Defect Compensation Research Articles

High‐Permittivity Double Rare‐Earth‐Doped Barium Titanate Ceramics with Diffuse Phase Transition

On the basis of Ti‐vacancy defect compensation mode, high‐permittivity La‐ and Ce‐doped barium titanate ceramics (BLTC) with perovskite structure, i.e., (Ba1−xLax)(Ti1−x/4−yCey)O3, wherex=0.01–0.05 andy=0.05, were prepared by conventional ceramic processing techniques. Dielectric characteristics, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and hysteresis loops were measured. Defect chemistry and diffuse phase transition (DPT) in BLTC are discussed. Co‐doping with the relatively smaller La3+ions at Ba sites and the relatively larger Ce4+ions at Ti sites in the BaTiO3host lattice resulted in a fine‐grained microstructure (0.8–1.1 μm), marked raising, and broadening of the Curie peak characteristic of DPT. The Curie temperature (TC) at 800 Hz decreased rapidly at a dramatic rate of −30°C/at.% La wheny=0.05. By means of co‐doping with La and Ce, this is the first time that highk“Y5V” ceramics (BLTC: 0.03≤x≤0.04,y=0.05) with ɛ′RT>10 000 over a frequency range of 1–100 kHz have been achieved in rare‐earth‐doped BaTiO3ceramics.

Physical Model for the Resistivity and Temperature Coefficient of Resistivity in Heavily Doped Polysilicon

One of the key benefits of using polysilicon as the material for resistors and piezoresistors is that the temperature coefficient of resistivity (TCR) can be tailored to be negative, zero, or positive by adjusting the doping concentration. This paper focuses on optimization of the boron doping of low-pressure chemical vapor deposited polysilicon resistors for obtaining near-zero TCR and development of a physical model that explains quantitatively all the results obtained in the optimization experiments encompassing the doping concentration ranges that show negative, near-zero, and positive TCR values in the polysilicon resistors. The proposed model considers single-crystal silicon grain in equilibrium with amorphous silicon grain boundary. The grain boundary carrier concentration is calculated considering exponential band tails in the density of states for amorphous silicon in the grain boundaries. Comparison of the results from the model shows excellent agreement with the measured values of resistivity as well as TCR for heavily doped polysilicon. It is shown that the trap density for holes in the grain boundary increases as the square root of the doping concentration, which is consistent with the defect compensation model of doping in the amorphous silicon grain boundaries.

Luminescent spectroscopy and imaging of textured sprayed Er-doped ZnO films in the near ultraviolet and visible regions

The textural dependence of the thermally sprayed Er-doped ZnO films on Er concentration is reported here. The [002] preferred growth orientation of hexagonal phase is obtained at the lower concentrations, while the [100] and [101] directions additionally raised from nearly 5at.% Er content onwards. The cathodoluminescent characteristics of the samples in the near ultraviolet (UV) and visible region depict a complete extinction of the visible emitted bands (λ=445, 526, and 665nm) at 1at.% Er content. Their deactivation below this concentration is explained by a compensation of oxygen defects in the material due to the oxygen-rich medium of the deposition bath. Their reactivation beyond this particular concentration is ascribed to the increase of the Er+3 ion shells whose internal radiative transitions lead to a recovering of these visible emitted bands. The radiative mechanism of the transitions from the (F9∕24) excited states to the (I15∕24) ground state, responsible for the λ=665nm emission, is predominant in that case. The respective normalized intensity of the violet (λ=445nm) and green (λ=526nm) emitted bands exhibits a maximal value for 3at.% Er content, reaching a stabilized regime from about 5at.% Er.

Compensation effects and compensation defects in kinetic and mechanistic interpretations of heterogeneous chemical reactions

AbstractA case is presented for kinetic compensation effects (KCEs) reported for sets of heterogeneous rate processes to be classified. Because many of these KCEs do not conform to the ideal of isokinetic behavior, a quantitative method for describing the degree of compensation (κ) is introduced. In the case of solid‐promoted catalytic reactions, it is suggested that (unlike simple homogeneous reactions) the effective concentrations and dispositions of surface intermediates can vary with temperature. Thus, the rate constants vary differently with temperature for the individual reactions of a set and, thereby, influence apparent magnitudes of the measured Arrhenius parameters. As a consequence, compensation is observed for sets of chemically related reactions occurring within a common temperature interval. KCEs are thus linked to mechanistic information and, depending on the magnitude of κ, for identifying shared features of catalytic rate controls. In this respect, the classification of KCEs is useful and can be based on similarities or differences between the reactants, catalysts, or experimental conditions in a given set of measurements. These ideas are demonstrated for selected sets of catalytic reactions. KCEs reported from a range of thermal decompositions of solids are also discussed. It is argued that, for mathematical as well as term definition reasons, compensation in this type of heterogeneous process is often artifactual and, therefore, cannot provide information of mechanistic value. Overall, it is concluded that a more thorough interpretation of compensation trends should lead to greater understanding of heterogeneous processes, particularly at the mechanistic level. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 464–473, 2006

