystem structure changes in the shelf region of the Chukchi and Bering Seas.
Winter and summer blocking variability in the North Atlantic region – evidence from long-term observational and proxy data from southwestern Greenland
Authors: Rimbu N. , Lohmann G.
Published: May 2011

Abstract. We investigate the interannual and decadal variability of the North Atlantic atmospheric blocking frequency and distribution in connection with long-term observational and proxy records from southwestern Greenland. It is shown that warm (cold) conditions in southwestern Greenland during winter are related with high (low) blocking activity in the Greenland-Scandinavian region. The pattern of winter temperature-blocking variability is more complex than the blocking pattern associated to the North Atlantic Oscillation (NAO). We find, furthermore, that a North Atlantic blocking index is significantly correlated with seasonally resolved stable isotope records from Greenland ice cores. Both suggest a possible reconstruction of blocking variability in this region. During summer, high (low) blocking activity in the Euro-Atlantic region is associated with cold (warm) conditions in southwestern Greenland. We conclude that historical temperature records, as well as proxy data from Greenland, can be used to obtain information related to interannual and multidecadal variation of winter and summer blocking during past periods.
MEP solution for a minimal climate model: success and limitation of a variational problem
Authors: Pascale S. , Gregory J. M. , Ambaum M. H. P. , Tailleux R. , Lucarini V.
Published: May 2011

Abstract. Maximum Entropy Production conjecture (MEP) is applied to a minimal four-box model of climate which accounts for both horizontal and vertical material heat fluxes. It is shown that, under condition of fixed insolation, a MEP solution is found with reasonably realistic temperature and heat fluxes, thus generalising results from independent two-box horizontal or vertical models. It is also shown that the meridional and the vertical entropy production terms are independently involved in the maximisation and thus MEP can be applied to each subsystem with fixed boundary conditions. We then extend the four-box model by increasing its number of degrees of freedom, and test its realism by comparing it with a GCM output. An order-of-magnitude evaluation of contributions to the material entropy production (≈50 mW m−2 K−1) due to horizontal and vertical processes within the climate system is carried out by using ad hoc temperature fields. It turns out that approximately 40 mW m−2 K−1 is the entropy production due to vertical heat transport and 5–7 mW m−2 K−1 to horizontal heat transport. A MEP solution is found which is fairly realistic as far as the horizontal large scale organisation of the surface climate is concerned whereas the vertical structure looks to be unrealistic and presents seriously unstable features. Finally a more general problem is investigated in which the longwave transmissivity is varied simultaneously with the temperature. This leads to a MEP solution characterised by a much warmer climate, with very vigorous vertical heat fluxes, in which the atmosphere is opaque to longwave radiation. A critical discussion about how to interpret MEP and how to apply it in a physically correct way concludes the paper.
Observations of the altitude of the volcanic plume during the eruption of Eyjafjallajökull, April–May 2010
Authors: Arason P. , Petersen G. N. , Bjornsson H.
Published: May 2011

Abstract. The eruption of Eyjafjallajökull volcano in 2010 lasted for 39 days, 14 April–23 May. The eruption had two explosive phases separated by a phase with lava formation and reduced explosive activity. The height of the plume was monitored every 5 min with a C-band weather radar located in Keflavík International Airport, 155 km distance from the volcano. Furthermore, several web cameras were mounted with a view of the volcano, and their images saved every five seconds. Time series of the plume-top altitude were constructed from the radar observations and images from a web camera located in the village Hvolsvöllur at 34 km distance from the volcano. This paper presents the independent radar and web camera time series and performs cross validation. The echo top radar series of the altitude of the volcanic plume are publicly available from the Pangaea Publishing Network (http://doi.pangaea.de/10.1594/PANGAEA.760690).
Hydrological impact of rainwater harvesting in the Modder river basin of central South Africa
Authors: Welderufael W. A. , Woyessa Y. E. , Edossa D. C.
Published: May 2011

