Single Linear Relationship Research Articles

Measurement of cardiac output during exercise by open-circuit acetylene uptake.

Noninvasive measurement of cardiac output (QT) is problematic during heavy exercise. We report a new approach that avoids unpleasant rebreathing and resultant changes in alveolar PO(2) or PCO(2) by measuring short-term acetylene (C(2)H(2)) uptake by an open-circuit technique, with application of mass balance for the calculation of QT. The method assumes that alveolar and arterial C(2)H(2) pressures are the same, and we account for C(2)H(2) recirculation by extrapolating end-tidal C(2)H(2) back to breath 1 of the maneuver. We correct for incomplete gas mixing by using He in the inspired mixture. The maneuver involves switching the subject to air containing trace amounts of C(2)H(2) and He; ventilation and pressures of He, C(2)H(2), and CO(2) are measured continuously (the latter by mass spectrometer) for 20-25 breaths. Data from three subjects for whom multiple Fick O(2) measurements of QT were available showed that measurement of QT by the Fick method and by the C(2)H(2) technique was statistically similar from rest to 90% of maximal O(2) consumption (VO(2 max)). Data from 12 active women and 12 elite male athletes at rest and 90% of VO(2 max) fell on a single linear relationship, with O(2) consumption (VO(2)) predicting QT values of 9.13, 15.9, 22.6, and 29.4 l/min at VO(2) of 1, 2, 3, and 4 l/min. Mixed venous PO(2) predicted from C(2)H(2)-determined QT, measured VO(2), and arterial O(2) concentration was approximately 20-25 Torr at 90% of VO(2 max) during air breathing and 10-15 Torr during 13% O(2) breathing. This modification of previous gas uptake methods, to avoid rebreathing, produces reasonable data from rest to heavy exercise in normal subjects.

Phenological development, leaf emergence, tillering and leaf area index, and duration of spring wheat across Europe in response to CO 2 and ozone

Phenological development, leaf emergence, tillering and leaf area index (LAI), and duration (LAD) of spring wheat cv. Minaret, grown in open-top chambers at different sites throughout Europe for up to 3 years at each site, were investigated in response to elevated CO 2 (ambient CO 2×2) and ozone (ambient ozone ×1.5) concentrations. Phenological development varied among experiments and was partly explained by differences in temperature among sites and years. There was a weak positive relationship between the thermal rate of development and the mean daylength for the period from emergence to anthesis. Main stems produced on average 7.7 leaves with little variation among experiments. Variation was higher for the thermal rate of leaf emergence, which was partly explained by differences in the rate of change of daylength at plant emergence among seasons. Phenological development, rate of leaf emergence and final leaf number were not affected by CO 2 and ozone exposure. Responses of tillering and LAI to CO 2 and ozone exposure were significant only in some experiments. However, the direction of responses was consistent for most experiments. The number of tillers and ears per plant, respectively, was increased as a result of CO 2 enrichment by about 13% at the beginning of stem elongation (DC31), at anthesis and at maturity. Exposure to ozone had no effect on tillering. LAI was increased as a result of CO 2 elevation by about 11% at DC31 and by about 14% at anthesis. Ozone exposure reduced LAI at anthesis by about 9%. No such effect was observed at DC31. There were very few interactive effects of CO 2 and ozone on tillering and LAI. Variations in tillering and LAI, and their responses to CO 2 and ozone exposure, were partly explained by single linear relationships considering differences in plant density, tiller density and the duration of developmental phases among experiments. Consideration of temperature and incident photosynthetically active radiation in this analysis did not reduce the unexplained variation. There was a negative effect of ozone exposure on leaf area duration at most sites. Direct effects of elevated CO 2 concentration on leaf senescence, both positive and negative, were observed in some experiments. There was evidence in several experiments that elevated CO 2 concentration ameliorated the negative effect of ozone on leaf area duration. It was concluded from these results that an analysis of the interactive effects of climate, CO 2 and ozone on canopy development requires reference to the physiological processes involved.

