Selective adsorption of sulphur dioxide and hydrogen sulphide by metal-organic frameworks.

The removal of highly toxic gasses such as SO2 and H2S is important in various industrial and environmental applications. Metal organic frameworks (MOFs) are promising candidates for the capture of toxic gases owing to their favorable properties such as high selectivity, moisture stability, thermostability, acid gas resistance, high sorption capacity, and low-cost regenerability. In this study, we perform first principles density functional theory (DFT) and grand-canonical Monte Carlo (GCMC) simulations to investigate the capture of highly toxic gases, SO2 and H2S, by the recently designed ZTF and MAF-66 MOFs. Our results indicate that ZTF and MAF-66 show good adsorption performances for SO2 and H2S capture. The nature of the interactions between H2S or SO2 and the pore surface cavities was examined at the microscopic level. SO2 is adsorbed on the pore surface through two types of hydrogen bonds, either between O of SO2 with the closest H of the triazole 5-membred ring or between O of SO2 with the hydrogen of the amino group. For H2S inside the pores, the principal interactions between H2S and surface pores are due to a relatively strong hydrogen bonds established between the nitrogens of the organic part of MOFs and H2S. Also, we found that these interactions depend on the orientation of SO2/H2S inside the pores. Moreover, we have studied the influence of the presence of water and CO2 on H2S and SO2 capture by the ZTF MOF. The present GCMC simulations reveal that the addition of H2O molecules at low pressure leads to an enhancement of the H2S adsorption, in agreement with experimental findings. However, the presence of water molecules decreases the adsorption of SO2 irrespective of the pressure used. Besides, SO2 adsorption is increased in the presence of a small number of CO2 molecules, whereas the presence of carbon dioxide in ZTF pores has an unfavorable effect on the capture of H2S.

In silico design of a new Zn-triazole based metal-organic framework for CO2 and H2O adsorption.

In search for future good adsorbents for CO2 capture, a nitrogen-rich triazole-type Metal-Organic Framework (MOF) is proposed based on the rational design and theoretical molecular simulations. The structure of the proposed MOF, named Zinc Triazolate based Framework (ZTF), is obtained by replacing the amine-organic linker of MAF-66 by a triazole, and its structural parameters are deduced. We used grand-canonical Monte Carlo (GCMC) simulations based on generic classical force fields to correctly predict the adsorption isotherms of CO2 and H2O. For water adsorption in MAF-66 and ZTF, simulations revealed that the strong hydrogen bonding interactions of water with the N atoms of triazole rings of the frameworks are the main driving forces for the high adsorption uptake of water. We also show that the proposed ZTF porous material exhibits exceptional high CO2 uptake capacity at low pressure, better than MAF-66. Moreover, the nature of the interactions between CO2 and the MAF-66 and ZTF surface cavities was examined at the microscopic level. Computations show that the interactions occur at two different sites, consisting of Lewis acid-Lewis base interactions and hydrogen bonding, together with obvious electrostatic interactions. In addition, we investigated the influence of the presence of H2O molecules on the CO2 adsorption on the ZTF MOF. GCMC simulations reveal that the addition of H2O molecules leads to an enhancement of the CO2 adsorption at very low pressures but a reduction of this CO2 adsorption at higher pressures.

Testing of primers for the study of cyanobacterial molecular diversity by DGGE.

Denaturing Gradient Gel electrophoresis (DGGE) is a PCR-based technique which is widely used in the study of microbial communities. Here, the use of the three specific 16S rRNA cyanobacterial specific primers CYA359F, CYA781R(a) and CYA781R(b) on the assessment of the molecular diversity of cyanobacterial communities is examined. Assignments of the reverse primers CYA781R(a) and CYA781R(b) with cyanobacterial strain sequences showed that the former preferentially targets filamentous cyanobacteria whereas the latter targets unicellular cyanobacteria. The influence of the GC clamp position on the forward or on reverse primer and the use of the two reverse primers separately or in equimolar mixture were investigated. Three environmental samples were subjected to amplification with 6 combinations of primers. The 6 banding patterns as well as the sequences of the bands extracted were analysed and compared. In addition, to assess the effect of the position of the GC clamp, the melting profiles of the sequences of Aphanizomenon flos-aquae PMC9707 and Synechococcus sp. MH305 were determined, with the GC clamp in the 3' or 5' position. Results showed that the use of two separate amplifications allowed a more complete study of the molecular diversity of the cyanobacterial community investigated. Furthermore, similar richness and identical phylogenetic assignments of extracted bands were obtained irrespective of the positioning of the GC clamp.

