Showing papers by "University of New Hampshire published in 1984"

Fast algorithms for finding nearest common ancestors

Abstract: We consider the following problem: Given a collection of rooted trees, answer on-line queries of the form, “What is the nearest common ancester of vertices x and y?” We show that any pointer machine that solves this problem requires $\Omega (\log \log n)$ time per query in the worst case, where n is the total number of vertices in the trees. On the other hand, we present an algorithm for a random access machine with uniform cost measure (and a bound of $\Omega (\log n)$ on the number of bits per word) that requires $O(1)$ time per query and $O(n)$ preprocessing time, assuming that the collection of trees is static. For a version of the problem in which the trees can change between queries, we obtain an almost-linear-time (and linear-space) algorithm.

Energy and the u.s. Economy: a biophysical perspective.

Abstract: A series of hypotheses is presented about the relation of national energy use to national economic activity (both time series and cross-sectional) which offer a different perspective from standard economics for the assessment of historical and current economic events. The analysis incorporates nearly 100 years of time series data and 3 years of cross-sectional data on 87 sectors of the United States economy. Gross national product, labor productivity, and price levels are all correlated closely with various aspects of energy use, and these correlations are improved when corrections are made for energy quality. A large portion of the apparent increase in U.S. energy efficiency has been due to our ability to expand the relative use of high-quality fuels such as petroleum and electricity, and also to relative shifts in fuel use between sectors of the economy. The concept of energy return on investment is introduced as a major driving force in our economy, and data are provided which show a marked decline in energy return on investment for all our principal fuels in recent decades. Future economic growth will depend largely on the net energy yield of alternative fuel sources, and some standard economic models may need to be modified to account for the biophysical constraints on human economic activity.

A 154-day periodicity in the occurrence of hard solar flares?

Abstract: An analysis of the temporal distribution of 139 solar flares monitored by the Gamma Ray Spectrometer aboard the Solar Maximum Mission is reported. It is found that, instead of being randomly distributed in time, these events have a tendency to occur in groups with a mean spacing of about 154 days (75 nHz) over the observing interval. A larger sample of flares with an X-ray classification of M 2.5 or larger recorded by the GOES satellite showed a similar regularity.

Structure, Morphology, and Crystal Growth of Bacterial Magnetite

Abstract: The biological synthesis of the mixed-valence iron oxide magnetite (Fe3O4) poses several fascinating and intriguing questions for the solid state and materials scientist. Preparation of magnetite in the laboratory requires an experimental regime which often includes high temperature, high pressure, and high pH. A further aspect of inorganic synthesis is the experimental difficulty involved in the preparation of particles of homogeneous shape and size. Biological reactions, however, are characterized by their selectivity and precision in functional design. In this way biosolid-state reactions can arise which establish the formation of magnetite under conditions of ambient temperature and pressure and at pH values close to neutral. Furthermore, precise biological control over the activation and regulation of the solid-state processes can result in magnetite particles of well-defined size and crystallographic morphology. These aspects of chemical, stereo, and crystallographic specificity in biosolid-state reactions are important criteria which need to be investigated and elucidated, as knowledge concerning such novel solid-state processes may be important in the development and design of new materials for technological use.

Identification of new genes involved in the regulation of yeast alcohol dehydrogenase II.

Abstract: Recessive mutations in two negative control elements, CRE1 and CRE2, have been obtained that allow the glucose-repressible alcohol dehydrogenase (ADHII) of yeast to escape repression by glucose. Both the cre1 and cre2 alleles affected ADHII synthesis irrespective of the allele of the positive effector, ADR1. However, for complete derepression of ADHII synthesis, a wild-type ADR1 gene was required. Neither the cre1 nor cre2 alleles affected the expression of several other glucose-repressible enzymes. A third locus, CCR4, was identified by recessive mutations that suppressed the cre1 and cre2 phenotypes. The ccr4 allele blocked the derepression of ADHII and several other glucose-repressible enzymes, indicating that the CCR4 gene is a positive control element. The ccr4 allele had no effect on the repression of ADHII when it was combined with the ADR1-5c allele, whereas the phenotypically similar ccr1 allele, which partially suppresses ADR1-5c, did not suppress the cre1 or cre2 phenotype. Complementation studies also indicated that ccr1 and snf1 are allelic. A model of ADHII regulation is proposed in which both ADR1 and CCR4 are required for ADHII expression. CRE1 and CRE2 negatively control CCR4, whereas CCR1 is required for ADR1 function.

Community Recovery After Storm Damage: A Case of Facilitation in Primary Succession

Abstract: Manipulations of early arriving, fast-growing algal stands, which appeared soon after a severe storm denuded a Southern California marine reef habiatat, indicated that the dense cover protected newly settled kelp plants from excessive damage by grazing fishes. This is an example of refuge facilitation in primary succession after a major natural disturbance, a mechanism that may contribute substantially to the regeneration of a kelp forest.

