On improvements of Double Beta Decay using FQTDA Model

The Quasiparticle Tamm-Dancoff Approximation (QTDA) is applied to describe the nuclear double beta decay with two neutrinos. Several serious inconveniences found in the Quasiparticle Random Phase Approximation (QRPA) are not present in the QTDA, as such as the ambiguity in treating the intermediary states, and further approximations necessary for evaluation of the nuclear matrix elements (NMEs) or, the extreme sensitivity of NME with the ratio between the pn and pp + nn pairings. Some years ago, the decay 48Ca → 48Ti was discussed within the particle-hole limit of QTDA. We found some mismatch in the numerical calculations when the full QTDA was being implemented, and a new performance in the particle-hole limit of QTDA is required to guarantee the fidelity of the approximation.Facultad de Ciencias ExactasInstituto de Física La Plat

On improvements of Double Beta Decay using FQTDA Model

The Quasiparticle Tamm-Dancoff Approximation (QTDA) is applied to describe the nuclear double beta decay with two neutrinos. Several serious inconveniences found in the Quasiparticle Random Phase Approximation (QRPA) are not present in the QTDA, as such as the ambiguity in treating the intermediary states, and further approximations necessary for evaluation of the nuclear matrix elements (NMEs) or, the extreme sensitivity of NME with the ratio between the pn and pp + nn pairings. Some years ago, the decay 48Ca → 48Ti was discussed within the particle-hole limit of QTDA. We found some mismatch in the numerical calculations when the full QTDA was being implemented, and a new performance in the particle-hole limit of QTDA is required to guarantee the fidelity of the approximation.Facultad de Ciencias ExactasInstituto de Física La Plat

Global regulatory developments for clinical stem cell research: diversification and challenges to collaborations

In this article, we explore regulatory developments in stem cell medicine in seven jurisdictions: Japan, China, India, Argentina, Brazil, the USA and the EU. We will show that the research methods, ethical standards and approval procedures for the market use of clinical stem cell interventions are undergoing an important process of global diversification. We will discuss the implications of this process for international harmonization and the conduct of multicountry clinical research collaborations. It will become clear that the increasing heterogeneity of research standards and regulations in the stem cell field presents a significant challenge to international clinical trial partnerships, especially with countries that diverge from the regulatory models that have been developed in the USA and the EU

On improvements of Double Beta Decay using FQTDA Model

The Quasiparticle Tamm-Dancoff Approximation (QTDA) is applied to describe the nuclear double beta decay with two neutrinos. Several serious inconveniences found in the Quasiparticle Random Phase Approximation (QRPA) are not present in the QTDA, as such as the ambiguity in treating the intermediary states, and further approximations necessary for evaluation of the nuclear matrix elements (NMEs) or, the extreme sensitivity of NME with the ratio between the pn and pp + nn pairings. Some years ago, the decay 48Ca → 48Ti was discussed within the particle-hole limit of QTDA. We found some mismatch in the numerical calculations when the full QTDA was being implemented, and a new performance in the particle-hole limit of QTDA is required to guarantee the fidelity of the approximation.Facultad de Ciencias ExactasInstituto de Física La Plat

Descripción y comparación morfológica de la lengua de dos marsopas (Phocoena dioptrica y P. spinipinnis, Phocoenidae: Cetacea), en adultos y juveniles.

Se presenta una descripción, comparativa e interpretativa, de las características anatómicas e histológicas de lenguas (de ejemplares adultos y juveniles) de dos especies de marsopas: Phocoena dioptrica y P. spinipinnis. Las muestras fueron estudiadas mediante microscopía electrónica de barrido y técnicas histológicas (HE, orceína, PAS). En ambas especies, la lengua posee superficie lisa en casi toda su extensión y papilas mecánicas marginales en el vértice. Estas últimas son de forma y tamaño variables, más numerosas en los juveniles, y especialmente en P. spinipinnis, donde se disponen en dos o tres hileras. Las papilas constan de tejido epitelial plano estratificado paracornificado y tejido conectivo laxo. En el cuerpo existen algunas papilas foliadas, pero sin corpúsculos gustativos (tampoco hallados en otras regiones). Además, en los juveniles y en el adulto de P. dioptrica existen estructuras vasculares (una arteria muscular central y dos o más venas periféricas), ausentes en adultos de P. spinipinnis. Hacia la raíz, la mucosa forma fositas y repliegues, en cuyo fondo desembocan conductos de glándulas mucosas. El tejido muscular forma haces ordenados en distintas direcciones. En la zona de transición, y en la raíz de los juveniles, existe tejido linfoide difuso y nodular asociado con conductos glandulares. En P. spinipinnis el tejido adiposo unilocular es más abundante, especialmente en juveniles. La diferencia en la cantidad de papilas marginales entre los juveniles podría relacionarse con la composición de la leche y el tiempo de lactancia. El tejido linfoide asociado a los conductos glandulares podría constituir un mecanismo de inmunidad de las mucosas solo en los juveniles. La disposición de la musculatura intrínseca favorecería movimientos de compresión y aplanamiento para la succión de presas. Las estructuras vasculares corresponderían a sistemas de contracorriente, que evitarían la pérdida de calor en los juveniles de ambas especies y los adultos de P. dioptric

Majoron emitting neutrinoless double beta decay in the electroweak chiral gauge extensions

Fundamental mechanisms for Majoron emitting neutrinoless double beta decay in SU(3)_C x G_W x U(1) models, for electroweak flavor chiral extensions, G_W = SU(3)_L and SU(4)_L are pointed out. Both kinds of known Majoron emitting processes, charged Majoron emitting where the massless Nambu-Goldstone boson itself carries lepton charge, $L=-2$, and the ordinary Majoron emitting where the boson has a small mass are found possible. PACS numbers: 11.15.Ex, 12.60.Fr, 14.80.CpComment: 18 pages, Revtex, 3 Postscript figures. To be published in Phys.Rev.D(1 May 1998