Abstract. Along the path of water flowing in a river basin are many water-related human interventions that modify the natural systems. Rainwater harvesting is one such intervention that involves harnessing of water in the upstream catchment. Increased water usage at upstream level is an issue of concern for downstream water availability to sustain ecosystem services. The upstream Modder River basin, located in a semi arid region in the central South Africa, is experiencing intermittent meteorological droughts causing water shortages for agriculture, livestock and domestic purpose. To address this problem a technique was developed for small scale farmers with the objective of harnessing rainwater for crop production. However, the hydrological impact of a wider adoption of this technique by farmers has not been well quantified. In this regard, the SWAT hydrological model was used to simulate the hydrological impact of such practices. The scenarios studied were: (1) Baseline scenario, based on the actual land use of 2000, which is dominated by pasture (combination of natural and some improved grass lands) (PAST); (2) Partial conversion of Land use 2000 (PAST) to conventional agriculture (Agri-CON); and (3) Partial conversion of Land use 2000 (PAST) to in-field rainwater harvesting which was aimed at improving the precipitation use efficiency (Agri-IRWH). SWAT was calibrated using observed daily mean stream flow data of a sub-catchment (419 km2) in the study area. SWAT performed well in simulating the stream flow giving Nash and Sutcliffe (1970) efficiency index of 0.57 for the monthly stream flow calibration. The simulated water balance results showed that the highest peak mean monthly direct flow was obtained on Agri-CON land use (18 mm), followed by PAST (12 mm) and Agri-IRWH land use (9 mm). These were 19 %, 13 % and 11 % of the mean annual rainfall, respectively. The Agri-IRWH scenario reduced direct flow by 38 % compared to Agri-CON. On the other hand it was found that the Agri-IRWH contributed to more groundwater flow (40 mm) compared to PAST (32 mm) and Agri-CON (19 mm) scenarios. These results are in line with the intended purpose of Agri-IRWH. Although there was a visible impact of the rainwater harvesting technique on the water yield when considered on a monthly time frame, the overall result suggests that the water yield of one of the upper Modder River Basin quaternary catchment may not be adversely affected by the Agri-IRWH land use scenario despite its surface runoff abstraction design.
Dependence of radon levels in Postojna Cave on outside air temperature
Authors: Gregorič A. , Zidanšek A. , Vaupotič J.
Published: May 2011

Abstract. Postojna Cave is the largest of 21 show caves in Slovenia. The radon concentration there was measured continuously in the Great Mountain hall from July 2005 to October 2009 and ranged from about 200 Bq m−3 in winter to about 3 kBq m−3 in summer. The observed seasonal pattern of radon concentration is governed by air movement due to the difference in external and internal air densities, controlled mainly by air temperature. The cave behaves as a large chimney and in the cold period, the warmer cave air is released vertically through cracks and fissures to the colder outside atmosphere, enabling the inflow of fresh air with low radon levels. In summer the ventilation is minimal or reversed and the air flows from the higher to the lower openings of the cave. Our calculations have shown that the effect of the difference between outside and cave air temperatures on radon concentration is delayed for four days, presumably because of the distance of the measurement point from the lower entrance (ca. 2 km). A model developed for predicting radon concentration on the basis of outside air temperature has been checked and found to be successful.
Derivation and analysis of a high-resolution estimate of global permafrost zonation
Authors: Gruber S.
Published: May 2011

