Capture Volume Research Articles

Modulating Distal Cavities in the α and β Subunits of Human HbA Reveals the Primary Ligand Migration Pathway

The free volume in the active site of human HbA plays a crucial role in governing the bimolecular rates of O(2), CO, and NO binding, the fraction of geminate ligand recombination, and the rate of NO dioxygenation by the oxygenated complex. We have decreased the size of the distal pocket by mutating Leu(B10), Val(E11), and Leu(G8) to Phe and Trp and that of other more internal cavities by filling them with Xe at high gas pressures. Increasing the size of the B10 side chain reduces bimolecular rates of ligand binding nearly 5000-fold and inhibits CO geminate recombination due to both reduction of the capture volume in the distal pocket and direct steric hindrance of Fe-ligand bond formation. Phe and Trp(E11) mutations also cause a decrease in distal pocket volume but, at the same time, increase access to the Fe atom because of the loss of the γ2 CH(3) group of the native Val(E11) side chain. The net result of these E11 substitutions is a dramatic increase in the rate of geminate recombination because dissociated CO is sequestered close to the Fe atom and can rapidly rebind without steric resistance. However, the bimolecular rate constants for binding of ligand to the Phe and Trp(E11) mutants are decreased 5-30-fold, because of a smaller capture volume. Geminate and bimolecular kinetic parameters for Phe and Trp(G8) mutants are similar to those for the native HbA subunits because the aromatic rings at this position cause little change in distal pocket volume and because ligands do not move past this position into the globin interior of wild-type HbA subunits. The latter conclusion is verified by the observation that Xe binding to the α and β Hb subunits has little effect on either geminate or bimolecular ligand rebinding. All of these experimental results argue strongly against alternative ligand migration pathways that involve movements through the protein interior in HbA. Instead, ligands appear to enter through the His(E7) gate and are captured directly in the distal cavity.

Hexapole-compensated magneto-optical trap on a mesoscopic atom chip

Magneto-optical traps on atom chips are usually restricted to small atomic samples due to a limited capture volume caused primarily by distorted field configurations. Here we present a magneto-optical trap based on a millimeter-sized wire structure which generates a magnetic field with minimized distortions. Together with the loading from a high-flux two-dimensional magneto-optical trap, we achieve a loading rate of $8.4\ifmmode\times\else\texttimes\fi{}{10}^{10}$ atoms/s and maximum number of $8.7\ifmmode\times\else\texttimes\fi{}{10}^{9}$ captured atoms. The wire structure is placed outside of the vacuum to enable a further adaptation to new scientific objectives. Since all magnetic fields are applied locally without the need for external bias fields, the presented setup will facilitate parallel generation of Bose-Einstein condensates on a conveyor belt with a cycle rate above $1$ Hz.

Mobility in musculokeletal disease: compromise and compensations: IP76. Why do People with Neurogenic Claudication Like Shopping?

