Search

Natural rubber latex (NRL) is mainly used for traditional industrial products, but currently, its target application is continuously expanding into tissue engineering. Here, we have presented the chondrogenesis ability of NRL nanoparticles against human mesenchymal stem cells (hMSCs). The effective gene expression of in vitro chondrogenesis of hMSCs with administration of NRL was confirmed as revealed by the chondrogenic gene expression analysis. We have successfully for the first time fabricated the cartilage/NRL biocomposites via hMSC spheroid formation, where the administration of NRL nanoparticles exhibited the mechanically stable structure with hard surface structure in the spheroid.

The authors unveil topological spin structures composed of skyrmion strings in a cubic centrosymmetric iron oxide that provides the missing experimental link between centrosymmetric lattices and a rich variety of helimagnetic order. This is the first observation of a three-dimensional topological spin texture in a bulk perovskite-type oxide, one of the most ubiquitous and important systems for oxide electronics. The study enlarges the family of topological spin textures and offers a promising route toward the design of novel oxide skyrmionics.

The thermal diffusivity of reactor irradiated (U,Gd)O 2 fuels has been measured, for burn-ups from 33 to 97 GWd tHM − 1 and for irradiation temperatures from 670 to 1580 K. Measurements under thermal annealing cycles were performed in order to investigate the recovery of the thermal conductivity as a function of temperature. The analysis of the results showed a lower thermal conductivity for (U,Gd)O 2 when compared to UO 2 , with similar effects of the burn-up and irradiation temperature. A correlation for the thermal conductivity could be proposed on the basis of that for UO 2 presented in an earlier work, which describes the separate effects of soluble fission products, of fission gas frozen in dynamical solution and of radiation damage.

In this study we attempted to clarify the mechanism of the inhibitory effects of PGE 2 on DNA synthesis in Gin-1 (fibroblasts derived from healthy human gingiva) from the aspect of the cyclic AMP-dependent protein kinase signal transduction pathway. PGE 2 upregulated intracellular cyclic AMP accumulation and inhibited DNA synthesis in Gin-1 in a dose-dependent manner. When the PGE 2 -induced intracellular cyclic AMP accumulation was further enhanced by treatment with the cyclic AMP-phosphodiesterase inhibitor, IBMX, the inhibitory effect of PGE 2 on DNA synthesis was also enhanced. Furthermore, when we examined the effects of forskolin, an activator of cyclic AMP production, on intracellular cyclic AMP accumulation and DNA synthesis, similar results were obtained. However, inhibitors of cyclic AMP-dependent protein kinase (protein kinase A) such as HA1004 did not diminish the inhibitory effect of PGE 2 on DNA synthesis in Gin-l. These results suggest that in Gin-l, PGE 2 -induced cyclic AMP accumulation may not lead to the activation of protein kinase A or protein kinase A activity may not relate directly to the growth inhibitory effect of PGE 2 , and that PGE 2 does not inhibit DNA synthesis through the cyclic AMP-protein kinase A signal transduction pathway in Gin-1.

In order to clarify, from the electronic structure, the origin of the appearance of the tri-valent Ce state in irradiated cerium dioxide with swift heavy ions, we performed comprehensive first-principles calculations on various defective structures in cerium dioxide. The calculated results show that an oxygen mono-vacancy or an oxygen Frenkel pair can induce two tri-valent Ce states neighboring the oxygen vacancy. The calculation of the oxygen Frenkel pair further reveals that an interstitial oxygen atom that moves from the lattice position and an oxygen atom on the lattice can form a dimer that behaves as an oxygen molecule of negative di-valence. This bonding state can also produce excess electrons and the tri-valent Ce state in cerium dioxide.

In light water commercial reactors, extensive change of grain structure was found at high burnup ceramic fuels. The mechanism is driven by bombardment of fission energy fragments and studies were conducted by combining accelerator based experiments and computer-science. Specimen of CeO2 was used as simulation material of fuel ceramics. With swift heavy ion (Xe) irradiation on CeO2, with 210 MeV, change of valence charge and lattice deviation of cations were observed by XPS and XRD. Combined irradiations of Xe implantation and swift heavy ion irradiation successfully produced sub-micrometer sized sub-grains, similar as that observed in commercial fuels. Studying components of mechanism scenarios, with first principle calculations using the VASP code, we found stable hyper-stoichiometric defect structures of UO2+x. Molecular dynamics studies revealed stability of Xe planar defects and also found rapid transport mode of oxygen-vacancy clusters.

We studied the migration dynamics of oxygen point defects in UO2 which is the primary ceramic fuel for light-water reactors. Temperature accelerated dynamics simulations are performed for several initial conditions. Though the migration of the single interstitial is much slower than that of the vacancy, clustered interstitial shows faster migration than those. This observation gives us important insight on the formation mechanism of high-burnup restructuring, including planar defects and grain sub-division (the rim structure), found in UO2.

