261 research outputs found
Structural and electronic properties of grain boundaries in graphite: Planes of periodically distributed point defects
We report on scanning tunneling microscopy and spectroscopy of grain
boundaries in highly oriented pyrolytic graphite. Grain boundaries showed a
periodic structure and an enhanced charge density compared to the bare graphite
surface. Two possible periodic structures have been observed along grain
boundaries. A geometrical model producing periodically distributed point
defects on the basal plane of graphite has been proposed to explain the
structure of grain boundaries. Scanning tunneling spectroscopy on grain
boundaries revealed two strong localized states at -0.3 V and 0.4 V.Comment: 5 pages, 5 figure
Assessing brain immune activation in psychiatric disorders:Clinical and preclinical PET imaging studies of the 18-kDa translocator protein
Accumulating evidence from different lines of research suggests an involvement of the immune system in the pathophysiology of several psychiatric disorders. During recent years, a series of positron emission tomography (PET) studies have been published using radioligands for the translocator protein (TSPO) to study microglia activation in schizophrenia, bipolar I disorder, major depression, autism spectrum disorder, and drug abuse. The results have been somewhat conflicting, which could be due to differences both in patient sample characteristics and in PET methods. In particular, further work is needed to address both methodological and biological sources of variability in TSPO levels, a process in which the use of animal models and small animal PET systems can be a valuable tool. Given this development, PET studies of immune activation have the potential to further increase our understanding of disease mechanisms in psychiatric disorders, which is a requisite in the search for new treatment approaches. Furthermore, molecular imaging could become an important clinical tool for identifying specific subgroups of patients or disease stages that would benefit from treatment targeting the immune system
Language Mapping in Multilingual Patients: Electrocorticography and Cortical Stimulation During Naming
Multilingual patients pose a unique challenge when planning epilepsy surgery near language cortex because the cortical representations of each language may be distinct. These distinctions may not be evident with routine electrocortical stimulation mapping (ESM). Electrocorticography (ECoG) has recently been used to detect task-related spectral perturbations associated with functional brain activation. We hypothesized that using broadband high gamma augmentation (HGA, 60–150 Hz) as an index of cortical activation, ECoG would complement ESM in discriminating the cortical representations of first (L1) and second (L2) languages. We studied four adult patients for whom English was a second language, in whom subdural electrodes (a total of 358) were implanted to guide epilepsy surgery. Patients underwent ECoG recordings and ESM while performing the same visual object naming task in L1 and L2. In three of four patients, ECoG found sites activated during naming in one language but not the other. These language-specific sites were not identified using ESM. In addition, ECoG HGA was observed at more sites during L2 versus L1 naming in two patients, suggesting that L2 processing required additional cortical resources compared to L1 processing in these individuals. Post-operative language deficits were identified in three patients (one in L2 only). These deficits were predicted by ECoG spectral mapping but not by ESM. These results suggest that pre-surgical mapping should include evaluation of all utilized languages to avoid post-operative functional deficits. Finally, this study suggests that ECoG spectral mapping may potentially complement the results of ESM of language
Sonar detection and monitoring of sunken heavy fuel oil on the seafloor
Abstract The oil products transported at sea that have the potential to become suspended in the water column and sink after weathering or mixing with sediment are quite numerous: asphalt, carbon black oil, bunker C, fuel oil n°5 and 6. In many incidents and accidents part of the spilled heavy oil product has actually sunk and has been difficult to track because of the lack of means of detection. To compensate this gap, a comprehensive sonar experiment has been performed through the use of a large seawater tank on the bottom of which several patches of three different heavy fuel oils have been laid on top of a sandy layer. In this facility several kinds of sonar have been tested as for their response according to their frequency, resolution and type (side scan sonar, multibeam/panoramic sonar, 3D acoustic camera). The results proved to be very valuable according to the acoustic specificity of the products involved. Indeed the acoustic properties are similar to those of the seawater when considering density and sound speed; however the attenuation is much more important and its variation has been measured from 100 kHz to 500 kHz preliminary to the testing. The results of the sonar experiment that have been obtained do confirm the capability of current sonars to detect heavy oil patches over sand seafloors, and should make it possible to select the most adequate survey strategy according to the oil patches dimensions and thickness and to the environmental conditions
Blind competition on the numerical simulation of continuous shallow steel‐fiber reinforced concrete beams failing in bending
This article describes the second blind simulation competition (BSC) organized
by the fib WG 2.4.1, which aims to assess the predictive performance of models
based on the finite element method (FEM) for the analysis and design of fiber
reinforced concrete (FRC) structures. Slabs supported on columns or piles have
becoming competitive applications for FRC due to the technical and economic
benefits may be obtained by combining properly the fiber reinforcement mechanisms to those provided by conventional reinforcement placed, as a strip, in
the alignment of columns/piles. Therefore, a representative zone of this structural system, namely a hybrid fiber reinforced concrete (R/FRC) shallow beam,
is chosen in this BSC to show the potentialities of FRC in these types of applications, as well as to assess the predictive performance of FEM-based computational models on the design verification at serviceability and at ultimate limit
state conditions (SLS and ULS, respectively). Two statically indeterminateshallow beams of two equal spans were tested up to their failure, by recording
the applied loads, the strains in the conventional reinforcements and in the
FRC of the critical zones of the structure. By using digital image correlation,
the average crack width at the level of the flexural reinforcements was
recorded. The participants had to predict these results by receiving information
about the mechanical properties of the materials, the geometry of the prototypes and their loading and support conditions. In this article, the rules and
the results of this 2nd BSC competition are presented, and the data obtained
experimentally is thoroughly analyzed.PID2021-125553NB-I00; PTDC/ECI-EST/6300/202
Validation of a simplified micromodel for analysis of infilled RC frames exposed to cyclic lateral loads
An RC frame structure with masonry infill walls (‘‘framed-masonry’’) exposed
to lateral loads acts as a composite structure. Numerical simulation of framed-masonry is
difficult and generally unreliable due to many difficulties and uncertainties in its modelling.
