Hydration, drinking and exercise performance

To counter progressive dehydration and thirst, athletes drink during exercise. However, despite decades of scientific research, there is still no conclusive answer regarding how much we should drink to optimize performance. The goal of this review article is to analyze the arguments underpinning contrasting perspectives and to critically analyze the available evidence. It seems that the respective argumentations of contrasting viewpoints are based on a different selective fraction of the available evidence. In studies using time trial performance protocols in which dehydration develops during exercise, it seems that end-exercise dehydration levels of up to 4% body mass do not compromise endurance performance in temperate to hot conditions – at least as long as the athlete is not prevented from drinking. In contrast, studies that induced dehydration pre-exercise consistently report performance impacts already at low levels of dehydration, i.e., 1 to 2 % body mass loss. Further factors like the perception of thirst have been suggested to influence performance, but performance effects cannot be explained solely by the perception of thirst as well. Nevertheless, no evidence was found against the hypothesis that drinking ad libitum may optimize performance outcomes. At the same time, arguments have been identified regarding why a drinking plan might assist athletes in different situations

Defunct brain stem cardiovascular regulation underlies cardiovascular collapse associated with methamphetamine intoxication

<p>Abstract</p> <p>Background</p> <p>Intoxication from the psychostimulant methamphetamine (METH) because of cardiovascular collapse is a common cause of death within the abuse population. For obvious reasons, the heart has been taken as the primary target for this METH-induced toxicity. The demonstration that failure of brain stem cardiovascular regulation, rather than the heart, holds the key to cardiovascular collapse induced by the pesticide mevinphos implicates another potential underlying mechanism. The present study evaluated the hypothesis that METH effects acute cardiovascular depression by dampening the functional integrity of baroreflex via an action on brain stem nuclei that are associated with this homeostatic mechanism.</p> <p>Methods</p> <p>The distribution of METH in brain and heart on intravenous administration in male Sprague-Dawley rats, and the resultant changes in arterial pressure (AP), heart rate (HR) and indices for baroreflex-mediated sympathetic vasomotor tone and cardiac responses were evaluated, alongside survival rate and time.</p> <p>Results</p> <p>Intravenous administration of METH (12 or 24 mg/kg) resulted in a time-dependent and dose-dependent distribution of the psychostimulant in brain and heart. <b/>The distribution of METH to neural substrates associated with brain stem cardiovascular regulation was significantly larger than brain targets for its neurological and psychological effects; the concentration of METH in cardiac tissues was the lowest among all tissues studied. In animals that succumbed to METH, the baroreflex-mediated sympathetic vasomotor tone and cardiac response were defunct, concomitant with cessation of AP and HR. On the other hand, although depressed, those two indices in animals that survived were maintained, alongside sustainable AP and HR. Linear regression analysis further revealed that the degree of dampening of brain stem cardiovascular regulation was positively and significantly correlated with the concentration of METH in key neural substrate involved in this homeostatic mechanism.</p> <p>Conclusions</p> <p>We conclude that on intravenous administration, METH exhibits a preferential distribution to brain stem nuclei that are associated with cardiovascular regulation. We further found that the concentration of METH in those brain stem sites dictates the extent that baroreflex-mediated sympathetic vasomotor tone and cardiac responses are compromised, which in turn determines survival or fatality because of cardiovascular collapse.</p

Equivalent efficiency of a simulated photon-number detector

Homodyne detection is considered as a way to improve the efficiency of communication near the single-photon level. The current lack of commercially available {\it infrared} photon-number detectors significantly reduces the mutual information accessible in such a communication channel. We consider simulating direct detection via homodyne detection. We find that our particular simulated direct detection strategy could provide limited improvement in the classical information transfer. However, we argue that homodyne detectors (and a polynomial number of linear optical elements) cannot simulate photocounters arbitrarily well, since otherwise the exponential gap between quantum and classical computers would vanish.Comment: 4 pages, 4 figure

Quantum Measurement and the Aharonov-Bohm Effect with Superposed Magnetic Fluxes

We consider the magnetic flux in a quantum mechanical superposition of two values and find that the Aharonov-Bohm effect interference pattern contains information about the nature of the superposition, allowing information about the state of the flux to be extracted without disturbance. The information is obtained without transfer of energy or momentum and by accumulated nonlocal interactions of the vector potential $\vec{A}$ with many charged particles forming the interference pattern, rather than with a single particle. We suggest an experimental test using already experimentally realized superposed currents in a superconducting ring and discuss broader implications.Comment: 6 pages, 4 figures; Changes from version 3: corrected typo (not present in versions 1 and 2) in Eq. 8; Changes from version 2: shortened abstract; added refs and material in Section IV. The final publication is available at: http://link.springer.com/article/10.1007/s11128-013-0652-

Using Chinese Version of MYMOP in Chinese Medicine Evaluation: Validity, Responsiveness and Minimally Important Change