Background: People with lumbar spinal stenosis commonly present with symptoms of pain in the legs which is brought on by walking, a presentation known as neurogenic claudication. The symptoms are often reported as being reduced when walking with a shopping trolley for support, but the mechanism of symptom improvement is not fully understood. This study was designed to explore the effects of pushing a shopping trolley on spinal posture and loading patterns. Methods: An exploratory study of kinematic and kinetic changes in walking with and without a shopping trolley was undertaken with a group of people with symptoms of neurogenic claudication (n = 8) and a group of asymptomatic controls (n = 8). Three-dimensional motion analysis was performed using the Vicon Motion Analysis system using the Vicon Plug-in-Gait protocol for spinal movement analysis. Vertical ground reaction force measures were captured simultaneously using a forceplate embedded in a walkway within the motion analysis capture volume. Changes in lumbar spinal sagittal posture and ground reaction force were measured during walking with and without the shopping trolley. Between group differences in spinal sagittal angle changes and vertical ground reaction force changes were analysed, and correlations between walking speed, ground reaction force and spinal posture were also explored. Results: Subjects with neurogenic claudication and asymptomatic controls walked with a significantly more flexed spinal posture (increase in flexion 3.40 degrees; z = 3.516; P = <.001) when walking with a shopping trolley. The extent of this postural effect was significantly correlated with individual subjects’ height, with taller subjects showing a greater increase in spinal flexion than shorter subjects (rho = −0.65; P = .006). In addition, mean ground reaction forces across the whole gait cycle were reduced in all participants when walking wtih a shopping trolley (-6.9% of bodyweight; z = −3.45; P = .001). However, at the midstance point of the gait cycle, controls showed minimal reliance on the trolley, whereas people with NC showed continued offloading. Conclusions: Both posture and loading are affected by pushing a shopping trolley; however, patients with NC were found to offload the spine throughout the stance phase of gait, whereas asymptomatic controls did not. Taller subjects offloaded to a greater extent than those of a shorter stature when pushing the shopping trolley. Disclosures: The authors have declared no conflicts of interest.

Sticker Shock: An Exploration of Supply Charge Capture Outcomes

Do you find supply item charge stickers in shocking places in nursing units? Capturing supply item charges to increase net revenue or achieve break-even are based on efficiency. To determine practical efficiency for a hospital in supply charge capture, the authors examined the quantity of supply charge capture items, volume, and relative size of the hospital in 10 hospitals in the midwestern and southeastern United States. What differences in supply charge capture information can determine if a hospital can break even? Results show that hospital size and number of supply charge capture items to manage are important factors.

Investigation to predict patellar tendon reflex using motion analysis technique

The investigation of patellar tendon reflex involves development of a reflex hammer holder, kinematic data collection and analysis of patellar reflex responses using motion analysis techniques. The main aim of this research is to explore alternative means of assessing reflexes as a part of routine clinical diagnosis. The motion analysis system was applied to provide quantitative data which is a more objective measure of the patellar tendon reflex. Kinematic data was collected from 28 males and 22 females whilst subjected to a knee jerk test. Further analysis of kinematic data was performed to predict relationships which might affect the patellar tendon reflex. All subjects were seated on a high stool with their legs hanging freely within the capture volume of the motion analysis system. Knee jerk tests were applied to all subjects, on both sides of the leg, by eliciting hypo, hyper, and normal reflexes. An additional reinforcement technique called the Jendrassik manoeuvre was also performed under the same conditions to elicit a normal patellar tendon reflex. The comparison of reflex response between genders showed that female subjects generally had a greater response compared to males. However, the difference in reflex response between the left leg and the right leg was not significant. Tapping strength to elicit a hyper-reflex produced greater knee-jerk compared to the normal clinical tapping strength. All results were in agreement with clinical findings and results found by some early researchers.

Application of a Full Body Inertial Measurement System in Alpine Skiing: A Comparison with an Optical Video Based System

This study aims at determining the accuracy of a full body inertial measurement system in a real skiing environment in comparison with an optical video based system. Recent studies have shown the use of inertial measurement systems for the determination of kinematical parameters in alpine skiing. However, a quantitative validation of a full body inertial measurement system for the application in alpine skiing is so far not available. For the purpose of this study, a skier performed a test-run equipped with a full body inertial measurement system in combination with a DGPS. In addition, one turn of the test-run was analyzed by an optical video based system. With respect to the analyzed angles, a maximum mean difference of 4.9° was measured. No differences in the measured angles between the inertial measurement system and the combined usage with a DGPS were found. Concerning the determination of the skier's trajectory, an additional system (e.g., DGPS) must be used. As opposed to optical methods, the main advantages of the inertial measurement system are the determination of kinematical parameters without the limitation of restricted capture volume, and small time costs for the measurement preparation and data analysis.

