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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Although the artery wall consists of three distinct layers, only the structures of the intima and media have been well characterized. The adventitia has generally been overlooked. Our examination focused on the organization of elastin and collagen which are the major components of this tunic. Canine infrarenal aortas were excised, stretched to their in vivo length, then pressure fixed in formalin. Transverse, longitudinal, and frontal sections were prepared with specific elastin and collagen stains. Areas of adventitia in these sections were examined with LM, and interconnections between collagen and elastin were photographed at various magnifications. Subsequently, the slides were fractured for attachment to SEM stubs, and the coverslips were demounted. The identical areas were then examined with SEM using the LM micrographs as a guide to identify elastin and collagen. Whole mount aortic ring preparations were digested in formic acid for 72 and 96 h at 45 degrees C to confirm adventitial elastin architecture. The adventitia was organized in alternating lamellae of collagen and elastin. The elastin lamellae consisted of continuous sheets of elastin with a longitudinal fibrillar substructure. Finer circumferential elastin fibers were also identified. These attached to both longitudinal elastin and adjacent collagen lamellae. Collagen lamellae were arranged in broad corrugated bands of fibrils. The unique architecture of the adventitia may explain some of the visco-elastic properties of the aorta in both normal and pathologic states.
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PMID:The architecture of adventitial elastin in the canine infrarenal aorta. 206 31

Seasonal changes in the hypothalamic-hypophyseal axis were investigated using tissue from 49 light-horse mares, of mixed breeding. Hypothalamic and pituitary tissues were collected at 5 intervals throughout the years 1981 and 1982, representing midbreeding season (July, n = 10), transition out of the breeding season (October, n = 11), midanestrus (December, n = 8), transition into the breeding season (March, n = 10), and again in the following midbreeding season (July, n = 10). The hypothalamic region was dissected into preoptic area, body and median eminence. Gonadotropin-releasing hormone (GnRH) was extracted from hypothalamic samples with methanol-formic acid and quantified by radioimmunoassay. The anterior pituitary was homogenized and receptors for GnRH were quantified in a crude membrane fraction. Concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured in the resulting supernatant. Content of GnRH in each of the 3 hypothalamic areas varied with season (P less than 0.01) and was lowest during midanestrus (P less than 0.05). There was no effect of season (P greater than 0.01) on either concentration or total number of receptors for GnRH, or concentration of FSH in the anterior pituitary. Concentrations of LH in the anterior pituitary varied with season (P less than 0.001). Means (+/- SEM) for the 5 collection times were 15.5 +/- 2.7, 9.7 +/- 2.4, 2.3 +/- 0.5, 2.7 +/- 0.4 and 11.7 +/- 1.5 microgram LH/mg anterior pituitary, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Seasonal variation in hypothalamic content of gonadotropin-releasing hormone (GnRH), pituitary receptors for GnRH, and pituitary content of luteinizing hormone and follicle-stimulating hormone in the mare. 632 38

The treatment of the simulated wastewater containing formic acid and Cu(II) ions was investigated using photocatalytic technology of immobilized TiO2 film. The technology could efficiently remove COD and Cu(II) from the solution. In parallel, a rapid deactivation for COD removal was observed in a successive batch experiment. By XRD, UV-Vis diffuse reflectance spectra, SEM image and TG analysis, it was inferred that the deactivation was attributed to the shield of the deposited Cu(0) from UV light. The Cu(0)-fouled TiO2 film could be regenerated using three kinds of methods, air oxidation, electrochemical oxidation and air-assisted electrochemical oxidation. The regeneration time was mainly dependent on the used regeneration strategy while the regeneration extent was obviously associated with the tested regeneration medium. For the deactivated film with a relative activity of about 20%, the regeneration time is in order air-assisted electrochemical oxidation < electrochemical oxidation < air oxidation, and HNO3 medium has a regeneration extent of 97.2% for the air-assisted electrochemical oxidation, more desirable than HCl and H2SO4 mediums.
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PMID:Strategies for regeneration of copper(0)-deposited TiO2 photocatalytic film. 1236 45

