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An experimental study of a nanosecond pulsed regime in a THz gyrotron oscillator operating in a self-consistent Q-switch regime has been carried out. The gyrotron is operated in the TE7,2 transverse mode radiating at a frequency of 260.5 GHz. The 5 W nanosecond pulses are obtained in a self-consistent Q-switch regime in which the cavity diffraction quality factor dynamically varies by nearly 2 orders of magnitude on a subnanosecond time scale via the nonlinear interaction of different mode-locked frequency-equidistant sidebands. The experimental results are in good agreement with numerical simulations performed with the TWANG code based on a slow time scale formulation of the self-consistent time-dependent nonlinear wave particle interaction equations. [ABSTRACT FROM AUTHOR]

Nuclear hyperpolarization in the liquid state by dynamic nuclear polarization (DNP) has been of great interest because of its potential use in NMR spectroscopy of small samples of biological and chemical compounds in aqueous media. Liquid state DNP generally requires microwave resonators in order to generate an alternating magnetic field strong enough to saturate electron spins in the solution. As a consequence, the sample size is limited to dimensions of the order of the wavelength, and this restricts the sample volume to less than 100 nL for DNP at 9 T (∼260 GHz). We show here a new approach that overcomes this sample size limitation. Large saturation of electron spins was obtained with a high-power (∼150 W) gyrotron without microwave resonators. Since high power microwaves can cause serious dielectric heating in polar solutions, we designed a planar probe which effectively alleviates dielectric heating. A thin liquid sample of 100 μm of thickness is placed on a block of high thermal conductivity aluminum nitride, with a gold coating that serves both as a ground plane and as a heat sink. A meander or a coil were used for NMR. We performed 1 H DNP at 9.2 T (∼260 GHz) and at room temperature with 10 μL of water, a volume that is more than 100× larger than reported so far. The 1 H NMR signal is enhanced by a factor of about -10 with 70 W of microwave power. We also demonstrated the liquid state of 31 P DNP in fluorobenzene containing triphenylphosphine and obtained an enhancement of ∼200.

A 550-fold increase in the liquid state (13)C NMR signal of a 50μL sample was obtained by first hyperpolarizing the sample at 20K using a gyrotron (260GHz), then, switching its frequency in order to apply 100W for 1.5s so as to melt the sample, finally, turning off the gyrotron to acquire the (13)C NMR signal. The sample stays in its NMR resonator, so the sequence can be repeated with rapid cooling as the entire cryostat stays cold. DNP and thawing of the sample are performed only by the switchable and tunable gyrotron without external devices. Rapid transition from DNP to thawing in one second time scale was necessary especially in order to enhance liquid (1)H NMR signal., (Copyright © 2016 Elsevier Inc. All rights reserved.)

After myocardial infarction, calcium channel blockers are the most prescribed anti-ischemic drugs followed by nitrate derivatives and beta blockers. In order to assess whether this attitude is justified by published data on their efficacy, a meta-analysis of trials of anti-ischemic drugs in myocardial infarction was performed. The early mortality was 13.3% in the group treated by IV nitrates in the acute phase of myocardial infarction and 17.2% in control groups, reducing the risk by a quarter (95% confidence interval of the odds ratio (CI): 0.55-0.95). When all nitrate derivative trials were grouped together, the reduction in the risk of death of 21% was significant (from 15% to 11.8%) (CI: 0.59-0.94). Although oral nitrate derivatives introduced during the acute phase and continued for several weeks induced a non-significant reduction in mortality of 16%, when given intravenously, the benefits on early and longer term mortality were unquestionable. The mortality was 9.8% in the groups treated by calcium channel blockers and 9.3% in control groups (NS); the recurrent infarct rate was 4.8% and 5.4% respectively (NS). In this family of drugs, there was no product which distinguished itself from the others with regard to beneficial or adverse effects. The early mortality decreased from 9.2% to 8.2% in the groups treated by oral beta-blockade--a risk reduction of 10% (NS) and from 4.2% to 3.7% with intravenous beta-blockers--a risk reduction of 12% (p = 0.03). Late mortality decreased from 9.4% to 7.6%, a reduction of 20% (p < 0.00001) in long term trials.2+ contraindication of betablockers in patients without cardiac failure.

Accelerated atherosclerosis of cardiac grafts is one of the factors limiting long-term survival after cardiac transplantation. The authors report the case of a patient who had a cardiac arrest associated with severe atherosclerosis 18 months after transplantation. The severity of the coronary lesions was underestimated by coronary angiography. An ergometrine test induced coronary spasm, a phenomenon which has only rarely been observed in transplanted hearts. The patient died one month later despite calcium inhibitor therapy. Autopsy revealed very severe triple vessel disease. This case illustrates the possible rapid evolution of coronary artery disease in cardiac transplant recipients, the difficulty in evaluating the severity of the lesions by coronary angiography and the additional possibility of observing coronary spasm in these cases.