152 research outputs found
FUSE Measurements of Far Ultraviolet Extinction. I. Galactic Sight Lines
We present extinction curves that include data down to far ultraviolet
wavelengths (FUV; 1050 - 1200 A) for nine Galactic sight lines. The FUV
extinction was measured using data from the Far Ultraviolet Spectroscopic
Explorer. The sight lines were chosen for their unusual extinction properties
in the infrared through the ultraviolet; that they probe a wide range of dust
environments is evidenced by the large spread in their measured ratios of
total-to-selective extinction, R_V = 2.43 - 3.81. We find that extrapolation of
the Fitzpatrick & Massa relationship from the ultraviolet appears to be a good
predictor of the FUV extinction behavior. We find that predictions of the FUV
extinction based upon the Cardelli, Clayton & Mathis (CCM) dependence on R_V
give mixed results. For the seven extinction curves well represented by CCM in
the infrared through ultraviolet, the FUV extinction is well predicted in three
sight lines, over-predicted in two sight lines, and under-predicted in 2 sight
lines. A Maximum Entropy Method analysis using a simple three component grain
model shows that seven of the nine sight lines in the study require a larger
fraction of grain materials to be in dust when FUV extinction is included in
the models. Most of the added grain material is in the form of small (radii <
200 A) grains.Comment: Accepted for publication in the Astrophysical Journal. 31 pages with
7 figure
РОЛЬ АДЪЮВАНТНОЙ ВНУТРИПУЗЫРНОЙ ХИМИОТЕРАПИИ В КОМБИНИРОВАННОМ ОРГАНОСОХРАНЯЮЩЕМ ЛЕЧЕНИИ НЕМЫШЕЧНО-ИНВАЗИВНОГО РАКА МОЧЕВОГО ПУЗЫРЯ
Objective: to enhance the efficiency of combined treatment for non-muscle-invasive bladder cancer ((NMIBC) and to assess the results of its treatment using transurethral resection (TUR) as monotherapy and in combination with intravesical adjuvant chemotherapy (CT).Subjects and methods. The results of treatment were analyzed in 59 patients with NMIBC. Twenty-two patients underwent TUR in Group 1; TUR and single intravesical injection of drugs were performed in 19 patients in Group 2; 18 patients had TUR and long-term intravesical CT.Results and discussion. The recurrence rates were 59.1, 57.9, and 38.89 % in Groups 1, 2, and 3, respectively. Intravesical CT was found to appreciably affect the prevention of recurrence in the area of resection. The rate of this recurrence was 31.81, 26.32, and 5.56 % in Groups 1, 2, and 3, respectively. Conclusion. Adjuvant intravesical chemotherapy CT is an effective method to prevent recurrent bladder cancer.Цель исследования – повысить эффективность комбинированного лечения больных немышечно-инвазивным (НМИ) раком моче-вого пузыря (РМП). Оценить результаты лечения НМИ РМП при применении трансуретральной резекции (ТУР) в качестве монотерапии и в комбинации с внутрипузырной адъювантной химиотерапией (ХТ).Материалы и методы. Проведен анализ результатов лечения 59 пациентов с НМИ РМП. В 1-й группе (n = 22) больным была выполнена ТУР, во 2-й (n = 19) – ТУР и однократное внутрипузырное введение химиопрепарата, в 3-й (n = 18) выполнены ТУР и длительное применение внутрипузырной ХТ.Результаты и обсуждение. Частота рецидивов в 1-й группе составила 59,1 %, во 2-й – 57,9 %, в 3-й – 38,89 %. Установлено, что внутрипузырная ХТ в большей степени оказывает влияние на профилактику рецидива в зоне резекции. Частота данного рецидива в 1-й группе составила 31,81 %, во 2-й – 26,32 % и в 3-й – 5,56 %.Выводы. Адъювантная внутрипузырная ХТ является эффективным методом профилактики рецидивов РМП.
