scholarly journals Sliding Wear Performance of AlCrN Coating on TiB2/Ti Composites at High Temperatures

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6771
Author(s):  
Remigiusz Michalczewski ◽  
Marek Kalbarczyk ◽  
Zbigniew Słomka ◽  
Edyta Osuch-Słomka ◽  
Maciej Łuszcz ◽  
...  

The aim of the study was to investigate effect of Ti/TiB2 composite composition and manufacturing technology parameters on the tribological behaviour of AlCrN coating-composite system. The AlCrN coating was deposited by PVD (Physical Vapour Deposition) method. The composites were manufactured by spark plasma sintering (SPS) from three variants of powders mixtures: Ti with TiB2, Ti6Al4V with TiB2 as well as Ti with B, using (five) different sintering temperatures. For each of the developed coating-composite systems, the wear resistance was evaluated using ball-on-disc SRV tester, at six temperatures (from room temperature up to 900 °C). The results confirmed that high-temperature wear resistance of the coating–substrate combination depends on Ti/TiB2 composite composition and manufacturing technology parameters. In the case of uncoated composite, two processes manage the wear at high temperatures: cracking propagation and surface oxidation. The presence of AlCrN coating on the composite surface protects the surface against deep cracking and surface oxidation. The composites of Group I, sintered at 1250 °C from a mixture of pure Ti and TiB2 (50/50 wt.% ratio) as well as Group III, sintered at 1350 °C from a mixture of pure Ti and B allow the achievement of a satisfactory surface quality, a high adhesion of the PVD coating and moderate wear at high temperatures. However, the composite made of pure Ti and B seems to be a better solution for temperatures exceeding 600 °C.

2021 ◽  
Vol 111 (2) ◽  
Author(s):  
Yakup Alpay ◽  
Timur Yildirim ◽  
Deniz Akbulut ◽  
Mustafa Cukurlu ◽  
Suheyla Esra Ozkocer ◽  
...  

Background In the Ponseti technique, the residual equinus deformity is corrected with percutaneous tenotomy. This experimental study aimed to compare the safety and effectiveness of a large-gauge needle, a corneal knife, and a No. 11 blade in percutaneous achillotomy performed in rats. Methods Ninety Achilles tendons of 45 Sprague-Dawley rats were analyzed, following division into three study groups. In the study, group I (needle), group II (corneal knife), and group III (No. 11 blade) were compared on the basis of bleeding, incision length, requirement for primary suture, range of motion, and resulting neurovascular injury at day 0. Moreover, the groups were compared in terms of range of motion, macroscopic and microscopic adhesions, and tenocyte morphology at days 21 and 42 postoperatively. Results On day 0, one suture was required in group III, whereas in groups I and II, no sutures were required. Postoperative bleeding was greater in group III and similar in groups I and II. Neurovascular injury was not observed in any of the groups. Three incomplete tenotomies were observed in group III and one incomplete tenotomy was observed in group II. Importantly, all tenotomies were complete in group I. In all groups, the range of motion was similar. The macroscopic adhesion score revealed high adhesion in group III (P = .009). According to Tang's criteria, microscopic adhesion was significantly higher on day 21 in group III compared with the other groups (P <0.001). No significant differences were observed in tenocyte morphology based on the Bonar criteria (P = .850). Conclusions In the results obtained from this animal study, we observed less bleeding, less adhesion, and less incomplete tenotomy in the large-gauge needle and corneal knife groups compared with the No. 11 blade group during the percutaneous Achilles tenotomy performed in rats.


Author(s):  
K.K. SEKHRI ◽  
C.S. ALEXANDER ◽  
H.T. NAGASAWA

C57BL male mice (Jackson Lab., Bar Harbor, Maine) weighing about 18 gms were randomly divided into three groups: group I was fed sweetened liquid alcohol diet (modified Schenkl) in which 36% of the calories were derived from alcohol; group II was maintained on a similar diet but alcohol was isocalorically substituted by sucrose; group III was fed regular mouse chow ad lib for five months. Liver and heart tissues were fixed in 2.5% cacodylate buffered glutaraldehyde, post-fixed in 2% osmium tetroxide and embedded in Epon-araldite.


