Kairomones and their use for management of entomophagous insects: II. Mechanisms causing increase in rate of parasitization byTrichogramma spp.

When the effect of the kairomone, tricosane, on parasitization byTrichogramma achaeae Nagaraja and Nagarkatti of eggs ofHeliothis zea (Boddie) was studied in petri dish tests, the greatest percentage parasitization ( = 64%) was obtained if the entire filter paper was treated. Treatment of smaller areas (about the eggs) resulted in decreased parasitism. In the greenhouse, highest parasitization ( = 71%) byT. pretiosum (Riley) ofH. zea eggs placed on pea seedlings grown in pie pans was obtained if the whole pan was treated; lowest parasitism ( = 29%) occurred when the pans were untreated. Parasitization was intermediate ( = 52%) in other pans treated only at selected spots. Dissections ofH. zea eggs collected from kairomonetreated and untreated field plots revealed that eggs ofTrichogramma spp. were more efficiently distributed (less superparasitism) among host eggs in treated plots. These kairomones increase parasitization ofTrichogramma spp. by releasing and continuously reinforcing an intensified searching behavior rather than by attracting and guiding the parasite directly to the host.Hymenoptera: Trichogrammatidae.In cooperation with the University of Georgia College of Agriculture Experiment Station, Coastal Plain Station, Tifton, Georgia.Mention of a proprietary product in this paper does not constitute an endorsement of this product by the USDA.     

On the determination of oxygen potentials and O/M ratios in mixed U-Pu oxides by means of solid state galvanic cells

Measurements of oxygen potential on uranium-plutonium mixed oxides by means of solid state galvanic cells are discussed and compared with precedent data. Discrepancies in the values at low temperature (1000 K) as well as in the versusT slopes are found, which disappear when the samples are thermally cycled. An analysis is performed of this effect, showing that the absence of a good homogeneization of the sample in oxygen and/or in plutonium content can give rise to mixed potentials and hence to erroneous results.     

Spin Labels as the Instrument for Analysis of Topochemistry of Polymer-Immobilized Ziegler Catalytic Systems

A spin labeling technique was used to investigate the topochemical characteristics of polymer carriers and immobilized metal complexes. Functionalized polyethylenes (PE) such as PE–grafted-polyallylamine (1), PE–grafted-polydiallyl-amine (2), and PE–grafted-poly-4-vinylpyridine (3), obtained by grafting polymerization of the corresponding monomers, were used as polymer carriers. Metal-containing polymers were obtained by immobilization to 2 with either TiCl₄ (2/Ti) or Al(C₂H₅)₂ Cl (2/Al). The stable nitroxyl radical 2,2,6,6-tetramethyl-4-(2-oxy-4,6-dichlorotriazine)piperidine-1-oxyl was used for spin labeling 2 to give , while 2,2,5,5,tetramethyl-3-(N-acetoamidiiodine)-pyrrollidine-1-oxyl was used for spin labeling 3 to give . Radical 2,2,6,6-tetramethyl-4-hydroxy-pyperidine-1-oxyl was bonded to 2/Ti and 2/Al to give and , respectively. The accessibility of the functionalized polymers 1–3 to interact with the spin labels and the immobilized metal complexes was examined. Estimation of the effective distances between the spin labels and the dynamic behavior of nitroxyl radicals in the functionalized polymer matrixes and metal-containing polymers revealed several important features of spin-labeled systems. Metallation of a functional covering makes the polymer more accessible for spin labeling and has a considerable effect on the dynamic characteristics of polymer matrix. A change of the rotational activation energy of the spin labels from 15 kcal/mol in to 44 kcal/mol for in the temperature range 100–150°C was observed.     

Synthesis and characterization of polyacrylonitrile grafted with poly(2,6-dimethyl-1,4-phenylene oxide)

Summary Free radical copolymerization of acrylonitrile (AN, M₁) with poly(2,6-dimethyl-1,4-phenylene oxide)--vinylbenzyl ether (PPO-VBE, M₂, _n + 4200g/mol, _w/ _n + 1.04) was performed at 60°C in either a mixture of N,N-dimethylformamide/toluene or tetrahydrofuran, using 2,2-azoisobutyronitrile (AIBN) as initiator. The characterization of the resulting polyacrylonitrile grafted with poly(2,6-dimethyl-1,4-phenylene oxide) (PAN-g-PPO) was performed by 200 MHz ¹H-NMR spectroscopy and solubility.     

