Machine learned interatomic potential for dispersion strengthened plasma facing components.

Tungsten (W) is a material of choice for the divertor material due to its high melting temperature, thermal conductivity, and sputtering threshold. However, W has a very high brittle-to-ductile transition temperature, and at fusion reactor temperatures (≥1000 K), it may undergo recrystallization and grain growth. Dispersion-strengthening W with zirconium carbide (ZrC) can improve ductility and limit grain growth, but much of the effects of the dispersoids on microstructural evolution and thermomechanical properties at high temperatures are still unknown. We present a machine learned Spectral Neighbor Analysis Potential for W-ZrC that can now be used to study these materials. In order to construct a potential suitable for large-scale atomistic simulations at fusion reactor temperatures, it is necessary to train on ab initio data generated for a diverse set of structures, chemical environments, and temperatures. Further accuracy and stability tests of the potential were achieved using objective functions for both material properties and high temperature stability. Validation of lattice parameters, surface energies, bulk moduli, and thermal expansion is confirmed on the optimized potential. Tensile tests of W/ZrC bicrystals show that although the W(110)-ZrC(111) C-terminated bicrystal has the highest ultimate tensile strength (UTS) at room temperature, observed strength decreases with increasing temperature. At 2500 K, the terminating C layer diffuses into the W, resulting in a weaker W-Zr interface. Meanwhile, the W(110)-ZrC(111) Zr-terminated bicrystal has the highest UTS at 2500 K.

Explicit Multielement Extension of the Spectral Neighbor Analysis Potential for Chemically Complex Systems.

A natural extension of the descriptors used in the Spectral Neighbor Analysis Potential (SNAP) method is derived to treat atomic interactions in chemically complex systems. Atomic environment descriptors within SNAP are obtained from a basis function expansion of the weighted density of neighboring atoms. This new formulation instead partitions the neighbor density into partial densities for each chemical element, thus leading to explicit multielement descriptors. For Nelem chemical elements, the number of descriptors increases as [Formula: see text], while the computational cost of the force calculation as implemented in LAMMPS is limited to [Formula: see text] and the favorable linear scaling in the number of atoms is retained. We demonstrate these chemically aware descriptors by producing an interatomic potential for indium phosphide capable of capturing high-energy defects that result from radiation damage cascades. This new explicit multielement SNAP method reproduces the relaxed defect formation energies with substantially greater accuracy than weighted-density SNAP, while retaining accurate representation of the bulk indium phosphide properties.

Klebsiella pneumoniae flocculation dynamics.

The bacterial pathogen Klebsiella pneumoniae is a cause of community- and hospital-acquired lung, urinary tract and blood stream infections. It is a common contaminant of indwelling catheters and it is theorized in that context that systemic infection follows shedding of aggregates off of surface-adherent biofilm colonies. In an effort to better understand bacterial proliferation in the host bloodstream, we develop a PDE model for the flocculation dynamics of Klebsiella pneumoniae in suspension. Existence and uniqueness results are provided, as well as a brief description of the numerical approximation scheme. We generate artificial data and illustrate the requirements to accurately identify proliferation, aggregation, and fragmentation of flocs in the experimental domain of interest.

Searching for globally optimal functional forms for interatomic potentials using genetic programming with parallel tempering.

Molecular dynamics and other molecular simulation methods rely on a potential energy function, based only on the relative coordinates of the atomic nuclei. Such a function, called a force field, approximately represents the electronic structure interactions of a condensed matter system. Developing such approximate functions and fitting their parameters remains an arduous, time-consuming process, relying on expert physical intuition. To address this problem, a functional programming methodology was developed that may enable automated discovery of entirely new force-field functional forms, while simultaneously fitting parameter values. The method uses a combination of genetic programming, Metropolis Monte Carlo importance sampling and parallel tempering, to efficiently search a large space of candidate functional forms and parameters. The methodology was tested using a nontrivial problem with a well-defined globally optimal solution: a small set of atomic configurations was generated and the energy of each configuration was calculated using the Lennard-Jones pair potential. Starting with a population of random functions, our fully automated, massively parallel implementation of the method reproducibly discovered the original Lennard-Jones pair potential by searching for several hours on 100 processors, sampling only a minuscule portion of the total search space. This result indicates that, with further improvement, the method may be suitable for unsupervised development of more accurate force fields with completely new functional forms.