C2D Spitzer-IRS spectra of disks around T Tauri stars: I. Silicate emission and grain growth
Infrared ~5--35 um spectra for 40 solar-mass T Tauri stars and 7
intermediate-mass Herbig Ae stars with circumstellar disks were obtained using
the Spitzer Space Telescope as part of the c2d IRS survey. This work
complements prior spectroscopic studies of silicate infrared emission from
disks, which were focused on intermediate-mass stars, with observations of
solar-mass stars limited primarily to the 10 um region. The observed 10 and 20
um silicate feature strengths/shapes are consistent with source-to-source
variations in grain size. A large fraction of the features are weak and flat,
consistent with um-sized grains indicating fast grain growth (from 0.1--1.0 um
in radius). In addition, approximately half of the T Tauri star spectra show
crystalline silicate features near 28 and 33 um indicating significant
processing when compared to interstellar grains. A few sources show large
10-to-20 um ratios and require even larger grains emitting at 20 um than at 10
um. This size difference may arise from the difference in the depth into the
disk probed by the two silicate emission bands in disks where dust settling has
occurred. The 10 um feature strength vs. shape trend is not correlated with age
or Halpha equivalent width, suggesting that some amount of turbulent mixing and
regeneration of small grains is occurring. The strength vs. shape trend is
related to spectral type, however, with M stars showing significantly flatter
10 um features (larger grain sizes) than A/B stars. The connection between
spectral type and grain size is interpreted in terms of the variation in the
silicate emission radius as a function of stellar luminosity, but could also be
indicative of other spectral-type dependent factors (e.g, X-rays, UV radiation,
stellar/disk winds, etc.).Comment: 17 pages, 13 figures, accepted for publication by ApJ, formatted with
emulateapj using revtex4 v4.
The Spectral Energy Distribution of HH30 IRS: Constraining The Circumstellar Dust Size Distribution
We present spectral energy distribution (SED) models for the edge-on
classical T Tauri star HH30 IRS that indicate dust grains have grown to larger
than 50 microns within its circumstellar disk. The disk geometry and
inclination are known from previous modeling of multiwavelength Hubble Space
Telescope images and we use the SED to constrain the dust size distribution.
Model spectra are shown for different circumstellar dust models: a standard ISM
mixture and larger grain models. As compared to ISM grains, the larger dust
grain models have a shallower wavelength dependent opacity. Models with the
larger dust grains provide a good match to the currently available data, but
mid and far-IR observations are required to more tightly constrain the dust
size distribution. The accretion luminosity in our models is L_acc<0.2 L_star
corresponding to an accretion rate of 4E-9M_sun/yr. Dust size distributions
that are simple power-law extensions (i.e., no exponential cutoff) yield
acceptable fits to the optical/near-IR but too much emission at mm wavelengths
and require larger disk masses. Such a simple size distribution would not be
expected in an environment such as the disk of HH30 IRS, particularly over such
a large range in grain sizes. However, its ability to adequately characterize
the grain populations may be determined from more complete observational
sampling of the SED in the mid to far-IR.Comment: ApJ Accepte
Dust Masses, PAH Abundances, and Starlight Intensities in the SINGS Galaxy Sample
Physical dust models are presented for 65 galaxies in SINGS that are strongly detected in the four IRAC bands and three MIPS bands. For each galaxy we estimate (1) the total dust mass, (2) the fraction of the dust mass contributed by PAHs, and (3) the intensity of the starlight heating the dust grains. We find that spiral galaxies have dust properties resembling the dust in the local region of the Milky Way, with similar dust-to-gas ratio and similar PAH abundance. The observed SEDs, including galaxies with SCUBA photometry, can be reproduced by dust models that do not require "cold" (T ≾ 10 K) dust. The dust-to-gas ratio is observed to be dependent on metallicity. In the interstellar media of galaxies with A_O ≡ 12 + log_(10)(O/H) > 8.1, grains contain a substantial fraction of interstellar Mg, Si, and Fe. Galaxies with A_O 8.1 have a median q_(PAH) = 3.55%. The derived dust masses favor a value X_(CO) ≈ 4 × 10^(20) cm^(-2) (K km s^(-1))^(-1) for the CO-to-H_2 conversion factor. Except for some starbursting systems (Mrk 33, Tol 89, NGC 3049), dust in the diffuse ISM dominates the IR power
Survival and Growth of Yeast without Telomere Capping by Cdc13 in the Absence of Sgs1, Exo1, and Rad9