Daily rhythms of metabolic rates: Role of chemical signals in coexistence of spiny mice of the genusAcomys

The common spiny mouseAcomys cahirinus and the golden spiny mouseA. russatus coexist in the extreme arid and hot parts of the Arava Rift Valley in Israel. The coexistence of these two species is through exclusion ofA. russatus from nocturnal activity byA. cahirinus, which is nocturnal. An attempt was made to study the daily activity rhythm response ofA. russatus to chemical signals released byA. cahirinus, in order to understand the mechanism of segregation. For this purpose oxygen consumption, O₂, was studied in individuals ofA. russatus kept alone in a metabolic chamber in a constant ambient temperature of 32°C under two photoperiod regimes: 12L:12D, and constant darkness (D:D). After three days of O₂ recording under these conditions, chemical signals released fromA. cahirinus were passed through the metabolic chamber. This treatment caused a shift in the activity rhythm only ofA. russatus kept at 12:12D, while a decrease in O₂ rates ofA. russatus was noted in both groups. These results suggest that chemical signals released byA. cahirinus may play a role in shiftingA. russatus toward its diurnal activity.     

Methane coupling at low temperatures on Ru(0001) and Ru(11¯20) catalysts

The conversion of methane to higher hydrocarbons on single crystal Ru catalysts has been investigated using combined elevated-pressure kinetic measurements/surface science studies. The reaction consists of activation of methane on Ru(0001) and Ru(11¯20) surfaces to produce carbonaceous intermediates at temperatures between 350 and 700 K and rehydrogenation of these species to ethane and propane at 370 K. It is found that under the reaction conditions employed, the maximum yield in ethane/propane production occurs at 500 K on both surfaces. Influence of the hydrogenation temperature on the production of ethane and propane is also examined. On Ru(0001), the yields of ethane and propane maximize at = 400 K, whereas no maximum yield was observed on Ru(11 0) in the 300–500 K temperature range. Under optimum reaction conditions, hydrocarbon products consist of 16% ethane and 2% propane. High-resolution electron energy-loss spectroscopy (HREELS) has been used to identify various forms of hydrocarbonaceous intermediates following methane decomposition. An effort is made to relate the hydrocarbon intermediates identified by HREELS to the gas phase products observed in the elevated pressure experiments.     

The influence of total monomer concentration on the “reactivity” of ω-(p-vinylbenzyl ether) macromonomers of poly(2,6-dimethyl-1,4-phenylene oxide) determined from radiacal copolymerization experiments with butyl methacrylate

Summary The influence of the total monomer concentration on the radical reactivity ratio r₁ of butyl methacrylate (BMA) (M₁)--(p-vinylbenzyl ether) macromonomer of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO-VBE) (M₂) monomer pair was investigated. For two different molecular weights of the PPO-VBE macromonomer ( , and ), the determined reactivity ratio r₁ decreases with the increase of the macromonomer concentration. Therefore, the reactivity of the macromonomer, 1/r₁, follows the opposite trend. This dependence is due to micelles formation during copolymerization. This microsegregation process partitionates the comonomer concentrations between the bulk of solvent and around the growing chain and therefore, the experimental r₁ is actually a product of the true reactivity ratio r₁ ⁰ and a partition coefficient k.     

