Mass for Plasma Photons from Gauge Symmetry Breaking

We derive the effective masses for photons in unmagnetized plasma waves using a quantum field theory with two vector fields (gauge fields). In order to properly define the quantum field degrees of freedom we re-derive the classical wave equations on light-front gauge. This is needed because the usual scalar potential of electromagnetism is, in quantum field theory, not a physical degree of freedom that renders negative energy eigenstates. We also consider a background local fluid metric that allows for a covariant treatment of the problem. The different masses for the longitudinal (plasmon) and transverse photons are in our framework due to the local fluid metric. We apply the mechanism of mass generation by gauge symmetry breaking recently proposed by the authors by giving a non-trivial vacuum-expectation-value to the second vector field (gauge field). The Debye length $\lambda_D$ is interpreted as an effective compactification length and we compute an explicit solution for the large gauge transformations that correspond to the specific mass eigenvalues derived here. Using an usual quantum field theory canonical quantization we obtain the usual results in the literature. Although none of these ingredients are new to physicist, as far as the authors are aware it is the first time that such constructions are applied to Plasma Physics. Also we give a physical interpretation (and realization) for the second vector field in terms of the plasma background in terms of known physical phenomena. Addendum: It is given a short proof that equation (10) is wrong, therefore equations (12-17) are meaningless. The remaining results are correct being generic derivations for nonmagnetized plasmas derived in a covariant QFT framework.Comment: v1: 1+6 pages v2: Several discussions rewritten; Abstract rewritten; References added; v3: includes Addendu

Gyrification, cortical and subcortical morphometry in neurofibromatosis type 1: an uneven profile of developmental abnormalities.

Background: Neurofibromatosis type 1 (NF1) is a monogenic disorder associated with cognitive impairments. In order to understand how mutations in the NF1 gene impact brain structure it is essential to characterize in detail the brain structural abnormalities in patients with NF1. Previous studies have reported contradictory findings and have focused only on volumetric measurements. Here, we investigated the volumes of subcortical structures and the composite dimensions of the cortex through analysis of cortical volume, cortical thickness, cortical surface area and gyrification. Methods: We studied 14 children with NF1 and 14 typically developing children matched for age, gender, IQ and right/left-handedness. Regional subcortical volumes and cortical gyral measurements were obtained using the FreeSurfer software. Between-group differences were evaluated while controlling for the increase in total intracranial volume observed in NF1. Results: Subcortical analysis revealed disproportionately larger thalami, right caudate and middle corpus callosum in patients with NF1. Cortical analyses on volume, thickness and surface area were however not indicative of significant alterations in patients. Interestingly, patients with NF1 had significantly lower gyrification indices than typically developing children primarily in the frontal and temporal lobes, but also affecting the insula, cingulate cortex, parietal and occipital regions. Conclusions: The neuroanatomic abnormalities observed were localized to specific brain regions, indicating that particular areas might constitute selective targets for NF1 gene mutations. Furthermore, the lower gyrification indices were accompanied by a disproportionate increase in brain size without the corresponding increase in folding in patients with NF1. Taken together these findings suggest that specific neurodevelopmental processes, such as gyrification, are more vulnerable to NF1 dysfunction than others. The identified changes in brain organization are consistent with the patterns of cognitive dysfunction in the NF1 phenotype. © 2013 Violante et al

Explicit Actions for Electromagnetism with Two Gauge Fields with Only one Electric and one Magnetic Physical Fields

We extend the work of Mello et al. based in Cabbibo and Ferrari concerning the description of electromagnetism with two gauge fields from a variational principle, i.e. an action. We provide a systematic independent derivation of the allowed actions which have only one magnetic and one electric physical fields and are invariant under the discrete symmetries $P$ and $T$. We conclude that neither the Lagrangian, nor the Hamiltonian, are invariant under the electromagnetic duality rotations. This agrees with the weak-strong coupling mixing characteristic of the duality due to the Dirac quantization condition providing a natural way to differentiate dual theories related by the duality rotations (the energy is not invariant). Also the standard electromagnetic duality rotations considered in this work violate both $P$ and $T$ by inducing Hopf terms (theta terms) for each sector and a mixed Maxwell term. The canonical structure of the theory is briefly addressed and the 'magnetic' gauge sector is interpreted as a ghost sector.Comment: v2: 12 pages; References added, discussion concerning degrees of freedom corrected; v3: is now used the standard normalization of 1/4 in the actions; the possibility of theta being a pseudo-scalar implied a title changing; eq (23) added; signs corrected in equations (39,45-47); references adde

