Maximum Frequency Shift Research Articles

プラズマ有機薄膜における吸着水の脱離現象を利用した揮発性有機ガスプルームの識別

The sensing capabilities of plasma organic films for gas plumes of volatile organic compounds (VOCs) have been examined by the newly developed measuring system using the VOC-impregnated beads. The humidity and flow rate of the system could be kept constant by means of the temperature-constant bath. Response curves to the VOC plumes are characterized by the maximum and minimum frequency shifts of quartz crystal resonator coated with plasma organic film. Using both parameters, the principal component analysis has shown that the score plot was discriminative between normal hydrocarbons, alcohols, and ketones. Each components in the same functional groups are enough separated by carbon chain length, using the humid air as the carrier gas. The negative shifts of response curves should play an important role in the discrimination of VOCs. This characteristic negative shifts are thought to be induced by desorption of the water adsorbates, which should contain the amphiphilic VOC, in the vicinity of the film surface.

The interference head wave and its parametric dependence

The interference head wave that can exist in the presence of a sound-speed gradient in the sediment, is a precursor arrival representing a transition between the first-order head wave and the zeroth-order refracted wave. Using a parabolic equation (PE) simulation, Choi and Dahl [J. Acoust. Soc. Am. 119, 2660–2668 (2006)] showed how the small shift in the dominant frequency of the interference head wave behaves as a function of the nondimensional parameter zeta, which itself is a function of center frequency, gradient, and range. For example, it was shown that the maximum frequency shift occurring in the vicinity of zeta equals 2. In this work, we investigate the amplitude and additional spectral properties of the interference head wave and analyze the cause of the frequency shift phenomenon using the ray theory. The limitation on the application of ray method also will be discussed. Finally, the conclusion will be verified by the time-dependent simulation using the RAM PE algorithm. [Work supported by the ONR.]

X-ray Structures and Dipole Moments of Tropones Annulated with Furan, Benzene, and Oxepin

Abstract The precise X-ray structures of furo[3,4-d]tropone (2), 2,4-dimethyl-8H-3-oxaheptalen-8-one (5), and 4,5-benzotropone (6) were determined. Their tropone rings show definite bond alternation and nearly planar conformation, though slightly boat-shaped like polycyclic tropone. The ground-state dipole moments of 2, 5, and 6, and also 8H-3-oxaheptalen-8-one (3) and 2-methyl-8H-3-oxaheptalen-8-one (4) were measured in benzene at 25 °C. Analyses of the ground-state dipole moments by means of ab initio calculations demonstrate that the polar structures of 2 and 6 having an annulated aromatic ring are based on the local dipoles of penta-1,4-dien-3-one and the induced dipole of the annulated ring, whereas those of 3 and 5 are based not only on the local dipoles but also on the partial intramolecular CT interaction from the olefinic oxepin ring to the pentadienone moiety. According to the McRae equation, the dipole moments of the two lowest excited states of 2, 3, 5, and 6 were evaluated by using the frequency shifts of the absorption maxima in a number of polar and nonpolar solvents. They are all oriented in the same direction as that of the ground state, but are greater in magnitude.

Electrochemical quartz crystal impedance study on the electrodeposition of LiOH onto a gold electrode in acetonitrile containing LiClO4· 3H2O and its application in preparing a Pt-plated porous polypyrrole thin film for the catalytic electrooxidation of methanol

