The “deer lactone”

Urine of the black-tailed deer is the source of the deer lactone, which is deposited on the tarsal gland tufts by rub-urination. The enantiomer composition of the lactone from the urine of the female is 89(R)-(–)/11(S)-(+). Responses by deer were strongest toward the synthetic racemic lactone in the social test and toward the natural lactone in the choice test. In both tests, the (–)- lactone released slightly stronger responses than its enantiomer.Odocoileus hemionus columbianus.     

Comparative study of diluent effects on the glass transition of polyvinylchloride and phenolphthalein

Summary Some binary polymer-diluent systems, previously studied by the Authors (SCANDOLA et al., 1982), showed an unusual T_g-concentration dependence. In order to investigate the relevance of the polymeric nature of the high-T_g component in determining this anomaly, two series of mixtures having the same diluent (di-n-Butylphthalate or Tricresylphosphate) and, as the high-T_g component, either a polymer (PVC) or a low-molecular weight substance (Phenolphthalein), have been examined. A discontinuity is found, as expected, in the polymeric systems PVC-di-n-Butylphthalate andPVC-Tricresylphosphate, as well as in Phenolphthalein-di-n-Butylphthalate mixtures where, however, the deviations from the calculated T_g-composition curve are much less marked. It is concluded that the presence of a polymer is not a necessary requirement for the occurrence of the above mentioned anomaly.     

Ethynylene-disilanylene copolymers

Polymers of structure (SiR₂SiR₂-C C-SiR₂SiR₂-C C) _n , in which ethynylene units alternate with disilylene units, have been prepared by two routes: (a) condensation of dichlorodisilanes with dilithium derivatives of 1,2-diethynyldisilanes and (b) ring-opening polymerization of strained cyclic disilanylene-acetylnes, (SiR₂SiR₂C C)₂. The polymers display UV absorption near 240 nm indicative of – conjugation between the Si₂ and the C C moieties. Polymers with R=R=n-Bu or R=n-Bu, R=Ph, undergo solid-state transitions to form liquid crystalline mesophases resembling those observed for many poly(silylenes). Single crystals were obtained for the polymer with R=R=CH₃, by precipitation from dilute cyclohexane solution. The solid-state properties and structures of this family of polymers are discussed.This paper was presented at the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.     

Theoretical aspects of bonding in silicon compounds

Ab initio-calculated bond dissociation energies of Si=Si and C=C are discussed by means of atomic ionization energies and p-p() AO overlap. At the same time ring strain energies of C- as well as Si-rings are estimated by homodesmic reactions where, according to Baeyer, the two-membered rings C=C and Si=Si are chosen to be the first members of the respective series. Thus, a better understanding of the double bonds can be gained. In addition, the exceptional structural and spectroscopic behavior of the five-membered Si-ring is discussed. Finally, the strikingly different results obtained in computational studies of the initial step for polymerization of the systems O=C=O and O=Si=O are discussed.     

Deposition of nanocrystals on flat supports by spin-coating

Monodisperse particles can be evenly distributed over flat supports by spin-impregnation. In this way Cu precursors have been deposited onto Si wafers. The effects of the rotation frequency and the concentration of the impregnation solution have been investigated. The mean diameter of the deposited particles can be varied from several nanometers upto several micrometers as is shown by microscopy images. Spin-impregnation appears a useful tool to prepare well-defined flat model catalysts, which are readily accessible both to quantitative characterisation and to catalytic testing.     

Random-coiled conformation of polypeptide chains

Summary Random-coiled conformation of poly(L-leucine), which has -branched side-chain, was theoretically analyzed by a conformational energy calculation based on intra-residue interactions. Calculated characteristic ratio 7.62 was obtained by using the transformation matrix statistically averaged over the entire side-chain conformational space of L-Leu residue. This value is smaller than those of poly(L-phenylalanine) (11.24) and poly(L-tyrosine) (12.33) which have -branched side-chain.     

