Acoustic scattering from a thermally driven buoyant plume

An examination is made of the use of broad bandwidth high-frequency acoustic scattering to infer remotely the spatial structure of the temperature field of a thermally driven buoyant plume. Application of the far-field Born approximation results in a linear relationship between the transfer function of the scattering process, G, the ratio of received to transmitted pressure, to the spatial Fourier transform of the temperature field, φ (K), where K = ks – ki is the Bragg wave-number vector. A series of experiments are devised to test this hypothesis. These experiments involve a geometry of scattering in which pairs of sources and receivers are placed on opposite sides and equidistant from the scattering volume, a buoyant plume generated by a small circular heating element at the base of a water tank. It is shown that the far-field approximation assuming incident plane waves breaks down when the scales of temperature variability of the plume are of order the Fresnel radius. These results are discussed for both an unstable and turbulent plume. Conditions for the recovery of the Bragg scattering condition are established. © 1996 Acoustical Society of America

Neutrino Flavor Mixing Constrained by Accelerator and Reactor Experiments and Solar Neutrino Observation

We derive the constraints imposed on neutrino masses and mixing angles by performing a combined analysis of the data from the Los Alamos and the other terrestrial neutrino oscillation experiments with the assumption of the flavor-mixing solutions to the solar neutrino problem. In a three-flavor mixing scheme which ignores the possibility of sterile neutrinos, we obtain severe constraints on the pattern of masses and flavor mixing of neutrinos. For example, we show that in the standard Kobayashi-Maskawa type mixing matrix s_{13}^2 \lsim 10^{-2} independent of the choice of the solar neutrino solutions. The constraint from the double $\beta$ decay is also discussed.Comment: 13 pages, REVTeX, no figures, slightly revised with no change in conclusio

How Patients\u27 Self-Disclosure about Sickle Cell Pain Episodes to Significant Others Relates to Living with Sickle Cell Disease

Objectives: This cross-sectional study examines to whom and how fully sickle cell disease (SCD) patients talk to others about sickle cell pain, how helpful it is to talk with others about these pain episodes, and the association between talking to others about sickle cell pain episodes and patients\u27 psychological adjustment and coping strategies in managing the disease. Methods: A convenience sample of 73 African American patients with SCD (30 men and 43 women), were recruited from two SCD clinics at the time of routine medical visits. Most participants had been diagnosed with hemoglobin SS, and they reported an average number of 8.61 pain episodes in the previous 12 months. Participants were asked to whom, how fully, and how helpful it was to talk to significant others about SCD pain episodes experienced in the last 12 months. Patients also completed measures of their psychological adjustment as well as how they would manage a future sickle cell pain episode. Self-report ratings were made on Likert-type scales. Results: Based on paired samples t-tests, participants talked significantly more fully about their thoughts and feelings concerning pain episodes to God and to their primary medical providers than to either their parents, siblings, or an intimate partner/close friend. Bivariate correlations indicated that amount and helpfulness of talking about pain episodes to God and to parents were significantly associated with better psychological adjustment on selected measures. Also, bivariate correlations indicated that helpfulness in talking with siblings, intimate partner/close friend, and primary medical providers was positively related with willingness to go to a physician in the event of a future pain episode. Conclusions: The results document to whom and how helpful it is to talk with others about SCD pain episodes and how SCD disclosure is related to strategies for managing this disease

Interactive Learning-Based Realizability for Heyting Arithmetic with EM1

We apply to the semantics of Arithmetic the idea of ``finite approximation'' used to provide computational interpretations of Herbrand's Theorem, and we interpret classical proofs as constructive proofs (with constructive rules for $\vee, \exists$) over a suitable structure \StructureN for the language of natural numbers and maps of G\"odel's system \SystemT. We introduce a new Realizability semantics we call ``Interactive learning-based Realizability'', for Heyting Arithmetic plus \EM_1 (Excluded middle axiom restricted to $\Sigma^0_1$ formulas). Individuals of \StructureN evolve with time, and realizers may ``interact'' with them, by influencing their evolution. We build our semantics over Avigad's fixed point result, but the same semantics may be defined over different constructive interpretations of classical arithmetic (Berardi and de' Liguoro use continuations). Our notion of realizability extends intuitionistic realizability and differs from it only in the atomic case: we interpret atomic realizers as ``learning agents''

Gravothermal oscillations in multi-component models of star clusters

In this paper, gravothermal oscillations are investigated in multi-component star clusters which have power law initial mass functions (IMF). For the power law IMFs, the minimum masses ($m_{min}$) were fixed and three different maximum stellar masses ($m_{max}$) were used along with different power-law exponents ($\alpha$) ranging from 0 to -2.35 (Salpeter). The critical number of stars at which gravothermal oscillations first appear with increasing $N$ was found using the multi-component gas code SPEDI. The total mass ($M_{tot}$) is seen to give an approximate stability condition for power law IMFs with fixed values of $m_{max}$ and $m_{min}$ independent of $\alpha$. The value $M_{tot}/m_{max} \simeq 12000$ is shown to give an approximate stability condition which is also independent of $m_{max}$, though the critical value is somewhat higher for the steepest IMF that was studied. For appropriately chosen cases, direct N-body runs were carried out in order to check the results obtained from SPEDI. Finally, evidence of the gravothermal nature of the oscillations found in the N-body runs is presented.Comment: 9 pages, 3 figures, 8 tables. Accepted for publication in MNRA

Quantum switches and quantum memories for matter-wave lattice solitons

We study the possibility of implementing a quantum switch and a quantum memory for matter wave lattice solitons by making them interact with "effective" potentials (barrier/well) corresponding to defects of the optical lattice. In the case of interaction with an "effective" potential barrier, the bright lattice soliton experiences an abrupt transition from complete transmission to complete reflection (quantum switch) for a critical height of the barrier. The trapping of the soliton in an "effective" potential well and its release on demand, without loses, shows the feasibility of using the system as a quantum memory. The inclusion of defects as a way of controlling the interactions between two solitons is also reported