Beetroot Juice Does Not Enhance Altitude Running Performance in Well-Trained Athletes

We hypothesized that acute dietary nitrate (NO3-) provided as concentrated beetroot juice supplement would improve endurance running performance of well-trained runners in normobaric hypoxia. Ten male runners (mean (SD): sea level V�O2max 66 (7) mL.kg^-1.min^-1, 10 km personal best 36 (2) min) completed incremental exercise to exhaustion at 4000 m and a 10 km treadmill time trial at 2500 m simulated altitude on separate days, after supplementation with ~7 mmol NO3- and a placebo, 2.5 h before exercise. Oxygen cost, arterial oxygen saturation, heart rate and ratings of perceived exertion (RPE) were determined during the incremental exercise test. Differences between treatments were determined using means [95% confidence intervals], paired sample t-tests and a probability of individual response analysis. NO3- supplementation increased plasma [nitrite] (NO3-, 473 (226) nM vs. placebo, 61 (37) nM, P < 0.001) but did not alter time to exhaustion during the incremental test (NO3-, 402 (80) s vs. placebo 393 (62) s, P = 0.5) or time to complete the 10 km time trial (NO3-, 2862 (233) s vs. placebo, 2874 (265) s, P = 0.6). Further, no practically meaningful beneficial effect on time trial performance was observed as the 11 [-60 to 38] s improvement was less than the a priori determined minimum important difference (51 s), and only three runners experienced a ´likely, probable´ performance improvement. NO3- also did not alter oxygen cost, arterial oxygen saturation, heart rate or RPE. Acute dietary NO3- supplementation did not consistently enhance running performance of well-trained athletes in normobaric hypoxia

International graduates’ experiences of reflection in postgraduate training : a cross-sectional survey

Background: Reflection is a key component of postgraduate training in general practice (GP). International medical graduates (IMG) are thought to be less familiar with reflection, with international medical schools favouring more didactic methods of education. Aim: To explore IMGs’ experiences of reflection prior to and during GP training, and the support available for developing skills in reflection. Design and setting: A cross sectional survey was sent to IMGs undertaking GP training in 12 of the 14 UK regions from March to April 2021. Method: A pre-tested self-administered on-line questionnaire was used to collect data on experiences of reflection both prior to and during GP training, and support available for developing skills in reflection. Results: 485 of 3413 IMG trainees completed the questionnaire (14.2% response rate, representative of national demographics). 79.8% of participants reported no experience of reflection as an undergraduate and 36.9% reported no formal training in reflection during GP training. 69.7% of participants agreed that reflection was beneficial for their training and 58.3% reported that the best support in reflection came from their supervisors. Experience of reflection, opinions on the benefits, and best sources of support all varied by where respondents' primary medical qualification was obtained (all p-values <.01). Conclusion: Most IMGs have not experienced reflection prior to commencing UK GP training. There is diversity in experience and culture within this group which must be considered when tailoring educational interventions to support IMGs in their transition to UK GP training

Measuring the bulk impedance of brain tissue in vitro

Theoretical and numerical models of brain activity suggest a link between seizures and electrical connectivity. We have therefore been motivated to measure electrical conductivity in brain tissue. Such measurements in vitro are difficult; it is necessary to use a conductive inorganic salt solution, artificial cerebrospinal fluid (ACSF), to keep the tissue alive. We have attempted to provide a robust method to make such measurements. Mouse brain tissue was sliced (400 μm) using established methods. Half the slices were placed in standard ACSF; half were placed in ACSF devoid of magnesium ions. The latter case promotes seizure activity. Electrical activity was measured with a tungsten electrode at various places on the slices. Sixty-nine samples of cortex (2 mm × 2 mm) were cut with a razor. Their areas were measured with a calibrated microscope. Each sample was placed between two flat Ag/AgCl electrodes in a Perspex sandwich. Excess ACSF was removed with filter paper. The impedance was measured at 25°C from 20 Hz to 2 MHz with an Agilent E4980A four-point impedance meter in a shielded room, using a low current. Between 1 kHz and 100 kHz the conductivity was approximately 0.2 S m⁻¹; outside this range dispersion occurred. Samples prepared in the magnesium-free ACSF had a conductivity about 10% lower. The Cole-Cole model of conductivity was fitted. There were few significant differences between the parameters for the different groups measured

