Search results for "Beck"

Nonlinear thermovoltage and thermocurrent in quantum dots

2013

Quantum dots are model systems for quantum thermoelectric behavior because of their ability to control and measure the effects of electron-energy filtering and quantum confinement on thermoelectric properties. Interestingly, nonlinear thermoelectric properties of such small systems can modify the efficiency of thermoelectric power conversion. Using quantum dots embedded in semiconductor nanowires, we measure thermovoltage and thermocurrent that are strongly nonlinear in the applied thermal bias. We show that most of the observed nonlinear effects can be understood in terms of a renormalization of the quantum-dot energy levels as a function of applied thermal bias and provide a theoretical m…

Quantum size effects in a one-dimensional semimetal

2006

We study theoretically the quantum size effects in a one-dimensional semimetal by a Boltzmann transport equation. We derive analytic expressions for the electrical conductivity, Hall coefficient, magnetoresistance, and the thermoelectric power in a nanowire. The transport coefficients of semimetal oscillate as the size of the sample shrinks. Below a certain size the semimetal evolves into a semiconductor. The semimetal-semiconductor transition is discussed quantitatively. The results should make a theoretical ground for better understanding of transport phenomena in low-dimensional semimetals. They can also provide useful information while studying low-dimensional semiconductors in general.

Thermoelectric Effects: Semiclassical and Quantum Approaches from the Boltzmann Transport Equation

2013

The thermoelectric efficiency of a material depends on its electronic and phononic properties. It is normally given in terms of the dimensionless figure of merit Z T = σ S 2 T ∕ κ. The parameters involved in Z T are the electrical conductivity σ, the Seebeck coefficient S, and the thermal conductivity κ. The thermal conductivity has two contributions, κ = κ e + κ L , the electron thermal conductivity κ e and the lattice thermal conductivity κ L . In this chapter all these parameters will be deduced for metals and semiconductors, starting from the Boltzmann transport equation (BTE). The electrical conductivity, the Seebeck coefficient, and the electronic thermal conductivity will be obtained…

Itinerant half-metallic ferromagnetsCo2TiZ(Z=Si, Ge, Sn):Ab initiocalculations and measurement of the electronic structure and transport properties

2010

This work reports on ab initio calculations and experiments on the half-metallic ferromagnetic Heusler compounds ${\text{Co}}_{2}\text{Ti}Z$ $(Z=\text{Si},\text{ }\text{Ge},\text{ }\text{Sn})$. Aim is a comprehensive study of the electronic-structure and thermoelectric properties. The impact of the variation in the main group element $Z$ on those properties is discussed. X-ray diffraction was performed on the compounds and the lattice parameters are compared to other ${\text{Co}}_{2}$-based compounds. Hard x-ray photoemission measurements were carried out and the results are compared to the calculated electronic structure. The experimentally determined electronic structure, magnetic propert…

The Ornstein-Uhlenbeck Process

2009

Violation of the Wiedemann-Franz Law in HF Metals

2014

Experimental observations of the much-studied compounds CeCoIn\(_5\) and YbRh\(_2\)Si\(_2\) at vanishing temperatures carefully probe the nature of their magnetic-field-tuned QCPs. The violation of Wiedemann-Franz (WF) law, along with jumps revealed both in the residual resistivity \(\rho _0\) and the Hall resistivity \(R_H\), provide vital clues to the origin of their non-Fermi-liquid behavior. The empirical facts point unambiguously to association of the observed QCP with FC forming flat bands.

Polypropylene-based melt mixed composites with singlewalled carbon nanotubes for thermoelectric applications: Switching from p-type to n-type by the …

2017

Abstract The thermoelectric properties of melt processed conductive nanocomposites consisting of an insulating polypropylene (PP) matrix filled with singlewalled carbon nanotubes (CNTs) and copper oxide (CuO) were evaluated. An easy and cheap route to switch p-type composites into n-type was developed by adding polyethylene glycol (PEG) during melt mixing. At the investigated CNT concentrations of 0.8 wt% and 2 wt% (each above the electrical percolation threshold of ∼0.1 wt%), and a fixed CuO content of 5 wt%, the PEG addition converted p-type composites (positive Seebeck coefficient (S)) into n-type (negative S). PEG was also found to improve the filler dispersion inside the matrix. Two co…

Maternal pre- and postnatal mental health trajectories and child mental health and development

2011

Pregnancy and early motherhood involve uncertainty and change, which can evoke mental health problems. We identified maternal mental health trajectories in pre- and postnatal period, and examined their association with later child mental health and development. Finnish mothers reported psychological distress (General Health Questionnaire [GHQ-36]) and depressive (Beck Depression Inventory [BDI-13]) symptoms in pregnancy (T1; N = 788) and two months (T2; N = 657) and 12 months (T3; N = 545) postpartum. Both parents accounted their child’s mental health (Behavior Assessment System for Children [BASC]) and social (Social Skills Rating System [SSRS], Child Behavior Scale [CBS]) and cognitive d…

Response und Remission in der Psychotherapieforschung

2010

Treatment effects of psychotherapy are usually studied using analysis of mean differences, tests of significance and effect size measures. These strategies, however, do not answer the question of how large the proportion of patients is who responded to treatment or who even reached remission. This article compares 2 competing methods of response and remission analysis: The Reliable Change Index (RCI) according to Jacobson et al. and the method of percent symptom reduction (PSR). We applied both methods using a sample of 338 patients with DSM-IV major depressive disorder. A pre-post treatment effect of Cohen's d=1,16 (intention-to-treat) resulted for the Beck Depression Inventory (BDI), corr…

Resilience as a predictor of Quality of Life in participants with borderline personality disorder before and after treatment.

2021

Abstract Background Studies have suggested that psychotherapy improves the Quality of Life (QoL) of participants with Borderline Personality Disorder (BPD). However, there are no studies on the differential efficacy of treatments on the QoL of participants with BPD. Moreover, the relationship between QoL and resilience has rarely been studied in participants with BPD. Objectives: a) to examine whether people with BPD have worse QoL than the non-clinical population; b) to examine whether there are statistically significant differences between Dialectical Behavioural Therapy (DBT), Systems Training for Emotional Predictability and Problem Solving (STEPPS), or Cognitive Behavioural Therapy-Tre…