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At least 1,315 records · Page 73Linked to original sources
PubMed2005

Quality assurance of I-125 seed permanent implant therapy using a self-color developing reflection-type dosimetry sheet film.

PURPOSE: We evaluated a self-color developing sheet-type film for the detection of dead seeds in I-125 permanent implant therapy for prostate cancer. MATERIALS AND METHODS: As a preliminary study, we irradiated X-rays to a self-developing reflection-type sheet film and created a relational curve between absorbed dose and film density. I-125 seeds were placed on a film and the approximate absorbed dose of I-125 was calculated from the relational curve of X-rays. A cartridge in which a dead seed was loaded among 10 I-125 seeds was placed on the film and the detectability of the dead seed was evaluated. RESULTS: Using the relational curve of X-rays, it was possible to measure the approximate absorbed dose of I-125 seeds and to easily detect a dead seed at a glance. Using sterilized film, it was possible to detect a dead seed. CONCLUSION: The self-developing film method is feasible for the detection of a dead seed in a cartridge without re-sterilization of seeds.

Brachytherapy↗
PubMedDate not supplied

[Influence of ambient storage temperature on radiographic density and contrast of dated and outdated film].

The authors studied the influence of storage conditions of date and outdated films and the action of environment temperature over the same films. Four groups of films were studied: twenty-five outdated and twenty-five date films were under refrigeration; twenty-five date and twenty-five outdated films were under 36 degrees C temperature and 70% hygrometric for thirty days. Afterward, the films were exposed to radiation X at standardized conditions, together with an AI stepwedge penetrometer, to measure optical density; also the processing conditions were standardized. The results showed that temperature action and films date and outdated produced changes in the optical density and radiographic contrast.

Humidity↗
PubMed1994

Portal films for relative exit dose determinations.

Portal films are radiographic images taken regularly in external photon beam radiotherapy in order to verify geometrical set-up. However, they also contain quantitative dose information. Absolute dosimetry with film is possible but the desired accuracy of +/- 5% is difficult to achieve. However, relative dosimetry with film would be useful in combination with a point determination of absolute dose, though a dose response linearisation is required for relative dosimetry over the range of doses given to portal films in routine clinical practice. For this purpose, a technique for the rapid dose response linearisation of portal films is investigated in simulated treatment situations and evaluated in terms of the ability to yield relative exit dose distributions from the portal films. A combination of such distributions with a single determination of radiation transmission with diodes should generate full two-dimensional transmission information. Distributions obtained from two anthropomorphic phantoms provided results consistent with distributions obtained from a treatment planning system to generally within +/- 5%, and most often within +/- 2%. It is concluded that the extraction of exit dose information from portal films would be useful for mantle, compensated, or other unusual treatment situations.

Calibration↗
PubMed1996

Comparison of two film holders for periapical radiography performed by dental students.

A clinical study was done at Howard University, College of Dentistry, to compare the difference in the incidence of radiographic technique faults between two similar intraoral film-holding, beam-aligning, devices in a series of 1,248 radiographs. The primary difference between a conventional Extension Cone Paralleling (XCP-I) film holder and a modified, all-metal, Extension Cone Paralleling (XCP-II) film holder is the incorporation of a collimated rectangular x-ray-beam-restricting plate. This latter film holder possessed an indicator rod attached to the bite block and a metal shield to reduce primary and back-scattered radiation behind the film. In the oral diagnosis clinic, 78 dentulous patients were randomly selected and randomly divided into two groups of 39 patients. One of the two film holders was used separately for the two groups of patients, and a full mouth series of 16 periapical radiographs were made for each patient. The difference in the occurrence of total errors between the two instruments was not statistically significant. However, the conventional instrument was associated with significantly more errors in improper film positioning, while the modified device had significantly more errors in cone cutting (p < 0.01).

Adult↗
PubMed1996

Intraalveolar bubbles and bubble films. I. formation and development during the first 48 hours of extrauterine life in rabbits.