Abstract. Permafrost underlies much of Earths' surface and interacts with climate, eco-systems and human systems. It is a complex phenomenon controlled by climate and (sub-) surface properties and reacts to change with variable delay. Heterogeneity and sparse data challenge the modeling of its spatial distribution. Currently, there is no data set to adequately inform global studies of permafrost. The available data set for the Northern Hemisphere is frequently used for model evaluation, but its quality and consistency are difficult to assess. A global model of permafrost extent and dataset of permafrost zonation are presented and discussed, extending earlier studies by including the Southern Hemisphere, by consistent data and methods, and most importantly, by attention to uncertainty and scaling. Established relationships between air temperature and the occurrence of permafrost are re-formulated into a model that is parametrized using published estimates. It is run with a high-resolution (<1 km) global elevation data and air temperatures based on the NCAR-NCEP reanalysis and CRU TS 2.0. The resulting data provides more spatial detail and a consistent extrapolation to remote regions, while aggregated values resemble previous studies. The estimated uncertainties affect regional patterns and aggregate number, but provide interesting insight. The permafrost area, i.e. the actual surface area underlain by permafrost, north of 60° S is estimated to be 13–18 × 106 km2 or 9–14 % of the exposed land surface. The global permafrost area including Antarctic and sub-sea permafrost is estimated to be 16–21 × 106 km2. The global permafrost region, i.e. the exposed land surface below which some permafrost can be expected, is estimated to be 22 ± 3 × 106 km2. A large proportion of this exhibits considerable topography and spatially-discontinuous permafrost, underscoring the importance of attention to scaling issues and heterogeneity in large-area models.
Short-Wavelength Automated Perimetry in Type I Diabetic Patients without Retinal Involvement: A Test Modification to Decrease Test Duration
Authors: Abrishami Majid , Daneshvar Ramin , Yaghubi Zakiyeh
Published: May 2011

Purpose

To compare short-wavelength automated perimetry (SWAP) between type I diabetic patients without clinical posterior segment involvement and nondiabetic control subjects.

Methods

Forty eyes of diabetic patients without obvious posterior segment involvement and 34 eyes of the nondiabetic control group were included in the study. A complete set of ophthalmic examination was followed by SWAP perimetry in all subjects. Short-wavelength automated perimetry results were compared between the 2 groups. In addition, as a modification to SWAP, the data of the central 16 points were omitted and the resulting data of the remaining 60 points (corrected data) were compared between the 2 groups.

Results

Mean deviation in the diabetic patients (group I) was −6.51 dB and in the control group (group II) −3.0 dB; the difference was statistically significant. Mean corrected sensitivity in group I was 19.79 dB and in group II 22.37 dB. Mean corrected total deviation in group I was −6.67 and in group II −3.22. Both differences were highly statistically significant. The mean corrected pattern deviation in group I was −3.29 and in group II −3.04, which was not a statistically significant difference.

Conclusions

Short-wave automated perimetry abnormalities precede diabetic retinopathy in type I diabetic patients and omission of central 16 points does not compromise test results in this situation.
Retinal Detachment in Morning Glory Syndrome with Large Hole in the Excavated Disc
Authors: Jo Young-Joon , Iwase Takeshi , Oveson Brian C. , Tanaka Nobushige
Published: May 2011

Purpose.

To present a case of morning glory syndrome (MGS) associated with retinal detachment and to discuss the pathogenesis of retinal tear.

Methods.

A 2-year-old-girl had a MGS with a large hole in the excavated disc and retinal detachment. The visual acuity was 4/200 in the affected eye. The excavated disc and retinal detachment were con-firmed by echogram. Optical coherence tomography demonstrated that the large hole was connected to the subretinal space. The excavated lesion did not show contractions. The detachment area and the volume of subretinal fluid rose and fell between initial examinations, but ultimately increased. After 2 years of observations, surgery was performed as the retinal detachment had enlarged to include the macula.

Results.

Surgery included triamcinolone-assisted vitrectomy, subretinal fluid drainage through the large hole in the excavated disc, retinal photocoagulation along the excavated disc, and long-acting gas tamponade. One month later, the retina was redetached due to incomplete closure of the hole. A second operation was performed using silicone oil tamponade. Ultimately, the retina was reattached after silicone oil-fluid exchange surgery.

Conclusions.