In order to understand the properties of ion tracks and the microstructural evolution under accumulation of ion tracks and Xe ions in CeO2, 70–210 MeV Xe10∼14+ ions irradiation examinations and pre-implantations of 240 keV Xe ions have been done at a tandem accelerator facility and an ion implanter facility of JAEA-Tokai. The microstructure observations were performed by means of a transmission electron microscope (TEM) and a scanning electron microscope (SEM) in CRIEPI. Measurements of the diameter of ion tracks with the irradiation temperature, between room temperature and 800 °C, clarify that the prominent changes of ion tracks are hardly observed up to 800 °C. By cross-sectional observation, it becomes clear that the threshold electronic stopping power of ion track formation is around 15–16 keV/nm in case of Xe ions irradiation. 210 MeV Xe14+ ion irradiations cause a surface roughness on CeO2 in the ion fluence range between 5 × 1014 ions/cm2 and 1 × 1015 ions/cm2.

In order to simulate the effects of high energy fission products on high-burnup UO 2 nuclear fuel pellets, CeO 2 thin films and bulk specimens were irradiated with 200 MeV Xe ions. Effects of the irradiation were studied by using Extended X-ray Absorption Fine Structure (EXAFS) measurement and X-ray photoelectron spectroscopy (XPS) at synchrotron radiation facilities. The EXAFS spectra for the irradiated thin films near the Ce K-edge show the formation of the oxygen deficiency around Ce ions. XPS Spectra show that the valence state of Ce atoms is changed from intrinsic Ce 4+ to Ce 3+ state by the irradiation. As such irradiation effects appear even for low fluence irradiation, the experimental result suggests that the oxygen deficiency and the change in Ce valence state are due to high-density electronic excitation induced by the 200 MeV Xe ions.

Ratios of equilibrium charge-state yields for singly to doubly ionized He-3 ions at an energy of 420 MeV were measured using the Grand Raiden magnetic spectrometer at RCNP. Targets with atomic numbers of 6, 12, 28, 40, 50 and 82 were used. It is found that theoretical calculations for atomic electron-capture and stripping cross sections, which have been successful in describing the data up to beam energies of 200 MeV, are also applicable at this higher energy. However, where at the lower energies the stripping cross sections were calculated with a combination of models by Bohr and Gillespie, the best description of the data at E(He-3) = 420 MeV is obtained when using only the model by Gillespie. The experimental results are also compared with calculations using the code CHARGE, originally developed for fast, heavy (Z > 29) projectiles, to test the extrapolation to low-Z projectiles. It is found that the code underestimates the production of singly-charged He-3 ions, in particular for heavier target nuclei. (c) 2007 Elsevier B.V. All rights reserved.

To clarify the origin of a characteristic fine grain structure formed under the high burn-up of the nuclear fuel, the comprehensive first-principles calculations for UO2 containing various types of point defect have been performed by the PAW-GGA+U with lattice relaxation for supercells containing 1, 2 and 8 unit cells of UO2. The electronic structure, the atomic displacement and the defect formation energies of defective systems are obtained, and the effects of supercell size on these properties are discussed. Based on this relatively high precise self-consistent formation energies dataset, thermodynamic properties of various types of point defects in UO2 are further investigated in the framework of the point defects model.

AlGaN/GaN HFETs were fabricated around micropipes and on a domain boundary in a semi-insulating silicon carbide (SI-SiC) substrate and the DC characteristics of the fabricated devices were measured. Devices around micropipe showed no pinch-off or large gate leakage. The devices on the domain boundaries showed no degradation in the performances, even though an X-ray topographic analysis indicated that crystal imperfections, due to the defects, propagated to the GaN layer across the hetero interface. Based on these results, we concluded that micropipe degrades the DC characteristics and that the domain boundary does not affect the DC characteristics. From Raman analysis on the devices around the micropipes, these degradations could be attributed to the free carriers introduced into the GaN crystal by the micropipes.

