Boron nitride nanotube-based biosensor for acetone detection: molecular structural mechanics-based simulation

In this study, an ultra-sensitive biosensor based on a single-walled boron nitride nanotube (SWBNNT) structure is proposed for acetone detection. The molecular structural mechanics-based simulation approach has been used to model the atomic structure of SWBNNTs. The cantilevered and bridged configurations of SWBNNT-based biosensor have been considered for analysis. The resonant frequency shift due to attached mass has been analysed for the mass-based detection of acetone molecules. The present simulation approach is validated by comparing obtained simulated results with the continuum mechanics-based analytical results. Along with detection of the attached molecule, identification of its intermediate landing position along the length of the nanotube is equally important for the better performance of the biosensor systems. The frequency shift-based analysis has been reported for the mass-based detection of acetone molecules as well as its intermediate landing position along the length of the nanotube. The resonant frequency shift variations of the higher order modes of vibration for both the considered configurations of SWBNNTs have been assistive for the identification of intermediate landing position of the acetone molecule. The proposed molecular structural mechanics-based simulation approach is found to be very effectual in terms of simulation of the real atomic structures of the nanotube. The proposed biosensor can achieve extremely high sensitivity at molecular level and it can be potentially used for real-time sensing capability for the acetone concentration for future health monitoring.     

Organ temperature measurement in a microwave oven by resonance frequency shift

An experimental system has been developed that can indirectly measure temperature in a high-intensity microwave field over a broad range of conditions. A RF amplifier connected closed-loop around a high Q cavity oscillates at one of the natural modes of the oven. A bandpass filter selects the mode of interest. As the frozen sample is thawed, an increase in dielectric constant occurs, decreasing the resonance frequency of the cavity. Calibration of the system is performed by measuring the frequency shift for samples whose temperatures are known, Rotation of samples during thawing often causes oscillations of the resonance frequency. These oscillations are generated by asymmetric sample properties and geometry, and hot spots developed during the thaw. Development of a method that would predict hot spot location from these resonance frequency oscillations and permit modulation of the magnetron or sample rotation to minimize thermal runaway is suggested.     

Raman and infrared studies of nucleosides at high pressures: II. Cytidine

Raman and mid-infrared (MIR) spectra have been recorded for crystalline cytidine at pressures up to 10 GPa at room temperature. Broadening and positive wavenumber shifts are observed for most of the Raman and MIR peaks with increasing pressure. However, some of the MIR peaks associated with hydrogen-stretching modes display a negative wavenumber shift as a result of charge transfer effects. Evidence of a phase transition near 4 GPa is presented and attributed to a change in the conformation of the five membered sugar ring.     

Pulse mode shear horizontal-surface acoustic wave (SH-SAW) system for liquid based sensing applications

In this work, we describe a novel pulse mode shear horizontal-surface acoustic wave (SH-SAW) polymer coated biosensor that monitors rapid changes in both amplitude and phase. The SH-SAW sensors were fabricated on 36 degrees rotated Y-cut X propagating lithium tantalate (36 YX.LT). The sensitivity of the device to both mass loading and visco-elastic effects may be increased by using a thin guiding layer of cross-linked polymer. Two acoustic modes are excited by the electrodes in this crystalline direction. Metallisation of the propagation path of the 36 YX.LT devices allows the two modes to be discriminated. Successive polymer coatings resulted in the observation of resonant conditions in both modes as the layer thickness was increased. Using the 36 YX.LT devices, we have investigated the application of a novel pulse mode system by sensing a sequence of deposition and removal of a biological layer consisting of vesicles of the phospholipid POPC. A continuous wave system was used to verify the accuracy of the pulse mode system by sensing a series of poly(ethylene glycol) (PEG) solutions. The data clearly demonstrates the ability of the 36 YX.LT pulse mode system to provide rapid measurements of both amplitude and phase for biosensing applications.     

Mutants of thermotaxis in Dictyostelium discoideum

Amoebae of Dictyostelium discoideum, strain HL50 were mutagenized with N-methyl-N′-nitro-N-nitrosoguanidine, cloned, allowed to form pseudoplasmodia and screened for aberrant positive and negative thermotaxis. Three types of mutants were found. Mutant HO428 exhibits only positive thermotaxis over the entire temperature range (no negative thermotaxis). HO596 and HO813 exhibit weakened positive thermotaxis and normal negative thermotaxis. The weakened positive thermotactic response results in a shift toward warmer temperatures in the transition temperature from negative to positive thermotaxis. Mutant HO209 exhibits weakened positive and negative thermotactic responses and has a transition temperature similar to the ‘wild type’ (HL50). The two types of mutants represented by HO428, HO596 and HO813 support the model that positive and negative thermotaxis have separate pathways for temperature sensing. The type of mutants which contains HO209 suggests that those two pathways converge at some point before the response.     