One possible reason for a large hole in an excavated disc is origination of the tear from a congenital defect, such as an optic pit. The retinal detachment in patients with MGS with a large hole in the disc can be treated with triamcinolone-assisted pars plana vitrectomy and retinal photocoagulation along the excavated disc. This case has shown that one critical component for a high success rate is the tamponade agent used in the vitreous.
What Is Really a Nonobstructive Hypertrophic Cardiomyopathy? The Importance of Orthostatic Factor in Exercise Echocardiography
Authors: Cotrim Carlos , Almeida Ana Rita , Lopes Luís , Fazendas Paula , João Isabel , Pereira Hélder
Published: May 2011

The authors report the case of a 23-year-old girl with nonobstructive hypertrophic cardiomyopathy evaluated by resting echocardiography. The patient complained of syncope after playing basketball. The patient was submitted to treadmill exercise echocardiogram, and she exercised for 9 minutes in standard Bruce protocol. The left ventricular outflow gradient did not occur at peak workload; however she developed intraventricular gradient greater than 100 mmHg after exercise in orthostatic position. There was fall in arterial pressure, and the patient was then put in supine position. The authors suggest the possible role of exercise stress echo in symptomatic patients with no significant gradient at baseline, as well as maintenance in orthostatic position after exercise, as an important stress factor. This can disclose the occurrence of left ventricular outflow tract obstruction that should not be detected in other way and has potential relevance in the patient's symptoms understanding.
Novel Strategy with Gemcitabine for Advanced Pancreatic Cancer
Authors: Komori Shuji , Osada Shinji , Yoshida Kazuhiro
Published: May 2011

5-fluorouracil (5-FU) is widely used in chemotherapy for gastric and colorectal cancer, but gemcitabine (GEM), and not 5-FU, is approved as a standard drug for use in pancreatic cancer. Interindividual variation in the enzyme activity of the GEM metabolic pathway can affect the extent of GEM metabolism and the efficacy of GEM chemotherapy. Human equilibrative nucleoside transporter 1 (hENT1) is recognized as a major transporter of GEM into cells. In addition, a factor that activates hENT1 is the inhibition of thymidylate synthase (TS), one of the 5-FU metabolic enzymes; TS inhibition mediates depleting intracellular nucleotide pools, resulting in the activation of the salvage pathway mediated through hENT1. In this paper, the role of 5-FU in GEM-based chemotherapy for pancreatic cancer is discussed with special emphasis on enzymes involved in the 5-FU and GEM metabolic pathways and in the correlation between GEM responsiveness and the expression of 5-FU and GEM metabolic enzymes.
Biomimetic Pathways for Nanostructured Poly(KAMPS)/aragonite Composites that Mimic Seashell Nacre
Authors: Pai Ranjith Krishna , Zhang Lihua , Nykpanchuk Dmytro , Cotlet Mircea , Korach Chad S.
Published: May 2011

Complex microstructures of biominerals such as seashell nacre, bone, and teeth are awe‐inspiring. Nature has devised schemes to combine hard inorganic platelets of aragonite (CaCO3) and an organic matrix that produce tough biocomposites. The ability of the organic‐inorganic components to “slide” internally leads to the toughening of the materials, though a recreation of this system at the nanoscale has yet to be shown. Here, we implement a poly(KAMPS)‐based assembly, which is carried out entirely from dilute aqueous solutions of the materials to create a “brick and mortar”‐type aragonite structure that mimics the platelet sliding and exhibits toughening. The negatively charged poly(KAMPS) chains are attracted to the positively charged divalent cations, by which addition of NaHCO3 to an aqueous mixture of Ca2+‐poly(KAMPS), results in the growth of aragonite nanorods with a width of 120 nm. The reversible nature of the physical gel formation of poly(KAMPS) in solution results in adhesion of the nanorods into a microscale structure. The new nacre‐like carbonate composite, has a modulus (44 GPa) and hardness (2.8 GPa) on a similar order as to that of nacre and other bio‐composites, exhibits limited creep, and demonstrates a mechanism with nanoscale deformation.
An Efficient Copper‐Catalyzed Homocoupling of Terminal Alkynes to Give Symmetrical 1,4‐Disubstituted 1,3‐Diynes
Authors: Zhang Songlin , Liu Xiaoyan , Wang Tongqiang
Published: May 2011

