Quintessence from Shape Moduli

We show that shape moduli in sub-millimeter extra dimensional scenarios, addressing the gauge hierarchy problem, can dominate the energy density of the universe today. In our scenario, the volume of the extra dimensions is stabilized at a sufficiently high scale to avoid conflicts with nucleosynthesis and solar-system precision gravity experiments, while the shape moduli remain light but couple extremely weakly to brane-localized matter and easily avoid these bounds. Nonlocal effects in the bulk of the extra dimension generate a potential for the shape moduli. The potential has the right form and order of magnitude to account for the present day cosmic acceleration, in a way analogous to models of quintessence as a pseudo Nambu-Goldstone boson.Comment: 8 pages, 1 figur

Dark Matter signals from Draco and Willman 1: Prospects for MAGIC II and CTA

The next generation of ground-based Imaging Air Cherenkov Telescopes (IACTs) will play an important role in indirect dark matter searches. In this article, we consider two particularly promising candidate sources for dark matter annihilation signals, the nearby dwarf galaxies Draco and Willman 1, and study the prospects of detecting such a signal for the soon-operating MAGIC II telescope system as well as for the planned installation of CTA, taking special care of describing the experimental features that affect the detectional prospects. For the first time in such a study, we fully take into account the effect of internal bremsstrahlung, which has recently been shown to considerably enhance, in some cases, the gamma-ray flux at the high energies where Atmospheric Cherenkov Telescopes operate, thus leading to significantly harder annihilation spectra than traditionally considered. While the detection of the spectral features introduced by internal bremsstrahlung would constitute a smoking gun signature for dark matter annihilation, we find that for most models the overall flux still remains at a level that will be challenging to detect unless one adopts rather (though by no means overly) optimistic astrophysical assumptions about the distribution of dark matter in the dwarfs.Comment: 10 pages, 4 figures, minor changes, matches the published version (JCAP

Array tomography: Characterizing FAC-sorted populations of zebrafish immune cells by their 3D ultrastructure

For 3D reconstructions of whole immune cells from zebrafish, isolated from adult animals by FAC-sorting we employed array tomography on hundreds of serial sections deposited on silicon wafers. Image stacks were either recorded manually or automatically with the newly released ZEISS Atlas 5 Array Tomography platform on a Zeiss FEGSEM. To characterize different populations of immune cells, organelle inventories were created by segmenting individual cells. In addition, arrays were used for quantification of cell populations with respect to the various cell types they contained. The detection of immunological synapses in cocultures of cell populations from thymus or WKM with cancer cells helped to identify the cytotoxic nature of these cells. Our results demonstrate the practicality and benefit of AT for high-throughput ultrastructural imaging of substantial volumes. LAY DESCRIPTION: To look at immune cells from zebrafish we employed array tomography, a technique where arrays of serial sections deposited on solid substrates are used for imaging. Cell populations were isolated from the different organs of zebrafish involved in haematopoiesis, the production of blood cells. They were chemically fixed and centrifuged to concentrate them in a pellet that was then dehydrated and embedded in resin. Using a custom-built handling device it was possible to place hundreds of serial sections on silicon wafers as well ordered arrays. To image a whole cell at a resolution that would allow identifying all the organelles (i.e. compartments surrounded by membranes) inside the cell, stacks of usually 50–100 images were recorded in a scanning electron microscope (SEM). This recording was either done manually or automatically using the newly released Atlas Array Tomography platform on a ZEISS SEM. For the imaging of the sections a pixel size of about 5 nm was chosen, which defines membrane boundaries very well and allows segmentation of the membrane topology. After alignment of the images, cellular components were segmented to locate the individual organelles within the 3D reconstruction of the whole cell and also to create an inventory of organelles. Based on their morphologies we could identify specific cell types in the different hematopoietic organs. We could also quantify the proportion of each cell type in the whole population isolated from a given organ. Some of these specific cells from zebrafish were grown in a culture dish together with human cancer cells. By time-lapse light microscopy we observed that the fish cells attacked the cancer cells and killed them. From this we concluded that these cells must be similar to the cytotoxic cells from humans that play an important role in defence against spontaneously arising cancer cells in our bodies. They form special structures, called immunological synapses that we could also identify on our arrays and reconstruct in 3D. This is the first time the potential of zebrafish immune cells to form immunological synapses has been demonstrated. Our study is a good example for the practicality and benefit of array tomography in high-throughput ultrastructure imaging of substantial volumes, applicable to many areas of cell and developmental biology

