Probability Of Disruption Research Articles

Indirect partner choice through manipulation of male behaviour by female fowl, Gallus gallus domesticus.

The direct and indirect consequences of female copulatory behaviour for copulation success have seldom been quantified. In feral fowl, most copulations were forced by males and copulation success was determined by two factors. First, female differential resistance and solicitation directly affected copulation success and were displayed non-randomly with respect to male social status. Second, another female copulatory behaviour, the distress call, had an indirect effect on both copulation success and the quality of copulation partners. Distress calls triggered male attention to a copulation, which increased the probability of higher-ranking males than the copulating male disrupting the copulation and inseminating the calling female. Females preferentially uttered distress calls when mounted by low-ranking males. Both copulation resistance and distress calling influenced copulation success, but only distress calling increased the probability of copulation disruption by other males. Consistent with the effect of direct selection, differential distress calling indirectly biased copulation success in favour of dominant males. Female fowl may thus ameliorate the effect of male sexual coercion by manipulating male behaviour.

Hydrogen-bond disruption probability in proteins by a modified self-consistent harmonic approach.

Modified self-consistent harmonic approach was employed to calculate the probability for the disruption of each individual hydrogen bonds (H bonds) in x-ray crystal structure of several proteins. The computed probability for 82% of intraprotein and water-protein H bonds studied were found to be roughly consistent with estimated free energies from protein engineering and hydrogen exchange experiments. Hydrogen bonds have been proposed as part of a stereochemical code for protein folding. Proteins fold into unique three-dimensional structures; therefore those bonds involved in the folding code are expected to be stable. We have applied this method to tens of hydrogen bonds in a protein assumed to be involved in the folding code of a protein. 58% of these H bonds were found to have a lower disruption probability (-1.8 kcal/mol). Our results showed that modified self-consistent harmonic approach might be explored as a method supplement to existing methods in analysis of hydrogen bonds in proteins.

Geologic factors controlling patterns of small‐volume basaltic volcanism: Application to a volcanic hazards assessment at Yucca Mountain, Nevada

The proposed high‐level radioactive waste repository at Yucca Mountain, Nevada, is located within an active volcanic field. Probabilistic volcanic hazard models for future eruptions through the proposed repository depend heavily on our understanding of the spatial controls on volcano distribution at a variety of scales. On regional scales, Pliocene‐Quaternary volcano clusters are located east of the Bare Mountain fault. Extension has resulted in large‐scale crustal density contrast across the fault, and vents are restricted to low‐density areas of the hanging wall. Finite element modeling indicates that this crustal density contrast can result in transient pressure changes of up to 7 MPa at 40 km depth, providing a mechanism to generate partial melts in areas where mantle rocks are already close to their solidus. On subregional scales, vent alignments, including one alignment newly recognized by ground magnetic mapping, parallel the trends of high‐dilation tendency faults in the Yucca Mountain region (YMR). Forty percent of vents in the YMR are part of vent alignments that vary in length from 2 to 16 km. Locally, new geological and geophysical data show that individual vents and short vent alignments occur along and adjacent to faults, particularly at fault intersections, and left‐stepping en echelon fault segments adjacent to Yucca Mountain. Conditions which formed these structures persist in the YMR today, indicating that volcanism will likely continue in the region and that the proposed repository site is within an area where future volcanism may occur. On the basis of these data the probability of volcanic disruptions of the proposed repository is estimated between 10−8/yr and 10−7/yr.

Modified self-consistent harmonic approach to thermal fluctuational disruption of disulfide bonds in proteins.

Disulfide bonds (covalent bonds between two sulfur atoms on separate amino acid cysteines) play an important role in the folding stability of many proteins. The determination of the dynamic stability of disulfide bonds can therefore facilitate an understanding of the mechanism of protein stability. We have examined whether a modified self-consistent harmonic approach, which has been successful in modeling hydrogen bond breaking dynamics in DNA and covalent bond disruption in drug-DNA systems, is useful in computing thermal fluctuational disruption probability of disulfide bonds in proteins. Our results on a number of protein x-ray crystal structures showed that the computed disruption probabilities are consistent with observations. The free energies derived from computed probabilities are comparable to the observed values from protein engineering experiments. The method presented here has a potential application in analyzing disulfide bond dynamics in a variety of biological processes.

