1,791 research outputs found
The Sizes of 1720 MHz OH Masers: VLBA and MERLIN Observations of the Supernova Remnants W44 and W28
We have used the NRAO Very Long Baseline Array (VLBA) to image OH(1720 MHz)
masers in the supernova remnants W28 and W44 at a resolution of 40 mas. We also
used MERLIN to observe the same OH(1720 MHz) masers in W44 at a resolution of
290 x 165 mas. All the masers are resolved by these VLBA and MERLIN
observations. The measured sizes range from 50 to 180 mas and yield brightness
temperature estimates from 0.3--20 x 10**8 K. We investigate whether these
measured angular sizes are intrinsic and hence originate as a result of the
physical conditions in the supernova remnant shock, or whether they are scatter
broadened sizes produced by the turbulent ionized gas along the line of sight.
While the current data on the temporal and angular broadening of pulsars,
masers and extragalactic soures toward W44 and W28 can be understood in terms
of scattering, we cannot rule out that these large sizes are intrinsic. Recent
theoretical modeling by Lockett et al. suggests that the physical parameters in
the shocked region are indicative of densities and OH abundances which lead to
estimates of sizes as large as what we measure. If the sizes and structure are
intrinsic, then the OH(1720 MHz) masrs may be more like the OH(1612 MHz) masers
in circumstellar shells than OH masers associated with HII regions. At two
locations in W28 we observe the classical S-shapes in the Stokes V profiles
caused by Zeeman splitting and use it to infer magnetic fields of order 2
milliGauss.Comment: 24 pages, 6 figures, accepted by Ap
The InfraâRed Absorption Spectra of Ethylene and TetraâDeuteroâEthylene under High Resolution
The fine structure of several infraâred absorption bands of C2H4 and C2D4 have been resolved. From the rotational constants so found, the CâC and CâH distances in this molecule were calculated to be 1.353 and 1.071A, and the HâCâH angle to be 119°55âČ. An assignment of fundamental frequencies has been made which is consistent with the observed data.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69770/2/JCPSA6-10-2-88-1.pd
Phycomyces
This monographic review on a fungus is not addressed to mycologists. None of the authors has been trained or has otherwise acquired a general proficiency in mycology. They are motivated by a common interest in the performances of signal handling exhibited by the sense organs of all organisms and by the desire to attack these as yet totally obscure aspects of molecular biology by the study of a microorganism with certain desirable properties.
The sporangiophore of the fungus Phycomyces is a gigantic, single-celled, erect, cylindrical, aerial hypha. It is sensitive to at least four distinct stimuli: light, gravity, stretch, and some unknown stimulus by which it avoids solid objects. These stimuli control a common output, the growth rate, producing either temporal changes in growth rate or tropic responses.
We are interested in the output because it gives us information about the reception of the various signals. In the absence of external stimuli, the growth rate is controlled by internal signals keeping the network of biochemical processes in balance. The external stimuli interact with the internal signals. We wish to inquire into the early steps of this interaction. For light, for instance, the cell must have a receptor pigment as the first
mediator. What kind of a molecule is this pigment? Which organelle contains it? What chemical reaction happens after a light quantum has been absorbed? And how is the information introduced by this primary photochemical event amplified in a controlled manner and processed in the next step? How do a few quanta or a few molecules trigger macroscopic responses? Will we find ourselves confronted with devices wholly distinct from anything now known in biology
Entanglement sharing among qudits
Consider a system consisting of n d-dimensional quantum particles (qudits),
and suppose that we want to optimize the entanglement between each pair. One
can ask the following basic question regarding the sharing of entanglement:
what is the largest possible value Emax(n,d) of the minimum entanglement
between any two particles in the system? (Here we take the entanglement of
formation as our measure of entanglement.) For n=3 and d=2, that is, for a
system of three qubits, the answer is known: Emax(3,2) = 0.550. In this paper
we consider first a system of d qudits and show that Emax(d,d) is greater than
or equal to 1. We then consider a system of three particles, with three
different values of d. Our results for the three-particle case suggest that as
the dimension d increases, the particles can share a greater fraction of their
entanglement capacity.Comment: 4 pages; v2 contains a new result for 3 qudits with d=
Entanglement, avoided crossings and quantum chaos in an Ising model with a tilted magnetic field
We study a one-dimensional Ising model with a magnetic field and show that
tilting the field induces a transition to quantum chaos. We explore the
stationary states of this Hamiltonian to show the intimate connection between
entanglement and avoided crossings. In general entanglement gets exchanged
between the states undergoing an avoided crossing with an overall enhancement
of multipartite entanglement at the closest point of approach, simultaneously
accompanied by diminishing two-body entanglement as measured by concurrence. We
find that both for stationary as well as nonstationary states, nonintegrability
leads to a destruction of two-body correlations and distributes entanglement
more globally.Comment: Corrections in two figure captions and one new reference. To appear
in Phys. Rev.
