Direct signal analysis applied to the determination of the relaxation parameters from TSDC spectra of polymers

A new method to evaluate the thermally stimulated depolarization current curves based on the direct signal analysis is first applied here to the fitting of computer-generated curves to test its validity and accuracy. The method consists in finding the N elementary curves that best fit the experimental spectrum. The adjustment of the τ₀ values associated with each energy bin is also included in the fitting. The results are presented for a monoenergetic peak and a peak generated with a Gaussian broadened energy distribution both with a single τ₀. Good agreement is also found when a random noise of width σ₀ ≤ 0.01 J_max is added to the data to simulate experimental errors. Experimental complex curves corresponding to the γ and β overlapping relaxations in DGEBA-EDA epoxy resin system are separated into their fine structure components. The complex band corresponding to water dipoles physisorbed in different sites of the microporosity of bituminous coal is analyzed and different processes are identified. The results are compared to those performed on cleaned peaks. Finally, the TSDC peak corresponding to the glass transition temperature in bisphenol-A polycarbonate is analyzed and could only be fitted by using a Vogel-Fulcher expression for the temperature dependence of the relaxation times. © 1994 John Wiley & Sons, Inc.     

Size-spectra and growth of particles bearing As,Se, Sb,and Zn in Washington,DC, area aerosol by instrumental neutron activation analysis

Aerosol particles smaller than 1.8 m were size-fractionated with micro-orifice impactors at two urban sites near Washington, DC, and analyzed for 44 elements including, As, Se, Sb, and Zn, i.e., elements strongly associated with coal combustion, incineration, and regionally transported secondary aerosol, by Instrumental Neutron Activation. Size distribution parameters were determined nonparametrically and with a least-squares peak-fitting method using impactor calibration data. Geometric and fitted mass mean aerodynamic diameters typically differed by <10% and increased continuously with increasing relative humidity (RH) in the range 56 to 79%, but along different curves for samples influenced by local and distant sources. The geometric mass mean diameters for samples influenced by winds from the direction of local sources were uniformly smaller than those influenced by westerly winds bearing aerosol from distant, regional, sources. At 60% RH, gmmads were As, 0.30±0.03 and 0.46±0.04; Se, 0.33±0.06 and 0.54±0.04; Sb, 0.39±0.03 and 0.53±0.04; and Zn, 0.39±0.06 and 0.53±0.08; respectively.     

Effect of alcohols on the micellar properties in aqueous solution of alkyltrimethylammonium bromides

The effect ofn-butanol,n-propanol, andn-hexanol on the critical micelle concentration (CMC) and degree of ionisation of the micelles of dodecyl-, tetradecyl- and hexadecyltrimethylammonium bromides in aqueous solution has been determined by conductimetric techniques. Increase of the molality of added alcohol over the concentration ranges examined (up to 0.3 mol kg^–1 butanol, 0.07 mol kg^–1 pentanol and 0.025 mol kg^–1 hexanol) caused a progressive decrease of CMC and increase of the degree of ionisation for each surfactant-alcohol system. At a constant molality of added alcohol the degree of ionisation increased with a) an increase of the chain length of the surfactant for each alcohol and b) an increase of the chain length of the alcohol for each surfactant. The distribution of each alcohol between the aqueous and micellar phases and the free energy of solubilization were determined from the change of CMC with molality of added alcohol.     

Ion induced ridge electrons and their diffraction in solid foil targets

We present detailed double differential distributions of electrons emitted downstream when 100 and 170 keV protons interact with thin carbon, gold and aluminuum foils and compare them to those obtained with protons and neutral hydrogen projectiles interacting with helium gas. The distributions obtained with the gas target show, besides the well known convoy electron peak produced by capture or loss of electrons into the continuum of the emerging ion, a narrow ridge that is aligned with the beam direction. This ridge, which is attributed to electrons moving in the two Coulomb center potential saddle determined by the target and projectile ions, also appears in the ion-solid electron distributions. A typical solid state effect consists in the appearance of two strong lateral humps which are explained as due to diffraction of the ridge electrons in the three dimensional lattice of the polycrystalline foil material. Contrarily the diffraction of convoy electrons is impeded by their strong correlation to the moving ions. In the case of the Aluminuun target the observed diffraction is typical for Al₂O₃. This indicates that the observed electrons originate from a thin polycrystalline oxyde layer close to the downstream surface of emission.     

