Effects of Inter-Layer Time Interval on Temperature Gradients in Direct Laser Deposited Ti-6Al-4V

Parts fabricated via additive manufacturing (AM) methods are prone to experiencing high temperature gradients during manufacture resulting in internal residual stress formation. In the current study, a numerical model for predicting the temperature distribution and residual stress in Directed Energy Deposited (DED) Ti–6Al–4V parts is utilized for determining a relationship between local part temperature gradients with generated residual stress. Effects of time-interval between successive layer deposits, as well as layer deposition itself, on the temperature gradient vector for the first and each layer is investigated. The numerical model is validated using thermographic measurements of Ti-6Al-4V specimens fabricated via Laser Engineered Net Shaping® (LENS), a blown-powder/laser-based DED method. Results demonstrate the heterogeneity in the part’s spatiotemporal temperature field, and support the fact that as the part number, or single part size or geometry, vary, the resultant residual stress due to temperature gradients will be impacted. As the time inter-layer time interval increases from 0 to 10 second, the temperature gradient magnitude in vicinity of the melt pool will increase slightly.Mechanical Engineerin

Data related to cyclic deformation and fatigue behavior of direct laser deposited Ti–6Al–4V with and without heat treatment

AbstractData is presented describing the strain-controlled, fully-reversed uniaxial cyclic deformation and fatigue behavior of Ti–6Al–4V specimens additively manufactured via Laser Engineered Net Shaping (LENS) – a Direct Laser Deposition (DLD) process. The data was collected by performing multiple fatigue tests on specimens with various microstructural states/conditions, i.e. in their ‘as-built’, annealed (below the beta transus temperature), or heat treated (above the beta transus temperature) condition. Such data aids in characterizing the mechanical integrity and fatigue resistance of DLD parts. Data presented herein also allows for elucidating the strong microstructure coupling of the fatigue behavior of DLD Ti–6Al–4V, as the data trends were found to vary with material condition (i.e. as-built, annealed or heat treated) [1]. This data is of interest to the additive manufacturing and fatigue scientific communities, as well as the aerospace and biomedical industries, since additively-manufactured parts cannot be reliably deployed for public use, until their mechanical properties are understood with high certainty

Estimating the Effects of Part Size on Direct Laser Deposition Parameter Selection via a Thermal Resistance Network Approach

A mathematical model for heat transfer during the Directed Energy Deposition (DED) process is proposed. The model employs the thermal resistance network analogy and is developed to aid one in predicting part size effects on its temperature distribution during manufacture, and in how to compensate such effects via suitable process parameter selection. The model predicts a pseudo steady-state temperature response in the melt pool. The temperature variation along the heat affected zone of a thin-walled part is estimated while assuming deposition is occurring far from the substrate. Predicted melt pool and bulk part temperatures are validated against Laser Engineering Net Shaping (LENSTM) experimental data obtained via a dual-wavelength pyrometer and in-chamber infrared camera, respectively. Results demonstrate that the model may be used to predict an average melt pool temperature. Bulk, calculated temperature distribution needs to be further investigated to find a more suitable heat transfer coefficient surrounding the part.Mechanical Engineerin

Multi-Objective Process Optimization of Additive Manufacturing: A Case Study on Geometry Accuracy Optimization

Despite recent research efforts improving Additive Manufacturing (AM) systems, quality and reliability of AM built products remains as a challenge. There is a critical need to achieve process parameters optimizing multiple mechanical properties or geometry accuracy measures simultaneously. The challenge is that the optimal value of various objectives may not be achieved concurrently. Most of the existing studies aimed to obtain the optimal process parameters for each objective individually, resulting in duplicate experiments and high costs. In this study we investigated multiple geometry accuracy measures of parts fabricated by Fused Filament Fabrication (FFF) system. An integrated framework for systematically designing experiments is proposed to achieve multiple sets of FFF process parameters resulting in optimal geometry integrity. The proposed method is validated using a real world case study. The results show that optimal properties are achieved in a more efficient manner compared with existing methods.Mechanical Engineerin

Characterization of lung fibroblasts more than two decades after mustard gas exposure