Maintenance of telomere capping is absolutely essential to the survival of eukaryotic cells. Telomere capping proteins, such as Cdc13 and POT1, are essential for the viability of budding yeast and mammalian cells, respectively. Here we identify, for the first time, three genetic modifications that allow budding yeast cells to survive without telomere capping by Cdc13. We found that simultaneous inactivation of Sgs1, Exo1, and Rad9, three DNA damage response (DDR) proteins, is sufficient to allow cell division in the absence of Cdc13. Quantitative amplification of ssDNA (QAOS) was used to show that the RecQ helicase Sgs1 plays an important role in the resection of uncapped telomeres, especially in the absence of checkpoint protein Rad9. Strikingly, simultaneous deletion of SGS1 and the nuclease EXO1, further reduces resection at uncapped telomeres and together with deletion of RAD9 permits cell survival without CDC13. Pulsed-field gel electrophoresis studies show that cdc13-1 rad9Δ sgs1Δ exo1Δ strains can maintain linear chromosomes despite the absence of telomere capping by Cdc13. However, with continued passage, the telomeres of such strains eventually become short and are maintained by recombination-based mechanisms. Remarkably, cdc13Δ rad9Δ sgs1Δ exo1Δ strains, lacking any Cdc13 gene product, are viable and can grow indefinitely. Our work has uncovered a critical role for RecQ helicases in limiting the division of cells with uncapped telomeres, and this may provide one explanation for increased tumorigenesis in human diseases associated with mutations of RecQ helicases. Our results reveal the plasticity of the telomere cap and indicate that the essential role of telomere capping is to counteract specific aspects of the DDR
The unusual protoplanetary disk around the T Tauri star ET Cha
We present new continuum and line observations, along with modelling, of the
faint (6-8) Myr old T Tauri star ET Cha belonging to the eta Chamaeleontis
cluster. We have acquired HERSCHEL/PACS photometric fluxes at 70 mic and 160
mic, as well as a detection of the [OI] 63 mic fine-structure line in emission,
and derived upper limits for some other far-IR OI, CII, CO and o-H2O lines. The
HERSCHEL data is complemented by new ANDICAM B-K photometry, new HST/COS and
HST/STIS UV-observations, a non-detection of CO J=3-2 with APEX, re-analysis of
a UCLES high-resolution optical spectrum showing forbidden emission lines like
[OI] 6300A, [SII] 6731A and 6716A, and [NII] 6583A, and a compilation of
existing broad-band photometric data. We used the thermo-chemical disk code
ProDiMo and the Monte-Carlo radiative transfer code MCFOST to model the
protoplanetary disk around ET Cha. Based on these models we can determine the
disk dust mass Mdust = (2.E-8 - 5.E-8) Msun, whereas the total disk gas mass is
found to be only little constrained, Mgas = (5.E-5 - 3.E-3) Msun. In the
models, the disk extends from 0.022 AU (just outside of the co-rotation radius)
to only about 10 AU. Larger disks are found to be inconsistent with the CO
J=3-2 non-detection. The low velocity component of the [OI] 6300A emission line
is consistent with being emitted from the inner disk. The model can also
reproduce the line flux of H2 v=1-0 S(1) at 2.122 mic. An additional
high-velocity component of the [OI] 6300A emission line, however, points to the
existence of an additional jet/outflow of low velocity (40 - 65) km/s with mass
loss rate ~1.E-9 Msun/yr. In relation to our low estimations of the disk mass,
such a mass loss rate suggests a disk lifetime of only ~(0.05 - 3) Myr,
substantially shorter than the cluster age. The evolutionary state of this
unusual protoplanetary disk is discussed.Comment: accepted by Astronomy & Astrophysics (18 pages, 11 figures and 7
tables). Additional 9-page appendix with 6 figures, 3 tables and 37 equation
The composition of the protosolar disk and the formation conditions for comets
Conditions in the protosolar nebula have left their mark in the composition
of cometary volatiles, thought to be some of the most pristine material in the
solar system. Cometary compositions represent the end point of processing that
began in the parent molecular cloud core and continued through the collapse of
that core to form the protosun and the solar nebula, and finally during the
evolution of the solar nebula itself as the cometary bodies were accreting.
Disentangling the effects of the various epochs on the final composition of a
comet is complicated. But comets are not the only source of information about
the solar nebula. Protostellar disks around young stars similar to the protosun
provide a way of investigating the evolution of disks similar to the solar
nebula while they are in the process of evolving to form their own solar
systems. In this way we can learn about the physical and chemical conditions
under which comets formed, and about the types of dynamical processing that
shaped the solar system we see today.
This paper summarizes some recent contributions to our understanding of both
cometary volatiles and the composition, structure and evolution of protostellar
disks.Comment: To appear in Space Science Reviews. The final publication is
available at Springer via http://dx.doi.org/10.1007/s11214-015-0167-
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