Submanifolds in five-dimensional pseudo-Euclidean spaces and four-dimensional FRW universes

Equations for submanifolds, which correspond to embeddings of the four-dimensional FRW universes in five-dimensional pseudo-Euclidean spaces, are presented in convenient form in general case. Several specific examples are considered.Comment: 7 pages, LaTeX, the mathematical part of this paper is based on the withdrawn preprint arXiv:1012.0320 [gr-qc

A national survey of services for the prevention and management of falls in the UK

Background: The National Health Service (NHS) was tasked in 2001 with developing service provision to prevent falls in older people. We carried out a national survey to provide a description of health and social care funded UK fallers services, and to benchmark progress against current practice guidelines. Methods: Cascade approach to sampling, followed by telephone survey with senior member of the fall service. Characteristics of the service were assessed using an internationally agreed taxonomy. Reported service provision was compared against benchmarks set by the National Institute for Health and Clinical Excellence (NICE). Results: We identified 303 clinics across the UK. 231 (76%) were willing to participate. The majority of services were based in acute or community hospitals, with only a few in primary care or emergency departments. Access to services was, in the majority of cases, by health professional referral. Most services undertook a multi-factorial assessment. The content and quality of these assessments varied substantially. Services varied extensively in the way that interventions were delivered, and particular concern is raised about interventions for vision, home hazard modification, medication review and bone health. Conclusion: The most common type of service provision was a multi-factorial assessment and intervention. There were a wide range of service models, but for a substantial number of services, delivery appears to fall below recommended NICE guidance

Planar Disjoint-Paths Completion

We introduce Planar Disjoint Paths Completion, a completion counterpart of the Disjoint Paths problem, and study its parameterized complexity. The problem can be stated as follows: given a, not necessarily connected, plane graph G, k pairs of terminals, and a face F of G, find a minimum-size set of edges, if one exists, to be added inside F so that the embedding remains planar and the pairs become connected by k disjoint paths in the augmented network. Our results are twofold: first, we give an upper bound on the number of necessary additional edges when a solution exists. This bound is a function of k, independent of the size of G. Second, we show that the problem is fixed-parameter tractable, in particular, it can be solved in time f(k) · n2

Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests

Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general he more 15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar δ15N values from tropical forests averaged 6.5‰ higher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in 15N than other tropical forests. The average δ15N values for tropical forest soils, either for surface or for depth samples, were almost 8‰ higher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems

Improving memory performance using a wearable BCI

Human ability to encode and memorize information fluctuates from moment to moment. Several studies have reported differences in electroencephalography (EEG) signals recorded during memorization of items that were forgotten at a later point of time compared to those that were remembered. Given these observations the question then arises whether or not a wearable BCI system can be designed to identify poorly encoded items. Such a device could be used to provide feedback to the user so as to improve the memory encoding process. This paper reports on an experimental study designed to assess this possibility

Dissecting the Red Sequence--II. Star Formation Histories of Early-Type Galaxies Throughout the Fundamental Plane

This analysis uses spectra of ~16,000 nearby SDSS quiescent galaxies to track variations in galaxy star formation histories along and perpendicular to the Fundamental Plane (FP). We sort galaxies by their FP properties (sigma, R_e, and I_e) and construct high S/N mean galaxy spectra that span the breadth and thickness of the FP. From these spectra, we determine mean luminosity-weighted ages, [Fe/H], [Mg/H], and [Mg/Fe] based on single stellar population models using the method described in Graves & Schiavon (2008). In agreement with previous work, the star formation histories of early-type galaxies are found to form a two-parameter family. The major trend is that mean age, [Fe/H], [Mg/H], and [Mg/Fe] all increase with sigma. However, no stellar population property shows any dependence on R_e at fixed sigma, suggesting that sigma and not dynamical mass (M_dyn ~ sigma^2 R_e) is the better predictor of past star formation history. In addition to the main trend with sigma, galaxies also show a range of population properties at fixed sigma that are strongly correlated with surface brightness residuals from the FP, such that higher surface brightness galaxies have younger mean ages, higher [Fe/H], higher [Mg/H], and lower [Mg/Fe] than lower-surface brightness galaxies. These latter trends are a major new constraint on star-formation histories.Comment: 23 pages, 14 figures. Accepted to Ap

Terahertz emission mechanism and laser excitation position dependence of nano-grating electrode photomixers

The emission mechanism of continuous wave (CW) terahertz (THz) photomixers that make use of nanostructured gratings (NSGs) is studied. Two different photomixer designs, based on a single-sided NSG and a double-sided NSG, embedded in the same antenna design and fabricated on an Fe doped InGaAsP substrate, are characterized with ∼1550 nm excitation. They are shown to exhibit similar performance in terms of spectral bandwidth and emitted power. The emission is mapped in terms of the laser excitation position, from which the emission mechanism is assigned to an enhanced optical electric field at the tips of the NSGs

Terahertz generation mechanism in nano-grating electrode photomixers on Fe-doped InGaAsP

We report the generation mechanism associated with nano-grating electrode photomixers fabricated on Fe-doped InGaAsP substrates. Two different emitter designs incorporating nano-gratings coupled to the same broadband antenna were characterized in a continuous-wave terahertz (THz) frequency system employing telecommunications wavelength lasers for generation and coherent detection. The current-voltage characteristics and THz emission bandwidth of the emitters is compared for different bias polarities and optical polarisations. The THz output from the emitters is also mapped as a function of the position of the laser excitation spot for both continuous-wave and pulsed excitation. This mapping, together with full-wave simulations of the structures, confirms the generation mechanism to be due to an enhanced optical electric field at the grating tips resulting in increased optical absorption, coinciding with a concentration of the electrostatic field

Wake Up and Smell the Coffee: Yet Another No Go for Cardiac Patients?: Editorial to “Caffeinated Coffee Blunts the Myocardial Protective Effects of Statins Against Ischemia–reperfusion Injury in the Rat” by Ye et al.

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Gut dendritic cell activation links an altered colonic microbiome to mucosal and systemic T-cell activation in untreated HIV-1 infection

HIV-1-associated disruption of intestinal homeostasis is a major factor contributing to chronic immune activation and inflammation. Dendritic cells (DCs) are crucial in maintaining intestinal homeostasis, but the impact of HIV-1 infection on intestinal DC number and function has not been extensively studied. We compared the frequency and activation/maturation status of colonic myeloid DC (mDC) subsets (CD1c(+) and CD1c(neg)) and plasmacytoid DCs in untreated HIV-1-infected subjects with uninfected controls. Colonic mDCs in HIV-1-infected subjects had increased CD40 but decreased CD83 expression, and CD40 expression on CD1c(+) mDCs positively correlated with mucosal HIV-1 viral load, with mucosal and systemic cytokine production, and with frequencies of activated colon and blood T cells. Percentage of CD83(+)CD1c(+) mDCs negatively correlated with frequencies of interferon-γ-producing colon CD4(+) and CD8(+) T cells. CD40 expression on CD1c(+) mDCs positively associated with abundance of high prevalence mucosal Prevotella copri and Prevotella stercorea but negatively associated with a number of low prevalence mucosal species, including Rumminococcus bromii. CD1c(+) mDC cytokine production was greater in response to in vitro stimulation with Prevotella species relative to R. bromii. These findings suggest that, during HIV infection, colonic mDCs become activated upon exposure to mucosal pathobiont bacteria leading to mucosal and systemic immune activation