44,741 research outputs found
Flexible high-voltage supply for experimental electron microscope
Scanning microscope uses a field-emission tip for the electron source, an electron gun that simultaneously accelerates and focuses electrons from the source, and one auxiliary lens to produce a final probe size at the specimen on the order of angstroms
Dietary patterns among Vietnamese and Hispanic immigrant elementary school children participating in an after school program
Immigrants in the U.S. may encounter challenges of acculturation, including dietary habits, as they adapt to new surroundings. We examined Vietnamese and Hispanic immigrant children's American food consumption patterns in a convenience sample of 63 Vietnamese and Hispanic children in grades four to six who were attending an after school program. Children indicated the number of times they consumed each of 54 different American foods in the past week using a food frequency questionnaire. We ranked each food according to frequency of consumption, compared the intake of foods to the USDA Healthy Eating Pattern, and performed dietary pattern analysis. Since the data were not normally distributed we used two nonparametric tests to evaluate statistical significance: the Kruskal-Wallis tested for significant gender and ethnicity differences and the Wilcoxon signed-rank test evaluated the food consumption of children compared with the USDA recommended amounts. We found that among USDA categories, discretionary food was most commonly consumed, followed by fruit. The sample as a whole ate significantly less than the recommended amount of grains, protein foods, and dairy, but met the recommended amount of fruit. Boys ate significantly more grains, proteins, and fruits than did girls. Dietary pattern analysis showed a very high sweet snack consumption among all children, while boys ate more fast food and fruit than girls. Foods most commonly consumed were cereal, apples, oranges, and yogurt. Ethnicity differences in food selection were not significant. The high intake of discretionary/snack foods and fruit, with low intake of grains, vegetables, protein, and dairy in our sample suggests Vietnamese and Hispanic immigrant children may benefit from programs to improve diet quality
Mixed-State Entanglement and Quantum Teleportation through Noisy Channels
The quantum teleportation with noisy EPR state is discussed. Using an optimal
decomposition technique, we compute the concurrence, entanglement of formation
and Groverian measure for various noisy EPR resources. It is shown analytically
that all entanglement measures reduce to zero when , where
is an average fidelity between Alice and Bob. This fact indicates
that the entanglement is a genuine physical resource for the teleportation
process. This fact gives valuable clues on the optimal decomposition for
higher-qubit mixed states. As an example, the optimal decompositions for the
three-qubit mixed states are discussed by adopting a teleportation with W-stateComment: 18 pages, 4 figure
A one-dimensional tunable magnetic metamaterial
We present experimental data on a one-dimensional superconducting
metamaterial that is tunable over a broad frequency band. The basic building
block of this magnetic thin-film medium is a single-junction (rf-)
superconducting quantum interference device (SQUID). Due to the nonlinear
inductance of such an element, its resonance frequency is tunable in situ by
applying a dc magnetic field. We demonstrate that this results in tunable
effective parameters of our metamaterial consisting of 54 SQUIDs. In order to
obtain the effective magnetic permeability from the measured data, we employ a
technique that uses only the complex transmission coefficient S21
Product Integral Formalism and Non-Abelian Stokes Theorem
We make use of the properties of product integrals to obtain a surface
product integral representation for the Wilson loop operator. The result can be
interpreted as the non-abelian version of Stokes' theorem.Comment: Latex; condensed version of hep-th/9903221, to appear in Jour. Math.
Phy
An automatic data system for vibration modal tuning and evaluation
A digitally based automatic modal tuning and analysis system developed to provide an operational capability beginning at 0.1 hertz is described. The elements of the system, which provides unique control features, maximum operator visibility, and rapid data reduction and documentation, are briefly described; and the operational flow is discussed to illustrate the full range of capabilities and the flexibility of application. The successful application of the system to a modal survey of the Skylab payload is described. Information about the Skylab test article, coincident-quadrature analysis of modal response data, orthogonality, and damping calculations is included in the appendixes. Recommendations for future application of the system are also made
Spinor Dynamics in an Antiferromagnetic Spin-1 Condensate
We observe coherent spin oscillations in an antiferromagnetic spin-1
Bose-Einstein condensate of sodium. The variation of the spin oscillations with
magnetic field shows a clear signature of nonlinearity, in agreement with
theory, which also predicts anharmonic oscillations near a critical magnetic
field. Measurements of the magnetic phase diagram agree with predictions made
in the approximation of a single spatial mode. The oscillation period yields
the best measurement to date of the sodium spin-dependent interaction
coefficient, determining that the difference between the sodium spin-dependent
s-wave scattering lengths is Bohr radii.Comment: 5 pages, 2 figures. Changes: added reference, minor correction
Reconceptualising Personas Across Cultures: Archetypes, Stereotypes & Collective Personas in Pastoral Namibia
The paucity of projects where persona is the research foci and a lack of consensus on this artefact keep many reticent about its purpose and value. Besides crafting personas is expected to differ across cultures, which contrasts the advancements in Western theory with studies and progress in other sites. We postulate User-Created Personas reveal specific characteristics of situated contexts by allowing laypeople to design persona artefacts in their own terms. Hence analysing four persona sessions with an ethnic group in pastoral Namibia –ovaHerero– brought up a set of fundamental questions around the persona artefact regarding stereotypes, archetypes, and collective persona representations: (1) to what extent user depictions are stereotypical or archetypal? If stereotypes prime (2) to what degree are current personas a useful method to represent end-users in technology design? And, (3) how can we ultimately read accounts not conforming to mainstream individual persona descriptions but to collectives
Partially composite 2-Higgs-doublet model
In the extra dimensional scenarios with gauge fields in the bulk, the
Kaluza-Klein (KK) gauge bosons can induce Nambu-Jona-Lasinio (NJL) type
attractive four-fermion interactions, which can break electroweak symmetry
dynamically with accompanying composite Higgs fields. We consider a possibility
that electroweak symmetry breaking (EWSB) is triggered by both a fundamental
Higgs and a composite Higgs arising in a dynamical symmetry breaking mechanism
induced by a new strong dynamics. The resulting Higgs sector is a partially
composite two-Higgs doublet model with specific boundary conditions on the
coupling and mass parameters originating at a compositeness scale .
The phenomenology of this model is discussed including the collider
phenomenology at LHC and ILC.Comment: To appear in the proceeding of LCWS06, Bangalore, Indi
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