A first-principles calculation for uranium dioxide (UO2) in an antiferromagnetic structure with four types of point defects, uranium vacancy, oxygen vacancy, uranium interstitial, and oxygen interstitial, has been performed by the projector-augmented-wave method with generalized gradient approximation combined with the Hubbard U correction. Defect formation energies are estimated under lattice relaxation for supercells containing 1, 2, and 8 unit cells of UO2. The electronic structure, the atomic displacement and the stability of defected systems are obtained, and the effects of cell sizes on these properties are discussed. The results form a self-consistent dataset of formation energies and atomic distance variations of various point defects in UO2 with relatively high precision. We show that a supercell with 8 UO2 unit cells or larger is necessary to investigate the defect behavior with reliable precision, since point defects have a wide-ranging effect, not only on the first nearest neighbor atoms of the defect, but on the second neighbors and on more distant atoms. [doi:10.2320/matertrans.47.2651]

A 10-/spl mu/m-thick GaAs/AlGaAs vertical-cavity surface-emitting laser (VCSEL) was fabricated by lifting off GaAs/AlGaAs epitaxial layers from the GaAs substrate to achieve high-density optoelectronic (OE) integration. It was found that the thin-film VCSEL array with a length of 0.25 to 3.0 mm warped due to internal stress in the film itself. The shift created by warping reached 100 /spl mu/m, and this warping was analyzed with a curved cantilever model with a uniform internal stress of 10/sup 7/ to 10/sup 9/ N/m/sup 2/. To fabricate a thin-film VCSEL array simultaneously on a mount, a diced chip with a thickness of 130 /spl mu/m was solder bonded onto a glass mount first, followed by lifting off epitaxial layers containing GaAs/AlGaAs VCSELs from the GaAs substrate. Current-voltage-light output characteristics as well as light-emission spectra for thin-film VCSELs were measured and compared at temperatures between 25/spl deg/C and 75/spl deg/C. It was found that the dependence of the device characteristics of thin-film VCSELs on temperature was similar to that of VCSELs with a GaAs substrate. The light output of thin-film VCSELs was measured for 1000 h during continuous operation at 25/spl deg/C and 50/spl deg/C. About a 20% decrease in optical output in devices without resin mold and no degradation in devices buried in resin mold were observed. Device degradation might be attributable to the internal stress of 10/sup 7/ N/m/sup 2/ and film warp of 0.5-1.0 /spl mu/m. The thin-film devices buried in resin mold had no changes in laser threshold current before or after 1000 h of continuous operation.

The mechanical properties of polycarbonate compounded with titanium dioxide are investigated. Titanium dioxide treated with methyl polysiloxane on alumina silica coating is compounded in the matrix polymer using twin screw extruder. Izod impact strength of this composite material is higher than that of the composite material compounded with untreated titanium dioxide. The dispersibility of this treated filler is evaluated by fracture surface and turbidity of the solution of the composite materials. The results suggest that the composite material compounded with titanium dioxide which is treated with methyl polysiloxane and alumina silica at the same time has higher dispersibility. And the melt viscosity of composite material shows same behavior with neat polycarbonate. This suggests that the melt viscosity is affected by the dispersibility of particles.

The lipid content and fatty acid composition of fresh immature and in vitro matured bovine oocytes cultured in media with or without serum, and also those of frozen-thawed immature oocytes were analysed. All oocytes were ranked (A or B) on the basis of their cytoplasmic quality. Fatty acid composition (mol %; w/w) in the total lipid fraction was analysed by gas chromatography. Triglyceride, total cholesterol, phospholipid (phosphocholine-containing phospholipid) and non-esterified fatty acid contents of immature and in vitro matured oocytes were determined using lipid analysis kits. Phosphocholine-containing phospholipid and non-esterified fatty acid contents were determined in frozen-thawed immature bovine oocytes. Palmitic acid was the most abundant fatty acid in immature oocytes (A: 35%, B: 36%), and in in vitro matured oocytes cultured in the medium containing serum (A: 36%, B: 35%) or polyvinyl alcohol (A: 33%, B: 36%). Oleic acid was the second most abundant fatty acid in all A ranked oocytes, whereas stearic acid was the second most abundant fatty acid in all B ranked oocytes. There were significant differences (P < 0.05) in linoleic and arachidonic acid fractions between A and B ranked immature oocytes. In vitro matured oocytes had significantly (P < 0.05) lower proportions of linoleic and arachidonic acids, and significantly (P < 0.01) lower contents of triglyceride and total cholesterol compared with those of immature oocytes. The fatty acid composition of in vitro matured oocytes cultured in medium containing fetal calf serum or polyvinyl alcohol was similar, but significant differences (P < 0.01) in triglyceride and the total cholesterol content were observed. There was a significant decrease (P < 0.05) in the arachidonic acid proportion in frozen-thawed immature oocytes compared with that in fresh immature oocytes. In addition, significant (P < 0.05) decreases in both phospholipid (15.8--10.6 pmol) and non-esterified fatty acid (11.0--4.1 pmol) were found in frozen--thawed immature oocytes. The results indicate that lipids are available for use as an energy source for maturation and that serum lipids are incorporated into the oocyte cytoplasm during in vitro maturation. The changes in the lipid content (mainly phospholipid) and fatty acid composition were also observed in frozen--thawed immature oocytes. The study indicates that the alteration of fatty acid composition in bovine oocytes might improve maturation and cryopreservation.

