Dynamic Volume Changes Research Articles

Dynamic volume change measurements of cereal materials by environmental scanning electron microscopy and videomicroscopy

Moisture migration induced volume change in cereal materials was studied by environmental scanning electron microscopy, videomicroscopy and stereoscopy. It is shown that the in situ volume change can be monitored by the changes of projection area with the assumption of isotropic swelling/shrinkage. The projection area change from videomicroscopy matches well with the volume change by stereoscopy after dimensional normalization. The arbitrary volume values in between two relative humidity levels are available by interpolating the equilibrium volumes at beginning and ending. The sorption/desorption curves were fitted by the 'parallel exponential kinetics' model, which described two independent, parallel processes as 'slow' and 'fast'. In the low relative humidity range, sorption curves match well with the 'parallel exponential kinetics' model and the two parallel processes tend to be identical when relative humidity increases. The diffusivity of water moisture in a cracker, which was estimated by the half-equilibrium principle, has a strong dependence on relative humidity.

Effect of postural changes on lower limb blood volume, detected with non-invasive photoplethysmography

This paper describes the effect of passive leg raising on blood volume change in the lower limb, using a dual probe photoplethysmography (PPG) system employing a tissue optics model. The normalized AC/DC ratio and DC value are introduced from the model to evaluate the dynamic pulsation and total blood volume changes due to postural effects. The AC and DC components of PPG signals were collected from a passive leg raising protocol. With the leg raised, the normalized AC/DC ratio significantly decreased when supine, while the normalized DC value increased significantly in both supine and reclining positions. The parameters from the stationary leg showed similar but smaller responses. These results demonstrate a local and systemic physiological phenomenon in the lower limb blood volume change caused by postural changes. The normalized AC/DC ratio and DC value derived from the tissue optics model could be applied to assess the blood volume change.

Noninvasive time-dependent cytometry monitoring by digital holography

Using a digital holographic microscope setup, it is possible to measure dynamic volume changes in living cells. The cells were investigated time-dependently in transmission mode for different kinds of stimuli affecting their morphology. The measured phase shift was correlated to the cellular optical thickness, and then of the cell volume as well as the refractive index were calculated and interpreted. For the characterization of the digital holographic microscope setup, we have developed a transparent three-dimensional (3-D) reference chart that can be used as a lateral resolution chart and step-height resolution chart included in one substrate. For the monitoring of living cells, a biocompatible and autoclavable flow chamber was designed, which allows us to add, exchange, or dilute the fluid within the flow chamber. An integrated changeable coverslip enables inverse microscopic applications. Trypsinization, cell swelling and shrinking induced by osmolarity changes, and apoptosis served as model processes to elucidate the potential of the digital holographic microscopy (DHM).

Modeling dynamic cerebral blood volume changes during brain activation on the basis of the blood‐nulled functional MRI signal

Recently, vascular space occupancy (VASO) based functional magnetic resonance imaging (fMRI) was proposed to detect dynamic cerebral blood volume (CBV) changes using the blood-nulled non-selective inversion recovery (NSIR) sequence. However, directly mapping the dynamic CBV change by the NSIR signal change is based on the assumption of slow water exchange (SWE) around the capillary regime without cerebral blood flow (CBF) effects. In the present study, a fast water exchange (FWE) model incorporating with flow effects was derived from the Bloch equations and implemented for the quantification of dynamic CBV changes using VASO-fMRI during brain activation. Simulated results showed that only subtle differences in CBV changes estimated by these two models were observed on the basis of previously published VASO results. The influence of related physiological and biophysical factors within typical ranges was evaluated in steady-state simulations. It was revealed that in the transient state the CBV curves could be delayed in comparison with measured NSIR curves owing to the imbalance between the inflowing and outflowing blood signals.

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Brain volume changes in the first year of illness and 5-year outcome of schizophrenia

Progressive brain volume changes have been reported in first-episode schizophrenia, but their relationship to the disease process or to other factors remains unclear. We examined such changes in the first year of illness, and related them to 5-year outcome. Progressive brain volume changes, in particular of grey matter, during the first year of illness were found to be significantly associated with clinical and functional outcome 5 years after the first episode. These findings suggest that early dynamic brain volume changes are related to the disease process and predict the longer-term outcome of schizophrenia.

