Growth of single crystals by vapor transport

The primary objectives of the program were to establish basic vapor transport and crystal growth properties and to determine thermodynamic, kinetic and structural parameters relevant to chemical vapor transport systems for different classes of materials. An important aspect of these studies was the observation of the effects of gravity-caused convection on the mass transport rate and crystal morphology. These objectives were accomplished through extensive vapor transport, thermochemical and structural studies on selected Mn-chalcogenides, II-VI and IV-VI compounds

Crystal growth of CdTe in space and thermal field effects on mass flux and morphology

The primary, long-range goals are the development of vapor phase crystal growth experiments, and the growth of technologically useful crystals in space. The necessary ground-based studies include measurements of the effects of temperature variations on the mass flux and crystal morphology in vapor-solid growth processes. For in-situ mass flux measurements dynamic microbalance techniques will be employed. Crystal growth procedures and equipment will be developed to be compatible with microgravity conditions and flight requirements. Emphasis was placed on the further development of crystal growth and the investigation of relevant transport properties of CdTe. The dependence of the mass flux on source temperature was experimentally established. The CdTe synthesis and pretreatment procedures are being developed that yield considerable improvements in mass transport rates, and mass fluxes which are independent of the amount of source material. A higher degree of stoichiometric control of CdTe than before was achieved during this period of investigation. Based on this, a CdTe crystal growth experiment, employing physical vapor transport, yielded very promising results. Optical microscopy and X-ray diffraction studies revealed that the boule contained several large sized crystal grains of a high degree of crystallinity. Further characterization studies of CdTe crystals are in progress. The reaction chamber, furnace dimensions, and ampoule location of the dynamic microbalance system were modified in order to minimize radiation effects on the balance performance

Manuelle Triggerpunktbehandlung gegen Kopfschmerzen

erworben im Rahmen der Schweizer Nationallizenzen (www.nationallizenzen.ch)Hintergrund: Spannungskopfschmerz ist ein verbreitetes Krankheitsbild mit erheblichen sozioökonomischen Auswirkungen. Patienten, die an Spannungskopfschmerz leiden, weisen vermehrt myofasziale Triggerpunkte (mTrP) in der Nacken-Schulter-Region auf. Ziel der Arbeit: Primäre Studien sollten hinsichtlich Wirksamkeit manueller TrP-Behandlung bei Spannungskopfschmerz untersucht werden. Material und Methode: Eine systematische Literatursuche wurde in den Datenbanken Medline, AMED, Cochrane, CINHAL, PEDro und Academic Journal Database durchgeführt. Basierend auf definierten Einschlusskriterien konnten 5 Studien ausgewählt und bewertet werden. Unter Berücksichtigung dieser Bewertung folgte eine Interpretation der jeweiligen Studienresultate. Homogene Studiendaten wurden mittels einer Metaanalyse zusammengefasst. Ergebnisse: Die Metaanalyse zeigt, dass mTrP-Behandlung in der Nacken-Schulter-Region im Vergleich zu Placebo oder keiner Therapie einen geringen Effekt auf die Intensität von Spannungskopfschmerzen hat. Für die Wirkung auf weitere Outcomes wie Frequenz und Dauer von Kopfschmerzepisoden ist die Evidenz jedoch unzureichend und von mangelnder methodologischer Qualität

Vapor transport crystal growth of mercury-cadmium-telluride in microgravity

Two epitaxial growth experiments of Hg(1-x)Cd(x)Te layers on (100) CdTe substrates in closed ampoules using HgI2 as a transport agent have been performed during the USML-1 mission. The characterization results to date demonstrate a considerable improvement of the space-grown epitaxial layers relative to ground-control specimens in terms of morphology, compositional uniformity, and structural micro homogeneity. These results show the effects of microgravity and fluid dynamic disturbances on-ground on the deposition and growth processes. The continued analysis of this technologically important system is designed to further elucidate the observed crystallographic improvements and their relation to mass flow

The physiological effects of the seed treatment Stamina on maize seedling length, ADP:O ratios, and respiration rates

