Bearings coefficients effects on chaotic and bifurcation behavior of flexible rotor systems subjected to rub-impact

This study investigates the influence of end-support conditions on the chaotic and bifurcation behavior of a rotating flexible shaft-disk system. The system is modeled as a continuous shaft with a rigid disk in its mid span whilst supported by multi-coefficients bearings. Both Coriolis and centrifugal effects due to shaft flexibility are included. The partial differential equations of motion are extracted using the Rayleigh beam theory and the assumed mode method is used to discretize them in order to be solved numerically. The analytical tools used in this work include time series, phase plane portrait, power spectrum, Poincaré map, bifurcation diagrams, and Lyapunov exponents. The main objective of the present study is to investigate the effects of end-supports stiffness and damping coefficients on the chaotic vibration behavior of a rotating system. Periodic, sub-harmonic, quasi-periodic, and chaotic states have been observed for each case. As demonstrated, inclusion of the bearing effects can primarily change the speed ratios at which rub-impact occurs. The principal and cross-coupling stiffness and damping coefficients have quite different effects in the chaotic behavior of the system

Electrospun Nano-fibers for biomedical and tissue engineering applications: A comprehensive review

Pharmaceutical nano-fibers have attracted widespread attention fromresearchers for reasons such as adaptability of the electro-spinning process and ease of production. As a flexible method for fabricating nano-fibers, electro-spinning is extensively used. An electro-spinning unit is composed of a pump or syringe, a high voltage current supplier, a metal plate collector and a spinneret. Optimization of the attained nano-fibers is undertaken through manipulation of the variables of the process and formulation, including concentration, viscosity, molecular mass, and physical phenomenon, as well as the environmental parameters including temperature and humidity. The nano-fibers achieved by electro-spinning can be utilized for drug loading. The mixing of two or more medicines can be performed via electro-spinning. Facilitation or inhibition of the burst release of a drug can be achieved by the use of the electro-spinning approach. This potential is anticipated to facilitate progression in applications of drug release modification and tissue engineering (TE). The present review aims to focus on electro-spinning, optimization parameters, pharmacological applications, biological characteristics, and in vivo analyses of the electro-spun nano-fibers. Furthermore, current developments and upcoming investigation directions are outlined for the advancement of electro-spun nano-fibers for TE. Moreover, the possible applications, complications and future developments of these nano-fibers are summarized in detail. © 2020 by the authors

The effect of deep cryogenic treatment on hardness and wear behavior of the H13 tool steel

In recent decades, cryogenic treatment has been used as the finishing operation between the quenching andtempering treatment on tool steels for the purpose of increasing hardness and wear resistance. H13 tool steel is ahot working steel widely used in manufacturing molds and hot working tools. In this research, the effect of deepcryogenic treatment at -196 °C for 24 hours has been investigated in comparison with the quenching-temperingtreatment on hardness, structure and wear resistance. In addition, the effect of TiC coating after cryogenictreatment on hardness and wear resistance has been studied. The results of this research showed that cryogenictreatment with or without coating leads to an increase in hardness levels of 5.7 % and 9.6 %, respectively, andan improvement in the wear resistance levels of 33 % and 60 % respectively, in comparison with the quenchingtemperingtreatments. Investigating the wear surfaces by scanning electron microscopy (SEM) showed that thewear mechanism is adhesive

Modified Amplitude of Gravitational Waves Spectrum

The spectrum of thermal gravitational waves is obtained by including the high frequency thermal gravitons created from extra-dimensional effect and is a new feature of the spectrum. The amplitude and spectral energy density of gravitational waves in thermal vacuum state are found enhanced. The amplitude of the waves get modified in the frequency range (10$^{-16}$ -10 $^{8}$ Hz) but the corresponding spectral energy density is less than the upper bound of various estimated results. With the addition of higher frequency thermal waves, the obtained spectral energy density of the wave in thermal vacuum state does not exceed the upper bound put by nucleosynthesis rate. The existence of cosmologically originated thermal gravitational waves due to extra dimension is not ruled out.Comment: 18 pages, 4 figures, to appear in Classical and Quantum Gravity. arXiv admin note: text overlap with arXiv:astro-ph/0503162, arXiv:astro-ph/0501329 by other author