Size effect for specific energy in grinding of silicon nitride

An investigation is reported of the `size effect' for specific energy in grinding of silicon nitride. Experimental measurements over a wide range of operating parameters using two different grit size diamond wheels show an increase in specific energy as the grit depth of cut (uncut chip thickness) is reduced. An attempt was made to account for these results by modifying an upper bound plowing model, which shows an increase in specific energy with a pyramidal tool as its semi-included angle increases. Fitting the measured specific energy to the upper bound model leads to a triangular grit cross-sectional cutting profile rounded at its tip, which can be characterized in terms of an average tip radius and semi-included angle. A plot of dimensionless specific grinding energy (specific energy divided by workpiece hardness) vs. dimensionless depth of cut (depth of cut divided by tip radius) yields a single inverse linear relationship whereby the dimensionless specific grinding energy increases steeply as the dimensionless grit depth of cut decreases below about 0.5. This would indicate that the `grit size effect' is mainly due to rounding at the abrasive cutting points.

Electronic, Spectral, and Electrochemical Properties of (TPPBr(x)())Zn Where TPPBr(x)() Is the Dianion of beta-Brominated-Pyrrole Tetraphenylporphyrin and x Varies from 0 to 8.

The electronic, spectral, and electrochemical characterization of (meso-tetraphenylporphyrinato)zinc(II) complexes bearing between 0 and 8 bromo substituents at the beta-pyrrole positions is reported. The investigated compounds are represented as (TPPBr(x)())Zn where TPPBr(x)() is the dianion of brominated 5,10,15,20-tetraphenylporphyrin and x varies between 0 and 8. Each porphyrin undergoes four well-defined one-electron transfer reactions to yield porphyrin pi-cation radicals and dications upon oxidation and porphyrin pi-anion radicals and dianions upon reduction. Half-wave potentials for the first reduction of (TPPBr(x)())Zn can be described by a single linear free energy relationship, and plots of E(1/2) versus the number of Br groups on the complex show a linear correlation with a positive slope of 63 mV per Br group. This is not the case for the other three electron transfer processes of the compounds where plots of E(1/2) versus the number of Br groups show distinctly different linear correlations for derivatives with 0-4 Br groups and those with 4-8 Br groups. The effect of increasing number of Br groups on the spectral and electrochemical properties of the neutral complexes was examined over the whole series of compounds, and these experimental results are compared to results of theoretical calculations by semiempirical molecular orbital AM1 methods using configurational interactions (CI) over the four Gouterman frontier pi-orbitals. The dihedral angle containing the four porphyrin macrocycle ring nitrogens is proposed as a measure of porphyrin ring nonplanarity, and this value increases with increasing number of Br substituents on (TPPBr(x)())Zn. Results of the AM1-CI = 4 calculations indicate that the spectrally determined HOMO-LUMO gap, i.e., the energy corresponding to the low-energy absorption band, varies in a nonlinear fashion with increasing number of Br substituents on the macrocycle and this is due to both the electronic effect of the substituents and the macrocycle nonplanarity. The HOMO-LUMO gaps theoretically calculated by AM1-CI = 4 methods thus parallel values which are experimentally obtained by electrochemistry or spectroscopy. The lack of well-defined linear free energy relationships for all processes except for the first reduction can be explained on the basis of electronic effects caused by the halogen substituents and nonplanar macrocyclic distortions induced by steric interactions among the peripheral substituents. In the case of porphyrin dication formation, the redox potentials are virtually independent of the bromo substituents.