Studies on nonisothermal solid state galvanic cells — effect of gradients on EMF

An expression for the EMF of a nonisothermal galvanic cell, with gradients in both temperature and chemical potential across a solid electrolyte, is derived based on the phenomenological equations of irreversible thermodynamics. The EMF of the nonisothermal cell can be written as a sum of the contributions from the chemical potential gradient and the EMF of a thermocell operating in the same temperature gradient but at unit activity of the neutral form of the migrating species. The validity of the derived equation is confirmed experimentally by imposing nonlinear gradients of temperature and chemical potential across galvanic cells constructed using fully stabilized zirconia as the electrolyte. The nature of the gradient has no effect on the EMF.Nomenclature J _i flux of speciesi - X _i generalized forces - L _ij Onsagar coefficient - ₁ electrochemical potential of ions - ₂ electrochemical potential of electrons - T absolute temperature - U ₁ ^* total energy of transfer of the ion - partial molar enthalpy of the ion - Q ₁ ^* heat of transport of the ion - Z ₁ charge on the ion - F Faraday constant - electrostatic potential - ₂ chemical potential of the electron - ₁ chemical potential of the ion - partial entropy of the ion - E _SE EMF developed across the solid electrolyte - E _Pt EMF developed across the platinum lead - ( ₂)_Pt chemical potential of electrons in platinum - partial entropy of electrons in platinum - (Q ₂ ^* )_Pt heat of transport of electrons in platinum - E _cell EMF developed across the whole cell - chemical potential of oxygen - chemical potential of oxygen in its standard state - R universal gas constant - partial pressure of oxygen - relative chemical potential of oxygen - _M relative chemical potential of metal M - a _M activity of metal M     

Fundamental studies on a new concept of flue gas desulphurization

A new process for removal of sulphur dioxide from waste gases is proposed consisting of both electrochemical and catalytic sulphur dioxide oxidation. In the catalytic step a part of the sulphur dioxide is oxidized by oxygen on copper producing sulphuric acid and copper sulphate. The other part is oxidized electrochemically on graphite. The cathodic reaction of this electrolysis is used for recovering the copper dissolved in the catalytic step. The basic reactions of this process have been studied experimentally in detail. It has been shown that sulphur dioxide can be electrochemically oxidized on carbon electrodes to sulphuric acid with high current efficiency. The reaction rate of the electrochemical copper deposition is increased by dissolved sulphur dioxide in the electrolyte. The catalytic oxidation of sulphur dioxide on copper has been investigated for different sulphur dioxide concentrations and temperatures. The ratio of the reaction products, sulphuric acid and copper sulphate, varies over a wide range depending on the experimental conditions.Nomenclature SO₂ concentration (gas phase) (vol % SO₂) - SO₂ concentration (electrolyte) (g l^–1) - E potential vs saturated calomel electrode (V) - E _s specific energy consumption (W g^–1 SO₂) - F Faraday constant (A s^–1 mol^–1) - i current density (mA cm^–2) - molecular weight (g mol^–1) - T temperature (° C) - U _c cell voltage (V) - v _e number of electrons being transferred - space-time yield of SO₂-oxidation (g SO₂ h^–1 dm^–3) - _cu space-time yield of Cu-corrosion (g Cu h^–1 dm^–3) - ratio - fractional conversion of SO₂ - current efficiency for SO₂ oxidation     

Dilute acid-hydrolized cotton cellulose An electron diffraction study

Summary A comparative morphological investigation by electron diffraction analysis was carried out on samples of cotton cellulose from different stages of dilute-acid-catalysed hydrolytic degradation reactions. Within the range from 13000 (native material) to 500 only a gentle decrease of the relative crystallinity was observed. For below 500 the crystallinity decreases much faster, together with a simultaneous marked increase in paracrystalline lattice distortion and the show up of crystallographic evidence for a new cellulose phase which became better defined as degradation proceeded. A clearly defined parallel can be established between the different kinetic stages of the degradation reaction and the degree-of-polymerization dependence of the morphological features. The resulting evidence is at odds with the traditionally held views about the effects of acid hydrolysis of cellulose on its morphological fine structure.     

Multi-arm star polyisobutylenes

Summary The first synthesis of a multi-arm radial-star polyisobutylene (*-PIB) is described. The synthesis occurred by the addition of excess divinylbenzene (DVB) linking reagent to a living polyisobutylene (PIB) charge i.e., by the arm first method under specific conditions. The radial structure of the *-PIB was proven by determining the molecular weight of a sample by light scattering, then selectively destroying the aromatic polydivinylbenzene (PDVB) core, and finally determining the molecular weight of the surviving alphatic PIB arms. The synthesis strategy, kinetic observations during synthesis, and procedures leading to a representative *-PIB are described. This product whose g/mole with , contained 90.3 mole% (78 wt.%) PIB arms and 9.7 mole% (22 wt.%) aromatic core; thus the number of PIB arms emanating from the core was (number average number of arms)=56 or (weight average number of arms)=110.     

