Artificial Truncation Research Articles

A Dismal Reality: Behavioural Analysis and Consumer Policy

Before the behavioural turn, the economic account of consumer policy concerns was too optimistic and reductive. After the turn, we, the consumers, are more likely to need from an economic perspective a more intrusive consumer policy. This is the dismality thesis defended in this article. The dismality thesis is a theoretical, comparative, and argumentative thesis, albeit normatively incomplete. It follows from two premises. First, pre-behavioural economics elaborated a restricted theory of consumer harm in unregulated markets (“consumer harm premise”) and, second, it overstated the effectiveness of information disclosure as a means of consumer policy (“institutional premise”). The dismality thesis is further supported by a comparison of the discussion of attributes control in the pre- and post-behavioural turn literature and by commenting on the main source of controversy about attributes control in the post-turn literature, the so-called “artificial truncation” of behavioural analysis.

Complex-Frequency Shifted PMLs for Maxwell’s Equations With Hyperbolic Divergence Cleaning and Their Application in Particle-in-Cell Codes

The simulation of unbounded domains inevitably requires an artificial truncation of the computational domain and spurious reflections resulting from this procedure are a common problem. In this paper, a perfectly matched layer formulation for Maxwell’s equations in purely hyperbolic form is presented. The model is applied to standard wave attenuation problems and particle-in-cell simulations of electron beam devices.

Singularities occurring in multimaterials with transparent boundary conditions

In many engineering problems one has to deal with two materials which can induce local singularities (infinite stresses) as soon as the interface reaches the boundary. This is the case of water pipes with an inner coating for avoiding rusting. Because the wave velocity is smaller in the coating, it appears Love waves which can be used in order to detect defects because they propagate further as in a wave guide. They can be cracks corresponding to a disconnection at the interface between the two materials. In order to detect them, one can use measurements performed at the extremities of the pipes even if the signal in the numerical model, is very much perturbed by the singularities appearing at the interface between the two media at the extremities of the pipe. The phenomenon is amplified when one considers an artificial truncation of the structure and adding transparent boundary conditions in order to avoid reflection for simulating what happens in the full structure. The goal of this paper is to focus on a numerical method which can be used for the analysis of the influence of the singularities on the signal processing analysis. First of all, we give a mathematical description of the singularity met in our problem. Then, we define the extension to our case of the method introduced for cracks by G. Fix. It consists in adding the singular function to finite element functional space used in a classical numerical simulation. The main point of the paper is then to analyze, in a mathematical framework, the error estimates on the coefficients of the singularities with respect to the mesh size. Few numerical tests illustrate the mathematical results obtained for the problem we are dealing with.

Artificial boundary conditions and domain truncation in electrical impedance tomography. Part I: Theory and preliminary results

Artificial boundary conditions have long been an active research topic in numerical approximation of scattering waves: The truncation of the computational domain and the assignment of the conditions along the fictitious boundary must be done so that no spurious reflections occur. In inverse boundary value problems, a similar problem appears when the estimation of the unknowns is restricted to a domain that represents the whole domain of the solutions of a partial differential equation with unknown coefficient. Thisproblem is significantly more challenging than general scattering problems, because the coefficients representing the unknown material parameter of interest are not known in the truncated portion and assigning suitable condition on the fictitious boundary is part of the problem also. The problem is addressed by defining a Dirichlet-to-Neumann map, or Steklov-Poincaré map, on the boundary of the domain truncation. In this paper we describe the procedure, provide a theoretical justification and illustrate with computed examples the limitations of imposing fixed boundary condition. Extensions of the proposed approach will be presented in a sequel article.

Artificial boundary conditions and domain truncation in electrical impedance tomography. Part II: Stochastic extension of the boundary map

In [3], the authors discussed the electrical impedance tomography (EIT) problem, in which the computational domain with an unknown conductivity distribution comprises only a portion of the whole conducting body, and a boundary condition along the artificial boundary needs to be set so as to minimally disturbs the estimate in the domain of interest. It was shown that a partial Dirichlet-to-Neumann operator, or Steklov-Poincare map, provides theoretically a perfect boundary condition. However, since the boundary condition depends on the conductivity in the truncated portion of the conductive body, it is itself an unknown that needs to be estimated along with the conductivity of interest. In this article, we develop further the computational methodology, replacing the unknown integral kernel with a low dimensional approximation. The viability of the approach is demonstrated with finite element simulations as well as with real phantom data.

