Earlier Derivations Research Articles

Gem-Difluorovinyl Derivatives as Insecticides and Acaricides

The insecticidal lead 1,1-difluorododec-1-ene was optimised. This compound has attractive insecticidal activity against tobacco budworm (Heliothis virescens), banded cucumber beetle (Diabrotica balteata), pea aphid (Aphis cracciovora), brown planthopper (Nilaparvata lugens), and green rice leafhopper (Nephotettix cincticeps). Among different pharmacophore analogues, only 1,1-dichlorododec-1-ene and 1,1-difluoro-2-iodododec-1-ene showed weak insecticidal activity, whereas similar compounds such as 1-chloro-1-fluorododec-1-ene, 1-fluorododec-1-ene, and 1,1-difluoro-2-bromododec-1-ene were inactive. Only bridge analogues with even-numbered carbon chains were active, for example 1,1-difluorodec-1-ene and 1,1-difluorotetradec-1-ene. Odd-numbered analogues such as 1,1-difluoronon-1-ene, 1,1-difluoroundec-1-ene, 1,1-difluorotridec-1-ene, and 1,1-difluoro-pentadec-1-ene showed no activity. Modification of the tail group led to the analogues 12,12-difluorododec-11-enoic acid and its methyl ester, 12,12-difluorododec-11-en-1-ol, 1,1-difluoro-12-methoxydodec-1-ene, and 12,12-difluorododec-11-enylamine, all of which showed insecticidal activity. 12,12-difluorododec-11-enoic acid methyl ester, 12,12-difluorododec-11-enoic acid, and 12,12-difluorododec-11-en-1-ol were also active against spider mites (Tetranychus ssp). Thus, in a first optimisation cycle, broad activity against insect pests and mites was discovered. Two requirements, the gem-difluorovinyl pharmacophore and an even-numbered carbon chain, were found to be essential for activity. This latter requirement is in line with the proposed mode of action, which involves inhibition of the ? -oxidation of fatty acids in insect mitochondria. In a second optimisation cycle, it was found that 6,6-difluorohex-5-enoic acid and its derivatives, such as acids, amides, and hydrazides, possess even superior properties as insecticides and acaricides. This led to the discovery of 6,6-difluorohex-5-enoic acid 2-[4-(4-trifluoromethylbenzyloxy)-phenoxy]-ethyl ester (CGA 304'111). This compound showed excellent performance in field trials against a wide range of pests, as well as a more favourable toxicological profile than earlier derivatives. For a largescale synthesis of CGA 304'111, five different synthetic routes for 6,6-difluorohex-5-enoic acid were developed. The best route involved radical addition of CBrClF2 to pent-4-enoic acid. Removal of bromine by hydrogenation, elimination of chloride and hydrolysis of the ester concluded this most efficient sequence. Thus, a practical synthesis for CGA 304'111 was identified, which allowed the preparation of samples on a several 100 g scale.

Quantum limits on noise in dual input-output linear optical amplifiers and attenuators

The input-output relations for linear amplifiers and attenuators that have two input and two output channels are used to derive inequalities that relate their gain profiles and output noise spectra. The results generalize earlier derivations, which mainly focus their attention on single-channel devices, to the two-ended amplifiers and attenuators often used in practical communications systems. The present inequalities are satisfied by the results of previous calculations for specific model systems. It is shown that; in contrast to single-channel devices, a two-ended system can act as an amplifier for some input signals and an attenuator for others, even when all the signal frequencies are the same. The output from the two-channel amplifier has a minimum noise determined by the sum of the gains for both input channels, even when only one input channel is used and the other is in its vacuum state. The conditions on device construction needed to achieve equal gains for signals that arrive at the two ends of the device are determined. The present results reduce to those of single-channel theory in special cases where the two output channels are each separately fed by only one of the two input channels.

