Elastic scattering of 17, 18O on 12, 13C at Ec.m. = 12.6 – 14.0 MeV

The angular distributions of the elastic scattering of ^{17, 18}O on ^{12, 13}C were measured at c.m. energies between 12.6 to 14.0 MeV. A rise of the cross section at backward angles was observed. Standard optical-model fits were found to reproduce reasonably well the forward part of the cross section, but fail at backward angles. Possible contributions of first-order cluster exchange and compound-nucleus reactions are discussed. Excitation functions of various exit channels in the ¹⁸O + ¹²C system were measured at backward angles in the energy range of 12.0 to 14.8 MeV c.m. No significant correlation was found between any of these cross sections.     

Dynamic helical chirality of an intramolecularly hydrogen-bonded bisoxazoline

The synthesis and conformational properties of 2,6-bis-[2-((4S)-4-methyl-4,5-dihydro-1,3-oxazol-2-yl)phenyl]carbam oylpyridines, 2, have been described. Bisoxazoline 2a was prepared in five steps from 2-nitrobenzoyl chloride in an overall yield of 71%. In contrast to related structures such as 1, bisoxazoline 2a exhibits a highly biased P-type helical conformation in solution and in the solid state. In the crystal lattice, 2a further assembles into a left-handed helical superstructure aligned along the crystallographic c axis. The barrier to helical interconversion, as measured by line-shape analysis of the temperature-dependent (1)H NMR spectra of thiobenzyl derivative 2b, was determined to be quite low ((Delta)G(++) = 12.3 kcal/mol), indicating the presence of a highly dynamic helical chirality.     

LIM is not slim

In this paper LIM, a recently proposed impartial combinatorial ruleset, is analyzed. A formula to describe the $\mathcal G $ -values of LIM positions is given, by way of analyzing an equivalent combinatorial ruleset LIM’, closely related to the classical nim. Also, an enumeration of $\mathcal P $ -positions of LIM with $n$ stones, and its relation to the Ulam-Warburton cellular automaton, is presented.     

A Constructive Existence Proof for the Extreme Stokes Wave

Stokes conjectured in 1880 that an extreme gravity wave on water (or ‘wave of greatest height’) exists, has sharp crests of included angle 2π/3 and has a boundary that is convex between successive crests. These three conjectures have all been proved recently, but by diverse methods that are not conspicuously direct. The present paper proceeds from a first approximate solution of the extreme form of the integral equation due to Nekrasov, to a contraction mapping for a related integral equation that governs a new dependent variable in the space L ₂(0,π). This method provides: (a) a constructive approach to an extreme wave with the sharp crests predicted by Stokes; and (b) a rather accurate second approximation. However, the method has not led (so far, at least) to the convexity.     

Über die Einwirkung der Bacillen des malignen Ödems auf Kohlehydrate und Milchsäure

Ohne Zusammenfassung     

Advanced features of SCD’s uncooled detectors

SCD has recently presented an uncooled detector product line based on the high-end VO_x bolometer technology. The first FPA launched, BIRD, is a 384×288 (or 320×240) configurable format with 25 μm pitch. Typical NETD values for these FPAs range at 50 mK with an F/1 aperture and 60 Hz frame rate. These detectors also exhibit a relatively fast thermal time constant of approximately 10 ms. In this paper we elaborate on the special advanced features that were incorporated within the ROIC and supporting algorithms. In this framework we have addressed two important issues: the power consumption and the time span between shutter activations. Minimum power consumption is a critical issue for many un-cooled applications. SCD has addressed this by introducing the “power-save” concept accompanied with flexible dilution architecture. The paper will present recent results exhibiting the various advantages. One of the limiting factors on the performance of uncooled detectors is their vulnerability to ambient drift. Usually, even minor temperature fluctuations are manifested as high residual non-uniformity (RNU) or fixed pattern noise (FPN). As a result frequent shutter operations must be applied, with the risk of blocking the scenery in critical time frames. The challenge is thus twofold: to increase the time span between shutter corrections and achieve better control of its activation. For this purpose BIRD provides two complementing mechanisms: A real-time (frame-by-frame) ambient drift compensation accompanied by an RNU prediction mechanism. The paper will discuss these features in detail and present illustrative system implementations. The paper presented there appears in Infrared Photoelectronics, edited by Antoni Rogalski, Eustace L. Dereniak, Fiodor F. Sizov, Proc. SPIE Vol. 5957, 59570N (2005).     

Search for direct photons from S-Au collisions at 200 GeV/nucleon

The CERES experiment has measured inclusive photon production in S-Au collisions of 200 GeV/nucleon at the CERN SPS. No evidence for direct emission of photons was found. For the kinematic region 2.1<y<2.65 and 0.4 GeV/c<p⊥<2.0 GeV/c the yield andp⊥-dependence of the observed photons are well reproduced by hadron decays. Furthermore, their production rate is found to be proportional to the charged particle density. The systematic errors comparing the measured and expected photon yield result in an upper limit of 14% for the emission of direct photons in central S-Au collisions. For a photon source with a yield depending quadratically on the charged particle density the limit can be reduced to 7%.     

Search for supermassive nuclei in nature

We report on a search for supermassive nuclei in nature with masses up to 10⁷ amu. Such exotic nuclei might consist, for example, of stable strange matter, which comprises a mixture of up, down, and strange quarks, or of relic particles from the early Universe. The experiments are based on Rutherford backscattering of heavy ions, preferably²³⁸U, from various target samples. The measured parameters of a detected particle are its time-of-flight, scattering angle, and specific ionization. From this information the mass of the target nucleus can be inferred. Upper limits for the abundance of strange supermassive nuclei with massesA?4·10² to 10⁷ amu relative to the number of nucleons were found to be in the range 10^?11 to 10^?15. For the narrower mass rangeA ?10³ to 10⁴ amu the limit is 2· 10^?17.