The <Emphasis Type="Italic">Adhesion</Emphasis> GPCR GPR125 is specifically expressed in the choroid plexus and is upregulated following brain injury

Background  

GPR125 belongs to the family of Adhesion G protein-coupled receptors (GPCRs). A single copy of GPR125 was found in many vertebrate genomes. We also identified a Drosophila sequence, DmCG15744, which shares a common ancestor with the entire Group III of Adhesion GPCRs, and also contains Ig, LRR and HBD domains which were observed in mammalian GPR125.     

Orientable polymer fluids—suggestions from Ericksen's theory of anisotropic fluids

Ericksen's theory incorporates in the constitutive equations a vector n_i that characterizes the anisotropy of a fluid particle arising from flow induced orientation. The present study is an appraisal of the potential of such an approach in studying orientable polymeric fluids. The behavior of a normalized version of n_i (n_i → 0 at rest and n_i → 1 when fully stretched) is studied in simple shear, elongational, and converging flow fields. Following a discussion of the merits and the problems with this approach, a modification is proposed where directional anisotropy and stretching of a fluid particle are separated. Empirical extensions include the incorporation of a simple structure parameter in viscoelastic fluid theories.     

Zur Behandlung von Zufallssehwingungen mechanischer Bauteile infolge mehrfachkorrelierter stochastischer Erregungen

Übersicht Neben der zur Behandlung mechanischer Zufallsschwingungen gebräuchlichen Spektralmethode wird die Kovarianzanalyse mit ihrer vorteilhaften Schwingungsvarianzberechnung vorgestellt. Es wird gezeigt, daß diese Methode auch für mehrfachkorrelierte, in der Natur meßbare Zufallsvorgänge genutzt werden kann. Am Beispiel eines winderregten Turmtragwerks wird ein Vergleich zwischen Spektralmethode und Kovarianzanalyse gezogen.

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On the analysis of random vibrations caused by multi-correlated excitations

Summary In comparison with the wellknown method for calculating variances of random vibrations using spectral densities the method of the covariance analysis is illustrated. The efficiency of this method is demonstrated for multi-correlated random excitations which can be found in nature. An example with windinfluenced vibrations of a televisiontower is discussed for both methods.

     

New bounds on the condition number of the Hessian of the preconditioned variational data assimilation problem

Data assimilation algorithms combine prior and observational information, weighted by their respective uncertainties, to obtain the most likely posterior of a dynamical system. In variational data assimilation the posterior is computed by solving a nonlinear least squares problem. Many numerical weather prediction (NWP) centers use full observation error covariance (OEC) weighting matrices, which can slow convergence of the data assimilation procedure. Previous work revealed the importance of the minimum eigenvalue of the OEC matrix for conditioning and convergence of the unpreconditioned data assimilation problem. In this article we examine the use of correlated OEC matrices in the preconditioned data assimilation problem for the first time. We consider the case where there are more state variables than observations, which is typical for applications with sparse measurements, for example, NWP and remote sensing. We find that similarly to the unpreconditioned problem, the minimum eigenvalue of the OEC matrix appears in new bounds on the condition number of the Hessian of the preconditioned objective function. Numerical experiments reveal that the condition number of the Hessian is minimized when the background and observation lengthscales are equal. This contrasts with the unpreconditioned case, where decreasing the observation error lengthscale always improves conditioning. Conjugate gradient experiments show that in this framework the condition number of the Hessian is a good proxy for convergence. Eigenvalue clustering explains cases where convergence is faster than expected.     

Isocyanide based multicomponent reactions of oxazolidines and related systems

N-Alkyloxazolidines react in a multicomponent reaction with carboxylic acids and isocyanides to give N-acyloxyethylamino acid amides. The previously reported reaction conditions were improved using a design of experiments approach (DoE). Under the optimised conditions, good yields of the N-acyloxyethylamino acid amide products are obtained both via a three- or four-component approach from N-alkylethanolamines, aldehydes/ketones, isocyanides and carboxylic acids. The reaction of oxazolidines without a nitrogen substituent was found to give either the expected Ugi products or the N-acyloxyethylamino acid amides depending on the choice of reaction conditions. Optimised reaction conditions were also developed for the ring-expansion of oxazolidines to morpholin-2-ones via reaction with an isocyanide followed by hydrolysis. The mechanistic pathway of the multicomponent reaction was briefly investigated using an ¹⁸O labelling experiment. The carboxylic acid component can be replaced by a range of other acidic nucleophiles including thiobenzoic acid, thiophenol or 5-phenyltetrazole, which are incorporated via an alternative pathway. These latter reactions can also be applied to 2-aminotetrahydrofurans, 2-aminotetrahydropyrans or 4-hydroxybut-2-one, further extending the structural diversity of the multicomponent reaction products.     

Synthesis and Modeling of Acridine Dyes as Potential Photosensitizers for Dye‐Sensitized Photovoltaic Applications †

We have synthesized novel aromatic amine‐substituted acridine dyes as potential candidates for the photosensitizers in dye sensitized nanocrystalline semiconductor based solar cells (DSSC) cells. The protonation and quaternization of the acridine nitrogen led to acridine dyes with extended absorption from 400–800 nm. Computational modeling was used to evaluate a variety of structures to achieve insights for correlating these types of molecular structures with predicted absorption spectra. Pertinent dihedral angles as well as bond lengths were evaluated to assess and compare planarity and conjugation for these dyes. Other predictions include plots of the HOMO and LUMO levels to qualitatively examine electron distributions and the potential for electron injection. The results from modeling along with the experimental data consisting of synthesis, characterization and UV‐visible absorption properties of the selected dyes are presented.     

Vibrational corrections to geometries of transition metal complexes from density functional theory

Zero-point vibrational corrections are computed at the BP86/AE1 level for the set of 50 transition-metal/ligand bonds that have recently been proposed as testing ground for DFT methods, because of the availability of precise experimental gas-phase geometries (Bühl and Kabrede, J Chem Theory Comput 2006, 2, 1282). These corrections are indicated to be transferable to a large extent between various density-functional/basis-set combinations, so that they can be used to estimate zero-point averaged r0g distances from re values optimized at other theoretical levels. Applying this approach to a number of popular DFT levels does not, in general, improve their overall accuracy in terms of mean and standard deviations from experiment. The hybrid variant of the meta-functional TPSS is confirmed as promising choice for computing structures of transition-metal complexes.