Largest Linear Dimension Research Articles

Analysis of technological gaps impact on radar cross-section of a collapsible corner reflector

Corner reflectors used for calibration of radar stations, despite their apparent simplicity, have a number of disadvantages that manifest themselves both in the design and in their manufacture and operation. One of the main disadvantages is that in order to achieve high values of the radar cross-section (RCS), corner reflectors must have large linear dimensions. In addition, to ensure reliable electrical contact, their designs are usually non-separable. All of the above together complicates their operation and transportation, due to the large dimensions and weight of the products. The aim of the article is to develop and investigate by strict electrodynamic methods a corner reflector of a collapsible lightweight design, as well as to evaluate the influence of design features on RCS. The paper presents the results of modeling corner reflectors of a prefabricated structure by strict electrodynamic methods and investigates the influence of design features on its RCS. In particular, the influence of gaps at the top and between the edges of the reflector has been analyzed, the limits of the permissible sizes of these defects have been determined. Based on the results of the study, a lightweight collapsible layout of a corner reflector with square faces has been developed and manufactured. The correspondence of the RCS of the manufactured corner reflector layout to the calculated values has been experimentally confirmed. The performed studies have shown the practical feasibility of lightweight corner reflectors of collapsible design and confirmed the possibility of their use in radar system testing. Information about the impact of defects in the manufacture of corner reflectors on their RCS enables developers to use simpler and cheaper technological and design solutions in the development of corner reflectors.

The associations of indices of echocardiography with polymorphism of genes of angiotensinogen and angiotensin receptor type I in examined patients with chronic rheumatic heart disease

The purpose of study is to evaluate associations of polymorphism of genes encoding components of renin-angiotensin system and indices of echocardiography in examined patients with rheumatic heart disease (RHD). The sampling consisted of 128 patients with RHD and average age 58,96±0,34 years. The echocardiography was implemented using Philips Affinity 50 machine. The genetic typing was carried out according polymorphic markers Thr174Met, Met235Thr and А1166С by polymerase chain reaction in real-time with electrophoretic scheme of detecting the result of "SNP-EXPRESS". The heterozygosis of Thr174Met results in larger dilatation of left sections of heart. The Thr174Thr homozygotes characterized by large linear dimensions of right heart. The Thr235Thr homozygotes characterized by minimal parameters reflecting hypertrophy of left ventricle of heart. There was no significant difference in echocardiography indices in patients with A1166A polymorphism. The mutations in codon 235 and 174 did not affect distance of 6-minute walk test. The statistically significant difference in the distance of 6-minute walk test was obtained only for А1166С: the minimum distance indicators is in the group of A1166C heterozygotes - 291,46 (273,83-309,09) meters and the maximum distance in С1166С homozygotes - 357,20 (309,21-405,19) meters. In patients with RHD, Thr174Met heterozygosis can lead to dilatation of left heart camera, while homozygosis for Thr174Mr leads to dilatation of right heart camera and left ventricular hypertrophy. The Met235Thr heterozygosis, on the contrary, are characterized by minimal sizes of left atrium and right ventricle. Polymorphism of the A1166C gene encoding angiotensin type I receptor had practically no effect on echocardiography indices in patients with RHD.

Finite-size scaling for a first-order transition where a continuous symmetry is broken: The spin-flop transition in the three-dimensional XXZ Heisenberg antiferromagnet.

Finite-size scaling for a first-order phase transition where a continuous symmetry is broken is developed using an approximation of Gaussian probability distributions with a phenomenological "degeneracy" factor included. Predictions are compared with data from Monte Carlo simulations of the three-dimensional, XXZ Heisenberg antiferromagnet in a field in order to study the finite-size behavior on a L×L×L simple cubic lattice for the first-order "spin-flop" transition between the Ising-like antiferromagnetic state and the canted, XY-like state. Our theory predicts that for large linear dimension L the field dependence of all moments of the order parameters as well as the fourth-order cumulants exhibit universal intersections. Corrections to leading order should scale as the inverse volume. The values of these intersections at the spin-flop transition point can be expressed in terms of a factor q that characterizes the relative degeneracy of the ordered phases. Our theory yields q=π, and we present numerical evidence that is compatible with this prediction. The agreement between the theory and simulation implies a heretofore unknown universality can be invoked for first-order phase transitions.