Multi-wavelength interferometry of evolved stars using VLTI and VLBA

We report on our project of coordinated VLTI/VLBA observations of the atmospheres and circumstellar environments of evolved stars. We illustrate in general the potential of interferometric measurements to study stellar atmospheres and envelopes, and demonstrate in particular the advantages of a coordinated multi-wavelength approach including near/mid-infrared as well as radio interferometry. We have so far made use of VLTI observations of the near- and mid-infrared stellar sizes and of concurrent VLBA observations of the SiO maser emission. To date, this project includes studies of the Mira stars S Ori and RR Aql as well as of the supergiant AH Sco. These sources all show strong silicate emission features in their mid-infrared spectra. In addition, they each have relatively strong SiO maser emission. The results from our first epochs of S Ori measurements have recently been published and the main results are reviewed here. The S Ori maser ring is found to lie at a mean distance of about 2 stellar radii, a result that is virtually free of the usual uncertainty inherent in comparing observations of variable stars widely separated in time and stellar phase. We discuss the status of our more recent S Ori, RR Aql, and AH Sco observations, and present an outlook on the continuation of our project.Comment: 9 pages, to appear in the proceedings of the ESO workshop "The Power of Optical/IR Interferometry: Recent Scientific Results and 2nd Generation VLTI Instrumentation", ESO Astrophysics Symposi

Development and Validation of a Tokamak Skin Effect Transformer model

A control oriented, lumped parameter model for the tokamak transformer including the slow flux penetration in the plasma (skin effect transformer model) is presented. The model does not require detailed or explicit information about plasma profiles or geometry. Instead, this information is lumped in system variables, parameters and inputs. The model has an exact mathematical structure built from energy and flux conservation theorems, predicting the evolution and non linear interaction of the plasma current and internal inductance as functions of the primary coil currents, plasma resistance, non-inductive current drive and the loop voltage at a specific location inside the plasma (equilibrium loop voltage). Loop voltage profile in the plasma is substituted by a three-point discretization, and ordinary differential equations are used to predict the equilibrium loop voltage as function of the boundary and resistive loop voltages. This provides a model for equilibrium loop voltage evolution, which is reminiscent of the skin effect. The order and parameters of this differential equation are determined empirically using system identification techniques. Fast plasma current modulation experiments with Random Binary Signals (RBS) have been conducted in the TCV tokamak to generate the required data for the analysis. Plasma current was modulated in Ohmic conditions between 200kA and 300kA with 30ms rise time, several times faster than its time constant L/R\approx200ms. The model explains the most salient features of the plasma current transients without requiring detailed or explicit information about resistivity profiles. This proves that lumped parameter modeling approach can be used to predict the time evolution of bulk plasma properties such as plasma inductance or current with reasonable accuracy; at least in Ohmic conditions without external heating and current drive sources

Morfologia do estômago do cervo-do-pantanal (Blastocerus dichotomus, Illiger 1815)

Based on the lack of information regarding the morphology of marsh deer, this work aims to describe some morphological aspects of the gastric chamber in this species, collaborating with future investigations, mainly related to rational handling in this cervid. This work aimed to describe the morphology of the gastric chamber of the marsh deer, characterizing the external and internal macroscopical details and the microscopical architecture of these structures by light microscopy. Macroscopically, the marsh deer stomach is formed by the rumen, reticulum, omasum and abomasum similar to the domestic ruminants. Microscopically, rumen and abomasum are similar to the domestic ruminants. The reticulum and the omasum, however, present specific characteristics such as keratin on the top of the reticulum, small epithelial projections and omasum folds covered with discrete papillae.Em razão da falta de informações sobre a morfologia do cervo-do-pantanal, objetivou-se apresentar a morfologia das câmaras gástricas desse cervídeo. Macroscopicamente, o estômago do cervo-do-pantanal é formado pelo rúmen, retículo, omaso e abomaso, assemelhando-se aos ruminantes domésticos. Microscopicamente, o rúmen e o abomaso são semelhantes aos animais domésticos, já o retículo e o omaso apresentam características específicas, como acentuada queratinização no ápice das pequenas projeções epiteliais do retículo e pregas omasais revestidas por discretas papilas.Unesp - Faculdade de Ciências Agrárias e Veterinárias, Câmpus de Jaboticabal, SPUniversidade Estadual Paulista (Unesp) - Câmpus de Ilha Solteira, SPUnesp - Faculdade de Ciências Agrárias e Veterinárias, Câmpus de Jaboticabal, SPUniversidade Estadual Paulista (Unesp) - Câmpus de Ilha Solteira, S