Substituent effects on the gas-phase basicities of 1-arylpropynes and 1-aryl-3,3-dimethylbutynes effects of the β-alkyl groups on the resonance demand of vinyl cations

The relative stabilities of 1-aryl-2-methylvinyl cations (1) and 1-aryl-2- t-butylvinyl cations (II) were determined by measuring the proton-transfer equilibria of 1-arylpropynes and 1-aryl-3,3-dimethylbutynes in the gas phase. The stabilities of 1-phenyl-2-methylvinyl cation and 1-phenyl-2- t-butylvinyl cation were found to be 1.8 and 5.5 kcal mol −1 higher than that of 1-phenylvinyl cation, respectively. The substituent effects on the stability of these vinyl cations could be correlated in terms of the Yukawa-Tsuno equation, giving an r + of 1.13 and a p of −9.5 for I, and 1.03 and −9.4 for II. Combined with the previous results, it was found that the r + value decreases with the increase in stability of the unsubstituted member of the respective vinylic carbocations while the p values remain constant for a series of the phenylvinyl cation system. This indicates that the π-delocalization of the positive charge into the aryl π-system decreases with the stabilization of a vinyl cation by the β-substituent. This trend is consistent with the observation for a series of ordinary sp 2-hybridized benzylic carbocations. In addition, it has been shown that both sp- and sp 2-carbocation systems obey a single linear relationship between the r + values and carbocation stabilities of the unsubstituted member of respective series. This result clearly demonstrates a continuous spectrum of varying resonance demands characteristic of the stabilities of carbocations. It was concluded that the π-delocalization mechanism in the vinyl cation system has no unique feature but it is a part of a continuous spectrum of resonance demands of varying benzylic carbocations.

Characterizaton of Pecvd Fluorinated Silicon Oxides and Stabilization of Interaction with Metals

ABSTRACTFluorinated silicon oxide films were prepared in a plasma enhanced chemical vapor deposition reactor using TEOS, O2, and either C2F6 or NF3. Properties such as deposition rate, film refractive index, dielectric constant, density, and fluorine concentration were investigated as a function of experimental conditions. Based on nuclear reaction analysis (NRA) and Fourier Transform Infrared (FTIR) measurements, no single linear relationship was found between fluorine concentration or film density and dielectric constant. Special attention was paid to the interaction of fluorine with metals. NRA and X-ray photoelectron spectroscopy (XPS) depth profiles showed that fluorine diffuses rapidly through aluminum and piles up at the free surface. The effect of various plasma treatments was investigated to passivate the surface of fluorinated silicon oxide. CF4 - O2 plasma treatment of the fluorinated oxide before aluminum deposition produced significant improvement in inhibiting fluorine diffusion into aluminum without increasing the dielectric constant.

Permeability Measurement of Base Materials Using Falling-Head Test Apparatus

The development of a new falling-head procedure for laboratory permeability measurement of pavement base materials is described. The main advantage of the falling-head test over the conventional constant-head test is its ability to determine permeability properties of the test material at different levels of hydraulic gradients in a single test. The test setup is simpler and the test duration is much shorter. Each test takes only a few minutes to complete. A large number of tests have been conducted with the proposed procedure on different materials, including compacted crushed stones, glass spheres, and cement stabilized base materials. The falling-head test results were verified by performing constant-head permeability tests on the same specimens at different hydraulic gradients. Analysis on the falling-head test data revealed that the relationship between specific discharge and hydraulic gradient over the range studied could not be represented by a single linear relationship as stated by Darcy’s law. The proposed approach can be a useful tool for determining the drainage properties of base materials within the range of hydraulic gradients encountered in actual pavements.

The global Cd/phosphate relationship in deep ocean waters and the need for accuracy

The relationship between Cd and phosphate is intriguing for unravelling geochemical cycling in the modern ocean. Moreover it is relevant for reconstructing Cd or phosphate distributions in paleoceanography. Whether the global Cd/phosphate data indicate a single linear relationship or whether the data are better described by two different linear relationships, one for the North Atlantic Ocean data and one for the Indo-Pacific Ocean data, is still a matter of debate. Recently, new data have become available for the Southern hemisphere which partly fill a gap that existed between the North Atlantic and Indo-Pacific Ocean data. The model with two different relationships for the North Atlantic and the Indo-Pacific Ocean deviated with statistical significance from a single global linear relationship. Yet, both models are characterized by a large residual variance likely due to apparent differences in accuracy between different laboratories. If these laboratory effects are taken into account in the models, the difference between the relationships of the North Atlantic and the Indo-Pacific Ocean remains statistically significant. However, when only two data sets with the smallest phosphate concentrations (PO4 < 1 μM) are left out the significance disappears. However, it is still risky to be too conclusive on basis of the present data. More accurate Cd- and phosphate-data are needed, especially in the low concentration area. Accuracy become be improved by the availability and use of international reference standards in combination with regular spike-recovery experiments.