Author(s):  
Anton Bózner ◽  
Mikuláš Gažo ◽  
Jozef Dostál

It is anticipated that Japanese quail /Coturnix coturnix japonica/ will provide animal proteins in long term space flights. Consequently this species of birds is of research interest of international space program INTERCOSMOS. In the year 1987 we reported on an experiment /2/ in which the effect of chronic acceleration of 2 G hypergravitation, the hypodynamy and the simultaneous effect of chronic acceleration and the location in the centre of the turntable of the centrifuge on the protein fractions in skeletal muscles was studied. The ultrastructure of the heart muscle was now in this experiments examined as well.Japanese quail cockerels, aged 48 days were exposed to 2 G hypergravitation /group IV/ in a 6,4 m diameter centrifuge, to hypodynamy /group III/ and their combination /group V/, respectively for 6 days / Fig.1/. The hypodynamy in group III was achieved by suspending the birds in jackets without contact the floor. The group II was located in the centre ofthe turntable of the centrifuge. The control group I. was kept under normal conditions. The quantitative ultrastructure of myocard was evaluated by the methods of Weibel/3/ - this enables to determine the number, relative size and volume of mitochondria volume of single mitochondria, defficiency of mitochondrial cristae and volume of myofibrils.


1998 ◽  
Vol 80 (09) ◽  
pp. 393-398 ◽  
Author(s):  
V. Regnault ◽  
E. Hachulla ◽  
L. Darnige ◽  
B. Roussel ◽  
J. C. Bensa ◽  
...  

SummaryMost anticardiolipin antibodies (ACA) associated with antiphospholipid syndrome (APS) are directed against epitopes expressed on β2-glycoprotein I (β2GPI). Despite a good correlation between standard ACA assays and those using purified human β2GPI as the sole antigen, some sera from APS patients only react in the latter. This is indicative of heterogeneity in anti-β2GPI antibodies. To characterize their reactivity profiles, human and bovine β2GPI were immobilized on γ-irradiated plates (β2GPI-ELISA), plain polystyrene precoated with increasing cardiolipin concentrations (CL/β2GPI-ELISA), and affinity columns. Fluid-phase inhibition experiments were also carried out with both proteins. Of 56 selected sera, restricted recognition of bovine or human β2GPI occurred respectively in 10/29 IgA-positive and 9/22 IgM-positive samples, and most of the latter (8/9) were missed by the standard ACA assay, as expected from a previous study. Based on species specificity and ACA results, IgG-positive samples (53/56) were categorized into three groups: antibodies reactive to bovine β2GPI only (group I) or to bovine and human β2GPI, group II being ACA-negative, and group III being ACA-positive. The most important group, group III (n = 33) was characterized by (i) binding when β2GPI was immobilized on γ-irradiated polystyrene or cardiolipin at sufficient concentration (regardless of β2GPI density, as assessed using 125I-β2GPI); (ii) and low avidity binding to fluid-phase β2GPI (Kd in the range 10–5 M). In contrast, all six group II samples showed (i) ability to bind human and bovine β2GPI immobilized on non-irradiated plates; (ii) concentration-dependent blockade of binding by cardiolipin, suggesting epitope location in the vicinity of the phospholipid binding site on native β2GPI; (iii) and relative avidities approximately 100-fold higher than in group III. Group I patients were heterogeneous with respect to CL/β2GPI-ELISA and ACA results (6/14 scored negative), possibly reflecting antibody differences in terms of avidity and epitope specificity. Affinity fractionation of 23 sera showed the existence, in individual patients, of various combinations of antibody subsets solely reactive to human or bovine β2GPI, together with cross-species reactive subsets present in all samples with dual reactivity namely groups III and II, although the latter antibodies were poorly purified on either column. Therefore, the mode of presentation of β2GPI greatly influences its recognition by anti-β2GPI antibodies with marked inter-individual heterogeneity, in relation to ACA quantitation and, possibly, disease presentation and pathogenesis.


