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At least 199 records · Page 11Linked to original sources
PubMed2005

Temperature variation of film tension above the bulk smectic-A-isotropic transition in freestanding liquid-crystal films.

We have measured the temperature variation of film tension above the bulk smectic-A-isotropic transition in freestanding films of two liquid-crystal compounds. Above the transition, the tension increases sharply with temperature, and the slope is proportional to the film's thickness regardless of whether or not the compound exhibits regular layer-by-layer thinning. The data can be interpreted in the context of theoretical models for layer thinning.

Journal Article↗
PubMed2006

Role of molecular weight and phase sequence in the temperature variation of film tension above the bulk isotropic transition in freestanding liquid-crystal films.

Building upon our previous report [Veum, Phys. Rev. E 17, 020701(R) (2005)] involving two compounds, we have performed a systematic study of the temperature variation of film tension above the bulk isotropic transition in freestanding films to include a total of six smectic liquid-crystal compounds. Consistent with the previous results, the tension increases sharply with temperature above the transition, the tension-temperature slope is proportional to the film's thickness, and the data can be interpreted in the context of theoretical models for layer thinning. Our data suggest that both molecular weight and bulk phase appearing below its isotropic phase play important roles in the slope values.

Journal Article↗
PubMed2005

Effects of the rate of evaporation and film thickness on nonuniform drying of film-forming concentrated colloidal suspensions.

In this paper, we report on nonuniform distribution of film-forming waterborne colloidal suspensions above the critical concentration phi(c) of the colloidal glass transition during drying. We found that colloidal suspension films dry nonuniformly when the initial rate of evaporation E and/or the initial thickness l(0) are high. We found that a Peclet number Pe, defined as Pe = El(0)/D, where D is the diffusion coefficient of the colloids in the diluted suspensions, does not predict uniformity of drying of the concentrated suspensions, contrary to the reported work on drying of diluted suspensions. Since the colloidal particles are crowded and their diffusive motion is restricted in concentrated suspensions, we assumed that above phi(c) water is transported to the drying surface by hydrodynamic flow along the osmotic pressure gradient. The permeability of water through channels between deforming particles is estimated by adapting the theory of foam drainage. We defined a new Peclet number Pe' by substituting the transport coefficient of flow (defined as the permeability divided by the viscosity, multiplied by the osmotic pressure gradient) for the diffusion coefficient. This extended Peclet number predicted the nonuniform drying with a criterion of Pe' > 1. These results indicate that the mechanism of water transport to the drying surface in concentrated suspensions is water permeation by osmotic pressure, which is faster than mutual diffusion between water and particles --that has been observed in diluted suspensions and discussed by Routh and Russel. The theory fits well the experimental drying curves for various thicknesses and rates of evaporation. The particle distribution in the drying films is also estimated and it is indicated that the latex distribution is nonuniform when Pe' > 1.

Journal Article↗
PubMed1996

Evaluation of soft-tissue foreign bodies: comparing conventional plain film radiography, computed radiography printed on film, and computed radiography displayed on a computer workstation.

OBJECTIVE: The study was performed to evaluate detection of soft-tissue foreign bodies using conventional radiography (film-screen radiography), computed radiography printed on films (computed radiography-hard copy), and computed radiography displayed on a computer workstation (computed radiography-soft copy). SUBJECTS AND METHODS: Fifteen foreign bodies of different size, shape, and composition were implanted at different locations in a fresh cadaveric hand, and images were obtained using three radiographic techniques. Images were evaluated by four board-certified radiologists to ascertain the conspicuity of the foreign bodies with the different techniques. A subjective grade was assigned to each image in an attempt to identify the relative conspicuity of foreign bodies when imaged with the three techniques. RESULTS: Computed radiography-soft copy is the preferred imaging technique for the detection of wood and plastic foreign bodies in soft tissue regardless of the size of the wood or the plastic. No significant differences in conspicuity among the three techniques were demonstrated with glass foreign bodies. CONCLUSION: Detection of soft-tissue foreign bodies is best done using computed radiography-soft copy instead of film-screen radiography and computed radiography-hard copy imaging.

Cadaver↗
PubMed2004

Properties of sodium caseinate film-forming dispersions and films.

The flow properties of sodium caseinate (NaCAS) film-forming dispersions were studied as a function of protein and glycerol concentration. Apparent viscosity vs. concentration profiles showed a disruption at about 10% (wt/wt) NaCAS. This was interpreted in terms of protein-water and protein-protein interactions. The presence of glycerol in the NaCAS film-forming suspensions reduced the viscosity of aqueous NaCAS as a consequence of decreasing protein-protein and protein-solvent interactions through the hydrogen bonding formation between the glycerol, the polypeptide chain of NaCAS, and water molecules. For higher concentration of glycerol, viscosity of NaCAS dispersions increased as a result of increasing total solid content. The glass transition temperature for solid films of 10% (wt/wt) NaCAS decreased with the glycerol content. The glycerol-protein interactions reduced the protein-protein interaction and, thus, increased the intermolecular spacing, leading to higher protein chain mobility and water vapor permeability.

