Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Electron Probe Microanalysis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources
PubMed2005

New titanium and nickel gallophosphates with layered structures.

Two new transition-metal gallophosphates, (H(2)C(4)H(10)N(2))(3)[(Ti(2.5)(H(2)O)(4)Ga(5.5)(PO(4))(10)].2H(2)O (TGP-1) and [H(3.5)(C(4)H(13)N(3))(2)][(Ni(0.5)(OH)(4)Ga(5.5)(PO(4))(3)(HPO(4))(4)].2H(2)O (NGP-1), have been synthesized under mild hydrothermal conditions and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, electron paramagnetic resonance, electron probe microanalysis, and magnetic susceptibility data. TGP-1 exhibits a unique two-dimensional structure consisting of tetrahedral and octahedral metals centers and is the foremost paramagnetic TiGaPO material ever prepared. NGP-1 as well represents the first NiGaPO compound and adopts a layer structure that is constructed from hexameric M-O clusters of trigonal bipyramids and octahedra. In both compounds, the transition metals incorporate with gallium into octahedral sites only, while the four- and five-coordinated metals centers are only Ga(3+) ions. The unique sites for Ti(3+) and Ni(2+) ions have been initially elucidated from single-crystal structure refinements and further confirmed by bond-valence-sum calculations, EPR, and magnetic susceptibility studies. Crystal data: TGP-1, monoclinic, P2(1)/c; a = 25.692(2) A, b = 9.6552(8) A, c = 9.8418(8) A, beta = 96.737(2)(o) , V = 2424.5(3) A(3), and Z = 2; NGP-1, monoclinic, C2/c, a = 20.8363(12) A, b = 11.9546(7) A, c = 16.4577(9) A, beta = 117.285(1)(o) , V = 3643.3(1) A(3), Z = 4.

Journal Article↗
PubMed2003

Nanoscale soldering of metal nanoparticles for construction of higher-order structures.

We demonstrated that platinum nanoparticles dispersed in pure water were "soldered" by gold into higher-order structures such as "nanowebs". In practice, gold nanoparticles in water containing the platinum nanoparticles were melted by irradiation of a pulsed 532-nm laser, which excites selectively the surface plasmon band of the gold nanoparticles, and the melted gold nanoparticles solder the platinum nanoparticles together into the nanowebs. Optical absorption spectroscopy and electron microscopy together with electron probe microanalysis were employed to observe the structure of the nanowebs and to elucidate their formation dynamics.

Journal Article↗
PubMed2006

Structural, magnetic, and magnetoresistive properties of electrodeposited Ni5Zn21 alloy nanowires.

Ni5Zn21 alloy nanowires were fabricated through template-assisted electrochemical deposition method. The morphology and microstructures of as-deposited nanowires were determined by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), electron diffraction (ED), and electron probe microanalysis (EPMA). The accurate composition was measured via induced coupling plasma atomic emission spectroscopy. SEM results show that Ni5Zn21 nanowires are deposited in most of the nanopores of the template, and they are continuous and dense throughout the whole length. The XRD result demonstrates that the nanowires are mainly composed of a cubic gamma phase Ni5Zn21 alloy, but there also exists a trace of Zn-rich eta phase. HRTEM and ED reveal that the alloy nanowires are polycrystalline with the crystallite size of several tens of nanometers. EPMA of a single nanowire illustrates that there exist Ni-rich microzones in as-deposited nanowires. Subsequent magnetic measurements of the array also confirmed the existence of them. In addition, it can be further inferred that the shape of Ni-rich microzones is probably barlike or disklike, from the anisotropy of zero field cooling/field cooling (ZFC/FC) curves as well as the vortex magnetization behavior of the Ni5Zn21 nanowire array. The low-temperature magnetoresistance of the Ni5Zn21 nanowire array was also measured. Giant magnetoresistance instead of anisotropic magnetoresistance is suggested to be responsible for contributing to the magnetoresistance.