Development of Process for Fast Plasma-Chemical Through Etching of Single-Crystal Quartz in SF6/O2 Gas Mixture

Process for deep plasma-chemical etching of single-crystal quartz plates in a SF6/O2 gas mixture was developed. The method of scientific experiment design based on the Taguchi matrix technique was used to rank basic technological parameters (bias voltage applied to the substrate holder, output power of the high-frequency generator, oxygen flow rate, and position of the substrate holder relative to the lower edge of the discharge chamber) as regards their influence on the etching rate. The ranking results were used to optimize the plasma-chemical etching process and perform a control experiment on through etching of windows with large linear dimensions (3 × 10 mm) in a single-crystal quartz plate (z-cut) with thickness of 369 μm.

Additive manufacturing of hierarchical injectable scaffolds for tissue engineering

We present a 3D-printing technology allowing free-form fabrication of centimetre-scale injectable structures for minimally invasive delivery. They result from the combination of 3D printing onto a cryogenic substrate and optimisation of carboxymethylcellulose-based cryogel inks. The resulting highly porous and elastic cryogels are biocompatible, and allow for protection of cell viability during compression for injection. Implanted into the murine subcutaneous space, they are colonized with a loose fibrovascular tissue with minimal signs of inflammation and remain encapsulation-free at three months. Finally, we vary local pore size through control of the substrate temperature during cryogenic printing. This enables control over local cell seeding density in vitro and over vascularization density in cell-free scaffolds in vivo. In sum, we address the need for 3D-bioprinting of large, yet injectable and highly biocompatible scaffolds and show modulation of the local response through control over local pore size. Statement of SignificanceThis work combines the power of 3D additive manufacturing with clinically advantageous minimally invasive delivery. We obtain porous, highly compressible and mechanically rugged structures by optimizing a cryogenic 3D printing process. Only a basic commercial 3D printer and elementary control over reaction rate and freezing are required. The porous hydrogels obtained are capable of withstanding delivery through capillaries up to 50 times smaller than their largest linear dimension, an as yet unprecedented compression ratio. Cells seeded onto the hydrogels are protected during compression. The hydrogel structures further exhibit excellent biocompatibility 3 months after subcutaneous injection into mice.We finally demonstrate that local modulation of pore size grants control over vascularization density in vivo. This provides proof-of-principle that meaningful biological information can be encoded during the 3D printing process, deploying its effect after minimally invasive implantation.

Simulation of mechanical parameters of graphene using the DREIDING force field

Molecular mechanics/molecular dynamics (MM/MD) methods are widely used in computer simulations of deformation (including buckling, vibration, and fracture) of low-dimensional carbon nanostructures (single-layer graphene sheets (SLGSs), single-walled nanotubes, fullerenes, etc). In MM/MD simulations, the interactions between carbon atoms in these nanostructures are modeled using force fields (e.g., AIREBO, DREIDING, MM3/MM4). The objective of the present study is to fit the DREIDING force field parameters (see Mayo et al. J Phys Chem 94:8897–8909, 1990) to most closely reproduce the mechanical parameters of graphene (Young’s modulus, Poisson’s ratio, bending rigidity modulus, and intrinsic strength) known from experimental studies and quantum mechanics simulations since the standard set of the DREIDING force field parameters (see Mayo et al. 1990) leads to unsatisfactory values of the mechanical parameters of graphene. The values of these parameters are fitted using primitive unit cells of graphene acted upon by forces that reproduce the homogeneous deformation of this material in tension/compression, bending, and fracture. (Different sets of primitive unit cells are used for different types of deformation, taking into account the anisotropic properties of graphene in states close to failure.) The MM method is used to determine the dependence of the mechanical moduli of graphene (Young’s modulus, Poisson’s ratio, and bending rigidity modulus) on the scale factor. Computer simulation has shown that for large linear dimensions of SLGSs, the mechanical parameters of these sheets are close to those of graphene. In addition, computer simulation has shown that accounting for in-layer van der Waals forces has a small effect on the value of the mechanical moduli of graphene.

