Round-robin measurements of two candidate materials for a Seebeck coefficient Standard Reference Material™

A Standard Reference Material (SRM^™) for the Seebeck coefficient is critical for inter-laboratory data comparison and for instrument calibration. To develop this SRM^™, we have conducted an international round-robin measurement survey of two candidate materials—undoped Bi₂Te₃ and constantan (55% Cu and 45% Ni alloy). Measurements were performed in two rounds by twelve laboratories involved in active thermoelectric research using a number of commercial and custom-built measurement systems and techniques. We report the results of these measurements and the statistical analysis performed. Based on this extensive study, we have selected Bi₂Te₃ as the prototype standard material.     

Operators with eigenvalues and extreme cases of stability

In the following, we consider some cases where the point spectrum of an operator is either very stable or very unstable with respect to small perturbations of the operator. The main result is about the shift operator on whose point spectrum is what we will call strongly stable. We also give some general perturbation results, including a result about the size of the set of operators that have an eigenvalue.

     

Effects of recombinant human growth hormone on HIV-1-specific T-cell responses,thymic output and proviral DNA in patients on HAART: 48-week follow-up

Background  

Efficacious immune-based therapy in treated chronic HIV-1 infection requires the induction of virus-specific CD4⁺ T cells and subsequent maturation and maintenance of specific memory CD8⁺ T cells. Concomitant daily administration of recombinant human growth hormone (rhGH) with highly active antiretroviral therapy (HAART) was used in chronically infected patients with lipodystrophy in an attempt to reconstitute these virus-specific T-cell responses.     

The kinetic limitation of anti-stokes luminescence of Er3+ and Yb3+ doped infrared upconversion materials

Infrared-to-visible wave-length conversion in the Yb³⁺−Er³⁺ doped phosphors system has been described by a simple three level model based on two ions mechanism. The excitation in the range of 900–1000 nm of an IR-photon is first absorbed by Yb³⁺ ion as a sensitizer attributed to the resonant energy transition in Er³⁺ ion from ⁴ I _3/2 → ⁴ S _15/2 and ¹ F _9/2 → ⁴ I _15/2, respectively for green and red emission. The essential energy transfer processes in this system i.e. upconversion from ⁴ I _11/2 and ¹ I _13/2, cross-relaxation from ⁴ S _3/2 and ¹ F _9/2 are taken into account. The limitations of the rate-equation approach are examined with a focus on the underlying dynamics of this rare-earth system.     

APPLICATION OF GENETIC ALGORITHM IN PARTICLE SIZE ANALYSIS BY MULTISPECTRAL EXTINCTION MEASUREMENTS

Both dependent and independent model algorithms are designed with genetic algorithm (GA) to retrieve aerosol size data from multispectral extinction measurements. Compared with the traditional dependent model algorithm, e.g., simplex, GA can locate the global optimized solution instead of local ones. As an independent model algonthm, when combined with B-splines, GA gives consistent results with Chahine and Phillip-Twomey-NNLS algorithms. Numerical simulations also show that GA has high stability and good resistance to relatively higher error levels. For a population size of 50 in the present paper, the feasible ranges for genetic operators Pc and pm are found to be [0.01, 0.5] and [0.01, 0.15], respectively, and the generation number Gen_Max should be larger than 250.     

Pseudo-jump inversion,upper cone avoidance,and strong jump-traceability

There are noncomputable c.e. sets, computable from every c.e. set relative to which ∅^′${\varnothing }^{\prime }$ is strongly jump-traceable. This yields a natural pseudo-jump operator, increasing on all sets, which cannot be inverted back to a minimal pair or even avoiding an upper cone.     

Weighted moments for a supercritical branching process in a varying or random environment

Let W be the limit of the normalized population size of a supercritical branching process in a varying or random environment. By an elementary method, we find sufficient conditions under which W has finite weighted moments of the form EWpl(W), where p > 1, l 0 is a concave or slowly varying function.     

On the parameterized complexity of short computation and factorization

A completeness theory for parameterized computational complexity has been studied in a series of recent papers, and has been shown to have many applications in diverse problem domains including familiar graph-theoretic problems, VLSI layout, games, computational biology, cryptography, and computational learning [ADF,BDHW,BFH, DEF,DF1-7,FHW,FK]. We here study the parameterized complexity of two kinds of problems: (1) problems concerning parameterized computations of Turing machines, such as determining whether a nondeterministic machine can reach an accept state in steps (the Short TM Computation Problem), and (2) problems concerning derivations and factorizations, such as determining whether a word can be derived in a grammar in steps, or whether a permutation has a factorization of length over a given set of generators. We show hardness and completeness for these problems for various levels of the hierarchy. In particular, we show that Short TM Computation is complete for . This gives a new and useful characterization of the most important of the apparently intractable parameterized complexity classes. Received August 1, 1994