Journal Article↗
PubMed2006

Preliminary studies in the electrodeposition of PbSe/PbTe superlattice thin films via electrochemical atomic layer deposition (ALD).

This paper concerns the electrochemical growth of compound semiconductor thin film superlattice structures using electrochemical atomic layer deposition (ALD). Electrochemical ALD is the electrochemical analogue of atomic layer epitaxy (ALE) and ALD, methods based on nanofilm formation an atomic layer at a time, using surface-limited reactions. Underpotential deposition (UPD) is a type of electrochemical surfaced-limited reaction used in the present studies for the formation of PbSe/PbTe superlattices via electrochemical ALD. PbSe/PbTe thin-film superlattices with modulation wavelengths (periods) of 4.2 and 7.0 nm are reported here. These films were characterized using electron probe microanalysis, X- ray diffraction, atomic force microscopy (AFM), and infrared reflection absorption measurements. The 4.2 nm period superlattice was grown after deposition of 10 PbSe cycles, as a prelayer, resulting in an overall composition of PbSe0.52Te0.48. The 7.0 nm period superlattice was grown after deposition of 100 PbTe cycle prelayer, resulting for an overall composition of PbSe0.44Te0.56. The primary Bragg diffraction peak position, 2theta, for the 4.2 superlattice was consistent with the average (111) angles for PbSe and PbTe. First-order satellite peaks, as well as a second, were observed, indicating a high-quality superlattice film. For the 7.0 nm superlattice, Bragg peaks for both the (200) and (111) planes of the PbSe/PbTe superlattice were observed, with satellite peaks shifted 1 degrees closer to the (111), consistent with the larger period of the superlattice. AFM suggested conformal superlattice growth on the Au on glass substrate. Band gaps for the 4.2 and 7.0 nm period superlattices were measured as 0.48 and 0.38 eV, respectively.

Journal Article↗
PubMed1999

Characterization of anodic spark-converted titanium surfaces for biomedical applications.

The aim of the present study was to characterize the surface morphology, microstructure and the chemical composition of anodic spark-converted titanium surfaces. The coatings were prepared in an electrochemical cell by the anodic spark deposition technique in an aqueous solution of Ca(H2PO4)2. The coatings were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The properties of the coatings are described in terms of morphology.

Journal Article↗
PubMed1976

Effect of parathyroid hormone on phosphate reabsorption in the presence of acetazolamide.

The hypothesis that parathyroid hormone and carbonic anhydrase inhibitors have a common mechanism or site of action on phosphate reabsorption by the renal tubule was tested by administration of parathyroid hormone in the absence and presence of acetazolamide in thyroparathyroidectomized dogs. Re-collection micropuncture and electron probe microanalysis methodologies were utilized. In the absence of acetazolamide, parathyroid hormone increased fractional delivery of phosphate (and volume) from the proximal tubule from 25 +/- 2 to 38 +/- 3%, P less than 0.025, and increased fractional phosphate excretion from 3.8 +/- 1.2 to 19.9 +/- 3.7%, P less than 0.005 (eight dogs). In the presence of acetazolamide, parathyroid hormone increased fractional delivery of phosphate (but not volume) from the proximal tubule from 50 +/- 4 to 58 +/- 5%, P less than 0.025, and increased fractional excretion of phosphate from 8.7 +/- 2.2 to 31.0 +/- 4.3%, P less than 0.001 (12 dogs). Thus, the effects of parathyroid hormone were additive to the effects of maximal inhibition of carbonic anhydrase indicating that parathyroid hormone and carbonic anhydrase inhibitors have different mechanisms of action on phosphate reabsorption by the renal tubule. In addition, phosphate reabsorption beyond the point of micropuncture in the late proximal tubule was much more markedly inhibited by parathyroid hormone than by acetazolamide.

Acetazolamide↗
PubMed1993

Ion content and cell volume in isolated collecting duct cells: effect of hypotonicity.

