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Naringenin is a natural product with several reported bioactivities and is the key intermediate for the entire class of plant flavonoids. The translation of flavonoids into modern medicine as pure compounds is often hampered by their low abundance in nature and their difficult chemical synthesis. Here, we investigated the possibility to use the filamentous fungus Penicillium rubensas a host for flavonoid production. P. rubensis a well-characterized, highly engineered, traditional “workhorse” for the production of β-lactam antibiotics. We integrated two plant genes encoding enzymes in the naringenin biosynthesis pathway into the genome of the secondary metabolite-deficient P. rubens4xKO strain. After optimization of the fermentation conditions, we obtained an excellent molar yield of naringenin from fed p-coumaric acid (88%) with a titer of 0.88 mM. Along with product accumulation over 36 h, however, we also observed rapid degradation of naringenin. Based on high-resolution mass spectrometry analysis, we propose a naringenin degradation pathway in P. rubens4xKO, which is distinct from other flavonoid-converting pathways reported in fungi. Our work demonstrates that P. rubensis a promising host for recombinant flavonoid production, and it represents an interesting starting point for further investigation into the utilization of plant biomass by filamentous fungi.

Selection of a single bacterial strain out of a mixture of microorganisms is of crucial importance in healthcare and microbiology research. Novel approaches that can externally control bacterial selection are a valuable addition to the microbiology toolbox. In this proof-of-concept, two complementary antibiotics are protected with photocleavable groups that can be orthogonally addressed with different wavelengths of light. This allows for the light-triggered selection of a single bacterial strain out of a mixture of multiple strains, by choosing the right wavelength. Further improvement toward additional orthogonally addressable antibiotics might ultimately lead to a novel methodology for bacterial selection in complex populations.

Screening of transport processes across biological membranes is hindered by the challenge to establish fragile supported lipid bilayers and the difficulty to determine at which side of the membrane reactants reside. Here, we present a method for the generation of suspended lipid bilayers with physiological relevant lipid compositions on microstructured Si/SiO2chips that allow for high-throughput screening of both membrane transport and viral membrane fusion. Simultaneous observation of hundreds of single-membrane channels yields statistical information revealing population heterogeneities of the pore assembly and conductance of the bacterial toxin α-hemolysin (αHL). The influence of lipid composition and ionic strength on αHL pore formation was investigated at the single-channel level, resolving features of the pore-assembly pathway. Pore formation is inhibited by a specific antibody, demonstrating the applicability of the platform for drug screening of bacterial toxins and cell-penetrating agents. Furthermore, fusion of H3N2 influenza viruses with suspended lipid bilayers can be observed directly using a specialized chip architecture. The presented micropore arrays are compatible with fluorescence readout from below using an air objective, thus allowing high-throughput screening of membrane transport in multiwell formats in analogy to plate readers.

Please close the pore!An organochemical photoswitch was introduced into two transmembrane segments that comprise the lateral gate of the bacterial‐membrane‐embedded protein‐conducting pore. Reversible switching of the azobenzene between the transand cisconfigurations by irradiation with visible and UV light enforced the opening and closure of the protein‐conducting pore (see scheme).

We investigate the generation of discrete spatial solitons in arrays of coupled waveguides. Light was launched into the center of the array, and different beam sizes and array geometries were tested. At low power, the propagating field spreads as it couples to more waveguides. When the intensity is increased, localization is observed around the input waveguides, leading to the formation of a discrete soliton. For wide input beams, exciting a few waveguides, soliton splitting, which is due to instability induced by multiphoton absorption, is observed. All of these effects are described well by a coupled-mode formalism.

Protein secretion in Escherichia coli is mediated by translocase, a multi-subunit membrane protein complex with SecA as ATP-driven motor protein and the SecYEG complex as translocation pore. A fluorescent assay was developed to facilitate kinetic studies of protein translocation. Single cysteine mutants of proOmpA were site-specific labeled with fluorescent dyes, and the SecA and ATP-dependent translocation into inner membrane vesicles and SecYEG proteoliposomes was monitored by means of protease accessibility and in gel fluorescent imaging. The translocation of fluorescently labeled proOmpA was largely independent on the position and the size of the fluorescent label (up to a size of 13-16 A). A fluorophore at the +4 position blocked translocation, but inhibition was completely relieved in the PrlA4 mutant. The kinetics of translocation of the fluorescently labeled proOmpA could be directly monitored by means of fluorescence quenching. Inner membrane vesicles containing wild-type SecYEG were found to translocate proOmpA with a turnover of 4.5 molecules proOmpA/SecYEG complex/min and an apparent K(m) of 180 nm, whereas the PrlA4 mutant showed an almost 10-fold increase in turnover rate and a 3-fold increase of the apparent K(m) for proOmpA translocation.

