Search

We report a new technique to measure direction and amplitude of electric fields generated by microelectrodes embedded in polar liquid environment, as often used in microfluidic devices. The method is based on optical tweezers which act as sensitive force transducer while a trapped charged microsphere behaves as a probe. When an electric field is applied the particles moves from its equilibrium position and finishes in a new equilibrium position where electric and optical forces are balanced. A trapped bead is moved to explore the electric field in a wide region around the microelectrodes. In such way maps of electric fields with high spatial resolution can be reconstructed even for complex electrode geometries where numerical simulation approaches can fail. Experimental results are compared with calculations based on finite element analysis simulation. [ABSTRACT FROM AUTHOR]

Abstract: Surface enhanced Raman scattering (SERS) has been employed for the first time to characterize particles produced in flames across the soot inception. The strong enhancement of Raman signal produced by SERS enabled the measurement of the Raman spectra of size-selected particles collected by a dilution probe-DMA system and deposited by electrophoresis in very low concentrations on SERS substrates. It also enables investigation of second order 2D Raman bands in soot and soot precursors, providing complementary information to the first order Raman bands. Raman spectra, together with the measurement of particle size distribution by DMA, help to characterize particles produced across the soot threshold limit. Three particle modes have been identified: flames with C/O<0.65 produce only modeI particles with a diameter of d ≈2nm, which present the typical bands of amorphous carbon and have a very low, if any, three-dimensional ordering of graphitic planes. Other aromatic macromolecules smaller than the lower detection limit of the DMA (d <1.5nm) are present in the flame, and are collected by thermophoretic sampling. In flames with higher C/O ratio the size distribution becomes bimodal with the formation of modeII particles, d ≈4nm. In non-sooting flames, the SERS spectra of modeI and modeII particles are similar except for features indicating the presence of a higher degree of disorder in modeII, likely due to distorted or five order rings. In soot-forming flames, larger modeIII particles collected with a diameter of 40nm present a higher ordering and a reduction of graphitic interplane distance, which, nevertheless, still remains larger than 3.50Ǻ. Two types of particles were observed in smaller modeII particles collected from sooting flame conditions: one with Raman spectra similar to the modeIII particles and the other with spectra similar to particles collected from leaner non-sooting flames. [Copyright &y& Elsevier]

Aims: To investigate the analytical and diagnostic accuracy of thyrotrophin (TSH) receptor antibody assays using recombinant human TSH receptors. Methods: Sera from 68 patients with Graves' disease, 23 patients with autoimmune thyroiditis, and 119 healthy controls were evaluated in four different laboratories using both radioactive and chemiluminescent tracers. Functional sensitivity, interlaboratory precision, optimal cutoff values for Graves' disease, and the correlation between the two methods were evaluated. Results: Functional sensitivity was 0.98 IU/litre for both assays. Interlaboratory precision, expressed as per cent coefficient of variation over a wide range of antibody concentrations, varied from 5.7% to 15.1 % for the radioligand, and from 6.6% to 19.9% for the chemiluminescence assay. The two methods (radioactive and chemiluminescent) were closely correlated. All the sera from untreated or relapsing patients with Graves' disease gave TSH receptor antibody values above 2.1 IU/litre, whereas in none of the healthy controls did values exceed 2.5 IU/litre. Receiver operating curve analysis allowed an optimal cutoff point to be defined at 1.99 IU/litre, according to a sensitivity of 100% and specificity of 99.1%. Conclusions: These data show the high analytical and diagnostic accuracy of the human TSH receptor assays, both with radioactive and chemiluminescent tracers, when both functional sensitivity and interlaboratory reproducibility are considered. These two methods could be proposed as first line diagnostic markers for Graves' disease. [ABSTRACT FROM AUTHOR]

This paper reports the latest findings on the stone observatory of Bric Pinarella (Finale Ligure, Savona, northern Italy), first described in 2006 at the conference of the Italian Society of Archaeoastronomy (SIA). The settlement is located near the upland plain of the Manie, which is an area known for the archaeological remains and the natural attractions. The settlement is constituted of three archaeological evidences: a small building, two short standing stones 44 centimetres apart, and a standing stone vertically fitted in the ground with a natural hole in its free end. Archeoastronomical investigations demonstrated that the hole in the standing stone allows positioning of the sunrise at the equinoxes over the Manie skyline, whereas the two standing stones allow tracing of the local meridian with azimuth 360-180. Other possible astronomical functions such as the identification of the elongation of the Sun from the east cardinal point and the study of the Sun and Moon's upper meridian transit (in this respect the site could be described as a rudimentary meridian circle) are discussed in the paper. Despite the fact that, to date, its construction time is still unknown, the most recent findings show that the whole site could be an old astronomical observatory.

