50 research outputs found
Conformal gravity: light deflection revisited and the galactic rotation curve failure
We show how Conformal Gravity (CG) has to satisfy a fine-tuning condition to
describe the rotation curves of disk galaxies without the aid of dark matter.
Interpreting CG as a gauge natural theory yields conservation laws and their
associated superpotentials without ambiguities. We consider the light
deflection of a point-like lens and impose that the two Schwarzschild-like
metrics with and without the lens are identical at infinite distances from the
lens. The energy conservation law implies that the parameter in the
linear term of the metric has to vanish, otherwise the two metrics are
physically inaccessible from each other. This linear term is responsible to
mimic the role of dark matter in disk galaxies and gravitational lensing
systems. Our analysis shows that removing the need of dark matter with CG thus
relies on a fine-tuning condition on . We also illustrate why the
results of previous investigations of gravitational lensing in CG largely
disagree. These discrepancies derive from the erroneous use of the deflection
angle definition adopted in General Relativity, where the vacuum solution is
asymptotically flat, unlike CG. In addition, the lens mass is identified with
various combinations of the metric parameters. However, these identifications
are arbitrary, because the mass is not a conformally invariant quantity, unlike
the conserved charge associated to the energy conservation law. Based on this
conservation law and by removing the fine-tuning condition on , i.e. by
setting , the energy difference between the metric with the
point-like lens and the metric without it defines a conformally invariant
quantity that can in principle be used for (1) a proper derivation of light
deflection in CG, and (2) the identification of the lens mass with a function
of the parameters and of the Schwarzschild-like metric.Comment: 16 pages, 1 figure. Revised version according to the referees
comments. The results reported in the original version remain unchange
In memoriam two distinguished participants of the Bregenz Symmetries in Science Symposia: Marcos Moshinsky and Yurii Fedorovich Smirnov
Some particular facets of the numerous works by Marcos Moshinsky and Yurii
Fedorovich Smirnov are presented in these notes. The accent is put on some of
the common interests of Yurii and Marcos in physics, theoretical chemistry, and
mathematical physics. These notes also contain some more personal memories of
Yurii Smirnov.Comment: Submitted for publication in Journal of Physics: Conference Serie
Supplementation with spray-dried porcine plasma in piglets at birth: effects on protein metabolism and performance.
Resumo: Este estudo foi planejado para avaliar se a suplementação de leitões com plasma sanguíneo suíno desidratado (PSSP) no dia do nascimento tem efeito positivo sobre o metabolismo proteico e ganho de peso (GP) em leitões, bem como no desempenho na fase de creche. Selecionamos 30 leitegadas de marrãs, das quais, no mínimo um casal de leitões para cada tratamento/leitegada foi selecionado. Os tratamentos foram: TA = controle sem PSSP, TB = administração oral de 10 g de PSSP e TC = 20 g de PSSP. No nascimento, os leitões foram pesados, identificados e distribuídos aleatoriamente. Os pesos corporais também foram avaliados nos dias 7, 14 e 19. Foram coletadas amostras de sangue para medir o nível de uréia, proteína total (PT), albumina (AB) e globulina (GB). No desmame, 70 leitões de cada tratamento foram distribuídos em cinco grupos (réplicas) de 14 leitões (sete machos e sete fêmeas). Os dados de pesos (animais e consumo de ração) foram coletados no pós-desmame e também a cada troca de dieta (dias 14, 28 e 42 da fase de creche). Durante as duas primeiras semanas na maternidade, não houve efeitos dos tratamentos para todas as variáveis avaliadas. Na terceira semana, os leitões de TC apresentaram níveis séricos mais altos para as variáveis PT e GB, mas o GT foi menor nos leitões comparado ao controle. Não houve efeito dos tratamentos no GT durante todo o período lactente. Não houve efeitos residuais no desempenho da fase de creche; no entanto, os leitões tratados tiveram menos necessidade de medicamentos. A suplementação com PSSP não influenciou o desempenho zootécnico nas duas primeiras semanas ou durante todo o período lactente. O grupo TC apresentou níveis mais altos de globulina do que o grupo TA. Na fase de creche, não houve efeitos no desempenho; no entanto, houve uma maior incidência de animais doentes do grupo TA. Abstract: This research was designed to evaluate whether supplementation of piglets with spray dried porcine plasma (SDPP) on the day of birth, have positive effect on protein metabolism and weight gain (WG) in suckling piglets, as well as on performance at the nursery phase. We selected 30 litters from gilts of at least one pair of piglets for each treatment, TA= control without SDPP, TB= oral administration of 10 g of SDPP, and TC= 20 g of SDPP. At birth, the piglets were weighed, identified and randomly distributed. Body weights were also measured on days 7, 14 and 19. Blood samples were collected to measure the level of urea, total protein (TP), albumin (AB) and globulin (GB). At weaning, 70 piglets from each treatment were distributed in five groups (replicates) of 14 piglets (seven males and seven females). Weights (animals and feed intake) were taken at post-weaning and at each feed change (days 14, 28 and 42 of raising). During the first two weeks of lactation, there were no effects of the treatments for the all evaluated variables. In the third week, TC piglets had higher serum levels of TP and GB, but lower WG than did control piglets. There was no effect of treatments on WG during the entire suckling period. There were no residual effects on nursery phase performance; however, treated piglets had less need for medications. SDPP supplementation did not influence zootechnical performance in the first two weeks or during the entire suckling period. The TC group had higher globulin levels than did the TA group. In the weaning phase, there were no