Regularisation Techniques for the Radiative Corrections of Wilson lines and Kaluza-Klein states

Within an effective field theory framework we compute the most general structure of the one-loop corrections to the 4D gauge couplings in one- and two-dimensional orbifold compactifications with non-vanishing constant gauge background (Wilson lines). Although such models are non-renormalisable, we keep the analysis general by considering the one-loop corrections in three regularisation schemes: dimensional regularisation (DR), Zeta-function regularisation (ZR) and proper-time cut-off regularisation (PT). The relations among the results obtained in these schemes are carefully addressed. With minimal re-definitions of the parameters involved, the results obtained for the radiative corrections can be applied to most orbifold compactifications with one or two compact dimensions. The link with string theory is discussed. We mention a possible implication for the gauge couplings unification in such models.Comment: 37 pages, 1 Figure, LaTeX; minor correction

Molecular spintronics: Coherent spin transfer in coupled quantum dots

Time-resolved Faraday rotation has recently demonstrated coherent transfer of electron spin between quantum dots coupled by conjugated molecules. Using a transfer Hamiltonian ansatz for the coupled quantum dots, we calculate the Faraday rotation signal as a function of the probe frequency in a pump-probe setup using neutral quantum dots. Additionally, we study the signal of one spin-polarized excess electron in the coupled dots. We show that, in both cases, the Faraday rotation angle is determined by the spin transfer probabilities and the Heisenberg spin exchange energy. By comparison of our results with experimental data, we find that the transfer matrix element for electrons in the conduction band is of order 0.08 eV and the spin transfer probabilities are of order 10%.Comment: 13 pages, 6 figures; minor change

On the complete classification of the unitary N=2 minimal superconformal field theories

Aiming at a complete classification of unitary N=2 minimal models (where the assumption of space-time supersymmetry has been dropped), it is shown that each modular invariant candidate of a partition function for such a theory is indeed the partition function of a minimal model. A family of models constructed via orbifoldings of either the diagonal model or of the space-time supersymmetric exceptional models demonstrates that there exists a unitary N=2 minimal model for every one of the allowed partition functions in the list obtained from Gannon's work. Kreuzer and Schellekens' conjecture that all simple current invariants can be obtained as orbifolds of the diagonal model, even when the extra assumption of higher-genus modular invariance is dropped, is confirmed in the case of the unitary N=2 minimal models by simple counting arguments.Comment: 53 pages; Latex; minor changes in v2: intro expanded, references added, typos corrected, footnote added on p31; renumbering of sections; main theorem reformulated for clarity, but contents unchanged. Minor revisions in v3: typos corrected, footnotes 5, 6 added, lemma 1 and section 3.3.2 rewritten for greater generality, section 3.3 review removed. To appear in Comm. Math. Phy

Unexpected sequences and structures of mtDNA required for efficient transcription from the first heavy-strand promoter

Human mtDNA contains three promoters, suggesting a need for differential expression of the mitochondrial genome. Studies of mitochondrial transcription have used a reductionist approach, perhaps masking differential regulation. Here we evaluate transcription from light-strand (LSP) and heavy-strand (HSP1) promoters using templates that mimic their natural context. These studies reveal sequences upstream, hypervariable in the human population (HVR3), and downstream of the HSP1 transcription start site required for maximal yield. The carboxyterminal tail of TFAM is essential for activation of HSP1 but not LSP. Images of the template obtained by atomic force microscopy show that TFAM creates loops in a discrete region, the formation of which correlates with activation of HSP1; looping is lost in tail-deleted TFAM. Identification of HVR3 as a transcriptional regulatory element may contribute to between-individual variability in mitochondrial gene expression. The unique requirement of HSP1 for the TFAM tail may enable its regulation by post-translational modifications. © Uchida et al