Ly49H signaling through DAP10 is essential for optimal natural killer cell responses to mouse cytomegalovirus infection

The activating natural killer (NK) cell receptor Ly49H recognizes the mouse cytomegalovirus (MCMV) m157 glycoprotein expressed on the surface of infected cells and is required for protection against MCMV. Although Ly49H has previously been shown to signal via DAP12, we now show that Ly49H must also associate with and signal via DAP10 for optimal function. In the absence of DAP12, DAP10 enables Ly49H-mediated killing of m157-bearing target cells, proliferation in response to MCMV infection, and partial protection against MCMV. DAP10-deficient Ly49H+ NK cells, expressing only Ly49H–DAP12 receptor complexes, are partially impaired in their ability to proliferate during MCMV infection, display diminished ERK1/2 activation, produce less IFN-γ upon Ly49H engagement, and demonstrate reduced control of MCMV infection. Deletion of both DAP10 and DAP12 completely abrogates Ly49H surface expression and control of MCMV infection. Thus, optimal NK cell–mediated immunity to MCMV depends on Ly49H signaling through both DAP10 and DAP12

Histomorfología comparada del esófago de dos especies de Arctocephalus: A. australis y A. tropicalis (Mammalia, Carnivora, Pinnipedia, Otariidae).

La estructura del sistema digestivo de los pinnípedos se relaciona directamente con los hábitos alimenticios y la dieta de cada especie. Se estudiaron las características histomorfológicas del esófago de dos otáridos: Arctocephalus australis y Arctocephalus tropicalis, mediante técnicas histológicas convencionales. El esófago consta de cuatro túnicas: mucosa, submucosa, muscular y adventicia/serosa. La mucosa incluye: a) tejido epitelial plano estratificado paracornificado, que en A. tropicalis posee menor cantidad de capas en sus estratos; b) lámina propia de tejido conectivo; c) muscular de la mucosa, de tejido muscular liso, discontinua y de espesor creciente hacia caudal. Existen glándulas acinares en toda su extensión; hacia caudal alcanzan la submucosa. Son más abundantes en A. australis, mientras que forman pequeñas agrupaciones en A. tropicalis. Poseen secreción mucosa, pero en A. tropicalis algunas son mixtas. La submucosa posee tejido conectivo denso irregular. La túnica muscular posee dos capas de tejido muscular estriado esquelético (interna, oblicua/espiralada; externa, longitudinal); hacia caudal la capa interna cambia progresivamente a tejido muscular liso, y la externa continúa con tejido muscular estriado esquelético. Entre ambas existen abundantes vasos y un plexo nervioso mientérico bien desarrollados. La adventicia está muy vascularizada e inervada. Las especies consideradas se alimentan principalmente bajo el agua mientras nadan, mediante la captura de presas que degluten enteras. La musculatura estriada que predomina en casi toda la extensión del órgano, junto con el gran desarrollo glandular, podrían facilitar el pasaje hacia el estómago de un alimento que no es procesado en la cavidad oral. Esto se complementaría con los movimientos corporales multidireccionales (algunos antigravitacionales) que realizan mientras ingieren sus presas. Las diferencias histológicas encontradas podrían atribuirse al tipo de dieta, más generalista en A. tropicalis (cefalópodos, peces y krill), mientras que en A. australis está constituida principalmente por peces, cuyo transporte sería más dificultoso e involucraría mayor fricció

Nuclear pairing: new perspectives

Nuclear pairing correlations are known to play an important role in various single-particle and collective aspects of nuclear structure. After the first idea by A. Bohr, B. Mottelson and D. Pines on similarity of nuclear pairing to electron superconductivity, S.T. Belyaev gave a thorough analysis of the manifestations of pairing in complex nuclei. The current revival of interest in nuclear pairing is connected to the shift of modern nuclear physics towards nuclei far from stability; many loosely bound nuclei are particle-stable only due to the pairing. The theoretical methods borrowed from macroscopic superconductivity turn out to be insufficient for finite systems as nuclei, in particular for the cases of weak pairing and proximity of continuum states. We suggest a simple numerical procedure of exact solution of the nuclear pairing problem and discuss the physical features of this complete solution. We show also how the continuum states can be naturally included in the consideration bridging the gap between the structure and reactions. The path from coherent pairing to chaos and thermalization and perspectives of new theoretical approaches based on the full solution of pairing are discussed.Comment: 47 pages, 11 figure

Ly49P recognition of cytomegalovirus-infected cells expressing H2-Dk and CMV-encoded m04 correlates with the NK cell antiviral response

Natural killer (NK) cells are crucial in resistance to certain viral infections, but the mechanisms used to recognize infected cells remain largely unknown. Here, we show that the activating Ly49P receptor recognizes cells infected with mouse cytomegalovirus (MCMV) by a process that requires the presence of H2-Dk and the MCMV m04 protein. Using H2 chimeras between H2-Db and -Dk, we demonstrate that the H2-Dk peptide-binding platform is required for Ly49P recognition. We identified m04 as a viral component necessary for recognition using a panel of MCMV-deletion mutant viruses and complementation of m04-deletion mutant (Δm04) virus infection. MA/My mice, which express Ly49P and H2-Dk, are resistant to MCMV; however, infection with Δm04 MCMV abrogates resistance. Depletion of NK cells in MA/My mice abrogates their resistance to wild-type MCMV infection, but does not significantly affect viral titers in mice infected with Δm04 virus, implicating NK cells in host protection through m04-dependent recognition. These findings reveal a novel mechanism of major histocompatability complex class I–restricted recognition of virally infected cells by an activating NK cell receptor