173 research outputs found
Statistical Analysis of Water Masers in Star-Forming Regions: Cepheus A and W75 N
We have done a statistical analysis of Very Long Baseline Array (VLBA) data
of water masers in the star-forming regions (SFRs) Cepheus A and W75 N, using
correlation functions to study the spatial clustering and Doppler-velocity
distribution of these masers. Two-point spatial correlation functions show a
characteristic scale size for clusters of water maser spots < or ~1 AU, similar
to the values found in other SFRs. This suggests that the scale for water maser
excitation tends to be < or ~1 AU. Velocity correlation functions show
power-law dependences with indices that can be explained by regular velocity
fields, such as expansion and/or rotation. These velocity fields are similar to
those indicated by the water maser proper-motion measurements; therefore, the
velocity correlation functions appear to reveal the organized motion of water
maser spots on scales larger than 1 AU.Comment: 16 pages, 8 figures, and 3 tables. Accepted by The Astrophysical
Journa
Ethnic Minority Children’s Active Commuting to School and Association with Physical Activity and Pedestrian Safety Behaviors
Background: Children\u27s active commuting to school, i.e. walking or cycling to school, was associated with greater moderate-to-vigorous physical activity, although studies among ethnic minorities are sparse. Objectives: Among a low-income, ethnic minority sample of fourth grade students from eight public schools, we examined (1) correlates of active commuting to school and (2) the relationship between active commuting to school and moderate-to-vigorous physical activity. Methods: We conducted a cross-sectional analysis of baseline measurements from a sample of participants (n=149) aged 9-12 years from a walk to school intervention study in Houston, Texas. The primary outcome was the weekly rate of active commuting to school. Daily moderate-to-vigorous physical activity, measured by accelerometers, was a secondary outcome. Child self-efficacy (alpha=0.75), parent self-efficacy (alpha=0.88), and parent outcome expectations (alpha=0.78) were independent variables. Participant characteristics (age, gender, race/ethnicity, distance from home to school, acculturation, and BMI percentile) were independent sociodemographic variables. We used mixed-model regression analyses to account for clustering by school and a stepwise procedure with backward elimination of non-significant interactions and covariates to identify significant moderators and predictors. School-level observations of student pedestrians were assessed and compared using chi-square tests of independence. Results: Among our sample, which was 61.7% Latino, the overall rate of active commuting to school was 43%. In the mixed model for active commuting to school, parent self-efficacy (std. beta = 0.18, p=0.018) and age (std. beta = 0.18, p=0.018) were positively related. Latino students had lower rates of active commuting to school than non-Latinos ( 16.5%, p=0.040). Distance from home to school was inversely related to active commuting to school (std. beta = 0.29, p\u3c0.001). In the mixed model for moderate-to-vigorous physical activity, active commuting to school was positively associated (std. beta = 0.31, p \u3c0.001). Among the Latino subsample, child acculturation was negatively associated with active commuting to school (std. beta = -0.23, p=0.01). With regard to school-level pedestrian safety observations, 37% of students stopped at the curb and 2.6% looked left-right-left before crossing the street. Conclusion: Although still below national goals, the rate of active commuting was relatively high, while the rate of some pedestrian safety behaviors was low among this low-income, ethnic minority population. Programs and policies to encourage safe active commuting to school are warranted and should consider the influence of parents, acculturation, and ethnicity
Kinematics of the H2O masers at the centre of the PN K3-35
We have studied the kinematics traced by the water masers located at the
centre of the planetary nebula (PN) K3-35, using data from previous Very Large
Array (VLA) observations. An analysis of the spatial distribution and
line-of-sight velocities of the maser spots allows us to identify typical
patterns of a rotating and expanding ring in the position-velocity diagrams,
according to our kinematical model. We find that the distribution of the masers
is compatible with tracing a circular ring with a ~0.021 arcsec (~100 AU)
radius, observed with an inclination angle with respect to the line of sight of
55 degrees. We derive expansion and rotation velocities of 1.4 and 3.1 km/s,
respectively. The orientation of the ring projected on the plane of the sky, at
PA 158 degrees, is almost orthogonal to the direction of the innermost region
of the jet observed in K3-35, suggesting the presence of a disc or torus that
may be related to the collimation of the outflow.Comment: 7 pages, 4 figures, 2 tables. Accepted by MNRA
SEED ABORTION IN NATURALLY POLLINATED FLOWERS OF MEXICAN NATIVE PLANTS OF \u3ci\u3ePhaseolus coccineus\u3c/i\u3e L.