In this paper, we reviewed the usability of an advanced non-linear FEM computer
program to accurately predict the behaviour of framed-masonry elements when exposed to
cyclic lateral loading. Numerical results are validated against the test results of framedmasonry
specimens, with and without openings. Initial simplified micromodels were calibrated
by adjustment of the input parameters within the physically justifiable borders, in
order to obtain the best correlation between the experimental and numerical results. It has
been shown that the use of simplified micromodels for the investigation of composite
masonry-infilled RC frames requires in-depth knowledge and engineering judgement in
order to be used with confidence. Modelling problems were identified and explained in
detail, which in turn offer an insight to practising engineers on how to deal with them
Thinking Outside a Less Intact Box: Thalamic Dopamine D2 Receptor Densities Are Negatively Related to Psychometric Creativity in Healthy Individuals
Several lines of evidence support that dopaminergic neurotransmission plays a role in creative thought and behavior. Here, we investigated the relationship between creative ability and dopamine D2 receptor expression in healthy individuals, with a focus on regions where aberrations in dopaminergic function have previously been associated with psychotic symptoms and a genetic liability to schizophrenia. Scores on divergent thinking tests (Inventiveness battery, Berliner Intelligenz Struktur Test) were correlated with regional D2 receptor densities, as measured by Positron Emission Tomography, and the radioligands [11C]raclopride and [11C]FLB 457. The results show a negative correlation between divergent thinking scores and D2 density in the thalamus, also when controlling for age and general cognitive ability. Hence, the results demonstrate that the D2 receptor system, and specifically thalamic function, is important for creative performance, and may be one crucial link between creativity and psychopathology. We suggest that decreased D2 receptor densities in the thalamus lower thalamic gating thresholds, thus increasing thalamocortical information flow. In healthy individuals, who do not suffer from the detrimental effects of psychiatric disease, this may increase performance on divergent thinking tests. In combination with the cognitive functions of higher order cortical networks, this could constitute a basis for the generative and selective processes that underlie real life creativity
Anthropometric and reproductive factors and risk of esophageal and gastric cancer by subtype and subsite: results from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort
Obesity has been associated with upper gastrointestinal cancers; however, there are limited prospective data on associations by subtype/subsite. Obesity can impact hormonal factors, which have been hypothesized to play a role in these cancers. We investigated anthropometric and reproductive factors in relation to esophageal and gastric cancer by subtype and subsite for 476,160 participants from the European Prospective Investigation into Cancer and Nutrition cohort. Multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox models. During a mean follow‐up of 14 years, 220 esophageal adenocarcinomas (EA), 195 esophageal squamous cell carcinomas, 243 gastric cardia (GC) and 373 gastric noncardia (GNC) cancers were diagnosed. Body mass index (BMI) was associated with EA in men (BMI ≥30 vs. 18.5–25 kg/m2: HR = 1.94, 95% CI: 1.25–3.03) and women (HR = 2.66, 95% CI: 1.15–6.19); however, adjustment for waist‐to‐hip ratio (WHR) attenuated these associations. After mutual adjustment for BMI and HC, respectively, WHR and waist circumference (WC) were associated with EA in men (HR = 3.47, 95% CI: 1.99–6.06 for WHR >0.96 vs. 98 vs. 0.82 vs. 84 vs. 2 vs. 0) and age at first pregnancy and GNC (HR = 0.54, 95% CI: 0.32–0.91; >26 vs. <22 years); whereas bilateral ovariectomy was positively associated with GNC (HR = 1.87, 95% CI: 1.04–3.36). These findings support a role for hormonal pathways in upper gastrointestinal cancers
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