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Статті в журналах з теми "621.318:537.6"
1
Meng, Ran, Lin Zhang, Chengxu Zhou, Kai Liao, Peng Xiao, Qijun Luo, Jilin Xu, Yanze Cui, Xiaodi Hu, and Xiaojun Yan. "Genome Sequence of Chrysotila roscoffensis, a Coccolithphore Contributed to Global Biogeochemical Cycles." Genes 13, no. 1 (December 23, 2021): 40. http://dx.doi.org/10.3390/genes13010040.
Повний текст джерелаАнотація:
Chrysotila is a genus of coccolithophores. Together with Emiliania, it is one of the representative genera in the Haptophyta which have been extensively studied. They are photosynthetic unicellular marine algae sharing the common characteristic of the production of CaCO3 platelets (coccoliths) on the surface of their cells and are crucial contributors to global biogeochemical cycles. Here, we report the genome assembly of Chrysotila roscoffensis. The assembled genome size was ~636 Mb distributed across 769 scaffolds with N50 of 1.63 Mb, and maximum contig length of ~2.6 Mb. Repetitive elements accounted for approximately 59% of the genome. A total of 23,341 genes were predicted from C. roscoffensis genome. The divergence time between C. roscoffensis and Emiliania huxleyi was estimated to be around 537.6 Mya. Gene families related to cytoskeleton, cellular motility and morphology, and ion transport were expanded. The genome of C. roscoffensis will provide a foundation for understanding the genetic and phenotypic diversification and calcification mechanisms of coccolithophores.
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Chen, Cheng, Chenhao Zhao, Zhibiao Hu, and Kaiyu Liu. "Synthesis of Se/chitosan-derived hierarchical porous carbon composite as Li–Se battery cathode." Functional Materials Letters 10, no. 02 (April 2017): 1650074. http://dx.doi.org/10.1142/s1793604716500740.
Повний текст джерелаАнотація:
The hierarchical porous carbon with overall macropores and surface micropores has been prepared from carbonization of chitosan/[Formula: see text][Formula: see text] gel-like composite. The specific surface area and pore volume of this carbon can come to 2358.9[Formula: see text][Formula: see text] g[Formula: see text] and 1.14[Formula: see text]cm3 g[Formula: see text], respectively, and the active component Se with amorphous structure is uniformly encapsulated into the microporous structure to form Se/carbon composite. As Li–Se battery cathode, the composite delivers a second discharge capacity of 537.6[Formula: see text]mAh g[Formula: see text] at 0.2[Formula: see text]C, and a discharge capacity of 517.9[Formula: see text]mA h g[Formula: see text] can be retained after 100 cycles. Even at a high rate of 5[Formula: see text]C, the composite still reveals a stable discharge capacity of 325.2[Formula: see text]mAh g[Formula: see text]. The excellent electrochemical performances of Se/carbon composite may attribute to high specific surface area and hierarchical porous feature.
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Kunda, J. J., Ahmed Abubakar Jajere, Otabe E. A., Chindo Musa Muhammed, Umar Muhammed Bibi, and Yusuf Maina-Bukar. "Empirical Model Valuation of Urban Agriculture Vulnerability to Flooding in Makurdi, Benue State, Nigeria." Environment and Pollution 10, no. 2 (June 3, 2021): 20. http://dx.doi.org/10.5539/ep.v10n2p20.
Повний текст джерелаАнотація:
For this study, geospatial technology was used to assess agricultural lands vulnerable to flooding in Makurdi, Benue State, Nigeria. Six thematic layers of factors influencing flood occurrences in the study area were generated from monthly rainfall, land use/cover, drainage density, soil, digital elevation model and slope. Pairwise comparison of the Analytical Hierarchy Process was used to derive the weights for each factor using expert’s judgements and literature. Weighted overlay model from the spatial analysis tool in the ArcGIS 10.4 environment was used to perform the vulnerability modelling. Expert’s judgement on the relative factors influencing flood in the study area was: rainfall (25%), elevation (22%), slope (20%), drainage density (13%), soil type (8%) and land use/cover (12%). The consistency ratio of the analysis was reasonable: (CR= 0.078). Results from the model demonstrated land vulnerability to urban agricultural flooding in the study area ranging from areas of very highly vulnerable to very low vulnerable areas, with farmlands along the floodplains of River Benue falls within the very highly vulnerable areas. The elements at Risk are; Farmland 537.6 (66.1%), Irrigation Land 40.5 (5.0%) and Built-up Land 125.8 (15.5%).
