An Investigation of Spin and Charge States Associated with Metastable Defects in N-Type Hydrogenated Amorphous Silicon

1991 ◽  
Vol 219 ◽  
Author(s):  
R. J. Rasmussen ◽  
J. D. Cohen ◽  
J. M. Essick
Keyword(s):  
Total Spin ◽  
Charge Ratio ◽  
Defect States ◽  
Large Magnitude ◽  
Experimental Conditions ◽  
Joint Application ◽  
Depletion Width ◽  
Wide Range ◽  
Capacitance Transient ◽  
Hydrogenated Amorphous

ABSTRACTDepletion-width-modulated (DWM) ESR spectroscopy and junction capacitance techniques were employed to investigate deep-defect states in various metastable states of 10 and 80 Vppm PH3-doped a-Si:H. From the joint application of these methods, we enumerate the change in total spin and charge associated with emission of carriers from states within the mobility gap resulting from a modulated bias voltage. We conclude that the magnitude of the modulated spin-to-charge ratio is nearly unity, consistent with earlier similar investigations of n-type a-Si:H, where the D-/D0 transition was shown to dominate. Furthermore, we present results of a previously unreported “quadrature” DWM-ESR signal of large magnitude under a wide range of experimental conditions. Similar related effects are also reported from spin- and capacitance-transient studies. These results clearly demonstrate that the changes in spin significandy lag corresponding changes in charge.

Dependence of Steady-State Defect Density in Hydrogenated Amorphous Silicon on Carrier Generation Rate Studied Over a Wide Range

1993 ◽  
Vol 297 ◽  
Author(s):  
Nobuhiro Hata ◽  
Gautam Ganguly ◽  
Akihisa Matsuda
Keyword(s):  
Steady State ◽  
Amorphous Silicon ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Continuous Light ◽  
Effective Rate ◽  
Defect States ◽  
Carrier Generation ◽  
Wide Range ◽  
Hydrogenated Amorphous

Measurements of the steady-state defect density (Nst) in hydrogenated amorphous silicon under illumination of pulse-laser light, as well as of continuous light, were carried out; and the dependence of Nst on the effective rate of carrier generation (G) is presented. The values of G ranged from 8 x 1021 to 2.4 × 1023 cm-3 s-1, while the illumination temperature was kept at 30 °C or at 105 °C. The results showed trends of Nst increasing with G similarly to the trends in the literature, but covered a higher and wider G range, and fitted a defect model which assumes a limited number of possible defect states.

Characterization of Gap Defect States in Hydrogenated Amorphous Silicon Materials

2008 ◽  
Vol 1066 ◽  
Author(s):  
Lihong Jiao ◽  
C. R. Wronski
Keyword(s):  
Amorphous Silicon ◽  
Energy Levels ◽  
Hydrogenated Amorphous Silicon ◽  
Defect States ◽  
Wide Range ◽  
Silicon Materials ◽  
Energy Dependent ◽  
Hydrogenated Amorphous ◽  
Dependent Density ◽  
Gap State

ABSTRACTAn enhanced simulation model based on the carrier recombination through these states was developed to characterize the gap defect states in hydrogenated amorphous silicon materials (a-Si:H). The energy dependent density of electron occupied gap states, kN(E), was derived directly from Dual Beam Photoconductivity (DBP) measurements at different bias currents. Through Gaussian de-convolution of kN(E), the energy peaks of the multiple defect states, including both neutral and charged states, were obtained. These energy levels, together with the information on the capture cross sections, were used as known input parameters to self-consistently fit the subgap absorption spectra, the electron mobility-lifetime products over a wide range of generation rates, as well as the energy dependent density of electron occupied gap state spectra. Accurate gap state information was obtained and the nature of the defect states was studied. Simulation results on light degraded hydrogen diluted, protocrystalline a-Si:H show that the density of charged states is 2.3 times that of neutral states. The two states close to the midgap act as effective recombination centers at low generation rates and play key roles in photoconductivity studies.

