Simple explanation of tunneling spin-polarization of Fe, Co, Ni and its alloys

1977 ◽  
Vol 5 (2) ◽  
pp. 167-171 ◽  
Author(s):  
Mary Beth Stearns
Keyword(s):  
Spin Polarization ◽  
Simple Explanation ◽  
Ni And Its Alloys

Spin Injection and Spin Dynamics at CuPC/GaAs(100) Interface

2006 ◽  
Vol 965 ◽  
Author(s):  
Huanjun Ding ◽  
Yongli Gao ◽  
Marina Sanchez-Albaneda ◽  
Jan-Peter Wüstenberg ◽  
Mirko Cinchetti ◽  
...  
Keyword(s):  
Spin Polarization ◽  
Optical Pumping ◽  
Copper Phthalocyanine ◽  
Spin Dynamics ◽  
Spin Injection ◽  
Simple Explanation ◽  
Time Resolved ◽  
Two Photon ◽  
Blue Excitation ◽  
Long Lifetime

ABSTRACTSpin injection from GaAs(100) to organic semiconductor copper phthalocyanine (CuPc) has been investigated experimentally with spin-resolved two-photon photoemission (SR-2PPE) spectroscopy. With SR-2PPE, the dynamics of both electron and spin relaxation have been studied with femtosecond time resolution. The spin-polarized electrons are originally generated in GaAs through optical pumping and injected into CuPc. We observed an enhancement in spin polarization at the interface after initial CuPc deposition. This demonstrates that interface spin scattering is insignificant, which is similar to our previous result of spin injection at CuPc/Co interface. The spin polarization dropped when the CuPc film became thick, an effect attributed to bulk attenuation in CuPc. The lifetime of the unoccupied orbits in CuPC was also studied with red-blue excitation of photon energy 1.56 eV and 3.12 eV, respectively. There was a strong asymmetry in the time-resolved spectra, and an unexpected long lifetime when the lower unoccupied orbital was excited. A simple explanation of this phenomenon will be discussed.

CONCEPT-BASED LEARNING DAN KEMAMPUAN BERFIKIR KRITIS MATEMATIS

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Maifalinda Fatra ◽  
A Rizki ◽  
Tita Khalis Maryati
Keyword(s):  
Critical Thinking ◽  
Mathematics Learning ◽  
Sampling Technique ◽  
Thinking Skills ◽  
Learning Model ◽  
Critical Thinking Skills ◽  
Control Group ◽  
Simple Explanation ◽  
Critical Thinking Ability ◽  
Thinking Ability

Mathematical Critical thinking is one of  mathematical abilities that must be obtained by students. Critical thinking is one of the high order thinking processes that can make concepts in student knowledge.  Students with critical thinking in mathematics learning mostly do rational activities such as interpreting information based on a particular theoretical framework, linking theory with practice, making claims and justifying it, utilizing data in support of argumentation, making relations or relationships between various ideas, asking questions, evaluating knowledge, predict, describe something, analyze, synthesize, and categorize. This study aims to analyze the effect of the Concept-Based Learning Model on the critical thingking mathematical abilities.The purpose of this research is to analyze the effect of Concept-Based Learning Model toward mathematics critical thinking ability. The method used in this research is quasi experiment by Randomize Control Group Post Test Only Design with cluster random sampling technique. Indicators of mathematics critical thinking skills measured in this study include providing simple explanations, building basic skills, concluding, making more explanations, and deciding an action. The results showed that the mathematics critical thinking ability of students in the experimental class for the five indicators that being analyze was higher than the ability of students in the control class. A fairly high difference in the indicator showed in give a simple explanation and concluding. and it means that the application of Concept-Based Learning Model significantly influences the  abilities  of students' mathematics critical thinking.

Behavioural and EEG atypicalities during rest, visual perception, and cognitive control in autistic adults

2020 ◽  
Author(s):  
Amandine Lassalle ◽  
Michael X Cohen ◽  
Laura Dekkers ◽  
Elizabeth Milne ◽  
Rasa Gulbinaite ◽  
...  
Keyword(s):  
Visual Perception ◽  
Cognitive Control ◽  
Visual Processing ◽  
Autism Spectrum ◽  
Neural Dynamics ◽  
Simple Explanation ◽  
Control Task ◽  
Neural Structure ◽  
Eeg Power ◽  
Autistic Adults

Background: People with an Autism Spectrum Condition diagnosis (ASD) are hypothesized to show atypical neural dynamics, reflecting differences in neural structure and function. However, previous results regarding neural dynamics in autistic individuals have not converged on a single pattern of differences. It is possible that the differences are cognitive-set-specific, and we therefore measured EEG in autistic individuals and matched controls during three different cognitive states: resting, visual perception, and cognitive control.Methods: Young adults with and without an ASD (N=17 in each group) matched on age (range 20 to 30 years), sex, and estimated Intelligence Quotient (IQ) were recruited. We measured their behavior and their EEG during rest, a task requiring low-level visual perception of gratings of varying spatial frequency, and the “Simon task” to elicit activity in the executive control network. We computed EEG power and Inter-Site Phase Clustering (ISPC; a measure of connectivity) in various frequency bands.Results: During rest, there were no ASD vs. controls differences in EEG power, suggesting typical oscillation power at baseline. During visual processing, without pre-baseline normalization, we found decreased broadband EEG power in ASD vs. controls, but this was not the case during the cognitive control task. Furthermore, the behavioral results of the cognitive control task suggest that autistic adults were better able to ignore irrelevant stimuli.Conclusions: Together, our results defy a simple explanation of overall differences between ASD and controls, and instead suggest a more nuanced pattern of altered neural dynamics that depend on which neural networks are engaged.

