Composition variations in directionally solidified InSb-GaSb alloys

Melts containing 10%, 30% and 50% InSb were directionally solidified horizontally, vertically and in Skylab 3 and 4. The resulting concentration profiles were much more uniform in the ingots solidified horizontally. Fluctuations in composition occurred sooner as the InSb content increased and later in the horizontally processed ingots. In the 10% InSb ingot processed in SL-3 a large orientation-dependent segregation was observed at about 2 cm from the initial position of the interface. A radial variation in composition was also observed, and tentatively attributed to surface-tension driven convection.     

Correlation of Dual Colour Single Particle Trajectories for Improved Detection and Analysis of Interactions in Living Cells

Interactions between objects inside living cells are often investigated by looking for colocalization between fluorescence microscopy images that are recorded in separate colours corresponding to the fluorescent label of each object. The fundamental limitation of this approach in the case of dynamic objects is that coincidental colocalization cannot be distinguished from true interaction. Instead, correlation between motion trajectories obtained by dual colour single particle tracking provides a much stronger indication of interaction. However, frequently occurring phenomena in living cells, such as immobile phases or transient interactions, can limit the correlation to small parts of the trajectories. The method presented here, developed for the detection of interaction, is based on the correlation inside a window that is scanned along the trajectories, covering different subsets of the positions. This scanning window method was validated by simulations and, as an experimental proof of concept, it was applied to the investigation of the intracellular trafficking of polymeric gene complexes by endosomes in living retinal pigment epithelium cells, which is of interest to ocular gene therapy.     

Fluorescence lifetime standards for time and frequency domain fluorescence spectroscopy

A series of fluorophores with single-exponential fluorescence decays in liquid solution at 20 degrees C were measured independently by nine laboratories using single-photon timing and multifrequency phase and modulation fluorometry instruments with lasers as excitation source. The dyes that can serve as fluorescence lifetime standards for time-domain and frequency-domain measurements are all commercially available, are photostable under the conditions of the measurements, and are soluble in solvents of spectroscopic quality (methanol, cyclohexane, water). These lifetime standards are anthracene, 9-cyanoanthracene, 9,10-diphenylanthracene, N-methylcarbazole, coumarin 153, erythrosin B, N-acetyl-l-tryptophanamide, 1,4-bis(5-phenyloxazol-2-yl)benzene, 2,5-diphenyloxazole, rhodamine B, rubrene, N-(3-sulfopropyl)acridinium, and 1,4-diphenylbenzene. At 20 degrees C, the fluorescence lifetimes vary from 89 ps to 31.2 ns, depending on fluorescent dye and solvent, which is a useful range for modern pico- and nanosecond time-domain or mega- to gigahertz frequency-domain instrumentation. The decay times are independent of the excitation and emission wavelengths. Dependent on the structure of the dye and the solvent, the excitation wavelengths used range from 284 to 575 nm, the emission from 330 to 630 nm. These lifetime standards may be used to either calibrate or test the resolution of time- and frequency-domain instrumentation or as reference compounds to eliminate the color effect in photomultiplier tubes. Statistical analyses by means of two-sample charts indicate that there is no laboratory bias in the lifetime determinations. Moreover, statistical tests show that there is an excellent correlation between the lifetimes estimated by the time-domain and frequency-domain fluorometries. Comprehensive tables compiling the results for 20 (fluorescence lifetime standard/solvent) combinations are given.     

Monitoring the early-age hydration of self-compacting concrete using ultrasonic p-wave transmission and isothermal calorimetry

The early-age hydration (≤48 h) of a series of self-compacting concretes and corresponding mortars and one traditionally vibrated concrete and mortar is monitored in a continuous way using ultrasonic testing and isothermal calorimetry. The mixtures differ in type of mineral addition, superplasticizer, cement, cement-to-powder ratio and water-to-powder ratio. The influence of these different mixture compositions on the kinetics of the hydration during the first days of the hydration is characterized by the heat production rate q and the evolution of the p-wave velocity, which is a consequence of the microstructural changes. The variations in the acceleration caused by mineral additions and the deceleration caused by superplasticizers lead to a significantly different behavior. Separating the impact of each of the affecting factors is not always possible due to their combined actions. The nature of the acceleration due to limestone additions and the deceleration caused by polycarboxylate ether superplasticizers can be distinguished clearly, but cannot be quantified. The correlation between the ultrasonic and isothermal calorimetric results is investigated based on parameters related to the start and the end of the setting and reveals the meaningfulness of these parameters when assessing the hydration of self-compacting mixtures with continuous ultrasonic techniques.     

Characterization of Cell Wall Enzyme Activities, Pectin Composition, and Technological Criteria of Strawberry Cultivars (Fragaria×ananassa Duch)

ABSTRACT: The effects of physical characteristics and cell wall enzymatic activities of several strawberry culti-vars were investigated for possible industrial use. The enzymes study showed that the softest varieties had the highest pectin methylesterase (PME) and polygalacturonase (PG) activities. Differences in alcohol-insoluble pectin, water-soluble pectin, and parietal residue compositions were observed between Darsanga ("firm fruit") and Senga sengana ("soft fruit"). Finally, the study of pectin composition of Darsanga and Senga sengana indicated that the softest fruit had the highest water-soluble pectin content. The measurement of fruit PME activity permitted a preliminary screening of fruit maturity characteristics.     

Influence of the uterine environment on the development of in vitro-produced equine embryos

The necessity for early interaction between the embryo and the oviductal and/or uterine environment in the horse is reflected by several striking differences between equine embryos that develop in vivo and those produced in vitro. Better understanding of the salient interactions may help to improve the efficiency of in vitro equine embryo production. In an initial experiment, cleavage-stage in vitro-produced (IVP) equine embryos were transferred into the uterus of recipient mares that had ovulated recently to determine whether premature placement in this in vivo environment would improve subsequent development. In a second experiment, an important element of the uterine environment was mimicked by adding uterocalin, a major component of the endometrial secretions during early pregnancy, to the culture medium. Intrauterine transfer of cleavage-stage IVP equine embryos yielded neither ultrasonographically detectable pregnancies nor day 7 blastocysts, indicating that the uterus is not a suitable environment for pre-compact morula stage horse embryos. By contrast, exposure to uterocalin during IVP improved capsule formation, although it did not measurably affect the development or expression of a panel of genes known to differ between in vivo and in vitro embryos. Further studies are required to evaluate whether uterocalin serves purely as a carrier protein or more directly promotes improved capsule development.     

Tuning the Chiral Structures from Self-Assembled Carbohydrate Derivatives (Small 25/2023)

Carbohydrates have been regarded as one of the most ideally suited candidates for chirality study via self-assembly owning to their unique chemical structures, abundance, and sustainability. Much efforts have been devoted to design and synthesize diverse carbohydrate derivatives and self-assemble them into various supermolecular morphologies. Nevertheless, still inadequate attention is paid to deeply and comprehensively understand how the carbohydrate structures and self-assembly approaches affect the final morphologies and properties for future demands. Herein, to fulfill the need, a range of recently published studies relating to the chirality of carbohydrates is reviewed and discussed. Furthermore, to tune the chirality of carbohydrate-based structures on both molecular and superstructural levels via chirality transfer and chirality expression, the designing of the molecules and choosing of the proper approaches for self-assembly are elucidated.