Experimental characterization of vertical-axis wind turbine noise.

Vertical-axis wind turbines are wind-energy generators suitable for use in urban environments. Their associated noise thus needs to be characterized and understood. As a first step, this work investigates the relative importance of harmonic and broadband contributions via model-scale wind-tunnel experiments. Cross-spectra from a pair of flush-mounted wall microphones exhibit both components, but further analysis shows that the broadband dominates at frequencies corresponding to the audible range in full-scale operation. This observation has detrimental implications for noise-prediction reliability and hence also for acoustic design optimization.

Fourier transform infrared identification of the ν5(σu) fundamental of SiC5Si.

The Fourier transform infrared spectrum of SiC5Si was observed by trapping the vapor from the Nd:YAG laser ablation of sintered Si/C rods in solid Ar at ∼20 K. Measurements of (13)C and (29,30)Si isotopic shifts have enabled the identification of the ν5(σu) vibrational fundamental of the linear isomer of SiC5Si at 1590.8 ± 0.2 cm(-1). The results are in excellent agreement with the predictions of density functional theory calculations at the B3LYP/cc-pVDZ level. A second fundamental, ν4(σu), can only be tentatively identified at 2021.0 cm(-1), because its isotopic shifts are overlapped by absorptions from other species.

Fourier transform infrared isotopic study of SiC5: identification of the ν(4)(σ) mode.

SiC5 in its (3)Σ ground state has been produced by trapping the products from the laser evaporation of a sintered silicon-carbon rod in solid Ar. For the first time a vibrational fundamental has been measured, the ν4(σ) asymmetric stretch at 936.9 ± 0.2 cm(-1). Comparison of observed (13)C and (29,30)Si isotopic shifts with the predictions of DFT-B3LYP/cc-pVDZ calculations confirms the identification.

The right tree for the job? perceptions of species suitability for the provision of ecosystem services.

Stakeholders in plantation forestry are increasingly aware of the importance of the ecosystem services and non-market values associated with forests. In New Zealand, there is significant interest in establishing species other than Pinus radiata D. Don (the dominant plantation species) in the belief that alternative species are better suited to deliver these services. Significant risk is associated with this position as there is little objective data to support these views. To identify which species were likely to be planted to deliver ecosystem services, a survey was distributed to examine stakeholder perceptions. Stakeholders were asked which of 15 tree attributes contributed to the provision of five ecosystem services (amenity value, bioenergy production, carbon capture, the diversity of native habitat, and erosion control/water quality) and to identify which of 22 candidate tree species possessed those attributes. These data were combined to identify the species perceived most suitable for the delivery of each ecosystem service. Sequoia sempervirens (D.Don) Endl. closely matched the stakeholder derived ideotypes associated with all five ecosystem services. Comparisons to data from growth, physiological and ecological studies demonstrated that many of the opinions held by stakeholders were inaccurate, leading to erroneous assumptions regarding the suitability of most candidate species. Stakeholder perceptions substantially influence tree species selection, and plantations established on the basis of inaccurate opinions are unlikely to deliver the desired outcomes. Attitudinal surveys associated with engagement campaigns are essential to improve stakeholder knowledge, advancing the development of fit-for-purpose forest management that provides the required ecosystem services.

Fourier transform infrared isotopic study of ZnC3: identification of the ν1(a') mode.

An isomer of ZnC(3) with bent structure in its (1)A(') electronic state has been detected in the products from the dual laser ablation of carbon and zinc rods that were trapped in solid Ar at ~12 K. Measurements of (13)C isotopic shifts have enabled the identification of the ν(1)(a(')) asymmetric carbon stretching fundamental at 1858.9 cm(-1). The experimental results are in good agreement with the predictions of DFT-B3LYP/6-311G(d) calculations that indicate a singlet bent isomer ground state structure with triplet linear and singlet cyclic isomers lying slightly higher in energy. This is the first optical detection of any isomer of ZnC(3).

Fourier transform infrared matrix and density functional theory study of the vibrational spectrum of the linear MgC3(-) anion.

