Spectroscopic fingerprints of toroidal nuclear quantum delocalization via ab initio path integral simulations

We investigate the quantum‐mechanical delocalization of hydrogen in rotational symmetric molecular systems. To this purpose, we perform ab initio path integral molecular dynamics simulations of a methanol molecule to characterize the quantum properties of hydrogen atoms in a representative system by means of their real‐space and momentum‐space densities. In particular, we compute the spherically averaged momentum distribution n(k) and the pseudoangular momentum distribution n(k_θ). We interpret our results by comparing them to path integral samplings of a bare proton in an ideal torus potential. We find that the hydroxyl hydrogen exhibits a toroidal delocalization, which leads to characteristic fingerprints in the line shapes of the momentum distributions. We can describe these specific spectroscopic patterns quantitatively and compute their onset as a function of temperature and potential energy landscape. The delocalization patterns in the projected momentum distribution provide a promising computational tool to address the intriguing phenomenon of quantum delocalization in condensed matter and its spectroscopic characterization. As the momentum distribution n(k) is also accessible through Nuclear Compton Scattering experiments, our results will help to interpret and understand future measurements more thoroughly. © 2012 Wiley Periodicals, Inc.     

Rectangular loop-gap resonator with the light access to the sample

A modified rectangular loop-gap resonator for X-band electron paramagnetic resonance (EPR) studies of aqueous samples, enabling the light access, is described. Changes introduced into rectangular resonator geometry, previously presented in Piasecki et al. (1998) [1], and redesigned coupling structure lead to the better thermal and mechanical stability. The modified structure makes provision for the controlled light access to the sample placed in a flat cell during an EPR experiment. The sensitivity of the resonator for aqueous samples as well as an experimentally tested microwave magnetic field homogeneity are presented. Results of simulations and experimental tests indicate that the presence of light access holes in the resonator's front side does not disturb the uniformity of microwave magnetic field distribution in the nodal plane. The optimal flat cell thickness for unsaturable and saturable aqueous samples has been calculated for this new structure. A modified rectangular geometry of the loop-gap resonator ensures a good performance for aqueous samples allowing its convenient and efficient light illumination during EPR signal recording .     

Measurements and predictions of hooded crow (Corvus corone cornix) call propagation over open field habitats

In a study of hooded crow communication over open fields an excellent correspondence is found between the attenuation spectra predicted by a "turbulence-modified ground effect plus atmospheric absorption" model, and crow call attenuation data. Sound propagation predictions and background noise measurements are used to predict an optimal frequency range for communication ("sound communication window") from an average of crow call spectra predicted for every possible combination of the sender/receiver separations 300, 600, 900, and 1200 m and heights 3,6,9 m thereby creating a matrix assumed relevant to crow interterritorial communication. These predictions indicate an optimal frequency range for sound communication between 500 Hz and 2 kHz. Since this corresponds to the frequency range in which crow calls have their main energy and crow hearing in noise is particularly sensitive, it suggests a specific adaptation to the ground effect. Sound propagation predictions, together with background noise measurements and hearing data, are used to estimate the radius of the hooded crow active space. This is found to be roughly 1 km in moderately windy conditions. It is concluded that the propagation modeling of the sort introduced here could be used for assessing the impact of human noise on animal communication.     

Experimental investigation of the plasma-wall transition

We report on measurements of the ion velocity distribution as a function of distance to a target immersed in a magnetized argon plasma. Two situations are investigated: (a) practically the whole plasma streams onto a large target, and (b) the size of the target is significantly smaller than the plasma diameter. The Mach number M=u/c_{s} decreases from M=1 at the target surface to values around 0.5 at a typical scale of lambda_{a}=30 mm and lambda_{b}=5 mm, respectively. In order to explain these small decay lengths, the measurements of case (a) are compared with a source-diffusion model and those of (b) to Hutchinson's model. In (a) good agreement between modeling and experiment is obtained assuming a low neutral gas temperature. The data in (b) also agree excellently with modeled profiles, although the large fitting parameter D=20 m;{2}/s indicates that other processes than diffusion contribute significantly to the transport.     

The significance of anti-neuronal antibodies for acute psychiatric disorders: a retrospective case–controlled study

Background

The clinical significance of anti-neuronal antibodies in patients with psychiatric disorders, but without encephalitis, remains unknown. In patients admitted to acute psychiatric inpatient care we aimed to identify clinical features distinguishing anti-neuronal antibody positive patients from matched controls.