A Validated Nomogram to Predict Upstaging of Ductal Carcinoma in Situ to Invasive Disease.

Approximately 8-56% of patients with a core needle biopsy (CNB) diagnosis of ductal carcinoma in situ (DCIS) will be upstaged to invasive disease at the time of excision. Patients with invasive disease are recommended to undergo axillary nodal staging, most often requiring a second operation. We developed and validated a nomogram to preoperatively predict percentage of risk for upstaging to invasive cancer. We reviewed 834 cases of DCIS on CNB between January 2004 and October 2014. Multivariable analysis was used to evaluate CNB and imaging factors to develop a nomogram to predict the risk of upstaging from DCIS to invasive cancer. This nomogram was validated with an external dataset of 579 similar patients between November 1998 and September 2016. An area under the receiver operating characteristic curve was constructed to evaluate nomogram discrimination. The rate of upstaging to invasive disease was 118/834 (14.1%). On multivariable analysis, grade on CNB and imaging factors, including mass lesion, multicentric disease, and largest linear dimension, were associated with upstage to invasive disease, and was used to develop a nomogram (c-statistic 0.71). In the external validation dataset, 62/579 (10.7%) patients were upstaged to invasive disease. Our nomogram was validated in this dataset with a c-statistic of 0.71. For patients with a CNB diagnosis of DCIS, our validated nomogram using DCIS grade on biopsy, and imaging factors of mass lesion, multicentric disease, and largest linear dimension, may be used for preoperative assessment of risk of upstaging to invasive disease, allowing patient counseling regarding axillary staging at the time of definitive surgery.

QUASI-DISTRIBUTED FIBER-OPTIC RECIRCULATING SYSTEM FOR TEMPERATURE MEASUREMENT BASED ON WAVELENGTH-DIVISION MULTIPLEXING TECHNOLOGIES

Providing quality and reliable operation as well as temperature monitoring of modern systems are directly related on the use of innovative fiber optic technology based on the concept of so-called distributed and quasi-distributed sensors having large linear dimensions, in which the optical fiber is both sensor and data channel. Existing fiber optic sensors based on stimulated Raman scattering and stimulated Brillouin scattering have relatively high measurement error, long and complicated measurement method, high cost. The purpose of this paper was to develop an automated quasi-distributed fiber optic recirculating temperature measurement system using wavelength division multiplexing technology. Measurement method based on the registration arising due to temperature changes of the frequency of single optical pulses recirculating at adjacent wavelengths. Thus there is a periodic signal restoration on waveform, amplitude and duration. The sensing element is a segment of a multimode silica fiber coated with metal, separated spectrally selective elements, which are mainly offered to use dichroic mirrors. With the help of the developed mathematical model that takes into account the temperature dependence of the coefficient of linear expansion and Young’s modulus of the fiber, the spectral and temperature dependence of the refractive index, the chemical composition of the fibers, the type of metal coating system response function was calculated, which allows to evaluate the sensitivity and measurement accuracy. These studies determined: number of measuring sections (8), the maximal measured temperature (500 °C), the sensitivity (3,28 Hz/°C), the measurement error (±0,2 °C), and the optimum beginning time measurement after starting circulation (15 min), and counting time of the frequency meter (1 s). Carried out estimations have shown that the proposed measuring system can outperform existing analogues on set specifications.

Low-dose chemotherapy with methotrexate and vinblastine for desmoid tumors: A single institution experience.

