Fractional Volume Change Research Articles

Carbogen-induced increases in tumor oxygenation depend on the vascular status of the tumor: A multiparametric MRI study in two rat glioblastoma models

The alleviation of hypoxia in glioblastoma with carbogen to improve treatment has met with limited success. Our hypothesis is that the eventual benefits of carbogen depend on the capacity for vasodilation. We examined, with MRI, changes in fractional cerebral blood volume, blood oxygen saturation, and blood oxygenation level dependent signals in response to carbogen. The analyses were performed in two xenograft models of glioma (U87 and U251) recognized to have different vascular patterns. Carbogen increased fractional cerebral blood volume, blood oxygen saturation, and blood oxygenation level dependent signals in contralateral tissues. In the tumor core and peritumoral regions, changes were dependent on the capacity to vasodilate rather than on resting fractional cerebral blood volume. In the highly vascularised U87 tumor, carbogen induced a greater increase in fractional cerebral blood volume and blood oxygen saturation in comparison to the less vascularized U251 tumor. The blood oxygenation level dependent signal revealed a delayed response in U251 tumors relative to the contralateral tissue. Additionally, we highlight the considerable heterogeneity of fractional cerebral blood volume, blood oxygen saturation, and blood oxygenation level dependent within U251 tumor in which multiple compartments co-exist (tumor core, rim and peritumoral regions). Finally, our study underlines the complexity of the flow/metabolism interactions in different models of glioblastoma. These irregularities should be taken into account in order to palliate intratumoral hypoxia in clinical trials.

Undersaturated Oil Compressibility Prediction for Mishrif Reservoir in the Southern Iraqi Oil Fields Using Artificial Neural Network

Coefficient of Isothermal oil compressibility is required in transient fluid flow problems, extension of fluid properties from values at the bubble point pressure to higher pressures of interest and in material balance calculations [1, 2]. Coefficient of Isothermal oil compressibility is a measure of the fractional change in volume as pressure is changed at constant temperature [3]. Coefficients of isothermal oil compressibility are usually obtained from reservoir fluid analysis. Reservoir fluid analysis is an expensive and time consuming operation that is not always available when the volumetric properties of reservoir fluids are needed. For this reason correlations have been developed and are being developed for predicting fluid properties including the coefficient of isothermal oil compressibility.
 This paper presents an application of Artificial Neural Network (ANN) methods for estimation of isothermal oil compressibility for the Mishrif reservoir oils among of commonly available field data, according to the fact that this method is useful when relationships of parameters are too complicated. The method is proposed as a more effective prognostic tool than are currently available procedures.
 In this study, back propagation (BPN) network was used to develop an ANN model to predict isothermal oil compressibility. A three layer feed-forward network has been selected which has the best correlation coefficient in testing the models. The new model of undersaturated oil compressibility in which the first layer consists of five neurons representing the input values of pressure above bubble point, solution gas oil ratio at bubble point, oil gravity API, reservoir temperature and gas specific gravity. The second (hidden) layer contains 12 neurons, and the third layer contains one neuron representing the output values of undersaturated oil compressibility. It was found that the new model estimate undersaturated oil compressibility for Mishrif reservoir crudes in the southern Iraqi oil fields much better than the published ones. The present model predicts undersaturated oil compressibility with an average absolute relative error of 3.86% for the testing data set.

Annealing Effect Reversal by Water Sorption–Desorption and Heating above the Glass Transition Temperature—Comparison of Properties

Our objective is to compare the physical properties of materials obtained from two different methods of annealing reversal, that is, water sorption-desorption (WSD) and heating above glass transition temperature (HAT). Trehalose was annealed by storing at 100 °C for 120 h. The annealing effect was reversed either by WSD or HAT, and the resulting materials were characterized by differential scanning calorimetry (DSC), water sorption studies, and positron annihilation spectroscopy (PAS). While the products obtained by the two methods of annealing reversal appeared to be identical by conventional characterization methods, they exhibited pronounced differences in their water sorption behavior. Positron annihilation spectroscopy (PAS), by measuring the fractional free volume changes in the processed samples, provided a mechanistic explanation for the differences in the observed behavior.

FMRI response in the medial prefrontal cortex predicts cocaine but not sucrose self-administration history.

