Angularly resolved light scattering from aerosolized spores: observations and calculations

Angularly resolved elastic light scattering patterns from individual aerosolized Bacillus subtilis spores were qualitatively compared with simulations. Two-dimensional angular optical scattering patterns of the spores were collected for polar scattering angles varying from approximately 77 degrees to 130 degrees and azimuthal angles varying from 0 degrees to 360 degrees . Computations were performed with single T-matrix formalism by simulating a spore with three different particle shapes: (1) a finite-length cylinder with spherical end caps, (2) a spheroid, and (3) two spheres in contact. Excellent agreement between computation and measurement was found for the finite-length cylinder with spherical end caps, poorer agreement was found for the spheroids, and the poorest agreement was for the two spheres in contact.     

Ultracompact waveguide bends with simple topology in two-dimensional photonic crystal slabs for optical communication wavelengths

Ultracompact waveguide bends with simple topology in two-dimensional photonic crystal slabs are proposed by using an annular air groove at the bend corner to improve transmissions of the bends. Analysis indicates that the guided light wave experiences a very slight difference of propagation properties between straight waveguides and bends (with 60 degrees and 120 degrees bending angles). Transmissions of more than 90% can be achieved in the 60 degrees and 120 degrees bends for light waves at 1.55 microm with bandwidths of 101 and 74 nm, respectively.     

Minimum audible movement angle in the horizontal plane as a function of stimulus frequency and bandwidth, source azimuth, and velocity.

Minimum audible movement angles (MAMAs) were measured in the horizontal plane for four normal-hearing adult subjects in a darkened anechoic chamber. On each trial, a single stimulus was presented, and the subject had to say whether it came from a stationary loudspeaker or from a loudspeaker that was moving at a constant angular velocity around him. Thresholds were established by adaptively varying stimulus duration. In experiment 1, MAMAs were measured as a function of center frequency (500-5000 Hz), velocity (10 degrees-180 degrees/s), and direction of motion (left versus right). There was no effect of direction of motion. MAMAs increased with velocity, from an average of 8.8 degrees of arc for a target moving at 10 degrees/s to an average of 20.2 degrees of arc for a target moving at 180 degrees/s. MAMAs were higher for a 3000-Hz tone than for tones of lower or higher frequencies, as has been previously reported [D. R. Perrott and J. Tucker, J. Acoust. Soc. Am. 83, 1522-1527 (1988)]. In experiment 2, minimum audible angles (MAAs) were measured with sequentially presented stationary tone pulses (500-5000 Hz), and were shown to exhibit the same dependence on signal frequency that the MAMAs showed (average MAA at 3000 Hz: 8.4 degrees; average MAA at the other frequencies: 3.4 degrees). In experiment 3, MAMAs and MAAs were measured as a function of stimulus bandwidth (centered at 3000 Hz) and listening azimuth (0 degrees vs 60 degrees). Average MAAs decreased monotonically as stimulus bandwidth increased from 0 Hz to wideband (from 8.4 degrees to 1.2 degrees at 0 degrees azimuth; from 11.3 degrees to 1.5 degrees at 60 degrees azimuth). As in experiment 1, MAMAs increased with stimulus velocity, from values comparable to the MAAs for the slowest-velocity (10 degrees/s) targets to 70 degrees of arc or more in the poorest condition (third-octave band of noise presented at a velocity of 180 degrees/s and an azimuth of 60 degrees). MAMAs obtained in the slower-velocity conditions depended in the same way on stimulus bandwidth and listening azimuth that MAAs depended on these variables. In no case was the MAMA ever smaller than the MAA. It is hypothesized that a minimum integration time is required to achieve optimal performance in a dynamic spatial resolution task. Average estimates of this minimum time based on the current data vary from 336 ms (for targets presented at midline) to 1116 ms (for narrow-band targets presented at 60 degrees azimuth).(ABSTRACT TRUNCATED AT 400 WORDS)     

INTERNAL FLOW PATTERNS OF AN INCLINED CLOSED TWO-PHASE THERMOSYPHON AT CRITICAL STATE: CASE STUDY II,EFFECT OF BOND NUMBER