Influence of the partial pressure of oxygen on the redox chemistry of multivalent elements in molten sodium tetraborate

Voltammetric determinations based on current measurements have been developed in order to allow anin situ evaluation of the redox ratios of multivalent elements in molten sodium tetraborate. The same technique has been used to study the influence of the partial pressure of oxygen in the gaseous atmosphere on the redox properties of sodium tetraborate melts. Experiments were carried out at 1273 K in solutions of chromium with oxidation states VI and III and of antimony with oxidation states V and III; the values ranged from 5×10^–5 atm to 1 atm. Log [Ox]/[Red] plotted against log shows linear relationships with slopes of 0.72 and 0.54 in the case of chromium and antimony solutions, respectively. These values lie close to the theoretical values of 0.75 and 0.50, respectively, which are deduced assuming conditions of equilibrium between oxygen and the solute. In agreement with these results, voltammetric and potentiometric determinations confirm Nernstian behaviour of the oxygen-oxide redox system.     

Molecular weight averages as criteria for quality assessment of heated oils and fats

A simple method for quality assessment of heated oils and fats is described. The proposed method involves precise determination of molecular weight averages (MWA)viz., the weight average molecular weight ( ), the number average molecular weight ( ) and the Z-average molecular weight ( ) by high performance size exclusion chromatography (HPSEC) and their quantitative correlation to percent polar material obtained by column chromatography (CC). Change in MWA on heat treatment of fourteen different edible oils and fats at 180° ± 2°C for eight 8-hr days is studied. Relative standard deviations and regression coefficients of correlation between MWA and their ratios ( , { }, { }, { }, { } and { )vs percent polar material have been reported. Probable discard time was predicted for all the oils based on the above-mentioned correlations and also from the percent of high molecular weight (H. Mwt) species formed. It was observed that the oils which are generally recommended for coronary patients deteriorated faster. A possibility of extending this methodology to the frying oils is suggested. Part of the work was presented at “40th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy” at Georgia World Congress Centre, USA, 1989. IICT Communication No. 2630.     

Copper recovery from dilute solutions in the Falling-Film cell

The removal of copper from dilute solutions is examined in electrochemical reactors where the electrolyte flows as a thin film in an inclined channel between a plane plate and a sheet of expanded metal (Falling-Film cell). Copper is recovered as a thin sheet from the plane plate. The results are compared with a known simplified model and the variations of the faradaic yield with the operating conditions are discussed.Nomenclature A _e electrode surface area - b width of inclined channel - C(t) copper concentration at timet - C ₀ initial copper concentration - d interelectrode distance - overall current density - overall limiting current density - overall mass transfer coefficient - L length of the channel - Q _v volumetric flow rate - Q _vl volumetric flow rate per unit of channel width (=Q _v/b) - t time - t _s residence time in the reactor, defined by Equation 1 - mean flow velocity of the liquid film, defined by Equation 2 - V volume of electrolyte in the circuit - V _R reactor volume - v _sn normalized space velocity, defined by Equation 9 - inclination angle with respect to the horizontal - instantaneous faradaic yield - time-averaged faradaic yield - v _e number of electrons exchanged in the electrochemical reaction     

Structure of Atomic and Molecular Adsorbates on Low-Miller-Index ZnO Surfaces Using X-ray Absorption Spectroscopy

We review our X-ray absorption spectroscopy studies of adsorbate geometries on the O-terminated (000 ) and Zn-terminated (0001) basel faces, as well as the non-polar (10 0) prism face of ZnO. Studies employing near-edge X-ray absorption fine-structure (NEXAFS) and surface X-ray absorption fine-structure (SEXAFS) are included.     

Mass transfer at the electrodes of the ‘falling-film cell’

In the falling-film cell the electrolyte flows as a thin film in the channel between an inclined plane plate and a sheet of expanded metal which work as electrodes. The present work gives the mass transfer coefficients at both electrodes; the experimental variables are the electrolyte flow-rate, the angle of inclination of the channel and the interelectrode distance. The results allow three different flow regimes to be characterized. At low flow rates, there exists a particular regime where capillary effects are present; in this regime the mass transfer coefficient decreases with increasing flow rate, which is interesting from the point of view of possible industrial electrolytic applications.Nomenclature b width of the inclined channel - D diffusion coefficient - d interelectrode distance - e _m mean film thickness - Grashof number, based ond - Grashof number, based onL - ¯k overall mass transfer coefficient, defined by Equation 9 - L electrode length - Q _v volumetric flow rate - volumetric flow rate per unitQ _vl width of channel - Reynolds number - Schmidt number - Sherwood number, based ond - Sherwood number, based onL - mean velocity of the liquid film - inclination angle of the channel with respect to the horizontal - kinematic viscosity of them electrolyte     

