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Summary Areas infested with Solanum carolinense, an introduced perennial weed, have increased quickly in Japan. The genetic structure of a S. carolinense population along the Takano River in Kyoto, Japan was investigated using amplified fragment length polymorphism (AFLP) analysis to reveal how introductions and local spread have contributed to the development of this population. Along a terrace beside the river and an adjacent roadside, we defined a cluster of above-ground shoots in the population as a subpopulation and 60 subpopulations were identified. Seventeen of these were selected and 165 shoots were analyzed by AFLP analysis using three primer pairs. The AFLP profiles revealed 69 genotypes and the presence of several clones, i.e. genotypes that were present in more than one individual. In total, 19 clones, comprising 2–34 identical genotypes, could be identified in the population. Each of these clones, except one, was allocated within each of the subpopulations. Clustering of the subpopulations was supported by high bootstrap values in all cases. Therefore, introductions from distant regions have mainly contributed to the development of this population, and local spread by seed or vegetative reproduction has rarely been important. The most likely introduction route of S. carolinense to this population was via planting associated with construction works.

Silicon microphones based on capacitive micromachined ultrasonic transducer membranes and radio frequency detection overcome many of the limitations in bandwidth, uniformity of response, and durability associated with micromachined condenser microphones. These membranes are vacuum-sealed to withstand submersion in water and have a flat mechanical response from dc up to ultrasonic frequencies. However, a sensitive radio frequency detection scheme is necessary to detect the small changes in membrane displacement that result from utilizing small membranes. In this paper we develop a mathematical model for calculating the expected output signal and noise level and verifies the model with measurements on a fabricated microphone. Measurements on a sensor with 1.3 mm2 area demonstrate less than 0.5 dB variation in the output response between 0.1 Hz to 100 kHz under electrostatic actuation and an A-weighted equivalent noise level of 63.6 dB(A) SPL in the audio band. Because the vacuum-sealed membrane structure has a low mechanical noise floor, there is the potential for improved sensitivity using higher carrier frequencies and more sophisticated detection circuitry.

This prospective observational study evaluates the efficacy and safety of thermal Balloon endometrial ablation using the Cavaterm system for the treatment of dysfunctional uterine bleeding. Seventy-seven women with a mean age of 43 years who met the inclusion and exclusion criteria were treated under general anaesthesia. A 9-mm diameter catheter with a silicone balloon at its tip was inserted transcervically into the uterus and was inflated with sterile 1.5% glycine and connected to a control unit that maintained the temperature of the circulating heated fluid at 75 degrees C, monitored the pressure and terminated the treatment after 15 minutes. There were no intra-operative complications and patients tolerated the treatment well. Satisfaction rates were 90% at both 12 and 24 months. At 24 months 10% of patients had heavy periods, 5% normal periods, 39% light periods and 46% amenorrhoea. Cavaterm balloon ablation seems a safe and effective option for women with menorrhagia. The procedure does not require additional training and expertise in operative hysteroscopy and compares favourably with established techniques.

A requirement for extended periods of free water retention for fungal infection continues to limit the development of many potential bioherbicides. The use of hydrophilic polymers in the formulation of bioherbicides to overcome this limitation was investigated, using the potential bioherbicide Colletotrichum orbiculare and weed Xanthium spinosum as a model system. The relative humidity (RH) requirement of C. orbiculare required for adequate infection was &#83 95%. Water activity (a w ) required for growth of C. orbiculare was > 0.95 a w . A range of three natural and four artificial polymers, including gums and polyacrylamides was tested. All polymers were found to be non-toxic to the fungal spores and thus suitable for use in bioherbicide formulations. Once incorporated into the formulation, little improvement compared to the non-polymer controls was observed on treated plants in the absence of dew. Water loss studies of the polymer suspensions were carried out at RHs of 33 and 75%. There were significan...