A facile and efficient pathway for the copper iodide and ligand N,N,N′,N′‐tetramethylethane‐1,2‐diamine promoted homocoupling reaction of terminal alkynes under ambient temperature and air as an oxidant was reported. The alkynes, including aromatic alkynes and aliphatic alkynes, could afford the symmetrical 1,4‐disubstituted 1,3‐diynes in good to excellent yields.
In‐vivo‐Festphasen‐Mikroextraktion in der Metabolomik: Möglichkeiten zur direkten Erforschung biologischer Systeme
Authors: Vuckovic Dajana , Risticevic Sanja , Pawliszyn Janusz
Published: May 2011

Die Probenpräparation hat einen großen Einfluss auf die Qualität von Metabolomikstudien. Der Einsatz der Festphasen‐Mikroextraktion (SPME), besonders in Form ihrer In‐vivo‐Variante, ermöglicht die Erfassung eines repräsentativeren Metaboloms und bietet die Möglichkeit, seltene, kurzlebige Metaboliten und/oder instabile Substanzen zu detektieren, die von traditionellen Methoden nicht leicht erfasst werden. Diese Technik eignet sich ideal sowohl für zeitliche, räumliche und longitudinale Studien des gleichen lebenden Systems als auch für Multikompartimentstudien desselben Organismus. SPME ist für die Untersuchungen von biologischen Systemen geeignet, die in ihrer Komplexität zwischen Zellen und Säugetiergewebe liegen. Dieser Kurzaufsatz präsentiert ausgewählte Beispiele, um diese neue Technik in den Kontext der konventionellen Probenpräparationsmethoden für die Metabolomik einzuordnen.
Thermal destruction of carbon black network structure in natural rubber vulcanizate
Authors: Kato Atsushi , Suda Toshiya , Ikeda Yuko , Kohjiya Shinzo
Published: May 2011

To investigate thermal destruction and rearrangement of the carbon black (CB) network consisting of CB aggregates in rubbery matrix, the proper heat‐treatment temperature without thermal decomposition of rubber matrix were examined by using differential scanning calorimetry, dynamic mechanical measurements, and thermal expansion measurements. 383 K was chosen as the heat‐treatment temperature under vacuum. The volume resistivity (ρv) of 50 phr CB‐filled natural rubber vulcanizate (CB‐50) increased rapidly up to a heat‐treatment time of 24 h and it decreased by further heat‐treatment time, whereas the ρv of CB‐80 remained almost constant without depending on heating time. Three‐dimensional electron microscope (3D‐TEM) observations revealed that after the heat‐treatment for 75 h, the average lengths of the crosslinked and the branched chains and the crosslinked points density (Dcross) of the CB network decreased, whereas the branched points density (Dbranch) increased with decrease of Dcross. After the heat‐treatment, their fractions (Fcross′s) of crosslinked chains decreased, whereas their fractions (Fbranch′s) of the branched ones increased. Especially, Fbranch of CB‐50 became larger than that of CB‐80, while the decrease of Fcross of CB‐50 was almost the same as that of CB‐80 by the heat‐treatment. And, Fcross and Fbranch of the heat‐treated CB‐50 were the same compositions (Fcross and Fbranch = ca. 0.7 and ca. 0.3, respectively) as those of the heat‐treated CB‐80. It is suggested that the CB network of CB‐80 is more thermal stable than that of CB‐50. These results directly indicate that CB network is broken and is rearranged by a heat‐treatment. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation and properties of nylon 6/carboxylic silica nanocomposites via in situ polymerization
Authors: Zhang Lala , Xiong Yuzi , Ou Encai , Chen Zhongming , Xiong Yuanqin , Xu Weijian
Published: May 2011