Bayesian analysis of neutrinos observed from supernova SN 1987A

We present a Bayesian analysis of the energies and arrival times of the neutrinos from supernova SN 1987A detected by the Kamiokande II, IMB, and Baksan detectors, and find strong evidence for two components in the neutrino signal: a long time scale component from thermal Kelvin-Helmholtz cooling of the nascent neutron star, and a brief $(\ensuremath{\sim}1 \mathrm{s}),$ softer component similar to that expected from emission by accreting material in the delayed supernova scenario. In the context of this model, we show that the data constrain the electron antineutrino rest mass to be less than 5.7 eV with 95% probability. Our analysis takes advantage of significant advances that have occurred in the years since the detections in both our understanding of the supernova mechanism and our ability to analyze sparse data. This has led to significant improvement over previous studies in two important respects. First, our comparison of the data with parametrized models of the neutrino emission uses a consistent and straightforward Bayesian statistical methodology. This methodology helps us distinguish the complementary tasks of parameter estimation and model assessment, and fully accounts for the strong, nonlinear correlations between inferred values of neutrino emission model parameters. It also clarifies and improves the derivation of the likelihood function (the probability for the data), improving on earlier derivations in two ways: more consistent accounting for the energy-dependent efficiencies of the detectors; and inclusion of the empirically measured detector background spectra. These improvements lead to significant differences between our inferences and those found in earlier studies. Inclusion of detector background spectra proves crucial for proper analysis of the Baksan data and for demonstrating its consistency with data from other detectors. Second, we compare the data with a much wider variety of neutrino emission models than was explored previously, several of them inspired by recent numerical calculations of collapse and explosion based on the delayed supernova mechanism. This allows us to compare predictions of both the prompt and delayed mechanisms with the data, and ensures that our conclusions are robust. We find that two-component models for the neutrino signal are $\ensuremath{\sim}100$ times more probable than single-component models. Moreover, single-component models imply a radius and binding energy for the nascent neutron star significantly larger than those implied by even the stiffest acceptable equations of state for neutron star matter. In contrast, the radius and binding energy implied by two-component models are in agreement with predictions. Taking this agreement with prior expectations into account increases the odds in favor of two-component models by more than an order of magnitude. The inferred characteristics of the neutrino emission are in spectacular agreement with the salient features of the theory of stellar collapse and neutron star formation that had developed over several decades in the absence of direct observational data. We compare our work with previous work that used more conventional ``frequentist'' methods (including our own previous maximum likelihood analysis). We identify several methodological and technical weaknesses in earlier analyses, and show how these are overcome in our Bayesian analysis.

Quasi-static analysis of floating-electrode unidirectional SAW transducers.

The quasi-static theory of SAW transducers is a simplified Green's function analysis that has previously been shown to be effective for transducers in which short-circuit reflections are negligible. Here, the theory is extended to allow for floating electrodes, which occur in floating-electrode unidirectional transducers (FEUDTs). An analysis for the coupled-mode (COM) parameters of FEUDTs is developed, giving the capacitance, transduction, and reflection parameters and the locations of the transduction and reflection centers. For a FEUDT with six electrodes per period, algebraic results are obtained in terms of Legendre function expressions, giving the COM parameters as functions of metalization ratio. These results agree with earlier derivations by other authors, but they are obtained much more simply. Numerical results are straightforward to obtain. A FEUDT with five electrodes per period is also analyzed, showing that it performs similarly to the six-electrode type.

Volume Change of Seismic Sources from Moment Tensors

In this note, the estimation of the volume change in the focal region of a seismic event from the isotropic part of the moment tensor is discussed. The moment tensor of a spherically symmetric source (explosion or implosion), as given in an earlier derivation, is supported with new arguments. The moment tensor of an explosion currently in use in studies of non-double-couple earthquakes is not confirmed. It turns out, however, that this moment tensor agrees with the isotropic part of the moment tensor of an arbitrarily shaped crack with tensile dislocation components, which is another realistic model of a source with volume change. If the moment M , representing the isotropic part of an observed moment tensor, is converted into a volume change with the model of a crack, Δ V cr = M /(λ + 2μ/3) is obtained (λ,μ = Lame parameters). The explosion or implosion model gives the spherical volume Δ V sph = M /(λ + λ2μ), a significantly lower value. It is argued that the two values, which correspond to very different geometrical forms of a volume change (flat 2D versus compact 3D), approximately mark the range of possible volume changes of a seismic event. Earthquakes in volcanic and geothermal areas with significant isotropic moment-tensor parts should be interpreted by giving these limits until their source processes are better understood. Manuscript received 12 October 2000.

Generalizing from single target search to multiple target search

This study was conducted to generalize from models of human performance in single target search to multiple target search. The specific issue was exhaustive search for the complete set of targets on a search field, extending the work of Chan and Chan from a two-target exhaustive search. Mathematical modelling was based on earlier derivations of search for the first of a set of targets. Model and simulation results showed three quite different relationships between mean search time and the number of targets remaining in a search field. The human search strategy for multiple targets was close to the systematic strategy for the first few targets and was close to the random strategy for the last few targets. Plotting mean search time for multiple targets against the number of targets remaining would be a useful and unique way to show human use of systematic search strategy.

Airway area by acoustic reflection: a corrected derivation for the two-microphone method.

