Investigation of caving-in incident of MIG 21 aircraft

In an accident, the starboard (STBD) side of front fuselage was ‘caved in’ during ground run of the Mig-21. A post-incident inspection revealed vertical and horizontal cracking occurred at the edges of the additional air intake shutter (AAITS). The guard of the AAITS was sucked in causing extensive damage to the aeroengine. However, port side fuselage remained un-affected. The chemical composition and evaluation of the mechanical properties of the alloy match with the Russian specification D16AT, D16ATB. It means that the duralumin alloy is in hardened and aged condition. Characterization of microstructure in optical, SEM and TEM illustrate more or less negligible variation for fresh and service exposed material. From the investigation it can be inferred, on the starboard side near some of the rivet holes at the edges of AAITS opening, primary cracks were formed owing to fretting fatigue. The structural non-uniformity of annular area on the starboard side with respect to port side raised the air pressure around the frame #5 and the skin ‘caved-in’. As engine demanded more air, under severe suction pressure, the skin containing micro-cracks became unable to withstand the load and the guard was sucked in from outside towards the engine causing overload failure to the areas away from rivet hole and rest of the zones near the AAITS

Reducible Correlations in Dicke States

We apply a simple observation to show that the generalized Dicke states can be determined from their reduced subsystems. In this framework, it is sufficient to calculate the expression for only the diagonal elements of the reudced density matrices in terms of the state coefficients. We prove that the correlation in generalized Dicke states $|GD_N^{(\ell)}>$ can be reduced to $2\ell$-partite level. Application to the Quantum Marginal Problem is also discussed.Comment: 12 pages, single column; accepted in J. Phys. A as FT

NLO Corrections to lepton pair production beyond the Standard Model at hadron colliders

We consider lepton pair production at a hadron collider in a class of effective theories with the relevant operators being four-fermion contact interaction. Despite the nonrenormalizable nature of the interaction, we explicitly demonstrate that calculating QCD corrections is both possible and meaningful. Calculating the corrections for various differential distributions, we show that these can be substantial and significantly different from those within the SM. Furthermore, the corrections have a very distinctive flavour dependence. And finally, the scale dependence of the cross sections are greatly reduced once the NLO corrections are taken into account.Comment: 23 pages, 14 figures, few typos corrected, written in JHEP styl

Negative Differential Conductance in Nano-junctions: A Current Constrained Approach

A current constrained approach is proposed to calculate negative differential conductance in molecular nano-junctions. A four-site junction is considered where a steady-state current is forced by inserting only the two central sites within the circuit. The two lateral sites (representing e.g. dangling molecular groups) do not actively participate in transport, but exchange electrons with the two main sites. These auxiliary sites allow for a variable number of electrons within the junction, while, as required by the current constrained approach, the total number of electrons in the system is kept constant. We discuss the conditions for negative differential conductance in terms of cooperativity, variability of the number of electrons in the junction, and electron correlations

Screening the risk factors of type 2 diabetes mellitus in minor ethnic Bishnupriya Manipuri community in Bangladesh

Background: Type 2 diabetes mellitus (T2DM) development involves various interrelated risk factors, including age, gender, obesity, and inactivity. However, research lacks insights into the risk factors within the minor ethnic Bishnupriya Manipuri community in Bangladesh. This study aimed to identify T2DM risk factors within this community. Methods: This survey-based prospective observational study was conducted in different villages of Kamalgonj Upazila under the Moulvibazar district in Bangladesh from March 2023 to June 2023 enrolled 280 individuals using purposive sampling. Data collection involved a questionnaire, verbal agreement, and diagnostic documentation. Analysis utilized Microsoft Office and the student’s t-test. Results: Participants exhibited a 1:1.2 male-female ratio, with 64% aged 36-65. 43% were housewives, 55% engaged in moderate work, 15% smoked, and 41% had a family history of diabetes. Diabetic cases accounted for 39%, with an average age of 57.39±11.99 years, significantly higher than non-diabetic cases (46.79±17.93 years). Diabetic cases also showed significantly higher waist circumference (94.11±6.63 cm versus 84.71±14.76 cm) and body mass index (BMI) (26.12±7.61 kg/m2 versus 21.44±6.97 kg/m2). Conclusions: T2DM predominantly affects older individuals in the Bishnupriya Manipuri community. Increased waist circumference, overweight, and obesity emerged as significant risk factors for T2DM within this population

A comparative study of the phase diagrams of spin-121 \over 2 and spin-11 antiferromagnetic chains with dimerization and frustration

