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Peening techniques are nowadays attracting more research attention due to their association with the extending of the service life and improving surface texture of engineering components. Ultrasonic pulsating water jet peening represents a new way of mechanical surface treatment. Accelerated water droplets via hammer effect cause small elastic-plastic deformations on the surface. This work deals with peening of aluminum alloy using an ultrasonic pulsating water jet, where periodically acting water droplets were used as the peening medium. The aim of the work was the feasibility study of the peening process and to observe the effects of pressure (p = 10, 20 and 30 MPa) and pattern trajectory (linear hatch and cross hatch). The peened surfaces were analyzed by the surface roughness profile parameters Ra and Rz and the microhardness along the peening axis into the material. Graphically processed results show a clear increase of measured values with increasing pressure (p = 10, 20 and 30 MPa), where the roughness values ranged from 1.89 µm to 4.11 µm, and the microhardness values ranged from 43.3 HV0.005 to 47 HV0.005, as compared to 40.3 HV0.005 obtained for the untreated sample. The achieved results indicate potential using of an ultrasonic pulsating water jet as a new method of surface treatment of metals. By controlled distribution of water droplets, it is possible to achieve a local distribution of surface roughness, and at the same time, strengthening of the subsurface layers in the material without thermal influence on the material. 相似文献
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Justus von Sonntag Igor Janovský Sergej Naumov Reiner Mehnert 《Macromolecular chemistry and physics.》2001,202(8):1355-1360
N‐Alkylmaleimide radical cations were generated by electron beam irradiation of the freon matrix containing the monomers at 77 K. Their transformations with increasing temperature were followed by EPR. The spectra were compared with quantum chemical calculations (density functional B3LYP, Gaussian 98 W). The N‐alkylmaleimide radical cations are found to initiate free radical polymerisation in all cases. 相似文献
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Brjánn Ljótsson Gerhard Andersson Erik Andersson Erik Hedman Perjohan Lindfors Sergej Andréewitch Christian Rück Nils Lindefors 《BMC gastroenterology》2011,11(1):1-13
Background
A colonoscopy may frequently miss polyps and cancers. A number of techniques have emerged to improve visualization and to reduce the rate of adenoma miss.Methods
We conducted a randomized controlled trial (RCT) in two clinics of the Gastrointestinal Department of the Sanitas University Foundation in Bogota, Colombia. Eligible adult patients presenting for screening or diagnostic elective colonoscopy were randomlsy allocated to undergo conventional colonoscopy or narrow-band imaging (NBI) during instrument withdrawal by three experienced endoscopists. For the systematic review, studies were identified from the Cochrane Library, PUBMED and LILACS and assessed using the Cochrane risk of bias tool.Results
We enrolled a total of 482 patients (62.5% female), with a mean age of 58.33 years (SD 12.91); 241 into the intervention (NBI) colonoscopy and 241 into the conventional colonoscopy group. Most patients presented for diagnostic colonoscopy (75.3%). The overall rate of polyp detection was significantly higher in the conventional group compared to the NBI group (RR 0.75, 95%CI 0.60 to 0.96). However, no significant differences were found in the mean number of polyps (MD -0.1; 95%CI -0.25 to 0.05), and the mean number of adenomas (MD 0.04 95%CI -0.09 to 0.17). Meta-analysis of studies (regardless of indication) did not find any significant differences in the mean number of polyps (5 RCT, 2479 participants; WMD -0.07 95% CI -0.21 to 0.07; I2 68%), the mean number of adenomas (8 RCT, 3517 participants; WMD -0.08 95% CI -0.17; 0.01 to I2 62%) and the rate of patients with at least one adenoma (8 RCT, 3512 participants, RR 0.96 95% CI 0.88 to 1,04;I2 0%).Conclusion
NBI does not improve detection of colorectal polyps when compared to conventional colonoscopy (Australian New Zealand Clinical Trials Registry ACTRN12610000456055). 相似文献126.
