Vibration in dwellings from road and rail traffic — Part III: towards a common methodology for socio-vibrational surveys

While a range of international standards defining noise, vibration and other physical environmental measures have been established, common methodologies for measuring people's reactions to these same environmental effects are still in their infancy. This reduces the comparability of prevalence statistics and exposure-effect relationships developed by different researchers. The public authorities are served incompatible or seemingly conflicting information from different surveys when deciding on appropriate guidelines and limits. Drawing on experiences with the 1998 Norwegian Socio-vibrational Survey and a Swedish socio-acoustic survey supplemented with vibration measures, a new Nordtest Method: NT ACOU 106 Acoustics—Assessment of annoyance by vibrations in dwellings from road and rail traffic has been defined. The method describes sampling requirements, and proposes a mandatory verbal 5-point categorical annoyance scale and an optional 11-point numerical annoyance scale, both with lower anchoring point “Do not notice”. A survey data output format is specified to allow researchers to pool data from different surveys.     

Vibration in dwellings from road and rail traffic — Part I: a new Norwegian measurement standard and classification system

Protection against vibration nuisance in order to maintain satisfactory conditions during work, sleep, rest and recreation in buildings was specified in the European Directive on Construction Products and introduced in the Norwegian Building Regulations in 1997. As a qualified vibration measurement method was lacking, work with a new standard, NS 8176, was initiated. An empirical method for determination of statistical maximum velocity, v_w,95 or alternatively acceleration, v_w,95, was introduced. The vibration measure is obtained as the 95-percentile of maximum weighted vibration velocities (or acceleration) from a minimum number of representative road and rail traffic events. The measurement procedure was evaluated by means of a Round Robin test. A classification system for dwellings was defined on the basis of the 1998 Norwegian Socio-vibrational Study. This study provided relationships between different values of the new vibration exposure measure, v_w95, and the strength of people's reactions.     

Surface‐enhanced Raman spectroscopy (SERS) on silver colloids for the identification of ancient textile dyes. Part II: pomegranate and sumac

The effectiveness of surface‐enhanced Raman spectroscopy (SERS) spectrocsopy on Ag colloids has been successfully demonstrated for the identification of a yellow dye in two ancient wool threads found in the Royal Tumulus of In Aghelachem, Libyan Sahara, belonging to the Garamantian period (2nd–3rd century A.D.). High‐performance liquid chromatography (HPLC) highlighted the presence of ellagic acid in the extracts from the threads, excluding other chromophores. This result, together with the abundance of malic acid detected by gas chromatography‐mass spectrometry (GC‐MS), suggested the possible use of pomegranate rind or sumac berries as source of the yellow dye, both plants being documented in the Fezzan area during the Garamantian period. HPLC analyses and SERS spectra acquired on the extracts of the ancient threads were therefore compared with those obtained from pomegranate and sumac extracts of the corresponding fruits and reference dyed wool samples, allowing us to identify the yellow dye as deriving from pomegranate (Punica granatum L.). SERS spectra of ellagic acid and dyes extracted from pomegranate rind and sumac berries are reported here for the first time. A methodological improvement is also presented, based on the use of NaClO₄ as aggregating agent, that leads to a significant increase of the signal‐to‐noise ratio in the SERS spectra. Copyright © 2010 John Wiley & Sons, Ltd.     

Secondary ion emission from polymer layers by atomic and molecular ion bombardment: Data evaluation based on linear-cascade sputtering theory

This paper constitutes an attempt to rationalise impact-energy dependent yields of molecular secondary ions emitted from polymer samples under bombardment with atomic and molecular primary ions. The evaluation was based upon a comparison with sputtering yields calculated from linear-cascade sputtering theory, including threshold effects. To explore general trends, sputtering yields for carbon, silicon and silver were calculated under impact of normally incident C, F, S, Ga, Xe, Au, SF₅, C_11, C₆₀ and Au₅. The yields of carbon, for example, bombarded with C₆₀ are larger than for Ga by factors of ∼5 and ∼10 at 10 and 100 keV, respectively. However, owing to the fact that the effective threshold energy for sputtering increases with the number of constituents of the projectile, the yields for molecular ion impact start to exceed the yields for atomic ions only at energies between 0.5 and 5 keV. The analysed experimental results relate to molecular ion emission from one monolayer (1 ML) and 9 ML films of polymethacrylate on silver bombarded with Xe and SF₅ ions at energies E between 0.5 and 10 keV. Comparison of (initial) secondary ion yields S⁺ (m/z 143) with calculated sputtering yields suggests that S⁺ constitutes the sum of two contributions. The first, labelled , prevails at low energies and appears to reflect molecule ejection due to the mean effect of nuclear energy deposition (“ordinary” linear-cascade sputtering). The second contribution, , dominates at E > 1.5 keV, increases with a high power of E, but does not correlate with the calculated sputtering yield. It is suggested that is a measure of those impact events which occasionally generate a very high energy density at the surface, thus providing optimum conditions for very efficient ejection of molecules that are located at the rim of the agitated area. The SF₅/Xe secondary ion yield ratios are distinctly different for the two contributions, only about 0.3 for but ∼4 (1 ML) and ∼20 (9 ML) for . The pronounced secondary ion “yield enhancement” frequently reported in the literature for molecular versus atomic ion bombardment appears to be due to an enlargement of the contribution, more so the higher the impact energy and the more massive the projectile. The total (integrated) secondary ion yields, estimated by making use of the reported damage cross sections, were found to be the same for SF₅ bombardment of the 1-ML and the 9-ML samples. This finding calls for more attention towards obtaining high secondary ion yields at minimum sample consumption.     