Strongly Coupled Redox-Linked Conformational Switching at the Active Site of the Non-Heme Iron-Dependent Dioxygenase, TauD

2019 ◽  
Author(s):  
Christopher John ◽  
Greg M. Swain ◽  
Robert P. Hausinger ◽  
Denis A. Proshlyakov
Keyword(s):  
Active Site ◽  
Structural Model ◽  
Heme Iron ◽  
Chemical Transformations ◽  
Experimental Conditions ◽  
Strongly Coupled ◽  
Non Heme Iron ◽  
Reversible Redox ◽  
Wide Range ◽  
Complex Structural

2-Oxoglutarate (2OG)-dependent dioxygenases catalyze C-H activation while performing a wide range of chemical transformations. In contrast to their heme analogues, non-heme iron centers afford greater structural flexibility with important implications for their diverse catalytic mechanisms. We characterize an <i>in situ</i> structural model of the putative transient ferric intermediate of 2OG:taurine dioxygenase (TauD) by using a combination of spectroelectrochemical and semi-empirical computational methods, demonstrating that the Fe (III/II) transition involves a substantial, fully reversible, redox-linked conformational change at the active site. This rearrangement alters the apparent redox potential of the active site between -127 mV for reduction of the ferric state and 171 mV for oxidation of the ferrous state of the 2OG-Fe-TauD complex. Structural perturbations exhibit limited sensitivity to mediator concentrations and potential pulse duration. Similar changes were observed in the Fe-TauD and taurine-2OG-Fe-TauD complexes, thus attributing the reorganization to the protein moiety rather than the cosubstrates. Redox difference infrared spectra indicate a reorganization of the protein backbone in addition to the involvement of carboxylate and histidine ligands. Quantitative modeling of the transient redox response using two alternative reaction schemes across a variety of experimental conditions strongly supports the proposal for intrinsic protein reorganization as the origin of the experimental observations.

scholarly journals Low-Energy Electron Damage to Condensed-Phase DNA and Its Constituents

2021 ◽  
Vol 22 (15) ◽  
pp. 7879
Author(s):  
Yingxia Gao ◽  
Yi Zheng ◽  
Léon Sanche
Keyword(s):  
Condensed Phase ◽  
Genetic Material ◽  
High Energy ◽  
Dna Lesions ◽  
Low Energy ◽  
Experimental Investigations ◽  
Experimental Conditions ◽  
Strand Breaks ◽  
Sequence Of Events ◽  
Wide Range

The complex physical and chemical reactions between the large number of low-energy (0–30 eV) electrons (LEEs) released by high energy radiation interacting with genetic material can lead to the formation of various DNA lesions such as crosslinks, single strand breaks, base modifications, and cleavage, as well as double strand breaks and other cluster damages. When crosslinks and cluster damages cannot be repaired by the cell, they can cause genetic loss of information, mutations, apoptosis, and promote genomic instability. Through the efforts of many research groups in the past two decades, the study of the interaction between LEEs and DNA under different experimental conditions has unveiled some of the main mechanisms responsible for these damages. In the present review, we focus on experimental investigations in the condensed phase that range from fundamental DNA constituents to oligonucleotides, synthetic duplex DNA, and bacterial (i.e., plasmid) DNA. These targets were irradiated either with LEEs from a monoenergetic-electron or photoelectron source, as sub-monolayer, monolayer, or multilayer films and within clusters or water solutions. Each type of experiment is briefly described, and the observed DNA damages are reported, along with the proposed mechanisms. Defining the role of LEEs within the sequence of events leading to radiobiological lesions contributes to our understanding of the action of radiation on living organisms, over a wide range of initial radiation energies. Applications of the interaction of LEEs with DNA to radiotherapy are briefly summarized.

scholarly journals Review of the Upright Balance Assessment Based on the Force Plate

2021 ◽  
Vol 18 (5) ◽  
pp. 2696
Author(s):  
Baoliang Chen ◽  
Peng Liu ◽  
Feiyun Xiao ◽  
Zhengshi Liu ◽  
Yong Wang
Keyword(s):  
Postural Balance ◽  
Force Plate ◽  
Assessment Method ◽  
Balance Assessment ◽  
Experimental Conditions ◽  
Methodological Research ◽  
Assessment Tests ◽  
Wide Range ◽  
Foot Posture ◽  
Plate System