Nucleon charge exchange on the deuteron: A critical review

The existing experimental data on the d(n,p)nn and d(p,n)pp cross sections in the forward direction are reviewed in terms of the Dean sum rule. It is shown that the measurement of the ratio of the charge exchange on the deuteron to that on the proton might, if taken together with other experimental data, allow a direct construction of the np -> np scattering amplitude in the backward direction with few ambiguities.Comment: 7 pages with 3 figure

Mode B ultrasonography and abdominal Doppler in crab-eating-foxes ( Cerdocyon thous )

Annually hundreds of crab-eating foxes (Cerdocyon thous) are referred to rehabilitation centers and zoos in Brazil. The ultrasonographic study of wildlife species is an important tool for a non-invasive and accurate anatomical description and provides important information for wildlife veterinary care. The aim of the present study was to determine the characteristics of the main abdominal organs as well as the vascular indexes of the abdominal aorta and renal arteries of crab-eating foxes (Cerdocyon thous) using mode B ultrasonography and Doppler ultrasonography, respectively. Ultrasonographic features of the main abdominal organs were described and slight differences were noticed between ultrasound imaging of abdominal organs of crab-eating foxes and other species. The bladder presented wall thickness of 12 +/- 0.01 mm, with three defined layers. Both, the right and left kidneys presented corticomedullary ratio of 1: 1 and similarly to the adrenals and the liver, they were homogeneous and hypoechoic compared to the spleen. The spleen was homogeneous and hyperechoic compared to the kidneys. The stomach presented 3 to 5 peristaltic movements per minute, wall thickness of 39 +/- 0.05 mm and lumen and mucosa with hyperechoic and hypoechoic features, respectively. Small and large intestines presented 2 to 3 peristaltic movements per minute, wall thickness of 34 +/- 0.03 mm and three defined layers with hyperechogenic (submucosa and serosa) and hypoechogenic (muscular) features. Ovaries of the female crab-eating fox were hypoechoic compared to the spleen and with heterogeneous parenchyma due to the presence of 2x2 mm ovarian follicles. Prostates of the six males were regular and with a well defined boundary, with a homogeneous and hyperechoic parenchyma compared to the spleen. Vascular indexes of the abdominal aorta (PSV: 25.60 +/- 0.32 cm/s; EDV: 6.96 +/- 1.68cm/s; PI: 1.15 +/- 0.07 e RI: 0.73 +/- 0.07) and right (PSV: 23.08 +/- 3.34cm/s; EDV: 9.33 +/- 2.36cm/s; PI: 1.01 +/- 0.65 e RI: 0.65 +/- 0.16) and left renal arteries (PSV: 23.74 +/- 3.94cm/s; EDV: 9.07 +/- 3.02cm/s; PI: 1.04 +/- 0.31 e RI: 0.64 +/- 0.10) were determined. Thus, conventional and Doppler ultrasonographic imaging provides basic information that can be used as reference for the species as well for other wild canids and it is a precise and non-invasive method that can be safely used to evaluate and diagnose abdominal injuries in these patients.O objetivo desse estudo foi descrever os achados ultrassonográficos convencionais dos principais órgãos abdominais e determinar com a utilização da ultrassonografia Doppler os índices vasculares da aorta abdominal e artérias renais em cachorros-do-mato (Cerdocyon thous). Foram avaliados nove cachorros-do-mato (Cerdocyon thous). Por meio da ultrassonografia convencional do abdômen dos animais, estudaram-se os achados ultrassonográficos normais e a biometria dos principais órgãos dessa cavidade como fígado, baço, bexiga, estômago, intestinos, adrenais, rins, ovários, próstata e tecido linfoide