Darstellung,Eigenschaften und Kristallstruktur von [2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]acetylacetonatopalladium(II)

Synthesis, Properties, and Structure of [2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]-palladium(II) Acetylacetonate The reaction of Di-μ-chloro-bis[2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]palladium(II) with Thallium(I) acetylacetonate yields [2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]palladium(II) acetylacetonate. The complex crystallizes monoclinic in the space group P2₁/n with the lattice constants a = 1302.4(3), b = 836.0(2), c = 1341.3(3) pm, β = 93.69(3)°. Pd has a squareplanar coordination by two O atoms of acetylacetonate, the N atom of the imidazole ring, and the C atom of the phenyl group. I.r., n.m.r., and mass spectra are reported.     

Heats of combustion of biofuels obtained by pyrolysis and by transesterification and of biofuel/diesel blends

The obtained heats of combustion were 46.65 ± 0.20; 38.09 ± 0.31; 39.67 ± 0.22; 41.88 ± 0.31; 37.86 ± 0.46; 39.89 ± 0.09; 41.28 ± 0.31 MJ/kg for diesel, transesterified soybean oil, pyrolysed soybean oil and crude soybean oil, transesterified palm tree oil (Elaeis sp.), pyrolysed palm tree oil, crude palm tree oil, respectively. The results show the heats of combustion of biofuels are approximately 17% smaller than traditional diesel. The data also show the heats of combustion depend on the methodology used for the biofuel production. Addition of biofuels to traditional diesel fuel results in a linear decrease of the heat of combustion with the amount of the alternative fuel added to the diesel. However, for blends with 5% biofuels, which is the limit demanded by Brazilian legislation, no significant decrease of the heat of combustion of the commercial diesel was observed.     

Determination of the alternative butanol/gasoline and butanol/diesel fuel blends heats of combustion by a heat-loss compensated semi-microcalorimeter

The heat of combustion (HOC) of butanol/gasoline and butanol/diesel fuel blends was systematically determined in a Parr 6725/6772 heat-loss compensated semi-microcalorimeter under controlled temperature and pressure conditions. A set of blends containing 15 and 30% of butanol, in mass fraction, was tested, and the results were compared to those obtained for pure ethanol, pure gasoline, pure diesel, and Brazilian commercial gasoline. In view of the high volatility of samples, the use of gelatin capsules was necessary to avoid evaporation losses during the critical step of sampling. Results evidenced that despite a slight energy reduction observed for all blends, HOC values remained quite close to those measured for gasoline and diesel, even when considering blends with 30% of butanol in mass fraction, which reduction does not exceed 8.5%. Compared to ethanol, a HOC up to 14.7% higher was achieved for butanol. The present work confirms that in mass fractions up to 30%, butanol can be satisfactorily blended with gasoline and diesel without causing major impacts on the fuel energy density and, more than that, can offer energy advantage compared to ethanol.

     

LePaProGen—lepton pair production generator

A Monte Carlo generator “LePaProGen” for simulation of lepton pair production at hadron colliders is presented. Higher order electroweak radiative effects are implemented. A new algorithm for selection of the optimal phase space parameterization is applied.     

Single-photon space-like antibunching

We use heralded single photons to perform an antibunching experiment in which the clicks at the detectors are space-like separated events. The idea of such experiment dates back to the 5th Solvay conference, when it was proposed by Einstein as an expression of his concerns about quantum theory.