A corrected derivation is provided for the relationship between the impulse response of a wave tube termination and pressure signals measured at two different locations within the tube. This derivation yields exactly the same final result as was reported previously by Louis et al. (1993), despite the omission of the active source term in that earlier derivation. This technique has become the basis of an important medical diagnostic technology. This report revises and corrects the earlier theory upon which that technology rests.

An assessment of the capabilities and limitations of radars in measurements of upper atmosphere turbulence

The basic procedures used to determine atmospheric turbulence intensities from measurements made with atmospheric radars are outlined. The method which utilizes the spectral width of the signal is especially discussed, and missing assumptions which have not been fully considered in earlier derivations are considered in more detail. It is shown that previous relations linking spectral widths and turbulent energy dissipation rates will need modifications and these modifications reduce previous radar estimates of energy dissipation rates by up to a factor of 2 or 3.

Optical approaches to the determination of composition of semiconductor alloys during epitaxy

Realization of sample-driven closed-loop feedback control of the epitaxial growth of semiconductor alloys requires that the fluctuations of the composition of the most recently deposited material be determined over an outermost region that is ideally no more than several angstroms thick. This information is encoded in the dielectric function /spl epsiv///sub 0/ of the region. The standard approach for obtaining /spl epsiv//sub 0/ is to mathematically subdivide the sample into thin layers and analyze them sequentially outward from the substrate by solving the Fresnel equations. However, the feed-forward nature of this approach leads to instabilities if thicknesses are reduced below a few tens of angstroms, a value too large for practical control applications. Derivative methods avoid these instabilities by allowing /spl epsiv//sub 0/ to be determined for dynamic processes involving deposition or etching even if nothing is known about the underlying sample structure. The limited accuracy of earlier derivative approaches based on the exponential-spiral form of interference expressions for optically thick films has been improved to acceptable levels with the recently developed virtual-interface (V-I) approach. Here, a background of the field is provided, the various methods of obtaining /spl epsiv//sub 0/ from the perspective of control applications are discussed, and V-I theory is used to obtain analytic expressions describing the accuracy of the earlier derivative methods. For ellipsometric measurements the best combination of speed and accuracy is obtained with the virtual-substrate approximation. For situations where higher accuracy is needed, a hybrid V-I-Fresnel method is proposed that retains the stability of derivative approaches yet is exact.

A kinetic model for Brownian motion

The Fokker-Planck equation for the distribution function of a Brownian sphere is derived from the exact hierarchy of kinetic equations for a massive sphere in a bath of smaller spheres, using a multiple-time-scale analysis. Our earlier derivation is specialized to the limiting cases where the bath is either an ideal or Boltzmann gas. The resulting simplifications allow more physical insight, and lead to explicit expressions for the friction coefficient.

Bonn potential and sd-shell nuclei.

Using a G-matrix folded diagram method and the Bonn nucleon-nucleon potential, the s-d shell effective interaction is derived and applied to evaluate the spectra of some light sd-shell nuclei. Due to the relatively weak tensor-force characteristic for the Bonn potential, the effective interaction matrix elements, particularly those with isospin T=0, come out generally more attractive than in earlier derivations in which local, strong tensor-force potentials were used. As a consequence of this, our results for the effective interaction and the spectra are in considerably better agreement with empirical determinations and experimental data. The sensitivity of the above nuclear structure calculations to the strength of the nuclear tensor force is demonstrated systematically and the dependence of the s-d shell matrix elements on the nuclear mass number is studied.

Wave motion in a viscous fluid of variable depth Part 2. Moving contact line

An earlier derivation (Miles 1990a) of the partial differential equation for the complex amplitude of a gravity–capillary wave in a shallow, viscous liquid of variable depth and fixed contact line is extended to accommodate a meniscus with a moving contact line at which the slope of the meniscus is assumed to be proportional to (but not necessarily in phase with) the velocity. The motion of the contact line implies capillary dissipation, which is absent for a fixed contact line. The results are applied to the normal reflection of a wave incident from a region of uniform depth on a beach of uniform slope. The reflection coefficient has the form R = R1RνRc, where R1 is the coefficient for an ideal fluid, and Rν and Rc comprise the respective effects of viscosity and capillarity.

Off-shell form factors and low energy theorems for pion photoproduction.

The derivation of the low energy theorem for threshold photoproduction of neutral pions on a nucleon is reconsidered. Instead of considering explicitly the Born terms, as done in earlier derivations, a more general class of diagrams is separated from the total amplitude. Gauge invariance is imposed on the operator level and the partial conservation of the axial-vector current constraint is incorporated. Besides recovering the older results in this approach, relations for the off-shell behavior of the strong and electromagnetic vertices are derived.