Synthesis of new metal-containing side-chain monomers and polymers

New metal-containing vinyl monomers, hexyl-6-oxy-{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate and hexyl-6-oxy-{4-[4-(4-ferrocenoyl phenyl)phenyl]benzoyloxy}methacrylate, and the corresponding homopolymers and random copolymers with hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate were synthesized. The compounds were characterized by¹H NMR; their thermal behavior was investigated by means of differential scanning calorimetry. Monomers and polymers containing the ferrocene unit melt at lower temperatures than those derived from the cyclopentadienyl managanese tricarbonyl moiety. The melting temperatures of the monomers and polymers ranged from 399 to about 515 K, Both monomers and polymers failed to exhibit mesogenic behavior. Values ofM _n,M _w,M _w/M _n, and degree of polymerization were obtained by gel permeation chromatography. TheM _n ranged from 16,500 for the copolymer containing hexyl-6-oxy-{4-[4-(4-ferrocenoyl phenyl)phenyl] benzoyloxy}methacrylate and hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate at a 1:3 ratio to 26,000 for the copolymer containing hexyl-6-oxy-{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate and hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate at a 1:3 ratio.M _w/M _n ranged from 1.6 in the case of the copolymer containing hexyl-6-oxy-{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate and hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate at a 1:3 ratio to 2.2 in the case of poly(hexyl-6-oxy{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate).     

On the preparation and properties of CuZSM-5 catalysts for NO decomposition

Equilibrium exchange isotherms were determined for the exchange of Cu²⁺ with NaZSM-5 at varying Cu(Ac)₂ concentrations in solutions of constant volume and zeolite weight. At low Cu²⁺ levels the solid scavenged all the copper ions. When copper could be detected in the equilibrated solutions, overexchange was observed. The extent of overexchange was higher at pH 6 than at pH 4. These results were analyzed in relation to catalytic activity.On leave from the Central Institute for Chemistry, Hungarian Academy of Sciences, H1525 Budapest, Hungary.     

Role of plant volatiles in resistance of selected rice varieties to brown planthopper,Nilaparvata lugens (Stål) (Homoptera: Delphacidae)

Rice plant volatiles extracted as steam distillates significantly affected the behavior and biology of the brown planthopper,Nilaparvata lugens (Stål). In a multichoice test, more females settled and fed on tillers of a susceptible rice variety Taichung Native 1 (TN1), sprayed with its own extract or acetone than on TN1 tillers sprayed with the extract of the resistant variety ARC6650 or Ptb33. In another test,N. lugens females ingested significantly more of a 10% sucrose solution mixed with TN1 steam distillate extract than of plain sucrose solution or that mixed with extracts of resistant varieties. Topical application of the extracts of resistant varieties Mudgo, ASD7, Rathu Heenati, Babawee, Ptb33, and ARC6650 caused significantly higher mortality of females than did the TN1 extract. Likewise, significantly more first-instar nymphs died when they were caged on susceptible TN1 plants sprayed with the extracts of resistant varieties than on plants sprayed with TN1 extract. The extract of 60-day-old resistant plants was more toxic than the extract of 30-, 45-, or 100-day-old plants. However, toxicity of the extract from susceptible TN1 remained low at all plant growth stages.Principal Research Scientist (ICIPE), based at International Rice Research Institute (IRRI), P.O. Box 933, Manila, Philippines.     

Some Problems in Drawing and Texturing of Vidlon Polycaproamide Fibres

The nature and causes of separation of white powder in drawing and accumulation of deposits on machine chamber walls in texturing of Vidlon polycaproamide fibres are investigated. It was found that the quality of the titanium dioxide suspension and the oiling agent significantly affect separation of powder and passage of the fibre in drawing. Thermooxidative and thermal and mechanical degradation processes in the polymer determine the structure of the fibres and their behavior in drawing and texturing. The amount of white powder separated is a function of the moisture content of the as-spun fibres and the climatic conditions in winding, conditioning, and drawing. The concentration of cross-links in the polymer and inorganic elements on the surface of the fibres and the amount of white powder and deposits on the walls of texturing machine chambers are closely correlated with their passability in drawing.     

