Influence of geometric parameters on 3D periodic lattice effective properties

Lattice materials are generated by tessellating a unit cell, composed of a specific truss configurations, in an infinite periodicity to combine the effect of bulk material properties and geometric periodicity. They offer enhanced mechanical and dynamic properties per unit mass, and the ability to engineer the material response by optimizing the unit cell. Characterizing lattice properties through experiments can be a time consuming and costly process, so analytical and numerical methods are crucial. Specifically, the Bloch-wave homogenization approach allows one to characterize the effective static properties of the lattice unit cell while simultaneously analyzing wave propagation properties. While this analysis has been used for some time, a thorough study of this approach on 3D lattice materials with different symmetries and geometries is presented here. Using Bloch-wave homogenization, multiple periodic lattices with cubic, transversely isotropic, and tetragonal symmetry, including an auxetic geometry, over a wide range of relative densities are analyzed within a finite element framework. The effect of geometric parameters on lattice properties is discussed and a comparison between lattices based on their anisotropy index is presented. Method studied in this thesis can be extended for designing multifunctional metamaterials with optimized static and dynamic properties simultaneously. This work can also serve as the basis for nondestructive evaluation of metamaterials properties using ultrasonic velocity measurements

Achieving Fairness in the Stochastic Multi-armed Bandit Problem

We study an interesting variant of the stochastic multi-armed bandit problem, called the Fair-SMAB problem, where each arm is required to be pulled for at least a given fraction of the total available rounds. We investigate the interplay between learning and fairness in terms of a pre-specified vector denoting the fractions of guaranteed pulls. We define a fairness-aware regret, called $r$-Regret, that takes into account the above fairness constraints and naturally extends the conventional notion of regret. Our primary contribution is characterizing a class of Fair-SMAB algorithms by two parameters: the unfairness tolerance and the learning algorithm used as a black-box. We provide a fairness guarantee for this class that holds uniformly over time irrespective of the choice of the learning algorithm. In particular, when the learning algorithm is UCB1, we show that our algorithm achieves $O(\ln T)$ $r$-Regret. Finally, we evaluate the cost of fairness in terms of the conventional notion of regret.Comment: arXiv admin note: substantial text overlap with arXiv:1905.1126

Morbidity following emergency and elective cholecystectomy:a retrospective comparative cohort study

INTRODUCTION: An emergency laparoscopic cholecystectomy (EMLC) is commonly performed for all biliary pathology, yet EMLC can be challenging due to acute inflammation. Understanding the risks of EMLC is necessary before patients can make an informed decision regarding operative management. The aim of the present study was to compare rates of operative and post-operative outcomes between EMLC and elective LC (ELLC) using a large contemporary cohort, to inform the consent process and influence surgical decision making. METHODS: All patients who underwent EMLC and ELLC in one UK health board between January 2015 and December 2019 were considered for inclusion. Data were collected retrospectively from multiple regional databases using a deterministic records-linkage methodology. Patients were followed up for 100 days post-operatively for adverse outcomes and outcomes were compared between groups using both univariate and multivariate analysis adjusting for pre-operative factors. RESULTS: A total of 2768 LCs were performed [age (range), 52(13–92); M:F, 1:2.7]. In both the univariate and multivariate analysis, EMLC was positively associated with subtotal cholecystectomy (RR 2.0; p < 0.001), post-operative complication (RR 2.8; p < 0.001), post-operative imaging (RR 2.0; p < 0.001), post-operative intervention (RR 2.3; p < 0.001), prolonged post-operative hospitalisation (RR 3.8; p < 0.001) and readmission (RR 2.2; p < 0.001). EMLC had higher rates of post-operative mortality in univariate analysis (RR 10.8; p = 0.01). DISCUSSION: EMLC is positively associated with adverse outcomes versus ELLC. Of course this study does not focus on a specific biliary pathology; nevertheless, it illustrates the additional risk associated with EMLC. This should be clearly outlined during the consent process but should be balanced with the risk of further biliary attacks. Further studies are required to identify particular patient groups who benefit from elective surgery