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JHA, T. N. "Characteristics of radiative and non-radiative energy fluxes over monsoon trough zone." MAUSAM 52, no. 3 (January 11, 2022): 581–92. http://dx.doi.org/10.54302/mausam.v52i3.1729.
Повний текст джерелаАнотація:
In order to describe behaviour of radiative and non-radiative erergy fluxes in the surface layer, computation of net radiation, sensible, latent and heat soil flux has been done using hourly global radiation, slow response data of MONTBLEX-90 and surface observation of Varanasi and Jodhpur during rainy and non-rainy days in July 1990. Daily and hourly ground temperature is calculated solving one dimensional heat conduction equation and soil heat flux is computed using force restored method .Outgoing Longwave Radiation (OLR) is calculated by Stefan-Boltzrnann law of radiation and the largest diurnal variability was found over dry convective zone. Results show that OLR from the ground lies in the range 473.0-537.6 Wm-2 at Jodhpur and 497.4 -548.4 Wm-2 at Varanasi during generally cloudy day. The dip in OLR is increascd by 10% with increase of relative humidity and cloudiness. Daily mean of the largest downward soil heat flux are found as 206.4 and 269.4 Wm-2 at Varanasi and Jodhpur respectively during cloudy day. About 40-50% of net radiation is imparted to soil heat flux at Varanasi and Jodhpur. Sum of the hourly non- radiative energy fluxes has not been balanced by net radiation while daily cumulative value of the fluxes balances the net radiation during non-rainy day.
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Tulbah, Alaa S., and Wing-Hin Lee. "Physicochemical Characteristics and In Vitro Toxicity/Anti-SARS-CoV-2 Activity of Favipiravir Solid Lipid Nanoparticles (SLNs)." Pharmaceuticals 14, no. 10 (October 19, 2021): 1059. http://dx.doi.org/10.3390/ph14101059.
Повний текст джерелаАнотація:
The rise of coronavirus (COVID-19) cases worldwide has driven the need to discover and develop novel therapeutics with superior efficacy to treat this disease. This study aims to develop an innovative aerosolized nano-formulation of favipiravir (FPV) as an anti-viral agent against coronavirus infection. The local delivery of FPV nanoparticles (NPs) via nebulization ensures that the drug can reach the site of infection, the lungs. Solid lipid NPs of favipiravir (FPV-SLNs) were formulated utilizing the hot-evaporation method. The physicochemical formulation properties were evaluated using dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The aerosol formulation performance was evaluated using an Andersen Cascade Impactor (ACI) at a flow rate of 15 L/min. The FPV-SLN formulation’s in vitro anti-viral activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was also evaluated using the SARS-CoV-2 pathogen (hCoV-19/Egypt/NRC-3/2020 isolate). The FPV-SLNs’ morphology was defined utilizing transmission electron microscopy, showing an irregular shape. By means of FPV-SLNs’ nebulization, a fine particle fraction of 60.2 ± 1.7% was produced with 60.2 ± 1.7%, and this finding suggests that FPV-SLNs were appropriate for inhalation drug delivery with a particle size of 537.6 ± 55.72 nm. Importantly, the FPV-SLNs showed anti-viral activity against SARS-CoV-2 with CC50 and IC50 values of 449.6 and 29.9 µg/mL, respectively. This study suggests that inhaled solid lipid NPs of favipiravir could potentially be used against coronavirus.
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Rastogi, Bhawana, Ankush Arora, Kumkum Gupta, Manish Jain, Vijendra Pal Singh, and Avinash Rastogi. "Effect of Midazolam and 0.5% Levobupivacaine Combination in Ultrasound-guided Supraclavicular Brachial Plexus Block for Upper Limb Surgeries - A Clinical Study." Open Anesthesiology Journal 10, no. 1 (November 29, 2016): 27–33. http://dx.doi.org/10.2174/1874321801610010027.
