scholarly journals Optical Conductivity of Colossal Magnetoresistance Manganites

2021 ◽  
Author(s):  
◽  
Ocean Ripeka Mercier
Keyword(s):  
Energy Range ◽  
Optical Conductivity ◽  
Colossal Magnetoresistance ◽  
Normal Incidence ◽  
Optical Investigation ◽  
Temperature Dependent ◽  
Two Samples ◽  
Before And After ◽  
Interacting Electrons ◽  
Metallic Ferromagnet

<p>The colossal magnetoresistance manganites are a group of materials whose unusual physical properties are a symptom of strongly interacting electrons and phonons. In order to elucidate some of these electronic and vibrational properties, an infrared optical investigation of manganites with a broad range of physical characteristics has been performed. Temperature-dependent normal incidence reflectivity measurements have been made on two samples of manganites, in the energy range of 60 cm-1 - 50000 cm-1, 1 for La0.9 Ca0.1 MnO3, an insulating ferromagnet, and 2 La0.735 Ca0.265 MnO3, a metallic ferromagnet. Temperature-dependent ellipsometric reflection measurements were performed in the energy range of 50 cm-1 - 5000 cm-1, on four faces of two samples of structurally anisotropic manganite, probing the 3. ab plane and c-axis of La1.2 Sr1.8 Mn2O7, a metallic ferromagnet, and 4. the ab plane and c-axis of PrSr2 Mn2O7, an insulating antiferromagnet. The optical conductivity for each of the first two samples has been deduced by a careful Kramers-Kronig analyis of the normal incidence reflectivity. For samples 3. and 4. the optical conductivity has been deduced by inversion of the ellipsometric constants, and a careful subsequent fitting to account for their anisotropy. The transition temperatures and types of magnetic order for all samples have also been characterised by magnetisation measurements. Treatment of the surface is shown to be critical in reflectivity measurements by the observation of hugely contrasting spectra, measured from a polished sample of metallic-like La0.735 Ca0.256 MnO3, before and after annealing. Several features observed in the measurements, especially for the layered materials, are consistent with the idea that a polaron, or electron-lattice interaction, is hugely important in a description of the electron dynamics of these materials. The correlation between spectral features and the structural and magnetic properties of the materials is investigated, finding that the cause of charge transport modification seen in the metallic-like materials could be explained by either a polaron or localisation due to disorder.</p>

scholarly journals Optical Conductivity of Colossal Magnetoresistance Manganites

2021 ◽  
Author(s):  
◽  
Ocean Ripeka Mercier
Keyword(s):  
Energy Range ◽  
Optical Conductivity ◽  
Colossal Magnetoresistance ◽  
Normal Incidence ◽  
Optical Investigation ◽  
Temperature Dependent ◽  
Two Samples ◽  
Before And After ◽  
Interacting Electrons ◽  
Metallic Ferromagnet

<p>The colossal magnetoresistance manganites are a group of materials whose unusual physical properties are a symptom of strongly interacting electrons and phonons. In order to elucidate some of these electronic and vibrational properties, an infrared optical investigation of manganites with a broad range of physical characteristics has been performed. Temperature-dependent normal incidence reflectivity measurements have been made on two samples of manganites, in the energy range of 60 cm-1 - 50000 cm-1, 1 for La0.9 Ca0.1 MnO3, an insulating ferromagnet, and 2 La0.735 Ca0.265 MnO3, a metallic ferromagnet. Temperature-dependent ellipsometric reflection measurements were performed in the energy range of 50 cm-1 - 5000 cm-1, on four faces of two samples of structurally anisotropic manganite, probing the 3. ab plane and c-axis of La1.2 Sr1.8 Mn2O7, a metallic ferromagnet, and 4. the ab plane and c-axis of PrSr2 Mn2O7, an insulating antiferromagnet. The optical conductivity for each of the first two samples has been deduced by a careful Kramers-Kronig analyis of the normal incidence reflectivity. For samples 3. and 4. the optical conductivity has been deduced by inversion of the ellipsometric constants, and a careful subsequent fitting to account for their anisotropy. The transition temperatures and types of magnetic order for all samples have also been characterised by magnetisation measurements. Treatment of the surface is shown to be critical in reflectivity measurements by the observation of hugely contrasting spectra, measured from a polished sample of metallic-like La0.735 Ca0.256 MnO3, before and after annealing. Several features observed in the measurements, especially for the layered materials, are consistent with the idea that a polaron, or electron-lattice interaction, is hugely important in a description of the electron dynamics of these materials. The correlation between spectral features and the structural and magnetic properties of the materials is investigated, finding that the cause of charge transport modification seen in the metallic-like materials could be explained by either a polaron or localisation due to disorder.</p>

scholarly journals The Effect of Acetic Acid Treatments on the Quality of Stored Carrot (Daucus carota L.) Seeds