Repeated cocaine exposure induces long-lasting neuroadaptations that alter subsequent responsiveness to the drug. However, systems-level investigation of these neuroplastic consequences is limited. We employed a rodent model of drug addiction to investigate neuroadaptations associated with prolonged forced abstinence after long-term cocaine self-administration (SA). Since natural rewards also activate the mesolimbic reward system in a partially overlapping fashion as cocaine, our design also included a sucrose SA group. Rats were trained to self-administer cocaine or sucrose using a fixed-ratio one, long-access schedule (6 h/day for 20 days). A third group of naïve, sedentary rats served as a negative control. After 30 days of abstinence, the reactivity of the reward system was assessed with functional magnetic resonance imaging (fMRI) following an intravenous cocaine injection challenge. A strong positive fMRI response, as measured by fractional cerebral blood volume changes relative to baseline (CBV%), was seen in the sedentary control group in such cortico-limbic regions as medial prefrontal cortex and anterior cingulate cortex. In contrast, both the cocaine and sucrose SA groups demonstrated a very similar initial negative fMRI response followed by an attenuated positive response. The magnitude of the mPFC response was significantly correlated with the total amount of reinforcer intake during the training sessions for the cocaine SA but not for the sucrose SA group. Given that the two SA groups had identical histories of operant training and handling, this region-specific group difference revealed by regression analysis may reflect the development of neuroadaptive mechanisms specifically related to the emergence of addiction-like behavior that occurs only in cocaine SA animals.

Abstract 1317: Dose-dependent effects of bevacizumab on human HCC xenografts

Abstract Introduction: Bevacizumab has demonstrated positive clinical treatment effect and is currently approved for treatment of colorectal carcinoma and NSCLC in combination with standard chemotherapy. Preclinical studies have shown decrease in microvascular density. We aim to determine if DCE-MRI is a sensitive enough technique to detect changes in fractional intravascular volume after administration of a single dose of bevacizumab. Materials and Methods: Mice: Twenty-seven male BALB/c mice (6 weeks old, 24 ± 2g) formed the study population & were under 1-2 % isoflurane during the scanning. They were implanted with human-derived HCC xenograft line, sensitive to bevacizumab therapy. Two dose levels were investigated: low dose (n = 4) at 1 mg/kg and high dose (n=8) at 10 mg/kg. Mice were scanned at baseline, day 1 and 5 after therapy. Fifteen control mice were similarly imaged after receiving omalizumab, a human anti-IgE antibody, at 10 mg/kg. Tumors were sectioned and stained immunohistochemically to identify CD34 for quantification of MVD. DCE-MRI: MRI was performed on a 7T scanner (Bruker ClinScan, Bruker BioSpin MRI GmbH, Germany). A 3D VIBE sequence was used with following parameters: TR = 3.04 ms, TE = 1.23 ms, FOV = 36 × 36 mm, 128 × 128 matrix, 8 slices with thickness of 1 mm, & temporal resolution 2 s. Five sets of baseline images were acquired with ≤ = 6° & 14°. It was followed by a dynamic sequence of 130 sets of images (α = 14°). A dose of 100 µL of Gd-DOTA (Dotarem, Guerbet SA, France) at 1 mmol/kg was injected through the tail vein after the first set of dynamic images. Data Processing: Region of interests corresponding to the xenograft and major artery were manually outlined. Blood volume was derived from the standard two-compartment model. Results: Baseline blood volume for the control group was 7.32 ± 3.47 %. The values were 9.67 ± 1.72 % for the group treated with bevacizumab 1 mg/kg and 10.02 ± 3.85 % for the group dosed with bevacizumab 10 mg/kg. A reduction of 52.69 ± 24.77 % in blood volume at Day 1 and 75.25 ± 12.58 % at Day 5 was observed in the higher dose group, while a reduction of 6.10 ± 31.86 % at Day 1 and 56.99 ± 9.18 % at Day 5 was observed in the lower dose group. An increase of 29.31 ± 66.84 % at Day 1 was observed in the control group. There is a good correlation between percentage of MVD derived by CD34 staining with percentage of blood volume derived by the two-compartment model (r = 0.806, p = 0.0002). Conclusion: The results showed that the effects of bevacizumab are dose-related. A more gradual drop of blood volume was observed in group treated with bevacizumab 1 mg/kg. On the other hand, a steep and immediate drop of blood volume was observed in group treated with bevacizumab 10 mg/kg. The results suggested potential of DCE-MRI as a sensitive biomarker of MVD and as a reliable non-destructive testing method for time course observation of MVD changes in animals. This facilitates translation and clinical application to early time points after anti-angiogenic therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1317. doi:1538-7445.AM2012-1317

Dosimetric Analysis of Inter fractional Dose and Volume Changes in Bladder and Rectum during Intensity Modulated Radiation Therapy for Gynecological Cancers with Daily Cone Beam CT guidance

To assess the changes in dose volume histograms from inter fractional changes in bladder and rectum as evaluated by daily KV cone beam CT (CBCT) during Intensity Modulated Radiation Therapy (IMRT) for post operative endometrial cancers.

