Packing T-joins

A consequence of Seymour's characterization of binary clutters with the Max Flow Min Cut property is that the minimum cardinality of a T-cut is equal to the largest number of edge-disjoint T-joins in every graph that cannot be T-contracted to an odd K_2,3. We give a simple “graphic” proof of this fact. © 1996 John Wiley & Sons, Inc.     

Interactions between oligopeptides and oxidised titanium surfaces detected by vibrational spectroscopy

Five alternating polar/hydrophobic oligopeptides derived from EAK 16 (AEAEAKAKAEAEAKAK) were examined in comparison with EAK 16 (peptide 1) both after solubilisation/lyophilisation and deposition on oxidised titanium surfaces. The peptides were synthesised for their possible use as biomimetic materials due to their self‐assembling properties and the presence, in one of them, of the arginine‐glycine‐aspartic (RGD) sequence, an active modulator of cell adhesion. Infrared (IR) and Raman spectroscopies were used to investigate the influence of the amino acid substitution on the self‐assembling properties of the peptides under both experimental conditions. In the lyophilised peptides, β‐sheet was the prevailing conformation (65–69%) as in EAK 16, irrespective of acid substitution (E→D, peptide 2), basic substitution (K→O, peptide 3), hydrophobic spacer substitution (A→Abu, peptide 4 and A→Y, peptide 5) and RGD insertion (peptide 6). After deposition on oxidised titanium, the main conformation remained β‐sheet. The side‐chain shortening of the acidic amino acid residue (peptide 2) or the insertion of a rigid and bulky residue such as Y (peptide 5) decreased the self‐assembling ability more than the side‐chain shortening of the basic amino acid residue (peptide 3) or the insertion of the RGD head (peptide 6). The interaction with the oxidised titanium surface was mainly due to carboxylate groups with a bidentate bridging coordination and C  O peptidic groups. Copyright © 2010 John Wiley & Sons, Ltd.     

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.     

Holographic watermarking for authentication of cut images

A watermarking technique, with a Computer Generated Hologram (CGH) coding system of the mark, is introduced and tested. The CGH watermarking can be used to authenticate parts of the original image. The hologram of the mark is embedded in the spatial domain by a blind additive embedding technique. The use of holography allows authenticating cuts of the original image, is the major novelty of this paper. The proposed methodology is characterized as an authentication technique, since it does not rely on the original image to decide whether the watermarked image has been altered or not and at the same time it is able to detect and localize any possible malicious change. Asymmetric cryptography is used to hide the hash information in an unambiguous way (non-repudiation property).     

Optimization of high-order harmonic generation by adaptive control of a sub-10-fs pulse wave front

We present a method for the optimization of high-order harmonic generation based on wave-front correction of the driving laser beam. The technique exploits wave-front adaptive control by means of a deformable mirror, governed by an optimization procedure.     

Diffusion Monte Carlo method with lattice regularization

We introduce an efficient lattice regularization scheme for quantum Monte Carlo calculations of realistic electronic systems. The kinetic term is discretized by a finite difference Laplacian with two mesh sizes, a and a', chosen so that the electrons can diffuse in a configuration space which is in practice indistinguishable from the continuum, and the different length scales in the system can be efficiently taken in account. The regularized Hamiltonian goes to the continuous limit for a --> 0 and allows the inclusion of nonlocal potentials in a consistent variational scheme, substantially improving the accuracy upon previous nonvariational approaches.     

Phase shifting photoelasticity in white light

The availability of image acquisition systems has led to the development of digital photoelasticity both in monochromatic and white light. In particular white light has been used mainly with the following methods: Spectral Content Analysis, RGB photoelasticity and phase shifting photoelasticity. Phase shifting photoelasticity in the colour domain has been used effectively for the determination of the isoclinic parameter in order to reduce the influence of the isochromatic fringes. The method has been also proposed for the determination of the isochromatic fringe order. This paper concerns the general characteristics of phase shifting photoelasticity in the colour domain. Special attention is drawn towards the influence of spectral content of the light source, the spectral response of the colour camera filters, the dispersion of the birefringence and the error of quarter wave plates.     

Informational analysis of seismic sequences by applying the Fisher Information Measure and the Shannon entropy: An application to the 2004–2010 seismicity of Aswan area (Egypt)

The interevent-time (IET) and interevent-distance (IED) series of seismic events occurred at Aswan area (Egypt) from 2004 to 2010 were investigated by means of the Fisher Information Measure and the Shannon entropy. The analysis was performed varying the depth and the magnitude thresholds. The results point out to an increase of level of organization and order with the decrease of magnitude threshold and the increase of depth threshold for the IET series, while the IED series are characterized by a level of uncertainty approximately constant with the threshold magnitude. The complexity measure, calculated as the product of the Fisher Information Measure and the Shannon entropy power, presents very similar pattern for both the types of seismic series, indicating an increasing complexity with the decrease of the threshold magnitude and the increase of the threshold depth.     

Microwave-assisted acylation of 7-amino-5-aryl-6-cyanopyrido[2,3-d]pyrimidines

A microwave-assisted method is described for monoacylating 7-amino-5-aryl-6-cyanopyrido[2,3-d]pyrimidines using excess acid chlorides in pyridine. A diacylated intermediate is effectively deacylated to the product amide by a macroporous-Tris resin. A small library of 17 amides was prepared to validate the method. The integration of commercial microwave technology into the ArQule chemistry platform is also discussed.