Abstract The electrochemical quartz crystal impedance (EQCI) analysis method was used for the first time to quantitatively examine the precipitation of LiOH onto a gold electrode at potentials negative to ca. −0.7 V vs. SCE during the cathodic sweep reduction of dissolved oxygen and coexisting water in acetonitrile (ACN) containing LiClO 4 · 3H 2 O, as a result of the poor solubility of electrogenerated LiOH in the ACN medium. The suggested LiOH-precipitation mechanism was supported by comparative experiments conducted in ACN containing NaClO 4 · 2H 2 O (or tetrabutyl ammonium chloride/bromide), since large EQCI responses implying a similar precipitation of electrogenerated NaOH were also obtained in the NaClO 4 · 2H 2 O system, but the quartz crystal impedance responses were negligibly small in the two systems of quarternary ammonium salts. The effects of concentrations of LiClO 4 · 3H 2 O and the foreign water added in ACN on the EQCI responses were individually examined, and the maximum frequency shift induced by the LiOH precipitation was found to be as large as about −5 kHz. The cyclic voltammetric growth of polypyrrole (PPY) films at several Au electrodes in fresh ACN solutions of 1 mol L −1 pyrrole + 0.1 mol L −1 LiClO 4 · 3H 2 O were comparatively conducted over three potential-sweep ranges, 0 to 0.85 (A, PPY A ), −1.6 to 0.85 (B, PPY B ) and −2.0 to 0.85 V vs. SCE, respectively, giving that the accompanying precipitation of LiOH notably influenced the polymer growth and porosity. Compared with the normal PPY film (PPY A ), the PPY B after removing the LiOH precipitate formed during the cyclic voltammetric growth of the polymer was more porous, as examined by EQCI and SEM techniques, which resulted in a larger Pt dispersion when Pt particles were electrodeposited on the PPY B /Au electrode in acidic chloroplatinic solution and a higher electrocatalytic activity toward methanol oxidation in aqueous H 2 SO 4 . The proposed protocol of increasing the PPY porosity by introducing removable electrodeposits during PPY’s growth may be of some general interests for other polymers using other removable precipitates.

A spectral vibration detection system based on tunable micromechanical resonators

We present a frequency selective vibration detection system based on tunable micromechanical resonators for the frequency range 1–10 kHz. The Single Crystal Reactive Etching and Metallization (SCREAM)-fabricated sensor structure consists of an array of eight resonators with stepped base frequencies between 2.8 and 10.2 kHz. The resonators provide a resonance frequency tuning capability by electrostatic forces to set the detection frequency to the desired value. Experimental results of the fabricated resonator arrays are presented. A maximum tuning voltage of 35 V is required for continuous resonance frequency tuning from 1 to 10 kHz. The amplitude range of the resonators amounts to 10 μm. Over the whole amplitude range, a maximum resonance frequency shift of 0.7% was measured. An increase of ambient temperature from 30 to 150 °C results in a small resonance shift of 0.5% and to an increase of resonance peak bandwidth of 23%. The sensor structure is part of a vibration detection system, which is completed with analogue and digital circuitry. Test measurements with the system demonstrate its functionality and applicability in an industrial environment.

Bis(Guanidinium) Zirconium bis(Nitrilotriacetate) Hydrate, [C(NH2)3]2Zr[N(CH2COO)3]2 � H2O - A New Crystal for Raman Laser Converters

High-order stimulated Raman scattering (SRS) in crystalline acentric bis(guanidinium) zirconium bis(nitrilotriacetate) hydrate, [C(NH2)3]2Zr[N(CH2COO)3]2 · H2O, was observed under picosecond laser excitation. All scattering components were identified and put in relation with the SRS-active vibration modes (ωSRS1 ≈ 1008 cm—1 and ωSRS2 ≈ 2940 cm—1) of this crystal. The investigated new metal-organic single crystal is classified as a promising χ(3) active medium for Raman laser converters providing a maximum frequency shift among all known χ(3) solid-state materials used in experimental physics and laser technique.

Quantification of the Raf-C1 interaction with solid-supported bilayers.

