New Species of Paussus, Subgenus Scaphipaussus (Coleoptera: Carabidae: Paussinae), from Southeast Asia Reveal Ambiguities in Species Group Limits and High Species Diversity in the Oriental Region.

Paussus, commonly known as ant nest beetles, is the most diverse genus of Paussinae (Coleoptera: Carabidae) with a very complex taxonomic history. Biodiversity research in Southeast and South Asia yields new species that can contribute to a better understanding of the morphological disparity and species-group or subgenus delimitation. Here, we describe nine new species from Southeast Asia and China: Paussus (Scaphipaussus) fencli sp. nov. (China), P. (S.) mawdsleyi sp. nov. (Borneo), P. (S.) bakeri sp. nov. (Philippines), P. (S.) jendeki sp. nov. (Laos), P. (S.) saueri sp. nov. (India), P. (S.) annamensis sp. nov. (Vietnam), P. (S.) phoupanensis sp. nov. (Laos, Vietnam), P. (S.) bilyi sp. nov. (Thailand), and P. (S.) haucki sp. nov. (Thailand). We also bring new data on P. (S.) corporaali Reichensperger, 1927 (Java) and P. (S.) madurensis Wasmann, 1913 (India). Besides formal descriptions, we provide photographs of the habitus in the dorsal and dorsolateral view, antennal club, head crest, and male genitalia if the male is available. Based on the comparison of new and earlier described species, we show that the antennae are highly diverse within the Scaphipaussus. Considering other characters, some species are placed in Scaphipaussus, but they differ from putative relatives in the antennal morphology. The presence of the frontal protuberances and crests is a more reliable character. Additional species show that Scaphipaussus is most diverse in southeastern Asia, especially in Indo-Burma. Concerning its supposed late Miocene origin, the group underwent rapid radiation. The species diversity of Scaphipaussus almost doubled in the last decade, and it is highly probable that further species will be described in the future.

New species of Ceratoderus and Melanospilus from Southeast Asia (Coleoptera: Carabidae: Paussinae).

Ceratoderus Westwood, 1841 and Melanospilus Westwood, 1847 are highly modified Paussinae ground beetles placed in close relationships with Paussus Linnaeus, 1775 in the latest studies. Four new species are described from Southeast Asia: Ceratoderus anthicoides sp. nov. (Philippines), C. kalamensis sp. nov. (Sulawesi), Melanospilus pilosus sp. nov. (Malay Peninsula), and M. spectabilis sp. nov. (Thailand). The present findings show how diversity is incompletely known, even in areas where many entomologists conducted field research.

Paussus (Edaphopaussus) asseyi sp. nov. (Coleoptera: Carabidae: Paussinae) from the Nguru Mountains of the Eastern African Arc in Tanzania.

A new species of Paussus L., 1775 (Coleoptera: Carabidae) is described from the Nguru Mountains of the Eastern African Arc in Tanzania. Paussus asseyi sp. nov. is diagnosed by the shape of the antennal club, which bears two sharp edges at the outer margin, the blunt spines on tibiae, and the characteristic colouration that allows this species to be distinguished from all other species in Paussus (Series I) defined in the latest molecular phylogeny. Other characters, i.e., the shape of the pronotum and absent pronotal setae, place the new species in the subgenus Edaphopaussus Kolbe, 1920. The colouration resembles P. dichrous Janssens, 1950 from Democratic Republic Congo and Angola and some Asian species, yet all are morphologically different from the new species. The robust head, small eyes, and clypeus shape resemble distantly related P. (Hylotorus) cephalotes Raffray, 1886. The individual mountain massifs of Eastern Tanzania represent rainforest islands set in much drier lowlands with savannah ecosystems. The new species contributes to our understanding of the isolated mountain ranges' relatively poorly investigated beetle fauna.

An algebraic correction for the Westervelt equation to account for the local nonlinear effects in parametric acoustic array.

This work presents a simple computational approach for the calculation of parametrically generated low-frequency sound fields. The Westervelt wave equation is employed as a model equation that accounts for the wave diffraction, attenuation, and nonlinearity. As it is known that the Westervelt equation captures the cumulative nonlinear effects correctly and not the local ones, an algebraic correction is proposed, which includes the local nonlinear effects in the solution of the Westervelt equation. This way, existing computational approaches for the Westervelt equation can be used even in situations where the generated acoustic field differs significantly from the plane progressive waves, such as in the near-field, and where the local effects manifest themselves strongly. The proposed approach is demonstrated and validated on an example of the parametric radiation from a baffled circular piston.

