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Time-lapse lab-based x-ray nano-CT study of corrosion damage. J Microsc 2017; 267:98-106. [PMID: 28419456 DOI: 10.1111/jmi.12551] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 02/06/2017] [Accepted: 02/11/2017] [Indexed: 01/28/2023]
Abstract
An experimental protocol (workflow) has been developed for time-lapse x-ray nanotomography (nano-CT) imaging of environmentally driven morphological changes to materials. Two case studies are presented. First, the leaching of nanoparticle corrosion inhibitor pigment from a polymer coating was followed over 14 days, while in the second case the corrosion damage to an AA2099 aluminium alloy was imaged over 12 hours. The protocol includes several novel aspects relevant to nano-CT with the use of a combination of x-ray absorption and phase contrast data to provide enhanced morphological and composition information, and hence reveal the best information to provide new insights into the changes of different phases over time. For the pigmented polymer coating containing nominally strontium aluminium polyphosphate, the strontium-rich components within the materials are observed to leach extensively whereas the aluminium-rich components are more resistant to dissolution. In the case of AA2099 it is found that the initial grain boundary corrosion is driven by the presence of copper-rich phases and is then followed by the corrosion of grains of specific orientation.
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Novel approaches to characterize age-related remodelling of the dermal-epidermal junction in 2D, 3D andin vivo. Skin Res Technol 2016; 23:131-148. [DOI: 10.1111/srt.12312] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/21/2016] [Indexed: 12/21/2022]
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A comparison of different approaches for imaging cracks in composites by X-ray microtomography. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:20160037. [PMID: 27242291 PMCID: PMC4901256 DOI: 10.1098/rsta.2016.0037] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/07/2016] [Indexed: 05/14/2023]
Abstract
X-ray computed tomography (CT) has emerged as a key imaging tool in the characterization of materials, allowing three-dimensional visualization of an object non-destructively as well as enabling the monitoring of damage accumulation over time through time-lapse imaging. However, small defects and cracks can be difficult to detect, particularly in composite materials where low-contrast, plate-like geometries of large area can compromise detectability. Here, we investigate a number of strategies aimed at increasing the capability of X-ray CT to detect composite damage such as transverse ply cracking and delamination, looking specifically at a woven glass fibre-reinforced three-dimensional composite. High-resolution region of interest (ROI) scanning, in situ loading, phase contrast and contrast agents are examined systematically as strategies for improving the defect detectability. Spatial resolution, contrast, signal-to-noise ratio, full width at half maximum, user friendliness and measurement time are all considered. Taken together, the results suggest that high-resolution ROI scanning combined with the increased contrast resulting from staining give the highest defect detectability. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'.
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Dynamic loading of electrospun yarns guides mesenchymal stem cells towards a tendon lineage. J Mech Behav Biomed Mater 2014; 39:175-83. [PMID: 25129861 PMCID: PMC4180006 DOI: 10.1016/j.jmbbm.2014.07.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 07/14/2014] [Accepted: 07/15/2014] [Indexed: 11/17/2022]
Abstract
Alternative strategies are required when autograft tissue is not sufficient or available to reconstruct damaged tendons. Electrospun fibre yarns could provide such an alternative. This study investigates the seeding of human mesenchymal stem cells (hMSC) on electrospun yarns and their response when subjected to dynamic tensile loading. Cell seeded yarns sustained 3600 cycles per day for 21 days. Loaded yarns demonstrated a thickened cell layer around the scaffold׳s exterior compared to statically cultured yarns, which would suggest an increased rate of cell proliferation and/or matrix deposition, whilst maintaining a predominant uniaxial cell orientation. Tensile properties of cell-seeded yarns increased with time compared to acellular yarns. Loaded scaffolds demonstrated an up-regulation in several key tendon genes, including collagen Type I. This study demonstrates the support of hMSCs on electrospun yarns and their differentiation towards a tendon lineage when mechanically stimulated.