Shifts from Liability to Solidarity: The Example of Compensation of Birth Defects

Being born is not without its dangers. Compared to the risks of medical treatment in general, the risk of a pregnant woman and her unborn child sustaining some kind of peri-natal injury is quite considerable.1 Sometimes the physician or the hospital involved can be held accountable for the injuries that result. Roughly speaking three sets of cases typically arise. First, complications can arise in the delicate delivery process in which the physician does not act or react with the required competence (e.g., the obstetrician may fail to respond adequately to sudden asphyxia during labour, causing cerebral palsy). Second, during pregnancy the physician can err in diagnosing correctly and thus fail to read the early signs of complications or even fail to detect severe genetic defects. In the latter case, the parents may want to argue that they would have terminated pregnancy if they had known of the defects. Third, after correct diagnosis of a defect, the physician fails to properly terminate the pregnancy as requested by the parents and, therefore, leads to the birth of an unwanted handicapped child.

Digital Signal Processing for Biaxial Position Measurement With a Pyroelectric Sensor Array

This paper proposes a new full digital approach to estimate biaxial position with a pyroelectric sensor array. The previously developed analog interface shows its limits in the calibration procedure, requiring several trimming adjustments. A DSP-based hardware has been developed to experimentally evaluate three digital methods: radial basis function (RBF) neural network, best fitted plane (BFP), and look-up table (LUT) in the least mean square (LMS) error sense. Experimental results show that no dramatic improvements are obtained by the RBF, despite the long training required and the external PC support for weight calculation. The BFP reaches performances comparable to the analog processing system using only nine calibration points, but the best tradeoff has been found with the LUT technique. Actually, with a 64-point calibration set, LUT gives a root mean square error (RMSE) of 0.5% with respect to full scale (FS), offering a valid in-circuit compensation of array structural defects.

A proposed regional hierarchy in recovery of post-stroke aphasia

Activation studies in patients with aphasia due to stroke or tumours in the dominant hemisphere have revealed effects of disinhibition in ipsilateral perilesional and in contralateral homotopic cortical regions, referred to as collateral and transcallosal disinhibition. These findings were supported by studies with selective disturbance of cortical areas by repetitive transcranial magnetic stimulation (rTMS) in healthy volunteers and in patients with focal brain lesions. Both, collateral as well as transcallosal disinhibition might be relevant for the compensation of lesions within a functional network. From these data a hierarchical organization of recovery of aphasia after stroke and of compensation of language defects due to brain tumours can be deduced, by which the reactivation of undamaged network areas of the ipsilateral hemisphere usually lead to better outcome than the involvement of homotopic contra-lateral regions. rTMS can be used to identify areas relevant for speech production and might play a role in treatment strategies targeted at modulating the activity of contralateral homotopic areas of the functional network which might interfere with language recovery.

Photoluminescence study of potential fluctuations in thin layers of Cu(In0.75Ga0.25)(SySe1−y)2

Thin layers of the pentenary material Cu(In,Ga)(S,Se)2 (CIGSSe) are studied using photoluminescence (PL) spectroscopy. The layers were produced by a two-stage deposition process, which produces thin chalcopyrite films with a high degree of compositional uniformity throughout the thickness of the layer. It is shown that potential fluctuations, caused by compensation and high concentrations of defects, dominate the PL behavior of the investigated layers. This is inferred from a number of PL studies such as variable temperature and excitation power measurements. It is deduced that the average amplitude of fluctuations increases with increasing sulfur mole fraction S∕(Se+S). Thus, sulfur incorporation increases the degree of compensation (and hence the charged defect concentration). From the strong asymmetry and the observed weak shift of the low energy tails in the PL spectra with increasing sulfur content, it is also concluded that a significant fraction of defect states associated with the quaternary CIGSSe is still present in the pentenary layers.

