Tunable Fano Resonances in Mid-Infrared Waveguide-Coupled Otto Configuration

A planar silicon carbide/dielectric multilayer structure is investigated in Otto geometry, where surface phonon polaritons and planar waveguide mode can be coupled to realize Fano resonances under transverse magnetic polarization. The resonance coupling is analytically demonstrated using the coupled harmonic oscillator model and numerically presented through rigorous coupled-wave analysis calculations, which shows that the coupling strength between different resonances and the resonant wavelength matching condition plays an important role in the bandwidth and position of the Fano resonance (FR); the magnetic field distribution was also shown to explain the origin of FRs qualitatively.

     

The application of the acoustic spectrophonometer to biomolecular spectrometry: a step towards acoustic "fingerprinting"

A tunable acoustic biosensor for investigating the properties of biomolecules at the solid-liquid interfaces is described. In its current, format the device can be tuned to frequencies between 6.5 MHz and 1.1 GHz in order to provide a unique detection feature: a variable evanescent wave thickness at the sensor surface. The key to its successful implementation required the careful selection of antennae designs that could induce shear acoustic waves at the solid-liquid interface. This non-contact format makes it possible to recover resonant shear acoustic waves over 100 different harmonic frequencies as a result of the electrical characteristics of the spiral coil. For testing this multifrequency sensing concept the surface of a quartz disc was exposed to solutions of immunoglobulin G (IgG) to form an adsorbed monolayer, whence protein A and IgG were added again in order to form multilayers. Spectra at frequencies between 6 and 600 MHz were generated for each successive layer and revealed two characteristic phases: an initial phase at the low megahertz frequencies consistent with the conventional Sauerbrey relation, and a possible additional phase towards the high megahertz to gigahertz frequencies, that we believe relates to the structure of the biomolecular film. This two-phase behaviour evident from differences between high and low frequencies, rather than from any distinct frequency transition, was anticipated from the reduction in evanescent wave thickness down to nanometre dimensions, and thin film resonance phenomena that are known to occur for film and fluid systems. These measurements suggested that the single element acoustic biosensor we present here may form the basis from which to generate acoustic molecular spectra, or "acoustic fingerprints", in a manner akin to optical spectroscopy.     

Possible mechanism for the influence of weak magnetic fields on biological systems

A physical mechanism is suggested for a resonant interaction of weak magnetic fields with biological systems. An ion inside a Ca(2+)-binding protein is approximated by a charged oscillator. A shift in the probability of ion transition between different vibrational energy levels occurs when a combination of static and alternating magnetic fields is applied. This in turn affects the interaction of the ion with the surrounding ligands. The effect reaches its maximum when the frequency of the alternating field is equal to the cyclotron frequency of this ion or to some of its harmonics or sub-harmonics. A resonant response of the biosystem to the magnetic field results. The proposed theory permits a quantitative explanation for the main characteristics of experimentally observed effects.     

Micro-machined piezoelectric membrane-based immunosensor array

This paper reports a micro-machined piezoelectric membrane-based biosensor array for immunoassay. Goat immunoglobulin G (IgG) and HBsAg were immobilized as the probe molecules on the square piezoelectric membranes of the sensors that have dimensions of 3.5 microm x 500 microm x 500 microm. Due to the mass sensitive nature of these sensors, their resonant frequencies were depressed after the anti-goat IgG or anti-HBsAg was captured by the goat IgG or HBsAg. The resonant frequencies of the sensors were measured by an impedance analyzer. The experimental results demonstrate that the measured frequency change varies from 100 to 700 Hz, and the mass sensitivity of the device is estimated to be about 6.25 Hz/ng. A near linear relationship between the frequency change and the concentration of goat IgG was obtained, and the mass of the attached anti-goat IgG was calculated. The preliminary results discussed in this work indicate that the micro-machined piezoelectric membrane-based biosensor has a potential application as an immunosensor.     

