A device for feline head positioning and stabilization during magnetic resonance imaging

Minimization of head movement and reproduction of standard head positions are essential for reliable brain functional magnetic resonance imaging. Devices for stabilization and alignment of feline preparations are not available currently. We describe a system that involves minimal surgery, allows for both acute and chronic atraumatic positioning, and has the potential to be used for unanesthetized animals. The device uses non-metallic materials and stabilizes the head by means of an apparatus that fixes the head with nylon screws and dental cement in the frontal sinuses. Application of the head-stabilizing device decreases head movements by more than a factor of ten. Anatomical images show that this device provides 3 dimensional head placement at a precision comparable to that of a stereotactic frame, i.e. within 1 mm.     

Information, relative entropy of entanglement, and irreversibility

Previously proposed measures of entanglement, such as entanglement of formation and assistance, are shown to be special cases of the relative entropy of entanglement. The difference between these measures for an ensemble of mixed states is shown to depend on the availability of classical information about particular members of the ensemble. Based on this, relations between relative entropy of entanglement and mutual information are derived.     

Pseudo-non-contact AFM imaging?

Recent non-contact atomic force microscopy studies have demonstrated that imaging of single atom defects is possible. However, the imaging mechanism was unclear. Long-range forces of attraction, which are normally associated with non-contact mode, are not known to produce sufficient lateral resolution to image atoms. In this study, we suggest a mechanism that could be responsible for the resolution achieved. We use realistic interatomic interaction parameters to do numerical simulations. These simulations are in good agreement with experimental data. As a result, we are able to ‘separate' the attractive and repulsive forces acting between the AFM tip and the sample surface. Calculations indicate that the force responsible for image contrast in the experimental studies mentioned above, is in most cases the repulsive contact force, and not the long-range attractive force. We check our conclusions against a variety of interatomic interaction parameters and our results remain valid for any reasonable set of such parameters, including the power law of the attractive potential N<9.     

Optical and photoemission evidence for a Tomonaga-Luttinger liquid in the Bechgaard salts

Combined optical and photoemission experiments on the quasi-one dimensional Bechgaard salts reveal the non-Fermi liquid character of these prototype quasi-one dimensional interacting electron systems. We show that various aspects of the exotic normal state properties along the chains are consistent with the predictions of the Tomonaga-Luttinger liquid theory. We also discuss the effect of interchain coupling on the insulator-metal transition, associated with the electron confinement-deconfinement crossover. Received 17 May 1999 and Received in final form 13 July 1999     

Activation of dinitrogen at binuclear sites

TMC Literature Highlights-22,Transition Met. Chem.,15, 251 (1990).     

Classification of behavior using vocalizations of Pacific white-sided dolphins (Lagenorhynchus obliquidens)

Surface behavior and concurrent underwater vocalizations were recorded for Pacific white-sided dolphins in the Southern California Bight (SCB) over multiple field seasons spanning 3 years. Clicks, click trains, and pulsed calls were counted and classified based on acoustic measurements, leading to the identification of 19 key call features used for analysis. Kruskal-Wallis tests indicated that call features differ significantly across behavioral categories. Previous work had discovered two distinctive click Types (A and B), which may correspond to known subpopulations of Pacific white-side dolphins in the Southern California Bight; this study revealed that animals producing these different click types also differ in both their behavior and vocalization patterns. Click Type A groups were predominantly observed slow traveling and milling, with little daytime foraging, while click Type B groups were observed traveling and foraging. These behavioral differences may be characteristic of niche partitioning by overlapping populations; coupled with differences in vocalization patterns, they may signify that these subpopulations are cryptic species. Finally, random forest decision trees were used to classify behavior based on vocalization data, with rates of correct classification up to 86%, demonstrating the potential for the use of vocalization patterns to predict behavior.     

On managerial risk-taking incentives when compensation may be hedged against

We consider a continuous time principal-agent model where the principal/firm compensates an agent/manager who controls the output’s exposure to risk and its expected return. Both the firm and the manager have exponential utility and can trade in a frictionless market. When the firm observes the manager’s choice of effort and volatility, there is an optimal contract that induces the manager to not hedge. In a two factor specification of the model where an index and a bond are traded, the optimal contract is linear in output and the log return of the index. We also consider a manager who receives exogenous share or option compensation and illustrate how risk taking depends on the relative size of the systematic and firm-specific risk premia of the output and index. Whilst in most cases, options induce greater risk taking than shares, we find that there are also situations under which the hedging manager may take less risk than the non-hedging manager.     

Defining topological features of membrane proteins by nanoelectrospray ionisation mass spectrometry

The D‐galactose‐H⁺ symport protein, GalP, of Escherichia coli is the bacterial homologue of the human glucose transport protein, GLUT1. Here we demonstrate that mass spectrometry can be used to map modification by covalently bound reagents, and also to detect structural changes in the GalP protein that occur upon substrate binding. The small thiol‐group‐specific reagent N‐ethylmaleimide (NEM) was used to modify the cysteine residues in GalP(His)₆ both alone and in the presence of D‐glucose, a known substrate. Employing a mixture of proteolysis and thermal degradation methods, the three cysteine residues were found to undergo sequential reactions with NEM, with Cys374 being modified first, followed by Cys389 and finally Cys19, thus indicating their different accessibilities within the three‐dimensional structure of the protein. Prior binding of the substrate D‐glucose to the protein protected Cys19 and Cys374 against NEM modification, but not Cys389. Cys374 had been expected to be shielded by D‐glucose binding while Cys389 had been expected to be unaffected, consistent with their proposed respective locations in the vicinity of, and distant from, the sugar binding site. However, the inaccessibility of Cys19 was unexpected and suggests a structural change in the protein promoted by D‐glucose binding which changes the proximity of Cys19 with respect to the D‐glucose‐binding site. Copyright © 2010 John Wiley & Sons, Ltd.