e22524 Background: Desmoid tumor (DT) is a rare and locally invasive proliferative disease. Although, the absence of metastatic potential, it has the propensity for locally invasive growth and recur. Chemotherapy may be considered in inoperable and/or recurrent disease. Methods: Patients with histological diagnosis of DT and treated with weekly low-dose chemotherapy with vinblastine and methotrexate between January 1998 and December 2015 were identified and their medical records were analyzed. Results: Of 23 patients analyzed, most of them were women (female-to-male ratio 2.8:1). The median age at presentation was 29 years (range, 18-59 years). Tumors location was: thoracoabdominal wall (n: 11, 47.8%), extremities (n: 7, 30.4%), abdominal cavity (n: 1; 4 %), and head and neck (n: 4, 17.3%). Tumor sizes were documented in 18 cases and ranged from 3 to 20 cm in largest linear dimension (median, 10 cm). Eight (34.7%) female had pregnancy history and 2 (8%) had familial adenomatous polyposis history. Eleven (47,8%) underwent surgery as first-line treatment. Five (21.7%) patients received first-line treatment with vinblastine and methotrexate, four (17.3%) patients as second-line, and 14 (60.8%) patients as third and fourth-line. Fourteen ( 60.8%) patients had stable disease, four (17.3%) had partial response, and five (21.7%) patients had progressive disease during chemotherapy treatment. After a median follow-up of 58 months, 12 patients had progression disease and 2 patients died. The median PFS was 29 months, without any progression after 32 months. Conclusions: Weekly low-dose chemotherapy with vinblastine and methotrexate appears to have significant activity. Chemotherapy could be an acceptable alternative to radical surgery in selected patients with desmoid tumors.

Giant quiescent solar filament observed with high-resolution spectroscopy

A giant, quiet-Sun filament was observed with the high-resolution Echelle spectrograph at the Vacuum Tower Telescope at Observatorio del Teide on 2011 November 15. A mosaic of spectra (10 maps of 100" X 182") was recorded simultaneously in the chromospheric absorption lines H-alpha and Na I D2. Physical parameters of the filament plasma were derived using Cloud Model (CM) inversions and line core fits. The spectra were complemented with full-disk filtergrams (He I 10830 A, H-alpha, and Ca II K) of the Chromspheric Telescope (ChroTel) and full-disk magnetograms of HMI. The filament had extremely large linear dimensions (817"), which corresponds to about 658 Mm along a great circle on the solar surface. A total amount of 175119 H-alpha contrast profiles were inverted using the CM approach. The inferred mean line-of-sight (LOS) velocity, Doppler width, and source function were similar to previous works of smaller quiescent filaments. However, the derived optical thickness was larger. LOS velocity trends inferred from the H-alpha line core fits were in accord, but smaller, than the ones obtained with CM inversions. Signatures of counter-streaming flows were detected in the filament.The largest conglomerates of brightenings in the line core of Na I D2 coincided well with small-scale magnetic fields as seen by HMI. Mixed magnetic polarities were detected close to the ends of barbs. The computation of photospheric horizontal flows based on HMI magnetograms revealed flow kernels with a size of 5-8 Mm and velocities of 0.30-0.45 km/s at the ends of the filament. The physical properties of extremely large filaments are similar to their smaller counterparts, except for the optical thickness which in our sample was found to be larger. We found that a part of the filament, which erupted the day before, is in the process of reestablishing its initial configuration.

Influence of the magnetization-distribution nonuniformity on the sensitivity of anisotropic magnetoresistive sensors

The specific features of numerical calculation of the magnetization-reversal process in thin-film components with large linear dimensions and a complex topology in relation to magnetoresistive transducers (sensors) are considered. The calculated value of the sensor sensitivity obtained within the framework of a uniform and micromagnetic magnetization-reversal model is compared with experimental data. Calculations of the magnetization-reversal process within the framework of the micromagnetic model show the positive effect of edge magnetization pinning which is manifested in the mutual compensation of current and magnetization- distribution nonuniformities; it can be used to enhance the sensitivity of anisotropic magnetoresistive (AMR) sensors.

Phase Transitions in the Antiferromagnetic Heisenberg Model on a Triangular Lattice with the Next-Nearest Neighbor Interactions

The critical behavior and phase transitions (PT) of the three-dimensional antiferromagnetic Heisenberg model on a layered triangular lattice with nearest-neighbor (J) and next-to-nearest neighbor (J1) interactions is studied by the replica Monte Carlo method. The first order phase transition has been revealed in the studied model based on the histogram method of processing data of the Monte Carlo for systems with large linear dimensions. Shown that the system exhibits the pseudouniversal critical behavior in the case of small lattices.

