Repository UNSAP (Universitas Sebelas April)
Not a member yet
1145 research outputs found
Sort by
Digital control system for the TCV Tokamak
No full textThis paper presents the hardware and software approach to replacing the current analogue linear feedback system on the TCV Tokamak with a DSP based system to allow for non-linear control. After preliminary combination, over 120 control signals are reduced to 32 parameters which enter an array of 32 DSP processors each of which is passed the complete parameter set. Apart from data transfer and storage, each DSP will run its separate control algorithm with a repetition rate up to 20 kHz. A separate DSP board is dedicated to the plasma vertical control which requires a 200 kHz feedback rate. This paper presents the hardware and the software that is being designed to put this control block in the hands of non DSP-expert physics users.CRPPSPCPart
Direct comparison between modelling and experiment: an alpha-Fe ion implantation study
No full textCRPPSP
The Neuron Phenotype Ontology: A FAIR Approach to Proposing and Classifying Neuronal Types
No full textThe challenge of defining and cataloging the building blocks of the brain requires a standardized approach to naming neurons and organizing knowledge about their properties. The US Brain Initiative Cell Census Network, Human Cell Atlas, Blue Brain Project, and others are generating vast amounts of data and characterizing large numbers of neurons throughout the nervous system. The neuroscientific literature contains many neuron names (e.g. parvalbumin-positive interneuron or layer 5 pyramidal cell) that are commonly used and generally accepted. However, it is often unclear how such common usage types relate to many evidence-based types that are proposed based on the results of new techniques. Further, comparing different types across labs remains a significant challenge. Here, we propose an interoperable knowledge representation, the Neuron Phenotype Ontology (NPO), that provides a standardized and automatable approach for naming cell types and normalizing their constituent phenotypes using identifiers from community ontologies as a common language. The NPO provides a framework for systematically organizing knowledge about cellular properties and enables interoperability with existing neuron naming schemes. We evaluate the NPO by populating a knowledge base with three independent cortical neuron classifications derived from published data sets that describe neurons according to molecular, morphological, electrophysiological, and synaptic properties. Competency queries to this knowledge base demonstrate that the NPO knowledge model enables interoperability between the three test cases and neuron names commonly used in the literature.BBP-COR
Correcting surface coil excitation inhomogeneities in single-shot SPEN MRI
No full textGiven their high sensitivity and ability to limit the field of view (FOV), surface coils are often used in magnetic resonance spectroscopy (MRS) and imaging (MRI). A major downside of surface coils is their inherent radiofrequency (RF) B1 heterogeneity across the FOV, decreasing with increasing distance from the coil and giving rise to image distortions due to non-uniform spatial responses. A robust way to compensate for B1 inhomogeneities is to employ adiabatic inversion pulses, yet these are not well adapted to all imaging sequences –including to single-shot approaches like echo planar imaging (EPI). Hybrid spatiotemporal encoding (SPEN) sequences relying on frequency-swept pulses provide another ultrafast MRI alternative, that could help solve this problem thanks to their built-in heterogeneous spatial manipulations. This study explores how this intrinsic SPEN-based spatial discrimination, could be used to compensate for the B1 inhomogeneities inherent to surface coils. Experiments carried out in both phantoms and in vivo rat brains demonstrate that, by suitably modulating the amplitude of a SPEN chirp pulse that progressively excites the spins in a direction normal to the coil, it is possible to compensate for the RF transmit inhomogeneities and thus improve sensitivity and image fidelity.LIFMETGR-COCIB
Macromolecular Crowding Is Surprisingly Unable to Deform the Structure of a Model Biomolecular Condensate
No full textSimple Summary The cytoplasm of a living cell is a crowded place, containing hundreds of types of protein and other macromolecules. Cells reliably and continually perform thousands of biochemical reactions to maintain their health. Biomolecular condensates are fluid protein compartments that provide distinct local environments, within which they carry out cellular functions. How they prevent their contents mixing with the external environment without being encapsulated inside a lipid membrane is not fully understood. Many researchers approach this question by studying simpler systems in a test tube that contain only a few protein types although it is hard to relate their results to the complex cellular milieu. Computer simulations are used to explore the predictions of simple models of cellular behavior, but are also limited by the ability of human experimenters to recreate important aspects of the cytoplasm, in particular, its crowded nature. We have used a novel computer framework to perform dozens of simultaneous simulations that map out the influence of macromolecular crowding on the formation and structure of a biomolecular condensate. We find that the spatial structure of the model condensate is surprisingly insensitive to the composition and concentration of external macromolecules, even when its formation is assisted by steric repulsion from its environment. The crowded interior of a living cell makes performing experiments on simpler in vitro systems attractive. Although these reveal interesting phenomena, their biological relevance can be questionable. A topical example is the phase separation of intrinsically disordered proteins into biomolecular