140 research outputs found
Discovery of an old nova shell surrounding the cataclysmic variable V1315 Aql
Following our tentative discovery of a faint shell around V1315 Aql reported in Sahman et al., we undertook deep Hα imaging and intermediate-resolution spectroscopy of the shell. We find that the shell has its geometric centre located on V1315 Aql. The mass, spectral features, and density of the shell are consistent with other nova shells, rather than planetary nebulae or supernova remnants. The radial velocity of the shell is consistent with the systemic velocity of V1315 Aql. We believe this evidence strongly suggests that the shell originates from an earlier nova event. This is the first nova shell discovered around a nova-like and supports the theory of nova-induced cycles in mass transfer rates (hibernation theory) first proposed by Shara et al
ПРИНЦИПИ РЕВІТАЛІЗАЦІЇ РОЗВИТКУ СІЛЬСЬКИХ ТЕРИТОРІЙ, ЯКІ ПОСТРАЖДАЛИ ВНАСЛІДОК ВІЙСЬКОВИХ ДІЙ
Introduction. The full-scale war worsened the ecological condition of the territories. Part of Ukraine’s agricultural land was suffered significant environmental damage. There is a need for the latest technologies for monitoring the state of land and determining ways of revitalisation both individual land plots and integral agricultural landscapes, territories of communities and districts.Purpose of the study is to determine the characteristics of the territories affected by military operations, to identify the factors of influence of military operations on these territories, to determine the system of principles of revitalisation of the development of rural areas, and to develop an appropriate structural and logical model.Results. Two groups of factors are to out: direct and indirect influence of military aggression on the territory. It is suggested that the factors of direct impact include: the movement of military equipment, the physical impact of military operations, mining the territory, the construction of protective structures, destroyed military equipment in the fields, and demining the territory. Factors of indirect influence include the formation of craters from bombardment, landslides, soil contamination with heavy metals; cluttering the territory, destruction of the surface, and accessibility of the territory after demining.A system of principles for the revitalisation of sustainable development of rural areas affected by military operations is proposed. The main components of the system of principles are: the potential of territories (ecological, geographical; resource, economic, social), complexity and balance of sustainable development of rural territories. At the same time, the components of the system are in interaction and interconnection.The authors singled out the consequences of military influence on the soil. Compaction of the soil. The change in its structure. Change in the physical parameters of the soil (of vibration, radioactive and thermal effects). Disturbance of soil cover, lack of natural moisture, desertification, development of wind and water erosion, and migration of heavy metals into the vegetative mass of plants. Environmental degradation, emissions to the surface of sand, clay and other sedimentary rocks, destruction of the humus horizon, and loss of physical and chemical properties of the soil. A structural and logical model of the system of principles of revitalisation of sustainable development of rural areas was developed. The model assumes that the complexity and balance of the sustainable development of rural areas affected by military actions take into account the potential of the territories, which makes it possible to take into account the peculiarities of these territories and ensure the revitalisation of sustainable development.Conclusion. Conclusions. Further developments should focus on identifying ways to restore lands, particularly soils, and intact agro-landscapes depending on the consequences of military damage. It is necessary to pay special attention to soil restoration technologies and their use depending on the condition of the soil and the potential of the territories, in particular ecological, geographical, resource, economic, and social. As a result, there is a need to form directions for spatial and territorial development of communities, rational use of reclaimed land, and effective functioning of the environment of territorial communities.Проблема. В результаті повномасштабної війни погіршився екологічний стан територій. Частина сільськогосподарських угідь України зазнала значних екологічних пошкоджень. Виникає потреба у дослідженні стану земель, визначенні шляхів ревіталізації як окремих земельних ділянок, так і цілісних агроландшафтів, територій громад і районів. Мета дослідження полягає у визначенні особливостей територій, які постраждали внаслідок війни, виокремленні факторів впливу військових дій на території, визначенні системи принципів ревіталізації розвитку сільських територій та розробці відповідної структурно-логічної моделі. Результати. Виокремлено дві групи факторів: прямого і опосередкованого впливу військової агресії на території. Запропоновано до факторів прямого впливу віднести: рух техніки, фізичний вплив військових дій, замінування територій, будівництво захисних споруд, залишена знищена військова техніка на полях, розмінування територій. До факторів опосередкованого впливу запропоновано віднести: утворення кратерів від бомбардування, зсуви ґрунтів, забруднення ґрунтів важкими металами; захаращення територій, руйнування поверхні, доступність територій після розмінування.