Fine Nylon Thread Research Articles

Scattering measurements from a dissolving bubble

A laboratory-scale study on acoustic scattering from a single bubble undergoing dissolution in undersaturated fresh water is presented. Several experiments are performed with the acoustic source driven with five-cycle tone bursts, center frequency of 120 kHz, to insonify a single bubble located on axis of the combined beam of the set of transducers. The bubble is placed on a fine nylon thread located in the far field of the transducer set, arranged in bistatic configuration, in a tank filled with undersaturated water. Backscattered waveforms from the bubble target are acquired every few seconds for several hours until the bubble has completely dissolved, and detailed dissolution curves are produced from the acoustic data. The rate of bubble dissolution is calculated using the solution developed by Epstein and Plesset [J. Chem. Phys. 18, 1505-1509 (1950)]. The results of the experiments performed are in agreement with the calculations.

Suppression of proliferative cholangitis in a rat model by local delivery of paclitaxel.

Proliferative cholangitis (PC) leads to biliary stricture, which is the main cause of hepatolithiasis, recurrent cholangitis, and biliary cirrhosis. The aim of this study was to determine whether local delivery of paclitaxel, which inhibits cell proliferation by overstabilization of microtubules, prevents PC in a rat model. PC was induced by introducing a fine nylon thread into the bile duct in a rat. Paclitaxel (100 microl of 10, 100, and 1000 micromol/l) or solvent vehicle was administered into the bile duct for 15 min. One week after treatment, histopathologic examination and 5-bromodeoxyuridine (BrdU) labeling of the bile duct were performed. In comparison with the control, the mean thickness of the bile duct was reduced by 29% in the 1000 micromol/l paclitaxel-treated group (2.61 +/- 0.31 microm vs 3.67 +/- 0.25 micro m, P << 0.05). The luminal area increased ( P << 0.0001) and the grade of epithelial-glandular proliferation was decreased ( P << 0.01) as the dose of paclitaxel increased. Ductal fibrosis and inflammatory cell infiltration were similar in both groups. The BrdU labeling index was significantly lower in the paclitaxel-treated group ( P << 0.05). Local delivery of paclitaxel suppressed PC in a rat model by the inhibition of epithelial-glandular proliferation and may offer an effective therapeutic option for biliary stricture.

Suppression of Proliferative Cholangitis by E2F Decoy Oligodeoxynucleotide

Background. Proliferative cholangitis (PC) associated with hepatolithiasis results in stricture of the main bile ducts and is a major cause of residual and/or recurrent stones after repeated treatment for hepatolithiasis. The transcription factor E2F controls the expression of several genes involved in cell proliferation. The aim of this study was to inhibit PC using cytostatic gene therapy by transferring fusigenic anionic liposome–hemagglutinating virus of Japan (HVJ–anionic liposome) complexes containing a synthetic double-stranded oligodeoxynucleotide with high affinity for E2F (E2F decoy).Materials and methods. PC was induced by introducing a fine nylon thread into the bile duct in a rat model. HVJ–anionic liposomes containing the E2F decoy were administered directly into the biliary tract. HVJ–anionic liposomes containing a missense oligodeoxynucleotide (scramble decoy) were also given as a control. The count of peribiliary glands in the bile duct, 5′-bromodeoxyuridine (BrdU) labeling index, and immunohistochemical staining for proliferating cell nuclear antigen (PCNA) in the bile duct were compared among untransfected, scramble decoy-transfected, and E2F decoy-transfected rats.Results. E2F decoy-transfected bile ducts showed inhibition of the papillary proliferation of the biliary epithelium and peribiliary gland hyperplasia. BrdU incorporation and PCNA expression in the bile ducts were inhibited in E2F decoy-transfected rats.Conclusion. Our cytostatic gene therapy approach using direct E2F decoy transfer into the biliary tract suppressed PC in a rat model and may offer an effective therapeutic option for reducing recurrence following treatment for hepatolithiasis.