Spatial structures based on color centers created by electrons in lithium fluoride crystals: Absorption and luminescence characteristics

We have shown that in spatial structures based on color centers created by electrons in a lithium fluoride crystal, the distances between centers reach 1.6 nm and 3.6 nm for F₁ and F₂ centers respectively. This suggests considerable potential opportunities for using electron technology to form structures in the crystals with spatial resolution of such an order of magnitude. We measured the decrease in fluorine content on the irradiated surface of the crystal. We found the concentrations of F₁, F₂, F₃⁺, F₃(R₂), and F₄(N₁) centers. We established that the specific characteristics of color center formation by electrons leads to an increase in the efficiency of creation of F₃ and F₄ centers. We determined the decrease in the average luminescence lifetimes of F₂ and F₃⁺ centers as a result of concentration quenching. We observed distortion of the luminescence contour for F₂ centers as a result of absorption of its short-wavelength portion by other centers and emission of radiation by the latter in its long-wavelength portion. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 102–110, January–February, 2008.     

Tb ions in presence of ZnS:Mn nanocrystals immobilized on silica: Energy transfer ZnS→Tb and coordination state of Mn ions

Three-component luminescent material consisting of silica xerogel as a support with immobilized ZnS:Mn²⁺ nanocrystals and Tb³⁺ ions was compared with such two-component materials as the silica support with ZnS:Mn²⁺ as well as the support with Tb³⁺. In each case the nanocrystals and the lanthanide ions were immobilized at silica surface by impregnation procedure. Size of the ZnS quantum dots doped with Mn²⁺ were estimated by Scherrer method from the X-ray diffraction (XRD) pattern. The materials have been characterized by EPR and optical spectroscopy techniques. EPR spectra allow to distinguish two different Mn²⁺ sites: the first is assigned to isolated Mn²⁺ substitutionally and incorporated into cubic ZnS lattice and the second is ascribed to the Mn²⁺ situated near the nanocrystal surface. From the optical spectra we have found that in the three-component material, energy transfer from excited ZnS:Mn²⁺ nanocrystals to Tb³⁺ ions takes place. The different mechanisms of such transfer are discussed.     

Intermediates in the hydrogenation of benzene to cyclohexene on Pt(1 1 1) and Pd(1 1 1): A comparison from DFT calculations

Catalytic hydrogenation of aromatic compounds is an important process in petroleum industry. Understanding it through experimental or theoretical research can help to improve its efficiency. This work presents a first principles density functional theory study of the intermediates for the first four hydrogenations steps of the smallest aromatic compound, benzene, into C₆H₁₀ species, on two popular catalytic metals, palladium and platinum, described by periodic models. Different structures have been studied for the intermediate C₆H_6+n species, with a various degree of conservation of the conjugation. Some intermediates would present in gas phase a closed-shell conjugated structure, while other would correspond to multiple radicals with a massive destruction of the benzene π system. The Pd and Pt(1 1 1) surfaces strongly differ in terms of most stable structure for the intermediates. On Pd the most conjugated intermediates, i.e. the most stable in gas phase, is clearly preferred. In contrast, on Pt, multiple radical species, highly unstable in gas phase, are strongly stabilized by coupling with the surface. This thermodynamic study indicates a different trend for the hydrogenation mechanism: a clear successive 1-2-3… hydrogenation of neighboring carbon atoms on Pd keeping the largest conjugated fragment, and a nonconsecutive attack, with a maximum breaking of benzene conjugation on Pt.     

Heat capacity anomaly in UO2 in the vicinity of 1300 K: an improved description based on high resolution X-ray and neutron powder diffraction studies

X-ray and neutron powder diffraction studies of UO₂ were performed under controlled oxygen partial pressure between room temperature and 1673 K. More than 40 neutron diffraction patterns were recorded. The thermal expansion coefficient of UO₂ and the temperature dependence of Debye-Waller factors for oxygen and uranium atoms were determined. The dependence of Debye-Waller factors as a function of temperature is linear and the thermal expansion coefficient follows the classical Debye regime within the temperature range 300-1000 K. Above 1200 K, a departure from this quasi-harmonic behavior is clearly observed. Both an abnormal increase of the thermal expansion and of the oxygen sublattice disorder are evidenced. The departure of the lattice parameter from a linear thermal variation is found to be thermally activated with an effective activation energy close to 1 eV, very similar to the activation energy already found for the electrical conductivity. This new result suggests that polarons may affect the mean lattice parameter. A new thermodynamic model is then proposed to explain the heat capacity thermal variation by only three contributions: harmonic phonons, thermal expansion and polarons.     

A computational study (DFT,MP2, and GIAO‐DFT) of substituent effects on protonation regioselectivity in β,β‐disubstituted vinyldiazonium cations: formation of highly delocalized carbenium/diazonium dications

Protonation reactions were studied by quantum‐chemical theoretical methods (DFT and MP2) for a series of β,β‐disubstituted vinyldiazonium cations ( 1 ⁺ – 14 ⁺ ), bearing stabilizing electron‐releasing groups (H₃CO? , (H₃C)₂N? , H₃C? , (H₃C)₃Si? , as well as halogens F, Cl). Taking into account the various mesomeric forms that these species can represent, protonations at C_α, at the β‐substituent, and at N_β were considered. The energetically most favored pathway in all cases was C_α protonation, which formally corresponds to trapping of the mesomeric diazonium ylid. Based on the computed properties (optimized geometries, NPA‐charge densities, and multinuclear GIAO‐NMR chemical shifts), the resulting dications can best be viewed as carbenium/diazonium dications, in which the carbocation is further delocalized into the β‐substituent. For the α‐nitro derivative 15 , protonation of the nitro group was predicted to be the most favored reaction, while C_α‐ and N_β‐protonation resulted in the loss of the nitronium ion. Copyright © 2009 John Wiley & Sons, Ltd.