Thermoelectric properties of nanostructured semiconductors: Si/Ge quantum dot arrays and ZrCoBi/ZrNiSn half-Heusler heterostructures

Diese Arbeit befasst sich mit der Untersuchung der thermoelektrischen Eigenschaften von Germanium Quantenpunktkristallen in Silizium, sowie Heterostrukturen aus ZrCoBi und ZrNiSn Halb-Heusler Materialien. Dazu werden die elektronischen Bandstrukturen wegen der verschiedenen Systemgrößen im ersten Fall mittels der Tight-Binding Methode im zweiten Fall mit der Dichtefunktionaltheorie berechnet. Aus den Bandstrukturen werden, basierend auf der semiklassischen Boltzmann-Transporttheorie, die relevanten Größen, wie die Leitfähigkeit und der Seebeckkoeffizient, die in die thermoelektrische Gütezahl ZT eingehen, ausgerechnet. Für die Quantenpunktkristalle wird für die Bandstruktur ein detailliertes Modell für band- und energieabhängige Streuzeiten entwickelt und gezeigt, wie die Anwesenheit der Quantenpunkte die Bandstruktur, Streuprozesse und damit auch Leitfähigkeit und Seebeckkoeffizient beeinflusst. Es wurde experimentell nachgewiesen, dass die Wärmeleitfähigkeit durch das Einbringen der Quantenpunkte stark reduziert ist und dieses System einen vielversprechenden Kandidaten für ein n-leitendes Thermoelektrikum darstellt. Im Falle der ZrCoBi und ZrNiSn Schichtsysteme werden zunächst Bulkeigenschaften beider Materialien bestimmt, da über beide Materialien wenig bekannt ist. Weil ZrCoBi schwer zu synthetisieren ist, gibt es darüber praktisch kaum Untersuchungen. Unter anderem werden Bandstrukturen, Deformationspotentiale und elastische Konstanten berechnet, sowie die Bulkleitfähigkeit und der Seebeckkoeffizient. Weiterhin wird der Einfluss von Defekten im Ni(Co)-Untergitter auf Bandstruktur und mögliche Dotierung untersucht. Für die Heterostrukturen werden dann Leitfähigkeit und Seebeckkoeffizient für verschiedene Schichtdicken und Grenzflächenorientierungen berechnet. Diese lassen sich mit den zuvor berechneten Eigenschaften der Bulkmaterialien verglichen. Durch einfache Modelle, basierend auf den Phononspektren der beiden Materialien, wird zusätzlich die Wärmeleitfähigkeit für die Grenzflächen und Bulkmaterialien abgeschätzt, damit ein Wert für ZT angegeben werden kann. Um die Wärmeleitfähigkeit für die Heterostruktur zu erhalten, werden Grenzflächen-Wärmeleitfähigkeit und Bulkwärmeleitfähigkeit, genauer gesagt die Widerstände, in einem Modell aus in Reihe geschalteten Widerständen verwendet.This work deals with the computational investigation of the thermoelectric properties of germanium quantum dot crystals in silicon, as well as heterostructures of ZrCoBi and ZrNiSn half-heusler materials. For this, the electronic band structures are calculated. In the first case by the tight-binding method and in the second case with the density functional theory. Based on the semiclassical Boltzmann transport theory, the relevant variables, such as conductivity and the Seebeck coefficient, which enter in the thermoelectric figure of merit ZT, are calculated from the obtained band structures. For the quantum dot crystals a detailed model for band- an energy dependent scattering time is developed and shown how the presence of the quantum dots influence the scattering processes and thus conductivity and Seebeck coefficient. It has been experimentally proven, that the thermal conductivity by the introduction of the quantum dots is greatly reduced and this system is a promising candidate for an thermoalectrical application. In the case of the ZrCoBi and ZrNiSn layer systems, bulk properties are initially determined for both materials, because little is known at least for the ZrCoBi system. Because ZrCoBi is difficult to synthesize, there are only a few studies about it. Band structures, deformation potentials and elastic constants, bulk conductivity and the Seebeck coefficient are calculated. Furthermore, the influence of defects in the Ni(Co) sublattice is examined as it may have an effect on band structure and additional doping. Then conductivity and Seebeck coefficient can be calculated for different layer thicknesses and interface orientations and compared to the properties of the bulk materials mentioned previously. Simple models based on the phonon spectra of the half-heuslers are used to estimate the bulk thermal conductivity and the one for the interface between them, so a value for the figure of merit ZT can be specified. In order to obtain the thermal conductivity of the heterostructure, the thermal resistivities of the bulk and the interfaces are used in a model of series-connected resistors

