RESUMO
The polycrystalline samples of Mn1.90Cr0.10O3(MCO) and Mn1.90Fe0.10O3(MFO) have been investigated for their temperature dependent magnetic and structural properties. The Cr and Fe substitutions have significant effect on the magnetic and structural properties of Mn2O3. Like pristine Mn2O3, the Cr and Fe substituted samples MCO and MFO also exhibit two antiferromagnetic transitions; one at â¼77 K, â¼80 K, respectively and another at â¼40 K. Our room temperature synchrotron x-ray powder diffraction (SXRD) results confirm that both the MCO and MFO samples crystallize in cubic symmetry. The temperature dependent SXRD results demonstrate the cubic to orthorhombic structural transition for the studied samples. The pristine Mn2O3shows cubic to orthorhombic transition around 310 K, whereas this structural transition shifted towards lower temperature side with these substitutions i.e. around 240 K for MCO and 260 K for MFO. Interestingly, the centrosymmetricPcabto non-centrosymmetricPca21change in symmetry is also resolved at the ferroelectric ordering temperature for MCO.
RESUMO
The combined effect of grain size variation and plastic deformation on the acoustic nonlinearity parameter has been investigated in an austenitic stainless-steel material of grade 304. The nonlinear behavior of this parameter with grain growth has deviated to linear fit with deformation. This is due to the interaction of elastic waves with the strain-induced dislocation substructure in the grains. The normalized mean square strain of the deformed specimens has been estimated through angle dispersive x-ray diffraction studies using a synchrotron source, and this has been correlated with the change in the acoustic non-linearity parameter with deformation. The nonlinearity parameter is found to be very sensitive to the plastic deformation even in the presence of grain size variations. The results infer that the variations in the nonlinearity parameter can be used to have an estimate of the extent of localized deformations often occurring during the fabrication of metallic components.
RESUMO
BACKGROUND: The purpose of this review is to systematically appraise the peer-reviewed literature about the genetic and environmental determinants of psychiatric comorbidity, focusing on four of the most prevalent types of psychopathology: anxiety disorders, depression, conduct disorder and substance abuse. METHODS: We summarize existing empirical research on the relative contribution that genetic, nonshared and shared environmental factors make to the covariance between disorders, and evidence about specific genes and environmental characteristics that are associated with comorbidity. RESULTS: Ninety-four articles met the inclusion criteria and were assessed. Genetic factors play a particularly strong role in comorbidity between major depression and generalized anxiety disorder or posttraumatic stress disorder, while the non-shared environments make an important contribution to comorbidity in affective disorders. Genetic and non-shared environmental factors also make a moderate-to-strong contribution to the relationship between CD and SA. A range of candidate genes, such as 5HTTLPR, MAOA, and DRD1-DRD4, as well as others implicated in the central nervous system, has been implicated in psychiatric comorbidity. Pivotal social factors include childhood adversity/life events, family and peer social connections, and socioeconomic and academic difficulties. LIMITATIONS: Methodological concerns include the use of clinical case-control samples, the focus on a restricted set of individual-level environmental risk factors, and restricted follow-up times. CONCLUSIONS: Given the significant mental health burden associated with comorbid disorders, population-based research on modifiable risk factors for psychiatric comorbidity is vital for the design of effective preventive and clinical interventions.
