Evidence for multiple structural genes for the γ chain of human fetal hemoglobin

A sequence with a specific residue at each position was proposed for the γ chain of human fetal hemoglobin by Schroeder et al. (1) after a study in which hemoglobin from a number of individual infants was used. We have now examined in part the fetal hemoglobin components of 17 additional infants and have observed that position 136 of the γ chain may be occupied not only by a glycyl residue, as previously reported, but also by an alanyl residue

Feasibility analysis of reciprocating magnetic heat pumps

The conceptual design selected for detailed system analysis and optimization is the reciprocating gadolinium core in a regenerative fluid column within the bore of a superconducting magnet. The thermodynamic properties of gadolinium are given. A computerized literature search for relevant papers was conducted and is being analyzed. Contact was made with suppliers of superconducting magnets and accessories, magnetic materials, and various types of hardware. A description of the model for the thermal analysis of the core and regenerator fluids is included

Truncated Variational Sampling for "Black Box" Optimization of Generative Models

We investigate the optimization of two probabilistic generative models with binary latent variables using a novel variational EM approach. The approach distinguishes itself from previous variational approaches by using latent states as variational parameters. Here we use efficient and general purpose sampling procedures to vary the latent states, and investigate the "black box" applicability of the resulting optimization procedure. For general purpose applicability, samples are drawn from approximate marginal distributions of the considered generative model as well as from the model's prior distribution. As such, variational sampling is defined in a generic form, and is directly executable for a given model. As a proof of concept, we then apply the novel procedure (A) to Binary Sparse Coding (a model with continuous observables), and (B) to basic Sigmoid Belief Networks (which are models with binary observables). Numerical experiments verify that the investigated approach efficiently as well as effectively increases a variational free energy objective without requiring any additional analytical steps

Advances in Control of Onion Thrips (Thysanoptera: Thripidae) in Cabbage

Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), feeding injury results in discoloration and a rough texture on cabbage, Brassica oleracea capitata (L.), leaves, and damage may occur deep inside the head. It has become a key pest of cabbage in the United States and many other countries. Previous studies have indicated poor control using insecticides. The present study identified imidacloprid drenches and sprays of acetamiprid, dimethoate, spinosad, and imidacloprid as insecticides that performed better than the industry standard, lambda-cyhalothrin. However, additional tests with foliar sprays of dimethoate and acetamiprid indicated there was not an ideal crop stage (precupping, cupping, or postcupping) at which either insecticide could be applied for reliable control of T. tabaci, possibly because of multiple flights of thrips into the crop or the asynchrony of flights and susceptible crop stages. In tests in a commercial field, a soil drench of imidacloprid 4 wk after transplanting reduced the number of damaged leaves in the head by 32%, whereas five sprays of acetamiprid reduced damage by 51%. Combining both insecticide regimes reduced damage by 85%, but resulted in a very costly management program. Cabbage varieties varied considerably in susceptibility with some having negligible thrips injury, regardless of being treated with an insecticide. Planting date affected susceptibility of cabbage to some degree, but not as much as other tactics. Overall, these studies indicate that increased emphasis should be placed on breeding cabbages to be resistant to T. tabaci as the foundation for its managemen

NS-NS fluxes in Hitchin's generalized geometry

The standard notion of NS-NS 3-form flux is lifted to Hitchin's generalized geometry. This generalized flux is given in terms of an integral of a modified Nijenhuis operator over a generalized 3-cycle. Explicitly evaluating the generalized flux in a number of familiar examples, we show that it can compute three-form flux, geometric flux and non-geometric Q-flux. Finally, a generalized connection that acts on generalized vectors is described and we show how the flux arises from it.Comment: 21 pages, 1 figure; v3: minor change

Surprisingly Little O VI Emission Arises in the Local Bubble

This paper reports the first study of the O VI resonance line emission (1032, 1038 Angstroms) originating in the Local Bubble (or Local Hot Bubble) surrounding the solar neighborhood. In spite of the fact that O VI absorption within the Local Bubble has been observed, no resonance line emission was detected during our 230 ksec Far Ultraviolet Spectroscopic Explorer observation toward a ``shadowing'' filament in the southern Galactic hemisphere. As a result, tight 2 sigma upper limits are set on the intensities in the 1032 and 1038 Angstrom emission lines: 500 and 530 photons cm^{-2} s^{-1} sr^{-1}, respectively. These values place strict constraints on models and simulations. They suggest that the O VI-bearing plasma and the X-ray emissive plasma reside in distinct regions of the Local Bubble and are not mixed in a single plasma, whether in equilibrium with T ~ 10^6 K or highly overionized with T ~ 4 to 6 x 10^4 K. If the line of sight intersects multiple cool clouds within the Local Bubble, then the results also suggest that hot/cool transition zones differ from those in current simulations. With these intensity upper limits, we establish limits on the electron density, thermal pressure, pathlength, and cooling timescale of the O VI-bearing plasma in the Local Bubble. Furthermore, the intensity of O VI resonance line doublet photons originating in the Galactic thick disk and halo is determined (3500 to 4300 photons cm^{-2} s^{-1} sr^{-1}), and the electron density, thermal pressure, pathlength, and cooling timescale of its O VI-bearing plasma are calculated. The pressure in the Galactic halo's O VI-bearing plasma (3100 to 3800 K cm^{-3}) agrees with model predictions for the total pressure in the thick disk/lower halo. We also report the results of searches for other emission lines.Comment: accepted by ApJ, scheduled for May 2003, replacement astro-ph submission corrects typos and grammatical errors in original versio

Nongeometry, Duality Twists, and the Worldsheet

In this paper, we use orbifold methods to construct nongeometric backgrounds, and argue that they correspond to the spacetimes discussed in \cite{dh,wwf}. More precisely, we make explicit through several examples the connection between interpolating orbifolds and spacetime duality twists. We argue that generic nongeometric backgrounds arising from duality twists will not have simple orbifold constructions and then proceed to construct several examples which do have a consistent worldsheet description.Comment: v2-references added; v3-minor correction (eqn. 4.17

D-Terms from Generalized NS-NS Fluxes in Type II

Orientifolds of type II string theory admit a certain set of generalized NS-NS fluxes, including not only the three-form field strength H, but also metric and non-geometric fluxes, which are related to H by T-duality. We describe in general how these fluxes appear as parameters of an effective N=1 supergravity theory in four dimensions, and in particular how certain generalized NS-NS fluxes can act as charges for R-R axions, leading to D-term contributions to the effective scalar potential. We illustrate these phenomena in type IIB with the example of a certain orientifold of T^6/Z_4.Comment: 31+1 pages, uses utarticle.cls; v2: references adde