Mitigation of Physical Aging of Polymeric Membrane Materials for Gas Separation: A Review.

The first commercial hollow fiber and flat sheet gas separation membranes were produced in the late 1970s from the glassy polymers polysulfone and poly(vinyltrimethyl silane), respectively, and the first industrial application was hydrogen recovery from ammonia purge gas in the ammonia synthesis loop. Membranes based on glassy polymers (polysulfone, cellulose acetate, polyimides, substituted polycarbonate, and poly(phenylene oxide)) are currently used in various industrial processes, such as hydrogen purification, nitrogen production, and natural gas treatment. However, the glassy polymers are in a non-equilibrium state; therefore, these polymers undergo a process of physical aging, which is accompanied by the spontaneous reduction of free volume and gas permeability over time. The high free volume glassy polymers, such as poly(1-trimethylgermyl-1-propyne), polymers of intrinsic microporosity PIMs, and fluoropolymers Teflon® AF and Hyflon® AD, undergo significant physical aging. Herein, we outline the latest progress in the field of increasing durability and mitigating the physical aging of glassy polymer membrane materials and thin-film composite membranes for gas separation. Special attention is paid to such approaches as the addition of porous nanoparticles (via mixed matrix membranes), polymer crosslinking, and a combination of crosslinking and addition of nanoparticles.

Temperature Dependence of Light Hydrocarbons Sorption and Transport in Dense Membranes Based on Tetradecyl Substituted Silicone Rubber.

Solubility-selective polymer membranes are promising materials for C3+ hydrocarbons removal from methane and other permanent gas streams. To this end, a dense solubility-selective membrane based on crosslinked poly(tetradecyl methyl siloxane) was synthesized. Sorption of methane, ethane, and n-butane in the polymer was measured in the temperature range of 5-35 °C. An abnormal temperature dependence of sorption was detected, contradicting the generally accepted view of sorption as an exothermic process. In particular, methane shows minimal sorption at 5 °C. The abnormal temperature behavior was found to be related to crystallization of the alkyl side chains at temperatures below ~10 °C. Gas permeability determined by sorption and permeation methods are in reasonable agreement with each other and decrease in the order n-C4H10 > C2H6 > CH4. The solubility of these alkanes changes in the same order indicating that poly(tetradecyl methyl siloxane) is indeed the sorption-selective membrane. The diffusivities and permeabilities of studied alkanes declined with decreasing temperature, whereas the n-C4H10/CH4 permselectivity increases with decreasing temperature, reaching a value of 23 at 5 °C.

[Management of obstructive jaundice in patients with neoplasms of the major duodenal papilla]. / Taktika lecheniya mekhanicheskoi zheltukhi u patsientov s novoobrazovaniyami bol'shogo sosochka dvenadtsatiperstnoi kishki.

OBJECTIVE: To develop the indications and assess an effectiveness of treatment of patients with ampullary tumors followed by mechanical jaundice. MATERIAL AND METHODS: There were 26 patients with major duodenal papilla neoplasms for the period 2015-2020 at the Sklifosovsky Research Institute for Emergency Care. RESULTS: Twenty patients underwent transpapillary interventions: papillosphincterotomy followed by lithoextraction and bilio-duodenal stenting in 4 (15.3%) patients, bilio-duodenal stenting in 12 (46.1%) patients, nasobiliary drainage in 2 (7.6%) patients, pancreaticoduodenal stenting in 2 (7.6%) patients. Percutaneous transhepatic microcholecystostomy was performed in 6 (23.4%) patients. In all cases, laboratory values decreased in 5-7 days after drainage. Eight (30.7%) patients refused further surgical treatment and were discharged in satisfactory condition. Another 8 (44.5%) patients underwent endoscopic submucosal papillectomy. There were no postoperative complications. Patients were discharged after 5-7 days. Four (22.2%) patients underwent tumor resection via laparotomy. One of these patients required redo laparotomy in postoperative period due to acute perforated duodenal ulcer. Six (33.3%) patients underwent palliative bilio-duodenal stenting. CONCLUSION: Invasion of muscle layer or distal parts of the common bile duct, as well as abnormal vascularization are indications for open surgery or palliative endoscopic treatment. Tumor location within mucous and muscle layers without invasion of distal third of the common bile duct and no abnormal vascularization of tumor justify endoscopic papillectomy. Endoscopic approach can be considered as a final minimally invasive method with minimal risk of postoperative complications in case of benign ampullary tumor.