Zea mays L. is an important crop in the Midwest, and each year there is a push to plant earlier in the spring. Early planting can leave seeds and seedlings vulnerable to low temperature stress. Low temperature stress causes damage to maize seedlings. It has been postulated that Strobilurin fungicides have positive physiological related effects on growth and yield. The goal of this study was to determine if the strobilurin Stamina protects maize seedlings against mitochondrial damage due to low temperature stress. In this study, three seed treatments and two seed lots/hybrids were used. Treatments included: Stamina (binders plus active ingredients), binders only, and control (untreated) seedlings. To determine the effects of Stamina on maize respiration, seedling lengths, ADP:O ratios, respiration rates, and alternative oxidase (appendix) were measured under optimal temperature and low temperature conditions in the presence and absence of the alternative oxidase inhibitor salicylhydroxamic acid (SHAM). Seedlings were grown in dark growth chambers at a constant 25°C for 5 days or for 10 days at 10°C and 4 days at 25°C. In the optimal temperature study, seedlings from Stamina and only binders treated seeds had mesocotyl lengths that were 0.48 cm and 0.41 cm longer than control seeds, respectively. Seedlings from Stamina treated seeds had total lengths that were 0.38 cm and 0.87 cm longer than seeds treated with binders only and control seedlings, respectively. Stamina had no effect on ADP:O ratios, AOX ratios, respiration rates, or respiration rate ratios. In the low temperature stress study, there was a hybrid by treatment interaction. Stamina did not affect seedling length of seed lot/hybrid A, but it did of seed lot/hybrid B. Seedlings from Stamina treated seeds of seed lot/hybrid B had mesocotyl lengths that were 0.9 cm longer than both seedlings treated with only binders and control seedlings. Seedlings from Stamina treated seeds of the same seed lot/hybrid had total lengths that were 1.16 cm and 1.21 cm longer than seedlings treated with only binders and control seedlings, respectively. Seedlings from Stamina treated seeds and control seedlings had AOX ratios that were slightly larger than AOX ratios for seedlings treated with only binder when 20 mM SHAM was used. Seedlings from Stamina treated seeds and control seedling of seed lot/hybrid A had slightly larger respiration rate ratios than seedlings from seeds treated with only binders when 10 mM SHAM was used. Seedlings from Stamina treated seeds had slightly larger respiration rate ratios than control seedlings of seed lot/hybrid B when 10 mM SHAM was used

Vapor growth of GeTe single crystals in micro-gravity

The positive effects of micro-gravity on crystal growth and fundamental properties of the vapor transport reaction were established by analyzing the results of GeSe and GeTe vapor transport experiments performed on board Skylab. The analysis was based on a direct comparison of GeSe and GeTe crystals and of mass transport rate data obtained on earth and in space. For this purpose, a total of six transport experiments employing different concentrations of transport agent (GeI4) and two temperature gradients were performed during the Skylab 3 and 4 missions. Extensive ground-based studies demonstrated that the crystal morphology and the mass transport rates of the above systems are affected by the transport conditions, in particular by gravity-driven convection. The results demonstrate unambiguously a considerable improvement of the space crystals in terms of surface perfection, crystalline homogeneity and defect density. The observation of greater mass transport rates than expected in micro-gravity environment is of basic scientific and technological significance. This indicates that conventional transport models are incomplete and demonstrates that crystals of improved quality can be grown at reasonable rates by this technique in space. Results are of practical importance for the modification of crystal growth techniques on earth

Accuracy of digital complete-arch, multi-implant scans made in the edentulous jaw with gingival movement simulation: An in vitro study

STATEMENT OF PROBLEM The use of computer-aided design and computer-aided manufacturing (CAD-CAM) technologies is widely established, with single restorations or short fixed partial dentures having similar accuracy when generated from digital scans or conventional impressions. However, research on complete-arch scanning of edentulous jaws is sparse. PURPOSE The purpose of this pilot in vitro study was to compare the accuracy of a digital scan with the conventional method in a workflow generating implant-supported complete-arch prostheses and to establish whether interference from flexible soft tissue segments affects accuracy. MATERIAL AND METHODS An edentulous maxillary master cast containing 6 angled implant analogs was used and digitized with mounted scan bodies by using a high-precision laboratory scanner. The master cast was then scanned 10 times with 4 different intraoral scanners: TRIOS 3 with a complete-arch scanning strategy (TRI1) or implant-scanning strategy (TRI2), TRIOS Color (TRC), CEREC Omnicam (CER), and CEREC Primescan (PS). The same procedure was repeated with 4 different levels of free gingiva (G0-G3). Ten conventional impressions were obtained. Differences in implant position and direction were evaluated at the implant shoulder as mean values for trueness and interquartile range (IQR) for precision. Statistical analysis was performed by using the Kruskal-Wallis and post hoc Conover tests (α=.05). RESULTS At G0, position deviations ranged from 34.8 μm (IQR 23.0 μm) (TRC) to 68.3 μm (12.2 μm) (CER). Direction deviations ranged from 0.34 degrees (IQR 0.18 degrees) (conventional) to 0.57 degrees (IQR 0.37 degrees) (TRI2). For digital systems, the position deviation ranged from 48.4 μm (IQR 5.9 μm) (PS) to 76.6 μm (IQR 8.1 μm) (TRC) at G1, from 36.3 μm (IQR 9.3 μm) (PS) to 79.9 μm (IQR 36.1 μm) (TRI1) at G2, and from 51.8 μm (IQR 14.3 μm) (PS) to 257.5 μm (IQR 106.3 μm) (TRC) at G3. The direction deviation ranged from 0.45 degrees (IQR 0.15 degrees) (CER) to 0.64 degrees (IQR 0.20 degrees) (TRC) at G1, from 0.38 degrees (IQR 0.05 degrees) (PS) to 0.925 degrees (IQR 0.09 degrees) (TRI) at G2, and from 0.44 degrees (IQR 0.07 degrees) (PS) to 1.634 degrees (IQR 1.08 degrees) (TRI) at G3. Statistical analysis revealed significant differences among the test groups for position (G0: P<.001; G1: P<.05; G2: P<.001; G3: P<.001) and direction (G0: P<.005; G1: P<.001; G2: P<.001; G3: P<.001). CONCLUSIONS Without soft tissue interference, the accuracy of certain digital scanning systems was comparable with that of the conventional impression technique. The amount of flexible soft tissue interference affected the accuracy of the digital scans