First results on label-free detection of DNA and protein molecules using a novel integrated sensor technology based on gravimetric detection principles

A novel integrated bio-sensor technology based on thin-film bulk acoustic wave resonators on silicon is presented and the feasibility of detecting DNA and protein molecules proofed. The detection principle of these sensors is label-free and relies on a resonance frequency shift caused by mass loading of an acoustic resonator, a principle very well known from quartz crystal micro balances. Integrated ZnO bulk acoustic wave resonators with resonance frequencies around 2 GHz have been fabricated, employing an acoustic mirror for isolation from the silicon substrate. DNA oligos have been thiol-coupled to the gold electrode by on-wafer dispensing. In a further step, samples have either been hybridised or alternatively a protein has been coupled to the receptor. The measurement results show the new bio-sensor being capable of both, detecting proteins as well as the DNA hybridisation without using a label. Due to the substantially higher oscillation frequency, these sensors already show much higher sensitivity and resolution comparable to quartz crystal micro balances. The potential for these sensors and sensors arrays as well as technological challenges will be discussed in detail.     

Mode Evolution and Transmission Suppression in a Perforated Ultrathin Metallic Film with a Triangular Array of Holes

We theoretically study the evolution of the resonant modes and the transmission suppression (TS) effect in a perforated ultrathin metallic film (PUMF) with a periodic triangular array of holes. It is found that the properties of different resonances change as the hole radius increases, and the non-monotonic shift of resonant frequency can be interpreted qualitatively from the electric field distribution other than the Fano model. In addition, we analyze the strong mode interaction phenomenon in PUMF. When the diameter of holes approaches to four fifths of the lattice constant, the coupling between dipolar resonance and decapolar resonance can lead to an anticrossing and a large Rabi splitting, which is not available in PUMFs with square lattice; the resulting hybrid modes can be ascribed to the quasi-inphase and quasi-antiphase interferences between dipolar resonance and decapolar resonance. By comparing the TS effect of different resonances under different hole radii, we conclude that although dipolar resonance, short-range surface plasmons, and hybrid modes can all contribute to TS effect; the prominent TS effect in our structure should be mainly caused by the collective dipolar resonance of the structure. These findings might be of interest for the future studies in PUMF-based structures and devices.     

Large Power Amplification in Magneto‐Mechano‐Electric Harvesters through Distributed Forcing

Energy harvesting from extremely low frequency magnetic fields using magneto‐mechano‐electric (MME) harvesters enables wireless power transfer for operating Internet of Things (IoT) devices. The MME harvesters are designed to resonate at a fixed frequency by absorbing AC magnetic fields through a composite cantilever comprising of piezoelectric and magnetostrictive materials, and a permanent magnetic tip mass. However, this harvester architecture limits power generation because volume of the magnetic end mass is closely coupled with the resonance frequency of the device structure. Here, a method is demonstrated for maintaining the resonance frequency of the MME harvesters under all operating conditions (e.g., 60 Hz, standard frequency of electricity in many countries) while simultaneously enhancing the output power generation. By distributing the magnetic mass over the beam, the output power of the harvester is significantly enhanced at a constant resonance frequency. The MME harvester with distributed forcing shows 280% improvement in the power generation compared with a traditional architecture. The generated power is shown to be sufficient to power eight different onboard sensors with wireless data transmission integrated on a drone. These results demonstrate the promise of MME energy harvesters for powering wireless communication and IoT sensors.     

A comparison of resonance tuning with positive versus negative sensory feedback

We used a computational model of rhythmic movement to analyze how the connectivity of sensory feedback affects the tuning of a closed-loop neuromechanical system to the mechanical resonant frequency (ω_r). Our model includes a Matsuoka half-center oscillator for a central pattern generator (CPG) and a linear, one-degree-of-freedom system for a mechanical component. Using both an open-loop frequency response analysis and closed-loop simulations, we compared resonance tuning with four different feedback configurations as the mechanical resonant frequency, feedback gain, and mechanical damping varied. The feedback configurations consisted of two negative and two positive feedback connectivity schemes. We found that with negative feedback, resonance tuning predominantly occurred when ω_r was higher than the CPG’s endogenous frequency (ω_CPG). In contrast, with the two positive feedback configurations, resonance tuning only occurred if ω_r was lower than ω_CPG. Moreover, the differences in resonance tuning between the two positive (negative) feedback configurations increased with increasing feedback gain and with decreasing mechanical damping. Our results indicate that resonance tuning can be achieved with positive feedback. Furthermore, we have shown that the feedback configuration affects the parameter space over which the endogenous frequency of the CPG or resonant frequency the mechanical dynamics dominates the frequency of a rhythmic movement.     

