Microstructural Evolution,Tensile Failure,Fatigue Behavior and Wear Properties of Al2O3 Reinforced Al2014 Alloy T6 Heat Treated Metal Composites

The paper focused on an experimental study on the microstructural, mechanical, and wear characteristics of 15 wt.% alumina (Al₂O₃) particulates with an average particle size of 20 µm, reinforced in Al2014 alloy matrix composite as-cast and heat-treated samples. The metal matrix composite (MMC)samples were produced via a novel two-stage stir-casting technique. The fabricated composite samples were subjected to evaluate hardness, tensile strength, fatigue behavior and wear properties for both as cast and T6 heat-treated test samples. The Al2014 alloy and Al2014-15 wt.% Al₂O₃ MMCs were in solution for 1 h at a temperature of 525 °C, quenched instantly in cold water, and then artificially aged for 10 h at a temperature of 175 °C. SEM and X-ray diffraction analyses were used to investigate the microstructure and dispersion of the reinforced Al₂O₃ particles in the composite and the base alloy Al2014. The obtained results indicated that the hardness, tensile and fatigue strength and wear resistance increased when an amount of Al₂O₃ particles was added, compared to the as-cast Al2014 alloy and it was observed that after subjecting the same composite samples to heat treatment, there was further enhancement in the mechanical and wear properties in the Al2014 matrix alloy and Al2014-15 wt.% Al₂O₃ composite samples.     

Prevalence and correlates of COVID-19 vaccine hesitancy among the elderly in Qatar: A cross-sectional study

Older individuals are more vulnerable to severe coronavirus disease 2019 and medical complications. Vaccination stands as an efficient and safe vanguard against infection. However, negative attitudes and perceptions pertaining to available vaccines might hinder community inoculation. The aim of this study was to assess vaccine hesitancy and its psychosocial determinants among the elderly in Qatar.We conducted a cross-sectional study between October 15 and November 15, 2020, using a composite online survey including the Vaccine Attitudes Examination Scale in addition to questions on sociodemographic correlates and the role of healthcare professionals.The vaccine hesitancy rate was 19.5%. The main reasons for willingness to vaccinate included understanding the nature of disease and role of vaccination, in addition to information provided by physicians. Fears mainly centered around vaccine safety. Vaccine hesitators were more likely to be non-Qatari and having received the influenza vaccine at least once. Gender, marital status, socioeconomic status, educational level, and having completed childhood vaccinations were not associated with vaccine hesitancy.Efforts should be directed toward raising awareness of vaccine efficacy and safety profiles. Physicians should additionally be educated about their pivotal role in advocating vaccine acceptance. We recommend reassessing vaccine hesitancy and its associated factors following a year of campaigning and vaccine administration to identify and target vulnerable groups.     

The in vivo antioxidant effectiveness of alpha-tocopherol in oxidative stress induced by sodium nitroprusside in rat red blood cells

Reactive oxygen species avidly reacts with nitric oxide (NO) producing cytotoxic reactive nitrogen species capable of nitrating proteins and damaging other molecules which leads to the reduction of erythrocyte deformability. The aim of this investigation was to assess the importance of alpha-tocopherol (Vit-E) in the total antioxidant status of the erythrocytes in sodium nitroprusside (SNP), a nitric oxide donor, induced oxidative stress and its relation to erythrocyte deformability. Male Swiss Albino rats were used in 4 groups, comprising of 10 animals in each group. The first group was the control, and the other groups were administered SNP (10 mg/kg, i.p.), Vit-E (10 mg/kg, i.p.) + SNP, and SNP + L-NAME (10 mg/kg, i.p.), respectively. Relative filtration rate (RFR), relative filtration time (RFT) and relative resistance (Rrel) were determined as the indexes of erythrocyte deformability. In addition, malondialdehyde (MDA, as an index of lipid peroxidation) and nitric oxide levels and the antioxidant activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) were also determined in the red blood cells of all groups revealing the oxidant-antioxidant activity. RFT and the Rrel of the erythrocytes of the SNP-treated rats increased significantly (p<0.05) whereas the RFR of the erythrocytes decreased (p<0.05) in comparison to all groups reflecting the impaired deformability. This reduction in RFR was prevented with both L-NAME or Vit-E incubation. Vit-E has also reduced the Rrel of the erythrocyte which reveals that it has improved the erythrocyte deformability. Lipid peroxidation was suppressed by Vit-E and L-NAME significantly, where the red blood cell deformability was improved. Furthermore, SOD and CAT activities were significantly stimulated with SNP treatment (p<0.05), where as GSH-Px remained unchanged. In the contrary, GSH-Px activity was triggered significantly by Vit-E administration, whereas the SOD and CAT activities were reduced (p<0.05). As a result, these data reveal that Vit-E improves the erythrocyte deformability in SNP-induced oxidative stress by its antioxidant effects on the lipid peroxidation and antioxidant enzyme activities.     

