1,398 research outputs found
Open Strings in PP-Wave Background from Defect Conformal Field Theory
We consider open strings ending on a D5-brane in the pp-wave background,
which is realized in the Penrose limit of with an
brane. A complete list of gauge invariant operators in the
defect conformal field theory is constructed which is dual to the open string
states.Comment: 14+1 pages, no figures, LaTex (v2: references added, typos corrected,
discussion expanded in section 4
On the Propagation of Slip Fronts at Frictional Interfaces
The dynamic initiation of sliding at planar interfaces between deformable and
rigid solids is studied with particular focus on the speed of the slip front.
Recent experimental results showed a close relation between this speed and the
local ratio of shear to normal stress measured before slip occurs (static
stress ratio). Using a two-dimensional finite element model, we demonstrate,
however, that fronts propagating in different directions do not have the same
dynamics under similar stress conditions. A lack of correlation is also
observed between accelerating and decelerating slip fronts. These effects
cannot be entirely associated with static local stresses but call for a dynamic
description. Considering a dynamic stress ratio (measured in front of the slip
tip) instead of a static one reduces the above-mentioned inconsistencies.
However, the effects of the direction and acceleration are still present. To
overcome this we propose an energetic criterion that uniquely associates,
independently on the direction of propagation and its acceleration, the slip
front velocity with the relative rise of the energy density at the slip tip.Comment: 15 pages, 6 figure
Twin paradox and space topology
If space is compact, then a traveller twin can leave Earth, travel back home
without changing direction and find her sedentary twin older than herself. We
show that the asymmetry between their spacetime trajectories lies in a
topological invariant of their spatial geodesics, namely the homotopy class.
This illustrates how the spacetime symmetry invariance group, although valid
{\it locally}, is broken down {\it globally} as soon as some points of space
are identified. As a consequence, any non--trivial space topology defines
preferred inertial frames along which the proper time is longer than along any
other one.Comment: 6 pages, latex, 3 figure
Singular shell embedded into a cosmological model
We generalize Israel's formalism to cover singular shells embedded in a
non-vacuum Universe. That is, we deduce the relativistic equation of motion for
a thin shell embedded in a Schwarzschild/Friedmann-Lemaitre-Robertson-Walker
spacetime. Also, we review the embedding of a Schwarzschild mass into a
cosmological model using "curvature" coordinates and give solutions with
(Sch/FLRW) and without the embedded mass (FLRW).Comment: 25 pages, 2 figure
Single-cell profiling of alveolar rhabdomyosarcoma reveals RAS pathway inhibitors as cell-fate hijackers with therapeutic relevance
Rhabdomyosarcoma (RMS) is a group of pediatric cancers with features of developing skeletal muscle. The cellular hierarchy and mechanisms leading to developmental arrest remain elusive. Here, we combined single-cell RNA sequencing, mass cytometry, and high-content imaging to resolve intratumoral heterogeneity of patient-derived primary RMS cultures. We show that the aggressive alveolar RMS (aRMS) subtype contains plastic muscle stem-like cells and cycling progenitors that drive tumor growth, and a subpopulation of differentiated cells that lost its proliferative potential and correlates with better outcomes. While chemotherapy eliminates cycling progenitors, it enriches aRMS for muscle stem-like cells. We screened for drugs hijacking aRMS toward clinically favorable subpopulations and identified a combination of RAF and MEK inhibitors that potently induces myogenic differentiation and inhibits tumor growth. Overall, our work provides insights into the developmental states underlying aRMS aggressiveness, chemoresistance, and progression and identifies the RAS pathway as a promising therapeutic target
Cubic Interactions in PP-Wave Light Cone String Field Theory
We use the supergravity modes to clarify the role of the prefactor in the
light-cone superstring field theory on PP-wave background. We verify some of
the proposals of the recent paper hep-th/0205089 and give further evidence for
the correspondence between N=4 SYM gauge theory and string theory on PP-wave.
We also consider energy-preserving processes and find that they give vanishing
cubic interaction Hamiltonian matrix.Comment: 16+1 pages, no figures, LaTeX (v3: references, minor changes and a
clarification about Neumann matrices added; to appear in Physical Review D
KG-COVID-19: A Framework to Produce Customized Knowledge Graphs for COVID-19 Response.
Integrated, up-to-date data about SARS-CoV-2 and COVID-19 is crucial for the ongoing response to the COVID-19 pandemic by the biomedical research community. While rich biological knowledge exists for SARS-CoV-2 and related viruses (SARS-CoV, MERS-CoV), integrating this knowledge is difficult and time-consuming, since much of it is in siloed databases or in textual format. Furthermore, the data required by the research community vary drastically for different tasks; the optimal data for a machine learning task, for example, is much different from the data used to populate a browsable user interface for clinicians. To address these challenges, we created KG-COVID-19, a flexible framework that ingests and integrates heterogeneous biomedical data to produce knowledge graphs (KGs), and applied it to create a KG for COVID-19 response. This KG framework also can be applied to other problems in which siloed biomedical data must be quickly integrated for different research applications, including future pandemics
Transverse-Momentum Dependence of the J/psi Nuclear Modification in d+Au Collisions at sqrt(s_NN)=200 GeV
We present measured J/psi production rates in d+Au collisions at sqrt(s_NN) =
200 GeV over a broad range of transverse momentum (p_T=0-14 GeV/c) and rapidity
(-2.2<y<2.2). We construct the nuclear-modification factor R_dAu for these
kinematics and as a function of collision centrality (related to impact
parameter for the R_dAu collision). We find that the modification is largest
for collisions with small impact parameters, and observe a suppression
(R_dAu<1) for p_T<4 GeV/c at positive rapidities. At negative rapidity we
observe a suppression for p_T1) for p_T>2
GeV/c. The observed enhancement at negative rapidity has implications for the
observed modification in heavy-ion collisions at high p_T.Comment: 384 authors, 24 pages, 19 figures, 13 tables. Submitted to Phys. Rev.
C. Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/info/data/ppg123_data.htm
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A Chemistry of Organization: Combinatory Structural Analysis and Design
This paper is a response to the call for models of organization design as a science revealing the inner composition of organization and specifying the laws to be respected when crafting it. It maintains that the needed science is a chemistry of organization, addressing the combination of 'organizational elements' playing a role analogous to that of chemical elements in composing a variety of substances. Drawing both on classic organization design theory and on configurational and complementarity-based approaches, the paper specifies a set of basic organizational elements and a set of combinatory laws regulating their effective combinations. Testable propositions are derived on the necessary and sufficient conditions that the composition of organizations should have respect for achieving high levels of efficiency and innovation. These propositions are tested empirically on a sample of firms, using an innovative application of Boolean algebra
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