By use of the quartz crystal microbalance technique, the interaction of the Raf-Ras binding domain (RafRBD) and the cysteine-rich domain Raf-C1 with lipids was quantified by using solid-supported bilayers immobilized on gold electrodes deposited on 5 MHz quartz plates. Solid-supported lipid bilayers were composed of an initial octanethiol monolayer chemisorbed on gold and a physisorbed phospholipid monolayer varying in its lipid composition as the outermost layer. The integrity of bilayer preparation was monitored by impedance spectroscopy. For binding experiments, a protein construct comprising the RafRBD and Raf-C1 linked to the maltose binding protein and a His tag, termed MBP-Raf-C1, was used. Dissociation constants and rate constants of the association and dissociation were obtained for various 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/1,2-dimyristoyl-sn-glycero-3-phosphoserine (DMPS) lipid mixtures. Independently of the phosphatidylserine (PS) content, the dissociation constants were in the order of 5x10(-7) M, while the on-rate constants were in the range of 2x10(3) (M s)(-1) and the off-rate constants in the range of 1x10(-3) s(-1). The maximum frequency shift increased significantly with increasing amounts of DMPS; this indicates that this negatively charged lipid is the primary binding site for MBP-Raf-C1. Exchange of DMPS for 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) did not alter the thermodynamics and kinetics of protein binding, which implies that the protein interaction is mainly electrostatically driven. Scanning force microscopy (SFM) was employed to render protein adsorption visible and to confirm the assumption of a protein monolayer on the lipid layer. SFM images clearly revealed that the protein binds preferentially, but not solely, to negatively charged phosphatidylserine headgroups. We hypothesize that PS-enriched domains are initial binding sites with high affinity for Raf-C1, but that lateral interactions may account for protein domain growth.

Intensity clamping of a femtosecond laser pulse in condensed matter

We measured the supercontinuum spectrum of an intense femtosecond Ti:sapphire laser pulse propagating in condensed optical media (water, chloroform and glass), at various input laser energies, below and above the threshold for filamentation of the laser pulse. It is found that the maximum positive frequency shift of the supercontinuum spectrum remains constant at pulse energies that generate single and mutiple filamentation. The constant shift is due to clamping of the peak intensity inside the filaments.

On the Possibility of a Considerable Frequency Shift for ``Whispering Gallery'' Waves with the Use of Sound

An analysis of the propagation of “whispering gallery” waves in a dynamic cavity was carried out. The cavity was formed by a tapered quartz rod and the plane interface of two regions of the rod with different refractive indexes moving along its axis. The maximum frequency shift of light in such a cavity was shown to be determined by its Q factor and an attainable jump Δn. The possibility of using acoustic waves to realize the dynamic cavity was considered.

EMPIRICAL ESTIMATE OF p-MODE FREQUENCY SHIFT FOR SOLAR CYCLE 23

We have obtained empirical relations between the p-mode frequency shift and the change in solar activity indices. The empirical relations are determined on the basis of frequencies obtained from BBSO and GONG stations during solar cycle 22. These relations are applied to estimate the change in mean frequency for the cycle 21 and 23. A remarkable agreement between the calculated and observed frequency shifts for the ascending phase of cycle 23 indicates that the derived relations are independent of epoch and do not change significantly from cycle to cycle. We propose that these relations could be used to estimate the shift in p-mode frequencies for past, present and future solar activity cycles, if the solar activity index is known. The maximum frequency shift for cycle 23 is estimated to be 265 \pm 90 nHz corresponding to the predicted maximum smoothed sunspot number 118.1 \pm 35.

Real-time bulk acoustic wave studies of the inhibition behavior of mercaptobenzothiazole on copper

The corrosion inhibition behavior of mercaptobenzothiazole (MBT) on copper in 0.1 M H 2SO 4 solutions was investigated by bulk acoustic wave (BAW) sensor under open-circuit condition in this paper. The growth process of Cu-MBT complex film was monitored by the BAW sensor and the frequency shift curves were acquired. The frequency shift curves were fitted with a proposed model and the maximum frequency shift and the apparent rate constant of film formation were obtained. The relations between them and the concentration of MBT indicated the inhibition ability of the Cu-MBT complex film. The synergistic effects of Br − and I − on the Cu-MBT complex film formation were also compared. It was found that the effect of I − was more obvious than that of Br − at the same concentration of MBT and the growth kinetics of Cu-MBT film changed with the concentration of KI.

