Temporal Narrowing of Neutrons Produced by High-Intensity Short-Pulse Lasers.

The production of neutron beams having short temporal duration is studied using ultraintense laser pulses. Laser-accelerated protons are spectrally filtered using a laser-triggered microlens to produce a short duration neutron pulse via nuclear reactions induced in a converter material (LiF). This produces a ∼3 ns duration neutron pulse with 10(4) n/MeV/sr/shot at 0.56 m from the laser-irradiated proton source. The large spatial separation between the neutron production and the proton source allows for shielding from the copious and undesirable radiation resulting from the laser-plasma interaction. This neutron pulse compares favorably to the duration of conventional accelerator sources and should scale up with, present and future, higher energy laser facilities to produce brighter and shorter neutron beams for ultrafast probing of dense materials.

Histidine metabolism after Bretschneider cardioplegia in cardiac surgical patients.

Bretschneider (histidine-tryptophan-ketoglutarate) solution with its high histidine concentration (198 mM) is one of many cardioplegic solutions, which are routinely used for cardiac arrest. The aim of this study was to evaluate the physiological biochemical degradation of administered histidine to histamine and its major urinary metabolite N-methylimidazole acetic acid. A total number of thirteen consecutive patients scheduled for elective isolated coronary artery bypass grafting with cardiopulmonary bypass were enrolled in the prospective observational designed study at the Department of Thoracic and Cardiovascular Surgery between 04/2016 and 06/2016. Patients received 1.7 l Bretschneider solution on average. Before and at the end of operation as well as in the postoperative course, urine samples gathered from the urinary catheter bag were analyzed. During the operative period, urinary histidine concentration significantly increased from 29 micromol/mmol creatinine to 9,609 micromol/mmol creatinine. Postoperatively, histidine excretion reduced while histamine as well as N-methylimidazole acetic acid excretion rose significantly. Patients showed elevated levels of histidine, histamine as well as N-methylimidazole acetic acid in urine, but no unmanageable hemodynamic instability possibly arising from the histamine's biological properties. Chemically modified histidine might reduce uptake and metabolization while maintaining the advantages of buffer capacity.

The organism and the open system. Ervin Bauer and Ludwig von Bertalanffy.

In this historical treatise two biological-system theories, formulated in the 1920s and 1930s, are roughly sketched. The first part discusses the concept of a thermodynamically open system, as coined by the Russian pathologist Ervin Bauer (1890-1942). Like Bertalanffy, Bauer wanted to prove the specificity of the biological sciences against physics. To achieve this, he postulated the necessity to formulate specific laws of motion which are valid for living matter alone. In the second part of the paper, the organismic-system theory of the Austrian-Canadian philosopher and biologist Ludwig von Bertalanffy (1901-1972) is outlined. The focus of this theory relied on the process dynamics that is inherent inside an organismic system. Both theories exemplify closure models for a living organism from a methodical point of view that distinguishes these earlier models from semantic closure, developed by Howard Pattee as an epistemic clue in solving the enigma of living phenomena. The objective here is to disclose the essential differences between these closure conceptions. To encourage further research on closure, the essay concludes with a few questions concerning clarification of the term.