BACKGROUND: Aeration of mature lungs at birth depends on formation of intraalveolar bubbles and bubble films (Scarpelli 1978. Pediatr. Res., 12:1070-1076). Bubbles establish immediately structural stability and pulmonary gas exchange. Given that air spaces are cleared in minutes of fetal liquid (the initial substrate for bubble formation), in formation possible beyond this period? If so, is this related to early development of pulmonary function and structure? METHODS: Mature, spontaneously breathing rabbit pups at 1-10 min and 1, 3, 8, 24, and 48 h after vaginal birth were anesthetized, trachea was occluded at "resting volume" (approximately functional residual capacity), and lungs were rapidly exposed to preserve in vivo intrapulmonary status. The entire lung was examined by stereomicroscopy. Other determinations included resting volume, lung wet weight, volume-pressure curves, histological sections, lung dry weight, tissue hydroxyproline (OH-Pro), and lavage phospholipids (PL). Bubble mobility in situ was tested. Bubbles were released into bathing liquid by incision of peripheral units and monitored over time. RESULTS: Pup activity and gross appearance of the lungs, together with septal thinning, secondary septal development, clearance of intraluminal liquid, increasing tissue OH-Pro, and PL distribution indicated normal postnatal development. Each aerated unit examined at resting volume (all lobes, all ages) contained intraalveolar bubbles. Transition to free gas exclusively in conducting airways and bubbles/bubble films in peripheral gas exchange units occurred within 1 h. Bubbles appeared to be exclusively within alveoli at 4 h and thereafter. Bubbles persisted and new bubbles were formed during subsequent inflation to maximal volume and deflation to atmospheric pressure (P0). Volume of intact lungs at P0 was maintained by the counterforce of rigid bubble films against tissue retraction. When bubbles were released either at resting volume or at P0, the bubble-free loci became airless. Constant size and stability of released bubbles support preferential incorporation of surfactants into bubble films and constant "near-zero surface tension" (Scarpelli 1978. Pediatr. Res., 12:1070-1076). CONCLUSIONS: We show the ubiquitous presence of intraalveolar bubbles and bubble films in vivo throughout the first 48 h of postnatal life. Bubble film rigidity sustains aeration and prevents collapse, while low surface tension of the films facilitate liquid removal from the air spaces. Bubbles in situ are stable and, within apparent limits, mobile; after birth they are quickly restricted to the alveolar spaces, leaving airways bubble free.

Air↗
PubMed1997

Qualitative and quantitative analysis of the secondary structure of cytochrome C Langmuir-Blodgett films.

A qualitative and quantitative analysis of the conformation of Langmuir-Blodgett (LB) dried films of cytochrome C on silicon wafers was performed by Fourier transform ir (FTIR) spectroscopy. A deconvolution procedure was applied to the amide I band analysis, in order to determine the percentage of the different secondary structures. Qualitative analysis was performed by examining difference spectra. Films obtained by spreading protein solutions at pH 7.4 and 1, dried at 25 and 100 degrees C, on silicon wafers were also examined in order to detect spectral components associated with denatured protein domains, and to compare them with cytochrome C LB films. FTIR spectroscopy showed that the following important changes characterise LB film spectra: (a) the alpha-helix component is higher (its percentage is 57 and 54%) than the one estimated in dried film obtained by spreading the solutions at pH 7.4 on a silicon substrate (43%), (b) there is an increase in the intensity of bands attributed to protonated carboxy group bands, involved and not involved in the formation of hydrogen bonds, and a decrease in those attributed to deprotonated carboxy groups, (c) the intensity of several bands attributed to aromatic amino acids and aliphatic chains increases, and (d) bands due to O-H stretching vibrations of crystallization water are present. These conformational changes could be induced by protein-protein interaction caused by the close packing of molecules that occurs during LB film formation; it cannot be excluded that they may be accompanied by partial changes in the tertiary structure of the protein. A preferential orientation of protein molecules in LB films is also a possibility.

Animals↗
PubMed2000

Reflection and absorption of millimeter waves by thin absorbing films.

