The surface structure and composition of the low index single crystal faces of the ordered alloy Pt3Sn

The surface composition and structure of 111, 100, and 110 oriented single crystals of the ordered alloy Pt₃Sn (Ll₂ or Cu₃Au-type) were determined using the combination of low energy electron diffraction (LEED) and low energy ion scattering spectroscopy (LEISS). The clean annealed surfaces displayed LEED patterns and Sn/Pt LEISS intensity ratios consistent with the surface structures expected for bulk termination. In the case of the 100 and 110 crystals, preferential termination in the mixed (50% Sn) layer was indicated, suggesting this termination to be the consequence of a thermodynamic preference for tin to be at the surface.     

Relationship between preferential adsorption coefficient and intrinsic viscosity in ternary systems

Summary The relation proposed between the preferential adsorption coefficient, , and the intrinsic viscosity, ¦¦ ¦¦=¦¦+AK has been applied in this paper to previously published data. This equation is found to be valid in theta condi tions and far away from them. The obtained results are compared to the ones calculated with the Dondos-Benoit equation.     

Synthesis and characterization of polyvinylpyridine macromonomers

Summary Macromonomers of polyvinylpyridine were obtained anionically, by reacting unsaturated electrophiles onto a living polyvinylpyridine solution. The end-standing unsaturation is either a methacrylic ester function or an -methylstyrene group. Several experimental problems had to be solved to get polymers of adequate and predetermined molecular weight and of low polydispersity, and to have the molecules fitted quantitatively with unsaturation at chain end. A careful characterization procedure was used to check the ability of the method to yield well defined macromonomers.     

Poly(β-malic acid) : a new polymeric drug-carrier

Summary Poly(-malic acid) is a new synthetic functional polyester of the poly(-hydroxy-acid)-type whose properties are investigated in regard to possible uses as bioresorbable polyvalent drug-carrier. Degradation of polymer chains in 0.15 N phosphate buffer at pH=7.5 is monitored by aqueous GPC on SEPHADEX gels and by enzymatic titration of ultimate degradation products. It is shown that the rate of degradation obeys first order kinetics at the begining and that poly(-malic acid) degrades to malic acid at last.Presented at the 26th IUPAC Microsymposium on Macromolecules: Polymers in Medicine and Biology, Prague, July 9–12, 1984     

Cooperative inclusion of sodium 1-pyrenesulfonate by γ-cyclodextrin

Summary The interaction of -cyclodextrin(-CD) with sodium 1-pyrenesulfonate(PS) was studied spectrophotometrically. -CD was found to cause much larger decrease in the absorption maxima of PS than -CD. The fluorescence spectra of PS in the presence of -CD showed excimer emission, while those of PS with -CD showed only monomer emission, indicating that -CD forms 12 (-CDPS) complexes in which two PS molecules are included in the -CD cavity in a face-to-face fashion. The binding isotherm showed a sigmoidal curve. The association constants were estimated by computer simulation of the binding curve. The 12 (CDPS) complex was found to be much more stable (K=10⁶ M^–1) than the 11 complex (K=1 M^–1). At high concentration of -CD another -CD cooperates in binding two PS molecules, resulting in the formation of a 22 complex.     

Field test of the pheromone hypothesis for homing by pacific salmon

Experimental groups of juvenile coho salmon (Oncorhynchus kisutch) were released to elucidate the relative importance of site-specific (imprinted) odors and intraspecific odors (pheromones) in homing. Adult salmon returned to their release site rather than a hatchery containing both adult and juvenile salmon of their population. Furthermore, salmon sharing the same parents returned to different sites, suggesting that local movements are not strongly influenced by siblings or other conspecifics.     

Processing of boron-nitrogen preceramic polymers

A number of new oligomeric and polymeric reagents rich in boron and nitrogen have recently been derived by several research groups. These reagents offer potential for the formation of boron nitride (BN) as controlled morphology powders as well as nonpowder forms. Specifically, it has been found that a family of 3-point and 2-point poly(borazinylamine) reagents may be processed by techniques used in organic polymer chemistry, with subsequent formation of BN ceramic fibers, coatings, xerogels, aerogels, and aerosols.     

Molybdenum nitride for the direct decomposition of NO

The physico-chemical properties of passivated -Mo₂N have been investigated. The material showed high activities for NO direct decomposition: nearly 100% NO conversion and 95% N₂ selectivity were achieved at 450C. The amount of O₂ taken up by -Mo₂N increased with temperature rise and reached 3133.9 molg^–1 at 450C; we conclude that there formation of Mo₂O_xN_y occurred. This oxygen-saturated -Mo₂N material was catalytically active: NO conversion and N₂ selectivity were 89 and 92% at 450C. We found that by means of H₂ reduction at 450C, Mo₂O_xN_y could be reduced back to -Mo₂N and the oxidation/reduction cycle is repeatable; such a behaviour and the high oxygen capacity (3133.9 molg^–1) of -Mo₂N suggest that -Mo₂N is a promising catalytic material for automobile exhaust purification.     