Author(s):  
Ahmed Mousa ◽  
Ossama M. Zakaria ◽  
Mai A. Elkalla ◽  
Lotfy A. Abdelsattar ◽  
Hamad Al-Game'a

AbstractThis study was aimed to evaluate different management modalities for peripheral vascular trauma in children, with the aid of the Mangled Extremity Severity Score (MESS). A single-center retrospective analysis took place between 2010 and 2017 at University Hospitals, having emergencies and critical care centers. Different types of vascular repair were adopted by skillful vascular experts and highly trained pediatric surgeons. Patients were divided into three different age groups. Group I included those children between 5 and 10 years; group II involved pediatrics between 11 and 15 years; while children between 16 and 21 years participated in group III. We recruited 183 children with peripheral vascular injuries. They were 87% males and 13% females, with the mean age of 14.72 ± 04. Arteriorrhaphy was performed in 32%; end-to-end anastomosis and natural vein graft were adopted in 40.5 and 49%, respectively. On the other hand, 10.5% underwent bypass surgery. The age groups I and II are highly susceptible to penetrating trauma (p = 0.001), while patients with an extreme age (i.e., group III) are more susceptible to blunt injury (p = 0.001). The MESS has a significant correlation to both age groups I and II (p = 0.001). Vein patch angioplasty and end-to-end primary repair should be adopted as the main treatment options for the repair of extremity vascular injuries in children. Moreover, other treatment modalities, such as repair with autologous vein graft/bypass surgery, may be adopted whenever possible. They are cost-effective, reliable, and simple techniques with fewer postoperative complication, especially in poor/limited resources.


2015 ◽  
Vol 18 (3) ◽  
pp. 098
Author(s):  
Cem Arıtürk ◽  
Serpil Ustalar Özgen ◽  
Behiç Danışan ◽  
Hasan Karabulut ◽  
Fevzi Toraman

<p class="p1"><span class="s1"><strong>Background:</strong> The inspiratory oxygen fraction (FiO<sub>2</sub>) is usually set between 60% and 100% during conventional extracorporeal circulation (ECC). However, this strategy causes partial oxygen pressure (PaO<sub>2</sub>) to reach hyperoxemic levels (&gt;180 mmHg). During anesthetic management of cardiothoracic surgery it is important to keep PaO<sub>2</sub> levels between 80-180 mmHg. The aim of this study was to assess whether adjusting FiO<sub>2</sub> levels in accordance with body temperature and body surface area (BSA) during ECC is an effective method for maintaining normoxemic PaO<sub>2</sub> during cardiac surgery.</span></p><p class="p1"><span class="s1"><strong>Methods:</strong> After approval from the Ethics Committee of the University of Acıbadem, informed consent was given from 60 patients. FiO<sub>2</sub> adjustment strategies applied to the patients in the groups were as follows: FiO<sub>2</sub> levels were set as 0.21 × BSA during hypothermia and 0.21 × BSA + 10 during rewarming in Group I; 0.18 × BSA during hypothermia and 0.18 × BSA + 15 during rewarming in Group II; and 0.18 × BSA during hypothermia and variable with body temperature during rewarming in Group III. Arterial blood gas values and hemodynamic parameters were recorded before ECC (T1); at the 10th minute of cross clamp (T2); when the esophageal temperature (OT) reached 34°C (T3); when OT reached 36°C (T4); and just before the cessation of ECC (T5).</span></p><p class="p1"><span class="s1"><strong>Results:</strong> Mean PaO<sub>2</sub> was significantly higher in Group I than in Group II at T2 and T3 (<em>P</em> = .0001 and <em>P</em> = .0001, respectively); in Group I than in Group III at T1 (<em>P</em> = .02); and in Group II than in Group III at T2, T3, and T4 <br /> (<em>P</em> = .0001 for all). </span></p><p class="p1"><span class="s1"><strong>Conclusion: </strong>Adjustment of FiO<sub>2</sub> according to BSA rather than keeping it at a constant level is more appropriate for keeping PaO<sub>2</sub> between safe level limits. However, since oxygen consumption of cells vary with body temperature, it would be appropriate to set FiO<sub>2</sub> levels in concordance with the body temperature in the <br /> rewarming period.</span></p>


