1,655 research outputs found
An HI interstellar bubble surrounding WR85 and RCW118
We analyze the distribution of the interstellar matter in the environs of the
Wolf-Rayet star LSS3982 (= WR85, WN6+OB?) linked to the optical ring nebula
RCW118. Our study is based on neutral hydrogen 21cm-line data belonging to the
Southern Galactic Plane Survey (SGPS).
The analysis of the HI data allowed the identification of a neutral hydrogen
interstellar bubble related to WR 85 and the 25' diameter ring nebula RCW118.
The HI bubble was detected at a systemic velocity of -21.5 km/s, corresponding
to a kinematical distance of 2.8+/-1.1 kpc, compatible with the stellar
distance. The neutral stucture is about 25' in radius or 21+/-8 pc, and is
expanding at 9+/-2 km/s. The associated ionized and neutral masses amount to
3000 Mo. The CO emission distribution depicts a region lacking CO coincident in
position and velocity with the HI structure. The 9'.3 diameter inner optical
nebula appears to be related to the approaching part of the neutral atomic
shell. The HI void and shell are the neutral gas counterparts of the optical
bubble and have very probably originated in the action of the strong stellar
wind of the central star during the O-type and WR phases on the surrounding
interstellar medium. The HI bubble appears to be in the momentun conserving
stage.Comment: 9 pages, 7 figures, accepted in MNRA
Estimation of genetic parameters for height using spatial analysis in Tsuga heterophylla full-sibling family trials in British Columbia
Non-spatial and spatial analyses were carried out to study the effects on genetic parameters in ten-year height growth data across two series of 10 large second-generation full-sib progeny trials of western hemlock [Tsuga heterophylla (Raf.) Sarg.] in British Columbia. To account for different and complex patterns of environmental heterogeneity, spatial single trial analyses were conducted using an individual-tree mixed model with a two-dimensional smoothing surface with tensor product of B-spline bases. The spatial single trial analysis, in all cases, showed sizeable lower Deviance Information Criterion values relative to the non-spatial analysis. Also, fitting a surface displayed a consistent reduction in the posterior mean as well as a decrease in the standard deviations of error variance, no appreciable changes in the additive variance, an increase of individual narrow-sense heritability, and accuracy of breeding values. The tensor product of cubic basis functions of B-spline based on a mixed model framework does provide a useful new alternative to model different and complex patterns of spatial variability within sites in forest genetic trials. Individual narrow-sense heritabilities estimates from the spatial single trial analyses were low (average of 0.06), but typical of this species. Estimated dominance relative to additive variances were unstable across sites (from 0.00 to 1.59). The implications of these estimations will be discussed with respect to the western hemlock genetic improvement program in British Columbia.Fil: Cappa, Eduardo Pablo. British Columbia Ministry of Forests and Range; Canadá. University of British Columbia; Canadá. Instituto Nacional de TecnologÃa Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Recursos Biológicos; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Yanchuk, A. D.. British Columbia Ministry of Forests and Range; CanadáFil: Cartwright, C. V.. British Columbia Ministry of Forests and Range; Canad
Molecular gas associated with IRAS 10361-5830
We analyze the distribution of the molecular gas and the dust in the
molecular clump linked to IRAS 10361-5830, located in the environs of the
bubble-shaped HII region Gum 31 in the Carina region, with the aim of
determining the main parameters of the associated material and investigating
the evolutionary state of the young stellar objects identified there.
Using the APEX telescope, we mapped the molecular emission in the J=3-2
transition of three CO isotopologues, 12CO, 13CO and C18O, over a 1.5' x 1.5'
region around the IRAS position. We also observed the high density tracers CS
and HCO+ toward the source. The cold dust distribution was analyzed using
submillimeter continuum data at 870 \mu\ obtained with the APEX telescope.
Complementary IR and radio data at different wavelengths were used to complete
the study of the ISM.
The molecular gas distribution reveals a cavity and a shell-like structure of
~ 0.32 pc in radius centered at the position of the IRAS source, with some
young stellar objects (YSOs) projected onto the cavity. The total molecular
mass in the shell and the mean H volume density are ~ 40 solar masses and
~(1-2) x 10 cm, respectively. The cold dust counterpart of the
molecular shell has been detected in the far-IR at 870 \mu\ and in Herschel
data at 350 \mu. Weak extended emission at 24 \mu\ from warm dust is projected
onto the cavity, as well as weak radio continuum emission.
A comparison of the distribution of cold and warm dust, and molecular and
ionized gas allows us to conclude that a compact HII region has developed in
the molecular clump, indicating that this is an area of recent massive star
formation. Probable exciting sources capable of creating the compact HII region
are investigated. The 2MASS source 10380461-5846233 (MSX G286.3773-00.2563)
seems to be responsible for the formation of the HII region.Comment: Accepted in A&A. 11 pages, 10 Postscript figure
Unveiling the molecular environment of the ring nebula RCW 78
We present a study of the ionized, neutral atomic, and molecular gas
associated with the ring nebula RCW 78 around the WR star HD 117688 (= WR 55).
