Reduction In Resonant Frequency Research Articles

Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria

A structurally transformed lytic bacteriophage having a broad host range of Staphylococcus aureus strains and a penicillin-binding protein (PBP 2a) antibody conjugated latex beads have been utilized to create a biosensor designed for discrimination of methicillin resistant (MRSA) and sensitive (MSSA) S. aureus species (1,2). The lytic phages have been converted into phage spheroids by contact with water-chloroform interface. Phage spheroid monolayers have been moved onto a biosensor surface by Langmuir-Blodgett (LB) technique (3). The created biosensors have been examined by a quartz crystal microbalance with dissipation tracking (QCM-D) to evaluate bacteria-phage interactions. Bacteria-spheroid interactions led to reduced resonance frequency and a rise in dissipation energy for both MRSA and MSSA strains. After the bacterial binding, these sensors have been further exposed to the penicillin-binding protein antibody latex beads. Sensors analyzed with MRSA responded to PBP 2a antibody beads; although sensors inspected with MSSA gave no response. This experimental distinction determines an unambiguous discrimination between methicillin resistant and sensitive S. aureus strains. Equally bound and unbound bacteriophages suppress bacterial growth on surfaces and in water suspensions. Once lytic phages are changed into spheroids, they retain their strong lytic activity and show high bacterial capture capability. The phage and phage spheroids can be utilized for testing and sterilization of antibiotic resistant microorganisms. Other applications may include use in bacteriophage therapy and antimicrobial surfaces.

Miniaturization of Slot Antennas Using Wire Loading

The design of a miniaturized slot antenna based on wire-loading is presented. The miniaturization can be achieved with minimal increase in the lateral space along the slot width. Both the cases of a slot antenna on dielectric substrate and a slot antenna on ground plane are considered. For the former case, a miniaturization of 28.83% is achieved. The radiation characteristics of the size-reduced antenna are almost similar to the unloaded slot, with low cross-polarization levels. For the slot antenna on a ground plane, the miniaturization is affected by a cavity-backed design with the loading wires penetrated into the cavity. A 45.52% reduction in resonant frequency is achieved relative to the unloaded slot. The radiation characteristics in the upper hemisphere are almost unperturbed compared to the unloaded slot.

Chronic Ketamine Reduces the Peak Frequency of Gamma Oscillations in Mouse Prefrontal Cortex Ex vivo

Abnormalities in EEG gamma band oscillations (GBO, 30–80 Hz) serve as a prominent biomarker of schizophrenia (Sz), associated with positive, negative, and cognitive symptoms. Chronic, subanesthetic administration of antagonists of N-methyl-D-aspartate receptors (NMDAR), such as ketamine, elicits behavioral effects, and alterations in cortical interneurons similar to those observed in Sz. However, the chronic effects of ketamine on neocortical GBO are unknown. Thus, here we examine the effects of chronic (five daily i.p. injections) application of ketamine (5 and 30 mg/kg) and the more specific NMDAR antagonist, MK-801 (0.02, 0.5, and 2 mg/kg), on neocortical GBO ex vivo. Oscillations were generated by focal application of the glutamate receptor agonist, kainate (KA), in coronal brain slices containing the prelimbic cortex. This region constitutes the rodent analog of the human dorsolateral prefrontal cortex, a brain region strongly implicated in Sz-pathophysiology. Here we report the novel finding that chronic ketamine elicits a reduction in the peak oscillatory frequency of KA-elicited oscillations (from 47 to 40 Hz at 30 mg/kg). Moreover, the power of GBO in the 40–50 Hz band was reduced. These findings are reminiscent of both the reduced resonance frequency and power of cortical oscillations observed in Sz clinical studies. Surprisingly, MK-801 had no significant effect, suggesting care is needed when equating Sz-like behavioral effects elicited by different NMDAR antagonists to alterations in GBO activity. We conclude that chronic ketamine in the mouse mimics GBO abnormalities observed in Sz patients. Use of this ex vivo slice model may be useful in testing therapeutic compounds which rescue these GBO abnormalities.