Triggered Star Formation by Massive Stars
We present our diagnosis of the role that massive stars play in the formation
of low- and intermediate-mass stars in OB associations (the Lambda Ori region,
Ori OB1, and Lac OB1 associations). We find that the classical T Tauri stars
and Herbig Ae/Be stars tend to line up between luminous O stars and
bright-rimmed or comet-shaped clouds; the closer to a cloud the progressively
younger they are. Our positional and chronological study lends support to the
validity of the radiation-driven implosion mechanism, where the Lyman continuum
photons from a luminous O star create expanding ionization fronts to evaporate
and compress nearby clouds into bright-rimmed or comet-shaped clouds. Implosive
pressure then causes dense clumps to collapse, prompting the formation of
low-mass stars on the cloud surface (i.e., the bright rim) and
intermediate-mass stars somewhat deeper in the cloud. These stars are a
signpost of current star formation; no young stars are seen leading the
ionization fronts further into the cloud. Young stars in bright-rimmed or
comet-shaped clouds are likely to have been formed by triggering, which would
result in an age spread of several megayears between the member stars or star
groups formed in the sequence.Comment: 2007, ApJ, 657, 88
The Bible Story Producer App
The Bible Story Producer team at Cedarville University has been spending the past year on the Bible Story Producer app for Android. This app is a tool whose purpose is to facilitate the translation of Bible stories by bilingual laypersons in places where the Bible is unavailable in the vernacular. The aim of the app is to facilitate the oral translation of Bible stories transmitted as templates consisting of voice narration in a Language of Wider Communication (LWC). The narration is accompanied by a series of high-quality illustrations animated by the Ken Burns (pan and zoom) effect. An instance of oral translation may not involve writing down the translated words since some languages do not yet have an alphabet. Field testing has, so far, shown the controversial notion of oral translation to be effective. In our presentation, we will discuss the translation process that our client introduced to us as well as different implementation decisions that went into the making of the app
Parallel transport in an entangled ring
This paper defines a notion of parallel transport in a lattice of quantum
particles, such that the transformation associated with each link of the
lattice is determined by the quantum state of the two particles joined by that
link. We focus particularly on a one-dimensional lattice--a ring--of entangled
rebits, which are binary quantum objects confined to a real state space. We
consider states of the ring that maximize the correlation between nearest
neighbors, and show that some correlation must be sacrificed in order to have
non-trivial parallel transport around the ring. An analogy is made with lattice
gauge theory, in which non-trivial parallel transport around closed loops is
associated with a reduction in the probability of the field configuration. We
discuss the possibility of extending our result to qubits and to higher
dimensional lattices.Comment: 31 pages, no figures; v2 includes a new example of a qubit rin
Pharmacokinetics of oral busulphan in children with beta thalassaemia major undergoing allogeneic bone marrow transplantation
The pharmacokinetics of busulphan were studied in 23 thalassaemic children undergoing BMT. Patients received busulphan at a dose of either 16 mg/kg with cyclophosphamide and ATG (Group A) or 600 mg/m2 (with cyclophosphamide alone) (Group B) in 16 divided doses every 6 h over 4 days. Busulphan levels were analyzed by a modified GC-MS method. The dose of busulphan/kg for patients in group B was 64% (range 56-71%) higher than that for patients in group A. The mean AUC, Css, Cmax and MRV were significantly higher in group B as compared with group A for both doses 1 and 13. There was no significant difference in Vd/F, T1/2 and Kel between the two groups. A significant decrease in AUC and Css was found between 1st and 13th doses in group B, but not in group A. The Cl/F values in group A were significantly higher than those in group B after dose 1, but not after dose 13. No increase in toxicity due to the higher dose of busulphan was noted. We conclude that busulphan at 600 mg/m2 results in much higher systemic exposure to the drug as compared to 16 mg/kg, without increase in toxicity in children with beta thalassaemia major
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