Strong Logarithmic Relationship Research Articles

Hydraulic conductivity of cement and fly ash stabilised clay mixes – Application to soil mixing techniques for seepage barrier construction

In-situ ground improvement techniques, namely, deep soil mixing, jet grouting, cutter soil mixing, and mass stabilisation are often utilized to improve the strength of soft grounds, and construct seepage barriers. Due to economic and environmental concerns, there is a global shift towards using industrial wastes such as fly ash (FA) from conventional binders such as ordinary Portland cement and lime. There is a plethora of literature on unconfined compressive strength (UCS) of cement-treated clays, and clays treated with fly ash-cement mixes with alkali activator (FCAA) binders. However, much remains unclear about the hydraulic conductivity of the FCAA-treated clays as low permeable hydraulic barrier systems. In this paper, the hydraulic conductivities of cement-treated and FCAA-treated clays are studied both quantitatively and qualitatively for different binder-content, FA:cement ratios, curing periods, and effective confining stress. The hydraulic conductivity of treated clay is measured by performing a series of accelerated permeability tests using a custom-fabricated triaxial system. The trends obtained from the measured hydraulic conductivity values are explained from the observations of X-ray diffraction analysis and scanning electron microscopy analysis. Results showed that the values of hydraulic conductivity for cement-treated clay were mostly higher than those of untreated clay. On the contrary, the hydraulic conductivities for the FCAA clay mixes were comparable to, or even lower than those for the untreated clay. The hydraulic conductivity reduced with the increase in effective confining stress; the influence of effective confining stress, however, became less substantial for 28 days curing period and higher cement-content (40 and 50 %). The relationships between the hydraulic conductivity, UCS, and water-binder (w/b) ratios were also determined for both cement-treated and FCAA-treated clays. The exponential function was found suitable to express the relationship between hydraulic conductivity and UCS of treated clays. In contrast, a strong logarithmic relationship was obtained for measured values of hydraulic conductivity and adopted w/b ratios. The results shall serve as a guide to adopting suitable binder-content or target UCS for achieving design hydraulic conductivity in ground improvement projects that involve cement and/or FCAA-treatment of clays.

Advanced hemodynamics for prognostication in heart failure: the pursuit of the patient-specific tipping point.

Objective tools to define the optimal time for referral for advanced therapies and to help guide escalation and de-escalation of support can improve management decisions and outcomes for patients with advanced heart failure. The current parameters have variable prognostic potential depending on the patient population being studied and often have arbitrary thresholds. Here, a mathematical and physiological framework to define the patient-specific tipping point of myocardial energetics is defined. A novel hemodynamic parameter known as the myocardial performance score (MPS), a marker of power and efficiency, is introduced that allows for the objective assessment of the physiological tipping point. The performance of the MPS and other advanced hemodynamic parameters including aortic pulsatility index (API) and cardiac power output (CPO) in predicting myocardial energetics and the overall myocardial performance was evaluated using a validated computer simulation model of heart failure (Harvi) as well as a proof-of-concept clinical validation using a cohort of the Society for Cardiovascular Angiography and Interventions (SCAI) Stage C cardiogenic shock patients. Approximately 1010 discrete heart failure scenarios were modeled. API strongly correlated with the left ventricular coupling ratio (R2 = 0.81) and the strength of association became even stronger under loaded conditions where pulmonary capillary wedge pressure (PCWP) was >20 mmHg (R2 = 0.94). Under loaded conditions, there is a strong logarithmic relationship between MPS and mechanical efficiency (R2 = 0.93) with a precipitous rise in potential energy (PE) and drop in mechanical efficiency with an MPS <0.5. An MPS <0.5 was able to predict a CPO <0.6 W and coupling ratio of <0.7 with sensitivity (Sn) of 87%, specificity (Sp) of 91%, positive predictive value of 81%, and negative predictive value of 94%. In a cohort of 224 patients with SCAI Stage C shock requiring milrinone initiation, a baseline MPS score of <0.5 was associated with a 35% event rate of the composite endpoint of death, left ventricular assist device, or transplant at 30 days compared with 3% for those with an MPS >1 (p < 0.001). Patients who were able to augment their MPS to >1 after milrinone infusion had a lower event rate than those with insufficient reserve (40% vs. 16%, p = 0.01). The MPS, which defines the patient-specific power-to-efficiency ratio and is inversely proportional to PE, represents an objective assessment of the myocardial energetic state of a patient and can be used to define the physiological tipping point for patients with advanced heart failure.

