Homogeneous assay technology based on upconverting phosphors

Upconversion photoluminescence can eliminate problems associated with autofluorescence and scattered excitation light in homogeneous luminescence-based assays without need for temporal resolution. We have demonstrated a luminescence resonance energy-transfer-based assay utilizing inorganic upconverting (UPC) lanthanide phosphor as a donor and fluorescent protein as an acceptor. UPC phosphors are excited at near-infrared and they have narrow-banded anti-Stokes emission at visible wavelengths enabling measurement of the proximity-dependent sensitized emission with minimal background. The acceptor alone does not generate any direct emission at shorter wavelengths under near-infrared excitation. A competitive model assay for biotin was constructed using streptavidin-conjugated Er3+,Yb3+-doped UPC phosphor as a donor and biotinylated phycobiliprotein as an acceptor. UPC phosphor was excited at near-infrared (980 nm) and sensitized acceptor emission was measured at red wavelength (600 nm) by using a microtitration plate fluorometer equipped with an infrared laser diode and suitable excitation and emission filters. Lower limit of detection was in the subnanomolar concentration range. Compared to time-resolved fluorometry, the developed assay technology enabled simplified instrumentation. Excitation at near-infrared and emission at red wavelengths render the technology also suitable to analysis of strongly colored and fluorescent samples, which are often of concern in clinical immunoassays and in high-throughput screening.     

Rapid synthesis of nanostructured porous silicon carbide from biogenic silica

Nanostructured silicon carbide (SiC) is an exceptional material with numerous applications, for example, in catalysis, biomedicine, high-performance composites, and sensing. In this study, a fast and scalable method of producing nanostructured SiC from plant materials by magnesiothermic reduction via self-propagating high-temperature synthesis (SHS) route was developed. The produced biogenic material possessed a high surface area above 200 m²/g with a SiC crystallite size below 10 nm, which has not been done previously by SHS. This method enables affordable synthesis of the material plant-based precursors in a reaction that only takes a few seconds, thereby paving a way for nanostructured SiC production in high volumes using renewable resources. The material was also functionalized with carboxylic acid and bisphosphonate moieties, and its use as metal adsorbent in applications such as wastewater remediation was demonstrated.     

Leg extension power and walking speed in very old people living independently

BACKGROUND: Leg extension power can be determined as the product of the force and velocity of movement. Its association with maximal walking speed was studied in 131 80- and 85-year-old men and women. METHODS: Leg extension power was measured with the help of a sledge ergometer in a sitting position using a facilitated "jump test." The participant was attached by belts to a sliding chair on rails inclined at 12.6 degrees to the floor. The feet were placed on the force plate attached perpendicularly to the rails, and the knee angle was 90 degrees at the starting position. The participant was advised to extend his or her legs powerfully. The highest value of five to eight attempts was accepted as the result. The results were adjusted for body mass and expressed as watts.kilogram-1. Maximal walking speed was measured in the laboratory corridor over a distance of 10 m. RESULTS: Men and 80-year-old subjects exhibited greater leg extension power and were faster walkers than women and 85-year-old persons. Leg extension power correlated positively with maximal walking speed in all groups: the correlation coefficients were .412 in the 80-year-old men (n = 41, p = .007), .619 in the 80-year-old women (n = 56, p < .001), .939 in the 85-year-old men (n = 8, p = .001), and.685 in the 85-year-old women (n = 23, p < .001). The regression lines for leg extension power and walking speed were coincident, indicating that the power requirements to attain a given walking speed were similar for both sexes. The minimum power threshold for those with a maximal walking speed of 1.30-1.49 m.s-1 was on the order of 4 W.kg-1; a maximal walking speed of 1.50-1.99 m.s-1 required 7 W.kg-1; and for a speed over 2.00 m.s-1 the power threshold was 9.5 W.kg-1. CONCLUSIONS: Their lower average leg extension power may be one of the factors explaining the greater prevalence of mobility problems among women than men.     

