Nanowire Structural Evolution from Fe3O4 to ϵ‐Fe2O3

The ?‐Fe₂O₃ phase is commonly considered an intermediate phase during thermal treatment of maghemite (γ‐Fe₂O₃) to hematite (α‐Fe₂O₃). The routine method of synthesis for ?‐Fe₂O₃ crystals uses γ‐Fe₂O₃ as the source material and requires dispersion of γ‐Fe₂O₃ into silica, and the obtained ?‐Fe₂O₃ particle size is rather limited, typically under 200 nm. In this paper, by using a pulsed laser deposition method and Fe₃O₄ powder as a source material, the synthesis of not only one‐dimensional Fe₃O₄ nanowires but also high‐yield ?‐Fe₂O₃ nanowires is reported for the first time. A detailed transmission electron microscopy (TEM) study shows that the nanowires of pure magnetite grow along [111] and <211> directions, although some stacking faults and twins exist. However, magnetite nanowires growing along the <110> direction are found in every instance to accompany a new phase, ?‐Fe₂O₃, with some micrometer‐sized wires even fully transferring to ?‐Fe₂O₃ along the fixed structural orientation relationship, (001) ∥ (111), [010] ∥ <110>. Contrary to generally accepted ideas regarding epsilon phase formation, there is no indication of γ‐Fe₂O₃ formation during the synthesis process; the phase transition may be described as being from Fe₃O₄ to ?‐Fe₂O₃, then to α‐Fe₂O₃. The detailed structural evolution process has been revealed by using TEM. 120° rotation domain boundaries and antiphase boundaries are also frequently observed in the ?‐Fe₂O₃ nanowires. The observed ?‐Fe₂O₃ is fundamentally important for understanding the magnetic properties of the nanowires.     

Natural organic matter and sunlight accelerate the degradation of 17ß-estradiol in water

Nanomolar concentrations of steroid hormones such as 17β-estradiol can influence the reproductive development and sex ratios of invertebrate and vertebrate populations. Thus their release into surface and ground waters from wastewater facilities and agricultural applications of animal waste is of environmental concern. Many of these compounds are chromophoric and susceptible to photolytic degradation. High intensity UV-C radiation has been demonstrated to degrade some of these compounds in engineered systems. However, the degradation efficacy of natural solar radiation in shallow fresh waters is less understood. Here photolytic experiments with 17β-estradiol demonstrated modest photodegradation (~ 26%) when exposed to simulated sunlight between 290 and 720 nm. Photodegradation significantly increased (~ 40-50%) in the presence of 2.0-15.0 mg/l of dissolved organic carbon (DOC) derived from humic acids of the Suwannee River, GA. However, rates of photodegradation reached a threshold at approximately 5.0 mg/l DOC. Observed suppression of photolysis in the presence of a radical inhibitor (i.e. 2-propanol) indicated that a significant proportion of the degradation was due to radicals formed from the photolysis of DOC. Although photodegradation was greatest in full sunlight containing UV-B (290-320 nm), degradation was also detected with UV-A (320-400 nm) and visible light (400-720 nm) alone.     

Chemical synthesis and physiological activity of sulfonium analogues of platelet activating factor

Phosphatidylsulfocholine (PSC), the sulfonium analogue of phosphatidylcholine (PC), occurs naturally in some diatoms. The replacement of the −N⁺(CH₃)₃ group by a −S⁺(CH₃)₂ results in an increase in the polar head group size in PSC relative to that of PC, consistent with the observed increase in permeability of PSC bilayers towards urea. It was of interest to see whether replacement of the −N⁺(CH₃)₃ group in platelet activating factor (PAF) by an −S⁺(CH₃)₂ group leads to any change in platelet aggregation or other physiological activity. Synthesis of the sulfonium analogue of PAF was carried out by suitable modifications of known procedures. The PAF-sulfonium analogue was found to have almost the same platelet aggregating activity as PAF itself, in the concentration range 1–20 μM, but a much lower activity in the range 0.01–1 μM. The analogue had little or no effect on the platelet aggregation activity of PAF when added in the concentration range 0.01–1 μM and had about half the hypotensive activity of PAF towards hypertensive CDF male rats. The sulfonium analogue, however, was much more cytotoxic to HL-60 cells than PAF itself, in the concentration range 0–15 μM; replacement of the acetate group by a benzyl group increased the cytotoxicity to the level of that of the methoxy analogue of PAF. Thus, replacement of the −N⁺(CH₃)₃ group by a −S⁺(CH₃)₂ group in the polar head group region of PAF results in a relatively small change in its platelet aggregation activity and a decrease in its hypotensive activity, but greatly increases its antitumor activity. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 8–12, 1989.     