Laser-stimulated compensation of bulk defects in p-CdZnTe

The data on the interaction of infrared laser radiation with {Dirac_h}{omega}<<E{sub g} and power density W, no higher than the thermal destruction threshold of low-resistivity p-CdZnTe crystals (4 {<=} {rho} {<=} 25 {omega} cm) are presented. It is shown that the laser-stimulated defects, until attaining a stable state, pass two nonequilibrium stages depending on the interaction time and W. During these stages, the crystal properties partially relax to the initial or the stable state, respectively. In the stable state, the optical transmittance ({lambda} {<=} 20 {mu}m) and resistivity attain values that satisfy the requirements to the CdZnTe substrates for the HgCdTe IR photodetectors. The laser-stimulated transformations in the lattice are considered using a model that attributes the generation of activated centers in a bulk and their migration to entrainment by free carriers in an electric field of the laser wave.

Defect compensation, clustering, and magnetism in Cr-doped anataseTiO2

The origin of the magnetism in recently reported Cr doped anatase $\mathrm{Ti}{\mathrm{O}}_{2}$ is investigated with first principles full-potential linearized augmented plane wave calculations. Through a systematic study over a range of defect compensation, we predict a strikingly different behavior of ${\mathrm{Cr}}^{3+}$ (compensated species) and ${\mathrm{Cr}}^{4+}$ (noncompensated species): ${\mathrm{Cr}}^{3+}$ tends to distribute uniformly but contributes only to paramagnetism. By contrast, ${\mathrm{Cr}}^{4+}$ tends to form clusters which induces strong ferromagnetism. The same $p\text{\ensuremath{-}}d$ hopping interaction found in Mn:GaAs also explains the presence or absence of ferromagnetism and its dependence on the compensation; this short-range bonding interaction is also one of the major sources for the predicted clustering of ${\mathrm{Cr}}^{4+}$. Our results thus contradict the experimental interpretation that oxygen vacancies induced the ferromagnetic coupling between ${\mathrm{Cr}}^{3+}$ through the F-center bound magnetic polaron (FCBMP) mechanism. We show that large size magnetic polarons cannot form in $\mathrm{Cr}:\mathrm{Ti}{\mathrm{O}}_{2}$ and that the FCBMP mechanism does not apply.

Increased Expression of Mitotic Checkpoint Genes in Breast Cancer Cells with Chromosomal Instability

Most breast cancers have chromosomal instability that seems related to defective mitotic spindle checkpoints. Because the molecular basis of this defect is unknown, we evaluated breast cancer cell lines and tissues for possible defects involving the major mitotic checkpoint genes responsible for maintaining chromosomal stability. We analyzed sequences and expression levels (RNA and protein) of eight major spindle checkpoint genes (MAD1L1, MAD2L1, MAD2L2, BUB1, BUB1B, BUB3, CDC20, and TTK) in a panel of 12 breast cancer cell lines, most with established genetic instability and defective spindle damage checkpoint response. mRNA levels of these genes were also measured in primary tumor samples, and immunohistochemical staining was used to evaluate BUB1B protein levels in a panel of 270 additional cases of breast cancer. No functionally significant sequence variations were found for any of the eight genes in the breast cancer cell lines with chromosomal instability. More surprisingly, the mRNA and protein levels for these checkpoint genes are significantly higher in the genetically unstable breast cancer cell lines and in high-grade primary breast cancer tissues than in the stable (and checkpoint proficient) MCF-10A and normal mammary epithelial cells, or in normal breast tissues. In fact, overexpression of the BUB1B protein is a marker that recognizes nearly 80% of breast cancers in paraffin-embedded tissues. Defective mitotic spindle checkpoints in breast cancer are most likely not caused by low expression or mutations of these eight checkpoint genes. High levels of these particular transcripts could represent a cellular compensation for defects in other molecular components of the mitotic spindle damage checkpoint, and increased expression of these genes might be markers of breast cancers with chromosomal instability.

EPR of Nd3+ in congruent and nearly stoichiometric lithium niobate

AbstractLithium niobate crystals doped with neodymium were studied with the help of electron paramagnetic resonance, EPR in the temperature range of 4.2–20 K. Tremendous narrowing of the EPR lines in nearly stoichiometric samples in comparison with congruent ones allowed us to distinguish four non‐equivalent centers, as well as line splitting caused by hyperfine interaction of neodymium electrons with nuclear spins of both magnetic isotopes 143Nd and 145Nd. It is shown that one of the centers has axial C3 symmetry, whereas all others have lowest C1 symmetry due to presence of intrinsic defects or/and charge compensation defects in the near neighborhood of Nd3+. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

First Principles Investigation of Mineral Component of Bone: CO3 Substitutions in Hydroxyapatite

First principles calculations are used to investigate carbonated hydroxyapatite, a naturally occurring mineral and also the inorganic component of animal bone. Two types of carbonate substitution are studied: A-type in which the carbonate ion substitutes for an OH and B-type where the substitution is for a phosphate. Both types have unbalanced charges and various forms of charge compensation are treated. The methods, which are based on density functional theory and first principles pseudopotentials, yield equilibrium atomic arrangements, changes in lattice parameters, and total energies for different types of substitution. When calculated energies of selected stable compounds are used, the formation energies of different carbonate substitutions with accompanying charge compensation defects can be compared. The results indicate that compact complexes are energetically favored, and a B-type material with charge compensation by a calcium vacancy together with a hydrogen atom which bonds to a neighboring phosphate is the most stable of all those considered.

