49,627 research outputs found
Unusual Tunneling Characteristics of Double-quantum-well Heterostructures
We report tunneling phenomena in double InGaAs quantum-well
structures that are at odds with the conventional parallel-momentum-conserving
picture of tunneling between two-dimensional systems. We found that the
tunneling current was mostly determined by the correlation between the emitter
and the state in one well, and not by that between those in both wells. Clear
magnetic-field-dependent features were first observed before the main
resonance, corresponding to tunneling channels into the Landau levels of the
well near the emitter. These facts provide evidence of the violation of
in-plane momentum conservation in two-dimensional systems.Comment: Submitted to ICPS-27 conference proceeding as a contributed pape
Factors associated with nursing home placement for older persons with dementia in Hong Kong
Conference Theme: The Social and Behavioral Importance of Increased LongevityBACKGROUND: “Aging in place” refers to “the ability to live in one's own home and community safely, independently, and comfortably, regardless of age, income, or ability level.' (CDC, 2013). For older persons with dementia, the concept of “home” is particularly important as it provides them with a source of familiarity and autonomy (Aminzadeh, Dalziel, Molnar & Garcia, 2010). Research indicates that the idea of home remains salient even in patients at advanced stage of dementia (Frank, 2005). To facilitate aging in place for older adults with dementia, a large variety of services are provided to support them and their caregivers. Whether these services actually delay nursing home placement, however, is unknown. The goal of this study is to answer this question through examining ...postprin
Low-frequency method for magnetothermopower and Nernst effect measurements on single crystal samples at low temperatures and high magnetic fields
We describe an AC method for the measurement of the longitudinal (Sxx) and
transverse (Sxy, i.e. Nernst) thermopower of mm-size single crystal samples at
low temperatures (T30 T). A low-frequency (33
mHz) heating method is used to increase the resolution, and to determine the
temperature gradient reliably in high magnetic fields. Samples are mounted
between two thermal blocks which are heated by a sinusoidal frequency f0 with a
p/2 phase difference. The phase difference between two heater currents gives a
temperature gradient at 2f0. The corresponding thermopower and Nernst effect
signals are extracted by using a digital signal processing method due. An
important component of the method involves a superconducting link, YBa2Cu3O7+d
(YBCO), which is mounted in parallel with sample to remove the background
magnetothermopower of the lead wires. The method is demonstrated for the quasi
two-dimensional organic conductor a-(BEDT-TTF)2KHg(SCN)4, which exhibits a
complex, magnetic field dependent ground state above 22.5 T at low
temperatures.Comment: 11 pages, 6 figures, 15 reference
The Golden Era of Neutron Stars: from Hadrons to Quarks
Neutron stars were first posited in the early thirties, and discovered as
pulsars in late sixties; however, only recently are we beginning to understand
the matter they contain. This talk describes the continuing development of a
consistent picture of the liquid interiors of neutron stars, driven by four
advances: observations of two heavy neutron stars with masses 2.0
solar masses; inferences of masses and radii simultaneously for an increasing
number of neutron stars in low mass X-ray binaries, and future determinations
via the NICER observatory; the observation of the binary neutron star merger,
GW170817, through gravitational waves as well as across the electromagnetic
spectrum; and an emerging understanding in QCD of how nuclear matter can turn
into deconfined quark matter in the interior. We describe the modern
quark-hadron crossover equation of state, QHC18, and the corresponding neutron
stars, which agree well with current observations.Comment: 6 pages, 6 figures, Proceedings, 8th Intl. Conference on Quarks and
Nuclear Physics 2018 (Tsukuba, Japan), Nov. 201
Monolithic arrays of surface emitting laser NOR logic devices
Monolithic, cascadable, laser-logic-device arrays have been realized and characterized. The monolithic surface-emitting laser logic (SELL) device consists of an AlGaAs superlattice lasing around 780 nm connected to a heterojunction phototransistor (HPT) in parallel and a resistor in series. Arrays up to 8×8 have been fabricated, and 2×2 arrays show uniform characteristics. The optical logic output is switched off with 40 μW incident optical input
Monolithic arrays of surface emitting laser NOR logic devices
Monolithic, cascadable, laser-logic-device arrays have been realized and characterized. The monolithic surface-emitting laser logic (SELL) device consists of an AlGaAs superlattice lasing around 780 nm connected to a heterojunction phototransistor (HPT) in parallel and a resistor in series. Arrays up to 8×8 have been fabricated, and 2×2 arrays show uniform characteristics. The optical logic output is switched off with 40 μW incident optical input
Multivalued memory effects in electronic phase-change manganites controlled by Joule heating
Non-volatile multivalued memory effects caused by magnetic fields, currents,
and voltage pulses are studied in Nd_{0.65}Ca_{0.35}MnO_3 and
(Nd_{1-y}Sm_{y})_{0.5}Sr_{0.5}MnO_3 (y=0.75) single crystals in the hysteretic
region between ferromagnetic metallic and charge-ordered insulating states. The
current/voltage effects observed in this study are explained by the
self-heating effect, which enable us to control the colossal electroresistance
effects. This thermal-cycle induced switching between electronic solid and
liquid states can be regarded as electronic version of atomic crystal/amorphous
transitions in phase-change chalcogenides.Comment: 5 pages, 4 figures. to appear in Phys. Rev.
Zeta Potential of Modified Multi-walled Carbon Nanotubes in Presence of poly (vinyl alcohol) Hydrogel
The main objective of this study is investigate the behavior of the Zeta Potential of the MWCNT modified with SDS(Sodium Dodecyl Sulfate) and CTAB(Cetyl Tetraethyl Ammonium Bromide) in presence of PVA. Full hydrolyzed PVA was used. As a result, adding PVA in the CNT solution led to decrease the Zeta Potential. The Zeta Potential of suspended colloid varied from 42.00mV to 6.48mV and -45.00mV to -6.4mV at 1.5% concentration of PVA; according with the changing pH, the Zeta Potential dropped to near zero at pH 3 and 11. The pH and PVA has strong influence in the reduction of ZP of MWCNT solution. MWCNT-PVA solution with 33.30mV, -35.69mV at 0.01% of PVA was exposed under AC field; a uniform coat was obtained, with the SDS-MWCNT-PVA solution.National Natural Science Foundation of China Project (Grant No.51073024), the Royal Society-NSFC international joint project (Grant No.51111130207) and Beijing Municipal Science and Technology Plan Projects (No. Z111103066611005)
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