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1.
Phys Rev Lett ; 131(1): 015101, 2023 Jul 07.
Artículo en Inglés | MEDLINE | ID: mdl-37478421

RESUMEN

We describe the direct measurement of the expulsion of a magnetic field from a plasma driven by heat flow. Using a laser to heat a column of gas within an applied magnetic field, we isolate Nernst advection and show how it changes the field over a nanosecond timescale. Reconstruction of the magnetic field map from proton radiographs demonstrates that the field is advected by heat flow in advance of the plasma expansion with a velocity v_{N}=(6±2)×10^{5} m/s. Kinetic and extended magnetohydrodynamic simulations agree well in this regime due to the buildup of a magnetic transport barrier.

2.
Phys Rev Lett ; 130(6): 061002, 2023 Feb 10.
Artículo en Inglés | MEDLINE | ID: mdl-36827578

RESUMEN

Linelike features in TeV γ rays constitute a "smoking gun" for TeV-scale particle dark matter and new physics. Probing the Galactic Center region with ground-based Cherenkov telescopes enables the search for TeV spectral features in immediate association with a dense dark matter reservoir at a sensitivity out of reach for satellite γ-ray detectors, and direct detection and collider experiments. We report on 223 hours of observations of the Galactic Center region with the MAGIC stereoscopic telescope system reaching γ-ray energies up to 100 TeV. We improved the sensitivity to spectral lines at high energies using large-zenith-angle observations and a novel background modeling method within a maximum-likelihood analysis in the energy domain. No linelike spectral feature is found in our analysis. Therefore, we constrain the cross section for dark matter annihilation into two photons to ⟨σv⟩≲5×10^{-28} cm^{3} s^{-1} at 1 TeV and ⟨σv⟩≲1×10^{-25} cm^{3} s^{-1} at 100 TeV, achieving the best limits to date for a dark matter mass above 20 TeV and a cuspy dark matter profile at the Galactic Center. Finally, we use the derived limits for both cuspy and cored dark matter profiles to constrain supersymmetric wino models.

3.
Phys Rev Lett ; 129(19): 195001, 2022 Nov 04.
Artículo en Inglés | MEDLINE | ID: mdl-36399760

RESUMEN

Shock ignition enables high gain at low implosion velocity, reducing ablative Rayleigh-Taylor instability growth, which can degrade conventional direct drive. With this method, driving a strong shock requires high laser power and intensity, resulting in inefficiencies in the drive and the generation of hot electrons that can preheat the fuel. A new "shock-augmented ignition" pulse shape is described that, by preconditioning the ablation plasma before launching a strong shock, enables the shock ignition of thermonuclear fuel, but importantly, with substantially reduced laser power and intensity requirements. The reduced intensity requirement with respect to shock ignition limits laser-plasma instabilities, such as stimulated Raman and Brillouin scatter, reducing the risk of hot-electron preheat and restoring the laser coupling advantages of conventional direct drive. Simulations indicate that, due to the reduced power requirements, high gain (∼100) ignition of large-scale direct drive implosions (outer radius ∼1750 µm, deuterium-tritium ice thickness ∼165 µm) may be possible within the power and energy limits of existing facilities such as the National Ignition Facility. Moreover, this concept extends to indirect drive implosions, which exhibit substantial yield increases at reduced implosion velocity. Shock-augmented ignition expands the viable design space of laser inertial fusion.

4.
Phys Rev Lett ; 127(6): 065001, 2021 Aug 06.
Artículo en Inglés | MEDLINE | ID: mdl-34420313

RESUMEN

We use a subignition scale laser, the 30 kJ Omega, and a novel shallow-cone target to study laser-plasma interactions at the ablation-plasma density scale lengths and laser intensities anticipated for direct drive shock-ignition implosions at National Ignition Facility scale. Our results show that, under these conditions, the dominant instability is convective stimulated Raman scatter with experimental evidence of two plasmon decay (TPD) only when the density scale length is reduced. Particle-in-cell simulations indicate this is due to TPD being shifted to lower densities, removing the experimental back-scatter signature and reducing the hot-electron temperature. The experimental laser energy-coupling to hot electrons was found to be 1%-2.5%, with electron temperatures between 35 and 45 keV. Radiation-hydrodynamics simulations employing these hot-electron characteristics indicate that they should not preheat the fuel in MJ-scale shock ignition experiments.

