Microstructural characterization of friction stir welded AA5083 aluminum alloy joints

The objective of the current work is to apply Taguchi L9 orthogonal array to enhance the welding process factors for friction stir welding (FSW) of AA5083 aluminium alloy plates. Using a randomized procedure, the Taguchi orthogonal array was implemented to identify the FSW process parameters such as the rotating speed of the tool, welding speed, and tilting angle of the tool. The optimum welding parameters for the ultimate tensile strength and hardness of the joints were predicted and the individual rank of each process parameter on the ultimate tensile strength and hardness of the friction stir weld was assessed by investigative ANOVA results and the S/N ratio (signal-to- noise ratio). The most desirable rotational speed of the tool, welding speed and tilting angle of the tool were 600 rev. per. min, 70 millimeter/min and 1o appropriately for the ultimate eluting strength and 600 rev. per. min, 80 millimeter/min and 1o correspondingly for summit joint hardness. The outcomes of Analysis of Variance (ANOVA) designated that the tilting angle of the tool has the higher statistical effect succeeded by the welding velocity and rotational speed of the tool. Furthermore, metallurgical properties of the weld cross-sections were investigated by using optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis. The microstructure of the stir zone reveals finer grain structure, directed to the higher hardness, which gives rise to higher tensile strength

Pulse control protocols for preserving coherence in dipolar-coupled nuclear spin baths.

Coherence of solid state spin qubits is limited by decoherence and random fluctuations in the spin bath environment. Here we develop spin bath control sequences which simultaneously suppress the fluctuations arising from intrabath interactions and inhomogeneity. Experiments on neutral self-assembled quantum dots yield up to a five-fold increase in coherence of a bare nuclear spin bath. Numerical simulations agree with experiments and reveal emergent thermodynamic behaviour where fluctuations are ultimately caused by irreversible conversion of coherence into many-body quantum entanglement. Simulations show that for homogeneous spin baths our sequences are efficient with non-ideal control pulses, while inhomogeneous bath coherence is inherently limited even under ideal-pulse control, especially for strongly correlated spin-9/2 baths. These results highlight the limitations of self-assembled quantum dots and advantages of strain-free dots, where our sequences can be used to control the fluctuations of a homogeneous nuclear spin bath and potentially improve electron spin qubit coherence

Moduli Stacks of Vector Bundles and Frobenius Morphisms

We describe the action of the different Frobenius morphisms on the cohomology ring of the moduli stack of algebraic vector bundles of fixed rank and determinant on an algebraic curve over a finite field in characteristic p and analyse special situations like vector bundles on the projective line and relations with infinite Grassmannians.Comment: 19 page

Direct measurement of hyperfine shifts and radio frequency manipulation of the nuclear spins in individual CdTe/ZnTe quantum dots

We achieve direct detection of electron hyperfine shifts in individual CdTe / ZnTe quantum dots. For the previously inaccessible regime of strong magnetic fields Bz≳0.1T, we demonstrate robust polarization of a few-hundred-particle nuclear spin bath, with an optical initialization time of ∼1 ms and polarization lifetime exceeding ∼1s. Nuclear magnetic resonance spectroscopy of individual dots reveals strong electron-nuclear interactions characterized by Knight fields |Be|≳50 mT, an order of magnitude stronger than in III–V semiconductor quantum dots. Our studies confirm II–VI semiconductor quantum dots as a promising platform for hybrid electron-nuclear spin qubit registers, combining the excellent optical properties comparable to III–V dots and the dilute nuclear spin environment similar to group-IV semiconductors

Comprehensive analysis of temporal alterations in cellular proteome of bacillus subtilis under curcumin treatment

Curcumin is a natural dietary compound with antimicrobial activity against various gram positive and negative bacteria. This study aims to investigate the proteome level alterations in Bacillus subtilis due to curcumin treatment and identification of its molecular/cellular targets to understand the mechanism of action. We have performed a comprehensive proteomic analysis of B. subtilis AH75 strain at different time intervals of curcumin treatment (20, 60 and 120 min after the drug exposure, three replicates) to compare the protein expression profiles using two complementary quantitative proteomic techniques, 2D-DIGE and iTRAQ. To the best of our knowledge, this is the first comprehensive longitudinal investigation describing the effect of curcumin treatment on B. subtilis proteome. The proteomics analysis revealed several interesting targets such UDP-N-acetylglucosamine 1-carboxyvinyltransferase 1, putative septation protein SpoVG and ATP-dependent Clp protease proteolytic subunit. Further, in silico pathway analysis using DAVID and KOBAS has revealed modulation of pathways related to the fatty acid metabolism and cell wall synthesis, which are crucial for cell viability. Our findings revealed that curcumin treatment lead to inhibition of the cell wall and fatty acid synthesis in addition to differential expression of many crucial proteins involved in modulation of bacterial metabolism. Findings obtained from proteomics analysis were further validated using 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) assay for respiratory activity, resazurin assay for metabolic activity and membrane integrity assay by potassium and inorganic phosphate leakage measurement. The gene expression analysis of selected cell wall biosynthesis enzymes has strengthened the proteomics findings and indicated the major effect of curcumin on cell division