Detail Reproduction Research Articles

Adaptive cluster dot dithering

Cluster dot dithering is one of the most common halfton- ing techniques. It is fast, low in complexity and allows for variability and inconsistencies in point spreads in printer outputs. Determina- tion of the basic dither cell size is critical for the quality of the half- toning. There is a basic tradeoff between large and small cell sizes: spatial resolution versus gray tone resolution. Large dither cell sizes produce good tone resolution but poorly reproduce spatial details in the image. Small dither cells, on the other hand, produce fine spatial resolution but lack the tone resolution which produces smooth gray tone gradients in halftone images. Typically, cluster dot dithering assumes a predefined dither cell size that compromises between fine detail reproduction and good gray tone reproduction. It is clearly advantageous to allow variability in the dither cell size using small cell sizes in image regions of fine details and using large cell sizes in image regions where gray tones are to be accurately reproduced. In this paper, we introduce and discuss several adaptive dithering techniques based on cluster dot dithering. © 1999 SPIE and IS&T. (S1017-9909(99)00402-X)

Experimental observation and statistics of multipath from terrain with application to overland height finding

Data is presented from an airborne experiment designed to evaluate electromagnetic pulse scattering from a variety of terrain types for the application of overland height finding. The one-way propagation data was collected at ultrahigh frequency (UHF) and very high frequency (VHF) frequencies using a 3-MHz pulsed CW signal with the radars mounted on two aircraft. A statistical analysis of the data shows that the probability of a detectable ground reflection and the strength of that reflection vary as a function of the terrain roughness. We introduce a broad-band synthesis technique in which Fourier theory is used to generate a time-domain response from a CW propagation model. Results from this technique agree well with the experimental observations, but the lack of detailed terrain information does not allow exact reproduction of the fine details.

Comparison of the surface detail reproduction of flexible die material systems

Statement of problem. Flexible die materials have been introduced to facilitate the fabrication of indirect provisional or definitive restorations in 1 appointment. Purpose. This study compared the surface detail reproduction of 7 potential flexible die materials when used in combination with 7 elastomeric impression materials. Methods. Surface detail reproduction of 17 impression material/flexible die material systems was compared with a control system containing an elastomeric impression material and a Type IV dental stone. Test dies of each system were prepared in a random order with the American Dental Association apparatus for testing detail reproduction, compatibility, and dimensional stability. Results. One flexible die system had better surface detail reproduction than the control stone die, other systems had similar or worse reproduction. Surface detail reproduction was adversely affected when a separator was required between the impression and flexible die material. Conclusions. Impregum F die material with Extrude Light impression material produced better surface detail reproduction than the control dies. Impregum F impressions were incompatible with Blu-Mousse, Impregum F, or Imprint die materials. Polyvinyl siloxane impressions were incompatible with polyvinyl siloxane dies unless a separator was used. When a separator was used, the surface detail reproduction was not as good as the control die system or the Extrude Light impression material/Impregum F die material combination. (J Prosthet Dent 1998;80:485-9.)

The Wet Collodion Process—A Scientific Approach

The wet collodion process was the first successful photographic negative process. The tone and detail reproduction of both negatives and prints are remarkably good. There are a lot of collodion plates still in existence, but detailed knowledge of how the excellent image quality was achieved has been lost. The Institute of Applied Photophysics in Dresden, Germany, harbors the photographic work of the German pioneer Hermann Krone (1827–1916). He became prominent after using the wet collodion method for landscape photography in 1853. It is extremely difficult to make satisfactory reproductions from those historic negatives on contemporary photographic materials or to digitize the old pictures. The aim of the present work is to gain knowledge of how to reproduce satisfactorily the tone and detail of wet collodion negatives and prints on modern materials. To gain more knowledge of the process, wet collodion layers were poured and then investigated using tools of modern imaging science. Sensitometric curves and relative spectral sensitivities were investigated for a range of emulsions with varying iodide–bromide ratios. Granularity noise and resolution were measured by means of a high-resolution CCD microdensitometer.