Повний текст джерелаАнотація:
Background: The present study was designed to evaluate the hypothesis that midazolam as an adjuvant to levobupivacaine would safely enhance the duration of analgesia without any adverse effects when compared with levobupivacaine alone, in ultrasound-guided supraclavicular brachial plexus block. Primary end points were the duration of sensory and motor block and secondary end points were sedation score and any other complications. Patients and Method: Eighty consenting patients of both sexes, aged 18-60 years of ASA physical status I-II were randomized into two groups of 40 patients each. Patients in Group LS received 19 ml of 0.5% levobupivacaine with 1 ml normal saline and patients in Group LM received 19 ml of 0.5% levobupivacaine with 1ml midazolam (50µg/kg) for supraclavicular brachial plexus block using ultrasound guidance. Onset time and duration of sensory and motor blockade and VAS scores were assessed as primary end points. Hemodynamic changes, sedation or any other drug or technique related adverse effects were taken as secondary effects. Results: Onset of sensory and motor blockade was lower in patients of Group LM. The mean duration of sensory analgesia was significantly prolonged in patients of Group LM (537.6 ± 101.01 vs. 319.80 ± 87.09 mins). The mean duration of motor blockade was also significantly enhanced in patients of Group LM (405.0 ± 61.62 mins) compared to Group LS (274.8 ± 46.30 mins). VAS scores were higher in Group LS than group LM. Sedation scores were similar in both the groups. Conclusion: Midazolam with 0.5% levobupivacaine has effectively enhanced the duration of sensory and motor block without significant sedation and any other side effect.
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Kreisel, Stefan H., Mark Stroick, Martin Griebe, Angelika Alonso, Björn Reuter, Michael G. Hennerici, and Marc Fatar. "True Effects or Bias? MMP-2 and MMP-9 Serum Concentrations after Acute Stroke." Cerebrovascular Diseases 42, no. 5-6 (2016): 352–60. http://dx.doi.org/10.1159/000446405.
Повний текст джерелаАнотація:
Background: Average serum matrix metalloproteinase (MMP) concentrations in patients with acute stroke have shown to be varying across studies. Possibly, next to true effects, other factors may influence MMP levels. The aim of this study was to investigate the dynamics of these enzymes in repeated measurements in the acute post-stroke period, in respect to different stroke etiologies, and highlight potential sources for variability. Methods: Serum in 233 patients with acute ischemic or hemorrhagic stroke (stroke cohort; SC) was ascertained within 24 h after onset and then 1, 3 and 7 days thereafter. One hundred five controls (control cohort; Co) were recruited. Multi-variable adjustment was carried out using salient extraneous covariates including stroke etiology, clinical severity and lesion size next to a set of routine laboratory parameters. Results: Unadjusted SC MMP-2 concentrations are significantly lower (SC 165.4, 95% CI 158.5-172.4; Co 203.7 ng/ml, 95% CI 190.7-216.5; p < 0.001) and MMP-9 concentrations significantly higher than in controls (SC 608.5 ng/ml, 95% CI 555.3-661.8; Co 475.6 ng/ml, 95% CI 413.6-537.6; p < 0.001). Adjustment mitigates associations between MMP concentrations and stroke etiology, clinical severity, lesion size or differences in temporal profile shown present without adjustment. Salient covariates absorb much of the effect: age, leukocyte count and albumin concentrations are associated significantly with MMP-2 concentrations; only leukocyte count is significantly associated with MMP-9. Conclusions: Concentrations of MMP-2 and MMP-9 in serum in humans measured after acute stroke are potentially influenced by extraneous covariates rather than being directly associated with characteristics of the underlying stroke.
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Naim, Mona M., Nouf F. Al-harby, Mervette El Batouti, and Mahmoud M. Elewa. "Macro-Reticular Ion Exchange Resins for Recovery of Direct Dyes from Spent Dyeing and Soaping Liquors." Molecules 27, no. 5 (February 28, 2022): 1593. http://dx.doi.org/10.3390/molecules27051593.
