1,491 research outputs found
Jamming phase diagram for frictional particles
The non-equilibrium transition from a fluid-like state to a disordered
solid-like state, known as the jamming transition, occurs in a wide variety of
physical systems, such as colloidal suspensions and molecular fluids, when the
temperature is lowered or the density increased. Shear stress, as temperature,
favors the fluid-like state, and must be also considered to define the system
'jamming phase diagram' [1-4]. Frictionless athermal systems [1], for instance,
can be described by the zero temperature plane of the jamming diagram in the
temperature, density, stress space. Here we consider the jamming of athermal
frictional systems [8-13] such as granular materials, which are important to a
number of applications from geophysics to industry. At constant volume and
applied shear stress[1, 2], we show that while in absence of friction a system
is either fluid-like or jammed, in the presence of friction a new region in the
density shear-stress plane appears, where new dynamical regimes are found. In
this region a system may slip, or even flow with a steady velocity for a long
time in response to an applied stress, but then eventually jams. Jamming in
non-thermal frictional systems is described here by a phase diagram in the
density, shear-stress and friction space
Praziquantel: its use in control of schistosomiasis in sub-Saharan Africa and current research needs
Treatment with praziquantel (PZQ) has become virtually the sole basis of schistosomiasis control in sub-Saharan Africa and elsewhere, and the drug is reviewed here in the context of the increasing rate that it is being used for this purpose. Attention is drawn to our relative lack of knowledge about the mechanisms of action of PZQ at the molecular level, the need for more work to be done on schistosome isolates that have been collected recently from endemic areas rather than those maintained in laboratory conditions for long periods, and our reliance for experimental work mainly on Schistosoma mansoni, little work having been done on S. haematobium. There is no evidence that resistance to PZQ has been induced in African schistosomes as a result of its large-scale use on that continent to date, but there is also no assurance that PZQ and/or schistosomes are in any way unique and that resistant organisms will not be selected as a result of widespread drug usage. The failure of PZQ to produce complete cures in populations given a routine treatment should therefore solicit considerable concern. With few alternatives to PZQ currently available and/or on the horizon, methods to monitor drug-susceptibility in African schistosomes need to be devised and used to help ensure that this drug remains effective for as long a time as possibl
Wilson Fermions with Four Fermion Interactions
Contribution to proceedings of the 33rd International Symposium on Lattice Field Theory (Lattice 2015), 14-18 July 2015, Kobe, JapanWe present a lattice study of a four fermion theory, known as Nambu Jona-Lasinio (NJL) theory, via Wilson fermions. Four fermion interactions naturally occur in several extensions of the Standard Model as a low energy parameterisation of a more fundamental theory. In models of dynamical electroweak symmetry breaking these operators, at an effective level, are used to endow the Standard Model fermions with masses. Furthermore these operators, when sufficiently strong, can drastically modify the fundamental composite dynamics by, for example, turning a strongly coupled infrared conformal theory into a (near) conformal one with desirable features for model building. As first step, we study spontaneous chiral symmetry breaking for the lattice version of the NJL model
Template Composite Dark Matter : SU(2) gauge theory with 2 fundamental flavours
Contribution to proceedings of the 33rd International Symposium on Lattice Field Theory (Lattice 2015), 14-18 July 2015, Kobe, JapanWe present a non perturbative study of SU(2) gauge theory with two fundamental Dirac flavours. We discuss how the model can be used as a template for composite Dark Matter (DM). We estimate one particular interaction of the DM candidate with the Standard Model : the interaction through photon exchange computing the electric polarizability of the DM candidate. Finally, we briefly discuss the viability of the model given the present experimental constraints
Correlations and Omori law in Spamming
The most costly and annoying characteristic of the e-mail communication
system is the large number of unsolicited commercial e-mails, known as spams,
that are continuously received. Via the investigation of the statistical
properties of the spam delivering intertimes, we show that spams delivered to a
given recipient are time correlated: if the intertime between two consecutive
spams is small (large), then the next spam will most probably arrive after a
small (large) intertime. Spam temporal correlations are reproduced by a
numerical model based on the random superposition of spam sequences, each one
described by the Omori law. This and other experimental findings suggest that
statistical approaches may be used to infer how spammers operate.Comment: Europhysics Letters, to appea
Radiosurgery for trigeminal neuralgia using a linear accelerator with BrainLab system: report on initial experience in Lausanne, Switzerland
