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The recently developed Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) is investigated for a wide range of model parameters including the parameter m representing the chain length and the thermodynamic temperature T and pressure p. This approach is based upon the first-order thermodynamic perturbation theory for chain molecules developed by Wertheim and Chapman et al. and includes dispersion interactions via the second-order perturbation theory of Barker and Henderson. We systematically study a hierarchy of models which are based on the PC-SAFT approach using analytical model calculations and Monte Carlo simulations. For one-component systems we find that the analytical model in contrast to the simulation results exhibits two phase-separation regions in addition to the common gas-liquid coexistence region: One phase separation occurs at high density and low temperature. The second demixing takes place at low density and high temperature where usually the ideal gas phase is expected in the phase diagram. These phenomena, which are referred to as "liquid-liquid" and "gas-gas" equilibria, give rise to multiple critical points in one-component systems, as well as to critical end points (CEP) and equilibria of three fluid phases, which can usually be found in multicomponent mixtures only. Furthermore, it is shown that the "liquid-liquid" demixing in this model is not a consequence of a "softened" repulsive interaction as assumed in the theoretical derivation of the model. Experimental data for the melt density of polybutadiene with molecular mass Mw=45000g/mol are correlated here using the PC-SAFT equation. It is shown that the discrepancies in modeling the polymer density at ambient temperature and high pressure can be traced back to ..., Comment: 33 pages, 14 figures

A complex mutation in DFNA5, resulting in exon 8 skipping, causes autosomal dominant hearing impairment, which starts in the high frequencies between 5 and 15 years of age and progressively affects all frequencies. To study its function in vivo, Dfna5 knockout mice were generated through the deletion of exon 8, simultaneously mimicking the human mutation. To test the hearing impairment, frequency-specific Auditory Brainstem Response (ABR) measurements were performed at different ages in two genetic backgrounds (C57Bl/6J and CBA/Ca), but no differences between Dfna5-/- and Dfna5+/+ mice could be demonstrated. Morphological studies demonstrated significant differences in the number of fourth row outer hair cells between Dfna5-/- mice and their wild-type littermates. These results were obtained in both genetic backgrounds, albeit with opposite effects. In contrast to the results obtained in Dfna5-/- zebrafish, we did not observe different UDP-glucose dehydrogenase and hyaluronic acid levels in Dfna5-/- mice when compared to Dfna5+/+ mice.

The data collection parameters used in a diffraction experiment have a strong impact on the quality of the acquired data. A careful choice of parameters leads to better data and can make the difference between success and failure in phasing attempts and better data will also result in a more accurate atomic model. The selection of data acquisition parameters has to account for the application of the data in various phasing methods or high-resolution refinement. Furthermore, experimental factors like crystal characteristics and the properties of X-ray source and detector have to be considered. Hybrid Pixel Detectors are now for several years in use in macromolecular crystallography and an increasing number of synchrotron beamlines as well as laboratory instruments are equipped with such detectors. Photon-counting Hybrid Pixel Detectors have fundamentally different characteristics and offer various advantages over other detector technologies. To fully exploit the advantages of Hybrid Pixel Detectors, different data collection strategies than those established for other detector types have to be applied. Fine φ-slicing is a strategy particularly well suited because of the fast readout time and the absence of readout noise. This strategy was systematically investigated collecting a large number of data sets from crystals of four different proteins to investigate the benefit of fine φ-slicing on data quality with a noise-free detector in practice. The results show that fine φ-slicing can substantially improve scaling statistics and anomalous signal. Furthermore, when collecting data in continuous rotation at high frame rates up to hundreds of images per second, quality might be impaired by detector readout. Results on the influence of readout time on data quality will be presented and strategies to easily avoid detrimental effects of detector readout will be discussed.

