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Morphology Changes (morphology + change)

Distribution by Scientific Domains

Polymers and Materials Science	46%
Medical Sciences	26%
Physics and Astronomy	13%

Selected Abstracts

Abrupt Morphology Change upon Thermal Annealing in Poly(3-Hexylthiophene)/Soluble Fullerene Blend Films for Polymer Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2010
Minjung Shin
Abstract The in situ morphology change upon thermal annealing in bulk heterojunction blend films of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) is measured by a grazing incidence X-ray diffraction (GIXD) method using a synchrotron radiation source. The results show that the film morphology,including the size and population of P3HT crystallites,abruptly changes at 140,°C between 5 and 30,min and is then stable up to 120,min. This trend is almost in good agreement with the performance change of polymer solar cells fabricated under the same conditions. The certain morphology change after 5,min annealing at 140,°C is assigned to the on-going thermal transition of P3HT molecules in the presence of PCBM transition. Field-emission scanning electron microscopy measurements show that the crack-like surface of blend films becomes smaller after a very short annealing time, but does not change further with increasing annealing time. These findings indicate that the stability of P3HT:PCBM solar cells cannot be secured by short-time annealing owing to the unsettled morphology, even though the resulting efficiency is high. [source]

Morphology Change of Undoped and Sulfate-Ion-Doped Yttria Powders during Firing

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2004
Ikegami Takayasu
Morphologic changes that occurred during firing in undoped and sulfate-ion-doped yttria powders were examined in the present study. Clear scanning electron microscopy (SEM) images of uncoated insulators were achieved and charging of electrons was avoided by observing small samples, throughout which most of the electrons of the incident beam penetrated. SEM observation and firing of the samples were repeated several times. Searching the observed areas or particles started at low magnification, with the aid of photographs taken earlier. The sulfate-ion dopant inhibited volume diffusion and/or grain-boundary diffusion, and then particle growth of the sulfate-ion-doped yttria proceeded by surface diffusion or evaporation,condensation along with pore growth, which resulted in collapse of the agglomerates of primary particles. Although most of the other particles exhibited slight pore growth along with particle growth at temperatures as low as 800°C, a hardening of the agglomerated particles, because of pore elimination by volume diffusion and/or grain-boundary diffusion, occurred at temperatures >850°C. [source]

Abrupt Morphology Change upon Thermal Annealing in Poly(3-Hexylthiophene)/Soluble Fullerene Blend Films for Polymer Solar Cells

Mitochondrial morphology transition is an early indicator of subsequent cell death in Arabidopsis

NEW PHYTOLOGIST, Issue 1 2008
Iain Scott
Summary ,,Mitochondrial morphology and dynamics were investigated during the onset of cell death in Arabidopsis thaliana. Cell death was induced by either chemical (reactive oxygen species (ROS)) or physical (heat) shock. ,,Changes in mitochondrial morphology in leaf tissue, or isolated protoplasts, each expressing mitochondrial-targeted green fluorescent protein (GFP), were observed by epifluorescence microscopy, and quantified. ,,Chemical induction of ROS production, or a mild heat shock, caused a rapid and consistent change in mitochondrial morphology (termed the mitochondrial morphology transition) that preceded cell death. Treatment of protoplasts with a cell-permeable superoxide dismutase analogue, TEMPOL, blocked this morphology change. Incubation of protoplasts in micromolar concentrations of the calcium channel-blocker lanthanum chloride, or the permeability transition pore inhibitor cyclosporin A, prevented both the mitochondrial morphology transition and subsequent cell death. ,,It is concluded that the observed mitochondrial morphology transition is an early and specific indicator of cell death and is a necessary component of the cell death process. [source]

Activation Sequence Modification During Cardiac Resynchronization by Manipulation of Left Ventricular Epicardial Pacing Stimulus Strength

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2007
USHA B. TEDROW M.D.
Background: Success of cardiac resynchronization therapy (CRT) depends on altering electrical ventricular activation (VA) to achieve mechanical benefit. That increases in stimulus strength (SS) can affect VA has been demonstrated previously in cardiomyopathy patients undergoing ablation. Objective: To determine whether increasing SS can alter VA during CRT. Methods: In 71 patients with CRT devices, left ventricle (LV) pacing was performed at escalating SS. Timing from pacing stimulus to right ventricular (RV) electrogram, ECG morphology, and maximal QRS duration on 12 lead ECG were recorded. Results: Demographics: Baseline QRS duration 153 ± 25 ms, ischemic cardiomyopathy 48%, ejection fraction 24%± 7%. With increased SS, conduction time from LV to right ventricle (RV) decreased from 125 ± 56 ms to 111 ± 59 ms (P = 0.006). QRS duration decreased from 212 ± 46 ms to 194 ± 42 ms (P = 0.0002). A marked change in QRS morphology occurred in 11/71 patients (15%). The RV ring was the anode in 6, while the RV coil was the anode in 5. Sites with change in QRS morphology showed decrease in conduction time from LV to RV from 110 ± 60 ms to 64 ± 68 ms (P = 0.04). Twelve patients (16%) had diaphragmatic stimulation with increased SS. Conclusions: Increasing LV SS reduces QRS duration and conduction time from LV to RV. Recognition of significant QRS morphology change is likely clinically important during LV threshold programming to avoid unintended VA change. [source]