Estimation of surface net radiation in the boreal forest and northern prairie from shortwave flux measurements

The relationships between net radiation and surface shortwave fluxes were explored by using one year of 15 min surface flux data for nine sites in central Canada. The sites were located throughout a 50,000 km2 area, in conjunction with the BOREAS project, across a gradient in surface cover from prairie grassland to boreal forest. When insolation alone was used to estimate instantaneous net radiation, the r2 values at the nine sites ranged from 0.93 to 0.98. The use of the net shortwave flux as a predictor improved the range in r2 values to between 0.96 and 0.99. The root‐mean‐square error across sites varied from 26 to 41 W m−2 without albedo to a range of 18–36 W m−2 when albedo was included. The data for all sites were combined to produce a single linear relationship with an r2 value of 0.97 and a root‐mean‐square error (RMSE) of 29 W m−2 when the surface albedo is included. Cross validations were performed where the data for eight sites were used to predict net radiation at a ninth (excluded) site, revealing little site‐specific bias. Classifications of the data by season and by transmittance provided little improvement in estimated net radiation at any site. Our study suggests that a single equation using net shortwave flux alone can be used to estimate net radiation for large portions of the boreal forest and northern prairie, regardless of spatial and temporal variation in surface cover and atmospheric conditions.

Detecting leaf area and surface resistance during transition seasons

In this study we seek empirical relationships among canopy resistance to water vapor transport, the time-varying leaf area index (LAI), in situ radiative flux observations, and a satellite-based estimate of leaf state (NDVI, the normalized difference vegetation index) from a leafless deciduous forest to a covered canopy and vice versa. These relationships can be used in numerical models such as verification in global climate models. They also can be useful tools for developing remote sensing techniques. LAI was found through analysis of frequent video images of canopy evolution in spring and autumn during 1992 and 1993 at a deciduous forest in central Massachusetts. We examined the impact of leaf presence on water vapor transport during spring and autumn using an LAI time series during leaf emergence and leaf fall for the four study seasons. The canopy resistance to water vapor transport ( r c) decreased abruptly at leaf emergence in each year but then also continued to decrease slowly during the remaining growing season, owing to slowly increasing LAI. One remarkable result is that a single linear relationship between r c. and LAI during leaf emergence can be used to estimate the minimum seasonal r c associated with the maximum foliage cover. Canopy resistance and PAR-albedo (albedo from photosynthetically active radiation (PAR) instruments) began to increase about 1 month before leaf fall with the diminishment of CO 2 gradient above the canopy as well, at which time evaporation began to be controlled as if the canopy were leafless. We present empirical linear regressions relating NDVI, r c, and PAR-albedo. The NDVI linear regressions with surface measurements indicate that tower-based measurements can represent at least a satellite pixel region. These results reinforce the notion that relationships among these parameters are scale independent from tower-based measurements spatial scale to a satellite pixel resolution (1.1 km X 1.1 km area)., at least.