Assessing Asphalt Pavement Pre-Compaction with Paver Screed Frequency Measurements

The quality and longevity of an asphalt road depends on the accurate compaction of the asphalt pavement. Particular emphasis should be placed on the pre-compaction process involving the paver’s screed. Inadequate or excessive pre-compaction can result in paving errors and inhomogeneities within the pavement, which even expert roller operation cannot rectify. In practical paving, however, the degree of pre-compaction is rarely determined, so that one is dependent on the empirical knowledge and assessments of the paving personnel. Within the context of the research initiative, InfraROB (Grant Agreement No.: 955337), an innovative system was devised to infer the extent of pre-compaction by leveraging the resonance frequency of the paver’s screed. This system comprises a rugged, enclosed acceleration sensor capable of capturing high-speed accelerations and a Wi-Fi-enabled control unit for data storage and processing. To validate this system, a series of test pavements were constructed using an asphalt binder mix (AC 16 BS), deliberately varying the speed of the tamper compaction unit in four steps from 0 rpm up to 1500 rpm. Half of the test lanes were longitudinally compacted with rollers, allowing for the examination of the asphalt pavement in its partially pre-compacted state. To achieve this, drill cores were extracted, and their density was assessed in the laboratory. Through the application of Fast Fourier Transformation, the measured resonance frequency data was analysed and subsequently correlated with the outcomes of the drill core inspections. This analysis revealed a strong logarithmic relationship between the average peak acceleration and the bulk densities measured, with a high coefficient of determination exceeding 0.9. The presented method enables real-time assessment of the pre-compaction status of asphalt pavement, offering support to paving personnel, optimising roller usage, and enhancing asphalt pavement quality.

Relating LC3 microstructure, surface resistivity and compressive strength development

Concrete surface resistivity can be measured non-destructively, providing an indirect measurement of microstructural development which can be related to strength development. However, relating surface resistivity and strength can be challenging for limestone calcined clay cements (LC3) since they contain mineral components of varying composition and reactivity. In this study of LC3 formulations, concrete surface resistivity until 56 days of hydration and mortar compressive strength at 3, 7, and 28 days were investigated to explore the relationship between these properties while examining the influence of mixture proportioning, limestone particle size and gypsum dosage on LC3 surface resistivity and strength development. Microstructural development of these blends was also assessed by thermogravimetric analysis and formation factor. The results suggest a strong logarithmic relationship between the resistivity and strength development, which can both be predicted by the portlandite consumption. These correlations can allow prediction of later-age strength based on early-age resistivity and portlandite consumption.

Improved calibration of the Green–Ampt infiltration module in the EROSION-2D/3D model using a rainfall-runoff experiment database

Abstract. Soil infiltration is one of the key factors that has an influence on soil erosion caused by rainfall. Therefore, a well-represented infiltration process is a necessary precondition for successful soil erosion modelling. Complex natural conditions do not allow the full mathematical description of the infiltration process, and additional calibration parameters are required. The Green–Ampt-based infiltration module in the EROSION-2D/3D model introduces a calibration parameter “skinfactor” to adjust saturated hydraulic conductivity. Previous studies provide skinfactor values for several combinations of soil and vegetation conditions. However, their accuracies are questionable, and estimating the skinfactors for other than the measured conditions yields significant uncertainties in the model results. This study brings together an extensive database of rainfall simulation experiments, the state-of-the-art model parametrisation method and linear mixed-effect models to statistically analyse relationships between soil and vegetation conditions and the model calibration parameter skinfactor. New empirically based transfer functions for skinfactor estimation significantly improving the accuracy of the infiltration module and thus the overall EROSION-2D/3D model performance are provided in this study. Soil moisture and bulk density were identified as the most significant predictors explaining 82 % of the skinfactor variability, followed by the soil texture, vegetation cover and impact of previous rainfall events. The median absolute percentage error of the skinfactor prediction was improved from 71 % using the currently available method to 30 %–34 % using the presented transfer functions, which led to significant decrease in error propagation into the model results compared to the present method. The strong logarithmic relationship observed between the calibration parameter and soil moisture however indicates high overestimation of infiltration for dry soils by the algorithms implemented in EROSION-2D/3D and puts the state-of-the-art parametrisation method in question. An alternative parameter optimisation method including calibration of two Green–Ampt parameters' saturated hydraulic conductivity and water potential at the wetting front was tested and compared with the state-of-the-art method, which paves a new direction for future EROSION-2D/3D model parametrisation.