Dynamic neuroimaging of retinal light responses using fast intrinsic optical signals

Transient intrinsic optical responses associated with neural activation offer an attractive strategy for dynamic imaging of neural activity, and may provide a noninvasive methodology for imaging of retinal function. Here we demonstrate the feasibility of near infrared imaging of fast intrinsic optical changes in isolated frog retina activated by visible light. Using a photodiode detector in a transmitted light geometry, we routinely measured dynamic transmitted optical responses in single passes, at the level of one part in 10 4 of background light. Rapid CCD image sequences acquired with transmitted light (bright field) illumination disclosed larger fractional responses and showed evidence of multiple response components with both negative- and positive-going signals with different timecourses. Dark field imaging further enhanced the contrast and sensitivity of optical measures of neural activation. High-resolution imaging disclosed optical responses in single pixels often exceeding 5%, of background light, allowing dynamic imaging at the resolution of single cells, in single passes. Fast optical signals are closely related to identified response components of the electroretinogram. Optical responses showed complex but consistent spatial organization from frame to frame. Our experimental results and theoretical analysis suggest that the optical responses may result from dynamic volume changes corresponding to ion and water flow across the cell membrane, directly associated with the electrophysiological response.

Dynamic Volume Change Measurement in Environmental Scanning Electron Microscope

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006

3D Set-up Accuracy for Moving Pulmonary Tumors on a CT-on-Rails System Evaluated with Fluoroscopic Real-Time Tumor-Tracking System

Purpose/Objective: It is known that a CT-on-rails system is useful for precise radiotherapy as visualizing either a static target or a moving target before treatment. We tried evaluating 3D set-up accuracy for moving pulmonary tumors on a CT-on-rails system using fluoroscopic real-time tumor-tracking radiotherapy (RTRT) system which has been installed in the same treatment room. Materials/Methods: Gold markers of 1.5 mm in diameter as an internal fiducial marker were embedded in a static phantom and adjacent area to patient pulmonary tumors. An in-room CT scans were performed. CT helical imaging parameters were as follows: pitch, 1.5; FOV, 400 mm; slice thickness, 3 mm. Gold marker positions were projected to surface of the skin and surface of an immobilization device with three laser localizers equipped in CT. They were marked at three points with a pen. Then a couch was rotated 180 degrees from CT to a linac RTRT system and the gold marker was placed to the isocenter of RTRT system after shifting the couch three dimensionally with laser alignment. A position of the gold marker was measured with two sets of fluoroscopy on RTRT system. Two image intensifiers are mounted to the ceiling and corresponding x-ray generators are embedded under the floor of the treatment room. (1) As a control study, a static phantom with twenty gold markers was scanned five times with the CT. Set-up error for each marker was measured with RTRT system after a CT-guided marking(n=100).(2) In clinical study, six patients with pulmonary tumor underwent breath-hold helical CT scans at the expiratory phase before every RTRT treatment in order to verify spatial relationship between a gold marker and a target. Set-up error for eight gold markers was measured with RTRT system after a CT-guided marking(n=45). Results: (1) Mean discrepancy±standard deviation(n=100) was 0.48±0.39 mm, 0.79±0.55 mm, 0.28±0.23 mm in the each x, y, z axis for the static phantom in the measurement using fluoroscopic RTRT. (2) Mean discrepancy±standard deviation(n=45) was 0.95±0.74 mm, 1.85±1.73 mm, 1.23±1.08 mm in the each x, y, z axis for eight gold markers in 6 patients in the measurement using fluoroscopic RTRT. x, y, z represent right-left direction, head-foot direction, anterior-posterior direction, respectively. Conclusions: 3D set-up accuracy of our CT-on-rails system for moving pulmonary tumors was estimated to be within a few mm using RTRT system. Physiological dynamic volume change of the lung during expiratory phase might affect our results.