The linear MgC(3)(-) anion has been identified in the products from the dual Nd:YAG laser ablation of carbon and magnesium rods trapped in solid Ar at ∼12 K. Measurements of (13)C isotopic shifts confirm the identification of the ν(1)(σ) vibrational fundamental at 1797.5 cm(-1). A second fundamental ν(2)(σ) has been tentatively identified at 1190.1 cm(-1). The results are in good agreement with the predictions of density functional theory calculations using the B3LYP functional with the 6-311+G(d) basis set. This is the first optical detection of the linear isomer of MgC(3)(-).

Isotopic study of new fundamentals and combination bands of linear C5, C7, and C9 in solid ar.

A high yield of carbon chains has been produced by the laser ablation of carbon rods having (13)C enrichment. FTIR spectroscopy of these molecules trapped in solid Ar has resulted in the identification of two new combination bands for linear C(5) and C(9). The (ν(1) + ν(4)) combination band of linear C(5) has been observed at 3388.8 cm(-1), and comparison of (13)C isotopic shift measurements with the predictions of density functional theory calculations (DFT) at the B3LYP/cc-pVDZ level makes possible the assignment of the ν(1)(σ(g)(+)) stretching fundamental at 1946 cm(-1). Similarly, the observation of the (ν(2) + ν(7)) combination band of linear C(9) at 3471.8 cm(-1) enables the assignment of the ν(2)(σ(g)(+)) stretching fundamental at 1871 cm(-1). The third and weakest of the infrared stretching fundamentals of linear C(7), the ν(6)(σ(u)(+)) fundamental at 1100.1 cm(-1), has also been assigned.

Infrared observation of linear GeC3 trapped in solid Ar.

Linear GeC(3) has been synthesized and its vibrational spectrum observed for the first time. The cluster was detected by Fourier transform infrared spectroscopy when the products from the dual laser ablation of either a pair of carbon and germanium rods or a single, sintered germanium-carbon rod were trapped in solid Ar at approximately 10 K. Comparison of (13)C isotopic shift measurements with the predictions of density functional theory calculations at the B3LYP/cc-pVDZ level has resulted in the identification of the nu(1)(sigma) and nu(2)(sigma) modes of linear GeC(3) at 1903.9 and 1279.6 cm(-1), respectively. For the related group IV clusters, this result is in contrast to SiC(3) for which two cyclic isomers have been observed but similar to C(4) for which only the linear isomer has been observed spectroscopically.

The vibrational spectrum of fanlike ScC(3) in solid Ar.

Fourier transform infrared spectra of fanlike (C(2v)) ScC(3) have been obtained by trapping the vapor from the Nd:YAG (yttrium aluminum garnet) laser ablation of (13)C-enriched graphite and Sc rods in solid Ar at approximately 10 K. Three vibrational fundamentals, the nu(5)(b(2))=1478.0 cm(-1) asymmetric carbon stretch, the nu(3)(a(1))=557.0 cm(-1) symmetric metal-carbon stretch, and the nu(1)(a(1))=1190.7 cm(-1) symmetric carbon stretch have been observed for the first time. The measured isotopic spectra are in good agreement with DFT-B3LYP/6-311G(3df,3pd) simulated spectra and indicate a (2)A(2) ground state rather than (4)B(1) as suggested by other theoretical calculations. The frequency of the nu(3)(a(1)) fundamental is consistent with a frequency of 560+/-30 cm(-1) reported in a photoelectron spectroscopy investigation of ScC(3).

FTIR identification of the nu4(sigmau) and nu6(piu) modes of linear GeC3Ge trapped in solid Ar.