Dimensional stability and detail reproduction of irreversible hydrocolloid and elastomeric impressions disinfected by immersion

Statement of problem. Because irreversible hydrocolloid impressions imbibe blood and saliva, immersion rather than spray disinfection may be more effective. Polyether has been shown to be dimensionally sensitive to immersion disinfection. Purpose. The aim of this study was to determine whether irreversible hydrocolloid and polyether impressions could be disinfected by immersion without sacrificing accuracy and surface quality. Material and methods. Impressions were made of a master mandibular arch containing a crown preparation. Changes between the master and working casts were assessed. Irreversible hydrocolloids (Jeltrate; Palgaflex), a polyether (Impregum F), and an addition silicone (President) were used. Disinfectants were an iodophor (Biocide), a glyoxal glutaraldehyde (Impresept de), and a phenol glutaraldehyde (Sporicidin). The control was without disinfection. Casts were formed in Type IV gypsum. The roughness of working dies was also recorded and an analysis of variance was used for statistical evaluation. Results. Casts from disinfected irreversible hydrocolloid and elastomeric impressions maintained accuracy for anteroposterior and cross arch dimensions where differences from the master was less than 0.1%. Buccolingual and mesiodistal dimensions of working dies (disinfected and control) were 6 to 8 μm larger than the master for addition silicones and 11 to 16 μm for polyethers. The occlusogingival dimension of dies for control and disinfected polyether was 9 μm longer than the master compared with −3 μm for addition silicone. The range of mean surface roughness of working dies made from irreversible hydrocolloids was 1.4 to 1.7 μm and ranged from 0.5 to 0.7 μm for elastomeric impressions. Conclusion. Immersion disinfection of Jeltrate material with iodophor and Palgaflex material with glyoxal glutaraldehyde produced casts and dies as accurate as the control. Control and disinfected elastomeric impression produced dies as clinically accurate and smooth as the master. Disinfection of irreversible hydrocolloid impressions with the glyoxal and phenol glutaraldehyde produced a surface smoother than controls. (J Prosthet Dent 1998;79:446-53.)

A porous flow model of magma migration within Mt. Etna: The influence of extended sources and permeability anisotropy

The isotropic point-source model of porous flow proposed by Bonafede and Boschi is employed to model magma flow within the edifice of Mt. Etna in probabilistic terms. The flow pattern is found to be nearly horizontal, suggesting magma propagation through lateral dykes departing radially from the central conduits. The point source model is able to provide a detailed description of eruption site distribution for a few sections of Mt. Etna, but it fails to explain simultaneously the eruption distribution along the mutually orthogonal N–S and E–W sections. The solution is then generalized to deal with extended sources and with anisotropic media, employed, respectively, to simulate a hypothetical N–S-trending fracture system at the base of the volcano or the influence of the regional stress field on the directional probability of dyke opening. The results show that both models are able to explain the presence on Mt. Etna of the N–S-trending rift. In particular, the anisotropic model provides the best fits to the north, south, west and east topographic sections. Several features of the eruption distribution on Mt. Etna remain unexplained, however, by a porous flow model and apparently require the intervention of specific structural effects. For instance, a detailed reproduction of the three-lobe distribution of eruptive sites (observed in recent historic times) seems to require permeability heterogeneities, the effect of local topographic loading or the presence of a local axial stress field related to the inflation of Mt. Etna.

Expanding the limits of “equilibrium” second-moment turbulence closures

The paper discusses possibilities for refinements of conventional “equilibrium” second-moment turbulence closure models, aimed at improving model performances in predicting turbulent flows of greater complexity. In focus are the invariant modelling of the low-Re-number and wall proximity effects, as well as extra strain-rates and control of the turbulence length-scale. In addition to satisfying most of the basic physical constraints, the main criterion for model validation was the quality of reproduction of flow and turbulence details, particularly, in the vicinity of a solid wall, in a broad variety of non-equilibrium flows featured by different phenomena. It is demonstrated that the new model, which includes several new modifications, but also some proposed in the past, can satisfactorily reproduce a range of attached and separating flows with strong time- or space-variations or abrupt changes of boundary conditions. Cases considered cover a wide range of Re-numbers involving in some cases also the laminar-to-turbulent or reverse transition.