The OP-FTIR measurement technique and other remote sensing systems (for example UV-DOAS and TDL) become more and more established methods to monitor the ambient air quality. Some quality assurance procedures have to be done on the field measurement data to get more reliable results. Both the German and US-EPA standardization documents for the OP-FTIR technique prescribe such procedures to check the data. To assess the applicability of these procedures, OP-FTIR field measurement data of a three month continuous measurement campaign were evaluated concerning the signal strength, the influence of stray light, water vapor concentration, baseline noise, wave number shifts and the detection limits. In addition the long time signal stability of the OP-FTIR systems and the UV-DOAS systems are intercompared. The results of the several quality assurance procedures will be presented in this paper.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We investigate the phase behavior of symmetric AB diblock copolymers confined into a thin film. The film boundaries are parallel, impenetrable and attract the A component of the diblock copolymer. Using a self-consistent field technique [M.W. Matsen, J.Chem.Phys. {\bf 106}, 7781 (1997)], we study the ordered phases as a function of incompatibility $\chi$ and film thickness in the framework of the Gaussian chain model. For large film thickness and small incompatibility, we find first order transitions between phases with different number of lamellae which are parallel oriented to the film boundaries. At high incompatibility or small film thickness, transitions between parallel oriented and perpendicular oriented lamellae occur. We compare the self-consistent field calculations to Monte Carlo simulations of the bond fluctuation model for chain length N=32. In the simulations we quench several systems from $\chi N=0$ to $\chi N=30$ and monitor the morphology into which the diblock copolymers assemble. Three film thicknesses are investigated, corresponding to parallel oriented lamellae with 2 and 4 interfaces and a perpendicular oriented morphology. Good agreement between self-consistent field calculations and Monte Carlo simulations is found., Comment: to appear in J.Chem.Phys

We investigate interfacial properties between two highly incompatible polymers of different stiffness. The extensive Monte Carlo simulations of the binary polymer melt yield detailed interfacial profiles and the interfacial tension via an analysis of capillary fluctuations. We extract an effective Flory-Huggins parameter from the simulations, which is used in self-consistent field calculations. These take due account of the chain architecture via a partial enumeration of the single chain partition function, using chain conformations obtained by Monte Carlo simulations of the pure phases. The agreement between the simulations and self-consistent field calculations is almost quantitative, however we find deviations from the predictions of the Gaussian chain model for high incompatibilities or large stiffness. The interfacial width at very high incompatibilities is smaller than the prediction of the Gaussian chain model, and decreases upon increasing the statistical segment length of the semi-flexible component., Comment: to appear in J.Chem.Phys

The realizable integration level of rapid single-flux quantum (RSFQ) circuits has reached the order of magnitude of 20 000 Josephson junctions, which enables the creation of advanced complex circuits such as microprocessors or digital signal processors. During the design of those complex circuits, behavioral arrangement alone is insufficient; instead, the inclusion of statistical spread is required for timing and parameter verification. The simulation of complex circuits combined with the consideration of timing jitter effects is a very challenging task for both transient simulation on the electrical network level and simulation with hardware description languages. In this paper, a new approach based on discrete-event simulations is presented. By this method, the pulse-driven characteristics of RSFQ circuits can be directly transferred into a model describing the behavior on the transaction level. The realized models of basic RSFQ cells include stochastic timing effects. This approach is demonstrated by modeling a nontrivial cell and compared against the conventional transient simulation concerning the accuracy of the results and the computation time.

Monte Carlo simulations within the grand canonical ensemble are used to obtain the joint distribution of density and energy fluctuations $p_L(\rho,u)$ for two model fluids: a decorated lattice gas and a polymer system. In the near critical region the form of $p_L(\rho,u)$ is analysed using a mixed field finite-size-scaling theory that takes account of liquid-vapour asymmetry. Field mixing transformations are performed that map $p_L(\rho,u)$ onto the joint distribution of critical scaling operators \ptMEstar\ appropriate to the Ising fixed point. Carrying out this procedure permits a very accurate determination of the critical point parameters. By forming various projections of \ptMEstar , the full universal finite-size spectrum of the critical density and energy distributions of fluids is also obtained. In the sub-critical coexistence region, an examination is made of the influence of field mixing on the asymmetry of the density distribution., Comment: 19 pages Latex, 15 Figures available on request. Report Number #IP-94.153