Results

Patients who were serum-positive to N-methyl d-aspartate receptor (NMDAR) (n?=?21), contactin-associated protein 2 (CASPR2) (n?=?14) and/or glutamic acid decarboxylase 65 (GAD65) (n?=?9) antibodies (cases) were age and sex matched (1:2) with serum-negative patients from the same cohort (controls). The prevalence and severity of psychiatric symptoms frequently encountered in NMDAR, CASPR2 and GAD65 antibody associated disorders were compared in cases and controls. NMDAR, CASPR2 and GAD65 antibody positive patients did not differ in their clinical presentation from matched serum negative controls.

Conclusion

In this cohort, patients with and without NMDAR, CASPR2 and GAD65 antibodies admitted to acute psychiatric inpatient care had similar psychiatric phenotypes. This does not exclude their clinical relevance in subgroups of patients, and studies further investigating the clinical significance of anti-neuronal antibodies in patients with psychiatric symptomatology are needed.

     

Inhomogeneous Lattice Paths, Generalized Kostka Polynomials and A n −1 Supernomials

Inhomogeneous lattice paths are introduced as ordered sequences of rectangular Young tableaux thereby generalizing recent work on the Kostka polynomials by Nakayashiki and Yamada and by Lascoux, Leclerc and Thibon. Motivated by these works and by Kashiwara's theory of crystal bases we define a statistic on paths yielding two novel classes of polynomials. One of these provides a generalization of the Kostka polynomials, while the other, which we name the A_nу supernomial, is a q-deformation of the expansion coefficients of products of Schur polynomials. Many well-known results for Kostka polynomials are extended leading to representations of our polynomials in terms of a charge statistic on Littlewood-Richardson tableaux and in terms of fermionic configuration sums. Several identities for the generalized Kostka polynomials and the A_nу supernomials are proven or conjectured. Finally, a connection between the supernomials and Bailey's lemma is made.     

The Role of Coherence Transfer Efficiency in Design of TROSY-Type Multidimensional NMR Experiments

An improved method for TROSY-type (Pervushin et al., Proc. Natl. Acad. Sci. USA 94, 12366-12371 (1997)) heteronuclear two-dimensional correlation involving protons of negligible CSA is presented. Rather than applying a simple INEPT sequence for back-transfer to protons (Pervushin et al., J. Am. Chem. Soc. 120, 6394-6400 (1998)), we replace the pi/2 proton pulse in INEPT by a spin-state-selective coherence transfer element (Sorensen et al., J. Biomol. NMR 10, 181-186 (1997)) and maintain broadband decoupling during acquisition. Theoretically that results in a sensitivity enhancement of a factor of 2. The new method is demonstrated using a (13)C,(15)N-labeled protein sample, RAP 18-112 (N-terminal domain of alpha(2)-macroglobulin receptor associated protein), at 750 MHz.     

High-energy collision-induced dissociation mass spectrometry of synthetic mannose-6-phosphate oligosaccharides

The high-energy collision-induced dissociation spectra of a series of linear and branched synthetic mannosyl oligosaccharides that contain 6-phosphate substituents on either or both non-reducing terminal or penultimate residues have been studied. These phosphorylated structures were designed to mimic those of naturally derived N-glycans (Man-6-PO₄) on lysosomal enzymes and to probe the minimally required binding motif for the Man-6-PO₄ receptors. When a phosphate group was present, the spectra were dominated by ions that arise from cleavages at the glycosidic bonds (single and double) with charge retention on the phosphate-containing fragments. The spectra of linear structures that bear the nonreducing terminal Man-6-phosphate residues were devoid of Y-type ions, unlike those with similar phosphorylation at the penultimate residue. The location of the phosphorylated residue was deduced from the presence or absence of unique B and Y ions. In neutral branched structures, the ions were formed by cleavage at the glycosidic bond at either one or both of the branch points and the aglycon, which was attached to the disubstituted mannosyl residue. Branched oligosaccharides that contained one or two terminal Man-6-PO₄ residues also showed double cleavages with charge retention on the phosphate-containing fragment. Our investigation shows that positive mode high energy collision-induced dissociation mass spectrometry can determine the location—terminal or penultimate—of Man-6-PO₄ residues in N-linked type oligosaccharides.