Solvent extraction of oil from soybean flour II— pilot plant and two-solvent extractions

The process of grinding soybeans to a fine flour and extracting the flour with hexane was studied on a pilot plant scale. The crude oil from the pilot plant study had 15 ppm phosphorus and was suitable for physical refining after a light acid pretreatment and bleaching. The refined oil showed a Lovibond color of 1.4 yellow and 0.3 red. The pilot plant study also showed that grinding of the soybeans and the separation of solid from miscella were the most difficult steps in solvent extraction with fine flour. A laboratory study on separation of miscella from meal by aqueous ethanol reduced the hold-up volume, but it did not remove all the miscella. A test with betacarotene showed that only the miscella outside the flour particles was displaced. Aqueous ethanol solutions used as a second solvent extracted additional nontriglyceride materials (primarily phospholipids) from the meal. Also, the free fatty acid content of the oil was increased with aqueous ethanol solution wash. The quality of the extracted crude oil was lowered by using a second solvent, but it had the advantage of needing only one centrifugation to separate miscella from meal.     

Effect of moisture and particle size on the extractability of oils from seeds with supercritical CO2

Moisture level and particle size of soybeans, peanuts and cottonseed were correlated with the extraction rate and yield of oil when extracted with supercritical carbon dioxide (SC-CO₂) at a constant temperature (50 C) and pressure (8000 psig). The rate of extraction and ultimate oil yields were quite low with cracked soybeans. However, good extraction rates and nearly theoretical oil yields were obtained from ground or thinly flaked (<0.010″) seeds. Moisture levels between 3% and 12% had little effect on extracability. Oil composition was not influenced by either parameter. Scanning electron microscopy was used to study seed structure before and after extraction with SC-CO₂. Micrographs of SC-CO₂-extracted seeds were similar to hexane-extracted seeds. Presented at the AOCS Meeting, May 1983, Chicago.     

Association products and conformations of salt-dissociated and acid-extracted histones. A two-phase procedure for isolating salt-dissociated histones

We present an extremely rapid and efficient method for the separation of salt-dissociated histones from DNA in which the macromolecular components of chicken erythrocyte chromatin are partitioned in a two-phase system of the water-soluble, nonionic polymers, poly(ethylene glycol) and dextran. We have compared the association products and conformations of salt-dissociated histones purified with the two-phase procedure and histones that had been extracted with 0.4 M H2SO4. In the gel chromatography system of D. R. vander Westhuyzen and C. von Holt (1971), FEBS Lett. 14, 333-337] the association products of salt-dissociated and acid-extracted histones are indistinguishable. Furthermore, the circular dichroism spectra of histones prepared with the two methods are identical within experimental error. These results indicate that histones extracted, with sulfuric acid can adopt conformations at least very similar to those of salt-dissociated preperties of total erythrocyte histones are the same in 2 M NaCl as those of these histones bound to DNA in chromatin in 1 mM Tris-Cl (pH 7.5). This result and the studies of Weintraub et al. [Weintraub, H., Palter, K., and Van Lente, F. (1975), Cell 6, 68-110] on the patterns of tryptic digest products of histones strongly suggest that in 2 M NaCl the histones exist in conformations very similar to their conformations when bound to DNA. The concept of native histone conformations is discussed in light of our results.     

The artificial heart. Progress and promise

A multidisciplinary group has designed, fabricated, and evaluated an artificial heart. The heart consists of two smooth-surfaced sac-type pumps, two pneumatic power units, and an electronic control system. The artificial heart has been employed in 22 calves. A variety of problems have been encountered and overcome and a significant improvement in pump design has been made. As a result, a gradual increase in survival times has occurred. The last two calves in which the heart was tested lived for 60 and 42 days respectively. These animals ate well and gained weight. The ability of the control system to balance the output of the two pumps over long periods of time and to automatically increase cardiac output with treadmill exercise has been confirmed. No insurmountable problems in the development of the artificial heart have been identified. The date that an artificial heart will be available for clinical use depends on the availability of funds and on the tenacity of the investigators.     

The influence of food intake and ambient temperature on the rate of thyroxine utilization

Young growing pigs of both sexes were subjected to changes in (1) energy intake, (2) ambient temperature, and (3) bulk of food. The rate of disappearance of injected 125I-labelled thyroxine from the plasma (K) was measured. An analysis of variance revealed that the effect attributable to changes in the energy content of the food intake was statistically significant (P less 0-01). A change in ambient temperature had no statistically significant effect on K, nor did a change in the bulk of food when energy intake was constant (P less than 0-05).     

Increased prolactin and thyrotrophin secretion following oral metoclopramide: dose-response relationships

In pregnant female rat, oxygen tension was measured in vivo with an oxygen microelectrode and the following statistically significant data (Student's test) were obtained: -- not significant variability in four groups of six control rats; -- highly significant decrease of oxygen tension twenty-four hours after biovariectomy in four groups of six operated rats; -- in twelve operated and treated by substitutive hormonotherapy rats, pO2 was at the same level than in control rats; -- in eighteen operated rats, the oxygen tension measured after embryonic death was identical to control rats. These experiments clearly demonstrate twenty four hours after biovariectomy a decreased oxygen tension. Simultaneously to this decrease, a diminution of uterine blood flow takes place. This pO2 diminution should be dependent on decrease of ovarian hormones since the substitutive hormonotherapy prevents its appearance. A good explanation of this phenomenon is the high requirement of hypoxic embryo for oxygen; moreover after the embryonic death, the intra-uterine pO2 increases.