Inverted Solution Processable OLEDs Using a Metal Oxide as an Electron Injection Contact.

A new type of bottom‐emission electroluminescent device is described in which a metal oxide is used as the electron‐injecting contact. The preparation of such a device is simple. It consists of the deposition of a thin layer of a metal oxide on top of an indium tin oxide covered glass substrate, followed by the solution processing of the light‐emitting layer and subsequently the deposition of a high‐workfunction (air‐stable) metal anode. This architecture allows for a low‐cost electroluminescent device because no rigorous encapsulation is required. Electroluminescence with a high brightness reaching 5700 cd m^–2 is observed at voltages as low as 8 V, demonstrating the potential of this new approach to organic light‐emitting diode (OLED) devices. Unfortunately the device efficiency is rather low because of the high current density flowing through the device. We show that the device only operates after the insertion of an additional hole‐injection layer in between the light‐emitting polymer (LEP) and the metal anode. A simple model that explains the experimental results and provides avenues for further optimization of these devices is described. It is based on the idea that the barrier for electron injection is lowered by the formation of a space–charge field over the metal‐oxide–LEP interface due to the build up of holes in the LEP layer close to this interface.     

High quality LTCC resonator for voltage-controlled oscillator

Design and technology of microwave conductor lines embedded in low-temperature cofired ceramic (LTCC) multilayer substrates are summarized with a focus on achieving the highest possible quality (Q) factor for a given line inductance. The work was initiated to test the integrability of base station voltage-controlled oscillators (VCOs) in ceramic multilayer substrates. This approach leads to a miniaturization of current versions by a factor of 2 to 4. However, base station specifications for phase noise and hence resonator Q are extremely demanding. Therefore, both the design and the processing technology were optimized. By choosing a twin-line design with two parallel lines vertically separated by a single LTCC layer, Q factors of 90 and 180 have been achieved for integrated 5.5 nH inductors at frequencies of 640 MHz and 1650 MHz, respectively. Application of this result to VCO modules in standard LTCC technology already yields low phase noise levels, e.g., -136 dBc/Hz at 100 kHz offset, which is suitable for base station applications. However, further noise reduction is expected from a dedicated high Q fabrication process that uses conventional via punching and filling steps to replace the ceramic material between the two lines by conductive silver paste. This raises the Q to 120 and 200, respectively, at the two frequencies and adds extra degrees of freedom to LTCC design for low-loss wireless solutions.     

Task-dependent scheduling of feedback gains in animal motorsystems: too much, too soon for FES control?

Summary form only given. The idea that certain parts of the mammalian nervous system, such as the cerebellum, might be specialized for setting transmission parameters elsewhere is discussed. Experiences with the control of electrical stimulation in paretic patients, experiences which have shown that transducer systems are still far too primitive to allow this level of sophistication, even in laboratory-bound devices, are described. At best controllers rely on fixed-parameter feedback from one or two sensors to cycle through a simple finite-state control sequence. Kinematic variables are essentially driven open-loop. The author's approach to functional electrical stimulation (FES) control is constrained by transducer technology, and evolves virtually without reference to the features of the animal control systems described     

Association of the glycogen synthase locus on 19q13 with NIDDM in Pima Indians

Skeletal muscle glycogen synthase (encoded by GYS1 on chromosome 19q13.3) is the rate-limiting enzyme in insulin-mediated non-oxidative glucose disposal. Our previous studies have demonstrated an impairment of insulin-stimulated GYS1 activities in insulin-resistant Pima Indians, and associations of non-insulin-dependent diabetes mellitus (NIDDM) with the GYS1 locus were reported recently in Finnish and Japanese populations. We have performed linkage and association analyses of GYS1 and seven additional DNA markers on 19q with NIDDM, and with parameters of insulin action in the Pima Indians. We have found a significant association of NIDDM with GYS1 genotypes (p = 0.009), and with common GYS1 alleles (p = 0.022) in the Pima Indians. We have performed a detailed comparative analysis of the GYS1 gene, mRNA, and protein product in insulin-sensitive and insulin-resistant Pima Indians. No mutations in GYS1 coding sequences were detected; nor did we find alterations of GYS1 mRNA expression or of its basal enzymatic activity in insulin-resistant Pima Indians. These results contrasted with a 25% reduction of immunoreactive protein in insulin-resistant subjects as detected by Western blotting with an antibody specific for the C-terminal end of GYS1 (t-test p = 0.024; Wilcoxon's rank-sum test, p = 0.04). Because no mutations were detected in the DNA encoding this epitope, the difference in immunoreactivity may reflect post-translational modification(s) of the protein rather than a difference in the gene itself, or it could have occurred by chance. We conclude that our data do not indicate alterations in the GYS1 gene as the cause for the observed association, and that a different locus near GYS1 may be the contributing genetic element.     

Properties of the Stimulus Router System, a Novel Neural Prosthesis

Various types of neural prostheses (NPs) have been developed to restore motor function after neural injury. Surface NPs are noninvasive and inexpensive, but are often poorly selective, activating nontargeted muscles and cutaneous sensory nerves that can cause discomfort or pain. Implantable NPs are highly selective, but invasive and costly. The stimulus router system (SRS) is a novel NP consisting of fully implanted leads that “capture” and route some of the current flowing between a pair of surface electrodes to the vicinity of a target nerve. An SRS lead consists of a “pick-up” terminal that is implanted subcutaneously under one of the surface electrodes and a “delivery” terminal that is secured on or near the target nerve. We have published a preliminary report on the basic properties of the SRS [L. S. Gan , “A new means of transcutaneous coupling for neural prostheses,” IEEE Trans. Biomed. Eng., vol. 54, no. 3, pp. 509–517, Mar. 2007]. Here, we further characterize the SRS and identify aspects that maximize its performance as a motor NP. The surface current needed to activate nerves with an SRS, was found to depend on the proximity of the delivery terminal(s) to the nerve, electrode configurations, contact areas of the surface electrodes and implanted terminals, and the distance between the surface anode and the delivery terminal.      

