Simultaneous preparation of N2 and CO2 from water nitrates for δ15N and δ18O analysis on the example of the Zemborzycki Reservoir studies.

Nitrates are bioavailable compounds, which are necessary for every living organisms. However, their excess could be harmful, because it could lead to, i.e., methemoglobinemia, formation of carcinogenic nitrosamines and reservoir eutrophication. Isotopic analysis of δ15N and δ18O in nitrates allows to distinguish their different sources. To simplify the way of nitrate source monitoring, we developed a less complex and cheap "off-line" method for nitrate isotopic analysis, in which we obtain both gases required for isotopic analysis of NO3-, N2 for δ15N and CO2 for δ18O measurements, in one procedure. The developed method is based on simultaneous conversion of AgNO3 (mixed with C and placed into PtIr boat) to N2 and CO2 in a glass vacuum apparatus. A small amount of sample (8 mg of AgNO3) required for this procedure and a good reproducibility of the isotopic analysis (better than 0.3‰ for δ18O and 1‰ for δ15N) make this method a useful tool for environmental research. Using the developed method, we analyzed the isotopic composition of N and O in nitrates in the Zemborzycki Reservoir near Lublin (Poland), in 2015. The results indicate a large variation of δ15N (from -1.4 to +37.7‰) and δ18O (from +5.5 to +25.9‰) values in NO3- ions, while the concentration of NO3- varied from 0.2 to 15.3 mg/dm3. These preliminary results suggest that nitrate fertilizers probably are the main source of NO3- pollution. Our study points out the input of manure and/or sewage to the analyzed reservoir in the subsequent periods of sample collection.

An electronic criterion for assessing intrinsic brittleness of metallic glasses.

Bulk metallic glasses (BMGs) are characterized by a number of remarkable physical and mechanical properties. Unfortunately, these same materials are often intrinsically brittle, which limits their utility. Consequently, considerable effort has been expended searching for correlations between the phenomenologically complex mechanical properties of metallic glasses and more basic properties, such correlations might provide insight into the structure and bonding controlling the deformation properties of BMGs. While conducting such a search, we uncovered a weak correlation between a BMG's work function and its susceptibility to brittle behavior. We argue that the basis for this correlation is a consequence of a component of the work function - the surface dipole - and a fundamental bond property related to the shape of the charge density at a bond critical point. Together these observations suggest that simple first principle calculations might be useful in the search for tougher BMGs.

Lamotrigine Decreased Hippocampal Damage and Improved Vascular Risk Markers in a Rat Model of Pentylenetetrazole Induced Kindling Seizure

Various antiepileptic drugs (AEDs) especially enzyme-inducing AEDs might be associated with increased vascular risk, through impairment of the endogenous antioxidative ability which may trigger oxygen-dependent tissue injury. Lamotrigine (LTG) a non-enzyme-inducing AED has scarce information regarding its effects on oxidative stress. The present study aimed to study the possible modulation of vascular risk factors of epileptogenesis by LTG, in a rat model of kindling seizure induced by pentylenetetrazole (PTZ). Four groups of male Wister rats were used; vehicle control group, PTZ group (alternate day PTZ, 30 mg/kg, i.p), LTG/PTZ group (LTG 20 mg/kg/day p.o and alternate day PTZ) and LTG group. The study period was 5 weeks. Lipoproteins and total homocysteine (tHcy), malondialdehyde (MDA) and reduced glutathione (GSH) were measured. Aortic endothelial function study and histopathological examination of the rats' brains, aortas and coronaries were conducted. Serum total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C), tHcy, MDA, GSH levels were significantly higher in epileptic rats than normal controls rats. A decrease in HDL-cholesterol with high atherosclerotic index was also demonstrated. The administration of LTG improved the PTZ-kindled seizures. It produced a significant decrease in TC, TG and LDL-cholesterol, MDA, aortic GSH and increase in HDL-cholesterol with no significant effect on serum GSH and tHcy levels. LTG improved endothelium-dependent relaxation, decreased hippocampal neurodegenerative changes and atherosclerotic changes of aortas and coronaries. LTG decreased seizures severity, hippocampal damage and improved vascular risk markers in this rat model of kindling seizures.

Genetic Variability of Antigen B among Echinococcus granulosus Egyptian Isolates

Genetic polymorphisms of encoding antigen B2 gene (AgB2) in Echinococcus granulosus were studied using PCR-RFLP and DNA sequencing among 20 Egyptian isolates. Five isolates from different host origins (humans, camels, pigs, and sheep) were collected and used. All examined isolates of each host group gave very similar patterns of PCR-RFLP after restriction enzyme digestion with AluI, with the gene size of approximately 140 bp and 240 bp for sheep and human isolates, and approximately 150 bp and 250 bp for pig and camel isolates. No digestion pattern was obtained after incubation of all studied isolates with EcoRI. These results reveal high intra-group homogeneity. DNA sequence analysis highlighted that human infecting strain showed 100% identity with respect to sheep infecting isolate, 96% and 99% with pig and camel infecting isolates, respectively.

Sulfur isotopic composition of H2S and SO4(2-) from mineral springs in the Polish Carpathians.

A number of springs in Carpathian Mts. contain dissolved H2S and SO4(2-) in concentrations above 10 mg/dm3. In this study we have investigated the sulfur isotope composition (delta34S) of the dissolved sulfur species in the springs from the flysch area in the Carpathian Mts. along the tectonic dislocation. It is believed that some of these springs may carry a major fraction of dissolved sulfur species of extremely deep sulfur (of mantle origin), which is subjected to SO4(2-)-H2S isotope exchange at high temperatures. The original isotopic compositions may be modified by reduction/oxidation at low temperatures and by admixture of sulfur from other sources. In order to distinguish the sulfur of mantle origin we investigated delta34S of dissolved sulfide and sulfate and on the basis of known concentrations we calculated delta34S of total dissolved sulfur. The isotope fractionation between sulfate and sulfide helped to distinguish the sulfur origin. Evaluating the sulfur isotope exchange, we selected 4 springs which likely have only weakly disturbed sulfur of mantle origin.

A modified technique for the preparation of SO2 from sulphates and sulphides for sulphur isotope analyses.

A modified technique for the conversion of sulphates and sulphides to SO2 with the mixture of V2O5-SiO2 for sulphur isotopic analyses is described. This technique is more suitable for routine analysis of large number of samples. Modification of the reaction vessel and using manifold inlet system allows to analyse up to 24 samples every day. The modified technique assures the complete yield of SO2, consistent oxygen isotope composition of the SO2 gas and reproducibility of delta34S measurements being within 0.10 per thousand. It is observed, however, oxygen in SO2 produced from sulphides differs in delta18O with respect to that produced from sulphates.

Low-Temperature Thermal Decomposition of Sulfates to SO(2) for On-Line (34)S/(32)S Analysis.

We describe a fast, inexpensive, and safe method of direct SO(2) extraction from BaSO(4) for sulfur isotopic analysis by mass spectrometry. Only two reagents are used: (1) pure NaPO(3), which is mixed with BaSO(4) sample, and (2) Cu foil, from which reaction boats are manufactured. The extraction precedes in the Cu boat placed into a quartz tube connected to a vacuum line. The boat is heated to 650-700 °C while pure SO(2) produced is collected in a "cold finger". Reaction is complete in 7-10 min. We have proven by means of (18)O-enriched BaSO(4) specimens that the oxygen isotopic composition of the SO(2) is totally controlled by (18)O content in NaPO(3), when the weight ratio of the reagent to sample exceeds 6:1. The method described can be used for "on-line" SO(2) preparation for isotopic analysis.