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  • BioMed Central  (10)
  • American Institute of Physics (AIP)  (6)
  • 2015-2019  (16)
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  • 1
    Publication Date: 2016-07-26
    Description: To increase the thermoelectric efficiency and reduce the thermal fatigue upon cyclic heat loading, alloying of amorphous NbO 2 with all 3d and 5d transition metals has systematically been investigated using density functional theory. It was found that Ta fulfills the key design criteria, namely, enhancement of the Seebeck coefficient and positive Cauchy pressure (ductility gauge). These quantum mechanical predictions were validated by assessing the thermoelectric and elastic properties on combinatorial thin films, which is a high-throughput approach. The maximum power factor is 2813  μ W m −1  K −2 for the Ta/Nb ratio of 0.25, which is a hundredfold increment compared to pure NbO 2 and exceeds many oxide thermoelectrics. Based on the elasticity measurements, the consistency between theory and experiment for the Cauchy pressure was attained within 2%. On the basis of the electronic structure analysis, these configurations can be perceived as metallic, which is consistent with low electrical resistivity and ductile behavior. Furthermore, a pronounced quantum confinement effect occurs, which is identified as the physical origin for the Seebeck coefficient enhancement.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 2
    Publication Date: 2016-07-31
    Description: DNA methylation is an important regulator of gene expression and chromatin structure. Methylated DNA immunoprecipitation sequencing (MeDIP-Seq) is commonly used to identify regions of DNA methylation in eukary...
    Electronic ISSN: 1471-2105
    Topics: Biology , Computer Science
    Published by BioMed Central
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  • 3
    Publication Date: 2015-05-07
    Description: Background: DNA methylation has essential roles in transcriptional regulation, imprinting, X chromosome inactivation and other cellular processes, and aberrant CpG methylation is directly involved in the pathogenesis of human imprinting disorders and many cancers. To address the need for a quantitative and highly multiplexed bisulfite sequencing method with long read lengths for targeted CpG methylation analysis, we developed single-molecule real-time bisulfite sequencing (SMRT-BS). Results: Optimized bisulfite conversion and PCR conditions enabled the amplification of DNA fragments up to ~1.5 kb, and subjecting overlapping 625–1491 bp amplicons to SMRT-BS indicated high reproducibility across all amplicon lengths (r = 0.972) and low standard deviations (≤0.10) between individual CpG sites sequenced in triplicate. Higher variability in CpG methylation quantitation was correlated with reduced sequencing depth, particularly for intermediately methylated regions. SMRT-BS was validated by orthogonal bisulfite-based microarray (r = 0.906; 42 CpG sites) and second generation sequencing (r = 0.933; 174 CpG sites); however, longer SMRT-BS amplicons (〉1.0 kb) had reduced, but very acceptable, correlation with both orthogonal methods (r = 0.836-0.897 and r = 0.892-0.927, respectively) compared to amplicons less than ~1.0 kb (r = 0.940-0.951 and r = 0.948-0.963, respectively). Multiplexing utility was assessed by simultaneously subjecting four distinct CpG island amplicons (702–866 bp; 325 CpGs) and 30 hematological malignancy cell lines to SMRT-BS (average depth of 110X), which identified a spectrum of highly quantitative methylation levels across all interrogated CpG sites and cell lines. Conclusions: SMRT-BS is a novel, accurate and cost-effective targeted CpG methylation method that is amenable to a high degree of multiplexing with minimal clonal PCR artifacts. Increased sequencing depth is necessary when interrogating longer amplicons (〉1.0 kb) and the previously reported bisulfite sequencing PCR bias towards unmethylated DNA should be considered when measuring intermediately methylated regions. Coupled with an optimized bisulfite PCR protocol, SMRT-BS is capable of interrogating ~1.5 kb amplicons, which theoretically can cover ~91% of CpG islands in the human genome.
    Electronic ISSN: 1471-2164
    Topics: Biology
    Published by BioMed Central
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  • 4
    Publication Date: 2015-12-30
    Description: Androgens play an important role for the development of male fertility and gained interest as growth and survival factors for certain types of cancer. Androgens act via the androgen receptor (AR/Ar), which is inv...