Cross slot multifrequency patch antennas

Two simple single layer single feed cross slot patch antennas with air dielectric (er = 1) substrate providing multiple frequency operation is proposed.At first a cross slot rectangular patch antenna providing quad frequency operation is proposed and experimentally studied. The measured quad frequencies are 1.93, 2.57, 3.18, and 3.56 GHz. Another cross slot trapezium patch antenna providing quad frequency operation is proposed and experimentally studied. The measured quad frequencies are at 1.43, 1.81, 2.97, and 3.58 GHz. Trapezium patch antenna is found to be more compact in size and as well as reduction in resonant frequency compared to rectangular patch antenna. Measured values are in good agreement with simulated results. The measured radiation patterns at each measured resonant frequency are also shown. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:612–615, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25765

Apparent mass of the human body in the vertical direction: Inter-subject variability

The biodynamic responses of the seated human body to whole-body vibration vary considerably between people, but the reasons for the variability are not well understood. This study was designed to determine how the physical characteristics of people affect their apparent mass and whether inter-subject variability is influenced by the magnitude of vibration and the support of a seat backrest. The vertical apparent masses of 80 seated adults (41 males and 39 females aged 18–65) were measured at frequencies between 0.6 and 20 Hz with four backrest conditions (no backrest, upright rigid backrest, reclined rigid backrest, reclined foam backrest) and with three magnitudes of random vibration (0.5, 1.0 and 1.5 m s -2 rms). Relationships between subject physical characteristics (age, gender, weight, and anthropometry) and subject apparent mass were investigated with multiple regression models. The strongest predictor of the modulus of the vertical apparent mass at 0.6 Hz, at resonance, and at 12 Hz was body weight, with other factors having only a marginal effect. After correction for other variables, the principal resonance frequency was most consistently associated with age and body mass index. As age increased from 18 to 65 years, the resonance frequency increased by up to 1.7 Hz, and when the body mass index was increased from 18 to 34 kg m −2 the resonance frequency decreased by up to 1.7 Hz. These changes were greater than the 0.9-Hz increase in resonance frequency between sitting without a backrest and sitting with a reclined rigid backrest, and greater than the 1.0-Hz reduction in resonance frequency when the magnitude of vibration increased from 0.5 to 1.5 m s −2 rms. It is concluded that the effects of age, body mass index, posture, vibration magnitude, and weight should be taken into account when defining the vertical apparent mass of the seated human body.

Taking into account the impact of coupling elements on the resonance phenomena in biconical resonators

Investigations of the impact of dimensions of the coupling holes in open and closed biconical resonators on their field structure and resonance properties were performed. A number of concrete results were obtained that specified the extent of rise of the transfer ratio and the distortion of electromagnetic field structure and also the reduction of the resonance frequency and loaded Q-factor under conditions of the increasing size of the coupling holes in biconical resonators. The conditions under which the values of resonance frequency and loaded Q-factor of the open biconical resonator would be only slightly different from values of the same parameters of closed resonator were also obtained.

Nonlinear electromagnetic generators with polymeric materials for power harvesting from vibrations

The power consumption reduction of electronic devices has allowed supplying them through the harvesting and subsequent conversion of electrical energy that is present in different forms in the measurement environment. Mechanical energy from vibrations is the most common energy source. In the proposed nonlinear electromagnetic generators, the vibrations generate an oscillatory movement of a planar inductor placed in a constant magnetic field, thereby generating a voltage on the coil due to the change in magnetic flux. In the case of low-frequency vibrations, it is necessary to consider two conflicting demands: firstly, in the hypothesis of linearity, the resonant frequency reduction requires an increase in mass and softness of the spring, against the size reduction requires structural stiffening and an obvious reduction in mass. The generator considers a proposed nonlinear elastic behavior of the suspension on which the inductor is placed, improving the system efficiency than the linear case, and especially by introducing behaviors that are not intuitively predictable and potentially exploitable for the proposed purpose. A mathematical model is used to study the nonlinear behaviors; the model is referred to a mass-spring-damper system with harmonic force support. The retraction force is nonlinear by adding a cubic term, and damping is proportional to the speed with an electrical and mechanical component. The generators are built and tested using a specially designed experimental setup. The working frequencies of the generators are between 25–40 Hz. The experimental results are compared with results obtained by the mathematical model, getting a good match.