Airborne microwave radiometry on a semi-arid area during HAPEX-Sahel

Airborne microwave radiometric measurements in the framework of the HAPEX-Sahel Experiment were performed by the Push Broom Microwave Radiometer (PBMR) and the PORTOS radiometer. The flights of both radiometers produced an original set of data covering the 1.4–90 GHz range of frequency. The East and West Central Super Sites were the areas most intensively observed by the microwave radiometers. Over those sites, several brightness temperature ( T B) maps are available at seven dates distributed over a 1 month period in the middle of the rainy season. A comparison of the two radiometers demonstrates their radiometric quality and the precision of the localization of the microwave observations. At 1.4 GHz, the vegetation had very little effect on the soil microwave emission. Maps of soil moisture were developed using a single linear relationship between T B and the surface soil moisture. There is an important spatial heterogeneity in the soil moisture distribution, which is explained by both the soil moisture hydrodynamic properties and the localization of the precipitation fields. At 5.05 GHz, the vegetation must be accounted for to infer soil moisture from the microwave observations. A method based on a simple radiative transfer model and on microwave data has shown encouraging results.

Application of oxidation induction time and compensation effect to the diagnosis of HV polymeric cable insulation

Oxidative stability tests were performed on field and laboratory-aged crosslinked polyethylene (XLPE), ethylene-propylene rubber (EPR) and polypropylene (PP) insulations using differential scanning calorimetry. Flat films and miniature cables aged in the laboratory were subjected to a wide range of aging conditions that included thermal, electrical and a combination of thermal-electrical aging, in dry and wet environments. The results were analyzed using the Eyring rate theory. It is shown that for a given material the oxidative stability data can be described by a single linear relationship between the activation entropy /spl Delta/S and the activation enthalpy /spl Delta/H of the oxidative process, and thus are governed by the so called compensation effect. It is argued that the position of a data point representing a certain operating condition of an insulation on the /spl Delta/S vs. /spl Delta/H compensation plot is a measure of the degree of degradation and can be used as a diagnostic indicator of the operating conditions of the insulation.

DNA supercoiling depends on the phosphorylation potential in Escherichia coli.

ATP/ADP ratios were varied in different ways and the degree of negative supercoiling was determined in Escherichia coli. Independent of whether the ATP/ ADP ratio was reduced by a shift to anaerobic conditions, by addition of a protonophore (dinitrophenol) or by potassium cyanide addition, DNA supercoiling decreased similarly with the ATP/ADP ratio. The experiments were performed under well-defined conditions, where oxidative phosphorylation was the dominant route for ATP synthesis, i.e. using a minimal salts medium with succinate as the sole free-energy and carbon source, and in the presence or absence of ammonia as the nitrogen source. The results of the different experiments were consistent with a single linear relationship between the log(ATP/ADP) and the change in linking number. The dependence of DNA supercoiling on the ATP/ADP ratio was not influenced by inhibitors of transcription or translation. Because the ATP/ADP ratio was modulated in different ways, the unique relationship suggests coupling between the phosphorylation potential and DNA supercoiling. This was most probably mediated by the DNA gyrase, independent of topoisomerase I or transcription.

Dependence of Runoff Phosphorus on Extractable Soil Phosphorus

AbstractThe sustainable management of fertilizer and manure P to minimize freshwater eutrophication requires identification of soil P levels that exceed crop P requirements and have the potential for P enrichment of runoff. Although several states have established such P levels, insufficient data are available to theoretically justify them. Thus, this study investigates the relationship between the concentrations of P in runoff and in soil. Surface samples (0–10 cm) of 10 Oklahoma soils were packed in 0.15 m2 boxes, incubated for 7 d with poultry litter (0–20 Mg ha−1) to obtain a range in Mehlich‐3 P contents (7–360 mg kg−1), and received five 30‐min rainfalls applied at 1‐d intervals. The concentration of dissolved, bioavailable, and particulate P in runoff was related (r2 &gt; 0.90; P &lt; 0.1) to the Mehlich‐3 P content of surface soil (0–1 cm), with regression slopes ranging from 2.0 to 7.2, increasing as soil P sorption maxima increased (r2 = 0.93). Two soils of 200 mg kg−1 Mehlich‐3 P supported a dissolved P concentration in runoff of 280 μg L−1 (San Saba clay; fine, montmorillonitic, thermic Udic Pellustert) and 1360 μg L−1 (Stigler silt loam; fine, mixed, thermic Aquic Paleudalf). Thus, relationships between runoff and soil P will have to be soil specific for use in management recommendations. A single linear relationship described the dependence of dissolved (r2 = 0.86) and bioavailable P (r2 = 0.85) on soil P sorption saturation. The added complexity of the P saturation approach may limit its application; however, the approach integrates the effect of soil type with soil P content to better estimate the potential for P loss in runoff than soil P alone.