2016 ◽  
pp. 108-111
Author(s):  
T.F. Tatarchuk ◽  
◽  
D.G. German ◽  

The article presents the comparative analysis of the state of the cervix in women with endometrial polyps and micropolyps. Patients and methods. The study involved 130 patients aged 18-35 years: 70 patients with endometrial polyps (group I), 30 patients with micropolyps (group II) and 30 patients of the control group (group III). Results. According to the anamnesis of women in the I group were significantly more frequent diseases of the cervix, which corrected physical surgery methods, in particular cryodestruction. In group II, the representatives of these indicators were similar to healthy. Normal colposcopic picture met significantly less frequently in patients and I, and II group. The differences in the incidence of HPV high oncogenic risk in all groups were not statistically significant. Conclusion. Destructive methods used in the detection of any changes in the cervix are often overly aggressive, form scars and contributing to inflamaciones process. In the chain of events leading to the formation of PE, cervical pathology and its correction can take the basic place. Key words: endometrial polyp, micropolyps, chronic endometritis, uterine cervix, colposcopy.


Author(s):  
Г.В. ШИРЯЕВ ◽  
Ю.Г. ТУРЛОВА ◽  
Г.С. НИКИТИН

Изучено влияние кормовой добавки в форме индивидуальных болюсов Метраболь на возможность снижения негативного влияния субклинического кетоза (СКК) и результативность искусственного осеменения высокопродуктивных молочных коров в посттранзитный период. Животные были подобраны по принципу условных аналогов и разделены на 3 группы в зависимости от концентрации β-оксимасляной кислоты в их крови. В I группе (n=18) у коров не было СКК, концентрация кислоты составляла <1,0 ммоль/л, во II группе (n=21) у животных зарегистрирован СКК, концентрация кислоты — 1,0…1,4 ммоль/л. С целью поиска решения по снижению негативного влияния СКК на репродуктивные показатели была сформирована III группа коров, переболевших СКК (n=24) с концентрацией β-оксимасляной кислоты в крови 1,0…1,4 ммоль/л, но с использованием болюсов, применяемых для ускоренного восстановления репродуктивной функции коров после отела. Важной составляющей опыта явилось то, что к моменту гормональной синхронизации у коров всех 3 групп фиксировалось отсутствие СКК (снижение β-оксимасляной кислоты до уровня <1,0 ммоль/л). Для синхронизации полового цикла выбрана схема Пресинх-овсинх. Установлено, что гормональная синхронизация животных, перенесших СКК, в сравнении со здоровыми, не позволяет снизить негативное влияние данного нарушения обмена веществ. Во II группе у животных зафиксированы самые низкие репродуктивные показатели (количество использованных доз; индекс осеменения, сервис-период; время от первого до успешного осеменения; результат первичного осеменения; количество животных, осемененных 3 и более раз). В III группе применение болюсов позволило, в сравнении с животными II группы, не только избежать отрицательного воздействия СКК, но и превзойти по изучаемым параметрам животных из I группы. The effect of the feed additive in the form of individual boluses Metrabol on the possibility of reducing the negative effect of subclinical ketosis (CCK) and the effectiveness of artificial insemination of highly productive dairy cows in the post-transit period was studied. The animals were selected according to the principle of conditional analogs and divided into 3 groups depending on the concentration of β-hydroxybutyric acid in their blood. In group I (n=18), the cows did not have SSC, the acid concentration was <1.0 mmol/L, in group II (n=21), SSC was registered in animals — 1.0...1.4 mmol / L. In order to find a solution to reduce the negative effect of CCB on reproductive indices, a group III of cows was formed who had CCB (n = 24) with a concentration of β-hydroxybutyric acid in their blood of 1.0...1.4 mmol/L, but using boluses, used to accelerate the restoration of the reproductive function of cows after calving. An important component of the experiment was that by the time of hormonal synchronization, cows of all 3 groups had no SSC (decrease in β-hydroxybutyric acid to a level of <1.0 mmol/L). To synchronize the sexual cycle, the Pressinh-ovsinh scheme was chosen. It was found that hormonal synchronization of animals that underwent SSC, in comparison with healthy ones, does not allow reducing the negative effect of this metabolic disorder. In group II, animals had the lowest reproductive indices (number of doses used; insemination index, service period; time from first to successful insemination; result of primary insemination; number of animals inseminated 3 or more times). In group III, the use of boluses made it possible, in comparison with animals of group II, not only to avoid the negative effect of SSC, but also to surpass the animals from group I in terms of the studied parameters.