Straining to Make Mechanical Ventilation Safe and Simple

Straining to Make Mechanical Ventilation Safe and Simple

Dynamic Microbubble Contrast-enhanced US to Measure Tumor Response to Targeted Therapy: A Proposed Clinical Protocol with Results from Renal Cell Carcinoma Patients Receiving Antiangiogenic Therapy

To develop and implement an evidence-based protocol for characterizing vascular response of renal cell carcinoma (RCC) to targeted therapy by using dynamic contrast material-enhanced (DCE) ultrasonography (US). The study was approved by the institutional research ethics board; written informed consent was obtained from all patients. Seventeen patients (four women; median age, 58 years; range, 42-72 years; 13 men, median age, 62 years; range, 45-81 years) with metastatic RCC were examined by using DCE US before and after 2 weeks of treatment with sunitinib (May 2007 to October 2009). Two contrast agent techniques--bolus injection and disruption-replenishment infusion of microbubbles--were compared. Changes in tumor blood velocity and fractional blood volume were measured with both methods, together with reproducibility and effect of compensation for respiratory motion. Tumor changes were assessed with computed tomography, by using the best response with the Response Evaluation Criteria in Solid Tumors (RECIST) and progression-free survival (PFS). Follow-up RECIST measurements were performed at 6-week intervals until progressive disease was detected. In response to treatment, median tumor fractional blood volume measured with the disruption-replenishment infusion method decreased by 73.2% (interquartile range, 46%-87%) (P < .002), with repeated-measure reproducibility of 9%-15%. Significant decreases were also seen with the bolus method, but with poor correlation of changes in bolus peak (r = 0.46, P = .066) and area under the curve (r = 0.47, P = .058), compared with infusion measurements. Changes in DCE US parameters over 2 weeks did not correlate with PFS and could not be used to predict long-term assessment of best response by using RECIST. Follow-up times ranged 28-501 days; the median was 164 days. DCE US provides reproducible and sensitive assessment of vascular changes in response to antiangiogenic therapy. The disruption-replenishment infusion protocol is a flexible method suitable for many tumor types, but further studies are needed to assess whether this protocol may be predictive of patient outcome.

Correlation between plasticity and other materials properties of Cu–Zr bulk metallic glasses: An atomistic simulation study

The correlation between experimentally observed plasticity and various materials properties that have been mentioned as being related to the mechanical properties of bulk metallic glasses (BMGs) has been investigated for Cu–Zr binary BMG alloys using a molecular dynamics simulation. Most of the properties examined show a roughly comparable correlation with plasticity, but the accuracy is not sufficient to be used for alloy design. The pentagon fraction obtained from a Voronoi polygon analysis and atomic displacement during plastic deformation directly computed using the atomistic approach can be selected as quantities that have an acceptable correlation with plasticity, even though the clearness and the statistical stability are unsatisfactory. The fractional volume change of mixing is proposed as a new materials property that shows a clear and statistically stable correlation with plasticity, and its physical origin as a tool to estimate the plasticity of and to design BMG alloys with improved plasticity is discussed.

SU-FF-J-146: Sequential Volume Change Estimation of Breast Tumor From Whole Breast Automated Ultrasound by Reader Study

Purpose: To evaluate use of image based registration in volume change estimation of breast tumor by expert reader study of three‐dimensional (3D) ultrasound(US) whole breast image volumes. Methods: 3D US volumes of tumors in nearly whole breast sweeps using mammography‐style compression were acquired using the Logiq‐9 10L transducer(GE Healthcare, Waukesha, WI). Nearly whole breast scanning was performed before, during and after 115±14 days of chemotherapy on 7 patients. Three breast radiologists marked a 3D ellipsoid around the tumor on pairs of pre‐ chemotherapy with mid‐ or post‐chemotherapy USimage volumes, spatially unregistered or registered in a pseudo‐random order. Additional information including pre‐chemotherapy US hand scan(s), mammograms and a clinical findings report without tumor dimensions was provided. Results: Preliminary results on the first 3 of 7 cases showed that registration provided a nearly significant reduction in the statistical uncertainty in reader estimates of normalized fractional tumor volume change due to chemotherapy (p‐value<0.08). The time taken to mark the tumor boundary decreased significantly from 10 min (9.8–10.3) without registration to 5.5 min (3.6–6.6) with registration (p‐value<0.02). Mean intersection‐to‐union volume ratio also improved with registration, by 33% from 0.15±0.1 (p‐value<0.05). A negligible improvement in confidence in identifying tumor margin in the automated USimage volumes was seen with registration. The normalized, between‐reader, mean separation of the centers of identified tumors decreased insignificantly with registration by 47% (p‐value<0.3). Conclusion: Successful spatial registration appears to aid ultrasound measurement of tumor changes in response to neoadjuvant chemotherapy. Visual segmentation speed and volume overlap between readers were increased with the help of registration. Larger studies would be appropriate with focus on treatment response, breast cancer screening and diagnostic applications.