Запропоновано систему принципів ревіталізації сталого розвитку сільських територій, які постраждали внаслідок військових дій. До основних компонентів системи віднесено: моніторинг земель, потенціал територій (екологічний, географічний, ресурсний, економічний, соціальний), комплексність та збалансованість сталого розвитку сільських територій. При цьому складові системи перебувають у взаємодії та взаємозв’язку.Виокремлено наслідки військового впливу на ґрунти, зокрема ущільнення ґрунтів, зміна їх структури, зміна фізичних параметрів ґрунту внаслідок вібраційного, радіоактивного та теплового впливу, порушення ґрунтового покриву, дефіцит природного зволоження, опустелювання, розвиток вітрової та водної ерозії, міграція важких металів у вегетативну масу рослин, деградація довкілля, викиди на поверхню піску, глини та інших осадових порід, руйнування гумусового горизонту, втрата фізико-хімічних властивостей ґрунту.Розроблено структурно-логічну модель системи принципів ревіталізації сталого розвитку сільських територій. Модель передбачає, що комплексність та збалансованість сталого розвитку сільських територій, які постраждали внаслідок військових дій, ґрунтуються на потенціалі територій, що дає можливість враховувати особливості цих територій та забезпечувати ревіталізацію сталого розвитку.Висновки. Подальші розробки повинні зосереджуватись на визначенні шляхів відновлення земель, зокрема ґрунтів, та цілісних агроландшафтів залежно від наслідків пошкодження військовими діями. Необхідно звернути особливу увагу на технології відновлення ґрунтів та використання ґрунтів залежно від стану і потенціалу територій, зокрема екологічного, географічного, ресурсного, економічного, соціального. В результаті виникає потреба у формуванні напрямів просторово-територіального розвитку громад, раціонального використання відновлених земель та ефективного функціонування навколишнього середовища територіальних громад
An Age Difference of 2 Gyr between a Metal-Rich and a Metal-Poor Globular Cluster
Globular clusters trace the formation history of the spheroidal components of
both our Galaxy and others, which represent the bulk of star formation over the
history of the universe. They also exhibit a range of metallicities, with
metal-poor clusters dominating the stellar halo of the Galaxy, and higher
metallicity clusters found within the inner Galaxy, associated with the stellar
bulge, or the thick disk. Age differences between these clusters can indicate
the sequence in which the components of the Galaxy formed, and in particular
which clusters were formed outside the Galaxy and later swallowed along with
their original host galaxies, and which were formed in situ. Here we present an
age determination of the metal-rich globular cluster 47 Tucanae by fitting the
properties of the cluster white dwarf population, which implies an absolute age
of 9.9 (0.7) Gyr at 95% confidence. This is about 2.0 Gyr younger than inferred
for the metal-poor cluster NGC 6397 from the same models, and provides
quantitative evidence that metal-rich clusters like 47 Tucanae formed later
than the metal-poor halo clusters like NGC 6397.Comment: Main Article: 10 pages, 4 figures; Supplementary Info 15 pages, 5
figures. Nature, Aug 1, 201
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SUPREME-HN: a retrospective biomarker study assessing the prognostic value of PD-L1 expression in patients with recurrent and/or metastatic squamous cell carcinoma of the head and neck.
BACKGROUND:Programmed cell death ligand-1 (PD-L1) expression on tumor cells (TCs) is associated with improved survival in patients with head and neck squamous cell carcinoma (HNSCC) treated with immunotherapy, although its role as a prognostic factor is controversial. This study investigates whether tumoral expression of PD-L1 is a prognostic marker in patients with recurrent and/or metastatic (R/M) HNSCC treated with standard chemotherapy. METHODS:This retrospective, multicenter, noninterventional study assessed PD-L1 expression on archival R/M HNSCC tissue samples using the VENTANA PD-L1 (SP263) Assay. PD-L1 high was defined as PD-L1 staining of ≥ 25% TC, with exploratory scoring at TC ≥ 10% and TC ≥ 50%. The primary objective of this study was to estimate the prognostic value of PD-L1 status in terms of overall survival (OS) in patients with R/M HNSCC. RESULTS:412 patients (median age, 62.0 years; 79.9% male; 88.2% Caucasian) were included from 19 sites in seven countries. 132 patients (32.0%) had TC ≥ 25% PD-L1 expression; 199 patients (48.3%) and 85 patients (20.6%) had TC ≥ 10% and ≥ 50%, respectively. OS did not differ significantly across PD-L1 expression (at TC ≥ 25% cutoff median OS: 8.2 months vs TC < 25%, 10.1 months, P = 0.55) or the ≥ 10% and ≥ 50% cutoffs (at TC ≥ 10%, median OS: 9.6 months vs TC < 10%, 9.4 months, P = 0.32, and at TC ≥ 50%, median OS 7.9 vs TC < 50%, 10.0 months, P = 0.39, respectively). CONCLUSIONS:PD-L1 expression, assessed using the VENTANA PD-L1 (SP263) Assay, was not prognostic of OS in patients with R/M HNSCC treated with standard of care chemotherapies. Trial registration ClinicalTrials.gov, NCT02543476. Registered September 4, 2015
The origin of intergalactic thermonuclear supernovae
The population synthesis method is used to study the possibility of
explaining the appreciable fraction (20^+12_15%) of the intergalactic (no-host)
type Ia supernovae observed in galaxy clusters (Gal-Yam ete al. 2003) by binary
whote dwarf merginngs in the cores of globular clusters. In a typical globular
cluster, the number of merging double white dwarfs is fount to be smaller than