We based our study on CO observations carried out with the SEST and NANTEN
telescopes. We report the detection of molecular gas with velocities in the
range -56 to -33 km/s. The CO emission is mainly connected to the western
section, with a total molecular mass of 1.3 x 10^5 solar masses. The analysis
of the HI gas distribution reveals the HI envelope of the molecular cloud,
while the radio continuum emission shows a ring-like structure, which is the
radio counterpart of the optical nebula. The gas distribution is compatible
with the western section of RCW 78 having originated in the photodissociation
and ionization of the molecular gas by HD 117688, and with the action of the
stellar winds of the WR star. A number of infrared point sources classified as
YSO candidates showed that stellar formation activity is present in the
molecular gas linked to the nebula. The fact that the expansion of the bubble
have triggered star formation in this region can not be discarded.Comment: 15 pages, 11 Postscript figures, to be published in A&
870 micron continuum observations of the bubble-shaped nebula Gum 31
We are presenting here a study of the cold dust in the infrared ring nebula
Gum 31. We aim at deriving the physical properties of the molecular gas and
dust associated with the nebula, and investigating its correlation with the
star formation in the region, that was probably triggered by the expansion of
the ionization front. We use 870 micron data obtained with LABOCA to map the
dust emission. The obtained LABOCA image was compared to archival IR,radio
continuum, and optical images. The 870 micron emission follows the 8 micron
(Spitzer), 250 micron, and 500 micron (Herschel) emission distributions showing
the classical morphology of a spherical shell. We use the 870 micron and 250
micron images to identify 60 dust clumps in the collected layers of molecular
gas using the Gaussclumps algorithm. The clumps have effective deconvolved
radii between 0.16 pc and 1.35 pc, masses between 70 Mo and 2800 Mo, and volume
densities between 1.1x10^3 cm^-3 and 2.04x10^5 cm^-3. The total mass of the
clumps is 37600 Mo. The dust temperature of the clumps is in the range from 21
K to 32 K, while inside the HII region reaches ~ 40 K. The clump mass
distribution is well-fitted by a power law dN/dlog(M/Mo) proportional to
M^(-alpha), with alpha=0.93+/-0.28. The slope differs from those obtained for
the stellar IMF in the solar neighborhood, suggesting that the clumps are not
direct progenitors of single stars/protostars. The mass-radius relationship for
the 41 clumps detected in the 870 microns emission shows that only 37% of them
lie in or above the high-mass star formation threshold, most of them having
candidate YSOs projected inside. A comparison of the dynamical age of the HII
region with the fragmentation time, allowed us to conclude that the collect and
collapse mechanism may be important for the star formation at the edge of Gum
31, although other processes may also be acting.Comment: 15 pages, 10 figures. Accepted for publication in A&
Molecular gas and star formation towards the IR dust bubble S24 and its environs
We present a multi-wavelength analysis of the infrared dust bubble S24, and
its environs, with the aim of investigating the characteristics of the
molecular gas and the interstellar dust linked to them, and analyzing the
evolutionary status of the young stellar objects (YSOs) identified there. Using
APEX data, we mapped the molecular emission in the CO(2-1), CO(2-1),
CO(2-1), and CO(3-2) lines in a region of about 5'x 5' in size
around the bubble. The cold dust distribution was analyzed using ATLASGAL and
Herschel images. Complementary IR and radio data were also used.The molecular
gas linked to the S24 bubble, G341.220-0.213, and G341.217-0.237 has velocities
between -48.0 km sec and -40.0 km sec. The gas distribution
reveals a shell-like molecular structure of 0.8 pc in radius bordering
the bubble. A cold dust counterpart of the shell is detected in the LABOCA and
Herschel images.The presence of extended emission at 24 m and radio
continuum emission inside the bubble indicates that the bubble is a compact HII
region. Part of the molecular gas bordering S24 coincides with the extended
infrared dust cloud SDC341.194-0.221. A cold molecular clump is present at the
interface between S24 and G341.217-0.237. As regards G341.220-0.213, the
presence of an arc-like molecular structure at the northern and eastern
sections of this IR source indicates that G341.220-0.213 is interacting with
the molecular gas. Several YSO candidates are found to be linked to the IR
extended sources, thus confirming their nature as active star-forming regions.