On scattering from a bubble located near a flat air–water interface: Laboratory measurements and modeling

Scattering by a single bubble near a flat air-water interface is investigated theoretically and experimentally. A ray-acoustic interpretation is used to describe the four scattering paths, from source to bubble to receiver, that determine the response of the bubble. Multiple scattering effects are accounted for using a closed-form solution derived from the multiple scattering series. Experiments are performed by placing a bubble with radius a approximately 425 microm on a fine nylon thread, which is approximately 100 microm in diameter and practically transparent to sound, at a distance d from the interface. The primary variable is d and it ranges from 1 a to 100 a. The bubble is excited by tone bursts with a center frequency of 120 kHz, with the transducers arranged in both bistatic and monostatic configurations. Theory and experiment are in good agreement, verifying the dominant effect of the four paths in the response of the bubble, with multiple scattering playing a role for kd < 1, where k is the wave number of the medium. In the long-range limit our simulations agree with those of Ye and Feuillade [J. Acoust. Soc. Am. 102, 798-805 (1997)] including the shifting of the bubble's resonant frequency. The dependence of scattering on transducer arrangement, range to bubble, grazing angle, and phase relation among the four paths, vis-à-vis monostatic and bistatic scattering, is discussed.

On scattering effects due to the proximity and relative position of two bubbles in a sound field

Recently the authors published results from a theoretical and experimental investigation on scattering of sound from two bubbles symmetrically arranged about the combined beam axis of a set of transducers [J. Acoust. Soc. Am. 107, 3006–3017 (2000)]. In this presentation the investigation is extended to two additional geometries, with the two bubble array placed at angles of 0° and 45° from the combined beam axis. For each angle, the half interbubble distance d is varied such that the dimensionless variable kd ranges from 0.2–5 (for the 0° case) and 0.2–10 (for the 45° case), where k is the acoustic wave number. Modeling is accomplished by using a closed-form solution derived from the multiple scattering series, with the bubble scattering function expressed in terms of spherical harmonics. Experimental data are obtained by symmetrically arranging two bubbles, each of radius a≊425 μm, on a fine nylon thread, with the bubbles insonified by tone bursts with a center frequency of 120 kHz. The data closely agree with the simulations, and it is verified that, regardless of the geometry, for kd≤1 the response of the two bubble array drastically departs from the one due to single scattering. This departure is attributed to multiple scattering and is manifested as a reduction in backscattered radiation.

Monostatic and bistatic scattering by a single bubble near a pressure release interface: Laboratory measurements and modeling

Scattering by a single bubble near a flat pressure release interface is investigated theoretically and experimentally. A ray-acoustic interpretation is used to describe the four scattering paths, from source to bubble to receiver. Multiple scattering effects are accounted for using a closed-form solution derived from the multiple scattering series. A bubble with radius a≊425 μm is placed on a fine nylon thread, which is practically transparent to sound, at a distance dB from the interface. The primary variable is dB and it ranges from 1a to 100a. Experiments are performed at a frequency of 120 kHz with the transducers arranged in both bistatic and monostatic configuration. Theory and experiment are in excellent agreement, verifying the dominant effect of the four paths in the response of the bubble, with multiple scattering playing a role for kdB&amp;lt;1, where k is the wave number of the medium. In the long-range limit our simulations agree with those of Ye and Feuillade [J. Acoust. Soc. Am. 102, 798–805 (1997)] including the shifting of the bubble’s resonant frequency. The dependence of scattering on transducer arrangement, range to bubble, grazing angle, and phase relation among the four paths, vis-à−vis monostatic and bistatic scattering, are discussed.

Suppression of proliferative cholangitis in a rat model with direct adenovirus-mediated retinoblastoma gene transfer to the biliary tract.

Proliferative cholangitis (PC) associated with hepatolithiasis develops the stricture of main bile ducts, and is the main cause of residual and/or recurrent stones after repeated treatments for hepatolithiasis. The aim of this study was to inhibit PC using the cytostatic gene therapy with direct adenovirus-mediated retinoblastoma (Rb) gene transfer to the biliary tract. PC was induced by introducing a fine nylon thread into the bile duct in a rat model. The adenovirus vector encoding a nonphosphorylatable, constitutively active form of retinoblastoma gene product (AdRb) was administered directly into the biliary tract. The adenovirus vector encoding beta-galactosidase (AdlacZ) was also given as a control. The bile duct wall thickness and 5'-bromodeoxyuridine (BrdU) labeling index were compared among uninfected, AdlacZ-infected, and AdRb-infected PC rats. The Rb expression in the bile duct was detected using reverse-transcription polymerase chain reaction (RT-PCR) and immunohistochemical study. AdRb-infected bile ducts showed inhibition of the epithelial and fibrous tissue proliferation and the peribiliary gland hyperplasia, resulting in a significant reduction of wall thickness compared with uninfected and AdlacZ-infected ones. The BrdU labeling index was 4.87% +/- 3.06% in the AdRb-infected bile ducts, while those of uninfected and AdlacZ-infected ones were 15.48% +/- 4.61% and 11.72% +/- 1.23%, respectively (P < .05). In conclusion, our cytostatic gene therapy approach using direct Rb gene transfer into the biliary tract suppressed PC in a rat model and may offer an effective therapeutic option for reducing recurrences following treatments against hepatolithiasis.