Reflection, transmission, and absorption of mm-waves by thin absorbing films were determined at two therapeutic frequencies: 42. 25 and 53.57 GHz. Thin filter strips saturated with distilled water or an alcohol-water solution were used as absorbing samples of different thicknesses. The dependence of the power reflection coefficient R(d) on film thickness (d) was not monotonic. R(d) passed through a pronounced maximum before reaching its steady-state level [R(infinity)]. Similarly, absorption, A(d), passed two maximums with one minimum between them, before reaching its steady-state level [A(infinity)]. At 42.25 GHz, A(d) was compared with absorption in a semi-infinite water medium at a depth d. When d < 0.3 mm, absorption by the film increased: at d = 0.1 mm the absorption ratio for the thin layer sample and the semi-infinite medium was 3.2, while at d = 0.05 mm it increased up to 5.8. Calculations based on Fresnel equations for flat thin layers adequately described the dependence of the reflection, transmission, and absorption on d and allowed the determination of the refractive index (n), dielectric constant (epsilon), and penetration depth (delta) of the absorbing medium for various frequencies. For water samples, epsilon was found to be 12.4-19.3j, delta = 0.49 mm at 42.25 GHz, and epsilon = 9.0-19.5j, delta = 0.36 mm at 53.57 GHz. The calculated power density distribution within the film was strongly dependent on d. The measurements and calculations have shown that the reflection and absorption of mm-waves by thin absorbing layers can significantly differ from the reflection and absorption in similar semi-infinite media. The difference in reflection, absorption, and power density distribution in films, as compared to semi-infinite media, are caused by multiple internal reflections from the film boundaries. That is why, when using thin phantoms and thin biological samples, the specifics of the interaction of mm-waves with thin films should be taken into account.

Absorption↗
PubMed2000

Nanostructured thin films of C60-aniline dyad clusters: electrodeposition, charge separation, and photoelectrochemistry.

Clusters of C60-aniline dyads are deposited as thin films on nanostructured SnO2 electrodes under the influence of an electric field. At low applied DC voltage (<5 V) the clusters in toluene/acetonitrile (1:3) mixed solvent grow in size (from 160 nm to approximately 200 nm in diameter) while at higher voltages (>50 V) they are deposited on the electrode surface as thin films. The C60- aniline dyad cluster films when cast on nanostructured SnO2 films are photoelectrochemically active and generate photocurrent under visible light excitation. These nanostructured fullerene films are capable of delivering relatively large photocurrents (up to approximately 0.2 mA cm(-2), photoconversion efficiency of 3-4%) when employed as photoanodes in photoelectrochemical cells. Both luminescence and transient absorption studies confirm the formation of charge transfer product (C60 anion) following UV/Vis excitation of these films. Photo-induced charge separation in these dyad clusters is followed by the electron injection from C60-anion moiety into the SnO2 nanocrystallites. The oxidized counterpart is reduced by the redox couple present in the electrolyte, thus regenerating the dyad clusters. The feasibility of casting high surface area thin fullerene films on electrode surfaces has opened up new avenues to utilize dyad molecules of sensitizer bridge donor type in light energy conversion devices, such as solar cells.

Journal Article↗
PubMed2000

Protein-lipid interactions in edible films and coatings.

Proteins and lipids are capable of interacting in a many different ways to form effective edible films and coatings. Combinations of proteins and lipids function in a variety of colloidal systems such as emulsions and microemulsions. Edible films and coatings can be formed from both of these starting systems. In addition, laminant films can be developed by overlaying proteins and lipids. Covalent bonding of lipids to proteins through lipophilization offers unique opportunities for film formation with improved properties. This manuscript reviews recent research on film formation and properties of each of these film types and discusses their relative advantages and disadvantages. Applications of protein-lipid films to food systems are examined. Promising areas for future research are identified.

Emulsions↗
PubMed2003

Electrochemistry of metallofullerene films: the major isomer of Dy@C82.