[Skin changes in patients with Lyme borreliosis]. / Kozne promene u obolelih od Lyme borreliosis.

In introduction some clinical characteristics of Erythema migrans, Borrelia lymphocytoma and acrodermatitis chronica atrophica has been described. The importance of atypical forms of Erythema migrans and the difficulties in differential diagnosis of cutaneous manifestation has been stressed. In a prospective, and partly retrospective investigation of 1292 persons with tick bites, signs of Lyme borreliosis have been found in 18.96%. Number of such persons seen in dermatology wards is rising, and 18.2% of these are children less than 15 years of age. Patients seen in dermatology are mostly women (56.5%:43.5%). Nearly half of the patients with Erythema migrans did not known that they had a tick bite (42.5%). Lyme borreliosis was manifested mainly as Erythema migrans, 89% of patients. Borrelia lymphocytoma was encountered in 2%, and Acrodermatitis chronica atrophicans in 0.4% of patients, significantly less than in other reports. Sclerotic skin lesions were found in 4.1% of patients, and some macular and urticarial lesions were recorded. An incubation period generally less than three weeks preceded to skin manifestations, but in some patients this period could not be recorded. Skin lesions were located on lower extremities in 50.4% of patients, trunk in 25.5%, and upper extremities in 10.5% of patients. In 87% of patients skin lesions lasted less than three weeks. Symptoms were present in 62% of patients. Seropositivity to Borrelia burgdorferi has been found in 10.2% of patients, mostly three weeks after the tick bite.

[Cutaneous manifestations of Lyme disease and results of our study]. / Kutane manifestacije lajmske bolesti i rezultati naseg istrazivanja.

An investigation of 395 patients with tick bites or suspected tick bites has been conducted. Patients were from 14 months to 86 years old. Erythema migrans was found in 83 (21.01%), lympocytoma in 2 (0.5%) and scleroderma lesions in 2 (0.5%) patients. There were 12 asymptomatic seropositive patients. The presence of Borrelia burgdorferi in two Ixodes ricinus ticks was investigated and demonstrated.

[Lyme disease in children and adolescents]. / Lajmska bolesti u dece i adolescenata.

148 children and adolescents with Lyme borreliosis and tick bite or suspection on tick bite were examined. The examined patients were aged from 14 months to 24 years and divided into four age groups. Skin lesions were discovered in 25 percent of patients with tick bite. Erythema migrans occurred in 91 percent, Lymphocytoma in 3 percent and sclerodermatous lesions (Lichen sclerosus et atrophicus and Morphea) in 6 percent of patients with Lyme disease. Serologic tests on the presence of antibodies to Borreliae burgdorferi were performed in 96 percent of cases with tick bite. Antibody titer 1:80 or higher in 8 percent of patients with tick bite, was discovered. We found positive serologic test results in 5 (29 percent) of 29 persons with Erythema migrans, in 4 (4 percent) of 110 patients with tick bite (without skin lesions), as well as, in 1 patient with Lymphocytoma. Antibiotic therapy was applied in all cases with Erythema migrans, in person with Lymphocytoma, as well as, in patients with asymptomatic infections (patients without skin lesion recalling a tick bite and with antibodies against Borrelia burgdorferi). A general sensitivity, to infection with Borrelia burgdorferi, is stressed, a fact based on appearance by Lyme borreliosis in all age groups even in the newborn children.