Investigation of New Microstrip Bandpass Filter Based on Patch Resonator with Geometrical Fractal Slot

A compact dual-mode microstrip bandpass filter using geometrical slot is presented in this paper. The adopted geometrical slot is based on first iteration of Cantor square fractal curve. This filter has the benefits of possessing narrower and sharper frequency responses as compared to microstrip filters that use single mode resonators and traditional dual-mode square patch resonators. The filter has been modeled and demonstrated by Microwave Office EM simulator designed at a resonant frequency of 2 GHz using a substrate of ε_r = 10.8 and thickness of h = 1.27 mm. The output simulated results of the proposed filter exhibit 22 dB return loss, 0.1678 dB insertion loss and 12 MHz bandwidth in the passband region. In addition to the narrow band gained, miniaturization properties as well as weakened spurious frequency responses and blocked second harmonic frequency in out of band regions have been acquired. Filter parameters including insertion loss, return loss, bandwidth, coupling coefficient and external quality factor have been compared with different values of perturbation dimension (d). Also, a full comparative study of this filter as compared with traditional square patch filter has been considered.     

Modelling of Polarization-Dependent Loss in Plasmonic Nanowire Waveguides

We have investigated the potential of using gold nanowires embedded in a dielectric cladding environment as polarization-independent long-range surface plasmon polariton waveguides at telecom wavelengths. We performed finite-element analysis on various symmetric and close-to-symmetric cross-sectional geometries and evaluated the effects of cladding thickness on the propagation and coupling loss. The calculations confirm that fabrication of polarization-independent waveguides with reasonable tolerances is feasible and that straight-waveguide insertion losses around 1.5 dB for short (0.5 mm) devices can be realized when coupling to and from conventional dielectric waveguide geometries.     

An in vivo method for measuring the adsorption of plasma proteins to titanium in humans

A novel method of collecting in vivo plasma proteins of humans from osteotomies prepared during insertion of an oral implant is described. A rod containing a collecting portion with a predetermined surface is introduced into the osteomy, removed, and transferred for enzyme-linked immunosorbent assay analysis. Two experiments were used to examine the feasibility of the method. In the first, titanium (Ti) rods with different roughness were exposed for 10 min to the blood. Blasted and acid-etched surfaces adsorbed four times more and acid-etched surfaces adosorbed two times more plasma proteins as compared to machined surfaces. In the second experiment, blasted and acid-etched rods were wetted for 10 s prior to the insertion. The adsorption for fibronectin, albumin, fibrinogen, and IgG was enhanced significantly compared with nonwetted rods. These results are discussed in the light of previous methods used in studies on adsorption. Thus, use of the collecting instrument enables aspects of human plasma–implant interface to be studied in a more realistic manner.     

Theoretical Investigation of an Interferometer-type Plasmonic Biosensor Using a Metal-insulator-silicon Waveguide

This work proposes and investigates theoretically a biosensor that is an integrated plasmonic Mach–Zehnder interferometer. The biosensor consists of three sections. The first and third sections are input and output dielectric waveguides whose core is a silicon film. The second section is a combination of a surface plasmon polariton waveguide and a metal-insulator-silicon waveguide, which are separated by a thick gold film. The former and the latter function as sensing and reference arms, respectively. The latter supports a mode whose fields are highly enhanced in a thin insulator, silicon nitride film, and it has relatively small propagation loss. It is shown that the biosensor has insertion loss lower than 2 dB, and that it is very compact since the length of its second section for sensing is shorter than 6 μm. In addition, it is discussed that it can be easily implemented by using simple fabrication processes. Analyzed are the characteristics of sensing a refractive index change of liquid covering the biosensor. Despite its compactness, they are similar to those of previous surface plasmon interferometers. Also, its characteristics as a DNA sensor are analyzed. The analysis demonstrates that the biosensor can detect sensitively target single-stranded DNAs whose total weight is smaller than 10 fg.     

