On Estimating a Constant Stress Life Test Model Using Time-Censored Data from the Linear Failure Rate Distribution

In this paper, a constant stress partially accelerated life test model is considered and investigated using type-I censored data from the linear failure rate distribution. The maximum likelihood estimates (point and interval) of the distribution parameters and the acceleration factor are obtained. For accuracy reasons, the mean squared errors are calculated using different sizes of samples. For illustration, Monte Carlo simulation studies are presented.Предложена модель частично ускоренных испытаний на циклическую долговечность с постоянным напряжением с использованием данных, подвергнутых цензурированию типа I с линейным распределением скорости разрушения. Получены точечные и интервальные оценки максимального правдоподобия параметров распределения и коэффициента ускорения. С целью повышения точности прогнозов расчет среднеквадратических погрешностей осуществлялся для образцов разных размеров. Для иллюстрации работоспособности модели выполнено моделирование тестовых задач с использованием метода Монте-Карло.Запропоновано модель частково прискорених випробувань на циклічну довговічність з постійною напругою з використанням даних, які було піддано цензуруванню типу I із лінійним розподілом швидкості руйнування. Отримано точкові й інтервальні оцінки максимальної правдоподібності параметрів розподілу і коефіцієнта прискорення. Із метою підвищення точності прогнозів розрахунок середньоквадратичних похибок проводився для зразків різних розмірів. Для ілюстрації роботоздатності моделі виконано моделювання тестових задач із використанням методу Монте-Карло

Boric acid enhances in vivo Ehrlich ascites carcinoma cell proliferation in Swiss albino mice

Boric acid occurs in nature as the mineral sassolite.It is widely used in industrial, agricultural,and cosmetic applications, besides its traditional use in the health care system. Boric acid is fairly rapidly absorbed after its administration and appears to be rapidly distributed through the body water via passive diffusion.The influence of boric acid, a boron carrier, on Ehrlich ascites carcinoma (EAC) cell-bearing mice was investigated in view of its importance in the boron neutron capture therapy and the influence of boron on proliferation and progression of cancer cells mediated by proteoglycans and collagen. The present study included the evaluation of boric acid for the effects on total count and viability of EAC cells in addition to their non-protein sulfhydryls (NP-SH) and malondialdehyde (MDA) contents as parameters for conjugative detoxication potency and possible oxidative damage. The EAC cell-bearing animals were also observed for the effect on survival, body weight changes, and histopathological evaluation of the tumors grown at the site of inoculation. The treatment with boric acid significantly increased the total number of peritoneal EAC cells and their viability. A significant increase in the body weight was observed that dose-dependently reached plateau levels by 20 days of treatment. Conversely, a reduction in the duration of survival of these animals was evident with the same protocol. Boric acid treatment resulted in a decrease in NP-SH contents with a concomitant increase in MDA levels in EAC cells as revealed by the results of the biochemical analysis. These data are supported by our results on histopathological investigations, which apparently showed fast growth, in addition to several mitotic figures and mixed inflammatory reaction, after treatment with boric acid. It seems likely that a particular combination of properties of boric acid, rather than a single characteristic alone, will provide useful information on the use of this boron carrier in neutron capture therapy

Association between tocilizumab and emerging multidrug-resistant organisms in critically ill patients with COVID-19: A multicenter, retrospective cohort study

Background: Tocilizumab is an IgG1 class recombinant humanized monoclonal antibody that directly inhibits the IL-6 receptor. Several randomized clinical trials have evaluated its safety and efficacy in patients with coronavirus disease 2019 (COVID-19), and these studies demonstrate conflicting results. Our study aimed to determine the association between tocilizumab treatment and microbial isolation and emergence of multidrug-resistant bacteria in critically ill patients with COVID-19. Methods: A multicenter retrospective cohort study was conducted at two tertiary government hospitals in Saudi Arabia. All critically ill patients admitted to intensive care units with a positive COVID-19 PCR test between March 1 and December 31, 2020, who met study criteria were included. Patients who received tocilizumab were compared to those who did not receive it. Results: A total of 738 patients who met our inclusion criteria were included in the analysis. Of these, 262 (35.5%) received tocilizumab, and 476 (64.5%) were included in the control group. Patients who received tocilizumab had higher odds for microbial isolation (OR 1.34; 95% CI 0.91–1.94, p = 0.13); however, the difference was not statistically significant. Development of resistant organisms (OR 1.00; 95% CI 0.51–1.98, p = 0.99) or detection of carbapenem-resistant Enterobacteriaceae (CRE) (OR 0.67; 95% CI 0.29–1.54, p = 0.34) was not statistically significant between the two groups. Conclusions: Tocilizumab use in critically ill patients with COVID-19 is not associated with higher microbial isolation, the emergence of resistant organisms, or the detection of CRE organisms. © 2021, The Author(s).Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Production and Optimization of Xylanase and α-Amylase from Non-Saccharomyces Yeasts (Pichia membranifaciens)

The xylanolytic and amylolytic yeasts were qualitatively determined by Cong red xylan agar and soluble starch agar plates, respectively. The most xylanase and α-amylase inducible strain (AUN-02) was selected and identified using PCR amplification of 26S rRNA gene and sequence analysis. The comparison of the alignment results and phylogenetic analysis of the sequences of the isolated yeast to published rRNA gene sequences in GenBank, confirmed the identification of the isolate as Pichia membranifaciens. Xylanase and α-amylase production by isolated P. membranifaciens were investigated at different pH values (4-8), temperature degrees (20-45°C), incubation time (1-7 days) and various substrates.A higher production of xylanase (38.8 U/mL) and a-amylase (28.7 U/mL) was obtained after 4 days of fermentation of P. membranifaciens. Higher activity of xylanase (36.83 U/mL) and a-amylase (27.7 U/mL) was obtained in the fermentation of P. membranifaciens in a culture medium adjusted to pH 7.0. The optimum temperature showed maximum xylanase and a-amylase activity (42.6 and 32.5 units/mL, respectively) was estimated at 35 °C. The xylanase and a-amylase activities of P. membranifaciens were estimated and compared for the different substrates tested. The strain revealed 100% relative activity of xylanase and a-amylase on beechwood and potato starch, respectively. The affinity of enzymes towards substrate was estimated using Km values. The Km values of xylanase and α-amylase increased in the order of pH’s 7.0, 6.0 and 4.5 (0.85, 1.6 and 3.4 mg xylan/mL and 0.22, 0.43 and 2.8 mg starch/mL, respectively). the yeast P. membranifaciensis is suitable for produce neutral xylanase and α-amylase enzymes. So, it could be used as a promising strain for production of these enzymes in industrial field