4,418 research outputs found
Analysis of a Mathematical Model of Real-Time Competitive Binding on a Microarray
A mathematical model of competitive binding on a microarray in real-time yields a planar system of nonlinear ordinary differential equations. This model can be used to explore dimensionless formulation, linear approximation, and reduction. Real-time competitive binding is proposed as an uncommon approach to advance the study of planar systems of differential equations
The integrated planning method of project planning, development and implementation
Present comprehensive planning endeavors lack a consistent methodology which will produce realistic, useable results. The validity of this statement should be obvious after one has read Miller\u27s Evaluation of City and Region Planning Techniques. This paper contains a methodology, The Integrated Planning Method, which will go a long way toward correcting this gross inadequacy that planners presently encounter in directing planning efforts. Two government developed planning and analysis procedures that, up until this time have been applied almost exclusively to hardware systems, have been combined into one integrated planning methodology that will provide not only meaningful and rigorous definition and analysis of any problem faced by the planner but a path to a solution that, if followed, will produce a complete system for planning and implementation. Analysis of existing plans, planning methodologies and planning problems is to be the suggested use of the Value Analysis procedure that up to the present has only been used by the Department of Defense and industrial organizations to improve hardware systems. Phase Project Planning as developed by the National Aerounatics and Space Administration for use in planning for space hardware systems and their supporting personnel and equipment will be the suggested method for developing the desired plans. Each, in the past has been utilized separately. This report lays out a method of combining them into an Integrated Planning Method which will be applicable to all planning efforts --Abstract, pages ii-iii
Comparison of Knoop and Vickers Surface Microhardness and Transverse Microradiography for the Study of Early Caries Lesion Formation in Human and Bovine Enamel
Objective
The aims of the present laboratory study were twofold: a) to investigate the suitability of Knoop and Vickers surface microhardness (SMH) in comparison to transverse microradiography (TMR) to investigate early enamel caries lesion formation; b) to compare the kinetics of caries lesion initiation and progression between human and bovine enamel.
Design
Specimens (90 × bovine and 90 × human enamel) were divided into six groups (demineralization times of 8/16/24/32/40/48 h) of 15 per enamel type and demineralized using a partially saturated lactic acid solution. SMH was measured before and after demineralization and changes in indentation length (ΔIL) calculated. Lesions were characterized using TMR. Data were analyzed (two-way ANOVA) and Pearson correlation coefficients calculated.
Results
ΔIL increased with increasing demineralization times but plateaued after 40 h, whereas lesion depth (L) and integrated mineral loss (ΔZ) increased almost linearly throughout. No differences between Knoop and Vickers SMH in their ability to measure enamel demineralization were observed as both correlated strongly. Overall, ΔIL correlated strongly with ΔZ and L but only moderately with the degree of surface zone mineralization, whereas ΔZ and L correlated strongly. Bovine demineralized faster than human enamel (all techniques).
Conclusions
Lesions in bovine formed faster than in human enamel, although the resulting lesions were almost indistinguishable in their mineral distribution characteristics. Early caries lesion demineralization can be sufficiently studied by SMH, but its limitations on the assessment of the mineral status of more demineralized lesions must be considered. Ideally, complementary techniques to assess changes in both physical and chemical lesion characteristics would be employed
Glucocorticoid receptor expression in 20 solid tumor types using immunohistochemistry assay.
BackgroundGlucocorticoid receptor (GR) activity plays a role in many aspects of human physiology and may play a crucial role in chemotherapy resistance in a wide variety of solid tumors. A novel immunohistochemistry (IHC) based assay has been previously developed and validated in order to assess GR immunoreactivity in triple-negative breast cancer. The current study investigates the standardized use of this validated assay to assess GR expression in a broad range of solid tumor malignancies.MethodsArchived formalin-fixed paraffin-embedded tumor bank samples (n=236) from 20 different solid tumor types were analyzed immunohistochemically. Nuclear staining was reported based on the H-score method using differential intensity scores (0, 1+, 2+, or 3+) with the percent stained (out of at least 100 carcinoma cells) recorded at each intensity.ResultsGR was expressed in all tumor types that had been evaluated. Renal cell carcinoma, sarcoma, cervical cancer, and melanoma were those with the highest mean H-scores, indicating high levels of GR expression. Colon, endometrial, and gastric cancers had lower GR staining percentages and intensities, resulting in the lowest mean H-scores.ConclusionA validated IHC assay revealed GR immunoreactivity in all solid tumor types studied and allowed for standardized comparison of reactivity among the different malignancies.ImpactBaseline expression levels of GR may be a useful biomarker when pharmaceutically targeting GR in research or clinical setting
Enamel demineralization and remineralization under plaque fluid-like conditions – a QLF study