ABSTRACTEnterocin P is a bacteriocin produced by Enterococcus faeciumP13. We studied the mechanism of its bactericidal action using enterocin-P-sensitive E. faeciumT136 cells. The bacteriocin is incapable of dissipating the transmembrane pH gradient. On the other hand, depending on the buffer used, enterocin P dissipates the transmembrane potential. Enterocin P efficiently elicits efflux of potassium ions, but not of intracellularly accumulated anions like phosphate and glutamate. Taken together, these data demonstrate that enterocin P forms specific, potassium ion-conducting pores in the cytoplasmic membrane of target cells.

The contribution to polarization dynamics from a combination of linear birefringence, anisotropic nonlinear refraction, and a longitudinal magneto-optic effect is discussed. A Hamiltonian formalism is developed using Stokes parameters. It is found that by periodic reversal of the magnetic field, avenues are opened up to exploit Faraday rotation, for example, as an optical isolator, and polarization switching in an integrated optical environment. A practical implementation is discussed that uses semiconductors and a shaped-surface conductor.

CsaA from the Gram-positive bacterium Bacillus subtilis has been identified previously as a suppressor of the growth and protein-export defect of Escherichia coli secA(Ts) mutants. CsaA has chaperone-like activities in vivo and in vitro. To examine the role of CsaA in protein export in B. subtilis, expression of the csaA gene was repressed. While export of most proteins remained unaffected, export of at least two proteins was significantly reduced upon CsaA depletion. CsaA co-immunoprecipitates and co-purifies with the SecA proteins of E. coli and B. subtilis, and binds the B. subtilis preprotein prePhoB. Purified CsaA stimulates the translocation of prePhoB into E. coli membrane vesicles bearing the B. subtilis translocase, whereas it interferes with the SecB-mediated translocation of proOmpA into membrane vesicles of E. coli. The specific interaction with the SecA translocation ATPase and preproteins suggests that CsaA acts as a chaperone that promotes the export of a subset of preproteins in B. subtilis.

The propagation of solitons in low-birefringent optical fiber is considered when four-wave-mixing leads to energy exchange between polarization components. The stability of stationary solutions is addressed with a linear stability analysis expressed as an eigenvalue equation. It is shown that in the vicinity of the bifurcation point the eigenvalues must be either pure real (stable) or pure imaginary (unstable). The transition between these (zero eigenvalue) lends itself to analytical solutions, in spite of the nonintegrability of the original system of partial differential equations. It is demonstrated that the marginally stable perturbations of phase shift and temporal shift also apply to mixed-mode stationary solutions. The bifurcation point is found exactly along with the corresponding eigenfunction. This analysis provides the elliptically polarized stationary solution just above the bifurcation point. It is also shown that the fast-mode soliton just below the bifurcation point and the elliptically polarized soliton just above the bifurcation point are stable.

A description of the second-order nonlinear optical susceptibility of semiconductor materials is considered. The Lie algebra su(3) arises from a 3-level quantum model for each state in the Brillouin zone, which is obtained by truncation of the true infinite-dimensional basis. The accuracy of several approximations inherent in this approach is analysed, in particular the electric dipole and minimal replacement Hamiltonians which specify the electrodynainical interaction in a finite-dimensional quantum system. The three-level model is extended by adding relaxation processes and utilising the rotating wave approximation to account for resonant nonlinear effects. Analytical forms for the transition rates associated with two-photon absorption and electromagnetically induced transparency are derived.

