2,061 research outputs found
Simultaneous current-, force- and work function measurement with atomic resolution
The local work function of a surface determines the spatial decay of the
charge density at the Fermi level normal to the surface. Here, we present a
method that enables simultaneous measurements of local work function and
tip-sample forces. A combined dynamic scanning tunneling microscope and atomic
force microscope is used to measure the tunneling current between an
oscillating tip and the sample in real time as a function of the cantilever's
deflection. Atomically resolved work function measurements on a silicon
(111)-() surface are presented and related to concurrently recorded
tunneling current- and force- measurements.Comment: 8 pages, 4 figures, submitted to Applied Physics Letter
Statistical mechanics of temporal association in neural networks with transmission delays
We study the representation of static patterns and temporal sequences in neural networks with signal delays and a stochastic parallel dynamics. For a wide class of delay distributions, the asymptotic network behavior can be described by a generalized Gibbs distribution, generated by a novel Lyapunov functional for the determination dynamics. We extend techniques of equilibrium statistical mechanics so as to deal with time-dependent phenomena, derive analytic results for both retrieval quality and storage capacity, and compare them with numerical simulations
Lorentz angle measurements in irradiated silicon detectors between 77 K and 300 K
Future experiments are using silicon detectors in a high radiation
environment and in high magnetic fields. The radiation tolerance of silicon
improves by cooling it to temperatures below 180 K. At low temperatures the
mobility increases, which leads to larger deflections of the charge carriers by
the Lorentz force. A good knowledge of the Lorentz angle is needed for design
and operation of silicon detectors. We present measurements of the Lorentz
angle between 77 K and 300 K before and after irradiation with a primary beam
of 21 MeV protons.Comment: 13 pages, 9 figures, submitted to ICHEP2000, Osaka, Japa
Disclosure of Agency Legal Materials
This proposed recommendation identifies statutory reforms that, if enacted by Congress, would provide clear standards as to what legal materials agencies must publish and where they must publish them (whether in the Federal Register, on their websites, or elsewhere). The amendments would also account for technological developments and correct certain statutory ambiguities and drafting errors. The objective of these amendments would be to ensure that agencies provide ready public access to important legal materials in the most efficient way possible.
Professor Bernard W. Bell (Rutgers Law School), Professor Cary Coglianese (University of Pennsylvania Law School), Professor Michael Eric Herz (Benjamin N. Cardozo School of Law), Professor Margaret Kwoka (Ohio State University Moritz College of Law), and Professor Orly Lobel (University of San Diego School of Law) are serving as the consultants for this project. Professor Kwoka is serving as the lead consultant.
An Ad Hoc Committee, co-chaired by Public Member Aaron Nielson and Government Member Roxanne Rothschild, considered this project in spring 2023
Harmonic lattice behavior of two-dimensional colloidal crystals
Using positional data from video-microscopy and applying the equipartition
theorem for harmonic Hamiltonians, we determine the wave-vector-dependent
normal mode spring constants of a two-dimensional colloidal model crystal and
compare the measured band-structure to predictions of the harmonic lattice
theory. We find good agreement for both the transversal and the longitudinal
mode. For , the measured spring constants are consistent with the
elastic moduli of the crystal.Comment: 4 pages, 3 figures, submitte
Measuring the equation of state of a hard-disc fluid
We use video microscopy to study a two-dimensional (2D) model fluid of
charged colloidal particles suspended in water and compute the pressure from
the measured particle configurations. Direct experimental control over the
particle density by means of optical tweezers allows the precise measurement of
pressure as a function of density. We compare our data with theoretical
predictions for the equation of state, the pair-correlation function and the
compressibility of a hard-disc fluid and find good agreement, both for the
fluid and the solid phase. In particular the location of the transition point
agrees well with results from Monte Carlo simulations.Comment: 7 pages, to appear in EPL, slightly corrected versio
Humalog Mix25 improves 24-hour plasma glucose profiles compared with the human insulin mixture 30/70 in patients with type 2 diabetes mellitus
Objective. To compare the effects of Humalog Mix25 (Humalog Mix75/25 in the USA) (Mix25) and human insulin 30/70 (30/70) on the 24-hour inpatient plasma glucose (PG) profile in patients with type 2 diabetes mellitus (T2DM).
Design. A randomised, open-label, 8-week crossover study. Study insulins were injected twice daily, 5 minutes before breakfast and dinner.
Setting. Four-week outpatient (dose-adjustment) treatment phase, and 3-day inpatient (test) phase.
Patients. Twenty-five insulin-treated patients with T2DM (ages 40 - 66 years), mean (± standard error of the mean) (SEM) HbA1c 7.7% ± 0.23%, and body mass index (BMI) 29.3 ± 0.83 kg/m2.
Outcome measures. 24-hour PG profiles, PG excursions after meals, PG area under the curve (AUC), and 30-day hypoglycaemia rate.
Results. The 2-hour PG excursions following breakfast (5.5 ±
0.34 v. 7.2 ± 0.34 mmol/l, p = 0.002) and dinner (2.4 ± 0.27 v. 3.4 ± 0.27 mmol/l, p = 0.018) were smaller with Mix25 than with 30/70. PG AUC between breakfast and lunch was smaller with Mix25 than with 30/70 (77.6 ± 3.8 v. 89.5 ± 4.3 mmol/h/ml, p = 0.001). PG AUC between lunch and dinner, dinner and bedtime, and bedtime and breakfast did not differ between treatments. Pre-meal and nocturnal PG were comparable. The postprandial insulin requirement for lunch meals was supplied equally by the two insulin treatments. The thirty-day hypoglycaemia rate was low (Mix25 0.049 ± 0.018 v. 30/70 0.100 ± 0.018 episodes/patient/30 days, p = 0.586) for both treatments.
Conclusion. In patients with T2DM, Mix25 improved the 24-hour PG profile with lower postprandial PG excursions than with human insulin 30/70.
(South African Medical Journal: 2003 93(3): 219-223
Impact of nuclear lattice relaxation on the excitation energy transfer along a chain of pi-conjugated molecules
We have investigated the extent to which delocalization of the ground-state and excited-state wave functions of a -conjugated molecule affects the excitation energy transfer Í‘EETÍ’ between such molecules. Using femtosecond photoluminescence spectroscopy, we experimentally monitored the EET along well-defined supramolecular chains of extended conjugated molecules. Comparison with Monte Carlo simulations reveals that only a model incorporating a localized emitter and delocalized absorber wave function accurately reproduces these data. Our findings demonstrate that self-localization of the initially excited state, following fast relaxation of the nuclear lattice, has a significant impact on the EET dynamics in molecular assemblies
New magnetic phase in metallic V_{2-y}O_3 close to the metal insulator transition
We have observed two spin density wave (SDW) phases in hole doped metallic
V_{2-y}O_3, one evolves from the other as a function of doping, pressure or
temperature. They differ in their response to an external magnetic field, which
can also induce a transition between them. The phase boundary between these two
states in the temperature-, doping-, and pressure-dependent phase diagram has
been determined by magnetization and magnetotransport measurements. One phase
exists at high doping level and has already been described in the literature.
The second phase is found in a small parameter range close to the boundary to
the antiferromagnetic insulating phase (AFI). The quantum phase transitions
between these states as a function of pressure and doping and the respective
metamagnetic behavior observed in these phases are discussed in the light of
structurally induced changes of the band structure.Comment: REVTeX, 8 pages, 12 EPS figures, submitted to PR
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