A comprehensive review of advancements in eddy current (EC) modeling is presented. This paper contains three main sections: a general treatise of EC theory, the thin skin EC forward modeling, and the EC inverse problem. (1) The general treatise of eddy current theory begins with an exposition of the reciprocity formulas for evaluating probe impedance changes, which are derivable from first principles. Two versions of the reciprocity formulas, one with a surface integral and the other with a volume integral, are given. Any particular type of defect, as well as both one-port and two-port probes, can be treated. Second, a brief account of analytical and numerical methods for calculating the field distributions is presented. Third, theory of probe/material interactions with various defect types is described. (2) The paper then proceeds to the forward modeling section, which contains a detailed treatment of the eddy current forward problem for surface breaking cracks and EDM notches in the thin skin approximation. (3) The inverse problem section begins with a general review of commonly used inversion methods, exemplified by selected references from the literature, followed by more detailed examinations of EC inversions for surface breaking cracks and slots. The last part of this section is devoted to the inverse problem for layered structures. Although being a review in nature, the paper contains a number of new accounts for time-domain eddy current interactions. In particular, a modification is proposed to the reciprocity formula in order to take a better account of pulsed eddy current signals.

A piezoelectric polymer film such as polyvinylidene fluoride (PVDF) offers the possibility of making cheap ultrasonic transducers which can be permanently bonded to structures for NDE applications. However, before this can be achieved it is necessary to have a full understanding of the behaviour of PVDF in the context of a transducer application. This paper describes the development of an interactive computer program to implement a one-dimensional model of a thin film transducer system mounted on a solid substrate. Starting from a typical transducer system mounted on a solid substrate. Starting from a typical tranducer equivalent circuit, this paper explains how that circuit can be expanded into a complete model representing a PVDF transducer with one or more backing layers bonded to an arbitrary solid substrate. The computer program uses this model to provide immediate predictions of electrical input impedence, acoustic response and pulse-echo response. A series of experiments has been performed using PVDF transducers bonded to a variety of materials in order to validate the model. This has enabled the degree of accuracy required for various parameters within the model, such as mechanical and dielectric loss values, to be assessed. Once validated, the model has been used as a tool to predict the effect of physical parameters, such as bond and electrode thickness, on the performance of a transducer.

A general formula and a computational scheme for estimating the power spectrum of the displacement correlation function of suspended test masses such as those used in interferometric gravitational wave detectors are presented. Unlike previous mode-summation approaches, the fluctuation-dissipation theorem has been applied directly to the displacement correlation. The resulting formula expresses the correlation in terms of material damping parameters and mechanical Green’s functions, and provides an efficient and flexible method to compute thermally induced surface displacements of arbitrarily shaped anisotropic elastic bodies. The formula can be used for optimizing the shape and size of test masses in gravitational wave receivers. A simple one-dimensional example is included to clarify the relationship with the modal expansion approach and to illustrate the advantage of the Green’s function method. This paper presents the theoretical formulation; numerical evaluations of the formula will be presented elsew...

An approximate theory is presented for torsional modes in a solid cylinder having a larger‐diameter central section. Modes in a narrow frequency range just above the cutoff of each branch are ‘‘trapped’’ such that, in long samples, the amplitudes decay exponentially with distance from the central section. To confirm the theory, measurements were performed on aluminum alloy cylinders using noncontacting electromagnetic‐acoustic transduction. Vibrational amplitudes of a trapped mode measured as a function of position along the length of a sample are in good agreement with theoretical calculations. The resonant frequencies of three samples with different dimensions also closely match the theory for trapped modes. Additional generally weak resonances that are observed may be associated with torsional modes that vary sinusoidally along the entire length of the samples.

The transverse resonance approach to guided wave analysis is applied to shear horizontal (SH) wave propagation in periodically layered composites. It is found for SH waves that at high values of the guided wavevector /spl beta/, the wave energy is trapped in the slower of the two media and propagates accordingly at the slower wavespeed. At low values of /spl beta/, however, the modes demonstrate a clustering behavior, indicative of the underlying Floquet wave structure. The number of modes in a cluster is observed to correlate with the number of unit cells in the layered plate. New physical insights into the behavior of these systems are obtained by analyzing the partial waves of the guided SH modes in terms of Floquet waves. We show that the fast and slow shear waves in the periodically layered composite play an analogous role to the longitudinal and shear partial waves comprising Lamb waves in a homogeneous plate.