Transition to classical behavior in mesoscopic magnetic systems and quantum decoherence

A mesoscopic CrNi6 system is used to demonstrate the possibility of transitions from quantum to classical behavior in thermally stimulated tunneling processes. The main mechanism responsible for these transitions is assumed to be quantum decoherence produced as a result of thermal interaction between the spin system and its neighborhood. Results are presented of calculations of the disruption probability for a mesoscopic system as a function of temperature. It is shown that the main characteristic which can reveal the decoherence effect is the nonmonotonic behavior of the disruption probability at low temperatures.

Giant Craters on Mathilde

Mathilde possesses at least five giant craters, where crater diameters are comparable to the mean radius of the body. Initially, it seems remarkable that this asteroid survived such an onslaught of impacts without disrupting. We consider implications of giant cratering on Mathilde, including effects of oblique impacts. Experimental databases and theory indicate that oblique impacts are (1) less likely to disrupt a target, (2) produce less ejecta relative to a normal impact, and (3) most often do not generate elongated craters. Moreover, oblique impacts reduce crater sizes and ejecta volumes particularly in the case of giant craters, where projectile fragments can miss the target. The morphology of giant craters on Mathilde and the lack of obvious ejecta are consistent with formation by oblique impacts, which could help explain why Mathilde survived. The composition and low density of Mathilde probably indicate a porous and volatile-rich body. Target porosity attenuates shock waves and enhances survival without catastrophic disruption. It is not surprising that several giant craters can be formed on a body without disrupting it. For a realistic projectile population, the probability of making a giant crater on Mathilde is 2.1 to 2.6 times greater than the probability of disruption. The probability of Mathilde surviving the formation of five giant craters is approximately 1 in 5 to 1 in 7.

Managing Corporate FX Risk: A Value-Maximizing Approach

This paper develops a new approach for evaluating FX management programs. It presents a value-maximizing strategy based on minimizing the probability of business disruption. It argues that such a policy is an appropriate objecting for a corporate FX hedging program and shows that minimization of the variance of the hedged cash flow is neither necessary no sufficient for an FX hedging program to be optimal.

PtGAs—Genetic Algorithms Evolving Noncoding Segments by Means of Promoter/Terminator Sequences

In this article we present work on chromosome structures for genetic algorithms (GAs) based on biological principles. Mainly, the influence of noncoding segments on GA behavior and performance is investigated. We compare representations with noncoding sequences at predefined, fixed locations with "junk" code induced by the use of promoter/terminator sequences (ptGAs) that define start and end of a coding sequence, respectively. As one of the advantages of noncoding segments a few researchers have identified the reduction of the disruptive effects of crossover, and we solidify this argument by a formal analysis of crossover disruption probabilities for noncoding segments at fixed locations. The additional use of promoter/terminator sequences not only enables evolution of parameter values, but also allows for adaptation of number, size, and location of genes (problem parameters) on an artificial chromosome. Randomly generated chromosomes of fixed length carry different numbers of promoter/terminator sequences resulting in genes of varying size and location. Evolution of these ptGA chromosomes drives the number of parameters and their values to (sub)optimal solutions. Moreover, the formation of tightly linked building blocks is enhanced by self-organization of gene locations. We also introduce a new, nondisruptive crossover operator emerging from the ptGA gene structure with adaptive crossover rate, location, and number of crossover sites. For experimental comparisons of this genetic operator to conventional crossover in GAs, as well as properties of different ptGA chromosome structures, an artificial problem from the literature is utilized. Finally, the potential of ptGA is demonstrated on an NP-complete combinatorial optimization problem.