Caseins↗
PubMedDate not supplied

Evaluation of new film high-light system by comparison with conventional film.

The 3M "High Light System" has been used in a clinical environment for one and one-half years. The inherent advantages, as well as the disadvantages, of this system are discussed. An objective comparison of the blue based HL film and the conventional Type R film was made. This comparison indicates that image quality is similar with either film and, hence, radiographs produced with either system will be of diagnostic quality.

Evaluation Studies as Topic↗
PubMed1997

Effect of film size on production of foreign body sarcoma by perforated film implants.

Sarcoma may arise on unabsorbable foreign bodies in rodents and more rarely in man. Perforations of the implant reduce its carcinogenicity so that nitrocellulose filters of pore size 0.45 micron have failed to induce tumour. We examined whether increase of surface area would restore carcinogenesis to film with such pore size. Nitrocellulose filters of 25 mm diameter and pore size 0.45 micron were implanted singly, in pairs and in trios subcutaneously in 3 respective groups of BALB/c mice (total 97) and observed for sarcomagenesis for 100 weeks. No tumour arose on the singles (surface area 0.98 mm2), while 7 arose on the paired (1.96 mm2) at a mean of 54 weeks and 16 on the trios (2.95 mm2) at a mean of 46 weeks (differences significant at p > 0.01). A sufficiency of surface area restores carcinogenicity to perforated foreign surfaces in mice. Surface area is dominant over film perforation size in film sarcomagenesis.

Animals↗
PubMed1990

A film phantom for routine film dosimetry in the clinical environment.

This paper describes a new film phantom we have designed that eliminates many of the problems found in phantoms used in film dosimetry. This phantom employs two sheets of solid water attached with nylon hinges and aligned with pins. It is made light-impermeable through the use of nylon hook-and-loop fasteners. This new design shows good agreement with ion-chamber measurements over the full depth of electron penetration.

Film Dosimetry↗
PubMedDate not supplied

[Clinical and comparative study of the image quality of 3 digital radiographic systems, E-speed film and digitalized film]].

The aim of this study was to evaluate, subjectively, the image quality of two CCD digital systems, a digital storage phosphor system, a digitized film and an E-speed film. Five objects were radiographed with 50, 60 and 70 kVp, with exposure times of 0.08, 0.13, 0.2, 0.4 and 0.8 s. In order to maximize the fidelity of the results, the dental X-ray unit employed was submitted to an evaluation so that the relation between exposure time and dose could be established. A good reproducibility was obtained. Six evaluators analyzed 375 images, using a scoring scale which ranged from 0 to 4. The results revealed different responses, indicating that the storage phosphor system had the best performance, in the various exposures employed. However, it was possible to conclude that all systems studied, except for the Sens-A-Ray, can offer images in ideal conditions for the diagnosis, as long as their latitudes are respected.

Humans↗
PubMed1986

[Foam-gel film and gel film in trauma surgery].

Presented are the experiences with new wound dressings in the treatment of open wounds and burns in traumatologic surgery. The foam-gel-film stimulates secondary healing wounds in the development of granulation tissue and the gel-film is used as a wound dressing after skin transplantation and in burns.

Bandages↗
PubMed1986

Are malaria films requested appropriately? A study of all film requests in one health district.

In a 12-month period 238 patients had blood films examined for malaria parasites in a London district general hospital. All the available medical records of these patients were studied. The ethnic origin and country from which the patients had travelled were typical of an area with a large immigrant population. 27 of the films were positive. 39 were judged to have been requested inappropriately, usually because an adequate travel history had not been taken. Imported malaria is an important problem in this health district and contributes significantly to the laboratory workload.

Clinical Laboratory Techniques↗
PubMed2006

Automated dynamic headspace organic solvent film microextraction for benzene, toluene, ethylbenzene and xylene. Renewable liquid film as a sampler by a programmable motor.