5.
Opt Express ; 29(8): 12240-12251, 2021 Apr 12.
Artículo en Inglés | MEDLINE | ID: mdl-33984988

RESUMEN

In a recent experimental campaign, we used laser-accelerated relativistic hot electrons to ensure heating of thin titanium wire targets up to a warm dense matter (WDM) state [EPL114, 45002 (2016)10.1209/0295-5075/114/45002]. The WDM temperature profiles along several hundred microns of the wire were inferred by using spatially resolved X-ray emission spectroscopy looking at the Ti Kα characteristic lines. A maximum temperature of ∼30 eV was reached. Our study extends this work by discussing the influence of the laser parameters on temperature profiles and the optimisation of WDM wire-based generation. The depth of wire heating may reach several hundreds of microns and it is proven to be strictly dependent on the laser intensity. At the same time, it is quantitatively demonstrated that the maximum WDM temperature doesn't appear to be sensitive to the laser intensity and mainly depends on the deposited laser energy considering ranges of 6×1018-6×1020 W/cm2 and 50-200 J.

6.
Phys Rev Lett ; 125(2): 021301, 2020 Jul 10.
Artículo en Inglés | MEDLINE | ID: mdl-32701326

RESUMEN

On January 14, 2019, the Major Atmospheric Gamma Imaging Cherenkov telescopes detected GRB 190114C above 0.2 TeV, recording the most energetic photons ever observed from a gamma-ray burst. We use this unique observation to probe an energy dependence of the speed of light in vacuo for photons as predicted by several quantum gravity models. Based on a set of assumptions on the possible intrinsic spectral and temporal evolution, we obtain competitive lower limits on the quadratic leading order of speed of light modification.

7.
Sci Rep ; 10(1): 8100, 2020 May 12.
Artículo en Inglés | MEDLINE | ID: mdl-32393805

RESUMEN

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

8.
Sci Rep ; 9(1): 18805, 2019 Dec 11.
Artículo en Inglés | MEDLINE | ID: mdl-31827132

RESUMEN

X-ray phase contrast imaging (XPCI) is more sensitive to density variations than X-ray absorption radiography, which is a crucial advantage when imaging weakly-absorbing, low-Z materials, or steep density gradients in matter under extreme conditions. Here, we describe the application of a polychromatic X-ray laser-plasma source (duration ~0.5 ps, photon energy >1 keV) to the study of a laser-driven shock travelling in plastic material. The XPCI technique allows for a clear identification of the shock front as well as of small-scale features present during the interaction. Quantitative analysis of the compressed object is achieved using a density map reconstructed from the experimental data.

9.
Rev. Fac. Odontol. (B.Aires) ; 33(74): 40-43, ene.-jun. 2018. ilus
Artículo en Español | LILACS | ID: biblio-969729

RESUMEN

El carcinoma mucoepidermoide intraóseo (CMEI) es una neoplasia maligna de los maxilares muy poco frecuente. Es idéntica en casi todos sus aspectos al carcinoma mucoepidermoide de glándulas salivales pero, a diferencia de éste, asienta completamente en tejido óseo. Presentamos un caso clínico de CMEI en una paciente de 66 años de edad. Se describen las características clínicas, radiográficas e histopatológicas, tratamiento y evolución. Además se llevó a cabo una revisión de la literatura en PubMed acerca de CMEI de mandíbula publicada en los últimos diez años (AU)


Intraosseous mucoepidermoid carcinoma (IMCC) is an infrequent malignant tumor of the jaws that is identical in most respects to the mucoepidermoid carcinoma of salivary glands but arises entirely within the bone. We report a case of IMEC in a 66-year old woman. We describe the clinical, radiographic and histopathologic aspects as well as the treatment and follow-up. Additionally, we performed a literature review on PubMed regarding IMEC of the mandible published in last ten years (AU)


Asunto(s)
Humanos , Femenino , Anciano , Neoplasias Mandibulares , Carcinoma Mucoepidermoide , Procedimientos Quirúrgicos Orales , Argentina , Colgajos Quirúrgicos , Estudios de Seguimiento , Servicio Odontológico Hospitalario
10.
Nature ; 551(7678): 67-70, 2017 11 02.
Artículo en Inglés | MEDLINE | ID: mdl-29094694

