Search results for "sublimation"
showing 10 items of 38 documents
Perovskite solar cells employing organic charge-transport layers
2013
Thin-film photovoltaics play an important role in the quest for clean renewable energy. Recently, methylammonium lead halide perovskites were identified as promising absorbers for solar cells(1). In the three years since, the performance of perovskite-based solar cells has improved rapidly to reach efficiencies as high as 15%(1-10). To date, all high-efficiency perovskite solar cells reported make use of a (mesoscopic) metal oxide, such as Al2O3, TiO2, or ZrO2, which requires a high-temperature sintering process. Here, we show that methylammonium lead iodide perovskite layers, when sandwiched between two thin organic charge-transporting layers, also lead to solar cells with high power-conve…
Study and optimization of freeze-drying cycles of a model probiotic strain
2018
This work is based on the experimental study of the freeze-drying process to understand the impact of numerous factors on the survival rates of a model probiotic strain of Lactobacillus casei type. With the aim to find out if cell density in the matrix and survival rates are linked, we have studied the location of the cells after freeze drying inside a porous matrix composed of a lactose basis with a polymer, the polyvinylpyrrolidone (PVP) in various amounts. The best survival rate were obtained at slow freezing rate for a formulation containing 5% (m/V) of lactose and 5% (m/V) of PVP. Keywords: Freeze-Drying; Freezing; Probiotics; L. Casei ATCC 393
Analysis of variability in divergence and turn-over induced by three idealized convective systems with a 3D cloud resolving model
2020
Abstract. The sensitivity of upper tropospheric and lower stratospheric convective outflows and related divergence fields is analysed using an ensemble of cloud resolving model (CM1) simulations in LES-mode including various physically manipulated simulations for three different convective systems initialized with an idealized trigger. The main goal of this study is to assess to what extend the divergence field depends on cloud microphysical processes, the mode of convection and on the processes of convective momentum transport and moist static energy redistribution. We find that latent heat release (representing the microphysical uncertainty) plays an essential role by explaining much of m…
Study of the ZnO crystal growth by vapour transport methods
2004
Abstract The crystal growth of ZnO by vapour transport is classically made with the assistance of additional species that produce a gaseous mixture, the role of which remains often uncertain in the transport and growth process. Initially, in order to study the mass transport process, a numerical simulation is made to analyse which are the requirements to have an effective transport. As the pressure of each gaseous species is generally unknown, the numerical study has been performed for different total pressures. It is found that, if congruent and equilibrium conditions are assumed at the sublimation and crystallisation interfaces, effective growth conditions can only be attained for a narro…
Effect of impurities on Raman and photoluminescence spectra of AlN bulk crystals
2003
ABSTRACTRaman scattering and photoluminescence (PL) spectroscopy with sub-bandgap excitation has been applied to explore tracing of common impurities (in particular of oxygen) in AlN. Bulk AlN crystals grown by the high temperature sublimation method were studied. PL bands have been observed at around 375 nm and at 560–660 nm and have been attributed to oxygen and to nitrogen vacancy/aluminium excess defects, respectively. The 375 nm UV PL band was found to shift with oxygen concentration. Micro-Raman spectra of the bulk AlN samples were measured in different polarisations. Besides normal Raman modes of AlN the presence of additional vibrational modes was detected. The modes were discussed …
Preservation of Microbial Strains in the Wine Industry
2011
Publisher Summary This chapter provides a general description of the most commonly used methods for the preservation of microbial strains. Long-term preservation methods are considered the most appropriate option wherever possible, since they involve stopping the growth of the microbial cells and keeping them in a viable state. This guarantees maximum genetic stability by preventing the appearance of successive generations. Nevertheless, the possibility that the preparation method itself leads to changes cannot be ruled out. There are two preservation methods belonging to this group: freezing and lyophilization. In the first long-term preservation method, the cells are frozen suspended in a…
Interrogating on the Essence of the Zombie World
2019
The chapter discusses critically the ontology of zombie world, as well as its interlink with the Thana-capitalism, as a new stage of capitalism where the Other’s death is gazed, consumed and preferred. The paradigm of the zombie world is debated in this chapter. In this respect, the culture of zombies situates in a futurist—apocalyptic—world, where technology and modern science have contributed to the end of mankind. The survivors not only struggle against zombies in a hostile world but also redeem the human nature according to two contrasting forces, the needs of survival which led to extreme individualism and the needs of re-foundation. The figure of the zombie represents the pauperized o…
Enhanced Thermal Stability of Gold and Silver Nanorods by Thin Surface Layers
2007
Using in situ transmission electron microscopy, we find that a carbon shell governs the morphological transitions of gold and silver nanorods upon heating. Encapsulated Ag nanorods show a surprising nonuniform sublimation behavior starting from one side and leaving behind the shell. Uncovered gold nanorods transform their shape to spheres well below the bulk melting temperature through surface diffusion, which is prevented by a thin carbon shell.
η⇌μ exchange bonding mode of bidentate tmeda ligand. Molecular structure of [Y(tmhd)3]2(μ-tmeda)
2003
Abstract The reaction between the yttrium β-diketonate complexes Y(tmhd)3(H2O)x (x=0 or 1) and 0.5 or 1 equivalent of N,N,N′,N′-tetramethylethylenediamine (tmeda=Me2NCH2CH2NMe2) in hexane at room temperature afforded [Y(tmhd)3]2(tmeda) (1) and Y(tmhd)3(tmeda) (2) derivatives, respectively. They have been characterized by FT-IR, 1H NMR spectroscopy and by single crystal X-ray diffraction for 1. Variable temperature 1H NMR experiments indicated an equilibrium between 1 and 2. Their thermal behaviors were characterized by TGA and sublimation experiments. 2 is converted into compound 1 by heating over 100 °C. These precursors were used for the growth of Y2O3 and YBa2Cu3O7 − x films by pulsed in…
CVD elaboration and in situ characterization of barium silicate thin films.
2010
International audience; This study is concerned with the elaboration of barium silicate thin films by metal organic chemical vapor deposition (MOCVD) and in situ characterization by X-ray photoemission spectroscopy (XPS) with an apparatus connected to the deposition reactor. The difficulty to find an efficient metal organic precursor for barium is described. After characterizations of the selected reactant, Ba(TMHD)2tetraglyme, the development of an original specific vapor delivering source which allows reactant sublimation in the CVD reactor was performed. In the most optimized cases, including use of oxygen introduction during the deposition, barium silicate films were obtained. Moreover,…