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  • American Institute of Physics (AIP)  (19)
  • American Association for the Advancement of Science (AAAS)  (5)
  • American Geophysical Union (AGU)
  • American Association of Petroleum Geologists (AAPG)
  • 1
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    Titanium dioxide/silicon hole-blocking selective contact to enable double-heterojunction crystalline silicon-based solar cell (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-03-27
    Description: In this work, we use an electron-selective titanium dioxide (TiO 2 ) heterojunction contact to silicon to block minority carrier holes in the silicon from recombining at the cathode contact of a silicon-based photovoltaic device. We present four pieces of evidence demonstrating the beneficial effect of adding the TiO 2 hole-blocking layer: reduced dark current, increased open circuit voltage (V OC ), increased quantum efficiency at longer wavelengths, and increased stored minority carrier charge under forward bias. The importance of a low rate of recombination of minority carriers at the Si/TiO 2 interface for effective blocking of minority carriers is quantitatively described. The anode is made of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) heterojunction to silicon which forms a hole selective contact, so that the entire device is made at a maximum temperature of 100 °C, with no doping gradients or junctions in the silicon. A low rate of recombination of minority carriers at the Si/TiO 2 interface is crucial for effective blocking of minority carriers. Such a pair of complementary carrier-selective heterojunctions offers a path towards high-efficiency silicon solar cells using relatively simple and near-room temperature fabrication techniques.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Communication: Visible line intensities of the triatomic hydrogen ion from experiment and theory (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-23
    Description: The visible spectrum of H 3 + is studied using high-sensitivity action spectroscopy in a cryogenic radiofrequency multipole trap. Advances are made to measure the weak ro-vibrational transitions from the lowest rotational states of H 3 + up to high excitation energies providing visible line intensities and, after normalisation to an infrared calibration line, the corresponding Einstein B coefficients. Ab initio predictions for the Einstein B coefficients are obtained from a highly precise dipole moment surface of H 3 + and found to be in excellent agreement, even in the region where states have been classified as chaotic.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 3
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    Sequence-selective recognition of DNA by strand displacement with a thymine-substituted polyamide (1991)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1991-12-06
    Description: A polyamide nucleic acid (PNA) was designed by detaching the deoxyribose phosphate backbone of DNA in a computer model and replacing it with an achiral polyamide backbone. On the basis of this model, oligomers consisting of thymine-linked aminoethylglycyl units were prepared. These oligomers recognize their complementary target in double-stranded DNA by strand displacement. The displacement is made possible by the extraordinarily high stability of the PNA-DNA hybrids. The results show that the backbone of DNA can be replaced by a polyamide, with the resulting oligomer retaining base-specific hybridization.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nielsen, P E -- Egholm, M -- Berg, R H -- Buchardt, O -- New York, N.Y. -- Science. 1991 Dec 6;254(5037):1497-500.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry B, Panum Institute, Copenhagen, Denmark.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1962210" target="_blank"〉PubMed〈/a〉
    Keywords: Base Sequence ; Molecular Sequence Data ; Molecular Structure ; Nylons/*chemistry ; Oligonucleotides/*chemistry ; Photochemistry ; Thermodynamics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Extensive arsenic contamination in high-pH unconfined aquifers in the Indus Valley (2017)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2017-08-24
    Description: Arsenic-contaminated aquifers are currently estimated to affect ~150 million people around the world. However, the full extent of the problem remains elusive. This is also the case in Pakistan, where previous studies focused on isolated areas. Using a new data set of nearly 1200 groundwater quality samples throughout Pakistan, we have created state-of-the-art hazard and risk maps of arsenic-contaminated groundwater for thresholds of 10 and 50 μg/liter. Logistic regression analysis was used with 1000 iterations, where surface slope, geology, and soil parameters were major predictor variables. The hazard model indicates that much of the Indus Plain is likely to have elevated arsenic concentrations, although the rest of the country is mostly safe. Unlike other arsenic-contaminated areas of Asia, the arsenic release process in the arid Indus Plain appears to be dominated by elevated-pH dissolution, resulting from alkaline topsoil and extensive irrigation of unconfined aquifers, although pockets of reductive dissolution are also present. We estimate that approximately 50 million to 60 million people use groundwater within the area at risk, with hot spots around Lahore and Hyderabad. This number is alarmingly high and demonstrates the urgent need for verification and testing of all drinking water wells in the Indus Plain, followed by appropriate mitigation measures.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Lateral isotopic discontinuity in the lower crust: an example from antarctica (1987)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1987-09-04
    Description: The lower continental crust is one of the least known variables in the crust-mantle evolutionary equation. In order to study the nature and compositional heterogeneity of the lower crust, more than 20 inclusions of lower crustal granulites in volcanic rocks from the McMurdo Sound region of Antarctica were analyzed for strontium and oxygen isotopes. These inclusions were erupted from volcanic centers covering an area of 12,000 square kilometers. Along with results from analyses of major and trace elements, the isotopic data reveal a profound discontinuity in the composition and probably the age of the lower crust that coincides with the boundary between the Transantarctic Mountains and the Ross Embayment. Although this topographic boundary between East and West Antarctica is largely a Cenozoic development, which apparently reflects a simple subvertical faulting relationship due to crustal rifting, the isotopic differences in the lower crust across the boundary suggest that the current faulting and rifting may coincide with an older crustal suture, the age of which is uncertain.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kalamarides, R I -- Berg, J H -- Hank, R A -- New York, N.Y. -- Science. 1987 Sep 4;237(4819):1192-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17801643" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
    Electronic Resource
    Electronic Resource