On isolated inner medullary collecting duct (IMCD) cells of the rat kidney the capability of osmoregulatory adaptation was investigated in vitro. IMCD cells were isolated by differential centrifugation at 600 mOsm (268 mM NaCl) and subsequently exposed to hypotonic buffers (300 mOsm, 118 mM NaCl). The alterations of ion content and cell volume following this change in extracellular osmolarity were studied by electron probe microanalysis and determination of intracellular water. After swelling within 40 seconds to 152 +/- 15% of control (P < 0.001; N = 9) cell volume was restored after 15 minutes. This regulatory volume decrease (RVD) was observed irrespective whether extracellular osmolarity was changed by using NaCl or mannitol as the major osmolyte. During RVD the cells lost sodium (48 +/- 11%) and chloride (14 +/- 5%), and the potassium content remained nearly unchanged. Correspondingly, sodium and chloride concentrations were progressively lowered, whereas the potassium concentration changed only transiently. RVD was diminished by 10(-4) M NPPB, 10(-3) M SITS and in the absence of HCO3-. Twenty millimoles of ouabain or 5 mM barium also inhibited RVD with little additive effect. A total of 10(-3) M amiloride and 10(-4) M bumetanide showed no effect on the hypoosmotic volume response. The experiments show that in isolated IMCD cells exposed to hypotonic conditions, rapid reversible changes in cell volume and sustained alterations in cell inorganic ion content occur, and thereby transmembrane sodium and potassium gradients are maintained. Since the loss in inorganic electrolytes does not account for RVD, the major part of volume regulation seems to occur via changes in organic osmolytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1969

A fluorescence probe of energy-dependent structure changes in fragmented membranes.

The reaction of the fluorochrome, 8-anilino-1-naphthalene-sulfonic acid (ANS), with fragmented membranes from beef heart mitochondria has been studied. ANS fluorescence is found to be enhanced 25-fold on binding to the membrane fragments in the absence of energy conservation, and this enhancement is increased to 35-fold in the membrane energized by substrate plux oxygen. The fluorescence of bound ANS depends upon the energy state of the membrane fragments, as indicated by the effects of ATP, substrates of the respiratory chain, oligomycin, and uncouplers. It is concluded that the changes of ANS fluorescence indicate structural changes of the mitochondrial membrane associated with energy conservation. The time course of energization is readily followed by ANS, and has a half-time of two seconds at 26 degrees .

Adenosine Triphosphate↗
PubMed1992

Saturable binding of halothane to rat brain synaptosomes.

The hypothesis that volatile anesthetics act directly on or bind specifically to membrane proteins remains controversial. In earlier in situ electron probe microanalysis studies in cardiac muscle we showed preferential partitioning of halothane into mitochondria. To determine whether partitioning represents saturable binding or simple solubility, a photoaffinity labeling method was developed for halothane to examine binding in rat brain synaptosomes. Radioligand binding assays were then used to determine binding parameters for this important inhalational anesthetic. UV-light exposure of synaptosomes incubated with clinical concentrations of [14C]halothane resulted in sufficient labeling to allow characterization of binding sites. Analysis of saturation and competition curves showed that greater than 60% of [14C]halothane photolysis product binding to synaptosomes was specific, with low affinity (Kd = 0.49 +/- 0.16 mM) and high binding site concentration (Bmax = 1.87 +/- 0.75 nmol/mg of protein). Halothane photoaffinity labeling was partially inhibited by isoflurane (20%), chloroform (44%), 2-bromotrifluoroethane (20%), and dichlorotrifluoroethane (20%) but not by ethanol. The Kd measured with this photoaffinity approach is similar to the concentration of halothane required to produce anesthesia in rats.

Affinity Labels↗
PubMed2004

Identification of second harmonic optical effects from vaccine coated gold microparticles.