Contribution of sorption to global mass transfer during pervaporation of ethyl tert-butyl ether–ethanol mixtures through a polyurethaneimide film

The pervaporation of ethyl tert-butyl ether–ethanol mixtures through a polyurethaneimide block-copolymer film has been investigated over the entire composition range. Experiments revealed the system to be unstable at a critical feed mixture, inducing strong flux oscillations. Pervaporation selectivity towards ethanol is higher than that of the sorption method. The features of sorption were examined in relation to the corresponding pervaporation properties and analysed in terms of the activity of each penetrant to take account of the system non-ideality. Original sorption isotherms could be expressed in terms of a single linear relationship for ethyl tert-butyl ether and two linear relationship in the case of ethanol. The discontinuity in the EtOH isotherm corresponds to the composition of the critical feed mixture and was ascribed to the complete monosolvation of the polymer's most basic sites, i.e. urethane groups, by the protic penetrant.

Cation-exchange selectivity in Na + - and in H + - phillipsite

The selectivity of phillipsite in exchange reactions involving a series of cations (Li +, K +, NH 4 +, Cu 2+, Zn 2+, Cd 2+, Ba 2+ and Pb 2+) is investigated. Phillipsite was initially treated to give the Na +- and H +-exchanged forms. The selectivity sequences found were Ba 2+ ⪢ Pb 2+ ⪢ Cd 2+ > NH 4 + > Cu 2+ ≈ Zn 2+ ≈ K + > Na + ⪢ Li + for Na +-exchanged phillipsite and Ba 2+ ≈ Pb 2+ > Cd 2+ ≈ NH 4 + > K + ≈ Cu 2+ ≈ Zn 2+ > H 3O + ⪢ Li + for acid-treated phillipsite. A single linear relationship was found between the ionic radius multiplied by the valency of the cation and the logarithm of the selectivity coefficient. The results show that phillipsite is a suitable sequester for heavy metal ions in dilute solutions.

Relationship between CO(2)-dependent O(2) evolution and photosystem II activity in oak (Quercus petraea) trees grown in the field and in seedlings grown in ambient or elevated CO(2).

The light-response of the apparent quantum yield of photosynthetic O(2) evolution (Phi(O(2) )) under non-photorespiratory conditions was measured together with the photochemical efficiency of PS II (DeltaF/F(m)'), the photochemical efficiency of open PS II reaction centers (F(v)'/F(m)') and the photochemical fluorescence quenching (q(p)) of leaf disks punched from oak leaves of seedlings grown in ambient (350 micro mol mol(-1)) or elevated (700 micro mol mol(-1)) CO(2) in a greenhouse, and from sunlit leaves of mature oak trees (Quercus petraea (Matt.) Liebl.). There were marked differences between seedlings and trees. In seedlings, CO(2) concentration during growth did not modify the light response of photosynthesis or PS II activity. There was a single linear relationship between Phi(O(2) ) and DeltaF/F(m)' in seedling leaves that was independent of the CO(2) concentration imposed during growth. In contrast, this relationship was curvilinear in sunlit leaves of adult trees. In seedling leaves, the decrease in q(p) (i.e., the proportion of open PS II reaction centers) largely accounted for the decrease in DeltaF/F(m)', whereas the decrease in DeltaF/F(m)' in sunlit leaves of mature oak trees was dependent on both q(p) and F(v)'/F(m)'.