We present a new Monte-Carlo method for estimating the chemical potential of model polymer systems. The method is based upon the gradual insertion of a penetrable `ghost' polymer into the system and is effective for large chain lengths and at high densities. Insertion of the ghost chain is facilitated by use of an expanded ensemble in which weighted transitions are permitted between states characterising the strength of the excluded volume and thermal interactions experienced by the ghost chain. We discuss the implementation and optimisation of the method within the framework of the bond fluctuation model, and demonstrate its precision by a calculation of the finite-size corrections to the chemical potential., Comment: 12 pages Latex, Report Number #IP-94.127

The data-collection parameters used in a macromolecular diffraction experiment have a strong impact on data quality. A careful choice of parameters leads to better data and can make the difference between success and failure in phasing attempts, and will also result in a more accurate atomic model. The selection of parameters has to account for the application of the data in various phasing methods or high-resolution refinement. Furthermore, experimental factors such as crystal characteristics, available experiment time and the properties of the X-ray source and detector have to be considered. For many years, CCD detectors have been the prevalent type of detectors used in macromolecular crystallography. Recently, hybrid pixel X-ray detectors that operate in single-photon-counting mode have become available. These detectors have fundamentally different characteristics compared with CCD detectors and different data-collection strategies should be applied. Fine φ-slicing is a strategy that is particularly well suited to hybrid pixel detectors because of the fast readout time and the absence of readout noise. A large number of data sets were systematically collected from crystals of four different proteins in order to investigate the benefit of fine φ-­slicing on data quality with a noise-free detector. The results show that fine φ-slicing can substantially improve scaling statistics and anomalous signal provided that the rotation angle is comparable to half the crystal mosaicity.

The chemokine receptor CXCR3 binds CXCL9, CXCL10 and CXCL11 and promotes the trafficking of activated T-cells. Although these chemokines are highly elevated in the CNS in MS and the animal model, experimental autoimmune encephalomyelitis (EAE), their role is unknown. Here we show that while IFN-γ is the principal mediator of CXCR3 ligand gene expression in the CNS in EAE, the cellular localization of the individual chemokine genes is divergent suggesting functional specialisation of the CXCR3 ligand chemokines. Transgenic mice (GF-) were generated with astrocyte-production of CXCL9, CXCL10 or CXCL11. These mice do not develop neurological disease. In GF-CXCL10 and -CXCL11 mice, modest non-reactive leukocytic infiltrates were seen in the CNS. Thus, these chemokines when produced chronically are a poor stimulus for the CNS recruitment and activation of T-cells. The role of CXCR3 signaling in MOG-induced EAE was examined in CXCR3 KO mice and in GF-CXCL9, -CXCL10 or -CXCL11 mice. CXCR3 KO, GF-CXCL9 and -CXCL11 mice had more severe EAE with widely disseminated demyelinating lesions throughout the CNS. In CXCR3 KO mice with EAE the number of suppressor Treg cells in the brain was reduced. Thus, in EAE, CXCR3 chemokine ligands:have non-redundant functions,are not involved in the initial recruitment of effector T-cells to the CNS, andretain T-cells to the perivascular space and foster Treg cell interactions thereby limiting lesion spread and tissue destruction. Support: NIH NS044905.

Molecular dynamics simulations of a short-chain polymer melt between two brush-covered surfaces under shear have been performed. The end-grafted polymers which constitute the brush have the same chemical properties as the free chains in the melt and provide a soft deformable substrate. Polymer chains are described by a coarse-grained bead-spring model with Lennard-Jones interactions between the beads and a FENE potential between nearest neighbors along the backbone of the chains. The grafting density of the brush layer offers a way of controlling the behavior of the surface without altering the molecular interactions. We perform equilibrium and non-equilibrium Molecular Dynamics simulations at constant temperature and volume using the Dissipative Particle Dynamics thermostat. The equilibrium density profiles and the behavior under shear are studied as well as the interdigitation of the melt into the brush, the orientation on different length scales (bond vectors, radius of gyration, and end-to-end vector) of free and grafted chains, and velocity profiles. The viscosity and slippage at the interface are calculated as functions of grafting density and shear velocity., Comment: 12 pages, submitted to J Chem Phys