Numerical Investigation on Elliptic Cylindrical Nanowire Hybrid Plasmonic Waveguide–Based Polarization Beam Splitter

A novel design of elliptic cylindrical nanowire hybrid plasmonic waveguide (ECNHPW)–based polarization beam splitter (PBS) is proposed. In the proposed design, the ECNHPW arm acts as an input port and a bar port; on the other hand, a regular silicon wire (RSW) arm acts as a cross port. By selecting the physical parameters of the proposed PBS accurately, the transverse electric (TE) mode is merely satisfied with the phase-matching condition. In contrast, the transverse magnetic (TM) mode does not propagate to the RSW arm. Consequently, the TM input mode goes directly to the ECNHPW arm, while the TE input mode in ECNHPW is coupled with RSW arm. As a result, the two different polarization modes are meritoriously separated, and they pass through two different arms. For the proposed PBS, the insertion loss (IL) of both polarizations lies below 1 dB. For TE input, the value of the polarization extinction ratio (PER) is 27.2 dB, and for TM input, it is 23.9 dB at 1550 nm operating wavelength. Further optimization is implemented by varying the wavelength, thickness of SiO₂, and the gap between the waveguides using the finite element method (FEM). The proposed PBS is designed with 150 nm bandwidth, high PER, and low IL, which can be suitable for photonic integrated circuits (PICs).

     

Wide Bandpass and Narrow Bandstop Microstrip Filters Based on Hilbert Fractal Geometry: Design and Simulation Results

This paper presents new Wide Bandpass Filter (WBPF) and Narrow Bandstop Filter (NBSF) incorporating two microstrip resonators, each resonator is based on 2^nd iteration of Hilbert fractal geometry. The type of filter as pass or reject band has been adjusted by coupling gap parameter (d) between Hilbert resonators using a substrate with a dielectric constant of 10.8 and a thickness of 1.27 mm. Numerical simulation results as well as a parametric study of d parameter on filter type and frequency responses are presented and studied. WBPF has designed at resonant frequencies of 2 and 2.2 GHz with a bandwidth of 0.52 GHz, −28 dB return loss and −0.125 dB insertion loss while NBSF has designed for electrical specifications of 2.37 GHz center frequency, 20 MHz rejection bandwidth, −0.1873 dB return loss and 13.746 dB insertion loss. The proposed technique offers a new alternative to construct low-cost high-performance filter devices, suitable for a wide range of wireless communication systems.     

STUDIES ON THE ORGANIZATION OF THE BRUSH BORDER IN INTESTINAL EPITHELIAL CELLS : II. Fine Structure of Fractions of Tris-Disrupted Hamster Brush Borders

Two of the fractions obtained by density gradient centrifugation of Tris-disrupted brush borders from hamster intestinal mucosa have been identified as the microvillus cores and their surrounding membranous coats, respectively. This identification has the following morphological basis. In shadowed preparations one fraction (cores) appears as rounded, compact rods, and the other fraction (coats) appears as flattened sheets. Both rods and sheets have dimensions appropriate to the identities assigned to them. In addition, negative staining shows that the rods are composed of aligned particles of roughly 60 A, consistent with the appearance of the core in tissue section, where 60-A fibrils are characteristic. The sheets are covered by non-aligned particles of approximately the same size. Sectioned preparations show that the core fraction contains predominantly fibrous material with some membranous contamination and that the coat fraction is apparently composed exclusively of elongated sacs with a unit membrane structure. Some details of the structure of the core are evident in cases where the compact rod appears to be loosened, revealing a doubled strand. The strand is approximately 350 A wide; the compact rod is roughly twice this width. With negative staining the strand shows a dense central region. The morphological identification presented here is consistent with the distribution of enzymic activity among the density gradient fractions described in the preceding paper.     

Terminal Twist-Induced Writhe of DNA with Intrinsic Curvature

Supercoiling of a closed circular DNA rod may result from an application of terminal twist to the DNA rod by cutting the rod, rotating one of the cut faces as the other being fixed and then sealing the cut. According to White's formula, DNA supercoiling is probably accompanied by a writhe of the DNA axis. Deduced from the elastic rod model for DNA structure, an intrinsically straight closed circular DNA rod does not writhe as subject to a terminal twist, until the number of rotation exceeds a rod-dependent threshold. By contrast, a closed circular DNA rod with intrinsic curvature writhes instantly as subject to a terminal twist. This noteworthy character in fact belongs to many intrinsically curved DNA rods. By solving the dynamic equations, the linearization of the Euler–Lagrange equations governing intrinsically curved DNA rods, this paper shows that almost every clamped-end intrinsically curved DNA rod writhes instantly when subject to a terminal twist (clamped-end DNA rods include closed circular DNA rods and topological domains of open DNA rods). In terms of physical quantities, the exceptions are identified with points in ℝ⁶ whose projections onto ℝ⁵ (through ignoring the total energy density of a rod) form a subset of a quadratic hypersurface. This paper also suggests that the terminal twist induced writhe is due to the elasticity and the clamped-end boundary conditions of the DNA rods. To my sister for her 50th birthday.     