Microstructural Coarsening During Sintering of Boron Carbide

The sintering behavior of boron carbide was investigated with particular attention given to microstructure development at various stages in the sintering process. Hot-pressing and pressureless sintering techniques were employed and the effects of heating rate, firing atmosphere, and composition were used to characterize the sintering behavior. Pressureless sintering at temperatures up to 2300°C produces only limited densification. Microstructural coarsening is responsible for this since it leads to conditions where densification is slow. Hot-pressing and carbon additions suppressed coarsening and permitted densification to >95% of theoretical density.     

Cytopathological analysis of sputum in patients with airflow obstruction and significant smoking histories

Advances in the understanding of lung cancer biology have led to observations that specific genetic changes occur in premalignant dysplasia. These observations have occurred predominantly in molecular studies of resected lung tumors and consequently, they may not be fully representative of those biological abnormalities characterizing premalignant lesions in individuals without overt lung cancer. Studies of premalignant epithelial cell biology and chemoprevention are needed in this patient subgroup. Such an initiative is now underway through the lung cancer Specialized Program of Research Excellence (SPORE) grant awarded to the University of Colorado Cancer Center (and affiliated institutions) by the National Cancer Institute. To identify participants for the early detection and chemoprevention trials of the Colorado SPORE, we initiated a sputum cytology screening program targeting persons with chronic obstructive pulmonary disease and smoking histories of 40 or more pack-years. During the first 26 months after activation of the screening program, sputum samples from 632 participants were evaluated. Of these, 533 (84%) of the subjects submitted specimens deemed adequate for cytopathological interpretation; 99 (16%) provided sputum samples unsuitable for cytodiagnosis. Of those participants who submitted adequate samples, 48% had cytodiagnoses of mild dysplasia, 26 % had moderate to severe dysplasia, and 2% presented with carcinoma in situ or invasive carcinoma. Logistic regression modeling was pursued to determine whether selected demographic and/or clinical status variables could be identified as statistically significant predictors of the specific cytological outcome to be expected (mild dysplasia, moderate dysplasia, and so forth). The only apparent associations found from both univariate and multivariate analyses were that the total number of pack-years of smoking history decreased with severity of cytodiagnosis and that those individuals with mild or moderate dysplasia were more likely to be ex-smokers than those with grades of regular metaplasia or lower. Based on the initial results of the Colorado SPORE sputum cytology screening program, we conclude that persons with chronic obstructive pulmonary disease and 40 or more pack-years of smoking history have a high prevalence of premalignant dysplasia detectable through sputum cytology and should be targeted for research programs focusing on lung cancer prevention, early detection, and exploratory biomarker studies.     

An autosomal genomic scan for loci linked to prediabetic phenotypes in Pima Indians

Type 2 diabetes mellitus is a common chronic disease that is thought to have a substantial genetic basis. Identification of the genes responsible has been hampered by the complex nature of the syndrome. Abnormalities in insulin secretion and insulin action predict the development of type 2 diabetes and are, themselves, highly heritable traits. Since fewer genes may contribute to these precursors of type 2 diabetes than to the overall syndrome, such genes may be easier to identify. We, therefore, undertook an autosomal genomic scan to identify loci linked to prediabetic traits in Pima Indians, a population with a high prevalence of type 2 diabetes. 363 nondiabetic Pima Indians were genotyped at 516 polymorphic microsatellite markers on all 22 autosomes. Linkage analyses were performed using three methods (single-marker, nonparametric multipoint [MAPMAKER/SIBS], and variance components multipoint). These analyses provided evidence for linkage at several chromosomal regions, including 3q21-24 linked to fasting plasma insulin concentration and in vivo insulin action, 4p15-q12 linked to fasting plasma insulin concentration, 9q21 linked to 2-h insulin concentration during oral glucose tolerance testing, and 22q12-13 linked to fasting plasma glucose concentration. These results suggest loci that may harbor genes contributing to type 2 diabetes in Pima Indians. None of the linkages exceeded a LOD score of 3.6 (a 5% probability of occurring in a genome-wide scan). These findings must, therefore, be considered tentative until extended in this population or replicated in others.     

Conformal mapping of the unit circle or of the upper half plane onto a polygon

The aim of this paper is to reduce the problem of conformal mapping onto a polygon and the inverse mapping problem to simple engineering exercises. In particular, both analytical and numerical methods are combined to eliminate the need for complicated mathematical analysis. A FORTRAN IV-program is presented which offers many conveniences to the user including graphic representation of the mapping. Finally, the results of 15 examples relating to quadrilaterals, pentagons and heptagons are given for reference. The high degree of accuracy of the calculated values, to about 10 significant digits, should be noted.     

Immiscible Blends of PC and PET,Current Knowledge and New Results: Rheological Properties

This paper deals with immiscible blends of poly(ethylene terephthalate) obtained by melt blending with polycarbonate. A large survey of the current knowledge in the field of these blends is presented. Resolved and unresolved issues concerning the effect of exchange reactions on the miscibility of the components are addressed. The experimental part of the paper focuses on the rheological behavior of PET/PC blends. Blends containing various polymer ratios were obtained by melt blending with and without transesterification catalysts. Oscillatory shear flow in the melt was used to characterize the rheology of the various samples. A plot of the oscillatory data, similar to the Van Gurp Palmen plot, is used to point out the broadening of the co‐continuity window when in situ compatibilization takes place.