We report the description of a laser spectrometer based on difference-frequency generation. As a pump laser, we used a master-slave diode laser configuration emitting at 785 nm, while for a signal laser, we used a diode-pumped Nd : YAG laser. The wavelength of the idler radiation is continuously tunable in the spectral region between 2.88 to 3.02 μm. In this range lie the ν1 fundamental vibrational symmetric stretching mode of water vapor and the relatively strong combination band ν1+ν3 of nitrous oxide that are both investigated in this work. We show that both molecules can be simultaneously detected by using a simple absorption scheme and by tuning the spectrometer frequency within few gigahertz. A systematic study of pressure broadening for a N2O line has been performed in presence of the main air constituents, i.e., nitrogen and oxygen. Finally, the estimation of the minimum detectable N2O concentration at 500 torr of nitrogen resulted in 2.6(2) ppmV with 0.9-m absorption path-length. [ABSTRACT FROM PUBLISHER]

In this paper we investigate the mid-infrared spectrum of the H216O molecule between 3367 and 3447 cm−1 to study the gas-collision-broadened linewidths. The coherent radiation used in this experiment is produced through difference frequency generation in a periodically poled lithium niobate crystal. The spectroscopic analysis has concerned nine H2O lines in the ν1 fundamental vibrational band. For these lines the self-, N2-, and O2-broadening coefficients are measured at room temperature. From these data, the widths due to air broadening are also determined. The experimental collisional broadening coefficients are compared with other experimental data and with theoretical calculations based on the Anderson–Tsao–Cornutte and Robert–Bonamy theories. Lineshape analysis is performed using both the standard Voigt profile and the Nelkin–Ghatak profile for the hard collision regime. For all the investigated lines the agreement between the Voigt profile and the measured profiles is found to be good. [Copyright &y& Elsevier]

We report the realisation of a laser spectrometer in the mid-infrared spectral region based on difference-frequency generation in a periodically poled LiNbO3 crystal. Tunable coherent radiation around 3 μm was produced by mixing a diode-pumped monolithic cw Nd-YAG laser and an injection-locked diode laser at 0.785 μm. High sensitivity N2O detection was demonstrated by observing pure absorption spectra of lines in the ν1+ν3 combination band. We estimate a minimum detectable pressure of pure N2O of 1×10−2 Pa with 0.9 m absorption path-length, corresponding to an absorbance of 3×10−4. Nitrous oxide was also detected in presence of O2, N2 and air. Collisional broadening coefficients for the P(33) line at 3447.678 per cm are reported for N2O&z.sbnd;N2 and N2O&z.sbnd;O2 mixtures. [ABSTRACT FROM AUTHOR]

We report the realization and characterization of a spectrometer based on difference frequency generation using a periodically poled lithium niobate crystal. As signal and pump lasers we used a diode-pumped Nd–YAG laser (λ=1.064 μm) and an extended cavity semiconductor diode laser (λ=0.785 μm), respectively. The mid-infrared coherent radiation was produced at 3 μm with a maximum power of about 160 nW obtained with 340 mW of signal and only 3.4 mW of pump. That corresponds to an efficiency of 0.01%/W cm, which is in good agreement with other data available in literature. The generated radiation around 3 μm has allowed us to study fundamental absorption bands of molecules of great atmospheric and physical interest such as water vapor and the hydroxyl free radical. In this work we report preliminary spectroscopic results concerning the ν1 541→652 H2O line at 2.968 μm. In particular, for this line we provide the first experimental estimation of self-, N2- and O2-broadening coefficients. [Copyright &y& Elsevier]

Autoregulatory mechanisms affecting serotonin [5-hydroxytryptamine (5-HT)] release and synthesis during the early period of development were investigated in dissociated cell cultures raised from embryonic rostral rat rhombencephalon. The presence of 5-HT1A and 5-HT1B receptors in serotoninergic neurons was assessed using binding assays. The involvement of 5-HT1A and 5-HT1B receptors in the control of the synthesis and release of [3H]5-HT was studied using biochemical approaches with several serotoninergic receptor ligands. A mean decrease of 30% in [3H]5-HT synthesis and release was observed in the presence of 5-HT (10-8 M), the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), the 5HT1B/1A agonist 5-methoxy-3-(1,2,5,6-tetrahydro-4-pyridinyl)-1H-indole (RU 24969), the 5-HT1B agonist 3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo[3,2-b]pyrid-5-one (CP-93, 129), and the 5-HT1D/1B agonist sumatriptan. Inhibition of 5-HT synthesis and release induced by 8-OH-DPAT was blocked by chiral N-tert-butyl-3-[1-[1-(2-methoxy)phenyl]piperazinyl]-1-phenylpropionamide dihydrochloride quaternary-hydrate (WAY 100135) (10-7 M) or methyl 4-[4-[4-(1,1,3-trioxo-2H-1,2-benzoisothiazol-2-yl)butyl]-1-piperazinyl]-1H-indole-2-carboxylate (SDZ 216-525) (10-7 M), and that of CP-93, 129 was blocked by methiothepin (10-7 M). Paradoxically, extracellular levels of [3H]5-HT increased in the presence of 8-OH-DPAT and RU 24969 at 10-6 M. 5-HT uptake experiments showed that these two agonists interacted with the 5-HT transporter. 5-HT1 binding sites (620 fmol/mg of protein) and 5-HT1A (482 fmol/mg of protein) and 5-HT1B (127 fmol/mg of protein) receptors were detected in 12-day in vitro cell cultures. Experiments carried out with tetrodotoxin suggested that 5-HT1A receptors are located on nerve cell bodies, whereas 5-HT1B receptors are located on the nerve terminals. We concluded that autoregulatory mechanisms involving 5-HT1A and 5-HT1B autoreceptors are functionally mature in cells from rostral raphe nuclei during the early period of development. [ABSTRACT FROM AUTHOR]

A correction to the article "Progression of Nailfold Capillaroscopic Patterns and Correlation With Organ Involvement in Systemic Sclerosis: A 12 Year Study" by A. Sulli and colleagues is presented.