Interfacial topological states are a key element of interest for topological insulator thin films, and their properties can depend sensitively on the atomic bonding configuration. We employ in situ ...nonresonant and resonant surface x-ray scattering to study the interfacial and internal structure of a prototypical topological film system: Bi2Te3 grown on Si(111). The results reveal a Te-dominated buffer layer, a large interfacial spacing, and a slightly relaxed and partially strained bottom quintuple layer of an otherwise properly stacked bulklike Bi2Te3 film. The presence of the buffer layer indicates a nontrivial process of interface formation and a mechanism for electronic decoupling between the topological film and the Si(111) substrate.
We use real-time diffuse surface x-ray diffraction to probe the evolution of island size distributions and its effects on surface smoothing in pulsed laser deposition (PLD) of SrTiO3. We show that ...the island size evolution obeys dynamic scaling and two distinct regimes of island growth kinetics. Our data show that PLD film growth can persist without roughening despite thermally driven Ostwald ripening, the main mechanism for surface smoothing, being shut down. The absence of roughening is concomitant with decreasing island density, contradicting the prevailing view that increasing island density is the key to surface smoothing in PLD. We also report a previously unobserved crossover from diffusion-limited to attachment-limited island growth that reveals the influence of nonequilibrium atomic level surface transport processes on the growth modes in PLD. We show by direct measurements that attachment-limited island growth is the dominant process in PLD that creates step flowlike behavior or quasistep flow as PLD “self-organizes” local step flow on a length scale consistent with the substrate temperature and PLD parameters.
Data must be collected over a wide pH range to accurately model the adsorption of protons and metal onto bacterial surfaces; however, alterations in the structural and chemical properties of ...bacterial surfaces resulting from exposure to acidic solutions may affect the mechanisms of cation binding. Binding properties of bacteria may also be affected by nutrient and oxygen levels present during their growth. We measured Cd, Co, and Pb adsorption onto bacteria by using (1) bacteria washed with acidic solutions (pH≈1.5), (2) non-acid-washed bacteria exposed to acidic parent solutions, and (3) non-acid-washed bacteria exposed to neutral parent solutions. The purpose was to determine the effect of acidic conditions on the adsorptive properties of
Pseudomonas mendocina,
Pseudomonas aeruginosa,
Bacillus subtilis, and
Bacillus cereus. We also measured Co adsorption onto bacteria (
Pseudomonas fluorescens) grown under nutrient-rich and nutrient-limited conditions and onto the facultative bacterium
Shewanella oneidensis MR-1 grown under aerobic and anaerobic conditions. Bacteria exposed to acidic solutions adsorbed more metals than bacteria not exposed to such solutions. We attribute the increase in adsorption to the irreversible displacement of structurally bound Mg and Ca by protons. After displacement, the protonated sites can participate in reversible metal adsorption reactions. Thermodynamic modeling suggests that concentrations of functional group sites on bacterial surfaces increase by as much as five times in response to acid washing, assuming that stability constants for the bacterial surface complexes remain the same. Although the sizes of the bacteria changed markedly in response to nutrient limits and oxygen content during growth, the mass-normalized extent of Co adsorption onto both
P. fluorescens and
S. oneidensis MR-1 was independent of growth conditions. We conclude that adsorption constants derived from experiments in which the bacteria are never exposed to acidic conditions probably provide the most accurate estimates of the extent of bacteria–metal adsorption in natural settings.
We use time-resolved surface x-ray diffraction measurements with microsecond range resolution to study the growth kinetics of pulsed laser deposited . Time-dependent surface coverages corresponding ...to single laser shots were determined directly from crystal truncation rod intensity transients. Analysis of surface coverage evolution shows that extremely fast nonequilibrium interlayer transport, which occurs concurrently with the arrival of the laser plume, dominates the deposition process. A much smaller fraction of material, which is governed by the dwell time between successive laser shots, is transferred by slow, thermally driven interlayer transport processes.
Anti-lymphocyte monoclonal antibody HNK-1 (Leu-7) reacts with the cell surfaces of natural killer (NK) lymphocytes and with myelin-associated glycoprotein (MAG). This antibody reacts intensely with ...normal and neoplastic adrenal medullary cells. A small proportion of normal pancreatic islet cells, anterior pituitary, and gastroenteropancreatic endocrine cells also show Leu-7 immunoreactivity. In adrenal medulla, ultrastructural immunocytochemical studies and immunoblot analyses reveal that Leu-7 reacts with an intracellular protein of MW 75 KD which is localized within the matrices of the chromaffin granules. The MW of this protein differs from those of MAG and chromogranin A. The findings suggest that Leu-7 immunoreactivity might be a new marker for specific subsets of secretory granules.
Eighteen patients with lymphoid malignancies and abnormalities of the short arm of chromosome 17 were evaluated, in order to analyse whether this anomaly was associated with a particular subgroup of ...lymphoid malignancies. The patients suffered from acute lymphoblastic leukemia, high-grade non-Hodgkin's lymphoma or plasma cell leukemia. No 17p anomaly was found in any patient with chronic lymphocytic leukemia or low-grade non-Hodgkin's lymphoma. In four cases the aberration of the short arm of chromosome 17 was the sole cytogenetic abnormality, in fourteen patients additional chromosomal aberrations were found. Five out of 18 cases were Burkitt's lymphoma/leukemia showing the typical rearrangement of 8q24. In cases with a karyotype evolution the 17p anomaly was always a late event. Concerning the clinical outcome of the patients with abnormalities of the short arm of chromosome 17 eight of nineteen patients died within 90 days after the diagnosis of the 17p anomaly only three were alive at the last follow up (26 months to 40 months after diagnosis of a 17p aberration). Rearrangements of 17p, especially as secondary cytogenetic events, seem to be associated with a poor clinical outcome in lymphoid malignancies.
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