Information on responses of auditory nerve fibers in birds is generally limited to the low and mid‐frequency ranges of hearing, due to anatomical constraints using the standard ganglion cell approach through the opened tympanic recess. Intracranially recorded responses of single units from the auditory nerve and the overlying cochlear nuclei in the pigeon (Columba livia) were compared to those recorded from the ganglion. Characteristic frequencies (CFs) of auditory units ranged from 0.08–5.7 kHz with intracranial compared to 0.06–1.6 kHz with intrascalar recordings. Response properties were qualitatively and quantitatively comparable in the overlapping CF ranges (0.08–1.6 kHz). Mean spontaneous firing rate decreased monotonically with CF. The CF thresholds were lowest (0–5 dB SPL) in the CF range 0.6–1.5 kHz. Mean sharpness of tuning (Q10 dB) varied nonmonotonically with CF, with a maximum near 2 kHz. In addition, Q10 dB of pigeon auditory units up to CFs of 2 kHz was much higher than that of gerbil (Meriones unguiculatus) primary fibers in the same CF range, recorded in the same setup. As it is highly improbable that mechanical tuning in birds would by far exceed that in mammals, this finding is further evidence for a difference in avian and mammalian tuning mechanisms. [Work supported by the DFG, SFB 269.]

Extending the Swendsen-Wang cluster algorithm to include both bulk (H) and surface fields (H_1) in L x L x D Ising films of thickness D and two free L x L surfaces, a Monte Carlo study of the capillary condensation critical point of the model is presented. Applying a finite-size scaling analysis where the lateral linear dimension L is varied over a wide range, the critical temperature T_c(D) and the associated critical field H_c(D) are estimated for 4, Comment: 34 pages, RevTex, 16 postscript figures, accepted for publication in J. Chem. Phys

We study the effect of surface fields on the interfacial properties of a binary polymer melt confined between two parallel walls. Each wall attracts a different component of the blend by a non-retarded van der Waals potential. An interface which runs parallel to the surfaces is stabilized in the center of the film. Using extensive Monte Carlo simulations we study the interfacial properties as a function of the film thickness, the strength of the surface forces and the lateral size over which the profiles across the film are averaged. We find evidence for capillary wave broadening of the apparent interfacial profiles. However, the apparent interfacial width cannot be described quantitatively by a simple logarithmic dependence on the film thickness. The Monte Carlo simulations reveal that the surface fields give rise to an additional reduction of the intrinsic interfacial width and an increase of the effective interfacial tension upon decreasing the film thickness. These modifications of the intrinsic interfacial properties are confirmed by self-consistent field calculations. Taking account of the thickness dependence of the intrinsic interfacial properties and the capillary wave broadening, we can describe our simulation results quantitatively., to appear in J.Chem.Phys

This article presents an overview of the SmartSite research project that adopts machine learning, decision theory and distributed artificial intelligence to design and test a multi-agent system (MAS) for asphalt road construction. SmartSite puts major emphasis on sensing and communication technologies that integrate real-time automated information exchange in the supply chain of road construction. As part of the larger SmartSite project, this article introduces a novel real-time path planning system for compactors and presents the results of several simulation and field realistic experiments conducted to evaluate the system in a sophisticated simulation and harsh construction environment, respectively. The system operates based on Belief-Desire-Intention (BDI) software agents and real-time sensory inputs. The newly developed integrated and information rich process benefits asphalt compactor operators, as they are now capable to control their machinery and react to changing environmental, material-related and process-related disturbances or changes. This improves the quality of the delivery and laying of asphalt material, prevents compactors from over-compacting certain road segments, increases the road's pavement longevity during the operational life cycle phase; refocuses the work tasks of the site managers, and reduces the construction budget and schedule. The system's ability to maneuver an asphalt roller during real-word operation also makes it an important step towards a fully automated asphalt compactor.