Observation of the V2O5(001) surface using ambient atomic force microscopy

Constant force images of the V₂O₅(001) surface were recorded in ambient conditions with atomic force microscopy. All images exhibit the 11.5 Å × 3.5 Å. periodicity expected for a bulk terminated surface. However, images reveal differences from the ideal structure. The experimental results are interpreted in terms of preferential adsorption sites for water molecules. Because these sites are thought to influence the catalytic properties of the surface, their characterization is an important step towards understanding how the atomic-scale structure of a surface influences its properties.     

Determination of Very Slow Diffusion of Paramagnetic Ions by NMR Spectroscopy

In this paper, we propose a new method of measuring the very slow paramagnetic ion diffusion coefficient using a commercial high-resolution spectrometer. If there are distinct paramagnetic ions influencing the hydrogen nuclear magnetic relaxation time differently, their diffusion coefficients can be measured separately. A cylindrical phantom filled with Fricke xylenol gel solution and irradiated with gamma rays was used to validate the method. The Fricke xylenol gel solution was prepared with 270 Bloom porcine gelatin, the phantom was irradiated with gamma rays originated from a ⁶⁰Co source and a high-resolution 200 MHz nuclear magnetic resonance (NMR) spectrometer was used to obtain the phantom ¹H profile in the presence of a linear magnetic field gradient. By observing the temporal evolution of the phantom NMR profile, an apparent ferric ion diffusion coefficient of 0.50 μm²/ms due to ferric ions diffusion was obtained. In any medical process where the ionizing radiation is used, the dose planning and the dose delivery are the key elements for the patient safety and success of treatment. These points become even more important in modern conformal radio therapy techniques, such as stereotactic radiosurgery, where the delivered dose in a single session of treatment can be an order of magnitude higher than the regular doses of radiotherapy. Several methods have been proposed to obtain the three-dimensional (3-D) dose distribution. Recently, we proposed an alternative method for the 3-D radiation dose mapping, where the ionizing radiation modifies the local relative concentration of Fe²⁺/Fe³⁺ in a phantom containing Fricke gel and this variation is associated to the MR image intensity. The smearing of the intensity gradient is proportional to the diffusion coefficient of the Fe³⁺ and Fe²⁺ in the phantom. There are several methods for measurement of the ionic diffusion using NMR, however, they are applicable when the diffusion is not very slow.     

Examination of time-reversal acoustics in shallow water and applications to noncoherent underwater communications

The shallow water acoustic communication channel is characterized by strong signal degradation caused by multipath propagation and high spatial and temporal variability of the channel conditions. At the receiver, multipath propagation causes intersymbol interference and is considered the most important of the channel distortions. This paper examines the application of time-reversal acoustic (TRA) arrays, i.e., phase-conjugated arrays (PCAs), that generate a spatio-temporal focus of acoustic energy at the receiver location, eliminating distortions introduced by channel propagation. This technique is self-adaptive and automatically compensates for environmental effects and array imperfections without the need to explicitly characterize the environment. An attempt is made to characterize the influences of a PCA design on its focusing properties with particular attention given to applications in noncoherent underwater acoustic communication systems. Due to the PCA spatial diversity focusing properties, PC arrays may have an important role in an acoustic local area network. Each array is able to simultaneously transmit different messages that will focus only at the destination receiver node.     

Changes in cerebral activity after decreased upper-limb hypertonus: an EMG-fMRI study

Objective

Whereas several studies have used functional magnetic resonance imaging (fMRI) to investigate motor recovery, whether therapy to decrease post-stroke hypertonus alters central motor patterns remains unclear. In this study, we used continuous electromyography (EMG)-fMRI to investigate possible changes in movement-related brain activation in patients receiving Botulinum toxin (BoNT-A) for hand-muscle hypertonus after chronic stroke.

Methods

We studied eight stroke patients all of whom had hemiparesis and associated upper-limb hypertonus. All patients underwent an fMRI-EMG recording and clinical-neurological assessment before BoNT-A and 5 weeks thereafter. The handgrip motor task during imaging was fixed across both patients and controls. The movements were metronome paced, movement amplitude and force were controlled with a plastic orthosis, dynamometer and EMG recording. An age-matched control group was recruited from among healthy volunteers underwent the same fMRI-EMG recording.