Morphology and mechanical properties of direct injection molded polypropylene/thermotropic copolyester blends

POLYMER COMPOSITES, Issue 6 2000
G. Guerrica-Echevarría
Blends of two grades of polypropylene (PP) with thermotropic copolyester (Rodrun) contents of up to 40% were obtained by direct injection molding at different processing temperatures. In the skin of the molded specimens rather long fibers were seen in blends with low-viscosity PP, whereas sheets were found when the high-viscosity PP was the matrix. In the core, the viscosity of the matrix played a more relevant role than the viscosity ratio on the orientation level of the dispersed Rodrun phase. The better mechanical properties of the blends with the low viscosity PP are attributed to the morphology change of the dispersed phase from sheets to fibers when the viscosity of the matrix decreased. [source]

Hydrothermal synthesis of nano-crystalline BaMoO4 under mild conditions using simple additive

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2010
Guangru Tian
Abstract Large-scale high-quality BaMoO4 nanocrystals have been synthesized in aqueous solutions under mild conditions with citrate as a simple additive. The crystals have bone-like, spindle-like and wheatear-like morphologies assembled from nanoparticles, nanofibers and have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. The results showed that experimental parameters had great influences on the shape evolution of products. The adjustment of these parameters such as room temperature stirring time, reaction temperature and reaction time of hydrothermal reaction, can lead to obvious morphology changes of products, and the growth mechanism has been proposed. Room-temperature photoluminescence indicated that the as-prepared BaMoO4 nanocrystals had a strong blue emission peak at 481.5 nm. This facile route could be employed to synthesize more promising nanomaterials with interesting self-assembly structures. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Cover Picture: Tuning the Dimensions of C60 -Based Needlelike Crystals in Blended Thin Films (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 6 2006
Mater.
Abstract A new ordered structure of the C60 derivative PCBM is obtained in thin films based on the blend PCBM:P3HT, as detailed by Swinnen, Manca, and co-workers on p.,760. Needlelike crystalline PCBM structures, whose dimensions and spatial distribution ca be tuned by adjusting the blend ratio and annealing conditions, are formed. In typical solar-cell applications of these blended films, these results indicate that during long-term operation under normal conditions (50,70,°C) morphology changes and a decrease in cell performance could occur. A new ordered structure of the C60 derivative PCBM ([6-6]-phenyl C61 -butyric acid methyl ester) is obtained in thin films based on the blend PCBM:regioregular P3HT (poly(3-hexylthiophene)). Rapid formation of needlelike crystalline PCBM structures of a few micrometers up to 100,,m in size is demonstrated by submitting the blended thin films to an appropriate thermal treatment. These structures can grow out to a 2D network of PCBM needles and, in specific cases, to spectacular PCBM fans. Key parameters to tune the dimensions and spatial distribution of the PCBM needles are blend ratio and annealing conditions. The as-obtained blended films and crystals are probed using atomic force microscopy, transmission electron microscopy, selected area electron diffraction, optical microscopy, and confocal fluorescence microscopy. Based on the analytical results, the growth mechanism of the PCBM structures within the film is described in terms of diffusion of PCBM towards the PCBM crystals, leaving highly crystalline P3HT behind in the surrounding matrix. [source]

Imaging and Spectroscopy of Multiwalled Carbon Nanotubes during Oxidation: Defects and Oxygen Bonding (Adv. Mater.