A Disequilibrium Analysis of Incidental Teaching

An important goal of reinforcement models and procedures is to predict the direction and magnitude of reinforcement effects. Although traditional models of reinforcement have been unable to adequately predict effects, Timberlake and Farmer-Dougan (1991) have suggested that the disequilibrium model provides such a framework for specifying reinforcers ahead of time. Further, they suggest that incidental teaching may be one procedure in which such predictions may be made. The present experiment investigated the reinforcement effects produced by changes in the probability of disruption of an initiation to a toy item. Four preschoolers served as the participants in the experiment. Results indicated that there appeared to be an optimal level for disrupting ongoing behavior, above or below which reinforcement effects greatly suffered. These findings, although not a direct test of the disequilibrium model ol reinforcement, are consistent with and predicted by the model.

Vibrational normal modes and dynamical stability of DNA triplex poly(dA). 2poly(dT): S-type structure is more stable and in better agreement with observations in solution

A normal-mode and statistical mechanical calculation was carried out to determine the vibrational normal modes, contribution of internal fluctuations to the free energy, and hydrogen bond disruption of DNA triplex poly(dA).2poly(dT). The calculation was performed on both the x-ray fiber diffraction model with a N-type sugar conformation, and a newly proposed model with a S-type sugar conformation. Our calculated normal modes for the S-type structure are in better agreement with observed IR spectra for samples in D2O solution. We also find that the contribution of internal fluctuations to free energy, premelting hydrogen bond disruption probability, and hydrogen bond melting temperatures for the Hoogsteen and Watson-Crick hydrogen bonds all show that the S-type structure is dynamically more stable than the N-type structure in a nominal solution environment. Therefore our calculation supports experimental findings that the triplex d(T)n.d(A)nd(T)n most likely adopts a S-type sugar conformation in solution or at high humidity. Our calculations, however, do not preclude the possibility of an N-type conformation at lower humidities.

Sequence and temperature effect on hydrogen bond disruption in DNA determined by a statistical analysis.

We use the modified self-consistent phonon approximation theory to calculate temperature dependent interbase hydrogen bond disruption profiles for a number of six base pair repeating sequence infinite B-DNA polymers with various guanine-cytosine/adenine-thymine ratios. For comparison we also include results we have obtained in our earlier work on several B-DNA homopolymers, copolymers and a four-base-pair repeating sequence polymer. Our theory gives a statistical estimate of thermal fluctuational disruption probability of individual hydrogen bonds in individual base pairs in DNA as a function of temperature. The calculated probabilities show no sequence dependence at premelting temperatures, in agreement with proton exchange measurements. These probabilities however become very sensitive to base sequence at temperatures close to the observed melting temperatures. Multiphasic critical transitions are found in which a portion of base pairs are disrupted at temperature below the final disruption temperature. These transitions include localized as well as non-localized base pair opening. The localized transitions involve disruption of a few base-pairs at every other location without large scale base unstacking, and they may not appear in the observed UV curves with current resolution. On the other hand the overall disruption behavior is consistent with observations. The midpoint transition temperatures are close to the observed melting temperatures and these temperatures show the observed linear dependence on guanine-cytosine content. Our calculations indicate that our theory can be used effectively to calculate H-bond disruption behavior of different DNA sequences.

Melting profile and temperature dependent binding constant of an anticancer drug daunomycin-DNA complex.

We calculate thermal fluctuational base pair opening probability and the drug binding constant of a daunomycin-bound Poly d(CGTA).Poly d(TACG) at temperatures from room temperature to its melting temperature. For comparison we also carry out a calculation on a drug-free DNA with the same sequence. Our calculations are carried out by means of a statistical approach using microscopic structures and established force fields and with cooperative effects incorporated into the algorithm. Both hydrogen bond disruption probabilities and drug unstacking probability are determined self-consistently. These probabilities are then used to determine temperature dependent base pair opening probabilities and the drug binding constant. The calculated base pair opening probabilities and drug binding constant are found to be in fair agreement with experiments carried out at room temperature. Our calculation shows cooperative base pair disruption and drug dissociation at certain critical temperatures close to the observed melting temperatures for similar helices. We find that the temperature dependence of the drug binding constant fits well to the van't Hoff relation, in agreement with observations. Our calculation indicates the occurrence of a premelting transition in the drug-bound DNA helix. Some comments are made about this premelting transition.

Suppression of psi ' and J/ psi in high-energy heavy-ion collisions.

