Light thresholds in Grand Unified Theories

In a generic Grand Unified Theory with a relatively small dispersion of the spectrum around the $Z$-boson and the unification masses, a connection is established, exact at one loop level, between $M_Z$, $G_{\rm F}$, $\alpha(M_Z)$ and the strong coupling constant $\alpha_3(M_Z)$. At this level of precision, this avoids the logical and phenomenological inconsistency of predicting $\alpha_3(M_Z)$ by means of the electroweak couplings as extracted from the data in the Standard Model rather than in the complete theory. Attention is paid to the independence of the physical results from regularization and/or renormalization schemes. As a particularly relevant example, the analysis is specialized to the case of the Minimal Supersymmetric Standard Model, with emphasis on light charginos and neutralinos.Comment: 8 pages; all figures are now included in a uuencoded fil

Flat World of Dilatonic Domain Walls

We study dilatonic domain walls specific to superstring theory. Along with the matter fields and metric the dilaton also changes its value in the wall background. We found supersymmetric (extreme) solutions which in general interpolate between isolated superstring vacua with non-equal value of the matter potential; they correspond to the static, planar domain walls with {\it flat} metric in the string (sigma model) frame. We point out similarities between the space-time of dilatonic walls and that of charged dilatonic black holes. We also comment on non-extreme solutions corresponding to expanding bubbles.Comment: 11 pgs (+2 figures available upon request), UPR-560-

Charged string solutions with dilaton and modulus fields

We find charged, abelian, spherically symmetric solutions (in flat space-time) corresponding to the effective action of $D=4$ heterotic string theory with scale-dependent dilaton \p and modulus \vp fields. We take into account perturbative (genus-one), moduli-dependent `threshold' corrections to the coupling function f(\p,\vp) in the gauge field kinetic term f(\p,\vp) F^2_{\m\n}, as well as non-perturbative scalar potential V(\p, \vp), e.g. induced by gaugino condensation in the hidden gauge sector. Stable, finite energy, electric solutions (corresponding to on abelian subgroup of a non-abelian gauge group) have the small scale region as the weak coupling region (\phi\ra -\infty) with the modulus \vp slowly varying towards smaller values. Stable, finite energy, abelian magnetic solutions exist only for a specific range of threshold correction parameters. At small scales they correspond to the strong coupling region (\p\ra \infty) and the compactification region (\vp\ra 0). The non-perturbative potential $V$ plays a crucial role at large scales, where it fixes the asymptotic values of $\phi$ and \vp to be at the minimum of $V$.Comment: 42 pages, 5 figures, harvmac, CERN-TH.6911/93, UPR-573-T (minor corrections in Section 6

Evaluation of the Effect of Nandrolone Decanoate on Experimental Spinal Cord Injury in Rats

Background: Acute spinal cord injury, a common cause of neurological dysfunction in humans and animals, impairs motor, sensory and autonomic functions and may result in permanent disability. Nandrolone decanoate (ND) is a steroid widely studied for its predominantly anabolic effect and low androgenic potential. Several researchers have described the positive interference of ND in neurological tissue, such as increased synthesis and release of neurotrophic substances, but to date no studies have evaluated the action of this steroid in acute spinal cord injury. The aim of this study was therefore to evaluate the effect of ND in rats subjected to acute spinal cord injury. Materials, Methods & Results: Thirty-two young adult Wistar rats (Rattus norvegicus), weighing between 240 and 260 g, were divided into three groups. The first group (GNAN) (n=13) was subjected to acute spinal cord injury and treated with ND; the control group (GCON) (n=13) was subjected to spinal cord injury without treatment; and the third group (GLAM) (n=6) underwent laminectomy without prior spinal cord injury, in order to control changes caused by the procedure. A 20 g metal device was released from a height of 25 cm to produce the spinal cord injury. After exposing the spinal canal, a 2-mm diameter metal rod was placed directly in contact with the spinal cord, and when the weight was released, the rod was struck, causing the spinal cord injury. An intramuscular injection of 2 mg/kg of ND was administered the immediate postoperative period. The animals were assessed to ascertain the recovery of their motor function on five occasions, namely at 24 h, 48 h, 72 h, 7 and 14 days after undergoing spinal cord injury. This assessment was performed using the Basso, Beattie and Bresnahan (BBB) model. The animals were euthanized 14 days post-op and fragments of the spinal cord and urinary bladder were collected for histological evaluation. Discussion: The animals subjected to spinal cord injury presented paraplegia, failing to score on the BBB scale in the first three assessments. Starting 7 days after surgery, the GNAN (0-13) and GCON (0-5) groups gradually began showing locomotor improvements, with scale variations. On day 14 after spinal cord injury, 22% of the animals in GNAN and 11% in GCON had failed to recover their locomotor function, scoring zero on the BBB scale. After spinal cord injury, all the animals showed urine retention. The urinary function returned on average on day 5 post surgery, with no significant difference between the groups. The locomotor assessment of the animals subjected to acute spinal cord injury revealed that the injury varied in intensity in GNAN and GCON, with signs of pelvic limb paraplegia and asymmetric non-ambulatory paraparesis. Time was a determining factor in the clinical evolution of the animals, with no evidence of the influence of ND. The histological findings revealed variations in the intensity of the injury, with a tendency for lower intensity in the cranial and epicentral segments of the lesion in the animals subjected to ND treatment, albeit without statistically significant evidence (P ≥ 0.05). The spinal cord assessments of the GLAM group indicated that the surgical procedure did not cause histological alterations, since the normal architecture of the neural tissue was preserved. The histopathological evaluations of the urinary bladder revealed an inflammatory response characterized by lymphohistiocytosis and neutrocytosis in the animals of GNAN and GCON, without interference of ND in the change (P ≥ 0.05). The method to elicit spinal cord injury reproduced functional, sensory and motor incapacity heterogeneously in rats. In the dose evaluated here, ND did not significantly influence the return of locomotor function and the intensity of spinal cord histopathological alterations.  

