900 research outputs found
CLIC Main Linac Beam-Loading Compensation by Drive Beam Phase Modulation
The CLIC final focus momentum acceptance of ± 0.5 % limits the bunch-to-bunch energy variation in the main beam to less than ± 0.1 %, since the estimated single-bunch contribution is ± 0.4 %. On the other hand, a relatively high beam-loading of the main accelerating structures (about 16 %) is unavoidable in order to optimize the RF-to-beam efficiency. Therefore, a compensation method is needed to reduce the resulting bunch-to-bunch energy spread of the main beam. Up to now, it has been planned to obtain the RF pulse shape needed for compensation by means of a charge ramp in the drive beam pulse. On the other hand, the use of constant-current drive beam pulses would make the design and operation of the drive beam injector considerably simpler. In this paper we present a possible solution adapted to the CLIC two-beam scheme with constant-current pulses, based on phase modulation of the drive beam bunches
On the relation between circular velocity and central velocity dispersion in high and low surface brightness galaxies
In order to investigate the correlation between the circular velocity Vc and
the central velocity dispersion of the spheroidal component sigma_c, we
analyzed these quantities for a sample of 40 high surface brightness disc
galaxies (hereafter HSB), 8 giant low surface brightness spiral galaxies
(hereafter LSB), and 24 elliptical galaxies characterized by flat rotation
curves. We find that the Vc-sigma_c relation is descri ed by a linear law out
to velocity dispersions as low as sigma_c~50km/s, while in previous works a
power law was adopted for galaxies with sigma_c>80k/ms.
Elliptical galaxies with Vc based on dynamical models or directly derived
from the HI rotation curves follow the same relation as the HSB galaxies in the
Vc-sigma_c plane. On the contrary, the LSB galaxies follow a different
relation, since most of them show either higher Vc (or lower sigma_c) with
respect to the HSB galaxies. This argues against the relevance of baryon
collapse in the radial density profile of the dark matter haloes of LSB
galaxies. (abridged)Comment: 18 pages, 4 figures, ApJ in pres
Chandra observations of NGC4698: a Seyfert-2 with no absorption
We present Chandra ACIS-S observations of the enigmatic
Seyfert-2 galaxy NGC4698. This object together with several other bona-fide
Seyfert-2 galaxies show no absorption in the low spatial resolution ASCA data,
in contrast to the standard unification models. Our Chandra observations of
NGC4698 probe directly the nucleus allowing us to check whether nearby sources
contaminate the ASCA spectrum. Indeed, the Chandra observations show that the
ASCA spectrum is dominated by two nearby AGN. The X-ray flux of NGC4698 is
dominated by a nuclear source with luminosity L(0.3-8 keV) ~ 10^39, erg s-1
coincident with the radio nucleus. Its spectrum is well represented by a
power-law, ~ 2.2, obscured by a small column density of 5x10^20 cm-2 suggesting
that NGC4698 is an atypical Seyfert galaxy.
On the basis of its low luminosity we then interpret NGC4698 as a Seyfert
galaxy which lacks a broad-line region.Comment: 12 pages, to appear in Ap
Massive Pericardial Effusion in a 14-Year-Old Girl with Mild Fatigue and Neck Pain
Pericardial effusion is rare in pediatric patients and is characterized by a variable clinical presentation. Mild symptoms may be present despite severe effusion. We here report the case of a patient with massive pericardial effusion with mild clinical presentation. Our case points out the need not to exclude this diagnosis in patients with mild general impairment. This clinical suspicion can be lifesaving
Contabilidade ambiental em emergia do processamento de rocha calcĂĄria para uso agrĂcola.
Resumo: O presente estudo propĂ”e uma contabilidade ambiental do processamento de calcĂĄrio de rocha para uso agrĂcola, com aplicação da metodologia da sĂntese em emergia de um empreendimento atuante no referido setor, localizado no municĂpio de Arcos - MG. Na produção agrĂcola, o calcĂĄrio Ă© utilizado com a finalidade de corrigir o pH do solo e fornecer suplemento de cĂĄlcio e magnĂ©sio para as plantas. Os estudos de contabilidade ambiental via mĂ©todo da sĂntese em emergia de empreendimentos agrĂcolas tĂȘm utilizado apenas a transformidade da rocha calcĂĄria, sem consideração para etapas de processamento. Neste sentido, o presente estudo visa calcular a transformidade do CalcĂĄrio AgrĂcola, que Ă© a rocha calcĂĄria processada. A metodologia apresenta resultados sintĂ©ticos e de fĂĄcil entendimento que auxiliam na busca do desenvolvimento sustentĂĄvel. As anĂĄlises indicam que a emergia total do sistema Ă© de 8,70E+21 sej/ano, resultando em uma transformidade de 2,81E+6 sej/J como co-produto e de 4,30E+6 sej/J como ?Split?. Em relação Ă transformidade da rocha calcĂĄria calculada por Odum (1996; 2000) o CalcĂĄrio AgrĂcola representa um aumento de 2% no co-produto e 55% no ?Split?
