Structural and electronic properties of Y1-xGexTe (Y=Sn,Pb) by DFT

The structural, electronic, and chemical bonding properties of the Ge doped PbTe and SnTe in the rock salt phase have been calculated by full potential linearized augmented plane wave method within density functional theory. Generalized gradient approximation of Wu and Cohen has been utilized for calculating these properties. With doping of Ge in Pb1–xGexTe and Sn1–xGexTe, the lattice constant reduces linearly as the concentration increases. Also, it is observed that electronic properties of these compounds are affected by varying concentration of doping Ge. The band gap of corresponding compounds varies with respect to the composition, so the electronic properties alter as doping increases. The alloys have direct band gap which varies in the range 0 to 0.19 eV. The alloys Pb1–xGexTe and Sn1–xSnxTe show covalent bonding nature which enhances by increasing the Ge concentration. As the physical properties vary widely with doping therefore the resulted materials can be used in thermoelectric, optical storage devices, Infrared detectors, Bragg’s reflectors and optical devices working in lower frequency regime

A Characterization of the Two-weight Inequality for Riesz Potentials on Cones of Radially Decreasing Functions

We establish necessary and sufficient conditions on a weight pair $(v,w)$ governing the boundedness of the Riesz potential operator $I_{\alpha}$ defined on a homogeneous group $G$ from $L^p_{dec,r}(w, G)$ to $L^q(v, G)$, where $L^p_{dec,r}(w, G)$ is the Lebesgue space defined for non-negative radially decreasing functions on $G$. The same problem is also studied for the potential operator with product kernels $I_{\alpha_1, \alpha_2}$ defined on a product of two homogeneous groups $G_1\times G_2$. In the latter case weights, in general, are not of product type. The derived results are new even for Euclidean spaces

Layer-By-Layer Microcapsules for the Delivery of Lipophilic Drugs

About 40% of new compounds have low water solubility, however they are therapeutically active. For such drugs, different methods of formulation development should be proposed. Layer by layer assembly has recently been studied to solve this problem in which lipophilic drugs have been encapsulated. In this layer by layer process, adsorption of different components is done which is facilitated by the electrostatic attraction resulting in the formation of multilayer shells of nanometer size. These drug delivery systems include nano- and micro-particles and emulsions. In this review article, the formulation methodology, advantages, and uses of layer-by-layer assembly approach have been discussed. Keywords: Lipophillic drugs, Layer-by-layer microcapsules, Drug deliver

CONFLICT BETWEEN EURO-AMERICAN AND NATIVE AMERICAN ATTITUDES TOWARDS NATURE: AN ECOCRITICAL STUDY OF TRACKS AND LOVE MEDICINE BY LOUISE ERDRICH

Euro-American and Native American approaches to Nature are conflicting: the former consists in competition with Nature whereas the latter is characterized by harmony with it. Unlike the Whites, the Natives realize their dreams of culture and society in Nature, not against it. Contrarily, the whites realize themselves in controlling Nature which is only euphemism for destroying it. Nature in the Euro-American literature finds its place only as a background, rather than the central feature as the canonical American works bear witness. Even Wordsworth, the representative white poet of Nature, only utilizes Nature for his pantheistic ideas; Nature in itself does not carry significant position in his works. In Hemingway, Nature is predominant but only as a facilitator for the realization of sublime self of the code hero. So it is in Eugene O’Neill and Emerson and Whitman. But, for Native Americans Nature is an animate being, as living as they themselves are and sometimes it becomes even more significant when it gets religious sanctity. Bear, eagle and its feathers, the sun, and even water are a source of life to be depended and worshipped and requested to in all moments of crises and celebration. This article explores the shift of attitude towards Nature which actually reflects shift in man’s position in the universe

Impact of Crew Training and Safety Management System on Operational Management in Aviation Industry of Pakistan