Forced Response of a Squeeze Film Damper and Identification of Force Coefficients From Large Orbital Motions

Experimentally derived damping and inertia force coefficients from a test squeeze film damper for various dynamic load conditions are reported. Shakers exert single frequency loads and induce circular and elliptical orbits of increasing amplitudes. Measurements of the applied loads, bearing displacements and accelerations permit the identification of force coefficients for operation at three whirl frequencies (40, 50, and 60 Hz) and increasing lubricant temperatures. Measurements of film pressures reveal an early onset of air ingestion. Identified damping force coefficients agree well with predictions based on the short length bearing model only if an effective damper length is used. A published two-phase flow model for air entrainment allows the prediction of the effective damper length, and which ranges from 82% to 78% of the damper physical length as the whirl excitation frequency increases. Justifications for the effective length or reduced (flow) viscosity follow from the small through flow rate, not large enough to offset the dynamic volume changes. The measurements and analysis thus show the pervasiveness of air entrainment, whose effect increases with the amplitude and frequency of the dynamic journal motions. Identified inertia coefficients are approximately twice as large as those derived from classical theory.

Effects of phospholemman expression on swelling-activated ion currents and volume regulation in embryonic kidney cells.

Phospholemman (PLM) is a 72-amino-acid phosphoprotein that is a major substrate for cAMP-dependent protein kinase, protein kinase C, and NIMA kinase. In lipid bilayers, PLM forms ion channels selective for Cl-, K+, and taurine. Effluxes of these abundant intracellular osmolytes play an important role in the control of dynamic cell volume changes in many cell types. We measured swelling-activated ion currents and regulatory volume decrease (RVD) in human embryonic kidney cells stably overexpressing canine cardiac PLM. In response to swelling, two clonal cell lines overexpressing PLM had increased swelling-activated ion current densities and faster and more extensive RVD. A third clonal cell line overexpressing mutant PLM showed reduced ion current densities and a diminished RVD response. These results suggest a role for PLM in the regulation of cell volume, perhaps as a modulator of an endogenous swelling-activated signal transduction pathway or possibly by participating directly in swelling-induced osmolyte efflux.

Can the cerebral metabolic rate of oxygen be estimated with near-infrared spectroscopy?

We have measured the changes in oxy-haemoglobin and deoxy-haemoglobin in the adult human brain during a brief finger tapping exercise using near-infrared spectroscopy (NIRS). The cerebral metabolic rate of oxygen (CMRO2) can be estimated from these NIRS data provided certain model assumptions. The change in CMRO2 is related to changes in the total haemoglobin concentration, deoxy-haemoglobin concentration and blood flow. As NIRS does not provide a measure of dynamic changes in blood flow during brain activation, we relied on a Windkessel model that relates dynamic blood volume and flow changes, which has been used previously for estimating CMRO2 from functional magnetic resonance imaging (fMRI) data. Because of the partial volume effect we are unable to quantify the absolute changes in the local brain haemoglobin concentrations with NIRS and thus are unable to obtain an estimate of the absolute CMRO2 change. An absolute estimate is also confounded by uncertainty in the flow–volume relationship. However, the ratio of the flow change to the CMRO2 change is relatively insensitive to these uncertainties. For the finger tapping task, we estimate a most probable flow–consumption ratio ranging from 1.5 to 3 in agreement with previous findings presented in the literature, although we cannot exclude the possibility that there is no CMRO2 change. The large range in the ratio arises from the large number of model parameters that must be estimated from the data. A more precise estimate of the flow–consumption ratio will require better estimates of the model parameters or flow information, as can be provided by combining NIRS with fMRI.

Expression of a cauliflower tonoplast aquaporin tagged with GFP in tobacco suspension cells correlates with an increase in cell size.

In plants, vacuoles are essential organelles that undergo dynamic volume changes during cell growth due to rapid and high flow of water through tonoplast water-carrying channels composed of integral proteins (tonoplast aquaporins). The tonoplast BobTIP26-1 from cauliflower has previously been shown to be an efficient active aquaporin in Xenopus leavis oocytes. In this study we used tobacco (Nicotiana tabacum cv. Wisconsin 38) suspension cells to examine the effect of BobTIP26-1 expression. In order to follow the intracellular localisation of the protein in real time, the gfp sequence was fused downstream to the BobTIP26-1 coding region. The fusion protein BobTIP26-1::GFP is less active than BobTIP26-1 by itself when expressed in Xenopus oocytes. Nevertheless, this fusion protein is well targeted to the tonoplast of the plant suspension cell when expressed via Agrobacterium co-cultivation. A complex tonoplast labelling is shown when young vacuolated cells are observed. The expression of the fusion protein does not affect the growth rate of the cells but increases their volume. We postulate that the increase in cell volume is triggered by the fusion protein allowing vacuolar volume increase.