Quantitative assessment is crucial for the evaluation of human postural balance. The force plate system is the key quantitative balance assessment method. The purpose of this study is to review the important concepts in balance assessment and analyze the experimental conditions, parameter variables, and application scope based on force plate technology. As there is a wide range of balance assessment tests and a variety of commercial force plate systems to choose from, there is room for further improvement of the test details and evaluation variables of the balance assessment. The recommendations presented in this article are the foundation and key part of the postural balance assessment; these recommendations focus on the type of force plate, the subject’s foot posture, and the choice of assessment variables, which further enriches the content of posturography. In order to promote a more reasonable balance assessment method based on force plates, further methodological research and a stronger consensus are still needed.

scholarly journals Towards Reduced CNNs for De-Noising Phase Images Corrupted with Speckle Noise

Photonics ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 255
Author(s):  
Marie Tahon ◽  
Silvio Montresor ◽  
Pascal Picart
Keyword(s):  
Phase Error ◽  
Speckle Noise ◽  
Experimental Conditions ◽  
Benchmark Data ◽  
Wide Range ◽  
Phase Images ◽  
Different Depths ◽  
Phase Data ◽  
Do So

Digital holography is a very efficient technique for 3D imaging and the characterization of changes at the surfaces of objects. However, during the process of holographic interferometry, the reconstructed phase images suffer from speckle noise. In this paper, de-noising is addressed with phase images corrupted with speckle noise. To do so, DnCNN residual networks with different depths were built and trained with various holographic noisy phase data. The possibility of using a network pre-trained on natural images with Gaussian noise is also investigated. All models are evaluated in terms of phase error with HOLODEEP benchmark data and with three unseen images corresponding to different experimental conditions. The best results are obtained using a network with only four convolutional blocks and trained with a wide range of noisy phase patterns.

scholarly journals Creep Behaviour and Microstructural Characterization of VAT 36 and VAT 32 Superalloys

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 877 ◽  
Author(s):  
Vagner Gobbi ◽  
Silvio Gobbi ◽  
Danieli Reis ◽  
Jorge Ferreira ◽  
José Araújo ◽  
...  
Keyword(s):  
Failure Analysis ◽  
Creep Resistance ◽  
High Performance ◽  
Creep Behaviour ◽  
Ductile Failure ◽  
Microstructural Characterization ◽  
Dislocation Slip ◽  
Creep Tests ◽  
Experimental Conditions ◽  
Wide Range

Superalloys are used primarily for the aerospace, automotive, and petrochemical industries. These applications require materials with high creep resistance. In this work, evaluation of creep resistance and microstructural characterization were carried out at two new nickel intermediate content alloys for application in aerospace industry and in high performance valves for automotive applications (alloys VAT 32 and VAT 36). The alloys are based on a high nickel chromium austenitic matrix with dispersion of intermetallic L12 and phases containing different (Nb,Ti)C carbides. Creep tests were performed at constant load, in the temperature range of 675–750 °C and stress range of 500–600 MPa. Microstructural characterization and failure analysis of fractured surfaces of crept samples were carried out with optical and scanning electron microscopy with EDS. Phases were identified by Rietveld refinement. The results showed that the superalloy VAT 32 has higher creep resistance than the VAT 36. The superior creep resistance of the alloy VAT 32 is related to its higher fraction of carbides (Nb,Ti)C and intermetallic L12 provided by the amount of carbon, titanium, and niobium in its chemical composition and subsequent heat treatment. During creep deformation these precipitates produce anchoring effect of grain boundaries, hindering relative slide between grains and therefore inhibiting crack formation. These volume defects act also as obstacles to dislocation slip and climb, decreasing the creep rate. Failure analysis of surface fractures of crept samples showed intergranular failure mechanism at crack origin for both alloys VAT 36 and VAT 32. Intergranular fracture involves nucleation, growth, and subsequent binding of voids. The final fractured portion showed transgranular ductile failure, with dimples of different shapes, generated by the formation and coalescence of microcavities with dissimilar shape and sizes. The occurrence of a given creep mechanism depends on the test conditions. At creep tests of VAT 32 and VAT 36, for lower stresses and higher temperature, possible dislocation climb over carbides and precipitates would prevail. For higher stresses and intermediate temperatures shear mechanisms involving stacking faults presumably occur over a wide range of experimental conditions.