Comparison of a preliminary procedure for the general unknown screening of drugs and toxic compounds using a quadrupole-linear ion-trap mass spectrometer with a liquid chromatography-mass spectrometry reference technique

Liquid chromatography-tandem mass spectrometry (LC-MS-MS) might be a complement to GC-MS and HPLC-diode array detection for the general unknown screening (GUS) of drugs and toxic compounds, particularly when using information- or data-dependent acquisition (IDA or DDA), an auto-adaptive MS-MS product-ion scan mode where, at each unit time, the m/z ratios above a given intensity threshold are selected for fragmentation. A new quadrupole-linear ion-trap mass spectrometer (LC-QqQlinear ion-trap) was evaluated for GUS using IDA. For the first detection step (so-called "survey scan") the single quadrupole "enhanced" MS mode (EMS), where ions are accumulated then filtered in the Q3-linear ion-trap, was used. The so-called "enhanced" parent ion scan mode (EPI) used at two alternated fragmentation energies gave the best signal intensity and the best mass spectral information when adding mass spectra obtained in low and high fragmentation conditions, respectively, both in the positive (+20 and +50 eV) and negative (-15 and -40 eV) modes. Solid-phase extracts of serum spiked with eight test compounds (chosen for their retention times distributed along the 30-min long chromatogram and for ionising in both the positive and negative modes) were analysed in parallel with this LC-MS-MS technique and with a reference LC-MS method run on a single-quadrupole instrument where low and high in-source fragmentation conditions in the positive and the negative ion modes are alternated. A C(18), 5 microm (150 x 1 mm I.D.) column and a gradient elution of acetonitrile in pH 3, 2 mM ammonium formate, were used for both. Higher signal-to-noise ratios were obtained with the LC-QqQlinear ion-trap instrument than with the reference technique, resulting in mass spectra devoid of contaminant ions and at least as informative as the reconstructed single-MS spectra. After optimisation of the IDA intensity threshold for the detection of tiny chromatographic peaks in noise, five out of the eight compounds (milrinone, lorazepam, fluometuron, piretanide and warfarin) could be unambiguously identified at the concentration of 0.1 mg/l in serum, in the positive or negative modes, or in both, versus only two by LC-MS. All of them could be identified at 1 mg/l by both techniques. These preliminary results show that the sensitivity and mass structural information brought by this new LC-QqQlinear ion-trap instrument may help design an efficient toxicological GUS procedure.     

Haemoglobin adducts as biomarkers of exposure to tobacco-related nitrosamines

A sensitive gas chromatography/mass spectrometry (GC/MS) method was developed to measure nitrosamine-haemoglobin adducts (HPB-Hb) (4-hydroxy-3-pyridinyl-1-butanone) at trace levels in red blood cells of smoking and non-smoking mothers and their newborn babies. GC/MS methods with chemical ionization (CI) of methane reagent gas in both positive and negative ion mode as well as electron ionization (EI) were studied to determine differences in sensitivity among the various ionization methods. Detection limits using both positive and negative chemical ionization modes were found to be 30 fmol HPB, whereas detection using electron impact modes yielded a detection limit of 80 fmol HBP. In order to apply the various methods of detection to tobacco-exposed samples from human populations, we characterized adduct levels in maternal as well as paired fetal samples obtained from mothers exposed to tobacco smoke during pregnancy. Maternal samples were characterized using serum cotinine levels and were classified as non-smokers, passively smoke-exposed women, less than one pack per day smokers and greater than one pack per day smokers. Paired maternal and fetal blood samples were obtained at delivery for qualitative and qualitative analysis of nitrosamine adducts. Comparative derivatization of HPB released under alkaline hydrolysis conditions was performed using O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA) and 2,3,4,5,6-pentafluorobenzoylchloride (PFBC). Both negative CI and positive CI modes of analysis were compared to the more widely accepted EI modes of mass spectrometric analysis. These results suggest that both NICI and PICI modes of detection offer a greater sensitivity of adduct characterization when compared with EI ionization techniques and that either NICI or PICI modes are preferably applicable towards the detection of human biomarker assessment of tobacco-related nitrosamines.     