Influence of molecular weight on the crystallization of poly(vinylidene fluoride)

Five samples of Poly (vinylidene fluoride) with a molecular weight from 45,000 to 260,000 were analyzed by means of FT-IR spectroscopy in order to study the influence of molecular weight on the crystallization process. The spectra of films obtained from methylethylketone solutions revealed the prevalence of form II () in the case of lower and of form III () in the higher molecular weight samples. The amount of form III was found to increase as the Mv decreased and as annealing temperatures increased. The deconvolution technique of vibrational spectra allowed detection of small amounts of other forms accompanying the prevailing one.     

The viscosity dependence on concentration,molecular weight and shear rate of xanthan solutions

Summary This paper concerns the viscosity dependence of Xanthan as a function of polymer concentration, shear rate and molecular weight in the ordered conformation. The different samples with various molecular weights are obtained by ultrasonication. A unique curve is obtained for the reduced specific viscosity ( ) as a function of γ · γ _r ⁻¹ for the different molecular weight samples and polymer concentrations below an overlap concentration C [η]₀⩽ 1.5. The master curve giving the relation as a function of C [η]₀ is drawn and compared with that of polystyrene in good solvent. The largest increase of in semidilute solution may be due to larger interchain interactions and to larger stiffness of the Xanthan molecule.     

Surface characterization of zirconium titanate (ZrTiO4) powder by measurements of electrical photoconductance and photoassisted oxygen isotope exchange

The photosensitivity of a ZrTiO₄ sample (33 m²/g) prepared by a sol-gel method has been assessed in the presence of O₂ by both photoconductance and oxygen isotope exchange (OIE) measurements at room temperature at wavelengths > 290 nm. For oxygen pressures < ca. 13.3 Pa, the steady-state photoconductance of ZrTiO₄ was unaffected by , which indicated that the direct recombination of the photoproduced charges played the dominant role. At higher pressures, varied as the reciprocal of , which was consistent with the fact that the electronic equilibrium was then governed by O₂ + e^– O ₂ ^– . OIE over ZrTiO₄ occurred predominantly via the overall mechanism which involves the exchange of two surface oxygen atoms for each exchange act. It was very slow as compared with OIE over photocatalytically active anatase samples which, in addition, occurs via another mechanism. These results allow one to predict that this ZrTiO₄ sample is a poorly active photocatalyst for oxidations involving gaseous oxygen, and further illustrate the interest of and OIE measurements to evaluate the photosensitivity of semiconductor oxide samples.     

Blackening in yttria stabilized zirconia due to cathodic processes at solid platinum electrodes

The DC cathodic voltage current density (V-J) characteristics at the contact between a solid disc Pt-13% Rh electrode and yttria stabilized zirconia (YZr) electrolyte were investigated to evaluate the conditions under which blackening occurred in the anionic conductor. Polycrystalline and single crystal samples have been studied using oxygen-argon mixtures between 10⁰ and 10^–3 atm oxygen and at temperatures in the range 800 to 1450°C. It is shown that the rate determining step of the overall cathodic reaction, O₂(g)+2Vö+4ear2O _o ^x under low field, ohmic conditions is the first electronation step, but true activation polarization at higher fields is masked by mass transfer limitations. The limiting current density in the polycrystalline material was directly proportional to the oxygen partial pressure whereas at low temperatures, below 1000°C, in the single crystal.The former behaviour is attributed to a flux limit in the ambient oxygen gas, whereas the regime is believed to be a consequence of molecular dissociation, coupled with surface exchange, onto the mobile interfacial layer. It is further shown that blackening is a consequence of thermionic emission of electrons across the cathodic interface into anion vacancy traps and the cathodicV-J characteristics of the blackened material saturate to obey aJV ² law above about 2 V, indicative of a space charge limited current. A tentative model is proposed.