Regenerated silk fibroin (SF) filaments were prepared by the wet spinning technique. The rheological behavior of the SF dope solution prepared with formic acid was examined and the drawing effect on the structural characteristics and mechanical properties of SF filament was comparatively studied with those of natural silk fiber. SF dope exhibited shear thinning, but, as the dope concentration increased, the effect of shear thinning decreased, an indication that a higher concentration of dope solution will result in good spinnability. Wet-spun SF filaments exhibited a uniform and circular cross-sectional shape and dense morphology under SEM observation. X-ray diffraction (XRD) results revealed that the crystallinity of wet-spun regenerated filaments was hardly affected by the draw ratio, whereas the crystalline and amorphous orientation of regenerated SF filament showed different features depending on the drawing. The crystalline orientation of regenerated filaments increased with an increase of draw ratio and was lower than that of natural silk fiber. On the contrary, the amorphous orientation was constant throughout 1X-5X draw ratios, after an abrupt increase at 1X, and was higher than that of natural silk fiber. These differences in the orientation behaviors are attributed to the different spinning mechanisms involved. The tensile property was strongly dependent on the draw ratio. The breaking strength and elongation of the regenerated filament at 5X draw ratio were 2.2 g/day and 17%, respectively.
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PMID:Wet spinning of silk polymer. II. Effect of drawing on the structural characteristics and properties of filament. 1517 15

Regenerated silk fibroin materials show properties dependent on the methods used to process them. The molecular structures of B. mori silk fibroin both in solution and in solid states were studied and compared using X-ray diffraction, FTIR, and (13)C NMR spectroscopy. Some portion of fibroin protein molecules dissolved in formic acid already have a beta-sheet structure, whereas those dissolved in TFA have some helical conformation. Moreover, fibroin molecules were spontaneously assembled into an ordered structure as the acidic solvents were removed from the fibroin-acidic solvent systems. This may be responsible for the improved physical properties of regenerated fibroin materials from acidic solvents. Regenerated fibroin materials have shown poor mechanical properties and brittleness compared to their original form. These problems were technically solved by improving the fiber forming process according to a method reported here. The regenerated fibroin fibers showed much better mechanical properties compared to the native silk fiber and their physical and chemical properties were characterized by X-ray diffraction, solid state (13)C NMR spectroscopy, SinTech tensile testing, and SEM.
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PMID:Structural studies of Bombyx mori silk fibroin during regeneration from solutions and wet fiber spinning. 1587 99

Two types of platinised TiO2 films, i.e., Pt-TiO2/ITO and Pt(TiO2)/ITO, were prepared by a procedure of dip-coating and subsequent photo-deposition, and photo-deposition and subsequent dip-coating, respectively. They were well characterized by DRS, XRD spectra, SEM microscopy and photoelectrochemical measurement. Their photocatalytic, dark catalytic and photoelectrocatalytic activities were investigated using formic acid as a model organic pollutants. Compared with pure TiO2/ITO film, the photocatalytic activity of the platinised TiO2 films were apparently improved. However, the improvement was considerably dependent on the preparation method of these films. Pt-TiO2/ITO not only possessed higher photocatalytic activity but also showed a dark catalytic activity towards HCOOH degradation. As a sequence, it was first emphasized that the dark catalytic effect of Pt-TiO2/ITO was partly responsible for degradation of formic acid in the photocatalytic oxidation process. Although the Pt(TiO2)/ITO film does not exhibit the dark catalytic activity, its photocatalytic degradation efficiencies towards HCOOH are higher than that of Pt-TiO2/ITO film. Therefore, in view of enhanced photocatalytic activity, the Pt(TiO2)/ITO was more favored than Pt-TiO2/ITO film.
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PMID:Comparison of catalytic activity of two platinised TiO2 films towards the oxidation of organic pollutants. 1628 99

Intermetallic PtPb nanoparticles have been synthesized by two solution-phase reduction methods. In the first (PtPb-B), Pt and Pb salts were reduced by sodium borohydride in methanol at room temperature. In the second (PtPb-N), metal-organic Pt and Pb precursors were reduced by sodium naphthalide in diglyme at 135 degrees C. Both methods produced small agglomerated nanoparticles of the ordered intermetallic PtPb (mean crystal domain size <15 nm) which were characterized by pXRD, SEM, UHV-STEM, BET, EDX, and electron diffraction. The electrocatalytic activity of PtPb nanoparticles produced by both methods toward formic acid and methanol oxidation was investigated and compared to Pt and PtRu. Both PtPb-B and PtPb-N nanoparticles exhibited enhanced electrocatalytic activity compared to commercially available Pt black and PtRu nanoparticles. For formic acid oxidation, the PtPb nanoparticles exhibited considerably lower onset potentials and higher current densities than Pt or PtRu. For methanol oxidation, the PtPb nanoparticles had onset potentials slightly positive of PtRu but exhibited higher current densities at potentials about 100 mV positive of onset. The general applicability of these methods for the synthesis of nanoparticles of ordered intermetallic phases is discussed.
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PMID:Synthesis, characterization, and electrocatalytic activity of PtPb nanoparticles prepared by two synthetic approaches. 1712 17

