Candidate Pre-Mainsequence F Stars with Circumstellar Dust Identified Using Combined 2MASS and uvby Data

We propose a method that uses near-infrared plus uvby photometry to identify potentially extensive circumstellar dusty environment about F and A stars. The method has been applied to a sample of ~900 metal rich reddened F stars with 2MASS and uvby data, suggesting the presence of circumstellar dust emitting in the near infrared for ~70 stars. The log T_e - M_V diagram suggests that most, if not all, of them are likely pre-mainsequence (PMS). They seem to be consistent with being a continuation of the class of Herbig Ae/Be PMS stars into the spectral type F. Their number drops sharply downward of log T_e ~ 3.84 (spectral types later than ~F5), which may provide new clues to the PMS evolution of stars with 1 to 2 solar mass. We present a list of 21 most conspicuous candidate stars with circumstellar dust. About half of them are associated with the extended star-forming region around rho Oph. The brightest of these 21 stars, with V < 7.5, turn out to be IRAS sources, suggesting the presence of heated dust emitting in the far infrared. Also in this list, HD 81270 is reported as a very unusual star moving away from the Galactic plane at a projected speed of 70 km/sec.Comment: 8 pages, 4 figures, 1 table. To appear in ApJ, part 2, v. 570, 2002 May

Impact of climate changes on indicator specie and predicted socio-economical effects

Impact of the above-mentioned factors can be seen on particular representatives of flora and fauna, communities, landscape elements and elementary associations, and is demonstrated on the example of model species and communities

Genus <i>Nicotiana</i> L.: a review of traits significant for ornamental crop production

Background. The collection of Nicotiana L. species (Solanaceae) maintained at the All-Russian Scientific Research Institute of Tobacco, Makhorka and Tobacco Products (VNIITTI) is a valuable genetic resource used in breeding and genetic research on interspecific hybridization, cytoplasmic male sterility, and as a genebank for resistance to major tobacco diseases. Many species have ornamental features and properties: bright color and unusual morphology of the corolla, aroma, peculiar plant shape and others, and are promising for use in landscaping and garden designing. To identify and evaluate such species the collection was for the first time screened for a set of morphological and ornamental characters.Materials and methods. Thirty-seven accessions of Nicotiana spp. were studied in the greenhouses and at the experimental breeding site of VNIITTI using breeding methods and agricultural practices developed at the Institute and generally accepted in crop production.Results and conclusion. Phenotypic assessment of 37 Nicotiana accessions resulted in identifying for the first time 14 traits of ornamental value and selecting 18 original species and 10 hybrids of N. alata × N. × sanderae environmentally adapted to the local conditions and promising for landscaping and garden designing: with bright flowers, prolonged flowering, and relative resistance to stressful weather conditions. The typicality and stability of their progeny was assessed, and their germplasm was maintained and preserved in vivo

The evolution of mass loaded supernova remnants: II. Temperature dependent mass injection rates

We investigate the evolution of spherically symmetric supernova remnants in which mass loading takes place due to conductively driven evaporation of embedded clouds. Numerical simulations reveal significant differences between the evolution of conductively mass loaded and the ablatively mass loaded remnants studied in Paper I. A main difference is the way in which conductive mass loading is extinguished at fairly early times, once the interior temperature of the remnant falls below ~ 107 K. Thus, at late times remnants that ablatively mass load are dominated by loaded mass and thermal energy, while those that conductively mass load are dominated by swept-up mass and kinetic energy. Simple approximations to the remnant evolution, complementary to those in Paper I, are given