Повний текст джерелаАнотація:
Dyes are a major class of organic pollutants that are well-known for their harmful impact on aquatic life and humans. Several new strategies for removing colours from industrial and residential effluents have recently emerged, with adsorption being the best option. The current study looked at the recovery of direct dyes from aqueous streams for reuse using macro-reticular ion exchange resins (IERs). The investigation includes dyeing single jersey cotton grey textiles with direct dyes from the Isma dye Company in Kafr El Dawar, Egypt. After centrifuging and separating the supernatant liquid, solutions from thirteen different dyes, produced at an average concentration between the wasted and soaping liquor concentrations, were calculated spectrophotometrically from the first dyeing trials. Kinetic data were well fitted with pseudo-second-order rate kinetics. The amounts of dye retained by the anion exchangers increased with a rise in temperature in the case of Strong Base Resin (SBR) and vice versa for Weak Base Resin (WBR). Batch adsorption experiments with SBR and WBR were conducted for each dye, and both Freundlich and Langmuir isotherms were constructed. It was found that adsorption obeyed both isotherms, that monolayer adsorption took place, and that the dye molecular weight, structure, and solubility, as well as the type of anionic resin used, had varying effects on the extent of absorption. The monolayer sorption capacities Q0 determined from the Langmuir isotherm model for the strongly and weakly basic anion exchangers were found to be 537.6 and 692 mg/g for Direct Yellow RL, respectively. As a result, Yellow RL exhibited the greatest adsorption on both SBR and WBR. Orange GRLL, Blue 3B, and Congo Red, on the other hand, were the poorest colours absorbed by the IERs, whereas Blue RL demonstrated good adsorption by SBR and accelerated adsorption by WBR. Most of the dyes may be recovered and reused in this manner.
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Jandosov, Jakpar, Mo Alavijeh, Shynggyskhan Sultakhan, Alzhan Baimenov, Maria Bernardo, Zuriyadda Sakipova, Seytkhan Azat, et al. "Activated Carbon/Pectin Composite Enterosorbent for Human Protection from Intoxication with Xenobiotics Pb(II) and Sodium Diclofenac." Molecules 27, no. 7 (April 1, 2022): 2296. http://dx.doi.org/10.3390/molecules27072296.
Повний текст джерелаАнотація:
The use of enterosorbents—materials which can be administered orally and eliminate toxic substances from the gastrointestinal tract (GIT) by sorption—offers an attractive complementary protection of humans against acute and chronic poisoning. In this study, we report the results of developing a microgranulated binary biomedical preparation for oral use. It was designed with a core-shell structure based on pectin with low degree of esterification as the core, and nanoporous activated carbon produced from rice husk, AC-RH, as the shell, designated as AC-RH@pectin. The adsorption properties of the synthesized materials were studied in aqueous solutions for the removal of lead (II) nitrate as a representative of toxic polyvalent metals and sodium diclofenac as an example of a medicinal drug. The composite enterosorbent demonstrated high adsorption capacity for both adsorbates studied. Adsorption kinetics of lead and diclofenac adsorption by AC-RH, pectin, and AC-RH@pectin, fitted well a pseudo-second-order model. According to the Langmuir adsorption isotherm model, the best fitted isotherm model, the maximum adsorption capacity, qmax, of AC-RH@pectin for diclofenac and for lead (II) was 130.9 mg/g and 227.8 mg/g, respectively. Although qmax of AC-RH for diclofenac, 537.6 mg/g, and qmax of pectin for lead (II), 245.7 mg/g, were higher, the maximum adsorption capacity of AC-RH for lead (II), 52.7 mg/g, was much lower than that of the composite AC-RH@pectin and the adsorption capacity of pectin for diclofenac was negligible. Therefore, the composite material AC-RH@pectin demonstrated substantial efficiency of removing both species which potentially defines it as a more universal enterosorbent suitable for treating poisoning caused by substances of different chemical nature.
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Cornelius, Mero-Lee Ursula, Alechine Emmanuel Ameh, Chuks Paul Eze, Olanrewaju Fatoba, Asel Sartbaeva, and Leslie Felicia Petrik. "The Behaviour of Rare Earth Elements from South African Coal Fly Ash during Enrichment Processes: Wet, Magnetic Separation and Zeolitisation." Minerals 11, no. 9 (August 31, 2021): 950. http://dx.doi.org/10.3390/min11090950.
Повний текст джерелаАнотація:
Rare earth elements (REEs) are essential raw materials in a variety of industries including clean energy technologies such as electric vehicles and wind turbines. This places an ever-increasing demand on global rare earth element production. Coal fly ash (CFA) possesses appreciable levels of REEs. CFA, a waste by-product of coal combustion, is therefore a readily available source of REEs that does not require mining. CFA valorisation to zeolites has been achieved via various synthesis pathways. This study aimed to evaluate one such pathway by monitoring how REEs partition during CFA processing by the wet, magnetic separation process and zeolitisation. South African CFA was subjected to wet, magnetic separation and subsequent zeolitisation of the nonmagnetic fraction (NMF); solid products were characterised by XRD, SEM, XRF and LA-ICP-MS. The wet, magnetic separation process resulted in the partitioning of a specific set of transition metals (such as Fe, Mn, Cr, V, Ni, Zn, Cu, Co and Mo) into the magnetic fraction (MF) of CFA, while REEs partitioned into the NMF with a total REE content of 530.2 ppm; thus, the matrix elements of CFA were extracted with ease. Zeolitisation resulted in a solid zeolite product (hydroxysodalite) with a total REE content of 537.6 ppm. The process of zeolitisation also resulted in the selective enrichment of Ce (259.1 ppm) into the solid zeolite product (hydroxysodalite), while other REEs were largely partitioned into the liquid phase. CFA valorisation by wet, magnetic separation and zeolitisation therefore allowed for the partitioning of REEs into various extraction products while recovering the matrix elements of CFA such as Fe, Si and Al. The findings of this study highlight the geopolitical importance of REEs in terms of the development of alternative processes for REE recovery from waste and alternative sources, which may potentially give countries that employ and develop the technology a key advantage in the production of REEs for the global market.
