12,429 research outputs found
Wormwholes: A Commentary On K.F. Schaffer\u27s Genes, Behavior, And Developmental Emergentism
Although Caenorhabditis elegans was chosen and modified to be an organism that would facilitate a reductionist program for neurogenetics, recent research has provided evidence for properties that are emergent from the neurons. While neurogenetic advances have been made using C. elegans which may be useful in explaining human neurobiology, there are severe limitations on C. elegans to explain any significant human behavior
Water Vapor in the Inner 25 AU of a Young Disk around a Low-Mass Protostar
Water is one of the key molecules in the physical and chemical evolution of
star- and planet-forming regions. We here report the first spatially resolved
observation of thermal emission of (an isotopologue of) water with the Plateau
de Bure Interferometer toward the deeply embedded Class 0 protostar NGC
1333-IRAS4B. The observations of the H2-18-O 3_13-2_20 transition at 203.4 GHz
resolve the emission of water toward this source with an extent of about 0.2"
corresponding to the inner 25 AU (radius). The H2-18-O emission reveals a
tentative velocity gradient perpendicular to the extent of the protostellar
outflow/jet probed by observations of CO rotational transitions and water
masers. The line is narrow, about 1 km/s (FWHM), significantly less than what
would be expected for emission from an infalling envelope or accretion shock,
but consistent with emission from a disk seen at a low inclination angle. The
water column density inferred from these data suggests that the water emitting
gas is a thin warm layer containing about 25 M_Earth of material, 0.03% of the
total disk mass traced by continuum observations.Comment: accepted for publication in ApJ Letters; 12 pages, 3 figure
Wavelets in mathematical physics: q-oscillators
We construct representations of a q-oscillator algebra by operators on Fock
space on positive matrices. They emerge from a multiresolution scaling
construction used in wavelet analysis. The representations of the Cuntz Algebra
arising from this multiresolution analysis are contained as a special case in
the Fock Space construction.Comment: (03/11/03):18 pages; LaTeX2e, "article" document class with
"letterpaper" option An outline was added under the abstract (p.1),
paragraphs added to Introduction (p.2), mat'l added to Proofs in Theorems 1
and 6 (pgs.5&17), material added to text for the conclusion (p.17), one add'l
reference added [12]. (04/22/03):"number 1" replace with "term C" (p.9),
single sentences reformed into a one paragraph (p.13), QED symbol moved up
one paragraph and last paragraph labeled as "Concluding Remarks.
Observations of nitrogen isotope fractionation in deeply embedded protostars
(Abridged) The terrestrial planets, comets, and meteorites are significantly
enriched in 15N compared to the Sun and Jupiter. While the solar and jovian
nitrogen isotope ratio is believed to represent the composition of the
protosolar nebula, a still unidentified process has caused 15N-enrichment in
the solids. Several mechanisms have been proposed to explain the variations,
including chemical fractionation. However, observational results that constrain
the fractionation models are scarce. While there is evidence of 15N-enrichment
in prestellar cores, it is unclear how the signature evolves into the
protostellar phases. Our aim is to measure the 14N/15N ratio around three
nearby, embedded low-to-intermediate-mass protostars. Isotopologues of HCN and
HNC were used to probe the 14N/15N ratio. A selection of H13CN, HC15N, HN13C,
and H15NC transitions was observed with the APEX telescope. The 14N/15N ratios
were derived from the integrated intensities assuming a standard 12C/13C ratio.
The assumption of optically thin emission was verified using radiative transfer
modeling and hyperfine structure fitting. Two sources, IRAS 16293A and R CrA
IRS7B, show 15N-enrichment by a factor of around 1.5-2.5 in both HCN and HNC
with respect to the solar composition. Solar composition cannot be excluded for
the third source, OMC-3 MMS6. Furthermore, there are indications of a trend
toward increasing 14N/15N ratios with increasing outer envelope temperature.