Secondary nucleation of magnesium sulphate from single seed crystal by fluid shear in agitated supersaturated aqueous solution

Distributions of the waiting time, the time required for a first nucleation at a constant degree of supercooling, and supercooling temperatures (or the maximum undercoolings) were measured for the fluid shear secondary nucleation from a single seed crystal (0.014-0.018 g) suspended by a fine nylon thread (0.1 mm in diameter) in an agitated supersaturated solution. These data are analysed by a stochastic model (random nucleation model) which deals with the nucleation as a random process. The waiting time is distributed exponentially. From the distribution, the nucleation probability B, a probability of nucleation per unit time and per seed crystal, was determined at undercooling of 3.0–7.0°C for the solution saturated at 40.0°C. The average supercooling temperature predicted by the model using B thus determined is in good agreement with the values measured at cooling rates of 3.35 × 10 -3, 6.75 × 10 -3 and 1.33 × 10 -2°C/s. The model explains reasonably well the cooling rate dependence of the supercooling temperature.

Contact nucleation of MgSO 4 · 7 H 2O at low impact energy levels

Secondary nuclei were produced by low energy collisions between a rotating glass impeller and a seed crystal suspended in the stirred solution by a fine nylon thread. This collision method was devised to simulate the crystal-impeller collision in a real crystallizer. The number of nuclei per contact increased linearly with an increase of the impact energy. It also increased proportionally to the 1.52th power of the supercooling. These results are of importance for the description of nucleation in a real crystallizer.

Phasic Growth of the Leaves of Cereals

DURING some recent experiments on leaf growth, observations were made which do not appear to have been previously recorded in the literature. Initial measurements were made on a potted plant of cape barley (Hordeum vulgare L.) which had been defoliated several times and was growing vigorously in the vegetative phase. A continuous record of leaf elongation was taken in the following manner: a very fine nylon thread was attached to the leaf tip and to the short arm of a thermograph from which the bimetallic element had been removed. The pen arm maintained the leaf in a taut condition and was adjusted to present minimum frictional drag on the lever. The recorder and plant were placed in a draught-free and shock-free position to obtain full autumn sunlight through glass. A continuous record of leaf elongation was obtained covering the weekly thermograph chart by raising the recording unit whenever the lower chart limit was reached. Free water was present in the pot tray at all times during the experiments. This record is illustrated in Fig. 1, in which the original sense of direction of elongation is reversed about the lever fulcrum. The lever magnification was ten times, and the original chart width 3 in.

On Energy Separation by Aerodynamic Processes

Expressions for Damping Matrices in Linear Vibration Problems P. LANCASTER 256 F RECENT CONTRIBUTIONS to the Readers' Forum have given further consideration to the heating effects in the Hartmann generator which were first investigated by Sprenger. Interest seems now to be concentrated on certain unsteady-flow phenomena associated with supersonic exciting jets: alternating swallowing and spilling of the jet accompanied by the movement of pressure pulses out of and into the resonator. Recent attempts to analyze the heating process' 4 have used models based on these unsteady phenomena and have hinged on the question of whether or not the pressure pulses steepen into shocks. I t seems judicious to recall at this time that Sprenger found very large heating effects for subsonic jets also—provided that turbulence was introduced into the jet. (He used a fine nylon thread across the nozzle to accomplish this.) This subsonic heating was also observed by Sibulkin and Vrebalovich. I t seems quite impossible to explain it using the shock-tube theories presently being formulated. Sprenger found too that the heating produced within a resonance tube by supersonic jets was increased (by a factor as great as four) by the introduction of turbulence. Another aerodynamic-heating effect was reported in the Readers' Forum by Glassman and John. They discovered that the total temperature increased along the center line of both supersonic and subsonic free jets, the ambient and jet total temperatures being equal. The rise in temperature began only at the end of the potential core of the jet. The nozzle used in the supercritical case was designed to produce a shockless jet.