A Multi-Plane Model for Defect Nucleation at Cracks

1993 ◽  
Vol 319 ◽  
Author(s):  
G. E. Beltz ◽  
S. Schmauder
Keyword(s):  
Dislocation Nucleation ◽  
Moderate Increase ◽  
Crack Plane ◽  
Plane Model ◽  
Dislocation Generation ◽  
Slip Planes ◽  
Primary Dislocation ◽  
Defect Nucleation ◽  
Crack Tip Blunting

AbstractA mathematical model (2D) of dislocation generation at cracks on interfaces is presented, which takes into account the role of slip processes on several slip planes in the vicinity of a crack. The work investigates the effects of other incipient dislocations on the nucleation and emission of the primary dislocation that emits first and is responsible for crack-tip blunting on atomic length scales. The modeling makes use of the recently-developed Peierls-Nabarro framework for dislocation nucleation. It is found that there is a moderate increase in the critical load necessary to emit a dislocation, when incipient slip activity is allowed to occur on the prolongation of the crack plane. Furthermore, the slip at the tip, the quantity which characterizes to what extent an incipient dislocation forms before it emits, decreases when the dual slip-plane model is used. Implications for the ductile versus brittle response of Ni are discussed.

Atomistic Study of Cleavage and Dislocation Emission in NiAl

1994 ◽  
Vol 364 ◽  
Author(s):  
M. Ludwig ◽  
P. Gumbsch
Keyword(s):  
Finite Element ◽  
Mixed Mode ◽  
Crack Tip ◽  
Mode I ◽  
Crack Plane ◽  
Dislocation Emission ◽  
Dislocation Generation ◽  
Embedded Atom ◽  
Atomistic Study ◽  
Eam Potential

AbstractThe atomistic processes during fracture of NiAl are studied using a new embedded atom (EAM) potential to describe the region near the crack tip. To provide the atomistically modeled crack tip region with realistic boundary conditions, a coupled finite element - atomistic (FEAt) technique [1] is employed. In agreement with experimental observations, perfectly brittle cleavage is observed for the (110) crack plane. In contrast, cracks on the (100) plane either follow a zig-zag path on (110) planes, or emit dislocations. Dislocation generation is studied in more detail under mixed mode I/II loading conditions.

Cloning and expression of two plasma membrane aquaporins expressed during the ripening of grape berry

2003 ◽  
Vol 30 (6) ◽  
pp. 621 ◽  
Author(s):  
Sarah Picaud ◽  
Frédéric Becq ◽  
Fabienne Dédaldéchamp ◽  
Agnès Ageorges ◽  
Serge Delrot
Keyword(s):  
Plasma Membrane ◽  
Xenopus Oocytes ◽  
Potential Role ◽  
Grape Berry ◽  
Cloning And Expression ◽  
Vitis Vinifera L ◽  
Moderate Increase ◽  
Grape Berries ◽  
Urea Uptake

The ripening of grape (Vitis vinifera L.) berry is accompanied by dramatic accumulation of sugars and water. Two full-length clones and several partial clones encoding plasma membrane aquaporins (PIP) were cloned from grape berries collected at the beginning of ripening. Based on their sequences, on a phylogenetic analysis and on functional properties, both clones, called VvPIP1a and VvPIP1b were assigned to the PIP1 subfamily. RNA gel blot studies with berries at various stages of development indicated that VvPIP expression was highest at stages following veraison. Injection of Xenopus oocytes with VvPIP1a cRNA induced a moderate increase of water permeability and a large increase in glycerol permeability, whereas injection with VvPIP1b cRNA did not affect these permeabilities. Injection of VvPIP1a cRNA, but not VvPIP1b cRNA, inhibited urea uptake by the oocyte, and this inhibition was sensitive to HgCl2. The data are discussed in relation with the potential role of aquaporins in fruit physiology.

scholarly journals Functional Cooperation of the Proapoptotic Bcl2 Family Proteins Bmf and Bim In Vivo

2009 ◽  
Vol 30 (1) ◽  
pp. 98-105 ◽  
Author(s):  
Anette Hübner ◽  
Julie Cavanagh-Kyros ◽  
Mercedes Rincon ◽  
Richard A. Flavell ◽  
Roger J. Davis
Keyword(s):  
Moderate Increase ◽  
Related Gene ◽  
Normal Lymphocyte ◽  
Bcl2 Family ◽  
Lymphocyte Homeostasis ◽  
Cooperative Activity ◽  
Redundant Functions ◽  
Interdigital Webbing

ABSTRACT Bcl2-modifying factor (Bmf) is a member of the BH3-only group of proapoptotic proteins. To test the role of Bmf in vivo, we constructed mice with a series of mutated Bmf alleles that disrupt Bmf expression, prevent Bmf phosphorylation by the c-Jun NH2-terminal kinase (JNK) on Ser74, or mimic Bmf phosphorylation on Ser74. We report that the loss of Bmf causes defects in uterovaginal development, including an imperforate vagina and hydrometrocolpos. We also show that the phosphorylation of Bmf on Ser74 can contribute to a moderate increase in levels of Bmf activity. Studies of compound mutants with the related gene Bim demonstrated that Bim and Bmf exhibit partially redundant functions in vivo. Thus, developmental ablation of interdigital webbing on mouse paws and normal lymphocyte homeostasis require the cooperative activity of Bim and Bmf.