Effect of moisture absorption on damping and dynamic stiffness of carbon fiber/epoxy composites

In this paper, the damping and dynamic stiffness of UHN125C carbon fiber/epoxy composite beam was experimentally measured. The effect of fiber orientation angle and stacking sequences on damping, resonance frequency, and dynamic stiffness was discussed with a focus on the effect of moisture absorption. Dried specimens were immersed in distilled water for a certain period to absorb water for 8, 16, and 24 d, respectively, and the moisture content absorbed in the specimen was measured. Furthermore, using the impact hammer technique, the measurements of dynamic responses were conducted on a cantilever beam specimen with one end clamped by bolts and metal plates. The damping properties in terms of loss factor were approximated by half-power bandwidth technique. The dynamic stiffness was evaluated using resonance frequency as a function of moisture content. The damping increased with the increase of moisture content; however, the dynamic stiffness reduced with the reduction of resonance frequency. The results of the dynamic stiffness were aided by measuring the dynamic strain using DBU-120A strain-indicating software. The increment in the dynamic strain strengthened the results obtained for dynamic stiffness.

Electric Field Dependence of Piezoelectric Constants and Resonance Characteristics in Modified PZT Ceramics

The practical application of piezoelectric ceramics is applied not only under low electric fields. Therefore, an examination for characteristics of piezoelectric ceramics under high electric fields can contribute to reducing the susceptibility of multifarious applications and to facilitating production of control circuits. These contributions can lead to the expansion of industrial applications. In this research, we fabricated disk-type piezoelectric ceramic samples using conventional methods, measured the resonance characteristics of these samples from low to high voltages driving conditions, and calculated the piezoelectric constants. Resonance frequency and voltage reduction ratio decreased steeply in the specific input voltage sections in PZT-PMNS ceramics.

RESONANCE ON TRANSFORMERS EXCITED BY SQUARE WAVES AND EXPLANATION OF THE HIGH VOLTAGE ON TESLA TRANSFORMER

This paper presents an analysis about resonance on coupled systems when excited by square waves, generated through experiments using planar and ring coils. Because of the phenomenon described by its transfer function, a sum of responses appear when the square wave frequency increases, which causes a resonance response with high voltage, in several cases, greater than common turn ratio of the transformer. With parallel capacitances inserted on output, the resonance frequency reduction and change of gain is observed. Due to this efiect, explanation of how output of Tesla transformer presents high voltage which is shown and strategies to reach the maximal value on output are proposed.

支持脚にき裂を有する多脚円筒形容器の振動特性(機械力学,計測,自動制御)

Analysis method of resonant frequency and leg's load of cylindrical vessel with cracked legs is proposed. Cylindrical vessel supported by legs is installed in shaking table, and is excited to investigate resonant frequency and leg's load. During the vibration tests, some of the legs have simulated penetrated cracks. So, the resonant frequency reduced from original case. The test data coincide well with analytical one, and so the proposed analysis method is verified. It is clarified that the resonant frequency has good correlation with the crack location coefficient. It is also shown that resonant frequency reduction is less than 10% even if there are 3 cracked legs.

Cantilever driven transduction apparatus

An electromechanical transducer which provides orthogonal translated motion to a piston through an attached lever arm connected to and driven by at least two electromechanical cantilever members, mounted on a separate inertial tail mass, and which under full array loading conditions provide a reduced resonance frequency that yields velocity control in the vicinity of that resonance.