El rol ambivalente de las redes sociales digitales: entre los efectos negativos y las posibilidades de representación saludables

Como decíamos ayer (Rodrigues, Capoano y Barredo, 2021), la pandemia de Covid-19 que inició en 2020 favoreció la transformación digital que se venía desarrollando, de manera teórica-práctica, desde hacía décadas. Podríamos remontarnos, de hecho, a la célebre máquina de Alan Turing (años 30 – siglo XX) como un anhelo humano de automatizar los procesos de comunicación, aunque de forma mecánica (Ilcic & García, 2020). El mismo Turing describía la existencia de las llamadas «máquinas-niño», capaces de aprender por sí mismas y de generar opciones de respuesta. Y aunque Turing no pudo acceder las redes sociales digitales -cuya expansión global se daría desde principios del año 2000 en adelante, en una progresiva masificación-, las “máquinas-niño” se están convirtiendo en “máquinas-adulto”, en la medida en que tienen amplios repositorios de datos sobre la forma en que se comunican y se relacionan las distintas sociedades

A troca contingente: perversidades do espelhamento reticular em O Gambito da Rainha

In this study, we analyzed the success of Queen’s Gambit, produced and shown on the Netflix platform. Through the collection and analysis of 160 comments to a Facebook post that mentions the success of audiences in the series, we have outlined a critical reflection around the socio-technical dynamics that privileges the formation of clusters of people with similar tastes, where we reflect on the false sense of authenticity, the issue of emotional self-exploration, the presence of reticular narcissism and the purge of diversified consumption. In addition, the data collected allowed us to cross with a set of critical reflections on emotional and homophilic tribes, which are organized around successful cases and which reveal a considerable absence of critical sense. We conclude that the creation of networks around private tastes made public generates an illusion of a community, and that the formation of digital social networks around the call and the connection of equals prevents the constitution of communities, before meaning a network mirroring, a reflection of the Self, very unreflective.Neste estudo, analisamos o sucesso de O Gambito da Rainha, série produzida e exibida na plataforma Netflix. Através da recolha e análise de 160 comentários a uma publicação de Facebook que menciona o sucesso de audiências da série, esboçamos uma reflexão crítica em torno da dinâmica sociotécnica que privilegia a formação de clusters de pessoas com gostos semelhantes, onde refletimos sobre a falsa sensação de autenticidade, a questão da autoexploração emocional, a presença de um narcisismo reticular e a expulsão do consome diferente. Além disso, os dados recolhidos permitiram-nos o cruzamento com um conjunto de reflexões críticas sobre tribos emocionais e homofílicas, que se organizam em torno de casos de sucesso e que revelam considerável ausência de sentido crítico. Concluímos que a criação de redes em torno de gostos privados tornados públicos gera uma ilusão de uma comunidade, e que a formação de redes sociais digitais em torno da convocatória e da conexão de iguais impede a constituição de comunidades, antes significando um espelhamento em rede, um reflexo do Eu, muito pouco reflexivo