33,849 research outputs found
Differential pulse polarography and voltammetry with an automated microprocessor-based polarograph and a static mercury drop electrode
Differential pulse polarography using an automated, microprocessor- based polarographic
analyzer equipped with a static mercury drop electrode has been evaluated with respect to pulse
amplitude, scan rate, drop time (t), and drop area. Variation of peak current, z"p' with drop area and
t - Y2, with some pulse amplitudes agree reasonably well with theory. However, dependence of and E
or i scan rate and on pulse amplitude at very large and very small amplitudes was found to devide fron i
theory. Similar trends were also found for anodic stripping voltammetry when differential pulse
stripping was used. The precision attainable by both techniques was good. Copper peaks demonstrated
good precision only when copper was plated out individually during anodic stripping voltammetry
Nuclear isotope thermometry
We discuss different aspects which could influence temperatures deduced from
experimental isotopic yields in the multifragmentation process. It is shown
that fluctuations due to the finite size of the system and distortions due to
the decay of hot primary fragments conspire to blur the temperature
determination in multifragmentation reactions. These facts suggest that caloric
curves obtained through isotope thermometers, which were taken as evidence for
a first-order phase transition in nuclear matter, should be investigated very
carefully.Comment: 9 pages, 7 figure
Aharonov-Bohm oscillations of a tunable quantum ring
With an atomic force microscope a ring geometry with self-aligned in-plane
gates was directly written into a GaAs/AlGaAs-heterostructure. Transport
measurements in the open regime show only one transmitting mode and
Aharonov-Bohm oscillations with more than 50% modulation are observed in the
conductance. The tuning via in-plane gates allows to study the Aharonov-Bohm
effect in the whole range from the open ring to the Coulomb-blockade regime.Comment: 3 pages, 3 figure
Implementation of Design for Manufacture and Assembly principles in the construction project: A case study
Design for manufacture and assembly (DfMA) has been increasingly advocated by the global construction industry since it provides methodological procedures for evaluating and improving design for both manufacture and assembly. Many studies have investigated the DfMA principles suitable for different types of construction projects and advocated a wide implementation of DfMA in construction. However, it would be difficult to persuade stakeholders to implement DfMA principles in their projects without a clear specification of implementation procedures. This study aims to offer an intelligible description and analysis of implementation procedures of DfMA in a real construction project. It does so by undertaking a case study on a prefabricated bamboo building, in which a DfMA-focused design was required by the client. The study reveals how the knowledge of designer, engineer, and contractor has been integrated to implement DfMA principles in the design of building components and sub-components. This study also identifies the best practice of ensuring engineering performance and meanwhile attaining aesthetics in the application of DfMA principles
Resonant Excitation of Graphene K-Phonon and Intra-Landau-Level Excitons in Magneto-Optical Spectroscopy
Precise infrared magnetotransmission experiments have been performed in
magnetic fields up to 32 T on a series of multilayer epitaxial graphene
samples. We observe changes in the spectral features and broadening of the main
cyclotron transition when the incoming photon energy is in resonance with the
lowest Landau level separation and the energy of a K point optical phonon. We
have developed a theory that explains and quantitatively reproduces the
frequency and magnetic field dependence of the phenomenon as the absorption of
a photon together with the simultaneous creation of an intervalley,
intra-Landau-level exciton, and a K phonon.Comment: Main manuscript (5 pages); Supplementary Material (18 pages
Maximum likelihood estimation of photon number distribution from homodyne statistics
We present a method for reconstructing the photon number distribution from
the homodyne statistics based on maximization of the likelihood function
derived from the exact statistical description of a homodyne experiment. This
method incorporates in a natural way the physical constraints on the
reconstructed quantities, and the compensation for the nonunit detection
efficiency.Comment: 3 pages REVTeX. Final version, to appear in Phys. Rev. A as a Brief
Repor
Modeling the impacts of biomass burning on air quality in and around Mexico City
The local and regional impacts of open fires and trash burning on ground-level ozone (O[subscript 3]) and fine carbonaceous aerosols in the Mexico City Metropolitan Area (MCMA) and surrounding region during two high fire periods in March 2006 have been evaluated using WRF-CHEM model. The model captured reasonably well the measurement-derived magnitude and temporal variation of the biomass burning organic aerosol (BBOA), and the simulated impacts of open fires on organic aerosol (OA) were consistent with many observation-based estimates. We did not detect significant effects of open fires and trash burning on surface O[subscript 3] concentrations in the MCMA and surrounding region. In contrast, they had important influences on OA and elemental carbon (EC), increasing primary OA (POA) by ~60%, secondary OA (SOA) by ~22%, total OA (TOA = POA + SOA) by ~33%, and EC by ~22%, on both the local (urban) and regional scales. Although the emissions of trash burning are substantially lower than those from open fires, trash burning made slightly smaller but comparable contributions to OA as open fires did, and exerted an even higher influence on EC. Of the ~22% enhancement in SOA concentrations (equivalent to a ~15% increase in TOA) simulated, about two third was attributed to the open fires and one-third to the trash burning. On the annual basis and taking the biofuel use emissions into consideration, we estimated that open fires, trash burning and biofuel use together contributed about 60% to the loading of POA, 30% to SOA, and 25% to EC in both the MCMA and its surrounding region, of which the open fires and trash burning contributed about 35% to POA, 18% to SOA, and 15% to EC. The estimates of biomass burning impacts in this study may contain considerable uncertainties due to the uncertainties in their emission estimates in magnitude, temporal and spatial distribution, extrapolations and the nature of spot comparison. More observation and modeling studies are needed to accurately assess the impacts of biomass burning on tropospheric chemistry, regional and global air quality, and climate change.National Science Foundation (U.S.) (Award 1135141
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