Semiconductors are the basis of many vital technologies such as electronics, computing, communications, optoelectronics, and sensing. Modern semiconductor technology can trace its origins to the ...invention of the point contact transistor in 1947. This demonstration paved the way for the development of discrete and integrated semiconductor devices and circuits that has helped to build a modern society where semiconductors are ubiquitous components of everyday life. A key property that determines the semiconductor electrical and optical properties is the bandgap. Beyond graphene, recently discovered two-dimensional (2D) materials possess semiconducting bandgaps ranging from the terahertz and mid-infrared in bilayer graphene and black phosphorus, visible in transition metal dichalcogenides, to the ultraviolet in hexagonal boron nitride. In particular, these 2D materials were demonstrated to exhibit highly tunable bandgaps, achieved via the control of layers number, heterostructuring, strain engineering, chemical doping, alloying, intercalation, substrate engineering, as well as an external electric field. We provide a review of the basic physical principles of these various techniques on the engineering of quasi-particle and optical bandgaps, their bandgap tunability, potentials and limitations in practical realization in future 2D device technologies.
We tested the hypothesis that administration of omega (o)-9, rn-3, and rn-6 to mice can prevent oxidative alterations responsible for behavioral and cognitive alterations related with aging. ...Twenty-eight-day- old mice received skim milk (SM group), SM enriched with omega oil mixture (EM group), or water (control group) for 10 and 14 months, equivalent to middle age. Mice were evaluated for behavioral alterations related to depression and memory and oxidative status brain levels of thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), and myeloperoxidase (MPO). The 10-month EM group increased immobility time during the forced swimming test compared with control, indicating increased stress response. The 14-month SM- and EM-treated groups increased sucrose consumption compared with control, showing an expanded motivational state. The 14-month SM group decreased the number of rearings compared with the 14- month control and EM groups. The number of entries and time spent in the central square of the open field was higher in the 10-month EM group than in the control, revealing an anxiolytic-like behavior. TBARS decreased in the hippocampus and striatum of the 10-month EM group compared with the control. A similar decrease was observed in the striatum of the 10-month SM group. GSH levels were higher in all 14-month treated groups compared with 10-month groups. MPO activity was higher in the 14- month EM group compared with the 14-month control and SM groups, revealing a possible pro-inflammatory status. In conclusion, omega oils induced conflicting alterations in middle-aged mice, contributing to enhanced behavior and anxiolytic and expanded motivational state, but also to increased stress response and pro-inflammatory alterations. Key words: Aging; Nutraceuticals; Omega 3 fatty acids; Omega 6 fatty acids; Omega 9 fatty acids; Oxidative stress markers
The incidence of malaria in the East African highlands has increased since the end of the 1970s. The role of climate change in the exacerbation of the disease has been controversial, and the specific ...influence of rising temperature (warming) has been highly debated following a previous study reporting no evidence to support a trend in temperature. We revisit this result using the same temperature data, now updated to the present from 1950 to 2002 for four high-altitude sites in East Africa where malaria has become a serious public health problem. With both nonparametric and parametric statistical analyses, we find evidence for a significant warming trend at all sites. To assess the biological significance of this trend, we drive a dynamical model for the population dynamics of the mosquito vector with the temperature time series and the corresponding detrended versions. This approach suggests that the observed temperature changes would be significantly amplified by the mosquito population dynamics with a difference in the biological response at least 1 order of magnitude larger than that in the environmental variable. Our results emphasize the importance of considering not just the statistical significance of climate trends but also their biological implications with dynamical models.
In tumors, somatic mutations of the PTEN suppressor gene are associated with advanced disease, chemotherapy resistance, and poor survival. PTEN loss of function may occur by inactivating mutation, by ...deletion, either affecting one copy (hemizygous loss) leading to reduced gene expression or loss of both copies (homozygous) with expression absent. Various murine models have shown that minor reductions in PTEN protein levels strongly influence tumorigenesis. Most PTEN biomarker assays dichotomize PTEN (i.e. presence vs. absence) ignoring the role of one copy loss. We performed a PTEN copy number analysis of 9793 TCGA cases from 30 different tumor types. There were 419 (4.28%) homozygous and 2484 (25.37%) hemizygous PTEN losses. Hemizygous deletions led to reduced PTEN gene expression, accompanied by increased levels of instability and aneuploidy across tumor genomes. Outcome analysis of the pan-cancer cohort showed that losing one copy of PTEN reduced survival to comparable levels as complete loss, and was associated with transcriptomic changes controlling immune response and the tumor microenvironment. Immune cell abundances were significantly altered for PTEN loss, with changes in head and neck, cervix, stomach, prostate, brain, and colon more evident in hemizygous loss tumors. These data suggest that reduced expression of PTEN in tumors with hemizygous loss leads to tumor progression and influences anticancer immune response pathways.