A novel construct of an electrochemical acetylcholinesterase biosensor for the investigation of malathion sensitivity to three different insect species using a NiCr2O4/g-C3N4 composite integrated pencil graphite electrode

Herein, an electrochemical biosensor has been prepared to assess the sensitivity of an organophosphate insecticide, malathion, to acetylcholinesterase (AChE) enzyme of three insects including Apis mellifera (honeybee), Tribolium castaneum (red flour beetle), and Zootermopsis nevadensis (dampwood termite). A composite of nickel chromite (NiCr₂O₄) and graphitic carbon nitride (g-C₃N₄) was prepared and characterized for its morphological, chemical and electrical properties. The NiCr₂O₄/g-C₃N₄ composite integrated pencil graphite electrodes were used to covalently immobilize insect AChE enzymes and amperometric response of bioelectrodes was determined through cyclic voltammetry. The prepared bioelectrodes exhibited high enzyme immobilization efficiency and electro-catalytic performance. The integrated bioelectrodes could efficiently detect malathion induced inhibition of insects'' AChEs. The linear ranges for malathion were found to be 0.1–1.6 μM, 1–40 nM and 2–100 nM, and LODs were 2 nM, 0.86 nM and 2.3 nM for A. mellifera, T. castaneum, and Z. nevadensis, respectively. Additionally, the biosensing platform developed using A. mellifera AChE was found highly sensitive and effective for malathion recoveries from spiked wheat flour samples with high recovery rates. Moreover, the proposed method was adequately reproducible and selective. The results revealed that A. mellifera AChE is less sensitive to inhibition by malathion as compared to T. castaneum, and Z. nevadensis AChE. The experimental results were validated through computational docking of malathion with insect AChEs and the results were in correspondence to experimental outcomes. The proposed method can be a plausible alternate to conventional analytical methods to assess the pesticide sensitivity and toxicity of various compounds against insect enzymes.

An innovative electrochemical assay has been established to determine pesticide sensitivity against acetylcholinesterase and possible toxicity against insects. The analytical efficiency of three common insect AChEs was determined through this method.     

Identification and comparison of insulin pharmacokinetics injected with a new 4‐mm needle vs 6‐ and 8‐mm needles accounting for endogenous insulin and C‐peptide secretion kinetics in non‐diabetic adult males

Aims/Introduction

Many patients with diabetes now use 5‐, 6‐ or 8‐mm needles for insulin injection. However, it is unclear whether needle length, particularly for shorter needles, affects the pharmacokinetic properties of insulin.

Materials and Methods

This was a three‐way, randomized, cross‐over, single‐center study involving 12 healthy Japanese adult males (age 27.4 ± 4.14 years; weight 64.2 ± 5.2 kg; body fat percentage 18.2 ± 1.5%). Participants received a subcutaneous (abdomen) dose of insulin lispro (1.5 U for participants weighing 55 to <65.0 kg; 2.0 U for participants weighing 65.0 to <80.0 kg) delivered using a 32‐G × 4 mm (32G × 4), 31‐G × 8 mm (31G × 8) or 32‐G × 6 mm (32G × 6) needle with a 3–7‐day washout between doses. Pharmacokinetic parameters of exogenous insulin were identified using non‐linear least squares, where the total insulin concentration was fit to the measured plasma insulin concentration using an overall combined model that accounted for C‐peptide/insulin secretion in addition to the injected dose.

Results

Maximum concentration and area under the curve for 0 to infinity min for insulin were bioequivalent for the 32G × 4 needle relative to the 32G × 6 and the 31G × 8 needles. The time to the maximum insulin concentration was bioequivalent for the 32G × 4 needle relative to the 32G × 6 needle, but not the 31G × 8 needle.

Conclusions

The use of 4‐mm needles is unlikely to change the pharmacokinetic properties of insulin when injected subcutaneously in adults. This trial was registered with UMIN‐CTR (no. UMIN000004469).     