The effects of Bond number (Bo) on internal flow patterns of an inclined, closed, two-phase thermosyphon at critical state are considered in this article. The thermosyphons used employed a glass tube for the evaporator and the adiabatic section, and a copper tube for the condenser section. The internal diameters of the thermosyphon were 10, 12, and 28.5 mm. The aspect ratios were 5 and 30, with inclination angles of 90 degrees, 60 degrees, and 5 degrees (against the horizontal axis). R123 was used as working fluid, with a filling ratio of 80% and 150% of the evaporator section. A solution of water and ethylene glycol was used to carry heat from the condenser, while water was employed to supply heat to the thermosyphon. A video camera was used to record all the flow patterns, while a still camera was used to record the internal flow patterns at specific times. Heat transfer rate was measured by means of a calorimeter in the condenser section. It was found from the experiments that, as under normal operating conditions, an Le/d of 10 is an important value at which changes of internal flow patterns can be observed. At an Le/d< 10 and with low Bo, the internal flow pattern at critical state changed from bubble flow at vertical to slug flow at an inclined position. Although the flow patterns were the same as with high Bo, the bubbles generated were smaller and appeared only on the upper side. In cases of Le/d>10, the pattern changed from annular flow at vertical to stratified flow at inclined positions for all Bo. Generated bubbles were comparatively small at low Bo. A flow pattern map at each angle was also created by using modified Kutateladze numbers and Reynolds numbers of the vapor.     

空间姿态敏感器表面材料辐射与反射性能测量方法研究

论述了空间姿态敏感器表面材料测量的基本原理,即光谱漫反射基本原理和光谱相对空间反射分布测量原理。通过上述测量可以全面地考察敏感器表面材料对不同光谱成分的反射能力,以及光辐射在材料表面的反射情况。结果表明,敏感器表面材料在入射和反射角大于60°的近红外区(波长为800~2500nm),敏感器表面材料的反射辐射能量明显升高了。在紫外至可见光区(波长为250~700nm),在入射和反射角小于60°的条件下,反射辐射能量很低。     

Heavy-ion particle spectrometry by track pattern in muscovite detectors

Muscovite mica detectors were irradiated with the ions: ¹⁹F of 47.5 MeV, ²⁴Mg of 57 MeV, ²⁸Si of 28 and 74 MeV, ³²S of 32 and 74 MeV, ⁶³Cu of 78.75 MeV and with neutron induced uranium fission fragments. Using optical microscopy, after an appropriate chemical etching, two characteristic etched track structure patterns were observed: a rhombic pyramid terrace structure for the Mg, Si and S ions, and a rhombic prism structure for the Cu ions and fission fragments. The use of these etched track patterns to discriminate two groups of ions between them, for the energy range covered in this work, is proposed.     

离心压气机进口导叶尾涡非定常发展的数值研究

本文在不同攻角和不同雷诺数Re下,对离心压气机进口导叶的内部流动进行了数值分析,探讨了导叶翼型绕流尾涡的非定常发展过程。结果表明,对本文所研究的导叶,攻角在30°～60°范围内,当雷诺数Re低于80时,流动是稳定的,翼型后方不出现大尺寸的流动分离;雷诺数Re大于80时,流动是非稳态的,此时翼型后方出现流动分离,并伴随有显著的涡脱落。     

Simulation of 3-D radiation beam patterns propagated through a planar interface from ultrasonic phased array transducers

Phased array transducers are quite often mounted on solid wedges with specific angles in many practical ultrasonic inspections of thin plates <10 mm in their thickness or welded joints with convex crowns. For the reliable application of phased array techniques with testing set-up, it is essential to have thorough understanding on the characteristics of radiation beam pattern produced in the interrogated medium. To address such a need, this paper proposes a systematic way to calculate full 3-D radiation beam patterns produced in the interrogated solid medium by phased array transducers mounted on a solid wedge. In order to investigate the characteristics of radiation beam patterns in steel, simulation is carried out for 7.5 MHz array transducers mounted on an acrylic wedge with the angle of 15.45 degrees with various of steering angles and/or focal planes.     