The total gas mass in the region and the H ambient density amount to 10300
M and 5900 cm, indicating that G341.220-0.213, G341.217-0.237,
and the S24 HII region are evolving in a high density medium. A triggering star
formation scenario is also investigated.Comment: 17 pages, 16 figures. Submitted to A&A. Revised according to the
referee repor
Zymomonas mobilis in Bread Dough: Characterization of Dough Leavening Performance in Presence of Sucrose
Zymomonas mobilis, because of its fermentative metabolism, has potential food applications in the development of leavened baked goods consumable by people with adverse responses to Saccharomyces cerevisiae. Since Z. mobilis is not able to utilize maltose present in flour, the effect of sucrose addition (2.5 g/100 g flour) on bread dough leavening properties was studied. For comparison purposes, leavening performances of S. cerevisiae with and without sucrose were also investigated. Doughs leavened by Z. mobilis without sucrose addition showed the lowest height development (14.95 +/- 0.21 mm) and CO2 production (855 +/- 136 mL). When sucrose was added, fermentative performances of Z. mobilis significantly (p < 0.05) improved (+80% and +85% of gas production and retention, respectively), with a dough maximum height 2.6 times higher, results indicating that Z. mobilis with sucrose can be leavened in shorter time with respect to the sample without addition. S. cerevisiae did not benefit the sucrose addition in terms of CO2 production and retention, even if lag leavening time was significantly (p < 0.05) shorter (about the half) and time of porosity appearance significantly (p < 0.05) longer (about 26%) with respect to S. cerevisiae alone. Results demonstrate that in the presence of sucrose, Z. mobilis can efficiently leaven a bread dough, thus providing innovation possibilities in the area of yeast-free leavened products
Influence of Cooking Conditions on Nutritional Properties and Sensory Characteristics Interpreted by E-Senses: Case-Study on Selected Vegetables
This study investigates the effects of three cooking methods (boiling, steaming and microwaving) on the nutritional and physical properties of cauliflowers, carrots and sweet potatoes; e-senses were applied to interpret the sensory characteristics according to physico-chemical aspects. The nutritional quality was evaluated by determining the concentrations of key components and the antioxidant activity; e-sense data, combined with texture parameters, were processed by a principal component analysis. The cooking method and time significantly influenced the quality of the three products. Boiling, which detrimentally affected ascorbic acid, total phenolic concentration and antioxidant activity, enhanced carotene accessibility. Steaming produced losses in ascorbic acid, increasing total phenolics and carotenoids. Microwaving resulted in minor changes in ascorbic acid concentrations, preserved carotenoids and increased total phenolics. The nutritional quality was better preserved or enhanced using shorter cooking times. The elaboration of the data collected by the e-senses showed a clear evolution according to the cooking method and time. The results helped to determine the cooking method that best preserves the nutritional properties of the vegetables, highlighting the applicability of rapid instrumental methods to interpret the evolution of sensory characteristics
GLUTEN-FREE BREAD: OPTIMIZATION OF FORMULATION AND PROCESS CONDITIONS
The aim of this PhD research project was to identify the formulations and to define the process conditions that most influence the quality and the shelf-life of gluten-free (GF) bread. Raw materials that are commonly used in GF bread production were first characterized, in particular as regards the rheological properties of different starchy gels during a short term ageing. Waxy rice flour (WRF) and rice bran (RB), at 25% and 50% substitution level, came out to be very effective in reducing gel stiffness and storage modulus (G\u2019) of the mixtures containing corn starch (CS) or rice flour (RF). The effects of High Hydrostatic Pressure treatments on CS, RF and WRF were also investigated. A partial gelatinization of RF treated at 400MPa and 600MPa was evidenced by the viscoamylographic test and the formation of a more compact structure and a higher water retention capacity were registered for CS treated at 600MPa. The effect of Psyllium (Psy) and sugar beet (SB) fibers on dough and bread properties was also evaluated. The presence of 2.5% Psy generally determined an increase of dough height and CO2 production during leavening. Psy fiber also showed an anti-staling effect, higher than SB fiber. Taking into account all these results, a GF sourdough (SD) containing selected bacteria and yeasts (Lactobacillus sanfranciscensis and Candida humilis) was developed; then it was constantly refreshed and monitored in terms of number and type of microorganisms, capability to produce/retain CO2 and pH variations. When a stable microbial association was achieved, as well as constant SD properties, some breadmaking trials were performed. GF SD combined with compressed yeast resulted an excellent opportunity to improve GF bread quality and shelf-life
Multifrequency study of the ring nebula SG13
We investigate the morphology and kinematics of the interstellar medium in
the environs of the open cluster Mrk50, which includes the Wolf-Rayet star
WR157 and a number of early B-type stars. The analysis was performed using
radio continuum images at 408 and 1420 MHz, and HI 21cm line data taken from
the Canadian Galactic Plane Survey, molecular observations of the 12CO (J=1-0)
line at 115 GHz from the Five College Radio Astronomy Observatory and available
mid and far IR observations obtained with the MSX and IRAS satellites,
respectively. This study allowed identification of the radio continuum and
molecular counterpart of the ring nebula SG13, while no neutral atomic
structure was found to be associated. The nebula is also detected in images in
the mid and far infrared, showing the existence of dust well mixed with the
ionized gas. We estimate the main physical parameters of the material linked to
the nebula. The interstellar gas distribution in the environs of Mrk50 is
compatible with a stellar wind bubble created by the mass loss from WR157. The
distribution of young stellar object (YSO) candidates in the region shows that
stellar formation activity may be present in the molecular shell that encircles
the ring nebula.Comment: Accepted for publication in MNRAS, 13 pages, 11 figure
- …