condensates, which is proposed to underlie the membrane-less compartmentalization of many cellular functions. How a cell reliably controls biochemical reactions in compartments open to the compositionally-varying cytoplasm is an important question for understanding cellular homeostasis. Computer simulations are often used to study the phase behavior of model biomolecular condensates, but the number of relevant parameters increases as the number of protein components increases. It is unfeasible to exhaustively simulate such models for all parameter combinations, although interesting phenomena are almost certainly hidden in their high-dimensional parameter space. Here, we have studied the phase behavior of a model biomolecular condensate in the presence of a polymeric crowding agent. We used a novel compute framework to execute dozens of simultaneous simulations spanning the protein/crowder concentration space. We then combined the results into a graphical representation for human interpretation, which provided an efficient way to search the model's high-dimensional parameter space. We found that steric repulsion from the crowder drives a near-critical system across the phase boundary, but the molecular arrangement within the resulting biomolecular condensate is rather insensitive to the crowder concentration and molecular weight. We propose that a cell may use the local cytoplasmic concentration to assist the formation of biomolecular condensates, while relying on the dense phase to reliably provide a stable, structured, fluid milieu for cellular biochemistry despite being open to its changing environment.BBP-COR
Spatial patterns of benthic biofilm diversity among streams draining proglacial floodplains
No full textGlacier shrinkage opens new proglacial terrain with pronounced environmental gradients along longitudinal and lateral chronosequences. Despite the environmental harshness of the streams that drain glacier forelands, their benthic biofilms can harbor astonishing biodiversity spanning all domains of life. Here, we studied the spatial dynamics of prokaryotic and eukaryotic photoautotroph diversity within braided glacier-fed streams and tributaries draining lateral terraces predominantly fed by groundwater and snowmelt across three proglacial floodplains in the Swiss Alps. Along the lateral chronosequence, we found that benthic biofilms in tributaries develop higher biomass than those in glacier-fed streams, and that their respective diversity and community composition differed markedly. We also found spatial turnover of bacterial communities in the glacier-fed streams along the longitudinal chronosequence. These patterns along the two chronosequences seem unexpected given the close spatial proximity and connectivity of the various streams, suggesting environmental filtering as an underlying mechanism. Furthermore, our results suggest that photoautotrophic communities shape bacterial communities across the various streams, which is understandable given that algae are the major source of organic matter in proglacial streams. Overall, our findings shed new light on benthic biofilms in proglacial streams now changing at rapid pace owing to climate-induced glacier shrinkage.RIVE
Nanometer scale resolution luminescence imaging of quantum wire structure with a scanning tunneling microscope
No full textLMIS
Observation of shell effects in superconducting nanoparticles of Sn
No full textIn a zero-dimensional superconductor, quantum size effects(1,2) (QSE) not only set the limit to superconductivity, but are also at the heart of new phenomena such as shell effects, which have been predicted to result in large enhancements of the superconducting energy gap(3-6). Here, we experimentally demonstrate these QSE through measurements on single, isolated Pb and Sn nanoparticles. In both systems superconductivity is ultimately quenched at sizes governed by the dominance of the quantum fluctuations of the order parameter. However, before the destruction of superconductivity, in Sn nanoparticles we observe giant oscillations in the superconducting energy gap with particle size leading to enhancements as large as 60%. These oscillations are the first experimental proof of coherent shell effects in nanoscale superconductors. Contrarily, we observe no such oscillations in the gap for Pb nanoparticles, which is ascribed to the suppression of shell effects for shorter coherence lengths. Our study paves the way to exploit QSE in boosting superconductivity in low-dimensional systems.LSE
Chemically disruptable molecule switch and use thereof
No full textThe invention relates to chemically disruptable molecule (CDM) switch, their use in controlling cell signaling components, and their use for treatments and therapies. Further disclosed are methods of treating and/or preventing a disease, such as e.g. a cancer, an inflammatory disease, a genetic disorder, an infectious disease, and a degenerative diseaseAVP-R-TTOLPDIAlternative title(s) :
(fr) Commutateur moléculaire pouvant être perturbé chimiquement et son utilisatio
Versatile High Repetition Rate 2-μm Pulsed Source Based on Wideband Parametric Conversion
No full textWe report an all-fiber pulsed source based on parametric conversion followed by thulium amplification able to deliver picosecond pulses at a repetition rate selectable between 2 and 5 GHz, of which central wavelength can be freely selected in the 2-μm region. A very versatile Nyquist pulse shaping of the parametric pump, which allows for the electrical control of the pulse train, enables such a freedom in the repetition rate selection, as well as some control in the pulse duration. We also show that data can be embedded in the output pulse train resulting in a high-quality Gb/s return-to-zero transmitter. Such a programmable short-wave infrared laser is of high interest for sensing or nonlinear optics applications around 2000 nm that require a fine adjustment in both the spectral and temporal domains.PHOS