Loop Diameter Research Articles

X-ray diffractometry and high-resolution electron microscopy of neutron-irradiated SiC to a fluence of 1.9×10 27 n/m 2

Neutron-induced damage in SiC up to a fluence of 1.9×10 27 n/m 2 ( E>0.1 MeV) was examined by means of X-ray diffractometry and high-resolution electron microscopy. Specimens of β-SiC were irradiated in fast breeder reactors at 370 to 650°C. The lattice parameters of all specimens were increased by the irradiation, but above 2×10 26 n/m 2 lattice expansion decreased and was accompanied by significant peak broadening. Electron microscopy revealed a high density of interstitial loops on {111}, where X-ray diffraction peaks showed marked broadening. Peak broadening could be attributed mainly to the crystallite size effect at lower fluences, but a strain contribution was significant above 2×10 26 n/m 2. Electron diffraction patterns and high-resolution images indicated preservation of crystallinity up to the highest fluence observed. Thermal annealing up to 1000°C did not affect the peak broadening and average loop diameter. Above 1400°C, decrease in lattice strain and increase in crystallite size with increasing annealing temperature were observed.

Carotid wall viscosity increase is related to intima-media thickening in hypertensive patients.

Increases in arterial wall viscosity and intima-media thickness (IMT) were found in hypertensive patients. Because smooth muscle cells are responsible for the viscous behavior of the arterial wall and they are involved in the process of thickening of the intima-media complex, this study evaluates the relationship between carotid thickness and wall viscosity. The simultaneous and noninvasive assessment of the intima-media complex and arterial diameter waveform was performed using high-resolution ultrasonography. This technique was contrasted against sonomicrometry in sheep, showing that the waveforms obtained by both methods were similar. The common carotid arteries of 11 normotensive subjects (NTA) and 11 patients with mild to moderate essential hypertension (HTA) were measured noninvasively by using tonometry and an automatic densitometric analysis of B-mode images to obtain IMT and instantaneous pressure and diameter loops. A viscoelastic model was used to derive the wall viscosity index (eta) using the hysteresis loop elimination criteria. In NTA, eta was 2.73+/-1.66 (mm Hg x s/mm) and IMT was 0.58+/-0.08 (mm), whereas in HTA, eta was 5.91+/-2.34 (P<.025) and IMT was 0.70+/-0.12 (P<.025), respectively. When all data of eta versus IMT of NTA and HTA were pooled in a linear regression analysis, a correlation coefficient of r=.71 (P<.05) was obtained. Partial correlation between eta and IMT holding constant pressure was r=.59 (P<.05). In conclusion, wall viscosity increase was associated with a higher IMT even maintaining blood pressure fixed, suggesting that the intima-media thickening might be related to smooth muscle alterations manifested as an increase in viscous behavior.

Hemolysis complicating coil occlusion of patent ductus arteriosus.

We report on 5 patients who developed hemolysis (the Hemolysis group) following coil occlusion for PDA, and compare their data to 66 cases which were not complicated by hemolysis despite residual leak (the No Hemolysis group). A significant leak with a heart murmur was more frequent in the Hemolysis group than in the No Hemolysis group. The ratio of the sum of the loop diameter of coils to the minimal diameter of the ductus (C/D) in those who developed persistent hemolysis that needed a second intervention (2.2+/-0.4) was significantly smaller than in the No Hemolysis group (3.1+/-1.1). Persistent hemolysis can occur if a significant residual shunt remains after implantation of coils with small C/D. As this complication may be avoided by complete closure or, if not complete, a minimal leak, we should be careful to make residual leaks as small as possible by the use of multiple coils.

Dislocation recovery kinetics in single‐crystal calcite

We investigated static recovery of dislocations in calcite by annealing a deformed single crystal at 873–1073 K in a CO2 atmosphere (pCO2=0.1 MPa) for different times. The sample used for the annealing experiments was shortened ∼5% parallel to at 873 K and at a strain rate of ∼10−5 s−1. Slip occurred primarily on and with minor contributions from . Intensively jogged dislocations and sinusoidal, curved dislocations with short wavelengths of∼0.15 μm are common in both the as‐deformed sample and the annealed samples. There is no observable decrease in the average apparent diameter (∼0.1 μm) of dislocation loops in the annealed samples. The activation energy for dislocation recovery is 184±22 kJ mol−1. The recovery kinetics and dislocation substructures suggest that dislocation recovery may be rate controlled by dislocation climb, which is, in turn, controlled by vacancy core diffusion. The dimensions of the bowed‐out dislocation segments and prismatic loops suggest that the source‐sink distance for vacancies along dislocation lines is smaller than the mean free path of core vacancies and may allow core diffusion to be dominant.