Дисертації з теми "621.318:537.6"
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Кovalenko, Viktoriya, and Oksana Tykhenko. "Wireless communication safety analysis." Thesis, Proceedings the Seventh World Congress «Aviation in the XXI-st Century», September 19 – 21, 2016. – P. 5.4.46 – 5.4.48, 2016. http://er.nau.edu.ua/handle/NAU/29355.
Повний текст джерела
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Vasilev, Nikolay. "Critical and surface phenomena in quantum fluids investigated by neutron scattering." Thesis, Lancaster University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664265.
Повний текст джерелаАнотація:
Neutron scattering from the free surface of liquid He has been used to investigate the distribution of 3He atoms in extremely dilute 3He-4He solutions at temperatures down to 0.08 K In particular evidence has been sought and found for the existence of Andreev trapping states for 3He just below the surface. The experiments were conducted in ISIS at the Rutherford Appleton Laboratory using the CRISP instrument (a general purpose reflectometer). The neutron scattering from the surface of 4 He (industrial and high purity) also was investigated and compared with dilute 3He-4He solutions. The 3He surface layer was observed for the first time using a small-angle neutron scattering (SANS) technique. The thickness of the layer is strongly dependent on temperature and 3He concentration. Even in the case of industrial 4He and even at 2.3 K (higher than superfiuid transition) a substantial amount of 3He atoms was found close to the surface. In the case of extremely pure 4He the 3He atoms on the surface were not observed. At low temperature (0.4 K) a very thin layer of 3He atoms was observed and the calculated thickness (based on our experimental results) is approximately ~10 A of pure 3He on the top of the mixture. It is followed by a diffusive interface area (also observed experimentally) of 3He-4He mixture of thick layer approximately ~200 A, just below that almost pure 3He thin layer on the top. With increase of the concentration the thickness of the top layer increases until it reaches a limit above which the 3He starts dissolving in the bulk superfiuid liquid 4He. Neutron critical opalescence from 3He gas/vapour was observed for the first time and the information for 3He density was obtained in a broad range of temperatures 1.4 - 50 K. The data was compared with the results gathered by using different techniques. Far from the critical temperature all methods yield similar results. However, near the critical temperature of Tc = 3.32 K, the densities obtained from neutron transmission results are lower than other published results.
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Hadden, J. P. "Photonic structures and techniques for enhanced measurement of spin qubits in diamond." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664971.
Повний текст джерелаАнотація:
The negatively charged nitrogen vacancy centre is a promising candidate for use as a single photon source for linear optical quantum information, and as a solid state spin for solid state quantum information and room temperature magnetometry. However low photon collection efficiency is a problem for each of these applications. We demonstrate how photon losses due to refraction can be eliminated through the use of Solid Immersion Lenses (SILs) nano-fabricated on the surface of diamond. Coherent electron spin manipulation and readout is demonstrated on NV- centres under SILs. We show initial investigations into the effects of FIB fabrication on the NV- centre's coherence time, and demonstrate unitary quantum process discrimination on between two non orthogonal processes. In order to improve collection efficiency further it is necessary to couple NV- centres to optical micro cavities. This requires a higher degree of precision in the measurement of the NV- centres position than is possible using conventional confocal microscopy. We investigate spectral self interferometric microscopy as a method for precision measurement of the depth of an NV- centre. Finally we show coherent manipulation of photons emitted from a near infra-red colour centre in diamond using a single integrated waveguide chip. This is used to verify wave particle duality of the photons.