Signature properties of water: Their molecular electronic origins

Water challenges our fundamental understanding of emergent materials properties from a molecular perspective. It exhibits a uniquely rich phenomenology including dramatic variations in behavior over the wide temperature range of the liquid into water's crystalline phases and amorphous states. We show that many-body responses arising from water's electronic structure are essential mechanisms harnessed by the molecule to encode for the distinguishing features of its condensed states. We treat the complete set of these many-body responses nonperturbatively within a coarse-grained electronic structure derived exclusively from single-molecule properties. Such a "strong coupling" approach generates interaction terms of all symmetries to all orders, thereby enabling unique transferability to diverse local environments such as those encountered along the coexistence curve. The symmetries of local motifs that can potentially emerge are not known a priori. Consequently, electronic responses unfiltered by artificial truncation are then required to embody the terms that tip the balance to the correct set of structures. Therefore, our fully responsive molecular model produces, a simple, accurate, and intuitive picture of water's complexity and its molecular origin, predicting water's signature physical properties from ice, through liquid-vapor coexistence, to the critical point.

Characterization of the native form and the carboxy-terminally truncated halotolerant form of α-amylases from Bacillus subtilis strain FP-133.

Two amylases, amylase I and amylase II from Bacillus subtilis strain FP-133, were purified to homogeneity and characterized. Their stabilities toward temperature, pH, and organic solvents, and their substrate specificities toward polysaccharides and oligosaccharides were similar. Under moderately high salt conditions, both amylases were more stable than commercial B. licheniformis amylase, and amylase I retained higher amylase activity than amylase II. The N-terminal amino acid sequence, genomic southern blot analysis, and MALDI-TOFF-MS analysis indicated that the halotolerant amylase I was produced by limited carboxy-terminal truncation of the amylase II peptide. The deduced amino acid sequence of amylase II was >95% identical to that of previously reported B. subtilis α-amylases, but their carboxy-terminal truncation points differed. Three recombinant amylases--full-length amylase corresponding to amylase II, an artificially truncated amylase corresponding to amylase I, and an amylase with a larger artificial C-terminal truncation--were expressed in B. subtilis. The artificially truncated recombinant amylases had the same high amylase activity as amylase I under moderately high salt conditions. Sequence comparisons indicated that an increased ratio of Asp/Glu residues in the enzyme may be one factor responsible for increasing halotolerance.

Isogeometric analysis of sound propagation through laminar flow in 2-dimensional ducts

We consider the propagation of sound through a slowly moving fluid in a 2-dimensional duct. A detailed description of a flow-acoustic model of the problem using B-spline based isogeometric analysis is given. The model couples the non-linear, steady-state, incompressible Navier–Stokes equation in the laminar regime for the flow field, to a linear, time-harmonic acoustic equation in the low Mach number regime for the sound signal. B-splines are used both to represent the duct geometry and to approximate the flow and sound fields. This facilitates an exact representation of complex duct geometries, as well as high continuity approximations of state variables. Acoustic boundary conditions on artificial truncation boundaries are treated using a mode matching formulation. We validate the model against known acoustic modes for a uniform flow through a straight duct. Improved error convergence rates are found when the acoustic pressure is approximated by higher order polynomials. Based on the model, we examine how the acoustic signal varies with sound frequency, flow speed and duct geometry. A combination of duct geometry and sound frequency is identified for which the acoustic signal is particularly sensitive to the flow speed.

Scaling calibration in region of interest reconstruction with the 1D and 2D ATRACT algorithm

Recently, a reconstruction algorithm for region of interest (ROI) imaging in C-arm CT was published, named Approximate Truncation Robust Algorithm for Computed Tomography (ATRACT). Even in the presence of substantial data truncation, the algorithm is able to reconstruct images without the use of explicit extrapolation or prior knowledge. However, the method suffers from a scaling and offset artifact in the reconstruction. Hence, the reconstruction results are not quantitative. It is our goal to reduce the scaling and offset artifact so that Hounsfield unit (HU) values can be used for diagnosis. In this paper, we investigate two variants of the ATRACT method and present the analytical derivations of these algorithms in the Fourier domain. Then, we propose an empirical correction measure that can be applied to the ATRACT algorithm, to effectively compensate the scaling and offset issue. The proposed method is evaluated on ten clinical datasets in the presence of different degrees of artificial truncation. With the proposed correction approach, we achieved an average relative root-mean-square error (rRMSE) of 2.81% with respect to non-truncated Feldkamp, Davis, and Kress reconstruction, even for severely truncated data. The rRMSE is reduced to as little as 10% of the image reconstructed without the scaling calibration. The reconstruction results show that ROI reconstruction of high accuracy can be achieved since the scaling and offset artifact are effectively eliminated by the proposed method. With this improvement, the HU values may be used for post-processing operations such as bone or soft tissue segmentation if some tolerance is accepted.