Parametric acoustic array lensed by a gradient-index phononic crystal.

This work presents a theoretical study of a parametric transmitter employing a small ultrasonic transducer and an acoustic lens for the collimation of the non-directional primary ultrasonic waves into a highly-directional beam. The acoustic lens is represented by a gradient-index phononic crystal (GRIN PC) composed of an array of toroidal scatterers. Parameters of the GRIN PC lens are determined employing an optimization procedure that maximizes the minimum value of the primary-wave amplitude over a wide frequency range at a distant point in front of the transducer-lens system. The Westervelt equation is used as a wave equation taking into account diffraction, nonlinearity, and thermoviscous attenuation. The wave equation is solved numerically in the quasi-linear approximation in the frequency domain employing the finite element method. The numerical results show that employing a simple GRIN PC lens, a highly-directional low-frequency beam can be parametrically radiated from a small ultrasonic transducer.

A versatile computational approach for the numerical modelling of parametric acoustic array.

This work presents a versatile computational approach for the numerical modelling of a parametrically generated low-frequency sound. The proposed method is based on the quasi-linear approximation, and it does not employ the paraxial approximation. The primary acoustic field is calculated by the Rayleigh integral or the boundary element method; the secondary difference-frequency field is calculated by the finite element method. As governing wave equations, a general second-order wave equation for acoustic pressure, the Westervelt equation, and Kuznetsov equation are tested, and the corresponding numerical results are compared. The proposed approach allows studying the near-field, far-field, as well as the off-axis field of the difference-frequency wave parametrically radiated from complex emitters. As numerical examples, parametric radiation from a baffled piston and a piston combined with a horn are examined.

Optimized reactive silencers composed of closely-spaced elongated side-branch resonators.

This paper reports a theoretical study of the sound propagation in a rectangular waveguide loaded by closely-spaced elongated side-branch resonators forming a simple low-frequency broadband reactive silencer. Semi-analytical calculations account for the evanescent modes both in the main waveguide and side-branch resonators and for the viscothermal losses in the silencer elements. Reasonable accuracy is maintained in the evaluation of transmission, reflection, and absorption coefficients, while the calculation time is reduced by a few hundred times in comparison with the finite element method. Therefore, the proposed method is particularly suitable for optimization procedure. The lengths of the individual equally spaced side-branch resonators are optimized by a heuristic evolutionary algorithm that maximizes the minimum transmission loss (TL) over a pre-defined frequency range. Numerical results indicate that the minimum TL of the optimized silencers is reduced due to the destructive effect of the evanescent coupling from the resonators of the nearest side-branches. In the opposite, the TL increases linearly with the number of the side-branch resonators.

Optimized reactive silencers with narrow side-branch tubes.

This paper presents a theoretical study of the sound propagation in a waveguide loaded by an array of flush-mounted narrow side-branch tubes, forming a simple low-frequency reactive silencer. The individual tube-lengths and the distances between the adjacent tubes are optimized in order to maximize the minimum transmission loss over a given frequency range. The transmission properties of the silencer are calculated using the transfer matrix method, heuristic evolutionary approach is employed for the determination of the optimal parameters. The numerical results are validated against the finite element method simulation. A comprehensive parametric study is performed to demonstrate the optimized silencer performance as a function of the number of side-branch tubes, and the frequency range. It is shown that for the given frequency range, the minimum transmission loss of the optimized silencer increases linearly with the number of the side-branch tubes.

Numerical study of the influence of the convective heat transport on acoustic streaming in a standing wave.

Within this work, acoustic streaming in an air-filled cylindrical resonator with walls supporting a temperature gradient is studied by means of numerical simulations. A set of equations based on successive approximations is derived from the Navier-Stokes equations. The equations take into account the acoustic-streaming-driven convective heat transport; as time-averaged secondary-field quantities are directly calculated, the equations are much easier to integrate than the original fluid-dynamics equations. The model equations are implemented and integrated employing commercial software COMSOL Multiphysics. Numerical calculations are conducted for the case of a resonator with a wall-temperature gradient corresponding to the action of a thermoacoustic effect. It is shown that due to the convective heat transport, the streaming profile is considerably distorted even in the case of weak wall-temperature gradients. The numerical results are consistent with available experimental data.