There is an interesting analogy between the spatial problem of Fresnel diffraction and the temporal problem of first-order dispersion. This space-time analogy was recently extended to propose a time-domain analog to spatial imaging that allows for the distortionless expansion of compression of optical waveforms in time. This process is called temporal imaging. The extension includes the idea of a time-lens as a dual of a spatial lens (regular lens). The time-lens is simply a quadratic optical phase modulator in time, which is approximated by a portion of a sinusoidal phase modulator. Thus, by using phase modulators as lenses and grating pairs as dispersive elements, complete temporal imaging systems can be constructed in exact duality with spatial imaging systems. However, for practically useful time-lenses, considerable modulation is required at fairly high frequencies. The main body of the paper is the detailed design and development of a practical time-lens. This is addressed in Section II, where a resonant microwave modulator is developed based on a LiNbO/sub 3/ loaded waveguide. Multiple passes are obtained through the modulator using an off-axis path in a stable optical resonator. At 5.2-GHz operation, 44 radians of phase modulation is obtained at 1.06-/spl mu/m wavelength for 13 W of microwave power. This corresponds to a time-lens with 31-ps aperture and 1.9-ps resolution. This was confirmed by demonstrating temporal focusing of 45-ps pulses to 1.9 ps. By optimizing the design of the time-lens and better thermal engineering, it may be possible to obtain subpicosecond resolution. >

Two ultrasonic techniques employing electromagnetic‐acoustic transduction are presented for performing measurements of the resonant torsional frequencies and Q of solid cylindrical metallic rods. One of these techniques uses long radio‐frequency pulses to drive the sample into resonance and the other uses continuous‐wave excitation. Measurements are performed on an aluminum alloy. Since the transduction involves no mechanical coupling, the background damping is low; the Q is 1.2×105 at 755 kHz with the sample simply supported on its side. The shear velocity is determined with an accuracy of better than 2 parts in 104 (limited by the uncertainty in the measurement of the sample radius).

Piezoresistive silicon based process monitoring devices (PMDs) employing flexible circuitry and substrates have been developed which are compatible with standard VLSI fabrication processes. These solid state sensors offer cost effective batch fabrication and a high degree of uniformity to produce either single elements or flexible conformable arrays. This is a state of the art report on emerging technology.

A 20-GHz dielectric-resonator/optical modulator is developed and used as an FM mode locker at the 84th harmonic of a conventional 238-MHz diode-pumped Nd:BEL laser cavity. Depending on the mode-locker drive frequency, two distinct regimes of mode locking were observed: 2.9-ps pulses at a repetition rate of 238 MHz and 3.9-ps pulses at a repetition rate of 20 GHz. These are to our knowledge the shortest pulses ever reported for active mode locking of a Nd laser.

Optical polarization changes and mode coupling due to spatially varying anisotropic perturbations in caused by electro-optic, acousto-optic, and other effects have been widely studied for both plane-wave and fiber mode propagation. A new optical S-parameter analysis of these effects, applicable to arbitrary optical field distributions, is presented. It is applied to evaluating the performance of the longitudinal electro-optic probe used for noninva-sively examining GaAs integrated circuits. Error in probe measurements of circuit voltage distributions can be characterized by considering the probe as a scanned electro-optic spatial filter.

Bartholin's abscess and cyst account for 2% of all gynaecological visits per annum. This article reviews the anatomy, epidemiology and pathophysiology of the Bartholin's gland. The management of Bartholin's abscess including antibiotic use in the early stage of the condition together with options for surgical intervention are discussed and in so doing the variation of clinical practice in other countries is considered. The use of the word catheter, carbon dioxide laser are compared with traditional surgical techniques of incision and drainage and marsupialisation. The outcomes of treatment particularly the high recurrence rate (2-25%) and the associated morbidity are reviewed. Finally the issue of cancerous pathology as an aetiology is highlighted in the postmenopausal age group.

