•History summary of X-ray spectroscopy with respect to laboratory XAS and XES.•Review of the current state of laboratory X-ray spectroscopy.•Summary of current laboratory setup to perform XAS, ...XANES/EXAFS and non-resonant XES.•Capabilities of recent experimental setups.•Application of Laboratory XAS in catalysis.
X-ray spectroscopy is an important tool for scientific analysis. While the earliest demonstration experiments were realised in the laboratory, with the advent of synchrotron light sources most of the experiments shifted to large scale synchrotron facilities. In the recent past there is an increased interest to perform X-ray experiments also with in-house laboratory sources, to simplify access to X-ray absorption and X-ray emission spectroscopy, in particular for routine measurements. Here we summarise the recent developments and comment on the most representative example experiments in the field of in-house laboratory X-ray spectroscopy. We first give an introduction and some historic background on X-ray spectroscopy. This is followed by an overview of the detection techniques used for X-ray absorption and X-ray emission measurements. A short paragraph also puts related high energy resolution and resonant techniques into context, though they are not yet feasible in the laboratory. At the end of this section the opportunities using wavelength dispersive X-ray spectroscopy in the laboratory are discussed. Then we summarise the relevant details of the recent experimental laboratory setups split into two separate sections, one for the recent von Hamos setups, and one for the recent Johann/Johansson type setups. Following that, focussing on chemistry and catalysis, we then summarise some of the notable X-ray absorption and X-ray emission experiments and the results accomplished with in-house setups. In a third part we then discuss some applications of laboratory X-ray spectroscopy with a particular focus on chemistry and catalysis.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This Progress Report discusses the chemical sensitivity of Kβ valence to core X‐ray emission spectroscopy (vtc‐XES) and its applications for investigating 3d‐transition‐metal based materials. Vtc‐XES ...can be used for ligand identification and for the characterization of the valence electronic levels. The technique provides information that is similar to valence band photoemission spectroscopy but the sample environment can be chosen freely and thus allows measurements in presence of gases and liquids and it can be applied for measurements under in situ/operando or extreme conditions. The theoretical basis of the technique is presented using a one‐electron approach and the vtc‐XES spectral features are interpreted using ground state density functional theory calculations. Some recent results obtained by vtc‐XES in various scientific fields are discussed to demonstrate the potential and future applications of this technique. Resonant X‐ray emission spectroscopy is briefly introduced with some applications for the study of 3d and 5d‐transition‐metal based systems.
The chemical bond is usually described in terms of molecular orbitals, which are not physically observable. For transition‐metal‐based systems, Kβ valence to core X‐ray emission spectroscopy combined with ground state density‐functional‐theory calculations provide the bridge between the real chemical world and the tools we use to describe it. The technique is bulk‐sensitive, element‐selective, and probes the occupied electronic levels of the material under investigation.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A folding voltage-to-time converter (VTC) is proposed for low-power time-based (TB) flash ADCs performing voltage-to-time-to-digital conversion. Conventional VTCs in TB flash ADCs generate multiple ...time outputs or have nonlinear conversion gain, resulting in a large power consumption in time-to-digital converters (TDCs) due to power-inefficient architectures using a lot of comparators. The proposed VTC generates a single time output with a large-and-linear conversion gain because the proposed VTC folds the whole voltage input range several times and each voltage-to-time conversion is defined within the voltage range reduced by folding. This allows the TDC power consumption to be reduced by using power-efficient architectures. Moreover, the VTC generates digital outputs as a result of the folding operation, thereby relaxing the resolution requirement of the TDC. A 7-bit TB ADC is implemented with a <inline-formula> <tex-math notation="LaTeX">4\times </tex-math></inline-formula> folding VTC having a 2-bit digital output and a 5-bit pipelined TDC for high-speed low-power operation. A TB ADC fabricated in a 1-V 65-nm CMOS process achieves a 4-GS/s sampling frequency, 11.3-mW power consumption, a 34.58-dB SNDR, and a 64.5-fJ/conv.-step figure of merit (FoM).