All chordates share several characteristic features including a dorsal hollow neural tube, a notochord, a pharynx and an endostyle. Unlike other chordate taxa, ascidians have a biphasic life-history with two distinct body plans. During metamorphosis, the larval nerve cord and notochord degenerate and the pharyngeal gill slits and endostyle form. While ascidians, like other marine invertebrates, metamorphose in response to specific environmental cues, it remains unclear how these cues trigger metamorphosis. We have identified a novel gene (Hemps) which encodes a protein with a putative secretion signal sequence and four epidermal growth factor (EGF)-like repeats which is a key regulator of metamorphosis in the ascidian Herdmania curvata. Expression of Hemps increases markedly when the swimming tadpole larva becomes competent to undergo metamorphosis and then during the first 24 hours of metamorphosis. The Hemps protein is localised to the larval papillae and anterior epidermis of the larva in the region known to be required for metamorphosis. When the larva contacts an inductive cue the protein is released, spreading posteriorly and into the tunic as metamorphosis progresses. Metamorphosis is blocked by incubating larvae in anti-Hemps antibodies prior to the addition of the cue. Addition of recombinant Hemps protein to competent larvae induces metamorphosis in a concentration-dependent manner. A subgroup of genes are specifically induced during this process. These results demonstrate that the Hemps protein is a key regulator of ascidian metamorphosis and is distinct from previously described inducers of this process in terrestrial arthropods and aquatic vertebrates.

Clusterin was first characterized as an apoptosis-associated transcript after it was identified as testosterone-repressed prostate message (TRPM-2) that is expressed in the epithelial cells of the regressing rat ventral prostate. Increases in clusterin mRNA and protein have been consistently detected in apoptotic cell death paradigms, establishing clusterin gene expression as a prominent marker of apoptotic cell loss. However, enhanced protein expression has also been reported in surviving cells. This ambiguity makes it difficult to define the contribution of clusterin to apoptosis. To address this problem, a panel of polyclonal and monoclonal antibodies were raised against the clusterin alpha-chain, beta-chain, and mixed alpha/beta epitopes. These antibodies detect changes in the biogenesis of clusterin during apoptosis by Western analysis and immunohistochemistry. A 42-kDa glyco/isoform of clusterin appears to be up-regulated in dying epithelial cells. This glyco/isoform is apparently generated as a result of apoptosis-induced stimulation of a normal but under-utilized, synthetic pathway. These data demonstrate that clusterin synthesized by apoptotic cells can be immunologically distinguished from clusterin synthesized by surviving cells in damaged tissue.

Considerable work has been reported on the influence of fertilizer elements, particularly potassium, on yields and lodging of corn (Zea maysL.). Additional information is needed on the influence of other nutrients and different genotypes on stalk quality characteristics and yield. This paper reports the influence of four levels of nitrogen, phosphorus, and potassium on the percent of senescent stalks, crushing strength, rind thickness, stalk lodging, and yield of the six F1hybrids of a four‐parent diallel of inbreds T101, T105, Till, and T115. The data were obtained using three independent experiments; one associated with each fertility element for 3 years. Nitrogen and phosphorus had little or no influence on stalk characteristics. Potassium additions reduced the percent of senescent stalks and stalk lodging and increased crushing strength and rind thickness. The influence of potassium on senescent stalks was dependent on the hybrid involved. Yield increased with additions of nitrogen and potassium, but phosphorus had little influence.

The high-frequency behavior of wave fields in free space is characterized by localization in phase space, exemplified by the description of geometrical optics in which distinct wave vectors are associated with the rays passing through each spatial point. I explore the manifestation of phase-space localization in discrete representations of the wave field, in particular the discrete Fourier transform (DFT) and the Gabor representation. A number of auxiliary concepts, such as spectral truncation, the Lagrange manifold, and the Landau–Pollak (LP) theorem, are described and exploited in the process of understanding the behavior of high-frequency fields, and it is shown that the Lagrange manifold is the source in phase space of the dominant contributions to these discrete representations in a number of specially selected examples. The LP theorem specifies the number of discrete degrees of freedom required for a given field to be approximated to a prescribed accuracy, and the theorem controls both the number of samples for DFT implementation and the number of Gabor coefficients required. The behavior of the Gabor coefficients away from the Lagrange manifold is studied for a Fresnel wave (quadratic phase variation on a line), and it is shown that these coefficients decay exponentially, signifying the localization of the Gabor representation. The number of operations required for computing the Gabor representation is compared with the fast-Fourier-transform (FFT) implementation of the DFT, with the LP dimension used as the common cardinality of the two representations, the result being that the FFT is asymptotically more efficient than the Gabor representation even after one allows for the localization of the latter. However, the Gabor representation can be used in circumstances in which the FFT is inapplicable, when the explicit localization is a significant advantage.

