4,556 research outputs found
Phase Transitions in a Dusty Plasma with Two Distinct Particle Sizes
In semiconductor manufacturing, contamination due to particulates
significantly decreases the yield and quality of device fabrication, therefore
increasing the cost of production. Dust particle clouds can be found in almost
all plasma processing environments including both plasma etching devices and in
plasma deposition processes. Dust particles suspended within such plasmas will
acquire an electric charge from collisions with free electrons in the plasma.
If the ratio of inter-particle potential energy to the average kinetic energy
is sufficient, the particles will form either a liquid structure with short
range ordering or a crystalline structure with long range ordering. Otherwise,
the dust particle system will remain in a gaseous state. Many experiments have
been conducted over the past decade on such colloidal plasmas to discover the
character of the systems formed, but more work is needed to fully understand
these structures. The preponderance of previous experiments used monodisperse
spheres to form complex plasma systems
A history of the development and implementation of a whole language curriculum in a rural Iowa middle school
The purpose of this project was to examine the history of a whole language curriculum which was developed and implemented for grades five and six in a rural Iowa middle school and to discuss any insights gained from the process. This project presents a description of the whole language curriculum and a rationale for its development. It also explains the purpose of a whole language curriculum and its importance to students, teachers, administrators, and parents.
The project describes the procedures used by the middle school in the development and implementation of the curriculum. The project concludes with a description of the strengths and weaknesses of the curriculum, the status of the curriculum today, and recommendations for other schools that wish to develop and implement a whole language curriculum
Quantum Monte Carlo calculations of neutron-alpha scattering
We describe a new method to treat low-energy scattering problems in
few-nucleon systems, and we apply it to the five-body case of neutron-alpha
scattering. The method allows precise calculations of low-lying resonances and
their widths. We find that a good three-nucleon interaction is crucial to
obtain an accurate description of neutron-alpha scattering.Comment: 4 pages, 2 figures, submitted to Physical Review Letter
Proton-tetraneutron elastic scattering
We analyze the elastic scattering of protons on a 4n system. This was used as
part of the detection technique of a recent experiment [1] to search for the 4n
(tetraneutron) as a bound particle. We show that it is unlikely that this
process alone could yield the events reported in ref. [1], unless the 4n has an
anomalously large backward elastic scattering amplitude.Comment: 6 pages, 2 figures, accepted for publication in Phys. Rev.
Increasing Tetrahydrobiopterin in Cardiomyocytes Adversely Affects Cardiac Redox State and Mitochondrial Function Independently of Changes in NO Production
Tetrahydrobiopterin (BH4) represents a potential strategy for the treatment of cardiac remodeling, fibrosis and/or diastolic dysfunction. The effects of oral treatment with BH4 (Sapropterin™ or Kuvan™) are however dose-limiting with high dose negating functional improvements. Cardiomyocyte-specific overexpression of GTP cyclohydrolase I (mGCH) increases BH4 several-fold in the heart. Using this model, we aimed to establish the cardiomyocyte-specific responses to high levels of BH4. Quantification of BH4 and BH2 in mGCH transgenic hearts showed age-based variations in BH4:BH2 ratios. Hearts of mice (\u3c6 \u3emonths) have lower BH4:BH2 ratios than hearts of older mice while both GTPCH activity and tissue ascorbate levels were higher in hearts of young than older mice. No evident changes in nitric oxide (NO) production assessed by nitrite and endogenous iron–nitrosyl complexes were detected in any of the age groups. Increased BH4 production in cardiomyocytes resulted in a significant loss of mitochondrial function. Diminished oxygen consumption and reserve capacity was verified in mitochondria isolated from hearts of 12-month old compared to 3-month old mice, even though at 12 months an improved BH4:BH2 ratio is established. Accumulation of 4-hydroxynonenal (4-HNE) and decreased glutathione levels were found in the mGCH hearts and isolated mitochondria. Taken together, our results indicate that the ratio of BH4:BH2 does not predict changes in neither NO levels nor cellular redox state in the heart. The BH4 oxidation essentially limits the capacity of cardiomyocytes to reduce oxidant stress. Cardiomyocyte with chronically high levels of BH4 show a significant decline in redox state and mitochondrial function
Center-of-mass effects on the quasi-hole spectroscopic factors in the 16O(e,e'p) reaction
The spectroscopic factors for the low-lying quasi-hole states observed in the
16O(e,e'p)15N reaction are reinvestigated with a variational Monte Carlo
calculation for the structure of the initial and final nucleus. A computational
error in a previous report is rectified. It is shown that a proper treatment of
center-of-mass motion does not lead to a reduction of the spectroscopic factor
for -shell quasi-hole states, but rather to a 7% enhancement. This is in
agreement with analytical results obtained in the harmonic oscillator model.
The center-of-mass effect worsens the discrepancy between present theoretical
models and the experimentally observed single-particle strength. We discuss the
present status of this problem, including some other mechanisms that may be
relevant in this respect.Comment: 14 pages, no figures, uses Revtex, to be published in Phys. Rev. C 58
(1998
Waldhausen Additivity: Classical and Quasicategorical
We use a simplicial product version of Quillen's Theorem A to prove classical
Waldhausen Additivity of wS., which says that the "subobject" and "quotient"
functors of cofiber sequences induce a weak equivalence wS.E(A,C,B)--> wS.A x
wS.B . A consequence is Additivity for the Waldhausen K-theory spectrum of the
associated split exact sequence, namely a stable equivalence of spectra
K(A)vK(B)--> K(E(A,C,B)). This paper is dedicated to transferring these proofs
to the quasicategorical setting and developing Waldhausen quasicategories and
their sequences. We also give sufficient conditions for a split exact sequence
to be equivalent to a standard one. These conditions are always satisfied by
stable quasicategories, so Waldhausen K-theory sends any split exact sequence
of pointed stable quasicategories to a split cofiber sequence. Presentability
is not needed. In an effort to make the article self-contained, we recall all
the necessary results from the theory of quasicategories, and prove a few
quasicategorical results that are not in the literature.Comment: 83 pages. The revised and copy-edited version of this obsolete arXiv
version will be soon published in the Journal of Homotopy and Related
Structures. https://link.springer.com/journal/volumesAndIssues/40062 . The
final, pre-copy-edit, pre-publication accepted version is at
http://www-personal.umd.umich.edu/~tmfiore/1/research.html and will replace
this arXiv version after the embargo perio
Dusty Plasma Correlation Function Experiment
Dust particles immersed within a plasma environment, such as those in
protostellar clouds, planetary rings or cometary environments, will acquire an
electric charge. If the ratio of the inter-particle potential energy to the
average kinetic energy is high enough the particles will form either a "liquid"
structure with short-range ordering or a crystalline structure with long range
ordering. Many experiments have been conducted over the past several years on
such colloidal plasmas to discover the nature of the crystals formed, but more
work is needed to fully understand these complex colloidal systems. Most
previous experiments have employed monodisperse spheres to form Coulomb
crystals. However, in nature (as well as in most plasma processing
environments) the distribution of particle sizes is more randomized and
disperse. This paper reports experiments which were carried out in a GEC rf
reference cell modified for use as a dusty plasma system, using varying sizes
of particles to determine the manner in which the correlation function depends
upon the overall dust grain size distribution. (The correlation function
determines the overall crystalline structure of the lattice.) Two dimensional
plasma crystals were formed of assorted glass spheres with specific size
distributions in an argon plasma. Using various optical techniques, the pair
correlation function was determined and compared to those calculated
numerically.Comment: 6 pages, Presented at COSPAR '0
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