Coupling of a slow and a fast oscillator can generate bursting

A general mechanism underlying bursting is proposed and described. It consists of two coupled nonlinear oscillators with different frequencies, where the slower oscillator alternatively switches the faster one on and off. This mechanism is shown to work in an extended Bonhoefer-van der Pol oscillator as well as in a modified version of the Hodgkin-Huxley equations.     

Conversion of fast magnetosonic waves into Alfvén waves in a longitudinally inhomogeneous gyrotropic plasma

A model is considered of the conversion of running fast magnetosonic waves into Alfvén waves in a longitudinally inhomogeneous gyrotropic plasma in a magnetic field with open field lines. The set of equations for the amplitudes of the interacting modes is obtained and investigated in the Wentzel-Kramers-Brillouin approximation. In the synchronization region, where the wave vectors of the two modes approach one another, most of the energy of fast magnetosonic waves is converted into the Alfvén wave energy. The phases of the waves are matched in such a way that the phase difference is most favorable for wave conversion. The fact that the conversion is resonant in nature may help to explain the onset of quasi-monochromatic signals in the Earth’s magnetosphere and in the magnetospheres of the giant planets.     

The complex circadian system of Gonyaulax polyedra

Circadian oscillations are a fundamental biological property from bacteria to humans. The molecular mechanisms which produce a ca 24-h rhythmicity are still unknown but it has become clear that they are part of the biochemical machinery of the single cell. The cellular circadian system can be favorably studied in single-cell organisms such as the dinoflagellate Gonyaulax polyedra . The complexity of this circadian model system, which consists of at least two circadian oscillators, receives light via two input systems with different spectral sensitivities, and has several feed–back loops between the central oscillator(s) and the environment, is described here.     

Conformational chemistry of surface-attached calmodulin detected by acoustic shear wave propagation

A thickness shear-mode acoustic wave device, operated in a flow-through format, was used to detect the binding of ions or peptides to surface-attached calmodulin. On-line surface attachment of the protein was achieved by immobilisation of the biotinylated molecule via a neutravidin-biotin linkage onto the surface of the gold electrode of the detector. The interaction between calmodulin, and calcium and magnesium ions induced an increase in resonant frequency and a decrease in motional resistance, which were reversible on washing with buffer. Interestingly, the changes in resonant frequency and motional resistance induced by the binding were opposite to the normal operation of the detector. The response was interpreted as a decrease in surface coupling (partial slip at the liquid/solid interface) instigated by exposure of hydrophobic domains on the protein, and an increase in the thickness, and hence effective wavelength, of the acoustic device, corresponding to an increase in the length of calmodulin by 1.5 A. This result is consistent with the literature value of 4 A. In addition, the interaction of the protein with peptide together with calcium ions was detected successfully, despite the relatively low molecular mass of the 2-kDa peptide. These results confirm the potential of acoustic wave physics for the detection of changes in the conformational chemistry of monolayer of biochemical macromolecules at the solid/liquid interface.     

Elucidating the ticking of an in vitro circadian clockwork

A biochemical oscillator can be reconstituted in vitro with three purified proteins, that displays the salient properties of circadian (daily) rhythms, including self-sustained 24-h periodicity that is temperature compensated. We analyze the biochemical basis of this oscillator by quantifying the time-dependent interactions of the three proteins (KaiA, KaiB, and KaiC) by electron microscopy and native gel electrophoresis to elucidate the timing of the formation of complexes among the Kai proteins. The data are used to derive a dynamic model for the in vitro oscillator that accurately reproduces the rhythms of KaiABC complexes and of KaiC phosphorylation, and is consistent with biophysical observations of individual Kai protein interactions. We use fluorescence resonance energy transfer (FRET) to confirm that monomer exchange among KaiC hexamers occurs. The model demonstrates that the function of this monomer exchange may be to maintain synchrony among the KaiC hexamers in the reaction, thereby sustaining a high-amplitude oscillation. Finally, we apply the first perturbation analyses of an in vitro oscillator by using temperature pulses to reset the phase of the KaiABC oscillator, thereby testing the resetting characteristics of this unique circadian oscillator. This study analyzes a circadian clockwork to an unprecedented level of molecular detail.     