Experimental study on the contribution of the quantum tunneling effect to theimprovement of the conductivity and piezoresistivity of a nickel powder-filled cement-basedcomposite

The voltage–current characteristics of a nickel powder (NP)-filled cement-based composite(NPCC) and the variation of electrical resistivity of NPCC under compressionare studied by using a four-pole method based on embedded loop electrodes.The generation of conductivity and piezoresistivity in NPCC is investigated byexamining the morphology of NPCC by SEM and studying the variation ofdistance between NP particles under compression. Experimental results indicatethat the electrical conductivity of NPCC is ohmic when the voltage is below3.5 V. Although NP particles are dispersed in the cement matrix and they do notform a connected conductive network, NPCC has a low electrical resistivity of2.29 × 103Ω cm without loading. A decrease of 0.042% in the fractional change in volume of NPCC undercompression causes the tunneling distance to decrease 0.60–1.42 nm and the fractionalchange in electrical resistivity to reach 62.61%. It is therefore concluded that theimprovement of conductivity and piezoresistivity of NPCC is due to the quantum tunnelingeffect.

Property‐averaging applied to determination of volume contraction in binary‐solid liquid‐fluidized beds

AbstractThis communication examines experimental information from the literature on the volume contraction that can occur when two monocomponent particle species that have a diameter ratio and a buoyancy‐corrected density ratio on opposite sides of unity are subjected to liquid fluidization as a binary mixture. Attempts are made to predict this volume contraction by applying monocomponent bed expansion equations using averaged properties of the binary solids. It was found that this method works better if the equations are anchored to experimental monocomponent voidages by the fractional bed volume change that they predict than if the equations are used directly. However, greater prediction accuracy can be achieved by correlation of the adjustable parameter G of the Westman, Am Ceramic Soc, 19, 127–129, (1936) equation, originally applied to binary packed beds.

Exact statistical mechanical lattice model and classical Lindemann theory of melting of inert gas solids

A modified form of Lindemann’s model shows that the melting points of the heavy inert gases and other effectively spherical molecular species are proportional to the depths of their diatomic potential wells. The success of the model when compared with experiment seems to rely on the almost constant value of the ratio of the fractional volume and entropy changes during fusion. The Lindemann proposal can be incorporated into an exactly treated statistical mechanical lattice model utilising expandable clusters which reproduces the solid–liquid melting phenomenon for argon with a realistic volume change and melting line.

Predicting Human Tumor Drug Concentrations from a Preclinical Pharmacokinetic Model of Temozolomide Brain Disposition

Knowledge of drug concentrations in tumors is critical for understanding the determinants of drug accumulation in tumors. Because significant obstacles prevent making these measurements in humans, development of a predictive pharmacokinetic model would be of great value to the translation of preclinical data to the clinic. Our goal was to show how the latter could be achieved for temozolomide, an agent used in the treatment of brain tumors, using an orthotopic brain tumor model in rats. Rats bearing i.c. tumors received 20 mg/kg i.v. of temozolomide followed by the subsequent measurement of serial plasma, cerebrospinal fluid (CSF), normal brain, and brain tumor temozolomide concentrations. The resultant data provided the framework to develop a hybrid physiologically based pharmacokinetic model for temozolomide in brain. The preclinical pharmacokinetic model was scaled to predict temozolomide concentrations in human CSF, normal brain, and brain tumor, and through a series of Monte Carlo simulations, the accumulation of temozolomide in brain tumors under conditions of altered blood-brain barrier permeability, fractional blood volume, and clinical dosing schedules was evaluated. The developed physiologically based pharmacokinetic model afforded a mechanistic and accurate prediction of temozolomide brain disposition in rats, which through model scale-up procedures accurately predicted the CSF/plasma area under the drug concentration-time curve ratios of 0.2 reported in patients. Through a series of model simulations, it was shown that the brain tumor accumulation of temozolomide varied substantially based on changes in blood-brain barrier permeability and fractional tumor blood volume but minimally based on clinical dosing regimens. A physiologically based pharmacokinetic modeling approach offers a means to translate preclinical to clinical characteristics of drug disposition in target tissues and, thus, a means to select appropriate drug dosing regimens for achieving optimal target tissue drug concentrations.