Properties of electrochemically generated primary cationradicals of phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles

1980 ◽  
Vol 45 (6) ◽  
pp. 1669-1676 ◽  
Author(s):  
Pavel Kubáček
Keyword(s):  
Electrochemical Oxidation ◽  
Spin Polarization ◽  
High Spin ◽  
Epr Spectroscopy ◽  
Half Life ◽  
Electrochemical Behaviour ◽  
Epr Spectra ◽  
Electrochemical Generation ◽  
Splitting Constant ◽  
Reduced Temperature

The first step of electrochemical oxidation of 2-phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles in anhydrous acetonitrile produces relatively stable cationradicals which have been studied by means of EPR spectroscopy using the method of internal electrochemical generation of radicals under reduced temperature. The same electrochemical behaviour of the both studied derivatives and identical EPR spectra of their cationradicals can be explained within the Huckel MO method. The largest contribution to the magnitude of splitting constant of nitrogen nucleus is due to π-σ-spin polarization of C-N bonds caused by high spin abundance of pz-AO of carbon atoms. Half-life of decomposition of the studied cationradicals is 4 min at -30°C.

Anion effect on alkali ion-crown complex formation in a moderately concentrated solutions: A sensitive probe of hidden interionic interactions operating in dissociating protic solvents

1990 ◽  
Vol 55 (5) ◽  
pp. 1149-1161
Author(s):  
Jiří Závada ◽  
Václav Pechanec ◽  
Oldřich Kocián
Keyword(s):  
Hydrogen Bond ◽  
Complex Formation ◽  
Charge Density ◽  
Macrocyclic Ligand ◽  
Simple Explanation ◽  
Anion Effect ◽  
Protic Solvents ◽  
The Individual ◽  
Alkali Salts ◽  
Alkali Ion

A powerful anion effect destabilizing alkali ion-crown complex formation has been found to operate in moderately concentrated protic (H2O, CH3OH, C2H5OH) solution, following the order HO- > AcO- > Cl- > Br- > NO3- > I- > NCS-. Evidence is provided that the observed effect does not originate from ion-pairing. A simple explanation is provided in terms of concordant hydrogen bond bridges of exalted stability between the gegenions, M+···OR-H···(OR-H)n···OR-H···A-. It is proposed that encapsulation of alkali ion by the macrocyclic ligand leads to a dissipation of the cation charge density destroying its ability to participate in the hydrogen bond bridge. An opposition against the alkali ion-crown complex formation arises accordingly in the solution in dependence on strength of the hydrogen bridge; for a given cation, the hydrogen bond strength increases with increasing anion charge density from NCS- to HO-(RO-). It is pointed out, at the same time, that the observed anion effect does not correlate with the known values of activity coefficients of the individual alkali salts which are almost insensitive to anion variation under the investigated conditions. As a resolution of the apparent paradoxon it is proposed that, in absence of the macrocyclic ligand, the stabilizing (concordant) bonding between the gegenions is nearly balanced by a destabilizing (discordant) hydrogen bonding between the ions of same charge (co-ions). Intrinsic differences among the individual salts are thus submerged in protic solvents and become apparent only when the concordant bonding is suppressed in the alkali ion-crown complex formation.

Dynamical Nuclear Polarization

2018 ◽  
Author(s):  
M. M. Glazov
Keyword(s):  
Spin Polarization ◽  
Nuclear Spin ◽  
Nuclear Polarization ◽  
Magnetic Moments ◽  
Nonlinear Effects ◽  
Many Body ◽  
Nuclear Spin Polarization ◽  
Optical Resonances ◽  
Dynamical Nuclear Polarization ◽  
Temperature Concept

The transfer of nonequilibrium spin polarization between the electron and nuclear subsystems is studied in detail. Usually, a thermal orientation of nuclei in magnetic field is negligible due to their small magnetic moments, but if electron spins are optically oriented, efficient nuclear spin polarization can occur. The microscopic approach to the dynamical nuclear polarization effect based on the kinetic equation method, along with a phenomenological but very powerful description of dynamical nuclear polarization in terms of the nuclear spin temperature concept is given. In this way, one can account for the interaction between neighbouring nuclei without solving a complex many-body problem. The hyperfine interaction also induces the feedback of polarized nuclei on the electron spin system giving rise to a number of nonlinear effects: bistability of nuclear spin polarization and anomalous Hanle effect, dragging and locking of optical resonances in quantum dots. Theory is illustrated by experimental data on dynamical nuclear polarization.

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