Passive athermalization and achromatization of a two-component system with air gap.

Passive athermalization allows keeping spatial resolution through the given spectral range while working within a wide temperature range without refocusing. Existing works concerning the problem of passive athermalization usually analyze two-lens components with zero thickness and air gaps. In our work, we have included an air gap into the consideration and derived general expressions for an athermal achromatic case. We have shown that including the air gap into the analysis led to the expanded area of solutions and can be considered as basic for more complex schemes. The method suggested provides the basis for designing athermal systems for various optic electronic devices.

[Diagnosis and treatment of benign neoplasms of the major duodenal papilla]. / Diagnostika i lechenie dobrokachestvennykh novoobrazovanii bol'shogo sosochka dvenadtsatiperstnoi kishki.

OBJECTIVE: To evaluate an efficacy of surgical treatment of patients with benign tumors of the major duodenal papilla. MATERIAL AND METHODS: For the period from January 2015 to January 2020, sixteenth patients with benign tumors of the major duodenal papilla were treated at the Sklifosovsky Research Institute for Emergency Care. There were 7 men (43.7%) and 9 women (56.3%). Tumor dimension ranged from 1.0 to 4.0 cm (mean 2.5 cm). RESULTS AND DISCUSSION: Tumor resection through laparotomy was performed in 4 (25%) patients. Six (37.5%) patients underwent endoscopic submucosal papillectomy. Other 6 (37.5%) patients refused surgical treatment due to regression of symptoms. Postoperative re-laparotomy was performed in 1 patient (10%) with acute perforated duodenal ulcer. There were no complications after endoscopic papillectomy. Control endoscopic examination identified no signs of tumor recurrence in all patients after 3 and 6 months. In our opinion, endoscopic papillectomy is preferable for adenoma of the major duodenal papilla due to reduced surgical trauma. We assume that stenting of the bile ducts and the major pancreatic duct prevented acute pancreatitis and obstructive jaundice. CONCLUSION: Endoscopic papillectomy is an effective minimally invasive treatment of tumors of the major duodenal papilla. Despite a considerable number of complications, most of them can be resolved by conservative treatment or endoscopic procedures. Thus, endoscopic papillectomy may be considered as preferable method in the treatment of patients with benign tumors of the major duodenal papilla.

Enantioselective retention mechanisms of dipeptides on antibiotic-based chiral stationary phases. II. Effect of the methanol content in the mobile phase.

Effect of mobile phase (water-methanol) composition on the enantioseparation of dipeptides on the chiral stationary phase Chirobiotic R was investigated using Ala-Ala, Leu-Leu, Gly-Leu, and Leu-Gly as case studies. The lipophilicity of dipeptides was found to be an essential factor in the dependence of their retention on the methanol percentage, the retention factor of lipophobic dipeptides increasing monotonously and that of lipophilic dipeptides changing according to an asymmetric U-shaped trajectory as methanol concentration increases. The behavior of enantioselectivity as a function of the methanol content also depends on the lipophilicity of dipeptide. For lipophilic Leu-Leu, the dependence has a dome-like shape, and for more lipophobic dipeptides, Ala-Ala and Gly-Leu, it is an increasing function of the methanol concentration. The importance of solvation equilibria in the bulk liquid and on the surface of the stationary phase for the total retention is discussed from the thermodynamic point of view. Special consideration is given to the adsorption of the water-methanol mixture on the surface of the Chirobiotic R stationary phase.

Enantioselective retention mechanisms of dipeptides on antibiotic-based chiral stationary phases: Leucyl-leucine, glycyl-leucine, and leucyl-glycine as case studies.

