bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface and Catalytic Properties of γ-Irradiated Cr2O3/Al2O3 Solids
Authors: El-Shobaky G.A. , Ghozza A.M. , Mohamed G.M. 
Published: July 2017

Two samples of Cr2O3/Al2O3 were prepared by mixing a known mass of finely powdered Al(OH)3 with a calculated amount of CrO3 solid followed by drying at 120°C and calcination at 400°C. The amounts of chromium oxide employed were 5.66 and 20 mol% Cr2O3, respectively. The calcined solid specimens were then treated with different doses of γ-rays (20–160 Mrad). The surface and catalytic properties of the different irradiated solids were investigated using nitrogen adsorption at −196°C and the catalysis of CO oxidation by O2 at 300–400°C. The results revealed that γ-rays brought about a slight decrease in the BET surface area, SBET (15%), and in the total pore volume, Vp (20%), of the adsorbent containing 5.66 mol% Cr2O3. The same treatment increased the total pore volume, Vp (36%), and the mean pore radius, r̄ (43%), of the other adsorbent sample without changing its BET surface area. The catalytic activities of both catalyst samples were found to increase as a function of dose, reaching a maximum value at 80–160 Mrad and 40 Mrad for the solids containing 5.66 and 20 mol% Cr2O3, respectively. The maximum increase in the catalytic activity measured at 300°C was 59% and 100% for the first and second catalyst samples, respectively. The induced effect of γ-irradiation on the catalytic activity was an increase in the concentration of catalytically active sites taking part in chemisorption and in the catalysis of CO oxidation by O2 without changing their energetic nature. This was achieved by a progressive removal of surface hydroxy groups during the irradiation process.
The Effect of Sulphur Dioxide on the Adsorption Properties of Activated Carbon towards Chloropicrin
Authors: Anstice P.J.C. , Alder J.F. 
Published: July 2017

Sulphur dioxide is believed to be adsorbed on activated carbons in both physically and chemically bound states. Sulphuric acid and a variety of oxygenated and hydrated sulphur oxide species are believed to be present on humidified carbons exposed to sulphur dioxide. Samples of ASC/T impregnated carbons were exposed to sulphur dioxide mixtures in humid air at 80% RG and 22°C. The sulphur dioxide-loaded carbons were then exposed to chloropicrin challenge at 5 mg/dm3 in air at 80% RH and 22°C and the chloropicrin breakthrough times measured. A relationship was found between the extra mass gain of the carbons (due to oxygen and water) with increasing sulphur dioxide loading, as predicted by other workers. The effect of sulphur dioxide loading on the chloropicrin breakthrough times was a gradual reduction to about one-third the time for unexposed carbon, with an adsorbed mass of sulphur dioxide equal to ca. 10% of the carbon mass in a 20 mm bed-depth filter.
Surface and Catalytic Properties of NiO and Fe2O3 Solids
Authors: El-Aal A. Abd. , Ghozza A.M. , El-Shobaky G.A. 
Published: July 2017

The surface characteristics, viz., the specific surface area SBET, the total pore volume Vp and the mean pore radius r̄, of NiO and Fe2O3 were determined from N2 adsorption isotherms conducted at −196°C for the different adsorbents preheated in air at temperatures in the range 300–800°C. The catalytic activities exhibited in CO oxidation by O2 on the various solids were investigated at temperatures varying between 150°C and 400°C. The effect of heating the NiO and Fe2O3 solids in CO and O2 atmospheres at 175–275°C on their catalytic activities was also studied. The results showed that increasing the calcination temperature in the range 300–800°C resulted in a progressive decrease in the SBET value of NiO and Fe2O3. The computed values of the apparent activation energy for the sintering of the oxides were 71 and 92 kJ/mol, respectively. The sintering of NiO and Fe2O3 took place mainly via a particle adhesion mechanism. The catalytic activity of NiO decreased progressively on increasing its calcination temperature from 300°C to 800°C, due to a decrease in its SBET value and the progressive removal of excess O2 which was present as non-stoichiometric NiO. This treatment also decreased the catalytic activity of Fe2O3. The decrease was, however, more pronounced when the temperature increased from 300°C to 400°C which was a result of the crystallization of the ferric oxide into the α-Fe2O3 phase. An increase in the calcination temperature for both oxides from 300°C to 800°C did not modify the mechanism of oxidation of CO by O2 over the various solids but rather changed the concentration of catalytically active sites. Heating NiO and Fe2O3 in CO and O2 atmospheres at 175–275°C modified their catalytic activities, with Fe2O3 being influenced to a greater extent than NiO.
Studies of the Adsorption of SO2, H2 and O2 on a Cr2O3 Surface by an Electrical Conductivity Technique
Authors: Khader Mahmoud M. , Saleh Mahmoud M. , Mohammad Ahmad M. 
Published: July 2017