10^{-13} per year per average cluster star during the entire evolution of the
cluster, which is a factor of 3 higher than in a Milky-Way-type galaxy. From 5
to 30% of the merging white dwarfs are dynamically expelled from the cluster
with barycenter velocities up to 150 km/s. SN Ia explosions during the mergers
of binary white dwarfs in dense star clusters may account for \sim 1% of the
total rate of SN Ia in the central parts of galaxy clusters if the baryon mass
fraction in such star clusters is \sim 0.3%.Comment: 8 pages, 3 figs. Astronomy Letters (in press
Two distinct sequences of blue straggler stars in the globular cluster M30
Stars in globular clusters are generally believed to have all formed at the
same time, early in the Galaxy's history. 'Blue stragglers' are stars massive
enough that they should have evolved into white dwarfs long ago. Two possible
mechanisms have been proposed for their formation: mass transfer between binary
companions and stellar mergers resulting from direct collisions between two
stars. Recently, the binary explanation was claimed to be dominant. Here we
report that there are two distinct parallel sequences of blue stragglers in
M30. This globular cluster is thought to have undergone 'core collapse', during
which both the collision rate and the mass transfer activity in binary systems
would have been enhanced. We suggest that the two observed sequences arise from
the cluster core collapse, with the bluer population arising from direct
stellar collisions and the redder one arising from the evolution of close
binaries that are probably still experiencing an active phase of mass transfer.Comment: Published on the 24th December 2009 issue of Natur
Constraints on the Progenitor System of the Type Ia Supernova SN 2011fe/PTF11kly
Type Ia supernovae (SNe) serve as a fundamental pillar of modern cosmology,
owing to their large luminosity and a well-defined relationship between
light-curve shape and peak brightness. The precision distance measurements
enabled by SNe Ia first revealed the accelerating expansion of the universe,
now widely believed (though hardly understood) to require the presence of a
mysterious "dark" energy. General consensus holds that Type Ia SNe result from
thermonuclear explosions of a white dwarf (WD) in a binary system; however,
little is known of the precise nature of the companion star and the physical
properties of the progenitor system. Here we make use of extensive historical
imaging obtained at the location of SN 2011fe/PTF11kly, the closest SN Ia
discovered in the digital imaging era, to constrain the visible-light
luminosity of the progenitor to be 10-100 times fainter than previous limits on
other SN Ia progenitors. This directly rules out luminous red giants and the
vast majority of helium stars as the mass-donating companion to the exploding
white dwarf. Any evolved red companion must have been born with mass less than
3.5 times the mass of the Sun. These observations favour a scenario where the
exploding WD of SN 2011fe/PTF11kly, accreted matter either from another WD, or
by Roche-lobe overflow from a subgiant or main-sequence companion star.Comment: 22 pages, 6 figures, submitte
The Lower Main Sequence and Mass Function of the Globular Cluster Messier 4
The deepest optical image ever in a globular star cluster, a Hubble Space
Telescope (HST) 123 orbit exposure in a single field of Messier 4, was obtained
in 2 filters (F606W, F814W) over a 10 week period in early 2001. A somewhat
shallower image obtained in 1995 allowed us to select out cluster and field
objects via their proper motion displacement resulting in remarkably clean
color-magnitude diagrams that reach to V = 30, I = 28. The cluster main
sequence luminosity function contains very few stars fainter than MV = 15.0, MI
= 11.8 which, in both filters, is more than 2 magnitudes brighter than our
limit. This is about the faintest luminosity seen among field Population II
subdwarfs of the same metallicity. However, there remains a sprinkling of
potential cluster stars to lower luminosity all the way down to our limiting
magnitudes. These latter objects are significantly redder than any known
metal-poor field subdwarf. Comparison with the current generation of
theoretical stellar models implies that the masses of the lowest luminosity
cluster stars observed are near 0.09 Msun. We derive the mass function of the
cluster in our field and find that it is very slowly rising towards the lowest
masses with no convincing evidence of a turnover even below 0.1 Msun. The
formal slope between 0.65 and 0.09 Msun is alpha = 0.75 (Salpeter of 2.35) with
a 99% confidence interval 0.55 - 1.05. A consistency check between these slopes
and the number of observed cluster white dwarfs yields a range of possible
conclusions, one of which is that we have indeed seen the termination of the
white dwarf cooling sequence in M4.Comment: 12 pages, 3 diagrams. To be published in the Astrophysical Journal
Letters August 2002. Several minor edits and a different figure 2 from
original submissio
Effects of a Cognitive Behavioral Therapy Intervention Trial to Improve Disease Outcomes in Children with Inflammatory Bowel Disease:
Studies testing the efficacy of behavioral interventions to modify psychosocial sequelae of IBD in children are limited. This report presents outcomes through a six month follow up from a large RCT testing the efficacy of a cognitive-behavioral intervention for children with IBD and their parents
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