Entwicklung einer tropfenbasierten mikrofluidischen Plattform für das High-Throughput-Screening multizellulärer Systeme

Im Bereich der tropfenbasierten Mikrofluidik werden medizinische, biologische oder auch chemische Experimente in diskrete Reaktionsräume überführt. Diese als Tropfen bezeichneten Reaktionsräume besitzen als seriell angeordnete Mikroreaktoren ein hohes Anwendungspotenzial, sei es zur Optimierung von Screening-Prozessen für die Medikamentenentwicklung oder zur Manipulation von Zellen und 3D Zellstrukturen. Für solche Anwendungen bieten die derzeit existierenden Konzepte jedoch nicht die erforderliche Zuverlässigkeit und Praktikabilität. Vor allem die Aufrechterhaltung reproduzierbarer und stabiler Prozessbedingungen sind ausschlaggebende Faktoren als Voraussetzung für einen Durchbruch dieser Technologie am Markt. Insbesondere bei Anwendungen mit multizellulären Systemen wie nativen Gewebefragmenten oder in vitro kultivierten Sphäroiden sind besondere Voraussetzungen zu erfüllen. Beispielsweise ist die Verwendung oberflächenaktiver Substanzen (Tenside), die bei der Mehrzahl tropfenbasierter mikrofluidischer Applikationen zur Stabilisierung der Tropfen eingesetzt werden, nachteilig für Untersuchungen dieser Proben. Der Verzicht auf Tenside ist ein wichtiger Schritt in Richtung einer grundlegenden Akzeptanz tropfenbasierter Verfahren. Die in dieser Arbeit präsentierten Ergebnisse zeigen eine Alternative auf, bei der für das Handling und die Kultivierung multizellulärer Systeme auf die Verwendung von Tensiden verzichtet werden kann. Das im Rahmen der Forschungsarbeiten entwickelte technische System beruht auf neuartigen, mikrofluidischen Komponenten, die die hohen Ansprüche für das Handling multizellulärer Systeme erfüllen. Neben der Beschreibung der Systementwicklung steht die Charakterisierung der Einflussfaktoren auf die Tropfengenerierung im Mittelpunkt der Arbeit. Relevante Einflussgrößen wie die Kanalanordnung und deren Oberflächenbeschaffenheit sowie der Einfluss der Volumenströme und unterschiedlicher Probenmedien auf die Tropfengenerierung wurden untersucht. Die Arbeit beschreibt weiterhin die Entwicklung eines biomimetischen Ansatzes zur Steigerung der Stabilität der Tropfengenerierung durch die Verringerung des Adhäsionspotenzials wässriger Proben mit den Kanaloberflächen der Mikrosysteme. Damit ist die im Rahmen dieser Arbeit entwickelte mikrofluidische Plattform insbesondere für Anwendungen im Bereich der Biowissenschaften prädestiniert.In droplet-based microfluidics, medical, biological or chemical experiments take place in discrete reaction spaces named “droplets”. The droplet-based microfluidics offers a considerable potential for applications like optimization of screening processes for the development of drugs or for the manipulation of cells and 3D cell structures, respectively. However, for such applications the currently available concepts do not provide the necessary reliability and practicability. In particular, the maintenance of reproducible and stable process conditions are decisive factors for a breakthrough of this technology on the market. Applying multicellular systems like native tissue or spheroids cultivated in vitro, special requirements have to be fulfilled. For example, the use of surface-active substances (surfactants), which are applied for stabilizing the droplets in the majority of droplet-based microfluidics applications, is disadvantageous for investigations of cells and 3D cell structures in droplets. The abandonment of surface-active substances is an important step towards a fundamental acceptance of droplet-based microfluidic processes. The results presented in this work show an alternative to avoid the use of surface-active substances for the handling and cultivation of cells and 3D cell structures in droplets. The technical system developed as part of the research work is based on novel microfluidic components and meets the high demands on reproducibility and stability for handling cells and 3D cell structures. The results of the research work include the development of the entire droplet-based system as well as the investigations on the droplet generation process. This includes the investigation of basic parameters like surface properties of the microfluidic channels, the arrangement of the channels, the fluid flow conditions, and the kind of sample medium. Partial aspects of the extensive experiments that were performed to analyze the influence of the above mentioned parameters were also investigated by numerical simulations. In addition, the work describes the development of a biomimetic approach to increase the stability of droplet generation and to reduce the adhesion of aqueous droplets to the microchannel surfaces of the polymer chips. This approach succeeded even with samples containing anticoagulated whole blood. Concluding, the newly developed and characterized droplet-based microfluidic system points out a high application potential for the life sciences and especially for the field of individual medicine