Secondary Creep Analysis of FG Rotating Cylinder with Exponential,Linear and Quadratic Volume Reinforcement

Creep is an irreversible time-dependent deformation in which a material under constant mechanical stress and elevated temperature for a considerably prolonged period of time, starts to undergo permanent deformation. Creep deformation occurs in three stages namely, primary, secondary and tertiary. Out of these three stages, secondary or steady state creep is particularly an area of engineering interest as it has almost a constant creep rate. Creep deformation plays a significant role in understanding effective service life of an engineering component working under high temperature conditions as such components such as super-heater and re-heater tubes and headers in a boiler, jet engines operating at temperature as high as 1200 ∘C, usually experience a failure or rupture due to creep phenomenon. Design engineers keep a close attention on working stress conditions and elevated temperature under which an engineering component is expected to work as these conditions determine the onset of creep behavior in an engineering component. By recognizing the parameters of material response to creep behavior, engineers can analyse the useful service life and hazardous working conditions for an engineering components. Recognizing the creep phenomenon as high temperature design limitation, ASME Boiler and Pressure Vessel Code have provided guidelines on maximum allowable stresses for materials to be used in creep range. One of the criteria for determination of allowable stresses is 1% creep deformation of material in 100,000 h of service. Thus, the study of creep behavior in engineering components pertaining to high stress and temperature working conditions is very important as it affects the reliability and performance of the engineering components. The aim of our study is to understand the behavior of secondary creep deformation so that an advanced reinforced functionally graded material with better creep resistance, can be designed. In this paper, a secondary creep analysis of functionally graded (FG) thick-walled rotating cylinder under internal and external pressure is conducted. The novelty of the model intends to specify secondary creep stresses and strains by employing exponential, linear and quadratic volume reinforcement for SiCp ceramic in Al metal matrix in radial direction. This will help us to understand the effect of volume reinforcement in FG cylinder under internal/external pressure and rotating centrifugal body force by obtaining secondary creep stresses and strains. The response of the FG cylinder with isotropic material is analyzed and the solution for stress–strain rates in radial and tangential directions are obtained in closed form. Comparison of steady state creep stresses and strains under exponential, linear and quadratic volume reinforcement profiles are discussed and presented graphically.     

Circulatory and hepatic failure at admission predicts mortality of severe scrub typhus patients: A prospective cohort study

Objective: To study the spectrum and outcome of severe scrub typhus in adult patients and to predict the hospital mortality by organ failure on admission.Methods: This was a prospective observational cohort study conducted between July 2017 and October 2020 at the medical emergency centre of PGIMER, Chandigarh, India. One hundred and twenty-six patients aged ≥13 years were diagnosed with scrub typhus. Severe disease was defined as the presence of organ failure based on the Sequential Organ Failure Assessment(SOFA) score on admission.Results: About two-thirds of the patients were from geographic regions outside the endemic sub-Himalayan belt. Fever(99.21%) and dyspnea(79.36%) were the most frequent complaints. Respiratory failure(81.75%) was the most common organ failure, followed by hepatic(52.38%), coagulative(47.62%), circulatory(33.33%), renal(21.43%), and cerebral dysfunction(13.49%). The median(Q1, Q3) SOFA score was 8(6, 9), and 48.41% of the patients had a quick-SOFA score ≥2. Organ supports with invasive ventilation(40.48%), vasopressors(36.51%), and renal replacement therapy(7.14%) were frequently required. The in-hospital mortality was 11.90% and was independently predicted by circulatory and hepatic failures on multivariate logistic regression(OR 11.12, 95% CI 1.73-71.31 and OR 8.49, 95% CI 1.18-61.41, respectively).Conclusions: Most patients had pulmonary dysfunction; circulatory or hepatic failure on admission strongly predicts death.     

A Comparative Evaluation of the Linear Dimensional Accuracy of Four Impression Techniques using Polyether Impression Material

There is much discussion in the dental literature regarding the superiority of one impression technique over the other using addition silicone impression material. However, there is inadequate information available on the accuracy of different impression techniques using polyether. The purpose of this study was to assess the linear dimensional accuracy of four impression techniques using polyether on a laboratory model that simulates clinical practice. The impression material used was Impregum Soft?, 3 M ESPE and the four impression techniques used were (1) Monophase impression technique using medium body impression material. (2) One step double mix impression technique using heavy body and light body impression materials simultaneously. (3) Two step double mix impression technique using a cellophane spacer (heavy body material used as a preliminary impression to create a wash space with a cellophane spacer, followed by the use of light body material). (4) Matrix impression using a matrix of polyether occlusal registration material. The matrix is loaded with heavy body material followed by a pick-up impression in medium body material. For each technique, thirty impressions were made of a stainless steel master model that contained three complete crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring eight dimensions (mesiodistal, faciolingual and inter-abutment) on stone dies poured from impressions of the master model. A two-tailed t test was carried out to test the significance in difference of the distances between the master model and the stone models. One way analysis of variance (ANOVA) was used for multiple group comparison followed by the Bonferroni’s test for pair wise comparison. The accuracy was tested at α = 0.05. In general, polyether impression material produced stone dies that were smaller except for the dies produced from the one step double mix impression technique. The ANOVA revealed a highly significant difference for each dimension measured (except for the inter-abutment distance between the first and the second die) between any two groups of stone models obtained from the four impression techniques. Pair wise comparison for each measurement did not reveal any significant difference (except for the faciolingual distance of the third die) between the casts produced using the two step double mix impression technique and the matrix impression system. The two step double mix impression technique produced stone dies that showed the least dimensional variation. During fabrication of a cast restoration, laboratory procedures should not only compensate for the cement thickness, but also for the increase or decrease in die dimensions.     