A multi-pellet injector system has been developed as a fundamental fueling tool for the Large Helical Device (LHD). Since a primary goal of the LHD project is demonstration of steady-state high-temperature plasmas, highly reliable and reproducible performance is prerequisite for the LHD pellet injector. The helium Gifford-McMahon (GM) cycle cryogenic refrigerator and conventional pipe-gun mechanism have been employed along with these requirements. Since the triple point temperature of hydrogen is lower than those of isotopes; deuterium and tritium, a careful and steady temperature control is necessary in pellet formation. The amount of propellant gas has been minimized by small reservoir to reduce heat load and inflow into the plasma vacuum chamber. Both robustness and flexibility have been realized by using the programmable logic controller combined with GUI on WindowsNT. The pellet injector has demonstrated continuous hundreds of injection without any fail and has been applied for the LHD experiment successfully.

1. The roles of ATP-sensitive K+ channels (KATP channels) in ischaemic or pharmacological preconditioning in the rabbit heart remain unclear. Infarct limitation by ischaemic preconditioning was abolished by the KATP channel blocker glibenclamide under ketamine/xylazine anaesthesia, but not under anaesthesia induced by pentobarbital. Infarct limitation by the KATP channel opener pinacidil was detected under ketamine/xylazine anaesthesia, but not under pentobarbital anaesthesia. Thus, these effects appear to be anaesthetic dependent. 2. In the present study, we examined whether nicorandil (a KATP channel opener nitrate) exhibits cardioprotective actions under halothane anaesthesia, another commonly used volatile anaesthetic. Control animals were subjected to 40 min coronary occlusion and 120 min reperfusion. Before 40 min ischaemia, the nicorandil group received nicorandil (100 microg/kg per min, i.v., for 10 min), the 5' preconditioning (PC) group received 5 min ischaemia/20 min reperfusion, the 2.5'PC group received 2.5 min preconditioning ischaemia/20 min reperfusion, the nicorandil +2.5'PC group received both nicorandil and 2.5 min ischaemia/20 min reperfusion, the nicorandil +2.5'PC + 5-hydroxydecanoate (5HD) group received both nicorandil and 2.5 min ischaemia/20 min reperfusion in the presence of 5-hydroxydecanoate (5HD; a KATP blocker) and the 5HD group received 5 mg/kg, i.v., 5HD alone. Myocardial infarct size in control (n = 7), nicorandil (n = 5), 5'PC (n = 8), 2.5'PC (n = 5), nicorandil + 2.5'PC (n = 5), nicorandil + 2.5'PC + 5HD (n = 5) and 5HD (n = 4) groups averaged 44.4 +/- 3.6, 41.7 +/- 5.7, 17.8 +/- 3.2,* 34.1 +/- 4.8, 21.3 +/- 4.2,* 39.1 +/- 5.6 and 38.9 +/- 5.0% of the area at risk, respectively (*P

A BWR design UO2 fuel irradiated to a burnup of 7.9% FIMA was selected for a careful calculational and experimental analysis because the rod experienced an unusual power history: it had two high power periods at 1.7% FIMA and between 4 and 5% FIMA causing increased fuel temperatures and thus increased gas release and damage recovery. As a consequence, two parameters generally considered to be important for grain subdivision (rim structure formation) were locally different from normal fuel, i.e. fission gas inventory and extent of radiation damage. Histories of temperature, fission rate and fission gas release were calculated at different radial positions. Microstructure observations (TEM, SEM) revealed the typical high burnup grain subdivision process (polygonization) which extended to a maximum of 1.65 mm (r/r0 = 0.73) from the pellet surface inwards. For this radial position, the calculations yielded a local temperature of 1200°C and predicted that more than half of the fission gas was released during the second high power period for this radial position. The results give thus information on the importance of the fission gas inventory for the burnup threshold of restructuring.

The high burnup LWR UO2 fuels show a notable micro-structural change around the pellet outer zone which is called the rim structure. It is observed at temperatures as low as 400°C so that fission track and cascade mixing could be the key mechanism. SEM observation revealed that the structure primarily appears on free surfaces of UO2, indicating that strong sink for point defects may play a big role. And as generic observations, increase of lattice parameter indicates extensive amounts of vacancies are stored in high burnup fuel, which may induce the restructuring interacting with dislocations of high density at high burnup. Considering these observations a model of reaction-diffusion process of defects with irradiation induced transport is proposed. The equations are investigated numerically. The model indicates that an instability starts when the dislocation network starts intensive interaction with vacancy flux which is modified by interstitial diffusion between spatial segments. It appeared to be similar to the Turing type instability which indicates that the rim structure formation is one kind of the self-organizing processes of open reaction-diffusion systems.