The dynamic volume changes of polymerising polymethyl methacrylate bone cement.

The Swedish hip register found an increased risk of early revision of vacuum-mixed cemented total hip replacements. The influence of cement mixing technique on the dynamic volume change in polymerising PMMA is not well understood and may be relevant to this observation. Applying Archimedes' principle, we have investigated the dynamic volume changes in polymerising cement and determined the influence of mixing technique. All specimens showed an overall volume reduction: hand-mixed 3.4% and vacuum-mixed 6.0%. Regression analysis of sectional porosity and volume reduction showed a highly significant relationship. Hand-mixed porous cement showed a transient volume increase before solidification. However, vacuum-mixed cement showed a progressive volume reduction throughout polymerisation. Transient expansion of porous cement occurs at the critical time of micro-interlock formation, possibly improving fixation. Conversely, progressive volume reduction of vacuum-mixed cement throughout the formation of interlock may damage fixation. Stable fixation of vacuum-mixed cement may depend on additional techniques to offset the altered volumetric behaviour of vacuum-mixed cement.

The dynamic volume changes of polymerising polymethyl methacrylate bone cement

The Swedish hip register found an increased risk of early revision of vacuum-mixed cemented total hip replacements. The influence of cement mixing technique on the dynamic volume change in polymerising PMMA is not well understood and may be relevant to this observation.Applying Archimedes' principle, we have investigated the dynamic volume changes in polymerising cement and determined the influence of mixing technique. All specimens showed an overall volume reduction: hand-mixed 3.4% and vacuum-mixed 6.0%. Regression analysis of sectional porosity and volume reduction showed a highly significant relationship.Hand-mixed porous cement showed a transient volume increase before solidification. However, vacuum-mixed cement showed a progressive volume reduction throughout polymerisation.Transient expansion of porous cement occurs at the critical time of micro-interlock formation, possibly improving fixation. Conversely, progressive volume reduction of vacuum-mixed cement throughout the formation of interlock may damage fixation. Stable fixation of vacuum-mixed cement may depend on additional techniques to offset the altered volumetric behaviour of vacuum-mixed cement.

Heat‐induced Changes in Angel Food Cakes Containing Egg‐white Protein or Whey Protein Isolate

ABSTRACT: Angel food cakes made from egg white or whey protein foams were compared. Cakes were evaluated based on final volume, dynamic volume change, and rheological transitions during baking. Cake expansion during baking was a function of protein concentration regardless of protein type. Cakes containing whey proteins had a lower ability to prevent collapse once starch gelatinization started during baking. Heat‐treating whey proteins or adding xanthan gum increases cake volume, but not to the extent of egg‐white proteins. Cakes containing egg‐white proteins became more elastic at 60 to 85 °C than those containing whey proteins, indicating physical differences in the heat‐set protein foam network associated with protein type.

Real-time three-dimensional echocardiography for improved evaluation of diastolic function using volume-time curves.

Accurate assessment of left ventricular function is of the greatest importance in clinical cardiology for decision making. Diastolic dysfunction is getting more concern as a cause of heart failure while, currently used non-invasive modalities for diagnosing diastolic abnormalities have significant limitations. Dynamic left ventricular volume change was applied for the evaluation of diastolic function by various techniques that have been demonstrated to be of diagnostic value. However, it has not been accepted into clinical practice because existing techniques are either invasive, inaccurate, expensive or time consuming. REAL-TIME THREE-DIMENSIONAL ECHOCARDIOGRAPHY: Real-time three-dimensional (3-D) echocardiography is a new ultrasound technique that provides transthoracic volumetric images of the heart in real time. Thereby, the acquired images are ideally suited for the assessment of dynamic left ventricular volume change. Generation and analysis of left ventricular volume-time curves by real-time 3-D echocardiography has been demonstrated to be feasible in normal subjects and patients and accuracy of volume-time curves was good compared to magnetic resonance imaging. We compare the new real-time 3-D echo approach with the advantages and limitations of existing noninvasive and invasive techniques.