The enhanced 15N abundances in HCN and HNC found in two Class~0 sources
(14N/15N of 160-290) and the tentative trend toward a temperature-dependent
14N/15N ratio are consistent with the chemical fractionation scenario, but
14N/15N ratios from additional tracers are indispensable for testing the
models. Spatially resolved observations are needed to distinguish between
chemical fractionation and isotope-selective photochemistry.Comment: Accepted for publication in Astronomy and Astrophysics. 16 pages, 13
figure
The Public Relations Efforts of South Dakota Colleges and Universities as Reflected by the Attitudes of South Dakota High School Seniors
This study will concentrate on one small, yet vital, public--the public composed of high school seniors. If this public is aware of what the South Dakota colleges and universities have to offer, then the public relations programs of those schools are having some effect. If the students are preparing for a college career, then it is important to the future of the state\u27s higher education that they are aware of the costs and the offerings of its schools. Daniel Gladstone, a high school senior from New Jersey, supported this thinking in a personal opinion column in Saturday Review. He said that high school seniors rarely or never have a say in what occurs in their school or what will occur in the college or university they are planning to attend. Yet, in both cases, they as students are exposed to the decisions made by others and have to abide by them. Why, he asks, can\u27t the high school seniors let their opinions be known? Generally, we may consider the influence of background factors on high school students as threefold--home experiences, school experiences, and post high school experiences. Therefore, perhaps an even broader public attitude can be presented through a survey of high school seniors, since they may also be reflecting the thoughts of friends both older and younger. In past decades, many children of unskilled laborers were found not to be interested in going on to college. This attitude probably reflected the thinking of the parent, who had found his own experiences with any education as disheartening or unprofitable. Most students, by the time they reach college age, will have attitudes and responses that are deeply rooted in their pasts, McCloskey says. And,\u27\u27 he adds, the more (students) perceive education as a means of further achievement and satisfaction, the more favorable their attitudes toward it will be. If the communications specialist can generate interest through his efforts, then perhaps he can cause the student to take a second look at whether or not to attempt higher education. From the communications standpoint, McCloskey continues, it is important to note that the opinion-forming process opens minds, generates interest, and influences actions, particularly when the person\u27s existing conditions are considered unsatisfactory. Often, a student\u27s favorable change in opinion toward a form of education takes place while his attitudes remain unchanged toward education as a whole
A cold complex chemistry toward the low-mass protostar B1-b: evidence for complex molecule production in ices
Gas-phase complex organic molecules have been detected toward a range of
high- and low-mass star-forming regions at abundances which cannot be explained
by any known gas-phase chemistry. Recent laboratory experiments show that UV
irradiation of CH3OH-rich ices may be an important mechanism for producing
complex molecules and releasing them into the gas-phase. To test this ice
formation scenario we mapped the B1-b dust core and nearby protostar in CH3OH
gas using the IRAM 30m telescope to identify locations of efficient non-thermal
ice desorption. We find three CH3OH abundance peaks tracing two outflows and a
quiescent region on the side of the core facing the protostar. The CH3OH gas
has a rotational temperature of ~10 K at all locations. The quiescent CH3OH
abundance peak and one outflow position were searched for complex molecules.
Narrow, 0.6-0.8 km s-1 wide, HCOOCH3 and CH3CHO lines originating in cold gas
are clearly detected, CH3OCH3 is tentatively detected and C2H5OH and HOCH2CHO
are undetected toward the quiescent core, while no complex molecular lines were
found toward the outflow. The core abundances with respect to CH3OH are ~2.3%
and 1.1% for HCOOCH3 and CH3CHO, respectively, and the upper limits are
0.7-1.1%, which is similar to most other low-mass sources. The observed complex
molecule characteristics toward B1-b and the pre-dominance of HCO-bearing
species suggest a cold ice (below 25 K, the sublimation temperature of CO)
formation pathway followed by non-thermal desorption through e.g. UV photons
traveling through outflow cavities. The observed complex gas composition
together with the lack of any evidence of warm gas-phase chemistry provide
clear evidence of efficient complex molecule formation in cold interstellar
ices.Comment: 23 pages, 7 figures, accepted for publication in Ap
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