The authors present a model predicting the influence of various design parameters (geometrical dimensions, metal thickness, or groove depth) on the resonant frequency of surface transverse wave (STW) resonators. The model is based on the near-stopband approximation and the formalism of cascaded transfer matrices. Results are obtained in the case of a three-grating configuration (mirror-cavity-mirror) for both grooved and metal strip gratings. Based on simple analytical expressions, a design procedure is used, and the influence of various parameters is demonstrated and compared to already published experimental data. Experimental results obtained on metal strip quartz STW resonators are presented and discussed. >

A resonant microwave optical phase modulator in LiNbO3 with multiple passes, based on an off‐axis path in a stable optical resonator, is demonstrated as a time‐lens. With 1 W of cw microwave power at 5.2 GHz, 45 ps pulses at 1.06 μm were temporally focused to 6.7 ps (FWHM). Increasing the drive power to 13 W, at 10% duty cycle, produced 1.9 ps pulses. The aperture of the time‐lens is about 31 ps. This is the first demonstration of a useful time‐lens.

We report the first subpicosecond shockwaves ever generated and measured by entirely electronic means. These shockwaves have 880 fs fall times with 3.5 V amplitudes. This was accomplished at T=77 K with a monolithic nonlinear transmission line and diode sampling bridge fabricated on GaAs. We have used these circuits with integrated antennas to generate freely propagating pulses and have detected measurable radiation beyond 3 THz.

An ultrafast GaAs Schottky photodiode is monolithically integrated with a microwave detector. By using this new optoelectronic circuit in place of a nonlinear crystal in an optical correlation setup, the high‐speed photodiode can measure laser pulse durations without using expensive sampling oscilloscopes. Key advantages are that this circuit works over a broad wavelength range and at low peak optical powers. The correlated temporal response of the circuit is measured to be 1.9 ps full width at half maximum. Due to its wavelength flexibility, cross correlation with different lasers may be performed with this single device.

We report the use of electro‐optic sampling techniques in the measurement of the electro‐optic frequency response of a poled organic layer, to 20 GHz. The organic material tested was a Disperse Red 1/poly(cyclohexyl methacrylate) guest/host system which was deposited and poled on top of a GaAs based coplanar waveguide transmission line. The GaAs substrate also served as the reference electro‐optic material in the hybrid structure, which was optically sampled from both sides.

John Moulder’s lifetime coincided with a period of exceptionally creative innovation in the theory and practice of eddy current testing (ECT). But, as an unusually gifted experimentalist arriving on the scene at the ideal moment, he contributed far more than his share to the advances made during this period.

summaryof the important features will be repeated below, as well as some modifications which were made to improve theperformance in a spectroscopy system application. We used NLTL's, integrated with magnetic dipole (slot) antennas measuring 5 tm wide and 190 tm long to realize a free-space picosecond pulse generator integrated circuit (IC). High-resistivity (10 k1-cm) silicon hyper-hemispheres [12] were used to collect and focus the quasi-optical beam. Off-axis paraboloidal mirrors collimatedand redirected the beam onto a detector chip. The detector IC consisted of an all-electronic two-diode sampler [13]whose RF port was driven by a slot antenna identical to the one used in the generator IC and whose LO port wasdriven by an NLTL. The generator and detector are each driven by synthesized microwave signal generators andmicrowave amplifiers capable of producing a +30 dBm, 5 to 10 GHz microwave signal. The two signal generatorswere phase-locked and offset in frequency by an IF frequency from 0.5 to 10 Hz. A portion of each signal was fedto a mixer to provide a trigger signal to an audio frequency spectrum analyzer which was connected to the IF portof the detector.The complete system is shown in Figure 1. Due to the difficulty in maintaining a stable 77°K environment forperforming spectroscopic measurements, only 300°K NLTL's were used in the experiments reported in this paper.Figure 1: Experimental setup

An electromagnetic-acoustic transducer (EMAT) of novel design is used to excite and detect only those resonant modes of a cylinder that have a specific, integral number of nodes on the circumference. Because the nodal pattern is fixed and the coupling between the cylinder and transducer is weak, the resonances have very well defined frequencies which allow applications that include measurements of accurate shear wave velocities in commercial alloys, case depth in hardened steel shafts and axial stress in solid cylinders