Methodological approach to identify chemical oviposition stimulants from maize for European corn borer

The noncontingent distribution ofO. nubilalis Hbn. eggs on various corn varieties has allowed their classification as either favorable or nonfavorable hybrids. This classification is based on a chemical communication system using volatile compounds active at a distance from the insect or active when in contact with the insect as soluble sugar components. Under this hypothesis, gas chromatography is the best way of investigating for the chemical differences between corn silk extracts from the two types of hybrids. A first experiment, using a desorption-trapping system on Tenax coupled to a gas chromatograph showed a quantitative difference between two compounds from the two hybrids. A second experiment showed the advantages and disadvantages of this method and allowed the development of two complementary techniques: (1) direct extraction of corn silk with trichlorofluo-romethane and direct injection into a capillary column with an apolar stationary phase using an on-column system; and (2) extraction under vacuum of volatile compounds from corn silk and their trapping on Tenax, followed by a second desorption. This allows a direct injection on the same capillary column. The first technique allows identification by mass spectrometry of many alkanes with high molecular weights. The second technique seems to confirm the presence of phenylacetaldehyde. Both techniques show quantitative differences in the composition of corn silk extracts from favorable and nonfavorable hybrids; however, the biologically active chemicals remain unknown.     

Chemical detection of “self” and conspecifics by crayfish

Stimulus waters were used to examine behaviorally chemical communication in female crayfishProcambarus clarkii. Animals detected conspecifics. Response to stimulus water drawn from the animal's own tank, self water, mimicked either response to distilled water or response to water drawn from the tank of another animal. The response to self water depended on the relative concentration of substance(s) in self water stimuli to that of the same substance(s) in the test animal's tank.     

Dynamics and self-organization of catalytic systems

The kinetics of a catalytic reaction is frequently formulated in terms of simple concepts of the Langmuir type. Apart from limitations arising from the non-uniformity of the catalyst's surface and from the coverage dependence of the rate constants, several other complications may come into play. These may arise on the quantum level where energy flow between the various degrees of freedom may cause failure of simple transition state theory, as well as on the continuum level where formulation of rate equations in terms of coupled non-linear differential equations may give rise to a rich scenario of spatio-temporal self-organization, including kinetic oscillations, chaos, and formation of concentration patterns. Several of these phenomena are illustrated by selected examples.     

The efficient synthesis of poly(silapropynylenes) via condensation of NaCэCNa with R1R2SiCL2 activated by pyridine

Summary To efficiently prepare poly(silapropynylenes), the condensation of NaCCNa with R₁R₂SiCl₂ activated by pyridine were investigated. The condensation produced tactable polymers(Mw ca. 2100–9000) with significantly higher yields of 80–97% than those from R₁R₂SiCl₂ itself and also gave rise to much more improvement in the yields and molecular weight than with acetylenic di Grignard or di lithium salts. The activation of R₁R₂SiCl₂ by pyridine accelerated the condensation reaction, which resulted in production of macrocyclic polymers as well as linear polymers.     

Current Waves Generated by Detonation of an Explosive in a Magnetic Field

The structure of the electromagnetic field in detonation of a condensed explosive in a magnetic field is analyzed qualitatively. Propagation of a detonation wave in a magnetic field leads to generation of an electric current in explosion products. The physical reason for current generation is the freezing of the magnetic field into the conducting substance at the detonation front and subsequent extension of the substance and the field in the unloading wave. The structure of the current layer depends on the character of the boundary magnetic fields and conditions on the surface of initiation of the explosive. Detonation of the explosive in an external magnetic field B₀ generates a system of two currents identical in magnitude but opposite in direction. The structure of the arising current and its absolute value are determined by the parameter R₁ = _{0 0}D²t (₀ is the magnetic permeability of vacuum, ₀ is the electrical conductivity of detonation products, D is the detonationfront velocity, and t is the time). The value of the current increases with the detonationwave motion, and the linear current density is limited from above by 2B₀/₀. For R₁ 1, the electric field in the conducting layer is significantly nonuniform; for detonation products with a polytropic equation of state, a region of a constantdensity current is adjacent to thedetonation front. The results of this analysis are important for interpretation of experiments performed and development of new methods for studying the state of the substance in the detonation wave.     

