Rank rigidity for CAT(0) cube complexes

We prove that any group acting essentially without a fixed point at infinity on an irreducible finite-dimensional CAT(0) cube complex contains a rank one isometry. This implies that the Rank Rigidity Conjecture holds for CAT(0) cube complexes. We derive a number of other consequences for CAT(0) cube complexes, including a purely geometric proof of the Tits Alternative, an existence result for regular elements in (possibly non-uniform) lattices acting on cube complexes, and a characterization of products of trees in terms of bounded cohomology.Comment: 39 pages, 4 figures. Revised version according to referee repor

Symmetric spaces of higher rank do not admit differentiable compactifications

Any nonpositively curved symmetric space admits a topological compactification, namely the Hadamard compactification. For rank one spaces, this topological compactification can be endowed with a differentiable structure such that the action of the isometry group is differentiable. Moreover, the restriction of the action on the boundary leads to a flat model for some geometry (conformal, CR or quaternionic CR depending of the space). One can ask whether such a differentiable compactification exists for higher rank spaces, hopefully leading to some knew geometry to explore. In this paper we answer negatively.Comment: 13 pages, to appear in Mathematische Annale

The type numbers of closed geodesics

A short survey on the type numbers of closed geodesics, on applications of the Morse theory to proving the existence of closed geodesics and on the recent progress in applying variational methods to the periodic problem for Finsler and magnetic geodesicsComment: 29 pages, an appendix to the Russian translation of "The calculus of variations in the large" by M. Mors

A theoretical investigation of low energy proton on hydrogen collisions

The Proton on Hydrogen collision problem is treated in the time-dependent formalism using a new self-consistent nuclear trajectory model in conjunction with a simple semi-classical approximation. In this method the nuclear trajectory is dependent on the time-evolution of the electronic wavefunction which is described by a basis of H₂⁺ eigenfunctions. The small-energy, large scattering angle region is well described in this way and agreement with available experimental data is obtained. Tile inclusion of the semi-classical approximation and the use of a larger molecular basis than hitherto employed allow these limits to be quite reasonably extended to describe the small angle and moderate energy region also. Results of charge exchange probabilities and differential-scattering cross-sections in the range 150-1000 e.v. (lab. energy of incident proton beam) are presented along with some inelastic calculations on excitation into the Hydrogen 2p±1 and 2S states. It is further shown that the inclusion of the Gerarde states (2Sσg, 3Dσg) in the basis set has a significant effect on the results obtained for collision energies of 700 e.v. and 1Kev. A new numerical method is described which enables very rapid computation of all quantities required for the basis set, and leads to quick and simple integral calculations

Effects of Caffeinated and Non-Caffeinated Gum on Premotor, Motor, and Overall Reaction Time

Chewing gum and caffeine when used independently and concurrently increase neural activity ultimately improving reaction time but less is known about how caffeinated gum influences distinct phases of the reaction time response. Physically active college females (n=14) completed a 60-second reaction time test on a visuomotor board under the following counterbalanced conditions: 1) Baseline, 2) Non-caffeinated gum, 3) Caffeinated gum (300 mg caffeine). Point of application #1: Chewing gum improved premotor reaction time compared to baseline, but caffeine did not provide additional benefit. Point of application #2: Neither non-caffeinated nor caffeinated gum improved motor reaction times from baseline. Point of application #3: Chewing gum improved overall reaction time compared to baseline, but caffeine did not provide additional benefit. Keywords: Chewing, Visuomotor, Visual processin

Entropy of semiclassical measures for nonpositively curved surfaces

We study the asymptotic properties of eigenfunctions of the Laplacian in the case of a compact Riemannian surface of nonpositive sectional curvature. We show that the Kolmogorov-Sinai entropy of a semiclassical measure for the geodesic flow is bounded from below by half of the Ruelle upper bound. We follow the same main strategy as in the Anosov case (arXiv:0809.0230). We focus on the main differences and refer the reader to (arXiv:0809.0230) for the details of analogous lemmas.Comment: 20 pages. This note provides a detailed proof of a result announced in appendix A of a previous work (arXiv:0809.0230, version 2

Dual-tip-enhanced ultrafast CARS nanoscopy

Coherent anti-Stokes Raman scattering (CARS) and, in particular, femtosecond adaptive spectroscopic techniques (FAST CARS) have been successfully used for molecular spectroscopy and microscopic imaging. Recent progress in ultrafast nanooptics provides flexibility in generation and control of optical near fields, and holds promise to extend CARS techniques to the nanoscale. In this theoretical study, we demonstrate ultrafast subwavelentgh control of coherent Raman spectra of molecules in the vicinity of a plasmonic nanostructure excited by ultrashort laser pulses. The simulated nanostructure design provides localized excitation sources for CARS by focusing incident laser pulses into subwavelength hot spots via two self-similar nanolens antennas connected by a waveguide. Hot-spot-selective dual-tip-enhanced CARS (2TECARS) nanospectra of DNA nucleobases are obtained by simulating optimized pump, Stokes and probe near fields using tips, laser polarization- and pulse-shaping. This technique may be used to explore ultrafast energy and electron transfer dynamics in real space with nanometre resolution and to develop novel approaches to DNA sequencing.Comment: 11 pages, 6 figure