A simple, fast and efficient dynamic headspace-organic solvent film microextraction (DHS-OSFME) method using a new automatic device was developed. The renewable organic films were formed inside a microsyringe barrel using the uniform and repeated movement of the syringe plunger enabled by programmable stirring motor. The plunger speed, number of extraction cycles, and dwell time (stop time after each half round) were controlled by a computer software, which was written by C++ Builder. A theoretical treatment of the DHS-OSFME based on the consecutive first-order process is proposed in this report. A mathematical solution for the dynamic process of the mass transfer was obtained by correlating the variation of analyte concentration in the syringe volume with the plunger speed and the amount of analyte extracted to the OSF. Benzene, toluene, ethylbenzene, and o-xylene (BTEX) were employed as model compounds to assess the extraction procedure and were determined by gas chromatography-flame ionization detection. Of the three organic solvents (1-octanol, benzyl alcohol and n-dodecane) studied as extractants, n-dodecane proved to be the most sensitive solvent for the extraction of these analytes. Several parameters, including the syringe withdrawal rate, dwelling time, number of extraction cycles, sampling volume, sample temperature, and ionic strength of the solution, were investigated for their effects on the extraction performance. The calibration graphs were linear in the range of 0.5-200 ng ml(-1), with the detection limits between 0.18 and 0.35 ng ml(-1). Wastewater samples were extracted by the optimized method, and determined using the standard addition method.

Automation↗
PubMed2006

Digitisation of electron microscope films: six useful tests applied to three film scanners.

A series of simple tests have been used to measure the performance of flat-bed film scanners suitable for digitisation of electron micrographs. Two of the film scanners evaluated are commercially available and one has been constructed in the laboratory paying special attention to the needs of the electron microscopist. The tests may be useful for others.

Image Processing, Computer-Assisted↗
PubMed1998

Amperometric biosensor with a composite membrane of sol-gel derived enzyme film and electrochemically generated poly(1,2-diaminobenzene) film.

A sol-gel silicate-based biosensor for glucose was made by utilizing a composite membrane of sol-gel enzyme film and electrochemically generated poly(1,2-diaminobenzene) film to improve the selectivity of the sol-gel enzyme sensors. The stability of the sensor was improved by exposing the enzyme layer to glutaraldehyde vapor. The glucose sensor responded rapidly (ca. 15 s) to glucose at 0.6 V (versus Ag/AgCl), without any interferences from electroactive species such as L-ascorbate and urate below 0.2 mM. Reliable results were obtained in the assays of glucose in controlled human sera, with both the steady-state and flow-injection measurements. Subsequently, the same sol-gel procedure was applied to the preparation of the sensors for galactose and cholesterol. The galactose and cholesterol sensors responded rapidly to galactose and cholesterol, respectively, although the sensitivity of these sensors was inferior to that of glucose sensor.

Biocompatible Materials↗
PubMed2002

Degradation of aliphatic polyester films by commercially available lipases with special reference to rapid and complete degradation of poly(L-lactide) film by lipase PL derived from Alcaligenes sp.

Commercial lipases were examined for their degradation efficiency of aliphatic polyester films. In 100 days immersion of polyester films in lipase solutions at 37 degrees C at pH 7.0, Lipase Asahi derived from Chromobacterium viscosum degraded polybutylene succinate-co-adipate (PBSA), poly (e-caprolactone) (PCL) and polybutylene succinate (PBS), and Lipase F derived from Rhizopus niveus degraded PBSA and PCL during 4-17 days. Lipase F-AP15 derived from Rhizopus orizae could degrade PBSA in 22 days. In these cases, PBS and PBSA were mainly degraded to dimers, whereas PCL was mainly degraded to monomers. Only poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB/V) and poly (L-lactide) (PLA) were not degraded in the experiments. However, PLA degraded completely at 55 degrees C, pH 8.5 with Lipase PL during 20 days. This result could be explained with the sequential reactions of the chemical hydrolysis of the polymer to oligomers at higher pH and temperature, and the succeeding enzymatic hydrolysis of oligomers to the monomers.

Adipates↗
PubMed1982

[Studies on the precorneal tear film. First communication: an optical system for demonstrating tear film without fluorescein (author's transl)].

Tear film is usually studied by using fluorescein. An optical system is described which despenses with the use of fluorescein. It mainly consists in an equal diffuse illumination of the cornea, provided through an opaque truncated cone that is illuminated from behind. The cone is situated as close as possible to the front of the eye. The cornea and its surface can be observed through a hole at the narrow end of the cone. Interferences in the lipid layer of the tear film are recognizable as "colors of thin layers". The physical background to interferences in thin, convex layers is discussed. Break-ups are visualized by using a supplementary "Schlieren" method.

Biomechanical Phenomena↗
PubMed2000

Edge dislocation in a vertical smectic-A film: line tension versus temperature and film thickness near the nematic phase

The line tension of a dislocation is measured in a vertical smectic-A film as a function of temperature and film thickness. There are two contributions to the line tension: a bulk contribution that corresponds to the energy of the dislocation in an infinite medium and a surface correction that accounts for interactions with the two free surfaces. Both terms are measured in pure 8CB (octylcyanobiphenyl) as a function of temperature when the bulk nematic-smectic-A transition temperature T(c) is approached.

Journal Article↗