Striations in the Taurus molecular cloud: Kelvin-Helmholtz instability or MHD waves?

The origin of striations aligned along the local magnetic field direction in the translucent envelope of the Taurus molecular cloud is examined with new observations of 12CO and 13CO J=2-1 emission obtained with the 10~m submillimeter telescope of the Arizona Radio Observatory. These data identify a periodic pattern of excess blue and redshifted emission that is responsible for the striations. For both 12CO and 13CO, spatial variations of the J=2-1 to J=1-0 line ratio are small and are not spatially correlated with the striation locations. A medium comprised of unresolved CO emitting substructures (cells) with a beam area filling factor less than unity at any velocity is required to explain the average line ratios and brightness temperatures. We propose that the striations result from the modulation of velocities and the beam filling factor of the cells as a result of either the Kelvin-Helmholtz instability or magnetosonic waves propagating through the envelope of the Taurus molecular cloud. Both processes are likely common features in molecular clouds that are sub-Alfvenic and may explain low column density, cirrus-like features similarly aligned with the magnetic field observed throughout the interstellar medium in far-infrared surveys of dust emission.Comment: 11 pages, 4 figures. Accepted for publication in MNRA

The effect of vitamin E on mast cells in small intestine of broilers under heat stress

ΔΕΝ ΥΠΑΡΧΕΙ ΕΛΛΗΝΙΚΗ ΠΕΡΙΛΗΨΗThe aim of this study is to identify the effect of vitamin E (DL-α-tocopherol acetate) (300 IU/kg) on mast cells in the small intestine (duodenum, jejunum and ileum) under heat stress. In the study, 42 one-day-old Ross 308 male broiler chicks were used. The chicks were randomly separated into 3 groups as follows; control (22±2°C), heat stress (35°C, 5 hours/per day) and vitamin E (300 IU/kg/per day) + heat stress (35°C, 5 hours/per day). The applications of heat stress and vitamin E began on the fifteenth day and ended on the thirty-fifth day. Tissue samples were taken from animals in each group of four and five-week-old chickens. Tissue samples were fixed in BLA (Basic Lead Acetate) solution. The sections were stained with toluidine blue (TB) (pH 0.5) and alcian blue-critical electrolyte concentration (AB-CEC) (pH 5.8, 0.3 M MgCl2) / Safranin O (SO) (pH 1.0) combined method. It was determined that increasing of the exposure duration to heat stress increased the number of mast cells in the small intestine of the boilers. Also, it was revealed that vitamin E reduced mast cell population under heat stress. Consequently, heat stress may play a role in the pathogenesis of small intestine-associated with disorders and the supplementation of vitamin E can contribute to regulate small intestine functions of broilers by decreasing mast cell proliferation and activation under heat stress

Warm and cold gas in low-mass protostars : Herschel Space Observatory and ground-based surveys

The primary focus of this thesis is the formation of low-mass protostars, specifically the earliest deeply embedded phase, when material from the collapsing envelope is still accreted onto the growing young star. Rotational transitions of CO and O2 data are obtained by the Herschel Space Observatory key projects, WISH and HOP, together with ground-based observations from APEX and the JCMT. We have found that CO and its isotopologs have different line profiles tracing different materials in the protostellar regions. Our new high-J rotational transitons of CO is key to characterize the warmer parts of the protostellar envelope and quantify feedback of the protostars on their surroundings in terms of shocks, ultraviolet (UV) heating, photodissociation, and outflow dispersal. Radiative transfer modeling was performed to determine the CO abundance structure in the envelope, showing evidence for significant freeze-out in the coldest regions in the parts of the envelope where the temperature exceeds 25 K. A tentative detection of O2 is reported toward the source position of a protostar, which originates from the surrounding cloud. These kind of detailed studies of the physical and chemical structure of low-mass protostars are important for a complete understanding of the evolution of young stellar objects (YSOs).Interstellar matter and star formatio

Seasonal variations in phytoplankton composition and biomass in a small lowland river-lake system (Melen River, Turkey)

