Enhanced polarization in zirconia-P(VDF-TrFE) laminar composite dielectrics

Zirconia-P(VDF-TrFE) double-layered laminar composites are experimentally investigated to understand inorganic–organic interfacial effects in composite dielectrics. The DC and AC electrical response of the individual phases were characterized in addition to the zirconia-P(VDF-TrFE) composite. The measured real part of permittivity for the laminar composite is found to be higher than theoretically calculated values using series mixing rules for zirconia and P(VDF-TrFE). Additional polarization of the composite structure can be attributed to either the presence of interfacial polarization of zirconia and P(VDF-TrFE) or modification of polymer. Impedance spectroscopy has shown that dielectric properties of laminar composites are dominated by zirconia thin films in low frequency region. The impedance spectroscopy shows that zirconia blocks charge carrier motion and hence partially contribute towards additional interfacial polarization in the laminar composite. The dielectric response of the laminar composite was also modeled through a Maxwell–Wagner interfacial polarization mechanism, which was found to inadequately describe the polarization response. Equivalent circuit modeling of the composite has revealed an additional interfacial circuit element for the additional polarization, suggesting a structurally modified polymer at the interface.     

Neuropsychological performance in Hallervorden-Spatz syndrome: A report of two cases.

Hallervorden-Spatz disease (HSD) is a rare progressive disorder characterized by iron deposition in the globus pallidus and zona reticularis of the substantia nigra. The cases of 2 Black female patients (aged 20–38 yrs) with diagnoses of probable HSD are evaluated, based on typical clinical course in conjunction with magnetic resonance imaging abnormalities restricted to the region of the globus pallidus. Ss' deficits included slowed cognitive processing speed, motor sequencing difficulty, constructional dyspraxia, and impaired recent memory functions. The constellation of behavioral deficits can be attributed to dysfunction of the frontal lobe, basal ganglia, or disruption of their functional interconnections. Additional deficits in language and visuospatial processing were also observed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Knowledge representation and sharing using visual semantic modeling for diagnostic medical image databases.

Information technology offers great opportunities for supporting radiologists' expertise in decision support and training. However, this task is challenging due to difficulties in articulating and modeling visual patterns of abnormalities in a computational way. To address these issues, well established approaches to content management and image retrieval have been studied and applied to assist physicians in diagnoses. Unfortunately, most of the studies lack the flexibility of sharing both explicit and tacit knowledge involved in the decision making process, while adapting to each individual's opinion. In this paper, we propose a knowledge repository and exchange framework for diagnostic image databases called "evolutionary system for semantic exchange of information in collaborative environments" (Essence). This framework uses semantic methods to describe visual abnormalities, and offers a solution for tacit knowledge elicitation and exchange in the medical domain. Also, our approach provides a computational and visual mechanism for associating synonymous semantics of visual abnormalities. We conducted several experiments to demonstrate the system's capability of matching synonym terms, and the benefit of using tacit knowledge in improving the meaningfulness of semantic queries.     

Uniform syntax for type expressions and declarators

A declaration mechanism is proposed that allows common type information to be factored into a type expression, yet allows related but distinct types to be declared together. The mechanism is a unification of declarations in Pascal and C. The choice of syntax is quite important. The proposed syntax uses a postfix operator for dereferencing pointers instead of the prefix operator * for pointer dereferencing in C.     

Gelastic, quiritarian, and cursive epilepsy. A clinicopathological appraisal

A patient is reported with episodes of epileptic laughter, crying, and running occurring alone or in combination. He was found to have discrete, well-circumscribed tumour of the left temporal lobe. The neurology of these epileptic events is discussed in relation to the pathological lesion.     

Fabrication and characterization of novel silicon-compatible high-density capacitors

System integration and miniaturization demands are driving component technologies towards integrated thin films with higher volumetric efficiencies and component densities. Among the various system components, achieving higher densities with capacitors, integrated in thin film form has been a major challenge for the past few decades. This paper reports the first proof-of-concept demonstration of a novel silicon-compatible high-density capacitor technology. The key novelty stems from the tremendous enhancement in surface area from thin and porous copper nanoelectrodes and conformal alumina dielectric on such nanoelectrodes. Atomic Layer Deposition was chosen as the dielectric process because of its self-limiting, defect-free and conformal deposition on 3-D structures. Alumina with its moderate permittivity and superior dielectric properties over large voltage ranges was employed as the representative dielectric. Thin copper particulate electrodes with conformal counter electrodes showed 10 times higher capacitance density compared to the planar devices, with similar leakage properties. Thicker electrodes showed enormous enhancement in surface area but inferior leakage properties. Combination of compositional and morphological techniques was used to show alumina conformality on complex 3-D structures of copper particulate electrode. Capacitance–Voltage and Current–Voltage characterizations were carried out to confirm the feasibility of the novel high density 3-D capacitor structure.     

Mechanistic interaction study of thin oxide dielectric with conducting organic electrode

This paper aims at understanding the interaction of intrinsic conducting polymer, PEDT, with ALD-deposited Al₂O₃ and thermally oxidized Ta₂O₅ dielectrics, and the underlying mechanisms for increase in leakage currents in PEDT-based capacitors. Conducting polymers offer several advantages as electrodes for high surface area capacitors because of their lower resistance, self-healing and enhanced conformality. However, capacitors with in situ polymerized PEDT show poor electrical properties that are attributed to the interfacial interaction between the organic electrode and the oxide dielectric. This study focuses on characterizing these interactions. A combination of compositional, structural and electrical characterization techniques was applied to polymer-solid-state-capacitor to understand the interfacial chemical behavior and dielectric property deterioration of alumina and tantalum-oxide films. XPS and impedance studies were employed to understand the stiochiometric and compositional changes that occur in the dielectric film on interaction with in situ deposited PEDT. Based on the observations from several complimentary techniques, it is concluded that tantalum-pentoxide has more resistance towards chemical interaction with in situ polymerized PEDT. The thermally oxidized Ta₂O₅-PEDT system showed leakage current of 280 nA μF⁻¹ at 3 V with a breakdown voltage of 30 V. On the other hand, Al₂O₃-PEDT capacitor showed leakage current of 50 μA μF⁻¹ and a breakdown voltage of 40 V. The study reports direct evidence for the mechanism of resistivity drop in alumina dielectric with in situ polymerized PEDT electrode.     

Challenges of long-term vascular access in pediatric hemodialysis: Recommendations for practitioners

Kidney transplantation is the preferred treatment of end-stage renal disease in children. However, time to transplant varies, making a well-functioning long-term vascular access essential for performing hemodialysis efficiently and without disruption until a kidney becomes available. However, establishing long-term vascular access in pediatric patients can present distinct challenges due to this population's unique characteristics, such as smaller body size and lower-diameter blood vessels. There are three main pediatric long-term vascular access options, which include central venous catheters (CVC), arteriovenous fistula (AVF), and arteriovenous graft (AVG). CVC are currently the most widely used modality, although various studies and guidelines recommend AVF or AVG as the preferred option. Although AVF should be used whenever possible, it is crucial that clinicians consider factors such as patient size, physical exam findings, comorbidities, predicted duration of treatment to decide on the most optimal long-term vascular access modality. This article reviews the three long-term vascular access methods in children and the benefits and complications of each.