Weak Gel Behaviour of Poly(vinyl alcohol)-Borax Aqueous Solutions

Thermal transition of PVA-borax aqueous gels with a PVA concentration of 60 g/L and a borax concentration of 0.28 M was investigated at temperatures ranging from 15 to 60C using static light scattering (SLS), dynamic light scattering (DLS), and dynamic viscoelasticity measurements. Three relaxation modes, i.e. two fast and one slow relaxation modes, were observed from DLS measurements. Two fast relaxation modes located around 10^–310¹ sec, with one fast mode (_f1) being scattering vector q-dependent and the other fast mode (_f2, with _f2>_f1) being q-independent. The _f1 mode was attributed to the gel mode whilst the _f2 mode could be due to the hydrodynamics of intra-molecular hydrophobic domains formed by uncharged segments of polymer backbones. The slow relaxation mode with relaxation time located around 10¹10³ sec in DLS data was due to the motion of aggregated clusters and was observed only at temperatures above 40C. The amplitude and relaxation time of slow mode decrease as temperature is increased from 40 to 60C. At temperatures below 40C, no slow relaxation mode was observed. The SLS measurements showed PVA-borax-water system had fractal dimensions D _f2.4 and D _f2.0 as temperature was below and above 40C, respectively. The simple tilting test indicated gel behaviour for the PVA-borax aqueous system at temperatures below 40C with a creep flow after a long time exposure in the gravity field. But the dynamic viscoelasticity measurements demonstrated a solution behaviour for PVA/borax/water at temperatures below 40C, the critical gel point behaviour for G() and G() was not observed in this system as those reported for chemical crosslinked gels. These results suggest that the PVA-borax aqueous system is a thermoreversible weak gel.     

Numerical Simulation of Thermochemical Conversion of a High–Ash Coal in a Low-Temperature Fluidized Bed under Pressure

The paper considers a mathematical model, an algorithm, and a program for calculating nonstationary processes of air gasification of a high-ash coal under pressure in a pilot-scale circulating fluidized bed gasifier reactor. The effect of operation parameters on the course of the process is analyzed. It is shown that hot spots (short-duration local heatings) can form at various points of the bed, at which maximum temperature can be close or even exceed the fluid slagging point. Possible mechanisms of formation of hot spots are analyzed.     

Characterization of some organic poly(aminiumphosphate)s

Summary Metachromatic reactions of MB and AO are studied with poly(aminium phosphate)s. The main band() at 665 m and 492 m for MB and AO are shifted to 580 m and 455 m respectively (-bands). The metachromatic values at different concentrations of poly(aminium phosphate)s are also reported. The dye association for MB with these polymer derivatives is investigated conductometrically as well. It is observed that MB can be at the most bind with the phosphate residue of polymer upto 11 molar ratio. The polymeric nature was further established by paper chromatographic technique in Terry's, Ebel's & Pfrengle's solvents.     

General regularities of explosion initiation in determining impact and friction sensitivity of an explosive

The impact and friction sensitivities of explosives were measured by 12 methods used in Russia and abroad. Correlations between explosion frequency on devices No. 1 and No. 2 with a lower sensitivity limit according to Russian standard 4545–88 and critical clamping pressure for the I-6-2 device are obtained. Almost all results are well correlated with critical stress p₁ thus representing a good base for explanation of experimental results for impact and friction. The values we obtained determining friction sensitivity are often proportional to p₁. The regularities obtained are explained.Mendeleev Russian University of Chemistry and Technology, Moscow 125190. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 2, pp. 80–90, March–April, 1995.     

Formation of a phase structure of the “fibrils in matrix” type in a composite fibre based on high-density polyethylene and polyethylene terephthalate

Conclusions Regions of component ratio and conditions for obtaining a composite fibre of the fibrils in matrix type have been determined for the HDPE-PET system.At an HDPE-PET ratio of 60:40, phase inversion takes place and a structure of the interpenetration networks type is realized.Under identical fibre spinning conditions, the formation of a phase structure of the fibrils in matrix type can be regulated by varying the temperature.Translated from Khimicheskie Volokna, No. 4, pp. 38–40, July–August, 1987.