Investigating star formation in the young open cluster NGC 6383

By studying young open clusters, the mechanisms important for star formation over several Myr can be examined. For example, accretion rate as a function of rotational velocity can be investigated. Similarly, sequential star formation triggered by massive stars with high mass-loss rates can be studied in detail. We identified and characterized probable members of NGC 6383, as well as determined cluster parameters. New Stromgren uvby CCD photometry, obtained by us, is presented. This new data, together with Johnson UBV and 2MASS data in the NIR, was used to investigate characteristics of pre- as well as zero age main sequence cluster members. We present Stromgren uvby CCD photometry for 272 stars in the field of NGC 6383 and derive its reddening, E(b-y)=0.21(4)mag, as well as distance, d=1.7(3)kpc from the Sun. Several stars with NIR excess and objects in the domain of the classical Herbig Ae/Be and T Tauri stars were detected. Two previously known variables were identified as rapidly-rotating PMS stars. The field population is clearly separated from the probable members in the color-magnitude diagram. NGC 6383 is a young open cluster, with an age of less than 4 Myr, undergoing continuous star formation. True pre-main sequence members might be found down to absolute magnitudes of +6mag, with a variety of rotational velocities and stellar activities.Comment: 7 pages, 6 figures, accepted by A&

Маркеры развития рестеноза зоны реконструкции после эндоваскулярных вмешательств на артериях нижних конечностей

Restenosis of the reconstruction zone is one of the main postoperative complications of vascular reconstructions, which develops in 18–40% of cases and leads to an increase in the risk of limb loss to 20–25%. The search for new markers for predicting the development of this complication is an urgent problem today.Aim of study. To assess the dynamics of markers of apoptosis and cell proliferation at different times after endovascular intervention and their role in the development of restenosis of the reconstruction zone in patients with peripheral arterial disease (PAD).Material and methods. The clinical study included 30 patients with PAD stage III disease. After further examination, the patients underwent endovascular intervention on the arteries of the femoral-popliteal segment. If restenosis developed, the patients were re-operated. In patients before surgery, within the first hour, and then on days 1, 7, 14, 21, 30 after the operation, venous blood was taken to determine the markers Bax, sFas, PDGF BB using enzyme immunoassay.Results. After endovascular intervention, the first wave of apoptosis was triggered with an increase in the amount of proapoptotic protein Bax (p=0,00003) from 1 to 24 hours, followed by a decrease by day 7 (p=0.0008) compared to the amount on day 1. The PDGF BB level increased from day 1 after surgery (p=0.03) with maximum values on day 7 (p=0.0002) compared to the level on day 1. Then the second wave was triggered with a peak decrease in the level of the apoptosis inhibitor sFas on day 21 (p=0.002). After 9-12 months, restenosis of the intervention zone with a return of limb ischemia developed in 10 patients. During the first hour (p=0.004) in patients with restenosis, the level of Bax protein was significantly increased, with an increase in the level of PDGF BB by day 7 (p=0.011), and sFas by day 21 (p=0.0001), PDGF BB by the end of 1 month (p=0.004) compared to values in patients without this complication.Conclusion. 1. Endovascular intervention causes two waves of apoptosis in the postoperative period. The first wave is associated with an increase in Bax protein in the first hours, followed by an increase in PDGF BB on day 7. The second wave of apoptosis is due to a decrease in the inhibitor of apoptosis — sFas for 21 days against the background of the shift of the PDGF BB to the initial level. 2. An increase in Bax protein within the first hours after surgery in the course of PDGF BB growth on day 7 with an increased amount of sFas on day 21 leads and PDGF BB by the end of 1 month leads to the development of restenosis of the intervention area. Рестеноз зоны реконструкции является одним из основных послеоперационных осложнений оперативных вмешательств на артериях нижних конечностей, который развивается в 18–40% случаев и ведет к развитию тромбоза зоны реконструкции и увеличению риска потери конечности до 20–25%. Поиск новых маркеров прогнозирования развития данного осложнения у пациентов с облитерирующим атеросклерозом артерий нижних конечностей (ОААНК) является актуальной проблемой на сегодняшний день.Цель исследования. Оценка динамики маркеров апоптоза и пролиферации клеток в различные сроки после эндоваскулярного вмешательства и их роль в развитии рестеноза зоны реконструкции у пациентов с ОААНК.Материал и методы. В исследование были включены 30 пациентов с ОААНК с III стадией заболевания. После дообследования пациентам было выполнено эндоваскулярное вмешательство на артериях бедренно-подколенного сегмента. В случае развития рестеноза зоны вмешательства пациенты были повторно оперированы. У пациентов до операции в первый час, а затем на 1-е, 7-е, 14-е, 21-е, 30-е сутки после операции была взята венозная кровь для определения маркеров Вах, sFas, PDGF BB с помощь иммуноферментного анализа.Результаты. После эндоваскулярного вмешательства происходил запуск первой волны апоптоза с повышением в крови количества белка Вах (р=0,00003) с 1 по 24 часа с его последующим снижением к 7-м суткам (р=0,0008) по сравнению с количеством на 1-е сутки. Уровень PDGF BB возрастал с 1-х суток после операции (р=0,03) с максимальными значениями на 7-е сутки (р=0,0002) по сравнению с уровнем на 1-е сутки. Затем происходил запуск второй волны с пиковым снижением уровня ингибитора апоптоза sFas на 21-е сутки (р=0,002). У 10 пациентов через 9–12 месяцев развился рестеноз зоны вмешательства с возвратом ишемии конечности. В первый час (р=0,004) у пациентов с рестенозом был статистически значимо повышен уровень белка Вах, при повышении PDGF ВВ на 7-е сутки (р=0,011), а sFas на 21-е сутки (р=0,0001), PDGF ВВ к концу 1-го месяца (р=0,004) по сравнению со значениями у пациентов без данного осложнения.Выводы. 1. Эндоваскулярное вмешательство вызывает две волны апоптоза в послеоперационном периоде. Первая волна связана с повышением содержания белка Вах в первые часы с последующим увеличением PDGF ВВ на 7-е сутки. Вторая волна апоптоза обусловлена снижением уровня ингибитора апоптоза — sFas на 21-е сутки на фоне сдвига PDGF ВВ к исходному уровню. 2. Повышение содержания белка Вах в первые часы после операции на фоне роста PDGF BB на 7-е сутки при увеличенном количестве sFas на 21-е сутки и PDGF ВВ к концу 1-го месяца ведет к развитию рестеноза зоны вмешательства.

