Sparsity Enhanced Beamforming in The Presence of Coherent Signals

In order to find the directions of coherent signals, a sparsity enhanced beam-forming method is proposed. Unlike the conventional minimum variance distortless response (MVDR) method, the minimum variance in the proposed method corresponds to the orthogonal relationship between the noise subspace and the sparse representation of the received signal vector, whereas the distortless response corresponds to the nonorthogonal relationship between the signal subspace and the sparse representation of the received signal vector. The proposed sparsity enhanced MVDR (SEMVDR) method is carried out by the iterative reweighted Lp-norm constraint minimization. for direction finding of coherent signals. Simulation results are shown that SEMVDR has better performance than the existing algorithms, such as MVDR and MUSIC, when coherent signals are present.

Exploring the orthogonal relationship between controlled and automated processes

After identifying some of the weaknesses associated with linear, or serial, models of skill learning—with a focus on their failure to fully account for the ongoing relevance of motor control and attention to action—this chapter synthesizes the evidence presented over the course of this book to construct a model of skilled action that captures the complex relationship between automaticity and attentional focus. This model explains how these two processes operate in a synergistic fashion to help experts overcome the challenges they face in seeking to not only maintain but to continue to improve performance proficiency over long timescales, to update and improve motor execution in training contexts, and to stabilize performance under pressurized conditions. The chapter concludes by briefly discussing the role metacognition plays in allowing expert performers to identify and apply situationally appropriate modes of control.

Structural and Magnetic Studies on Nickel(II) and Cobalt(II) Complexes with Polychlorinated Diphenyl(4-pyridyl)methyl Radical Ligands

New magnetic metal complexes with organic radical ligands, [M(hfac)2(PyBTM)2] (M = NiII, CoII; hfac = hexafluoroacetylacetonato, PyBTM = (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical), were prepared and their crystal structures, magnetic properties, and electronic structures were investigated. Metal ions in [M(hfac)2(PyBTM)2] constructed distorted octahedral coordination geometry, where the two PyBTM molecules ligated in the trans configuration. Magnetic investigation using a SQUID magnetometer revealed that χT increased with decreasing temperature from 300 K in the two complexes, indicating an efficient intramolecular ferromagnetic exchange interaction taking place between the spins on PyBTM and M with J/kB of 21.8 K and 11.8 K for [NiII(hfac)2(PyBTM)2] and [CoII(hfac)2(PyBTM)2]. The intramolecular ferromagnetic couplings in the two complexes could be explained by density functional theory calculations, and would be attributed to a nearly orthogonal relationship between the spin orbitals on PyBTM and the metal ions. These results demonstrate that pyridyl-containing triarylmethyl radicals are key building blocks for magnetic molecular materials with controllable/predictable magnetic interactions.

2-[(1E)-[(Z)-2-({[(1Z)-[(E)-2-[(2-Hydroxyphenyl)methylidene]hydrazin-1-ylidene]({[(4-methylphenyl)methyl]sulfanyl})methyl]disulfanyl}({[(4-methylphenyl)methyl]sulfanyl})methylidene)hydrazin-1-ylidene]methyl]phenol: crystal structure, Hirshfeld surface analysis and computational study

The complete molecule of the title hydrazine carbodithioate derivative, C32H30N4O2S4, is generated by a crystallographic twofold axis that bisects the disulfide bond. The molecule is twisted about this bond with the C—S—S—C torsion angle of 90.70 (8)° indicating an orthogonal relationship between the symmetry-related halves of the molecule. The conformation about the imine bond [1.282 (2) Å] is E and there is limited delocalization of π-electron density over the CN2C residue as there is a twist about the N—N bond [C—N—N—C torsion angle = −166.57 (15)°]. An intramolecular hydroxyl-O—H...N(imine) hydrogen bond closes an S(6) loop. In the crystal, methylene-C—H...π(tolyl) contacts assemble molecules into a supramolecular layer propagating in the ab plane: the layers stack without directional interactions between them. The analysis of the calculated Hirshfeld surfaces confirm the importance of H...H contacts, which contribute 46.7% of all contacts followed by H...C/C...H contacts [25.5%] reflecting, in part, the C—H...π(tolyl) contacts. The calculation of the interaction energies confirm the importance of the dispersion term and the influence of the stabilizing H...H contacts in the inter-layer region.