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Assessment of regional climate model simulation estimates over the northeast United States. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012jd018137] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
The extensor carpi ulnaris musculotendinous unit has important agonist and antagonist action in wrist motion, including the dart-throwing action, and is a dynamic stabilizer of the distal radioulnar joint during forearm rotation. Despite its functional and clinical importance, little is known about its internal structure. Investigation of the ultrastructure of the human extensor carpi ulnaris (ECU) tendon was undertaken using plane polarized light microscopy and microcomputer tomography with 3D reconstruction. The study demonstrates that the tendon comprises fibre bundles (fascicles) approximately 0.1 mm in diameter that are arranged in a gradual spiral. The spiralling fibres make an angle of 8º to the longitudinal axis of the tendon. The spiral structure of the human ECU tendon has important biomechanical implications, allowing fascicular sliding during forearm rotation. The observed features may prevent injury.
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Using Synchrotron X-Ray Nano-CT to Characterize SOFC Electrode Microstructures in Three-Dimensions at Operating Temperature. ACTA ACUST UNITED AC 2011. [DOI: 10.1149/1.3615824] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Abstract
An extensive array of measurements extending back to the mid-19th century was used to investigate large-scale changes in precipitation over Northern Hemisphere land areas. Significant increases in mid-latitude precipitation and concurrent decreases in low-latitude precipitation have occurred over the last 30 to 40 years. Although these large-scale trends are consistent with general circulation model projections of precipitation changes associated with doubled concentrations of atmospheric carbon dioxide, they should be viewed as defining large-scale natural climatic variability. Additional work to refine regional variations and address potential network inhomogeneitics is needed. This study attempts to show secular precipitation fluctuations over hemispheric and continental-scale areas of the Northern Hemisphere.
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Synoptic climatology of the Western United States in relation to climatic fluctuations during the twentieth century. ACTA ACUST UNITED AC 2007. [DOI: 10.1002/joc.3370010202] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
The underlying causes of late-Holocene climate variability in the tropics are incompletely understood. Here we report a 1,500-year reconstruction of climate history and glaciation in the Venezuelan Andes using lake sediments. Four glacial advances occurred between anno Domini (A.D.) 1250 and 1810, coincident with solar-activity minima. Temperature declines of -3.2 +/- 1.4 degrees C and precipitation increases of approximately 20% are required to produce the observed glacial responses. These results highlight the sensitivity of high-altitude tropical regions to relatively small changes in radiative forcing, implying even greater probable responses to future anthropogenic forcing.
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Variability of snow accumulation and isotopic composition on Nevado Sajama, Bolivia. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2003jd003623] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Modeling δ
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O in precipitation over the tropical Americas: 1. Interannual variability and climatic controls. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2001jd002038] [Citation(s) in RCA: 187] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Modeling δ
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O in precipitation over the tropical Americas: 2. Simulation of the stable isotope signal in Andean ice cores. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2001jd002039] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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A silica micro-balance; its construction and manipulation, and the theory of its action. ACTA ACUST UNITED AC 2002. [DOI: 10.1088/0950-7671/30/3/306] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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The Energetics and Statistical Mechanics of the Kinetics of Solid-->Solid Reactions. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j150544a002] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Design, synthesis, and biological evaluation of potent thiazine- and thiazepine-based matrix metalloproteinase inhibitors. J Med Chem 1999; 42:4547-62. [PMID: 10579818 DOI: 10.1021/jm990330y] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The synthesis and enzyme inhibition data for a series of thiazine- and thiazepine-based matrix metalloproteinase (MMP) inhibitors are described. The thiazine- and thiazepine-based inhibitors were discovered by optimization of hetererocyclic sulfonamide-based inhibitors. The most potent series of inhibitors was obtained by modification of the amino acid D-penicillamine. This amino acid provides a gem-dimethyl group on the thiazine or thiazepine ring which has a dramatic effect on the in vitro potency of this series. In particular, the sulfide 4a and the sulfone 5a were potent, broad-spectrum inhibitors of the MMPs with IC(50)'s against MMP-1 of 0.8 and 1.9 nM, respectively. The binding mode of this novel thiazepine-based series of MMP inhibitors was established based on X-ray crystallography of the complex of stromelysin and 4a.
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Abstract
A novel series of conformationally constrained matrix metalloprotease inhibitors was identified. The potencies observed for these inhibitors were highly dependent upon the substitution pattern on the caprolactam ring as well as the succinate moiety.