Dopamine receptor pruning during the peripubertal period is not attenuated by NMDA receptor antagonism in rat.

D(1) and D(2) receptors are overproduced and pruned in the mammalian striatum during the periadolescent period. The mechanism that underlies this process in striatum is unknown. However, previous research has shown that the activity-dependent pruning of dendrites and synapses in somatosensory cortex and the visual fields is mediated by glutamatergic actions via N-methyl-D- aspartate (NMDA) receptor and is prevented by pretreatment with the NMDA antagonist MK-801. In order to test the hypothesis that the pruning of dopamine D(1) and D(2) receptors that occurs in the striatum after puberty (which occurs at approximately 40 days of age; P40), male and female rats were treated with saline vehicle or MK-801 (0.3 mg/kg) for 20 or 40 days and sacrificed immediately after the 20 day treatment (P60), 40 day treatment (P80), or 40 day treatment with 40 day recovery (P120). Analyses of the data reveal that none of these three treatment regimens altered striatal D(1) or D(2) receptor density in males or females relative to vehicle controls. At P60, MK-801 treatment failed to alter either D(1) (F1,16=0.06, P>0.5) or D(2) receptors (F1,16=0.39, P>0.5) for either sex. Similarly, MK-801 treatment did not affect D(1) or D(2) receptors at P80 (P>0.3) or at P120 (P>0.7). These data suggest that the normal 40% reduction in striatal dopamine receptor density that occurs between puberty and adulthood is not dependent on post-pubertal glutamatergic transmission through NMDA receptors.

8-aminoquinolines as anticoccidials - Part III.

Analogues of the antimalarial pentaquine, 1, in which the nature of the side-chain on the 8-amino position was varied, were prepared and evaluated for anticoccidial activity both in vitro and in vivo. Specifically, both the inter-nitrogen distance and the nature of the terminal amino group were investigated. Novel analogues of equal or improved efficacy in vitro and in vivo to pentaquine were discovered.

Comparison of WAIS-R and WISC-III scores with a sample of 16-year-old youth.

Scores on the Wechsler Adult Intelligence Scale-Revised (WAIS-R) and Wechsler Intelligence Scale for Children-Third Edition (WISC-III) were compared for 46 youth in the overlapping 16-yr.-age range. Students were administered the tests in a counterbalanced order with an average retest interval of 40 days. Self-reported grade average was also obtained from students. Criteria for parallel tests (equal means, equal variances, equal covariances) were applied in the analyses. WAIS-R and WISC-III summary IQs were parallel, but corresponding subtest scores as a group were not parallel.

8-Aminoquinolines as anticoccidials--II.

During a chemistry program aimed at finding a novel analogue of pentaquine with improved in vivo activity, a number of hypotheses concerning the way this drug acts in the chicken were investigated. Consideration of the products of monoamine oxidase metabolism of pentaquine suggested that pentaquine aldehyde is the likely active metabolite. Although isolation of this unstable compound was not possible, oxime and cyclic acetal and ketal derivatives were obtained and shown to possess in vitro anticoccidial activity.

The unusual adrenergic-like excitatory action of acetylcholine on the ventricular cardiac muscle of the horned shark, Heterodontus portusjacksoni.

The atypical excitatory effect of acetylcholine on cardiac ventricular muscle was investigated in the horned shark, Heterodontus portusjacksoni. Electrically paced ventricular strips produced a massive 391.45% (+/-26.39%) increase in basal force of contraction in response to exogenously applied acetylcholine. The response was similar in nature to that produced by applied adrenaline, which caused a 382.52% (+/-72.47%) increase. The response to acetylcholine was blocked by the muscarinic cholinoceptor antagonist atropine and the competitive beta-adrenoceptor antagonist propranolol and was reduced by bretylium, an agent known to inhibit the release of catecholamines from adrenergic nerves. These findings strongly suggest that acetylcholine mediates a localised release of a catecholamine via muscarinic cholinoceptors in shark heart. A cholinergically controlled catecholamine store has been proposed (cholinergic-adreno complex), implying that elasmobranchs may be capable of finer control of cardiac output than has previously been suspected. This complex may represent a transitional adrenergic state between humoral and neuronal regulation. The spontaneously beating atrium showed no evidence of such an excitatory response to applied acetylcholine but produced an atropine-sensitive slowing, a response typical of other vertebrates.

