Determination of tolerance limits for the reliability of semiconductor devices using longitudinal data

Design and production of semiconductor devices for the automotive industry are characterized by high reliability requirements, such that the proper functioning of these devices is ensured over the whole specified lifetime. Therefore, manufacturers let their products undergo extensive testing procedures that simulate the tough requirements their products have to withstand. Such tests typically are highly accelerated, to test the behavior of the products over the whole lifetime. In case of drift of electrical parameters, manufacturers then need to find appropriate tolerance limits for their final electrical product tests, such that the proper functioning of their devices over the whole specified lifetime is ensured. In this study, we present a statistical model for the determination of tolerance limits that minimize yield loss. The model considers longitudinal measurements of continuous features, based on censored data from stress tests. The tolerance limits are derived from multivariate distributions where the dependence structure is described by different copulas. Based on extensive numerical testing, we are able to provide insights into the properties of our model for different drift behaviors of the devices.     

Inverse Gaussian process model with frailty term in reliability analysis

Traditional reliability analysis techniques focus on the occurrence of failures over time. Nevertheless, in certain cases where the occurrence of failures is tiny or almost null, the estimation of the quantities that describe the failure process is compromised. In this context, we introduce a reliability model for systems adopting the degradation process using frailty. The evolved degradation model has as experimental data, not the failure, but a quality feature attached to it. Degradation analysis can provide information about the lifetime distribution components without actually observing failures. In this paper, we propose an inverse Gaussian process model with frailty as a possible tool to investigate the effect of unobserved covariates. Moreover, a comparative study with the classical inverse Gaussian process based on simulated data was performed, revealing that the asymptotic properties of the maximum likelihood estimators are compromised when the presence of frailty is ignored. The application was based on two real data sets in the literature, showing that the inverse Gaussian process frailty models are propitious to use; however, gamma and inverse Gaussian distributions for frailty present similar results.     

Stabilization of a system modeling temperature and porosity fields in a Kelvin�CVoigt-type mixture

In this paper, we investigate the asymptotic behavior of solutions to the initial boundary value problem for the interaction between the temperature field and the porosity fields in a homogeneous and isotropic mixture from the linear theory of porous Kelvin?CVoigt materials. Our main result is to establish conditions which insure the analyticity and the exponential stability of the corresponding semigroup. We show that under certain conditions for the coefficients we obtain a lack of exponential stability. A numerical scheme is given.     

Assessment of scientific profiles and capabilities of Ph.D. programs in Chile: A scientometric approach

It is well known that the quality of a doctorate program is related to the level of involvement of its faculty in research. Thus, we worked with the hypothesis that postulates that if the in-house scientific output of the core faculty involved in a Ph.D. program can be appraised in such a manner that the achievements render quantitative and qualitative indicators, it is possible to depict profiles amenable for comparisons. We describe the methodology, that uses performance scientometric indicators, and results obtained after studying five Ph.D. programs in the field of Cell and Molecular Biology/Biochemistry in three different Chilean universities and show that the approach serves to portray the in-house capacity of each programvis a vis national and international standards.     

Room-temperature diffusion in Cu/Ag thin-film couples caused by anodic dissolution

Thin, 100-nm films of first silver and then copper were deposited consecutively onto inert substrates by magnetron sputter deposition. Constant anodic current densities were applied at room temperature to dissolve the outer copper film to varying depths. The 50Cu/50Ag interface, derived from the auger electron spectroscopic concentration-depth profile, initially moved into the copper toward the outer dissolving surface, indicating enhanced diffusion of copper into silver. After longer times at all anodic current densities, the interface reversed and moved back toward the underlying silver-rich layer, indicating that eventually diffusion of silver into copper predominated. The reversal time was inversely proportional to the anodic current density. These effects are explained by anodic formation of subsurface vacancies which migrate as divacancies to the copper/silver interface where they affect interface movements by the well-known Kirkendall mechanism. Calculated diffusivities up to 10⁻¹² cm²/s at maximum anodic current densities of 900 μA/cm² are dramatically above any that are normally observed at room temperature.     