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NF-protocadherin, a novel member of the cadherin superfamily, is required for Xenopus ectodermal differentiation. Curr Biol 1998; 8:325-34. [PMID: 9512415 DOI: 10.1016/s0960-9822(98)70132-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND The assembly of complex tissues during embryonic development is thought to depend on differential cell adhesion, mediated in part by the cadherin family of cell-adhesion molecules. The protocadherins are a new subfamily of cadherins; their extracellular domains comprise cadherin-like repeats but their intracellular domains differ significantly from those of classical cadherins. Little is known about the ability of protocadherins to mediate the adhesion of embryonic cells, or whether they play a role in the formation of embryonic tissues. RESULTS We report the isolation and characterization of a novel protocadherin, termed NF-protocadherin (NFPC), that is expressed in Xenopus embryos. NFPC showed a striking pattern of expression in early embryos, displaying predominant expression within the deep, sensorial layer of the embryonic ectoderm and in a restricted group of cells in the neural folds, but was largely absent from the neural plate and surrounding placodal regions. Ectopic expression in embryos demonstrated that NFPC could mediate cell adhesion within the embryonic ectoderm. In addition, expression of a dominant-negative form of NFPC disrupted the integrity of embryonic ectoderm, causing cells in the deep layer to dissociate, though leaving the outer layer relatively intact. CONCLUSIONS Our results indicate that NFPC is required as a cell-adhesion molecule during embryonic development, and its function is distinct from that of classical cadherins in governing the formation of a two-layer ectoderm. These results suggest that NFPC, and protocadherins in general, are involved in novel cell-cell adhesion mechanisms that play important roles in tissue histogenesis.
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Global interdecadal and century-scale climate oscillations during the past five centuries. Nature 1995. [DOI: 10.1038/378266a0] [Citation(s) in RCA: 177] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
The proto-oncogene Wnt-1 plays an essential role in fetal brain development and causes hyperplasia and tumorigenesis when activated ectopically in the mouse mammary gland. When expressed in certain mammary epithelial cell lines, the gene causes morphological transformation and excess cell proliferation at confluence. Like other members of the mammalian Wnt family, Wnt-1 encodes secretory glycoproteins which have been detected in association with the extracellular matrix or cell surface but which have not previously been found in a soluble or biologically active form. We show here that conditioned medium harvested from a mammary cell line expressing Wnt-1 contains soluble Wnt-1 protein and induces mitogenesis and transformation of mammary target cells. By immunodepletion of medium containing epitope-tagged Wnt-1, we show that at least 60% of this activity is specifically dependent on Wnt-1 protein. These results provide the first demonstration that a mammalian Wnt protein can act as a diffusible extracellular signaling factor.
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Expression of Wnt-1 in PC12 cells results in modulation of plakoglobin and E-cadherin and increased cellular adhesion. J Cell Biol 1993; 123:1857-65. [PMID: 8276903 PMCID: PMC2290857 DOI: 10.1083/jcb.123.6.1857] [Citation(s) in RCA: 214] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The Wnt-1 gene plays an essential role in fetal brain development and encodes a secreted protein whose signaling mechanism is presently unknown. In this report we have investigated intracellular mechanisms by which the Wnt-1 gene induces morphological changes in PC12 pheochromocytoma cells. PC12 cells expressing Wnt-1 show increased steady-state levels of the adhesive junction protein plakoglobin, and an altered distribution of this protein within the cell. This effect appears similar to a modulation of the plakoglobin homolog, Armadillo, that occurs in Drosophila embryos in response to the Wnt-1 homolog, wingless (Riggleman, B., P. Schedl, and E. Wieschaus. 1990. Cell. 63:549-560). In addition, PC12/Wnt-1 cells show elevated expression of E-cadherin and increased calcium-dependent cell-cell adhesion. These results imply evolutionary conservation of cellular responses to Wnt-1/wingless and indicate that in certain cell types Wnt-1 may act to modulate cell adhesion mechanisms.