Role Played by Isopropyl Substituents in Stabilizing the Putative Triple Bond in Ar′EEAr′ [E = Si, Ge, Sn; Ar′ = C6H3-2,6-(C6H3-2,6-Pri2)2] and Ar*PbPbAr* [Ar* = C6H3-2,6-(C6H2-2,4,6-Pri3)2

A theoretical study of the bonding in ArEEAr (where E = Si, Ge, Sn, Pb; Ar = terphenyl ligand) revealed for the first time why bulky isopropyl substituents electronically are required in order to isolate stable ArEEAr species. This was accomplished by combining the natural orbitals for chemical valence (NOCV) method with the extended transition state (ETS) scheme. The NOCV-ETS analysis was based on two ArE fragments in their doublet ground state with the configuration σ(2)π(1). For E = Si, Ge, and Sn, it revealed one π-bond perpendicular to the CEEC plane and two σ/π-type bonds in the plane, whereas the ArPbPbAr system was found to have a single σ bond with a C-Pb-Pb trans-bent angle close to 90°. While similar bonding pictures have been obtained in previous model studies with Ar = H and CH3, the NOCV-ETS scheme was able to obtain quantitative estimates for the strength of various σ/π components without artificial truncations or twisting of the system. More importantly, NOCV-ETS analysis was able to show that the electronic influence of the isopropyl substituents on the σ/π components differs little from that found in a system where they are replaced by hydrogen. Instead, the favorable role of the isopropyl substituents is due to dispersive van der Waals attractions between Pr(i) groups on aryl rings attached to different E atoms as well as hyperconjugation involving donation into σ* orbitals on Pr(i). Dispersive interaction amounts to -27.5 kcal/mol (Si), -29.1 kcal/mol (Ge), -26.2 kcal/mol (Sn), and -44.0 kcal/mol (Pb). The larger dispersive stabilization for Pb reflects the fact that the longer Pb-Pb and Pb-C bonds sterically allow for more isopropyl groups with Ar = C6H3-2,6-(C6H2-2,4,6-Pr(i)3)2. This is compared to the other elements where Ar = C6H3-2,6-(C6H3-2,6-Pr(i)2)2. It is finally concluded from the analysis that real ArEEAr systems reveal little character of the EE bond in contrast to the findings of previous studies on model systems.

Wall accumulation and spatial localization in particle-laden wall flows

AbstractWe study the two main phenomenologies associated with the transport of inertial particles in turbulent flows, turbophoresis and small-scale clustering. Turbophoresis describes the turbulence-induced wall accumulation of particles dispersed in wall turbulence, while small-scale clustering is a form of local segregation that affects the particle distribution in the presence of fine-scale turbulence. Despite the fact that the two aspects are usually addressed separately, this paper shows that they occur simultaneously in wall-bounded flows, where they represent different aspects of the same process. We study these phenomena by post-processing data from a direct numerical simulation of turbulent channel flow with different populations of inertial particles. It is shown that artificial domain truncation can easily alter the mean particle concentration profile, unless the domain is large enough to exclude possible correlation of the turbulence and the near-wall particle aggregates. The data show a strong link between accumulation level and clustering intensity in the near-wall region. At statistical steady state, most accumulating particles aggregate in strongly directional and almost filamentary structures, as found by considering suitable two-point observables able to extract clustering intensity and anisotropy. The analysis provides quantitative indications of the wall-segregation process as a function of the particle inertia. It is shown that, although the most wall-accumulating particles are too heavy to segregate in homogeneous turbulence, they exhibit the most intense local small-scale clustering near the wall as measured by the singularity exponent of the particle pair correlation function.