Antiproliferative effects of chalcones on T cell acute lymphoblastic leukemia‐derived cells: Role of PKCβ
In this study, a series of 20 chalcone derivatives was synthesized, and their antiproliferative activity was tested against the human T cell acute lymphoblastic leukemia\u2010derived cell line, CCRF\u2010CEM. On the basis of the structural features of the
most active compounds, a new library of chalcone derivatives, according to the structure\u2013activity relationship design, was synthesized, and their antiproliferative activity was tested against the same cancer cell line. Furthermore, four
of these derivatives (compounds 3, 4, 8, 28), based on lower IC50 values (between 6.1 and 8.9 \u3bcM), were selected for further investigation regarding the modulation of the protein expression of RACK1 (receptor for activated C kinase), protein kinase
C (PKC)\u3b1 and PKC\u3b2, and their action on the cell cycle level. The cell cycle analysis indicated a block in the G0/G1 phase for all four compounds, with a statistically significant decrease in the percentage of cells in the S phase, with no indication of
apoptosis (sub\u2010G0/G1 phase). Compounds 4 and 8 showed a statistically significant reduction in the expression of PKC\u3b1 and an increase in PKC\u3b2, which together with the demonstration of an antiproliferative role of PKC\u3b2, as assessed by treating cells with a selective PKC\u3b2 activator, indicated that the observed antiproliferative effect is likely to be mediated through PKC\u3b2 induction
Studies on the RF Deflectors for CTF3
The bunch train compression scheme for the CLIC Test Facility CTF3 relies on the feasibility of fast RF deflectors. They are essentially RF cavities or TW sections working on transverse. deflecting mode. The most demanding issues in the deflector design are those related to the beam dynamics, including the beam loading effects on the fundamental deflecting mode, while the efficiency required by the CTF3 parameters can be met by already existing structures. The analysis of the beam dynamics, which addresses the deflector design is reported in this paper, and different structures representing possible solutions are compared
Spatially resolved spectroscopy of Coma cluster early-type galaxies IV. Completing the dataset
The long-slit spectra obtained along the minor axis, offset major axis and
diagonal axis are presented for 12 E and S0 galaxies of the Coma cluster drawn
from a magnitude-limited sample studied before. The rotation curves, velocity
dispersion profiles and the H_3 and H_4 coefficients of the Hermite
decomposition of the line of sight velocity distribution are derived. The
radial profiles of the Hbeta, Mg, and Fe line strength indices are measured
too. In addition, the surface photometry of the central regions of a subsample
of 4 galaxies recently obtained with Hubble Space Telescope is presented. The
data will be used to construct dynamical models of the galaxies and study their
stellar populations.Comment: 40 pages, 7 figures, 6 tables. Accepted for publication in ApJ
Stellar kinematics in double-barred galaxies: the sigma-hollows
We present SAURON integral-field stellar velocity and velocity dispersion
maps for four double-barred early-type galaxies: NGC2859, NGC3941, NGC4725 and
NGC5850. The presence of the inner bar does not produce major changes in the
line-of-sight velocity, but it appears to have an important effect in the
stellar velocity dispersion maps: we find two sigma-hollows of amplitudes
between 10 and 40 km/s on either side of the center, at the ends of the inner
bars. We have performed numerical simulations to explain these features. Ruling
out other possibilities, we conclude that the sigma-hollows are an effect of
the contrast between two kinematically different components: the high velocity
dispersion of the bulge and the more ordered motion (low velocity dispersion)
of the inner bar.Comment: 5 pages, 2 figures. Accepted for publication in ApJ Letter
Activity of a Pediatric Emergency Department of a Tertiary Center in Bologna, Italy, during SARS-CoV-2 Pandemic
During the SARS-CoV-2 pandemic, the pediatric emergency department (ED) of Bologna, Emilia-Romagna, Italy faced a reorganization to better deal with the new clinical needs. We herein describe the main changes in the organization and in the attendances to our pediatric ED. From the 1 March 2020 to the 31 January 2022, 796 children positive for SARS-CoV-2 presented to our pediatric ED, but only 26 required hospitalizations, of which only 9 for COVID-19 related reasons. During this period, we also registered a temporal correlation between multisystem inflammatory syndrome in children (MIS-C) admissions and the peaks of SARS-CoV-2 infection in the Italian population. Respiratory syncytial virus (RSV) remained during last year the viral infection with the highest hospitalization rate. The analysis and description of the changes in the activity of the pediatric ED during the SARS-CoV-2 pandemic may help to better understand the routinary activity and be prepared for any possible new challenge
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