Mechanisms of Oxygen Vacancy Aggregation in SiO2 and HfO2

Dielectric oxide films in electronic devices undergo significant structural changes during device operation under bias. These changes are usually attributed to aggregation of oxygen vacancies resulting in formation of oxygen depleted regions and conductive filaments. However, neutral oxygen vacancies have high diffusion barriers in ionic oxides and their interaction and propensity for aggregation are still poorly understood. In this paper we briefly review the existing data on static configurations of neutral dimers and trimers of oxygen vacancies in technologically relevant SiO2 and HfO2 and then provide new results on the structure and properties of these defects in amorphous SiO2 and HfO2. These results demonstrate weak interaction between neutral O vacancies, which does not explain their quick aggregation. We propose that trapping of electrons, injected from an electrode, by the vacancies may result in creation of new neutral vacancies in the vicinity of pre-existing vacancies. We describe this mechanism in aSiO2 and demonstrate that this process becomes more efficient as the vacancy clusters grow larger

Modeling of Diffusion and Incorporation of Interstitial Oxygen Ions at the TiN/SiO2 Interface

Silica-based resistive random access memory devices have become an active research area due to complementary metal-oxide-semiconductor compatibility and recent dramatic increases in their performance and endurance. In spite of both experimental and theoretical insights gained into the electroforming process, many atomistic aspects of the set and reset operation of these devices are still poorly understood. Recently a mechanism of electroforming process based on the formation of neutral oxygen vacancies (VO0) and interstitial O ions (Oi2-) facilitated by electron injection into the oxide has been proposed. In this work, we extend the description of the bulk (Oi2-) migration to the interface of amorphous SiO2 with the polycrystaline TiN electrode, using density functional theory simulations. The results demonstrate a strong kinetic and thermodynamic drive for the movement of Oi2- to the interface, with dramatically reduced incorporation energies and migration barriers close to the interface. The arrival of Oi2- at the interface is accompanied by preferential oxidation of undercoordinated Ti sites at the interface, forming a Ti-O layer. We investigate how O ions incorporate into a perfect and defective ∑5(012)[100] grain boundary (GB) in TiN oriented perpendicular to the interface. Our simulations demonstrate the preferential incorporation of Oi at defects within the TiN GB and their fast diffusion along a passivated grain boundary. They explain how, as a result of electroforming, the system undergoes very significant structural changes with the oxide being significantly reduced, interface being oxidized, and part of the oxygen leaving the system

Understanding mixed sequence DNA recognition by novel designed compounds: the kinetic and thermodynamic behavior of azabenzimidazole diamidines

Sequence-specific recognition of DNA by small organic molecules offers a potentially effective approach for the external regulation of gene expression and is an important goal in cell biochemistry. Rational design of compounds from established modules can potentially yield compounds that bind strongly and selectively with specific DNA sequences. An initial approach is to start with common A·T bp recognition molecules and build in G·C recognition units. Here we report on the DNA interaction of a synthetic compound that specifically binds to a G·C bp in the minor groove of DNA by using an azabenzimidazole moiety. The detailed interactions were evaluated with biosensor-surface plasmon resonance (SPR), isothermal calorimetric (ITC), and mass spectrometry (ESI-MS) methods. The compound, DB2277, binds with single G·C bp containing sequences with subnanomolar potency and displays slow dissociation kinetics and high selectivity. A detailed thermodynamic and kinetic study at different experimental salt concentrations and temperatures shows that the binding free energy is salt concentration dependent but essentially temperature independent under our experimental conditions, and binding enthalpy is temperature dependent but salt concentration independent. The results show that in the proper compound structural context novel heterocyclic cations can be designed to strongly recognize complex DNA sequences

Not Available

Not AvailableThe present study was conducted in four villages of Parbhani and Beed districts of Marathwada region of Maharashtra State. Work related musculoskeletal problems and risk factors data was collected with the help of interview schedule cum questionnaire. Incidences of musculoskeletal problems of the subjects were identified by using the body map. It was found that 96.66 per cent of the selected female workers who performed the cotton picking activity had pain in neck, knees as well as in calf muscles. About 76 to 93 per cent women suffered from problem of thigh muscles, hand, wrists and shoulder. it can be concluded that maximum musculoskeletal problems of female workers while performing cotton picking activity with conventional method were very severe pain in case of lower back, knee, ankles and feet, arm and leg muscles because of many postural changes and repetitive hand movements while performing cotton picking activity continuously for 8 hrs per day during the season.Not Availabl

Not Available

Not AvailableErgonomics is the scientific study of the relationship between man and his working environment. The ergonomically designed things make the life style better. Women’s contribution to agriculture is seldom recognized in spite of their active role in the agriculture as well as household activities in developed as well as developing world. The selected 30 farm women who were engaged in cotton picking since 5 yrs belonging to age groups of 20 – 50 yrs were selected for the experiment. The present study was conducted in four villages of Parbhani and Beed districts of Marathwada region of Maharashtra State. Comparative evaluation was worked out between cotton picking apron developed by AICRP Family Resource Management, College of Home Science M.K.V. Parbhani and pick bag developed by Family Resource Management, College of Home Science, CCS, H.A.U. Hisar. The heart rate of female workers was more while performing cotton picking activity in pick bag method. The rated perceived exertion was highest in case of pick bag method. Ergonomically physiological workload of cotton picking was at par in case of traditional, pick bag and apron method. It has been concluded that there was reduction in physiological cost of work when cotton picking activity was performed with cotton picking apron. From this study it was concluded that cotton picking is recommended for reduction of drudgery with certain improvements.Not Availabl