Transmission electron microscopy and scanning force microscopy of poly r(A-U) and poly r(A-U)-ethidium bromide.

Transmission electron microscopy and scanning force microscopy of negative-stained, carbon-coated replica and mica-adsorbed preparations of 200 microM poly r(A-U) and 50 microM ethidium bromide/200 microM poly r(A-U) have been employed to evaluate ethidium-induced changes in poly r(A-U) topology. Poly r(A-U) alone exhibits elongated conformations 85-115 nm in length that possess a number of hairpin loops as well as single-stranded domains. While the double-stranded domains are found predominately at the base of the hairpin loops (diameter = 5-30 nm), other rod-like (presumably double-stranded) regions ranging from 25-80 nm in length are present in other portions of the poly r(A-U). In contrast with the poly r(A-U) alone, the EB/poly r(A-U) combination appears as a heterogeneous population of condensed structures whose lengths and widths vary from 12-88 nm and 15-45 nm, respectively. These conformational changes are due to a number of factors, including the displacement of ordered water surrounding the poly r(A-U) and charge shielding of the phosphate groups of the poly r(A-U) upon the binding of the ethidium.

Multiturn split-conductor transmission-line resonator

A split-conductor parallel-plate transmission line resonator is a simple structure made from bending a strip of double-face copper-clad printed-circuit board into a loop with alternate electrical discontinuities (gaps) on opposite sides. Its natural resonant frequency (Fn) is determined by the transmission line characteristic impedance, the loop diameter or strip length, and the number (Ng) of gaps. It is easy to design high frequency resonators simply by increasing Ng. We propose here a single-gap multiturn resonator for low frequency operation as well as a simplified expression for the determination of Fn. A design procedure of this type of resonator is outlined and illustrative examples with parallel-plate as well as ordinary 50 Ω coaxial transmission lines are given. Also, for a given cable length, numerical calculation shows that the minimum resonator frequency can be attained with a form factor of the order of 2.

A simple method for making reproducible fibre loops for protein cryocrystallography

A practical, step-by-step description of the construction of loops for protein cryocrystallography using pulled-out micro-injection capillaries is described. The advantages of this method are the high reproducibility of the loops, the ease of adjustment of the loop diameter and the formation of thin films owing to the narrow base of the loop. During assembly, the loop does not make contact with either glue or cement.

リント回路基板近傍磁界の時間軸波形計測

This paper describes a time domain magnetic field measurement process for measuring magnetic fields near printed circuit boards (PCBs) with a loop probe. In carrying out these measurements, the loop probe needs to be calibrated in the frequency domain. In this process, a microstrip line with a teflon substrate serving as the standard magnetic field source is employed as a means of calibrating the probe. The standard magnetic field intensities of the line are calculated by using an approximate equation obtained from Ampere's law to simplify the calibration. The sensor-factor of the probe obtained from this method agrees with that obtained through the use of a standard G-TEM cell in 2 dB at frequencies below 1 GHz. The waveforms of magnetic fields near a PCB having a four-layer construction are measured using a 10 mm diameter loop probe as the calibrated magnetic field sensor. The generation of magnetic field waveforms causing the radiated emission from the PCB is found to depend on the circuit operating conditions. Our results clarify the fact that the time domain magnetic field measurement process is an effective tool for analyzing the sources of emission radiated from PCBs and for investigating the radiation mechanism. © 1998 Scripta Technica, Electr Eng Jpn, 125(4): 9–18, 1998

Removal of Bacteria from Beef Tissue by Spray Washing after Different Times of Exposure to Fecal Material

