82,262 research outputs found
Pyramidal micromirrors for microsystems and atom chips
Concave pyramids are created in the (100) surface of a silicon wafer by anisotropic etching in potassium hydroxide. High quality micromirrors are then formed by sputtering gold onto the smooth silicon (111) faces of the pyramids. These mirrors show great promise as high quality optical devices suitable for integration into micro-optoelectromechanical systems and atom chips. We have shown that structures of this shape can be used to laser-cool and hold atoms in a magneto-optical trap
EUV Spectra of the Full Solar Disk: Analysis and Results of the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)
We analyze EUV spectra of the full solar disk from the Cosmic Hot
Interstellar Plasma Spectrometer (CHIPS) spanning a period of two years. The
observations were obtained via a fortuitous off-axis light path in the 140 --
270 Angstrom passband. The general appearance of the spectra remained
relatively stable over the two-year time period, but did show significant
variations of up to 25% between two sets of Fe lines that show peak emission at
1 MK and 2 MK. The variations occur at a measured period of 27.2 days and are
caused by regions of hotter and cooler plasma rotating into, and out of, the
field of view. The CHIANTI spectral code is employed to determine plasma
temperatures, densities, and emission measures. A set of five isothermal
plasmas fit the full disk spectra well. A 1 -- 2 MK plasma of Fe contributes
85% of the total emission in the CHIPS passband. The standard Differential
Emission Measures (DEMs) supplied with the CHIANTI package do not fit the CHIPS
spectra well as they over-predict emission at temperatures below log(T) = 6.0
and above log(T) = 6.3. The results are important for cross-calibrating TIMED,
SORCE, SOHO/EIT, and CDS/GIS, as well as the recently launched Solar Dynamics
Observatory.Comment: 27 Pages, 13 Figure
Color naming reflects both perceptual structure and communicative need
Gibson et al. (2017) argued that color naming is shaped by patterns of
communicative need. In support of this claim, they showed that color naming
systems across languages support more precise communication about warm colors
than cool colors, and that the objects we talk about tend to be warm-colored
rather than cool-colored. Here, we present new analyses that alter this
picture. We show that greater communicative precision for warm than for cool
colors, and greater communicative need, may both be explained by perceptual
structure. However, using an information-theoretic analysis, we also show that
color naming across languages bears signs of communicative need beyond what
would be predicted by perceptual structure alone. We conclude that color naming
is shaped both by perceptual structure, as has traditionally been argued, and
by patterns of communicative need, as argued by Gibson et al. - although for
reasons other than those they advanced
Method for Cooling Nanostructures to Microkelvin Temperatures
We propose a new scheme aimed at cooling nanostructures to microkelvin
temperatures, based on the well established technique of adiabatic nuclear
demagnetization: we attach each device measurement lead to an individual
nuclear refrigerator, allowing efficient thermal contact to a microkelvin bath.
On a prototype consisting of a parallel network of nuclear refrigerators,
temperatures of mK simultaneously on ten measurement leads have been
reached upon demagnetization, thus completing the first steps toward ultracold
nanostructures.Comment: 4 pages, 3 (color) figure
Competitive Foods
Describes the types of food items available to middle and high school students in forty California public secondary schools, as well as how well they match the nutrient standards defined in California's SB 12 legislation
Two-dimensional array of microtraps with atomic shift register on a chip
Arrays of trapped atoms are the ideal starting point for developing registers
comprising large numbers of physical qubits for storing and processing quantum
information. One very promising approach involves neutral atom traps produced
on microfabricated devices known as atom chips, as almost arbitrary trap
configurations can be realised in a robust and compact package. Until now,
however, atom chip experiments have focused on small systems incorporating
single or only a few individual traps. Here we report experiments on a
two-dimensional array of trapped ultracold atom clouds prepared using a simple
magnetic-film atom chip. We are able to load atoms into hundreds of tightly
confining and optically resolved array sites. We then cool the individual atom
clouds in parallel to the critical temperature required for quantum degeneracy.
Atoms are shuttled across the chip surface utilising the atom chip as an atomic
shift register and local manipulation of atoms is implemented using a focused
laser to rapidly empty individual traps.Comment: 6 pages, 4 figure
Powering down technology
This paper will examine the issue of energy consumption resulting from the use of technology. It will identify and evaluate potential solutions currently being deployed by data center managers. In addition, the paper will recommend guidelines for reducing energy consumption for both the individual and business consumer
- …