Selective capture of CO2 over N2 and CH4: B clusters and their size effects

Using density-functional theory (DFT), we investigate the selectivity of adsorption of CO2 over N2 and CH4 on planar-type B clusters, based on our previous finding of strong chemisorption of CO2 on the B10-13 planar and quasiplanar clusters. We consider the prototype B8 and B12 planar-type clusters and perform a comparative study of the adsorption of the three molecules on these clusters. We find that, at room temperature, CO2 can be separated from N2 by selective binding to the B12 cluster and not to the B8 cluster. Selective adsorption of CO2 over CH4 at room temperature is possible for both clusters. Based on our DFT-adsorption data (including also a semi-infinite Boron sheet) and the available literature-adsorption value for N2 on the planar-type B36 cluster, we discuss the selectivity trend of CO2 adsorption over N2 and CH4 with planar-cluster size, showing that it extends over sizes including B10-13 clusters and significantly larger.Comment: 4 figures, 20 page

Contamination of Cow Milk by Heavy Metals in Serbia

Background: Dairy cows are exposed to numerous environmental hazards, such as heavy metals. Milk and dairy products could be harmful to humans when maximum tolerable amounts of heavy metals are exceeded. Analysis of heavy metals in milk is important because milk is a source of essential nutrients and is an indicator of environmental contamination. Some heavy metals are essential to maintain proper metabolic activity in living organisms, but at exceeded levels they could be toxic to living organisms. The main objective of the present study was to determine the residue levels of ten heavy metals (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in cow milk in Serbia.Materials, Methods & Results: The experiment was conducted at three farms at Vojvodina district, Serbia. Cows from all three farms were on pasture during spring and summer time. Randomly 50 cows from each farm were taken for this experiment. The cows have similar body condition score they were in their third or fourth lactation and gave approximately the same amount of milk in the previous lactation. Total 150 milk samples were collected from cows during the morning milking, in the period between April to May in 2016. All 150 milk samples were transported to laboratory as soon as possible and analyzed for the heavy metals. Heavy metals were analyzed by Inductance coupled plasma - optical emission spectrometry. Data are presented as mean values ± sd. Statistical analysis was done by one way repeated measures analysis of variance (ANOVA). The level of significance was set at P < 0.05. The highest average concentration in cow milk was determined for Iron (283.9 mg/kg), then for Zinc (60.21 mg/kg) and Copper (4.404 mg/kg), while the lowest concentration was for Cobalt and Lead (less than 0.005 mg/kg).Discussion: Bioaccumulation is one of the biggest problems with heavy metals. Heavy metals residues in milk can be very dangerous for the calves and humans as well. The existence of trace elements and heavy metals in dairy products and milk has been recorded in various countries since it is considered as one of the most dangerous aspects of food contamination. The presence of heavy metals in cow's milk may be attributed to contamination due to exposure of lactating cow to environmental pollution or consumption of contaminated feeding stuffs and water. Heavy metals after intake in cow organism distributed to all organs and glands such as udder. By that, secretory udder tissue gets intoxicated with heavy metals and after that they can be found in milk. After analyses the results in this experiment the highest average concentration of Fe in cow milk it might be because cows were fed with hay from pasture rich in iron between April to May. Some researchers found the amounts of Cu in the milk of individual varied from 0.2 to 0.8 mg/kg. Contrary to this finding, in current study the average value of Cu in cow milk was 4.404 mg/kg. It is found that the highest concentration of Zn in cow milk is 10.75 mg/kg, lower compare to result in current study (60.21 mg/kg). Arsenic (As) concentration was 0.058 mg/kg, cadmium (Cd) was 0.01 mg/kg, cobalt (Co) was 0.002 mg/kg, chrome (Cr) was 0.018 mg/kg, manganese (Mn) was 0.493 mg/kg, nickel (Ni) was 0.119 mg/kg and lead (Pb) was 0.08 mg/kg what is just above recommended values by International Dairy Federation. The results showed that most of the milk samples from the different farm contained all the studied metals with concentration higher than those recommended by International Dairy Federation and Codex for cow milk

Ostaci pesticida u organskim proizvodima

Food from organic production systems in recent years gain increasingly significant place in the market. Awareness of the benefits of the food products that were created with no application of agrochemicals is becoming increasingly prominent. The presence of chemical agents can not be totally excluded, even when applying all the principles of organic production because residues present in the soil, applied long before the mandatory conversion time of five years, may affect the quality of organic products. The aim of this study was to determine the presence of 50 pesticide in vegetables from organic production. The vegetable samples were taken from green markets. Pesticide residues, higher than the detection limit and less than the maximum allowable concentration (MAC) are present in 52%, 23% and 2% respectively for organochlorine, carbamate and organophosphate insecticides, while carbamates were not detected in any sample. MAC is exceeded in one sample of kohlrabi, eggplant, parsley, potatoes, peppers, beets and cabbage, for the content of HCH and metabolites, aldrin and metabolites, endrine, heptachlor and metabolites, phosalone and azinphos-methyl.Poljoprivredni proizvodi iz organskog sistema proizvodnje poslednjih godina imaju sve značajnije mesto na tržištu. Svest ljudi o prednostima ishrane proizvodima koji su nastali uz minimalnu primenu agrohemikalija, postaje sve izraženija. Prisustvo hemijskih sredstava se ne može potpuno isključiti, čak i kada se primenjuju svi principi organske proizvodnje, jer rezidue prisutne u zemljištu aplicirane mnogo pre početka obaveznog vremena konverzije mogu da utiču na kvalitet organskih proizvoda. Cilj ovog istraživanja je utvrđivanje prisustva ostataka perzistentnih i drugih pesticida u povrću iz organske proizvodnje. U uzorcima povrća: blitve, brokolija, bundeve, celera, cvekle, karfiola, kelerabe, krastavca, krompira, kupusa, paprike, patlidžana, peršuna, šargarepe i tikvica, uzetim na novosadskim zelenim pijacama, ispitan je sadržaj ostataka 50 pesticida i njihovih metabolita. Ostaci pesticida, viši od limita detekcije primenjene metode, a manji od maksimalno dozvoljene koncentracije (MDK) su prisutni u 52 %, 23 % i 2 % uzoraka, respektivno za organohlorne, karbamatne i organofosforne insekticide, dok karbamati nisu detektovani ni u jednom uzorku. MDK vrednost je premašena u po jednom uzorku kelerabe, patlidžana, peršuna, krompira, paprike, cvekle i kupusa u pogledu sadržaja HCH i metabolita, aldrina i metabolita, endrina, heptahlora i metabolita, fosalona i azinfosmetila