Borderline personality disorder (BPD) is a severe psychiatric condition that affects up to 2.7% of the population and is highly linked to functional impairment and suicide. Despite its severity, ...there is a lack of knowledge about its pathophysiology. Studies show genetic influence and childhood violence as factors that may contribute to the development of BPD; however, the involvement of neuroinflammation in BPD remains poorly investigated. This article aimed to explore the pathophysiology of BPD according to the levels of brain-derived neurotrophic factor (BDNF), inflammatory cytokines, and oxidative stress substances that exacerbate neuronal damage. Few articles have been published on this theme. They show that patients with BPD have a lower level of BDNF and a higher level of tumor necrosis factor (TNF)-α and interleukin (IL)-6 in peripheral blood, associated with increased plasma levels of oxidative stress markers, such as malondialdehyde and 8-hydroxy-2-deoxyguanosine. Therefore, more research on the topic is needed, mainly with a pre-clinical and clinical focus.
Variations on a critical distance theme Navarro, A.; Chaves, V.; Balbín, J.A.
International journal of fatigue,
November 2021, 2021-11-00, 20211101, Letnik:
152
Journal Article
Recenzirano
Odprti dostop
We investigate how the fatigue limit of notched specimens calculated with the Theory of Critical Distance (TCD) changes when variations in the value of the critical distance itself are considered. We ...motivate our study by showing how attempts at introducing a plastic zone correction in the derivation of the formula for the critical distance lead to a new length which can be significantly larger than the original one. The predictions effected with both lengths were not found to be so different, though. And this led us to study circular holes and V-notches, for which solutions for the ratio Kf∕Kt can be derived analytically.
•Studies sensitivity of TCD predictions to changes in critical length.•Motivated by attempt at introducing plastic zone correction in TCD formula.•Derive alternative formula that yields larger characteristic length.•Calculations with the two different lengths render similar notched strengths.
•The propagation of short cracks from corrosion pits has been studied through a micromechanical model.•Pit-to-crack transition and fatigue endurance are assessed taking into account the effects of ...pit local topology and the environment.•Model validation is carried out using available pitting corrosion fatigue data in open literature.
A microstructural model is presented to assess pit-to-crack transition and corrosion fatigue strength in pitted components in different environments. The model is first validated using available experimental data in the literature for pitting corrosion fatigue strength and S-N curves for both carbon and stainless steels. The value of the method proposed and its applicability is then shown by the development of fatigue knock down factor maps to the in-air S-N curve. Finally, the influence of pit local topology on pit-to-crack transition damage tolerance and the links to the NDE methods quantitative resolution necessary to account for defect shape or acuity in structural integrity assessments are discussed.
We present a list of candidate gravitationally lensed dusty star-forming galaxies (DSFGs) from the HerMES Large Mode Survey and the Herschel Stripe 82 Survey. Together, these partially overlapping ...surveys cover 372 deg super(2) on the sky. After removing local spiral galaxies and known radio-loud blazars, our candidate list of lensed DSFGs is composed of 77 sources with 500 mum flux densities (S sub(500)) greater than 100 mJy. Such sources are dusty starburst galaxies similar to the first bright sub-millimeter galaxies (SMGs) discovered with SCUBA. We expect a large fraction of this list to be strongly lensed, with a small fraction made up of bright SMG-SMG mergers that appear as hyper-luminous infrared galaxies (L sub(IR)> 10 super(13)L sub(middot in circle)). Thirteen of the 77 candidates have spectroscopic redshifts from CO spectroscopy with ground-based interferometers, putting them at z> 1 and well above the redshift of the foreground lensing galaxies. The surface density of our sample is 0.21 + or - 0.03 deg super(-2). We present follow-up imaging of a few of the candidates to confirm their lensing nature. The sample presented here is an ideal tool for higher-resolution imaging and spectroscopic observations to understand the detailed properties of starburst phenomena in distant galaxies.
Current models for predicting the fatigue endurance of notched solids use the stresses along a straight line, beginning at the notch root, as a simplification of the real crack propagation path. In ...this work, the experimental crack paths for hollow notched samples were analysed through different microscopy techniques, with the objective of establishing high cycle fatigue crack growth directions in a mild steel. Fully reversed tension–compression fatigue tests (R=−1) of thin-walled tube specimens with a passing-through hole were carried out. The crack paths observed in the outer cylindrical surface were studied in each case, with special attention to the crack initiation point and the crack direction along the first grains. Moreover, the analysis of the fracture surfaces allowed the same analysis to be performed to determine the internal crack paths. It was observed that the crack initiation point was close to the maximum principal stress point at the hole contour as obtained from linear elastic finite element analysis, and the crack direction in its initiation was generally close to Mode I direction, contrary to the conventionally accepted 45∘ crack growth direction.
•Fully reversed axial fatigue tests were performed on mild steel notched specimens.•Crack initiation points and crack directions were studied microscopically.•Fatigue cracks initiated close to the point of maximum principal stress.•Crack directions were close to that of Mode I direction from their initiation.
PDF
