Electron beam seals outer surfaces of porous bodies

Porous tungsten plugs provide even airflow for frictionless bearings used in air bearing supported gyros. The plugs have their outer cylindrical surface sealed by an electron beam process to ensure unidirectional airflow through their exit ends

Zebrafish Exploit Visual Cues and Geometric Relationships to Form a Spatial Memory

Animals use salient cues to navigate in their environment, but their specific cognitive strategies are largely unknown. We developed a conditioned place avoidance paradigm to discover whether and how zebrafish form spatial memories. In less than an hour, juvenile zebrafish, as young as 3 weeks, learned to avoid the arm of a Y-maze that was cued with a mild electric shock. Interestingly, individual fish solved this task in different ways: by staying in the safe center of the maze or by preference for one, or both, of the safe arms. In experiments in which the learned patterns were swapped, rotated, or replaced, the animals could transfer the association of safety to a different arm or to a different pattern using either visual cues or location as the conditioned stimulus. These findings show that juvenile zebrafish exhibit several complementary spatial learning modes, which generate a flexible repertoire of behavioral strategies

Statistical mechanics of temporal association in neural networks with transmission delays

We study the representation of static patterns and temporal sequences in neural networks with signal delays and a stochastic parallel dynamics. For a wide class of delay distributions, the asymptotic network behavior can be described by a generalized Gibbs distribution, generated by a novel Lyapunov functional for the determination dynamics. We extend techniques of equilibrium statistical mechanics so as to deal with time-dependent phenomena, derive analytic results for both retrieval quality and storage capacity, and compare them with numerical simulations

Harmonic lattice behavior of two-dimensional colloidal crystals

Using positional data from video-microscopy and applying the equipartition theorem for harmonic Hamiltonians, we determine the wave-vector-dependent normal mode spring constants of a two-dimensional colloidal model crystal and compare the measured band-structure to predictions of the harmonic lattice theory. We find good agreement for both the transversal and the longitudinal mode. For $q\to 0$, the measured spring constants are consistent with the elastic moduli of the crystal.Comment: 4 pages, 3 figures, submitte

Measuring the equation of state of a hard-disc fluid

We use video microscopy to study a two-dimensional (2D) model fluid of charged colloidal particles suspended in water and compute the pressure from the measured particle configurations. Direct experimental control over the particle density by means of optical tweezers allows the precise measurement of pressure as a function of density. We compare our data with theoretical predictions for the equation of state, the pair-correlation function and the compressibility of a hard-disc fluid and find good agreement, both for the fluid and the solid phase. In particular the location of the transition point agrees well with results from Monte Carlo simulations.Comment: 7 pages, to appear in EPL, slightly corrected versio

Distances sets that are a shift of the integers and Fourier basis for planar convex sets

The aim of this paper is to prove that if a planar set $A$ has a difference set $\Delta(A)$ satisfying $\Delta(A)\subset \Z^++s$ for suitable $s$ than $A$ has at most 3 elements. This result is motivated by the conjecture that the disk has not more than 3 orthogonal exponentials. Further, we prove that if $A$ is a set of exponentials mutually orthogonal with respect to any symmetric convex set $K$ in the plane with a smooth boundary and everywhere non-vanishing curvature, then # (A \cap {[-q,q]}^2) \leq C(K) q where $C(K)$ is a constant depending only on $K$. This extends and clarifies in the plane the result of Iosevich and Rudnev. As a corollary, we obtain the result from \cite{IKP01} and \cite{IKT01} that if $K$ is a centrally symmetric convex body with a smooth boundary and non-vanishing curvature, then $L^2(K)$ does not possess an orthogonal basis of exponentials

Collection of relevant results obtained with the Skylab images by the Institute for Space Research, INPE

There are no author-identified significant results in this report

Humalog Mix25 improves 24-hour plasma glucose profiles compared with the human insulin mixture 30/70 in patients with type 2 diabetes mellitus

Objective. To compare the effects of Humalog Mix25 (Humalog Mix75/25 in the USA) (Mix25) and human insulin 30/70 (30/70) on the 24-hour inpatient plasma glucose (PG) profile in patients with type 2 diabetes mellitus (T2DM). Design. A randomised, open-label, 8-week crossover study. Study insulins were injected twice daily, 5 minutes before breakfast and dinner. Setting. Four-week outpatient (dose-adjustment) treatment phase, and 3-day inpatient (test) phase. Patients. Twenty-five insulin-treated patients with T2DM (ages 40 - 66 years), mean (± standard error of the mean) (SEM) HbA1c 7.7% ± 0.23%, and body mass index (BMI) 29.3 ± 0.83 kg/m2. Outcome measures. 24-hour PG profiles, PG excursions after meals, PG area under the curve (AUC), and 30-day hypoglycaemia rate. Results. The 2-hour PG excursions following breakfast (5.5 ± 0.34 v. 7.2 ± 0.34 mmol/l, p = 0.002) and dinner (2.4 ± 0.27 v. 3.4 ± 0.27 mmol/l, p = 0.018) were smaller with Mix25 than with 30/70. PG AUC between breakfast and lunch was smaller with Mix25 than with 30/70 (77.6 ± 3.8 v. 89.5 ± 4.3 mmol/h/ml, p = 0.001). PG AUC between lunch and dinner, dinner and bedtime, and bedtime and breakfast did not differ between treatments. Pre-meal and nocturnal PG were comparable. The postprandial insulin requirement for lunch meals was supplied equally by the two insulin treatments. The thirty-day hypoglycaemia rate was low (Mix25 0.049 ± 0.018 v. 30/70 0.100 ± 0.018 episodes/patient/30 days, p = 0.586) for both treatments. Conclusion. In patients with T2DM, Mix25 improved the 24-hour PG profile with lower postprandial PG excursions than with human insulin 30/70. (South African Medical Journal: 2003 93(3): 219-223

Explicit solution of the quantum three-body Calogero-Sutherland model

Quantum integrable systems generalizing Calogero-Sutherland systems were introduced by Olshanetsky and Perelomov (1977). Recently, it was proved that for systems with trigonometric potential, the series in the product of two wave functions is a deformation of the Clebsch-Gordan series. This yields recursion relations for the wave functions of those systems. In this note, this approach is used to compute the explicit expressions for the three-body Calogero-Sutherland wave functions, which are the Jack polynomials. We conjecture that similar results are also valid for the more general two-parameters deformation introduced by Macdonald.Comment: 10 page