Electrical conductivity measurements have been used to detect extremely small changes in the oxygen content of oxide semiconductors in contact with reducing or oxidizing gases. In continuation of previous studies, the oxygen loss of chromium oxide in H2 and SO2 flows, as well as the oxygen gain in an oxygen atmosphere, were studied. In SO2, the conductivity dropped instantaneously to minimum values due to its adsorption on adsorbed oxygen sites. The treatment of Cr2O3 in SO2 led to the elimination of chemisorbed oxygen and the covering of the surface with polymeric SO2. In contrast, in an H2 flow, the conductivity of Cr2O3 initially exhibited an induction period during which the value was constant. At the end of the induction period, the conductivity increased rapidly to a maximum value and then dropped sharply to a minimum. The induction period may be regarded as the time necessary to create an oxygen vacancy, the activation energy for such a process being 21.1 kJ/mol. A hydrogen molecule is then adsorbed on to the oxygen vacancy possibly as a hydride ion, and leading to the initial increase in the conductivity. The hydride ion then migrated to a chemisorbed oxygen site, where it formed a surface hydroxy group and caused a consequent decrease in the electrical conductivity. The surface then dehydroxylated due to the interaction of surface hydroxy groups with gaseous hydrogen, leaving coordinatively unsaturated surface chromium ions behind. In an oxygen flow at 400°C and above, either SO2 or H2 treatments led to a sharp increase in conductivity due to oxygen adsorption. In contrast, at temperatures less than 350°C, oxygen adsorption was retarded after an SO2 flow, possibly due to the strong adsorption of a polymeric film of SO2. Correspondingly, after H2 treatments, oxygen was adsorbed instantaneously at temperatures as low as 200°C, presumably because of the weak sorption of H2 on the surface chromium ions. After discontinuing the hydrogen flow, further oxygenation caused a subsequent decrease in the conductivity, possibly due to surface hydroxylation. Hydrogen trapped in the bulk of the Cr2O3 could spill over the surface and cause such a hydroxylation process.
Surface Properties and Catalytic Activity of Ni/Al2O3–AlPO4 Catalysts
Authors: El-Hakam S.A. , El-Khouly A.A. , Khder A.S. 
Published: July 2017

A series of Ni/Al2O3–AlPO4 catalysts has been prepared, thereby allowing the effect of nickel content and calcination temperature on the structural and catalytic activity of such solids to be investigated. The textural parameters of all the prepared samples were determined from nitrogen adsorption studies conducted at −196°C, while thermal analysis methods (DTA, TGA and DrTGA) and X-ray diffraction techniques were used to elucidate their structures. Their surface acidities were measured by the amine titration method, while the conversion of isopropanol on the prepared catalysts was investigated using a pulse microcatalytic reactor. Significant changes in the structure, texture, surface acidity and catalytic activity of the prepared solids were observed as a result of varying their nickel content and calcination temperatures. Thus, XRD studies demonstrated the presence of nickel metal, nickel aluminate spinel, γ-alumina and tridymite phases while both the surface areas and the porous structures were found to depend on the metal content and calcination temperatures. The catalytic selectivity for isopropanol conversion was found to depend on the number of surface acid sites present.
Notes on the Modeling of Preform Compaction: I -Micromechanics at the Fiber Bundle Level
Authors: Simacek Pavel , Karbhari Vistasp M. 
Published: July 2017