Adhesive bond stiffness of Staphylococcus aureus with and without proteins that bind to an adsorbed fibronectin film

Staphylococcus aureus is known to cause biomaterial-associated infections of implants and devices once it has breached the skin and mucosal barriers. Adhesion is the initial step in the development of a biomaterial-associated infection, and strategies to prevent staphylococcal adhesion and thus biomaterial-associated infections require understanding of the adhesive bond. The aim of this study was to compare the adhesive bond stiffnesses of two S. aureus strains with and without fibronectin-binding proteins (FnBPs) adhering to a fibronectin-coated quartz crystal microbalance (QCM) sensor surface on the basis of a coupled- resonance model. Both fibronectin adsorption and staphylococcal adhesion were accompanied by negative frequency shifts, regardless of the absence or presence of FnBPs on the staphylococcal cell surfaces. This is the opposite of the positive frequency shifts often observed for other bacterial strains adhering to bare sensor surfaces. Most likely, adhering staphylococci sink into and deform the adsorbed protein layer, creating stiff binding with the sensor surface due to an increased bacterium-substratum contact area. S. aureus 8325-4 possesses FnBPs and yields less negative frequency shifts (Δf) that are further away from the zero-crossing frequency than S. aureus DU5883. This suggests that FnBPs on S. aureus 8325-4 create a stiffer bond to the fibronectin coating than has been observed for S. aureus DU5883. Due to a limited window of observation, as defined by the available resonance frequencies in QCM, we could not determine exact stiffness values.     

Monitoring blood coagulation with magnetoelastic sensors

The determination of blood coagulation time is an essential part of monitoring therapeutic anticoagulants. Standard methodologies for the measurement of blood clotting time require dedicated personnel and involve blood sampling procedures. A new method based on magnetoelastic sensors has been employed for the monitoring of blood coagulation. The ribbon-like magnetoelastic sensor oscillates at a fundamental frequency, which shifts linearly in response to applied mass loads or a fixed mass load of changing elasticity. The magnetoelastic sensors emit magnetic flux, which can be detected by a remotely located pick-up coil, so that no direct physical connections are required. During blood coagulation, the viscosity of blood changes due to the formation of a soft fibrin clot. In turn, this change in viscosity shifts the characteristic resonance frequency of the magnetoelastic sensor enabling real-time continuous monitoring of this biological event. By monitoring the signal output as a function of time, a distinct blood clotting profile can be seen. The relatively low cost of the magnetoelastic ribbons enables their use as disposable sensors. This, along with the reduced volume of blood required, make the magnetoelastic sensors well suited for at-home and point-of-care testing devices.     

Manipulating Magnetoinductive Coupling with Graphene-Based Plasmonic Metamaterials in THz Region

Coupling between physical modes can trigger some new physical phenomena such as frequency shift, new mode, and Rabi splitting. Resonant modes in graphene-based metamaterials provide a new platform for the research of coupling. In this work, we demonstrate that the plasmonic coupling of split ring resonator (SRR) dimer in graphene-based metamaterials can be easily manipulated. This magnetoinductive coupling can switch on/off the dark modes easily, which is usually done by symmetry-breaking structure previously. Furthermore, the dark mode can also be activated by Fermi energy as well as carrier concentration changing with either physical or chemical methods conveniently. In addition, different graphene-based SRR dimer configurations present different coupling strengths, which benefits the designing and optimizing of graphene-based metamaterials. The demonstration could enhance the versatility of both coupling studies in terahertz (THz) region and graphene-based metamaterials for THz devices.     

Theoretical Differential Phase Analysis for Characterization of Aqueous Solution Using Surface Plasmon Resonance

Surface plasmon resonance (SPR)-based differential phase analysis has been presented. Real as well as complex plane analysis of resonance parameters have been undertaken for the optimum selection of metal thicknesses in a bimetallic SPR configuration working under both angular and spectral regime. Theoretically, we can characterize the aqueous solution in terms of this differential phase variation due to the variation of sample parameters such as concentration and temperature. In this respect, two case studies, namely, concentration of hemoglobin in human blood and sensing of temperature of water have been demonstrated and proposed theoretically. By monitoring the change of differential phase, proposed approach leads to a very sensitive measurement of concentration and temperature.     

Gravimetric biosensors based on acoustic waves in thin polymer films

Most gravimetric biosensors use thin piezoelectric quartz crystals, either as resonating crystals (quartz crystal microbalance, QCM), or as bulk/surface acoustic wave (SAW) devices. In the majority of these the mass response is inversely proportional to the crystal thickness which, at a limit of about 150 microns, gives inadequate sensitivity. A new system is described in which acoustic waves are launched in very thin (10 microns) tensioned polymer films to produce an oscillatory device. A theoretical equation for this system is almost identical to the well-known Sauerbrey equation used in the QCM method. Because the polymer films are so thin, a 30-fold increase in sensitivity is predicted and verified by adding known surface masses. Temperature sensitivity is a problem so a separate control sensor and careful temperature regulation are necessary. Preliminary results showing the real time binding of protein (IgG), a step towards immunosensor development, and the use of mass enhancing particles are presented. Inexpensive materials are used so disposable gravimetric biosensors may become feasible.     