斜入射激光超声体波声场的实验研究

为研究微烧蚀状态下圆形光斑斜入射时激光超声声场的指向性,使用脉冲激光辐照半圆柱形铝质工件表面,并使用压电探头和电磁超声探头分别接收纵波和横波信号。根据速度参数确定了超声信号的类型,提取了信号的峰-峰值,并绘制出声场指向性曲线。通过分析获得以下结论:激光斜入射角度在0~60°范围内变化时,纵波声场的声束轴线方向保持不变,且与工件内法线平行;另外,横波声场的峰-峰值仍然在±35°的方向上取最大值,但是横波指向图形的主瓣易受激光入射方向的影响,当倾斜角度大于等于45°时,横波主瓣的范围变得较宽。     

稀土配合物中重叠峰分离的相分辨光声光谱研究

首次利用相分辨光声光谱法对稀土配合物中不同吸收中心的重叠谱峰进行了分离。在Nd(Trp) 3 Cl3 ·H2 O固态配合物中 (Trp :色氨酸 ) ,30 0～ 4 0 0nm这一波段内由于色氨酸配体强的π π 跃迁吸收 ,Nd3 +的光声峰被掩盖。通过光声谱同相和交相信号可以计算配体光声吸收的位相为 10 6° ,位相改变 90°后就得到仅与Nd3 +相关的光声光谱。相分辨光声光谱法用于谱峰分离时有它独特的优点 ,它不受谱峰形状和重叠程度的限制 ,而仅与不同吸收峰对应的光声位相有关     

EPR and HYSCORE investigation of the electronic structure of the model complex Mn(imidazole)6: exploring Mn(II)-imidazole binding using single crystals

The electronic structure of the Mn(II)-imidazole binding was studied by EPR spectroscopy using the model complex Mn(Im)(6) diluted in a single crystal of Zn(Im)(6)Cl(2).4(H(2)O). The second rank zero-field splitting (ZFS) tensor (D tensor) of the two sites, a and b, present in the crystal was determined by measuring the orientation patterns of the echo-detected EPR spectra in three different planes at 10K (D(a)=-106, D(b)=-118, E(a)=-17, E(b)=-22x10(-4)cm(-1). Euler angles with respect to the crystal habitus: alpha(a)=13 degrees , beta(a)=76 degrees , gamma(a)=108.5 degrees , alpha(b)=14 degrees , beta(b)=73.5 degrees , gamma(b)=103.5 degrees ). The contribution of cubic ZFS terms to the spectrum allowed us to determine the orientation of the N-Mn-N directions of the complex as well (Euler angles in the D tensor reference frame alpha=100 degrees , beta=23 degrees , gamma=0 degrees , both centers having the same orientation). The hyperfine interactions with (14)N were explored by HYSCORE spectroscopy. The correlation patterns and modulation amplitudes in the 2D experiments were studied for different electron spin transitions and orientations of the crystal. Signals of three different pairs of nitrogens were found. The results were analyzed considering that the N-Mn binding directions are principal directions of the hyperfine and nuclear quadrupole tensor of (14)N. All three pairs of nitrogens were found to be almost equivalent with an isotropic contribution of A(iso) approximately 3.2MHz and an almost axial anisotropic coupling of 2T approximately 1.1MHz along the N-Mn bonding direction. The nuclear quadrupole principal values are 1.5MHz along the bonding direction, -0.6MHz in the direction perpendicular to the imidazole plane, and -0.9MHz in the direction perpendicular to both.     

ODMR and EPR investigations of Fe centers in KTaO3

The analysis of EPR spectra obtained from iron doped KTaO₃ crystals in the as-grown state revealed three dominant iron centers: Fe³⁺-O_I, axial Fe-centers with spinS = 3/2 and rhombic Fe³⁺. By comparison with data from literature possible assignments for the center withS = 3/2 are discussed. For the rhombic species the temperature dependence of the main parameters of the Spin- Hamiltonian was measured. The result makes it most plausible that only one rhombic iron center exists in KTaO₃, in contrast with literature. The understanding of the EPR spectra allows us to assign transitions, observed at very low magnetic fields by optically detected magnetic resonance (ODMR), to this rhombic Fe center. On this basis, the magnetic circular dichroism (MCD) of this defect could be identified using the method of tagged-MCD. This spectrum is compared to the tagged-MCD of Fe³⁺-O₁ and of axial Fe⁴⁺ centers, which may be generated metastably by optical charge transfer. Considerably different structures in the MCD spectra of both Fe³⁺ centers indicate different local surroundings and electronic states.Dedicated to O. F. Schirmer on the occasion of his 60th birthday     