Analysis and purification of IgG4 bispecific antibodies by a mixed-mode chromatography

Therapeutic non-hinge-modified IgG4 molecules form bispecific hybrid antibodies with endogenous human IgG4 molecules via a process known as Fab-arm exchange (or called half molecule exchange). Analysis of the bispecific hybrids is critical for studies of half molecule exchange. A number of analytical methods are available to detect IgG4 hybrids. These methods mostly necessitate labeling or alteration of the model IgG4 molecules, or rely on time-consuming immunoassays and mass spectrometry. In addition, these methods do not allow isolation of hybrid antibodies. We report here the only analytical method to date that relies on chromatographic separation for detection of hybrids formed from intact antibodies in their native forms using pembrolizumab as an example. This method employs a mixed-mode chromatography using a Sepax Zenix SEC-300 column to separate a bispecific hybrid from the parental antibodies. The simultaneous quantitative monitoring of the newly formed hybrid and parental antibodies was achieved by UV absorption and/or protein fluorescence. The bispecific hybrid antibodies were purified with the same method for further biochemical characterization. The method has allowed monitoring of half molecule exchange between a human serum IgG4 and a tested IgG4 molecule, and has been implemented for the analysis of in vitro as well as in vivo samples.     

TRPM channels are required for rhythmicity in the ultradian defecation rhythm of <Emphasis Type="Italic">C. elegans</Emphasis>

Background  

Ultradian rhythms, rhythms with a period of less than 24 hours, are a widespread and fundamental aspect of life. The mechanisms underlying the control of such rhythms remain only partially understood. Defecation in C. elegans is a very tightly controlled rhythmic process. Underlying the defecation motor programme is an oscillator which functions in the intestinal cells of the animal. This mechanism includes periodic calcium release and subsequent intercellular calcium waves which in turn regulate the muscle contractions that make up the defecation motor programme. Here we investigate the role of TRPM cation channels in this process.     

Long-period waves in an island reef harbor

Surface waves of periods between 2 and 600 min are of common occurrence in coastal embayments and harbors. These long-period waves may affect water circulation and exchange, may cause moored ships to range, and may contribute to extreme low or high water levels. Long-period waves, excluding those caused by wave groups, are generally unimportant unless they coincide with a harbor resonance. Studies of harbor resonance are reviewed. Data for Seeadler Harbour, Manus Island are presented, and it is shown that long waves of well-defined periods occur in bursts of three to seven waves every few days during the monsoon season. Some of these bursts match abrupt changes in wind stress, but others cannot be explained by this mechanism. Through spectral and frequency-time analyses, the principal long waves present are identified. Of the five long waves present, three are shown to be resonant oscillations whereas an oceanic source is postulated for the other two. Long waves at the fundamental period of seiching of reef or island lagoons may generate currents and mass flows of water as great as the tides, and may have a significant influence on lagoon flushing and reef entrance sediment transport.     

A novel distributed swarm control strategy based on coupled signal oscillators

The miniaturization of microrobots is accompanied by limitations of signaling, sensing and agility. Control of a swarm of simple microrobots has to cope with such constraints in a way which still guarantees the accomplishment of a task. A recently proposed communication method, which is based on the coupling of signal oscillators of individual agents [13], may provide a basis for a distributed control of a simulated swarm of simple microrobots (similar to I-Swarm microrobots) engaged in a cleaning scenario. This self-organized communication method was biologically inspired from males of chorusing insects which are known for the rapid synchronization of their acoustic signals in a chorus. Signal oscillator properties were used to generate waves of synchronized signaling (s-waves) among a swarm of agents. In a simulation of a cleaning scenario, agents on the dump initiated concentrically spreading s-waves by shortening their intrinsic signal period. Dirt-carrying agents localized the dump by heading against the wave front. After optimization of certain control parameters the properties of this distributed control strategy were investigated in different variants of a cleaning scenario. These include a second dump, obstacles, different agent densities, agent drop-out and a second signal oscillator.     