ADVANCED MATERIALS, Issue 19 2009
19/2009)
Photoelectron spectromicroscopy studies revealed the morphology changes and the abundance of various oxygenated functional groups on individual multiwalled carbon nanotubes exposed to oxidizing environments. Alexei Barinov and co-workers show on page 1916 that carbonyl type bonding configurations prevail when fragmentation and extinction of the nanotubes occur. [source]

The Morphology Changes in Limb Leads after Ablation of Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia and Their Correlation with Recurrence

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2008
SHU-YUAN YAO Ph.D
Objectives: This study was designed to explore the morphology changes in limb leads of ECGs after successful ablation of verapamil sensitive idiopathic left ventricular tachycardia (ILVT) and their correlation with tachycardia recurrence. Methods: Between January 2001 and December 2006, 116 patients who underwent successful ablation of ILVT were included in the study. Twelve-lead surface ECG recordings during sinus rhythm were obtained in all patients before and after ablation to compare morphology changes in limb leads. Results: The ECG morphology changes after ablation were divided into two categories: one with new or deepening Q wave in inferior leads and/or disappearance of Q wave in leads I and aVL, and the other without change. The changes in any Lead II, III, or aVF after ablation occurred significantly more in patients without recurrence of ventricular tachycardia (VT) (P < 0.0001, 0.002, and 0.0001, respectively). The patients with recurrence of VT tended to have no ECG changes, compared with those without recurrence of VT (P = 0.009). The sensitivity of leads II, III, and aVF changes in predicting nonrecurrence VT were 66.7%, 78.7%, and 79.6%, specificity were 100%, 75%, and 87.5%, and nonrecurrence predictive value of 100%, 97.7%, and 98.9%, respectively. When inferior leads changes were combined, they could predict all nonrecurrence patients with 100% specificity. Conclusions: Successful radiofrequency ablation of ILVT could result in morphology changes in limb leads of ECG, especially in inferior leads. The combined changes in inferior leads can be used as an effective endpoint in ablation of this ILVT. [source]

Self-assembly and morphology of polydimethylsiloxane supramolecular thermoplastic elastomers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2008
Nicole E. Botterhuis
Abstract Functionalization of polydimethylsiloxanes (PDMS) polymers with hydrogen-bonding ureidopyrimidinone (UPy) groups leads to supramolecular thermoplastic elastomers. In previous studies, no lateral stacking of UPy dimers was observed in UPy-functionalized polymers, unless additional urethane or urea groups were built into the hard block. However, we have shown that when PDMS is used as the soft block, this lateral aggregation of UPy dimers does take place, since long fibers could be observed in the atomic force microscopy (AFM) phase image. Also in bulk, the presence of these interactions was proven by oscillatory shear experiments. We attribute this aggregation to the incompatibility of soft block and hard block, leading to phase separation. Moreover, we have shown that additional urethane or urea groups in the hard block do lead to materials with more fibers and higher melting points. For the UPy-urea functionalized PDMS even single fibers are observed with AFM when dropcasted from a very diluted solution. When the length of the soft block is increased, the morphology changes from fibrous to spherical. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3877,3885, 2008 [source]

The nucleation of HCl and Cl2 -based HVPE GaN on mis-oriented sapphire substrates

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010
Tim Bohnen
Abstract The nucleation of both classic HCl-based and novel Cl based HVPE GaN on mis-oriented sapphire substrates was investigated. The use of Cl2in HVPE increases the growth rate by a factor of 4-5 and strongly reduces the parasitic deposition, allowing for the growth of much thicker wafers than HCl-based HVPE. Morphological SEM surface studies of the HCl-based HVPE sample surface show that at 600 °C a nanocrystalline layer is deposited on the sapphire. During the subsequent annealing phase, the morphology changes to a ,m-sized island structure. During overgrowth at 1080 °C, the islands coalesce. Small voids or pinholes are then formed in between the coalescing GaN islands. These pinholes lead to numerous pits on the surface of the GaN at thicknesses of 5 ,m. The pits disappear during continued overgrowth and can no longer be found on the surface, when the GaN film reaches a thickness of 45 ,m. This particular coalescence mechanism also applies to Cl2 -based HVPE GaN on sapphire (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Gene profiling and pathway analysis of neuroendocrine transdifferentiated prostate cancer cells

THE PROSTATE, Issue 1 2009
Ryutaro Mori
Abstract BACKGROUND Neuroendocrine (NE) cells are present in both normal prostate and prostate cancer. In addition, NE differentiation can be induced by various factors, such as IL-6, in vitro and in vivo. However, the mechanism of this differentiation and the role of NE cells in prostate cancer are not well understood. In this study, we evaluated the gene expression and analyzed the pathways in prostate cancer cells exposed to various NE differentiation inducing factors in vitro. METHODS Gene expression signatures between control LNCaP cells and each treatment induced NE cell line were compared using Affymetrix GeneChip with network and pathway analysis. RESULTS All treatments were able to transdifferentiate LNCaP cells into NE phenotype as shown by morphology changes and NE marker measurements. Of the 54,675 oligonucleotide-based probe sets in microarray, 44,975 were mapped into the Ingenuity Pathway Analysis database and were filtered according to the t -test P value. At P,<,0.002, the number of genes that were differentially expressed included 302 of the IL-6 treated cells, 201 of genistein, 233 of epinephrine, and 191 of the charcoal stripped serum ones. A pooled data approach also showed 346 differentially expressed genes at the same P value. Gene ontology analysis showed that cancer-related function had the highest significance. CONCLUSIONS Despite some overlap, each NE transdifferentiation inducing treatment was associated with a changed expression of a unique set of genes, and such gene profiling may help to elucidate the molecular mechanisms involved in NE transdifferentiation of prostate cancer cells. Prostate 69: 12,23, 2009. © 2008 Wiley,Liss, Inc. [source]