Thiolated Salmonella antibody immobilization onto the gold surface of piezoelectric quartz crystal

An improved antibody-coated sensor system based on quartz crystal microbalance analysis on Salmonella spp. was developed making use of thiolated antibody immobilization onto one gold electrode of the piezoelectric quartz crystal surface. The best results in sensitivity and stability were obtained with the thin layer of a thiol-cleavable, heterobifunctional cross-linker, sulfosuccinimidyl 6-[3-(2-pyridyldithio)propionamido]hexanoate (sulfo-LC-SPDP). The long bridge of this reagent could function as a spacer, facilitating antibody- Salmonella interaction on the gold electrode. After the addition of a S. typhimurium suspension into a reaction cell with 0.1 M sodium phosphate buffer, pH 7.2, the resonant frequency decreased conspicuously. The time required for maximum frequency shift was about 30∼90 min. Sensor response was observed for the microbial suspensions ranging from 9.9×10 5 to 1.8×10 8 CFU/ml.

Resonator frequency shift due to ultrasonically induced microparticle migration in an aqueous suspension: Observations and model for the maximum frequency shift

Aqueous suspensions of plastic and hollow-glass microspheres are subjected to the radiation pressure of an ultrasonic standing wave. It is well known that the particles are attracted to the pressure nodes of the standing wave for the particle and host properties considered. We demonstrated that the radiation pressure induced migration of particles leads to a significant shift in the resonant frequency of a suitably designed chamber. This shift is easily resolved with a phase-locked loop even if the particle volume fraction is as small as 0.001. For sufficient ultrasonic amplitudes, the shift is found to saturate at a limiting value. To approximate the limiting frequency shift, the principle of adiabatic invariance is first applied to the case of a single compressible sphere in a standing wave and then superposition is used to give the collective shift for the suspension. The measured limiting shifts are typically within 25% of the calculated value and this method may have application to the characterization of dilute suspensions since the shift is proportional to the volume fraction and to a material contrast factor. The applicability of adiabatic invariance is confirmed by comparing frequency shifts for certain cases of idealized particle spatial distributions with results based on transfer matrix eigenvalues combined with an effective-medium approximation.

Bulk Acoustic Wave Biological Detection of Cefotaxime Sodium

A bulk acoustic wave (BAW) impedance sensor has been applied to rapid determination of in vitro concentrations of cefotaxime sodium. The method based on the growth frequency curve of Proteus Morganii, inhibited by cefotaxime sodium, is continuously monitored by using a BAW impedance sensor. The growth kinetic parameter, e.g. asymptote or maximum frequency shift (AF, Hz), estimated by fitting a modified Gompertz model to the growth frequency curve, is proportional to the logarithm of antibiotic concentration. The proposed method exhibits a favourable response to 0.25 – 20.0 μg mL−1 cefotaxime sodium with a detection limit of 0.03 μg mL−1, and the recoveries range from 97.3 to 107.5% (n=9). The results are in good agreement with those obtained by the conventional disk diffusion test (DDT) method. The effects of temperature and pH on the determination are discussed and in vitro susceptibility to cefotaxime of the genus Proteus has been investigated in detail. On leave from Department of Mathematics, Physics and Mechanics, Changsha Railway University.

Wideband Tuning of a High-Pressure CO2 Laser by means of Intracavity Active Frequency Shift

Intracavity active frequency shift, a unique method of shifting the frequency of pulsed lasers, was applied to a high-pressure CO2 laser which has a continuous gain profile over a wide range of the spectrum. In order to extend the amount of frequency shift, the dependence of the maximum frequency shift on the laser gas pressure was investigated. As a result, it was found that the maximum frequency shift was limited by the gain duration time rather than by the gain bandwidth at a pressure of 8–10 atm. By shortening the cavity length, the maximum frequency shift of 9 GHz was obtained at a pressure of 8 atm. Then, the grating-mirror cavity was applied to demonstrate the frequency shift starting from each lasing line of the CO2 laser. According to numerical calculations, the maximum frequency shifts starting from most lasing lines of a multi-isotope cw CO2 laser can exceed 10 GHz, resulting in coverage of almost the entire gain spectrum in the high-pressure CO2 laser.