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.     

Composition dependence of the oxygen-evolution reaction rate on Ir x Ti1−x O2 mixed-oxide electrodes

Mudcrack-free oxide films of Ir _x Ti_1–x O₂ (0 < x 1) on titanium substrates were obtained, and the effects of the oxide composition on the rate of oxygen-evolution reaction were investigated. At x 0.6, Ir-rich grains appear on the mudcrack-free surface. In the purely single-phase region (0 < x 0.5), the pseudo-capacitive charge is proportional to the surface composition, x _s, and the exchange-current density for the oxygen-evolution reaction increases linearly with x _s at 0.2 x _s 0.5, with an extrapolated intercept at x _s 0.15, below which the oxides are inactive.     

Effects of crystallinity and supermolecular formations on the interfacial shear strength and adhesion in GF/PP composites

Aim of this study was to screen the morphological effects on the interfacial shear strength (i) in glass fibre (GF) reinforced isotactic polypropylene (iPP) model composites. i was determined by a modified single fibre pull-out technique. It was established that the relation between i (5–6 MPa) and the yield stress of the iPP (y30 MPa) is at about 1:6 and that the i values were not influenced by the mophological superstructure set under isothermal crystallization conditions. Increased i was only observed when specimens were produced non-isothermally, by quenching (i9 MPa). This improvement could not be related to thermal shrinkage stresses. The enhancement in i was attributed to better wetting and improved adhesion due to the enlarged amorphous PP (aPP)-phase. A schematic adhesion model considering the wetting behaviour of aPP and iPP was proposed.     

Properties of Shock‐Compressed Carbogal. Equations of State for Carbogal and Plexiglas

This paper presents results from experimental studies of the properties of Carbogal (C₈F₁₆ or perfluoro1,3dimethylcyclohexane), at high pressures and temperatures, in particular, data on single compression and recompression, temperatures, and velocity of sound. Data are given on shockwave compressibility of porous Plexiglas with an initial density 10–60 times lower than the density of the solid sample. Thermodynamically complete equations of state for Carbogal and Plexiglas are developed on the basis of a model published previously and wellknown experimental data. It is shown that calculations using the developed equations of state are in agreement with available experimental data for Carbogal up to pressures of 70 GPa and for Plexiglas over the entire examined range of pressures.     

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.     

Temperature programmed oxidation of Cu/ZnO catalysts with N2O: an attempt for characterization of copper catalysts

For characterization of the surface structure of metallic copper formed on the support, temperature programmed oxidation (TPO) with N₂O was carried out over various Cu/ZnO catalysts. Four peaks of the N₂ formation (, , and ) were observed at 223, 400, 545 and 600 K in the TPO runs. The average copper crystallite size estimated from the sum of the amount of - and -peaks agreed fairly with those determined by X-ray diffraction and transmission electron microscopy. It was concluded that - and -peaks resulted from the oxidation of metallic copper atoms on the steps, corners and/ or defect sites, and on the flat sites of the surface of copper crystallites, respectively, while - and -peaks resulted from the bulk oxidation of copper.     

Upwind searching for an odor plume is sometimes optimal

A model is presented that suggests that the optimal strategy for an animal walking or crawling on a substrate while searching for the source of a chemical carried by a shifting wind or current may be to move upwind (or against the current). The requirements are that (1) the current direction fluctuates rapidly within a range that exceeds 30 ° on both sides of the mean direction, and (2) the searching animal can move accurately up- or downwind and, once within the influence of the chemical plume, can move efficiently to the source. Under these conditions, an upwind search is shorter (on the average) by 0.9–0.3 of the range of influence of the chemical stimulus. Thus, this strategy is relatively more important when the total search path is short, i.e., when sources are typically close by. The mean length of the downwind search path is given by L _d =d +r[(1/E) + cos ]/2 and the upwind search path by L _u =d +r[(2/E) – (/sin ) – cos ]/2 whered is the starting distance up- or downwind of the source,r is the range of stimulus influence,E is the efficiency with which the searcher moves to the source within the influence of the plume,a is the angle of the maximum extent of wind direction from the mean, and the average, , is taken over all starting positions across the wind direction that lead to search paths that intercept the area swept by the plume.     