Phase transitions in the two-dimensional antiferromagnetic Potts model on a triangular lattice

Phase transitions and thermodynamic properties in the two-dimensional three-state antiferromagnetic Potts model on a triangular lattice are investigated using the Monte Carlo method and the histogram analysis of the data. It is shown that pronounced first-order phase transitions are observed in this model for systems with rather large linear dimensions (L > 120). No first-order PTs are observed for systems with L < 120.

Five-year results of photodynamic therapy with and without supplementary antivascular endothelial growth factor treatment for polypoidal choroidal vasculopathy

To clarify the long-term efficacy of photodynamic therapy (PDT) in patients with symptomatic polypoidal choroidal vasculopathy (PCV). We retrospectively reviewed 60 naive eyes of 59 patients (45 men, 14 women; mean age, 73.8years) treated with full-fluence PDT (PDT group) and followed for at least 60months. Retreatment was either antivascular endothelial growth factor (VEGF) therapy or intravitreal triamcinolone acetonide if PDT alone was ineffective (supplemental retreatment group). The mean logarithm of the minimum angle of resolution best-corrected visual acuity (BCVA) levels at baseline and 60months were 0.66 and 0.71, respectively. The mean change at 60months was a decrease of 0.50 line. In the PDT group (36 eyes), the mean BCVAs at baseline and month 60 were 0.73 and 0.68, respectively (p = 0.60). In the supplemental retreatment group (24 eyes), the mean BCVAs at baseline and month 60 were 0.55 and 0.74, respectively (p = 0.076). The percentage of eyes with decreased BCVA at the time of the additional anti-VEGF treatment was significantly (p = 0.031) higher than at month 60. The risk factors identified by multiple regression analysis with a significant decrease in BCVA at month 60 were a large greatest linear dimension (GLD), classic choroidal neovascularization at baseline, and a hemorrhage over the arcade vessels after PDT. The efficacy of PDT for PCV depends on the GLD. Twenty-four of the 60 eyes needed additional treatment other than only PDT during 60months of follow-up. Additional anti-VEGF treatment may help maintain the BCVA of patients with exudative or anatomic recurrence.

High-resolution spectroscopy of a giant solar filament

AbstractHigh-resolution spectra of a giant solar quiescent filament were taken with the Echelle spectrograph at the Vacuum Tower Telescope (VTT; Tenerife, Spain). A mosaic of various spectroheliograms (Hα, Hα±0.5 Å and Na D2) were chosen to examine the filament at different heights in the solar atmosphere. In addition, full-disk images (He i 10830 Å and Ca ii K) of the Chromspheric Telescope and full-disk magnetograms of the Helioseismic and Magnetic Imager were used to complement the spectra. Preliminary results are shown of this filament, which had extremely large linear dimensions (~740″) and was observed in November 2011 while it traversed the northern solar hemisphere.

Complex Polarization Response in Plasmonic Nanospirals

Archimedean nanospirals exhibit many far-field resonances that result from the lack of symmetry and strong intra-spiral plasmonic interactions. Here, we present a computational study, with corroborating experimental results, on the plasmonic response of the 4π Archimedean spiral as a function of incident polarization, for spirals in which the largest linear dimension is less than 550 nm. We discuss the modulation of the near-field structure for linearly and circularly polarized light in typical nanospiral configurations. Computational studies of the near-field distributions excited by circularly polarized light illustrate the effects of chirality on plasmonic mechanisms, while rotation of linearly polarized light provides a detailed view of the effects of broken symmetry on nanospiral fields in any given direction in the plane of the spiral. The rotational geometry exhibits a preference for circular polarization that increases near-field enhancement compared to excitation with linearly polarized light and exchanges near-field configurations and resonant modes. By analyzing the effects of polarization and wavelength on the near-field configurations, we also show how the nanospiral could be deployed in applications such as tunable near-field enhancement of nonlinear optical signals from chiral molecules.