Voltage Control of the Resonance Frequency of Dielectric Electroactive Polymer (DEAP) Membranes

We report on the characterization, active tuning, and modeling of the first mode resonance frequency of dielectric electroactive polymer (DEAP) membranes. Unlike other resonance frequency tuning techniques, the tuning procedure presented here requires no external actuators or variable elements. Compliant electrodes were sputtered or implanted on both sides of 20-35-mum-thick and 2-4-mm-diameter polydimethylsiloxane membranes. The electrostatic force from an applied voltage adds compressive stress to the membrane, effectively softening the device and reducing its resonance frequency, in principle to zero at the buckling threshold. A reduction in resonance frequency up to 77% (limited by dielectric breakdown) from the initial value of 1620 Hz was observed at 1800 V for ion-implanted membranes. Excellent agreement was found between our measurements and an analytical model we developed based on the Rayleigh-Ritz theory. This model is more accurate in the tensile domain than the existing model for thick plates applied to DEAPs. By varying the resonance frequency of the membranes (and, hence, their compliance), they can be used as frequency-tunable attenuators. The same technology could also allow the fine-tuning of the resonance frequencies in the megahertz range of devices made from much stiffer polymers.

Enhanced bandwidth uniplanar compact electromagnetic bandgap structure with coplanar meander line inductance

A novel compact electromagnetic bandgap structure is presented. The coplanar meander line inductance is adopted to increase the surface equivalent inductance in order to improve the bandwidth of the bandgap and reduce unit cell size. The measured results show that 54.1% relative bandwidth and 25.2% reduction in resonant frequency could be obtained.

Influence of anteroposterior shifting of trunk mass centroid on vibrational configuration of human spine

This study attempts to determine the influence of anteroposterior (A-P) shifting of trunk mass from the upright sedentary posture on dynamic characteristics of the human lumbar spine. A three-dimensional finite element (FE) model comprising of the T12–Pelvis spine unit was used to mimic the human spine system. It is not clear how the A-P shifting of the upper part of human upper body affect on vibrational modality of the human lumbar spine under whole body vibration. Five trunk mass point locations were assumed by 2.0 cm anterior, 1.0 cm anterior, 1.0 cm posterior and 2.0 cm posterior to the upright sedentary posture including no shifting posture. FE modal analysis was used to extract the resonant frequencies and vibration modes of the human spine. The analytical results indicate that trunk mass centroid shifting onwards or rearwards may result in a reduction of vertical resonant frequency of the human spine. The human spine has the highest vertical resonant frequency at the normal upright sedentary posture with the trunk mass locating around 1.0 cm anterior to the L3–L4 vertebral centroid. Larger A-P deformations and rotational deformations were also found at the spine motion segments L3–L4 and L4–L5, which imply higher compressive stress and shear stress at the disc annulus of those spinal motion segments. The findings in this study may explain why long-term whole body vibration might induce the degeneration of human spine at the relevant spinal motion segments.

A Novel Multilayer Aperture-Coupled Cavity Resonator for Millimeter-Wave CMOS RFICs

A novel millimeter-wave cavity resonator, completely compatible with commercial CMOS fabrication techniques, has been designed and fabricated in a 0.25-mum CMOS process and tested. The resonator employs a capacitively loaded cavity topology effectively implemented using the CMOS multimetal-layer and via-hole structure. The CMOS capacitively loaded cavity resonator, including two coupling apertures and microstrip feed lines, occupies an area of 2 mmtimes1.4 mmtimes6.28 mum, which is much smaller than the cavity resonator designed without a capacitive load at the same resonant frequency. It resonates at 30 GHz with a corresponding insertion loss of 2 dB and unloaded quality factor of 22.2. The resonant-frequency reduction is approximately 50%, as compared to that without the capacitive load. The design and performance of a new CMOS coupling aperture, which is useful as a coupling mechanism and a vertical interconnect for highly dense millimeter-wave CMOS RF integrated circuits (RFICs) are also presented. The developed low-loss and compact CMOS cavity resonator can be used to realize various millimeter-wave on-chip passive components such as wideband bandpass filters and diplexers and is suitable for direct integration with other CMOS circuits on a single chip. It is attractive for CMOS RFIC design at millimeter-wave frequencies