We report the first subpicosecond shock-waves ever generated and measured by electronic circuits. We have used these circuits with integrated antennas to generate and detect freely-propagating THz radiation. The circuits are monolithic nonlinear transmission lines fabricated on GaAs and, for peak efficiency, they operate at liquid nitrogen temperatures. Nonlinear transmission lines (NLTL’s) have been used by several researchers for generating electronic shock-waves with picosecond transition times by compressing the wavefront generated by a ∼0.5 W, ∼5–10 GHz microwave power source.1,2,3 While the literature reflects continual decreases in these transition times, as measured both by diode sampling bridges and by electro-optic sampling, the fastest reported 10%–90% fall time thus far has been 1.4 ps, with a∼5V amplitude.4 However, generating and measuring a sub-picosecond transition with an all-electronic device has been an elusive goal because a fundamental limitation has been the NLTL diode series resistance. By immersing a packaged NLTL into liquid nitrogen, we were able to lower this resistance significantly, thereby producing voltage shock-waves with 880 fs fall times and 3.5 V amplitudes, as measured by an on-chip diode sampling bridge (Figure 1). We have used these circuits with integrated slot antennas to generate freely propagating THz radiation, and we have observed measurable radiation beyond 3 THz.

We have developed electronic circuits that generate and detect subpicosecond shock-waves. We have used these circuits with integrated antennas in a system capable of free space spectroscopy with greater than 10 dB signal to noise from 5 GHz to 1 THz. This system was used to characterize a submillimeter wave filter from 6.4 GHz to 1 THz. In particular, 250-375 GHz measurements are demonstrated with 2 dB accuracy over a 20 dB dynamic range.

We report a subpicosecond GaAs wafer probe system which incorporates a mechanical flexure and a micromachined GaAs IC for time domain on-wafer measurements. The micromachined GaAs IC incorporates a novel high speed pulse sharpener and a two diode sampling bridge with a micromachined GaAs tip.

This paper reviews the use of electrostatic capacitive probes for detections and evaluations of dielectric material properties and flaws. Interest in using both inductive and capacitive arrays for proximity sensing, surface feature characterization, material properties evaluation, and flaw detecting has increased steadily since the mid-1980’s [1–7]. Two other papers [6,7] in this proceedings also discuss the present state of the art, particularly with regard to the measurement of lossy dielectrics (complex permittivity). In traditional dielectrometry measurements (as well as in eddy-current measurements of material properties evaluation) varying the probe frequency has long been used as a tool for extracting information about dispersion and loss mechanisms. Use of a spatially periodic array probe interrogates the material, or flaw, with a field that penetrates into the sample to a degree determined by the periodicity. This controllable penetration phenomenon (artificial-skin effect or zoom effect) has been successfully exploited by Melcher, Zaretsky [5], and Goldfine [6] in what they call imposed w-k magnetometry and dielectrometry, using interdigital probes of different periodicities. Details are given in these proceedings. Gammell’s paper [7] gives a progress report on complex permittivity measurements using probes of more conventional type.

A range of plants was tested for their susceptibility to Drechslera avenacea (M.A. Curtis ex Cooke) Shoem., the possible active ingredient in a bioherbicide for use against the weed Avena fatua. Test plants were chosen on the basis of phylogenetic proximity to the weed, recorded susceptibility to closely related pathogens or physical proximity in agricultural systems to wheat, the crop in which the weed is to be controlled. The fungus caused mortality of A. fatua and Avena byzantina cv. Yarren. Sporulation occurred on A. fatua and, on one occasion (of three challenges), on Brassica napus cv. Oscar. Severe disease symptoms were recorded on 13 species of grass and mild infection on a further seven species. We observed a much broader host range than previously recorded. The reasons for, and implications of, this are discussed and the suitability of D. avenacea as a bioherbicide assessed.