Solution-cast films of the major isomer of Dy@C(82) (Dy@C(82)(I)) have been studied by cyclic voltammetry (CV) in acetonitrile. The films are found to display pronounced and stable redox responses in solution. The reduction/reoxidation processes exhibit large splittings between the first two reduction and reoxidation waves. However, a pair of reversible oxidation and rereduction waves is observed after the reoxidation of a reduced film. The characteristics and the inter-relationship of these waves are uncovered by the CV technique, scanning electron microscopy (SEM), and UV/Vis-NIR spectra. A possible mechanism is proposed for the film electrode processes, which emphasizes the redox-induced structural reorganization of the metallofullerene film by the incorporation and expulsion of electrolyte ions into and out of the film. The influence of the counter ion diffusivity and the ion-pair stability on the electrochemical activity of the metallofullerene film has also been indicated.

Journal Article↗
PubMed2002

Permeation of protein from porous poly(epsilon-caprolactone) films.

The objective of this study was designed to extend the application of poly(epsilon-caprolactone) (PCL) in delivery of macromolecular proteins. The strategy applied here is to create a porous structure in PCL films in order to control the diffusion rate of protein. Various amounts of both high-molecular-weight and low-molecular-weight poly(ethylene glycol) (PEG) were used as pore-forming agents. The porous films were prepared by a solvent-casting-leaching method. The thicknesses of the prepared films were controlled to be in the range of 75.3 +/- 0.6 similar 81.7 +/- 0.6 mum. The pore fraction of films was determined to be 27.7 +/- 1.0% similar 52.5 +/- 0.8% for PEG(10000) and 26.6 +/- 1.8% similar 48.8 +/- 1.4% for PEG(4000). The pore fraction initially increased with increasing amounts of PEG, independent of the molecular weight of PEG. In the permeation study, lysozyme was used as a model diffuser. The permeation rate of protein increased as the pore fraction of films increased, especially when 30 similar 40% of PEG was added initially, and this phenomenon was more prominent when low-molecular-weight PEG was used. This result was probably due to the highly porous structure creating interconnected channels in the films, further enhancing protein diffusion. In addition, the size of micropores formed by PEG(4000) was observed to be larger than by PEG(10000), which also accounted for faster permeation rate of lysozyme through PCL-PEG(4000) porous films.

Biocompatible Materials↗
PubMed2003

Extended delivery of the antimitotic agent colchicine from thermoresponsive N-isopropylacrylamide-based copolymer films to human vascular smooth muscle cells.

The aim of this study was to establish the capacity of thermoresponsive poly(N-isopropylacrylamide) copolymer films to deliver bioactive concentrations of an antimitotic agent to human vascular smooth muscle cells (HASMC) over an extended period of time. Copolymer films were prepared using a 50:50 (w/w) ratio of N-isopropylacrylamide (NiPAAm) monomer to the more hydrophobic N-tert-butylacrylamide (NtBAAm) and loaded with the antimitotic agent colchicine (0.1 micromol per film) at room temperature. Colchicine release from films was sustained over a 14-day period. At 24 h postloading, the concentration of colchicine in the medium overlying films was 2.12 +/- 0.16 microM; this fell to 0.20 +/- 0.01 microM at 7 days and decreased further to 0.12 +/- 0.01 microM after 14 days. Colchicine released from copolymer films inhibited proliferation when subsequently placed on HASMC: at 0.1 microM, released colchicine reduced proliferation to 18.5 +/- 0.8% of control cells (p < 0.001, n = 9). The antiproliferative effect of released colchicine was comparable to that of native colchicine, as observed in separate experiments. Furthermore, colchicine released from 50:50 polymer films inhibited the proliferation of cells grown in the same environment as the copolymer. Inhibition of cell proliferation was not due to the release of cytotoxic particles from the copolymer because medium incubated with copolymer for 5 days and then applied to HASMC did not alter cell viability. In conclusion, this study demonstrates that 50:50 NiPAAm:NtBAAm copolymers can deliver bioactive concentrations of the antimitotic agent colchicine to human vascular cells over an extended period of time.

Acrylamides↗
PubMed2007

Layer-by-layer assembly of polyelectrolyte films improving cytocompatibility to neural cells.