This study examined the effect of exposure time of beef-fat fascia to an inoculated fecal paste on the efficiency of removal of bacteria by spray washing or rinsing. Brisket fat (obtained <15 min postmortem) samples (10 by 10 by 2 cm) were inoculated, in the geometric center of their fascia surface, with four 0.64-cm diameter loops of a bovine fecal paste containing an inoculum (108 CFU/g) of streptomycin-resistant Escherichia coli ATTC 11370. Triplicate samples were spray washed with water (35°C, 20.7 bar) and then rinsed with solutions of 2% acetic acid, 5% hydrogen peroxide, or 12% trisodium phosphate, or spray washed with water at 35°C or 74°C (20.7 bar), in an automated spray-washing cabinet for 12 s, after 0, 2, or 4 h of exposure to the inoculated fecal paste. The samples were analyzed for streptomycin-resistant bacterial counts. Washing or washing/rinsing at time 0 (immediately after exposure to the inoculated fecal paste) with trisodium phosphate, 35°C water, hydrogen peroxide, acetic acid, and 74°C water removed 3.04 ± 0.40, 3.52 ± 0.55, 3.62 ± 0.67, 3.69±0.72 and 4.17±0.55 log CFU/cm2, respectively. Applying the spray-washing treatments 2 or 4 h after exposure to the fecal paste resulted in significantly (P < 0.05) less removal (1.76 to 3.89 log CFU/cm2 after 2 hand 0.94 to 2.58 Jog CFU/cm2 after 4 h) of bacteria. Thus, the time of exposure to fecal contamination affected the attachment of bacteria to beef-carcass tissue, as indicated by the decreasing numbers of bacteria removed by spray washing with increasing time of exposure, regardless of the washing treatment. The most effective washing agent was 74°C water at all washing times.

Precipitation strengthening behavior of AlLi single crystals

The precipitation strengthening behavior of AlLi single crystals has been studied using compression test and transmission electron microscopy. The strengthening behavior of AlLi single crystals during the early stage of aging is well described by a recent version of order hardening theory for a weak obstacle regime in a dilute solution. The interpretation of experimental data differs depending on the exact configuration of the trailing dislocation in the dislocation pair. Experimental results are best interpreted by the equation derived on the assumption that the trailing dislocation completely pulls off from the encountering particles. The antiphase boundary energy is determined to be 0.118 J m −2, which is in reasonable agreement with that obtained from the measurement of critical loop diameter for the transition from shearing to looping, and from the measurement of dislocation pair spacings.

MICROWAVE ABSORPTION STUDIES ON V-B GROUP METAL OXIDES DOPED Bi(Pb)-2223 CERAMIC SUPERCONDUCTOR

Microwave absorption studies have been carried out on samples Bi 1.6 Pb 0.3 V 0.1 Sr 2· Ca 2 Cu 3 O y, Bi 1.6 Pb 0.3 Nb 0.1 Sr 2 Ca 2 Cu 3 O y, and Bi 1.6 Pb 0.3 Ta 0.1 Sr 2 Ca 2 Cu 3 O y. DC Microwave absorption studies of all the samples showed the presence of single 2223 phase. Variation of Low Field Microwave Absorption (LFMA) signal amplitude of these samples showed definite peaks at 95 K, 83 K and 90 K respectively. The temperature dependent average Josephson loop diameter was estimated for all these samples. The experimental data was analyzed on the basis of Josephson Medium Model. From this model, the temperature dependent junction penetration depth λ j , Josephson junction upper and lower critical fields H C1j and H C2j and Josephson junction critical current densities J Cj were estimated.

The silent period induced by transcranial magnetic stimulation in muscles supplied by cranial nerves: normal data and changes in patients.

The silent period induced by transcranial magnetic stimulation of the sensorimotor cortex (Magstim 200, figure of eight coil, loop diameter 7 cm) in active muscles supplied by cranial nerves (mentalis, sternocleidomastoid, and genioglossus) was studied in 14 control subjects and nine patients with localised lesions of the sensorimotor cortex. In the patients, measurements of the silent period were also made in the first dorsal interosseus and tibialis anterior muscles. In the controls, there was a silent period in contralateral as well as ipsilateral cranial muscle and the duration of the silent period increased with increasing stimulus intensities. The mean duration of the silent period was around 140 ms in contralateral mentalis muscle and around 90 ms in contralateral sternocleidomastoid muscle at 1.2 x threshold stimulation strengths. Whereas the duration of the silent period in ipsilateral mentalis muscle was shorter than on the contralateral side it was similar on both sides in sternocleidomastoid muscle. In patients with focal lesions of the face associated primary motor cortex and corresponding central facial paresis, the silent period in mentalis muscle was shortened whereas it was unchanged or prolonged in limb muscles (first dorsal interosseus, tibialis anterior) with stimulation over the affected hemisphere. By contrast, in a patient with a lesion within the parietal cortex, the silent period in mentalis muscle was prolonged with stimulation of the affected side.