Multivariate nonparametric resampling scheme for generation of daily weather variables

A nonparametric resampling technique for generating daily weather variables at a site is presented. The method samples the original data with replacement while smoothing the empirical conditional distribution function. The technique can be thought of as a smoothed conditional Bootstrap and is equivalent to simulation from a kernel density estimate of the multivariate conditional probability density function. This improves on the classical Bootstrap technique by generating values that have not occurred exactly in the original sample and by alleviating the reproduction of fine spurious details in the data. Precipitation is generated from the nonparametric wet/dry spell model as described in Lall et al. [1995]. A vector of other variables (solar radiation, maximum temperature, minimum temperature, average dew point temperature, and average wind speed) is then simulated by conditioning on the vector of these variables on the preceding day and the precipitation amount on the day of interest. An application of the resampling scheme with 30 years of daily weather data at Salt Lake City, Utah, USA, is provided.

Imaging red blood cells with the atomic force microscope.

A novel technique for the reproduction of ultramorphological images and details of the surface of normal and pathological red blood cells (RBC) was investigated. The atomic force microscope (AFM) provided high-resolution images of cell surfaces. The RBC dimensions obtained by this technique revealed differences between native red cells in smears and glutaraldehyde-fixed red cells. It was shown that fixed red blood cells were best suited for the ultramorphological imaging of the cell surface.

Warm-Season Effects of the Gulf Stream on Mesoscale Characteristics of the Atmospheric Boundary Layer

The meteorological regime off the coast of North Carolina exhibits little synoptic-scale baroclinity during the summer months. As a result, the large-scale atmospheric forcing in this region is frequently weak. Given this weak synoptic forcing, mesoscale boundary layer circulations are dominant. One such circulation develops in response to the sea surface temperature discontinuity between the Gulf Stream and the relatively cooler water of the Continental Shelf. When synoptic conditions are favorable, differences in surface fluxes of heat and moisture across this discontinuity cause the development of an ageostrophic solenoidal circulation and the creation of an atmospheric boundary layer convergence zone. This resulting frontal zone, or Gulf Stream atmospheric front (GSAF), is a commonly observed feature in this region during the warm season. Simulations using The Pennsylvania State University–National Center for Atmospheric Research mesoscale model are combined with data gathered from the High-Resolution Remote Sensing Experiment to study the effects of the Gulf Stream on mesoscale circulations in the warm-season marine atmospheric boundary layer. Particular attention was given to determining whether a model with resolution and physics similar to those of operational mesoscale forecast models can adequately predict this phenomenon. Although limitations in the horizontal and vertical resolution of the model prevent detailed reproduction of the meso-γ-scale structure of the GSAF, the model does produce a significant meso-β boundary layer convergence zone in response to the local SST maximum associated with the Gulf Stream. The magnitude of the modeled response is primarily a function of air–sea temperature difference, the local wind vector, and the depth of the boundary layer.

Irreversible hydrocolloids for crown and bridge impressions: Effect of different treatments on compatibility of irreversible hydrocolloid impression material with type IV gypsums

Objectives. The aims of this research were: 1) to determine if the compatibility between irreversible hydrocolloids (alginates) and type IV gypsums (die stones) is affected by different treatments of the impressions before pouring, and 2) to present a rating system based on Ryge's system for clinical evaluation in order to classify the quality of gypsum casts using detail reproduction and surface structure as criteria. Methods. Impressions were taken on a Plexiglas staircase (heights of the steps 15–82 μm) with six irreversible hydrocolloids designed for crown and bridge and ten type I and II irreversible hydrocolloids. Impressions of each brand were divided into four groups. One group was treated with 2% potassium sulfate, the second with water, the third with an alginate stabilizer, Sorbanat (Guilini Chemie), and as a control, a fourth group which was not allowed to come into contact with any liquid, i.e., the impressions were poured dry. The differently treated impressions were poured with ten type IV gypsums. The quality of all gypsum casts was then judged according to the rating system. Results. All the irreversible hydrocolloids, if correctly treated before pouring with a compatible gypsum, could reproduce details of 20 μm. Detail reproduction did not improve with the use of 2% potassium sulfate solution compared to water or if the impressions were poured “dry”. In general, the alginate stabilizer produced casts with significantly better detail reproduction and surface structure. Significance. The results show that dentists and dental technicians need to know how each specific irreversible hydrocolloid should be treated and also with which type IV gypsum it is compatible. This research also indicates that an irreversible hydrocolloid impression should not come into contact with any liquid within the first 15 min.