The using of layer-by-layer assembly polyelectrolyte (PE) films has been suggested as a new versatile technique for surface modification aimed at tissue engineering and cell-based chips. In this study, we investigated the surface morphology of the hyaluronic acid (HA)-based PE films deposited on the amino-functionalized glass slides using atomic force microscopy. These thin films (bilayer number <9) were measured to have nanoscale roughness ranging from 10 to 100 nm. Then the primary hippocampal and cortical neural cells were cultured on the PE films, respectively. After 5 days of culturing, the cytocompatibility to neural cells was evaluated by cellular morphology, neurite outgrowth, and microtubule-associated protein 2 expressions. From the present results, the HA-based PE films were found to be able to support neural cell adhesion and neurite development, especially for the polycation-ending films. It is suggested these HA-based multilayer PE films or similar build-ups could thus be used in the future as a way to modify surfaces for nerve scaffolds and neuron-based chips.

Animals↗
PubMed1993

Morphology of nitric acid and water ice films.

Ice films have been used to simulate stratospheric cloud surfaces in order to obtain laboratory data on solubilities and heterogeneous reaction rates. To obtain intrinsic uptake and surface reaction probabilities which can be applied to atmospheric models, it is necessary to carefully characterize these films. In the present study, environmental scanning electron microscopy (ESEM) is used to study thin films of both water ice and nitric acid ice near the composition of the trihydrate. The ices are formed by vapor deposition onto aluminum or borosilicate-glass substrates cooled to about 200 K. Micrographs are recorded during the deposition process and during subsequent annealing at higher temperatures. The results show that the ice films are composed of loosely consolidated granules, which range from about 1 to 20 microns in size at temperatures between 197 and 235 K. Cubic water ice is sometimes observed at 200 K and converts to the hexagonal form at slightly higher temperatures. The loose packing of the granules confirms the high porosities of these films obtained from separate bulk porosity measurements. Average surface areas calculated from the observed granule sizes range from about 0.2 to 1 m2 g-1 and agree with surface areas obtained by gas-adsorption (BET) analysis of annealed ice films. For unannealed films, the BET areas are about an order of magnitude higher than the ESEM results and imply that the unannealed ices contain microporosity which is lost during the annealing process. The present results have important implications for the extraction of intrinsic reaction probabilities from laboratory rate data.

Colloids↗
PubMed2006

Effect of crosslinking on the elasticity of polyelectrolyte multilayer films measured by colloidal probe AFM.

A homemade colloidal probe atomic force microscope was used to perform nanoindentation with a spherical probe of 5 microm in diameter, at different approach velocities in order to extract the Young's modulus, E0, of poly(L-lysine)/hyaluronan (PLL/HA) films. This parameter is of prime importance to control cellular adhesion. The films were either kept in their native form or cross-linked with a mixture of 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide (EDC) and N-hydrosulfosuccinimide (sulfo-NHS), where the EDC concentration was varied from 1 up to 100 mg mL(-1) (approximately from 5 to 500 mM). A model based on Hertz mechanics was used to account for the interactions between film and probe. It is shown that the Young's modulus varies with the approach velocity for the native (PLL/HA) films, whereas for cross-linked ones, E0 is independent from the velocity over the whole range investigated. It is found that for native films, E0 takes a value of 3 kPa at low approach velocities, a velocity domain that should be relevant in cellular adhesion processes. The Young's modulus increases with the EDC concentration used to cross-link the films and levels off at a value of about 400 kPa for EDC concentrations exceeding 40 mg mL(-1). Thus, it is possible by crosslinking PLL/HA films to control their elastic properties with the aim to alter their behavior as to the cellular adhesion.

Cell Adhesion↗
PubMed2002

Development of polymer film dosage forms of lidocaine for buccal administration: II. Comparison of preparation methods.