Internal friction study of ion-implantation induced defects in silicon

Using a sensitive silicon paddle oscillator technique, we measured the internal friction of single-crystalline silicon substrate implanted with As +, Si +, B +, and H + ions with a dose of ∼ 1 0 19 m −2. A distinct internal friction peak at about 48 K is observed in all cases. The overall internal friction from 0.4 K to room temperature is also similar for the different species of ions used. The peak shifts to lower temperature at a reduced resonance frequency, characteristic of a thermally activated relaxation. The insensitivity of the peak to the ion species indicates that it is caused by a vacancy-type defect. Isochronal annealing study shows that the peak anneals away at a temperature between 200 and 300 ° C, and that is consistent with divacancy defects. By plasma etching the substrate layer by layer, we have identified that the defects are concentrated at a damaged crystalline layer right underneath the top amorphized layer in the Si + implanted sample. The exact mechanism that caused the relaxation peak is still not clear, although our quantitative analysis points to an electronic origin.

Piezoelectric-excited millimeter-sized cantilever (PEMC) sensors detect Bacillus anthracis at 300spores/mL

Piezoelectric-excited millimeter-sized cantilever (PEMC) sensors consisting of a piezoelectric and a borosilicate glass layer with a sensing area of 2.48 mm2 were fabricated. Antibody specific to Bacillus anthracis (BA, Sterne strain 7702) spores was immobilized on PEMC sensors, and exposed to spores (300 to 3x10(6) spores/mL). The resonant frequency decreased at a rate proportional to the spore concentration and reached a steady state frequency change of 5+/-5 Hz (n=3), 92+/-7 Hz (n=3), 500+/-10 Hz (n=3), 1030+/-10 Hz (n=2), and 2696+/-6 Hz (n=2) corresponding to 0, 3x10(2), 3x10(3), 3x10(4), and 3x10(6) spores/mL, respectively. The reduction in resonant frequency is proportional to the change in cantilever mass, and thus the observed changes are due to the attachment of spores on the sensor surface. Selectivity of the antibody-functionalized sensor was determined with samples of BA (3x10(6)/mL) mixed with Bacillus thuringiensis (BT; 1.5x10(9)/mL) in various volume ratios that yielded BA:BT ratios of 1:0, 1:125, 1:250, 1:500 and 0:1. The corresponding resonance frequency decreases were, respectively, 2345, 1980, 1310, 704 and 10 Hz. Sample containing 100% BT spores (1.5x10(9)/mL and no BA) gave a steady state frequency decrease of 10 Hz, which is within noise level of the sensor, indicating excellent selectivity. The observed binding rate constant for the pure BA and BT-containing samples ranged from 0.105 to 0.043 min-1 in the spore concentration range 300 to 3x10(6)/mL. These results show that detection of B. anthracis spore at a very low concentration (300 spores/mL) and with high selectivity in presence of another Bacillus spore (BT) can be accomplished using piezoelectric-excited millimeter-sized cantilever sensors.

Precision Fabrication Techniques and Analysis on High-<tex>$Q$</tex>Evanescent-Mode Resonators and Filters of Different Geometries

High-Q evanescent-mode resonators and filters are realized by both silicon micromachining and layer-by-layer polymer processing. Capacitively loaded cavities can be reduced to a size much smaller than a wavelength, but still have a much higher unloaded Q than lumped elements. The loaded resonators are utilized for reduced-size filters with a low insertion loss enabled by the relatively high-Q factor. The small fabrication tolerances of silicon micromachining and polymer stereolithography processing enable the realization of highly loaded evanescent-mode resonators and filters. A 14-GHz resonator micromachined in silicon has a volume of 5 mm /spl times/ 5 mm /spl times/ 0.45 mm, representing a resonant frequency reduction of 66.8% compared to an empty cavity of the same dimensions. The polymer-based fabrication is used to create resonators of different three-dimensional geometries with Q's up to 1940 and frequency reductions up to 49.9%. An insertion loss of 0.83 dB is measured in a 1.69% bandwidth filter created by polymer processing with a frequency reduction of 47% compared to an unloaded cavity. The frequency sensitivity to fabrication tolerances of these structures is also analyzed.