INTRODUCTION: Phaseolus coccineus L. plants require insects or hummingbirds to pollinate their flowers and set pods. The number of pods that can be produced by a plant is set by the number of flowers while the number of seeds is set by the number of ovules within the flowers (Stephenson, 1981). The arrest of the development of the seed after its partial differentiation, - seed abortion-, also determines the number of seeds per plant. The objective of this work is to determine the percentage of seed abortion per plant of two Mexican native varieties of Phaseolus coccineus L.
MATERIALS AND METHODS: Two varieties (accessions no. 8446 and 8448) were selected from the Mexican bean collection of the Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP). Seeds harvested in November 2014, were sown in pots on April 5, 2015 and seedlings were transplanted outdoors on April 20, distant 2 meter apart. The plants were of indeterminate growth, climbing type. There were a natural occurrence of bees, bumblebees, and hummingbirds pollinators during the flowering period. The experiment was a complete randomized design, with two treatments (varieties), five replications (one plant per replication) and five sampling dates (Oct. 14, Nov. 4, Nov. 25, Dec. 9, and Dec. 16). At each sampling date, the mature pods per plant were harvested and opened. The following data were registered: a) the number of normal seeds per pod; b) the number of aborted seeds per pod including early abortions detected with the stereoscopic microscope. The sum of (a) and (b) = c, which represented the potential number of seeds per POD in each sampling date. It was evident at this point that practically all the pods in a variety had the same potential number of seeds. Therefore, the potential number of seeds per PLANT in each sampling date represented by Y = c*n, where n represents the number of pods per plant in each sampling date. Following when applicable, the similar procedure for seed abortion: Z = total number of aborted seeds per plant in each sampling date. The percentage of seed abortion (Z/Y)*100 (total number of aborted seeds per plant in each sampling date/potential number of seeds per plant in each sampling date)
SEED ABORTION IN NATURALLY POLLINATED FLOWERS OF MEXICAN NATIVE PLANTS OF \u3ci\u3ePhaseolus coccineus\u3c/i\u3e L.
INTRODUCTION: Phaseolus coccineus L. plants require insects or hummingbirds to pollinate their flowers and set pods. The number of pods that can be produced by a plant is set by the number of flowers while the number of seeds is set by the number of ovules within the flowers (Stephenson, 1981). The arrest of the development of the seed after its partial differentiation, - seed abortion-, also determines the number of seeds per plant. The objective of this work is to determine the percentage of seed abortion per plant of two Mexican native varieties of Phaseolus coccineus L.
MATERIALS AND METHODS: Two varieties (accessions no. 8446 and 8448) were selected from the Mexican bean collection of the Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP). Seeds harvested in November 2014, were sown in pots on April 5, 2015 and seedlings were transplanted outdoors on April 20, distant 2 meter apart. The plants were of indeterminate growth, climbing type. There were a natural occurrence of bees, bumblebees, and hummingbirds pollinators during the flowering period. The experiment was a complete randomized design, with two treatments (varieties), five replications (one plant per replication) and five sampling dates (Oct. 14, Nov. 4, Nov. 25, Dec. 9, and Dec. 16). At each sampling date, the mature pods per plant were harvested and opened. The following data were registered: a) the number of normal seeds per pod; b) the number of aborted seeds per pod including early abortions detected with the stereoscopic microscope. The sum of (a) and (b) = c, which represented the potential number of seeds per POD in each sampling date. It was evident at this point that practically all the pods in a variety had the same potential number of seeds. Therefore, the potential number of seeds per PLANT in each sampling date represented by Y = c*n, where n represents the number of pods per plant in each sampling date. Following when applicable, the similar procedure for seed abortion: Z = total number of aborted seeds per plant in each sampling date. The percentage of seed abortion (Z/Y)*100 (total number of aborted seeds per plant in each sampling date/potential number of seeds per plant in each sampling date)
ALMA sub-mm maser and dust distribution of VY Canis Majoris
Cool, evolved stars have copious, enriched winds. The structure of these
winds and the way they are accelerated is not well known. We need to improve
our understanding by studying the dynamics from the pulsating stellar surface
to about 10 stellar radii, where radiation pressure on dust is fully effective.