RESUMEN

The merger of two neutron stars is predicted to give rise to three major detectable phenomena: a short burst of γ-rays, a gravitational-wave signal, and a transient optical-near-infrared source powered by the synthesis of large amounts of very heavy elements via rapid neutron capture (the r-process). Such transients, named 'macronovae' or 'kilonovae', are believed to be centres of production of rare elements such as gold and platinum. The most compelling evidence so far for a kilonova was a very faint near-infrared rebrightening in the afterglow of a short γ-ray burst at redshift z = 0.356, although findings indicating bluer events have been reported. Here we report the spectral identification and describe the physical properties of a bright kilonova associated with the gravitational-wave source GW170817 and γ-ray burst GRB 170817A associated with a galaxy at a distance of 40 megaparsecs from Earth. Using a series of spectra from ground-based observatories covering the wavelength range from the ultraviolet to the near-infrared, we find that the kilonova is characterized by rapidly expanding ejecta with spectral features similar to those predicted by current models. The ejecta is optically thick early on, with a velocity of about 0.2 times light speed, and reaches a radius of about 50 astronomical units in only 1.5 days. As the ejecta expands, broad absorption-like lines appear on the spectral continuum, indicating atomic species produced by nucleosynthesis that occurs in the post-merger fast-moving dynamical ejecta and in two slower (0.05 times light speed) wind regions. Comparison with spectral models suggests that the merger ejected 0.03 to 0.05 solar masses of material, including high-opacity lanthanides.

11.
Phys Rev E ; 95(6-1): 063205, 2017 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-28709273

RESUMEN

Multimegabar laser-driven shock waves are unique tools for studying matter under extreme conditions. Accurate characterization of shocked matter is for instance necessary for measurements of equation of state data or opacities. This paper reports experiments performed at the LULI facility on the diagnosis of shock waves, using x-ray-absorption radiography. Radiographs are analyzed using standard Abel inversion. In addition, synthetic radiographs, which also take into account the finite size of the x-ray source, are generated using density maps produced by hydrodynamic simulations. Reported data refer to both plane cylindrical targets and hemispherical targets. Evolution and deformation of the shock front could be followed using hydrodynamic simulations.

12.
Nucleus ; 7(2): 103-11, 2016 04 25.
Artículo en Inglés | MEDLINE | ID: mdl-26930442

RESUMEN

Nuclear lamins are the main components of the nuclear lamina at the nuclear periphery, providing mechanical support to the nucleus. However, recent findings suggest that lamins also reside in the nuclear interior, as a distinct and dynamic pool with critical roles in transcriptional regulation. In our work we found a functional and evolutionary conserved crosstalk between Lamin A/C and the Polycomb group (PcG) of proteins, this being required for the maintenance of the PcG repressive functions. Indeed, Lamin A/C knock-down causes PcG foci dispersion and defects in PcG-mediated higher order structures, thereby leading to impaired PcG mediated transcriptional repression. By using ad-hoc algorithms for image analysis and PLA approaches we hereby show that PcG proteins are preferentially located in the nuclear interior where they interact with nucleoplasmic Lamin A/C. Taken together, our findings suggest that nuclear components, such as Lamin A/C, functionally interact with epigenetic factors to ensure the correct transcriptional program maintenance.


Asunto(s)
Evolución Molecular , Lamina Tipo A/metabolismo , Proteínas del Grupo Polycomb/metabolismo , Transporte Activo de Núcleo Celular , Diferenciación Celular , Núcleo Celular/metabolismo , Células HEK293 , Humanos , Mioblastos/citología , Unión Proteica
13.
Rev Sci Instrum ; 87(1): 013504, 2016 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-26827318

RESUMEN

In this paper, a preliminary shadowgraph-based analysis of dust particles re-suspension due to loss of vacuum accident (LOVA) in ITER-like nuclear fusion reactors has been presented. Dust particles are produced through different mechanisms in nuclear fusion devices, one of the main issues is that dust particles are capable of being re-suspended in case of events such as LOVA. Shadowgraph is based on an expanded collimated beam of light emitted by a laser or a lamp that emits light transversely compared to the flow field direction. In the STARDUST facility, the dust moves in the flow, and it causes variations of refractive index that can be detected by using a CCD camera. The STARDUST fast camera setup allows to detect and to track dust particles moving in the vessel and then to obtain information about the velocity field of dust mobilized. In particular, the acquired images are processed such that per each frame the moving dust particles are detected by applying a background subtraction technique based on the mixture of Gaussian algorithm. The obtained foreground masks are eventually filtered with morphological operations. Finally, a multi-object tracking algorithm is used to track the detected particles along the experiment. For each particle, a Kalman filter-based tracker is applied; the particles dynamic is described by taking into account position, velocity, and acceleration as state variable. The results demonstrate that it is possible to obtain dust particles' velocity field during LOVA by automatically processing the data obtained with the shadowgraph approach.

