84 research outputs found
Representation of the earth's gravitational potential
Representation of earth gravitational potential outside sphere bounding eart
Block Spin Effective Action for 4d SU(2) Finite Temperature Lattice Gauge Theory
The Svetitsky-Yaffe conjecture for finite temperature 4d SU(2) lattice gauge
theory is confirmed by observing matching of block spin effective actions of
the gauge model with those of the 3d Ising model. The effective action for the
gauge model is defined by blocking the signs of the Polyakov loops with the
majority rule. To compute it numerically, we apply a variant of the IMCRG
method of Gupta and Cordery.Comment: LaTeX2e, 22 pages, 8 Figure
High frequency of ribosomal protein gene deletions in Italian Diamond-Blackfan anemia patients detected by multiplex ligation-dependent probe amplification assay
Diamond-Blackfan anemia is an autosomal dominant disease due to mutations in nine ribosomal protein encoding genes. Because most mutations are loss of function and detected by direct sequencing of coding exons, we reasoned that part of the approximately 50% mutation negative patients may have carried a copy number variant of ribosomal protein genes. As a proof of concept, we designed a multiplex ligation-dependent probe amplification assay targeted to screen the six genes that are most frequently mutated in Diamond-Blackfan anemia patients: RPS17, RPS19, RPS26, RPL5, RPL11, and RPL35A. Using this assay we showed that deletions represent approximately 20% of all mutations. The combination of sequencing and multiplex ligation-dependent probe amplification analysis of these six genes allows the genetic characterization of approximately 65% of patients, showing that Diamond-Blackfan anemia is indisputably a ribosomopathy
Critical Exponents of the 3D Ising Universality Class From Finite Size Scaling With Standard and Improved Actions
We propose a method to obtain an improved Hamiltonian (action) for the Ising
universality class in three dimensions. The improved Hamiltonian has suppressed
leading corrections to scaling. It is obtained by tuning models with two
coupling constants. We studied three different models: the +1,-1 Ising model
with nearest neighbour and body diagonal interaction, the spin-1 model with
states 0,+1,-1, and nearest neighbour interaction, and phi**4-theory on the
lattice (Landau-Ginzburg Hamiltonian). The remarkable finite size scaling
properties of the suitably tuned spin-1 model are compared in detail with those
of the standard Ising model. Great care is taken to estimate the systematic
errors from residual corrections to scaling. Our best estimates for the
critical exponents are nu= 0.6298(5) and eta= 0.0366(8), where the given error
estimates take into account the statistical and systematic uncertainties.Comment: 55 pages, 12 figure
Celestial Mechanics, Conformal Structures, and Gravitational Waves
The equations of motion for non-relativistic particles attracting
according to Newton's law are shown to correspond to the equations for null
geodesics in a -dimensional Lorentzian, Ricci-flat, spacetime with a
covariantly constant null vector. Such a spacetime admits a Bargmann structure
and corresponds physically to a generalized pp-wave. Bargmann electromagnetism
in five dimensions comprises the two Galilean electro-magnetic theories (Le
Bellac and L\'evy-Leblond). At the quantum level, the -body Schr\"odinger
equation retains the form of a massless wave equation. We exploit the conformal
symmetries of such spacetimes to discuss some properties of the Newtonian
-body problem: homographic solutions, the virial theorem, Kepler's third
law, the Lagrange-Laplace-Runge-Lenz vector arising from three conformal
Killing 2-tensors, and motions under inverse square law forces with a
gravitational constant varying inversely as time (Dirac). The latter
problem is reduced to one with time independent forces for a rescaled position
vector and a new time variable; this transformation (Vinti and Lynden-Bell)
arises from a conformal transformation preserving the Ricci-flatness
(Brinkmann). A Ricci-flat metric representing non-relativistic
gravitational dyons is also pointed out. Our results for general time-dependent
are applicable to the motion of point particles in an expanding
universe. Finally we extend these results to the quantum regime.Comment: 26 pages, LaTe
The fundamental constants and their variation: observational status and theoretical motivations
This article describes the various experimental bounds on the variation of
the fundamental constants of nature. After a discussion on the role of
fundamental constants, of their definition and link with metrology, the various