Evaluation of an Icelandic translation of the Basic Personality Inventory using a bilingual sample.

This study investigated the similarity of Icelandic and English versions of the Basic Personality Inventory (BPI), a 240-item measure of psychopathology. Eighty-nine native Icelandic graduate students studying in North America completed both language versions of the BPI in a counterbalanced order with a retest interval of approximately one month. The results of this bilingual retest study confirmed the adequacy of the Icelandic translation. Specifically, scale means, test-retest coefficients, and reliability coefficients demonstrated that the BPI performed highly similarly in both language versions. These findings provide additional support for the adequacy and applicability of the Icelandic translation of the BPI.

Test-retest evaluation of a four-subtest WAIS-R short form with young offenders.

The validity of a four-subtest short form (SF4) of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) was evaluated in a sample of incarcerated Caucasian and Native youth 16 to 18 years of age. A test-retest methodology was used in which 21 subjects received SF4 first and 26 subjects received the full WAIS-R first. Results showed that SF4 has validity as an estimate of Full Scale IQ, but with accuracy limitations. In addition to the IQ overestimates and misclassification rates that have been found in other short form research, this study showed that a large overestimate of about 11 points occurred on average when SF4 followed the standard administration.

Frequently cited sources in human sexology: a nineties update.

Counting citations in journals devoted to human sexology can provide increased awareness of important clinical and research contributions. The exercise also reveals trends in the field and serves as a guide to an ever increasing literature. This article provides lists of authors, books, and articles frequently cited in three authoritative sexuality journals. Frequency counts were based on 5,742 references over a two-year period. Results are discussed and compared with the findings from the same analysis a decade ago.

The stability of WAIS-R IQ for 16-year-old students retested after 3 and 8 months.

The stability of Wechsler Adult Intelligence Scale-Revised IQs was investigated for 52 students 16 years of age. Half of the subjects were retested after a 3-month interval; half after an 18-month interval. Stability coefficients were uniformly high for both retest intervals. Gains in Verbal, Performance, and Full Scale IQ over 3 months were similar to practice effects reported for adult subjects. However, IQs for males retested after 18 months increased beyond the practice effect. Females retested after 18 months showed the same result only on Verbal IQ. The findings remind clinicians of the important distinction between relative and absolute stability, especially for 16-year-old students tested with the WAIS-R.

Subtest scatter is not an indicator of inaccuracy for short-form estimates of IQ.

The range of scaled scores does not provide information about the inaccuracy of estimates of IQ based on short forms of the test. Subtest scatter on a short form of an intelligence test may justify the complete administration for elaborative or clinical reasons. The criteria for reliable and abnormal ranges of scores for estimates based on short forms are calculable and should be examined to evaluate their usefulness.

Methodological issues in the clinical evaluation of two- and four-subtest short forms of the WAIS-R.

The evaluation of two- and four-subtest short forms of the WAIS-R has proceeded with little empirical attention to the effects of shortened administration time upon test performance. Routinely, the full WAIS-R has been administered and short form estimates extracted from the complete set of test results. Time and motivational/attentional factors can be evaluated by the administration of short form subtests first, followed by the remaining subtests in standard order or, alternatively, by the test-retest paradigm with short and complete WAIS-R versions. Limitations of these methodologies and existing empirical results are discussed.

Frequently cited sources in human sexology.

Counting professional citations in the field of human sexology can yield an increased understanding of important clinical/research contributions, their authors and institutions, and central topics within an ever-increasing body of sexological information. This article provides lists of both authors and specific articles and books that are frequently cited in recent sex research. Frequency analyses were based on 4440 references in three major sex research journals for two complete years. Results are discussed in terms of citation patterns and their implications.

Extramarital sexual crisis: common themes and therapy implications.

The extramarital crisis situation is defined and six common themes presented. These distinguishing features: cognitive and emotional turmoil, unresolved relationship issues, defensiveness, pressures related to the extramarital partner(s), search for an interpretive framework, and decisions about the future, are elaborated in terms of existing literature in the field of extramarital sex. The six themes constitute a general profile from which therapists can formulate specific client assessments. Therapy implications are dealt with for each theme and collectively represent an approach to extramarital crises and a summarization of existing clinical strategies. Some research data is presented as further verification of the six-theme framework.