13,661 research outputs found
Diquaternary Ammonium Compounds in Zeolite Synthesis: Cyclic and Polycyclic N-Heterocycles Connected by Methylene Chains
An additional dimension has been added to our long-standing studies in high silica zeolite synthesis via a guest/host synergism. We have created and studied the impact of making symmetric diquaternary ammonium compounds, by varying the chain length between nitrogen charge centers, and the heterocycle size and geometry containing the nitrogen. This allows the introduction of a second spatial parameter in the use of the charged organo-cation guest in the zeolite synthesis. The series of 15 diquaternary ammonium compounds (5 heterocycles synthesized onto chain lengths of C4−C6) were tested in a total of 135 zeolite syntheses reactions. Nine screening reactions were employed for each guest molecule, and the conditions built upon past successes in finding novel high silica zeolites via introduction of boron, aluminum, or germanium as substituting tetrahedral framework atoms for silicon. Eighteen different zeolite structures emerged from the studies. The use of specific chain lengths for derivatives of the pyrrolidine ring system produced novel zeolite materials SSZ-74 and 75
Detection of SiO emission from a massive dense cold core
We report the detection of the SiO (J = 2 - 1) transition from the massive
cold dense core G333.125-0.562. The core remains undetected at wavelengths
shorter than 70 micron and has compact 1.2 mm dust continuum. The SiO emission
is localised to the core. The observations are part of a continuing
multi-molecular line survey of the giant molecular cloud G333. Other detected
molecules in the core include 13CO, C18O, CS, HCO+, HCN, HNC, CH3OH, N2H+, SO,
HC3N, NH3, and some of their isotopes. In addition, from NH3 (1,1) and (2,2)
inversion lines, we obtain a temperature of 13 K. From fitting to the spectral
energy distribution we obtain a colour temperature of 18 K and a gas mass of 2
x 10^3 solar mass. We have also detected a 22 GHz water maser in the core,
together with methanol maser emission, suggesting the core will host massive
star formation. We hypothesise that the SiO emission arises from shocks
associated with an outflow in the cold core.Comment: 6 pages, 4 figures, 1 table, to be published in MNRA
The use of music in the education of educable mentally retarded children
Thesis (M.M.)--Boston University.Much attention is being directed toward improving the education of the mentally retarded, who comprise three percent of our population. Music is an area which provides enrichment in the educational curriculum for the mentally retarded. The extent of music's potential as an educational medium for these children has not yet been fully explored. It was the purpose of this study (1) to summarize the general characteristics of educable retarded children and give attention to some special needs they have as a result of their limitations; (2) to list the educational aims which have been established for the educable mentally retarded who are attending special classes in the public schools; (3) to show how music can be a valuable means in helping to accomplish these educational goals, and how it can contribute to personality growth and development; (4) to describe specific musical activities appropriate for mentally retarded children, listing suggested songs, recordings, books, and other materials.
The research for this study consisted of a review of books, periodicals, and unpublished works dealing with the characteristics and education of mentally retarded children, and those concerned specifically with music for the mentally handicapped. [TRUNCATED
Trade and Aid
Originally published in 1982. Trade and Aid outlines the transition of U.S. foreign policy during the Eisenhower administration. In the years leading up to Eisenhower's election, America's predominant foreign economic program was based on the concept of "trade not aid," which deemphasized foreign aid and relied instead on liberalized world trade and the encouragement of private foreign investment to assure world economic growth. When Eisenhower took office in 1953, he embraced this doctrine. However, as problems in the Third World worsened, it became clear to Eisenhower and other architects of American foreign policy that trade and private investment were insufficient solutions to the economic woes of developing nations. In 1954 Eisenhower began to embrace economic aid as a core axis of his foreign economic policy. Burton I. Kaufman contextualizes Eisenhower's foreign policy leadership in the ongoing historical evaluation of Eisenhower's leadership prowess. He evaluates the outcomes of the Eisenhower administration's trade and aid program, arguing that developing countries were worse off by the time Eisenhower left office
Analysis of murine haematopoietic stem cell activity using the x-linked enzyme phosphoglycerate kinase-1
The Milky Way Heart: Investigating molecular gas and gamma-ray morphologies in the Central Molecular Zone
Since the discovery of a broad distribution of very high energy (VHE; >0.1
TeV) gamma-rays in the Central Molecular Zone (CMZ) of the Galaxy in 2006 by
the HESS collaboration, the correlation of this emission with the integrated
intensity of the CS(1-0) molecular line emission has inferred a hadronic origin
for the gamma-rays. Here we describe the beginning of our investigation into
the strength of this correlation utilising new multi-line millimeter data from
the Mopra CMZ and HOP surveys and multi-wavelength GBT radio continuum
observations towards the CMZ and compare these in detail with the diffuse TeV