Effect of physical aging on the gas transport properties of poly(methyl methacrylate) membranes

The gas transport properties of poly(methyl methacrylate) (PMMA) membranes were examined as a function of physical aging time. A clear decrease of the gas permeability coefficient was observed. Interpretation of the permeation properties using results from differential scanning calorimeter and dynamic mechanical analyzer indicated that the smaller segmental motion of the polymer chains would be more restrict with aging time, discriminating against molecules with decreasing free volume. Free volume variations of PMMA membranes as a function of aging time was investigated by means of positron annihilation lifetime spectroscopy. It is indicated that there is obviously change in the fractional free volume in an aged membrane. The trend of fractional free volume changes consistent with the I 3 variation. These results correlated well with gas transport properties of membranes. Physical aging reduced the measured solubility coefficients and calculated diffusivity coefficients, which was shown to be consistent with decreasing of the free volume. Both diffusivity and solubility selectivity decrease with increasing aging time, however, the effect of physical aging on selectivity coefficients of polymeric membrane was controlled by the change of diffusivity selectivity.

611 Surface detection and color-encoding applied to real-time three-dimensional echocardiographic images as a basis for automated assessment of left ventricular wall motion

Purpose: Color encoding of left ventricular (LV) endocardial motion in 2D echo (2DE) has been shown to improve visual detection of regional wall motion abnormalities (RWMA). Our goals were: 1) to extend this technique to color encode detected LV endocardial surfaces from real-time 3D echo (RT3DE) images; 2) to automatically detect systolic RWMA and test its accuracy against visual interpretation of 2DE images. Methods: 19 normal subjects (N), and 14 patients with RWMA (including 7 with global LV dysfunction) underwent RT3DE and 2DE (Philips). 2DE images (apical 2-, 3and 4-chamber) were reviewed by an expert cardiologist, who graded wall motion (18 segments model) as normal or abnormal (AB). RT3DE datasets were analyzed using custom software: frame-by-frame semiautomated LV surface detection was followed by logical operations applied to each pair of consecutive frames, to track and color encode endocardial motion in 3D. Then, regional fractional volume change (RFVC) in % of regional end-diastolic volume was calculated automatically by colored voxels count, and displayed as stacked color-histograms. In RWMA, RFVCs were compared with regional thresholds, derived from RFVC computed in N and optimized using ROC analysis, for automated classification of wall motion. Results: The generation of 3D color-encoded wall-motion and RFVC quantification took <10 sec. In RWMA, 182/252 segments were graded as AB (Figure 1, arrows). The automated technique agreed with the expert reader in 225/252 (89%) segments, with only 8/252 (3%) false positive and 19/252 (8%) false negative detections (sensitivity: 0.91; specificity: 0.80; accuracy: 0.84). Conclusions: The proposed technique could improve the visual assessment of wall motion from RT3DE images, and represent the basis for automated detection of RWMA.

Crowding and Confinement Effects on Protein Diffusion In Vivo

The first in vivo measurements of a protein diffusion coefficient versus cytoplasmic biopolymer volume fraction are presented. Fluorescence recovery after photobleaching yields the effective diffusion coefficient on a 1-mum-length scale of green fluorescent protein within the cytoplasm of Escherichia coli grown in rich medium. Resuspension into hyperosmotic buffer lacking K+ and nutrients extracts cytoplasmic water, systematically increasing mean biopolymer volume fraction, <phi>, and thus the severity of possible crowding, binding, and confinement effects. For resuspension in isosmotic buffer (osmotic upshift, or Delta, of 0), the mean diffusion coefficient, <D>, in cytoplasm (6.1 +/- 2.4 microm2 s(-1)) is only 0.07 of the in vitro value (87 microm2 s(-1)); the relative dispersion among cells, sigmaD/<D> (standard deviation, sigma(D), relative to the mean), is 0.39. Both <D> and sigmaD/<D> remain remarkably constant over the range of Delta values of 0 to 0.28 osmolal. For a Delta value of > or =0.28 osmolal, formation of visible plasmolysis spaces (VPSs) coincides with the onset of a rapid decrease in <D> by a factor of 380 over the range of Delta values of 0.28 to 0.70 osmolal and a substantial increase in sigmaD/<D>. Individual values of D vary by a factor of 9 x 10(4) but correlate well with f(VPS), the fractional change in cytoplasmic volume on VPS formation. The analysis reveals two levels of dispersion in D among cells: moderate dispersion at low Delta values for cells lacking a VPS, perhaps related to variation in phi or biopolymer organization during the cell cycle, and stronger dispersion at high Delta values related to variation in f(VPS). Crowding effects alone cannot explain the data, nor do these data alone distinguish crowding from possible binding or confinement effects within a cytoplasmic meshwork.