Polarity decrease at the adhesive junction between two model membranes containing gangliosides

The increased electrical conductance previously observed between two model membranes containing gangliosides suggests the creation of a new environment in the adhesive junction [Brewer, G. J., & Thomas, P.D. (1984) Biochim. Biophys. Acta 776, 279]. In order to provide a mechanism for this novel finding, we now report an investigation of the micropolarity in the adhesive junction. Emission from the fluorescent probe PRODAN is a sensitive measure of polarity of the probe environment. A bimodal linear relationship correlates the emission wavelength from PRODAN with the inverse of solvent dielectric constant (1/epsilon). A better single linear relationship is obtained using Reichardt's relative polarity measure (RPM). Creation of two macroscopic spherical lipid bilayers from phosphatidylcholine, brain gangliosides, and PRODAN allowed selective excitation and observation of fluorescence from either a single bilayer or the double bilayer in the adhesive junction. The reported PRODAN polarity of -0.57 in a single ganglioside-containing membrane was midway between the polarity of water and n-hexane, suggesting PRODAN localization near the lipid carbonyls. The adhesive junctional region exhibited two new less polar environments of PRODAN fluorescence, RPM = -0.45 and -0.29. These measures are consistent with a relatively dehydrated immobilized phase. These changes were not observed in the adhesion zone between two membranes made with phosphatidylcholine without gangliosides. The changes in molecular structure in the junction that could be responsible for the altered PRODAN emission are discussed. A decrease in the hydrocarbon thickness of junctional membranes or a decrease in the aqueous junctional polarity could be responsible for the polarity decrease reported by PRODAN.

Shock wave equation of state of muscovite

Shock wave data to provide an equation of state of muscovite (initial density: 2.835 g/cm3) were determined up to a pressure of 141 GPa. The shock velocity (Us) versus particle velocity (Up) data are fit with a single linear relationship: Us=4.62(±0.12) +1.27(±0.04)Up (km/s). Third‐order Birch‐Murnaghan equation of state parameters (isentropic bulk modulus and isentropic pressure derivative of bulk modulus) are Kos=52±4GPa and K'os=3.2±0.3. The pressure‐temperature relation along the Hugoniot suggests that muscovite may dehydrate to KAlSi3O8 (hollandite), corundum, and water, with a small volume change, above 80 GPa. Thermodynamic calculations of the equilibrium pressure for the dehydration yields a significantly lower value. Observed unloading paths from shock pressures up to about 80 GPa are steeper in a density‐pressure plane than the Hugoniot and become shallower with increasing shock pressure above that pressure. The changing slope may indicate that devolatilization occurs during unloading above 80 GPa. The present equation of state data for muscovite are compared with results of previously reported recovery experiments.

Denudation, vertical crustal movements and sedimentary basin infill

Denudation and vertical crustal movements are linked through the isostatic equation for conservation of lithospheric mass. Recent empirical results from a wide range of sources are presented on the rates of these processes. Denudation alone can cause non-tectonic (isostatic) surface uplift of the right magnitude predicted by theory. A case is made, following Ahnert, for a single linear relationship (although with much scatter) between denudation rate and mean drainage basin relief for large basins. Some recent determinations of denudational time constants have neglected to include tectonic and isostatic terms which oppose the reduction of relief by denudation. Application of diffusional transport models to determine the rate of sediment deposition are severely limited by inherent one-dimensionality and neglect of suspended and washload contributions. Basin infill sequences may be used to determine past sediment transfer coefficients from a hinterland, but problems arise in the apportionment of the various hinterland fluxes that occur in »real-world« three dimensional basins. Sediment yields in smaller half-graben and growth fold basins must reflect the magnitude of drainage basins and the complex local controls upon sediment yields. Examples are given from extensional basins in the Western USA and Greece. The »length« of tectonic relief produced in tilt blocks and growth folds will control the area of drainage basin developed (through the fractal form of Hack's Law) and hence the magnitude of deposition in sedimentary basins adjoining tectonic uplands.