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Phillips, Kathryn Louise. "Torque magnetometry studies on the breakdown of the quantum Hall effect." Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/55915/.
Повний текст джерелаАнотація:
Torque magnetometry techniques have been employed to study the quantum Hall effect in several AIGaAs/GaAs-heterostructure two-dimensional electron gas samples at filling factors between 1 and 4. Two magnetometers were employed to acquire measurements for three samples an existing instrument was used to acquire data for two samples and a novel instrument has been developed in which the output signal sensitivity is increased by 700% during experiments on a third sample. The third sample was also illuminated in situ. The samples exhibit breakdown-like behaviour in two forms. The first is the saturation of the magnetic moment peak size with respect to increasing sweep rate. A simple charge-up model, which treats the charge density of the sample in terms of a capacitance around the edge of the sample, was used to analyse experimental data. Temperature dependence of the longitudinal conductivity is analysed with respect to a published model of Polyakov and Shklovskii. The charge-up time constant, rc (10--105) seconds, decreased with increasing temperature and was found to follow a straight line when plotted on a logarithmic scale against temperature. Characteristic temperatures extracted from the data lie in the range T0 * (0.2--2.0) Kelvin. Decay time measurements were performed to acquire the decay time constant rd. Two regimes of decay were observed, the first exhibiting a time constant of the order of several seconds followed by a second phase with a much larger time constant many minutes or hours. The second form of breakdown was demonstrated as a type of noisy breakdown clearly observed at filling factor 2 in two samples. This noise, of the form of sudden jumps followed by more gradual growth, was interpreted using an edge charge-up model and is thought to be consistent with the sand-pile model of the theory of self-organised criticality. As a result the frequency of occurrence of noisy jumps as a function of their particular size is seen to follow a power law. Time constants of individual noise jumps were found to lie mainly in the range (1--10) seconds.
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Mouchliadis, Leonidas. "Transport and coherence properties of indirect excitions in coupled quantum wells." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54724/.
Повний текст джерелаАнотація:
This dissertation consists of a theoretical investigation into the transport and coherence properties of indirect excitons in coupled quantum wells (QWs) at helium temperatures. The motion of excitons along the quantum well plane is described through a quantum diffusion equation and the possibility of excitonic cloud formation is studied both due to the natural potential fluctuations and externally applied confining potentials. The photoluminescence (PL) of decaying excitons is used as a probe for their properties such as concentration, effective temperature and optical lifetime. The exciton thermalisation from an initial high energy to the lattice temperature is achieved within their lifetime due to a very effective coupling between the exciton states and a continuum of phonon states, a direct consequence of the relaxation of momentum conservation along the growth direction of a QW. Moreover, the natural spatial separation between electrons and holes prevents their recombination, resulting in long lifetimes. The dynamics of the system of excitons in optically-induced traps is also studied and the numerical solution of the quantum diffusion equation provides an insight into the extremely fast loading times of the trap with a highly degenerate exciton gas. The hierarchy of timescales in such a trap allows for the creation of a cold and dense gas confined within the trap, opening a new route towards the long sought Bose-Einstein Condensation (BEC) in solid state. Finally the issue of exciton spatial coherence is studied and an analytic expression for the coherence function, i.e., the measure of the coherence in a system, is derived. A direct comparison with large coherence lengths recently observed in systems of quantum well excitons and microcavity polaritons is attempted and interesting conclusions are drawn regarding the build up of spontaneous coherence in these systems.
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Styth, Melissa. "Excitons in a dilute magnetic semiconductor in the presence of an inhomogeneous magnetic field." Thesis, University of Bath, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.642018.
Повний текст джерелаАнотація:
Dilute magnetic semiconductors (DMSs) are ideal candidates for spintronic devices as they exhibit both semiconducting and magnetic properties. The defining feature of a DMS material is the exchange interactions between the magnetic ions and the band electrons and holes, which leads to many of the spin behaviours observed. A fundamental property of DMSs is that a relatively small external magnetic field can cause enormous Zeeman splittings of the electronic energy levels, which allows separating of states with different spins. The giant Zeeman effect present in the DMS systems also leads to the possibility of trapping quasiparticles in an inhomogeneous magnetic field. In this thesis the effect of inhomogeneous magnetic fields on excitons in a DMS quantum well is investigated. We look at the possibility of trapping excitons in hybrid structures composed of a DMS quantum well placed a few nanometres below a nanoscale and microscale ferromagnetic disk and a ferromagnetic strip. Quasiparticles in a DMS quantum well are shown to undergo a splitting between band states for different spin components due to the giant Zeeman interaction. Due to the inhomogeneous magnetic field created by a nanoscale ferromagnetic disk in the vortex state the quasiparticles are found to be confined in a small region on the quantum well. The behaviours of excitons in the presence of both a homogeneous and inhomogeneous magnetic field is then discussed. The binding energy of a heavy hole exciton in a finite DMS quantum well in the presence of a homogeneous is calculated. The study is extended to look at excitons in the presence of an inhomogeneous magnetic field. The behaviour of excitons in the presence of a inhomogeneous magnetic field, is found to depend on the type of magnetic field, and is shown to be different for a magnetic field created by a microscale and nanoscale ferromagnetic disk and a ferromagnetic strip.