Influence of small additives of rare-earth elements on the structure of fluorophosphate glasses

The physicochemical properties and Raman spectra of glasses of the composition 40Ba(PO3)2 · 60MgCaSrBaAl2F14 doped with europium and terbium have been investigated. The results of the performed investigations have been compared with the data of the analysis of the recorded EPR spectra of irradiated glasses of the same compositions in terms of the model of the effective capture volume and with the luminescence data available in the literature. The concentration ranges of terbium and europium ions (0.05–0.10) mol % or (0.7–1.3) × 1019 ions/cm3, in which these ions retain the oxygen environment according to the analysis of the studies carried out by different methods, are in satisfactory agreement. The dependence of the local environment of rare-earth ions in fluorophosphate glasses on their concentration has been established.

Evaluation of a mixed approach combining stationary and wearable systems to monitor gait over long distance

Thanks to decades of research, gait analysis has become an efficient tool. However, mainly due to the price of the motion capture systems, standard gait laboratories have the capability to measure only a few consecutive steps of ground walking. Recently, wearable systems were proposed to measure human motion without volume limitation. Although accurate, these systems are incompatible with most of existing calibration procedures and several years of research will be necessary for their validation. A new approach consisting of using a stationary system with a small capture volume for the calibration procedure and then to measure gait using a wearable system could be very advantageous. It could benefit from the knowledge related to stationary systems, allow long distance monitoring and provide new descriptive parameters. The aim of this study was to demonstrate the potential of this approach. Thus, a combined system was proposed to measure the 3D lower body joints angles and segmental angular velocities. It was then assessed in terms of reliability towards the calibration procedure, repeatability and concurrent validity. The dispersion of the joint angles across calibrations was comparable to those of stationary systems and good reliability was obtained for the angular velocities. The repeatability results confirmed that mean cycle kinematics of long distance walks could be used for subjects’ comparison and pointed out an interest for the variability between cycles. Finally, kinematics differences were observed between participants with different ankle conditions. In conclusion, this study demonstrated the potential of a mixed approach for human movement analysis.

Quantitative evaluation of depth of capture volume extension by constrained least-square-based image restoration

Using quantitative evaluation, we show that constrained least-square CLS-based image restoration extends depth of capture volume DCV significantly, and suggest that performance degradation characteristics of a feature extractor by defocus blurring should be con- sidered while developing unconstrained iris recognition systems. When developing an unconstrained iris recognition system assuming a rela- tively cooperative user the extension of the DCV clearly stands out as one of the most important problems. Although it has already been re- ported that CSL-based image restoration can improve recognition per- formance by mitigating the effect of defocus blurring, until now there have been no reports as to how much the DCV could be extended. This work inspects the Hamming distance HD distribution and error rate while changing the strength of defocus blurring with iris images of CASIA-IrisV3-Interval. It is derived that the ratio of the maximum blurring parameters satisfying a certain acceptable error rate is the ratio of the DCV. Using this fact, experimental results show that CLS-based image restoration extends the DCV by more than 70%. Additionally, it is ob- served that a log-Gabor filter is superior to a Gabor filter as the feature extractor. It should be noted that although these two feature extractors show a relatively small performance gap when a focused image set is used, the gap becomes significantly larger as the blurring becomes more severe. This is thought to suggest an important principle that perfor- mance characteristics should be considered with respect to defocus blur- ring when selecting or developing the feature extractor of an uncon- strained iris recognition system. © 2010 Society of Photo-Optical Instrumentation

Static and Dynamic Calibration of an Eight-Camera Optical System for Human Motion Analysis

An eight-camera Optitrack motion capture system was evaluated by performing static, linear dynamic, and angular dynamic calibrations using marker distances associated with upper and lower extremity gait and wheelchair models. Data were analyzed to determine accuracy and resolution within a defined capture volume using a standard Cartesian reference system. Static accuracy ranged from 99.31 to 99.90%. Static resolution ranged from 0.04 ± 0.15 to 0.63 ± 0.15 mm at the 0.05 level of significance. The dynamic accuracy ranged from 94.82 to 99.77%, and dynamic resolution ranged from 0.09 ± 0.26 to 0.61 ± 0.31 mm at the 0.05 level of significance. These values are comparable to those reported for a standard Vicon 524 (Oxford Metrics, Oxford, England) motion analysis system. The results support application of the lower cost Optitrack system for 3D kinematic assessment of upper and lower extremity motion during gait, assisted ambulation, and wheelchair mobility.