Chromatographic behaviors of dipeptides consisting of leucine and glycine were studied on two antibiotic-based chiral stationary phases (CSPs) with teicoplanin (Chirobiotic T) or ristocetin A (Chirobiotic R) as chiral selectors under reversed-phase conditions. The effect of mobile phase pH on the retention of stereoisomers of dipeptides was investigated and thermodynamic characteristic of adsorption were measured at different pH values. It was shown that the retention of dipeptides depends on the ionization of their molecules in the mobile phase, as different ionic forms have different affinity towards antibiotic selectors. Enantioselectivity of the bound antibiotics with respect to Leu-Leu stereoisomers was achieved via steric modulation of ion-ion interactions between the solute and the selector, while in the case of Gly-Leu enantiomers non-ionic interactions such as hydrogen bonding might play the key role. In both cases, the dipeptides terminating in D-Leu were retained stronger than their optical antipodes, whereas the enantiomers of Leu-Gly were hardly separated. The regression analysis of the retention data applying the Horvath-Melander-Molnar model revealed that different types of enantioselectivity resides in particular ionic forms of the compounds: cations are responsible for the separation of diastereomeric pairs and the anionic and zwitterionic forms have a universal enantioselectivity on the Chirobiotic T CSP, and the anions and zwitterions are the enantioselective forms for the Chirobiotic R CSP.

[External pancreatic fistulas management]. / Printsipy lecheniya bol'nykh s naruzhnymi pankreaticheskimi svishchami (s kommentariem).

The main principles of treatment of external postoperative pancreatic fistulas are viewed in the article. Pancreatic trauma was the reason of pancreatic fistula in 38.7% of the cases, operations because of acute pancreatitis - in 25.8%, and pancreatic pseudocyst drainage - in 35.5%. 93 patients recovered after the treatment. Complex conservative treatment of EPF allowed to close fistulas in 74.2% of the patients with normal patency of the main pancreatic duct (MPD). The usage of octreotide 600-900 mcg daily for at least 5 days to decrease pancreatic secretion was an important part of the conservative treatment. Endoscopic papillotomy was performed in patients with major duodenal papilla obstruction and interruption of transporting of pancreatic secretion to duodenum. Stent of the main pancreatic duct was indicated in patients with extended pancreatic duct stenosis to normalize transport of pancreatic secretion to duodenum. Surgical formation of anastomosis between distal part of the main pancreatic duct and gastro-intestinal tract was carried out when it was impossible to fulfill endoscopic stenting of pancreatic duct either because of its interruption and diastasis between its ends, or in the cases of unsuccessful conservative treatment of external pancreatic fistula caused by drainage of pseudocyst.

Regulation of peroxisome proliferator-activated receptors (PPAR) α and -γ of rat brain astrocytes in the course of activation by toll-like receptor agonists.

Peroxisome proliferator-activated receptors (PPAR)-α and -γ in astrocytes play important roles in inflammatory brain pathologies. Understanding the regulation of both activity and expression levels of PPARs is an important neuroscience issue. Toll-like receptor (TLR) agonists are inflammatory stimuli that could modulate PPAR, but the mechanisms of their control in astrocytes are poorly understood. In the present study, we report that lipopolysaccharide, peptidoglycan, and flagellin, which are agonists of TLR4, TLR1/2, and TLR5, respectively, exert time- and nuclear factor kappa-light-chain-enhancer of activated B cells-dependent suppression of mRNA, protein and activity of PPARα and PPARγ. In naïve astrocytes, PPARα and PPARγ mRNA have short turnover time (half-life about 30 min for PPARα, 75 min for PPARγ) with a nearly two-fold stabilization after TLR-activation. p38 inhibition abolished TLR-induced stabilization. The levels of PPARα and PPARγ mRNA, and protein and DNA-binding activity could be modified using c-Jun N-terminal Kinase and p38 inhibitors. In addition, the expression levels of both PPARα and PPARγ isotypes were induced after inhibition of protein synthesis. This induction signifies participation of additional regulatory proteins with short life-time. They are p38-sensitive for PPARα and c-Jun N-terminal Kinase-sensitive for PPARγ. Thus, PPARα and PPARγ are regulated in astrocytes on mRNA and protein levels, mRNA stability, and DNA-binding activity during TLR-mediated responses. Astrocytes have the triad of PPARα, PPARß/δ, and PPARγ in regulation of proinflammatory responses. Activation of Toll-like receptors (TLR) leads to PPARß/δ overexpression, PPARα and PPARγ suppression via TLR/NF-κB pathway on mRNA, protein and activity levels. Mitogen-activated protein kinases (MAPK) p38 and JNK are involved in regulation of PPAR expression. p38 MAPK plays a special role in stabilization of PPAR mRNA.

