On the Derivative Expansion at Finite Temperature

In this short note, we indicate the origin of nonanalyticity in the method of derivative expansion at finite temperature and discuss some of its consequences.Comment: 7 pages, UR-1363, ER40685-81

Dynamics of Weak First Order Phase Transitions

The dynamics of weak vs. strong first order phase transitions is investigated numerically for 2+1 dimensional scalar field models. It is argued that the change from a weak to a strong transition is itself a (second order) phase transition, with the order parameter being the equilibrium fractional population difference between the two phases at the critical temperature, and the control parameter being the coefficient of the cubic coupling in the free-energy density. The critical point is identified, and a power law controlling the relaxation dynamics at this point is obtained. Possible applications are briefly discussed.Comment: 11 pages, 4 figures in uuencoded compressed file (see instructions in main text), RevTeX, DART-HEP-94/0

Thermal Phase Mixing During First Order Phase Transitions

The dynamics of first order phase transitions are studied in the context of (3+1)-dimensional scalar field theories. Particular attention is paid to the question of quantifying the strength of the transition, and how `weak' and `strong' transitions have different dynamics. We propose a model with two available low temperature phases separated by an energy barrier so that one of them becomes metastable below the critical temperature $T_c$. The system is initially prepared in this phase and is coupled to a thermal bath. Investigating the system at its critical temperature, we find that `strong' transitions are characterized by the system remaining localized within its initial phase, while `weak' transitions are characterized by considerable phase mixing. Always at $T_c$, we argue that the two regimes are themselves separated by a (second order) phase transition, with an order parameter given by the fractional population difference between the two phases and a control parameter given by the strength of the scalar field's quartic self-coupling constant. We obtain a Ginzburg-like criterion to distinguish between `weak' and `strong' transitions, in agreement with previous results in (2+1)-dimensions.Comment: 28 pages RevTeX, 9 postscript figures, IMPERIAL/TP/93-94/58, DART-HEP-94/0

Microphysical Approach to Nonequilibrium Dynamics of Quantum Fields

We examine the nonequilibrium dynamics of a self-interacting $\lambda\phi^4$ scalar field theory. Using a real time formulation of finite temperature field theory we derive, up to two loops and $O(\lambda^2)$, the effective equation of motion describing the approach to equilibrium. We present a detailed analysis of the approximations used in order to obtain a Langevin-like equation of motion, in which the noise and dissipation terms associated with quantum fluctuations obey a fluctuation-dissipation relation. We show that, in general, the noise is colored (time-dependent) and multiplicative (couples nonlinearly to the field), even though it is still Gaussian distributed. The noise becomes white in the infinite temperature limit. We also address the effect of couplings to other fields, which we assume play the r\^ole of the thermal bath, in the effective equation of motion for $\phi$. In particular, we obtain the fluctuation and noise terms due to a quadratic coupling to another scalar field.Comment: 30 pages, LaTex (uses RevTex 3.0), DART-HEP-93/0

Brain structural covariance networks in obsessive-compulsive disorder: a graph analysis from the ENIGMA Consortium.