Effect of inhomogeneous temperature fields on acoustic streaming structures in resonators.

Acoustic streaming in 2D rectangular resonant channels filled with a fluid with a spatial temperature distribution is studied within this work. An inertial force is assumed for driving the acoustic field; the temperature inhomogeneity is introduced by resonator walls with prescribed temperature distribution. The method of successive approximations is employed to derive linear equations for calculation of primary acoustic and time-averaged secondary fields including the streaming velocity. The model equations have a standard form which allows their numerical integration using a universal solver; in this case, COMSOL Multiphysics was employed. The numerical results show that fluid temperature variations in the direction perpendicular to the resonator axis influence strongly the streaming field if the ratio of the channel width and the viscous boundary layer thickness is big enough; the streaming in the Rayleigh vortices can be supported as well as opposed, which can ultimately lead to the appearance of additional vortices.

Calculation of an axial temperature distribution using the reflection coefficient of an acoustic wave.

This work verifies the idea that in principle it is possible to reconstruct axial temperature distribution of fluid employing reflection or transmission of acoustic waves. It is assumed that the fluid is dissipationless and its density and speed of sound vary along the wave propagation direction because of the fluid temperature distribution. A numerical algorithm is proposed allowing for calculation of the temperature distribution on the basis of known frequency characteristics of reflection coefficient modulus. Functionality of the algorithm is illustrated on a few examples, its properties are discussed.

Finite amplitude standing waves in resonators terminated by a general impedance.

A general inhomogeneous Burgers equation describing finite-amplitude standing waves in resonators terminated by a general impedance is derived. This model equation can be used for modeling of nonlinear acoustic processes connected with some methods for enhancement of Q-factor of acoustic resonators. One of them is the method based on using a second-harmonics absorber. For better understanding of this method, it is convenient to know at least an approximate analytical solution of the model equation. This work presents some approximate solutions, which improve and extend the solutions that have been published previously. The solutions are compared with results obtained by numerical integration of the corresponding equations.

Optimal shaping of acoustic resonators for the generation of high-amplitude standing waves.

Within this paper, optimal shaping of acoustic resonators for the generation of high-amplitude standing waves through the use of evolutionary algorithms is discussed. The resonator shapes are described using sets of control points interconnected with cubic-splines. Positions of the control points are calculated by means of an evolutionary algorithm in order to maximize acoustic pressure amplitude at a given point of the resonator cavity. As an objective function for the optimization procedure, numerical solution of one-dimensional linear wave equation taking into account boundary-layer dissipation is used. Resonator shapes maximizing acoustic pressure amplitude are found in case of a piston, shaker, or loudspeaker driving. It is shown that the optimum resonator shapes depend on the method of driving. In all the cases, acoustic field attains higher amplitude in the optimized resonators than in simple-shaped non-optimized resonators of similar dimensions. Theoretical results are compared with experimental data in the case of a loudspeaker driving, good agreement of which is achieved.

Equations for description of nonlinear standing waves in constant-cross-sectioned resonators.

This work is focused on investigation of applicability of two widely used model equations for description of nonlinear standing waves in constant-cross-sectioned resonators. The investigation is based on the comparison of numerical solutions of these model equations with solutions of more accurate model equations whose validity has been verified experimentally in a number of published papers.

Non-paraxial model for a parametric acoustic array.

This study is concerned with parametric radiation from an arbitrary axisymmetric planar source with a special focus on low-frequency difference-frequency fields. As a model equation accounting for nonlinearity, diffraction, and dissipation, the Westervelt equation is used. The difference-frequency-field patterns are calculated in the quasi-linear approximation by the method of successive approximations. A multi-layer integral for calculation of the acoustic field is reduced to a three-dimensional one by employing an approximate analytical description of the primary field with the use of a multi-Gaussian beam expansion. This integral is subsequently reduced in the paraxial approximation to a one-dimensional form which has previously been published in literature and which represents a means for fast calculations of secondary acoustic fields. The three-dimensional integral is calculated numerically and the numerical results predict nonzero amplitude of the low-frequency field in the vicinity of the source which is an effect that cannot be correctly encompassed in the paraxial approximation.

Comparison of various strategies for colorectal cancer screening tests.