This study investigates the optical effects observed from uncoated and protein vaccine coated gold microparticles while imaging with two-photon excitation in the Mie scattering regime. When observed with time correlated single photon counting fluorescence lifetime microscopy, the emission from the gold microparticles appeared as an intense instrument-limited temporal response. The intensity of the emission showed a second-order dependence on the laser power and frequency doubling of the emitted light was observed for fundamental light between 890 and 970 nm. The optical effect was attributed to two-photon induced second harmonic generation. The vaccine coated gold microparticles had a much weaker second harmonic signal than the uncoated gold microparticles. Chemical analysis of the surface of the gold microparticles revealed that the vaccine coating decreases the surface charge thereby diminishing the observed second harmonic signal. These optical properties can be exploited to identify both the location of the protein vaccine coating as well as the gold microparticles in vitro and potentially to investigate the vaccine delivery kinetics in vivo.

Drug Delivery Systems↗
PubMed2000

Morphology and structure of various phases at the bonding interface of Al/steel formed by explosive welding

The bonding interface of explosively-welded aluminium and steel in three explosive conditions have been investigated by using scanning electron microscopy, transmission electron microscopy, electron diffraction and electron probe microanalysis methods. The results show that all the interfaces have the shape of waves with curled front formed by process of superplasticity and some discontinuous reacted zones. They consist of amorphous and nano sized crystals and quasi-crystals as well as the compounds such as AlFe, Al2Fe, Al3Fe and Al6Fe with various shapes. The basal steel crystal near the interface has structure of martensite and perlite crystals which are deformed by the process of superplasticity. The size of reacted zone becomes large with increasing amount of explosive charge powder and separation of the driver Al plate from the basal steel plate.

Journal Article↗
PubMed1978

Availability of Chloride Affects the Balance between Potassium Chloride and Potassium Malate in Guard Cells of Vicia faba L.

Electron probe microanalysis for K and Cl and enzymic determination of malate were performed on epidermal strips of Vicia faba L. which had been incubated with 0.1 equivalent of K(+) per liter in the absence or presence of Cl(-). In the absence of Cl(-), iminodiacetate, a presumed impermeant zwitterion, served as anion. With no Cl(-) in the medium, 91% of the K(+) imported into the guard cells during stomatal opening was neutralized by malate production; import of Cl(-) (presumably from the rest of the epidermal tissue) contributed 6%. In the presence of Cl(-), 50% of the necessary negative charges were provided by malate synthesis, 45% by Cl(-) import. Stomatal opening was not obviously affected by the chloride concentration in the incubation medium, but malate production declined roughly linearly with the logarithm of [Cl(-)] between 10(-5) and 10(-1) equivalent per liter.

Journal Article↗
PubMed1980

Potassium Chloride as Stomatal Osmoticum in Allium cepa L., a Species Devoid of Starch in Guard Cells.

K(+) and Cl(-) contents of guard cells and of ordinary epidermal cells were determined in epidermal samples of Allium cepa L. by electron probe microanalysis; malate contents of the same samples were determined by enzymic oxidation. KCl was, in general, the major osmoticum in guard cells, irrespective of whether stomata had opened on leaves or in epidermal strips floating on solutions. The solute requirement varied between 50 and 110 femtomoles KCl per micrometer increase in aperture per pair of guard cells. Stomata did not open on solutions of K iminodiacetate, presumably because its anion could not be taken up. Stomata opened if KCl or KBr was provided. Taken together, the results indicate that the absence of starch from guard cells deprived them of the ability to produce malate in amounts of osmotic consequence and that the presence of absorbable Cl(-) (or Br(-)) was necessary for stomatal opening.Previous nutrient supply of the plants determined whether the charges of K(+) in guard cells were completely balanced by Cl(-) or only partially. Addition of K(2)SO(4) to the nutrient solution reduced the participation of Cl(-) in stomatal ion transfer, even if epidermal strips of these plants were later exposed to KCl solution. The anion supplying the charge complement in these cases is not known.Although malate appeared not to participate in stomatal ion transfer in onion, epidermal samples of this species did contain malate. Malate accumulated in the epidermis of leaves put into the light but disappeared from illuminated epidermal strips floating on solutions. In whole leaves, epidermal malate content was positively correlated with stomatal opening; in epidermal strips floating on solutions, the correlation was negative or absent.

Journal Article↗