Smoothing Property of the Gain Term of the Boltzmann Collision Operator

In this paper, we prove estimates of the smoothing property of the gain part of the Boltzmann collision operator for the full kernel of the hard sphere model in ${\mathbb R}^3$ which are an improvement over estimates by Lions [J. Math. Kyoto Univ., 34 (1994), pp. 391–427, pp. 429–461] and Wennberg [Comm. Partial Differential Equations, 19 (1994), pp. 2057–2074]. In earlier works for different collision models, this type of smoothing estimate has always come with the compactness assumption [P.-L. Lions, J. Math. Kyoto Univ., 34 (1994), pp. 391–427, 429–461] for both variables of the collision kernel. Now we show that the decaying condition in the angular component which is caused by non-head-on collisions for the hard sphere model can replace the compactness assumption. Namely, no artificial truncation of the angular component at the boundary points is needed to prove the regularizing effect. Also the compactness assumption in relative velocity can be relaxed. For large relative velocity the smoothing esti...

On quantum effects in the theory of conductivity of fully ionized quasiclassical plasma

A study is made of the static conductivity of a fully ionized plasma in a parameter range where the effect of electron-electron collisions can be ignored. It is shown that a convergent expression for the static conductivity of a fully ionized, weakly nonideal plasma in the range of large wave vectors can be obtained from a quantum statistical description of correlation functions, without using an artificial truncation procedure.

A study of perfectly matched layers for joint multicomponent reverse-time migration

Reverse-time migration in finite space requires effective boundary processing technology to eliminate the artificial truncation boundary effect in the migration result. On the basis of the elastic velocity-stress equations in vertical transversely isotropic media and the idea of the conventional split perfectly matched layer (PML), the PML wave equations in reverse-time migration are derived in this paper and then the high order staggered grid discrete schemes are subsequently given. Aiming at the “reflections” from the boundary to the computational domain, as well as the effect of seismic event’s abrupt changes at the two ends of the seismic array, the PML arrangement in reverse-time migration is given. The synthetic and real elastic, prestack, multi-component, reverse-time depth migration results demonstrate that this method has much better absorbing effects than other methods and the joint migration produces good imaging results.

Expression of an extremely acidic β-1,4-glucanase from thermoacidophilic Alicyclobacillus sp. A4 in Pichia pastoris is improved by truncating the gene sequence

BackgroundAlicyclobacillus sp. A4 is thermoacidophilic and produces many glycoside hydrolases. An extremely acidic β-1,4-glucanase (CelA4) has been isolated from Alicyclobacillus sp. A4 and purified. This glucanase with a molecular mass of 48.6 kDa decreases the viscosity of barley-soybean feed under simulated gastric conditions. Therefore, it has the potential to improve the nutrient bioavailability of pig feed. For the study reported herein, the full-length gene, CelA4, of this glucanase (CelA4) was identified using the sequences of six peptides and cloned from strain A4. The gene fragment (CelA4F) encoding the mature protein was expressed in Pichia pastoris. Sequence truncation and glycosylation were found for recombinant CelA4F, both of which affected the expression efficiency. The physical properties of various forms of CelA4 as they affected enzymatic activity were characterized.ResultsWe located the full-length 2,148-bp gene for CelA4 (CelA4) in the genome of Alicyclobacillus sp. A4. CelA4 encodes a 715-residue polypeptide with a calculated molecular mass of 71.64 kDa, including an N-terminal signal peptide (residues 1-39), a catalytic domain (residues 39-497), and a C-terminal threonine-rich region (residues 498-715). Its deduced amino acid sequence and that of an Alicyclobacillus acidocaldarius endo-β-1,4-glucanase were identical at 44% of the residue positions. When the experimental molecular mass of CelA4F--a recombinant protein designed to mimic the CelA4 sequence lacking the N-terminal signal peptide that had been expressed in Pichia pastoris--was compared with its hypothetical molecular mass, it was apparent that CelA4F was truncated, possibly at residue 497. An artificially truncated gene fragment (CelA4T) without C-terminal threonine-rich region was expressed in P. pastoris, and the expression efficiency of CelA4T was substantially greater than that of CelA4F. Purified CelA4F and CelA4T had similar molecular masses (~60 kDa) and enzymatic properties (optimum pH, 3.4; optimum temperature, 60°C); they were relatively stable between pH 1.2 and 8.2 at 70°C and resistant to acidic and neutral proteases. However, their molecular masses and thermostabilities differed from those of CelA4 isolated from Alicyclobacillus sp. A4. A deglycosylated form of CelA4 (CelA4D) had properties similar to that of CelA4 except that it was thermoliable at 60°C.ConclusionsTruncation during expression of CelA4F or artificial truncation of its gene--both of which produced a form of CelA4 lacking a threonine-rich region that includes a putative linker--increased the level of enzyme produced in comparison with that produced by cultivation of Alicyclobacillus sp. A4. Glycosylation increased the thermostability of CelA4. Of the four forms of CelA4 studied, CelA4T was produced in highest yield and had the most favorable physical properties; therefore, it has potential for use in the feed industry.