Structure of the retinal chromophore in 7,9-dicis-rhodopsin

Bovine rhodopsin was bleached and regenerated with 7,9-dicis-retinal to form 7,9-dicis-rhodopsin, which was purified on a concanavalin A affinity column. The absorption maximum of the 7,9-dicis pigment is 453 nm, giving an opsin shift of 1600 cm-1 compared to 2500 cm-1 for 11-cis-rhodopsin and 2400 cm-1 for 9-cis-rhodopsin. Rapid-flow resonance Raman spectra have been obtained of 7,9-dicis-rhodopsin in H2O and D2O at room temperature. The shift of the 1654-cm-1 C = N stretch to 1627 cm-1 in D2O demonstrates that the Schiff base nitrogen is protonated. The absence of any shift in the 1201-cm-1 mode, which is assigned as the C14-C15 stretch, or of any other C-C stretching modes in D2O indicates that the Schiff base C = N configuration is trans (anti). Assuming that the cyclohexenyl ring binds with the same orientation in 7,9-dicis-, 9-cis-, and 11-cis-rhodopsins, the presence of two cis bonds requires that the N-H bond of the 7,9-dicis chromophore points in the opposite direction from that in the 9-cis or 11-cis pigment. However, the Schiff base C = NH+ stretching frequency and its D2O shift in 7,9-dicis-rhodopsin are very similar to those in 11-cis- and 9-cis-rhodopsin, indicating that the Schiff base electrostatic/hydrogen-bonding environments are effectively the same. The C = N trans (anti) Schiff base geometry of 7,9-dicis-rhodopsin and the insensitivity of its Schiff base vibrational properties to orientation are rationalized by examining the binding site specificity with molecular modeling.     

大蹄蝠多普勒正负补偿效应的声波特征与比较

利用单摆装置模拟大蹄蝠的飞行状态并实时记录其回声定位信号,以研究其多普勒频移补偿行为。与其静息状态下的超声波特征比较,发现大蹄蝠在接近目标的过程中有多普勒正补偿效应:叫声频率随相对速度改变而成正相关变化;当相对速度最大时,其叫声频率相对静息状态频率降低最多,而相对速度为零时,叫声频率回复到静息时频率。而当大蹄蝠远离目标时,有多普勒负补偿效应:叫声频率随相对速度改变成正相关变化,叫声频率在相对速度最大时,升高最多,但相同速度下升高之值较正补偿值低得多。另外,负补偿效应出现的频率较正补偿值低,这可能是由蝙蝠生理结构的限制以及自然状态下罕见的多普勒负补偿条件所决定。     

Effects of back-mounted biologgers on condition,diving and flight performance in a breeding seabird

Biologging devices are providing detailed insights into the behaviour and movement of animals in their natural environments. It is usually assumed that this method of gathering data does not impact on the behaviour observed. However, potential negative effects on birds have rarely been investigated before field-based studies are initiated. Seabirds which both fly and use pursuit diving may be particularly sensitive to increases in drag and load resulting from carrying biologging devices. We studied chick-rearing adult common guillemots Uria aalge equipped with and without back-mounted GPS tags over short deployments of a few days. Concurrently guillemots carried small leg-mounted TDR devices (time-depth recorders) providing activity data throughout. Changes in body mass and breeding success were followed for device equipped and control guillemots. At the colony level guillemots lost body mass throughout the chick-rearing period. When-equipped with the additional GPS tag, the guillemots lost mass at close to twice the rate they did when equipped with only the smaller leg-mounted TDR device. The elevated mass loss suggests an impact on energy expenditure or foraging performance. When equipped with GPS tags diving performance, time-activity budgets and daily patterns of activity were unchanged, yet dive depth distributions differed. We review studies of tag-effects in guillemots Uria sp. finding elevated mass loss and reduced chick-provisioning to be the most commonly observed effects. Less information is available for behavioural measures, and results vary between studies. In general, small tags deployed over several days appear to have small or no measurable effect on the behavioural variables commonly observed in most guillemot tagging studies. However, there may still be impacts on fitness via physiological effects and/or reduced chick-provisioning, while more detailed measures of behaviour (e.g. using accelerometery) may reveal effects on diving and flight performance.