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Linear Rate (linear + rate)
Selected AbstractsA Novel Tetracycline Labeling Schedule for Longitudinal Evaluation of the Short-Term Effects of Anabolic Therapy With a Single Iliac Crest Bone Biopsy: Early Actions of Teriparatide,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2006Robert Lindsay MD Abstract We describe a quadruple tetracycline labeling method that allows longitudinal assessment of short-term changes in bone formation in a single biopsy. We show that 1 month of hPTH(1-34) treatment extends the bone-forming surface, increases mineral apposition rate, and initiates modeling-based formation. Introduction: Iliac crest biopsy, with histomorphometric evaluation, provides important information about cellular activity in bone. However, to obtain longitudinal information, repeat biopsies must be performed. In this study, we show the capability to obtain short-term longitudinal information on bone formation in a single biopsy using a novel, quadruple labeling technique. Materials and Methods: Two tetracycline labels were administered using a standard 3 days on, 12 days off, 3 days on format. Four weeks later, the tetracycline labeling was repeated using the same schedule but with a different tetracycline that can be distinguished from the first by its color under fluorescent light. Iliac crest biopsies were performed 1 week later and prepared undecalcified for histomorphometry. Indices of bone formation 1 month apart were measured and calculated using the two sets of labels. We used this method to investigate the early effects of teriparatide [hPTH(1-34)] treatment on bone formation. The results were compared with those from a group of control subjects who were quadruple-labeled, but did not receive hPTH(1-34). Results: Treatment with hPTH(1-34) dramatically stimulated bone formation on cancellous and endocortical surfaces. This was achieved by both an increase in the linear rate of matrix apposition and extension of the bone-forming surface. New bone was deposited on previously quiescent surfaces (i.e., modeling-based formation), but a proportion of this could occur by encroachment from adjacent resorption cavities. Conclusions: A single transiliac crest bone biopsy, after sequential administration of two sets of tetracycline labels is a useful approach to study the short-term effects of anabolic agents on human bone. One month of hPTH(1-34) treatment extends the bone-forming surface, increases mineral apposition rate, and initiates modeling-based formation. [source] What is the Slowest-Yet-Normal Cervical Dilation Rate Among Nulliparous Women With Spontaneous Labor Onset?JOURNAL OF OBSTETRIC, GYNECOLOGIC & NEONATAL NURSING, Issue 4 2010Jeremy L. Neal ABSTRACT Objective: To integrate research literature that has provided insights into the cervical dilation rate that may best describe the slowest-yet-normal dilation rate among nulliparous women when beginning with criteria commonly associated with active labor onset. Data Sources: A literature search from 1950 through 2008 was conducted using the Medline electronic database, reference lists from identified articles, and other key references. Study Selection: Research reports written in English with a focus on the cervical dilation and/or labor duration of low-risk, nulliparous women with spontaneous labor onset. Data Extraction: Classic and contemporary research literature was reviewed and organized under the following subheadings: Friedman Studies, Partograph Studies, Active Management of Labor Studies, Additional Studies. Data Synthesis: An integrative review of the literature approximated the slowest-yet-normal cervical dilation rate for nulliparous women when beginning with criteria commonly associated with active labor. Conclusions: The slowest-yet-normal linear dilation rate approximates 0.5 cm/hour for low-risk, nulliparous women with spontaneous labor onset when starting at dilatations traditionally associated with active labor onset. However, this linear rate must be evaluated judiciously in light of the physiological acceleration of dilation that occurs during typical labor. Given this, cervical dilation for this population is likely slower than 0.5 cm/hour in earlier active labor and faster in more advanced active labor. Faster dilation expectations (e.g., 1 cm/hour) likely contribute to an overdiagnosis of dystocia ("slow, abnormal progression of labor") in contemporary practice and, subsequently, to an overuse of interventions aimed at accelerating labor progress. [source] Growth and aggregation of vaterite in seeded-batch experimentsAICHE JOURNAL, Issue 11 2004Jens-P. Abstract Seeded-batch crystallization experiments allowing study of the growth and aggregation of the Vaterite modification of calcium carbonate are reported. Results are reported for initial relative supersaturation (, = S , 1) values in the range 1.66 to 6.70, stirrer speeds in the range 400 and 1200 rpm, and at temperatures of 25 and 40°C. It is found that in all cases the linear rate of growth of the particles is size independent and depends on relative supersaturation squared. The aggregation process is apparently size independent with a rate constant that is directly proportional to the instantaneous growth rate and decreases with increasing stirrer speed. The behavior of the aggregation rate constant is very well described by the model recently proposed by Liew et al., in which the efficiency of the aggregation process is predicted to depend only on the dimensionless strength of the particles and the nature of the flow field. It is concluded that Vaterite forms aggregates with crystalline bridges having an effective strength of approximately 25% of that of calcite or calcium oxalate monohydrate. The fitted parameter L,*/M50 takes on a value of 0.18 ± 0.02. The kinetics and associated model are capable of describing the evolving particle size distributions very well. Finally, a hypothesis is advanced to describe the aggregation of small inorganic crystals in supersaturated solutions. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2772,2782, 2004 [source] Oxidation and Volatilization of Silica Formers in Water VaporJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2003Elizabeth J. Opila At high temperatures, SiC and Si3N4 react with water vapor to form a SiO2 scale. SiO2 scales also react with water vapor to form a volatile Si(OH)4 species. These simultaneous reactions, one forming SiO2 and the other removing SiO2, are described by paralinear kinetics. A steady state, in which these reactions occur at the same rate, is eventually achieved. After steady state is achieved, the oxide found on the surface is a constant thickness, and recession of the underlying material occurs at a linear rate. The steady-state oxide thickness, the time to achieve steady state, and the steady-state recession rate can be described in terms of the rate constants for the oxidation and volatilization reactions. In addition, the oxide thickness, the time to achieve steady state, and the recession rate also can be determined from parameters that describe a water-vapor-containing environment. Accordingly, maps have been developed to show these steady-state conditions as a function of reaction rate constants, pressure, and gas velocity. These maps can be used to predict the behavior of SiO2 formers in water-vapor-containing environments, such as combustion environments. Finally, these maps are used to explore the limits of the paralinear oxidation model for SiC and Si3N4. [source] | ||||||||||