Overcoming stability problems in microwave-assisted heterogeneous catalytic processes affected by catalyst coking

Microwave-assisted heterogeneous catalysis (MHC) is gaining attention due to its exciting prospects related to selective catalyst heating, enhanced energy-efficiency, and partial inhibition of detrimental side gas-phase reactions. The induced temperature difference between the catalyst and the comparatively colder surrounding reactive atmosphere is pointed as the main factor of the process selectivity enhancement towards the products of interest in a number of hydrocarbon conversion processes. However, MHC is traditionally restricted to catalytic reactions in the absence of catalyst coking. As excellent MW-susceptors, carbon deposits represent an enormous drawback of the MHC technology, being main responsible of long-term process malfunctions. This work addresses the potentials and limitations of MHC for such processes affected by coking (MHCC). It also intends to evaluate the use of different catalyst and reactor configurations to overcome heating stability problems derived from the undesired coke deposits. The concept of long-term MHCC operation has been experimentally tested/applied to for the methane non-oxidative coupling reaction at 700¿C on Mo/ZSM-5@SiC structured catalysts. Preliminary process scalability tests suggest that a 6-fold power input increases the processing of methane flow by 150 times under the same controlled temperature and spatial velocity conditions. This finding paves the way for the implementation of high-capacity MHCC processes at up-scaled facilities

Dynamic fuel retention in tokamak wall materials: An in situ laboratory study of deuterium release from polycrystalline tungsten at room temperature

International audienceRetention of deuterium ion implanted in polycrystalline tungsten samples is studied in situ in an ultra-high vacuum apparatus equipped with a low-flux ion source and a high sensitivity thermo-desorption setup. Retention as a function of ion fluence was measured in the 10^17 -10^21 D+/m^2 range. By combining this new fluence range with the literature in situ experimental data, we evidence the existence of a retention = fluence^ 0.645±0.025 relationship which describes deuterium retention behavior on polycrystalline tungsten on 8 orders of magnitude of fluence. Evolution of deuterium retention as a function of the sample storage time in vacuum at room temperature was followed. A loss of 50% of the retained deuterium is observed when the storage time is increased from 2 h to 135 h. The role of the surface and of natural bulk defects on the deuterium retention/release in polycrystalline tungsten is discussed in light of the behavior of the single desorption peak obtained with Temperature Programmed Desorption

Antibiotic-associated diarrhea: state-of-the-art

The aim of review. To analyse modern concepts on antibiotic-associated diarrhea, to determine its place in the pattern of total morbidity.Key points. Wide antibiotic application in all sections of medicine along with beneficial action has series of essential side effects, including antibiotic-associated diarrhea. Its extreme and most severe manifestation is pseudomembranous colitis, caused by toxin-producing Clostridium difficile strains. This etiological agent in modern world has got significant association with hospitals and assisted-care facilities, therefore it can spread in out-patient conditions as well at the present time. Mutations resulting in antibiotic resistance, increasing toxin production or promoting sporulation, considerably increase virulence and prevalence of these opportunistic microorganisms.Conclusion. The further studies on development of effective prophylactic and treatment methods of antibiotic-associated diarrhea are required, especially for most severe complication — pseudomembranous colitis. It is necessary to limit application of antibiotics, develop strict indications to their application

Results of formation of primary and secondary smallintestinal reservoirs at ulcerative colitis

Aim of investigation. Improvement of results of surgical treatment and quality of life of patients with severe forms of ulcerative colitis.Material and methods. Investigation is based on analysis of results of surgery of 123 ulcerative colitis patients operated in coloproctology center of Ministry of Health of Russia in 2007 to 2013, that was completed by reconstructive — plastic stage. Formation of smallintestinal reservoir in one stage with total resection of large intestine was carried out in 46 (37,4%) patients (the first group) and secondary, remote — in 77 (62,6%, the second group).Results. At analysis of complication types it was revealed, that complications related to stapling device prevailed in groups. At the present moment of 123 patients who have underwent surgical treatment with formation of smallintestinal reservoir, in 101 (82,1%) ileostoma was liquidated. Of them in the first group it has been closed in 31 (67,4%) patient, in the second — in 70 (90,1%). Thus only in 2 (4,3%) patients of the first and in 1 (1,2%) patient of the second group with developed postoperative complications closure of imposed ileostoma was not performed.Conclusions. Today formation of smallintestinal reservoirs is unique way of rehabilitation of patients with ulcerative colitis after total colectomy. Comparable results of treatment in analyzed groups have been received due to refusal of primary reservoir formation in patients with more severe course of disease and more intensive and long-term steroid therapy

Long-Term Results of Medical and Surgical Methods for Elimination of the Internal Anal Sphincter Spasm in Chronic Anal Fissure (NCT03855046)