Purpose: In patients with short-term exposure to the sulfur mustard gas, the delayed cellular effects on lungs have not been well understood yet. The lung pathology shows a dominant feature consistent with obliterative bronchiolitis, in which fibroblasts play a central role. This study aims to characterize alterations to lung fibroblasts, at the cellular level, in patients with delayed respiratory complications after short-term exposure to the sulfur mustard gas. Methods: Fibroblasts were isolated from the transbronchial biopsies of patients with documented history of exposure to single high-dose sulfur mustard during 1985-7 and compared with the fibroblasts of control subjects. Results: Compared with controls, patients' fibroblasts were thinner and shorter, and showed a higher population doubling level, migration capacity and number of filopodia. Sulfur mustard decreased the in vitro viability of fibroblasts and increased their sensitivity to induction of apoptosis, but did not change the rate of spontaneous apoptosis. In addition, higher expression of alpha smooth muscle actin showed that the lung's microenvironment in these patients is permissive for myofibroblastic differentiation. Conclusions: These findings suggest that in patients under the study, the delayed pulmonary complications of sulfur mustard should be considered as a unique pathology, which might need a specific management by manipulation of cellular components. © 2015 Pirzad Jahromi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Protection of hippocampal CA1 neurons against ischemia/Reperfusion injury by exercise preconditioning via modulation of Bax/Bcl-2 ratio and prevention of Caspase-3 Activation

Introduction: Ischemia leads to loss of neurons by apoptosis in specific brain regions, especially in the hippocampus. The purpose of this study was investigating the effects of exercise preconditioning on expression of Bax, Bcl-2, and caspase-3 proteins in hippocampal CA1 neurons after induction of cerebral ischemia. Methods: Male rats weighing 260-300 g were randomly allocated into three groups (sham, exercise, and ischemia). The rats in exercise group were trained to run on atreadmill 5 days a week for 4 weeks. Ischemia was induced by the occlusion of both common carotid arteries (CCAs) for 20 min. Levels of expression of Bax, Bcl-2, and caspase-3 proteins in CA1 area of hippocampus were determined by immunohistochemical staining . Results: The number of active caspase-3-positive neurons in CA1 area were significantly increased in ischemia group, compared to sham-operated group (P<0.001), and exercise preconditioning significantly reduced the ischemia/reperfusion-induced caspase-3 activation, compared to the ischemia group (P<0.05). Also, results indicated a significant increase in Bax/Bcl-2 ratio in ischemia group, compared to sham-operated group (P<0.001). Discussion: This study indicated that exercise has a neuroprotective effects against cerebral ischemia when used as preconditioning stimuli

PVDF membrane for oil-in-water separation via cross-flow ultrafiltration process

The objective of this study is to investigate the potential of ultrafiltration polyvinylidene fluoride (PVDF)-titanium dioxide (TiO2) membrane for oil-in-water separator. PVDF polymeric matrix membrane is excellent in term of chemical and thermal stabilities, which make it very promising to be used as a membrane matrix for water separation. However, poor hydrophilic property of the PVDF has led to the severe fouling during operation. Thus, current work was performed to investigate the effect of incorporation of two additives i.e. polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) in PVDF-TiO2 membrane, which fabricated using dry/wet phase inversion technique. Membranes characterizations were performed using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), contact angle and UV-vis spectrophotometer. Accordingly, modified PVDF membrane possessed good hydrophilicity property when the additives were added into PVDF-TiO2 membrane matrix. In term of filtration performance, the experimental results showed that oil rejection using PVDF-TiO2/PVP membrane were ~99.7%, which met the requirement for discharge. On the other hand, PVDF-TiO2/PEG membrane was shown more enhancement in terms of permeate flux by given over 64 (L/m2h) at pressure of 2 bar gauge

Dual EZH2 and EHMT2 histone methyltransferase inhibition increases biological efficacy in breast cancer cells