The use of graded-index fibers for optical communication systems is now under consideration for numerous civil and military applications, and in these either LED or laser sources can be developed. The bandwidth of the system depends on the source linewidth, the dispersion of refractive index in the fiber, the strength of excitation of the modes by the source, and the extent of mode mixing caused, by example, by microbending. In fibers with refractive-index profiles that have a nearly parabolic dependence upon radius, pulse broadening is a slight, but small departures from an optimum profile can cause a dramatic decrease in bandwidth. It is of considerable importance to predict the bandwidth of fibers from a knowledge of the refractive-index profile and source geometry. The purpose of the first part of this paper is to compare two computational methods by which the propagation characteristics of a fiber, hence the impulse response and system bandwidth, may be determined. In the second part, we shall describe a computer program that determines the excitation of modes in an arbitrarily graded refractive index fiber for a model of laser source.

Uniform spectral asymptotic descriptions of the scattered fields from general curved surfaces are discussed. Attention is then drawn to scattered fields from surfaces with positive Gaussian curvature, which encompasses the majority of practical reflector geometries. These specific surfaces are modeled by asymptotically approximating the physical optics solution in the spectral domain. A uniform edge correction using the geometrical theory of diffraction is systematically included in the spectral domain, with recovery of the spatial domain field by fast Fourier transform.

SecY is a central component of the export machinery that mediates the translocation of secretory proteins across the plasma membrane of Escherichia coli. We have cloned and sequenced the secY genes from Bacillus licheniformis and Staphylococcus carnosus. The deduced amino acid sequences are highly homologous to those of other known SecY polypeptides, all having the potential to form 10 transmembrane segments. Comparative analysis of 9 SecY polypeptides, derived from different bacteria, revealed that 14 amino acid positions (2,7%) are identical in all SecY proteins and 89 (16.9%) show conservative changes. Clusters of conserved amino acid residues were found in 4 of the 10 transmembrane segments and 2 of the 6 cytoplasmic domains. It is suggested that the conserved regions might be involved in the translocation activity of SecY or might be required for the correct interaction of SecY with other components of the secretion apparatus.

A class of linear and nonlinear dynamical problems that arise when studying the modulation of trains of nearly identical soliton pulses of the nonlinear Schrödinger equation is introduced. In the simplest case the dynamics of the nonlinear Schrödinger equation can be reduced to an equation that is a complex extension of the integrable Toda lattice equation, so that the latter asymptotically models the former in the case of large intersoliton separations.

Abstract: Picrophilus oshimae is an extremely acidophilic, thermophilic archaeon that grows optimally at 60°C and at pH 0.7. It is an obligatory acidophile that does not grow at pH values above 4.0. The proton motive force in respiring cells is composed of a large transmembrane pH gradient, inside less acid, and a reversed transmembrane electrical potential, inside positive. Cells maintain an intracellular pH at around 4.6 at extracellular pH values ranging from 0.8 to 4.0. Above pH 4.0 cells lyse rapidly and lose their viability. Liposomes prepared from lipids derived from P. oshimae have an extremely low proton permeability at acidic pH. However, at neutral pH, the lipids are unable to assemble into regular liposomal structures. These observations suggest that the loss of viability and cell integrity above pH 4.0 is due to an impairment of the barrier function of the cytoplasmic membrane.

Abstract:  We have studied gene expression during ascidian embryonic development using the technique of differential display and isolated partial cDNA sequences of 12 genes. Developmental regulation of these genes has been confirmed by northern hybridization analysis. Further cDNA cloning and sequence analysis of an mRNA that is present during gastrulation, neurulation and tailbud formation reveals that it encodes a novel serine protease containing a single kringle motif and catalytic domain. The spatial expression of this gene, designated Hmserp1, is restricted to precursor cells of the epidermis. The structure and expression of Hmserp1 is discussed in relation to possible functions during development.