Agronomy ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1176
Author(s):  
Hanna Dorna ◽  
Agnieszka Rosińska ◽  
Dorota Szopińska
Keyword(s):  
Acetic Acid ◽  
Distilled Water ◽  
Storage Duration ◽  
Seed Vigour ◽  
Daucus Carota L ◽  
Two Samples ◽  
Before And After ◽  
Alternaria Dauci ◽  
Acid Treatments

Alternaria dauci (J.G. Kühn) J.W. Groves et Skolko and A. radicina Meier, Drechsler et E.D. Eddy are important seed-transmitted pathogens of carrot. The aim of this study was to evaluate the effects of acetic acid treatments on the quality of stored carrot seeds. Seeds of two samples were soaked for 30 min in 0.5, 1 and 2% acetic acid. Controls included untreated seeds, seeds soaked in distilled water and seeds treated with fungicide Zaprawa Nasienna T 75 WS/DS (a.i. thiram 75%). Germination, vigour and health of untreated and treated seeds were evaluated before and after 5 and 12 months of storage at 4 and 20 °C. Seeds of both samples treated with 0.5 and 1% acetic acid were characterized by higher germination capacity after storage than untreated seeds. However, treatments with 1 and 2% acetic acid negatively affected seed vigour. Generally, seeds of both samples treated with acetic acid were characterized by lower infestation with A. alternata and A. radicina after storage than untreated seeds and seeds soaked in distilled water. Moreover, acetic acid often controlled these fungi more effectively than the fungicide. Regardless of the storage duration, infestation with fungi was higher if seeds of both samples were stored at a lower temperature.

Honesty in Personal Tax Reporting: Ethical Prompts, Individual Factors, and Tax Reform

2020 ◽  
Author(s):  
Charles D. Bailey ◽  
James M. Plecnik
Keyword(s):  
Tax Evasion ◽  
Large Scale ◽  
Tax Reform ◽  
Dark Triad ◽  
Individual Factors ◽  
Voluntary Compliance ◽  
Two Samples ◽  
Before And After ◽  
Tax Reporting ◽  
Jobs Act

This study focuses on whether an ethical prompt, adapted from Mazar et al. (2008), can reduce easily concealed tax evasion—i.e., tax evasion relating to cash-based income for which the IRS relies on voluntary compliance. We also consider the “Dark Triad” personality traits and other individual attitudes and characteristics that may drive or predict tax evasion intentions. We unexpectedly find that ethical prompts do not affect intent to engage in tax evasion, but our result is consistent with a newly released large-scale replication project that fails to find an effect for this much-discussed religious/ethical prompt, and the power of our test is about 80%. Of the variables studied, only psychopathy, commitment to the process of taxation, and fear of punishment predict intent to evade. These findings are consistent across two samples, taken both before and after the passage of the Tax Cuts and Jobs Act of 2017.

scholarly journals A Study of the Micropore Structure of Carbonized Rayon Yarn by Nitrogen Adsorption and Nonane Pre-Adsorption

1985 ◽  
Vol 2 (2) ◽  
pp. 89-95 ◽  
Author(s):  
J. N. Bohra ◽  
K. S. W. Sing
Keyword(s):  
External Surface ◽  
Nitrogen Adsorption ◽  
The Other ◽  
Adsorption Method ◽  
Micropore Structure ◽  
Surface Areas ◽  
Three Samples ◽  
Two Samples ◽  
Before And After ◽  
Gain Access

Adsorption isotherms of nitrogen have been determined at 77 K on three samples of carbonized rayon yarn, both before and after the pre-adsorption of n-nonane. In their original state the three samples were all highly microporous. Application of the αs-method of isotherm analysis reveals that their micropore volumes were 0·17–0·19 cm3g−1 and their external surface areas 20–27 m2g−1 (the corresponding BET areas being 427–483 m2g−1). Nonane pre-adsorption resulted in blockage of the entire micropore structure only in the case of one sample: micropore volumes ∼0·1 cm3g−1 were still available for nitrogen adsorption in the other two samples. It appears that nitrogen molecules were able to gain access to some parts of these micropore structures through wider pore entrances which were not completely blocked by the pre-adsorbed nonane. The work has shown that the nonane pre-adsorption method requires further investigation before it can be used with confidence for the assessment of microporosity.

