Effect of Ion Irradiation on the Artificial Structure and the Interlayer Coupling of Copper-Cobalt Multilayers

1994 ◽  
Vol 343 ◽  
Author(s):  
J-F. Bobo ◽  
E. Snoeck ◽  
M. Piecuch ◽  
M-J. Casanove
Keyword(s):  
Point Defects ◽  
Giant Magnetoresistance ◽  
Ion Irradiation ◽  
Interlayer Coupling ◽  
Structural Defects ◽  
Cross Sectional ◽  
Saturation Field ◽  
Artificial Structure ◽  
Short Circuits

ABSTRACTStructural defects like local ferromagnetic short-circuits are responsible for large reductions of the intrinsic interlayer coupling in the case of antiferromagnetically (AF) coupled multilayers (ML). We have investigated the role of such point defects in AF-coupled Cu-Co ML’s with tCu=8Å and tCo=12Å which have been irradiated with various doses of 200 keV xenon ions. A significant decrease of the giant magnetoresistance and of the saturation field is observed when the density of defects is increased. These results are compared with a micromagnetic model that takes into account local discontinuities of the AF coupling in an ideally AF-coupled ML. Evidence for the presence of such defects is investigated by TEM on cross-sectional specimens.

Irradiation-Induced Grain Growth: Role of Dislocations

1989 ◽  
Vol 157 ◽  
Author(s):  
Charles W. Allen ◽  
Lynn E. Rehn
Keyword(s):  
Grain Growth ◽  
Point Defects ◽  
Ion Irradiation ◽  
Boundary Migration ◽  
Dislocation Motion ◽  
Boundary Structure ◽  
Thermal Growth ◽  
Growth Phenomenon

ABSTRACTExisting theories of irradiation-induced grain growth assume that growth occurs by the boundary migration mechanism commonly observed for thermal growth and that it is only the point defects generated si boundaries during the irradiation which are responsible for boundary migration. In contrast, in situ observations during ion irradiation of Au films at temperatures less than 20 K even have clearly demonstrated that growth occurs both by boundary migration and by grain coalescence. Here we present further evidence for the latter. Furthermore, the substantial defect cluster activity observed during irradiation suggests that dislocations play a significant role in the growth phenomenon. Here, we also demonstrate qualitatively that glide of such dislocations to or “through” a boundary can produce essentially the same effect on boundary position or structure that the original point defects would have had if they had migrated individually to or through the boundary. Via dislocation motion, point defects originating far from a boundary may induce boundary migration or boundary structure change, and hence, grain growth.

Manifestation of structural defects in photoluminescence from GaN

2003 ◽  
Vol 798 ◽  
Author(s):  
M. A. Reshchikov ◽  
J. Jasinski ◽  
F. Yun ◽  
L. He ◽  
Z. Liliental-Weber ◽  
...  
Keyword(s):  
Point Defects ◽  
Molecular Beam ◽  
Stacking Faults ◽  
Structural Defects ◽  
Large Set ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
X Ray ◽  
Transmission Electron ◽  
Gan Crystal

ABSTRACTSharp peaks of unidentified nature are detected in the low-temperature photoluminescence (PL) spectrum of undoped GaN in the photon energy range between 3.0 and 3.46 eV. These PL lines are commonly attributed to excitons bound to yet unidentified structural defects. We analyzed X-ray diffraction data in a large set of GaN samples grown by molecular beam epitaxy in order to find any correlation between these unusual PL peaks and the GaN crystal structure. Moreover, in selected samples exhibiting such peaks, cross-sectional transmission electron microscopy was taken in an effort to detect the presence and density of various structural defects. The preliminarily results indicate that most of unusual PL lines in GaN (Y lines) are not directly related to the observed structural defects, such as edge, screw, mixed dislocations, or stacking faults. However, there exists the possibility that point defects trapped at dislocations or other structural defects are responsible for these PL lines.

Development of SEM Metallography for the Study of the Mg-MgH2 Phase Transformation

2007 ◽  
Vol 1042 ◽  
Author(s):  
Marco Vittori Antisari ◽  
Amelia Montone ◽  
Nadica Abazovic ◽  
Annalisa Aurora ◽  
Milica Drvendzija ◽  
...  
Keyword(s):  
Structural Defects ◽  
Cross Sectional ◽  
Metallographic Examination ◽  
Safe Technology ◽  
Additive Particles ◽  
Kinetic Mechanisms ◽  
The Subject ◽  
Observation Method ◽  
Sectional Analysis

AbstractThe study of sorption reactions of metal hydrides is the subject of numerous researches in connection with the development of a safe technology for hydrogen storage, and MgH2, in particular, is one of the most promising materials. Several efforts have been already carried out in order to understand the kinetic mechanisms involved in the MgH2 decomposition which is at the basis of H2 release. However, the role of additives and induced structural defects on the sorption cycles is not clear yet. With the purpose of supporting the reaction analysis we have developed an experimental protocol for the metallographic examination at high spatial resolution of partially desorbed MgH2 powders. In particular, this procedure allows cross-sectional analysis of powders embedded into conductive matrix, while the observation method produces a different contrast among metallic Mg, MgH2 and additive particles made of heavier materials.