Effect of Immersion in Disinfectant Solution on Properties of Die Stone - Part 2 Dimensional Change and Reproduction of Details -

Effect of Immersion in Disinfectant Solution on Properties of Die Stone - Part 2 Dimensional Change and Reproduction of Details -

A comparison of three methods for preparing reversible hydrocolloid duplicating material

This study compared the effects of repeated microwave oven and double-boiler liquefactions and prolonged autoduplicator storage on four physical properties of one reversible hydrocolloid duplicating material. No significant differences were observed between the linear dimensional change and detail reproduction of the three liquefaction techniques. Tear strength differences most clearly distinguished the techniques and effects of aging. Fifteen double-boiler remeltings produced tear strength values lower than those recorded for material stored in an autoduplicator for 2 weeks. Thirty microwave melting cycles still produced tear strength values equivalent to that of the autoduplicator material. After 30 melting cycles the compressive strengths of the microwave and double-boiler materials were inferior to that of the stored autoduplicator material.

Evaluation of detail reproduction for three die materials by using scanning electron microscopy and two-dimensional profilometry

This study evaluated the reproduction of detail by Fuji-rock artificial stone, Epoxydent epoxy resin, and Steady-plast polyurethane resin. A polyvinyl siloxane impression was made of a disk-shaped calibration model, with etched grooves ranging from 1 to 46 microns in depth. The die materials were poured in the silicone impression of the disk, then examined with a scanning electron microscope and two-dimensional profilometer. The results revealed that the artificial stone could not reproduce details smaller than 20 microns because of the size of the crystalline structure, whereas epoxy resin and polyurethane resin accurately reproduced details of 1 to 2 microns.

Disinfection of dental stone casts: Antimicrobial effects and physical property alterations

Objectives. The purpose of this study was to evaluate the effectiveness of disinfecting solutions incorporated into dental stone casts against a standard and representative group of microorganisms and to note changes in the physical properties of the casts.Methods. Irreversible hydrocolloid impressions were con-taminated individually with Escherichia coli, Staphylococcus aureus, Enterobacter cloacae, Pseudomonas aeruginosa, Klebsiella pneumoniae, Actinobacter calcoaceticus, Bacillus subtilis, Mycobacterium phlei and Candida albicans. Four readily available disinfecting solutions (glutaraldehyde, povidone-iodine, chlorhexidine and sodium hypochlorite) were added to the die stone mix used to pour up the impressions. The set cast surfaces were swabbed at 1 h and 24 h, the samples plated on agar and incubated at 37°C for 24 h and 3 d for M. phlei. Subsequently, colony forming units were counted. The physical properties assessed were setting time, setting expansion, compressive strength, detail reproduction and delayed expansion of the stone.Results. Only glutaraldehyde and povidone-iodine killed all contaminating microorganisms within 1 h, while the 1:5 dilution of sodium hypochlorite solution was equally effective after 24 h. Two percent glutaraldehyde was the most effective disinfectant with the least adverse effects on the physical properties of the set cast. Although povidone-iodine caused a decrease in the compressive strength of the set cast, it can be considered to be a sound alternative.Significance. This study supports the concept of incorporating disinfectants into model stone as a standard operating procedure for impressions of unknown history and, most sensibly, all dental impressions.

Gypsum Compatibility of Antimicrobial Alginates After Spray Disinfection

This investigation examined the gypsum compatibility of two antimicrobial alginates after spray disinfection. Subjective compatibility evaluations were compared with objective quantitative profilometer readings of gypsum cast surface roughness. COE Hydrophilic Gel Alginate, Jeltrate Plus, Antimicrobial Alginate, and their nonantimicrobial counterparts, Coe Alginate and Jeltrate Plus, were used in this study. After spray disinfection with water (control), Alcide LD, Biocide, OMC II, and 0.5% NaOCI, impressions of the American National Standards Institute/American Dental Association (ANSI/ADA) specification no. 18 detail reproduction die and impressions made simultaneously of a smooth glass die were cast in Microstone, Silky-Rock, and Die-Keen. Five specimens were made for each alginate/disinfectant/gypsum combination for a total of 300 samples each for both the subjective and objective analyses. For the subjective analysis of gypsum compatibility, the specimens made from the ANSI/ADA specification no. 18 test die were evaluated by using a 1-to-4 visual rating system at magnification x12. For the objective analysis, the arithmetic average surface roughness of each specimen made from the smooth glass die was recorded three times with a 200-mg skidless stylus instruments. The results of the ANSI/ADA specification no. 18 testing for gypsum compatibility showed that 11 of 60 possible combinations did not pass the test. All impressions made with nonantimicrobial COE Alginate passed the test regardless of the disinfectant/gypsum combination. The results of the three-factor analysis of variance for the subjective and objective analyses showed significant interactions between alginates, disinfectants, and stones at the P < .05 level. To further delineate these differences, unpaired t tests (P < .05) within brands for each disinfectant/gypsum combination were performed. The addition of 1% chlorhexidine diacetate to COE Hydrophilic Gel Alginate has decreased its compatibility with the dental stones and disinfectants tested when compared with its nonantimicrobial counterpart. In terms of gypsum compatibility, the nonantimicrobial COE Alginate was compatible with all disinfectant and gypsum combinations tested. The addition of 1.70% didecyldimethyl ammonium chloride to Jeltrate Plus Antimicrobial Alginate has increased its compatibility with all the dental stones tested. A strong positive correlation (r = 0.7398) was found between visual gypsum compatibility evaluation scores and surface roughness of gypsum casts.