Ascorbic acid is synthesised by eukaryotes, the known exceptions being primates and some other animal groups which have lost functional gulonolactone oxidase. Prokaryotes do not synthesise ascorbate ...and do not need an ascorbate supply, so the functions that are essential for mammals and plants are not required or are substituted by other compounds. The ability of ascorbate to donate electrons enables it to act as a free radical scavenger and to reduce higher oxidation states of iron to Fe2+. These reactions are the basis of its biological activity along with the relative stability of the resulting resonance stabilised monodehydroascorbate radical. The importance of these properties is emphasised by the evolution of at least three biosynthetic pathways and production of an ascorbate analogue, erythroascorbate, by fungi. The iron reducing activity of ascorbate maintains the reactive centre Fe2+ of 2-oxoglutarate-dependent dioxygenases (2-ODDs) thus preventing inactivation. These enzymes have diverse functions and, recently, the possibility that ascorbate status in mammals could influence 2-ODDs involved in histone and DNA demethylation thereby influencing stem cell differentiation and cancer has been uncovered. Ascorbate is involved in iron uptake and transport in plants and animals. While the above biochemical functions are shared between mammals and plants, ascorbate peroxidase (APX) is an enzyme family limited to plants and photosynthetic protists. It provides these organisms with increased capacity to remove H2O2 produced by photosynthetic electron transport and photorespiration. The Fe reducing activity of ascorbate enables hydroxyl radical production (pro-oxidant effect) and the reactivity of dehydroascorbate (DHA) and reaction of its degradation products with proteins (dehydroascorbylation and glycation) is potentially damaging. Ascorbate status influences gene expression in plants and mammals but at present there is little evidence that it acts as a specific signalling molecule. It most likely acts indirectly by influencing the redox state of thiols and 2-ODD activity. However, the possibility that dehydroascorbylation is a regulatory post-translational protein modification could be explored.
Display omitted
•The function and metabolism of ascorbate is compared between plants and mammals.•Ascorbate readily reduces radicals and Fe/Cu.•Ascorbate is synthesised by plants, protists and animals via different pathways.•Fungi synthesise the analogue D-erythroascorbate.•Plants and photosynthetic protists use ascorbate peroxidase to remove H2O2.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
SRAM is one of the essential components for portable devices which contributes significantly and determines the overall device performance. This paper analyzes the methods for calculating noise ...margin of conventional 6 transistor (6 T) and 8 transistor (8 T) SRAM cell. For calculation of noise margins in memory cell, this paper considered butterfly analysis and noise-curve methods. From the simulation results obtained from the above-mentioned method, the findings shows that 8 transistor SRAM cell provides higher read noise margin than 6 transistor SRAM cell. The aim of this paper is to verify and validate butterfly analysis and noise-curve methods for calculation of noise margins in memory cells. From the simulation data it is observed that major limitation of using butterfly analysis to measure SNM is the inability of measuring SNM using inline techniques and it’s time consuming and complex process. It may sometimes give inaccurate/ misleading results due to computational error. Whereas, N-curve method for SRAM cell analysis is used for inline testing and also provides additional information regarding current and voltage stability. Additionally, the N-curve can be utilized to perform an analysis of the power dissipation by the SRAM cell while it is undergoing read or write operation. Using 90 nm technology file, cadence virtuoso EDA tools simulate both 6 transistor and 8 transistor SRAM cells.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The acidocalcisome is an acidic organelle in the cytosol of eukaryotes, defined by its low pH and high calcium and polyphosphate content. It is visualized as an electron-dense object by transmission ...electron microscopy (TEM) or described with mass spectrometry (MS)–based imaging techniques or multimodal X-ray fluorescence microscopy (XFM) based on its unique elemental composition. Compared with MS-based imaging techniques, XFM offers the additional advantage of absolute quantification of trace metal content, since sectioning of the cell is not required and metabolic states can be preserved rapidly by either vitrification or chemical fixation. We employed XFM in
Chlamydomonas reinhardtii
to determine single-cell and organelle trace metal quotas within algal cells in situations of trace metal overaccumulation (Fe and Cu). We found up to 70% of the cellular Cu and 80% of Fe sequestered in acidocalcisomes in these conditions and identified two distinct populations of acidocalcisomes, defined by their unique trace elemental makeup. We utilized the