Quartz crystal microbalance investigation of the interaction of bacterial toxins with ganglioside containing solid supported membranes.

The binding of cholera toxin, tetanus toxin and pertussis toxin to ganglioside containing solid supported membranes has been investigated by quartz crystal microbalance measurements. The bilayers were prepared by fusion of phospholipid-vesicles on a hydrophobic monolayer of octanethiol chemisorbed on one gold electrode placed on the 5 MHz AT-cut quartz crystal. The ability of the gangliosides GM1, GM3, GD1a, GD1b, GT1b and asialo-GM1 to act as suitable receptors for the different toxins was tested by measuring the changes of quartz resonance frequencies. To obtain the binding constants of each ligand-receptor-couple Langmuir-isotherms were successfully fitted to the experimental adsorption isotherms. Cholera toxin shows a high affinity for GM1 (Ka = 1.8.10(8)M-1), a lower one for asialo-GM1 (Ka = 1.0.10(7)M-1) and no affinity for GM3. The C-fragment of tetanus toxin binds to ganglioside GD1a, GD1b and GT1b containing membranes with similar affinity (Ka approximately 10(6)M-1), while no binding was observed with GM3. Pertussis toxin binds to membranes containing the ganglioside GD1a with a binding constant of Ka = 1.6.10(6)M-1, but only if large amounts (40 mol%) of GD1a are present. The maximum frequency shift caused by the protein adsorption depends strongly on the molecular structure of the receptor. This is clearly demonstrated by an observed maximum frequency decrease of 99 Hz for the adsorption of the C-fragment of tetanus toxin to GD1b. In contrast to this large frequency decrease, which was unexpectedly high with respect to Sauerbrey's equation, implying pure mass loading, a maximum shift of only 28 Hz was detected after adsorption of the C-fragment of tetanus toxin to GD1a.

Flow pulsatility in the portal venous system: a study of Doppler sonography in healthy adults.

The purpose of our study was to describe Doppler sonography patterns of venous flow in the portal system of healthy subjects and to compare pulsatility of flow with subjects' body mass, degree of inspiration, and body position. Doppler signals from the main, right, and left portal veins; superior mesenteric vein; splenic vein; and inferior vena cava of 23 healthy adults were prospectively studied. Pulsatility of flow was quantified using an index of venous pulsatility (VPI = [maximum frequency shift-minimum frequency shift]/maximum frequency shift). Antegrade flow peak velocities were also related to ECG tracings the time between two R waves being divided into four equal parts for analysis. The caliber variations of the main portal vein and inferior vena cava were measured with M-mode sonography. Doppler tracings were obtained with subjects in supine and sitting positions and during mid and deep inspiration. The subjects' heights and weights were obtained and the body mass index calculated (weight/[height2]). In the portal vein, the VPI was 0.48 +/- 0.31 (mean +/- SD). Marked pulsatility of venous flow (VPI > 0.5) was found in 12 of 23 subjects. We found an inverse correlation between the VPI and the subjects' body mass index (r = -.76; p < .001). Portal vein pulsatility decreased significantly during sitting (p < .05) and deep inspiration (p < .01). The portal VPI was correlated with caliber variation of the inferior vena cava (r = .59; p < .05). In the portal venous system, antegrade flow peak velocities occurred most often during the third quarter of the cardiac cycle, particularly in the splenic vein. Doppler sonography shows pulsatile portal venous flow in healthy adults, especially in thin subjects. This pulsatility has an inverse correlation to body mass. The finding of a pulsatile portal vein needs to be interpreted in clinical context and does not necessarily imply dysfunction of the right side of the heart.