Alertness in individuals with profound intellectual and multiple disabilities:A literature review

Direct Support persons (DSPs) often face problems in observing and determining alertness in individuals with profound intellectual and multiple disabilities (PIMD). A literature study was carried out to gather information about the problems just described. A search of two electronic databases and the references found in relevant hits revealed 42 relevant publications. The results show that two types of descriptions of alertness can be distinguished: (1) those with a focus on the individual only or (2) those with a focus on the interaction of individual and environment. Several observation categories were used in the studies that were found. The reliability of the observations turned out to be a core problem in most of the studies. Only a limited number of environmental conditions that were expected to have an impact on alertness in individuals with PIMD were investigated. While modifications of the environment, interaction strategies, stimulation strategies and staff training were found to have a positive impact on alertness, studies about treatment activities led to conflicting results. Finally, we will formulate the resulting implications for future studies and for the development of an instrument for DSPs in order to observe alertness in individuals with PIMD in clinical practice. (C) 2008 Elsevier Ltd All rights reserved

Look closer:The alertness of people with profound intellectual and multiple disabilities during multi-sensory storytelling, a time sequential analysis

Introduction: Multi-sensory storytelling (MSST) is a storytelling method designed for individuals with profound intellectual and multiple disabilities (PIMD). It is essential that listeners be alert during MSST, so that they become familiar with their personalised stories. Repetition and the presentation of stimuli are likely to affect the alertness of listeners during MSST. Previous studies have only examined the overall level of alertness during MSST. This study focuses on changes in alertness over time during storytelling. Method: In this study, 27 direct support people read an MSST book 20 times with a person with PIMD. The 1st, 5th, 10th and 20th storytelling sessions were recorded. The relation between alertness and the active presentation of stimuli is analyzed using a time-window sequential analysis. We examined changes in alertness levels by comparing the four different storytelling sessions. Results: Higher levels of active alertness were observed when stimuli were actively presented. Alertness was not constant within storytelling sessions, and was related to the presentation of stimuli. Actively presented stimuli were associated with larger fluctuations in alertness. Discussion: Storytellers should present stimuli actively and for longer periods, in order to increase the alertness of listeners during storytelling

Haplotype of non-synonymous mutations within IL-23R is associated with susceptibility to severe malaria anemia in a P. falciparum holoendemic transmission area of Kenya

Abstract Background Improved understanding of the molecular mechanisms involved in pediatric severe malarial anemia (SMA) pathogenesis is a crucial step in the design of novel therapeutics. Identification of host genetic susceptibility factors in immune regulatory genes offers an important tool for deciphering malaria pathogenesis. The IL-23/IL-17 immune pathway is important for both immunity and erythropoiesis via its effects through IL-23 receptors (IL-23R). However, the impact of IL-23R variants on SMA has not been fully elucidated. Methods Since variation within the coding region of IL-23R may influence the pathogenesis of SMA, the association between IL-23R rs1884444 (G/T), rs7530511 (C/T), and SMA (Hb < 6.0 g/dL) was examined in children (n = 369, aged 6–36 months) with P. falciparum malaria in a holoendemic P. falciparum transmission area. Results Logistic regression analysis, controlling for confounding factor of anemia, revealed that individual genotypes of IL-23R rs1884444 (G/T) [GT; OR = 1.34, 95% CI = 0.78–2.31, P = 0.304 and TT; OR = 2.02, 95% CI = 0.53–7.74, P = 0.286] and IL-23R rs7530511 (C/T) [CT; OR = 2.6, 95% CI = 0.59–11.86, P = 0.202 and TT; OR = 1.66, 95% CI = 0.84–3.27, P = 0.142] were not associated with susceptibility to SMA. However, carriage of IL-23R rs1884444T/rs7530511T (TT) haplotype, consisting of both mutant alleles, was associated with increased susceptibility to SMA (OR = 1.12, 95% CI = 1.07–4.19, P = 0.030). Conclusion Results presented here demonstrate that a haplotype of non-synonymous IL-23R variants increase susceptibility to SMA in children of a holoendemic P. falciparum transmission area

In situ transmission electron microscopy of resistive switching in thin silicon oxide layers

Silicon oxide-based resistive switching devices show great potential for applications in nonvolatile random access memories. We expose a device to voltages above hard breakdown and show that hard oxide breakdown results in mixing of the SiOx layer and the TiN lower contact layers. We switch a similar device at sub-breakdown fields in situ in the transmission electron microscope (TEM) using a movable probe and study the diffusion mechanism that leads to resistance switching. By recording bright-field (BF) TEM movies while switching the device, we observe the creation of a filament that is correlated with a change in conductivity of the SiOx layer. We also examine a device prepared on a microfabricated chip and show that variations in electrostatic potential in the SiOx layer can be recorded using off-axis electron holography as the sample is switched in situ in the TEM. Taken together, the visualization of compositional changes in ex situ stressed samples and the simultaneous observation of BF TEM contrast variations, a conductivity increase, and a potential drop across the dielectric layer in in situ switched devices allow us to conclude that nucleation of the electroforming—switching process starts at the interface between the SiOx layer and the lower contact