Aviation plays a fundamental role in the growth of trade, tourism, economy as well as sustainable development in Pakistan. The two main influential factors Crew Training and Safety Management impacting operations of Engineering Management was found on the basis of literature and analyzed. Primarily, the numerous organizations training methodologies to get their crew staff training was collected from both primary sources that’s questionnaire instrument and secondary sources which is Literature. The reliability and validity of the instrument was tested with the help of Cronbach Alpha and the survey questionnaire was distributed to obtain primary data. The used Non-Probability Sampling technique analyzed thru Statistical Package for Social Sciences software. It was revealed that both the variables i-e Crew Training and Safety Management have a significant impact on improving aviation operational management. Therefore, the management should take remedial measures to work out on Crew Training and Safety Management factors that may augment aviation operational management according to latest National Aviation Policy 2019

Economic Institutions and Growth Nexus: The Role of Governance and Democratic Institutions—Evidence from Time Varying Parameters’ (TVPs) Models

The present study has investigated the channels through which the linkage between economic institutions and growth is gauged, by addressing the main hypothesis of the study that whether quality of governance and democratic institutions set a stage for economic institutions to promote the long-term growth process in Pakistan. To test the hypothesis empirically, our study models the dynamic relationship between growth and economic institutions in a time varying framework in order to capture institutional developments and structural changes occurred in the economy of Pakistan over the years. Study articulates that, along with some customary specifics, the quality of government and democracy are the substantial factors that affect institutional quality and ultimately cause to promote growth in Pakistan. JEL Classification: O40; P16; C14; H10 Keywords: Economic Institutions, Growth, Governance and Democracy, Rolling Window Two-stage Least Squares, Pakista

Corrosion fatigue short crack growth behaviour in a high strength steel

A frequent cause of the premature failure of structural components is Corrosion Fatigue Cracking. Historically corrosion fatigue studies have shown that this failure process depends strongly on the interactions between loading mode, metallurgical texture and electrochemical parameters. This has become a serious problem for concerns such as the nuclear, automobile, oil, gas, aerospace and marine industries. This research study was carried out using a quenched and tempered silico-manganese spring steel (DS 250A53). Smooth hour-glass shaped fatigue specimens were tested under fully reversed torsional loading in both laboratory air and aerated O.6M NaCI solution environments. Crack growth behaviour in both air and corrosion fatigue tests was monitored using a plastic replication technique. Intermittent air fatigue/corrosion fatigue tests were also conducted at sub-fatigue limit stress levels in an attempt to determine an environment-assisted critical (thresh-old) crack length necessary to cause subsequent air fatigue failure and therefore elucidate the mechanisms operative during the first stages of crack development and growth. To assist in this electrochemical experiments were performed to determine the corrosion characteristics for this metal-environment system. In air fatigue tests cracks initiated at non-metallic inclusions due to a strain incompatibility between the inclusion and the matrix. Air fatigue modelling was based on the observation that crack growth rate decreases as cracks approach microstructural barriers. In the present study it is suggested that the 4th prior austenite grain boundary was the major barrier to a growing crack. This regime of crack growth is described as the 8hort crack regime and may be represented by the following equation; After overcoming the major microstructural barrier crack growth rate increases with an increase in its length. This regime of crack growth is represented by long crack regime and may be quantified by the expression; (da/dN)la=Claa - Dt Corrosion fatigue crack initiation was associated with chemical pitting of these inclusions. Failure at stresses close to the 'in-air' fatigue limit was due to the coalescence of a small number of cracks. While at low stresses growth of individual cracks led to failure. Corrosion fatigue crack growth modelling suggested that a chemical driving force arising from chemical reactions was present in addition to the mechanical driving force of the applied stress. The presence of this additional force enabled a crack to continue its propagation at low stresses which would otherwise arrest under air fatigue conditions. Corrosion fatigue crack growth rate was calculated using the following superposition model. (da/dN)cf = (da/dN)a + (da/dN)e where (da/dN)a and (da/dN)e represent air fatigue crack growth rate and environmental crack growth rate respectively