Electrokinetic transport of rigid macroions in the thin double layer limit: A boundary element approach

A boundary element (BE) procedure is developed to numerically calculate the electrophoretic mobility of highly charged, rigid model macroions in the thin double layer regime based on the continuum primitive model. The procedure is based on that of O'Brien (R.W. O'Brien, J. Colloid Interface Sci. 92 (1983) 204). The advantage of the present procedure over existing BE methodologies that are applicable to rigid model macroions in general (S. Allison, Macromolecules 29 (1996) 7391) is that computationally time consuming integrations over a large number of volume elements that surround the model particle are completely avoided. The procedure is tested by comparing the mobilities derived from it with independent theory of the mobility of spheres of radius a in a salt solution with Debye–Hückel screening parameter, κ. The procedure is shown to yield accurate mobilities provided κa exceeds approximately 50. The methodology is most relevant to model macroions of mean linear dimension, L, with 1000 > κ L > 100 and reduced absolute zeta potential ( q | ζ | / k B T ) greater than 1.0. The procedure is then applied to the compact form of high molecular weight, duplex DNA that is formed in the presence of the trivalent counterion, spermidine, under low salt conditions. For T4 DNA (166,000 base pairs), the compact form is modeled as a sphere (diameter = 600 nm) and as a toroid (largest linear dimension = 600 nm). In order to reconcile experimental and model mobilities, approximately 95% of the DNA phosphates must be neutralized by bound counterions. This interpretation, based on electrokinetics, is consistent with independent studies.

Rotodynamic pump scaling.

Despite extensive theoretical knowledge of fluid dynamics, the design process for rotodynamic pumps still relies heavily on experimental data. One common technique is to model the design of a new pump based on the design of existing pumps, using the laws of similarity. Another, similar approach frequently used for atypically large or small pumps is to scale a final product design from conveniently sized laboratory prototypes that have been refined to the desired performance in extensive experiments. Both approaches to pump design are usually considered highly reliable. However, for blood pumps, this approach has been questioned. Due to the extremely small size of these pumps and the relatively low Reynolds Numbers, extraneous effects may overwhelm the assumptions made for similarity calculations that are satisfactory for significantly larger models. Three geometrically similar pumps with related scaling factors of 1, 3.2, and 6.4 were tested for the same range of nondimensional flow and pressure. The quality of similitude was determined by comparing the nondimensionalized pump data of the three pumps. It was found that the effects of large linear dimension scaling factors had only a small influence on the quality of similitude (maximum 5.8% error), whereas Reynolds Number effects, especially at high pump flows, had a strong impact on the quality of similitude (maximum 45.4% error). Because Reynolds Number similarity cannot always be achieved simultaneously with geometric similarity, a correction factor for Reynolds Number related departure from similarity was developed. It is based on the Reynolds Number, the Flow Coefficient, the specific speed, and the pump's relative surface roughness. Use of this correction factor reduces the error due to Reynolds Number effects to a maximum of 7.5%. We conclude that the use of scaling techniques in rotodynamic blood pump design is a valid approach, if Reynolds Number similarity is maintained or suitable correction factors are used.

Formation of two-dimensional monochromatic images of a laser jet by a spherically bent mica crystal

Two-dimensional x-ray images were obtained for a laser-generated plasma jet as it collided with an obstacle and expanded in a static magnetic field. A mica crystal bent to form a spherical surface of 100 mm radius was used. The images were formed by the radiation representing the resonance and inter-combination lines of the Mg XI ion. A shock-compressed zone formed near the obstacle and the expansion cone of the Mg XI ions became narrower in a transverse magnetic field. The spatial resolution in the plane of the image was better than 100 μm for objects of large linear dimensions (~10 mm).

A new mechanism of ultrasonic absorption in aqueous solutions of rigid macromolecules

The temperature- and frequency-dependences of the ultrasonic absorption in lyotropic liquid crystals of rod-like FD virus particles have been measured with the ultrasonic beam being parallel or perpendicular to the rod axis. The experimental results show a strongly anisotropic ultrasonic absorption in the lyotropic liquid crystals, which varies with temperature exactly as the shear viscosity of water. Experimental results are in good agreement with the following model for the absorption process. The authors believe that the absorption arises from differential flow of water between the relatively long and rigid rod-like macromolecules. This mechanism of ultrasonic absorption becomes dominant for frequencies of 1-100 MHz. The validity of this mechanism is, however, not restricted to the special lyotropic crystals discussed here. Instead, this absorption process is expected to be important also for other macromolecular solutions whenever the dissolved macromolecular objects have a sufficiently large linear dimension in the direction parallel to the sound beam.