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Lay, Joshua Henry. "Nanoscale investigations of the crystal structure and surface electronic properties of polycrystalline boron-doped diamond films." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664973.
Повний текст джерелаАнотація:
Existing as much more than just a gemstone or refractory material, boron-doped diamond is a semiconductor with enormous potential as an electronic material. Diamond will form the basis of future high-power electronic devices, radiation-hard electronics and radiation detectors. It is also a highly effective electron emitter and a unique, biocompatible material for biomedical devices. Still, many questions remain surrounding the versatile, easy to grow polycrystalline form of boron-doped diamond. What is the surface atomic structure of these films after growth? How uniform is the boron-induced conductivity? How and why does the work function vary across the films? All of these properties affect how diamond electronic devices can be designed, fabricated and used. In this thesis we investigate nanoscale variation in properties across the surfaces of a number of differently grown boron-doped diamond films under ultra-high vacuum and evaluate the potential impact of the changes in these properties to surface electronic applications of diamond. Kelvin probe force microscopy results demonstrate significant variation in work function across the diamond surface, with a step change in work function of 0.8 eV measured between hydrogen and oxygen surface terminations, and variations across a single diamond surface are calculated to correspond to a 310% change in dopant concentration . The effect of this dopant variation is demonstrated by conductive atomic force microscopy studies in which entire crystallites exhibit insulating behaviour, with significant variation in conduction also observed across the surface. Finally, scanning tunneling microscopy studies of the diamond surface demonstrate that nanoscale roughness on large microcrystals is caused by the existence of a layer of nanocrystalline diamond at the surface. These nanocrystals persist throughout the growth process and exhibit many different surface reconstructions. The implications of all of these discoveries are discussed, with possibilities and suggestions for further work given also.
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Putzke, Carsten Matthias. "Fermi surface and quantum critical phenomena of high-temperature superconductors." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680124.
Повний текст джерелаАнотація:
This thesis presents the results obtained from de Haas-van Alphen experiments in ironbased superconductors. Measurements of the quasi particle mass in the quantum critical system BaFe2(Asl- xPxh are presented, which show strong enhancement towards the critical composition Xc = 0.3. This is found to be in good agreement with the prediction of a diverging behaviour of the effective mass close to a quantum critical point. Further results obtained on the lower and upper superconducting critical field of this system will be presented, which are found to contradict the expectations from Ginzburg-Landau theory based on results of the quasi particle mass and London penetration depth. However we can reconcile the different experimental findings on superconducting and normal state properties, in this quantum critical system, by considering a significant contribution from Abrikosov vortex core states. The importance of understanding the normal state electronic structure and interactions is shown to be essential for an understanding of the superconducting ground state of a quantum critical system. Further we will show a detailed de Haas-van Alphen study of the il1-type iron-based superconductor LiFeP and its isovalent partner LiFeAs. To understand the formation of nodes on the superconducting gap structure in systems with little change in their Fermi surface topology, is essential for the formulation of a microscopic theory of the pairing mechanism in pnictide-superconductors. 'While we find both systems to be close to the geometric nesting condition, we are able to point to different possible scenarios of the origin of nodes based on quasi particle mass enhancement. Extending the study of quasi particle mass and its relation to the superconducting properties to the stoichiometric high-temperature cuprate superconductor YBa2 CU4 Os, we aim to study the Fermi surface evolution under hydrostatic pressure. As the system has a very stable oxygen stoichiometry which does not allow it to be doped by oxygen ordering, we use hydrostatic pressure to tune the system unexpectedly leading to an increase in the superconducting critical temperature with almost no change to the quasi particle mass .