Abstract: In extreme environments, mainly Archaea are encountered. The archaeal cytoplasmic membrane contains unique ether lipids that cannot easily be degraded, are temperature- and mechanically resistant, and highly salt tolerant. Moreover, thermophilic and extreme acidophilic Archaea possess membrane-spanning tetraether lipids that form a rigid monolayer membrane which is nearly impermeable to ions and protons. These properties make the archaeal lipid membranes more suitable for life and survival in extreme environments than the ester-type bilayer lipids of Bacteria or Eukarya.

Six normal endosperm maize (Zea maysL.) hybrids and their opaque‐2 counterparts were compared for kernel weight, volume, density, and number on six dates at 7‐day intervals beginning 28 days after pollination. Whole kernel concentration and content of P, K, Mg, Fe, Zn, protein, and oil were also determined. At 56 days after pollination, kernel weight, volume, and density of the opaque‐2 hybrids were 16.7, 6.9, and 10.2% less, respectively, than for the normal hybrids. Kernel weight was only slightly greater for the normal kernels at 28 and 35 days after pollination, but the difference between the endosperm types increased after the 35‐day harvest. Kernel volume was similar at 28, 35, 42, and 49 days but greater for the normal endosperm kernels at 56 and 63 days. Density of the normal endosperm kernels was higher at all harvest dates with the difference between endosperm types being similar at all dates. At 56 days after pollination, the opaque‐2 kernels were significantly greater in P, K, Mg, Fe, Zn, and oil concentration. When amounts of kernel constituents were expressed on a unit weight per 200 kernels basis, the normal kernels were higher than or similar to opaque‐2 kernels for all constituents except K, which was higher in the opaque‐2 kernels. The opaque‐2 kernels were higher in concentrations of all elements at all harvest dates and were higher in content of K per 200 kernels at all harvest dates.

The interrelationships among whole kernel protein, lysine, oil, P, K, Mg, Fe, and Zn concentrations and physical kernel characteristics were determined in a heterozygous opaque‐2 population and a homozygous opaque‐2 maize (Zea maysL.) population. Compared to normal kernels the opaque‐2 kernels were higher in lysine, P, K, Mg, Fe, and Zn concentrations. However, on a kernel weight or kernel volume basis, the opaque‐2 kernels were significantly greater only for lysine, K, and Zn. Our results indicated that the opaque‐2 gene, or closely linked genes, had a direct influence on K and Zn content as well as on lysine content. The correlation of the differences between the normal and opaque‐2 kernels for percent lysine and percent Zn was positive and significant. This relationship may indicate that modifier genes that are influencing the effect of the opaque‐2 gene on lysine concentration may also be influencing the effect of the opaque‐2 gene on Zn concentration in a similar manner. Several significant correlations were detected between percent lysine and the mineral element concentrations, but none were of sufficient magnitude to be of value as a selection criteria for lysine content. Percent lysine was not correlated with kernel weight or volume but was negatively correlated with kernel density. The coefficients for the correlation between percent lysine and percent protein were +0.50 and +0.70, respectively, for the normal and opaque‐2 kernels in the heterozygous population and +0.83 for the homozygous opaque‐2 population. The magnitude of these correlation coefficients indicated a rather strong tendency for lysine concentration to increase as protein concentration increased, especially in the opaque‐2 kernels. Protein concentration was found to be the best selection criteria for lysine concentration except for possibly the lysine concentration per se.

Lactococci are fastidious bacteria which require an external source of amino acids and many other nutrients. These compounds have to pass the membrane. However, detailed analysis of transport processes in membrane vesicles has been hampered by the lack of a suitable protonmotive force (pmf)-generating system in these model systems. A membrane-fusion procedure has been developed by which pmf-generating systems can be functionally incorporated into the bacterial membrane. This improved model system has been used to analyze the properties of amino acid transport systems in lactococci. Detailed studies have been made of the specificity and kinetics of amino acid transport and also of the interaction of the transport systems with their lipid environment. The properties of a pmf-independent, arginine-catabolism specific transport system in lactococci will be discussed.