WOS: 000294698400012A series of studies were carried out to determine the succession and phytoplankton community of the Melen River in the Western Black Sea region of Turkey. The study was conducted at 6 stations at monthly intervals between May 2003 and April 2004. It was observed that the abundance and biovolume of phytoplankton were low in winter, though higher values were recorded in late spring and summer. Among the values noted, the spring peak was 534.38 x 10(5) ind. L-1 and 7384.8 mm(3) L-1 belonging to Peridinium sp. The most common diatom, Cyclostephanos dubius, was favoured by low discharge at stations 1 and 2 in the early summer (214.29 x 10(5) in L-1 and 9.84 x 10(5) in L-1), respectively. Chlorophyll-a concentrations were between 0.86 and 64.2 mu g L-1. A total of 135 taxa belonging to Cyanophyta, Bacillariophyta, Chlorophyta, Dinophyta, Euglenophyta, Heterokontophyta, Streptophyta, and Xanthophyta were identified. The total biomass of the stations 1 and 2 was mainly characterised by Dinophyta and at other stations by Bacillariophyta. Five major genera (Peridinium, Ceratium, Phacus, Cyclostephanos, and Melosira) accounted for over 70% of the total phytoplankton abundance. Phytoplankton abundance was significant and positively correlated with Chl-a and temperature (r = 0.57 and r = 0.78, respectively P < 0.05). Species richness and diversity indices increased gradually throughout the course of the river.Gazi University, Scientific Projects Research ManagementGazi UniversityWe would like to thank Gazi University, Scientific Projects Research Management for financing this research and also the General Directorate of State Hydraulic Works (DSI) for analysing the physical and chemical parameters of the Melen River

The hot core towards the intermediate mass protostar NGC7129 FIRS 2: Chemical similarities with Orion KL

NGC 7129 FIRS 2 (hereafter FIRS 2) is an intermediate-mass (2 to 8 Msun) protostar located at a distance of 1250 pc. High spatial resolution observations are required to resolve the hot core at its center. We present a molecular survey from 218200 MHz to 221800 MHz carried out with the IRAM Plateau de Bure Interferometer. These observations were complemented with a long integration single-dish spectrum taken with the IRAM 30m telescope. We used a Local Thermodynamic Equilibrium (LTE) single temperature code to model the whole dataset. The interferometric spectrum is crowded with a total of ~300 lines from which a few dozens remain unidentified yet. The spectrum has been modeled with a total of 20 species and their isomers, isotopologues and deuterated compounds. Complex molecules like methyl formate (CH3OCHO), ethanol (CH3CH2OH), glycolaldehyde (CH2OHCHO), acetone (CH3COCH3), dimethyl ether (CH3OCH3), ethyl cyanide (CH3CH2CN) and the aGg' conformer of ethylene glycol (aGg'-(CH2OH)_2) are among the detected species. The detection of vibrationally excited lines of CH3CN, CH3OCHO, CH3OH, OCS, HC3N and CH3CHO proves the existence of gas and dust at high temperatures. In fact, the gas kinetic temperature estimated from the vibrational lines of CH3CN, ~405 K, is similar to that measured in massive hot cores. Our data allow an extensive comparison of the chemistry in FIRS~2 and the Orion hot core. We find a quite similar chemistry in FIRS 2 and Orion. Most of the studied fractional molecular abundances agree within a factor of 5. Larger differences are only found for the deuterated compounds D2CO and CH2DOH and a few molecules (CH3CH2CN, SO2, HNCO and CH3CHO). Since the physical conditions are similar in both hot cores, only different initial conditions (warmer pre-collapse phase in the case of Orion) and/or different crossing time of the gas in the hot core can explain this behavior.Comment: 30 pages, 9 figure

Gas generator pressure control in throttleable ducted rockets: A classical and adaptive control approach

