Showing papers by "University of Texas at Austin published in 1974"

Generalized second law of thermodynamics in black-hole physics

Abstract: In previous work we introduced the concept of black-hole entropy, which we identified with the surface area of the black hole in question expressed in units of the Planck length squared. We suggested that the appropriate generalization of the second law for a region containing a black hole is that the black-hole entropy plus the common entropy in the black-hole exterior never decreases. Here we establish the validity of this law for the infall of an entropy-bearing system into a much larger and more massive generic stationary black hole. To do this we determine a general lower bound for the increase in black-hole entropy, and an upper bound for the entropy of the system, while allowing for quantum effects at each stage. In passing we show that the generalized second law is a statistical law which becomes over-whelmingly probable in the limit of a macroscopic system. We also consider briefly more general situations. Finally, we give two simple examples of predictions made by the generalized second law for black-hole formation processes.

Gene Flow in Seed Plants

Abstract: Gene dispersal (flow, or migration) within and between plant populations has been of continuous interest to plant breeders and seed producers for many decades. Economic considerations have stimulated studies of gene flow as a function of distance, breeding system, pollinating agent, and planting design in numerous domestic plants. Only during the past two decades have a large body of plant evolutionists become interested in information accruing from these studies, and in the rates of gene flow in wild populations. Their efforts have concentrated primarily on related problems such as adaptations for and mechanics of pollen and seed (or fruit) dispersal, plant-pollinator coevolution, adaptive radiation in pollination and seed dispersal mechanisms, and colonization and the alteration of species boundaries. Early in this century, anecdoctal evidence on the movement of pollen and seed vectors, dispersal of pollen by wind, and the range extensions of weed species led to the casual assumption that gene flow must be extensive, and that it must play a major role in the cohesion of populations and population systems. This view eroded as more information became available and was more critically interpreted (e.g., Grant, 1958, 1971; Ehrlich and Raven, 1969; Stebbins, 1970a; Bradshaw, 1972).

A comparison of list schedules for parallel processing systems

Abstract: The problem of scheduling two or more processors to minimize the execution time of a program which consists of a set of partially ordered tasks is studied. Cases where task execution times are deterministic and others in which execution times are random variables are analyzed. It is shown that different algorithms suggested in the literature vary significantly in execution time and that the B-schedule of Coffman and Graham is near-optimal. A dynamic programming solution for the case in which execution times are random variables is presented.

Causes of death in cancer patients

Abstract: The records of 816 cancer patients who had a complete postmortem examination during a 3-year period were reviewed. Death resulted from infection in 47% of the patients, from organ failure in 25%, and from infarction, hemorrhage, and carcinomatosis in 11%, 7%, and 10%, respectively. The most common fatal infections were pneumonia, septicemia, and peritonitis. The majority of infections were caused by gram-negative bacilli, mainly E. coli, Pseudomonas spp., and Klebsiella spp. In 71% of the 816 patients, the underlying tumor precipitated the cause of death. Consequently, better modalities of cancer therapy and supportive therapy are needed.

Elephant Seals: Genetic Variation and Near Extinction

Abstract: Blood samples from northern elephant seals (Mirounga angustirostris), representing five breeding colonies in California and Mexico, were surveyed electrophoretically for protein variation reflecting underlying genetic differences. No polymorphisms were found among 21 proteins encoded by 24 loci. This uniform homozygosity may be a consequence of fixation of alleles brought about by the decimation of this species by sealers in the last century.

Amorphous semiconductor switching in melanins.

Abstract: Melanins produced synthetically and isolated from biological systems act as an amorphous semiconductor threshold switch. Switching occurs reversibly at potential gradients two to three orders of magnitude lower than reported for inorganic thin films, and comparable to gradients existing in some biological systems. Of a number of other biological materials tested, only cytochrome c acted similarly, but at the high potential gradients reported for thin film amorphous semiconductors.

Short forms of the Texas Social Behavior Inventory (TSBI), an objective measure of self-esteem

Abstract: Two short (16 item) forms of the Helmreich, Stapp, and Ervin (1974) Texas Social Behavior Inventory, a validated, objective measure of self-esteem or social competence are presented. Normative data and other statistics are described for males and females. Correlations between each short form and long (32-item) scale were .97. Factor analysis and part-whole correlations verified the similarity of the two forms. The utility of the scale in research is described.