Background: Many cancers show aberrant silencing of gene expression and overexpression of histone methyltransferases. The histone methyltransferases (HKMT) EZH2 and EHMT2 maintain the repressive chromatin histone methylation marks H3K27me and H3K9me, respectively, which are associated with transcriptional silencing. Although selective HKMT inhibitors reduce levels of individual repressive marks, removal of H3K27me3 by specific EZH2 inhibitors, for instance, may not be sufficient for inducing the expression of genes with multiple repressive marks. Results: We report that gene expression and inhibition of triple negative breast cancer cell growth (MDA-MB-231) are markedly increased when targeting both EZH2 and EHMT2, either by siRNA knockdown or pharmacological inhibition, rather than either enzyme independently. Indeed, expression of certain genes is only induced upon dual inhibition. We sought to identify compounds which showed evidence of dual EZH2 and EHMT2 inhibition. Using a cell-based assay, based on the substrate competitive EHMT2 inhibitor BIX01294, we have identified proof-of-concept compounds that induce re-expression of a subset of genes consistent with dual HKMT inhibition. Chromatin immunoprecipitation verified a decrease in silencing marks and an increase in permissive marks at the promoter and transcription start site of re-expressed genes, while Western analysis showed reduction in global levels of H3K27me3 and H3K9me3. The compounds inhibit growth in a panel of breast cancer and lymphoma cell lines with low to sub-micromolar IC50s. Biochemically, the compounds are substrate competitive inhibitors against both EZH2 and EHMT1/2. Conclusions: We have demonstrated that dual inhibition of EZH2 and EHMT2 is more effective at eliciting biological responses of gene transcription and cancer cell growth inhibition compared to inhibition of single HKMTs, and we report the first dual EZH2-EHMT1/2 substrate competitive inhibitors that are functional in cells

Barriers to Family Caregivers’ Coping With Patients With Severe Mental Illness in Iran

The broad spectrum of problems caused by caring for a patient with mental illness imposes a high burden on family caregivers. This can affect how they cope with their mentally ill family members. Identifying caregivers’ experiences of barriers to coping is necessary to develop a program to help them overcome these challenges. This qualitative content analysis study explored barriers impeding family caregivers’ ability to cope with their relatives diagnosed with severe mental illness (defined here as schizophrenia, schizoaffective disorders, and bipolar affective disorders). Sixteen family caregivers were recruited using purposive sampling and interviewed using a semi-structured in-depth interview method. Data were analyzed by a conventional content analytic approach. Findings consisted of four major categories: the patient’s isolation from everyday life, incomplete recovery, lack of support by the mental health care system, and stigmatization. Findings highlight the necessity of providing support for caregivers by the mental health care delivery service system.The study was supported by Grant TBZMED·REC.5825 from the deputy of research in Tabriz University of Medical Sciences

The Effects of Cognitive Therapy versus ‘No Intervention’ for Major Depressive Disorder

BACKGROUND: Major depressive disorder afflicts an estimated 17% of individuals during their lifetimes at tremendous suffering and costs. Cognitive therapy may be an effective treatment option for major depressive disorder, but the effects have only had limited assessment in systematic reviews. METHODS/PRINCIPAL FINDINGS: We used The Cochrane systematic review methodology with meta-analyses and trial sequential analyses of randomized trials comparing the effects of cognitive therapy versus 'no intervention' for major depressive disorder. Participants had to be older than 17 years with a primary diagnosis of major depressive disorder to be eligible. Altogether, we included 12 trials randomizing a total of 669 participants. All 12 trials had high risk of bias. Meta-analysis on the Hamilton Rating Scale for Depression showed that cognitive therapy significantly reduced depressive symptoms (four trials; mean difference -3.05 (95% confidence interval (Cl), -5.23 to -0.87; P<0.006)) compared with 'no intervention'. Trial sequential analysis could not confirm this result. Meta-analysis on the Beck Depression Inventory showed that cognitive therapy significantly reduced depressive symptoms (eight trials; mean difference on -4.86 (95% CI -6.44 to -3.28; P = 0.00001)). Trial sequential analysis on these data confirmed the result. Only a few trials reported on 'no remission', suicide inclination, suicide attempts, suicides, and adverse events without significant differences between the compared intervention groups. DISCUSSION: Cognitive therapy might be an effective treatment for depression measured on Hamilton Rating Scale for Depression and Beck Depression Inventory, but these outcomes may be overestimated due to risks of systematic errors (bias) and random errors (play of chance). Furthermore, the effects of cognitive therapy on no remission, suicidality, adverse events, and quality of life are unclear. There is a need for randomized trials with low risk of bias, low risk of random errors, and longer follow-up assessing both benefits and harms with clinically relevant outcome measures