Nucleation and first-stage growth processes of extrinsic defects in GaAs triggered by self-interstitials

The growth process of small self-interstitial clusters ${I}_{n}$ $(n\ensuremath{\le}7)$ in crystalline GaAs has been addressed by semi-empirical tight-binding molecular-dynamics technique. The ${I}_{n}$ ground-state structures have been found among many possible choices of topological properties and stoichiometric compositions. The stable structure have been fully characterised concerning the structural, electronic, energetic, and elastic properties; some remarkable findings emerged concerning, among the others, the stability scenario of the ground-state structures, the possible low-energy reaction paths involved in the growth process, the electrostatic and the elastic capture volumes and the Fermi-level pinning. It is demonstrated that compact geometries are no longer energetically favoured for $n\ensuremath{\ge}5$ and that the ${I}_{n}$ growth proceeds via capture processes involving either isolated interstitials or di-interstitials. An extended pentainterstitial $({I}_{5})$ ground-state structure has been identified as the possible core-basic structure of extrinsic linear defects along the {111} direction of the GaAs lattice.

Poissonian statistics of excitonic complexes in quantum dots

We report a detailed experimental investigation of the power dependence of excitonic complexes (neutral exciton, neutral biexciton, and charged exciton) confined in single self-assembled GaAs∕AlGaAs strain-free quantum dots grown by droplet epitaxy. By using the random population theory we show that, under stationary excitation, the power dependence of the excitonic complexes precisely follows the Poissonian statistics. This result allows us to determine with great accuracy the state filling condition of the quantum dots (QDs) and therefore to estimate the capture volume of the QDs.

An extended-release formulation of desferrioxamine for subcutaneous administration

Desferrioxamine mesylate (DFO) remains the first line iron chelating agent. Since it has a short half-life and poor absorption through the gastrointestinal tract, DFO must be administered parenterally, usually by daily subcutaneous infusion administered over 8–12 h. The objective of this paper was the development of multivesicular liposome (depofoam) for the extended-release of DFO and study of iron excretion efficiency compared to the free form of DFO. Depofoam particles were characterized by their morphology, particle size, capture volume, and in vitro release. Also, in vivo activity of this formulation in iron overload rats was studied. The in vitro studies in 0.9% sodium chloride at 37°C showed that the multivesicular liposomes released DFO slowly over several days without a rapid initial release, and 57% of DFO was released in 9 days. Administration of a single dose of 100 mg/kg of an optimized Depo-DFO formulation in an iron overload rats, as a single bolus subcutaneous injection, led to significant elevation of urinary iron excretion at the first day that were maintained at levels of more than 110 μg/kg for 3 days. Administration of the unencapsulated DFO at the same dose resulted in elevation of urinary iron excretion in the first day (~73% amount of iron excretion by Depo-DFO) followed by a quick decline to base line levels in the second day. The total urinary iron excreted by Depo-DFO is 3-times greater than that elicited by DFO. In conclusion, Depo-DFO appears to have potential usefulness as an extended-release formulation of DFO.

