133 research outputs found
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Heat Transfer Characteristics of Mark 15 Slugs for Different Bonding Conditions
A numerical heat transfer model based on the HEATING53 conduction code was developed to analyze poor bonding around the endcap of the outer Mark 15 slug. An analytical model could not be developed because of non-uniform heat generation in the core and the arrangement of the various materials in the cylindrical geometry. Results for air gaps are also included; however, they are not considered reasonable poor bond cases because the 300 area inspection tests can detect slugs with air gaps. This reports discusses the test results
Making things happen : a model of proactive motivation
Being proactive is about making things happen, anticipating and preventing problems, and seizing opportunities. It involves self-initiated efforts to bring about change in the work environment and/or oneself to achieve a different future. The authors develop existing perspectives on this topic by identifying proactivity as a goal-driven process involving both the setting of a proactive goal (proactive goal generation) and striving to achieve that proactive goal (proactive goal striving). The authors identify a range of proactive goals that individuals can pursue in organizations. These vary on two dimensions: the future they aim to bring about (achieving a better personal fit within one’s work environment, improving the organization’s internal functioning, or enhancing the organization’s strategic fit with its environment) and whether the self or situation is being changed. The authors then identify “can do,” “reason to,” and “energized to” motivational states that prompt proactive goal generation and sustain goal striving. Can do motivation arises from perceptions of self-efficacy, control, and (low) cost. Reason to motivation relates to why someone is proactive, including reasons flowing from intrinsic, integrated, and identified motivation. Energized to motivation refers to activated positive affective states that prompt proactive goal processes. The authors suggest more distal antecedents, including individual differences (e.g., personality, values, knowledge and ability) as well as contextual variations in leadership, work design, and interpersonal climate, that influence the proactive motivational states and thereby boost or inhibit proactive goal processes. Finally, the authors summarize priorities for future researc
Brane Inflation, Solitons and Cosmological Solutions: I
In this paper we study various cosmological solutions for a D3/D7 system
directly from M-theory with fluxes and M2-branes. In M-theory, these solutions
exist only if we incorporate higher derivative corrections from the curvatures
as well as G-fluxes. We take these corrections into account and study a number
of toy cosmologies, including one with a novel background for the D3/D7 system
whose supergravity solution can be completely determined. This new background
preserves all the good properties of the original model and opens up avenues to
investigate cosmological effects from wrapped branes and brane-antibrane
annihilation, to name a few. We also discuss in some detail semilocal defects
with higher global symmetries, for example exceptional ones, that could occur
in a slightly different regime of our D3/D7 model. We show that the D3/D7
system does have the required ingredients to realise these configurations as
non-topological solitons of the theory. These constructions also allow us to
give a physical meaning to the existence of certain underlying homogeneous
quaternionic Kahler manifolds.Comment: Harvmac, 115 pages, 9 .eps figures; v2: typos corrected, references
added and the last section expanded; v3: Few minor typos corrected and
references added. Final version to appear in JHE
Modulating bone marrow hematopoietic lineage potential to prevent bone metastasis in breast cancer
The presence of disseminated tumor cells in breast cancer patient bone marrow aspirates predicts decreased recurrence-free survival. Although it is appreciated that physiological, pathological, and therapeutic conditions impact hematopoiesis, it remains unclear if targeting hematopoiesis presents opportunities for limiting bone metastasis. Using pre-clinical breast cancer models, we discovered that marrow from mice treated with the bisphosphonate zoledronic acid (ZA) are metastasis-suppressive. Specifically, ZA modulated hematopoietic myeloid/osteoclast progenitor cell (M/OCP) lineage potential to activate metastasis-suppressive activity. Granulocyte-colony stimulating factor (G-CSF) promoted ZA resistance by redirecting M/OCP differentiation. We identified M/OCP and bone marrow transcriptional programs associated with metastasis suppression and ZA resistance. Analysis of patient blood samples taken at random revealed that women with high plasma G-CSF experienced significantly worse outcome with adjuvant ZA than those with lower G-CSF levels. Our findings support discovery of therapeutic strategies to direct M/OCP lineage potential and biomarkers that stratify responses in patients at risk of recurrence
Physics of Solar Prominences: II - Magnetic Structure and Dynamics
Observations and models of solar prominences are reviewed. We focus on
non-eruptive prominences, and describe recent progress in four areas of
prominence research: (1) magnetic structure deduced from observations and
models, (2) the dynamics of prominence plasmas (formation and flows), (3)
Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and
large-scale patterns of the filament channels in which prominences are located.
Finally, several outstanding issues in prominence research are discussed, along
with observations and models required to resolve them.Comment: 75 pages, 31 pictures, review pape
Warped Wilson Line DBI Inflation
We propose a novel inflationary scenario in string theory in which the
inflaton field is a 'Wilson line' degree of freedom in the worldvolume of a
probe Dp-brane, in a warped flux compactification. Kinetic terms for Wilson
line fields on the world volume of a D-brane take a nonstandard
Dirac-Born-Infeld (DBI) form. Thus, we work in the framework of DBI inflation.
This extends the original slow roll Wilson line inflationary scenario, where
only the quadratic piece was considered. Warped DBI Wilson line inflation
offers an attractive alternative to ordinary (position field) DBI inflation,
inasmuch as observational and theoretical constraints get considerably relaxed.
Besides the standard large non-Gaussianities in DBI scenarios, it is also
possible to achieve an observable amount of gravitational waves.Comment: v3: Typos corrected, Published in JCAP; 21 page
Cosmological perturbations in SFT inspired non-local scalar field models
We study cosmological perturbations in models with a single non-local scalar
field originating from the string field theory description of the rolling
tachyon dynamics. We construct the equation for the energy density
perturbations of the non-local scalar field and explicitly prove that for the
free field it is identical to a system of local cosmological perturbation
equations in a particular model with multiple (maybe infinitely many) local
free scalar fields.Comment: 21 pages, no figures, v3: presentation improved, results unchanged,
references adde
Lectures on inflation and cosmological perturbations
The purpose of these lectures is to give a pedagogical introduction to
inflation and the production of primordial perturbations, as well as a review
of some of the latest developments in this domain. After a short introduction,
we review the main principles of the Hot Big Bang model, as well as its
limitations. This motivates the study of cosmological inflation induced by a
slow-rolling scalar field. We then turn to the analysis of cosmological
perturbations, and explain how the vacuum quantum fluctuations are amplified
during an inflationary phase. The next step consists in relating the
perturbations generated during inflation to the perturbations of the
cosmological fluid in the radiation dominated phase. The final part of these
lectures gives a review of more general models of inflation, involving multiple
fields or non standard kinetic terms. Although more complicated, these models
are usually motivated by high energy physics and they can lead to specific
signatures that are not expected in the simplest models of inflation. After
introducing a very general formalism to describe perturbations in multi-field
models with arbitrary kinetic terms, several interesting cases are presented.
We also stress the role of entropy perturbations in the context of multi-field
models. Finally, we discuss in detail the non-Gaussianities of the primordial
perturbations and some models that could produce a detectable level of
non-Gaussianities.Comment: 56 pages, 5 figures; Lectures given at the Second TRR33 Winter School
on cosmology, Passo del Tonale (Italy), December 200
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