Results

Before BoNT-A, while patients moved the paretic hand, fMRI detected wide bilateral activation in the sensorymotor areas (SM1), in the supplementary motor area (SMA) and cerebellum. After BoNT-A blood oxygenation level-dependent (BOLD) activation decreased in ipsilateral and contralateral motor areas and became more lateralized. BOLD activation decreased also in ipsilateral cerebellar regions and in the SMA.

Conclusion

Changes in peripheral upper-limb hypertonus after BoNT-A were associated to an improvement in active movements and more lateralized and focalized activation of motor areas. The clinical and EMG-fMRI coregistration technique we used to study hand-muscle hypertonus in patients receiving BoNT-A after chronic stroke should be useful in future studies seeking improved strategies for post-stroke neurorehabilitation.     

Baryon polarization in low-energy unpolarized meson-baryon scattering

We compute the polarization of the final-state baryon, in its rest frame, in low-energy mesonbaryon scattering with unpolarized initial state, in unitarized BChPT. Free parameters are determined by fitting total and differential cross-section data (and spin-asymmetry or polarization data if available) for pK ⁻, pK ⁺ and pπ⁺ scattering. We also compare our results with those of leading-order BChPT.     

Metabolic Profiling of Murine Macrophages Exposed to Silver Nanoparticles at Dose and Time Dependencies

The macrophage time-dependent metabolic profile changing basal metabolism triggered by nanoparticles can be obtained and used to improve wound healing treatments. Herein this study demonstrates that metabolic status responds systematically to cytotoxicity manipulation, providing an interesting way of cellular control. Nuclear magnetic resonance (NMR) based metabolomics and cytotoxic assays are used to study RAW 264.7 cells exposed to AgNPs at different concentrations and incubation times. Cytotoxicity data show a slight decrease in cellular expansion rates accompanied by morphological changes in cells. Metabolomics show that despite the glycolytic activity of treated and non-treated cells remains unchanged; however, only the treated cells present a rich Citrate environment signaling up-regulation of Tricarboxylic-Acid-Cycle (TCA). Cells choose aerobic routes instead of anaerobic ones to produce energy and self-regulate their amino acid metabolism to balance TCA. Choline metabolism is down-regulated once its sub-products, Betaine and Glycine, are reduced, thus compromising Creatine synthesis. Phospholipid metabolism is down-regulated due to the decreasing of Phosphocholine and Sn-Glycerol-3-PC, in agreement with the cytotoxicity results. Pyroglutamate decreases in treated cells, signaling different levels of oxidative stress. These analytical tools can characterize AgNPs-treatments, even distinguishing dose and time dependencies. Therefore, the fine-tuning of exposition parameters can modulate cellular activity to achieve better wound healing.     

Classification of finite groups according to the number of conjugacy classes II

In the following,G denotes a finite group,r(G) the number of conjugacy classes ofG, β(G) the number of minimal normal subgroups ofG andα(G) the number of conjugate classes ofG not contained in the socleS(G). Let Φ _j = {G|β(G) =r(G) −j}. In this paper, the family Φ₁₁ is classified. In addition, from a simple inspection of the groups withr(G) =b conjugate classes that appear in ϒ _j ^=1/11 Φ _j , we obtain all finite groups satisfying one of the following conditions: (1)r(G) = 12; (2)r(G) = 13 andβ(G) > 1; …; (9)r(G) = 20 andβ(G) > 8; (10)r(G) =n andβ(G) =n −a with 1 ≦a ≦ 11, for each integern ≧ 21. Also, we obtain all finite groupsG with 13 ≦r(G) ≦ 20,β(G) ≦r(G) − 12, and satisfying one of the following conditions: (i) 0 ≦α(G) ≦ 4; (ii) 5 ≦α(G) ≦ 10 andS(G) solvable.     

A topological phase transition between small-worlds and fractal scaling in urban railway transportation networks?

Fractal and small-worlds scaling laws are applied to study the growth of urban railway transportation networks using total length and total population as observational parameters. In spite of the variety of populations and urban structures, the variation of the total length of the railway network with the total population of conurbations follows similar patterns for large and middle metropolis. Diachronous analysis of data for urban transportation networks suggests that there is second-order phase transition from small-worlds behaviour to fractal scaling during their early stages of development.