556 research outputs found
Thermomechanical Pulping of Loblolly Pine Juvenile Wood
Intensive forest management, with a heavy emphasis on ecosystem management and restoring or maintaining forest health, will result in the removal of smaller diameter materials from the forest. This increases the probability of higher juvenile wood content in the harvested materials. The purpose of this study was to compare the performance of loblolly pine juvenile and mature wood unbleached thermomechanical pulp (TMP). The TMPs were prepared without screening (unscreened TMP) and after screening (screened TMP). Pulp and paper properties were tested. Paper made from screened juvenile and mature wood TMP had better properties than those of paper made from unscreened juvenile and mature wood TMP. The results also show that screened juvenile wood TMP consumed a large amount of electrical energy to produce a long-fibered pulp with low fines content and low coarseness. It might be possible to substitute the screened juvenile wood TMP for some of the reinforcing kraft pulp needed to manufacture newsprint and printing and writing papers. This could lower production costs of these paper grades
Exact Description of Black Holes on Branes II: Comparison with BTZ Black Holes and Black Strings
We extend our recent discussion of four-dimensional black holes bound to a
two-brane to include a negative cosmological constant on the brane. We find
that for large masses, the solutions are precisely BTZ black holes on the
brane, and BTZ `black strings' in the bulk. For smaller masses, there are
localized black holes which look like BTZ with corrections that fall off
exponentially. We compute when the maximum entropy configuration changes from
the black string to the black hole. We also present exact solutions describing
rotating black holes on two-branes which are either asymptotically flat or
asymptotically . The mass and angular momentum on the brane agree with
that in the bulk.Comment: 30 page
Fluorescence Microscopy of Hardboards
We developed a microscopic technique and used it to explore the internal structure and resin distribution in hardboards. The technique will enable us better to understand the behavior of hard-boards in use. Glycol methacrylate (JB-4 embedding medium) proved to be satisfactory for preparing 10- to 15-ÎŒm sections of hardboards with a steel knife on a sliding microtome. This thickness of sample, when viewed in transmitted near-ultraviolet light, allowed a clear visualization of hardboard internal structure and resin distribution through the board thickness. We examined wet-formed and dry-formed hardboard samples. Wet-formed high-density and medium-density boards usually showed fibers consolidated into a compact structure and a uniform resin distribution. Dry-formed high-density boards had a compact structure and medium-density boards a less compact structure; both characteristically showed uneven resin distribution
Electron Microscopy Study of Hardboards
Wet-formed and dry-formed aspen fiber hardboards are examined by transmission electron microscopy to obtain information on the hardboard internal structure and fiber-resin interactions. These factors, when related to strength and dimensional properties of hardboards, may be helpful in determining hardboard quality and suitability for structural use.During hardboard manufacturing, the wood cells break apart at the middle lamella and come in contact again when subjected to pressure during hot-pressing. Occasionally fibers remain attached in bundles. Various stages of middle lamella degradation can be observed. When totally disintegrated, middle lamella appears as dark granular material. Voids of variable size exist in medium- and high-density wet- and dry-formed hardboards. In wet-formed boards the resin (which has high electron opaqueness and appears black) shows even distribution. In dry-formed boards the resin shows uneven distribution; it is present as large accumulations in some areas but absent in others
Amplification of TLO Mediator Subunit Genes Facilitate Filamentous Growth in Candida Spp
Funding: This work was funded by the National Institutes of Allergy and Infectious Disease (AI113390, LCM) and the National Institutes of General Medical Sciences (GM62483, LCM). The funders had no role in study design, data collection and analysis, decision topublish, or preparation of the manuscript.Non peer reviewedPublisher PD
The Decay of Magnetic Fields in Kaluza-Klein Theory
Magnetic fields in five-dimensional Kaluza-Klein theory compactified on a
circle correspond to ``twisted'' identifications of five dimensional Minkowski
space. We show that a five dimensional generalisation of the Kerr solution can
be analytically continued to construct an instanton that gives rise to two
possible decay modes of a magnetic field. One decay mode is the generalisation
of the ``bubble decay" of the Kaluza-Klein vacuum described by Witten. The
other decay mode, rarer for weak fields, corresponds in four dimensions to the
creation of monopole-anti-monopole pairs. An instanton for the latter process
is already known and is given by the analytic continuation of the \KK\ Ernst
metric, which we show is identical to the five dimensional Kerr solution. We
use this fact to illuminate further properties of the decay process. It appears
that fundamental fermions can eliminate the bubble decay of the magnetic field,
while allowing the pair production of Kaluza-Klein monopoles.Comment: 25 pages, one figure. The discussion of fermions has been revised: We
show how fundamental fermions can eliminate the bubble-type instability but
still allow pair creation of monopole
Black Holes Radiate Mainly on the Brane
We examine the evaporation of a small black hole on a brane in a world with
large extra dimensions. Since the masses of many Kaluza-Klein modes are much
smaller than the Hawking temperature of the black hole, it has been claimed
that most of the energy is radiated into these modes. We show that this is
incorrect. Most of the energy goes into the modes on the brane. This raises the
possibility of observing Hawking radiation in future high energy colliders if
there are large extra dimensions.Comment: 11 page
Uniqueness and non-uniqueness of static vacuum black holes in higher dimensions
We prove the uniqueness theorem for asymptotically flat static vacuum black
hole solutions in higher dimensional space-times. We also construct infinitely
many non-asymptotically flat regular static black holes on the same spacetime
manifold with the same spherical topology.Comment: to appear in Progress of Theoretical Physics Supplement No. 14
A Correspondence Principle for Black Holes and Strings
For most black holes in string theory, the Schwarzschild radius in string
units decreases as the string coupling is reduced. We formulate a
correspondence principle, which states that (i) when the size of the horizon
drops below the size of a string, the typical black hole state becomes a
typical state of strings and D-branes with the same charges, and (ii) the mass
does not change abruptly during the transition. This provides a statistical
interpretation of black hole entropy. This approach does not yield the
numerical coefficient, but gives the correct dependence on mass and charge in a
wide range of cases, including neutral black holes.Comment: 24 pages, one typo correcte
On the Nonlinear Stability of Asymptotically Anti-de Sitter Solutions
Despite the recent evidence that anti-de Sitter spacetime is nonlinearly
unstable, we argue that many asymptotically anti-de Sitter solutions are
nonlinearly stable. This includes geons, boson stars, and black holes. As part
of our argument, we calculate the frequencies of long-lived gravitational
quasinormal modes of AdS black holes in various dimensions. We also discuss a
new class of asymptotically anti-de Sitter solutions describing noncoalescing
black hole binaries.Comment: 26 pages. 5 figure
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