Association between bone mineral density and lumbar disc degeneration

Objectives

Higher vertebral bone mineral density (BMD) has been found to be related with lumbar disc degeneration (LDD), while relationship between femoral neck BMD and LDD remains controversial. The aim of our research was to study the relationship between LDD and BMD of the lumbar spine and femoral neck.

Study design

The study population consisted of 168 postmenopausal women (aged 63.3–75.0 years, mean 68.6 years) from the prospective OSTPRE and OSTPRE-FPS study cohorts. The severity of LDD was graded from T2-weighted MRI images using the five-grade Pfirrmann classification. Four vertebral levels (L1-L4) were studied (total 672 discs). The association between lumbar BMD and Z-score and the severity of LDD was studied separately for each vertebral level with AN(C)OVA analysis, using potential confounders as covariates.

Results

Higher lumbar BMD and Z-score were associated with more severe LDD at all studied levels (L1-L4): between L4-L5 disc and L4 BMD (p = 0.044) and L4 Z-score (p = 0.052), between L2-L3 disc and L3 BMD (p = 0.001) and at all other levels (p < 0.001). The mean degeneration grade of the studied discs was associated with the mean L1-L4 BMD and Z-score (p < 0.001). Statistical significance of any result did not alter after controlling for confounding factors. There was no significant association between femoral neck BMD and LDD.

Conclusions

Higher lumbar BMD/Z-score were associated with more severe LDD. There was no significant association between femoral neck BMD and disc degeneration. Femoral neck BMD may be a more reliable measurement for diagnosing osteoporosis in postmenopausal women with degenerative changes in the lumbar spine.     

Mortality‐risk‐based apnea–hypopnea index thresholds for diagnostics of obstructive sleep apnea

The severity of obstructive sleep apnea is clinically assessed mainly using the apnea–hypopnea index. Based on the apnea–hypopnea index, patients are classified into four severity groups: non‐obstructive sleep apnea (apnea–hypopnea index < 5); mild (5 ≤ apnea–hypopnea index < 15); moderate (15 ≤ apnea–hypopnea index < 30); and severe obstructive sleep apnea (apnea–hypopnea index ≥ 30). However, these thresholds lack solid clinical and scientific evidence. We hypothesize that the current apnea–hypopnea index thresholds are not optimal despite their global use, and aim to assess this clinical shortcoming by optimizing the thresholds with respect to the risk of all‐cause mortality. We analysed ambulatory polygraphic recordings of 1,783 patients with suspected obstructive sleep apnea (mean follow‐up 18.3 years). We simulated 79,079 different threshold combinations in 100 randomized subgroups of the population and studied the relative risk of all‐cause mortality corresponding to each combination and randomization. The optimal thresholds were chosen according to three criteria: (a) the hazard ratios increase linearly between severity groups towards more severe obstructive sleep apnea; (b) each group includes at least 15% of the study population; (c) group sizes decrease with increasing obstructive sleep apnea severity. The risk of all‐cause mortality varied greatly across simulations; the threshold defining non‐obstructive sleep apnea group having the largest effect on the hazard ratios. The apnea–hypopnea index threshold combination of 3‐9‐24 was optimal in most of the subgroups. In conclusion, the assessment of obstructive sleep apnea severity based on the current apnea–hypopnea index thresholds is not optimal. Our novel approach provides methods for optimizing apnea–hypopnea index‐based severity classification, and the revised thresholds better differentiate patients into severity groups, ensuring that an increase in the severity corresponds to an increase in the risk of all‐cause mortality.     

Treatment of antiviral‐resistant recurrent erythema multiforme with dapsone

Recurrent erythema multiforme (REM) is a chronic disease characterized by frequent episodes of target cutaneous lesions in an acral distribution. Conventional treatment includes systemic corticosteroids and antiviral therapy. The aim of this study was to evaluate dapsone as a potential steroid sparing‐agent for the treatment of REM after a failed trial of at least one antiviral therapy (acyclovir, famciclovir, or valacyclovir). A retrospective chart review was conducted on thirteen patients with a diagnosis of REM who underwent treatment with dapsone after failing at least one antiviral therapy. Out of 13 patients, 6 showed complete response (CR) and 5 showed partial response (PR). The underlying cause was identified in 5 patients with all showing at least PR. Adverse effects, observed in 4 patients, included fatigue, macrocytic anemia, anxiety, insomnia and involuntary movements, and drug‐induced lupus erythematosus. A continuous course of dapsone, titrated up from 25 mg/day to a dose at which clinical improvement is seen with acceptable patient tolerance, is a viable steroid sparing‐agent for REM treatment after a failed trial of antiviral therapy.