vtc1
mutant, defective in polyphosphate synthesis and failing to accumulate Ca, to show that Fe sequestration is not dependent on either. Finally, quantitation of the Fe and Cu contents of individual cells and compartments via XFM, over a range of cellular metal quotas created by nutritional and genetic perturbations, indicated excellent correlation with bulk data from corresponding cell cultures, establishing a framework to distinguish the nutritional status of single cells.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Areas of the fusiform gyrus (FG) within human ventral temporal cortex (VTC) process high-level visual information associated with faces, limbs, words, and places. Since classical cytoarchitectonic ...maps do not adequately reflect the functional and structural heterogeneity of the VTC, we studied the cytoarchitectonic segregation in a region, which is rostral to the recently identified cytoarchitectonic areas FG1 and FG2. Using an observer-independent and statistically testable parcellation method, we identify 2 new areas, FG3 and FG4, in 10 human postmortem brains on the mid-FG. The mid-fusiform sulcus reliably identifies the cytoarchitectonic transition between FG3 and FG4. We registered these cytoarchitectonic areas to the common reference space of the single-subject Montreal Neurological Institute (MNI) template and generated probability maps, which reflect the intersubject variability of both areas. Future studies can relate in vivo neuroimaging data with these microscopically defined cortical areas to functional parcellations. We discuss these results in the context of both large-scale functional maps and fine-scale functional clusters that have been identified within the human VTC. We propose that our observer-independent cytoarchitectonic parcellation of the FG better explains the functional heterogeneity of the FG compared with the homogeneity of classic cytoarchitectonic maps.
La movilidad urbana puede considerarse una cuestión de especial relevancia para un gran número de ciudades europeas debido a los altos niveles de contaminación que presentan alguna de ellas. Una ...situación anómala, se observó con la llegada de la Pandemia puesto que se observó una reducción de la movilidad urbana y como resultado de ello se registraron grandes reducciones de contaminación. Con la vuelta a la normalidad, los atascos y el vertido de partículas contaminantes ha vuelto a la normalidad y ello nos lleva a destacar la relevancia de la elección de la opción de movilidad que toman los usuarios, así como poder observar los posibles cambios que han resultado con la irrupción de la tecnología en el sector del transporte de las grandes ciudades. En este artículo, investigamos cómo evolucionan sus preferencias en la elección del medio de transporte mediante el modelo logit. Los datos estudiados se recogieron mediante encuestas a nivel nacional. Los resultados generados nos muestran información relevante para que el taxi y el VTC adapten sus estrategias en un entorno altamente competitivo e incierto como el que se enfrentan en la actualidad.
The use of videoconference technology to deliver health care diagnostics and treatment continues to grow at a rapid pace. Telepsychiatry and telepsychology applications are well-accepted by patients ...and providers, and both diagnostic and treatment outcomes have generally been similar to traditional face-to-face interactions. Preliminary applications of videoconference-based neuropsychological assessment (teleneuropsychology) have yielded promising results in the feasibility and reliability of several standard tests, although large-scale studies are lacking. This investigation was conducted to determine the reliability of video teleconference (VTC) - based neuropsychological assessment using a brief battery of standard neuropsychological tests commonly used in the evaluation of known or suspected dementia. Tests included the Mini-Mental State Examination (MMSE), Hopkins Verbal Learning Test-Revised, Digit Span forward and backward, short form Boston Naming Test, Letter and Category Fluency, and Clock Drawing. Tests were administered via VTC and in-person to subjects, counterbalanced using alternate test forms and standard instructions. Two hundred two adult subjects were tested in both rural and urban settings, including 83 with cognitive impairment and 119 healthy controls. We found highly similar results across VTC and in-person conditions, with significant intraclass correlations (mean=.74; range: 0.55-0.91) between test scores. Findings remained consistent in subjects with or without cognitive impairment and in persons with MMSE scores as low as 15. VTC-based neuropsychological testing is a valid and reliable alternative to traditional face-to-face assessment using selected measures. More VTC-based studies using additional tests in different populations are needed to fully explore the utility of this new testing medium.
PDF