GeC 3Ge was previously (1) produced by the dual laser ablation of germanium and carbon rods, and the nu 3(sigma u) carbon-carbon stretching fundamental was assigned at 1920.7 cm (-1). This paper presents results from new experiments that have enhanced the production of the molecule via laser ablation of a single sintered germanium-carbon rod, thus enabling the identification of two additional infrared active vibrational fundamentals. Ge participates strongly in one of these, the nu 4(sigma u) mode, and the corresponding Ge isotopic shifts reported here are the first for a germanium-carbon species. GeC 3Ge was produced by trapping the products from the laser evaporation of the Ge-C rod, in solid Ar at approximately 10 K, and recording the FTIR (Fourier transform infrared) spectra. Comparison of (70,72,73,74,76)Ge and (13)C isotopic shift measurements with the predictions of density functional theory calculations (DFT) at the B3LYP/cc-pVDZ level confirms the identification of the nu 4(sigma u) stretching fundamental at 735.3 cm (-1) and the nu 6(pi u) bending fundamental at 580.1 cm (-1) for linear GeC 3Ge.

Fourier transform infrared observation and density functional theory study of the AlC3 and AlC3Al linear chains trapped in solid Ar.

The vibrational spectra of linear AlC(3) and AlC(3)Al, formed by trapping the products of the dual laser evaporation of aluminum and carbon rods in solid Ar at approximately 10 K, were observed. Fourier transform infrared (FTIR) measurements of (13)C isotopic shifts are in good agreement with the predictions of density functional theory (DFT) B3LYP6-311+G(3df) calculations, enabling the first assignments of the nu(3)(sigma(u)) and nu(4)(sigma(u)) fundamentals of ((3)Sigma(g) (+)) linear AlC(3)Al at 1624.0 and 528.3 cm(-1), respectively, and the nu(2)(sigma) vibrational fundamental of ((2)Pi) linear AlC(3) at 1210.9 cm(-1).

Fourier transform infrared observation of the nu3(sigmau) vibration of NiC3Ni in solid Ar.

The Fourier transform infrared spectrum of linear NiC(3)Ni was observed by trapping the vapor produced from the dual ablation of nickel and carbon rods with Nd:YAG (yttrium aluminum garnet) lasers in solid Ar at approximately 10 K. Measurements of (13)C isotopic shifts have enabled the identification of the nu(3)(sigma(u)) vibrational fundamental at 1950.8+/-0.2 cm(-1), an asymmetric carbon stretching mode. Experimental results are in good agreement with the predictions of density functional theory at the B3LYP6-311G(*) level. Theoretical results suggest that the molecule is slightly floppy. Although other nickel carbide clusters have been studied theoretically or observed by photoelectron spectroscopy or mass spectrometry, this is the first report on the structure of NiC(3)Ni and its vibrational spectrum.

Fourier transform infrared observation of the nu1(sigma) mode of linear CoC3 trapped in solid Ar.

Fourier transform infrared (FTIR) and density functional theory (DFT) isotopic studies on cobalt-carbon species have resulted in the detection of linear CoC3. Dual laser ablation of carbon and cobalt rods, followed by trapping the products in solid Ar at approximately 10 K, produced the CoC3 chain. FTIR measurements of 13C isotopic shifts are in good agreement with the predictions of DFT calculations using the B3LYP and BPW91 functionals and the 6-311+G(3df) basis set, confirming the assignment of the nu1(sigma) fundamental of linear CoC3 at 1918.2 cm(-1).

Analytical approximations for the modal acoustic impedances of simply supported, rectangular plates.

Coupling of the in vacuo modes of a fluid-loaded, vibrating structure by the resulting acoustic field, while known to be negligible for sufficiently light fluids, is still only partially understood. A particularly useful structural geometry for the study of this problem is the simply supported, rectangular flat plate, since it exhibits all the relevant physical features while still admitting an analytical description of the modes. Here the influence of the fluid can be expressed in terms of a set of doubly infinite integrals over wave number: the modal acoustic impedances. Closed-form solutions for these impedances do not exist and, while their numerical evaluation is possible, it greatly increases the computational cost of solving the coupled system of modal equations. There is thus a need for accurate analytical approximations. In this work, such approximations are sought in the limit where the modal wavelength is small in comparison with the acoustic wavelength and the plate dimensions. It is shown that contour integration techniques can be used to derive analytical formulas for this regime and that these formulas agree closely with the results of numerical evaluations. Previous approximations [Davies, J. Sound Vib. 15(1), 107-126 (1971)] are assessed in the light of the new results and are shown to give a satisfactory description of real impedance components, but (in general) erroneous expressions for imaginary parts.