Solid-Phase Epitaxy - Role of Point Defects in Amorphous Solids

1993 ◽  
Vol 319 ◽  
Author(s):  
T.K. Chaki
Keyword(s):  
Epitaxial Growth ◽  
Point Defects ◽  
Solid Phase ◽  
Ion Irradiation ◽  
Amorphous Solid ◽  
Amorphous Layer ◽  
Amorphous Solids ◽  
Solid Phase Epitaxy ◽  
Self Diffusion

AbstractA model of solid-phase epitaxial growth (SPEG), explaining enhancing effects of ion-irradiation and dopants, is presented. The crystallization is by the adjustment of atomic positions in the amorphous side of the crystalline/amorphous (c-a) interface due to self-diffusion in the amorphous solid, assisted by a freeenergy decrease associated with the transformation from the amorphous (a) to crystalline (c) phase. Irradiation and electrically active dopants increase the selfdiffusivity of a-phase by generating point defects in the amorphous layer and thus enhance crystallization. An expression for the velocity of epitaxial growth is derived. The low activation energy of ion-induced SPEG is due to recombination of point defects in the a-phase.

Structural relationships in the synthesis of cubic boron nitride thin films by ion-assisted deposition

1994 ◽  
Vol 52 ◽  
pp. 638-639
Author(s):  
D. L. Medlin ◽  
T. A. Friedmann ◽  
P. B. Mirkarimi ◽  
M. J. Mills ◽  
K. F. McCarty
Keyword(s):  
Boron Nitride ◽  
Ion Irradiation ◽  
Cubic Boron Nitride ◽  
Film Stress ◽  
Bonded Phases ◽  
Structural Relationships ◽  
Precursor Material ◽  
Pressure Synthesis ◽  
Microstructure Of The Material

The allotropes of boron nitride include two sp2-bonded phases with hexagonal and rhombohedral structures (hBN and rBN) and two sp3-bonded phases with cubic (zincblende) and hexagonal (wurtzitic) structures (cBN and wBN) (Fig. 1). Although cBN is synthesized in bulk form by conversion of hBN at high temperatures and pressures, low-pressure synthesis of cBN as a thin film is more difficult and succeeds only when the growing film is simultaneously irradiated with a high flux of ions. Only sp2-bonded material, which generally has a disordered, turbostratic microstructure (tBN), will form in the absence of ion-irradiation. The mechanistic role of the irradiation is not well understood, but recent work suggests that ion-induced compressive film stress may induce the transformation to cBN.Typically, BN films are deposited at temperatures less than 1000°C, a regime for which the structure of the sp2-bonded precursor material dictates the phase and microstructure of the material that forms from conventional (bulk) high pressure treatment.

Psychological Resilience Provides No Independent Protection From Suicidal Risk

Crisis ◽  
2016 ◽  
Vol 37 (2) ◽  
pp. 130-139 ◽  
Author(s):  
Danica W. Y. Liu ◽  
A. Kate Fairweather-Schmidt ◽  
Richard Burns ◽  
Rachel M. Roberts ◽  
Kaarin J. Anstey
Keyword(s):  
Risk Factors ◽  
Well Being ◽  
Current Status ◽  
Psychological Resilience ◽  
Cross Sectional ◽  
Life Project ◽  
Resilience Factors ◽  
First Time

Abstract. Background: Little is known about the role of resilience in the likelihood of suicidal ideation (SI) over time. Aims: We examined the association between resilience and SI in a young-adult cohort over 4 years. Our objectives were to determine whether resilience was associated with SI at follow-up or, conversely, whether SI was associated with lowered resilience at follow-up. Method: Participants were selected from the Personality and Total Health (PATH) Through Life Project from Canberra and Queanbeyan, Australia, aged 28–32 years at the first time point and 32–36 at the second. Multinomial, linear, and binary regression analyses explored the association between resilience and SI over two time points. Models were adjusted for suicidality risk factors. Results: While unadjusted analyses identified associations between resilience and SI, these effects were fully explained by the inclusion of other suicidality risk factors. Conclusion: Despite strong cross-sectional associations, resilience and SI appear to be unrelated in a longitudinal context, once risk/resilience factors are controlled for. As independent indicators of psychological well-being, suicidality and resilience are essential if current status is to be captured. However, the addition of other factors (e.g., support, mastery) makes this association tenuous. Consequently, resilience per se may not be protective of SI.

