6,749 research outputs found
Involutions and the Gelfand character
The Gelfand representation of is the multiplicity-free direct
sum of the irreducible representations of . In this paper, we
use a result of Adin, Postnikov, and Roichman to find a recursive generating
function for the Gelfand character. In order to find this generating function,
we investigate descents of so-called -unimodal involutions
Development of methodologies and procedures for identifying STS users and uses
A study was conducted to identify new uses and users of the new Space Transporation System (STS) within the domestic government sector. The study develops a series of analytical techniques and well-defined functions structured as an integrated planning process to assure efficient and meaningful use of the STS. The purpose of the study is to provide NASA with the following functions: (1) to realize efficient and economic use of the STS and other NASA capabilities, (2) to identify new users and uses of the STS, (3) to contribute to organized planning activities for both current and future programs, and (4) to air in analyzing uses of NASA's overall capabilities
User benefits and funding strategies
The justification, economic and technological benefits of NASA Space Programs (aside from pure scientific objectives), in improving the quality of life in the United States is discussed and outlined. Specifically, a three-step, systematic method is described for selecting relevant and highly beneficial payloads and instruments for the Interim Upper Stage (IUS) that will be used with the space shuttle until the space tug becomes available. Viable Government and private industry cost-sharing strategies which would maximize the number of IUS payloads, and the benefits obtainable under a limited NASA budget were also determined. Charts are shown which list the payload instruments, and their relevance in contributing to such areas as earth resources management, agriculture, weather forecasting, and many others
An evaluation of Skylab (EREP) remote sensing techniques applied to investigations of crustal structure
The author has identified the following significant results. Film positives (70mm) from all six S190A multispectral photographic camera stations for any one scene can be registered and analyzed in a color additive viewer. Using a multispectral viewer, S190A and B films can be projected directly onto published geologic and topographic maps at scales as large as 1:62,500 and 1:24,000 without significant loss of detail. S190A films and prints permit the detection of faults, fractures, and other linear features not visible in any other space imagery. S192 MSS imagery can be useful for rock-type discrimination studies and delineation of linear patterns and arcuate anomalies. Anomalous color reflectances and arcuate color patterns revealed mineralized zones, copper deposits, vegetation, and volcanic rocks in various locations such as Panamint Range (CA), Greenwater (Death Valley), Lava Mountains (CA), northwestern Arizona, and Coso Hot Springs (CA)
Magnetic interaction of Co ions near the {10\bar{1}0} ZnO surface
Co-doped ZnO is the prototypical dilute magnetic oxide showing many of the
characteristics of ferromagnetism. The microscopic origin of the long range
order however remains elusive, since the conventional mechanisms for the
magnetic interaction, such as super-exchange and double exchange, fail either
at the fundamental or at a quantitative level. Intriguingly, there is a growing
evidence that defects both in point-like or extended form play a fundamental
role in driving the magnetic order. Here we explore one of such possibilities
by performing {\it ab initio} density functional theory calculations for the
magnetic interaction of Co ions at or near a ZnO \{100\} surface. We
find that extended surface states can hybridize with the -levels of Co and
efficiently mediate the magnetic order, although such a mechanism is effective
only for ions placed in the first few atomic planes near the surface. We also
find that the magnetic anisotropy changes at the surface from an hard-axis
easy-plane to an easy axis, with an associated increase of its magnitude. We
then conclude that clusters with high densities of surfacial Co ions may
display blocking temperatures much higher than in the bulk
Phase separation in fluids exposed to spatially periodic external fields
We consider the liquid-vapor type phase transition for fluids confined within
spatially periodic external fields. For a fluid in d=3 dimensions, the periodic
field induces an additional phase, characterized by large density modulations
along the field direction. At the triple point, all three phases (modulated,
vapor, and liquid) coexist. At temperatures slightly above the triple point and
for low (high) values of the chemical potential, two-phase coexistence between
the modulated phase and the vapor (liquid) is observed. We study this
phenomenon using computer simulations and mean-field theory for the Ising
model. The theory shows that, in order for the modulated phase to arise, the
field wavelength must exceed a threshold value. We also find an extremely low
tension of the interface between the modulated phase and the vapor/liquid
phases. The tension is of the order 10^{-4} kB T per squared lattice spacing,
where kB is the Boltzmann constant, and T the temperature. In order to detect
such low tensions, a new simulation method is proposed. We also consider the
case of d=2 dimensions. The modulated phase then does not survive, leading to a
radically different phase diagram.Comment: 11 pages, 14 figure
‘Still living with it even though it’s gone’: Using Interpretive Phenomenological Analysis to explore shared experiences of living with and beyond breast, prostate, and colorectal cancer
Purpose: Living with and beyond cancer is an increasingly common experience. While research is uncovering valuable individual experiences of those living with and beyond cancer, it has been argued that this idiographic approach is limited in outlook, reach and impact. This study contributes to the understanding of what it means to live with and beyond cancer by complementing idiographic knowledge with multiple perspectives from a group of participants who are living with and beyond cancer, to explore how individual experiences may be relevant to others. Method: Semi-structured interviews were conducted with people who had received treatment for breast (n = 6), prostate (n = 6) or colorectal cancer (n = 6). Data were analysed using interpretive phenomenological analysis. The early findings were then shared with a wider group of people who had received treatment for breast, prostate or colorectal cancer (n = 26) in six focus groups, to explore whether they had similar experiences. Results: While individual accounts of living with and beyond cancer detail unique features specific to each person's experience, focus group discussions illustrated how participant life worlds interact and overlap. The findings identified thematic similarities within and between individual and group levels and across cancer types. Three super-ordinate themes describe the shared experience of living with and beyond cancer: i) the cancer shock, ii) managing cancer and getting through and iii) getting over cancer. Conclusions: A multiple perspective approach informs our understanding of shared experiences of living with and beyond cancer. This knowledge can be used to direct, design, and deliver relevant supportive cancer care
Theory for the phase behaviour of a colloidal fluid with competing interactions
We study the phase behaviour of a fluid composed of particles which interact
via a pair potential that is repulsive for large inter-particle distances, is
attractive at intermediate distances and is strongly repulsive at short
distances (the particles have a hard core). As well as exhibiting gas-liquid
phase separation, this system also exhibits phase transitions from the uniform
fluid phases to modulated inhomogeneous fluid phases. Starting from a
microscopic density functional theory, we develop an order parameter theory for
the phase transition in order to examine in detail the phase behaviour. The
amplitude of the density modulations is the order parameter in our theory. The
theory predicts that the phase transition from the uniform to the modulated
fluid phase can be either first order or second order (continuous). The phase
diagram exhibits two tricritical points, joined to one another by the line of
second order transitions.Comment: 12 pages, 9 figures. Accepted for publication in J. Phys. Condens.
Matte
- …