Sustained maintenance of somatotopic information in brain regions recruited by tactile working memory

To adaptively guide ongoing behavior, representations in working memory (WM) often have to be modified in line with changing task demands. We used event-related potentials (ERPs) to demonstrate that tactile WM representations are stored in modality-specific cortical regions, that the goal-directed modulation of these representations is mediated through hemispheric-specific activation of somatosensory areas, and that the rehearsal of somatotopic coordinates in memory is accomplished by modality-specific spatial attention mechanisms. Participants encoded two tactile sample stimuli presented simultaneously to the left and right hands, before visual retro-cues indicated which of these stimuli had to be retained to be matched with a subsequent test stimulus on the same hand. Retro-cues triggered a sustained tactile contralateral delay activity component with a scalp topography over somatosensory cortex contralateral to the cued hand. Early somatosensory ERP components to task-irrelevant probe stimuli (that were presented after the retro-cues) and to subsequent test stimuli were enhanced when these stimuli appeared at the currently memorized location relative to other locations on the cued hand, demonstrating that a precise focus of spatial attention was established during the selective maintenance of tactile events in WM. These effects were observed regardless of whether participants performed the matching task with uncrossed or crossed hands, indicating that WM representations in this task were based on somatotopic rather than allocentric spatial coordinates. In conclusion, spatial rehearsal in tactile WM operates within somatotopically organized sensory brain areas that have been recruited for information storage

The role of gender in gait analysis in the elderly

The purpose of this study was to identify gender-related differences in the gait of functionally independent elderly men and women when walking at self selected walking velocity (SSWV). A quantitative gait analysis was conducted on 59 men (mean age 75.7, SD 5.8, range 69-91 years) and 127 women (mean age 75.2, SD 4.9, range 68-91 years) who could walk independently, regarded themselves to be in good health, and were independent in terms of activities of daily living. The analysis was based on foot placements in the sagittal plane recorded using a video camera. ANO VA gender comparisons revealed significant differences (p -0.0013) in all phases of walking, step length, standing height and knee length, but no significant differences in walking speed. Women were found to take shorter steps at greater frequency than men to attain the same walking velocity. When phase and step length variables were normalized to a percent of each individuals stride time (phase variables) and knee height as a measure of stature (step lengths), there were no significant gender differences. These findings suggest that at SSWV gait differences in older persons are due to stature and not to gender, and that the use of norms which are gender based may be inappropriate. Thus, the gait of elderly men and women walking at SSWV may be analysed together, provided that the step length data are normalized to stature and phase data to stride time

The Beagle landing site in Isidis Planitia

The Mars probe Beagle 2 will land in Isidis Planitia. This region satisfies the engineering constraints and has evidence for particularly volatile-rich subsoil. Isidis provides a suitable place for the lander to search for H2O and organic matter

Complications of syndesmotic screw removal

Background: Currently, the metallic syndesmotic screw is the gold standard in the treatment of syndesmotic disruption. Whether or not this screw needs to be removed remains debatable. The aim of the current study was to determine the complications which occur following routine removal of the syndesmotic screw following operative treatment of unstable ankle fractures. Methods: This was a retrospective study with consecutive cases in a Level-2 Trauma center. All patients with routine removal of a syndesmotic screw, following the treatment of an unstable ankle fracture, between January 1, 2004 and November 30, 2010 were included. Complications recorded were: 1) minor or major wound infection following removal of the syndesmotic screw, 2) recurrent syndesmotic diastasis, and 3) unnecessary removal of a broken screw, not recognized during preoperative planning prior to surgery. Results: A total of 76 patients were included. A wound infection occurred in 9.2% (N=7) of which 2.6% (N=2) were deep infections requiring reoperation. Recurrent syndesmotic diastasis was found in 6.6% (N=5) of patients, and in 6.6% (N=5) screws were broken at the time of implant removal. In the group with recurrent diastasis the screws were removed significantly earlier compared with the group without recurrent diastasis (Mann- Whitney U-test; p = 0.011) and the group with screw breakage had their screws significantly longer in place compared with the group without breakage (p = 0.038). Conclusion: A total of 22.4% complications occurred upon routine removal of the syndesmotic screw. Removal might therefore be considered only in selected c

The low energy limit of the non-commutative Wess-Zumino model

The non-commutative Wess-Zumino model is used as a prototype for studying the low energy behaviour of a renormalizable non-commutative field theory. We start by deriving the potential mediating the fermion-fermion and boson-boson interactions in the non-relativistic regime. The quantum counterparts of these potentials are afflicted by irdering ambiguities but we show that there exists an ordering prescription which makes them hermitean. For space/space noncommutativity it turns out that Majorana fermions may be pictured as rods oriented perpendicularly to the direction of motion showing a lack of localituy, while bosons remain insensitive to the effects of noncommutativity. For time/space noncommutativity bosopns and fermions can be regarded as rods oriented along the direction of motion. For both cases of noncommutativity the scattering state described scattered waves, with at least one wave having negative time delay signalizing the underlying nonlocality. The superfield formulation of the model is used to compute the corresponding effective action in the one- and two-loop approximations. In the case of time/space noncommutativity, unitarity is violated in the relativistic regime. However, this does not preclude the existence of the unitary low energy limit.Comment: 14 pages, 2 figures, minor correction