Superlattice, rhombus, square, and hexagonal standing waves in magnetically driven ferrofluid surface

Standing wave patterns that arise on the surface of ferrofluids by (single frequency) parametric forcing with an ac magnetic field are investigated experimentally. Depending on the frequency and amplitude of the forcing, the system exhibits various patterns including a superlattice and subharmonic rhombuses as well as conventional harmonic hexagons and subharmonic squares. The superlattice arises in a bicritical situation where harmonic and subharmonic modes collide. The rhombic pattern arises due to the nonmonotonic dispersion relation of a ferrofluid.     

The differential and total bulk acoustic scattering cross sections of some human and animal tissues

This paper describes methods that have been developed for the accurate measurement of total and differential bulk acoustic scattering cross sections. Analysis is made of the sources of uncertainty entailed in measurements of this kind and a complete derivation is developed for the angular variation of the interrogated scattering volume. Experimentally determined values of differential scattering cross sections are reported for specimens of skeletal muscle, blood, liver, and secondary tumors arising in liver, obtained in the frequency range 4-7 MHz for scattering angles in the practically attainable range 60 degrees-150 degrees and also at 180 degrees (backscatter). A basis for extrapolating these results to other scattering angles can be derived from a combination of theoretical and experimental considerations, as presented in a companion paper [J. Acoust. Soc. Am. 79, 2048-2054 (1986)]. Based on such extrapolation, values for total scattering cross sections are estimated for the above tissues, the values are compared with determinations by different techniques as reported by other authors, and corresponding estimates are derived for the contribution of scattering processes to total attenuation in the tissues.     

Charged particle spectra in16O induced nuclear collisions at the CERN SPS

Charged particle multiplicity distributions and pseudo-rapidity density distributions from¹⁶O induced nuclear collisions at 200 and 60A GeV are presented. The data were taken, using a minimumbias trigger, with the WA80 set-up at the CERN SPS. In this presentation we focus on how the yield of charged particles depends on the projectile energy, the mass number of the target nucleus and the energy measured in a uranium-plastic sampling calorimeter covering angles close to zero degrees. The data are compared to simulations from the event generator FRITIOF.     

Resolution in azimuth sound localization in the Mongolian gerbil (Meriones unguiculatus)

Minimum resolvable angles (MRAs) for sound localization in azimuth in the gerbil were determined in a behavioral study using tones, 300-Hz bands of noise centered at frequencies between 500 Hz and 8 kHz and broad-band noise of on average 60 dB SPL overall level. Using the method of constant stimuli, seven gerbils were trained in a two-alternative-forced-choice procedure to indicate if sounds were presented to them from the left or from the right by choosing the left or right arm of a Y-shaped cage. The MRA is the minimum angle between two loudspeaker locations that the gerbils discriminated. Animals were either stimulated from the front (N=4) or from the back (N=3). The MRA for broad-band noise randomly varying in level by +/- 6 dB was 23 degrees and 45 degrees for gerbils stimulated from the front or back, respectively. Generally a gerbil's MRA for tones declined up to 2 kHz reaching 20 degrees and 31 degrees for gerbils stimulated from the front or back, respectively, and the MRA was generally increased above this frequency. Results for narrow-band noise stimuli were similar. Results are discussed with respect to the available interaural cues and physiological mechanisms of sound localization in the gerbil.     