Numerical simulation of reconnection in an emerging magnetic flux region

Abstract: The resistive MHD equations are numerically solved in two dimensions for an initial-boundary-value problem which simulates reconnection between an emerging magnetic flux region and an overlying coronal magnetic field The emerging region is modelled by a cylindrical flux tube with a poloidal magnetic field lying in the same plane as the external, coronal field The plasma betas of the emerging and coronal regions are 10 and 01, respectively, and the magnetic Reynolds number for the system is 2 × 103 At the beginning of the simulation the tube starts to emerge through the base of the rectangular computational domain, and, when the tube is halfway into the computational domain, its position is held fixed so that no more flux of plasma enters through the base Because the time-scale of the emergence is slower than the Alfven time-scale, but faster than the reconnection time-scale, a region of closed loops forms at the base These loops are gradually opened and reconnected with the overlying, external magnetic field as time proceeds The evolution of the plasma can be divided into four phases as follows: First, an initial, quasi-steady phase during which most of the emergence is completed During this phase, reconnection initially occurs at the slow rate predicted by the Sweet model of diffusive reconnection, but increases steadily until the fast rate predicted by the Petschek model of slow-shock reconnection is approached Second, an impulsive phase with large-scale, super-magnetosonic flows This phase appears to be triggered when the internal mechanical equilibrium inside the emerging flux tube is upset by reconnection acting on the outer layers of the flux tube During the impulsive phase most of the flux tube pinches off from the base to form a cylindrical magnetic island, and temporarily the reconnection rate exceeds the steady-state Petschek rate (At the time of the peak reconnection rate, the diffusion region at the X-line is not fully resolved, and so this may be a numerical artifact) Third, a second quasi-steady phase during which the magnetic island created in the impulsive phase is slowly dissipated by continuing, but low-level, reconnection And fourth, a static, non-evolving phase containing a potential, current-free field and virtually no flow During the short time in the impulsive phase when the reconnection rate exceeds the steady-state Petschek rate, a pile-up of magnetic flux at the neutral line occurs At the same time the existing Petschek-slow-mode shocks are shed and replaced by new ones; and, for a while, both new and old sets of slow shocks coexist

The seagrass filter: purification of estuarine and coastal waters

Abstract: Seagrasses can provide a “filtering” mechanism in estuarine waters by trapping suspended sediments and taking up dissolved water column nutrients. These two processes are discussed from the perspective of water filtration by seagrasses in an effort to establish the plants1 benefit to the estuarine system. Previous examinations of such processes have stressed environmental influences on seagrass plants, overlooking the impact that seagrasses may have on the environment. Our approach to the concept of seagrass as a filter has been to examine previous work and combine it with results of measurements of suspended sediment and dissolved nutrient removal in culture tank systems with and without seagrasses. In manipulation experiments, suspended sediment removal was measured by the increase in light penetration, and varied according to added sediment type. Nutrient addition and subsequent depletion in the water column of the culture tanks was measured to determine seagrass community uptake rates. These rates were then extrapolated to a somewhat eutrophic coastal environment for evaluation of potential nutrient removal by seagrasses. A synopsis of these filtering experiments and other studies indicates that seagrass communities remove material of natural or human origin from estuarine waters, but excessive loading of nutrients or suspended material upsets the balance of the seagrass ecosystem, promoting degradation of the seagrass beds and loss of the filtering mechanism.

Surgical Electrotechnology: Quo Vadis?

Abstract: The development of the modern electrosurgical generator and its accessories is outlined. The use of the electrosurgical scalpel is compared to other thermal knives: the plasma scalpel and the laser. The evolution of the dispersive electrode is summarized. Some of the innovations in endoscopic electrosurgery and the associated problems are discussed, along with a summary of some current research in hazard detection and waveform generating techniques and its impact on the next generation of electrosurgical generators.

Dietary vanadyl(IV) sulfate inhibits chemically-induced mammary carcinogenesis.

Abstract: The induction of murine mammary carcinogenesis by 1-methyl-1-nitrosourea was blocked by the feeding of a purified diet formulation supplemented with 25 p.p.m. vanadium as vanadyl(IV) sulfate during the post initiation stages of the neoplastic process. Treatment with vanadyl(IV) sulfate reduced both cancer incidence and the average number of cancers per rat and prolonged the median cancer-free time without inhibiting the overall growth of the animals. Vanadyl(IV) sulfate appears to be an effective non-toxic agent for the chemoprevention of experimental breast cancer in the rat.