Role of the adrenal gland in the thermal response to morphine withdrawal in rats

1992 ◽  
Vol 70 (8) ◽  
pp. 1090-1095 ◽  
Author(s):  
Michael J. Katovich ◽  
David Pitman ◽  
Orit Schechtman
Keyword(s):  
Adrenal Gland ◽  
Skin Temperature ◽  
Core Temperature ◽  
Temperature Response ◽  
Thermal Response ◽  
Morphine Withdrawal ◽  
Ovariectomized Rats ◽  
Moderate Increase ◽  
Adrenalectomized Rats

Administration of naloxone to morphine-dependent rats results in an elevation of tail skin temperature and a fall in core temperature. Previous studies have demonstrated a role of the adrenal gland in the thermal responses that accompany morphine withdrawal in the rat. In the present study, experiments were designed to determine if the duration of adrenalectomy significantly influenced the thermal response observed in morphine withdrawal. In addition we evaluated the influence of the adrenal medulla and glucocorticoid replacement in adrenalectomized rats in mediating the thermal responses of the morphine-dependent rat. Ovariectomized rats were addicted to morphine and subsequently withdrawn by administration of naloxone. This treatment results in a significant rise in tail skin temperature and subsequent fall in colonic temperature. These thermal responses were not observed in morphine-naive rats. Adrenalectomy resulted in a significant attenuation of the rise in tail skin temperature associated with withdrawal. This reduced tail skin temperature response was not different among animals adrenalectomized for 1, 7, 14, 21, or 28 days. Likewise, the moderate increase in core temperature associated with morphine treatment was not observed in the adrenalectomized rats. Serum corticosteroid determinations confirmed the loss of the adrenal steroids in the adrenalectomized rats. In a subsequent experiment it was determined that adrenal demedullation did not reduce the tail skin temperature response during morphine withdrawal, and corticosteroids restored the naloxone-induced surge in tail skin temperature in morphine-dependent, adrenalectomized rats. Collectively, these data suggest a role for the adrenal gland, especially the cortical region, in allowing for full expression of the skin temperature changes associated with withdrawal in morphine-dependent animals.Key words: corticosterone, tail skin temperature, morphine withdrawal, adrenal gland, thermal response, naloxone.

Analysis of Probable Relationships Between Leaf-Potassium Percentage and Sucrose Content and Maturity of Sugarcane

1969 ◽  
Vol 46 (1) ◽  
pp. 15-22
Author(s):  
Gilberto Acevedo-Ramos
Keyword(s):  
Comparative Study ◽  
Marked Decrease ◽  
Growth Cycle ◽  
Potassium Content ◽  
Moderate Increase ◽  
Sucrose Content ◽  
Sugarcane Plant ◽  
Sugarcane Varieties

Data are presented on the potassium content of sugarcane leaves at specific ages from experiments performed under greenhouse conditions. A comparative study was conducted on the role of potassium in the sugarcane varieties M. 336 and P.R. 980 in an attempt to explain some relationships that probably exist throughout the physiological growth of the sugarcane plant. The results obtained indicate that there is first a marked decrease and later on a moderate increase in potassium content of the sugarcane leaves during its growth cycle. These data indicate that this fact may be related to sugarcane maturity. However, other facts are evaluated and discussed which can also explain such increases.

Rapid Thermal Processing of Buried Sil−xGex Strained Layers; Photoluminescence Decay and Misfit Dislocation Generation.

1990 ◽  
Vol 198 ◽  
Author(s):  
D.C. Houghton ◽  
N.L. Rowell
Keyword(s):  
Quantum Wells ◽  
Misfit Dislocation ◽  
Thermal Processing ◽  
Internal Quantum Efficiency ◽  
Dislocation Nucleation ◽  
Multiple Quantum ◽  
Misfit Dislocations ◽  
Dislocation Generation ◽  
Strained Layers ◽  
Wide Range

ABSTRACTThe thermal constraints for device processing imposed by strain relaxation have been determined for a wide range of Si-Ge strained heterostructures. Misfit dislocation densities and glide velocities in uncapped Sil-xGex alloy layers, Sil-xGex single and multiple quantum wells have been measured using defect etching and TEM for a range of anneal temperatures (450°C-1000°C) and anneal times (5s-2000s). The decay of an intense photoluminescence peak (∼ 10% internal quantum efficiency ) from buried Si1-xGex strained layers has been correlated with the generation of misfit dislocations in adjacent Sil-xGex /Si interfaces. The misfit dislocation nucleation rate and glide velocity for all geometries and alloy compositions (0<x<0.25) were found to be thermally activated processes with activation energies of (2.5±0.2)eV and (2.3-0.65x)eV, respectively. The time-temperature regime available for thermal processing is mapped out as a function of dislocation density using a new kinetic model.