Propagation phenomena of wideband guided waves in a bended pipe

Ultrasonic guided waves in pipes have been anticipated as a rapid screening technique for pipe inspection because of their long-range propagation due to low energy leakage. In this paper, the propagation phenomena of guided waves in a bended pipe were investigated using a wideband laser ultrasonic system. The laser ultrasonic system, together with wavelet transformation, is a powerful tool for observing the dispersive phenomena intrinsic to guided waves. Bended stainless steel (SUS304) pipes with 6-mm outer diameter and 1-mm wall thickness were used in the experiments. The bending angles of the pipes were set to 0 degrees (straight pipe), 10 degrees, 30 degrees, 60 degrees and 90 degrees. The radius of the bend was 12.5 mm in all the pipes. A Q-switched Nd:YAG laser was employed to generate the guided waves. The generated guided waves were detected with a heterodyne interferometer. The obtained time-domain signals and their wavelet coefficients indicated the following two conclusions: (1) The amplitude of the F(1,1) mode converted from the L(0,1) mode increased with the increase of the bending angle. (2) Mode conversions from the L(0,1) to F(1,1) modes and vice versa were clearly observed in the low-frequency range up to around 200 kHz.     

Unified Mie and fractal scattering by biological cells and subcellular structures

Angle-resolved light scattering spectroscopy of biological cells is investigated in the visible wavelength range. A unified Mie and fractal model is shown to provide an accurate global agreement with light scattering spectra from 1.1 degrees to 165 degrees scattering angles. It is found that light scattering in forward directions (<8 degrees ) is dominated by Mie scattering by the bare cell and nucleus, whereas light scattering at large angles (>20 degrees ) is determined by fractal scattering by subcellular structures. The findings are consistent with the results of experimental investigation of the contributions of different cellular components to light scattering by cells.     

Ultrasonic wave interaction with multidirectional composites: modeling and experiment

Phenomena of wave transmission through a multidirectional composite laminate immersed in a fluid have been investigated. Based on a recently-developed recursive stiffness matrix method time-domain beam models have been developed to simulate the problem. Experimental and theoretical results at frequency 2.25 MHz show that the transmission amplitude is highly dependent on lamina orientation and angle of incidence. Large transmission amplitude appears at small (<10 degrees) and large incident angles (45 degrees-60 degrees). At intermediate incident angles (16 degrees-40 degrees) the transmission amplitude is almost zero. At high frequency, the residue epoxy layers between each lamina become important and corresponding resonances may be observed. These transmission phenomena have been interpreted in terms of Floquet waves. It shows that the pass and stop bands of the three Floquet waves obtained from the unit cell stiffness matrix determine the transmission amplitude distribution in frequency, incident angle and rotation angle domains. The effect of random deviation of the laminated structure periodicity has also been assessed. At normal incidence, the variation of the thickness of the epoxy residual layer between composite lamina has little effect on the overall stop and pass band structures but introduces random reverberation and scattering in the pass bands. It is shown that for oblique incidence the transmittivity spectrum of a composite with random lamina lay-up converges with increase of randomness to that of a [0/-45/90/45]2s quasi-isotropic composite. Randomization of lamina lay-up produces a small effect in the transmittivity spectrum for a quasi-isotropic composite.     

Spectral cues and perception of the vertical position of targets by the big brown bat, Eptesicus fuscus

Big brown bats (Eptesicus fuscus) were trained to discriminate between vertical angles subtended by paired beads suspended from fishing line. Bats were rewarded for choosing the smaller of the two angles presented. The difference between the angles was changed systematically using a transformed up-down procedure and the bats' ability to detect the difference was measured at different vertical locations. When the beads were centered at +20 degrees (above the horizon), at 0 degree (the horizon), and at -20 degrees (below the horizon), vertical angle acuity (VAA) was maintained between 2.9 degrees and 4.1 degrees. At more extreme vertical positions both bats showed loss of acuity; when the beads were centered around -40 degrees, VAA was 6.7 degrees or 8.3 degrees and at +40, VAA was worse than 21 degrees (the largest difference tested). When the tragi of both ears were bent down and glued to the side of the face, bats showed severe loss of acuity for beads centered at -20 degrees (VAA 18.3 degrees and 20.1 degrees), but maintained their angle acuity for beads centered at +20 degrees (VAA 3.8 degrees and 4.9 degrees). The results are consistent with the spectral cues created by the filtering of the external ear.