An Energy Conserving Finite Difference Scheme for Simulation of Collisions

Nonlinear phenomena play an essential role in the sound production process of many musical instruments. A common source of these effects is object collision, the numerical simulation of which is known to give rise to stability
issues. This paper presents a method to construct numerical schemes that conserve the total energy in simulations of one-mass systems involving collisions, with no conditions imposed on any of the physical or numerical parameters.
This facilitates the adaptation of numerical models to experimental data, and allows a more free parameter adjustment in sound synthesis explorations. The energy preservedness of the proposed method is tested and demonstrated though several examples, including a bouncing ball and a non-linear oscillator, and implications regarding the wider applicability are discussed.

Genetic and morphological characterization of Cladobotryum species causing cobweb disease of mushrooms

Cladobotryum dendroides (= Dactylium dendroides) has hitherto been regarded as the major causal agent of cobweb disease of the cultivated mushroom, Agaricus bisporus. Nucleotide sequence data for the internal transcribed spacer (ITS) regions of four Cladobotryum/Hypomyces species reported to be associated with cobweb disease, however, indicate that the most common pathogen is now C. mycophilum. This cobweb pathogen varies somewhat in conidial septation from published descriptions of C. mycophilum and lacks the distinctive colony odor. ITS sequencing revealed minor nucleotide variation which split isolates of the pathogen into three subgroups, two comprising isolates that were sensitive to methylbenzimidazole carbamate (MBC) fungicides and one comprising MBC-resistant isolates. The MBC-resistant isolates, which were only obtained from Ireland and Great Britain, clustered together strongly in randomly amplified polymorphic DNA (RAPD) PCR analysis, suggesting that they may be clonal. The MBC-sensitive isolates were more diverse. A RAPD fragment of 800 to 900 bp, containing a microsatellite and found in the MBC-resistant isolates, also indicated their clonal nature; the microsatellites of these isolates contained the same number of GA repeats. Smaller, polymorphic microsatellites, similarly comprising GA repeats, in the MBC-sensitive isolates in general correlated with their geographic origin.

Molecular Phylogenies Support Homoplasy of Multiple Morphological Characters Used in the Taxonomy of Heteroscleromorpha (Porifera: Demospongiae)

Sponge classification has long been based mainly on morphocladistic analyses but is now being greatly challenged by more than 12 years of accumulated analyses of molecular data analyses. The current study used phylogenetic hypotheses based on sequence data from 18S rRNA, 28S rRNA, and the CO1 barcoding fragment, combined with morphology to justify the resurrection of the order Axinellida Lévi, 1953. Axinellida occupies a key position in different morphologically derived topologies. The abandonment of Axinellida and the establishment of Halichondrida Vosmaer, 1887 sensu lato to contain Halichondriidae Gray, 1867, Axinellidae Carter, 1875, Bubaridae Topsent, 1894, Heteroxyidae Dendy, 1905, and a new family Dictyonellidae van Soest et al., 1990 was based on the conclusion that an axially condensed skeleton evolved independently in separate lineages in preference to the less parsimonious assumption that asters (star-shaped spicules), acanthostyles (club-shaped spicules with spines), and sigmata (C-shaped spicules) each evolved more than once. Our new molecular trees are congruent and contrast with the earlier, morphologically based, trees. The results show that axially condensed skeletons, asters, acanthostyles, and sigmata are all homoplasious characters. The unrecognized homoplasious nature of these characters explains much of the incongruence between molecular-based and morphology-based phylogenies. We use the molecular trees presented here as a basis for re-interpreting the morphological characters within Heteroscleromorpha. The implications for the classification of Heteroscleromorpha are discussed and a new order Biemnida ord. nov. is erected.

On Irish stickleback:Morphological diversification in a secondary contact zone

Question: How parallel is adaptive evolution when it occurs from different genetic backgrounds? Background: Divergent evolutionary lineages of several post-glacial fish species including the threespine stickleback are found together in Ireland. Goals: To investigate the morphological diversity of stickleback populations in Ireland and assess whether morphology evolved in parallel between evolutionary lineages. Methods: We sampled stickleback from lake, river, and coastal habitats across Ireland. Microsatellite and mitochondrial DNA data revealed evolutionary history. Geometric morphometrics and linear trait measurements characterized morphology. We used a multivariate approach to quantify parallel and non-parallel divergence within and between lineages. Results: Repeated evolution of similar morphologies in similar habitats occurred across Ireland, concordant with patterns observed elsewhere in the stickleback distribution. A strong pattern of habitat-specific morphology existed even among divergent lineages. Furthermore, a strong signal of shared morphological divergence occurred along a marine-freshwater axis. Evidently, deterministic natural selection played a more important role in driving freshwater adaptation than independent evolutionary history. © 2013 Mark Ravinet.

Morphological consequences of lateral outfracture of the inferior turbinate

Objective: We report three cases of lateral outfracture of the inferior turbinate, which demonstrate a range of changes in the size, position and shape of the inferior turbinate.

Method: During a study of the validity of computer modelling of nasal airflow, computed tomography scans of the noses of patients who had undergone lateral outfracture of the inferior turbinate were collected. The pre-operative scan was compared with the post-operative scan six weeks later.

Results: In one patient, there was only a small lateral displacement of the inferior turbinate. In the other two cases, appreciable reduction in the volume of one inferior turbinate was noted, in addition to minor changes in the shape.