This paper describes the control of gas generator pressure in throttleable ducted rockets using nonlinear adaptive control as well as classical control approaches. Simulation results using the full nonlinear and time-varying dynamics of the gas generator are reported in both classical controller and adaptive controller cases. "Closed-loop Reference Model" structure is used together with the adaptive controller to improve transient response. Controllers are simulated to test their robustness by introducing uncertinities, disturbances and noise to the system. Cold Air Test Plant (CATP) is used as the test facility to compare the controllers and validate the results from simulations. Moreover, damping effect of CRM to oscillations in adaptive controller case is observed in CATP tests. © 2015 American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved

Pressure control of cold air testing plant with delay resistant closed-loop reference model adaptive control

This paper deals with the control problem of obtaining desired gas pressure inside a control volume with constant inlet mass flow rate of cold air. Cold air flow system dynamics is similar to that of a gas generator of a throttleable ducted rocket, which sends fuel in gaseous form, with metal additives, to ram combuster with desired amount of mass flow rate to obtain variable thrust. Being able to control gas pressure in cold air flow system is a milestone towards obtaining a fully developed throttleable ducted rocket gas generator controller. In this study, a detailed modeling of the cold air test plant together with a delay resistant closed-loop reference model adaptive controller design is presented. The proposed controller is compared with several other alternatives including a classical proportional-integral controller, model reference adaptive controller and a closed- loop reference model adaptive controller that does not have explicit delay compensation. Simulation results verifying the performance improvement of the delay resistant controller over the alternatives are presented. © 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved

Water distribution in shocked regions of the NGC1333-IRAS4A protostellar outflow

We present the study of the H2O spatial distribution at two bright shocked regions along IRAS4A, one of the strongest H2O emitters among the Class 0 outflows. We obtained Herschel-PACS maps of the IRAS4A outflow and HIFI observations of two shocked positions. The largest HIFI beam of 38 arcsec at 557 GHz was mapped in several key water lines with different upper energy levels, to reveal possible spatial variations of the line profiles. We detect four H2O lines and CO (16-15) at the two selected positions. In addition, transitions from related outflow and envelope tracers are detected. Different gas components associated with the shock are identified in the H2O emission. In particular, at the head of the red lobe of the outflow, two distinct gas components with different excitation conditions are distinguished in the HIFI emission maps: a compact component, detected in the ground-state water lines, and a more extended one. Assuming that these two components correspond to two different temperature components observed in previous H2O and CO studies, the excitation analysis of the H2O emission suggests that the compact (about 3 arcsec) component is associated with a hot (T~1000 K) gas with densities ~(1-4)x10^5 cm^{-3}, whereas the extended one (10-17 arcsec) traces a warm (T~300-500 K) and dense gas (~(3-5)x10^7 cm^{-3}). Finally, using the CO (16-15) emission observed at R2, we estimate the H2O/H2 abundance of the warm and hot components to be (7-10)x10^{-7} and (3-7)x10^{-5}. Our data allowed us, for the first time, to resolve spatially the two temperature components previously observed with HIFI and PACS. We propose that the compact hot component may be associated with the jet that impacts the surrounding material, whereas the warm, dense, and extended component originates from the compression of the ambient gas by the propagating flow.Comment: 13 pages, 11 figures. Accepted for publication in Astronomy and Astrophysic

Effect of anisotropy and destructuration on behavior of Haarajoki test embankment

This paper investigates the influence of anisotropy and destructuration on the behavior of Haarajoki test embankment, which was built by the Finnish National Road Administration as a noise barrier in 1997 on a soft clay deposit. Half of the embankment is constructed on an area improved with prefabricated vertical drains, while the other half is constructed on the natural deposit without any ground improvement. The construction and consolidation of the embankment is analyzed with the finite-element method using three different constitutive models to represent the soft clay. Two recently proposed constitutive models, namely S-CLAY1 which accounts for initial and plastic strain induced anisotropy, and its extension, called S-CLAY1S which accounts, additionally, for interparticle bonding and degradation of bonds, were used in the analysis. For comparison, the problem is also analyzed with the isotropic modified cam clay model. The results of the numerical analyses are compared with the field measurements. The simulations reveal the influence that anisotropy and destructuration have on the behavior of an embankment on soft clay