constraints on the variation of the fine structure constant, the gravitational,
weak and strong interactions couplings and the electron to proton mass ratio
are reviewed. This review aims (1) to provide the basics of each measurement,
(2) to show as clearly as possible why it constrains a given constant and (3)
to point out the underlying hypotheses. Such an investigation is of importance
to compare the different results, particularly in view of understanding the
recent claims of the detections of a variation of the fine structure constant
and of the electron to proton mass ratio in quasar absorption spectra. The
theoretical models leading to the prediction of such variation are also
reviewed, including Kaluza-Klein theories, string theories and other
alternative theories and cosmological implications of these results are
discussed. The links with the tests of general relativity are emphasized.Comment: 56 pages, l7 figures, submitted to Rev. Mod. Phy
Stochastic motion of test particle implies that G varies with time
The aim of this letter is to propose a new description to the time varying
gravitational constant problem, which naturally implements the Dirac's large
numbers hypothesis in a new proposed holographic scenario for the origin of
gravity as an entropic force. We survey the effect of the Stochastic motion of
the test particle in Verlinde's scenario for gravity\cite{Verlinde}. Firstly we
show that we must get the equipartition values for which
leads to the usual Newtonian gravitational constant. Secondly,the stochastic
(Brownian) essence of the motion of the test particle, modifies the Newton's
2'nd law. The direct result is that the Newtonian constant has been time
dependence in resemblance as \cite{Running}.Comment: Accepted in International Journal of Theoretical Physic
Repurposing anthelmintic agents to eradicate resistant leukemia
Despite rapid progress in genomic profiling in acute lymphoblastic leukemia (ALL), identification of actionable targets and prediction of response to drugs remains challenging. To identify specific vulnerabilities in ALL, we performed a drug screen using primary human ALL samples cultured in a model of the bone marrow microenvironment combined with high content image analysis. Among the 2487 FDA-approved compounds tested, anthelmintic agents of the class of macrocyclic lactones exhibited potent anti-leukemia activity, similar to the already known anti-leukemia agents currently used in induction chemotherapy. Ex vivo validation in 55 primary ALL samples of both precursor B cell and T-ALL including refractory relapse cases confirmed strong anti-leukemia activity with IC50 values in the low micromolar range. Anthelmintic agents increased intracellular chloride levels in primary leukemia cells, inducing mitochondrial outer membrane depolarization and cell death. Supporting the notion that simultaneously targeting cell death machineries at different angles may enhance the cell death response, combination of anthelmintic agents with the BCL-2 antagonist navitoclax or with the chemotherapeutic agent dexamethasone showed synergistic activity in primary ALL. These data reveal anti-leukemia activity of anthelmintic agents and support exploiting drug repurposing strategies to identify so far unrecognized anti-cancer agents with potential to eradicate even refractory leukemia
On the Possibility of Measuring the Gravitomagnetic Clock Effect in an Earth Space-Based Experiment
In this paper the effect of the post-Newtonian gravitomagnetic force on the
mean longitudes of a pair of counter-rotating Earth artificial satellites
following almost identical circular equatorial orbits is investigated. The
possibility of measuring it is examined. The observable is the difference of
the times required to in passing from 0 to 2 for both senses of
motion. Such gravitomagnetic time shift, which is independent of the orbital
parameters of the satellites, amounts to 5 s for Earth; it is
cumulative and should be measured after a sufficiently high number of
revolutions. The major limiting factors are the unavoidable imperfect
cancellation of the Keplerian periods, which yields a constraint of 10
cm in knowing the difference between the semimajor axes of the satellites,
and the difference of the inclinations of the orbital planes which, for
, should be less than . A pair of spacecrafts
endowed with a sophisticated intersatellite tracking apparatus and drag-free
control down to 10 cm s Hz level might allow to meet
the stringent requirements posed by such a mission.Comment: LaTex2e, 22 pages, no tables, 1 figure, 38 references. Final version
accepted for publication in Classical and Quantum Gravit
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