scholarly journals Partitional calorimetry

2019 ◽  
Vol 126 (2) ◽  
pp. 267-277 ◽  
Author(s):  
Matthew N. Cramer ◽  
Ollie Jay
Keyword(s):  
Heat Balance ◽  
Estimation Error ◽  
Fluid Replacement ◽  
Whole Body ◽  
Exposure Limits ◽  
Experimental Conditions ◽  
Direct Calorimetry ◽  
Fundamental Properties ◽  
Wide Range ◽  
Partitional Calorimetry

For thermal physiologists, calorimetry is an important methodological tool to assess human heat balance during heat or cold exposures. A whole body direct calorimeter remains the gold standard instrument for assessing human heat balance; however, this equipment is rarely available to most researchers. A more widely accessible substitute is partitional calorimetry, a method by which all components of the conceptual heat balance equation—metabolic heat production, conduction, radiation, convection, and evaporation—are calculated separately based on fundamental properties of energy exchange. Since partitional calorimetry requires relatively inexpensive equipment (vs. direct calorimetry) and can be used over a wider range of experimental conditions (i.e., different physical activities, laboratory or field settings, clothed or seminude), it allows investigators to address a wide range of problems such as predicting human responses to thermal stress, developing climatic exposure limits and fluid replacement guidelines, estimating clothing properties, evaluating cooling/warming interventions, and identifying potential thermoregulatory dysfunction in unique populations. In this Cores of Reproducibility in Physiology (CORP) review, we summarize the fundamental principles underlying the use of partitional calorimetry, present the various methodological and arithmetic requirements, and provide typical examples of its use. Strategies to minimize estimation error of specific heat balance components, as well as the limitations of the method, are also discussed. The goal of this CORP paper is to present a standardized methodology and thus improve the accuracy and reproducibility of research employing partitional calorimetry.

scholarly journals Lutetium oxide analysis by direct arc atomic emission spectrometry

2021 ◽  
Vol 25 (2) ◽  
pp. 70-83
Author(s):  
E. S. Koshel ◽  
◽  
A. A. Arkhipenko ◽  
V. B. Baranovskaya ◽  
◽  
...  
Keyword(s):  
Atomic Emission ◽  
Emission Spectrometry ◽  
Experimental Conditions ◽  
Impurity Composition ◽  
Operating Modes ◽  
Lutetium Oxide ◽  
Icp Ms ◽  
Wide Range ◽  
Sample Dissolution ◽  
Dc Arc

The requirements for the composition of initial oxides for the lutetium orthosilicate crystals are quite stringent: the content of the basic substance Lu2O3 is 99.999 wt%. Critical are coloring impurities: Fe, Ni, Cr, Co, Cu, V, Mn, the content of each should be no more than 0.0005 - 0.0010 wt%, Pr, Nd, Sm, Er, Tb, Yb no more than 0.0005 wt% for each one. It is also necessary to control the content of Al, As, Bi, Cd, Mg, Mo, Pb, Sb, Si, Sn, Ti, Zn, Y, La, Ce, Sc, Eu, Gd, Dy, Ho, Tm. To determine the impurity composition of lutetium oxide, one of the promising methods of analysis is direct arc atomic emission spectroscopy (DC Arc). The advantages of this method are the determination of the chemical composition without sample dissolution, a wide range of concentrations (10-6 - 10-1% wt%), a large number of determined elements. To realize the potential analytical capabilities of the method, the experimental conditions were studied: the interelectrode distance, the shape and size of graphite electrodes, the ratio of Lu2O3 to the spectral buffer, the type of carriers and operating modes of the generator. For most elements, the limits of determination are n ∙ 10-6 - n ∙ 10-4 wt%, that is significantly lower than in the current methods of DC Arc. The trueness of results is controlled by ICP-MS. The complex application of new approaches and modern capabilities of spectral equipment made it possible to develop a method with improved metrological characteristics.

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