INTRODUCTION: Colorectal cancer (CRC) is one of the most serious health problems worldwide and thus it is important to assess health and economic impacts of preventative CRC screening strategies. METHODS: For this reason, a theoretical model based on Markov chains is proposed to compare these strategies: fecal occult blood test, capsule endoscopy, once-life and twice-life colonoscopy, and no screening. The model predicts the health state of a population of individuals aged from 50 to 75 years. RESULTS: The numerical results show that the optimal timing for a once-lifetime colonoscopy screening method is before the age of 50 and that the twice-lifetime colonoscopy is the best screening strategy with respect to CRC incidence. In contrast, it is the most expensive one if the CRC treatment costs are not included. The model predicts that there is a minimal CRC incidence in the population when the second colonoscopy is appropriately timed. By using specific data, this age was found to be 59 years. CONCLUSION: The screening strategies probably save expenses on the treatment of the population and at the same time decreases mortality. Optimized twice-lifetime colonoscopy seems to be the most efficient strategy with respect to mortality and overall costs including subsequent treatment.

Propagation of nonlinear acoustic plane waves in an elastic gas-filled tube.

This paper deals with modeling of nonlinear plane acoustic waves propagating through an elastic tube filled with thermoviscous gas. A description of the interactions between gas and an elastic tube wall is carried out by the continuity equation of a wall velocity. Simplification on the basis of the local reaction assumption enables to model an acoustic treatment on the tube wall by using a wall impedance. Because there are considerable losses due to wall friction, the influences of the acoustic boundary layer were also considered. Using certain assumptions a special form of the Burgers equation was derived which enables to describe the propagation of nonlinear waves in the elastic tube. This model equation takes into account nonlinear, dissipative, and dispersion effects which compete each other. Characteristic lengths of the supposed effects and numerical results with respect to the source frequency were used for a qualitative analysis of the model equation. Applicability of this model equation was demonstrated by series of measurements. By application of the long-wave approximation the Korteweg-de Vries-Burgers and Kuramoto-Sivashinsky equations were derived from the modified Burgers equation.

Nonlinear interactions in elastic resonators.

This work is dedicated to nonlinear interactions in elastic resonators. It is supposed that a resonator wall yields locally to the inner pressure. The elastic wall of the resonator induces strong dispersion and dissipation of acoustic energy. The dispersion can significantly influence studied nonlinear interactions which are ineffective because the synchronous conditions are not satisfied and hence a coherence length is too short. In the frame of this work conditions for generation of subharmonics are studied on the basis of topological and numerical analyze. For this reason the method of local stability is applied. For description of nonlinear standing wave is derived modified inhomogeneous Burgers equation and the inhomogeneous Korteweg-de Vries-Burgers equation. These equations take into account thermo-viscous losses of supposed fluids, boundary layer losses, wall losses and dispersion effects caused by both the resonator wall and the acoustic boundary layer. Number of numerical solutions of these model equations is shown and unsteady solitary waves are investigated.

Nonlinear standing waves in 2-D acoustic resonators.

This paper deals with 2-D simulation of finite-amplitude standing waves behavior in rectangular acoustic resonators. Set of three partial differential equations in third approximation formulated in conservative form is derived from fundamental equations of gas dynamics. These equations form a closed set for two components of acoustic velocity vector and density, the equations account for external driving force, gas dynamic nonlinearities and thermoviscous dissipation. Pressure is obtained from solution of the set by means of an analytical formula. The equations are formulated in the Cartesian coordinate system. The model equations set is solved numerically in time domain using a central semi-discrete difference scheme developed for integration of sets of convection-diffusion equations with two or more spatial coordinates. Numerical results show various patterns of acoustic field in resonators driven using vibrating piston with spatial distribution of velocity. Excitation of lateral shock-wave mode is observed when resonant conditions are fulfilled for longitudinal as well as for transversal direction along the resonator cavity.

Asymptotic solutions of the inhomogeneous Burgers equation.

The method of the active second harmonic suppression in resonators is investigated in this paper both analytically and numerically. The resonator is driven by a piston which vibrates with two frequencies. The first one agrees with an eigenfrequency and the second one is equal to the two times higher eigenfrequency. The phase shift of the second piston motion is 180 deg. It is known that for this case it is possible to describe generation of the higher harmonics by means of the inhomogeneous Burgers equation. This model equation was solved for stationary state analytically by a number of authors but only for ideal fluids. Unlike their solutions, new asymptotic solutions are presented here which take into account dissipative effects. The asymptotic solutions are compared with numerical ones. For study of generation higher harmonics the solutions are developed in a spectral form.