Bacterial growth at the extremes of temperature has remained a fascinating aspect in the study of membrane function and structure. The stability of the integral membrane proteins of thermophiles make them particularly amenable to study. Respiratory enzymes of thermophiles appear to be functionally similar to the mesophilic enzymes but differ in their thermostability and unusual high turnover rates. Energy coupling at extreme temperatures seems inefficient as suggested by the high maintenance coefficients and the high permeability of the cell membrane to protons. Nevertheless, membranes maintain their structure at these extremes through changes in fatty acid acyl chain composition. Archaebacteria synthesize novel membrane-spanning lipids with unique physical characteristics. Thermophiles have adapted to life at extreme temperatures by using sodium ions rather than protons as coupling ions in solute transport. Genetic and biochemical studies of these systems now reveal fundamental principles of such adaptations. The recent development of reconstitution techniques using membrane-spanning lipids allows a rigorous biochemical characterization of membrane proteins of extreme thermophiles in their natural environment.

A controlled study of acute pharmacological intervention was designed to determine whether decreased sympathetic nerve activity in tetraplegic patients results in increased responsiveness of a-adrenoceptors which might contribute to vascular hyperreactivity and the clinical scenario of autonomic dysreflexia. The study took place in a university teaching hospital and included six male tetraplegic patients and six age-matched normal male controls. All tetraplegics were 5 months or longer post-traumatic spinal cord injury and all had experienced symptoms of autonomic dysreflexia on at least one occasion. The dorsal foot vein diameter was recorded with a tonometer during local infusions of noradrenaline 0.125–256 ng/min given through a short intravenous needle. In tetraplegic patients, there was a significant shift to the left of the dose—response curve indicating increased venous responsiveness to noradrenaline. The concentration of noradrenaline required to cause a 50% reduction of the resting vein diameter was decreased in tetraplegics (1.6 ng/min, geometric mean) compared to normal controls (10.9 ng/min,p < 0.02). a-Adrenoceptor responsiveness in dorsal foot veins is increased in patients with tetraplegia. Hypersensitivity of vascular a-adrenoceptors may contribute to autonomic dysreflexia in patients with high spinal cord injury.

Spectral methods for the construction of uniform asymptotic representations of the field diffracted by an aperture in a plane screen are reviewed. These are separated into contrasting approaches, roughly described as physical and geometrical. It is concluded that the geometrical methods provide a direct route to the construction of uniform representations that are formally identical to the equivalent-edge-current concept. Some interpretive and analytical difficulties that complicate the physical methods of obtaining uniform representations are analyzed. Spectral synthesis proceeds directly from the ray geometry and diffraction coefficients, without any intervening current representation, and the representation is uniform at shadow boundaries and caustics of the diffracted field. The physical theory of diffraction postulates currents on the diffracting screen that give rise to the diffracted field. The difficulties encountered in evaluating the current integrals are thoroughly examined, and it is concluded that the additional data provided by the physical theory of diffraction (diffraction coefficients off the Keller diffraction cone) are not actually required for obtaining uniform asymptotics at the leading order. A new diffraction representation that generalizes to arbitrary plane-convex apertures a formula given by Knott and Senior [ Proc. IEEE62, 1468 ( 1974)] for circular apertures is deduced.

Nisin and other lantibiotics have a bacteriocidal effect against Gram-positive bacteria, and also inhibit the outgrowth of bacterial spores. The bacteriocidal effect appears to be due to the formation of pores in the bacterial membrane. In the absence of anionic membrane phospholipids, the lantibiotic nisin acts as an anion selective carrier. In the presence of anionic phospholipids, nisin forms nonselective, transient, multi-state pores in cells, proteoliposomes, liposomes and black lipid membranes. Pore formation involves distinct steps. First, nisin associates tightly with the anionic membrane surface leading to a high local concentration. This results in a disturbance of the lipid dynamics near the phospholipid polar head group-water interface, and an immobilization of lipids. In the presence of a transmembrane electrical potential above the threshold level, the molecules reorient, presumably as an aggregate, from a surface-bound into a membrane-inserted configuration. Co-insertion of bound, anionic phospholipids results in bending of the lipid surface giving rise to a wedge-like, nonspecific, water-filled pore.

It is shown, by means of computation on a specific model, how pulse broadening in multimode gradedindex optical waveguides is significantly affected by the levels of excitation of the high-order modes. Pulse widths are computed as functions of the profile parametera, under conditions of equal excitation, high-order mode suppression and GaAs laser excitation.