LFMA and irreversibility line studies on Vanadium doped Bi(2223) superconducting system

Suresh Babu et al [7] have reported the stabilization of Bi high T c (105 K) phase by vanadium oxide doped Bi(2223) superconducting system. Stabilization of Bi high T c phase in the absence of Pb makes this system interesting. In this paper we report low field microwave absorption (LFMA) studies of Bi 2−xV x Sr 2 Ca 2 Cu 3 O y (x=0 and 0.4 superconducting samples. Temperature dependent LFMA signal amplitude of x=0 sample showed definite peaks at 97 K and 70 K which may correspond to the 2223 and 2212 phases. In the case of x=0.4 sample, it showed a single peak at 90 K corresponding to 2223 phase. The thermodynamical critical magnetic field H Cl ∗ and average Josephson loop diameter was estimated for these samples from the LFMA signals. In addition we have also determined the irreversibility line from ZFC and FC susceptibility measurements. The irreversibility line followed the universal law H ∗= H o(1- T ∗/ T c) a . n and H o were foud to be 2.8 and 4075 Oe respectively.

Multigap parallel-plate bracelet resonator frequency determination and applications

A loop made from a length of transmission line with alternate electrical discontinuities (gaps) on the two conductors behaves as a resonator whose resonant frequency is a function of the transmission line parameters as well as its form and the number (n) of gaps. For a given loop diameter, one can thus design a wide range of resonant frequency by choice of n and the characteristic impedance Zc of the line. The analysis is illustrated by a parallel-plate transmission line resonator in the form of a bracelet. Experimental resonant frequencies obtained from resonators of various dimensions are in good agreement with calculated values. Two resonators were tested on a 3 T NMR imager: A 11 cm diameter 1H surface coil, yielding results comparable to those obtained from a lumped capacitor coil and a 13 cm diameter volume coil to perform in vivo muscle 13C spectroscopy without 1H decoupling.

Scaling laws for single-phase natural circulation loops

The power-to-volume scaling laws used for the construction of scaled test facilities simulating the primary system of nuclear power plants result in loops of the same elevation (and length) with reduced diameters. The adequacy of these scaling laws for simulating single-phase natural circulation was tested in three rectangular loops, each having the same elevation but different loop diameters of 6 mm, 11 mm and 23.2 mm respectively. The experiments showed that the power-to-volume scaling principles adequately describe the steady state behaviour. The stability behaviour observed in the loop 23.2 mm in diameter, however, could not be reproduced in the smaller diameter loops. Subsequent theoretical investigation of the single-phase natural circulation phenomenon showed that the transient and stability behaviour can be simulated only if the diameter ratio D p/ D m is also simulated. The theoretical investigation suggested the following scaling laws for single-phase natural circulation: ( Gr m ) p =( Gr m ) m L p L m = D p D m = H p H m = (L h ) p (L h ) m ( St m ) p =( St m ) m For simulating the steady state behaviour alone, it is sufficient to simulate the product Gr m( D/ L).

The 30 nm chromatin fiber as a flexible polymer.

Our analysis of the data of van den Engh, Sachs, and Trask (Science 257, 1410 (1992)), for the dependence of the mean square distance between pairs of hybridization sites (< L2n >, micron 2) on the known genomic distance (n, bp) separating these sites on chromosome number 4 in G1 human fibroblast nuclei, shows that < L2n > is proportional to n2v with v = 3/5 for n < 1 Mbp. The v-value of 3/5 is characteristic of flexible polymer chains with excluded volume effects in dilute good solutions. Since the DNA concentration in nuclei is very high (ca. 1-10 mg/ml), and theory (Flory, J. Chem. Phys. 17, 303, 1949) predicts v = 1/2 for overlapping polymers, the finding of v = 3/5 means that the chromatin fibers do not overlap in interphase nuclei. The dependence of < L2n > on n for n < 4 Mbp is consistent with the model of large (approximately 6 Mbp, 3 microns diameter) loops of interphase chromatin attached to nuclear membrane sites. Using the constant (e.g., Widom, Ann. Rev. Biophys. Biophys. Chem. 18, 365 (1989)) and variable (Williams & Langmore, Biophys. J. 59, 606 (1991)) diameter fiber models, the Kuhn statistical segment of the 30 nm chromatin fiber was estimated to have a length of 196-272 nm with a corresponding DNA content of 21-37 kbp.(ABSTRACT TRUNCATED AT 250 WORDS)