    The thermal conductivity of an equimolar methane–ethane mixture in the critical region (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 717-736 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the thermal conductivity of an equimolar mixture of methane and ethane in the vicinity of the critical point. The new experimental data confirm that the thermal conductivity of a mixture does not diverge at the critical point but crosses over to a finite limiting behavior at the critical point. A quantitative representation of the thermal-conductivity data has been obtained in terms of a recently developed extension of the mode-coupling theory that incorporates the crossover between the behavior of the thermal conductivity close to and far away from the critical point. The same theory enables us also to predict other transport properties of the mixture in the vicinity of the critical point. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476611
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  • 7
    Electronic Resource
    Electronic Resource
    Giant nonlinear magneto-optical Kerr effects from Fe interfaces (invited) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6181-6185 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Second harmonic generation from magnetic materials is shown to lead to a nonlinear magneto-optical Kerr effect that can be orders of magnitude larger than its linear equivalent. The origin of this effect can be found in the differences between the linear and nonlinear solutions of the optical wave equations and in the symmetry properties of the corresponding optical tensors. Applications for the study of magnetic surfaces, thin films, and multilayers will be discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362066
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  • 8
    Electronic Resource
    Electronic Resource
    The micromagnetics of periodic arrays of defects in trilayers with interlayer exchange coupling (abstract) : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6559-6559 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A significant loss in the giant magnetoresistive signal of magnetic stacks with antiferromagnetic coupling across nonmagnetic intermediate layers is caused by regions with a ferro- rather than an antiferromagnetic coupling. The impact of these ferromagnetic coupling regions extends itself into the lateral direction due to the bulk exchange coupling. The present micromagnetic model provides a tool by which a detailed quantitative evaluation of the impact of periodic arrays of parallel line defects is possible. These defects have deviating exchange-coupling constants, and/or anisotropy constants or directions, bulk exchange constants, saturation magnetization, etc., in specific regions. Previously, we developed a phenomenological model of trilayers with two magnetic films separated by a nonmagnetic interlayer that contains one such defect. This model, with a relatively small number of free parameters, allows one to trace complete hysteresis curves. A large number of mode branches reveal themselves and jumpwise transitions between these modes frequently occur along the hysteresis loops. The present micromagnetic model requires a sufficiently accurate assessment of the starting magnetization configuration in order to get a convergence of the code. In general, the micromagnetic code is not capable of overcoming the above irreversible mode conversions. The mode branches evaluated by the phenomenological model are applied to provide the micromagnetic model with appropriate starting configurations after meeting a situation of nonstability.The micromagnetic theory of Brown constitutes the basis of the present approach. The micromagnetic effective field is calculated at grid points and the torque exerted by it on the magnetic dipole is made zero at each grid side by an iteration scheme. The long ranging magnetostatic fields are given by convolution integrals and are evaluated in the Fourier space by using two-dimensional fast Fourier transforms. The single defect is micromagnetically studied by zero padding techniques. Depending on the course of the external field, two different wall regions reveal themselves, to wit, the wall core and the so-called Néel tails. These tails were not incorporated into the phenomenological model. Provided that the defects are sufficiently wide spaced, the agreement between both models is rather good in the core regions. The impact on the GMR signal, in particular of the Néel tails, will be discussed with emphasis on systems with weak interlayer coupling, e.g., the decoupled systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358191
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  • 9
    Electronic Resource
    Electronic Resource
    Modeling of magnetic trilayers with interlayer coupling: Application to Co/Ru (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2601-2608 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A magnetization model is presented that is used to cover trilayers containing two magnetic layers that are exchange coupled via an intermediate nonmagnetic layer and that have different crystalline anisotropies. The interfaces are coupled to the bulk by a twisted magnetization configuration which is evaluated using the Ritz method. By minimizing the total energy, experimental magnetization curves of strongly coupled Co/Ru sandwiches can be reproduced with a good precision and with the same set of parameters in two perpendicular field directions. These physical parameters can be determined with a good reliability and are in agreement with the literature except for the bulk anisotropy of the Co layer first deposited, which is twice as large as the known bulk value. This originates in the magnetoelastic contributions due to lattice misfit and interface roughness. It is shown that the interlayer exchange coupling forces the magnetization of both layers to be along the same axis in the low-field range notwithstanding the opposite sign of the anisotropy constants in most stacks. It is also demonstrated that the differences in the orientations of the moments in one Co layer are modest and depend on the various parameters. In particular, the bulk exchange constant is a decisive parameter that makes the calculated curves close to the experimental ones. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361129
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  • 10
    Electronic Resource
    Electronic Resource
    The thermal conductivity of argon in the critical region (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6944-6963 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the thermal conductivity of argon at temperatures from 302 K down to 150.8 K and at densities up to 25 mol L−1. The data were obtained with a steady-state method and we employed a guarded parallel-plate apparatus designed especially for investigating the thermal conductivity of fluids in the critical region. To interpret the data in the critical region a scaled crossover equation of state for argon in the critical region has been constructed. Equations for the thermal conductivity and viscosity of argon as a function of density and temperature are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468322
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