Nylon 6/carboxylic acid‐functionalized silica nanoparticles (SiO2‐COOH) nanocomposites were prepared by in situ polymerization of caprolactam in the presence of SiO2‐COOH. The aim of this work was to study the effect of carboxylic silica on the properties of the nylon 6 through the interfacial interactions between the SiO2‐COOH nanoparticles and the nylon 6 matrix. For comparison, pure nylon 6, nylon 6/SiO2 (unmodified) and nylon 6/amino‐functionalized SiO2 (SiO2‐NH2) were also prepared via the same method. Fourier transform infrared spectrometer (FTIR) spectroscopy was used to evaluate the structure of SiO2‐COOH and nylon 6/SiO2‐COOH. The results from thermal gravimetric analysis (TGA) indicated that decomposition temperatures of nylon 6/SiO2‐COOH nanocomposites at the 5 wt % of the total weight loss were higher than the pure nylon 6. Differential scanning calorimeter (DSC) studies showed that the melting point (Tm) and degree of crystallinity (Xc) of nylon 6/SiO2‐COOH were lower than the pure nylon 6. Mechanical properties results of the nanocomposites showed that nylon 6 with incorporation of SiO2‐COOH had better mechanical properties than that of pure nylon 6, nylon 6/SiO2, and nylon 6/SiO2‐NH2. The morphology of SiO2, SiO2‐NH2, and SiO2‐COOH nanoparticles in nylon 6 matrix was observed using SEM measurements. The results revealed that the dispersion of SiO2‐COOH nanoparticles in nylon 6 matrix was better than SiO2 and SiO2‐NH2 nanoparticles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Timolol‐imprinted soft contact lenses: Influence of the template: Functional monomer ratio and the hydrogel thickness
Authors: Yañez Fernando , Chauhan Anuj , Concheiro Angel , Alvarez‐Lorenzo Carmen
Published: May 2011

Isothermal titration calorimetry (ITC) was used to identify the optimal timolol:functional monomer ratio for preparing soft contact lenses (SCLs) able to sustain drug release. ITC profiles revealed that each timolol molecule required six to eight acrylic acid (AAc) monomers to saturate the binding and that these ratios could be the most suitable for creating imprinted cavities. Various poly(hydroxyethyl methacrylate‐co‐AAc) hydrogels 0.2 and 0.9 mm thick were prepared with timolol:AAc molar ratios ranging from 1 : 6 to 1 : 32 and also in the absence of timolol. The hydrogels were reloaded with timolol by immersion in 0.04, 0.06, 0.08, and 0.10 mM drug solutions. Both imprinted and nonimprinted hydrogels showed a high affinity for the drug because of the presence of AAc. Nevertheless, the 1 : 6 and 1 : 8 imprinted hydrogels loaded less timolol but sustained the release better than the other hydrogels. These differences were explained in terms of the different arrangement of the functional monomers along the network. The imprinting effect was more noticeable in the case of the thinnest hydrogels, where the contribution of the diffusion path to the release rate was smaller. The results obtained prove the interest of ITC for the rational design of drug‐imprinted networks to be used as medicated SCLs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Study and characterization of composites materials based on polypropylene loaded with olive husk flour
Authors: Amar Boukerrou , Salem Krim , Hocine Djidjelli , Chadia Ihamouchen , Juan Martinez J.
Published: May 2011

In Algeria, a significant quantities of olive husk are rejected to nature causing by the way major nuisances to environment, to give us a reason for which our work is focused on the valorization of this waste by its incorporation in a polypropylene matrix. The hydrophilic nature of natural fibers affects negatively its adhesion to hydrophobic polymeric matrix. To improve interfacial adhesion, two modes of chemical treatments were done using vinyltriacetoxysilane (VTAS) and maleic‐anhydride‐polypropylene (PPMA) compatibilisant agent. Several formulations of PP filled with 10 and 20% by mass of olive husk flour treated (OHFT) and untreated (OHFUT) were prepared. The chemical modification of olive husk flour was studied by Fourier transform infrared (FTIR) spectroscopy. The tensile properties, the water‐absorption behavior, the thermal degradation properties, and crystallinity of the composites were investigated. It was found that, the incorporation of the treated and untreated OHF improves the thermal stability of the composites. However, the use of the compatibilizer agent PPMA leads to a better thermal stability compared with the treatment of the OHF by the VTAS and the OHFUT. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Investigation of nonisothermal crystallization of hydroxyapatite/ethylene‐vinyl acetate (HA/EVA) composite
Authors: Wang Yanying , Zhang Li , Zhou Song , Huang Di , Morsi Yos , Gao Shibo , Gong Mei , Li Yubao
Published: May 2011