A Phenomenological Model of Volumetric and Free Volume Hole Properties in Supercooled Liquids: Theortho-Terphenyl Case

A phenomenological model linking the macroscopic volume from dilatometry with the microscopic free volume from positron annihilation lifetime spectroscopy is presented. The temperature dependences of both quantities enable to obtain the so-called initial temperature Ti at which dynamic free volume change sets in, the corresponding initial volume Vi, and subsequently, all free volume characteristics. Application of this model on the literature data of a typical low-molecular weight glass former, o-terphenyl, leads to the findings that (i) Ti ≅ TK the Kauzmann temperature and (ii) a packing fraction of the extrapolated equilibrium liquid at Ti is close to the closest regular packing of hard spheres. The published viscosity−temperature data over 12 decades of magnitude are correlated with the free volume hole fraction fh, as determined from the PALS results, via the WLF−Doolittle type equation. These findings indicate that the orthopositronium (o-Ps) is able to detect the part of the total free volume distribution which is relevant for the viscosity over the measured temperature interval from Tg up to ∼ 1.5Tg. In addition, the change of the free volume hole behavior above Tr = 1.25Tg, lying in the vicinity of the crossover temperature Tc from the idealized version of mode-coupling theory, is critically analyzed within a modified bubble concept (the equilibrium interaction of o-Ps with the soft matrix).

Dynamic leg volume changes when sitting in a locked and free floating tilt oé ce chair

It is well established that prolonged sitting may lead to swelling of the lower extremities. However, activation of the vein pump system by repeated walking breaks or dynamic tiltable foot-rests have been shown to reduce foot and leg oedema. Some oé ce chairs incorporate tilt mechanisms facilitating movements of the body from the feet up. The present study was undertaken to establish whether a beneficial effect on the transcapillary fluid balance of the legs by enabling such mechanisms could be documented. An oé ce chair where the tilt mechanism could be locked or open was used for the study. The seat position and seat activity level was recorded by a transducer system developed for the study. Calf volume and calf muscle pump activity was detected by mercury strain gauge plethysmography. In the locked position there was a steady increase in volume of mean=1.2% (range=0.8–1.8%) for all participants in the 30-min study period. On the other hand, for all participants there was a decrease in calf volume (mean=0.7%, range=0.1–1.2%, p=0.008) when the tilt mechanism was open (30-min period), irrespective of what study period came first. The study showed that upward seat deflection was not associated with concomitant venous obstruction, since such obstruction was detected in less than 2% of the time period with more than 50% of maximal upward deflection. A locked seat mechanism does not prevent activation of the vein pump mechanism, but the study indicates that oé ce chairs that permit variation in seat angle per se stimulate movements of the leg. This, in turn, activates vein pumps and counteracts local oedema formation in seated working postures.

Sodium Chloride-Induced Volume Changes of Freshwater Cyanobacterium Synechococcus sp. PCC 7942 Cells Can Be Probed by Chlorophyll a Fluorescence

Freshwater species of the cyanobacterial genus Synechococcus import NaCl passively, and export Na+ actively, by means of primary and secondary extrusion mechanisms. As a result of the ion and water fluxes, cell volumes are enlarged. We show in this paper that the NaCl-induced volume enlargement of Synechococcus sp. PCC 7942 cells is attended by a rapid (k = 0.39 s−1) increase in chlorophyll (Chl) a fluorescence. The cell turgor threshold (measured by osmotic titration of Chl a fluorescence) was lower in the absence of NaCl (0.195 Osm kg−1) than in the presence of 0.4 M NaCl (0.248 Osm kg−1) indicating NaCl uptake by the cells. Turgor thresholds of cells suspended in NaCl-containing medium were enlarged further by protonophoric uncouplers, P-type ATPase inhibitors, and light starvation, conditions that are known to interfere with the active extrusion of Na+ ions. Cell swelling exerts probably a regulation on the distribution of phycobilisome (PBS) excitation between photosystem II (fluorescent Chl a) and photosystem I (nonfluorescent Chl a), since it affects PBS-sensitized Chl a fluorescence, but not directly excited Chl a fluorescence. The dependence of the Chl a fluorescence of cyanobacteria on cell volumes allows probing of bioenergetic phenomena that are related to dynamic osmotic volume changes, transmembrane solute and water fluxes, plasma membrane permeabilities, and internal osmotic conditions of cyanobacterial cells. Thus, cyanobacteria may serve as quite convenient models of aquatic microorganisms in experimental studies directed toward the elucidation of perception mechanisms and defense mechanisms of water and solute stresses.