Recently, many inhibitors of farnesyl protein transferase (FPTase) have been identified. Some of them interrupt cell growth in addition to Ras and nuclear lamin processing of Ras-transformed cells. We have tested the effect of the FPTase inhibitors manumycin, an analogue of farnesyl diphosphate, and KT7595, a gliotoxin derivative, on Ras farnesylation, DNA synthesis and the anchorage-dependent and -independent growth of human colon carcinoma (LoVo), hepatoma (Mahlavu and PLC/PRF/5) and gastric carcinoma (KATO III). Both drugs severely inhibited DNA synthesis, cellular proliferation and Ras farnesylation in LoVo and moderately reduced them in Mahlavu and PLC/PRF/5 but not in KATO III. Complete sequencing of ras genes, however, revealed that LoVo and KATO III have activated Ki-ras and activated N-ras, respectively, whereas Mahlavu and PLC/PRF/5 have no activated ras. We next checked whether the inhibition of the cellular proliferation is due to the blocking of nuclear lamin function. Neither drug disturbed lamin farnesylation and localization, as demonstrated using metabolic labelling, immunoblotting and indirect immunofluorescence. These results indicate that manumycin and KT7595 can inhibit Ras farnesylation and cell growth without disturbing the farnesylation and localization of the lamins on human tumour cell lines. Images Figure 5 Figure 6 Figure 7 Figure 8

Cisplatin is metabolized to high- and low-molecular mass complexes by exchanging of one or both chloride ligands with nucleophilic species. The decomposition of cisplatin and the formation of its metabolites in human biological fluids was investigated in-vitro. In nucleophile-free medium, cisplatin was decomposed by a reversible chloride ligand exchange reaction, which was dependent upon both chloride ion concentration and medium pH. The effect of pH was observed in the second-order rate constant for cisplatin re-formation, which was far smaller in neutral and alkaline media than in acidic media. In the medium containing nucleophilic species (glutathione, human albumin and globulin), cisplatin was irreversibly decomposed according to apparent first-order kinetics. The linear relationship between apparent decomposition rate constant and concentration of nucleophilic species suggested that nucleophilic species in biological fluids might react with cisplatin directly. Both high- and low-molecular mass metabolites were formed in human plasma and ascites; however, only a low-molecular mass metabolite was produced in urine. The faster decomposition of cisplatin and the greater ratio of fixed and mobile metabolites formed in plasma were mainly attributed to higher albumin concentration in plasma than in ascites and urine. The in-vitro decomposition of unchanged cisplatin and formation of high- and low-molecular mass metabolites in human biological fluids were simultaneously evaluated according to the kinetic model which combined both pathways via hydrolysis and by the direct reaction process with nucleophilic species.

The magnetic interactions in β-phase p-NPNN (p-nitrophenyl nitronyl nitroxide), a prototype genuine organic ferromagnet, have been studied by simultaneous measurements of magnetic heat capacity and susceptibility under hydrostatic pressures. A drastic reduction of the Curie temperature from 0.6 K at ambient pressure to 0.35 K at 7.2 kbar has been observed. This makes a significant contrast to the pressure-induced enhancement of the Neel temperature of organic antiferromagnets. A lowering of the magnetic lattice dimensionality is also observed at temperatures slightly above the Curie temperature under pressure. These observations are interpreted in terms of the virtual charge transfer mechanism.

The de Haas - van Alphen measurements of the deuterated molecular conductor (DMe-DCNQI) 2 Cu have been carried out to investigate the Fermi surface and the possibility of the mass enhancement of the conduction electrons near the insulating phase. The Fermi surfaces and the cyclotron masses of the deuterated samples which show the drastic metal - insulator - metal transition are found to be the same as those of the undeuterated sample. The fact shows that the additional mass enhancement due to many body effects is absent near the insulating phase.

Contaminant loading associated with stormwater runoff from recently burned areas is poorly understood, despite the fact that it has the potential to affect downstream water quality. The goal of the present study is to assess regional patterns of runoff and contaminant loading from wildfires in urban fringe areas of southern California. Postfire stormwater runoff was sampled from five wildfires that each burned between 115 and 658 km(2) of natural open space between 2003 and 2009. Between two and five storm events were sampled per site over the first one to two years following the fires for basic constituents, metals, nutrients, total suspended solids, and polycyclic aromatic hydrocarbons (PAHs). Results were compared to data from 16 unburned natural areas and six developed sites. Mean copper, lead, and zinc flux (kg/km(2)) were between 112- and 736-fold higher from burned catchments and total phosphorus was up to 921-fold higher compared to unburned natural areas. Polycyclic aromatic hydrocarbon flux was four times greater from burned areas than from adjacent urban areas. Ash fallout on nearby unburned watersheds also resulted in a threefold increase in metals and PAHs. Attenuation of elevated concentration and flux values appears to be driven mainly by rainfall magnitude. Contaminant loading from burned landscapes has the potential to be a substantial contribution to the total annual load to downstream areas in the first several years following fires.