14.
Artículo en Inglés | MEDLINE | ID: mdl-26565161

RESUMEN

We present a formulation of the model of laser-plasma interaction (LPI) at hydrodynamical scales that couples the plasma dynamics with linear and nonlinear LPI processes, including the creation and propagation of high-energy electrons excited by parametric instabilities and collective effects. This formulation accounts for laser beam refraction and diffraction, energy absorption due to collisional and resonant processes, and hot electron generation due to the stimulated Raman scattering, two-plasmon decay, and resonant absorption processes. Hot electron (HE) transport and absorption are described within the multigroup angular scattering approximation, adapted for transversally Gaussian electron beams. This multiscale inline LPI-HE model is used to interpret several shock ignition experiments, highlighting the importance of target preheating by HEs and the shortcomings of standard geometrical optics when modeling the propagation and absorption of intense laser pulses. It is found that HEs from parametric instabilities significantly increase the shock pressure and velocity in the target, while decreasing its strength and the overall ablation pressure.

15.
Rev Sci Instrum ; 86(7): 073507, 2015 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-26233383

RESUMEN

In an experiment at the laser facility ECLIPSE of the CELIA laboratory, University of Bordeaux, we measure the reflectivity of spherically bent crystals that are commonly used to investigate the propagation of fast electrons through the Kα radiation they generate in matter. The experimental reflectivity compares well with predictions from a ray-tracing code that takes into account the specific geometry, although the crystals seem to suffer from aging problems.

16.
Science ; 346(6213): 1080-4, 2014 Nov 28.
Artículo en Inglés | MEDLINE | ID: mdl-25378461

RESUMEN

Supermassive black holes with masses of millions to billions of solar masses are commonly found in the centers of galaxies. Astronomers seek to image jet formation using radio interferometry but still suffer from insufficient angular resolution. An alternative method to resolve small structures is to measure the time variability of their emission. Here we report on gamma-ray observations of the radio galaxy IC 310 obtained with the MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes, revealing variability with doubling time scales faster than 4.8 min. Causality constrains the size of the emission region to be smaller than 20% of the gravitational radius of its central black hole. We suggest that the emission is associated with pulsar-like particle acceleration by the electric field across a magnetospheric gap at the base of the radio jet.

17.
Nature ; 480(7375): 69-71, 2011 Nov 30.
Artículo en Inglés | MEDLINE | ID: mdl-22129725

RESUMEN

The tidal disruption of a solar-mass star around a supermassive black hole has been extensively studied analytically and numerically. In these events, the star develops into an elongated banana-shaped structure. After completing an eccentric orbit, the bound debris falls into the black hole, forming an accretion disk and emitting radiation. The same process may occur on planetary scales if a minor body passes too close to its star. In the Solar System, comets fall directly into our Sun or onto planets. If the star is a compact object, the minor body can become tidally disrupted. Indeed, one of the first mechanisms invoked to produce strong gamma-ray emission involved accretion of comets onto neutron stars in our Galaxy. Here we report that the peculiarities of the 'Christmas' gamma-ray burst (GRB 101225A) can be explained by a tidal disruption event of a minor body around an isolated Galactic neutron star. This would indicate either that minor bodies can be captured by compact stellar remnants more frequently than occurs in the Solar System or that minor-body formation is relatively easy around millisecond radio pulsars. A peculiar supernova associated with a gamma-ray burst provides an alternative explanation.

18.
Nature ; 476(7361): 421-4, 2011 Aug 24.
Artículo en Inglés | MEDLINE | ID: mdl-21866154

RESUMEN

Supermassive black holes have powerful gravitational fields with strong gradients that can destroy stars that get too close, producing a bright flare in ultraviolet and X-ray spectral regions from stellar debris that forms an accretion disk around the black hole. The aftermath of this process may have been seen several times over the past two decades in the form of sparsely sampled, slowly fading emission from distant galaxies, but the onset of the stellar disruption event has not hitherto been observed. Here we report observations of a bright X-ray flare from the extragalactic transient Swift J164449.3+573451. This source increased in brightness in the X-ray band by a factor of at least 10,000 since 1990 and by a factor of at least 100 since early 2010. We conclude that we have captured the onset of relativistic jet activity from a supermassive black hole. A companion paper comes to similar conclusions on the basis of radio observations. This event is probably due to the tidal disruption of a star falling into a supermassive black hole, but the detailed behaviour differs from current theoretical models of such events.