In previous studies, we prepared film dosage forms of lidocaine (LC) with hydroxypropylcellulose (HPC) as a film base using the solvent evaporation (SE) method. However, from the viewpoint of environmental issues, a reduction in organic solvent use in pharmaceutical and other industries is required. In this study, we prepared the LC films by direct compression of the physical mixture (DCPM method) and direct compression of the spray dried powder (DCSD method). Magnesium stearate, which was required as a lubricant for direct compression, showed no effect on the LC release rate. The LC release rate (%/h) was independent of the compression pressure, but a higher pressure was preferable to easily remove the film from the punches. An increase in the film weight decreased the LC release rate expressed in %/h, whereas no significant effect of film weight was observed on the LC release rate from unit surface area expressed in mg/h/cm(2). The LC release rate (%/h) was independent of the LC content, suggesting that the LC release rate (mg/h) can be quantitatively controlled by changing the LC content in the formulation. The LC release rate and penetration rate were affected by the preparation method; that is, DCPM method < DCSD method < SE method. The LC penetration rates through excised hamster oral mucosa were linearly correlated to the release rate of un-ionized LC, which was estimated by the LC release rate multiplied by the un-ionized fraction of LC for the HPC film dosage form.

Administration, Buccal↗
PubMed2004

Polypyrrole thin films formed by admicellar polymerization support the osteogenic differentiation of mesenchymal stem cells.

The objective of this study was to evaluate the attachment, proliferation, and differentiation of rat mesenchymal stem cells (MSC) toward the osteoblastic phenotype seeded on polypyrrole (PPy) thin films made by admicellar polymerization. Three different concentrations of pyrrole (Py) monomer (20, 35, and 50 x 10(-3) M) were used with the PPy films deposited on tissue culture polystyrene dishes (TCP). Regular TCP dishes and PPy polymerized on TCP by chemical polymerization without surfactant using 5 x 10(-3) M Py, were used as controls. Rat MSC were seeded on these surfaces and cultured for up to 20 d in osteogenic media. Surface topography was characterized by atomic force microscopy, X-ray photoelectron spectroscopy, and static contact angle. Cell attachment, proliferation, alkaline phosphatase (ALP) activity, and calcium content were measured to evaluate the ability of MSC to adhere and differentiate on PPy-coated TCP. Increased monomer concentrations resulted in PPy films of increased thickness and surface roughness. PPy films generated by different monomer concentrations induced drastically different cellular events. A wide spectrum of cell attachment characteristics (from excellent cell attachment to the complete inability to adhere) were obtained by varying the monomer concentration from 20 m to 50 x 10(-3) M. In particular the 20 x 10(-3) M PPy thin films demonstrated superior induction of MSC osteogenicity, which was comparable to standard TCP dishes, unlike PPy films of similar thickness prepared by chemical polymerization without surfactant. Adhesion of mesenchymal stem cells on tissue culture plates (TCP) coated with polypyrrole thin films made by admicellar polymerization.

Alkaline Phosphatase↗
PubMed2005

Structure of water incorporated in sulfobetaine polymer films as studied by ATR-FTIR.

The structure and hydrogen bonding of water in the vicinity of a thin film of a sulfobetaine copolymer (poly[(N,N-dimethyl-N-(3-sulfopropyl)-3'-methacrylamidopropanaminium inner salt)-ran-(butyl methacrylate)], poly(SPB-r-BMA)), were analyzed with band shapes of O-H stretching of attenuated total reflection infrared (ATR-IR) spectra. The copolymer could be cast as a thin film, of approximate thickness 10 microm, on a ZnSe crystal for the ATR-IR spectroscopy. At an early stage of sorption of water into the polymer film, the O-H stretching band of the IR spectra for the water incorporated in the film was similar to that for free water. This is consistent with the tendency for another zwitterionic polymeric material, poly[(2-methacryloyloxyethylphosphorylcholine)-ran-(butyl methacrylate)] (poly(MPC-r-BMA). It is, however, contradictory to the drastic change in the O-H stretching band for water incorporated into films of polymers such as poly(2-hydroxyethyl methacrylate), poly(methyl methacrylate) and poly(butyl methacrylate). These results suggest that polymers with a zwitterionic structure do not significantly disturb the hydrogen bonding between water molecules incorporated in the thin films. The investigation into the blood-compatibility of both the poly(SPB-r-BMA) and the poly(MPC-r-BMA) films indicate a definite correlation between the blood-compatibility of the polymers and the lack of effect of the polymeric materials on the structure of the incorporated water.

Betaine↗