Electron correlation effects in a wide channel from the ν=1\nu =1 quantum Hall edge states

The spatial behavior of Landau levels (LLs) for the $nu=1$ quantum Hall regime at the edge of a wide channel is studied in a self-consistent way by using a generalized local density approximation proposed here. Both exchange interaction and strong electron correlations, due to edge states, are taken into account. They essentially modify the spatial behavior of the occupied lowest spin-up LL in comparison with that of the lowest spin-down LL, which is totally empty. The contrast in the spatial behavior can be attributed to a different effective one-electron lateral confining potentials for the spin-split LLs. Many-body effects on the spatially inhomogeneous spin-splitting are calculated within the screened Hartree-Fock approximation. It is shown that, far from the edges, the maximum activation energy is dominated by the gap between the Fermi level and the bottom of the spin-down LL, because the gap between the Fermi level and the spin-up LL is much larger. In other words, the maximum activation energy in the bulk of the channel corresponds to a highly asymmetric position of the Fermi level within the gap between spin-down and spin-up LLs in the bulk. We have also studied the renormalization of the edge-state group velocity due to electron correlations. The results of the present theory are in line with those suggested and reported by experiments on high quality samples.Comment: 9 pages, 4 figure

Severe anal bleeding in Proteus syndrome: a case report

Proteus syndrome was originally described by Cohen and Hayden in 1979. The disorder was named Proteus syndrome by Wiedmann and colleagues in 1983 after Proteus, the giant Greek god of the sea. Proteus syndrome is a rare, sporadic, congenital polymorphic condition. Approximately 200 cases have been reported in the literature, but none has been associated with anal bleeding from hemorrhoids. We describe the case of a 21-year-old man with Proteus syndrome with severe anal bleeding. A hemorrhoidectomy was assumed to be too risky because of the massive venous abnormalities seen on CT. The patient was successfully treated by Doppler-guided haemorrhoidal artery ligation (DG-HAL). Six months after surgery, the patient has had no further episodes of anal bleeding

Microbial Inoculation to High Moisture Plant By-Product Silage: A Review

Use of microbial inoculants during silage making have drawn interest to silage producers including those who are feeding their livestock on silage produced from by-products (e.g. pulps). Many farmers in the developing countries rely on agro-industrial by-products to feed their livestock, which is limited by the high moisture content of the by-products. This review pertains to issues related to silage production from high moisture plant by-products (e.g. pulps or pomaces), challenges involved in the ensiling of these resources, the use of additives (e.g. microbial additives), and growth performance of the animals that are fed silage from these resources. This information will be helpful to better understand the key roles of silage production from these resources

Patient-derived oral mucosa organoids as an in vitro model for methotrexate induced toxicity in pediatric acute lymphoblastic leukemia

We have recently established a protocol to grow wildtype human oral mucosa organoids. These three-dimensional structures can be maintained in culture long-term, do not require immortalization, and recapitulate the multilayered composition of the epithelial lining of the oral mucosa. Here, we validate the use of this model to study the effect of Leucovorin (LV) on Methotrexate (MTX)-induced toxicity. MTX is a chemotherapeutic agent used in the treatment of pediatric acute lymphoblastic leukemia. Although effective, the use of MTX often results in s

A first-principles approach to electrical transport in atomic-scale nanostructures

We present a first-principles numerical implementation of Landauer formalism for electrical transport in nanostructures characterized down to the atomic level. The novelty and interest of our method lies essentially on two facts. First of all, it makes use of the versatile Gaussian98 code, which is widely used within the quantum chemistry community. Secondly, it incorporates the semi-infinite electrodes in a very generic and efficient way by means of Bethe lattices. We name this method the Gaussian Embedded Cluster Method (GECM). In order to make contact with other proposed implementations, we illustrate our technique by calculating the conductance in some well-studied systems such as metallic (Al and Au) nanocontacts and C-atom chains connected to metallic (Al and Au) electrodes. In the case of Al nanocontacts the conductance turns out to be quite dependent on the detailed atomic arrangement. On the contrary, the conductance in Au nanocontacts presents quite universal features. In the case of C chains, where the self-consistency guarantees the local charge transfer and the correct alignment of the molecular and electrode levels, we find that the conductance oscillates with the number of atoms in the chain regardless of the type of electrode. However, for short chains and Al electrodes the even-odd periodicity is reversed at equilibrium bond distances.Comment: 14 pages, two-column format, submitted to PR