Semi-insulating CdTe with a minimized deep-level doping

The possibility to prepare semi-insulating CdTe with a deep-level doping below the limit 1013 cm−3 demanded in detector industry is studied theoretically within quasi-chemical formalism. We show that proper thermal treatment, including low temperature (ca 200°C) dwell, allows fulfillment of this demand also in 7N or less purity materials. The procedure is demonstrated in Te-rich CdTe doped with a shallow donor. Its principle is based on enhanced defect selfcompensation, which affords at sufficiently low temperature extremely high compensation of shallow defects. New high-temperature transport data are used to refine on previous native defect properties for the modeling. The analysis of diffusion rates at lowered temperature approves the model for a real-time experimental verification.

Low frequency of CHEK2 1100delC allele in Australian multiple-case breast cancer families: functional analysis in heterozygous individuals

A protein-truncating variant of CHEK2, 1100delC, is associated with a moderate increase in breast cancer risk. We have determined the prevalence of this allele in index cases from 300 Australian multiple-case breast cancer families, 95% of which had been found to be negative for mutations in BRCA1 and BRCA2. Only two (0.6%) index cases heterozygous for the CHEK2 mutation were identified. All available relatives in these two families were genotyped, but there was no evidence of co-segregation between the CHEK2 variant and breast cancer. Lymphoblastoid cell lines established from a heterozygous carrier contained approximately 20% of the CHEK2 1100delC mRNA relative to wild-type CHEK2 transcript. However, no truncated CHK2 protein was detectable. Analyses of expression and phosphorylation of wild-type CHK2 suggest that the variant is likely to act by haploinsufficiency. Analysis of CDC25A degradation, a downstream target of CHK2, suggests that some compensation occurs to allow normal degradation of CDC25A. Such compensation of the 1100delC defect in CHEK2 might explain the rather low breast cancer risk associated with the CHEK2 variant, compared to that associated with truncating mutations in BRCA1 or BRCA2.

Phosphatidylinositol 3-kinase VPS34 of is involved in filamentous growth, secretion of aspartic proteases, and intracellular detoxification

The phosphatidylinositol (PI) 3-kinase Vps34p of Candida albicans influences vesicular intracellular transport, filamentous growth and virulence. To get a clearer understanding how these phenomena are connected, we analysed hyphal growth in a matrix under microaerophilic conditions at low temperature, the detoxification of metal ions and antifungal drugs, the secretion of aspartic proteinases (Saps), as well as expression of adhesion-associated proteins of the C. albicans vps34 null mutant strain. The hyphal growth in a matrix, which is repressed in the wild-type strain by Efg1p, was derepressed in the mutant. CZF1, which encodes an activator of hyphal growth in a matrix, was up-regulated in the mutant. In addition, CZF1 expression was pH-dependent in the wild-type. Expression of EFG1 was not changed. Examination of Saps secretion showed a reduction in the vps34 null mutant. Determination of sensitivity against metal ions and antimycotic drugs revealed defects in detoxification. Expression studies indicated that the vps34 mutant reacts to the phenotypical defects with an up-regulation of genes involved in these processes, including the aspartyl proteinases SAP2 and SAP9, adhesion proteins ALS1 and HWP1, and the ABC transporters CDR1 and HST6. We also found an increased expression of the PI 4-kinase LSB6 indicating a complex feed-back mechanism for the compensation of the multiple defects arising from the lack of the PI3-kinase VPS34.

Defective epidermal barrier in neonatal mice lacking the C-terminal region of connexin43.

More than 97% of mice in which the C-terminal region of connexin43 (Cx43) was removed (designated as Cx43K258stop) die shortly after birth due to a defect of the epidermal barrier. The abnormal expression of Cx43K258stop protein in the uppermost layers of the epidermis seems to perturb terminal differentiation of keratinocytes. In contrast to Cx43-deficient mice, neonatal Cx43K258stop hearts show no lethal obstruction of the right ventricular outflow tract, but signs of dilatation. Electrocardiographies of neonatal hearts reveal repolarization abnormalities in 20% of homozygous Cx43K258stop animals. The very rare adult Cx43K258stop mice show a compensation of the epidermal barrier defect but persisting impairment of cardiac function in echocardiography. Female Cx43K258stop mice are infertile due to impaired folliculogenesis. Our results indicate that the C-terminally truncated Cx43K258stop mice lack essential functions of Cx43, although the truncated Cx43 protein can form open gap junctional channels.