An electromagnetic acoustic transducer for inducing and sensing vibrations in a cylindrical object and methods of using an electromagnetic acoustic transducer to determine resonant frequencies and physical properties of cylindrical objects. The electromagnetic acoustic transducers produce specific modes of vibration in cylindrical objects including axial shear vibrations, torsional vibrations, radial vibrations and plane strain vibrations. The methods of determining physical properties of a cylindrical objects include comparing sensed resonant frequencies of the cylindrical object to known relationships between resonant frequency and the physical properties of interest. The methods can be used to determine the temperature, dimensions, elastic constants, and damping coefficients of cylindrical objects, the magnitude of a load applied to a cylindrical object, or the texture or grain orientation of the material forming a cylindrical object.

The identity, biology and pathology of a Phaeoramularia sp. isolated from crofton weed, Ageratina adenophora, were investigated to assess its potential as a mycoherbicide for control of crofton weed. Leaf infection by A. adenophora by a conidial suspension of Phaeoramularia sp. was studied using light and electron microscopy. Under optimum conditions, Phaeoramularia sp. could penetrate leaves via stomata 5 days after inoculation and express leaf-spot symptoms and produce conidiophores on the leaf surface within 7 days. An investigation of various host and environmental factors showed that the optimum conditions for infection of seedlings of crofton weed with Phaeoramularia sp. were an inoculum concentration of 106 conidia/mL, a dew period of at least 18 h and a temperature of 19 to 24°C during and after the dew period. The use of Phaeoramularia sp. as a mycoherbicide on A. adenophora has some potential if high inoculum concentrations are used and young plants are sprayed in moist warm conditions.

Factors likely to influence the production of Phaeoramularia sp. as a mycoherbicide to control crofton weed (Ageratina adenophora) were investigated. The fungus grew best on potato-dextrose agar (PDA) and carnation leaf-piece agar and sporulated best on PDA and a decoction agar made from A. adenophora. The fungus grew and sporulated best at 20 and 25°C and at water potentials between −0.4 and −1.5 MPa. For small scale production of conidia of the fungus a combination of submerged and solid culture with the fungus grown in liquid culture resulted in the greatest number of conidia. Comparative studies showed that mycelium was as pathogenic as conidia and that the former may have potential for further development as a mycoherbicide.

We have developed all-electronic integrated circuits that generate and detect picosecond pulses. We have used these circuits with integrated antennas in a system capable of free-space spectroscopy in the terahertz regime. With this system we have measured magnitude- and phase-transmission characteristics for a variety of samples in the frequency range of 200 GHz–1 THz.

(1994). Erratum: Silicon Sensors as Process Monitoring Devices. Research in Nondestructive Evaluation: Vol. 5, No. 3, pp. 237-237.

A 500 GHz bandwidth GaAs MMIC sampling wafer probe is reported which incorporates a mechanical flexure and a micromachined GaAs IC for time domain on-wafer measurements. The GaAs IC incorporates a novel high speed pulse sharpener and a two-diode sampling bridge with a micromachined GaAs tip.

A phase detector consisting of Schottky diode peak detector taps distributed along an integrated GaAs transmission line has been fabricated. Pulses counterpropagate on the line, forward biasing taps in the region of pulse overlap. The relative phase gain, determined from the captured overlap function, is 20 mV/ps.

An all-electronic system for generating, propagating and detecting picosecond electromagnetic pulses using monolithic integrated circuits is described. With a 1.8 ps (10%–90%) nonlinear transmission line step generator driving a monopole antenna for transmission and a similar antenna driving a diode sampler for reception, the system has shown spectral coverage from 90 to 170 GHz.

A scalar potential formulation of the δZ formula for the change in impedance of an eddy-current probe caused by a surface-breaking flaw is developed. The resulting formula is evaluated using a finite-difference method, which permits calculation of δZ for semielliptical flaws. The numerical results are checked by comparing calculations for rectangular-shaped flaws to previous calculations using an analytical solution for this geometry. Theoretical results are then verified by comparison with measurements on semielliptical fatigue cracks and EDM notches in aluminum alloy specimens using air-core eddy-current probes. An inversion method that compares features of the flaw profile, obtained by scanning the eddy-current probe along the length of the flaw, to a theoretical inversion chart (McFetridge chart) is demonstrated using the experimental data.