PPAR activation has dichotomous control on the expression levels of cytosolic and secretory phospholipase A2 in astrocytes; inhibition in naïve, untreated cells and enhancement in LPS-stimulated cells.

Despite the importance of cytosolic phospholipase A(2) type IVA (cPLA(2)) and secretory PLA(2) (sPLA(2)) in physiological and pathological responses of astrocytes in inflammatory conditions, the regulation of the expression of these genes is still unclear. Both genes have peroxisome proliferator-activated receptors (PPAR) binding sites in their promoters. The role of synthetic PPAR agonists in the regulation of gene expression in naïve and lipopolysaccharide (LPS)-stimulated rat astrocytes in culture was investigated. Exposure to LPS resulted in a time-dependent, fourfold transient increase of sPLA(2) expression, with maximum at 4 h; cPLA(2) expression was notably increased after 16-h LPS stimulation. Using selective PPARα, PPARß/δ, and PPARγ agonists, we found that expression of both cPLA(2) and sPLA(2) is under PPAR control, but with different isotypes sensitivity. In naïve astrocytes, all three PPAR agonists significantly suppressed the expression of sPLA(2), while only PPARα and PPARγ activation suppressed cPLA(2) expression. Astonishingly, simultaneous addition of LPS with PPAR agonists evoked the opposite effect. All three PPAR agonists induced potentiation of cPLA(2) expression level. Potentiation of sPLA(2) expression was induced only by simultaneous addition of LPS with PPARγ agonist. By knockdown of PPARα, PPARß/δ, and PPARγ, we confirmed the involvement of PPAR-dependent pathways. The important novelty of our findings is that both sPLA(2) and cPLA(2) are under dichotomous control of PPARs: suppression in naïve control cells, but induction in LPS-stimulated astrocytes.

[Incidence of ocular trauma in Clinical Hospital Oradea between 1997-1999]. / Incidenta traumatismelor oculare în spitalul clinic de oftalmologie oradea în perioada 1997-1999.

The purpose of the study is to analyse the great number of ocular injuries which were diagnosed and treated in the out-patients clinic or in the hospital in 1997-1999. Ocular trauma seems to be related to the working place or the main activities of the patients, such as agriculture or housekeeping. Ocular injuries in children are significant as number and prognosis. Blunt trauma, ocular perforations, ocular foreign bodies and burns were studied separately for children, housekeepers, unemployed, working and retired people. Due to their number and complexity, ocular trauma represent a very important part in the activity of an ophthalmology department. The conclusion of the study is the number of ocular injuries decreased over the years because of the reduced industrial activity in our town. Similar ocular injuries in retired and working people suggest that retired people are still active. The prognosis of ocular trauma is better if the patients come early to be seen by the specialist, if the treatment is adequate and if the department has a proper equipment for advanced surgery techniques.

Plasma levels of C-reactive protein after coronary stent implantation.

AIMS: This study was designed to investigate the role of inflammation on the occurrence of angiographic restenosis 6 months after coronary stent implantation and the influence of different kinds of antithrombotic and antiplatelet strategies on inflammation. METHODS AND RESULTS: In an open randomized trial, 40 consecutive patients were treated with aspirin (100 mg. day(-1)) and either ticlopidine (2x250 mg. day(-1)) (n=17), or phenprocoumon (INR 2.0-3.0) and dipyridamole (3x160 mg. day(-1)) (n=23) after successful elective coronary stent implantation. Plasma levels of C-reactive protein were determined one day before stent implantation and serially thereafter twice daily up to 120 h. C-reactive protein plasma levels increased significantly (P<0.0001) after stent implantation. Phenprocoumon and dipyridamole or ticlopidine had no effect on C-reactive protein plasma levels (P=0.51) or the occurrence of angiographic restenosis (P=0.48). C-reactive protein plasma levels were significantly higher in patients with lesion type C compared to types A or B (P=0.035), respectively. C-reactive protein plasma levels were significantly higher and mean shoulder levels occurred 48 h later in patients with restenosis compared to patients without restenosis after 6 months (P=0.038). CONCLUSIONS: Elevated C-reactive protein plasma levels still persisting 96 h after stent implantation might reflect a prolonged inflammatory reaction to coronary stent implantation which might causally be involved in pathophysiological mechanisms leading to restenosis.