Reliability for a walk/run test to estimate aerobic capacity in a brain-injured population

We investigated the effect of alpha-phenyl N-tert-butylnitrone (PBN), a spin trap reagent, on the proliferation of murine hematopoietic progenitor cells in vitro. During the addition of PBN to the liquid cultures of murine bone marrow cells containing a combination of interleukin-3, interleukin-6 and the c-kit ligand/stem cell factor, colony-forming cells in vitro (CFC) and the colony-forming unit in the spleen (CFU-S) increased about 1.6-fold and 2.0-fold, respectively, higher than the control culture. These effects were not observed when using dimethyl sulfoxide, which has the ability to scavenge radicals, and 5,5-dimethyl-1-pyrroline N-oxide, another spin trap reagent. Analysis of cultured cells from a 7-day liquid culture with PBN revealed that the ratio of the intracellular glutathione (GSH) and GSH/GSSG (oxidized GSH) content was higher than the control. Adding thiol N-acetylcysteine, a thiol reagent and a precursor of intracellular GSH, also showed similar effects on the liquid culture of murine hematopoietic progenitor cells and the level of intracellular GSH. In contrast, adding DL-buthionine-[S,R]-sulfoximine, a gamma-glutamylcysteine synthetase inhibitor, decreased the intracellular GSH level and did not increase the number of CFC and CFU-S. These results suggest that PBN regulates the content of intracellular thiol molecules, and the possibility of a relationship between the intracellular redox state and the proliferation and differentiation of hematopoietic stem cells.     

Prognosis of the skin UV-incidence increase in Poland

We studied the morphologic and immunohistochemical features of 10 peripheral T-cell lymphomas of a cytotoxic phenotype (CD3+/CD4-/CD8+), encountered among 98 peripheral T-cell lymphomas (PTCLs). Nine tumors were positive for both cytotoxic molecules, namely perforin (Pf) and granzyme B (GrB), and strong positivity was seen in the majority of the malignant cells. We also studied the expression of these molecules in 92 other cases of T-cell and natural killer (NK) cell neoplasms; 18 anaplastic large cell lymphomas (ALCLs); 63 CD4+ PTCLs; 10 CD56+ nasal lymphomas; and 1 NK-cell leukemia. Most of the CD4+ PTCLs (62 of 63) were negative for GrB, but all of the nasal lymphomas and the NK cell leukemia were positive for both Pf and GrB. Variable expression was seen among the 18 ALCLs. Within the 10 CD8+ PTCLs, 4 involved the skin, 3 of which were diagnosed as primary cutaneous lymphomas. Five patients died within 1 year of diagnosis. According to the Revised European-American Classification of Lymphoid Neoplasms, seven cases were categorized as "PTCL, unspecified," and three as "angioimmunoblastic T-cell lymphoma," "adult T-cell lymphoma/leukemia," or "small cell lymphoma," respectively. Three cases had characteristic morphologic features consisting of large lymphomatous cells with massive necrosis and nuclear fragmentation. Epstein-Barr virus mRNA was detected by in situ hybridization in three cases. Although the degree of apoptosis varied, apoptotic cells were detected in all cases by terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate-biotin nick end labeling. We conclude that CD8+ PTCLs are relatively rare, often involve extranodal sites, have an aggressive clinical course, and are often associated with Epstein-Barr virus. Compared with ALCLs, which have recently been considered as neoplasms of cytotoxic T-cells, we think that CD8+ PTCLs are more lineage-specific neoplasms of mature, cytotoxic, T lymphocytes.     

Becoming famous without being recognized: Unconscious influences of memory produced by dividing attention.

The familiarity of names produced by their prior presentation can be misinterpreted as fame. We used this false fame effect to separately study the effects of divided attention on familiarity versus conscious recollection. In a first experiment, famous and nonfamous names were presented to be read under conditions of full vs. divided attention. Divided attention greatly reduced later recognition memory performance but had no effect on gains in familiarity as measured by fame judgments. In later experiments, we placed recognition memory and familiarity in opposition by presenting only nonfamous names to be read in the first phase. Recognizing a name as earlier read on the later fame test allowed Ss to be certain that it was nonfamous. Divided attention at study or during the fame test reduced list recognition performance but had no effect on familiarity. We conclude that conscious recollection is an attention-demanding act that is separate from assessing familiarity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)