Giant magnetothermal conductivity and magnetostriction effect in charge ordered Nd0.8_{0.8}Na0.2_{0.2}MnO3_{3} compound

We present results on resistivity ($\rho$), magnetization ($M$), thermal conductivity ($\kappa$), magnetostriction ($\frac{\Delta L}{L(0)}$) and specific heat ($C_{p}$) of charge-orbital ordered antiferromagnetic Nd$_{0.8}$Na$_{0.2}$MnO$_{3}$ compound. Magnetic field-induced antiferromagnetic/charge-orbital ordered insulating to ferromagnetic metallic transition leads to giant magnetothermal conductivity and magnetostriction effect. The low-temperature irreversibility behavior in $\rho$, $M$, $\kappa$ and $\frac{\Delta L}{L(0)}$ due to field cycling together with striking similarity among the field and temperature dependence of these parameters manifest the presence of strong and complex spin-charge-lattice coupling in this compound. The giant magnetothermal conductivity is attributed mainly to the suppression of phonon scattering due to the destabilization of spin fluctuations and static/dynamic Jahn-Teller distortion by the application of magnetic field.Comment: 4 Pages, 4 Figure

Airglow emissions : fundamentals of theory and experiment

In this article, discovery of airglow and ionosphere has been discussed briefly in the historical and scientific perspectives. Mentioning about all significant atmospheric parameters, different areas of research in airglow and different ionospheric layers of importance have been briefly described. Different types of airglow emissions, related chemical kinetics, different excitation mechanisms of the involved atomic, molecular or ionic species have been discussed giving stress specially to four main airglow emissions. Different layers of ionosphere, their characteristic material content and specific ranges of responses to different kinds of interacting fields etc. have also been briefly discussesd. The Sun has been described as the main source of all kinds of energetic interactions with the terrestrial ionosphere. Specific solar parameters, that are representatives of various solar activity, have been discussed briefly in relation with the corresponding covariation of various ionospheric parameters involved in the calculations of airglow intensity. Different solar activity periodicities that have been discovered upto date are mentioned. Relations of different airglow emissions with ionospheric activities and specific ionospheric parameters have been briefly described. The important role of ozone in the stratosphere and lower thermosphere in the production of some airglow emissions has been discussed with exemplary works. Different wellknown features of airglow intensity variations such as altitudinal variation, latitudinal variation etc have also been mentioned. Different atmospheric models have been briefly described along with their usefulness. Descriptions of different missions and campaigns with which a number of airglow experiment sets are involved , have been presented in a tabular form. Discovery of some new airglow lines, some newly proposed excitation mechanisms and related kinetics, and some remeasured or reevaluated constants and coefficients have been reported too. Effect of different types of solar activity, of different kinds of lunar influences and of various terrestrial atmospheric features, such as, geomagnetic field alignment, geomagnetic storm, lightning, earthquake, dynamical coupling between layers of thermosphere, E x B drift and ring current etc on terrestrial airglow emissions have also been briefly discussed. Some interesting airglow related features which have been discovered in recent past are discussed. Applications of different airglow features have been reported. Lastly, facts and speculation about ionospheric compositions, activities and possible airglow emission features of other inner and outer planets, satellites, comets and meteors have been discussed very briefly.Author Affiliation: R Chattopadhyay and S K Midya 1.Haripal G.D. Institution, Khamarchandi, Hooghly-712 405, West Bengal, India 2.Department of Physics, Serampore College, Serampore, Hooghly-712 201, West Bengal, India 3.Centre for Space Physics, 43 Chalantika, Garia Station Road, Kolkata-700 084, India E-mail : [email protected] G.D. Institution, Khamarchandi, Hooghly-712 405, West Bengal, India 2Department of Physics, Serampore College, Serampore, Hooghly-712 201, West Bengal, India 3Centre for Space Physics, 43 Chalantika, Garia Station Road, Kolkata-700 084, Indi

Anomalous thermal expansion of Sb2_2Te3_3 topological insulator

We have investigated the temperature dependence of the linear thermal expansion along the hexagonal c axis ($\Delta L$), in-plane resistivity ($\rho$), and specific heat ($C_p$) of the topological insulator Sb$_2$Te$_3$ single crystal. $\Delta L$ exhibits a clear anomaly in the temperature region 204-236 K. The coefficient of linear thermal expansion $\alpha$ decreases rapidly above 204 K, passes through a deep minimum at around 225 K and then increases abruptly in the region 225-236 K. $\alpha$ is negative in the interval 221-228 K. The temperature dependence of both $\alpha$ and $C_p$ can be described well by the Debye model from 2 to 290 K, excluding the region around the anomaly in $\alpha$

Effects of Suction and Blowing on Flow Separation in a Symmetric Sudden Expanded Channel

A numerical simulation has been carried out to study the laminar flow in a symmetric sudden expanded channel subjected to a uniform blowing/suction speed placed at the lower and upper porous step walls. The governing equations for viscous flow have been solved using finite-difference techniques in pressure-velocity formulation. The results obtained here have been compared with the available experimental and numerical results of similar problems. It is noted that the recirculating region formed near the step walls diminishes in its length for increasing values of blowing speed applied at the porous step walls. For a suitable blowing speed, the recirculation zone disappears completely. The critical Reynolds number for the flow bifurcation (i.e. flow asymmetry) is obtained and it increases with the increase of the blowing speed. The critical Reynolds number for symmetry breaking of the flow decreases with the increasing values of suction speeds. The primary and the secondary recirculating regions formed near the channel walls are controlled using blowing

Laparoscopic versus open transhiatal oesophagectomy for oesophageal cancer

Surgery is the preferred treatment for resectable oesophageal cancers, and can be performed in different ways. Transhiatal oesophagectomy (oesophagectomy without thoracotomy, with a cervical anastomosis) is one way to resect oesophageal cancers. It can be performed laparoscopically or by open method. With other organs, laparoscopic surgery has been shown to reduce complications and length of hospital stay compared to open surgery. However, concerns remain about the safety of laparoscopic transhiatal oesophagectomy in terms of post-operative complications and oncological clearance compared with open transhiatal oesophagectomy