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Tyrrell, Sophie. "Ionothermal synthesis of chalgogenide semiconductor materials." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676604.
Повний текст джерелаАнотація:
Microcrystalline indium(III) selenide was prepared from a diphenyl diselenide precursor and a range of chloroindate(III) ionic liquids via a microwave-assisted ionothermal route. A mixture of nano- and micro-sized zinc(lI) selenide materials were also prepared using the same ionothermal procedure and chlorozincate ionic liquids. Influence of the reaction temperature and variation of the cation and the anion of the ionic liquid on the product morphology and composition were investigated. All products formed were characterised using PXRO, SEM and EOX. Additional characterisation was carried out using Raman spectroscopy and photoluminescence measurements. The investigation into the production of indium(III) selenide, zinc(II) selenide and gallium(III) selenide semiconductor materials using conventional heating methods was subsequently carried out and the products were characterized using SEM, EOX and ESI-MS. Electrochemical investigations into some of the stable homogeneous liquids that were formed between the chloroindatel chlorzincate ionic liquids with the diphenyl diselenide with conventional heating, have been carried out. An additional selenium precursor, selenium tetrachloride, was also investigated with the depositions analysed using SEM and EOX. Finally, the ternary compound copper indium selenide (CIS) has been prepared as nano- and micro-sized materials through colloidal synthesis using an indium(III) selenide precursor and copper(I) chloride via a microwave-assisted ionothermal route. The crystal structures of three intermediate structures were determined after formation through an ionothermal procedure utilising metal-containing imidazolium ionic liquids and a selenium precursor with conventional heating. A comparative study into the use of microwave irradiation over conventional heating with different ionic liquids on the stoichiometry of the resulting products was carried out. The influence of the reaction temperature, reaction time, order of addition of reagents and variation of ionic liquids on the final products was investigated, which have been characterized using PXRO, SEM and EOX. I
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Yoon, Minho. "New processing techniques for large-area electronics." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/43761.
Повний текст джерелаАнотація:
Recent advancements in the semiconductor industry have been driven by the extreme downscaling of device dimensions enabled by innovative photolithography methods. However, such nano-scale patterning technologies are impractical for large-area electronics primarily due to extremely high cost and incompatibility with large-area processing. Therefore, alternative techniques that are simpler, more scalable and compatible with large-area manufacturing are required. This thesis explores the technological potential of two recently developed patterning techniques namely interlayer lithography (IL) and adhesion-lithography (a-Lith) for application in the field of large-area nano/electronics. The IL method relies on the use of a pre-patterned metal electrode that acts as the mask during back illumination of a photoresist layer followed by a conventional lift-off process step. On the other hand in the a-Lith approach, the surface energy of a patterned metal electrode is modified through the use of surface energy modifiers such as organic self-assembling monolayer (SAM). Following, a second metal is evaporated on the entire substrate. However, because of the present of the SAM, regions of metal-2 overlapping with metal-1 can easily be peeled off with the aid of an adhesive layer (e.g. sticky tape) leaving behind the two metal electrodes in close proximity to each other. Analysis of the resulting structures reveals that inter-electrode distances < 20 nm can easily be achieved. The method was then used to develop innovative process protocols for the fabrication of functional self-aligned gate (SAG) transistor architectures. Best performing devices exhibited charge carrier mobility in the range of 0.5-1 cm2/Vs, high current on-off ratio (~104), negligible operating hysteresis and excellent switching speed. Using the same a-Lith process protocol, low-voltage organic ferroelectric tunnel junction memory devices were also developed by combining the metal-1/metal-2 nanogap electrodes with a ferroelectric copolymer deposited in-between them. Controllable ferroelectric tunnelling was observed enabling the devices’ conductivity to be programmed using low biases and hence been used as a non-volatile memory cell. The alternative and highly scalable patterning methods described in this thesis may one day play a significant role on how largearea electronics of the future would be manufactured.
Частини книг з теми "621.318:537.6"
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"Index Of Arabic Names." In Practical Materia Medica of the Medieval Eastern Mediterranean According to the Cairo Genizah, 605–11. BRILL, 2008. http://dx.doi.org/10.1163/ej.9789004161207.i-621.318.
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"Chapter One. The Politics Of Language In China And The West (The 19th Century)." In The Politics of Language in Chinese Education, 1895–1919, 1–76. BRILL, 2008. http://dx.doi.org/10.1163/ej.9789004163676.i-537.6.
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