A note on extensions of Baer and p.p-rings

Abstract: Baer rings are rings in which the left (right) annihilator of each subset is generated by an idempotent [6]. Closely related to Baer rings are left P.P.-rings; these are rings in which each principal left ideal is projective, or equivalently, rings in which the left annihilator of each element is generated by an idempotent. Both Baer and P.P.-rings have been extensively studied (e.g. [2], [1], [3], [7]) and it is known that both of these properties are not stable relative to the formation of polynomial rings [5]. However we will show that if a ring R has no nonzero nilpotent elements then R[X] is a Baer or P.P.-ring if and only if R is a Baer or P.P.-ring. This generalizes a result of S. Jondrup [5] who proved stability for commutative P.P.-rings via localizations – a technique which is, of course, not available to us. We also consider the converse to the well-known result that the center of a Baer ring is a Baer ring [6] and show that if R has no nonzero nilpotent elements, satisfies a polynomial identity and has a Baer ring as center, then R must be a Baer ring. We include examples to illustrate that all the hypotheses are needed.

The influence of sexual selection and interspecific competition on mockingbird song (mimus polyglottos)

Abstract: Versatility and individual variation in the song of mockingbirds, Mimus polyglottos, provide an excellent system for studying effects of natural selection. My observations focus on three aspects of mockingbird song: repertoire size, song diversity, and interspecific mimicry. Two hypotheses, not mutually exclusive, are tested: 1) Sexual selection influences repertoire size; males with larger repertoires have an advantage in acquiring territories and attracting mates. Repertoire size is enlarged through interspecific imitations. 2) Interspecific mimicry of territorial songs enables males to exclude close competitors from their territories. By reducing interspecific competition, better mimics have a higher reproductive success. The major selective force influencing bird song is sexual selection. Darwin (1871) postulated two aspects of sexual selection: intrasexual selection for those traits that function in acquisition and maintenance of a breeding territory, and intersexual selection for those traits that affect mate selection. Often intrasexually selected traits also influence mate selection. Primary (or advertizing) song functions both in intraspecific territorial defense and mate attraction. However, intrasexual and intersexual selective pressures are treated separately here to aid in discussion. Intrasexual competition for breeding territories is based on relatively qualitative traits such as aggression as well as quantitative attributes such as plumage characteristics and song. Traits that intimidate rivals will be selected. The

Wall pressure spectra calculations for equilibrium boundary layers

Abstract: Calculation of the flow direction wave-number spectrum of pressure fluctuations on the wall under a turbulent boundary layer. Particular attention is paid to finding the spectral density of the wall pressure fluctuations as a function of the streamwise wave number. For this purpose a five-dimensional integration is employed in which the equilibrium boundary layers are assumed to have velocity profiles given by the law of the wall plus Cole's wake function.

A regularization of the three body problem

Abstract: Letr 1,r 2,r 3 be arbitrary coordinates of the non-zero interacting mass-pointsm 1,m 2,m 3 and define the distancesR 1=|r 1−r 3|,R 2=|r 2−r 3|,R=|r 1−r 2|. An eight-dimensional regularization of the general three-body problem is given which is based on Kustaanheimo-Stiefel regularization of a single binary and possesses the properties: Although the requirementR≳ min (R 1,R 2) may involve occasional transformations to physical variables in order to re-label the particles, all integrations are performed in regularized variables. Numerical comparisons with the standard Kustaanheimo-Stiefel regularization show that the new method gives improved accuracy per integration step at no extra computing time for a variety of examples. In addition, time reversal tests indicate that critical triple encounters may now be studied with confidence. The Hamiltonian formulation has been generalized to include the case of perturbed three-body motions and it is anticipated that this procedure will lead to further improvements ofN-body calculations.

Optimal Facility Location with Concave Costs

Abstract: The following problem is considered: select plant sites from a given set of sites and choose their production and distribution levels to meet known demand at discrete points at minimum cost. The construction and operating cost of each plant is assumed to be a concave function of the total production at that plant, and the distribution cost between each plant and demand point is assumed to be a concave function of the amount shipped. There may be capacity restrictions on the plants. A branch-and-bound algorithm for identifying an optimal solution is described; it is equivalent to the solution of a finite sequence of transportation problems. The algorithm is developed as a particular case of a simplified algorithm for minimizing separable concave functions over linear polyhedra. Computational results are cited for a computer code implementing the algorithm.