    Electronic ISSN: 1471-2199
    Topics: Biology
    Published by BioMed Central
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  • 5
    Publication Date: 2015-07-03
    Description: We have synthesized RuO 2 and MnO 2 thin films under identical growth conditions using reactive DC sputtering. Strikingly different morphologies, namely, the formation of RuO 2 nanorods and faceted, nanocrystalline MnO 2 , are observed. To identify the underlying mechanisms, we have carried out density functional theory based molecular dynamics simulations of the growth of one monolayer. Ru and O 2 molecules are preferentially adsorbed at their respective RuO 2 ideal surface sites. This is consistent with the close to defect free growth observed experimentally. In contrast, Mn penetrates the MnO 2 surface reaching the third subsurface layer and remains at this deep interstitial site 3.10 Å below the pristine surface, resulting in atomic scale decomposition of MnO 2 . Due to this atomic scale decomposition, MnO 2 may have to be renucleated during growth, which is consistent with experiments.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 6
    Publication Date: 2016-07-07
    Description: In this work, isolated metal nanoparticles are supported on a dielectric thin film that is placed on a conducting plane. The optical scattering characteristics of these metal nanoparticles are directly correlated with the localized surface plasmon states of the nanoparticle—image particle dimer, formed in the conducting plane below. Quantification of plasmon resonance shifts can be directly correlated with the application of the plasmon nanoruler equation. This simple geometry shows that direct optical techniques can be used to resolve thickness variations in dielectrics of only a few nanometers.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 7
    Publication Date: 2015-12-13
    Description: Background: Glaucoma is a leading cause of blindness. The participation of primary care physicians (PCPs) in glaucoma care may improve health outcomes for glaucoma patients.ObjectivesTo investigate PCPs’ attitudes towards their role in glaucoma care, perceived barriers, and self-reported performance in glaucoma management. Methods: PCPs working in the Haifa and Western Galilee District of Clalit Health Services, Israel’s largest Health Maintenance Organization (HMO) were asked to complete a self-administered structured questionnaire. Physicians were asked to rate their agreement with statements describing the PCP’s role in glaucoma care, and to state how often they behave accordingly in their practice. In addition, physicians were asked to rate the extent that factors such as time constraints and knowledge gaps impede their performance in glaucoma care. Results: Eighty-two physicians completed the questionnaire. The majority thought that PCPs have a major role in early detection of glaucoma (99 %), discussing the importance of adherence to treatment (93 %), and encouraging patients to make regular visits to their ophthalmologist (99 %). However, only 30 % reported asking patients about family history of glaucoma, 64 % reported discussing adherence to treatment, and only 35 % stated that they explain how to use eye drops, while most of respondents (87 %) regularly provide refill prescriptions for glaucoma medications. Sixty percent claimed that during their residency they had not acquired adequate knowledge and competence to allow them to take proper care of glaucoma patients. The main barriers reported were lack of time (43 %), lack of knowledge regarding treatment options and recommended follow-up (46 %), and not being familiar with glaucoma medications’ side effects (54 %). Conclusions: There is a gap between PCPs’ perceptions of their role in glaucoma care and their report on actual performance in early detection and management of glaucoma. Further research is needed to develop and assess interventions that aim at closing this gap.
    Electronic ISSN: 1756-0500
    Topics: Biology , Medicine
    Published by BioMed Central
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  • 8
    Publication Date: 2015-01-16
    Description: Ge-nanocrystals (NCs) were synthesized in amorphous TaZrO x by thermal annealing of co-sputtered Ge-TaZrO x layers. Formation of spherical shaped Ge-NCs with small variation of size, areal density, and depth distribution was confirmed by high-resolution transmission electron microscopy. The charge storage characteristics of the Ge-NCs were investigated by capacitance-voltage and constant-capacity measurements using metal-insulator-semiconductor structures. Samples with Ge-NCs exhibit a maximum memory window of 5 V by sweeping the bias voltage from −7 V to 7 V and back. Below this maximum, the width of the memory window can be controlled by the bias voltage. The fitted slope of the memory window versus bias voltage characteristics is very close to 1 for samples with one layer Ge-NCs. A second layer Ge-NCs does not result in a second flat stair in the memory window characteristics. Constant-capacity measurements indicate charge storage in trapping centers at the interfaces between the Ge-NCs and the surrounding materials (amorphous matrix/tunneling oxide). Charge loss occurs by thermal detrapping and subsequent band-to-band tunneling. Reference samples without Ge-NCs do not show any memory window.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 9
    Publication Date: 2016-02-10
    Description: During dynamic random access memory (DRAM) capacitor scaling, a lot of effort was put searching for new material stacks to overcome the scaling limitations of the current material stack, such as leakage and sufficient capacitance. In this study, very promising results for a SrTiO 3 based capacitor with a record low capacitance equivalent thickness value of 0.2 nm at target leakage current are presented. Due to the material properties of SrTiO 3 films (high vacancy concentration and low band gap), which are leading to an increased leakage current, a physical thickness of at least 8 nm is required at target leakage specifications. However, this physical thickness would not fit into an 18 nm DRAM structure. Therefore, two different new approaches to develop a new ZrO 2 based DRAM capacitor stack by changing the inter-layer material from Al 2 O 3 to SrO and the exchange of the top electrode material from TiN to Pt are presented. A combination of these two approaches leads to a capacitance equivalent thickness value of 0.47 nm. Most importantly, the physical thickness of
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 10
    Publication Date: 2016-12-03
    Description: We have theoretically investigated the product of elastic modulus and linear coefficient of thermal expansion for 20 thermoelectrics. The product is inversely proportional to equilibrium volume, which is consistent with the Debye-Grüneisen model. Oxides exhibit larger products, while the products of Te-containing thermoelectrics are considerably smaller. This is likely due to strong bonding in these oxides, which makes them prone to thermal stress, thermal shock, and thermal fatigue. As this product is rarely available in literature and the equilibrium volume is easily measurable, this work provides a quick estimation for the thermomechanical response of thermoelectric phases.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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