The effect of initial mixture temperature on the experimentally measured detonation cell size for hydrogen-air-steam mixtures at 0.1 MPa has been investigated. Experiments were carried out in a 10-cm-inner-diameter, 6.1-m-long heated detonation tube with a maximum operating temperature of 700 K and spatial temperature uniformity of ±14 K. Detonation cell size measurements provide clear evidence that the effect of hydrogen-air initial gas mixture temperature, in the range 300–650 K, is to decrease cell size and, hence, to increase the sensitivity of the mixture to undergo detonations. The effect of steam content, at any given temperature, is to increase the cell size and, thereby, to decrease the sensitivity of stoichiometric hydrogen-air mixtures. The hydrogen-air detonability limits for the 10-cm-inside-diamter test vessel, based upon the onset of single-head spin, decreased from 15% hydrogen at 300 K down to about 9% hydrogen at 650 K. The experimental detonation cell size data were correlated using a Zel'dovich-von Neumann-Doring (ZND) model for the detonation using detailed chemical-kinetic reaction mechanisms. The proportionality constants used to scale the reaction zone length calculations from the ZND model varied from 30 to 51 for the hydrogen-air cell size data at 650 and 300 K, respectively.

The peripheral region of a high burnup light water reactor (LWR) fuel pellet shows a microstructure that is different from the as-fabricated microstructure. The region where the microstructure change occurs (the rim region) is highly porous, and the original grains in the rim region are divided into much smaller subgrains. The electron probe microanalysis data of high burnup fuels indicate fission gas depletion in the rim region as well as in the central region. The burnup in the rim region is enhanced by built-up plutonium derived from a 238 U self-shielding effect, which is called a rim effect. The rim effect accelerates microstructure change in the peripheral region. We developed a detailed burnup analysis code ANRB computing the rim effect in LWR fuels

Although the antibody response of vitamin A-deficient rats immunized with pneumococcal polysaccharide (SSS-III) was barely detectable, coimmunization with SSS-III plus 2 or 20 micrograms of Pseudomonas aeruginosa lipopolysaccharide (LPS) resulted in an anti-SSS-III response that was equal to or greater than that of vitamin A-sufficient rats immunized only with SSS-III. Doses of 2 and 20 micrograms of LPS, but not 0.1 and 0.5 micrograms, produced significant adjuvanticity, and LPS functioned as an adjuvant when given concomitantly with SSS-III (day 0) or up to 3 days later. Thus, vitamin A deficiency per se does not preclude the anti-SSS-III response, and LPS or factors released in response to LPS, even after initiation of the response to SSS-III, may substantially enhance antibody production to this thymus-independent, type 2 antigen.

At the early stage of embryogenesis, cells that inherit maternally derived determinants become specialized germline cells. After specialization, primordial germ cells (PGCs) migrate in passive and active modes until the gonad primordium is formed. In the active movement, a chemokine (stromal cell-derived factor 1) guides the migration pathway via its receptor (CXC chemokine receptor 4). After settling in the gonad, PGCs differentiate into the gamete. The sex of fish is determined by genetic and/or environmental factors. However, fish generally have high plasticity in sex determination. Indeed, a trans sex phenomenon has been observed in many fish species. Fish seem to change sex in order to maximize their reproductive efficiency.

Vitamin A deficiency severely compromises the magnitude of the primary and secondary antibody response to tetanus toxoid (TT) but does not impair the development of immunologic memory. To further characterize this immunodeficiency in antibody production, we have quantified the immunoglobulin G (IgG) subclasses (IgG1, IgG2a, IgG2b, and IgG2c) during the primary and secondary response to TT in normal, vitamin A-deficient, and retinol-repleted rats. In the primary response in normal rats, anti-TT IgG1 and IgG2b predominated. In vitamin A-deficient rats the production of anti-TT IgG2b was severely impaired, with little change in either IgG1 or IgG2a. In the secondary response vitamin A-deficient rats produced low levels of all anti-TT IgG subclasses. However, when vitamin A-deficient rats were repleted with retinol 2 days before reimmunization their secondary anti-TT IgG response was normal both in magnitude and IgG subclass distribution. This result implies that although vitamin A deficiency during the primary antibody response impaired anti-TT IgG2b production, it did not inhibit Ig heavy chain recombination or the differentiation of lymphocytes that formed memory B cells for each subclass; furthermore, these cells were activated in the secondary response after vitamin A status was improved. Thus, these experiments further support the concept that memory cell formation remains normal during vitamin A deficiency despite low levels of antibody production.