Characteristics of Modern Geostress and Removability of No. 15 Coal Reservoir, Yangquan Mining Area, China

Based on injection pressure drop test data and acoustic emission test data of 13 records for samples from the Wenjiazhuang and Sijiazhuang mines in the Yangquan mining area, the vertical distribution characteristics of modern in situ stress and its influence on permeability in the Yangquan mining area were analyzed, and the exploitation of the No. 15 coal reservoir was studied. The results show that the Yangquan mining area is a low-stress area within burial depths of 400–760 m, moderate-stress area within 760–950 m, and high-stress area within 950–1300 m. The Yangquan mining area hosts a strike–slip fault stress field within burial depths of 400–900 m and a normal fault stress field within burial depths of 900–1300 m, and the permeability showed a “decrease–increase–decrease” trend with an increase in burial depth. The pressure coefficient K of the modern in situ stress field in the Yangquan mining area decreased with increasing burial depth, and its relationship formula with burial depth was 68.25/H + 0.2846 ≤ K ≤ 397.63/H + 0.6061. The permeability of No. 15 coal seam had a strong logarithmic relationship with horizontal principal stress, a strong exponential relationship with horizontal principal stress difference, and a strong power function relationship with effective stress. With an increase in stress and in stress difference, permeability decreased rapidly. The results of the acoustic emission tests of the No. 15 coal were analyzed. The in situ stress type of the Sijiazhuang mine and Wenjiazhuang mine is the normal fault stress field type, which is consistent with the well test analysis results. The high ring counts in the horizontal direction of coal seam 15 lasted for a long time, which was conducive to the generation of several network-forming fractures in the process of fracturing. The No. 15 coal reservoir is located in strike–slip fault stress field and normal fault stress field areas, and the fractures generated by hydraulic fracturing expanded along the vertical direction and the maximum horizontal principal stress direction, which was favorable for the fracturing transformation of coal reservoirs and the production and development of coalbed methane.

Bloom-forming toxic cyanobacterium Microcystis: Quantification and monitoring with a high-frequency echosounder

Harmful cyanobacterial blooms pose a serious environmental threat to freshwater lakes and reservoirs. Investigating the dynamics of toxic bloom-forming cyanobacterial genus Microcystis is a challenging task due to its huge spatiotemporal heterogeneity. The hydroacoustic technology allows for rapid scanning of the water column synoptically and has a significant potential for rapid, non-invasive in situ quantification of aquatic organisms. The aim of this work is to develop a reliable cost-effective method for the accurate quantification of the biomass (B) of gas-bearing cyanobacterium Microcystis in water bodies using a high-frequency scientific echosounder. First, we showed that gas-bearing Microcystis colonies are much stronger backscatterers than gas-free phytoplanktonic algae. Then, in the tank experiments, we found a strong logarithmic relationship between the volume backscattering coefficient (sv) and Microcystis B proxies, such as Microcystis-bound chlorophyll a (Chl aMicro) and particle volume concentration. The sv/B ratio remained unchanged over a wide range of B concentrations when the same source of Microcystis material was used. Our measurements in Lake Dianchi (China) also revealed strong logarithmic relationship between sv and Chl aMicro. The biomass-calibrated echosounder was used to study the diurnal variability of Microcystis B in the lake. We found a sharp increase in the cyanobacterium B and sv/Chl aMicro ratio near the water surface during the daytime and more uniform distribution of these parameters during the nighttime. We argue that the variations in B and sv/Chl aMicro ratio could be associated with temporal changes in thermal stratification and turbulent mixing. Our data suggest that the sv/Chl aMicro ratio positively correlates with (i) the percentage of larger colonies in population and/or (ii) the content of free gas in cells. The last properties allow Microcystis colonies to attain rapid floating, which enables them to concentrate at the water surface at conducive ambient conditions. The sv/Chl aMicro ratio can be a new important variable reflecting the ability of Microcystis colonies to migrate vertically. Monitoring of this ratio may help to determine the early warning threshold for Microcystis scum formation. The proposed acoustic technology for in situ quantification of Microcystis biomass can be a powerful tool for accurate monitoring and assessment of this cyanobacterium at high spatiotemporal resolution in water bodies.