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Kamila Peterová Hana Brožová Jiří Klempíř Irena Lišková Ondřej Bezdicek Petr Ridzoň Manuela Vaněčková Sergej Zakharov Daniela Pelclová Michal Miovský Evžen Růžička 《Basic & clinical pharmacology & toxicology》2018,122(1):176-182
Neurological sequelae including gait impairment were reported in survivors after methanol intoxication; however, no systematic study has been published so far. We aimed to analyse gait and balance impairment in a group of Czech methanol poisoning survivors. We examined 43 patients (age 46 ± 13 years) 2–8 months after methanol poisoning and 43 healthy controls. Investigations contained a shortened version of Falls Efficacy Scale (FES), clinical tests of gait and balance including Timed Up and Go test (TUG) and gait analysis using GaitRite® system, neurological and neuropsychological examination, brain imaging, EMG and tests of alcohol consumption. Nineteen patients admitted balance and gait impairment according to FES. Mild to moderate parkinsonian signs showed seven patients. Patients were slower (8.8 versus 5.7 s, p < 0.001) and performed more steps (11.1 versus 7.9, p < 0.001) in TUG compared with the controls. Gait analysis revealed shorter step length (76.5 versus 88.7 cm, p < 0.001), increased double support phase (18.8 versus 15.5%, p < 0.001) and wider base of support (11.3 versus 9.6 cm, p = 0.006) in patients. Eleven patients had deficit of executive function and performed higher cadence compared to the patients with normal execution (122.7 versus 115.0 step/min., p = 0.025). Lower limb polyneuropathy was verified in nine patients, without relation with gait or balance parameters. Neuroimaging revealed lesions mainly in the basal ganglia. Methanol poisoning survivors presented slower wide‐based gait with shortened steps corresponding with frontal gait disorder. Higher stepping cadence associated with executive deficit supported the evidence of frontal lobe dysfunction related to impairment of basal ganglia and connections in frontal cortico‐basal ganglia loops. 相似文献
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Calcium Signalling in Mouse Bergmann Glial Cells Mediated by α1 -adrenoreceptors and H1 Histamine - Receptors 总被引:1,自引:0,他引:1
Sergej Kirischuk Sebastian Tuschick Alexej Verkhratsky Helmut Kettenmann 《The European journal of neuroscience》1996,8(6):1198-1208
The presence of adrenergic and histaminergic receptors in Bergmann glial cells from cerebellar slices from mice aged 20–25 days was determined using fura-2 Ca2+ microfluorimetry. To measure the cytoplasmic concentration of Ca2+ ([Ca2+]i), either individual cells were loaded with the Ca2+-sensitive probe fura-2 using the whole-cell patch-clamp technique or slices were incubated with a membrane-permeable form of the dye (fura-2/AM) and the microfluorimetric system was focused on individual cells. The monoamines adrenalin and noradrenalin (0.1-10 μM) and histamine (10-100 μM) triggered a transient increase in [Ca2+]i. The involvement of the α1-adrenoreceptor was inferred from the observations that monoamine-triggered [Ca2+]i responses were blocked by the selective α1-adreno-antagonist prazosin and were mimicked by the α1-adreno-agonist phenylephrine. The monoamine-induced [Ca2+]i signals were not affected by β- and α2-adrenoreceptor antagonists (propranolol and yohimbine), and were not mimicked by β- and α2-adrenoreceptor agonists (isoproterenol and clonidine). Histamine-induced [Ca2+]i responses demonstrated specific sensitivity to only H1 histamine receptor modulators. [Ca2+]i responses to monoamines and histamine did not require the presence of extracellular Ca2+ and they were blocked by preincubation of slices with thapsigargin (500 nM), indicating that the [Ca2+]i increase is due to release from intracellular pools. No [Ca2+]i responses were recorded after application of aspartate, bradykinin, dopamine, GABA, glycine, oxytocin, serotonin, somatostatin, substance P, taurine or vasopressin. We conclude that cerebellar Bergmann glial cells are endowed with α1 -adrenoreceptors and H1 histamine receptors which induce the generation of intracellular [Ca2+]i signals via activation of Ca2+ release from inositol-l,4,5-trisphosphate-sensitive intracellular stores. 相似文献
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