Transient state of a bunched electron beam subject to resistive-wall instability.

This paper analyzes the transient state of a bunched electron beam traversing a narrow beam pipe under the influence of transverse resistive-wall effects. Because the electron beam in the wigglers of future free-electron lasers (FEL's) is required to travel in pipes with small diameters, this study is relevant in determining the beam stability in these FEL's. The analysis is restricted to the case in which the first mode dominates. First, an integral representation of the single-mode solution is obtained. Second, the transient-state solution is obtained for the case in which the focusing force dominates the resistive-wall force. The maximum transient amplitude is derived for the case in which a single bunch is off-axis. Third, this result is used to compute the maximum transient amplitudes when the bunches enter the system with random and with equal initial displacements, respectively. These analytic expressions of maximum transient amplitudes are useful in predicting when the transient could become significant. They are compared with earlier derivations and with numerical simulations. These expressions are also applied to various proposed FEL's. Results showed that the transverse resistive-wall instability could not pose a problem in the operation of these FEL's.

Relativistic dynamics of charges in external fields: the Pauli algebra approach

The Pauli algebra is used to study the relativistic motion of charged particles in external electromagnetic fields. Plane-wave solutions to Maxwell's equations, in particular standing waves with electric and magnetic fields which are everywhere parallel, are easily represented and analysed in a gauge-independent treatment. The authors derive the 4-momentum of electromagnetic fields and show how the integrals for fields of a charged particle can be evaluated with integration limits specified in the rest frame of the moving charge. The general solution of the Lorentz force equation is shown to be a Lorentz transformation with time-dependent rotation and boost parameters which, in the case of parallel fields, are trivially related to the magnetic and electric fields, respectively. With the Pauli algebra, an earlier derivation in the Dirac algebra of the 4-velocity in constant uniform fields is greatly simplified and extended to arbitrary initial motion, and solutions are found to motion in a Coulomb fields and in the presence of arbitrarily polarised (monochromatic, directed) plane waves.

The linear stress triangular equilibrium model in plane elasticity

Advantage is taken of oblique coordinates to give a revised theory of the triangular equilibrium finite element model with linearly varying stresses for problems in plane linear elasticity. This new formulation has considerably improved computational efficiency over earlier derivations because equilibrium of the stresses within the element is enforced explicitly without recourse to the more expensive numerical methods used previously. The equilibrium model provides upper bounds to the elastic strain energy of a body under applied loading; it is the dual of a triangular finite element model with linear strains obtained from compatible quadratic displacements which provides corresponding lower bounds.

Non-linear heat conduction in dense fluids

In a dense fluid with very large heat flow J. the thermal conductivity lambda = lambda 0+ lambda 2J2. An estimate of lambda 2/ lambda 0 is made for hard spheres with mass and diameter appropriate to Ar and density just below the gas-solid transition. This estimate indicates that Fourier's law will hold in the form appropriate to low J if J<or approximately=109 W m-2 and that the J dependence of pressure and internal energy is of the same order as that of lambda . The calculation utilises an earlier derivation from the classical Liouville equation which expresses lambda at high density in terms of the thermodynamic pressure. The latter can be calculated with the aid of reciprocity and integrability conditions of extended non-equilibrium thermodynamics which treats J as a state variable.

Effect of light attenuation on the responsivity and detectivity of transverse and longitudinal detectors

It is shown that when account is taken of the attenuation of incident radiation into the bulk of a photoconductor, as a result of the absorption, the expressions for the responsivity and detectivity are modified. An earlier derivation [Infrared Phys. 20, 385 (1980)] attributed the difference in the operation of the detectors in the transverse and longitudinal geometries to carefully defined ‘‘effective’’ quantum efficiencies. Here we show that a more physically motivated view attributes the difference to the different photoconductive gains for the two geometries. It is shown that the appropriate gains for the responsivity and detectivity are not the same.

Critical dimensions of parastrings

A new and improved method is given for constructing parastring theories, in which their symmetries are manifest. Their critical dimensions are obtained without making one of the crucial assumptions which led to their earlier derivation. Various implications such as the analytic behavior of the one-loop amplitudes are pointed out.

Response function analysis of time-dependent diffusional defect processes

The loss rate of defects to cavities in a material subject to spatially uniform but arbitrarily time-dependent irradiation is re-derived by means of Response Function theory. The result coincides with that of our earlier derivation.