The Effects of Acute Rauwolscine (α-Yohimbine) Ingestion on Repeated Wingate Sprint Performance in Healthy Males

Topics in Exercise Science and Kinesiology Volume 4: Issue 1, Article 1, 2023. Background: Rauwolscine (RW), also known as α-Yohimbine, is an α-2-adrenergic receptor antagonist which possesses sympathomimetic properties. RW is commercially sold in pre-workout and energy supplements. However, the ergogenic potential of RW has not been determined. The purpose of this study was to investigate the effects of acute RW supplementation on repeated sprint performance. Methods: Healthy male participants (n=12) completed 3 × 15-second Wingate anaerobic tests (WAnT) separated by 2 minutes of active recovery. Blood lactate (La) was collected before exercise (Pre) and immediately following exercise (Post). Mean power, peak power, fatigue index, heart rate (HR), and rate of perceived exertion (RPE) were taken immediately after each WAnT. Point of application #1: Acute RW supplementation does not result in the enhancement of repeated anaerobic sprint performance. Point of application #2: HR and RPE are not altered during repeated sprints with RW ingestion. Point of application #3: RW ingestion results in higher La levels post-exercise despite no changes in fatigue index

On the Enigma of Glutathione-Dependent Styrene Degradation in Gordonia rubripertincta CWB2

Heine T, Zimmerling J, Ballmann A, et al. On the Enigma of Glutathione-Dependent Styrene Degradation in Gordonia rubripertincta CWB2. APPLIED AND ENVIRONMENTAL MICROBIOLOGY. 2018;84(9): 16.Among bacteria, only a single styrene-specific degradation pathway has been reported so far. It comprises the activity of styrene monooxygenase, styrene oxide isomerase, and phenylacetaldehyde dehydrogenase, yielding phenylacetic acid as the central metabolite. The alternative route comprises ring-hydroxylating enzymes and yields vinyl catechol as central metabolite, which undergoes meta-cleavage. This was reported to be unspecific and also allows the degradation of benzene derivatives. However, some bacteria had been described to degrade styrene but do not employ one of those routes or only parts of them. Here, we describe a novel "hybrid" degradation pathway for styrene located on a plasmid of foreign origin. As putatively also unspecific, it allows metabolizing chemically analogous compounds (e.g., halogenated and/or alkylated styrene derivatives). Gordonia rubripertincta CWB2 was isolated with styrene as the sole source of carbon and energy. It employs an assembled route of the styrene side-chain degradation and isoprene degradation pathways that also funnels into phenylacetic acid as the central metabolite. Metabolites, enzyme activity, genome, transcriptome, and proteome data reinforce this observation and allow us to understand this biotechnologically relevant pathway, which can be used for the production of ibuprofen. IMPORTANCE The degradation of xenobiotics by bacteria is not only important for bioremediation but also because the involved enzymes are potential catalysts in biotechnological applications. This study reveals a novel degradation pathway for the hazardous organic compound styrene in Gordonia rubripertincta CWB2. This study provides an impressive illustration of horizontal gene transfer, which enables novel metabolic capabilities. This study presents glutathione-dependent styrene metabolization in an (actino-) bacterium. Further, the genomic background of the ability of strain CWB2 to produce ibuprofen is demonstrated

Four-electron deoxygenative reductive coupling of carbon monoxide at a single metal site

Carbon dioxide is the ultimate source of the fossil fuels that are both central to modern life and problematic: their use increases atmospheric levels of greenhouse gases, and their availability is geopolitically constrained. Using carbon dioxide as a feedstock to produce synthetic fuels might, in principle, alleviate these concerns. Although many homogeneous and heterogeneous catalysts convert carbon dioxide to carbon monoxide, further deoxygenative coupling of carbon monoxide to generate useful multicarbon products is challenging. Molybdenum and vanadium nitrogenases are capable of converting carbon monoxide into hydrocarbons under mild conditions, using discrete electron and proton sources. Electrocatalytic reduction of carbon monoxide on copper catalysts also uses a combination of electrons and protons, while the industrial Fischer–Tropsch process uses dihydrogen as a combined source of electrons and electrophiles for carbon monoxide coupling at high temperatures and pressures6. However, these enzymatic and heterogeneous systems are difficult to probe mechanistically. Molecular catalysts have been studied extensively to investigate the elementary steps by which carbon monoxide is deoxygenated and coupled, but a single metal site that can efficiently induce the required scission of carbon–oxygen bonds and generate carbon–carbon bonds has not yet been documented. Here we describe a molybdenum compound, supported by a terphenyl–diphosphine ligand, that activates and cleaves the strong carbon–oxygen bond of carbon monoxide, enacts carbon–carbon coupling, and spontaneously dissociates the resulting fragment. This complex four-electron transformation is enabled by the terphenyl–diphosphine ligand, which acts as an electron reservoir and exhibits the coordinative flexibility needed to stabilize the different intermediates involved in the overall reaction sequence. We anticipate that these design elements might help in the development of efficient catalysts for converting carbon monoxide to chemical fuels, and should prove useful in the broader context of performing complex multi-electron transformations at a single metal site