Pertussis antibody levels in infants immunized with an acellular pertussis component vaccine, measured using whole-cell pertussis ELISA

A commercially available whole-cell pertussis IgG ELISA was used to test the response of 137 2-month-old infants to immunization with a trivalent acellular pertussis vaccine. The pre-immunization geometric mean (GM) IgG index was 6.96 (95% confidence interval (CI) 5.88-8.04) and the postimmunization GM index was 13.16 (95% CI 12. 20-14.11), P < 0.001. Eighty percent of subjects (110/137) had a significant 1.5-fold increase of pertussis IgG index (97/137, 71%) or a postimmunization IgG index > 10 (93/137, 68%). In single antigen ELISA, 83% showed at least a fourfold increase in pertussis toxin-specific IgG (PT-IgG) and 91% showed an increase in IgG specific for filamentous haemagglutinin (FHA-IgG). Four percent had high pre- immunization antibody levels (index > 20), likely to reflect recent maternal exposure to pertussis. This correlated with a smaller increase in pertussis IgG index. A decline in pertussis IgG index postimmunization occurred in 17/24 infants (71%) whose pre-immunization IgG index was > 10. This postimmunization pertussis IgG index was not significantly different to that of infants with a low pre-immunization index. A similar trend was noted with PT-IgG and FHA-IgG results. The whole-cell ELISA can detect a response to acellular pertussis vaccination in most infants if both antibody index and degree of seroconversion are calculated and at least one criterion is satisfied.     

Sensitive assay to detect thyroid stimulating antibody (TSAb) in the presence of thyroid stimulation blocking antibody (TSBAb) in serum.

The detection of thyroid stimulating antibody (TSAb) activity in the presence of thyroid stimulation blocking antibody (TSBAb) in Graves' serum is difficult because TSBAb blocks TSAb activity. We recently demonstrated that polyethylene glycol (PEG) augments TSAb activity in porcine thyroid cells (PTC) assay. This PEG-induced augmentation makes it possible to develop a sensitive assay to detect TSAb in the presence of TSBAb. We studied the effects of PEG on TSAb- and TSBAb-activities in PTC using 4 different preparations of the samples; (1) crude IgG using PEG 22.5% precipitated fraction (PF) from Graves' serum (0.2 ml), (2) crude IgG using PEG 12.5% PF, (3) serum (50 microl), and (4) serum (50 microl) in the presence of 5% PEG (final). When the effects of PEG on TSAb activity using crude IgG were examined, PEG 22.5% PF showed significantly higher TSAb activity than PEG 12.5% PF as reported previously. The augmentative effect of PEG on TSAb activity was also observed by the addition of 5% PEG to serum. We also demonstrated that PEG augmented TSAb-activities even in TSBAb-positive serum by two methods (crude IgG using PEG 22.5% PF and the addition of 5% PEG to serum). TSBAb activities were expressed by two calculation methods (A= [1 - (a - b)/(c - d) x 100] and B = [1 - (a - d)/(c - d) x 100], where a is cAMP produced in the presence of bTSH and patient's IgG, b is cAMP produced in the presence of patient's IgG, c is cAMP produced in the presence of bTSH and normal IgG, and d is cAMP produced in the presence of normal IgG). In the presence of TSAb, the values of A method were always higher than those of B method, since TSAb stimulated cAMP synthesis. We have developed two sensitive methods to detect TSAb even in the presence of TSBAb in serum using PEG; 1) incubation of crude IgG using PEG 22.5% PF from serum (0.2 ml), and 2) co-incubation of 5 % PEG with test serum (50 microl).     

Generation of ion-acoustic and magnetoacoustic waves in an RF helicon discharge

A study is made of the generation of ion-acoustic and magnetoacoustic waves in a discharge excited in an external magnetic field by an electromagnetic wave in the whistler frequency range (ω_LH ? ω ? ω_He, where ω_LH = $\sqrt {\omega _{He} \omega _{Hi} } $ and ω_He and ω_Hi are the electron and ion gyrofrequencies, respectively). The excitation of acoustic waves is attributed to the decay of a high-frequency hybrid mode forming a plasma waveguide into low-frequency acoustic waves and new high-frequency waves that satisfy both the decay conditions and the waveguide dispersion relations. The excitation of acoustic waves is resonant in character because the conditions for the generation of waveguide modes and for the occurrence of the corresponding nonlinear wave processes should be satisfied simultaneously. An unexpected effect is the generation of magnetoacoustic waves by whistlers. A diagnostic technique is proposed that allows one to determine the thermal electron velocity by analyzing decay conditions and dispersion relations for waves in the discharge channel.     

