Monte Carlo Simulation of Long Chain Polymer Melts: Crossover from Rouse to Reptation Dynamics

We present data of Monte Carlo simulations for monodisperse linear polymer chains in dense melts with degrees of polymerization between N=16 and N=512. The aim of this study is to investigate the crossover from Rouse-like dynamics for short chains to reptation-like dynamics for long chains. To address this problem we calculate a variety of different quantities: standard mean-square displacements of inner monomers and of the chain's center of mass, the recently proposed cubic invariant, persistence of bond-vector orientation with time, and the auto-correlation functions of the bond vector, the end-to-end vector and the Rouse modes. This analysis reveals that the crossover from non- to entangled dynamics is very protracted. Only the largest chain length N=512, which is about 13 times larger than the entanglement length, shows evidence for reptation.Comment: 38 pages of REVTeX, 14 PostScript figure

Free geometric adjustment of the SECOR Equatorial Network (Solution SECOR-27)

The basic purpose of this experiment is to compute reduced normal equations from the observational data of the SECOR Equatorial Network obtained from DMA/Topographic Center, D/Geodesy, Geosciences Div. Washington, D.C. These reduced normal equations are to be combined with reduced normal equations of other satellite networks of the National Geodetic Satellite Program to provide station coordinates from a single least square adjustment. An individual SECOR solution was also obtained and is presented in this report, using direction constraints computed from BC-4 optical data from stations collocated with SECOR stations. Due to the critical configuration present in the range observations, weighted height constraints were also applied in order to break the near coplanarity of the observing stations

Design of magnetic traps for neutral atoms with vortices in type-II superconducting micro-structures

We design magnetic traps for atoms based on the average magnetic field of vortices induced in a type-II superconducting thin film. This magnetic field is the critical ingredient of the demonstrated vortex-based atom traps, which operate without transport current. We use Bean's critical-state method to model the vortex field through mesoscopic supercurrents induced in the thin strip. The resulting inhomogeneous magnetic fields are studied in detail and compared to those generated by multiple normally-conducting wires with transport currents. Various vortex patterns can be obtained by programming different loading-field and transport current sequences. These variable magnetic fields are employed to make versatile trapping potentials.Comment: 11 pages, 14 figure

Exploring molecular complexity with ALMA (EMoCA): Detection of three new hot cores in Sagittarius B2(N)

The SgrB2 molecular cloud contains several sites forming high-mass stars. SgrB2(N) is one of its main centers of activity. It hosts several compact and UCHII regions, as well as two known hot molecular cores (SgrB2(N1) and SgrB2(N2)), where complex organic molecules are detected. Our goal is to use the high sensitivity of ALMA to characterize the hot core population in SgrB2(N) and shed a new light on the star formation process. We use a complete 3 mm spectral line survey conducted with ALMA to search for faint hot cores in SgrB2(N). We report the discovery of three new hot cores that we call SgrB2(N3), SgrB2(N4), and SgrB2(N5). The three sources are associated with class II methanol masers, well known tracers of high-mass star formation, and SgrB2(N5) also with a UCHII region. The chemical composition of the sources and the column densities are derived by modelling the whole spectra under the assumption of LTE. The H2 column densities are computed from ALMA and SMA continuum emission maps. The H2 column densities of these new hot cores are found to be 16 up to 36 times lower than the one of the main hot core Sgr B2(N1). Their spectra have spectral line densities of 11 up to 31 emission lines per GHz, assigned to 22-25 molecules. We derive rotational temperatures around 140-180 K for the three new hot cores and mean source sizes of 0.4 for SgrB2(N3) and 1.0 for SgrB2(N4) and SgrB2(N5). SgrB2(N3) and SgrB2(N5) show high velocity wing emission in typical outflow tracers, with a bipolar morphology in their integrated intensity maps suggesting the presence of an outflow, like in SgrB2(N1). The associations of the hot cores with class II methanol masers, outflows, and/or UCHII regions tentatively suggest the following age sequence: SgrB2(N4), SgrB2(N3), SgrB2(N5), SgrB2(N1). The status of SgrB2(N2) is unclear. It may contain two distinct sources, a UCHII region and a very young hot core.Comment: Accepted for publication in A&A, 24 pages, 23 figure

Space Storable Rocket Technology (SSRT) basic program

The Space Storable Rocket Technology Program (SSRT) was conducted to establish a technology for a new class of high performance and long life bipropellant engines using space storable propellants. The results are described. Task 1 evaluated several characteristics for a number of fuels to determine the best space storable fuel for use with LO2. The results indicated that LO2-N2H4 is the best propellant combination and provides the maximum mission/system capability maximum payload into GEO of satellites. Task 2 developed two models, performance and thermal. The performance model indicated the performance goal of specific impulse greater than or = 340 seconds (sigma = 204) could be achieved. The thermal model was developed and anchored to hot fire test data. Task 3 consisted of design, fabrication, and testing of a 200 lbf thrust test engine operating at a chamber pressure of 200 psia using LO2-N2H4. A total of 76 hot fire tests were conducted demonstrating performance greater than 340 (sigma = 204) which is a 25 second specific impulse improvement over the existing highest performance flight apogee type engines

Optimal cutoff-value of Siemens cardiac troponin I assay in patients with kidney disease for the early diagnosis of acute myocardial infarction

Purpose: The recent introduction of more sensitive cardiac troponin (cTn) assays improved the early diagnosis of acute myocardial infarction (AMI). However, its diagnostic utility has never been tested in patients with kidney disease (KD), who are known to have elevated levels of cTn already in the absence of AMI, which may lead to a lower diagnostic value of more sensitive cTn in this high-risk subgroup. Methods: We conducted an international multicenter study to examine the diagnostic accuracy of the Siemens cTnI Ultra assay in 1997 consecutive patients presenting to the emergency department with symptoms suggestive of AMI, of whom 343 (17%) were determined to have KD (MDRD GFR <60ml/min/1.73m2) and to derive the optimal cutoff-value for the diagnosis of AMI in patients with KD. The diagnostic accuracy was further compared to a conventional cTn assay (Roche Troponin T fourth generation). The final diagnosis was adjudicated by two independent cardiologists based on hs-cTnT. Results: AMI was the final diagnosis in 35% (n=120) of all KD-patients as compared to 18% in patients with normal kidney function (p<0.001). Among KD-patients with other diagnoses than AMI, baseline hs-cTnI-levels were elevated above the 99thpercentile in 20%, In patients with KD the diagnostic accuracy at presentation, quantified by the area under the receiver-operator-characteristic curve (AUC), was significantly greater for Siemens cTnI as compared to the standard cTnT assay (AUC for cTnI, 0.88 vs. AUC for the standard assay, 0.82, p=0.013). In patients presenting within three hours after the onset of chest pain, the superiority of Siemens cTnI over conventional cTnT was even more pronounced (AUC 0.86 vs. 0.72, p=0.005). In KD, the optimal hs-cTnI cutoff derived from the ROC curve was 46 ng/l compared to 19 ng/l in patients with normal kidney function (standard 99th percentile 40 ng/l, provided by the manufacturer). Conclusions: The Siemens cTnI Ultra assay has a very high diagnostic accuracy also in KD-patients and is superior to a conventional cTnT-assay. Mild cTnI elevations are common in non-AMI patients. The optimal cutoff-level in KD-patients seems to be around the 99th percentile of a standard population, whereas the optimal cutoff-level in patients with normal kidney function tends to be only half of the suggested cutoff-value. ClinicalTrials.gov number, NCT0047058