Brain structural covariance networks reflect covariation in morphology of different brain areas and are thought to reflect common trajectories in brain development and maturation. Large-scale investigation of structural covariance networks in obsessive-compulsive disorder (OCD) may provide clues to the pathophysiology of this neurodevelopmental disorder. Using T1-weighted MRI scans acquired from 1616 individuals with OCD and 1463 healthy controls across 37 datasets participating in the ENIGMA-OCD Working Group, we calculated intra-individual brain structural covariance networks (using the bilaterally-averaged values of 33 cortical surface areas, 33 cortical thickness values, and six subcortical volumes), in which edge weights were proportional to the similarity between two brain morphological features in terms of deviation from healthy controls (i.e. z-score transformed). Global networks were characterized using measures of network segregation (clustering and modularity), network integration (global efficiency), and their balance (small-worldness), and their community membership was assessed. Hub profiling of regional networks was undertaken using measures of betweenness, closeness, and eigenvector centrality. Individually calculated network measures were integrated across the 37 datasets using a meta-analytical approach. These network measures were summated across the network density range of K = 0.10-0.25 per participant, and were integrated across the 37 datasets using a meta-analytical approach. Compared with healthy controls, at a global level, the structural covariance networks of OCD showed lower clustering (P < 0.0001), lower modularity (P < 0.0001), and lower small-worldness (P = 0.017). Detection of community membership emphasized lower network segregation in OCD compared to healthy controls. At the regional level, there were lower (rank-transformed) centrality values in OCD for volume of caudate nucleus and thalamus, and surface area of paracentral cortex, indicative of altered distribution of brain hubs. Centrality of cingulate and orbito-frontal as well as other brain areas was associated with OCD illness duration, suggesting greater involvement of these brain areas with illness chronicity. In summary, the findings of this study, the largest brain structural covariance study of OCD to date, point to a less segregated organization of structural covariance networks in OCD, and reorganization of brain hubs. The segregation findings suggest a possible signature of altered brain morphometry in OCD, while the hub findings point to OCD-related alterations in trajectories of brain development and maturation, particularly in cingulate and orbitofrontal regions

When rats rescue robots

Robots are increasingly being used to monitor and even participate in social interactions with animals in their own environments. Robotic animals enable social behaviors to be observed in natural environments, or specifically elicited under the control of an experimenter. It is an open question to what extent animals will form positive social connections with such robots. To test this, we familiarized rats to two rat-sized robots, one exhibiting “social” behaviors, including helping, while the other was also mobile but not helpful. When given an opportunity to release the robots from restrainers, as they do for conspecifics, we found that rats did release the robots, and moreover, were significantly more likely to release the helpful than the unhelpful robot. These findings indicate that robots can elicit helpful behavior from rats, and that rats will even discriminate between robots on the basis of their behaviors

HLA-Identical Sibling Allogeneic Transplants versus Chemotherapy in Acute Myelogenous Leukemia with t(8;21) in First Complete Remission: Collaborative Study between the German AML Intergroup and CIBMTR

AbstractWe studied the role of HLA-matched sibling hematopoietic cell transplantation (HCT) in treating t(8;21) acute myelogenous leukemia (AML) in first remission. Outcomes of 118 patients receiving HCT and reported to the Center for International Blood and Marrow Transplant Research were compared with 132 similar patients receiving chemotherapy selected from 8 German AML Intergroup multicenter trials. Characteristics of the cohorts were similar except that chemotherapy recipients were significantly older. To adjust for time to treatment bias, outcomes were compared using left-truncated Cox regression models. Transplants were associated with higher treatment-related mortality (TRM; relative risk [RR] 6.76, 95% confidence interval [CI] 2.95-15.45, P < .001), lower relapse (RR 0.47, 95% CI 0.25-0.85, P = .01), and similar relapse-free survival (P = .2). Loss of sex chromosomes (LOS) in addition to t(8;21) had a negative impact on overall survival (OS) in patients receiving chemotherapy. Patients without LOS experienced shorter survival after HCT comparing to chemotherapy (RR 3.05, P = .02), whereas patients with LOS had similar survival regardless of postremission therapy. In both cohorts, white blood cell count (WBC) at diagnosis >25 × 109/L was associated with a higher relapse risk (RR = 2.09, P = .03), lower relapse-free (RR = 1.9, P = .008), and OS (RR = 1.91, P = .01). In this cohort of patients with t(8;21) AML, HCT did not improve OS, because reduction of relapse was offset by high TRM. In the group without LOS, survival after chemotherapy was far superior to HCT. These results suggest that patients with t(8;21) AML without poor prognostic factors have higher rates of survival after chemotherapy as a post remission therapy compared to HCT

Mapa de Favorabilidad Geotérmica Aplicando el Método de Análisis Geothermal Play Fairway Área 2, Sierras Subandinas, Cuenca de Tucumán y su Extensión en la Provincia de Santiago del Estero, Argentina.