gamma-ray emission from HESS. The benefit of these new data is that they allow
us to simultaneously observe and analyse correlations using a large number
(>10) of molecular species, some of which contain their isotopologue pairs. The
use of isotopologue pairs is especially powerful, since it allows one to
analyse the optical depth of a number of different molecular species, thus
investigating the nature of the correlation over a range of different physical
conditions. Here we begin by comparing the integrated line emission and
continuum radio emission with the diffuse gamma-ray emission, and, by using
isotopologue pairs such as HCN/HCN, obtain optical depths throughout the
CMZ corresponding to regions of both strong and weak gamma-ray emission. We
find that the radio continuum better matches the peak of the gamma-ray
emission, which corresponds to the more compact -- compared to the relatively
coarse resolution of the gamma-ray images -- sources in the CMZ. Using the
isotopologue pairs, we find that the optical depth at all positions and
velocities within the CMZ are about 2--4. This is similar to that found for the
CS(1--0) line and would underestimate the mass of the CMZ, potentially
explaining why molecular line emission peaks appear offset from the gamma-ray
peaks.Comment: 8 pages, 5 figures. Accepted to the Proceedings of the 25th Texas
Symposium on Relativistic Astrophysics (Heidelberg, 2010
Electrically driven magnetism on a Pd thin film
Using first-principles density functional calculations we demonstrate that
ferromagnetism can be induced and modulated on an otherwise paramagnetic Pd
metal thin-film surface through application of an external electric field. As
free charges are either accumulated or depleted at the Pd surface to screen the
applied electric field there is a corresponding change in the surface density
of states. This change can be made sufficient for the Fermi-level density of
states to satisfy the Stoner criterion, driving a transition locally at the
surface from a paramagnetic state to an itinerant ferromagnetic state above a
critical applied electric field, Ec. Furthermore, due to the second-order
nature of this transition, the surface magnetization of the ferromagnetic state
just above the transition exhibits a substantial dependence on electric field,
as the result of an enhanced magnetoelectric susceptibility. Using a linearized
Stoner model we explain the occurrence of the itinerant ferromagnetism and
demonstrate that the magnetic moment on the Pd surface follows a square-root
variation with electric field consistent with our first-principles
calculations.Comment: 8 pages, 7 figure
Measurements of Transverse Spin Effects with the Forward Pion Detector of STAR
Measurements by the STAR collaboration of neutral pion production at large
Feynman x (x_F) in the first polarized proton collisions at GeV
were reported previously. Cross sections measured at , 3.8 and 4.0
are found to be consistent with next-to-leading order perturbative QCD
calculations. The analyzing power is consistent with zero at negative x_F and
at positive x_F up to ~0.3, then grows more positive with increasing x_F. This
behavior can be described by phenomenological models including the Sivers
effect, the Collins effect or higher twist contributions in the initial and
final states. Forward calorimetry at STAR has been extended, and there are
plans for further expansion. An integrated luminosity of 6.8 pb^ with
average beam polarization of 60% from online polarimetry measurements was
sampled with the upgraded FPD in the 2006 RHIC run. This data sample will allow
for a detailed map of the \pi^0 analyzing power over kinematic variables
bounded by 0.3 < x_F < 0.6 and 1.2 < p_T < 5.0 GeV/c at GeV. The
expanded FPD has observed multi-photon final states expected to have "jet-like"
characteristics. The transverse spin dependence of jet-like events can
discriminate between the Collins and Sivers effects and lead to further
progress in understanding the origin of single spin asymmetries in forward
particle production. Data were also obtained at GeV for x_F ->
1 to test predictions based on phenomenological fits to earlier STAR results.
Recent results, the status of the analysis of 2006 run data and near-term plans
will be discussed.Comment: 4 pages, 3 figures, to be published in the proceedings of the 17th
International Spin Physics Symposium (SPIN2006), October 2-7, 2006, Kyoto,
Japa
Locating regions in a sequence under density constraints
Several biological problems require the identification of regions in a
sequence where some feature occurs within a target density range: examples
including the location of GC-rich regions, identification of CpG islands, and
sequence matching. Mathematically, this corresponds to searching a string of 0s
and 1s for a substring whose relative proportion of 1s lies between given lower
and upper bounds. We consider the algorithmic problem of locating the longest
such substring, as well as other related problems (such as finding the shortest
substring or a maximal set of disjoint substrings). For locating the longest
such substring, we develop an algorithm that runs in O(n) time, improving upon
the previous best-known O(n log n) result. For the related problems we develop
O(n log log n) algorithms, again improving upon the best-known O(n log n)
results. Practical testing verifies that our new algorithms enjoy significantly
smaller time and memory footprints, and can process sequences that are orders
of magnitude longer as a result.Comment: 17 pages, 8 figures; v2: minor revisions, additional explanations; to
appear in SIAM Journal on Computin
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