Double Bragg diffraction: A tool for atom optics

The use of retro-reflection in light-pulse atom interferometry under microgravity conditions naturally leads to a double-diffraction scheme. The two pairs of counterpropagating beams induce simultaneously transitions with opposite momentum transfer that, when acting on atoms initially at rest, give rise to symmetric interferometer configurations where the total momentum transfer is automatically doubled and where a number of noise sources and systematic effects cancel out. Here we extend earlier implementations for Raman transitions to the case of Bragg diffraction. In contrast with the single-diffraction case, the existence of additional off-resonant transitions between resonantly connected states precludes the use of the adiabatic elimination technique. Nevertheless, we have been able to obtain analytic results even beyond the deep Bragg regime by employing the so-called "method of averaging," which can be applied to more general situations of this kind. Our results have been validated by comparison to numerical solutions of the basic equations describing the double-diffraction process.Comment: 26 pages, 20 figures; minor changes to match the published versio

Modeling Friction Losses in the Water-Assisted Pipeline Transportation of Heavy Oil

In the lubricated pipe flow (LPF) of heavy oils, a water annulus acts as a lubricant and separates the viscous oil from the pipe wall. The steady state position of the annular water layer is in the high shear region. Significantly, lower pumping energy input is required than if the viscous oil was transported alone. An important challenge to the general application of LPF technology is the lack of a reliable model to predict frictional pressure losses. Although a number of models have been proposed to date, most of these models are highly system specific. Developing a reliable model to predict pressure losses in LPF is an open challenge to the research community. The current chapter introduces the concept of water lubrication in transporting heavy oils and discusses the methodologies available for modeling the pressure drops. It also includes brief descriptions of most important pressure loss models, their limitations, and the scope of future works

A comprehensive study on multiphase flow through pipeline and annuli using CFD approach

The physical phenomenon of more than one state or phase (i.e. gas, liquid or solid) simultaneously flowing is defined as multiphase flow. The overall performance of multiphase flow is more complex compared to single phase flow through pipeline or annuli. Calculation accuracy of pressure drop, and particle concentration is very important to design pipeline or annular geometry for multiphase flow. The objectives in the present study are to design a CFD model that can be used to predict multiphase fluid flow properties with more accuracy; to validate proposed CFD model with experimental data and existing empirical correlations at different orientations of geometry and combination of fluids; and to investigate the effects of pipe diameter, wall roughness, fluid velocity, fluid type, particle size, particle concentration, drill pipe rotation speed and drill pipe eccentricity on pressure losses and settling conditions. Three distinct phases of working fluids are used to fulfill the project. Simulation process is conducted using ANSYS fluent version 16.2 platform. Eulerian model with Reynolds Stress Model (RSM) turbulence closure is selected as optimum to analyze multiphase fluid flow. Pressure gradient and sand concentration profile are the primary output parameters to analyze. This article combines validation work at all possible cases to verify the developed model and parametric study to observe the effects of selected parameters on particle deposition. In parametric analysis, eccentricity of the annular pipe is varied from 0 – 50% and rotated about its own axis from 0 – 150 rpm. The diameter ratio of the simulated annuli is 0.56. Results show very good agreement with existing experiments and developed correlations. Also, the effects of different parameters are briefly analyzed with proper explanations. Fluid Structure Interaction (FSI) is introduced to observe the fluid flow effect on pipeline deformation

Nanosized Supramolecular Coordination Polymers Derived from Divalent Metal Ions, 4-Pyridylacetate and Auxiliary Ligands Containing Nitrogen and Phosphorus Donors

A series of coordination polymers of Co(II), Ni(II), Cu(II) or Cd(II) comprising 4-pyridylacetate (pya) and certain auxiliary ligands including benzimidazole (Hbzim), 1,10-phenanthroline (phen), 2,2'-bipyridine (2,2'-bipy),  2-amino-4-methylthiazole (A-Mtz), quinazole (Quz), 2,5-dimethylpyrazine (dpmz), bis(diphenylphosphino)methane (dpm), 1,2-bis(diphenylphosphino)ethane (dpe) and 1,3-bis(diphenylphosphino) propane (dpp) were prepared  and characterized by spectroscopic, magnetic and  thermal techniques. In these coordination polymers 4-pyridylacetate coordinates to the metal ions in a monodentate fashion through the carboxylate oxygens and/or the pyridyl nitrogen. Octahedral structures around the metal ions were suggested for all the complexes. The kinetic analyses of the thermal decomposition of the complexes were studied using the Coats-Redfern equation. The kinetic and thermodynamic parameters of the thermal decomposition were also calculated and discussed. From the X-ray powder diffraction data, the crystal parameters as well as the particle sizes (15.7-18.7 nm) of the complexes could be evaluated. Some of the compounds exhibit catalytic activity. The biological activity of the compounds was screened as well. DOI: http://dx.doi.org/10.17807/orbital.v13i1.155

Red- and blue-detuned magneto-optical trapping with liquid crystal variable retarders

We exploit red- and blue-detuned magneto-optical trapping (MOT) of 87Rb benefitting from a simplified setup and a novel approach based on liquid crystal variable retarders (LCVR). To maintain the trapping forces when switching from a red- to a blue-detuned MOT, the handedness of the circular polarization of the cooling beams needs to be reversed. LCVRs allow fast polarization control and represent compact, simple, and cost-efficient components, which can easily be implemented in existing laser systems. This way, we achieve a blue-detuned type-II MOT for 8.7 × 108 atoms of 87Rb with sub-Doppler temperatures of 44 μK well below the temperatures reached in a conventional 87Rb type-I MOT. The phase space density is increased by more than two orders of magnitude compared to the standard red-detuned type-I MOT. The setup can readily be transferred to any other systems working with 87Rb