The fungal pathogen Colletotrichum orbiculare which causes anthracnose of the exotic weed Xanthium spinosum is being evaluated for use as a mycoherbicide for biological control of the weed in Australia. Four experiments investigated the effects of potential stress factors on the host-pathogen interaction. The influences on disease development investigated (in controlled environment chambers) were host moisture stress, simulated rainfall after inoculation, cold temperatures and host age/flowering status (...)

Two diseases of Xanthium spinosum, caused by Colletotrichum orbiculare and an unidentified Phomopsis sp., were widely distributed in New South Wales. Phomopsis sp. occurred less frequently on X. occidentale, X. italicum, and X. orientale than on X. spinosum. Isolates of C. orbiculare were highly virulent on X. spinosum but were only weakly virulent to other Xanthium spp. in NSW and in the United States. Isolates of Phomopsis sp. were pathogenic to all Xanthium spp. However, isolates of Phomopsis sp. from X. spinosum, X. occidentale, and X. italicum were more virulent to X. spinosum than to the other Xanthium spp.

Summary: The native perennial shrub, Bassia birchii. occurs as a weed over large areas of semi-arid eastern Australia. Its germination requirements and seedling growth were investigated and related to field observations and to possible means of control. Seeds cannot germinate until the woody fruit has broken down. Laboratory experiments showed that seeds would germinate throughout the year with most germinating at autumn and spring temperatures. Seedling deaths in the field are attributed to poor root growth, before the effects of water stress occurs. The spasmodic appearance of Bassia birchii infestations, particularly after droughts, is related to the dependence on the death of mature plants to provide propagules and fruit breakdown for germination. The unpredictable infestation pattern and the early development of spined fruits and basal buds on seedlings hinder control. Short period rotational or strategic grazing are suggested as possible means of control of seedlings in areas where perennial pastures can be established. Resume: La biologie de Bassia birchii (F. Muell.) F. Muell. Bassia birchii, plante ligneuse vivace originaire d'Australie, y apparait comme une mauvaise herbe sur de vastes etendues dans la partie orientale semi-aride du pays. Les conditions de germination et de croissance des plantules ont fait l'objet de recherches et ont ete confrontees aux observations au champ et envisagees pour les moyens possibles de lutte. Les semences ne peuvent germer tant que le fruit ligneux n'a pas ete brise. Des experiences de laboratoire ont montre que les semences pouvaient germer tout au long de l'annee, avec un maximum aux temperatures printanieres et automnales. Les morts de pluntules, au champ, sont attribuables a un developpement insuffisant des racines, avant que les effets de la secheresse ne se manifestent. Le caractere irregulier des infestations de Bassia birchii, en particulier apres les periodes de secheresse est en relation avec la mort des plantes arrivees a maturite et leur faculte de produire des propagules et des fruits ouverts pour la germination. Les modalites imprevisibles d'infestation et le developpement precoce de fruits epineux et de bourgeons a la base des plantules fait obstacle a la lutte contre cette espece. De courtes periodes de paturage par rotation ou selon les necessites de la lutte sont suggerees comme etant des moyens possibles de detruire les plantules dans les regions ou des pâtures permanentes peuvent etre etablies. Zusammenfassung Die Biologie von Bassia birchii (F. Muell.) F. Muell. Der einheimische perennierende Strauch Bassia birchii kommt in grossen Gebieten des semi-ariden Ostaustralien als Unkraut vor. Es wurden die Keimbedingungen und das Samlingswachstum untersucht und mit Feldbeobachtungen sowie moglichen Bekampfungsmassnahmen in Beziehung gebracht. Die Samen konnen nicht keimen, bevor die holzige Frucht nicht zerfallen ist. Laboruntersuchungen ergaben, dass die Samen das ganze Jahr uber keimen konnen. Das Absterben von Keimpflanzen unter Feldbedingungen ist auf des schwache Wurzelwachstum zuruckufuhren und tritt ein, bevor Wassermangel auftritt. Die stark wechselnden Verseuchungen mit Bassia birchii, besonders nach Trockenperioden hangt mit dem Absterben alter Pflanzen zusammen, wodurch Verbreitungsorgange gebildet werden, die Fruchte zerfallen und damit die Voraussetzung fur die Samenkeimung schafft. Dadurch, dass die Verseuchung nicht vorhergesagt werden kann und durch die fruhe Entwicklung stacheliger Fruchte und von Basalknospen an den jungen Pflanzen, wird eine Bekampfung erschwert. In Gebieten mit Dauergrunland wird eine mogliche Bekampfung im abwechselnden oder gezielten Beweiden gesehen.