Relationship between inflammatory lesions and cerebral atrophy in multiple sclerosis

To investigate the temporal relationship between inflammation and cerebral atrophy in a longitudinal study of 19 patients with relapsing-remitting multiple sclerosis (RRMS) using serial monthly contrast enhanced MRI examinations and monthly measurements of brain fractional volume (BFV) for an average of 4 (range 2.4 to 10) years. In this retrospective study, all patients had an active MRI scan at entry with a minimum of two new contrast enhancing lesions (CEL) on baseline MRI examinations. Patients were followed for a minimum of 3 months during a baseline (pretreatment) phase and subsequently followed during treatment with recombinant interferon beta (IFN) and various other immunomodulatory agents. Pre- and post contrast axial images were obtained using 3-mm slice thickness and a gadolinium contrast dose of 0.1 mmol/kg. Monthly CEL were sequentially numbered on hardcopy films and monthly BFV was determined on precontrast T1W images using a semiautomated program. For BFV measurements, all T1W scans were registered to the entry examination, which served as a mask image. Cerebral atrophy was measured as percent brain fractional volume change (PBVC) compared to the entry baseline scan. The results demonstrate that cerebral atrophy paralleled that of contrast enhancing lesion accumulation. The correlation between cumulative CEL and PBVC ranged from R2 = 0.47 to 0.81. Immunomodulatory agents that effectively reduced CEL accumulation also slowed the rate of atrophy. The correlation between contrast enhancing lesions (CEL) and atrophy suggests that patients who are not responding to therapy with a decrease in CEL may also be at risk for developing increased atrophy.

On the use of quasi-static deformation to understand reservoir fluid flow

Deformation above a producing reservoir provides a valuable source of information concerning fluid flow and flow properties. Quasi-static deformation occurs when the displacements are so slow that we may neglect inertial terms in the equations of motion. We present a method for inferring reservoir volume change and flow properties, such as permeability, from observations of quasi-static deformation. Such displacements may represent surface deformation such as tilt, leveling, interferometric synthetic aperture radar (InSAR), or bathymetry observations or subsurface deformation, as inferred from time-lapse seismic surveys. In our approach, the equation for fluid flow in a deforming reservoir provides a mapping from estimated fractional volume changes to reservoir permeability variations. If the reservoir behaves poroelastically over the interval of interest, all the steps in this approach are linear. Thus, the inference of reservoir permeability from deformation data becomes a linear inverse problem. In an application to the Wilmington oil field in California, we find that observed surface displacements, obtained by leveling and InSAR, are indeed compatible with measured reservoir volume fluxes. We find that the permeability variations in certain layers coincide with fault-block boundaries suggesting that, in some cases, faults are controlling fluid flow at depth.

31P MAS-NMR of human erythrocytes: independence of cell volume from angular velocity.

31P magic angle spinning NMR (MAS-NMR) spectra were obtained from suspensions of human red blood cells (RBCs) that contained the cell-volume-sensitive probe molecule, dimethyl methylphosphonate (DMMP). A mathematical representation of the spectral-peak shape, including the separation and width-at-half-height in the 31P NMR spectra, as a function of rotor speed, enabled us to explore the extent to which a change in cell volume would be reflected in the spectra if it occurred. We concluded that a fractional volume change in excess of 3% would have been detected by our experiments. Thus, the experiments indicated that the mean cell volume did not change by this amount even at the highest spinning rate of 7 kHz. The mean cell volume and intracellular 31P line-width were independent of the packing density of the cells and of the initial cell volume. The relationship of these conclusions to other non-NMR studies of pressure effects on cells is noted.