Resin Transfer Molding (RTM) can be described as a two step process: fiber preforming followed by resin infusion and cure. In the first stage, the fabric form making up the preform element is placed in the tool and is compacted due to the pressure from tool closure. During this process, the microstructure, and the resultant properties, change considerably since compaction flattents the weft yarn bundles from the initial configuration into flat ellipsoids of higher aspect ratio, while simultaneously reorienting and flattening the bundles in the warp direction. The movement also results in nesting and inter-layer packing yielding a higher localized fiber volume fraction. An aspect unique to RTM and other allied resin infusion processes is the compaction of fibers in the dry (unlubricated) form. This gives rise to rather unique behavior at the fiber tow level, which in turn affects the compaction of the fabric form itself. It is thus essential that any model constructed for the specific purpose of investigating the compaction stage in RTM (or allied processes that involve the compaction of a dry preform) be able to reflect that the tow is dry, usually untwisted and when compressed in bulk it has frictional resistance to the shear mode of deformation. In this paper we focus on the possible tow behavior, rather than the behavior of the fabric structure, with the motivation being that of developing a simple, yet comprehensive model at that level which can then be intregrated into a fabric level model at a later stage.
Examining Alternatives for Reduction of Air Pollution
Authors: Ben-Aderet Nissim , Soloveitchik David 
Published: July 2017

The present paper attempts to present a medium and long-term solution for the choice of technology. The short-term solution, the use of low-sulphur fuel oil, has been in effect for about three years in Israel and its quantity has gradually increased. The time has now come to consider the long-term solutions. The results obtained indicate the existence of several alternatives that are more effective than the system in use today. The methodology presented is based on the optimization computer package CAPEX ** .
Reproductive toxicity and tissue concentrations of 3,3',4,4'-tetrachlorobiphenyl (PCB 77) in male adult rats
Authors: Faqi A S , Dalsenter P R , Mathar W , Heinrich-Hirsch B , Chahoud I 
Published: July 2017

1 The aim of this study was to ascertain the reproductive effects of PCB 77 on adult male rats and to determine its concentration in the liver and testis. Adult male rats (n=15/group) were treated subcutaneously with a singledoseof18 mg/kgbw(PC18)orwith60 mg/kg bw (PC60). The substance was dissolved in a 10 ml volume of peanut oil/kg. Control rats received the same volume of the vehicle. The reproductive effects as well as the concentration of PCB 77 in the liver and testis were investigated 1, 4 and 8 weeks after treatment. 2 In both groups, the daily sperm production (DSP; 6106) remained permanently reduced in the PC18 as well as in the PC60 groups throughout the entire investigation period (DSP week 8: control: 31+7; PC18: 22+5; PC60: 20+7). The sperm number (6106) per cauda epididymis was affected only at the 1st and 4th week after treatment (control week 1: 211+67; PC18 week 1: 135+62; PC60 week 1: 142+49). Moreover, a significant increase in the percentage of abnormal sperm was observed 4 weeks following treatment in the PC18 and PC60 groups and 8 weeks after treatment in the PC60 group. Abnormal tails were the most frequent changes observed. 3 The relative testicular and prostata weights (g) were slightly increased in the PC60 group at the 1st and 4th week following treatment (testis weight: control/I: 0.46+0.02; PC60/I: 0.51+0.03). 4 The serum testosterone concentrations and effects on testis morphology were not reported. 5 The maximum concentration of PCB 77 was detected in the liver and testis 1 week after treatment. The concentration declined 4 weeks after treatment in both organs, but still a significant amount of PCB 77 was detectable in the liver as well as in the testis 8 weeks after treatment. 6 The results demonstrate that PCB 77 affects sperm variables when applied to adult rats and that the elimination of PCB 77 in the testis parallels that of the liver.
Differential recovery of acetylcholinesterase in guinea pig muscle and brain regions after soman treatment
Authors: Lintern Maxine C , Wetherell Janet R , Smith Margaret E 
Published: July 2017

1 In brain areas of untreated guinea-pigs the highest activity of acetylcholinesterase was seen in the striatum and cerebellum, followed by the midbrain, medulla-pons and cortex, and the lowest in the hippocampus. The activity in diaphragm was sevenfold lower than in the hippocampus. 2 At 1 h after soman (27 mg/kg) administration the activity of the enzyme was dramatically reduced in all tissues studied. In muscle the three major molecular forms (A12, G4 and G1) showed a similar degree of inhibition and a similar rate of recovery and the activity had returned to normal by 7 days. 3 In the brain soman inhibited the G4 form more than the G1 form. The hippocampus, cortex and midbrain showed the greatest reductions in enzyme activity. At 7 days the activity in the cortex, medulla pons and striatum had recovered but in the hippocampus, midbrain and cerebellum it was still inhibited. 4 Thus the effects of soman administration varied in severity and time course in the different tissues studied. However the enzyme activity was still reduced in all tissues at 24 h when the overt signs of poisoning had disappeared.
Hepatic injury and disturbed amino acid metabolism in mice following prolonged exposure to organophosphorus pesticides
Authors: Gomes J , Dawodu A H , Lloyd O , Revitt D M , Anilal S V 
Published: July 2017