Hydroxyapatite/ethylene‐vinyl acetate (HA/EVA) composites were prepared by injection molding and characterized by X‐ray diffraction (XRD) and attenuated total multiple reflection infrared (ATR‐IR) spectroscopy. The nonisothermal crystallization behavior of HA/EVA composites at different cooling rates and with different HA content were examined by differential scanning calorimetry (DSC). The results exhibit the occurrence of interaction between HA and EVA, and the HA particles in EVA matrix act as effective nucleation agent. The addition of HA influences the mechanism of nucleation and growth of EVA crystallites. HA particles, as nucleus, are efficient to promote EVA crystallization at early stage but prevent EVA crystal growth in the late stage. The EVA crystallization in the composite is mainly through heterogeneous nucleation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Effect of macromer synthesis time on the properties of the resulting poly(β‐amino ester) degradable hydrogel
Authors: Hawkins Ashley M. , Puleo David A. , Hilt J. Zach
Published: May 2011

Poly(β‐amino ester) biodegradable hydrogels are common in biomedical applications because of their tunable properties and similarities to natural soft tissue. Previous work has shown property adjustments through the choice of monomers, the ratio between monomers and the addition of a crosslinking component. Here, we show that the reaction time for the creation of the macromer can affect the resulting hydrogel properties, and thus provides another method of tuning properties. Macromer was created through the reaction of isobutylamine with poly(ethylene glycol) diacrylate (n = 400). The reaction progress was analyzed using IR and GPC analysis. Hydrogels were created through UV photopolymerization from macromers synthesized for 24, 36, and 48 h. The degradation, compressive moduli, and swelling were measured in an aqueous solution. All showed significant differences between hydrogels of different macromer synthesis times. These differences likely stem from the incomplete macromer synthesis reaction and resulting PEG‐rich regions in hydrogels from shorter synthesis times. These regions will not readily degrade, but do increase the mechanical properties and extent of swelling. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Storage stability and solubility of poly(urea‐formaldehyde) microcapsules containing A‐olefin drag reducing polymer
Authors: Li Bing , Dong Guilin , Zhang Changqiao
Published: May 2011

Microcapsules containing α‐olefin drag reducing polymer were prepared by in situ and interfacial polymerization with urea, formaldehyde, and styrene as shell materials, respectively. IR spectrums of prepared shells indicated the formations of poly(urea‐formaldehyde) and polystyrene in the microencapsulating process. The morphologies of uncoated particles and microcapsules were observed by scanning electron microscopy (SEM) which proved that the α‐olefin drag reducing polymer particles were effectively coated. For the purpose of determining the stability of microcapsules in transportation and storage, the static pressure experiment was carried out and lasted for 6 months. In this process, microcapsules with polystyrene as shell material stuck together after 3 months; however, those with poly(urea‐formaldehyde) kept the state of particles. The thermal characteristics of uncoated particles (core), poly(urea‐formaldehyde) (shell), and microcapsules with that as shell material were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) which proved that thermal stable temperature of microcapsules containing α‐olefin drag reducing polymer with poly(urea‐formaldehyde) as shell material was below 225°C, and the mean heat absorbed by microcapsules in the temperature increasing process was 1.5–2.0 W/g higher than that by cores. The evaluation of drag reducing rate of microcapsules showed that the microencapsulating process had no influence on the drag reduction of α‐olefin drag reducing polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011