19.
Clin Exp Immunol ; 165(3): 338-51, 2011 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-21726211

RESUMEN

Leishmaniasis is caused by infection with the protozoan parasite, Leishmania, that parasitizes human cells, and the cellular immune response is essential for controlling infection. In order to measure the host T cell response to Leishmania infection, we have measured the expansion, activation state and functional potential of specific T cells as identified by their T cell receptor Vß region expression. In a group of cutaneous leishmaniasis (CL) patients, we evaluated these characteristics in nine different T cell subpopulations as identified by their Vß region expression, before and after specific Leishmania antigen stimulation. Our results show: (1) an increase in CD4(+) T cells expressing Vß 5·2 and Vß 24 in CL compared to controls; (2) a Leishmania antigen-induced increase in CD4(+) T cells expressing Vß 5·2, 11, 12 and 17; (3) a profile of previous activation of CD4(+) Vß 5·2-, 11- and 24-positive T cells, with higher expression of CD45RO, HLA-DR, interferon-γ, tumour necrosis factor-α and interleukin-10 compared to other Vß-expressing subpopulations; (4) a positive correlation between higher frequencies of CD4(+) Vß5·2(+) T cells and larger lesions; and (5) biased homing of CD4(+) T cells expressing Vß 5·2 to the lesion site. Given that CL disease involves a level of pathology (ulcerated lesions) and is often followed by long-lived protection and cure, the identification of specific subpopulations active in this form of disease could allow for the discovery of immunodominant Leishmania antigens important for triggering efficient host responses against the parasite, or identify cell populations most involved in pathology.


Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/metabolismo , Leishmania braziliensis/inmunología , Leishmaniasis Cutánea/inmunología , Leishmaniasis Cutánea/patología , Receptores de Antígenos de Linfocitos T alfa-beta/metabolismo , Subgrupos de Linfocitos T/inmunología , Adolescente , Adulto , Antígenos de Protozoos/inmunología , Recuento de Linfocito CD4 , Linfocitos T CD4-Positivos/patología , Movimiento Celular/inmunología , Citocinas/metabolismo , Femenino , Antígenos HLA-DR/metabolismo , Humanos , Interferón gamma/metabolismo , Interleucina-10/metabolismo , Leishmania braziliensis/aislamiento & purificación , Leishmaniasis Cutánea/diagnóstico , Antígenos Comunes de Leucocito/metabolismo , Leucocitos Mononucleares/inmunología , Activación de Linfocitos/inmunología , Masculino , Persona de Mediana Edad , Piel/inmunología , Piel/patología , Subgrupos de Linfocitos T/metabolismo , Subgrupos de Linfocitos T/patología , Factor de Necrosis Tumoral alfa/metabolismo , Adulto Joven
20.
J. venom. anim. toxins incl. trop. dis ; 16(3): 480-492, 2010. ilus, graf, tab
Artículo en Inglés | LILACS | ID: lil-557177

RESUMEN

The basic knowledge on neoplasms is increasing quickly; however, few advances have been achieved in clinical therapy against tumors. For this reason, the development of alternative drugs is relevant in the attempt to improve prognosis and to increase patients' survival. Snake venoms are natural sources of bioactive substances with therapeutic potential. The objective of this work was to identify and characterize the antitumoral effect of Crotalus durissus terrificus venom (CV) and its polypeptide, crotoxin, on benign and malignant tumors, respectively, pituitary adenoma and glioblastoma. The results demonstrated that CV possess a powerful antitumoral effect on benign (pituitary adenoma) and malignant (glioblastoma multiforme) tumors with IC50 values of 0.96 ± 0.11 µg/mL and 2.15 ± 0.2 µg/mL, respectively. This antitumoral effect is cell-cycle-specific and dependent on extracellular calcium, an important factor for crotoxin phospholipase A2 activity. The CV antitumoral effect can be ascribed, at least partially, to the polypeptide crotoxin that also induced brain tumor cell death. In spite of the known CV nephrotoxicity and neurotoxicity, acute treatment with its antitumoral dose established in vitro was not found to be toxic to the analyzed animals. These results indicate the biotechnological potential of CV as a source of pharmaceutical templates for cancer therapy.


Asunto(s)
Animales , Masculino , Femenino , Ratas , Adenoma , Crotalus cascavella , Neoplasias/terapia , Venenos de Crotálidos/uso terapéutico , Crotoxina
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