High-resolution electron microscopy of biological specimens in cubic ice

Images of two biological test specimens, catalase and TMV, were recorded in cubic ice, prepared by controlled devitrification at -130°C and -75°C or in vitrified buffer. Cubic ice provides a rigid support for biological specimens which is stable under the electron beam to within about 1 Å, as shown by images of the ice lattice. Neither catalase nor TMV were disrupted by the crystallization of vitrified water. Electron diffraction patterns of highly oriented rafts of TMV extending to 2.3 Å resolution were used to judge the quality of TMV images. Structural features at 5.75 Å (TMV) and 5.4 7Aring; (catalase) were observed directly by optical diffraction. The reproduction of high-resolution details of TMV was better in cubic ice, and the success rate for recording good images was higher than in vitrified medium.

Detail Reproduction of Impressions Made with Impression Materials : (3)An Evaluation of the Compatibility of Dental Stones and Reversible Hydrocolloid Impression Materials by Detail Reproduction and Surface Roughness

Detail Reproduction of Impressions Made with Impression Materials : (3)An Evaluation of the Compatibility of Dental Stones and Reversible Hydrocolloid Impression Materials by Detail Reproduction and Surface Roughness

Accuracy, detail reproduction, and hardness of gypsum casts produced from silicone impressions treated with glow discharge

Plasma treatment has been reported to improve the wettability of silicone impression materials. This study investigated whether plasma treatment of silicone impressions influenced the linear dimensional accuracy, detail reproducibility, and surface hardness of models produced from a type IV dental die stone. Five silicone impression materials were used in this study. Linear dimensional accuracy and detail reproduction were tested according to ISO standards. Surface hardness was evaluated with a Vickers hardness test. The results indicated that plasma-treated impressions from Xantopren and Provil silicone impression materials had significantly smaller dimensional change than their respective controls, and the other materials were not influenced. The detail reproduction was superior in casts produced from plasma-treated impressions from President silicone. Surface hardness was not influenced by the treatment. Plasma treatment of silicone impressions has no negative influence on the tested physical properties of die stone models.

Effects of disinfecting irreversible hydrocolloid impressions on the resultant gypsum casts: Part I—Surface quality

This study evaluated the effects of disinfection time (10, 30, and 60 minutes) on the surface quality of stone casts poured against an alginate impression material (Jeltrate). Five antimicrobial agents were tested: Sporicidin spray, sodium hypochlorite, and iodophor for spray; and Sporicidin cold sterilization solution and Cidexplus glutaraldehyde solution for immersion. Impressions, flushed with water and stored for 0, 10, 30, and 60 minutes before pouring, served as untreated controls. On completion of the disinfection treatments, the impressions were rinsed and poured in Velmix stone. The effects on cast surface were evaluated under a stereomicroscope by three experienced raters. A 1-to-4 scoring system was developed to rate the surface quality in terms of smoothness and detail reproduction. Both immersion disinfectants proved to be unacceptable for treating alginate impressions. The mean scores of other disinfectant-time combinations were compared with the use of the Tukey-Kramer method with a 95% confidence interval. The results indicated that treatment time had statistically significant effects on the quality of cast surface in Sporicidin spray, sodium hypochlorite, and untreated control groups but not in the iodophor spray group.