Ausgrabungen in der Kleinsiedlung Babunjë bei Apollonia (Albanien).: Bericht zu den Kampagnen 2018–2019

Field research at Babunjë, a small fortified settlement of ca. 5 ha lying between the Corinthian-Corcyraian colonies of Apollonia and Epidamnos, seeks to achieve a better understanding of the colonial settlement structure at the eastern coast of the southern Adriatic (and further south along the Ionian Sea). Babunjë was founded at the end of the 6th century BC and was abandoned in the last decades of the 4th century BC. The site had a fortification with a ‚bastion‘ or unusual large tower which was built some decades after Babunjë’s foundation. A planned urban layout shows long, narrow insulae with single rows of house-plots. A two-roomed house was excavated completely. Small settlements like Babunjë were, after the large colonies, most probably an important part of the colonial settlement structure on this coast

Electrolyte disorders and in-hospital mortality during prolonged heat periods: a cross-sectional analysis

BACKGROUND Heat periods during recent years were associated with excess hospitalization and mortality rates, especially in the elderly. We intended to study whether prolonged warmth/heat periods are associated with an increased prevalence of disorders of serum sodium and potassium and an increased hospital mortality. METHODS In this cross-sectional analysis all patients admitted to the Department of Emergency Medicine of a large tertiary care facility between January 2009 and December 2010 with measurements of serum sodium were included. Demographic data along with detailed data on diuretic medication, length of hospital stay and hospital mortality were obtained for all patients. Data on daily temperatures (maximum, mean, minimum) and humidity were retrieved by Meteo Swiss. RESULTS A total of 22.239 patients were included in the study. 5 periods with a temperature exceeding 25 °C for 3 to 5 days were noticed and 2 periods with temperatures exceeding 25 °C for more than 5 days were noted. Additionally, 2 periods with 3 to 5 days with daily temperatures exceeding 30 °C were noted during the study period. We found a significantly increased prevalence of hyponatremia during heat periods. However, in the Cox regression analysis, prolonged heat was not associated with the prevalence of disorders of serum sodium or potassium. Admission during a heat period was an independent predictor for hospital mortality. CONCLUSIONS Although we found an increased prevalence of hyponatremia during heat periods, no convincing connection could be found for hypernatremia or disorders of serum potassium

S-100 B Concentrations Are a Predictor of Decreased Survival in Patients with Major Trauma, Independently of Head Injury.

BACKGROUND Major trauma remains one of the principle causes of disability and death throughout the world. There is currently no satisfactory risk assessment to predict mortality in patients with major trauma. The aim of our study is to examine whether S-100 B protein concentrations correlate with injury severity and survival in patients with major trauma, with special emphasis on patients without head injury. METHODS Our retrospective data analysis comprised adult patients admitted to our emergency department between 1.12. 2008 and 31.12 2010 with a suspected major trauma. S-100 B concentrations were routinely assessed in major trauma patients. RESULTS A total of 27.7% (378) of all patients had major trauma. The median ISS was 24.6 (SD 8.4); 16.6% (63/378) of the patients died. S-100 B concentrations correlated overall with the ISS (p<0.0001). Patients who died had significantly higher S-100 B concentrations than survivors (8.2 μg/l versus 2.2 μg/l, p<0.0001). Polytraumatised patients with and without head trauma did not differ significantly with respect to S-100 B concentration (3.2 μg/l (SD 5.3) versus 2.9 μg/l (SD 3.8), respectively, p = 0.63) or with respect to Injury Severity Score (24.8 (SD 8.6) versus 24.2 (SD 8.1), respectively, p = 0.56). S-100 B concentrations correlated negatively with survival (p<0.0001) in all patients and in both subgroups (p = 0.001 and p = 0.006, respectively). CONCLUSIONS S-100 concentrations on admission correlate positively with greater injury severity and decreased survival in major trauma patients, independently of the presence of a head injury. S-100 B protein levels at admission in patients with major trauma may therefore be used to assess outcome in all polytraumatised patients. These measurements should be subject to further evaluation

Mixed Microscopic Eu2+ Occupancies in the Next-Generation Red LED Phosphor Sr[Li2Al2O2N2]:Eu2+ (SALON:Eu2+)