1 Chronic occupational exposure to organophosphorus and carbamate-type pesticides significantly inhibits acetylcholinesterase activity and causes morbidity. This study on mice was designed to evaluate their amino profile and to identify signs of hepatic dysfunction following their chronic exposure to mixtures of organophosphorus pesticides. 2 Laboratory mice were exposed to a formulated mixture of the six organophosphorus pesticides (Dimethoate, Chlorpyrifos, Profenofos, Pirimiphos methyl, Triazophos and Dimethoate) most commonly used in agriculture in this region of the Middle East. Doses (10% of LD50 of the mixture) were given once a week by gavage in corn oil for 7 weeks; the control group was given only corn oil. At the end of the exposure period, mice were culled and blood samples were collected to determine erythrocyte acetylcholinesterase activity, biochemical markers of liver function and concentrations of serum amino acids. 3 Erythrocyte acetylcholinesterase activity and total serum proteins decreased significantly in the exposed group. Serum concentrations of alanine aminotransferase and aspartate aminotransferase, alanine, glutamic acid, glycine, isoleucine, leucine, methionine, ornithine, proline, serine, threonine and valine were significantly increased in the exposed mice, while serum levels of cystine were decreased significantly. There were also non-significant increases in serum alkaline phosphatase, gama-glutamyl transpeptidase and some of the other amino acids. 4 Chronic exposure to mixtures of organophosphorus pesticides is associated with decreased acetylcholinesterase activity, hepatic dysfunction and disturbance of amino acids profile. Biochemical indices of hepatocellular injury and disturbed amino acid metabolism may be of value as markers of chronic exposure to such pesticides.
A comparative study of the repeat dose toxicity of grepafloxacin and a number of other fluoroquinolones in rats
Authors: Takizawa T , Hasimoto K , Itoh N , Yamashita S , Owen K 
Published: July 2017

1 Grepafloxacin is a new oral fluoroquinolone with potent activity against community acquired respiratory pathogens, including Streptococcus pneumoniae, and pharmacokinetic properties which allow once daily dosing. As part of its safety evaluation a study of 4 weeks duration was performed to compare the toxicity of grepafloxacin with that of a number of commercially available quinolones in the rat. 2 Groups of eight male Sprague-Dawley rats received either control material or grepafloxacin, enoxacin, lomefloxacin, ofloxacin or ciprofloxacin at an oral dosage of 300 mg/kg/day for 4 consecutive weeks. 3 Effects related to the antibacterial activity of the drugs were seen as increased caecal weight, decreased urinary excretion of sodium, increased water consumption, decreased urine volume, increased urine osmolality, soft stools and suppressed body weight gain. 4 It is well documented that fluoroquinolones can cause lesions in the cartilage of the major diarthrodial joints, and blister formation or erosion on the joint surface was observed in all quinolone-treated groups other than the grepafloxacin group. 5 Some quinolones, have been found to cause crystal-luria, which is often associated with secondary nephropathy in laboratory animals due to the poor solubility of quinolones under the alkaline conditions of the urine. In the present study, needle-like crystals in the urinary sediment were observed in enoxacin and ciprofloxacin treated groups only. 6 In conclusion, grepafloxacin was well tolerated and showed a low potential for joint toxicity and crystalluria compared to other quinolones.
Postmortem digoxin-like immunoreactive substances (DLIS) in patients not treated with digoxin
Authors: Bentur Yedidia , Tsipiniuk Alla , Taitelman Uri 
Published: July 2017