There are reports of fabrication of taste sensor by adsorbing lipids into Millipore filter paper, which improved the taste sensing efficiency of membrane remarkably. We have made an attempt to prepare taste sensor material by grafting polyacrylic acid (PAA) to cellulose. The research work covers polymer membrane preparation, morphology study, and structural characterization of the membrane and study of the taste sensing characteristics of this membrane for five different taste substances. FTIR spectroscopic analysis and SEM were done to get an idea about the structure and morphology of the PAA grafted cellulose membrane. Surface charge density of the membrane was estimated. The sensor characteristics like temporal stability, response stability, response to different taste substances, and reproducibility of sensing performance were studied using PAA grafted cellulose membrane. Sensor device prepared with this membrane has shown distinct response patterns for different taste substances in terms of membrane potential. Threshold concentrations of PAA grafted cellulose membrane for HCl, NaCl, quinine-hydrochloride (Q-HCl), sucrose and monosodium glutamate are 0.001 mM, 0.01 mM, 0.08 mM, 0.08 mM and 0.01 mM, respectively. The threshold concentrations except that in Q-HCl are below human threshold concentrations. Membranes also showed characteristic response patterns for organic acids like acetic acid, citric acid, formic acid, etc., mineral acids like HCl, H(2)SO(4) and HNO(3), etc., salts, bitter substances, sweet substances and umami substances. Sensor device prepared with this membrane has excellent shelf life.
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PMID:Taste sensing with polyacrylic acid grafted cellulose membrane. 1897 May 44

In this study, a novel kind of hydroxyapatite-polysaccharide capsules was prepared through a bio-inspired process in simulated body fluid for efficient encapsulation of formate dehydrogenase. In this process, a thin alginate/chitosan film formed immediately around the capsules coupled with in situ precipitation of hydroxyapatite when alginate HPO(4)(2-)-stock solution droplets were added into chitosan Ca(2+)-stock solution. The biomineralization of hydroxyapatite was mimicked by the counter-diffusion system in which calcium ions and phosphate ions migrated into the alginate/chitosan film from opposite directions. Formation of capsule was confirmed by Zoom Stereo Microscopy, the surface morphology of the capsule was characterized by SEM, the surface element composition of capsules was analyzed by EDX and the pore size distribution of capsule shell was determined by BET. As compared to the free formate dehydrogenase, hydroxyapatite-polysaccharide-formate dehydrogenase composite capsules exhibited significantly higher activity and storage stability in a broader temperature and pH range when converting CO(2) to formic acid.
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PMID:Biomimetic fabrication of hydroxyapatite-polysaccharide-formate dehydrogenase composite capsules for efficient CO(2) conversion. 1972 34

Photocatalytic activity of Ag/TiO(2) composites obtained by photoreduction treatment (PRT) was investigated. The composite materials, containing various ratio of silver nanoparticles (0.6-3.7 wt %) were obtained by depositing silver on the Evonic-Degussa P25 titania surface. Selected samples whose color varied between light rose and purple brown were examined by SEM, TEM, XPS, DRS, and BET techniques. Flat band potential was determined using Roy method. TEM analysis showed spherically shaped silver nanoparticles of the diameter 4-12 nm. The XPS measurements revealed that silver particles were obtained mainly in metallic form. DRS spectra and photovoltage measurements showed that silver nanoparticles modified the P25 spectral properties but they changed neither the band gap nor the location of flat band potential. The photocatalytic activity of Ag/P25 composite was compared to the photocatalytic activity of pure P25 in the photooxidation reaction of an important potable water contaminant humic acid (HA) and two model compounds, oxalic acid (OxA) and formic acid (FA). The photodecomposition reaction was investigated in a batch reactor containing aqueous suspension of a photocatalyst illuminated by either UV or artificial sunlight (halogen lamp). The tests proved that a small amount of silver nanoparticles deposited on the titania surface triggers the increase in photocatalytic activity; this increase depends, however, on the decomposed substance.
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PMID:Photocatalytic activity of titanium dioxide modified by silver nanoparticles. 2056 1


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