The gaseous oxidation of aliphatic alcohols. I. Ethyl alcohol: the products formed in the early stages

1956 ◽  
Vol 237 (1211) ◽  
pp. 530-542 ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Induction Period ◽  
Ethyl Alcohol ◽  
Critical Concentration ◽  
Volume Ratio ◽  
Analytical Investigation ◽  
Moderate Increase ◽  
Early Stages ◽  
Low Pressures

A detailed analytical investigation has been made of the reactions occurring during the early stages of the oxidation of ethyl alcohol (ethanol) in the temperature region 270 to 370° C. During an induction period the alcohol is converted quantitatively into acetaldehyde until a critical concentration of this intermediate has accumulated. The pressure then begins to rise autocatalytically, and methanol, formaldehyde and carbon monoxide become detectable; evidence is presented to show that these compounds arise from the further oxidation of acetaldehyde. The amount of ethanol consumed and of acetaldehyde formed at the end of the induction period are largely independent of the initial reactant pressures, except at low pressures of the alcohol. A study of the effect of added acetaldehyde shows that the minimum quantity required to eliminate the induction period is the same as that normally present at the end of the induction period. Hydrogen peroxide is the only product, other than acetaldehyde, detected during the induction period. Under optimum surface conditions the yields of hydrogen peroxide are equivalent to those of the aldehyde. A moderate increase in surface shortens the induction period, but a further increase retards reaction. In vessels of large surface: volume ratio, the yields of hydrogen peroxide are much reduced, while in a potassium chloride-coated vessel peroxides are invariably absent; in each case, the other products are unchanged. The mechanisms of the chain-initiating and propagating reactions are considered and the role of the surface in initiating and terminating chains is discussed.

Effect of a Surface Constraining Layer on the Plastic Deformation of Au Microspheres

MRS Advances ◽  
2018 ◽  
Vol 3 (8-9) ◽  
pp. 427-432
Author(s):  
AZM Ariful Islam ◽  
Robert J. Klassen
Keyword(s):  
Plastic Deformation ◽  
Small Volume ◽  
Dislocation Nucleation ◽  
Surface Layers ◽  
Loading Rates ◽  
Plastic Deformation Process ◽  
Sputter Deposited ◽  
Yield Force ◽  
Mechanisms Of Plastic Deformation

ABSTRACTSingle crystal Au microspheres, of 3 μm diameter, with sputter-deposited Ni surface layers, of 40 or 80 nm thickness, were tested in compression at three loading rates to investigate the role of thin passive layers on the mechanisms of plastic deformation of small-volume FCC ductile metal samples. The Ni layer resulted in an increase in the incipient yield force by about 10%. Micro-cracking of the Ni layer was observed to occur with incipient yielding. The estimated apparent activation volume of the incipient plastic deformation process was found to be nearly identical for the Ni-coated and the uncoated Au microspheres. This suggests that, while the stress required to initiate incipient plastic deformation was increased by the constraint imposed by the Ni layer, the subsequent plastic flow occurred by a dislocation nucleation and glide mechanism that is essentially the same as that occurring in an unconstrained Au microsphere.

scholarly journals Role of NADPH Phagocyte Oxidase in Host Defense against Acute Respiratory Acinetobacter baumannii Infection in Mice

2008 ◽  
Vol 77 (3) ◽  
pp. 1015-1021 ◽  
Author(s):  
Hongyu Qiu ◽  
Rhonda KuoLee ◽  
Greg Harris ◽  
Wangxue Chen
Keyword(s):  
Acinetobacter Baumannii ◽  
Host Defense ◽  
Multiple Drug Resistance ◽  
Bacterial Pathogen ◽  
Inflammatory Cells ◽  
Multiple Drug ◽  
Moderate Increase ◽  
Phagocyte Oxidase ◽  
Bacterial Replication

ABSTRACT Acinetobacter baumannii is an emerging bacterial pathogen that rapidly develops multiple-drug resistance and is responsible for many nosocomial pulmonary infections. This study investigated the role of the NADPH phagocyte oxidase (phox) and inducible nitric oxide synthase (NOS2) in the host defense against respiratory infection with A. baumannii in mouse models of intranasal A. baumannii infection. gp91phox−/− mice showed higher susceptibility to A. baumannii infection than wild-type (WT) C57BL/6 mice, with significantly greater bacterial counts in their lungs (1,000-fold) (P < 0.005) and spleens (10-fold) (P < 0.05). Moreover, all of the gp91phox−/− mice succumbed to infection within 48 h. In contrast, only a moderate increase in bacterial burdens was detected in the lungs of NOS2−/− mice, and all NOS2−/− mice survived infection. Compared to WT mice, the pulmonary influx of inflammatory cells and serum and local inflammatory cytokine/chemokine responses were not obviously impaired at 4 h and were significantly higher at 24 h (P < 0.05) in gp91phox−/− mice, but NADPH-deficient neutrophils were unable to control bacterial replication and extrapulmonary dissemination. Thus, NADPH phagocyte oxidase appears to play a crucial role in the neutrophil-mediated host defense against A. baumannii.

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