Bacterial evolution in high osmolarity environments

Bacteria must maintain a cytosolic osmolarity higher than that of their environment in order to take up water. High osmolarity environments therefore present a formidable stress to bacteria. To explore the evolutionary mechanisms by which bacteria adapt to high osmolarity environments, we selected Escherichia coli in media with a variety of osmolytes and concentrations for 250 generations. Adaptation was osmolyte-dependent, with sorbitol stress generally resulting in increased fitness in conditions with higher osmolarity, while selection in high concentrations of proline resulted in increased fitness specifically on proline. Consistent with these phenotypes, sequencing of the evolved populations showed that passaging in proline resulted in specific mutations in an associated metabolic pathway that increases the ability to utilize proline for growth, while evolution in sorbitol resulted in mutations in many different genes that generally improve growth in high osmolarity conditions at the expense of growth at low osmolarity. High osmolarity decreased growth rate but increased mean cell volume compared with growth on proline as the sole carbon source, demonstrating that osmolarity-induced changes in growth rate and cell size follow an orthogonal relationship from the classical Growth Law relating cell size and nutrient quality. Isolates from a sorbitol-evolved population that capture the likely temporal sequence of mutations revealed by metagenomic sequencing demonstrate a tradeoff between growth at high and low osmolarity. Our study highlights the utility of experimental evolution for dissecting complex cellular networks and environmental interactions, particularly in the case of behaviors that can involve both specific and general metabolic stressors.ImportanceFor bacteria, maintaining higher internal solute concentrations than the environment allows cells to take up water. As a result, survival is challenging in high osmolarity environments. To investigate how bacteria adapt to high osmolarity environments, we evolved Escherichia coli in a variety of high osmolarity solutions for hundreds of generations. We found that evolved populations adopted different strategies to improve their growth depending on the osmotic passaging condition, either generally adapting to high osmolarity conditions or better metabolizing the osmolyte as carbon source. Single-cell imaging demonstrated that enhanced fitness was coupled to faster growth, and metagenomic sequencing revealed mutations that reflect growth tradeoffs across osmolarities. Our study demonstrates the utility of long-term evolution experiments for probing adaptation during environmental stress.

Resonant Transmission Through a Single Subwavelength Slit for Varied Metallic Permittivities and Its Modal Orthogonality

This article investigates resonant transmission phenomena through a single metallic subwavelength slit when the permittivity of a real metal varies. The single metallic slit is utilized as a metal–insulator–metal waveguide, and a mode-matching technique is employed to obtain the transmitted power. The periodic resonant transmission phenomena (in terms of the metallic plate thickness) are solved, and the resonances can be understood by their guide wavelengths. Even when the permittivity of the real metal includes imaginary parts (i.e., metal with loss), the resonant transmittances are obtained. However, the peaks of the transmittances decrease, as the plate thickness increases. The orthogonal relationship of an incomplete orthogonal set is maintained despite metallic loss (given a relatively small amount of loss), due to the complex permittivity of the real metal.

N,N′-Bis(pyridin-3-ylmethyl)ethanediamide monohydrate: crystal structure, Hirshfeld surface analysis and computational study

The molecular structure of the title bis-pyridyl substituted diamide hydrate, C14H14N4O2·H2O, features a central C2N2O2 residue (r.m.s. deviation = 0.0205 Å) linked at each end to 3-pyridyl rings through methylene groups. The pyridyl rings lie to the same side of the plane, i.e. have a syn-periplanar relationship, and form dihedral angles of 59.71 (6) and 68.42 (6)° with the central plane. An almost orthogonal relationship between the pyridyl rings is indicated by the dihedral angle between them [87.86 (5)°]. Owing to an anti disposition between the carbonyl-O atoms in the core, two intramolecular amide-N—H...O(carbonyl) hydrogen bonds are formed, each closing an S(5) loop. Supramolecular tapes are formed in the crystal via amide-N—H...O(carbonyl) hydrogen bonds and ten-membered {...HNC2O}2 synthons. Two symmetry-related tapes are linked by a helical chain of hydrogen-bonded water molecules via water-O—H...N(pyridyl) hydrogen bonds. The resulting aggregate is parallel to the b-axis direction. Links between these, via methylene-C—H...O(water) and methylene-C—H...π(pyridyl) interactions, give rise to a layer parallel to (10\overline{1}); the layers stack without directional interactions between them. The analysis of the Hirshfeld surfaces point to the importance of the specified hydrogen-bonding interactions, and to the significant influence of the water molecule of crystallization upon the molecular packing. The analysis also indicates the contribution of methylene-C—H...O(carbonyl) and pyridyl-C—H...C(carbonyl) contacts to the stability of the inter-layer region. The calculated interaction energies are consistent with importance of significant electrostatic attractions in the crystal.

2-{[Bis(propan-2-yl)carbamothioyl]sulfanyl}acetic acid

The title compound, (iPr)2NC(=S)SCH2C(=O)OH (1), was synthesized by conventional methods and its X-ray crystal structure was determined by X-ray crystallography. The compound was further characterized by analytical, IR, UV, 1D NMR (1H and 13C{1H}), and 2D NMR (DEPT-135) spectroscopy, and density functional theory (DFT) methods. X-ray crystallography on 1 confirms the formulation and reveals a nearly orthogonal relationship between the planar NCS2 and C2O2 residues. In the crystal, hydroxyl-O–H⋯O(carbonyl) hydrogen bonds lead dimers via an eight-membered {⋯OCOH}2 ring.