Development of the Two-Step Delamination Identification Method by Resonant and Anti-Resonant Frequency Changes

Identification of the location and size of delamination is important for structural health monitoring of composite laminated structures, since delamination degrades compression stiffness of the structures. In the present study, a two-step delamination identification method using resonant and anti-resonant frequency changes is proposed. It is well known that resonant frequencies are changed depending on the location and size of delamination. As for anti-resonant frequencies, they also change mainly depending on the location of delamination. Since the resonant and anti-resonant frequencies are specified easily in the frequency response function, the present method is low cost and applicable to any structures. The present method is applied to delamination identification of carbon/epoxy cantilever beams, and effectiveness of the present method is discussed. Introduction Recently, composite laminated structures have been applied to many structures of vehicles because of its high specific stiffness and strength. Since interlaminar strength of composite laminated structure is relatively low, internal damage, such as delamination, can be easily induced in service. Since delamination degrades compression strength of the structure, it is necessary to identify the size and location of delamination nondestructively for the assessment of structural integrity. However, conventional nondestructive inspection methods, such as X-ray or ultrasonic inspection, are high cost, and application to large structures is difficult owing to size restriction of the apparatuses. The present study proposes a two-step delamination identification method using resonant and anti-resonant frequency changes. In order to examine effectiveness of the present method, delamination identification of a carbon/epoxy cantilever beam is conducted. As a preparation for delamination identification, the beam is divided into two domains based on the mode shapes. The delaminated domain in which delamination is supposed to exist is first identified from the anti-resonant frequency changes, and the delamination location and size are identified from the resonant frequency changes to the next. In order to analyze frequency response changes caused by delamination, finite element method was applied. Effectiveness of the present identification method was investigated both in analysis and experiment. Symmetry of Resonant Frequency Changes Fig.1 shows schematic of a carbon/epoxy cantilever beam with delamination. The beam is 1.45mm thick, 19mm wide and 200 mm long. The laminate configuration of the beam is [02/902]S, and a through width delamination is existed at one 0/90 interlayer. In order to examine effect of delamination location and size on the resonant frequencies of the beam, modal analyses of the beam were conducted by using ANSYS, a commercially available general-purpose finite element code. Table 1 shows material properties of uni-directional carbon/epoxy lamina used for calculation, where Key Engineering Materials Vols. 270-273 (2004) pp. 1852-1858 online at http://www.scientific.net © 2004 Trans Tech Publications, Switzerland Title of Publication (to be inserted by the publisher) subscript 1 means the direction parallel to the fiber and subscripts 2 and 3 means the direction perpendicular to the fiber. In the present paper, normalized values l/L and a/L are employed to express the delamination location and size respectively, where L is beam length. Fig.2 shows resonant frequency changes of the beam as a function of delamination location obtained by FEM analysis, where delamination size is constant value 0.1. In fig.2, abscissa means delamination location and ordinate means frequency value normalized by the intact value of each mode. In general, reduction of resonant frequency is caused by stiffness reduction of structures. For a composite laminated beam with delamination, reduction of the bending stiffness is caused when shear force acts on the delamination, and shear force distribution of each mode depend on each modal shape. For this reason, the resonant frequency changes of the cantilever beam shows quasi-symmetry in the region defined by 0.3≤l/L≤0.7 except for the first mode, though the cantilever beam is not a symmetric structure. This causes failure in identification of delamination location based on resonant frequency changes [1]. In order to make it possible to identify delamination location in the cantilever beam, another parameters that have information about delamination location and no symmetry. In the present study, anti-resonant frequency is adopted. (L=200mm, b=19mm, h=1.45mm) L h Delamination