Ray acoustic and adiabatic mode representations provide effective means for charting sound transmission in relatively complicated propagation and diffraction environments, under operating conditions that validate the use of such approximate waveforms. A principal limitation of these physically incisive and conveniently implemented algorithms is their failure in transition regions. For ray acoustics, transitions occur near caustics, foci, critical reflection angles, shadow boundaries, etc.; adiabatic modes undergo transitions when cutoff‐inducing or other smooth environmental changes transform their initially well trapped into radiated (leaky) energy. Instead of constructing the uniformized spectral representations required in transitional domains by an independent, more general, analysis, it is shown here that the uniformized spectral forms for a large variety of propagation and diffraction phenomena can be synthesized directly from ray acoustic or adiabatic mode data. This feature should be helpful in generalizing existing acoustic ray or adiabatic mode algorithms to accommodate transitional wave processes. The theory is presented for two‐dimensional configurations and fluid media, but the same considerations apply also in three dimensions and for multiwave effects due to elasticity or anisotropy.

To investigate the contribution of reflex vagal tone to the hemodynamic response after intravenous isoproterenol, 12 healthy subjects received isoproterenol by both bolus injection and continuous infusion before and after atropine, and during intravenous infusion of the β1-selective antagonist atenolol and the nonselective β-antagonist, propranolol. With bolus injections, atropine displaced the heart rate dose-response curve for atenolol to the right, implying reflex withdrawal of cardiac vagal tone, but did not alter the heart rate dose-response curve for propranolol. With continuous infusions of isoproterenol, atropine displaced the heart rate dose-response curves for both atenolol and propranolol to the left, implying the presence of a reflex increase rather than withdrawal in cardiac vagal tone. These reflex changes in cardiac vagal tone can be partly understood by changes in mean arterial pressure and pulse pressure. As the two methods of isoproterenol administration are associated with contrasting contributions from reflex vagal tone, dose ratios obtained for the displacement of the heart rate dose-response curve by β-antagonists may differ.

Equations of motion are derived for the nonlinear refractive coupling between two coherent optical beams in an anisotropic cubic medium, allowing for a phase mismatch between the beams. These equations contain orientation-dependent self-phase-modulation, cross-phase-modulation, and four-wave-mixing, terms plus additional anisotropic terms that, for example, can generate an orthogonal polarization component. Stationary solutions (eigenpolarizations) are identified in which the polarization state does not change, and these can be classified as stable or unstable. It is shown that TE and TM modes in the common semiconductor waveguide orientation for frequencies at the half band gap or below become unstable if the magnitude of the birefringence is sufficiently small. Diffraction is included, and the polarization-state evolution is obtained for mixed-mode (vector) spatial solitons. The polarization evolution dynamics of vector spatial solitons broadly follows the equivalent plane-wave examples.

We present experimental results on mixed-polarization solitary waves in AlGaAs waveguides. We show experimentally the complicated polarization dynamics of solitonlike beams that is related to the existence of linearly and elliptically polarized mixed-polarization spatial solitons in planar waveguides.

The Green’s function for a two‐dimensional planar wedge environment is derived in the spectral domain and using the Poisson summation formula the solution becomes rapidly convergent. This Green’s function field is calculated for two separate source positions to demonstrate its global modelike properties. A boundary‐value approach is formulated to model mode launching into the wedge structure using the spectral Green’s function allowing direct comparison with the parabolic equation method and the beam propagation method.

We report the observation of second-harmonic generation by type I quasi phase matching in a GaAs–AlAs superlattice waveguide. Quasi phase matching was achieved through modulation of the nonlinear coefficient χ^(2)_zxy, which we realized by periodically tuning the superlattice bandgap. Second-harmonic generation was demonstrated for fundamental wavelengths from 1480 to 1520 nm, from the third-order gratings with periods from 10.5 to 12.4µm . The second-harmonic signal spectra demonstrated narrowing owing to the finite bandwidth of the quasi-phase-matching grating. An average power of ∼110 nW was obtained for the second harmonic by use of an average launched pump power of ≲2.3mW .