Integrating willingness analysis into investment prediction model for large scale building energy saving retrofit: Using fuzzy multiple attribute decision making method with Monte Carlo simulation

Nowadays, it has emerged a trend to carry out large scale building energy saving retrofit (LSBESR) in China. LSBESR is determined by a range of endogenous and exogenous factors. In particular, uncertainties concerning owners’ willingness of retrofit exacerbate the difficulty of investment prediction. In this paper, an investment prediction model (IPM) for LSBESR is proposed by considering owners’ willingness factors that possess fuzzy attributes and random characteristics. By definition, IPM integrates fuzzy multiple attribute decision making (FMADM) and Monte Carlo (MC) analysis. First, this paper proposes analytic hierarchy process (AHP) of retrofit willingness. Second, the membership function is constructed. Third, the authors suggest using MC simulation to predict investment. Meanwhile, 100 public buildings of LSBESR in Shanghai are investigated, based on which the authors obtained double peak distribution of LSBESR investment. Compared with the high investment scheme ($154 million), the expected value of investment (EVI) is shown to be $89 million and the probability of greater than EVI is 60.5%. Moreover, the authors revealed a strong logarithmic relationship between willingness and EVI. Relying on investigation willingness factor, people can quickly get the EVI of LSBESR. In summary, this paper is capable of providing a new perspective to the decision maker.

Evidences and magnitude of nighttime transpiration derived from Populus euphratica in the extreme arid region of China

Extensive research has found that nighttime transpiration (En) is positively correlated to the vapour pressure deficit (VPD), that suggested En was highest during the night under high temperatures and low humidity along with high soil water availability, typically for the riparian forest in the extreme arid region of China. This study used the heat ratio method to measure sap velocity (Vs) for mature and saplings Populus euphratica Oliv., and then En was conservatively calculated as total nocturnal sap flow (Fs, the product of Vs and sapwood area As) between 01:00 to 06:00. A gas exchange system was used to measure the leaf transpiration rate (Tr) and stomatal conductance (gs) of saplings. For mature trees, nighttime Vs was extensive and logarithmic correlated to VPD (similar to daytime). For saplings, gs and Tr was extensive in different months, and also a strong logarithmic relationship was found between Vs and VPD for both daytime and nighttime periods. Both of stem sap flow and leaf gas exchange suggusted the occurrence of En, whether mature or sapling trees. En contribution to daily transpiration (Ed) was high just as expected for P. euphratica, which was confirmed by proportional En to Ed (En/Ed) means taken in 2012 (24.99%) and 2013 (34.08%). Compared to mature trees, En/Ed of saplings in 2013 was lower with means of 12.06%, that supported further by the shorter duration times and less Tr,n (16.64%) and gs,n (26.45%) of leaf, suggesting that En magnitude is associated to individual the tree size, that effect to stored water of individual trees, although this hypothesis requires further research.

Assessment of Head Tremor with Accelerometers Versus Gyroscopic Transducers.