Improved SiO2/ 4H-SiC Interface Defect Density Using Forming Gas Annealing

2019 ◽  
Vol 963 ◽  
pp. 465-468
Author(s):  
Stephan Wirths ◽  
Giovanni Alfieri ◽  
Alyssa Prasmusinto ◽  
Andrei Mihaila ◽  
Lukas Kranz ◽  
...  
Keyword(s):  
Defect Density ◽  
Deep Level ◽  
Flat Band ◽  
Temperature Dependent ◽  
Mos Capacitors ◽  
Interface Defect ◽  
Before And After ◽  
Oxide Deposition ◽  
Transient Spectroscopy ◽  
Post Deposition

We investigated the influence of forming gas annealing (FGA) before and after oxide deposition on the SiO2/4H-SiC interface defect density (Dit). For MOS capacitors (MOSCAPs) that were processed using FGAs at temperatures above 1050°C, CV characterization revealed decreased flat band voltage shifts and stretch-out for different sweep directions and frequencies. Moreover, constant-capacitance deep level transient spectroscopy (CC-DLTS) was performed and showed Dit levels below 1012 cm-2eV-1 for post deposition FGA at 1200°C. Finally, lateral MOSFETs were fabricated to analyze the temperature-dependent threshold voltage (Vth) shift.

Effect of thiol oxidation and thiol export from erythrocytes on determination of redox status of homocysteine and other thiols in plasma from healthy subjects and patients with cerebral infarction

1995 ◽  
Vol 41 (3) ◽  
pp. 361-366 ◽  
Author(s):  
A Andersson ◽  
A Lindgren ◽  
B Hultberg
Keyword(s):  
Cerebral Infarction ◽  
Healthy Subjects ◽  
Redox Status ◽  
Reduced Form ◽  
Temperature Dependent ◽  
First Order ◽  
First Order Kinetics ◽  
Before And After ◽  
Reduced Forms

Abstract Changes in concentration of reduced and oxidized low-M(r) thiols were measured in blood and plasma before and after the separation of blood cells. If centrifugation of blood was postponed, the reduced form of homocysteine in plasma increased with time at 22 degrees C; in contrast, the concentrations of other reduced thiols (cysteine, glutathione, and cysteinylglycine) decreased. In plasma the reduced forms of all thiols disappeared at a rate that followed first-order kinetics. The rates of disappearance ("half-lives") were temperature-dependent; they were about the same for glutathione and homocysteine (11.7 and 14.3 min, respectively, at 22 degrees C) and somewhat higher for cysteinylglycine and cysteine. After establishing proper sampling conditions for reduced thiols, we measured this thiol fraction as well as free (non-protein-bound) and total thiols in 10 reference subjects and 19 patients with cerebral infarction. Mild but significant hyperhomocysteinemia involving total and free homocysteine (but not reduced homocysteine) was found in the patients.

Advanced Telematics for Travel Decisions: A Quantitative Analysis of the Stopwatch Project in Southampton

1997 ◽  
Vol 29 (6) ◽  
pp. 1003-1016 ◽  
Author(s):  
H Ouwersloot ◽  
P Nijkamp ◽  
G Pepping
Keyword(s):  
Quantitative Analysis ◽  
Theoretical Model ◽  
Cost Minimization ◽  
Information Service ◽  
Uncertainty Reduction ◽  
Two Samples ◽  
Before And After ◽  
Travel Decisions ◽  
Reduction Of Uncertainty ◽  
New System

The effect of telematics technology on public transport use is analyzed on the basis of a theoretical model. Two possible mechanisms (reduction of uncertainty and a better choice of bus options, based on a general cost-minimization assumption) that may stimulate bus use are distinguished. The model is empirically tested by using microdata from the Southampton Stopwatch telematics project, which were collected both before and after the introduction of this telematics information service. The estimation of the model leads to interesting findings in explaining (anticipated) increases in bus use, for both the before and the after survey. It is shown that uncertainty reduction is the more important effect of the new system. Differences in the before and after data are found concerning the increase in bus use, but the explanatory model proves consistent over the two samples.

