Reply to Comments of Steuernagel on the Afshar’s Experiment

We respond to criticism of our paper “Paradox in Wave-Particle Duality for Non-Perturbative Measurements”. We disagree with Steuernagel’s derivation of the visibility of the Afshar experiment. To calculate the fringe visibility, Steuernagel utilizes two different experimental situations, i.e. the wire grid in the pattern minima and in the pattern maxima. In our assessment, this procedure cannot lead to the correct result for the complementarity properties of a wave-particle in one particular experimental set-up.     

Flow-through optosensor combined with photochemically induced fluorescence for simultaneous determination of binary mixtures of sulfonamides in pharmaceuticals, milk and urine

A sensitive and selective flow-through optosensor implemented with photochemically induced fluorescence (PIF) is proposed for the simultaneous determination of mixtures sulfamethoxazole/sulfanilamide and sulfathiazole/sulfanilamide. The resolution was accomplished by placing in the flow system a minicolumn filled with an appropriate solid support. Whereas one of the sulfonamides is not retained in the minicolumn and is determined by measuring its native fluorescence on the solid surface of the sensing microbeads in the detection area, the other one is retained and, after its elution, it is photochemically converted into a strongly fluorescent photoproduct which is transitorily retained on the sensing support in the flow cell and monitored. Linear calibration graphs were obtained over a concentration range of 2–3 orders of magnitude. The detection limits for the determination of sulfamethoxazole, sulfanilamide and sulfathiazole are 8.1, 2.9 and 5.7 ng mL⁻¹, respectively. The method was applied to pharmaceuticals, milk and human urine. The recovery of sulfamethoxazole from pharmaceuticals was 102.5% indicating no interference from trimethoprim which is not photochemically active. The recoveries for urine and milk samples fortified with sulfonamides at levels between 0.1 and 0.7 μg mL⁻¹ agreed within 95.0–107.5% of spiked levels.     

Transport and free carrier electromagnetic phenomena in semiconductor boundary layer: II. Reflectivity with non-normal incidence and surface plasmons

A classical analysis is given of the reflectivity at oblique incidence on semiconductor surfaces. The theory includes the effect of a space charge boundary layer and yields formulae from which one can obtain the dispersion relation for surface plasmons, for which the effects of the boundary layer are particularly important. An application to experimental data on n-InSb gives satisfactory agreement while yielding a plausible estimate of the surface excess ΔN. The electroreflectance is also studied, including numerical evaluations. It is suggested that measurements at almost grazing incidence could yield valuable information on the surface scattering of carriers.     

Instability conditions due to structural nonlinearities in regenerative chatter

Chatter is an instability condition in machining processes characterized by nonlinear behavior, such as the presence of limit cycles, jump phenomenon, subcritical Hopf and period doubling bifurcations. Although the use of nonlinear techniques has provided a better understanding of chatter, neither a unifying model nor an exact solution has yet been developed due to the intricacy of the problem. This work proposes a weakly nonlinear model with square and cubic terms in both structural stiffness and regenerative terms, to represent self-excited vibrations in machining. An approximate solution is derived by using the method of multiple scales. In addition, a qualitative analysis of the effect of the nonlinear parameters on the stability of the system is performed. The structural cubic term gives a better representation of the nonlinear behavior, whereas the square term represents a distant attractor in the stability chart. Instability due to subcritical Hopf bifurcations is established in terms of the eigenvalues of the model in normal form. An important contribution of this analysis is the representation of hysteresis in terms of new lobes within the conventional stability limits, useful in restoring stability. This analysis leads to a further understanding of the nonlinear behavior of regenerative chatter.     

Giant alkali-metal-induced lattice relaxation as the driving force of the insulating phase of alkali-metal/Si(111):B

Ab initio density-functional theory calculations, photoemission spectroscopy (PES), scanning tunneling microscopy, and spectroscopy (STM, STS) have been used to solve the 2sqrt[3]×2sqrt[3]R30 surface reconstruction observed previously by LEED on 0.5 ML K/Si:B. A large K-induced vertical lattice relaxation occurring only for 3/4 of Si adatoms is shown to quantitatively explain both the chemical shift of 1.14 eV and the ratio 1/3 measured on the two distinct B 1s core levels. A gap is observed between valence and conduction surface bands by ARPES and STS which is shown to have mainly a Si-B character. Finally, the calculated STM images agree with our experimental results. This work solves the controversy about the origin of the insulating ground state of alkali-metal/Si(111):B semiconducting interfaces which were believed previously to be related to many-body effects.     