Testing the Strain Theory of Suicide – The Moderating Role of Social Support

Crisis ◽  
2020 ◽  
Vol 41 (2) ◽  
pp. 82-88 ◽  
Author(s):  
Bob Lew ◽  
Ksenia Chistopolskaya ◽  
Yanzheng Liu ◽  
Mansor Abu Talib ◽  
Olga Mitina ◽  
...  
Keyword(s):  
Social Support ◽  
Suicidal Behavior ◽  
Online Survey ◽  
Perceived Social Support ◽  
Strain Theory ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Psychological Strains ◽  
Moderating Role

Abstract. Background: According to the strain theory of suicide, strains, resulting from conflicting and competing pressures in an individual's life, are hypothesized to precede suicide. But social support is an important factor that can mitigate strains and lessen their input in suicidal behavior. Aims: This study was designed to assess the moderating role of social support in the relation between strain and suicidality. Methods: A sample of 1,051 employees were recruited in Beijing, the capital of China, through an online survey. Moderation analysis was performed using SPSS PROCESS Macro. Social support was measured with the Multidimensional Scale of Perceived Social Support, and strains were assessed with the Psychological Strains Scale. Results: Psychological strains are a good predictor of suicidality, and social support, a basic need for each human being, moderates and decreases the effects of psychological strains on suicidality. Limitations: The cross-sectional survey limited the extent to which conclusions about causal relationships can be drawn. Furthermore, the results may not be generalized to the whole of China because of its diversity. Conclusion: Social support has a tendency to mitigate the effects of psychological strains on suicidality.

Role of Sildenafil in the Treatment of Persistent Pulmonary Hypertension of Newborn (PPHN) - Should it Be Withdrawn from Market of Bangladesh due to Threat of being Misuses

2020 ◽  
Vol 35 (2) ◽  
pp. 100-104
Author(s):  
Maksudur Rahman ◽  
Mohammad Abdullah Al Mamun ◽  
MAK Azad Chowdhury ◽  
Abu Sayeed Munsi
Keyword(s):  
Intensive Care Unit ◽  
Intensive Care ◽  
Neonatal Intensive Care ◽  
Cross Sectional Study ◽  
Sectional Study ◽  
Cardiac Intensive Care Unit ◽  
Cross Sectional ◽  
Cardiac Intensive Care ◽  
Hospital Protocol

Background: Recently it has been apprehended that sildenafil, a drug which has been successfully using in the treatment of PPHN and erectile dysfunction in adult, is going to be withdrawn from the market of Bangladesh due to threat of its misuses. Objective: The aim of this study was to see the extent of uses of sildenafil in the treatment of PPHN and importance of availability of this drugs in the market inspite of its probable misuses. Methods: This cross sectional study was conducted in neonatal intensive care unit (NICU), special baby care unit (SCABU) and cardiac intensive care unit (CICU) of Dhaka Shishu (Children) Hospital from June, 2017 to May 2018. Neonates with PPHN were enrolled in the study. All cases were treated with oral sildenefil for PPHN along with others management according to hospital protocol. Data along with other parameters were collected and analyzed. Results: Total 320 patients with suspected PPHN were admitted during the study period. Among them 92 (29%) cases had PPHN. Male were 49(53 %) cases and female were 43(47%) cases. Mean age at hospital admission was 29.7±13.4 hours. Based on echocardiography,13(14%) cases had mild, 38 (41%) cases moderate and 41(45%) cases severe PPHN. Mean duration of sildenafil therapy was 11.9±7.1 days. Improved from PPHN were 83 (90%) cases. Mortality was 10% (9). Conclusion: In this study it was found that the incidence of PPHN is 29% among the suspected newborns. Sildenafil is successfull in improving the oxygenation of PPHN and to decrease the mortality of neonates. DS (Child) H J 2019; 35(2) : 100-104

Role of Fibrinolytic Therapy in Empyema Thoracis – A Hospital Based one year Cross Sectional Study

2012 ◽  
Vol 2 (2) ◽  
pp. 345-350
Author(s):  
Dr. Girish.L Dandagi ◽  
◽  
Venkat kalyana kumar. P ◽  
Dr. Dr.Isaac Mathew ◽  
Dr. Dr.G S Gaude Dr. Dr.G S Gaude
Keyword(s):  
Cross Sectional Study ◽  
Fibrinolytic Therapy ◽  
Empyema Thoracis ◽  
Sectional Study ◽  
Cross Sectional ◽  
One Year
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