The experimental ratio of $\psi'$ to $J/\psi$ is approximately a constant in $pA$ collisions, but decreases as the transverse energy increases in nucleus-nucleus collisions. These peculiar features can be explained as arising from approximately the same $c \bar c$-baryon absorption cross section for $\psi'$ and $J/\psi$ but greater disruption probabilities for $\psi'$ than for $J/\psi$ due to the interaction of the $c\bar c$ system with soft particles produced in baryon-baryon collisions.

A model for the seismic reliability assessment of electric power transmission systems

A comprehensive model to evaluate the seismic reliability of electric power transmission systems is presented. The model provides information on the probability of structural failure of critical equipment at the major substations, from which the corresponding probabilities of power disruption to a given service area are determined. With the proposed methodology earthquake ground motions are defined as stochastic processes, and seismic capacities of electrical equipment are determined on the basis of available test data and simple modeling, from which fragility functions of critical equipment and specific substations are developed. Probabilities of power disruption resulting from network disconnectivity and abnormal power flow are assessed through Monte Carlo simulation. As a case study, the proposed model is applied to the electric power network in San Francisco and vicinity under the 1989 Loma Prieta earthquake, and the probabilities of power interruption are contrasted with the actual power failures observed during that earthquake.

Series ferroresonance in power systems

Nonlinear oscillations in power systems involving the excitation of nonlinear inductance with a linear capacitance in series have been termed ferroresonant oscillations, Such oscillations are unpredictable and their occurrence is of serious concern predominantly because of possible damage to equipment such as transformers. The probability of system disruption due to the occurrence of ferroresonance has increased with improvements in the characteristics of transformer steel and the use of higher and higher voltages for transmission of bulk power. Conditions that lead to the occurrence of ferroresonant oscillation, given a system, therefore, need to be known. It will be shown that for any disturbance the autonomous form of the nonlinear differential equation representing the system with two-degrees of freedom deca ys to a point attractor; that is, it is always stable. The non-autonomous form of the system's equation, however, exhibits the possibility of occurrence of a cyclic fold bifurcation which causes ferroresonant oscillations with two stable states to co-exist. Each stable state can, however, be either harmonic, periodic, subharmonic or aperiodic. Aperiodic oscillations occur when satisfactory conditions for the occurrence of subharmonic cascade exist.

Energy security Coping with multiple supply risks

This study starts from the observation that today's Western trading nations are exposed to multiple risks of energy supplies, eg simultaneous shortage of oil and gas supplies. To cope with these risks, both oil and gas can be stockpiled. Adopting the viewpoint of a policy maker who aims at minimizing the expected cost of security of supply, optimal simultaneous adjustments of oil and gas stocks to exogenous changes such as an increase in the probability of supply disruption are derived. Against this benchmark, one-dimensional rules such as ‘oil reserves for 90 days’ turn out to be not only suboptimal but also to suggest adjustments exacerbating suboptimality.

Three nonhomogeneous Poisson models for the probability of basaltic volcanism: Application to the Yucca Mountain region, Nevada

The distribution and timing of areal basaltic volcanism are modeled using three nonhomogeneous methods: spatio‐temporal nearest neighbor, kernel, and nearest‐neighbor kernel. These models give nonparametric estimates of spatial or spatio‐temporal recurrence rate based on the positions and ages of cinder cones and related vent structures and can account for migration and shifts in locus, volcano clustering, and development of regional vent alignments. The three methods are advantageous because (1) recurrence rate and probability maps can be made, facilitating comparison with other geological information; (2) the need to define areas or zones of volcanic activity, required in homogeneous approaches, is eliminated; and (3) the impact of uncertainty in the timing and distribution of individual events is particularly easy to assess. The models are applied to the Yucca Mountain region (YMR), Nevada, the site of a proposed high‐level radioactive waste repository. Application of the Hopkins F test, Clark‐Evans test, and K function indicates volcanoes cluster in the YMR at the >95% confidence level. Weighted‐centroid cluster analysis indicates that Plio‐Quaternary volcanoes are distributed in four clusters: three of these clusters include cinder cones formed <1 Ma. Probability of disruption within the 8 km2 area of the proposed repository by formation of a new basaltic vent is calculated to be between 1 × 10−4 and 5 × 10−4 in 104 years (the kernel and nearest‐neighbor kernel methods give a maximum probability of 5 × 10−4 in 104 years), assuming regional recurrence rates of 5–10 volcanoes/m.y. An additional finding, illustrating the strength of nonhomogeneous methods, is that maps of the probability of volcanic eruption for the YMR indicate the proposed repository lies on a steep probability gradient: volcanism recurrence rate varies by more than 2 orders of magnitude within 20 km. Insight into this spatial scale of probability variation is a distinct benefit of application of these methods to hazard analysis in areal volcanic fields.