Encapsulation of Seeds in Gel by Impact

A loop of wire, dipped into a solution of sodium alginate, captured a meniscus of gel. A seed, placed on top of the meniscus, was driven inside the drop and the drop was detached from the loop during impact. The detached drop of gel, with the seed inside, fell into a solution of calcium chloride where a skin of insoluble calcium alginate formed around the drop. Wire diameter, loop diameter, and gel concentration all affected the volume of gel in capsules formed. Wire loops in diameters ranging from 3.2 to 11.1 mm (0.13 to 0.44 in.) were fabricated from high-strength wire of diameters ranging from 0.56 to 1.04 mm (0.022 to 0.041 in.). Gels in concentrations ranging from 1.25 to 2.50% by weight were used. Capsules ranging in volume from 2.5 to 240 mL (1.53 ¥ 10–4 to 1.46 ¥ 10–2 in.3) were formed from gel at temperatures ranging from 5 to 35° C (41 to 95° F). A device with 16 wire loops, complete with a vacuum-powered seed singling unit, was capable of producing at least 160 capsules per minute.

Effects of composition and helium injection on dislocation loop development in pure FeNiCr alloys under Ni ion irradiation

Pure Fe35Ni7Cr, Fe45Ni7Cr, Fe40Ni13Cr and Fe45Ni15Cr alloys were irradiated by 4MeV Ni 2+ ions at 948 K to doses of about 0.05, 0.3 and 1.0 dpa without helium injection or with simultaneous helium injection. With increasing Ni content and decreasing Cr content, the diameter of radiation-induced dislocation loops increased, and the dose at which the dislocation loops disappeared to develop into dislocation networks decreased. The diameter of dislocation loops induced by Ni 2+ ions irradiation with simultaneous helium injection was larger than that without helium injection for the Fe35Ni7Cr and Fe45Ni7Cr alloys.

Magnetic flux tube model of gamma-ray burst †

We propose a new model of gamma-ray burst based on the assumption that the burst source is an old neutron star. We assume that there are two magnetic fields on the neutron star surface, one is the weak global dipole field, the other is strong localized magnetic loops. Using this model we can explain both the absorption features and the high-energy tail in the γ-ray burst spectrum. We calculated the Compton scattering cross section for a field of 1.7 × 10 12 G and found the parameter Λ (the product of the electron density and the diameter of the magnetic loops) to be about 10 21 cm −2.

Vortex-loop crinkling in the three-dimensional XY model: Numerical evidence in support of an ansatz.

A scaling theory for the three-dimensional (3D) XY ferromagnet was previously proposed, in terms of directed vortex loops of average diameter a=${\mathit{e}}^{\mathit{l}}$, and core size ${\mathit{a}}_{\mathit{c}}$(l). An ansatz was made for the loop self-energy from a 1/R potential, E\ensuremath{\sim}a ln[a/${\mathit{a}}_{\mathit{c}}$(l)]\ensuremath{\rightarrow}a ln${\mathit{K}}_{\mathit{l}}^{\mathrm{\ensuremath{-}}\mathit{x}}$, where ${\mathit{K}}_{\mathit{l}}$ is the screened coupling and x\ensuremath{\simeq}0.6 the self-avoiding random-walk exponent. Here, the central role of the core-size ansatz in producing known 3D XY exponents is brought out in numerical solutions of the scaling equations. We then relate the cutoff ${\mathit{a}}_{\mathit{c}}$(l) to radial fluctuations around the mean radius a/2, and provide partial numerical support for the ansatz by computer-generated vortex-loop configurations. A Flory-type polymer argument for the core size ${\mathit{a}}_{\mathit{c}}$(l) is given.