<p>Abstract</p> <p>Background</p> <p>Measure Yourself Medical Outcome Profile (MYMOP) is a patient generated outcome instrument applicable in the evaluation of both allopathic and complementary medicine treatment. This study aims to adapt MYMOP into Chinese, and to assess its validity, responsiveness and minimally important change values in a sample of patients using Chinese medicine (CM) services.</p> <p>Methods</p> <p>A Chinese version of MYMOP (CMYMOP) is developed by forward-backward-forward translation strategy, expert panel assessment and pilot testing amongst patients. 272 patients aged 18 or above with subjective symptoms in the past 2 weeks were recruited at a CM clinic, and were invited to complete a set of questionnaire containing CMYMOP and SF-36. Follow ups were performed at 2^ndand 4^thweek after consultation, using the same set of questionnaire plus a global rating of change question. Criterion validity of CMYMOP was assessed by its correlation with SF-36 at baseline, and responsiveness was evaluated by calculating the Cohen effect size (ES) of change at two follow ups. Minimally important difference (MID) values were estimated via anchor based method, while minimally detectable difference (MDC) figures were calculated by distribution based method.</p> <p>Results</p> <p>Criterion validity of CMYMOP was demonstrated by negative correlation between CMYMOP Profile scores and all SF-36 domain and summary scores at baseline. For responsiveness between baseline and 4^thweek follow up, ES of CMYMOP Symptom 1, Activity and Profile reached the moderate change threshold (ES>0.5), while Symptom 2 and Wellbeing reached the weak change threshold (ES>0.2). None of the SF-36 scores reached the moderate change threshold, implying CMYMOP's stronger responsiveness in CM setting. At 2^ndweek follow up, MID values for Symptom 1, Symptom 2, Wellbeing and Profile items were 0.894, 0.580, 0.263 and 0.516 respectively. For Activity item, MDC figure of 0.808 was adopted to estimate MID.</p> <p>Conclusions</p> <p>The findings support the validity and responsiveness of CMYMOP for capturing patient centred clinical changes within 2 weeks in a CM clinical setting. Further researches are warranted (1) to estimate Activity item MID, (2) to assess the test-retest reliability of CMYMOP, and (3) to perform further MID evaluation using multiple, item specific anchor questions.</p

Hamiltonian Dynamics and the Phase Transition of the XY Model

A Hamiltonian dynamics is defined for the XY model by adding a kinetic energy term. Thermodynamical properties (total energy, magnetization, vorticity) derived from microcanonical simulations of this model are found to be in agreement with canonical Monte-Carlo results in the explored temperature region. The behavior of the magnetization and the energy as functions of the temperature are thoroughly investigated, taking into account finite size effects. By representing the spin field as a superposition of random phased waves, we derive a nonlinear dispersion relation whose solutions allow the computation of thermodynamical quantities, which agree quantitatively with those obtained in numerical experiments, up to temperatures close to the transition. At low temperatures the propagation of phonons is the dominant phenomenon, while above the phase transition the system splits into ordered domains separated by interfaces populated by topological defects. In the high temperature phase, spins rotate, and an analogy with an Ising-like system can be established, leading to a theoretical prediction of the critical temperature $T_{KT}\approx 0.855$.Comment: 10 figures, Revte

Continuous Variable Quantum Cryptography using Two-Way Quantum Communication

Quantum cryptography has been recently extended to continuous variable systems, e.g., the bosonic modes of the electromagnetic field. In particular, several cryptographic protocols have been proposed and experimentally implemented using bosonic modes with Gaussian statistics. Such protocols have shown the possibility of reaching very high secret-key rates, even in the presence of strong losses in the quantum communication channel. Despite this robustness to loss, their security can be affected by more general attacks where extra Gaussian noise is introduced by the eavesdropper. In this general scenario we show a "hardware solution" for enhancing the security thresholds of these protocols. This is possible by extending them to a two-way quantum communication where subsequent uses of the quantum channel are suitably combined. In the resulting two-way schemes, one of the honest parties assists the secret encoding of the other with the chance of a non-trivial superadditive enhancement of the security thresholds. Such results enable the extension of quantum cryptography to more complex quantum communications.Comment: 12 pages, 7 figures, REVTe

Proposal for measurment of harmonic oscillator Berry phase in ion traps

We propose a scheme for measuring the Berry phase in the vibrational degree of freedom of a trapped ion. Starting from the ion in a vibrational coherent state we show how to reverse the sign of the coherent state amplitude by using a purely geometric phase. This can then be detected through the internal degrees of freedom of the ion. Our method can be applied to preparation of Schr\"odinger cat states.Comment: Replaced with revised versio

IFNβ Protects Neurons from Damage in a Murine Model of HIV-1 Associated Brain Injury.

Infection with human immunodeficiency virus-1 (HIV-1) causes brain injury. Type I interferons (IFNα/β) are critical mediators of any anti-viral immune response and IFNβ has been implicated in the temporary control of lentiviral infection in the brain. Here we show that transgenic mice expressing HIV-1 envelope glycoprotein 120 in their central nervous system (HIVgp120tg) mount a transient IFNβ response and provide evidence that IFNβ confers neuronal protection against HIVgp120 toxicity. In cerebrocortical cell cultures, neuroprotection by IFNβ against gp120 toxicity is dependent on IFNα receptor 1 (IFNAR1) and the β-chemokine CCL4, as IFNAR1 deficiency and neutralizing antibodies against CCL4, respectively, abolish the neuroprotective effects. We find in vivo that IFNβ mRNA is significantly increased in HIVgp120tg brains at 1.5, but not 3 or 6 months of age. However, a four-week intranasal IFNβ treatment of HIVgp120tg mice starting at 3.5 months of age increases expression of CCL4 and concomitantly protects neuronal dendrites and pre-synaptic terminals in cortex and hippocampus from gp120-induced damage. Moreover, in vivo and in vitro data suggests astrocytes are a major source of IFNβ-induced CCL4. Altogether, our results suggest exogenous IFNβ as a neuroprotective factor that has potential to ameliorate in vivo HIVgp120-induced brain injury