A model for constituent migration behavior in U-Pu-Zr metallic fast reactor fuel is proposed. It is based on diffusion equations for the ternary system under a radial temperature gradient, and it t...

The mechanism of the antiatherogenic activity of n -3 polyunsaturated fatty acids is not well understood. In these studies, we studied the metabolism of unsaturated fatty acids in murine macrophage-like J774A.1 cells. The major metabolic pathway of 18- and 20-carbon chain unsaturated fatty acids in these cells is the sequence of 2-carbon chain elongation, successive two steps of Δ 8 - and Δ 5 -desaturation, and additional elongation. Polyunsaturated fatty acids, arachidonic acid [20:4 ( n −6)] and eicosapentaenoic acid [20:5 ( n −3)], are elongated into 22:4 ( n −6) and 22:5 ( n −3) fatty acids, respectively. Accumulation of 22:4 ( n −6) and 22:5 ( n −3) fatty acids shows that J774A.1 cells have an active chain elongation activity, but lack Δ 4 -desaturase activity. Furthermore, J774A.1 cells demonstrated almost negligible Δ 6 -desaturase activity. Enrichment of the membrane lipids of J774A.1 cells with polyunsaturated fatty acids, arachidonic acid [(20:4 ( n −6)] and eicosapentaenoic acid [(20:5 ( n −3)], increased membrane fluidity and decreased the uptake of acetylated low density lipoprotein.

Magnetic properties of a stable organic biradical, meta-phenylene bis(α-nitronyl nitroxide) (abbreviated as m-BNN) were investigated. The molecular ground state of m-BNN is found to be triplet (S=1) from the solution EPR measurements. The temperature dependence of the product of paramagnetic susceptibility and temperature, ξpT, of the single crystal of m-BNN exhibits anomalous stationary behavior with decreasing temperature as a result of intermolecular exchange interactions. From the analysis based on the structure of magnetic energy spectrum in a solid state, the formation of unusual magnetic energy gaps in the crystal is deduced. An organic triradical, the 1,3,5-tri-substituted form (TNN), was also studied. By solution EPR measurements, this molecule is shown to have the quartet ( S= 3 2 ground state. A polycrystalline sample of the triradical exhibits a broad susceptibility maximum around 16 K. The value of the susceptibility extrapolated to 0 K is nonzero. This indicates the gapless nature of the triradical solid, in contrast to the gap formation in the biradical.

Magnetization isotherms up to 5.5 T and temperature dependence of magnetic susceptibility down to 1.8 K of the organic neutral radicals, 3- and 4-quinolyl nitronyl nitroxide and 2,6-pyridinediyl bis(nitronyl nitroxide), are described. 3-quinolyl nitronyl nitroxide exhibit ferromagnetic intermolecular interaction with the Weiss constant Θ = 0.27 K, whereas 4-quinolyl nitronyl nitroxide shows antiferromagnetic intermolecular interaction with the exchange coupling constant J/k = −7.8 K. This significant difference between the magnetic properties of two compounds are discussed in terms of their crystal structures. The temperature dependence of product of paramagnetic susceptibility and temperature, χ p T, of a biradical 2,6-pyridinediyl bis(nitronyl nitroxide) shows a plateau at low temperatures in addition to the usual plateau observed in the high-temperature region. This peculiar behavior is interpreted in terms of the multi-spin system associated with a combined effect of ferro- and antiferro-magnetic couplings.

The changes in electrical resistivity caused by electrolytically charged hydrogen in a series of palladium - rare earth (RE) solid solution alloys (RE  Sc, Gd, Dy, Tb, Ho, Er, Yb, Lu) were investigated in the low hydrogen concentration region of the α phase, together with measurements of the electrode potential.

Self-defect clusters in bulk matrix might affect the thermodynamic behavior of fission gases in nuclear fuel such as uranium dioxide. With first-principles LSDA+U calculations and taking xenon as a prototype, we find that the influence of oxygen defect clusters on the thermodynamics of gas atoms is prominent, which increases the solution energy of xenon by a magnitude of 0.5 eV, about 43% of the energy difference between the two lowest lying states at 700 K. Calculation also reveals a thermodynamic competition between the uranium vacancy and tri-vacancy sites to incorporate xenon in hyper-stoichiometric regime at high temperatures. The results show that in hypo-stoichiometric regime neutral tri-vacancy sites are the most favored position for diluted xenon gas, whereas in hyper-stoichiometric condition they prefer to uranium vacancies even after taking oxygen self-defect clusters into account at low temperatures, which not only confirms previous studies but also extends the conclusion to more realistic fuel operating conditions. The observation that gas atoms are ionized to a charge state of Xe+ when at a uranium vacancy site due to strong Madelung potential implies that one can control temperature to tune the preferred site of gas atoms and then the bubble growth rate. A solution to the notorious meta-stable states difficulty that frequently encountered in DFT+U applications, namely, the quasi-annealing procedure, is also discussed., 22 pages, 7 figures, accepted by Phys. Rev. B for publication