Penning collisions of laser-cooled metastable helium atoms

We present experimental results on the two-body loss rates in a magneto-optical trap of metastable helium atoms. Absolute rates are measured in a systematic way for several laser detunings ranging from -5 to -30 MHz and at different intensities, by monitoring the decay of the trap fluorescence. The dependence of the two-body loss rate coefficient $\beta$ on the excited state ($2^3P_2$) and metastable state ($2^3S_1$) populations is also investigated. From these results we infer a rather uniform rate constant $K_{sp}=(1{\pm}0.4)\times10^{-7}$ cm$^3$/s.Comment: 8 pages, 9 figures, Revte

Influence of optical aberrations in an atomic gyroscope

In atom interferometry based on light-induced diffraction, the optical aberrations of the laser beam splitters are a dominant source of noise and systematic effect. In an atomic gyroscope, this effect is dramatically reduced by the use of two atomic sources. But it remains critical while coupled to fluctuations of atomic trajectories, and appears as a main source of noise to the long term stability. Therefore we measure these contributions in our setup, using cold Cesium atoms and stimulated Raman transitions

Efficient magneto-optical trapping of a metastable helium gas

This article presents a new experiment aiming at BEC of metastable helium atoms. It describes the design of a high flux discharge source of atoms and a robust laser system using a DBR diode coupled with a high power Yb doped fiber amplifier for manipulating the beam of metastable atoms. The atoms are trapped in a small quartz cell in an extreme high vacuum. The trapping design uses an additional laser (repumper) and allows the capture of a large number of metastable helium atoms (approximately $10^9$) in a geometry favorable for loading a tight magnetostatic trap.Comment: 12 pages, 7 figures, Late

ALARMING SIGNALS OF DRUG ADDICTION AMONG THE SOUTHERN YOUTHS IN BANGLADESH: A SURVEY BASED RESEARCH

Background: Drug addiction is a serious public health crisis which affects almost every sphere in a community in a way or another and this in turn can possibly lead to social disharmony, severe crimes, degraded social status and most possibly physical and mental health deterioration. The sole purpose of our study was aimed to analyze the current awful situation of drug addiction at four different southern cities of Bangladesh. Methods: This cross sectional health based survey was carried out with a self-designed standard questionnaire by manual data collection over a nine months period (12.09.2015 to 10.04.2016) at four adjacent cities Gopalganj, Khulna, Bagerhat and Narail respectively. Total 300 substance abusers were investigated by majorly visiting at their home and sometimes visiting the places where they usually take drugs. Descriptive statistics were applied to the collected data and analyzed using Microsoft Excel software. Results: In this cross sectional study we observed that, 82% addicts are predominantly young males mostly between the ages of 10-30. About 48% are addicted by cannabis, 19% and 17% by yaba and phensedyl respectively. In case of first starting of drug use curiosity, surrounding environment were the primary reason and cannabis as their first drug (61%) followed by phensedyl (16%). At least 53% addict\u27s relayed on locality like friends and 30% used local dealers as a main source to collect these abused drugs. Healthy financial support is very important for collecting abused drugs and 30% addicts spend pocket money, 23% job, 20% business source to buy these costly substances. Although it is important to mention that 61% addicts are compromising either physical or psychological complications but it is one of good symptoms to observe that more than 60% of drug addicts are trying to give up addiction forming agents in these days. Conclusion: In recent years drug addiction has significantly increased in the whole world especially in South Asian countries. It must be emphasized as an alarming sign by the government as well as awareness among the peoples are very essential to stop this critical condition from affecting our future young leaders. Keywords: Drug; Addiction; Youths; Bangladesh

ALARMING SIGNALS OF DRUG ADDICTION AMONG THE SOUTHERN YOUTHS IN BANGLADESH: A SURVEY BASED RESEARCH

Background: Drug addiction is a serious public health crisis which affects almost every sphere in a community in a way or another and this in turn can possibly lead to social disharmony, severe crimes, degraded social status and most possibly physical and mental health deterioration. The sole purpose of our study was aimed to analyze the current awful situation of drug addiction at four different southern cities of Bangladesh. Methods: This cross sectional health based survey was carried out with a self-designed standard questionnaire by manual data collection over a nine months period (12.09.2015 to 10.04.2016) at four adjacent cities Gopalganj, Khulna, Bagerhat and Narail respectively. Total 300 substance abusers were investigated by majorly visiting at their home and sometimes visiting the places where they usually take drugs. Descriptive statistics were applied to the collected data and analyzed using Microsoft Excel software. Results: In this cross sectional study we observed that, 82% addicts are predominantly young males mostly between the ages of 10-30. About 48% are addicted by cannabis, 19% and 17% by yaba and phensedyl respectively. In case of first starting of drug use curiosity, surrounding environment were the primary reason and cannabis as their first drug (61%) followed by phensedyl (16%). At least 53% addict's relayed on locality like friends and 30% used local dealers as a main source to collect these abused drugs. Healthy financial support is very important for collecting abused drugs and 30% addicts spend pocket money, 23% job, 20% business source to buy these costly substances. Although it is important to mention that 61% addicts are compromising either physical or psychological complications but it is one of good symptoms to observe that more than 60% of drug addicts are trying to give up addiction forming agents in these days. Conclusion: In recent years drug addiction has significantly increased in the whole world especially in South Asian countries. It must be emphasized as an alarming sign by the government as well as awareness among the peoples are very essential to stop this critical condition from affecting our future young leaders. Keywords: Drug; Addiction; Youths; Bangladesh