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The mouse Wnt-1 gene can act via a paracrine mechanism in transformation of mammary epithelial cells. Mol Cell Biol 1992; 12:321-8. [PMID: 1530877 PMCID: PMC364112 DOI: 10.1128/mcb.12.1.321-328.1992] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The mouse Wnt-1 gene plays an essential role in fetal brain development and can contribute to tumorigenesis when activated aberrantly in the mammary gland. The gene encodes secretory glycoproteins associated with the extracellular or pericellular matrix, and it has been proposed that Wnt-1, as well as its Drosophila homolog wingless, may function in intercellular signalling. We show here that fibroblasts expressing Wnt-1 protein, although not transformed themselves, are able to elicit morphological transformation of neighboring C57MG mammary epithelial cells in coculture experiments. Heparin inhibits this effect, possibly by displacing Wnt-1 protein from its normal site of action. Our results indicate that the Wnt-1 gene can act via a paracrine mechanism in cell culture and strongly support the notion that in vivo the gene may function in cell-to-cell communication.
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Proposed Minimal Standards for the Description of New Genera and Species of Root- and Stem-Nodulating Bacteria. ACTA ACUST UNITED AC 1991. [DOI: 10.1099/00207713-41-4-582] [Citation(s) in RCA: 184] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Abstract
The proto-oncogene int-1 plays an important role in mammary tumorigenesis when activated by proviral insertions of the mouse mammary tumor virus. In normal mouse tissues the gene is expressed in the embryonic neural tube, suggesting a developmental function, while in Drosophila the homolog of int-1 is the segment polarity gene wingless. In order to study the protein products of int-1 we have derived fibroblast cell lines infected with multiple copies of a retroviral vector expressing int-1 cDNA. By Western blot analysis and immunoprecipitation we have identified a 44 kd form of int-1 protein which is secreted from these cells. The 44 kd species is distinct from the major intracellular forms of int-1 protein as judged by its slower mobility in SDS-polyacrylamide gels and by its longer half-life in pulse-chase experiments. Under normal growth conditions, little or none of the 44 kd protein is detectable in the cell culture medium but instead the majority is found associated with the extracellular matrix (ECM). The protein appears to bind heparin in vitro, suggesting that it might bind glycosaminoglycans in the ECM. These data support the view that int-1 protein may play a role in cell-cell communication over short distances.
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New health claim system ready. THE NATIONAL UNDERWRITER. LIFE & HEALTH INSURANCE EDITION 1982; 86:29. [PMID: 10255727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
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UB-82 and the ubiquitous health insurance claim form. COMPUTERS IN HOSPITALS 1982; 3:44. [PMID: 10255099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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Electronic claims submission: the revolution arrives. BEST'S REVIEW. LIFE-HEALTH INSURANCE EDITION 1982; 83:54, 56, 58 passim. [PMID: 10255061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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Abstract
Field observations on northeast Ellesmere Island indicate that the maximum advance of the northwest Greenland Ice Sheet was about 100 kilometers beyond its present margin. This occurred before the outermost Ellesmere Island ice advance, which took place more than 30,000 years before present (B.P.). Recession from the Ellesmere Island ice margin began at least 28,000 to 30,000 and possibly more than 35,000 years B.P. During this sequence of glacial events, significant land areas remained free of ice. The late Wisconsin ice extent along both northeast Ellesmere Island and northwest Greenland was extremely limited, leaving an ice-free corridor along Kennedy and Robeson channels. Recession from these ice margins is indicated by initial postglacial emergence around 8100 to 8400 years B.P. The relatively minor extent of late Wisconsin ice in the High Arctic probably reflects a period of extreme aridity occasioned by the buildup of the Laurentide Ice Sheet to the south.
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The Glaciation Level and Lowest Equilibrium Line Altitude in the High Canadian Arctic: Maps and Climatic Interpretation. ACTA ACUST UNITED AC 1975. [DOI: 10.2307/1550318] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Ionic and electronic conduction in cuprous, argentous and aurous cyanides at high pressure. ACTA ACUST UNITED AC 1969. [DOI: 10.1039/tf9696501920] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Electrical conductivity of phthalocyanine and of copper phthalocyanine under high pressure. ACTA ACUST UNITED AC 1962. [DOI: 10.1039/tf9625800776] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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The rate of growth of crystals of carbon tetrabromide and iodine from the vapour. ACTA ACUST UNITED AC 1959. [DOI: 10.1039/tf9595501848] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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