Aim: evaluation of long-term results of injection of botulinum toxin type A into the internal anal sphincter and performing lateral internal sphincterotomy in combination with excision of chronic anal fissure.Materials and methods. The study included 176 patients (73 (41.5 %) men and 103 (58.5 %) women) older than 18 years; randomization into the compared groups was carried out by random number generation in a computer program. Patients, researchers and surgeons were not blinded. Patients of the main group underwent fissure excision in combination with relaxation of the internal anal sphincter by botulinum toxin type A (BTA) at a dosage of 40 units, patients of the control group underwent lateral internal sphincterotomy (LIS) with excision of chronic anal fissure. Long-term results of complex treatment were studied in 126 patients (54 (43 %) men and 72 (57 %) women), the median follow-up was 12.3 (12.2; 15.7) months. Statistical analysis was carried out in the program Statistica 13.3 (TIBCO Software Inc., USA).Results. In the long-term postoperative period, the indicators of mean resting anal pressure were lower in the LIS group (p = 0.04). The compared groups were comparable in terms of the level mean squeeze anal pressure (p = 0.69); however, in patients of the BTA group, the level of this indicator increased over time (p = 0.001). None of the patients of the compared groups had anal incontinence and relapse of the disease.Discussion. In the framework of the performed study, in some patients from the compared groups, spasm of the internal anal sphincter persisted throughout the observation period, and in some patients it occurred again, while no signs of relapse fissure were detected. The functional and clinical results of treatment obtained by us cast doubt on the exclusivity of the increased tone of the internal anal sphincter as the main link in the pathogenesis of chronic anal fissure in some patients and indicates the presence of other factors in combination with which the course of the disease is determined. The above facts do not exclude the possibility of recurrence of anal fissure in a more distant period of observation.Conclusion. Medical relaxation with botulinum toxin type A at a dosage of 40 units can serve as an alternative to lateral internal sphincterotomy as a method of eliminating spasm of the internal anal sphincte

Редкий случай цистаденомы семенного пузырька у больного раком поперечной ободочной кишки

Primary tumors of the seminal vesicles (SVs) are uncommon in the routine practice of urologists. Their diagnosis is complicated by an absence of early signs of the disease. Therefore, usually SVs tumors are detected accidentally during instrumental examinations. Primary tumors of the SVs can be benign. In the Medline, PubMed, and Google Scholar databases we have found 25 descriptions of clinical cases of cystadenomas of the SVs, while in Russian medical literature no publications on the topic can be found. The main diagnostic methods are contrast-enhanced computed tomography, magnetic resonance imaging, and fine needle biopsy. Surgery scale varies from SV resection and vesiculec¬tomy to vesicle resection with prostatectomy and orthotopic neobladder reconstruction and lower anterior resection of the rectum. Considering that primary SV tumors are a rare pathology, there’s no consensus on the scale of surgical intervention.In view of the rarity of the disease and lack of its descriptions in Russian medical literature, we find it interesting to demonstrate a clinical observation of a patient with cystadenoma of the left SV.Первичные опухоли семенных пузырьков (СП) в рутинной практике врача-уролога встречаются редко. Их выявление крайне затруднительно в связи с отсутствием ранних признаков заболевания. Поэтому, как правило, образования СП являются случайной находкой при инструментальных методах исследования. Первичные поражения СП могут носить доброкачественный характер. В поисковых системах Medline, PubMed и Google Scholar нами были найдены описания 25 клинических случаев цистаденом СП, в то время как в отечественной литературе подобных публикаций не обнаружено. Основными диагностическими методами являются компьютерная томография с контрастированием, магнитно-резонансная томография и тонкоигольная биопсия. Объем операции варьирует от резекции СП и везикулэктомии до цистпростатвезикулэктомии с ортотопической деривацией мочи и низкой передней резекцией прямой кишки. В связи с тем, что первичное поражение СП является довольно редкой патологией, до сих пор нет единого мнения в отношении объема оперативного вмешательства.Ввиду редкости заболевания и отсутствия описания в отечественной литературе нам представляется интересным продемонстрировать клиническое наблюдение больного с цистаденомой левого СП

N2-H2 capacitively coupled radio-frequency discharges at low pressure. Part I. Experimental results: Effect of the H2 amount on electrons, positive ions and ammonia formation

The mixing of N2 with H2 leads to very different plasmas from pure N2 and H2 plasma discharges. Numerous issues are therefore raised involving the processes leading to ammonia (NH3) formation. The aim of this work is to better characterize capacitively-coupled radiofrequency plasma discharges in N2 with few percents of H2 (up to 5%), at low pressure (0.3-1 mbar) and low coupled power (3-13 W). Both experimental measurements and numerical simulations are performed. For clarity, we separated the results in two complementary parts. The actual one (first part), presents the details on the experimental measurements, while the second focuses on the simulation, a hybrid model combining a 2D fluid module and a 0D kinetic module. Electron density is measured by a resonant cavity method. It varies from 0.4 to 5 109 cm-3, corresponding to ionization degrees from 2 10-8 to 4 10-7. Ammonia density is quantified by combining IR absorption and mass spectrometry. It increases linearly with the amount of H2 (up to 3 1013 cm-3 at 5% H2). On the contrary, it is constant with pressure, which suggests the dominance of surface processes on the formation of ammonia. Positive ions are measured by mass spectrometry. Nitrogen-bearing ions are hydrogenated by the injection of H2, N2H+ being the major ion as soon as the amount of H2 is >1%. The increase of pressure leads to an increase of secondary ions formed by ion/radical-neutral collisions (ex: N2H+, NH4 +, H3 +), while an increase of the coupled power favours ions formed by direct ionization (ex: N2 +, NH3 +, H2 +).N. Carrasco acknowledges the financial support of the European Research Council (ERC Starting Grant PRIMCHEM, Grant agreement no. 636829). A. Chatain acknowledges ENS Paris-Saclay Doctoral Program. A. Chatain is grateful to Gilles Cartry and Thomas Gautier for fruitful discussions on the MS calibration. L.L. Alves acknowledges the financial support of the Portuguese Foundation for Science and Technology (FCT) through the project UID/FIS/50010/2019. L. Marques and M. J. Redondo acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2019