Rashba-induced spin texture and spin-layer-locking effects in the antiferromagnetic CrI3 bilayer

The antiferromagnetic (AFM) CrI3 bilayer is a particularly interesting representative of van der Waals 2D semiconductors, which are currently being studied for their magnetism and for their potential in spintronics. Using ab initio density-functional theory calculations, we investigate the spin texture in momentum space of the states of the (doubly degenerate) highest valence band of the AFM CrI3 bilayer with Cr-spin moments perpendicular to the layers. We find the existence, in the main central part of the Brillouin zone, of a Rashba in-plane spin texture of opposite signs on the two layers, resulting from the intrinsic local electric fields acting on each layer. To study the layer segregation of the wavefunctions, we apply a small electric field that splits the degenerate states according to their layer occupancy. We find that the wavefunctions of the highest valence band are layer-segregated, belonging to only one of the two layers with opposite in-plane spin textures, and the segregation occurs over nearly the whole Brillouin zone. The corresponding layer locking of the in-plane -canted spin is related to the separation in energy of the highest AFM band from the rest of the valence bands. We explain how the band interactions destroy the layer locking at the K, K ', and Gamma points. Furthermore, we compare the layer locking of the in-plane-canted spin in our AFM bilayer system with the hidden spin polarization in centrosymmetric nonmagnetic materials, pointing out the differences in segregation mechanisms and their consequences for the layer locking. We note that a similar Rashba effect with layer locking of in -plane-canted spin could occur in other van der Waals AFM bilayers with strong spin-orbit coupling and an isolated energy band

Challenges of the Republic of Serbia in the treatment of waste sludge contaminated with heavy metals

The interactions of heavy metals and cement phases in the solidification/stabilization (S/S) process have been examined. The S/S method was applied to the waste sludge contaminated with heavy metals to determine the conditions under which the treated materials can be safely disposed of at landfills for inert, non-hazardous, or hazardous waste. Sludge samples were mixed with soil and sand to simulate improper sludge disposal directly into the soil. S/S technology was selected using different cement fractions to treat these contaminated samples. The use of Portland cement or mixtures of different types of cement for the treatment of sludge containing heavy metals is widespread. Samples of leached content were analyzed for the presence of the following metals: arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and zinc (Zn). The study results lead to the conclusion that the sludge contaminated with heavy metals after the application of S/S with the addition of different cement fractions is transformed into non-hazardous, monolithic material

Modelling Creep (Relaxation) of the Urinary Bladder

We first present the results of an experiment in which the passive properties of the urinary bladder were investigated using strips of rabbit bladder. Under the assumption that the urinary bladder had orthopaedic characteristics, the strips were taken in the longitudinal and in the circumferential directions. The material was subjected to uniaxial tension, and stress-stretch curves were generated for various rates of deformation. We found that the rates did not have a significantly effect on the passive response of the material. Additionally, the stress-stretch dependence during relaxation of the material when exposed to isometric conditions was determined experimentally

Estradiol decreases blood pressure in association with redox regulation in preeclampsia

In this study, we tested a hypothesis that a short-term estradiol therapy may reduce blood pressure in preeclampsia by modulating plasma oxidative stress. The intramuscular injections of 10 mg 17-beta-estradiol were prescribed to preeclamptic pregnant women during the 3-day therapy before a labor induction. The analyses of mean arterial pressure (MAP), serum estradiol concentrations, plasma superoxide anion (O2.), hydrogen peroxide (H2O2), nitrites (NO2−), and peroxynitrite (ONOO−) were conducted before and during the therapy. We found that the plasma concentrations of oxidative stress markers, such as O2– and H2O2, are higher in preeclampsia and positively correlated with the MAP value. Moreover, it was shown that the plasma concentration of NO2– as an indicator of NO levels is higher in preeclampsia. A short-term intramuscular application of estradiol decreases the MAP value and the plasma concentration of O.–, H2O2, NO2−, and ONOO– in preeclampsia. A positive correlation between the decrease of MAP values and the decrease of plasma concentrations of O2–, H2O2, and ONOO– was found in preeclampsia during a short-term estradiol therapy. We conclude that the short-term estradiol therapy decreases the MAP value in preeclampsia by modulating the plasma oxidative stress. We speculate that the estradiol metabolism in preeclampsia is an important mechanism that contributes to vascular dysfunction