Characterisation of a label‐free biosensor based on long period grating

Optical fibre gratings, especially long period gratings, have been recently proposed as optical devices for biochemical sensing. A biochemical interaction along the grating portion induces a refractive index change and hence a change in the fiber transmission spectrum. This provides an alternative methodology with respect to other label‐free optical approaches, such as surface plasmon resonance, interferometric configurations and optical resonators. The fibre biofunctionalization has been carried out by means of a novel chemistry using Eudragit L100 copolymer as opposed to the commonly used silanization procedure. Antigen‐antibody interaction has been analysed by means of an IgG/anti‐IgG bioassay. The biosensor was fully characterised, monitoring the kinetics during the antibody immobilization and the antigen interaction and achieving the calibration curve of the assay. A comparison of the biosensor performance was made by using two different long period gratings with distinct periods. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Frequency response analysis of oxygen evolution by algae

Common photosynthetic organisms were excited with steps, pulses, or sine waves of light as dissolved oxygen was measured with a microelectrode. Frequency response analysis revealed two fundamental time constants of 4 and 16 s. These time constants are assigned provisionally to processes for mass transfer and to the biochemical reactions of reduction of carbon dioxide.     

Theory of the ICR heating of a plasma column: Methodological note

A set of wave equations is derived that describes electromagnetic waves at frequencies on the order of the ion gyrofrequency in a plasma column with an arbitrary electron temperature. This set takes into account, in particular, the resonant interaction of electrons with waves in the transit-time magnetic pumping regime. The effect of the amplification of the electromagnetic fields of current-carrying antennas by the plasma is analyzed. The evolution of the fields with an increase of plasma density from a zero value (vacuum) is considered. The main parameters are determined for minority ion cyclotron resonance heating in the planned EPSILON system.     

Oscillator decomposition of infant fNIRS data

The functional near-infrared spectroscopy (fNIRS) can detect hemodynamic responses in the brain and the data consist of bivariate time series of oxygenated hemoglobin (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb) on each channel. In this study, we investigate oscillatory changes in infant fNIRS signals by using the oscillator decompisition method (OSC-DECOMP), which is a statistical method for extracting oscillators from time series data based on Gaussian linear state space models. OSC-DECOMP provides a natural decomposition of fNIRS data into oscillation components in a data-driven manner and does not require the arbitrary selection of band-pass filters. We analyzed 18-ch fNIRS data (3 minutes) acquired from 21 sleeping 3-month-old infants. Five to seven oscillators were extracted on most channels, and their frequency distribution had three peaks in the vicinity of 0.01-0.1 Hz, 1.6-2.4 Hz and 3.6-4.4 Hz. The first peak was considered to reflect hemodynamic changes in response to the brain activity, and the phase difference between oxy-Hb and deoxy-Hb for the associated oscillators was at approximately 230 degrees. The second peak was attributed to cardiac pulse waves and mirroring noise. Although these oscillators have close frequencies, OSC-DECOMP can separate them through estimating their different projection patterns on oxy-Hb and deoxy-Hb. The third peak was regarded as the harmonic of the second peak. By comparing the Akaike Information Criterion (AIC) of two state space models, we determined that the time series of oxy-Hb and deoxy-Hb on each channel originate from common oscillatory activity. We also utilized the result of OSC-DECOMP to investigate the frequency-specific functional connectivity. Whereas the brain oscillator exhibited functional connectivity, the pulse waves and mirroring noise oscillators showed spatially homogeneous and independent changes. OSC-DECOMP is a promising tool for data-driven extraction of oscillation components from biological time series data.