LATERAL INTERSUBBAND PHOTOCURRENT STUDY ON InAs/InAlAs/InP SELF-ASSEMBLED NANOSTRUCTURES

2006 ◽  
Vol 05 (06) ◽  
pp. 729-735
Author(s):  
W. LEI ◽  
Y. H. CHEN ◽  
P. JIN ◽  
B. XU ◽  
X. L. YE ◽  
...  
Keyword(s):  
Energy Range ◽  
Photon Energy ◽  
Normal Incidence ◽  
Peak Shift ◽  
Excitation Level ◽  
High Excitation ◽  
Intersubband Absorption ◽  
Thermal Escape ◽  
Self Assembled ◽  
State Filling

We present lateral intersubband photocurrent (PC) study on self-assembled InAs/InAlAs/InP (001) nanostructures in normal incidence. With the help of interband excitation, a broad PC signal has been observed in the photon energy range of 150–630 meV arising from the bound-to-continuum intersubband absorption in the InAs nanostructures. The large linewidth of the intersubband PC signal is due to the size inhomogeneity of the nanostructures. With the increase of the interband excitation the intersubband PC signal firstly increases with a redshift of PC peak and reaches its maximum, then decreases with no peak shift. The increase and redshift of the PC signal at low excitation level can be explained by the state filling effect. However, the decrease of PC signal at high excitation level may be due to the change of the mobility and lifetime of the electrons. The intersubband PC signal decreases when the temperature is increased, which can be explained by the decrease of the mobility and lifetime of the electrons and the thermal escape of electrons.

scholarly journals Ion-pair chromatographic monitoring of photographic effluents

2007 ◽  
Vol 5 (2) ◽  
pp. 455-465
Author(s):  
Giedrė Kesiũnaitė ◽  
Birutė Pranaitytė ◽  
Audrius Padarauskas ◽  
Arvydas Dikčius ◽  
Romas Ragauskas
Keyword(s):  
Ionic Strength ◽  
Mobile Phase ◽  
Ion Pair ◽  
Chromatographic Technique ◽  
Two Samples ◽  
Neutral Compounds ◽  
Before And After ◽  
Rapid Monitoring ◽  
Chromatographic Monitoring

AbstractIon-pair chromatographic technique was developed for the rapid and simple determination of the main contaminants (bromide, iodide, sulphite, thiosulphate, thiocyanate, iron(III)-EDTA chelate, free EDTA, hydroquinone and phenidone) in spent photographic solutions. Free EDTA was converted into stable Ni(II)-EDTA chelate prior to analysis. The optimal mobile phase conditions were established by varying the concentrations of tetrabutylammonium (TBA) phosphate and acetonitrile, pH and ionic strength. Separation of five inorganic anions, two metal chelates and two neutral compounds was accomplished in about 30 min using a mobile phase containing 7.5 mmol/L TBA-phosphate, 10 mmol/L NaCl (pH 6.5) and 20% (v/v) acetonitrile. The detection limits (UV detection at 210 nm) ranged from 0.4 µmol/L for phenidone to 8 µmol/L for sulphite with a linearity of 2–2.5 orders of magnitude. The method was applied to the rapid monitoring of spent photographic solutions before and after decomposition. The recovery tests established for two samples were within the range 95–103%.

Subtest Scores of a Comprehensive Examination of Medical Knowledge as a Function of Retention Interval

1984 ◽  
Vol 55 (2) ◽  
pp. 579-586 ◽  
Author(s):  
Mohammadreza Hojat ◽  
J. Jon Veloski
Keyword(s):  
Retention Interval ◽  
Medical Training ◽  
Linear Trend ◽  
Medical Knowledge ◽  
Learning Theories ◽  
Jefferson Medical College ◽  
Medical College ◽  
Two Samples ◽  
Comprehensive Examination ◽  
Before And After

It was hypothesized that performance on particular subtests of a comprehensive examination of medical knowledge would be a function of the length of time between completion of the respective medical training and the administration of the comprehensive examination. Two samples of graduates of the Jefferson Medical College including 1086 students who graduated between 1975 and 1979, and 877 who graduated in 1980 through 1983 were studied. Each student in the junior year of medical school had been assigned to one of four groups. Each group took the required clerkship training in internal medicine, obstetrics/gynecology, pediatrics, psychiatry and surgery in a different rotational sequence. Statistical analyses indicated that there were no statistically significant differences among the four groups in the two samples, before and after the junior year on total comprehensive medical examination scores. However, an expected linear trend was found in scores on subtests of psychiatry, obstetrics/gynecology, and surgery in both samples. The observed trend indicated that the shorter the retention interval between clerkship training and the respective examination, the higher the score on that examination. Data were analyzed in terms of some hypotheses from learning theories, and implications for medical education were discussed.

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