Accelerometers and gyroscopes are used commonly in the assessment of hand tremor, but their validity in the assessment of head tremor has not been studied. We hypothesized that gyroscopy would be superior to accelerometry because head tremor is rotational motion, and gyroscopes record rotational motion, free of gravitational artifact. We also hypothesized a strong logarithmic relationship between 0 to 4-point tremor ratings and the transducer measures of tremor amplitude, similar to those previously reported for hand tremor. Head tremor was recorded for 1 minute in each of the five head positions used in the Essential Tremor Rating Assessment Scale, using a triaxial accelerometer and triaxial gyroscope mounted at the vertex of the head. Mean and maximum 3-second burst displacement tremor and rotation tremor were computed by spectral analysis. The minimum detectable change for the transducers was estimated using the residual mean squared error from repeated-measures analysis of variance. Tremor displacement and rotation (T) were logarithmically related to tremor ratings (tremor rating score; TRS): log(T) = α TRS + β, where α ≈ 0.47 for displacement and ≈0.64 for rotation, and β ≈ -1.8 and -1.4. Tremor ratings correlated more strongly with gyroscopy (r = 0.83-0.87) than with accelerometry (r = 0.71-0.75). Minimum detectable change (percent reduction) was approximately 66% of the baseline geometric mean. Gyroscopic transducers are superior to accelerometry for assessment of head tremor. Both measures of head tremor are logarithmically related to tremor ratings. The minimum detectable change of the transducer measures is comparable to those previously reported for hand tremor.

Influencing factor analysis based on electrical–thermal-pyrolytic simulation of carbon fiber composites lightning damage

The damage of carbon fiber reinforced polymer (CFRP) laminated composites under lightning strike is analyzed by coupled electrical–thermal-pyrolytic models, which is implemented by the ABAQUS/Standard finite element code coupled with user-defined subroutines USDFLD and HEATVAL. To clarify the effects of the lightning current waveform parameters and the thermal/electrical properties of CFRPs, the damages of CFRP laminated specimens under diverse lightning current waveforms are experimentally and numerically analyzed. The results reveal that the damage volume shows a strong logarithmic relationship with the action integral, and that the damage is strongly governed by the electrical properties of CFRPs, though thermal conductivity variation barely affects the damage volume.

Modeling of Non-Isothermal Austenite Formation in Cr5 Roller Steel

A modified model describing the austenite reaction was developed that took into account the effect of heating rate. The model considered the variation of activation energy during non-isothermal heating and one set of model parameter was adequate to predict the formation of austenite. To verify the theoretical model, the process of austenite formation during continuous heating in Cr5 roller steel with pearlite and ferrite mixed initial microstructure was analyzed by dilatation experiment. The results show that a strong logarithmic relationship between apparent activation energy and heating rate. Experimental kinetic transformations as well as critical temperatures of austenite reaction are in good agreement with the calculations. The model can be used to describe the transformation kinetics at an intermediate heating rate.

Fungal biodegradation of CCA-treated wood and removal of its metal components

In the present study, 5 isolates of brown-rot fungi were used for fungal bioprocessing (FB) of chromated copper arsenate (CCA)-treated wood wastes: Antrodia vaillantii SEL8501, Fomitopsis palustris TYP0507 and TYP6137, and Crustoderma sp. KUC8065 and KUC8611. The isolates showed notable capacity for the degradation of treated wood and removal of CCA components via the American Wood Protection Association soil block test. Among them, Crustoderma sp. KUC8611 effectively decayed the treated wood, causing a mass loss of up to 60%. F. palustris caused extensive leaching of CrO3 of up to 79% and As2O5 of up to 87%, but only moderate leaching of CuO of up to 50%. This high capacity for removal of CrO3 and As2O5 showed a strong logarithmic relationship with the amount of oxalic acid produced in the decayed wood. The majority of metals removed from treated wood during the decay process were deposited in the soil and feeder strip. Further investigation will be required to establish the capability of selected fungi for FB of full-sized lumber treated with CCA.