Some red supergiants have highly asymmetric nebulae, implicating additional
forces. We retrieved ALMA Science Verification data providing images of sub-mm
line and continuum emission from VY CMa. This enables us to locate water masers
with milli-arcsec precision and resolve the dusty continuum. The 658-, 321- and
325-GHz masers lie in irregular, thick shells at increasing distances from the
centre of expansion. For the first time this is confirmed as the stellar
position, coinciding with a compact peak offset to the NW of the brightest
continuum emission. The maser shells (and dust formation zone) overlap but
avoid each other on tens-au scales. Their distribution is broadly consistent
with excitation models but the conditions and kinematics appear to be
complicated by wind collisions, clumping and asymmetries.Comment: Letter 4 pages, 5 figures plus appendix with 3 figures. Accepted by
Astronomy and Astrophysics Letter
Refractory hyperactive bladder treated with sacral neuromodulator: case report and literature review
The overactive bladder syndrome is a chronic medical condition that affects the quality of life of patients whether men or women, has a prevalence of 16.5%, however, it is known to increase with age, affecting up to 25% of women older than 65 years and up to 80% in the elderly. More than 90% of cases have no apparent cause. The OAB (Overactive Bladder) It is a condition with characteristic symptoms of urinary urgency, usually accompanied by frequency and nocturia, with or without urge incontinence, in the absence of urinary tract infection or other obvious pathology. The different therapeutic steps are not always sufficient to restore the quality of life
Discrete Source Survey of 6 GHz OH emission from PNe & pPNe and first 6 GHz images of K 3-35
The aim of this study is to investigate the physical properties of molecular
envelopes of planetary nebulae in their earliest stages of evolution. Using the
100m telescope at Effelsberg, we have undertaken a high sensitivity discrete
source survey for the first excited state of OH maser emission (J=5/2, 2PI3/2
at 6GHz) in the direction of planetary and proto-planetary nebulae exhibiting
18cm OH emission (main and/or satellite lines), and we further validate our
detections using the Nan\c{c}ay radio telescope at 1.6-1.7GHz and MERLIN
interferometer at 1.6-1.7 and 6GHz. Two sources have been detected at 6035MHz
(5cm), both of them are young (or very young) planetary nebulae. The first one
is a confirmation of the detection of a weak 6035MHz line in Vy 2-2. The second
one is a new detection, in K 3-35, which was already known to be an exceptional
late type star because it exhibits 1720MHz OH emission. The detection of
6035MHz OH maser emission is confirmed by subsequent observations made with the
MERLIN interferometer. These lines are very rarely found in evolved stars. The
1612MHz masers surround but are offset from the 1720 and 6035MHz masers which
in turn lie close to a compact 22GHz continuum source embedded in the optical
nebula.Comment: 9 pages, 7 figures, published in A&
FLASHING: New high-velocity HO masers in IRAS 182860959
We discovered new high-velocity components of HO maser emission in one of
the "water fountain" sources, IRAS~182860959, which has been monitored using
the Nobeyama 45 m telescope in the new FLASHING (Finest Legacy Acquisitions of
SiO- and HO-maser Ignitions by Nobeyama Generation) project since 2018
December. The maser spectra show new, extremely high expansion velocities
(200~km~s projected in the line of sight) components, some of which
are located symmetrically in the spectrum with respect to the systemic
velocity. They were also mapped with KaVA (KVN and VERA Combined Array) in 2019
March. We located some of these maser components closer to the central stellar
system than other high velocity components (50--200~km~s) that have been
confirmed to be associated with the known bipolar outflow. The new components
would flash in the fast collimated jet at a speed over 300~km~s (soon)
after 2011 when they had not been detected. The fastest of the new components
seem to indicate rapid deceleration in these spectra, however our present
monitoring is still too sparse to unambiguously confirm it (up to
50~km~syr) and too short to reveal their terminal expansion
velocity, which will be equal to the expansion velocity that has been observed
(120~km~s). Future occurrences of such extreme velocity
components may provide a good opportunity to investigate possible recurrent
outflow ignitions. Thus sculpture of the parental envelope will be traced by
the dense gas that is entrained by the fast jet and exhibits spectacular
distributions of the relatively stable maser features.Comment: 11 pages, 5 figures, 2 table
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