effects on performance; however, there was a higher incidence of diseased animals in the TA group. Resumen: Este estudio fue diseñado para evaluar si la suplementación de lechones con plasma porcino secado por atomización (PPSA) el día del nacimiento, tiene un efecto positivo sobre el metabolismo de las proteínas y el aumento de peso (AP) en lechones lactantes, así como el rendimiento en la fase de cría. Seleccionamos 30 camadas de marranas al menos un par de lechones para cada tratamiento: TA = control sin PPSA, TB = administración oral de 10 g de PPSA y TC = 20 g de PPSA. Al nacer, los lechones fueron pesados, identificados y distribuidos al azar. Los pesos corporales también se midieron los días 7, 14 y 19. Se recogieron muestras de sangre para medir el nivel de urea, proteína total (PT), albúmina (AB) y globulina (GB). Al destete, se distribuyeron 70 lechones de cada tratamiento en cinco grupos (réplicas) de 14 lechones (siete machos y siete hembras). Los pesos (animales y consumo de alimento) se tomaron después del destete y en cada cambio de alimento (días 14, 28 y 42 de crianza). Durante las primeras dos semanas de lactancia, no hubo efectos de los tratamientos para todas las variables evaluadas. En la tercera semana, los lechones TC tenían niveles séricos más altos de TP y GB, pero un AP más bajo que los lechones de control. No hubo efecto de los tratamientos sobre el AP durante todo el período de lactancia. No hubo efectos residuales en el rendimiento de la fase de vivero; sin embargo, los lechones tratados tenían menos necesidad de medicamentos. La suplementación con SDPP no influyó en el rendimiento zootécnico en las primeras dos semanas o durante todo el período de lactancia. El grupo TC tenía niveles de globulina más altos que el grupo TA. En la fase de destete, no hubo efectos en el rendimiento; sin embargo, hubo una mayor incidencia de animales enfermos en el grupo TA
Recursion relations for Clebsch-Gordan coefficients of U(su) and U(su)
International audienceWe report in this article three- and four-term recursion relations for Clebsch-Gordan coefficients of the quantum algebras U_q(su_2) and U_q(su_{1,1}). These relations were obtained by exploiting the complementarity of three quantum algebras in a q-deformation of sp(8, \gr)
Potential Role of Biofeedback Visual Training in High-Speed Motorbike Drivers
Enzo Maria Vingolo,1 Carmelo Chines,2 Cesare Tanassi,3 Angel Charte,4 Lucio Cecchinello,5 Mauro Campigotto3 1University Sapienza of Rome, Department of Ophthalmology Polo Pontino Ospedale A. Fiorini, Terracina, Italy; 2Ophthalmology, Oculista Italiano Journal, Catania, Italy; 3Nidek Inc, Fremont, CA, USA; 4Medicine, Universitat de Barcelona, Barcelona, Catalunya, Spain; 5LCR Honda Motor, Tokyo, JapanCorrespondence: Enzo Maria Vingolo, University “Sapienza” of Rome, Polo Pontino Italy, Department of Ophthalmology, Ospedale A. Fiorini, Terracina, 04120, Italy, Email [email protected]: In several sports, appropriate training strategies remain a challenge for athletes and coaches, with the goal of improving performance. Extensive research has proposed several technical tools for obtaining parametric evaluations before competition in real life. This study aimed to assess whether some retinal performances might be improved using psychophysical techniques in health professionals involved in motorcycle sports (FIM MotoE).Methods: Two MotoE drivers were screened at baseline using complete ophthalmological examinations and evaluation of retinal reaction times, followed by a biofeedback training program. After 4 months of training, the subjects underwent a control visit using the same protocol as the baseline.Results: Central reaction time was shorter for 75% of drivers, with a consistent reduction (mean value of 20%). The peripheral reaction time showed an increasing trend after visual training. In both drivers, fixation stability improved dramatically (in 30% increments).Conclusion: The potential role of advanced technology was applied to high-speed drivers. Our results may be due to an attentional shift from the peripheral retina to the central retina during training. In our opinion, training potentiates the most useful pathways at the expense of less involved retinal and cortical areas, thus improving driving abilities and safety.Keywords: microperimetry, fixation, biofeedback, motorcycle, high-speed driver
Evaluation of spleen stiffness in healthy volunteers using point shear wave elastography
Introduction and Objectives: This study aims to measure the values of spleen stiffness (SS) in healthy subjects, the inter-operator agreement in SS measurement, and to detect statistically significant correlations between SS and age, sex, weight, BMI, portal vein dynamics and splenic dimensions. Materials and methods: The study included 100 healthy volunteers who had no substantial alcohol intake (<30 g/daily for man, <20 g/daily women), were negative on hepatitis B, hepatitis C, HIV blood serology, and had any history of lymphoproliferative disorders. Abdominal ultrasound, liver and spleen elastography were performed on each patient to search for focal splenic lesions, bile tract or portal vein dilatation, moderate/severe liver steatosis, and to measure liver and spleen stiffness. Results: The mean value was 18.14 (+/- 3.08) kPa. In the group of men (n= 49), the mean was 17.73 (+/- 2.91) kPa, whereas in the group of women (n= 51) it was 16.72 (+/- 3.32) kPa. Statistical analyses showed no correlation between spleen stiffness and sex, age, weight, and BMI. Regarding their splenoportal axis, statistically significant differences in SS were found in the means of the two subgroups of subjects stratified by their portal flow velocity (p= 0.003) and spleen area (p < 0.001). Spearman's rank showed a weak association between SS and portal flow velocty (r= 0.271) and splenic area (r = -0.237). ICC showed excellent (0.96) inter-operator agreement and Bland-Altman plot demonstrated no systematic over/under-estimation of spleen stiffness values. Conclusions: Our results may serve as a reference point in the evaluation of SS especially in patients affected by advanced liver disease