The present study investigated de- and remineralization in enamel lesions under plaque fluid (PF)-like conditions using quantitative light-induced fluorescence (QLF). Preformed lesions were exposed to partially saturated lactic acid solutions, varying in pH and fluoride concentration ([F]) based on a 5 × 3 factorial study design (0/0.1/0.5/1.5/4 ppm F; pH 4.9/5.2/5.5). Average fluorescence loss (ΔF) was monitored for 11 days. Subsequently, lesions were demineralized in a partially saturated acetic acid solution for two 24-hour periods. Data were analyzed using repeated measures analysis of covariance. Lesions exposed to PF at 4 ppm F and pH 5.5 showed not only the most remineralization (ΔΔF = 28.2 ± 14.0%) for all groups after 11 days, but also the most demineralization (ΔΔF = –19.3 ± 13.5%) after subsequent acetic acid exposure. Increased [F] resulted in more remineralization, regardless of pH. Higher pH values resulted in more remineralization. No remineralization was observed in lesions exposed to F-free solutions, regardless of pH. Remineralization was noticeable under the following conditions: pH 4.9 – [F] = 4 ppm, pH 5.2 – [F] ≧ 1.5 ppm, and pH 5.5 – [F] ≧ 0.5 ppm. Overall, [F] had a stronger effect on remineralization than pH. Subsequent demineralization showed that little protection was offered by PF-like solutions, and further demineralization compared with baseline was observed on lesions not remineralized initially. [F] had a stronger effect on net mineral change than pH. The present study has shown that QLF is a valuable tool in studying lesion de- and remineralization under PF-like conditions, where [F] was shown to be more important than pH
Artificial biofilm thickness and salivary flow effects on fluoride efficacy – A model development study
This laboratory model development study investigated the interaction between artificial biofilm thickness and salivary flow rate on fluoride-mediated prevention of enamel caries lesion formation. This 5-day pH cycling study on sound bovine enamel specimens utilized a continuous flow model and followed a 4 (agarose biofilm thickness-‘no biofilm’/1/2/3mm)×2 (remineralizing solution flow rate-0.05/0.5ml/min)×2 (fluoride-0/383ppm as sodium fluoride) factorial design. Vickers surface microhardness change was the outcome measure. Data were analyzed with three-way ANOVA. The three-way interaction gel thickness×flow rate×fluoride concentration was significant (p=0.0006). 383ppm fluoride caused less softening than 0ppm regardless of gel thickness or flow rate. 0.5ml/min flow rate caused less softening than 0.05ml/min for ‘no biofilm’ and 1mm biofilm thickness regardless of fluoride concentration, for 2 and 3mm with 0ppm F but not for 383ppm F. For 0.05ml/min, softening was reduced as gel thickness increased from ‘no biofilm’-1-2mm, but not from 2-3mm. For 0.5ml/min, ‘no biofilm’ caused more softening than 1, 2, and 3mm, but 1, 2, and 3mm were not different from each other for both 0 and 383ppm F. The present findings suggest that the efficacy of fluoride in preventing enamel demineralization is affected by both biofilm thickness and salivary flow rate, with both thicker biofilms and higher flow rate resulting in less demineralization
Analysis and modeling of broadband airgun data influenced by nonlinear internal waves
Author Posting. © Acoustical Society of America, 2004. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 116 (2004): 3404-3422, doi:10.1121/1.1819499.To investigate acoustic effects of nonlinear internal waves, the two southwest tracks of the SWARM 95 experiment are considered. An airgun source produced broadband acoustic signals while a packet of large nonlinear internal waves passed between the source and two vertical linear arrays. The broadband data and its frequency range (10–180 Hz) distinguish this study from previous work. Models are developed for the internal wave environment, the geoacoustic parameters, and the airgun source signature. Parabolic equation simulations demonstrate that observed variations in intensity and wavelet time–frequency plots can be attributed to nonlinear internal waves. Empirical tests are provided of the internal wave-acoustic resonance condition that is the apparent theoretical mechanism responsible for the variations. Peaks of the effective internal wave spectrum are shown to coincide with differences in dominant acoustic wavenumbers comprising the airgun signal. The robustness of these relationships is investigated by simulations for a variety of geoacoustic and nonlinear internal wave model parameters.This work was supported by an ONR Ocean Acoustics Graduate Traineeship Award and by ONR grants to Rensselaer, the University of Delaware, and Woods Hole Oceanographic Institution
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An econometric analysis of the desktop computer hardware market
The purpose of this study was to compare six competing econometric models which depict the relationship between hardware characteristics and machine cost for the desktop computer market. The Box-Cox methodology and multiyear data were used to facilitate this comparison. The analysis validated that the Box-Cox methodology is a viable means for evaluating competing model formulations within the field of information systems research. The results were consistent with past research that suggested a double natural log model formulation for representing the functional relationships among variables when modeling machine cost as a function of hardware attributes. Further, the more complex power transformation model formulations suggested by the Box-Cox methodology did not significantly outperform the more traditional and simpler double natural log model. More specifically, the results indicated that variables related to primary memory and microchip tedinology have the largest impact on machine cost. Additionally, variables related to madiine connectivity, machine expandability, and year of observation were also found to be significant explanatory variables for machine cost
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