Estimating root biomass in Salix viminalis × Salix schwerinii cultivar “Olof” using the electrical capacitance method

Non‐destructive assessment of root systems is important in order to understand and optimise the potential of resource capture and allocation by the plant. We studied the relationships between electrical capacitance (EC) and the below‐ and above‐ground biomass of willows. Cuttings of Salix viminalis × Salix schwerinii cv. Olof were maintained in pots and root development was followed up using a portable capacitance meter over the course of 2.5 months. Pot observations were compared with excavation of two‐year‐old established trees. A strong significant linear relationship (R 2 = 0.81, p < 0.001) was obtained between EC and root biomass (dry weight [DW]) for the pot experiment. EC also showed good correlations with stem and leaf biomass, as well as with stem height. In the excavated willow trees, there was a strong logarithmic relationship between EC and root biomass (R 2 = 0.66, p < 0.001). These results suggest that EC is a good estimator of below‐ground biomass in willow and may become useful in screening varieties for differences in root biomass traits, especially in distinguishing below‐ground resource allocation at an early stage.

Response of soil organic carbon spatial variability to the expansion of scale in the uplands of Northeast China

Abstract Soil organic carbon (SOC) plays an important role in maintaining and improving soil fertility and quality as well as mitigating climate change. Understanding SOC density spatial variability is fundamental for describing soil resources and predicting SOC. Three categories were used to create spatial scales: administrative category (county, city, province and region scale), soil taxonomic category (family, sub-group, great group and order scale) and soil type (zonal soil and azonal soil)-administrative category. Soil organic carbon density variability and its response to the expansion of scales in the topsoil (0–20 cm) and soil profile (a depth of 1 m) layers in the uplands of Northeast China were examined based on coefficient of variation (CV) values using data of 1041 profiles obtained from the Second National Soil Survey of China. The results depicted that SOC density variability increased not only in the topsoil layer but also in the soil profile layer with the expansion of scales in all categories. In the administrative category, there was a strong logarithmic relationship between upland areas or administrative areas and mean SOC density CV. Though mean SOC density CV within each soil order increased from family to order, the trend and range of increase varied greatly. Soil organic carbon density variability for zonal and azonal soils was similar in terms of trends but different in terms of rate with increasing scale from county to region. A strong logarithmic relationship between upland area and mean SOC density CV was also observed. These relationships indicated that reducing upland area by five orders of magnitude would halve the CV. Therefore, when estimating the SOC pool in uplands, both administrative and soil type scales should be considered in the sampling design, especially for azonal soil.

EFFECTS OF NITRATE CONCENTRATION AND IONIC STRENGTH ON NITRATE ANION EXCLUSION UNDER UNSATURATED FLOW CONDITIONS

//<![CDATA[ var theForm = document.forms['aspnetForm']; if (!theForm) { theForm = document.aspnetForm; } function __doPostBack(eventTarget, eventArgument) { if (!theForm.onsubmit || (theForm.onsubmit() != false)) { theForm.__EVENTTARGET.value = eventTarget; theForm.__EVENTARGUMENT.value = eventArgument; theForm.submit(); } } //]]>

Determination of Vitamin D-dependent calcium absorption by 45Ca gavage in the rat

Precise determination of Vitamin D-dependent intestinal calcium absorption in longitudinal studies is problematic. We have assessed Vitamin D-dependent intestinal calcium absorption by 45Ca gavage. Rats were gavaged with a 1mL solution containing 45Ca (CaCl2, 9.3MBq/mL) maintained at 37°C. Total Ca concentration of the gavage fluid was optimised by comparing the absorption curves for fluids made up to 0.025, 2.025, 4.025 and 40.025mmol/L with 40CaCl2. The effect of varying dietary Ca on fractional Ca absorption was determined in rats fed semi-synthetic diets containing either 0.05%, 0.2%, 0.4% or 1.0% Ca for 50 days. Serum 1,25 dihydroxyvitamin D (1,25D) was determined by radioimmunoassay. Total gavage Ca of 0.025mmol/L achieved the highest peak fractional absorption and was adopted for all future experiments. Fifty days after allocation to the diets both fractional Ca absorption and 1,25D were highest in rats fed 0.05% Ca and lowest in those fed 1.0% Ca (absorption, P<0.05 and 1,25D, P<0.05). There was a strong logarithmic relationship between 1,25D and fractional Ca absorption (R2 0.69, P<0.001). Weekly repetition of the procedure did not cause a fall in haematocrit over 7 weeks. Radiocalcium (45Ca) absorption by gavage provides a simple measure of Vitamin D-dependent Ca absorption for repetitive use in longitudinal studies.