Epidemiological trend of human leptospirosis in Italy between 1994 and 1996.

In the three-year period 1994 1996, 222 reports on human cases of leptospirosis were received by the Italian Ministry of Health. The average annual number of reports was 29.2% lower than in the preceding eight years. In all cases but two the infections were thought to have been acquired in Italy. As in previous years, the majority of cases was observed in the northern regions of the country (83.8%), mostly in males (88.9%). Cases occurred in all age groups, but were more common in the working-age population (15-64 years). There was no common-source outbreaks. The typical leptospiral seasonal course, with a peak in August, was observed. During 1994, leptospirosis was the reported cause of death in 19 patients. Mortality was higher among males than females. The overall fatality rate was 22.6%. During the study period, a total of 126 cases of leptospirosis were confirmed by the National Centre for Leptospirosis or one of the 12 Regional Leptospira Laboratories. Of the 103 patients for whom information on place of residence, contact with animals, occupational and recreational activities was available, 98 (95.1%) were people who live in rural areas or devote themselves to occupational or recreational activities at risk. The likely source of infection and the mode of exposure were known for 55 patients. Forty-five patients (81.8%) were likely infected by contaminating water (43 cases) or soil (2 cases), ten (18.2%) by direct contact with animals or animal urine. Both running (51.2%) and stagnant water (27.9%) have been reported as a source of infection. Rodents were implicated in 50.0% of the 10 cases involving animals. In comparison with the preceding eight-year period, the risk of contracting leptospirosis was found to have increased for recreational activities (from 34.7 to 38.2%) and decreased for occupational activities (from 45.8 to 32.7%). A large number of infections, however, was ascribed to accidental events (25.5%). As in the previous period, besides fever, the involvement of the liver was the most frequent clinical manifestation (70.8%). Influenza-like symptoms were the only signs of illness in 15.1% of cases. Infections by 9 different serogroups were detected. The most frequent antibodies were those against serovars icterohaemorrhagiae, poi, copenhageni and brattislava. The presence of co-agglutinins against serovars belonging to different serogroups prevented the identification of the presumptive infecting serogroup in 19.8% of subjects.

Lipoprotein pattern in end-stage renal disease and following successful renal transplantation.

Lipoprotein abnormalities are common in uremia and frequently persist after successful renal transplantation (RT). Based on the influence of immunosuppression on lipoprotein metabolism, this prospective study in 76 patients has been focused on lipoprotein pattern in end-stage renal disease and after successful RT during a follow-up period of 18 months. Additionally, the influence of different immunosuppressive regimes has been evaluated. Hyperlipidemia was present in 32% of the patients before and in 59% after grafting. Total cholesterol was 5.42 +/- 1.57 mmol/l (mean S D) before RT and continuously and significantly increased during the entire observation period, being highest 18 months after RT (6.8 +/- 1.63 mmol/l; p < 0.01). This was mainly due to an increase in LDL-cholesterol (before RT: 3.68 (1.41 mmol/l; 18 months after RT: 4.69 +/- 1.88 mmol/l; p < 0.05) while HDL-cholesterol values only slightly increased (before RT: 0.99 +/- 0.36 mmol/l; 18 months after RT: 1.13 +/- 0.3 mmol/l; p < 0.05). Changes in total HDL-cholesterol were mainly due to an increase in HDL 3, while HDL 2 moderately increasing remained at low concentrations. As corticosteroid dosage was substantially reduced during the entire observation period, other factors such as cyclosporin A have to be considered for hyperlipidemia in renal transplant recipients. The observation on LDL-cholesterol being highest 18 months after transplantation suggests lipid lowering interventions to be indicated and might improve long-term outcome in renal transplant recipients.

[An antigenic extract analyzed by bidimensional immunoelectrophoresis (author's transl)]. / Analisi immunoelettroforetica di un preparato antigene aspergillare

An antigenic extract from broth culture of Aspergillus fumigatus has been analyzed by bidimensional immunoelectrophoresis of Clark and Freeman against rabbit antiserum. The analysis has show the extract to be constituted by seven different antigens.