Calcification of cyanobacterial mats in Solar Lake, Sinai

Abstract: Pore-water samples were obtained from the shallow-water part of Solar Lake (Sinai) where luxurious cyanobacterial mats grow. These samples were analyzed for Ca/sup 2 +/, Mg/sup 2 +/, Sr/sup 2 +/, Cl/sup -/, SO/sub 4//sup 2 -/, and titration alkalinity (TA) to determine the role of cyanobacterial growth and degradation on the calcification of the mats. The data are modeled thermodynamically to predict mineral-pore-water equilibria. The data support earlier bacterial and sedimentological studies suggesting that the degradation of the cyanobacterial mat via sulfate reduction is of major importance in the calcification process. 34 references, 1 figure, 2 tables.

Eubacteria have 3 growth modes keyed to nutrient flow: consequences for the concept of maintenance and maximal growth yield

Abstract: Aerobic growth of Escherichia coli and Paracoccus denitrificans has been studied in chemostat, fed batch, and recycling fermentor modes under carbon and energy limitation. Two abrupt drops or discontinuities in molar growth yield, Y, have been found that occur over relatively short ranges in the value of specific growth rate.

The Imaging Compton Telescope Comptel on the Gamma Ray Observatory

Abstract: This instrument is based on a newly established concept of ?-ray detection in the very difficult 1-30 MeV range. It employs the unique feature of a two-step interaction of the y-ray: a Compton scattering collision in a first detector followed by an interaction in a second detector element. COMPTEL has been designed to perform a very sensitive survey of the y-ray sky. Extreme care has been taken to minimize background so that the detection limits of COMPTEL will be dominated by source counting statistics. It combines a wide field of view (about 1 steradian) with a good angular resolution. The design criteria of COMPTEL and the perforrmance of a Science Model are described.

Resonant acceleration and heating of solar wind ions: Anisotropy and dispersion

Abstract: This paper is an extension of recent work by Isenberg and Hollweg dealing with the preferential acceleration and heating of solar wind heavy ions by a resonant cyclotron interaction with a turbulent spectrum of ion-cyclotron waves. Two major approximations of the previous work are eliminated: that of isotropic ion distributions, and that of nondispersive waves. The wave action flux of finite-amplitude Alfven waves in a multi-ion, differentially flowing, gyrotropic plasma is derived. This quantity is incorporated into the wave-driven solar wind model of Isenberg and Hollweg, which is then applied to gyrotropic protons and alpha particles. It is found that allowing for nonisotropic ions yields enhanced preferential acceleration of alpha particles. However, when dispersion is included in the resonant interaction, the preferential effects are again reduced. These more realistic calculations show that the observations of solar wind alpha particles cannot be explained by a resonant cyclotron interaction.

Effects of Prostaglandin F2α on Agonist-Induced Progesterone Production in Cultured Bovine Luteal Cells

Abstract: The present study examines the effects of prostaglandin F2 alpha (PGF2 alpha) on basal and agonist-stimulated progesterone (P4) production utilizing long-term, serum-free cultures of bovine luteal cells. During the first 24 h of culture, PGF2 alpha had no significant effect on P4 production, and was unable to inhibit either luteinizing hormone (LH)- or dibutyryl cAMP (dbcAMP)-stimulated increases in P4. Treatment with PGF2 alpha on Day 1 produced a moderate, nonsignificant (P greater than 0.05) inhibition of cholera toxin (CT)- and forskolin (FKN)-stimulated P4 synthesis. Beyond Day 1 of culture (Days 3-11), PGF2 alpha continued to have no significant effect on basal P4 production, but suppressed all stimulatory effects of LH, dbcAMP, CT and FKN. Treatment with indomethacin inhibited prostaglandin synthesis by the cultured cells and also elevated levels of P4 from Days 3 to 11 of culture. Concurrent treatment with PGF2 alpha suppressed the steroidogenic effect of indomethacin. From these studies it was concluded that in cultured bovine luteal cells, PGF2 alpha does not affect basal P4 production, but is able to inhibit agonist-stimulated P4 production at a site beyond the accumulation of cAMP. This inhibitory effect is not apparent during the first 24 h of culture, but appears after Day 1 and persists throughout the remaining 10 days of the culture period.

Interpretation of the chemical and physical time-series retrieved from Sentik Glacier, Ladakh Himalaya, India

Abstract: Spectral analysis of time series of a c. 17 ± 0.3 year core, calibrated for total s activity recovered from Sentik Glacier (4908m) Ladakh, Himalaya, yields several recognizable periodicities including subannual, annual, and multi-annual. The time-series, include both chemical data (chloride, sodium, reactive iron, reactive silicate, reactive phosphate, ammonium, δD, δ(18O) and pH) and physical data (density, debris and ice-band locations, and microparticles in size grades 0.50 to 12.70 μm). Source areas for chemical species investigated and general air-mass circulation defined from chemical and physical time-series are discussed to demonstrate the potential of such studies in the development of paleometeorological data sets from remote high-alpine glacierized sites such as the Himalaya.