We use the density matrix renormalization group method to study the ground state `phase' diagram and some low-energy properties of isotropic antiferromagnetic spin-$1 \over 2$ and spin-$1$ chains with a next-nearest neighbor exchange $J_2 ~$ and an alternation $\delta$ of the nearest neighbor exchanges. In the spin-$1 \over 2$ chain, the system is gapless for $\delta=0$ and $J_2 < J_{2c} =0.241$, and is gapped everywhere else in the $J_2 - \delta$ plane. At $J_{2c}$, for small $\delta$, the gap increases as $\delta^{\alpha}$, where $\alpha = 0.667 \pm 0.001$. $2J_2 + \delta = 1$ is a disorder line. To the left of this line, the structure factor $S(q)$ peaks at $q_{max} = \pi$ (Neel `phase'), while to the right, $q_{max}$ decreases from $\pi$ to $\pi/2$ (spiral `phase') as $J_2$ increases. There is also a `$\uparrow \uparrow \downarrow \downarrow$ phase' for large values of both $J_2$ and $\delta$. In the spin-$1$ case, we find a line running from a gapless point at $(J_2 , \delta) = (0,0.25 \pm 0.01)$ upto a `gapless' point at $(0.73 \pm 0.005,0)$ such that the open chain ground state is four-fold degenerate below the line and is unique above it. There is a disorder line in this case also and it has the same equation as in the spin-$1 \over 2$ case, but the line ends at about $\delta =0.136$. Similar to the spin-$1 \over 2$ case, to the left of this line, the peak in the structure factor is at $\pi$ (Neel `phase'), while to the right of the line, it is at less than $\pi$ (spiral `phase'). For $\delta =1$, the system corresponds to a spin ladder and the system is gapped for all values of the interchain coupling for both spin-$1 \over 2$ and spin-$1$ ladders.Comment: 16 pages in latex; 9 figures available on reques

Low Viral Load Does Not Exclude Significant Liver Damage in Patients with Chronic HBV Infection in Bangladesh

Background: In general, it is assumed that patients with chronic hepatitis B virus (HBV) infection with high viral load exhibit increased liver damages. Accordingly, the treatment guidelines emphasize on reducing viral load in chronic HBV carriers. The ethical and scientific basis of these observations was mainly accumulated from investigations from developed countries of the world. More than 80% chronic HBV carriers live in the developing nations of the world, but little is known about relationship between HBV viral load and extent of liver damages in these countries. In this study, we addressed this issue to provide insights about this. Methods: In this retrospective study we reviewed the records of 210 chronic hepatitis B (CHB) patients from our pool of 561 Bangladeshi CHB patients. All of these 210 patients had low HBV DNA (&lt;105 copies/ml by PCR). Of them 16 were HBeAg +ve and rest 194 HBeAg -ve. They have also been tested for other serologic markers of HBV (i.e. HBsAg, anti-HBe), HCV (i.e. anti-HCV) and serum alaninetransaminase (ALT) level. All patients also underwent per-cutaneous liver biopsy. Results: 37.5% (6/16) HBeAg +ve patients with low HBV DNA had significant hepatic necro-inflammation (HAI-NI &ge;7), whereas this figure was 31.44% (61/194) in case of HBeAg -ve patients. On the other hand significant hepatic fibrosis (HAI-F &ge;3) was observed in 31.25% (5/16) and 14.4% (28/194) in HBeAg +ve and -ve patients respectively. Conclusion: This study shows that a correlation could not be established between viral load and liver damage in patients with CHB in Bangladesh. A significant percentage of patients with low HBV DNA may have marked hepatic necro-inflammation and fibrosis, more so in case of HBeAg +ve CHB. Further study may be needed to find out the influence of other factors on liver damages in CHB patients in developing nations like Bangladesh, where about 8 million chronic HBV carriers are living. Most of these patients have not been characterized and treatment modalities have not been defined for them. Our study may suggest the research direction for management of these cases. Key Words: Low HBV DNA; Chronic hepatitis B; Hepatic necro-inflammation; Hepatic fibrosis.DOI: 10.3329/bsmmuj.v1i1.3693 BSMMU J 2008; 1(1): 19-2

Heavy Meson Production in NN Collisions with Polarized Beam and Target -- A new facility for COSY

The study of near--threshold meson production in pp and pd collisions involving polarized beams and polarized targets offers the rare opportunity to gain insight into short--range features of the nucleon--nucleon interaction. The Cooler Synchrotron COSY at FZ--J\"ulich is a unique environment to perform such studies. Measurements of polarization observables require a cylindrically symmetrical detector, capable to measure the momenta and the directions of outgoing charged hadrons. The wide energy range of COSY leads to momenta of outgoing protons to be detected in a single meson production reaction between 300 and 2500 MeV/c. Scattering angles of protons to be covered extend to about $45^{\circ}$ in the laboratory system. An azimuthal angular coverage of the device around 98% seems technically achievable. The required magnetic spectrometer could consist of a superconducting toroid, providing fields around 3 T.Comment: 6 pages, 1 figure, submitted to Czechoslovak Journal of Physic

Geometric discord and Measurement-induced nonlocality for well known bound entangled states

We employ geometric discord and measurement induced nonlocality to quantify non classical correlations of some well-known bipartite bound entangled states, namely the two families of Horodecki's ($2\otimes 4$, $3\otimes 3$ and $4\otimes 4$ dimensional) bound entangled states and that of Bennett etal's in $3\otimes 3$ dimension. In most of the cases our results are analytic and both the measures attain relatively small value. The amount of quantumness in the $4\otimes 4$ bound entangled state of Benatti etal and the $2\otimes 8$ state having the same matrix representation (in computational basis) is same. Coincidently, the $2m\otimes 2m$ Werner and isotropic states also exhibit the same property, when seen as $2\otimes 2m^2$ dimensional states.Comment: V2: Title changed, one more state added; 11 pages (single column), 2 figures, accepted in Quantum Information Processin