Implementation and computational comparisons of primal, dual and primal-dual computer codes for minimum cost network flow problems

Abstract: : The paper presents extensive computational experience with a special purpose primal simplex algorithm. The performance is compared to that of several 'state of the art' out-of-kilter computer codes. The computational characteristics of several different primal feasible start procedures and pivot selection strategies are also examined. The study discloses the advantages, in both computation time and memory requirements, of the primal approach over the out-of-kilter method. The test environment has the following distinguishing properties: (1) all of the codes are tested on the same machine and the same problems, (2) the test set includes capacitated and uncapacitated transhipment networks, transportation problems, and assignment problems, and (3) problem sizes ranging from 100 to 8,000 nodes with up to 35,000 arcs are examined. (Author)

Metastatic patterns of choroidal melanoma.

Abstract: Twenty-five patients with choroidal melanoma are presented who subsequently developed disseminated disease. Fifteen of 25 patients developed hepatic metastases as the sole initial manifestation of metastatic disease. The median time from enucleation to hepatic metastases was 43 months and the survival from onset of metastatic spread was 7 months.

Anatomy of an Orogen

Abstract: Mapping a strip of 15′ quadrangles across the northern Coast Ranges of California by student colleagues and myself has resulted in the development of a model for the origin and emplacement of the Franciscan complex and its relation to the coeval Great Valley sequence that differs from earlier models. Rocks of both Franciscan and Great Valley are predominantly graywacke, silty mudstone, and local conglomerate. Most of the Great Valley rocks are graded, and bottom markings are common; these features are present but not characteristic of the Franciscan rocks. Franciscan graywacke and silty mudstone tend to be broken and sheared, or chaotically deformed. The chaotic zones typically contain exotic blocks, mostly of ophiolitic rocks, but also blue-schist, mica schist, metagraywacke, and blocks similar to the enclosing sheared matrix. These chaotic units are best characterized as melanges. Within the Franciscan complex, mappable units have been defined, based on lithology of matrix and content of exotic blocks. The units dip and face easterly and are oldest to the east (Tithonian or older for the South Fork Mountain Schist). Progressively younger rocks occur down section to the west; the youngest are the Coastal Facies largely of Eocene age. The probable origin involves deposition of Franciscan sediments in a trench, followed by thrusting of the sediments against and under the landward side of the trench, while the axis of the trench migrated progressively westward. The process began in Tithonian time, slowed during Late Cretaceous, and ceased in the Eocene. Models are suggested for the formation of melanges during sedimentation and underthrusting. Each melange unit contains a unique assemblage of exotic blocks. It is suggested that these assemblages in part reflect the lithology of the basement rocks on which the sediments were deposited. If true, the composition of the basement varied from dominantly ophiolite-suite rocks to dominantly blueschist. A melange of ophiolite blocks also formed, the basement beneath a part of the Great Valley sediments. Samples of radiolarian chert from the ophiolite suite throughout the Franciscan were determined to be of Tithonian age by Emile Pessagno. If the ophiolite represents ocean floor, formed at a spreading ridge, the ridge must have been located adjacent to the trench in Tithonian time; after the Tithonian, no oceanic rocks were added to the Franciscan pile. A diapiric origin for the Tithonian ophiolite is suggested. Northwest-trending isolated slabs of Great Valley—type rocks and of shallow-water to continental coal-bearing clastic rocks of Cretaceous to Miocene age are scattered within the Franciscan complex. Evidence is presented that these were deposited in separate, probably fault-controlled basins, developed on the surface of the tectonically active Franciscan complex during and following underthrusting. They do not appear to represent a klippen of a Coast Range thrust fault, as has been suggested by others.

Circulating concentrations of FSH, LH, estradiol, and progesterone associated with acute, male-induced puberty in female mice.

Abstract: Changes in circulating concentrations of pituitary gonadotropins and ovarian steroids were examined in young female mice undergoing male-induced, precocial puberty. Preliminary experiments revealed that body weight was the most critical factor in determining the rapidity with which puberty could be so induced. A restricted (lg) weight range, at which 80–85% of the immature females would uniformly achieve a complete ovulatory cycle in a 3-day period, was thus chosen as a model system for studying hormonal changes. Under these predictable conditions, male exposure was followed by a 4–5-fold increase in serum LH in 1–3 hr, and a 15–20-fold increase in plasma es-tradiol in 3–6 hr. Circulating concentrations of FSH and progesterone did not change during the first 24 hr of male exposure. A second peak in plasma estradiol levels was detected during the second day. FSH, but not LH, was totally depressed at this time. Normal, adult-like, periovulatory changes in serum LH and FSH and in plasma progesterone (but not...