Automated QT Analysis That Learns from Cardiologist Annotations

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2009
Iain Guy David Strachan Ph.D.
Background: Reliable, automated QT analysis would allow the use of all the ECG data recorded during continuous Holter monitoring, rather than just intermittent 10-second ECGs. Methods: BioQT is an automated ECG analysis system based on a Hidden Markov Model, which is trained to segment ECG signals using a database of thousands of annotated waveforms. Each sample of the ECG signal is encoded by its wavelet transform coefficients. BioQT also produces a confidence measure which can be used to identify unreliable segmentations. The automatic generation of templates based on shape descriptors allows an entire 24 hours of QT data to be rapidly reviewed by a human expert, after which the template annotations can automatically be applied to all beats in the recording. Results: The BioQT software has been used to show that drug-related perturbation of the T wave is greater in subjects receiving sotalol than in those receiving moxifloxacin. Chronological dissociation of T-wave morphology changes from the QT prolonging effect of the drug was observed with sotalol. In a definitive QT study, the percentage increase of standard deviation of QTc for the standard manual method with respect to that obtained with BioQT analysis was shown to be 44% and 30% for the placebo and moxifloxacin treatments, respectively. Conclusions: BioQT provides fully automated analysis, with confidence values for self-checking, on very large data sets such as Holter recordings. Automatic templating and expert reannotation of a small number of templates lead to a reduction in the sample size requirements for definitive QT studies. [source]

Membrane Permeabilization of a Mammalian Neuroendocrine Cell Type (PC12) by the Channel-Forming Peptides Zervamicin, Alamethicin, and Gramicidin

CHEMISTRY & BIODIVERSITY, Issue 6 2007

Abstract Zervamicin IIB (ZER) is a 16-mer peptaibol that produces voltage-dependent conductances in artificial membranes, a property considered responsible for its antimicrobial activity to mainly Gram -positive microorganisms. In addition, ZER appears to inhibit the locomotor activity of the mouse (see elsewhere in this Issue), probably by affecting the brain. To examine whether the electrophysiological properties of the neuronal cells of the central neural system might be possibly influenced by the pore forming ZER, the present study was undertaken as a first attempt to unravel the molecular mechanism of this biological activity. To this end, membrane permeabilization of the neuron-like rat pheochromocytoma cell (PC12) by the channel-forming ZER was studied with the whole-cell patch-clamp technique, and compared with the permeabilizations of the well-known voltage-gated peptaibol alamethicin F50/5 (ALA) and the cation channel-forming peptide-antibiotic gramicidin D (GRAM). While 1,,M GRAM addition to PC12 cells kept at a membrane potential Vm=0,mV causes an undelayed gradual increase of a leak conductance with a negative reversal potential of ca. ,24,mV, ZER and ALA are ineffective at that concentration and potential. However, if ZER and ALA are added in 5,10,,M concentrations while Vm is kept at ,60,mV, they cause a sudden and strong permeabilization of the PC12 cell membrane after a delay of 1,2,min, usually leading to disintegrating morphology changes of the patched cell but not of the surrounding cells of the culture at that time scale. The zero reversal potential of the established conductance is consistent with the known aselectivity of the channels formed. This sudden permeabilization does not occur within 10,20,min at Vm=0,mV, in accordance with the known voltage dependency of ZER and ALA channel formation in artificial lipid membranes. The permeabilizing action of these peptaibols on the culture as a whole is further supported by K+ -release measurements from a PC12 suspension with a K+ -selective electrode. Further analysis suggested that the permeabilizing action is associated with extra- or intracellular calcium effects, because barium inhibited the permeabilizing effects of ZER and ALA. We conclude, for the membrane of the mammalian neuron-like PC12 cell, that the permeabilizing effects of the peptides ZER and ALA are different from those of GRAM, consistent with earlier studies of these peptides in other (artificial) membrane systems. They are increased by cis -positive membrane potentials in the physiological range and may include calcium entry into the PC12 cell. [source]