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We model the decomposition reaction of a solid powder into a solid plus gas in a mixed homogeneous open solar reactor and derive criteria for stability. Instability may occur via a feedback mechanism whereby gas produced in the decomposition reaction reduces the inflow, which leads to even higher reaction rate. For a variety of reactions proposed for solar application, we list the limits of stable operation as the maximum fraction of solid educt in the input carrier gas both for complete as well as for partial decomposition.

We consider volumetric thermal absorbers exposed to nonuniform irradiance. The fluid flows perpendicular to the absorber surface. The fluid transport from front to rear surface elements is connected in a parallel configuration. We investigate the optimum adjustment of the local mass flux or, equivalently, the local absorber temperature. Three different strategies are compared: (1) strategy of uniform mass flux, (2) strategy of uniform exit temperature, and (3) a strategy with a locally optimized temperature-flow profile. Significant improvement of strategy (2) compared to (1) and of strategy (3) compared to (2) is observed for the case of a black-body absorber which is isothermal in the direction normal to the absorber surface. We find it to be advantageous to include even regions where the stagnation temperature is below the desired exit temperature.

Thermal surface absorbers convert all incident radiation to heat at a single local temperature. The fluid flows perpendicular to the radiation's propagation direction. In contrast, in volumetric absorbers the fluid flows parallel to the radiation's propagation direction, and the absorber may exhibit temperature stratification along the radiation's direction. This raises the question whether reabsorption of parts of the thermal emission coming from the hotter absorber sections renders the volumetric absorber superior to the surface absorber. For the case of isotropic radiation, we compare the efficiency of the volumetric and the surface absorber with each other and with an isothermal absorber. We find that the nonselective volumetric absorber is less efficient than the nonselective surface absorber for the assumption of perfect heat transfer between absorber and fluid. Thus we conclude that in practical high-flux applications, the superiority of volumetric absorbers stems from the enhanced heat transfer area. If the fluid flows against the direction of radiation propagation the volumetric absorber is slightly more efficient than if it flows with this direction. We also discuss the effect of the two-flux approximation on simulation of isotropic volumetric absorbers.

Background: The COVID‐19 pandemic has caused many adults with intellectual/developmental disabilities (IDD) to lose their daily routines and social support, and as a result, many adults with IDD are increasingly reliant on their family caregivers. Siblings often play a crucial support role for their brothers and sisters with IDD. As such, this study aimed to describe the experiences of adult siblings of people with IDD during the COVID‐19 pandemic. Methods: The Sibling Collaborative worked with researchers to codesign an online survey, completed by 91 people, exploring sibling supports and concerns during the COVID‐19 pandemic. The survey also aimed to identify helpful resources for siblings during this time. Results: The results showed that the majority of siblings are supporting their brother or sister with IDD during the COVID‐19 pandemic and are concerned about the health and well‐being of their brother/sister. The most common concern related to disruption of their brother's or sister's routine and activities. Although responses of older and younger siblings did not differ from each other, siblings whose brother or sister with IDD lived with family had some unique concerns relative to those whose siblings no longer lived with family. Siblings described how their own self‐care and relationships with others, as well as support for their brother/sister, were particularly helpful during the COVID‐19 pandemic. Conclusions: Siblings are providing key support to their brother or sister with IDD during the COVID‐19 pandemic, and they too must be supported. Siblings should be included in efforts to disseminate resources targeting people with IDD and their feedback and input must be obtained. It is also important to include sibling mental wellness as caregiver supports are created and implemented. More research is needed to further understand how to support sibling caregivers. [ABSTRACT FROM AUTHOR]

The reradiation losses, inherent to every thermal receiver, can be significantly reduced by exposing the working fluid to monotonously increasing irradiance and preventing energy exchange between parts of the receiver that are at different temperatures. In this way the highest temperatures are reached only near the end of the working fluid's path. The improvement is much more pronounced for nonuniform as compared to uniform irradiance. For a Gaussian distribution of irradiance we calculate improvements exceeding a factor of two for the efficiency at a given temperature (0.8 of the peak stagnation temperature), and for the temperature at a given efficiency of 0.8. These results are independent of the peak irradiance and of the width of the distribution. Even a coarse partitioning into two mutually isothermal parts can already produce a significant improvement over the totally isothermal receiver.

Discusses a model of a solar thermophotovoltaic (STPV) device both for improving the efficiency of one-band-gap photovoltaic cells by matching the photon energy to the band gap and for concentrating diffuse radiation. Definition of thermophotovoltaic; Investigation of a general SPTV system with ideal components; Characteristics of a one-band-gap photovoltaic cell.

Focuses on off-axis extra lines contained in powder sample electron paramagnetic resonance (EPR) spectrum of Cr3+ ions in YAlO3 crystals. Orientation dependence of the EPR spectrum; Transition between the central Kramers doublet in the powder system; Angular variations of the EPR spectra.

Investigates the flow in volumetric absorbers using a simple mathematical model. Restrictions and failure mechanisms inherent to the volumetric absorber; Expression of the limitation in terms of blow parameter; Existence of multiple steady solutions for certain parameter values.

Endothermic chemical reactions taking place at temperatures above 1000 K are candidates for the utilization of solar energy in highly concentrating solar furnaces. Special interest is focussed onto the question of whether light drives the reaction differently from heat. To observe such an effect it is important to monitor the chemical process of the sample under irradiation. In this paper we propose spectral reflectivity as a probe for chemical changes. We present laboratory measurements showing reflectivity changes associated with the oxidation of magnetite. We observed significant changes at temperatures coinciding with the oxidation temperature of magnetite. We further observed a change of the reflectivity associated with the phase transition of maghemite to hematite. Contrary to the literature, we find that this phase transition leads off at about 525 K. [ABSTRACT FROM AUTHOR]

The article presents information on the case State v. Sharp. In this case the Supreme Court of Louisiana held that a defendant convicted of violating a police jury ordinance, upon whom sentence was suspended, was not entitled to an appeal, on the ground that there had been no final judgment, and, therefore, no appeal would lie. However, in this particular case, there was a statute relative to the suspension of sentence, which expressly provided that, if sentence is suspended, neither the verdict of conviction nor the judgment entered thereon shall become final, except upon the conviction of the defendant of another felony or misdemeanor. Whether or not the holding of the court in the absence of this act would have been the same, depends upon the question whether or not the suspension of sentence is to be considered a final judgment. It will be seen then that, although the rules in the various jurisdictions differ, the matter of appeal is almost wholly within the determination of the defendant.

A sharp microwave response centered at zero magnetic field was observed in manganese- and iron-doped Na[sub 2]O-CaO-MgO-SiO[sub 2] glasses with phase opposite to the normal Mn[sup +2] and Fe[sup +3] paramagnetic signals. The response can be described as magneto-induced microwave conductivity in the dielectric glass that derives from spin-dependent charge migration within the first coordination sphere of the paramagnetic ion. In contrast to the spin-polarized tunneling in ferromagnets between different valence states of metals, the observed effect is due to spin-dependent tunneling that occurs in the vicinity of manganese or iron in diluted paramagnetic systems. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]