Protein solvation from theory and simulation: Exact treatment of Coulomb interactions in three-dimensional theories

Solvation forces dominate protein structure and dynamics. Integral equation theories allow a rapid and accurate evaluation of the effect of solvent around a complex solute, without the sampling issues associated with simulations of explicit solvent molecules. Advances in integral equation theories make it possible to calculate the angle dependent average solvent structure around an irregular molecular solution. We consider two methodological problems here: the treatment of long-ranged forces without the use of artificial periodicity or truncations and the effect of closures. We derive a method for calculating the long-ranged Coulomb interaction contributions to three-dimensional distribution functions involving only a rewriting of the system of integral equations and introducing no new formal approximations. We show the comparison of the exact forms with those implied by the supercell method. The supercell method is shown to be a good approximation for neutral solutes whereas the new method does not exhibit the known problems of the supercell method for charged solutes. Our method appears more numerically stable with respect to thermodynamic starting state. We also compare closures including the Kovalenko-Hirata closure, the hypernetted-chain (HNC) and an approximate three-dimensional bridge function combined with the HNC closure. Comparisons to molecular dynamics results are made for water as well as for the protein solute bovine pancreatic trypsin inhibitor. The proposed equations have less severe approximations and often provide results which compare favorably to molecular dynamics simulation where other methods fail.

Life-history traits and energetic status in relation to vulnerability to angling in an experimentally selected teleost fish.

In recreational fisheries, a correlation has been established between fishing-induced selection pressures and the metabolic traits of individual fish. This study used a population of largemouth bass (Micropterus salmoides) with lines of low vulnerability fish (LVF) and high vulnerability fish (HVF) that were previously established through artificial truncation selection experiments. The main objective was to evaluate if differential vulnerability to angling was correlated with growth, energetics and nutritional condition during the sub-adult stage. Absolute growth rate was found to be between 9% and 17% higher for LVF compared with HVF over a 6-month period in three experimental ponds. The gonadosomatic index in females was lower for LVF compared with HVF in one experimental pond. No significant differences in energy stores (measured using body constituent analysis) were observed between LVF and HVF. In addition, both groups were consuming the same prey items as evidenced by stomach content analysis. The inherent reasons behind differential vulnerability to angling are complex, and selection for these opposing phenotypes appears to select for differing growth rates, although the driving factors remain unclear. These traits are important from a life-history perspective, and alterations to their frequency as a result of fishing-induced selection could alter fish population structure. These findings further emphasize the need to incorporate evolutionary principles into fisheries management activities.

The Value of Dual-Energy Bone Removal in Maximum Intensity Projections of Lower Extremity Computed Tomography Angiography