Associations of vitamin D binding protein variants with the vitamin D-induced increase in serum 25-hydroxyvitamin D

Background: Vitamin D deficiency is a global problem that may be improved by vitamin D supplementation; however, the individual's response to the intervention varies. We aimed to investigate possible genetic factors that may modify the impact of environmental exposure on vitamin D status. The candidate gene variant we investigated was the Gc gene-rs4588 polymorphism at the vitamin D receptor (DBP) locus. Methods: A total of 619 healthy adolescent Iranian girls received 50000 IU of vitamin D3 weekly for 9 weeks. Serum 25(OH) D concentrations, metabolic profiles and dietary intake were measured at baseline and after 9 weeks of supplementation. The genotypes of the DBP variant (rs4588) were analyzed using the TaqMan genotyping assay. Results: Our results revealed that the rs4588 polymorphism might be associated with serum 25-hydroxy vitamin D both at baseline (p value=0.03) and after intervention (p value=0.008). It seemed that the outcome of the intervention was gene-related so that the subjects with common AA genotype were a better responder to vitamin D supplementation (Changes (%) 469.5(427.1) in AA carriers vs. 335.8(530) in GG holders), and carriers of the less common GG genotype experienced a rise in blood glucose after 9 weeks (Changes (%) 0 (1.5)). Our findings also showed that the statistical interaction between this variant and supplementation was statistically significant (intervention effect p-value<0.001 and p-value SNP effect=0.03). The regression model also revealed that after adjusted for potential confounders, likelihood of affecting serum 25(OH)D in individuals who were homozygous for the uncommon allele G was less than those homozygous for the more common AA genotype (OR=4.407 (1.82-8.89); p=0.001). Conclusion: Serum vitamin 25(OH) D following vitamin 25(OH) D3 supplementation appears to be modified by genetic background. The Gc genetic variant, rs4588 encoding the vitamin D receptor seems to influence the response to vitamin D supplementation. Key words: Total 25(OH) D, Supplementation, Gc gene, rs4588

Association between the rs2241883 polymorphism of the fatty acid-binding protein-1 (FABP1) gene and obesity in a population of MASHAD study cohort

Funding Information: We would like to thank Mashhad University of Medical Sciences Research Council for their financial supports.Peer reviewedPublisher PD

Acute toxicity, brine shrimp cytotoxicity and relaxant activity of fruits of callistemon citrinus curtis