BACKGROUND/AIMS: Radiosurgery is an effective treatment for trigeminal neuralgia (TN) with minimal complications. Most experience is based on gamma knife radiosurgery (GKRS) and to a lesser extent on linear accelerators. METHODS: We report our initial experience in 17 patients with TN treated by an adapted linear accelerator using the BrainLab system. The trigeminal root entry zone immediately adjacent to the pons (target volume: 0.01-0.09 cm3, mean: 0.02 cm3) was targeted by use of a multileaf collimator to deliver 40-45 Gy to the 80% isodose (dose max 50-56 Gy). Median follow-up was 12 months (range: 1-60). RESULTS: All patients reported some initial improvement in level of pain after treatment (mean time: 1 month). Initial pain responses were as follows: 6 patients (35%) had complete pain relief and required no medication, 6 (35%) had occasional pain but were off medication, and 5 (30%) experienced partial relief of pain but still required medication, usually in lower doses. Five patients (29%) who experienced initial pain relief had recurrences ranging from 4-13 months after procedure. There were no major or minor complications of radiosurgery except one case of mild facial itching. CONCLUSION: Stereotactic radiosurgery using a linear accelerator appears to be effective and can be a favourable alternative to other procedures, including GKRS. The procedure is very safe and side effects are rare and minor. However, a randomised trial with a longer follow-up comparing radiosurgery to other surgical procedures is needed to assess the long term effectiveness of this treatmen
Biophysical and biochemical characterization of a liposarcoma-derived recombinant MnSOD protein acting as an anticancer agent
A recombinant MnSOD (rMnSOD) synthesized by specific cDNA clones derived from a liposarcoma cell line was shown to have the same sequence as the wild-type MnSOD expressed in the human myeloid leukaemia cell line U937, except for the presence of the leader peptide at the N-terminus. These results were fully confirmed by the molecular mass of rMnSOD as evaluated by ES/MS analysis (26662.7 Da) and the nucleotide sequence of the MnSOD cDNA. The role of the leader peptide in rMnSOD was investigated using a fluorescent and/or 68Gallium-labelled synthetic peptide. The labelled peptide permeated MCF-7 cells and uptake could be inhibited in the presence of an excess of oestrogen. In vivo it was taken up by the tumour, suggesting that the molecule can be used for both therapy and diagnosis. The in vitro and in vivo pharmacology tests confirmed that rMnSOD is only oncotoxic for tumour cells expressing oestrogen receptors. Pharmacokinetic studies in animals performed with 125I- and 131I-labelled proteins confirmed that, when administered systemically, rMnSOD selectively reached the tumour, where its presence was unambiguously demonstrated by scintigraphic and PET scans. PCR analysis revealed that Bax gene expression was increased and the Bcl2 gene was down regulated in MCF7 cells treated with rMnSOD, which suggests that the protein induces a pro-apoptotic mechanism
Glassy states in lattice models with many coexisting crystalline phases
We study the emergence of glassy states after a sudden cooling in lattice
models with short range interactions and without any a priori quenched
disorder. The glassy state emerges whenever the equilibrium model possesses a
sufficient number of coexisting crystalline phases at low temperatures,
provided the thermodynamic limit be taken before the infinite time limit. This
result is obtained through simulations of the time relaxation of the standard
Potts model and some exclusion models equipped with a local stochastic dynamics
on a square lattice.Comment: 12 pages, 4 figure
A hard-sphere model on generalized Bethe lattices: Statics
We analyze the phase diagram of a model of hard spheres of chemical radius
one, which is defined over a generalized Bethe lattice containing short loops.
We find a liquid, two different crystalline, a glassy and an unusual
crystalline glassy phase. Special attention is also paid to the close-packing
limit in the glassy phase. All analytical results are cross-checked by
numerical Monte-Carlo simulations.Comment: 24 pages, revised versio
Agrammatic but numerate
A central question in cognitive neuroscience concerns the extent to
which language enables other higher cognitive functions. In the
case of mathematics, the resources of the language faculty, both
lexical and syntactic, have been claimed to be important for exact
calculation, and some functional brain imaging studies have shown
that calculation is associated with activation of a network of
left-hemisphere language regions, such as the angular gyrus and
the banks of the intraparietal sulcus. We investigate the integrity
of mathematical calculations in three men with large left-hemisphere
perisylvian lesions. Despite severe grammatical impairment
and some difficulty in processing phonological and orthographic
number words, all basic computational procedures were intact
across patients. All three patients solved mathematical problems
involving recursiveness and structure-dependent operations (for
example, in generating solutions to bracket equations). To our
knowledge, these results demonstrate for the first time the remarkable
independence of mathematical calculations from language
grammar in the mature cognitive system
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