The Minimum Stellar Mass in Early Galaxies

The conditions for the fragmentation of the baryonic component during merging of dark matter halos in the early Universe are studied. We assume that the baryonic component undergoes a shock compression. The characteristic masses of protostellar molecular clouds and the minimum masses of protostars formed in these clouds decrease with increasing halo mass. This may indicate that the initial stellar mass function in more massive galaxies was shifted towards lower masses during the initial stages of their formation. This would result in an increase of the number of stars per unit halo mass, i.e., the efficiency of star formation.Comment: 18 pages, 7 figure

The NICMOS Snapshot Survey of nearby Galaxies

We present ``snapshot'' observations with the NearInfrared Camera and MultiObject Spectrometer (NICMOS) on board the Hubble Space Telescope (HST) of 94 nearby galaxies from the Revised Shapley Ames Catalog. Images with 0.2 as resolution were obtained in two filters, a broad-band continuum filter (F160W, roughly equivalent to the H-band) and a narrow band filter centered on the Paschen alpha line (F187N or F190N, depending on the galaxy redshift) with the 51x51 as field of view of the NICMOS camera 3. A first-order continuum subtraction is performed, and the resulting line maps and integrated Paschen alpha line fluxes are presented. A statistical analysis indicates that the average Paschen alpha surface brightness {\bf in the central regions} is highest in early-type (Sa-Sb) spirals.Comment: Original contained error in flux calibration. Table 1 now has correct Paschen Alpha fluxes. 14 pages LaTeX with JPEG and PS figures. Also available at http://icarus.stsci.edu/~boeker/publications.htm