Thermal resistance between powdered cerium magnesium nitrate and liquid helium at very low temperatures

Experiments have been performed from magnetic temperatures of 2–20 mK on the effect of minute⁴He impurities and a magnetic field on the thermal resistance between powdered cerium magnesium nitrate (CMN) and liquid³He. The thermal resistance decreases with decreasingT and increasing small field but is increased dramatically at a givenT by the addition of roughly a monolayer of⁴He. The resistance is interpreted as resulting from a surface magnetic coupling between CMN and liquid³He.This work has been supported by the U.S. Atomic Energy Commission under Contract No. AT(04-3)-34, P.A. 143, and by the Air Force Office of Scientific Research, Office of Aerospace Research, United States Air Force, under Grant No. AF-AFOSR-631-67A.     

Reproductive efficiency as a social indicator

An index of reproductive effiency (RE) is proposed as a social indicator that will meet the need to consider various forms of pregnancy wastage, to compare their relative costs, and to guide reproductive health policy accordingly. This article discusses conceptual and measurement aspects of RE. Conversion of wanted to unwanted pregnancies and the reverse, interpretation of abortion in relation to other pregnancy outcomes, defining the end point for the reproductive process and criteria for the events to be included as significant outcomes are conceptual issues. Measurement problems include: whether aggregation is justified, prospective and retrospective tracking of outcomes, record limitations, duplication of adversities in a single pregnancy, and selection of optimal rate for comparison. A measurement of RE for the entire United States based on the National Natality Survey of 1964-1966 is presented, showing 74.5 percent of pregnancies resulting in healthy liveborn infants. For those years, data on abortions could not be included. Within the group of reported pregnancy losses, the importance of congenital abnormalities and low-birth-weight babies is enhanced by application of economic weights based on associated medical care costs. Changing opportunities for birth timing, prenatal and infant care, and control of family size are social means of reducing adverse outcomes associated with teenage pregnancy and high-parity births, often found together with poverty. Successive increments in RE may be progressively more expensive to achieve, and cost effectiveness comparison will be necessary.     

T cells of patients with the Wiskott-Aldrich syndrome have a restricted defect in proliferative responses

The Wiskott-Aldrich syndrome (WAS) is a disease of profound thrombocytopenia and severe immune defects caused by an unidentified defective X chromosome gene. In this study, T lymphocyte function is examined using a panel of allospecific WAS patient T cell lines, previously found to express the abnormal disease gene and the cytoarchitectural defect characteristic of the disease. Although T cell lines from normal individuals proliferate vigorously in response to immobilized anti-CD3 mAb OKT3 and SPV-T3b, five of seven WAS patient T cell lines failed to proliferate and two lines showed significantly decreased proliferation when challenged with the immobilized anti-CD3 mAb. The deficient responsiveness of the WAS T cell lines to immobilized anti-CD3 mAb is a restricted defect, because the cells proliferate normally when challenged with allospecific Ag, PHA, or PMA plus ionomycin. Addition of anti-CD28 mAb did not correct the deficient proliferation of the WAS cells challenged with immobilized anti-CD3. Deficient response of the WAS T cell lines to immobilized anti-CD3 was detected also when earlier events of the proliferation process, IL-2 production and up-regulation of activation Ag CD69 and CD28, were measured. On the other hand, WAS cell lines did not differ from normal cell lines in binding of anti-CD3 mAb, mobilization of Ca2+ in response to soluble OKT3, and tyrosine phosphorylation and GTP binding of the CD3 zeta-chain in response to OKT3. Cumulatively, these findings demonstrate a striking restricted defect in the proliferative response of WAS T cells, which because it is found in cell lines free of secondary changes that occur in the patient circulation must be a reflection of the inherited defective disease gene product.     

Ultrasonic assisted enzymatic digestion (USAED) coupled with high performance liquid chromatography and electrothermal atomic absorption spectrometry as a powerful tool for total selenium and selenium species control in Se-enriched food supplements

The suitability of hyphenated USAED with HPLC separation and ET-AAS determination as a new rapid methodology for Se control in Se-enriched food supplements is demonstrated. Total Se determination and Se speciation are accomplished in a single sample treatment using low sample amounts (ca. 10 mg), and low extracting volume (1 mL). The total Se content in seven of the 10 Se-enriched supplements studied was in agreement with the values obtained after microwave pressurized acid digestion, MW, (test t, p = 0.05). The Se species studied were Se(IV), Se(VI), SeMet, SeMeSeCys, and SeCys₂, being some of the most common found in the 10 supplements studied. Although SeMet was the Se species expected to be present at the highest concentration in most Se-enriched food supplements, we detected it in only three of the 10 samples studied. In the other seven samples, two of them had Se(IV) as the main Se species. The other five supplements had Se species that did not match with any of the five standards selected by us. We have also systematically demonstrated that ultrasonication does not alter the following Se species: Se(IV), Se(VI), SeMet, SeMeSeCys, and SeCys₂. The new procedure can be easily adapted to more Se species and can be routinely used for Se control in Se-enriched food supplements. Concerning the supplements studied, our results suggest that stricter control on the Se content in enriched food supplements in terms of Se species will need to become mandatory.     

Solution blow spun titania nanofibers from solutions of high inorganic/organic precursor ratio

In this work titania nanofibers were produced from different precursor solutions by solution blow spinning. Hydrophilic polyvinylpyrrolidone, hydrophobic poly(vinyl acetate) and amorphous and semi-crystalline poly(lactic acid) polymers were used with green-solvents and titanium isopropoxide as the inorganic precursor. Hybrid nanofibers with high inorganic loading content were successfully produced from all precursor solutions. The fibers were calcined at different annealing temperatures for evaluation of phase transitions. The minimum temperature to obtain pure titania fiber was found to be 500 °C, as assessed by thermal characterization. Anatase was the unique polymorph formed at this annealing temperature. This is of paramount importance due to its photocatalytic character. Calcination at high temperatures showed that rutile slightly appeared at 600 °C for the polyvinylpyrrolidone-based system and showed a strong peak at 700 °C for all systems, co-existing with anatase as minor phase. The use of amorphous and semicrystalline poly(lactic acid) polymers did not influence the anatase crystal size and phase conversion. This was found to be dependent on the annealing temperature and medium acidity, as currently found in powder synthesis.