An Ixodes scapularis protein required for survival of Anaplasma phagocytophilum in tick salivary glands

Anaplasma phagocytophilum is the agent of human anaplasmosis, the second most common tick-borne illness in the United States. This pathogen, which is closely related to obligate intracellular organisms in the genera Rickettsia, Ehrlichia, and Anaplasma, persists in ticks and mammalian hosts; however, the mechanisms for survival in the arthropod are not known. We now show that A. phagocytophilum induces expression of the Ixodes scapularis salp16 gene in the arthropod salivary glands during vector engorgement. RNA interference-mediated silencing of salp16 gene expression interfered with the survival of A. phagocytophilum that entered ticks fed on A. phagocytophilum-infected mice. A. phagocytophilum migrated normally from A. phagocytophilum-infected mice to the gut of engorging salp16-deficient ticks, but up to 90% of the bacteria that entered the ticks were not able to successfully infect I. scapularis salivary glands. These data demonstrate the specific requirement of a pathogen for a tick salivary protein to persist within the arthropod and provide a paradigm for understanding how Rickettsia-like pathogens are maintained within vectors.     

Targeting the spliceosome in chronic lymphocytic leukemia with the macrolides FD-895 and pladienolide-B

RNA splicing plays a fundamental role in human biology. Its relevance in cancer is rapidly emerging as demonstrated by spliceosome mutations that determine the prognosis of patients with hematologic malignancies. We report studies using FD-895 and pladienolide-B in primary leukemia cells derived from patients with chronic lymphocytic leukemia and leukemia-lymphoma cell lines. We found that FD-895 and pladienolide-B induce an early pattern of mRNA intron retention – spliceosome modulation. This process was associated with apoptosis preferentially in cancer cells as compared to normal lymphocytes. The pro-apoptotic activity of these compounds was observed regardless of poor prognostic factors such as Del(17p), TP53 or SF3B1 mutations and was able to overcome the protective effect of culture conditions that resemble the tumor microenvironment. In addition, the activity of these compounds was observed not only in vitro but also in vivo using the A20 lymphoma murine model. Overall, these findings give evidence for the first time that spliceosome modulation is a valid target in chronic lymphocytic leukemia and provide an additional rationale for the development of spliceosome modulators for cancer therapy.     

A study of cytokines in tuberculous meningitis: Clinical and MRI correlation

There is paucity of studies on cytokines in tuberculous meningitis (TBM) and their relation with clinical and radiological changes; therefore this study was undertaken. 16 TBM patients diagnosed on the basis of clinical, CSF and radiological criteria were included. They were subjected to TNF-α, IL-6, IL-8, IL-10, IL-1β, and IL-12p70 estimation in CSF. The cytokine levels were also estimated in 10 controls. Initial clinical examination, stage of TBM and MRI findings (infarct, hydrocephalus, tuberculoma and exudates) were recorded. The patients were treated with 4 drugs antitubercular (RHZE) therapy and after 3 months clinical examination, cytokine levels, and radiological studies were repeated. Outcome was defined by Barthel index score at 3 months into poor, partial and complete recovery. The patient's age ranged between 10 and 50 years, 5 were females. At 3 months, all the patients were clinically followed up and 14 underwent repeat MRI. 10 patients improved, 1 remained stable and 5 deteriorated. There was worsening with respect to tuberculoma in 3, infarction in 2 and exudate in 1 patient. TNF-α was expressed in 32% patients, IL-6, IL-10, IL-1β and IL-8 were significantly expressed in patients and declined after 3 months following treatment. The cytokine levels did not correlate with stage of meningitis, outcome and radiological deterioration or improvement.     

Simple scheme for identification of common species of enterobacteriaceae

We propose a simple scheme for the identification of enterobacteriaceae species which routinely necessitates numerous biochemical tests and prolonged time span. In the scheme, family enterobacteriaceae is initially divided into four major groups depending on two important biochemical reactions viz. Lactose fermentation (L) and Methyl red test (MR). Each of the four groups, Group I (L + MR+), Group II (L + MR-), Group III (L- MR-), Group IV (L- MR+) can further be differentiated by using few tests. Eleven genera and 23 species can be identified by this scheme using limited biochemical tests. As many as 990 strains of enterobacteriaceae were subjected to standard biochemical tests and proposed simple scheme for identification. The discrepancy was observed only with 8 atypical strains of E. coli.