Eye contact and video-mediated communication: A review

A relatively new form of human communication, video-conferencing has become more popular as video technology improves and with increasing demands for real-time communication across greater distances. The full effects of video-conferencing on human communication are still being explored. Video-conferencing is presumed to be a somewhat richer form of communication than email and telephone, but not quite as informative as face-to-face communication. This review explores research into the influence of eye contact on communication and how video-conferencing mediates both verbal and non-verbal interactions. Facilitation of eye contact is a challenge that must be addressed so that video-conferencing can approach the rich interactions of face-to-face communication.     

Impact of PLGA molecular behavior in the feed solution on the drug release kinetics of spray dried microparticles

The purpose of this study was to understand the impact of the poly (lactic-co-glycolic acid) (PLGA) molecular behavior in the feed solution on the drug release kinetics of PLGA microparticles prepared via spray drying. The PLGA molecular behavior in the feed solutions were characterized by using tube viscometry, which provides information about the polymer coil radius (R_coil), the Martin constant (K_m), and the overlap concentration (c*). The particle size and the drug surface enrichment were investigated by using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The drug release profiles were characterized by using the USP paddle method and analyzed by using the Crank's diffusion model to calculate the kinetic parameters. Multivariate data analysis using principal component analysis (PCA) was employed to display the relationship between the PLGA molecular behavior, particle properties and the drug release kinetics from the spray dried PLGA microparticles. Rheological studies suggested that an increased molar ratio of a poor solvent (methanol) in the solvent system resulted in a decreased R_coil, the increase in K_m and c*. The higher effective diffusion coefficient of drug calculated by using the Crank's diffusion model was observed in the polymer matrix prepared at an acetone-to-methanol molar ratio of 69:31. The PCA models indicated that the drug surface enrichment and the K_m were directly proportional to the drug burst release, while the entanglement index was inversely correlated. Further, the particle size had a less significant impact on the drug burst release. This study implies that the polymer molecular behavior would influence the microscopic connectivity and diffusivity of polymer matrix, which eventually affects the drug release kinetics.     

Troponin T and creatinine kinase isoenzyme MB mass in the diagnosis of myocardial infarction

The aim of this study was to compare troponin T (TnT) and creatine kinase isoenzyme MB mass (CK-MBm) with conventional enzymes, ie CK, CK-MB activity and lactate dehydrogenase isoenzyme 1, in the diagnosis of myocardial infarction (MI). 624 patients (351 men and 273 women, median age 69 years) were admitted to hospital with suspicion of an acute coronary heart disease event. TnT was elevated (> 0.10 microg/L) in 100%, CK-MBm (> 5.0 microg/L) in 99%, and both markers in 99% of the 89 patients with the diagnosis of a definite MI according to modified FINMONICA criteria. In the 60 patients with the diagnosis of a probable MI, TnT was elevated in 65%, CK-MBm in 67% and both markers in 60%. In the patients with unstable coronary artery disease (unstable angina or prolonged chest pain attack) and conventional enzymes within normal limits, TnT was elevated in 14%, CK-MBm in 17% and both markers in 9%. The use of TnT and CK-MBm did not lead to a major change in the diagnostics of definite MI. However, TnT and CK-MBm did not confirm the diagnosis of probable MI in one-third of the events. These new markers revealed a myocardial injury in about 15% of those patients who had unstable coronary artery disease and conventional enzymes within normal limits.     

Grip strength changes over 27 yr in Japanese-American men

The aim of this study was to describe changes in grip strength over a follow-up period of approximately 27 yr and to study the associations of rate of strength decline with weight change and chronic conditions. The data are from the Honolulu Heart Program, a prospective population-based study established in 1965. Participants at exam 1 were 8,006 men (ages 45-68 yr) who were of Japanese ancestry and living in Hawaii. At follow-up, 3,741 men (age range, 71-96 yr) participated. Those who died before the follow-up showed significantly lower grip-strength values at baseline than did the survivors. The average annualized strength change among the survivors was -1.0%. Steeper decline (>1.5%/yr) was associated with older age at baseline, greater weight decrease, and chronic conditions such as stroke, diabetes, arthritis, coronary heart disease, and chronic obstructive pulmonary disease. The risk factors for having very low hand-grip strength at follow-up, here termed grip-strength disability (相似文献