Author(s):  
J. P. Lakher ◽  
M. K. Awasthi ◽  
J. R. Khan ◽  
M. R. Poyam

The present study was conducted to investigate the efficacy of Ovsynch and Ovsynch plus protocol in postpartum (day 60) Sahiwal cows (n=18). Animals were randomly divided into three equal groups, viz., Ovsynch group Ovsynch plus group and Control group. Animals of group I (n = 6) were treated with traditional Ovsynch protocol. The animals (n = 6) of group II were treated with Ovsynch plus protocol which consisted of an initial intramuscular injection of eCG (Folligon) @ 250 IU on day 60 postpartum followed 3 days later by GPG (Ovsynch) protocol. In group-III Control, no treatment was given to animals (n = 6). Treated animals were inseminated at a fixed time between 14 and 20 hrs after second GnRH injection, irrespective of estrus detection. Blood samples were collected from each animal on days 50 and 60 postpartum to determine the status of cyclicity in animals based on serum concentrations of progesterone (P4). A third blood sample was collected on the day of prostaglandin treatment to determine the response of first GnRH injection. Four animals each were cyclic, and two were acyclic in both treatment groups. Four animals each responded to first GnRH treatment in both treatment groups. Similarly, two animals each got conceived giving conception rate of 50% (2/4) in each treatment. In the control group, one out of 6 animals got conceived yielding 16.66 % conception rate (1/6) during the study period. It may be thus concluded that Ovsynch and Ovsynch plus protocol may be used during the early postpartum period to improve the reproductive efficiency in postpartum Sahiwal cows.


Author(s):  
M. M. Chaudhary ◽  
C. T. Khasatiya ◽  
S. B. Patel ◽  
S. S. Chaudhary ◽  
V. B. Atara ◽  
...  

The serum progesterone and estradiol profiles during synchronization of estrus by buck effect and PGF2α treatments were monitored in Surti does. Total eighteen non-pregnant does selected were evenly divided into 3 groups, 6 does in each group. The does of Group I were teased with a sexuallyactive- apronized buck; and those of Group II were treated with PGF2α, i.e., Inj. Lutalyse® @ 7.5 mg/doe IM twice 11 days apart, while the Group III served as untreated control. Blood samples were collected from all the animals on day 0 (before 1st PGF2α injection), 3rd day (during treatment), 11th day (before 2nd PGF2α injection), 14th day (after treatment) and 40th day (post-service) by jugular vein puncture. The serum separated was stored at -20°C till further analysis. In all the three groups, 83.33% does, conceived at first service in the sampling cycle. The overall mean serum progesterone concentration of Group I does (5.82±0.72 ng/ml) was significantly higher (p less than 0.01) as compared to Group II (2.93±0.38 ng/ml) and III (2.88±0.30 ng/ml). Similarly, the overall mean serum progesterone concentration of Surti does on day 0 (2.65±0.46 ng/ml), 3rd (2.56±0.80 ng/ml), 11th (4.45±0.84 ng/ml) and 14th (3.40±0.63 ng/ml) did not differ significantly, but the overall mean level at day 40 (6.31±0.45 ng/ml) was significantly (p less than 0.01) higher, because most of animals became pregnant at that time. The overall mean serum oestradiol-17β levels of Group I (24.40±2.98 pg/ ml) was significantly higher (p less than 0.01) than in Group II (15.77±1.77 pg/ml) and III (12.21±1.45 pg/ ml). On the other hand, the overall mean serum oestradiol-17β levels of Surti does on day 0 (12.89±1.21 pg/ml), 3rd (15.84±1.74 pg/ml), 11th (14.81±1.96 pg/ml), 14th (22.15±2.97 pg/ml) and 40th (21.64±5.16 pg/ml) did not differ significantly (p>0.05) and the slightly higher overall mean level found at 40th day might be the influence of the non-pregnant does at first service in the cumulative animals. The hormonal profile reflected the initiation of cyclicity and establishment of pregnancy in treated and control animals.


Sign in / Sign up

Export Citation Format

Share Document