Proton MR spectroscopic and diffusion tensor brain MR imaging in X-linked adrenoleukodystrophy: initial experience.

To compare conventional magnetic resonance (MR) imaging, proton MR spectroscopic imaging, and diffusion tensor (DT) MR imaging findings in patients with X chromosome-linked adrenoleukodystrophy (X-ALD). Multisection proton MR spectroscopy and DT imaging were performed in 11 patients with X-ALD and in 11 healthy control subjects. Quantitative measures of N-acetylaspartate (NAA), choline, and creatine values and of isotropic apparent diffusion coefficient (IADC) and fractional anisotropy (FA) were obtained from coregistered regions of interest. DT imaging and metabolic parameters were compared by using regression analysis. In addition, differences in DT imaging and metabolite measurements between normal- and abnormal-appearing white matter on conventional MR images were evaluated by using a nonparametric (Mann-Whitney) test. A strong logarithmic relationship between NAA value and FA (r = 0.64, P <.001) and an inverse logarithmic relationship were found between NAA value and IADC (r = -0.69, P <.001). Creatine and choline values correlated poorly with IADC and FA. In the normal-appearing white matter of asymptomatic patients, the NAA value was 17% lower than that in the healthy control subjects (P =.016), whereas no significant difference in DT imaging measures was seen in these regions. In patients with X-ALD, MR spectroscopic imaging can depict abnormalities in white matter that have a normal appearance on both conventional MR and DT images; this finding suggests that it may be the most sensitive technique for detecting early abnormalities of demyelination or axonal loss in patients with X-ALD.

Volatile Organic Compound (VOC) Transport through Compacted Clay

Movement of volatile organic compounds (VOCs) through compacted clay liners was investigated using laboratory-scale column and tank tests. Hydraulic conductivity of the compacted clay was not significantly impacted by the introduction of VOCs in concentrations up to 20 mg/L. Soil-water partition coefficients of the seven VOCs tested had a strong logarithmic relationship with the octanol-water partition coefficient. Partition coefficients from batch tests were in good agreement with those measured directly on soil samples at the termination of the column/tank tests. The VOCs were degraded in the clay, with estimated half-lives ranging from 2 to 116 days. Mechanical dispersion was not significant in the range of the hydraulic conductivities of the test specimens (i.e., ≪10\U-7\N cm/s). Effective molecular diffusion coefficients were mostly in 10\U-6\N cm²/s and generally decreased with increasing aqueous solubility. Mass transport parameters of VOCs in clay liners can be estimated from laboratory batch tests and properly prepared small-scale column tests. However, accounting for degradation of VOCs and minimizing the number of transport parameters that are simultaneously estimated from a single response-time record are important considerations for accurate determination of transport parameters.

MEASURING FACTORY FOCUS: AN EMPIRICAL STUDY

Focus in the manufacturing plant is generally deemed to be an important element of success in manufacturing strategy. Yet, little work has been completed in the measurement of plant focus and a dearth of empirical evidence exists to support the broad popularity of this concept. This paper presents a plant focus measurement approach and reports the results of a field study that uses a site visit research design to apply the focus measure to a multi‐industry sample of manufacturing plants. Regression analysis is used to study the relationships between the plant focus variable and the environmental variables of plant size, number of product lines, plant age, number of processes, and type of processes. Although highly intuitive, these relationships have undergone very little empirical study in the literature. Our study provides evidence of a strong logarithmic relationship between our plant focus measure and the number of product lines. Support is also demonstrated in that our measure of plant focus is linked to the number and type of manufacturing processes. However, the variables of plant age and plant size do not appear related to the plant focus measure. The literature‐based multicriteria focus measure can be used by managers and researchers as an objective, formal, and generalizable approach for assessing plant focus, for identifying areas in the plant that detract from focus, and for tracking focus improvement efforts over time.