We present experimental evidence to demonstrate the feasibility of a promising new quasi-phase-matching technique in AlGaAs multiple-quantum-well waveguides. Non-phase-matched second-harmonic-generation measurements indicate that, for sub-half-bandgap excitation near 1.5??µm, quantum-well intermixing by impurity-free vacancy disordering results in a reduction of the nonlinear susceptibility χzxy2∼340 pm/V by 17%.?Relatively low intermixed waveguide losses, and the high spatial resolution of the impurity-free vacancy disordering process, suggest that periodic intermixing along the direction of propagation should lead to useful frequency-conversion efficiencies.

Amplitude-shift keying modulation of solitons is subject to limited capacity because of Gordon–Haus noise and soliton interaction. It is shown theoretically that the capacity can be increased beyond this limit by recoding of the modulation. The design strategy is to make the pulse train strongly interacting, which reduces the Gordon–Haus noise, and to apply subband coding to counter the effects of the information dispersion caused by the strong intersoliton interaction; the subband-coded complex is pulse-position modulated onto the soliton stream. An example shows a 2.35-times improvement in capacity at the transatlantic distance of 6000 km with this method.

Maysin is a flavone glycoside that exhibits antibiotic activity toward corn earworm [Heliothis zea(Boddie)] and can be present the silks of maize (Zea maysL.). Nine maize genotypes were grown at four locations in 1979 and five locations in 1980 and evaluated for relative content of maysin in their silks. Differences among maize genotypes for maysin content were highly, significant. ‘Golden Cross Bantam’ (corn earworm susceptible) and experimental hybrid 471‐U6 ✕ 81‐1 (corn earworm tolerant) consistently had the lowest relative maysin content whereas P39 ✕ ZC 2451, a susceptible sweet corn ✕ resistant dent corn cross, consistently had the highest relative maysin content although a significant genotype by environment interaction was present. When genotype maysin means among environments were correlated, the genotypes grown in Missouri demonstrated the least agreement with genotype maysin means from other environments. The relative maysin content of silks was highest in Georgia and lowest in Hawaii, and a significantly lower level occurred in 1980 than in 1979. At this time, no biological explanation can be offered for environmental differences in average maysin content.

It is shown that in the limit of a small step length a ray equation can be attributed to the beam-propagation method. The equation is valid in the nonparaxial case but does not agree with the standard geometrical optics ray equation even in the paraxial limit. The beam-propagation method will not therefore predict the correct focal length of a lens. This is illustrated by a numerical example.

The inheritance of percentage senescent stalks, crushing strength, and rind thickness, was studied in six maize (Zea maysL.) crosses by the generation mean analysis method. Heritability estimates also were obtained for crushing strength and rind thickness. Additive genetic effects were more important than non additive effects for the three characters. Heritability estimates ranged from 0.28 to 0.53 for crushing strength and from 0.33 to 0.62 for rind thickness for the six crosses. Results indicate that a selection procedure that takes advantage of additive genetic effects and variance would be effective in improving these characters.

Combining ability for concentrations and g/200 kernels of P, K, Mg, Fe, Zn, oil, and protein, and for kernel weight, volume, and density in a six‐parent diallel of maize (Zea maysL.) inbreds was examined. Correlations among certain variables were computed. Significant variation was detected among GCA effects for concentrations and g/200 kernels of all kernel constituents except K concentration but among SCA effects only for oil concentration. GCA and SCA effects were significant for kernel weight, volume, and density. Highly significant correlations were found between P and K, P and Mg, and K and Mg concentrations.

Normal and opaque‐2 kernels from segregating maize (Zea maysL.) ears were examined for kernel components, oil content, and fatty acid composition. Normal kernels were higher in kernel and endosperm weight and embryo oil concentration, and lower in embryo weight than opaque‐2 kernels. Compared to normal, the oil from opaque‐2 kernels was slightly but significantly higher in oleic acid and lower in linoleic acid composition. Comparison of normal and floury‐2 kernels from segregating ears showed kernel and endosperm weights of the normal kernels were greater than for floury‐2, and embryo weight was similar. In a comparison of near‐isogenic floury‐2 and normal single‐cross hybrids, the kernel components were heavier in normal, while percent oil was greater for floury‐2 owing largely to a greater proportion of embryo. Percent oil in embryo was less in floury‐2 hybrids.