A Compact Nanoplasmonics Filter and Intersection Structure Based on Utilizing a Slot Cavity and a Fabry–Perot Resonator

By combining a Fabry–Perot (FP) cavity with a slot cavity, a compact filter structure is proposed. The peak resonance wavelength is determined by applying the FP resonance condition of the FP cavity. The relationship between filtering wavelength and cavity parameters is investigated. The results show that the filtering wavelength can be manipulated by changing the nanocavities' parameters. By using the finite difference time domain method, the theoretical predictions are confirmed. An intersection structure for nanoplasmonic waveguides is proposed and designed by utilizing two perpendicular filters. In addition to having compact dimensions, the proposed arrangement provides higher throughput and low cross talk. The proposed structure can be useful for designing compact integrated nanoplasmonic circuits.     

Biomechanical factors affecting fracture stability and femoral bursting in closed intramedullary rod fixation of femur fractures

Intramedullary rodding of femur fractures, although a safe and rapidly performed procedure, can result in several complications. If the rod fit is too loose, fracture instability, rod migration, and delayed union may result. If the rod fit is too tight, cracking of the femur may occur during rod insertion. These complications were investigated in terms of geometric and mechanical parameters of the bone-implant system. Results showed that rods of the same nominal size from different manufacturers showed more than twofold difference in flexural rigidity and a threefold difference in torsional modulus. These differences appear to be due to differences in cross sectional shape and wall thickness of the rods. Measurements of pushout force and hoop stress in cadaver femora showed a large difference in pushout force with different rods, and significantly lower forces in distal than in proximal femoral fracture components. Pushout force decreased with fracture component length proximally and dropped to zero in distal components less than 170 mm long. An increase in ream diameter in the distal components of just 1 mm was found to decrease the mean pushout force from 740N to 90N. The most significant variable was found to be anterior offset of the starting hole more than 6 mm from the centerline of the medullary canal which resulted in consistent lifting of the anterior cortex during insertion of the rod.     

Hydrodynamic resistance and diffusion coefficients of a freely hinged rod

The seven-dimensional hydrodynamic resistance and diffusion tensors are evaluated for a rod which is freely hinged at its center and immersed in a viscous fluid. The hydrodynamic resistance tensor is first determined at the hinge, then transformed to other points and inverted to obtain the diffusion tensor. Hydrodynamic interactions between rod halves are neglected, which is asymptotically correct for long rods. In the long-rod limit, the diffusion coefficient characterizing translations over macroscopic distances is decreased by 3–6% from that for a rigid straight rod of same total length, while the average end-over-end rotational diffusion coefficient for each rod half is increased 4.67 times.     

Numerical analysis of models of the standard TSRH spinal instrumentation: effect of rod cross-sectional shape

A numerical technique, geometric element modeling and analysis, was used to investigate the effect of the cross-sectional shape of the rod (circular versus square) in three-dimensional models of the standard (dual-rod) Texas Scottish Rite Hospital (TSRH) spinal instrumentation on two biomechanical characteristics (namely, stiffness and the von Mises equivalent stress) of the instrumentation under compressive force and torque, applied separately. The model constraints are the same as those acting on the instrumentation clinically, that is, when it is attached to the vertebrae of the human spine. Furthermore, the magnitudes of the compressive and torsional loadings applied on the model are within the range of those experienced by the spine during normal walking. It was found that use of square cross-sectioned rods leads to better biomechanical performance of the model compared to the case when the rods are circular. This finding points the way to the possibility of using square cross-sectioned rods in the TSRH instrumentation.     