Radial velocities of stars in the globular cluster M4 and the cluster distance

The internal stellar velocity distribution of the globular cluster M4 is evaluated from nearly 200 new radial velocity measurements good to 1 km/s and a rederivation of existing proper motions. The mean radial velocity of the cluster is 70.9 +/- 0.6 km/s. The velocity dispersion is 3.5 +/- 0.3 km/s at the core, dropping marginally towards the outskirts. Such a low internal dispersion is somewhat at odds with the cluster's orbit, for which the perigalacticon is sufficiently close to the galactic center that the probability of cluster disruption is high; a tidal radius two-thirds the currently accepted value would eliminate the discrepancy. The cluster mass-to-light ratio is also small, M/L(sub V) = 1.0 +/- 0.4 in solar units. M4 thus joins M22 as a cluster of moderate and concentration with a mass-to-light ratio among the lowest known. The astrometric distance to the cluster is also smaller than expected, 1.72 +/- 0.14 kpc. This is only consistent with conventional estimates of the luminosity of horizontal branch stars provided an extinction law R = A(sub V)/E(B-V) approximately 4 is adopted, as has been suggested recently by several authors.

A Comparison of Mate Guarding Among Five Syntopic Tiger Beetle Species from Peninsular India (Coleoptera: Cicindelidae)

Male tiger beetles continue to ride in amplexus on the backs of females after copulation. In scrub forest of peninsular India, the duration of this post-copulatory behavior was significantly different among five syntopic, congeneric species. Field and laboratory tests showed generally that males were present in the mating area at a higher proportion than females and that males remained mounted on females significantly longer when another male was present than when pairs were alone. These results are consistent with the interpretation of this amplexus as mate guarding. Four tests of comparative behavioral and ecological conditions were then used to explain the differential duration of amplexus observed among these co-occurring tiger beetle species: operational sex ratios, harassment and potential displacement of mating pair by unmated males, duration of female stay in mating area following copulation, and distance between mating area and oviposition site. Species differences in duration of female stay in the mating area after copulation and to a lesser degree operational sex ratios predicted amplexus duration for three of the species. The distance between mating area and oviposition site predicted the amplexus duration of the final two species. Probability of disruption by unmated males and frequency of male displacement during mating had little or no relation to any of the species differences in amplexus duration.

Theory of pressure-dependent melting of the DNA double helix: Role of strained hydrogen bonds.

In this paper we study the effect of hydrostatic pressure on the thermal stability of DNA base pairs. The thermal stability of a base pair is predominantly determined by the fluctuational motion of the interbase hydrogen bonds in the base pair. We postulate that the pressure exerted on the surface of DNA creates a compressive stress in the interbase hydrogen bonds. This stress in turn induces a strain in these hydrogen bonds. The effect of this compressive stress on the thermal fluctuational motion of the strained interbase hydrogen bonds in DNA can be analyzed by the modified self-consistent phonon approximation theory. We calculate individual hydrogen bond disruption probabilities and base pair opening probabilities of two B-conformation DNA polymers, an adenine-thymine copolymer and a guanine-cytosine homopolymer, at various pressures and at temperatures both in the premelting region and in the helix-coil transition region. Our calculated pressure dependence of the melting temperature for both polymers is in fair agreement with experimental observations. Our values for the melting temperatures are also in agreement with observation and our theory is successful as a theory of cooperative melting.