1 Endogenous digoxin-like immunoreactive substances (DLIS) cross-react in immunoassays of digoxin. The postmortem rise in digoxin levels in patients treated with the drug may be due to its redistribution. It is unclear what is the contribution of DLIS to this increase and whether DLIS are present postmortem in patients not treated with digoxin. 2 The objectives of this study were to determine whether DLIS are present after death in patients not treated with digoxin, whether a postmortem increase in DLIS is detectable and whether sampling site can affect DLIS concentrations. 3 DLIS (measured as digoxin, TDx Abott) were determined in blood samples drawn antemortem from ICU patients; postmortem samples from femoral artery and cardiac chambers were taken at least 12 h after the death of these same patients. 4 DLIS concentrations ≥0.2 ng/ml were measured in 44 and 40% of patients antemortem and postmortem (femoral), respectively. No difference was found in DLIS levels between antemortem and postmortem femoral and cardiac samples. Age, ICU stay and postmortem sampling time did not affect the postmortem increase in DLIS. None of the levels was in the toxic range. 5 DLIS may be present after death and their concentration does not increase postmortem. The interpretation of postmortem digoxin concentrations that fall in the therapeutic range should be done cautiously; such measurable levels do not necessarily indicate misuse or malicious intent even in patients who had not been treated with the drug.
A sheep model for continuous intrathecal infusion of test substances
Authors: Hassenbusch Samuel J , Satterfield William C , Gradert Tamara Lee 
Published: July 2017

Pharmaceutical research and new drug development rely extensively on animal research. The development of novel agents for intrathecal administration requires preclinical studies of toxic effects in an animal model. We have developed a nonrodent animal model for this purpose. Our sheep model: 1 Is an animal whose neural axis is similar to the human 2 Allows for the percutaneous placement of intrathecal catheters 3 Has minimal possibilities of infection because the infusion system is totally implanted 4 Provides continuous infusion of the test agent 5 Generates behavioral, motor, neurological and histo-pathological information so that safety guidelines can be established prior to preclinical studies.
Species differences in hepatocyte induction of CYP1A1 and CYP1A2 by omeprazole
Authors: Shih Hsueh , Pickwell George V , Guenette Denis K , Bilir Bahri , Quattrochi Linda C 
Published: July 2017

1 Omeprazole, a proton pump inhibitor therapeutically administered for the treatment of gastric ulcers, induces the expression of cytochromes P4501A1/2 (CYP1A1/2) through transcriptional activation mediated by the Ah (dioxin)-receptor. Primary cultures of hepatocytes isolated from rabbit, rat, mouse and human livers were compared for CYP1A1/2 mRNA inducibility by omeprazole (1 to 100 μM). 2 Primary cultures of human hepatocytes were the most sensitive to the inducing effects of omeprazole. Rabbit hepatocytes were the only other cells studied that showed induced CYP1A1/2 mRNA expression from a concentration lower than 100 μM (i.e., 10 μM). Rat hepatocytes were the least sensitive to omeprazole induction. The response of mouse hepatocytes to omeprazole treatment was variable, with CYP1A1/2 mRNA expression being induced in only two of the three cultures examined. 3 Differences in the time dependence of CYP1A1/2 mRNA expression were observed between species. In general, after treatment of hepatocytes with omeprazole the levels of CYP1A1 mRNA peaked prior to that of CYP1A2 mRNA. 4 Due to the interspecific variability of CYP1A mRNA inducibility by omeprazole, we conclude that human hepatocytes in culture are probably the only appropriate animal model for prediction of CYP1A induction in humans.
The role of nitro-reduction and nitric oxide in the toxicity of chloramphenicol
Authors: Holt Daphne E , Bajoria Rekha 
Published: July 2017

1 Recent work on the toxicology of chloramphenicol suggests that its propensity to cause damage to the blood forming organs may be related to its potential for nitro-reduction and the subsequent production of nitric oxide. 2 In this study both aerobic and anaerobic nitro-reduction of chloramphenicol by human foetal and neonatal liver results in the production of the amine derivative. However intermediates of the reaction nitroso-or glutathionesulphinamido-chloramphenicol could not be detected by hplc. 3 Perfusion of chloramphenicol through isolated lobules of human placentae caused a decrease in blood pressure at a time which coincided with a peak of nitric oxide production. However, although the pressure drop could be reversed by an inhibitor of nitric oxide synthetase, the nitric oxide profile remained the same. 4 These observations suggest that involvement of the para-nitro group of chloramphenicol could cause both hemotoxicity and hypotension in susceptible individuals.