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Ti–6Al–4V reticulated meshes with different elements (cubic, G7 and rhombic dodecahedron) in Materialise software were fabricated by additive manufacturing using the electron beam ...melting (EBM) method, and the effects of cell shape on the mechanical properties of these samples were studied. The results showed that these cellular structures with porosities of 88–58% had compressive strength and elastic modulus in the range 10–300MPa and 0.5–15GPa, respectively. The compressive strength and deformation behavior of these meshes were determined by the coupling of the buckling and bending deformation of struts. Meshes that were dominated by buckling deformation showed relatively high collapse strength and were prone to exhibit brittle characteristics in their stress–strain curves. For meshes dominated by bending deformation, the elastic deformation corresponded well to the Gibson–Ashby model. By enhancing the effect of bending deformation, the stress–strain curve characteristics can change from brittle to ductile (the smooth plateau area). Therefore, Ti–6Al–4V cellular solids with high strength, low modulus and desirable deformation behavior could be fabricated through the cell shape design using the EBM technique.
Objective: Increased plasma dehydroepiandrosterone (DHEA) and dehydroepiandrosterone‐sulfate (DHEAS) have been demonstrated in post‐traumatic stress disorder (PTSD), but the documented beneficial ...effects of these steroids in enhancing mood and cognition, as well as neuroprotection, suggest their presence in PTSD may be associated with defensive rather than maladaptive effects.
Method: We, therefore, examined plasma DHEA, DHEAS, cortisol, and the DHEA/cortisol ratio in 40 male veterans with or without PTSD, and determined their relationships to PTSD symptom severity and symptom improvement.
Results: The PTSD group showed significantly higher plasma DHEA and non‐significantly higher DHEAS levels as well as a significantly lower cortisol/DHEA ratio, controlling for age. Regression analyses demonstrated that DHEA and DHEAS levels could be predicted by symptom improvement and coping, whereas the cortisol/DHEA ratio was predicted by severity of childhood trauma and current symptom severity.
Conclusion: That greater symptom improvement was related to DHEA levels may suggest for a role for these hormones in modulating recovery from PTSD.
Recently it has been proposed that information in working memory (WM) may not always be stored in persistent neuronal activity but can be maintained in 'activity-silent' hidden states, such as ...synaptic efficacies endowed with short-term synaptic plasticity. To test this idea computationally, we investigated recurrent neural network models trained to perform several WM-dependent tasks, in which WM representation emerges from learning and is not a priori assumed to depend on self-sustained persistent activity. We found that short-term synaptic plasticity can support the short-term maintenance of information, provided that the memory delay period is sufficiently short. However, in tasks that require actively manipulating information, persistent activity naturally emerges from learning, and the amount of persistent activity scales with the degree of manipulation required. These results shed insight into the current debate on WM encoding and suggest that persistent activity can vary markedly between short-term memory tasks with different cognitive demands.
We investigate polarization-dependent ultrafast photocurrents in the Weyl semimetal TaAs using terahertz (THz) emission spectroscopy. Our results reveal that highly directional, transient ...photocurrents are generated along the noncentrosymmetric c axis regardless of incident light polarization, while helicity-dependent photocurrents are excited within the ab plane. This is consistent with earlier static photocurrent experiments, and demonstrates on the basis of both the physical constraints imposed by symmetry and the temporal dynamics intrinsic to current generation and decay that optically induced photocurrents in TaAs are inherent to the underlying crystal symmetry of the transition metal monopnictide family of Weyl semimetals.
This paper presents a numerical study based on the discrete element method (DEM) to investigate the transverse mixing of wet particles in a rotating drum. The effects of the liquid surface tension, ...the drum rotation speed and the filling level on particle mixing were investigated. The results showed that particles had quick mixing in the transverse plane and the well mixed states were achieved within a few revolutions. The Lacey mixing index showed an exponential increase with mixing time. The presence of the capillary force in general reduced mixing performance. However, the mixing of dry particles was poorest at 64% filling level compared with other filling levels, and increasing cohesion at that level actually improved particle mixing. The analysis of particle movements indicated that particle mixing was dominated by the particle circulation period, which is the time required for a particle to complete one circulation in the drum, and its standard deviation. A model was proposed to estimate the circulation periods at different streamlines which were comparable with the simulation results, thus providing a general method to predict mixing performance in the transverse plane.
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► Transverse mixing of wet particles in rotating drums is investigated. ► Interparticle cohesion in general reduces mixing performance. ► Dry particles have the poorest mixing performance at 64% filling level. ► Particle mixing is affected by particle circulation period and its variance. ► A mathematical model is developed to predict mixing performance.
Prefrontal cortex (PFC) mediates an assortment of cognitive functions including working memory, behavioral flexibility, attention, and future planning. Unlike the hippocampus, where induction of ...synaptic plasticity in the network is well-documented in relation to long-term memory, cognitive functions mediated by the PFC have been thought to be independent of long-lasting neuronal adaptation of the network. Nonetheless, accumulating evidence suggests that prefrontal cortical neurons possess the cellular machinery of synaptic plasticity and exhibit lasting changes of neural activity associated with various cognitive processes. Moreover, deficits in the mechanisms of synaptic plasticity induction in the PFC might be involved in the pathophysiology of psychiatric and neurological disorders such as schizophrenia, drug addiction, mood disorders, and Alzheimer's disease.
Copolymer films of poly(4-vinylpyridine-co-ethylene glycol diacrylate) (p(4-VP-co-EGDA)) were synthesized and first deposited on various substrates via initiated chemical vapor deposition (iCVD). ...As-deposited copolymer films were converted to surface zwitterionic structures containing poly(carboxybetaine acrylic acetate) (pCBAA) units by a quaternization reaction with 3-bromopropionic acid (3-BPA). Conversion to a zwitterionic structure was confirmed by FTIR and high-resolution XPS N1s scans. Biopolymer adsorption of the deposited copolymer coatings was investigated by quartz crystal microbalance with dissipation (QCM-D) using a model foulant‐bovin serum albumin (BSA). The optimized copolymer films were then deposited onto commercial RO membranes and with subsequent zwitterionicalization. Inertness to bacterial adhesion of the modified membranes was investigated by counting the number of Escherichia coli and Pseudomonas aeruginosa cells attached on the membrane surface under static conditions. Bacterial adhesion studies revealed an almost 98% reduction in micro-organism attachment onto the surface of modified membranes compared to bare membranes, which clearly demonstrates the effectiveness and superior performance of the zwitterionic coating against bacterial adhesion. The salt rejection performance of the modified membranes resulted in improved salt rejection (98%); however, permeate flux was slightly compromised compared to virgin membranes. AFM analysis demonstrated that modified membranes showed lower RMS roughness compared to virgin membranes.
•Surface modification of commercial RO desalination membranes•p(4VP-co-EGDA) co-polymerization via initiated chemical vapor deposition•Functionalization of the co-polymer to carboxybetaine zwitterion surface moieties•Significant reduction of bacterial cell attachment on modified membrane surface•Perm selectivity under cross flow conditions comparable to virgin membranes
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