Rod sensitivity of neonatal mouse and rat

We have measured the sensitivity of rod photoreceptors isolated from overnight dark-adapted mice of age P12 (neonate) through P45 (adult) with suction-pipette recording. During this age period, the dark current increased roughly in direct proportion to the length of the rod outer segment. In the same period, the flash sensitivity of rods (reciprocal of the half-saturating flash intensity) increased by approximately 1.5-fold. This slight developmental change in sensitivity was not accentuated by dark adapting the animal for just 1 h or by increasing the ambient luminance by sixfold during the prior light exposure. The same small, age-dependent change in rod sensitivity was found with rat. After preincubation of the isolated retina with 9-cis-retinal, neonatal mouse rods showed the same sensitivity as adult rods, suggesting the presence of a small amount of free opsin being responsible for their lower sensitivity. The sensitivity of neonate rods could also be increased to the adult level by dark adapting the animal continuously for several days. By comparing the sensitivity of neonate rods in darkness to that of adult rods after light bleaches, we estimated that approximately 1% of rod opsin in neonatal mouse was devoid of chromophore even after overnight dark adaptation. Overall, we were unable to confirm a previous report that a 50-fold difference in rod sensitivity existed between neonatal and adult rats.     

A Genetically Encoded Reporter for Real-Time Imaging of Cofilin-Actin Rods in Living Neurons

Filament bundles (rods) of cofilin and actin (1:1) form in neurites of stressed neurons where they inhibit synaptic function. Live-cell imaging of rod formation is hampered by the fact that overexpression of a chimera of wild type cofilin with a fluorescent protein causes formation of spontaneous and persistent rods, which is exacerbated by the photostress of imaging. The study of rod induction in living cells calls for a rod reporter that does not cause spontaneous rods. From a study in which single cofilin surface residues were mutated, we identified a mutant, cofilinR21Q, which when fused with monomeric Red Fluorescent Protein (mRFP) and expressed several fold above endogenous cofilin, does not induce spontaneous rods even during the photostress of imaging. CofilinR21Q-mRFP only incorporates into rods when they form from endogenous proteins in stressed cells. In neurons, cofilinR21Q-mRFP reports on rods formed from endogenous cofilin and induced by all modes tested thus far. Rods have a half-life of 30–60 min upon removal of the inducer. Vesicle transport in neurites is arrested upon treatments that form rods and recovers as rods disappear. CofilinR21Q-mRFP is a genetically encoded rod reporter that is useful in live cell imaging studies of induced rod formation, including rod dynamics, and kinetics of rod elimination.     

Amyloid-β and Proinflammatory Cytokines Utilize a Prion Protein-Dependent Pathway to Activate NADPH Oxidase and Induce Cofilin-Actin Rods in Hippocampal Neurons

Neurites of neurons under acute or chronic stress form bundles of filaments (rods) containing 1∶1 cofilin∶actin, which impair transport and synaptic function. Rods contain disulfide cross-linked cofilin and are induced by treatments resulting in oxidative stress. Rods form rapidly (5–30 min) in >80% of cultured hippocampal or cortical neurons treated with excitotoxic levels of glutamate or energy depleted (hypoxia/ischemia or mitochondrial inhibitors). In contrast, slow rod formation (50% of maximum response in ∼6 h) occurs in a subpopulation (∼20%) of hippocampal neurons upon exposure to soluble human amyloid-β dimer/trimer (Aβd/t) at subnanomolar concentrations. Here we show that proinflammatory cytokines (TNFα, IL-1β, IL-6) also induce rods at the same rate and within the same neuronal population as Aβd/t. Neurons from prion (PrP^C)-null mice form rods in response to glutamate or antimycin A, but not in response to proinflammatory cytokines or Aβd/t. Two pathways inducing rod formation were confirmed by demonstrating that NADPH-oxidase (NOX) activity is required for prion-dependent rod formation, but not for rods induced by glutamate or energy depletion. Surprisingly, overexpression of PrP^C is by itself sufficient to induce rods in over 40% of hippocampal neurons through the NOX-dependent pathway. Persistence of PrP^C-dependent rods requires the continuous activity of NOX. Removing inducers or inhibiting NOX activity in cells containing PrP^C-dependent rods causes rod disappearance with a half-life of about 36 min. Cofilin-actin rods provide a mechanism for synapse loss bridging the amyloid and cytokine hypotheses for Alzheimer disease, and may explain how functionally diverse Aβ-binding membrane proteins induce synaptic dysfunction.     

Near-Field Coupling Method for Subwavelength Surface Plasmon Polariton Waveguides

A near-field coupling method for studying propagation properties of surface plasmon polariton (SPP) in subwavelength dielectric-loaded SPP waveguides (DLSPPWs) is presented. In this method, a tapered fiber probe is employed to generate a nanometer optical spot. When this spot is near the entrance of the DLSPPW with its polarization parallel to the waveguide, a strong guiding wave is observed by a leakage radiation microscope. For DLSPPWs with a dielectric height of about 600 nm, we observed SPP waves with zigzag propagation patterns at 650 nm wavelength. Such zigzag propagation results in a great reduction of propagation loss. In addition, the zigzag wave has a strong optical confinement. The bending loss for an L-bend DLSPPW is only about 0.4 dB.     