dos animais, obtendo-se resultados importantes para a caracterização sonográfica desses tecidos. A bexiga apresentou espessura da parede de 12 ± 0,01 mm, com três camadas bem definidas. O rim direito e esquerdo apresentaram relação corticomedular de 1:1 e com ecogenicidade semelhante as adrenais e fígado, homogêneas e hipoecoica em comparação ao baço. O baço apresentou-se homogêneo e hiperecoica em relação aos rins. O estômago apresentou de 3 a 5 movimentos peristálticos por minuto, espessura da parede de 39 ± 0,05mm e lúmen e mucosa com características hiperecoicas e hipoecoicas, respectivamente. O intestino delgado e grosso apresentaram de 2 a 3 movimentos peristálticos por minuto, espessura da parede de 34 ± 0,03mm e três camadas definidas, hiperecogênica (submucosa e serosa) e hipoecogênicas (musculares). Os ovários de uma fêmea se apresentaram hipoecoica, em comparação com o baço, e heterogêneos, devido à presença de folículos ovarianos de 2x2mm de diâmetro. As prostatas de seis machos eram regulares e com contornos definidos, parênquima homogêneo e hiperecoico em relação ao baço. Ao exame Doppler foram determinados os índices vasculares da aorta abdominal (PSV: 25,60±0,32cm/s; EDV: 6,96±1,68cm/s; PI: 1,15±0,07 e RI: 0,73±0,07) e das artérias renais direitas (PSV: 23,08±3,34cm/s; EDV: 9,33±2,36cm/s; PI: 1,01±0,65 e RI: 0,65±0,16) e esquerdas (PSV: 23,74±3,94cm/s; EDV: 9,07±3,02cm/s; PI: 1,04±0,31 e RI: 0,64±0,10). Pode-se concluir que a ultrassonografia convencional e Doppler podem ser ferramentas importantes no estudo morfofisiológico de órgãos abdominais em cachorros-do-mato, possibilitando o diagnóstico de alterações abdominais nesses animais e a utilização desses achados como referências para outros caninos silvestres.Univ Estadual Paulista Unesp, FCAV, Dept Reprod Anim, BR-14884900 Jaboticabal, SP, BrazilUNESP, Fac Ciencias Agr Vet, Dept Patol Anim, BR-14884900 Jaboticabal, SP, BrazilUniv Fed Rural Amazonia UFRA, Inst Socio Ambiental &Recursos Hidr, BR-66077830 Belem, Para, BrazilUniv Estadual Paulista Unesp, FCAV, Dept Reprod Anim, BR-14884900 Jaboticabal, SP, BrazilUNESP, Fac Ciencias Agr Vet, Dept Patol Anim, BR-14884900 Jaboticabal, SP, Brazi

Characterization of optical properties and surface roughness profiles: The Casimir force between real materials

The Lifshitz theory provides a method to calculate the Casimir force between two flat plates if the frequency dependent dielectric function of the plates is known. In reality any plate is rough and its optical properties are known only to some degree. For high precision experiments the plates must be carefully characterized otherwise the experimental result cannot be compared with the theory or with other experiments. In this chapter we explain why optical properties of interacting materials are important for the Casimir force, how they can be measured, and how one can calculate the force using these properties. The surface roughness can be characterized, for example, with the atomic force microscope images. We introduce the main characteristics of a rough surface that can be extracted from these images, and explain how one can use them to calculate the roughness correction to the force. At small separations this correction becomes large as our experiments show. Finally we discuss the distance upon contact separating two rough surfaces, and explain the importance of this parameter for determination of the absolute separation between bodies.}Comment: 33 pages, 14 figures, to appear in Springer Lecture Notes in Physics, Volume on Casimir Physics, edited by Diego Dalvit, Peter Milonni, David Roberts, and Felipe da Ros