Fil: Asato, Carlos Gabriel. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.Fil: Conde Serra, Alejandro. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.Fil: Seggiaro, Raúl E. Servicio Geológico Minero Argentino. Centro Salta; Argentina.Fil: Molina, Eduardo A. Servicio Geológico Minero Argentino. Centro Salta; Argentina.Fil: Cegarra, Marcelo I. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.Fil: Hernández, Mariano, Servicio Geológico Minero Argentino. Centro General Roca; Argentina.Fil: Carrizo, Noelia. Servicio Geológico Minero Argentino. Sub Centro Catamarca; Argentina.Fil: Peralta Arnold, Yésica J. Mariano, Servicio Geológico Minero Argentino. Centro Jujuy; Argentina.Fil: Larcher, Nicolás. Servicio Geológico Minero Argentino. Centro Jujuy; Argentina.Fil: Fernández, Diego. Servicio Geológico Minero Argentino. Centro Tucumán; Argentina.Fil: Peroni, Javier Ignacio. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.Fil: Ramé, Gustavo A. Servicio Geológico Minero Argentino. Centro Córdoba; Argentina.Fil: Naón, Virginia. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.En la presente contribución se da a conocer el resultado de la aplicación del método Geothermal Play Fairway en una región de aproximadamente 71.000 km2 que comprende parte de las Sierras Subandinas, Cordillera Oriental, Sistema de Santa Bárbara y Llanura Chaco-Pampeana, en las provincias de Jujuy, Salta, Tucumán, Santiago del Estero y Catamarca, denominada en su conjunto Área 2. De acuerdo a esta metodología que integra y modela diversos tipos de datos geológicos directos e indirectos, se generaron mapas de evidencias correspondientes a los tres factores geológicos principales para la existencia de un recurso geotermal: los subsistemas de Permeabilidad, Fluidos y Calor. Estos tres componentes en conjunto integran el mapa resultante de Potencial Geotérmico del Área 2. Se asignó mayor influencia en el cómputo de favorabilidad geotérmica al subsistema de Permeabilidad, el cual está condicionado por la presencia de estructuras (fallas y lineamientos) o conjuntos de estructuras que generan los espacios necesarios para el ascenso de fluidos geotermales. Estos rasgos, determinados por mapeo geológico y por métodos geofísicos en subsuelo, fueron ponderados según su tipología, edad, interacción con otras estructuras y profundidad de los sismos asociados a ellos. En segundo lugar de importancia se consideró al subsistema Calor, en donde se utilizaron evidencias geoquímicas (mediante cálculos geotermométricos de muestras de aguas termales), información de pozos y anomalías geofísicas, que determinaron una participación de fuentes profundas de calor. Finalmente, el menor peso fue asignado al subsistema de Fluidos, integrado por expresiones hidrotermales cuyos análisis hidroquímicos permitieron deducir la participación de fluidos geotérmicos de alta entalpía. La combinación de los distintos mapas de evidencias con sus respectivas ponderaciones constituye el mapa final de favorabilidad geotérmica para el Área 2, en el cual, se destacan zonas o áreas con características distintivas: Zona Norte: Se circunscribe a la región del Sistema de Santa Bárbara y es clasificada como un sistema conductivo. Se encuentran gradientes geotérmicos normales y se interpretan reservorios geotérmicos profundos asociados a fallas de alto ángulo que juegan un rol preponderante en la conducción de fluidos y/o la compartimentalización de bloques (barreras). Zona Sur: Abarca la llanura Tucumano-Santiagueña y se la clasifica como un sistema convectivo-conductivo. Presenta gradientes geotérmicos anómalos diseminados por el área, con indicios de fluencia ascendente de calor de origen mantélico a través del basamento y en asociación con estructuras profundas. Otros sectores con probabilidad de albergar sistemas ciegos (no aflorantes)