Demonstrating Weakly Acid-Fast Tubercle Bacteria in Sputum

Acid-fastness of the tubercle bacteria has long been used as the common method of diagnosis in sputum. It has been suggested sometimes that tuberculosis could occur without demonstrable bacteria, as well as with acid-fast bacteria, non-acid-fast bacteria or granules. It is shown in this paper that some of the sputa which are negative to the standard staining technic will show rods, rods with round polar bodies, or similar bodies without the rod portion. It is also pointed out that the decolorization of the smears by acid alcohol be shortened to approximately 3 to 5 seconds and picric acid be used as a counterstain. These forms are apparently the varying stages of the loss of acid-fastness. It is essential that a counterstain be used which will not interfere, and yellow is indicated because it does not absorb the red rays. Sputa which are negative to the standard acid-fast staining technic but which come from persons with a variable intermittent fever should be stained by this modified technic before they are pronounced germ-free.     

A MIM Filter Based on a Side-Coupled Crossbeam Square-Ring Resonator

In this paper, a surface plasmon polarition filter based on a side-coupled crossbeam square-ring resonator is presented and the transmission characteristics of the filter are analyzed by using the finite difference time domain method. The simulation results indicate that the proposed resonator supports multiple resonant modes, and these resonant modes can be adjusted all together by varying the length and refractive index of the outer square ring or partially adjusted by changing the width and refractive index of the crossbeam. By adding two coupled waveguides to the structure, we further demonstrate that a multiple wavelength download filter can be achieved via different coupled waveguides. The proposed structure has potential applications in plasmonic integrated circuits.     

The production and assessment of a plastic rod for the Chinese Reference Preparation for Opacity

A reference preparation for opacity consisting of a plastic rod was introduced by Perkins et al. in 1973. It was adopted as the International Reference Preparation for Opacity in 1975. This plastic rod opacity reference preparation has been used to standardize the Chinese National Bacterial Opacity Standard. The material was prepared from plastic sheet by a water-bath method and by a dry-heat method; the sheet was then machined into the plastic rods. We have studied the technical processes and set up methods for the examination of the sheets and rods. The water-bath method was found to be better than the dry-heat method in our tests. Collaborative assays in research institutes of biological products have shown that the plastic rod can replace the glass-powder suspension. The duration of validity of the plastic rod opacity reference preparation and that of the glass-powder suspension used for the Chinese National Bacterial Opacity Standard were studied and found to be similar. For this reason the plastic rod opacity reference preparation has not been widely used in China.     

High-resolution crystal structures of trimeric and rod phycocyanin

The phycobilisome light-harvesting antenna in cyanobacteria and red algae is assembled from two substructures: a central core composed of allophycocyanin surrounded by rods that always contain phycocyanin (PC). Unpigmented proteins called linkers are also found within the rods and core. We present here two new structures of PC from the thermophilic cyanobacterium Thermosynechococcus vulcanus. We have determined the structure of trimeric PC to 1.35 Å, the highest resolution reported to date for this protein. We also present a structure of PC isolated in its intact and functional rod form at 1.5 Å. Analysis of rod crystals showed that in addition to the α and β PC subunit, there were three linker proteins: the capping rod linker (L_R^8.7), the rod linker (L_R), and only one of three rod-core linkers (L_RC, CpcG4) with a stoichiometry of 12:12:1:1:1. This ratio indicates that the crystals contained rods composed of two hexamers. The crystallographic parameters of the rod crystals are nearly identical with that of the trimeric form, indicating that the linkers do not affect crystal packing and are completely embedded within the rod cavities. Absorption and fluorescence emission spectra were red-shifted, as expected for assembled rods, and this could be shown for the rod in solution as well as in crystal using confocal fluorescence microscopy. The crystal packing imparts superimposition of the three rod linkers, canceling out their electron density. However, analysis of B-factors and the conformations of residues facing the rod channel indicate the presence of linkers. Based on the experimental evidence presented here and a homology-based model of the L_R protein, we suggest that the linkers do not in fact link between rod hexamers but stabilize the hexameric assembly and modify rod energy absorption and transfer capabilities.