Complex evolution of the electronic structure of Cr with temperature

Employing state-of-the-art high resolution photoemission spectroscopy, we studied the electronic structure evolution of Cr with temperature. Experimental results reveal signature of a pseudogap much below the spin density wave transition temperature. A sharp peak appears near the Fermi level at low temperatures presumably related to the orbital Kondo effect. These results provide possible origin of the complex electronic properties observed in this system

Butea monosperma Silver Nanoparticles Anticancer Activity Against MCF 7 Human Breast Cancer Cell Line

In this research, silver nanoparticles were synthesized from Butea monosperma for in vitro cytotoxicity efficacy against MCF-7 cells. Silver nanoparticles are deemed the most positive, considering their strong volume surface region, and are of concern for study because of the improved microbial tolerance to antibiotics and medicines. Therefore, green synthesis of nanoparticles of silver using biomolecules derived from various plant sources in the form of extracts can be applied for the screening of different diseases which trigger microorganisms and for the physical and biological characterization of plant-derived silver nanoparticles. The experiment involved the green synthesis of silver nanoparticles (AgNPs) from Butea monosperma leaf extract. Biosynthesized Butea monosperma-AgNPs were characterized by UV-visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The intensity of peak broad range 200-800nm in UV-vis spectra, EDS test. The SEM shows the actual size of the nanoparticles. The MTT assays were carried out for cytotoxicity of various concentrations of biosynthesized silver nanoparticles. The biosynthesized silver nanoparticles showed a significant anticancer activity against both MCF-7. Our study thus revealed an excellent application of greenly synthesized silver nanoparticles. At the Concentration 80µg/ml, Sample Code A, B, C, D samples showed good percent inhibition MCF7cell line as compared to standard drug.The study also suggested the potential therapeutic use of these nanoparticles in cancer study

Structural, optical and gas sensing properties of barium titanate surface modified by nano silver

Paper represents the results of SO2 sensing performance of BaTiO3 surface modified by nano silver. Surface modification was performed by dipping of BaTiO3 thick films in the synthesized nano silver. The main objective was to investigate the effect of nano silver on gas sensing performance of BaTiO3 perovskite. Different intervals of dipping time were used to find the optimum dipping amount on the surface of perovskite oxide. Synthesized silver was characterized by UV-visible spectroscopy and transmission electron microscopy. Surface modified thick films were analyzed for structural, morphological, electrical and gas sensing properties by XRD, SEM with EDX, static gas sensing unit respectively. Selectivity of surface modified BaTiO3 thick films was also investigated

Synthesis, Characterization, and Antibacterial Studies of Mixed Ligand Dioxouranium Complexes with 8-Hydroxyquinoline and Some Amino Acids

Mixed ligand complexes of dioxouranium (VI) of the type [UO2(Q)(L)·2H2O] have been synthesized using 8-hydroxyquinoline (HQ) as a primary ligand and amino acids (HL) such as L-threonine, L-tryptophan, and L-isoleucine as secondary ligands. The metal complexes have been characterized by elemental analysis, electrical conductance, magnetic susceptibility measurements, and spectral and thermal studies. The electrical conductance studies of the complexes indicate their nonelectrolytic nature. Magnetic susceptibility measurements revealed diamagnetic nature of the complexes. Electronic absorption spectra of the complexes show intraligand and charge transfer transitions, respectively. Bonding of the metal ion through N- and O-donor atoms of the ligands is revealed by IR studies, and the chemical environment of the protons is confirmed by NMR studies. The thermal analysis data of the complexes indicate the presence of coordinated water molecules. The agar cup and tube dilution methods have been used to study the antibacterial activity of the complexes against the pathogenic bacteria S. aureus, C. diphtheriae, S. typhi, and E. coli