Mechanical Sensitivity and Detonation Parameters of Aluminized Explosives

Experiments were performed to study the effect of the species particle size and structure of aluminized mixture samples on the sensitivity and detonation parameters of HMX, nitroguanidine, bis(2,2,2trinitroethyl)nitramine, and their mixtures with an Al powder with a mean particle size of 0.1 – 150 m. The addition of ultrafine Al to HMX and bis (2,2,2trinitroethyl)nitramine substantially increases the sensitivity to mechanical effects and decreases the detonation velocity. In compositions with nitroguanidine, the detonation velocity practically does not vary. For nitroguanidine, the width of the chemicalreaction zone and Chapman–Jouguet parameters were determined by recording the detonationpressure profiles. The pressure profiles for bis(2,2,2trinitroethyl)nitramine show that detonation decomposition can occur in two stages. A twopeak detonationwave structure was detected for mixtures of HMX with Al. Temperature measurements indicate that Al interacts with detonation products in the immediate proximity to the front. The highest temperature was recorded for compositions containing ultrafine aluminum and an aluminum dust.     

Lamellar Morphology of Poly(3-hydroxybutyrate)/Poly(ethylene oxide) Blends as Studied via Small Angle X-ray Scattering

The lamellar morphology of a melt-miscible blend consisting of two crystalline constituents, poly(3-hydroxybutyrate) (PHB) and poly(ethylene oxide) (PEO) have been investigated by means of small angle X-ray scattering (SAXS). The blend was a crystalline/amorphous system when temperatures lay between the melting point of PEO (ca. T _m ^PEO=60C) and that of PHB (ca. T _m ^PHB=170C), while it became a crystalline/crystalline system below T _m ^PEO. The crystalline microstructures of the blends were induced by two types of crystallization history, i.e. one-step and two-step crystallizations. In the one-step crystallization, the blends were directly quenched from the melt to room temperature to allow simultaneous PHB and PEO crystallization. The two-step crystallization involved first cooling to 70C to allow PHB crystallization for 72 h followed by cooling to room temperature (ca. 19C) to allow PEO crystallization. In the crystalline/crystalline state, two scattering peaks have been observed in the Lorentz-corrected SAXS profiles, irrespective of the crystallization histories, meaning that crystallization created separate PHB and PEO lamellar stack domains. One-step crystallization yielded lamellar stack domains containing almost pure PHB and PEO lamellae. Two-step crystallization generated almost pure PHB lamellar domains and the PEO lamellar domains with inserted PHB lamellae. In the crystalline/amorphous state, the composition dependence of the amorphous layer thickness (l _a), the presence of zero-angle scattering, and the volume fraction of the PHB lamellar stack (_s) revealed that both one-step and two-step crystallizations, generated the interfibrillar segregation morphology, where the extent of interfibrillar segregation of amorphous PEO increased with increasing PEO content.     

Interactions between pheromone traps with different strength lures for the pine beauty moth,Panolis flammea (Lepidoptera: Noctuidae)

Catches of malePanolis flammea in traps baited with lures containing 25 g of sex attractant are enhanced when in the proximity of traps baited with 125-g lures. The degree of enhancement is increased as the intertrap distance is decreased, and when the low-dose trap is upwind of the high-dose one. The patterns of alteration in trap catch suggest that moths initially attracted by one lure may divert into other traps, which may be either upwind of the original trap (overshooting), or downwind (undershooting). Overshooting can result in up to fivefold increases in catch and may provide a useful method for estimating the attractant zone of particular lure/trap combinations.     

New polyisobutylene based model ionomers

Three-arm star polyisobutylene ionomers (¯M_n=8800) with terminal SO₃ M (M=K or Ca²) groups were synthesized and their mechanical properties investigated. Compression molded films displayed high elongations, i.e., -1000% for Ca² ionomers with lower values for the K counterions. Strain induced crystallinity was observed at higher elongations. Mechanical properties in general compared favorably with conventional covalently linked rubbery networks and were comparable and in some cases superior to EPDM-based ionomers carrying randomly distributed SO₃ M groups.For the first two parts see Proceedings, 28th IUPAC Macromolecular Symposium, Amherst, MA, July 11–16, 1982, p. 905 and 906     

Dynamic mechanical properties of crosslinked polyisoprene under deformation

Summary Molecular motions of elastomers under deformations were observed through dynamic mechanical measurements. Composite master curves of dynamic moduli E and E and loss tangent tan over a wide range of frequency and in a state of elongation were obtained by the time-temperature superposition procedure. It is found that both moduli increase with strain, . The slope of the dispersion curve of E become more gradual with the increase in , while that of E is almost unchanged. The increment of E is generally larger than that of E, which does not agree with the N. W. Tschoegl prediction, E ^* ()=f() E _o ^* (), where E ^* () and E _o ^* () are complex moduli at the strain of and O, respectively, and f() is the function of only . The difference in the strain dependence of E from E was found to correspond to the strain dependence of the equilibrium modulus.