Dual-energy computed tomography (CT) makes it possible to remove bones and intraluminal plaques from angiography datasets on the basis of spectral differentiation separating iodine from calcium. The objective of this study was to evaluate the feasibility and efficiency of this technique by comparing maximum intensity projections (MIP) created with different bone removal techniques: (a) dual-energy bone removal (DEBR); (b) purely software-based bone removal without manual corrections (SBBR - MC); and (c) manually corrected software-based bone removal (SBBR + MC). A further aim was to evaluate the dual-energy-based plaque removal tool. Fifty-one patients underwent dual-energy CT angiography of the lower-extremity arteries on a dual-source CT scanner. CT parameters were tube potentials, 140 and 80 kVp; exposure, 80 and 340 mAs/rot; and collimation, 14 x 1.2 mm. Bolus tracking was used in the descending aorta for timing (Ultravist 370). Bones were removed from the datasets using the 3 techniques and MIP datasets were generated. Two experienced radiologists assessed image quality ((1) correct removal of bones and preservation of vessels without artificial truncation, stenoses or occlusions of arteries; (2) minor errors with residual bone in the dataset or removal of side branches; (3) significant errors impeding diagnostic evaluation), number of vessel segmentation errors, and number of nonremoved bones. Additionally, time for MIP-generation was measured. The plaque removal tool was applied to DEBR MIPs and the outcome was rated as positive, neutral, or negative. DEBR showed better image quality than SBBR (P < 0.05; median image quality DEBR: 1; SBBR - MC: 3; SBBR + MC: 2). Less vessel segmentation errors occurred in DEBR (P < 0.05; median DEBR: 0; SBBR - MC: 5; SBBR + MC: 1). The number of nonremoved bones was not significantly different between DEBR and SBBR + MC, but significantly higher in SBBR - MC (median DEBR: 1; SBBR - MC: 2; SBBR + MC: 0). Time for generation of MIPs was lowest for SBBR - MC (P < 0.05), but also DEBR was significantly faster than manually corrected SBBR (DEBR: 160 +/- 16 seconds; SBBR - MC: 95 +/- 12 seconds; SBBR + MC: 373 +/- 69 seconds). The plaque removal tool lead to an improvement of image quality of the MIPs and a better depiction of the residual lumen in 43%. DEBR provides significant advantages, even over manually corrected SBBR. As it works completely automatically, it can effectively help to cope with the data load of CT angiography exams. Furthermore, it enables the removal of intraluminal plaques, which provides a benefit for the estimation of the residual lumen.

Physiological and Behavioral Consequences of Long‐Term Artificial Selection for Vulnerability to Recreational Angling in a Teleost Fish

Few studies have examined the physiological and behavioral consequences of fisheries-induced selection. We evaluated how four generations of artificial truncation selection for vulnerability to recreational angling (i.e., stocks selected for high and low vulnerability [HVF and LVF, respectively]) affected cardiovascular physiology and parental care behavior in the teleost fish largemouth bass Micropterus salmoides. Where possible, we compared artificially selected fish to control fish (CF) collected from the wild. Although, compared to control fish, resting cardiac activity was approximately 18% lower for LVF and approximately 20% higher for HVF, maximal values did not vary among treatments. As a result, the HVF had less cardiac scope than either LVF or CF. Recovery rates after exercise were similar for HVF and CF but slower for LVF. When engaged in parental care activities, nesting male HVF were captured more easily than male LVF. During parental care, HVF also had higher turning rates and pectoral and caudal fin beat rates, increased vigilance against predators, and higher in situ swimming speeds. Energetics simulations indicated that to achieve the same level of growth, the disparity in metabolic rates would require HVF to consume approximately 40% more food than LVF. Selection for angling vulnerability resulted in clear differences in physiological and energetic attributes. Not only is vulnerability to angling a heritable trait, but high vulnerability covaries with factors including higher metabolic rates, reduced metabolic scope, and increased parental care activity. Despite these energetically costly differences, HVF and LVF of the same age were of similar size, suggesting that heightened food consumption in HVF compensated for added costs in experimental ponds. Ultimately, angling vulnerability appears to be a complex interaction of numerous factors leading to selection for very different phenotypes. If HVF are selectively harvested from a population, the remaining fish in that population may be less effective in providing parental care, potentially reducing reproductive output. The strong angling pressure in many freshwater systems, and therefore the potential for this to occur in the wild, necessitate management approaches that recognize the potential evolutionary consequences of angling.

The generalized finite element method for Helmholtz equation. Part II: Effect of choice of handbook functions, error due to absorbing boundary conditions and its assessment

In Part I [T. Strouboulis, I. Babuška, R. Hidajat, The generalized finite element method for Helmholtz equation: theory, computation, and open problems, Comput. Methods Appl. Mech. Engrg. 195 (2006) 4711–4731] we introduced the q-version of the generalized finite element method (GFEM) for the Helmholtz equation and we addressed its: (a) pollution error due to the wave number; (b) exponential q-convergence; (c) robustness to perturbations of the mesh, the roundoff and numerical quadrature errors; and (d) a-posteriori error estimation. Here we continue the development of the GFEM for Helmholtz and we address the effects of: (a) alternative handbook functions and mesh types; (b) the error due to the artificial truncation boundary conditions and its assessment. The conclusions are: (1) the employment of plane-wave, wave-band, and Vekua handbook functions lead to equivalent results; and (2) for high q, the most significant component of error may be the one due to the artificial truncation boundary conditions. A rather straightforward approach for assessing this error is proposed.