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The balloon-borne cosmic-ray experiment CREAM (Cosmic Ray Energetics And Mass) has completed two flights in Antarctica, with a combined duration of 70 days. One of the detectors in the payload is the SCD (Silicon Charge Detector) that measures the charge of high energy cosmic rays. The SCD was assembled with silicon sensors. A sensor is a 4 x 4 array of DC-coupled PIN diode pixels with the total active area of 21 x 16 [mm.sup.2]. The SCD used during the first flight (December 2004-January 2005) was a single layer device, then upgraded to a dual layer device for the second flight (December 2005-January 2006), covering the total sensitive area of 779 x 795 [mm.sup.2]. Flight data demonstrated that adding a second layer improved SCD performance, showing excellent particle charge resolution. With a total dissipation of 136 W for the dual layer system, special care was needed in designing thermal paths to keep the detector temperature within its operational range. As a consequence, flight temperatures of the SCD, even at diurnal maximum were kept below 38[degrees]C. The SCD mechanical structure was designed to minimize the possibility of damage to the sensors and electronics from the impacts of parachute deployment and landing. The detector was recovered successfully following the flight and is being refurbished for the next flight in 2007. Details of construction, operation, and performance are presented for the dual-layered SCD flown for the second CREAM flight. Index Terms--Balloon payload, charge measurement, cosmic rays, silicon sensors.

RNA‐Schalter unterscheiden genau zwischen ihren eigentlichen Liganden und chemisch ähnlichen Molekülen. Ein bemerkenswertes Beispiel für eine sehr hohe Ligandenspezifität ist ein synthetischer auf Neomycin reagierender RNA‐Schalter. Paromomycin unterscheidet sich von Neomycin nur durch die Substitution einer Amino‐ durch eine Hydroxygruppe. Es bindet ebenfalls an den Neomycin‐RNA‐Schalter, schaltet ihn aber nicht. Hier zeigen wir, dass der Verlust einiger weniger wichtiger intermolekularer Wechselwirkungen an einer einzigen Position des Paromomycin‐Komplexes zu globalen Änderungen in der Konformationsdynamik der RNA führt. Außerdem identifizieren wir ein Netzwerk an intramolekularen Wechselwirkungen, über die der Verlust der lokalen intermolekularen Wechselwirkungen in entfernte Bereiche des Moleküls kommuniziert und in Änderungen der globalen Dynamik übersetzt wird. Daher beruht die Spezifität dieses RNA‐Schalters auf Unterschieden in der strukturellen Dynamik und nicht auf statischen Strukturunterschieden. Feinheiten: Ein synthetischer Neomycin‐RNA‐Schalter bindet auch Paromomycin, das sich von Neomycin nur durch die Substitution einer Amino‐ durch eine Hydroxygruppe unterscheidet, wird von diesem Liganden aber nicht geschaltet, da der Verlust einiger weniger wichtiger intermolekularer Wechselwirkungen an einer einzigen Position des Paromomycin‐Komplexes zu globalen Änderungen in der Konformationsdynamik der RNA führt. [ABSTRACT FROM AUTHOR]

To ensure appropriate metabolic regulation, riboswitches must discriminate efficiently between their target ligands and chemically similar molecules that are also present in the cell. A remarkable example of efficient ligand discrimination is a synthetic neomycin-sensing riboswitch. Paromomycin, which differs from neomycin only by the substitution of a single amino group with a hydroxy group, also binds but does not flip the riboswitch. Interestingly, the solution structures of the two riboswitch-ligand complexes are virtually identical. In this work, we demonstrate that the local loss of key intermolecular interactions at the substitution site is translated through a defined network of intramolecular interactions into global changes in RNA conformational dynamics. The remarkable specificity of this riboswitch is thus based on structural dynamics rather than static structural differences. In this respect, the neomycin riboswitch is a model for many of its natural counterparts. [ABSTRACT FROM AUTHOR]

Abstract: A key issue in fundamental physics is the nature of non-baryonic dark matter in the universe. Among the candidates proposed by the particle physics community are neutralinos whose annihilation in the Galactic halo can produce antiprotons with a characteristic spectrum. Several balloon and space borne experiments have been actively looking to detect the neutralino signature in cosmic antiprotons. This task is however hampered by the existence of a secondary “background” flux of antiprotons produced in the interactions of cosmic-ray particles in the interstellar medium. A notable difficulty is that a self-consistent and complete model of cosmic-ray propagation in the Galaxy has thus far been elusive. When subtracting the secondary background from the observed data, it is therefore critical that all viable models of secondary cosmic-ray antiproton propagation be thoroughly examined, and all uncertainties stemming from plurality of the models be duly considered. In this paper we concentrate on three particular models of Diffusion, Galactic Wind, and Distributed Stochastic Reacceleration, and discuss the predicted antiproton spectrum in each model. [Copyright &y& Elsevier]

Abstract: The Advanced Thin Ionization Calorimeter (ATIC) balloon experiment is designed to investigate the composition and energy spectra of cosmic rays at the highest energies currently accessible by direct measurements, i.e., the region up to 100TeV. The instrument consists of a silicon matrix for charge measurement, a graphite target (0.75 nuclear interaction length) to induce hadronic interactions, three layers of scintillator strip hodoscopes for triggering and trajectory reconstruction, and a Bismuth Germanate (BGO) crystal calorimeter (18 radiation lengths) to measure particle energies. ATIC has had two successful Long Duration Balloon (LDB) flights from McMurdo, Antarctica: one from 12/28/00 to 01/13/01 and the other from 12/29/02 to 01/18/03. We present the energy spectra of protons and helium extracted from the first flight, over the energy range from 100GeV to 100TeV, and compare them with the results from other experiments at both the lower and higher energies. ATIC-1 results do not indicate significant differences in spectral shape between protons and helium over the investigated energy range. [Copyright &y& Elsevier]

Abstract: The random nature of sources (the supernova remnants) leads to the fluctuations of cosmic ray intensity in space and time. We calculate the expected fluctuations in a flat-halo diffusion model for particles with energies from 0.1 to 103 TeV. The data on energy spectra and anisotropy of very high energy protons, nuclei and electrons, and the astronomical data on supernova remnants, the potential sources of cosmic rays, are used to constrain the value of the cosmic-ray diffusion coefficient and its dependence on energy. [Copyright &y& Elsevier]

The objective of this retrospective study was to analyze the effect of the intensity modulated radiotherapy (IMRT) of the head and neck region on root canal-treated teeth and their periapical changes due to radiation. Patients undergoing IMRT of the head and neck region were evaluated. Different types of teeth (molars, premolars, incisors and canines) were compared. Panoramic and dental radiographs were used to assess the periapical region of root canal-treated teeth using the periapical index (PAI) before and after radiotherapy (RT) and put in relation to the radiation dose per tooth. Further parameters (patient-, therapy- and tooth-related factors) were included in this study. One hundred and twenty-four root canal-treated teeth (maxilla and mandible) of 51 patients were observed. A radiolucency in the periapical region was seen in 34.7% of the samples before IMRT and an increasing number of 46% after IMRT (p-value 0.092). Clinical or radiological signs of osteoradionecrosis could not be determined. The only statistically significant difference was detected in regions irradiated with less than 40 Gy (p-value 0.045). In regions irradiated with higher doses (>40 Gy), comparable pathologies increased in non-significant numbers. A statistically significant increase of periapical pathologies was detected in premolars of the maxilla. The observations reported here suggest that a high radiation dose during IMRT has no significant consequences on root canal-treated teeth. To compare the success of endodontic treatment before versus after IMRT, further research needs to be done.