Conclusion: Lateral outfracture of the inferior turbinate produces varied and inconsistent changes in morphology which may affect the shape, size and position of the turbinate.

Physical and numerical constraints in source modeling for finite difference simulation of room acoustics

In finite difference time domain simulation of room acoustics, source functions are subject to various constraints. These depend on the way sources are injected into the grid and on the chosen parameters of the numerical scheme being used. This paper addresses the issue of selecting and designing sources for finite difference simulation, by first reviewing associated aims and constraints, and evaluating existing source models against these criteria. The process of exciting a model is generalized by introducing a system of three cascaded filters, respectively, characterizing the driving pulse, the source mechanics, and the injection of the resulting source function into the grid. It is shown that hard, soft, and transparent sources can be seen as special cases within this unified approach. Starting from the mechanics of a small pulsating sphere, a parametric source model is formulated by specifying suitable filters. This physically constrained source model is numerically consistent, does not scatter incoming waves, and is free from zero- and low-frequency artifacts. Simulation results are employed for comparison with existing source formulations in terms of meeting the spectral and temporal requirements on the outward propagating wave.

Control of morphological properties of porous biodegradable scaffolds processed by supercritical CO2 foaming

A low cost supercritical CO foaming rig with a novel design has been used to prepare fully interconnected and highly porous biodegradable scaffolds with controllable pore size and structure that can promote cancellous bone regeneration. Porous polymer scaffolds have been produced by plasticising the polymer with high pressure CO and by the formation of a porous structure following the escape of CO from the polymer. Although, control over pore size and structure has been previously reported as difficult with this process, the current study shows that control is possible. The effects of processing parameters such as CO saturation pressure, time and temperature and depressurisation rate on the morphological properties, namely porosity, pore interconnectivity, pore size and wall thickness- of the scaffolds have been investigated. Poly(d,l)lactic acid was used as the biodegradable polymer. The surfaces and internal morphologies of the poly(d,l)lactic acid scaffolds were examined using optical microscope and micro computed tomography. Preosteoblast human bone cells were seeded on the porous scaffolds in vitro to assess cell attachment and viability. The scaffolds showed a good support for cell attachment, and maintained cell viability throughout 7 days in culture. This study demonstrated that the morphology of the porous structure can be controlled by varying the foaming conditions, allowing the porous scaffolds to be used in various tissue engineering applications.

Trying similarity, doing difference:The role of interviewer self-disclosure in interview talk with young people

Advocates of semi-structured interview techniques have often argued that rapport may be built, and power inequalities between interviewer and respondent counteracted, by strategic self-disclosure on the part of the interviewer. Strategies that use self-disclosure to construct similarity between interviewer and respondent rely on the presumption that the respondent will in fact interpret the interviewer's behaviour in this way. In this article we examine the role of interviewer self-disclosure using data drawn from three projects involving interviews with young people. We consider how an interviewer's attempts to ‘do similarity’ may be interpreted variously as displays of similarity or, ironically, as indicators of difference by the participant, and map the implications that this may have for subsequent interview dialogue. A particular object of concern relates to the ways in which self-disclosing acts may function in the negotiation of category entitlement within interview interactions.

A Spherical Array Approach for Simulation of Binaural Impulse Responses using the Finite Difference Time Domain Method

The finite difference time domain (FDTD) method has direct applications in musical instrument modeling, simulation of environmental acoustics, room acoustics and sound reproduction paradigms, all of which benefit from auralization. However, rendering binaural impulse responses from simulated
data is not straightforward to accomplish as the calculated pressure at FDTD grid nodes does not contain any directional information. This paper addresses this issue by introducing a spherical array to capture sound pressure on a finite difference grid, and decomposing it into a plane-wave density
function. Binaural impulse responses are then constructed in the spherical harmonics domain by combining the decomposed grid data with free field head-related transfer functions. The effects of designing a spherical array in a Cartesian grid are studied, and emphasis is given to the relationships
between array sampling and the spatial and spectral design parameters of several finite-difference
schemes.

Morphological study of the uncommon rectus sterni muscle in German cadavers

Objective: The present investigation has been designed to study the incidence of the rectus stern muscle in German human cadavers dissected in the Kingdom of Saudi Arabia, trying to find a postulation for the development of such muscle when present. Design: Gross dissection of 130 cadavers, of both sexes, was performed throughout a period of 10 years. Setting: Department of Anatomy College of Medicine, King Faisal University, Dammam, Saudi Arabia. Intervention: Investigation of the origin and insertion of the rectus sterni and measurements of its length and width. Results: Two adult cadavers, one of each sex, had shown well-developed bilateral rectus stern muscles. All muscles identified were parasternal in position, being superficial to the medial portion of the pectoralis major muscle. Minor morphological differences were observed among the four muscle masses concerning their length, breadth, origin and insertion. Conclusion: The current study has determined the incidence of the rectus sterni muscle, in German cadavers to be 1.54% per bodies examined compared to 4% in cadavers from Saudis. Such a frequency is compared to that reported in different geographic populations. The rectus sterni muscle is innervated by the anterior cutaneous branches of the intercostal nerves. The description of the rectus sterni muscle and its incidence determined in the present study, might be of a great help for clinicians radiographing or tackling the pectoral region.