Doping properties of boron-doped microcrystalline silicon from B 2H 6 and BF 3: material properties and solar cell performance

We have studied the doping properties of boron-doped hydrogenated microcrystalline silicon (μc-Si:H) deposited by glow-discharge plasmas of different SiH 4/H 2/B 2H 6 and SiH 4/H 2/BF 3 gas mixtures. Regardless of dopant source gas, the solid-phase doping efficiency (hole/boron concentration ratio) increases monotonically as the boron concentration ( C B) increases in the film, and it approaches unity at C B>10 20 atoms/cm 3, generating sufficient hole concentrations for solar cells. This doping behavior suggests that the impurity activation in μc-Si:H is independent of defect–compensation process in contrast to that in hydrogenated amorphous silicon. Although material properties reveal no dependence on the type of dopant source gas, μc-Si:H p–i–n solar cells with p-layers doped from BF 3 provide higher conversion efficiencies than those from B 2H 6 at a lower C B range of <3 × 10 19 atoms/cm 3. Possible effects of the p-layer thickness on the doping properties are discussed.

Insulin secretion and incretin hormones after oral glucose in non-obese subjects with impaired glucose tolerance

Subjects with impaired glucose tolerance (IGT) are usually overweight and exhibit insulin resistance with a defective compensation of insulin secretion. In this study, we sought to establish the interrelation between insulin secretion and insulin sensitivity after oral glucose in non-obese subjects with IGT and we also examined this interrelation in relation to the 2 main incretins, glucagon-like peptide (GLP-1) and gastric inhibitory polypeptide (GIP). To that end, 13 women with IGT and 17 women with normal glucose tolerance (NGT) underwent an oral glucose tolerance test (OGTT) with measurements of glucose, insulin, C-peptide, GLP-1, and GIP. Insulin secretion (TIS) and insulin sensitivity (OGIS) were assessed using models describing the relationship between glucose, insulin and C-peptide data. These models allowed estimation also of the hepatic extraction of insulin. The age (54.2 ± 9.7 [mean ± SD] years) and body mass index (BMI; 26.0 ± 4.0 kg/m 2) did not differ between the groups. Subjects with IGT displayed lower TIS during the initial 30 minutes after oral glucose (0.97 ± 0.17 [mean ± SEM] v 1.75 ± 0.23 nmol/L in NGT; P = .018) and lower OGIS (397 ± 21 v 463 ± 12 mL/min/m 2; P = .005). The incremental 30-minute TIS times OGIS (reflecting insulin secretion in relation to insulin sensitivity) was significantly reduced in IGT (359 ± 51 v 774 ± 91 nmol/min/m 2, P = .001). This measure correlated inversely to the 2-hour glucose level ( r = −0.71; P < .001). In contrast, TIS over the whole 180-minute period was higher in IGT (26.2 ± 2.4 v 20.0 ± 2.0 nmol/L; P = .035). Hepatic insulin extraction correlated linearly with OGIS ( r = 0.71; P < .001), but was not significantly different between the groups although there was a trend with lower extraction in IGT ( P = .055). Plasma levels of GLP-1 and GIP increased after oral glucose. Total secretion of these incretin hormones during the 3-hour test did not differ between the 2 groups. However, the 30-minute increase in GLP-1 concentrations was lower in IGT than in NGT ( P = .036). We conclude that also in non-obese subjects with IGT, when adiposity is controlled for in relation to NGT, defective early insulin secretion after oral glucose is a key factor. This defective beta-cell function is associated with, and may be caused by, a reduced early GLP-1 response.

A reference standard of defect compensation for leather transactions

Defects exist on natural leather surfaces and they usually cannot be eliminated during processing. No international criterion specifies the compensatory counting for calf leather surface defects. So complicated negotiation causes additional cost and argument between suppliers and purchasers. The objective of this article is to establish a compensatory standard of leather defects for finished leather transactions. We start by collecting 170 samples of defective leather and classify the leather defects into seven types. By using digital image processing techniques, we can identify the defects and group nearby defects into a larger scrap area. The area of leather falling into disuse can be calculated. The compensatory standard corresponding to each type of leather defect is then defined. The established compensatory standard for finished leather transactions is evaluated for simulated practical leather transaction. Simulation results showed that the proposed approach is useful and beneficial for practical leather transactions.