The theory of electromagnetic flaw detection based on the Lorentz reciprocity theorem has been applied to quantitative modeling of the corrosion buildup problem in PWR steam generators. Formulation of the electromagnetic probe response in spatial Fourier transform domain clarifies the role of the probe as a spatial frequency filter. Examples are given of tailoring the spatial frequency response to achieve specific performance characteristics, such as liftoff noise discrimination and flaw shape characterization. The relationship of spatial frequency response to probe geometry is analyzed for two dimensional inductive and capacitive structures, and the use of signal compression for realizing good spatial resolution and improved signal‐to‐noise ratio in long probes is discussed.

Abstmcr-The objective of the present work was to gain a deeper mensions of the transducer are much smaller than the understanding of the behavior of lead zirconate titanate (PZT) polymer composites for applications such as ultrasonic medical diagnosis in the megahertz frequency range. These composites were originally developed for low-frequency hydrophone applications. The PZT rod-polymer composites have been prepared with five to 30 volume percent PZT using 0.28 mm and 0.45 mm rods. In a disc of PZT rod-polymer composite material, there are three principal types of resonance: the planar mode, the thickness mode, and various lateral modes caused by the regular periodicity of the PZT rod in the composite. These resonance modes have been studied with the following techniques: 1) electrical impedance measurement as a function of frequency and 2) laser probe dilatometry of the dynamic displacement as a function of frequency and position in the composite lattice. The observed resonance behavior is found to be a result of lateral interactions in the composite through the epoxy medium. The effect of temperature on the electromechanical properties of the composite has also been investigated. Implications of these results for optimizing the design of ultrasonic transducers are discussed.

1–3 piezoelectric-rod/passive-matrix composites offer advantages over the conventional piezoceramics and piezopolymers for the pulse-echo transducers used in medical ultrasonic imaging. Their benefits include high electromechanical coupling, acoustic impedance close to that of tissue, a wide range of dielectric constants, low dielectric and mechanical losses, an adjustable sound speed, low coupling to spurious oscillations, ease of subdividing into acoustically isolated array elements, and formability into complex curved shapes. Not all benefits are achieved simultaneously. In designing a material for a specific application, the material engineer can choose the piezoceramic, the passive matrix, their relative proportions and the spatial scale of the composite. We delineate the trade-offs in designing piezocomposites which enhance the performance of present ultrasonic transducers as well as make new transducer designs feasible.

The two basic physical phenomena involved in all piezoelectric devices are wave propagation and resonance. A general review is first presented of the connection between piezoelectricity and crystal symmetry, noting that a recent arrival on the scene (ferroelasticity) is intimately related to crystal symmetry rules for piezoelectricity and promises to be applicable to new devices in the future. Special features peculiar to wave propagation in piezoelectric materials are noted and a brief sketch is given of methods used for solving piezoelectric boundary value problems.

This paper presents a theoretical study of magnetostatic wave propagation as a function of the strength and orientation of an applied magnetic field. The dispersion relation is derived for an isolated ferrimagnetic plate with either cubic or uniaxial magnetic anisotropy. In the crystal symmetry planes where the magnetization is coplanar with the plate normal and the applied field the dispersion relation has a simple analytic form valid for propagation in any direction. The frequency limits for propagation of various modes are readily evaluated from this expression. Selected plots of these frequency bands and the associated dispersion curves are presented to illustrate the effects of field strength and orientation. Particular emphasis is given to applied fields less than the saturation magnetization oriented near the normal to the plate. This case is important for the potential use of magnetostatic waves to detect magnetic bubbles.