Red-emitting narrow-band phosphors are of utmost importance for next-generation white-light phosphor-converted light-emitting diodes (pc-wLEDs) for improved efficacy and optimized correlated color temperatures. A promising representative crystallizing in an ordered variant of the UCr4C4 structure type is Sr[Li2Al2O2N2]:Eu2+ (SALON:Eu2+) emitting at a desirable wavelength of 614 nm. Despite an expected eightfold coordination of the Eu2+ ions by four N3− and O2− ions, respectively, the exact local coordination symmetry and a 1:1 ratio between the two types of ligands is not straightforwardly proven by X-ray diffraction. Low-temperature luminescence spectroscopy in conjunction with ligand field theory are powerful alternatives to resolve local features of Eu2+ as its excited 4f65d1 configuration reacts sensitively to the polarity of the ligands. The dominant emission at 614 nm shows pronounced vibronic fine structure at 10 K. In addition, weak emission bands can be resolved at 570 and 650 nm even at a low doping concentration of 0.5 mol% and are assigned to Eu2+ ions being eightfold coordinated by N3− and O2− ions in a ratio different from 1:1. Due to the feature of vierer ring-type channels in SALON:Eu2+, those Eu2+ centers are sufficiently close for mutual energy transfer, which is characterized by time-resolved luminescence at 10 K

Angiopoietin-1 is associated with cerebral vasospasm and delayed cerebral ischemia in subarachnoid hemorrhage

<p>Abstract</p> <p>Background</p> <p>Angiopoietin-1 (Ang-1) and -2 (Ang-2) are keyplayers in the regulation of endothelial homeostasis and vascular proliferation. Angiopoietins may play an important role in the pathophysiology of cerebral vasospasm (CVS). Ang-1 and Ang-2 have not been investigated in this regard so far.</p> <p>Methods</p> <p>20 patients with subarachnoid hemorrhage (SAH) and 20 healthy controls (HC) were included in this prospective study. Blood samples were collected from days 1 to 7 and every other day thereafter. Ang-1 and Ang-2 were measured in serum samples using commercially available enzyme-linked immunosorbent assay. Transcranial Doppler sonography was performed to monitor the occurrence of cerebral vasospasm.</p> <p>Results</p> <p>SAH patients showed a significant drop of Ang-1 levels on day 2 and 3 post SAH compared to baseline and HC. Patients, who developed Doppler sonographic CVS, showed significantly lower levels of Ang-1 with a sustained decrease in contrast to patients without Doppler sonographic CVS, whose Ang-1 levels recovered in the later course of the disease. In patients developing cerebral ischemia attributable to vasospasm significantly lower Ang-1 levels have already been observed on the day of admission. Differences of Ang-2 between SAH patients and HC or patients with and without Doppler sonographic CVS were not statistically significant.</p> <p>Conclusions</p> <p>Ang-1, but not Ang-2, is significantly altered in patients suffering from SAH and especially in those experiencing CVS and cerebral ischemia. The loss of vascular integrity, regulated by Ang-1, might be in part responsible for the development of cerebral vasospasm and subsequent cerebral ischemia.</p

АСР температуры и расхода гелеобразного топлива в системе топливоподачи испытательного стенда

Объектом автоматизации является система топливоподачи испытательного стенда. Цель работы – проектирование автоматической системы регулирования температуры и расхода гелеобразного топлива в системе топливоподачи испытательного стенда. В процессе выполнения работы проводились экспериментальные исследования, анализ объекта автоматизации, составление структурной схемы автоматической системы регулирования температуры и расхода гелеобразного топлива в системе топливоподачи испытательного стенда, проектирование функциональной схемы, монтажной и принципиальной электрической схем, а также разработка чертежа общего вида щита автоматизации, выбор технических средств и приборов автоматизации с последующим составлением заказной спецификации, разработка мнемосхемы проекта.The object of automation is the fuel supply system of the test stand. The purpose of the work is to design an automatic system for controlling the temperature and the flow rate of gel-like fuel in the fuel dispensing system of the test bench. In the course of the work carried out, experimental studies, analysis of the automation facility, drafting structural diagram of the automatic temperature and flow gel-like fuel management system in the test bench system were carried out, Design of the functional circuit, mounting diagram and principle electrical circuits, as well as drawing of the general kind of automation shield, selection of technical means and automation devices with subsequent elaboration of the custom specification, development of the design mnemonic diagram