Pavlovian determiners of behavioral momentum

Abstract: Pigeons pecked keys on a six-component multiple schedule of food reinforcement arranged in successive pairs on three keys. On all three keys, the schedule in the first component was variable-interval 120 sec. On one key, the second component was variable-time 24 sec; on another, it was variable-time 120 sec; and on the third, extinction. Pairs of components were separated by timeout. In this arrangement, second-component stimuli were differentially correlated with food in their presence, and first-component stimuli were differentially correlated with second-component food in serial fashion. After baseline performance stabilized, resistance to change was assessed by prefeeding, by discontinuing food, and by presenting free food at random times throughout sessions. There was no consistent relation between baseline response rates in the first component and reinforcement rate in the second component. When assessed by prefeeding or extinction, resistance to change in the first component was positively related to reinforcement rate in the second component, demonstrating that serial stimulus-reinforcer contingencies affected resistance to change.

Benefit segmentation –20 years later

Abstract: During the more than twenty years since its inception the technique of Benefit Segmentation has become a familiar method of analyzing markets to discover segmentation opportunities. Almost every major marketer of consumer goods and services has attempted to use this method one or more times. However, the degree of success which has attended its use has varied. In this article its originator, Dr. Russell I. Haley, examines the reasons for this variation, offers guidelines for proper use, and suggests directions for further improvements in the method.

Implications of 10 16 eV γ rays from Cyg X-3

Abstract: Samorski and Stamm1 have reported and Lloyd-Evans et al.2 have recently confirmed the detection of high-energy quanta, presumably γ rays, with energies E>2×1015 eV from Cygnus X-3. These ultra-high energy (UHE) γ rays were detected with extensive air shower arrays and included four events with E>1016 eV. Temporal analyses1,2 of the events indicate that the flux is modulated with a 4.8-h period and is sharply pulsed. Here (1) we discuss the implications of these γ-ray detections and suggest that autocorrelating the air shower data may be the best way to determine the intrinsic width of the γ-ray pulses; (2) we argue that the radiating particles are accelerated by a pulsar and that if they are accelerated according to any pulsar mechanism we know of, then they must be ions; (3) we note that if the ions are accelerated to 1016 eV by a large amplitude Deutsch wave, then the gravitational wave luminosity Lg should exceed that of the Crab pulsar by a factor of ∼5×105, and the spin-down time should be ∼80 yr (requiring a truly remarkable object); and (4) we show that the ions can be accelerated in the near zone but only if, contrary to the standard view, pair production does not greatly reduce the vacuum potential drop in the near zone. We note that near-zone acceleration could be confirmed by detection of curvature radiation.

How disconfirmatory, confirmatory and combined strategies affect group problem solving

Abstract: This paper presents three experiments designed to test Karl Popper's idea that scientists should try to falsify, or disconfirm, their hypotheses instead of verifying them. Previous studies indicate that subjects trained to falsify do no better on scientific problem-solving tasks than subjects trained to confirm. But these studies have all focused on individual subjects. Scientists frequently work in groups. To see how groups disconfirm, subjects in the first two studies reported here were run in groups of four. They were asked to solve a series of related problems based on ‘New Eleusis’, a task designed to model the ‘search for truth’. In the first study, group members were either allowed to interact or told to work separately. This variable was crossed with a strategy (disconfirmatory vs. confirmatory) variable. There were no significant differences. In the second study, only interacting groups were run, some methodological problems with the strategy variable were cleared up and a third strategy that combined elements of confirmation and disconfirmation was added. Disconfirmatory groups solved significantly more problems (72 per cent) than confirmatory (25 per cent) with combined (50 per cent) falling in between. Disconfirmatory groups also made significantly more attempts to falsify their hypotheses. To see if the same results would hold for individuals working on a different task, subjects were trained to disconfirm, confirm or use no strategy on Wason's 2–4-6 task. Disconfirmatory subjects were again significantly more successful. The overall results suggest that a disconfirmatory strategy is superior for both groups and individuals on tasks that simulate scientific problems. Reasons why this effect was obtained in the present research but not in earlier studies are discussed.

Dewatering of an unvegetated muddy tidal flat during exposure-desiccation or drainage?

Abstract: An unvegetated muddy tidal flat was sampled to determine the changes in surface pore water content and salinity during exposure. Local evaporation accounted for 61% of the upper intertidal surface salinity, with evaporation rates increasing salinity as high as 2.2‰ per hour. In contrast, only 37% of the decrease in pore water content was attributed to evaporative processes. This suggests that drainage (a combination of porosity and permeability) controlled the water content rather than local evaporative conditions.