Chiropractic Manipulative Therapy of the Thoracic Spine in Combination with Stretch and Strengthening Exercises, in Improving Postural Kyphosis in Woman

Abstract: Purpose: This study serves to determine the effectiveness of either chiropractic spinal manipulative therapy to the thoracic spine or stretch and strengthening exercises (stretching the pectoralis major muscle and strengthening the rhomboid, middle and inferior trapezius muscles) versus the combined treatment of chiropractic spinal manipulative therapy to the thoracic spine in conjunction with stretch and strengthening exercises. Method: A randomised study design with thirty female participants between the ages of twenty and thirty nine was selected. Group 1 (n= 10) received chiropractic spinal manipulative therapy to the thoracic spine. Group 2 (n = 10) received chiropractic spinal manipulative therapy to the thoracic spine as well as stretch and strengthening exercises i.e. stretching the pectoralis major muscles and strengthening the rhomboid, middle and inferior trapezius muscles. Group 3 (n = 10) received stretch and strengthening exercises. The stretch and strengthening exercises were performed in the consultation rooms to ensure that the participants were complying with the treatment and doing the exercises properly. The study consisted of seven consultations for group 1 (they received treatment once a week for six weeks) and for groups 2 and 3 there were nineteen consultations (they received three treatments a week for six weeks). Objective data was recorded at the beginning of the first, fourth and seventh consultations for group 1, and the first, tenth and nineteenth consultations for groups 2 and 3. On the seventh consultation (for group 1) and nineteenth consultation for groups 2 and 3, only data collection was done. Objective data were obtained by using the Flexicurve® Ruler measurements for the angle of kyphosis. Visual analysis was done by taking lateral (sagittal) view photographs at the beginning of the initial and final consultations..

Suscetibilidade a inseticidas e parasitismo natural por Trichogramma sp. em Traça-do-tomateiro.

A traça-do-tomateiro é uma praga importante do tomate e inseticidas são freqüentemente empregados para o seu controle. Porém, devido ao impacto ambiental e a possibilidade de resistência aos produtos utilizados para o controle do inseto, o controle biológico com o uso de Trichogramma pode ser uma alternativa para eliminar os dois problemas. Neste trabalho foi avaliada em bioensaios de laboratório a eficiência da dose recomendada de inseticidas do grupo químico dos organofosforados, piretróides e benzoiluréia para o controle da traça-do-tomateiro. Foi também avaliada a ocorrência natural de Trichogramma sp. em áreas pulverizadas ou não pulverizadas com inseticidas. A ocorrência do parasitismo natural foi determinada por meio da coleta de folhas em campo contendo ovos de traça-do-tomateiro, a fim de determinar, em avaliações de laboratório, a percentagem de ovos parasitados. Os resultados mostraram que todos os inseticidas testados causaram uma mortalidade de larvas menor que 70%, o que sugere uma eficiência reduzida dos produtos. O parasitóide Trichogramma sp. ocorreu naturalmente em todas as áreas, mas a percentagem de parasitismo foi menor nas áreas pulverizadas. Outros estudos devem ser realizados a fim de avaliar o potencial dos parasitóides locais, provavelmente mais bem adaptados as condições locais, para o controle da traça-do-tomateiro. Se esses organismos forem efetivos, o uso de inseticidas em lavouras de tomate pode ser reduzido.bitstream/CNPH-2009/33237/1/bpd_28.pd

Bifurcations in the Lozi map

We study the presence in the Lozi map of a type of abrupt order-to-order and order-to-chaos transitions which are mediated by an attractor made of a continuum of neutrally stable limit cycles, all with the same period.Comment: 17 pages, 12 figure

Visual Cortex Plasticity Following Peripheral Damage To The Visual System: fMRI Evidence

Over the last two decades, functional magnetic resonance imaging (fMRI) has become a powerful research method to investigate cortical visual plasticity. Abnormal fMRI response patterns have been occasionally detected in the visually deprived cortex of patients with bilateral retinal diseases. Controversy remains whether these observations indicate structural reorganization of the visual cortex or unmasking of previously silent cortico-cortical connections. In optic nerve diseases, there is weak evidence showing that early visual cortex seems to lack reorganization, while higher-order visual areas undergo plastic changes which may contribute to optimise visual function. There is however accumulating imaging evidence demonstrating trans-synaptic degeneration of the visual cortex in patients with disease of the anterior visual pathways. This may preclude the use of restorative treatments in these patients. Here, we review and update the body of fMRI evidence on visual cortical plasticity.info:eu-repo/semantics/publishedVersio