Intensity measurement bend sensors based on periodically tapered soft glass fibers

We demonstrate a technique for tapering periodically an all-solid soft glass fiber, consisting of two types of lead silicate glasses, by the use of a focused CO(2) laser beam and investigate the bend sensing applications of the periodically tapered soft glass fiber. Such a soft glass fiber with periodic microtapers could be used to develop promising bend sensors with a sensitivity of -27.75 μW/m(-1) by means of measuring the bend-induced change of light intensity. The proposed bend sensor exhibits a very low measurement error of down to ±1%.     

A chiral HPLC-UV method for the quantification of dibenz[b,f]azepine-5-carboxamide derivatives in mouse plasma and brain tissue: eslicarbazepine acetate, carbamazepine and main metabolites

For the first time, a selective and sensitive chiral HPLC-UV method was developed and fully validated for the simultaneous quantification of eslicarbazepine acetate (ESL), carbamazepine (CBZ), S-licarbazepine (S-Lic), R-licarbazepine (R-Lic), oxcarbazepine (OXC) and carbamazepine-10,11-epoxide (CBZ-E), in mouse plasma and brain homogenate supernatant. After the addition of chloramphenicol as the internal standard, samples were processed using an SPE procedure. The chiral chromatographic analysis was carried out on a LiChroCART 250-4 ChiraDex column, employing a mobile phase of water and methanol (88:12, v/v) pumped at 0.9 mL/min and the UV detector set at 235 nm. The assay was linear (r(2) ≥0.995) for ESL, CBZ, OXC, S-Lic, R-Lic and CBZ-E in the range of, respectively, 0.2-4, 0.4-30, 0.1-60, 0.2-60, 0.2-60 and 0.2-30 μg/mL, in plasma, and of 0.06-1.5 μg/mL for ESL, 0.12-15 μg/mL for CBZ and CBZ-E and 0.06-15 μg/mL for OXC and both licarbazepine (Lic) enantiomers in brain homogenate supernatant. The overall precision was within 8.71% and accuracy ranged from -7.55 to 8.97%. The recoveries of all the compounds were over 92.1%. Afterwards, the application of the method was demonstrated using real plasma and brain samples obtained from mice administered simultaneously with ESL and CBZ.     

Changes in the optical properties of benzo[a]pyrene-coated aerosols upon heterogeneous reactions with NO2 and NO3

Chemical reactions can alter the chemical, physical, and optical properties of aerosols. It has been postulated that nitration of aerosols can account for atmospheric absorbance over urban areas. To study this potentially important process, the change in optical properties of laboratory-generated benzo[a]pyrene (BaP)-coated aerosols following exposure to NO(2) and NO(3) was investigated at 355 nm and 532 nm by three aerosol analysis techniques. The extinction coefficient was determined at 355 nm and 532 nm from cavity ring-down aerosol spectroscopy (CRD-AS); the absorption coefficient was measured by photoacoustic spectroscopy (PAS) at 532 nm, while an on-line aerosol mass spectrometer (AMS) supplied real-time quantitative information about the chemical composition of aerosols. In this study, 240 nm polystyrene latex (PSL) spheres were thinly coated with BaP to form 300 or 310 nm aerosols that were exposed to high concentrations of NO(2) and NO(3) and measured with CRD-AS, PAS, and the AMS. The extinction efficiencies (Q(ext)) changed after exposure to NO(2) and NO(3) at both wavelengths. Prior to reaction, Q(ext) for the 355 nm and 532 nm wavelengths were 4.36 ± 0.04 and 2.39 ± 0.05, respectively, and Q(ext) increased to 5.26 ± 0.04 and 2.79 ± 0.05 after exposure. The absorption cross-section at 532 nm, determined with PAS, reached σ(abs) = (0.039 ± 0.001) × 10(-8) cm(2), indicating that absorption increased with formation of nitro-BaP, the main reaction product detected by the AMS. The single-scattering albedo (SSA), a measure of particle scattering efficiency, decreased from 1 to 0.85 ± 0.03, showing that changes in the optical properties of BaP-covered aerosols due to nitration may have implications for regional radiation budget and, hence, climate.     

Polymorphism and isomerisation of an azobenzene derivative on gold

M-TBA (4-methoxy-3,30,5,50-tetra-tert-butylazobenzene) adsorbed on a gold (111) surface was found to form four different polymorphs, two of which isomerizable at -1.7 V, but with a low propensity for further isomerisation of nearby molecules (C. Dri, M. V. Peters, J. Schwarz, S. Hecht, L. Grill, Nat. Nanotechnol., 2008, 3, 649-653). Atomistic simulations investigate the origin of the effects.