Experiments were conducted in male Lewis rats to compare the efficacy with which β-carotene (βC) and retinol restore antibody production in the previously vitamin A-depleted rat immunized with pneumococcal polysaccharide (SSS-III). Weanling rats were fed a semipurified vitamin A-free diet for three weeks and were then repleted with either retinol or βC provided in various doses and by different routes. Pairfed control rats were fed the same diet with adequate vitamin A. When 45–46 days old, rats were immunized with SSS-III and antibody production was measured 5 d later. In rats beginning to manifest vitamin A deficiency, the splenic antibody response was reduced significantly in comparison to that of the pairfed control group as well as to groups repleted with retinyl palmitate or with βC [1500 retinol equivalents (R.E.) each]. When βC was provided in an aqueous dispersion and delivered either orally or intravenously, the splenic antibody response of both βC-repleted groups were similar to each other and both were significantly greater than the response of the vitamin A-deficient group. The antibody response of rats repleted intravenously with βC or retinol, provided in nutritionally equivalent amounts (1000 R.E.), was also similar in magnitude. These observations indicate that βC functions approximately equally well as retinol in enabling the previously vitamin A-deficient rat to respond to pneumococcal polysaccharide; however, βC did not show any superior effect to retinol in restoring this antibody response in the previously vitamin A-depleted rat.

It is shown that in addition to the precipitation of small gas filled pores, there is a pronounced reduction in the grain size at the surface of UO2 fuel at high burnup. These microstructure changes were first observed when the local burnup exceeded 70–80 MWd/kgM. Generally, the change in microstructure does not penetrate more than 200 μm. However, in a HWR fuel irradiated to 75 MWd/kgM a large part of the pellet cross section was found to have been affected. Temperature predictions for this fuel suggests that it is the restructuring accompanying thermally activated fission gas release at 1100 to 1200°C that limited the distance over which the microstructure changes occur. Apparently, the formation and fission of Pu is not directly responsible for the change in fuel microstructure. The porosity evidently contains part of the fission gas that is lost from the UO2 lattice in the region where the microstructure changes take place.

A mechanistic model of fission gas swelling and release has been developed for metallic fuel under operational conditions. This swelling model is based on gas bubble coalescence and growth by gas bubble random and/or biased migration occurring in grain boundaries. The gas release is modeled by open bubbles and tunnel formation. Experimental data are analyzed by this model. The result suggests that the model can predict fission gas bubble growth of metallic fuel.

The relationships between the formation of iron nitride films by plasma reactive evaporation and the plasma parameters (space potential V s , electron density N e and electron temperature T e ) were investigated. The V s , N e and T e of the reactive nitrogen plasma were determined by the single probe method. The formation of nitrides was found to depend strongly on both V s and N e . The nitrogen concentration increased with increasing N e and V s . In particular, an ?' phase was obtained when Ne=(1 to 3)×109 cm?3 and V s was either 50 V or between 300 and 500 V. The process of nitride formation in the plasma reactive evaporation was also investigated by using evaporated iron films exposed to nitrogen plasma. The nitrides were found to be formed mainly on the film surface.

We have previously shown that vitamin A deficiency severely impairs the young rat's ability to produce specific antibodies after primary immunization with tetanus toxoid (TT). In the present studies, we asked whether immunologic memory to TT is established even in the vitamin A-depleted animal, and if so, whether such memory can be elicited after subsequent repletion with retinol. Vitamin A-depleted rats produced very low concentrations of TT-specific IgM and IgG antibodies in both the primary and secondary responses; however, the ratios of secondary to primary IgM anti-TT and of IgG anti-TT were normal. When rats were repleted with retinol 1 day after immunization, IgM and IgG anti-TT concentrations in both the primary and secondary responses were at least as great as those of control rats. For rats repleted with retinol 2 days before the booster immunization, secondary IgM and IgG anti-TT concentrations were equal in magnitude to those of vitamin A-sufficient controls. For all groups, the kinetics of the antibody response were similar. We conclude that immunological memory is intact in the vitamin A-depleted animal, as shown by 1) the normal ratio of its secondary to primary antibody responses, 2) the restoration of a quantitatively normal secondary antibody response in previously vitamin A-depleted animals repleted with retinol just before boosting with TT, and 3) a normal class switch from IgM to IgG. Retinol deficiency is also characterized by an abnormal elevation of total plasma IgG, despite the inability of the vitamin A-depleted animal to produce normal quantities of specific antibodies after challenge with antigen.