Vibrational spectra of germanium-carbon clusters in solid Ar: identification of the nu4(sigma(u)) mode of linear GeC5Ge.

The linear GeC(5)Ge cluster has been detected in Fourier transform infrared spectra observed when the products from the dual laser evaporation of carbon and germanium rods were trapped in solid Ar at approximately 10 K. Comparison of (13)C isotopic shift measurements with the predictions of density functional theory calculations at the B3LYP/cc-pVDZ level confirms the identification of the nu(4)(sigma(u)) mode of GeC(5)Ge at 2158.0 cm(-1).

Fourier transform infrared isotopic study of linear CrC3: Identification of the nu1(sigma) mode.

A vibrational fundamental of linear CrC3 has been detected in the products from the laser ablation of chromium and carbon rods trapped in solid Ar at approximately 10 K. Fourier transform infrared measurements of frequencies and 13C isotopic shifts are in very good agreement with the predictions of density functional theory calculations at the B3LYP6-311G+(3df) level, resulting in the identification of the nu1(sigma) stretching mode at 1789.5 cm(-1). This is the first optical detection of the linear isomer of the transition-metal carbide CrC3 for which previous photoelectron spectroscopic studies have reported evidence of both linear and cyclic isomers.

Vibrational spectrum of cyclic TiC3 in solid Ar.

The Fourier transform infrared spectrum of TiC3 was observed by trapping the vapor produced during dual Nd:YAG laser ablation of Ti and C rods in solid Ar at approximately 9 K. Measurements of frequencies and 13C isotopic shifts have enabled the identification of the fanlike (C(2v)) isomer of TiC3 with fundamental vibrations nu3(a1) = 624.3 and nu5(b2) = 1484.2 cm(-1). A third fundamental nu4(b1) has been tentatively identified at 573.8 cm(-1). The results are in good agreement with the predictions of density functional theory calculations at the B3LYP6-311G(3df,3pd) level. The observed C(2v) structure and the observed nu3 metal-carbon stretching mode are also consistent with earlier results from photoelectron spectroscopy.

Vibrational spectra of germanium-carbon clusters. II. GeC(7) and GeC(9).

Experimental and theoretical studies of a novel family of germanium-carbon clusters (Ge(n)C(m)) that were initiated with our earlier identification of the GeC(3)Ge cluster have now been extended to the GeC(7) and GeC(9) chains. The new clusters, which were formed by laser ablation and trapped in solid Ar at approximately 10 K, have been identified using Fourier-transform infrared (FTIR) measurements coupled with density-functional theory (DFT) calculations. The nu(1)(sigma) vibrational fundamental of linear GeC(7) has been identified at 2063.6 cm(-1), and an absorption at 1928.3 cm(-1) has been assigned to the nu(4)(sigma) fundamental of linear GeC(9). FTIR measurements of the isotopic shifts for the assignments are in good agreement with the DFT predictions.

A role for tonsillectomy in the treatment of psoriasis?

Our objective was to determine whether tonsillectomy is beneficial in the treatment of recurrent childhood guttate psoriasis that is associated with recurrent streptococcal pharyngitis and tonsillitis. We retrospectively reviewed the cases of two children who were referred to our facility for treatment of repeated exacerbations of psoriasis and recurrent streptococcal pharyngotonsillitis. Both patients experienced a significant improvement in their psoriasis after undergoing adenotonsillectomy, and both were completely free of psoriatic outbreaks after 16 months of follow-up. We conclude that tonsillectomy appears to be of benefit in the treatment of children with recurrent guttate psoriasis and recurrent streptococcal pharyngotonsillitis, and we hope that further investigation will be undertaken.