<p>Abstract</p> <p>Background</p> <p><it>Callistemon citrinus </it>Curtis belongs to family Myrtaceae that has a great medicinal importance. In our previous work, fruits of <it>Callistemon citrinus </it>were reported to have relaxant (antispasmodic) activity. The current work describes the screening of fractions of the crude methanol extract for tracing spasmolytic constituents so that it shall help us for isolation of bioactive compounds. Acute toxicity and brine shrimp cytotoxicity of crude methanol extract are also performed to standardize it.</p> <p>Methods</p> <p>The crude methanol extract was obtained by maceration with distilled water (500 ml) three times and fractionated successively with <it>n-</it>hexane, chloroform, ethyl acetate and <it>n-</it>butanol (300 ml of each solvent). Phytochemical analysis for crude methanol extract was performed. Acute toxicity studies were performed in mice. Brine shrimp cytotoxicity studies were performed to determine its cytotoxicity and standardize it. In other series of experiments, rabbits' jejunum preparations were used in screening for possible relaxant activities of various fractions. They were applied in concentrations of 0.01, 0.03, 0.1, 0.3, 1.0, 3.0, 5.0 and 10.0 mg/ml on spontaneous rabbits' jejunum preparations. In similar fashion, fractions were also tested on KCl (80 mM) -induced contractions. Calcium chloride curves were constructed in K-rich Tyrode's solution. The effects of various fractions were tested on calcium chloride curves at concentrations 1.0, 3.0, 5.0 and 10.0 mg/ml. Curves of verapamil used as reference drug at concentration 0.1 μM and 0.3 μM were also constructed. The curves were compared with their respective controls for possible right shift.</p> <p>Results</p> <p>Methanol extract tested strongly positive for saponins and tannins. However, it tested mild positive for presence of proteins, amino acids, carbohydrates and phenolic compounds. LD₅₀value for crude methanol extract is 476.25 ± 10.3 (470-481, n = 4) mg/ml. Similarly, EC₅₀value for brine shrimp cytotoxicity is 65.5 ± 7.28 (60.8- 69.4, n = 4) mg/ml. All the fractions relaxed the spontaneous and KCl-induced contractions. EC₅₀values (mg/ml) for effects of ethyl acetate fraction on spontaneous and KCl induced contractions are 2.62 ± 0.78 (2.15-3.0, n = 4) and 3.72 ± 0.86 (3.38-4.28, n = 4) respectively. Respective EC₅₀values (mg/ml) for <it>n-</it>butanol fraction are 3.59 ± 0.2(3.07-3.9, n = 4) for spontaneous, and 5.57 ± 0.2 (5.07-6.11, n = 4) for KCl- induced contractions. EC₅₀value for control calcium chloride curve (without extract) is -2.73 ± 0.19 (-2.6 - -2.81, n = 4) while EC₅₀for curves treated with 5.0 mg/ml of chloroform is -2.22 ± 0.02 (-2.16 - -2.3, n = 4). EC₅₀value for ethyl acetate treated (1.0 mg/ml) tissues is -1.95 ± 0.10 (-1.88 - -2.0, n = 4) <it>vs</it>. control EC₅₀= -2.71 ± 0.08 (-2.66 - -2.76, n = 4). All the fractions, except <it>n-</it>hexane, showed a right shift like that of verapamil (EC₅₀= -1.72 ± 0.15 (-1.62 - -1.8, n = 4) vs. Control EC₅₀= -2.41 ± 0.06 (-2.38 - - 2.44, n = 4), a standard drug that blocks voltage operated calcium channels.</p> <p>Conclusion</p> <p>Relaxant constituents were more concentrated in ethylacetate fraction followed by chloroform, <it>n -</it>butanol and aqueous fractions that warrant for its isolation. The crude methanol extract is safe at concentration 250 mg/ml or below and results of brine shrimp cytotoxicity assay imply the plant specie may be a source of cytotoxic agents.</p

Serum levels of selenium and smoking habits at age 50 influence long term prostate cancer risk; a 34 year ULSAM follow-up

Background: Serum selenium level (s-Se) has been associated with prostate cancer (PrCa) risk. We investigated the relation between s-Se, smoking and non-screening detected PrCa and explored if polymorphisms in two DNA repair genes: OGG1 and MnSOD, influenced any effect of s-Se. Methods: ULSAM, a population based Swedish male cohort (n = 2322) investigated at age 50 for s-Se and s-Se influencing factors: serum cholesterol, erythrocyte sedimentation rate and smoking habits. At age 71 a subcohort, (n = 1005) was genotyped for OGG1 and MnSOD polymorphisms. Results: In a 34-year-follow-up, national registries identified 208 PrCa cases further confirmed in medical records. Participants with s-Se in the upper tertile had a non-significantly lower risk of PrCa. Smokers with s-Se in the two lower tertiles (&lt;= 80 mu g/L) experienced a higher cumulative incidence of PrCa than smokers in the high selenium tertile (Hazard Ratio 2.39; 95% CI: 1.09-5.25). A high tertile selenium level in combination with non-wt rs125701 of the OGG1 gene in combination with smoking status or rs4880 related variation of MnSOD gene appeared to protect from PrCa. Conclusions: S-Se levels and smoking habits influence long-term risk of PrCa. Smoking as a risk factor for PrCa in men with low s-Se is relevant to explore further. Exploratory analyses of variations in OGG1 and MnSOD genes indicate that hypotheses about patterns of exposure to selenium and smoking combined with data on genetic variation in genes involved in DNA repair can be valuable to pursue