Prompt and precise frequency tuning of a transversely excited CO 2 laser by means of intracavity active frequency shift

We have investigated the tuning characteristics of an injection-locked transversely excited CO 2 laser by means of intracavity active frequency shift which utilized an acousto-optic modulator and a Pockels cell inside the cavity. The frequency shift from the externally injected frequency was finely controllable as a linear function of the gated time for integration of acousto-optic frequency shift. The maximum frequency shift obtained was 2 GHz, which was limited by the pressure-broadened gain bandwidth of the laser medium. A numerical model was used to verify the characteristics of this technique and to explore the possibility of further shifting the frequency by increasing the pressure of the laser medium. Single-longitudinal-mode oscillation was obtained when the gate pulsewidth was a multiple of the round-trip time in the subcavity. Finally, prompt response by electrical control of the lasing frequencies was demonstrated in alternative frequency switching operation.

Spectroscopic studies of the adsorption and reactions of chlorofluorocarbons (CFC-11 and CFC-12) and hydrochlorofluorocarbon (HCFC-22) on oxide surfaces

Raman and Fourier transform infrared (FT-IR) spectroscopy have been applied to a systematic investigation of the adsorption and decomposition of dichlorodifluoromethane (CCl 2F 2, CFC-12), fluorotrichloromethane (CCl 3F, CFC-11), chlorodifluoromethane (CHClF 2, HCFC-22) and molecular chlorine on oxide surfaces. Additionally, the effects of heating and ultraviolet photolysis of the CFC and HCFCs adsorbed on the oxide surfaces have been investigated. Spectral features for these species indicated a small wavenumber shift (1−6 cm −1) associated with the adsorbed phase. Some evidence, specifically the appearance of the Raman band at 507 cm −1, is presented to show that chlorine decomposition species are associated with these oxide surfaces. It was concluded that the new spectral feature (at ca. 507 cm −1) related with the decomposition of the CFC and HCFC molecules was an important indicator of the extent to which the reaction between the adsorbed CFC and HCFC and oxide surface has taken place. The extent of CFC-surface interaction has been quantified in terms of a maximum (Raman) frequency shift parameter ( A M). Wavenumber shifts suggest both cation-adsorbate and non-specific adsorption interactions are occurring in the internal channels of the zeolites. Slow decomposition of the adsorbed CFCs under ultraviolet-visible photolysis (at λ > 300 nm) and/or thermal treatment was observed spectroscopically. Using FT-IR spectroscopy, the formation of gas-phase products (CO, CO 2, HCl) both onyn photolysis and heating was evident. Results of these measurements are compared with the observed atmospheric reactivity of these compounds.

Resonator-based touch-sensitive probe

Abstract This paper presents a design of a simple low-cost resonator-based touch-sensitive probe. The design exploits the fact that when a stiff element (probe) oscillating near the resonance frequency comes into physical contact with the surface of another body (workpiece), the frequency of vibrational resonance of the probe changes depending on the latter's stiffness. This change can be detected by monitoring the variations in the phase shift between the probe driving force and the resulting strain, which consequently prompts the trigger signal. Standard phase-lock-loop oscillator circuitry is used to adjust the drive frequency to maintain a pre-set phase difference between the input and output signals, thus ensuring that the oscillator remains locked at the probe resonance frequency as contact takes place. A prototype probe has been designed and tested. The probe is excited to resonate at its fundamental frequency by employing piezoelectric drive and pick-up arrangements. The operating frequency of the probe is set at 25.179 kHz (second-mode frequency), which seems to be an adequate choice for excellent static and dynamic characteristics. The shift in the natural frequency as the contact force progresses follows a non-linear trend before it saturates. The maximum frequency shift measured is about 2 kHz, which corresponds to 140 mN contact force in the axial direction, whilst the minimum detectable trigger force is 3.8 mN.