SU-FF-J-116: On the Development of Intra-Fraction Whole Body Motion Tracking During Total Body Irradiation

Purpose: The feasibility of total marrow irradiation (TMI) using highly conformal image‐guided Tomotherapy is recently being explored as a radiation dose escalation pre‐conditioning TMI regimen for high risk hematological malignancies. Though, initial trial shows potential of this technology, treatment procedure is at present an open loop. This is a concern for safety as well as accuracy of the treatment delivery. The primary objective of this study is to develop a real time optical tracking system (OTS) which will offer better understanding of intra‐fraction whole body motion and develop a closed loop feedback approach to treatment that will enhance the safety of this new treatment.Method and Materials: A stereoscopic camerasystem is utilized to track near‐infrared reflective markers placed on the Rando phantom. The cameras were calibrated to determine the 3D location of each detected marker. The entire stereoscopic marker detection system returns a set of 3D marker locations at a rate of 60 Hz. Five criteria for evaluating motion capture technology are considered for selection of the optical detection system — accuracy, bandwidth, frame rate, capture volume, and real time performance. The translational motion detection uncertainties in OTS are measured and compared with onboard three dimensional megavoltage CT (MVCT) scanning system for pre‐treatment setup verification. Results: The preliminary work has shown : (i) the translational motion with better than 4mm accuracy, (ii) the vision‐based acquisition can be performed very quickly (in second) compared to the MVCT scan (5–10 minutes) method currently used for initial patient positioning; (iii) bony portions of the body can be accurately tracked in three dimensions. Conclusion: The proposed method entices the effectiveness of vision‐based whole body patient motion tracking for use with the helical tomotherapy treatment.

Nonintrusive iris image acquisition system based on a pan-tilt-zoom camera and light stripe projection

Although iris recognition is one of the most accurate biometric technologies, it has not yet been widely used in practical applications. This is mainly due to user inconvenience during the image acquisition phase. Specifically, users try to adjust their eye position within small capture volume at a close distance from the system. To overcome these problems, we propose a novel iris image acquisition system that pro- vides users with unconstrained environments: a large operating range, enabling movement from standing posture, and capturing good-quality iris images in an acceptable time. The proposed system has the follow- ing three contributions compared with previous works: 1 the capture volume is significantly increased by using a pan-tilt-zoom PTZ camera guided by a light stripe projection, 2 the iris location in the large capture volume is found fast due to 1-D vertical face searching from the user's horizontal position obtained by the light stripe projection, and 3 zoom- ing and focusing on the user's irises at a distance are accurate and fast using the estimated 3-D position of a face by the light stripe projection and the PTZ camera. Experimental results show that the proposed sys- tem can capture good-quality iris images in 2.479 s on average at a distance of 1.5 to 3 m, while allowing a limited amount of movement by the user.

Local environment of Eu3+ and Tb3+ ions in fluorophosphate glasses of the Ba(PO3)2-MgCaSrBaAl2F14 system

The induced optical absorption and EPR absorption spectra of fluorophosphate glasses of the compositions 40Ba(PO3)2 · 60MgCaSrBaAl2F14 and 5Ba(PO3)2 · 95MgCaSrBaAl2F14 doped with Tb3+ and Eu3+ ions are investigated within the model of the effective capture volume of free carriers. The concentration dependences of the relative number of radiation centers on the dopant concentration in fluorophosphate glasses are analyzed. It is established that the character of the distribution of dopant ions in glasses depends on the dopant concentration and the structure of the glass. The critical concentrations at which the oxygen local environment of Eu3+ or Tb3+ ions in the structure of fluorophosphate glasses transforms into a mixed local environment are determined for glasses of the compositions under investigation.

Directly Trapping Atoms in a U-Shaped Magneto-Optical Trap Using a Mini Atom Chip

We experimentally demonstrate the trapping of 85Rb atoms directly on a chip-size U-shaped magneto-optical trap (U-MOT). The trap includes a U-shaped wire on the chip, two bias magnetic field coils and laser beams. The capture volume of the U-MOT is theoretically calculated, and the trap is experimentally realized. With 2 A current applied to the U-shaped wire and 2-Gauss horizontal bias field, more than 2 × 106 atoms are trapped. In contrast with an ordinary mirror-MOT, this U-MOT captures atoms directly from the background, thus the trap size is greatly reduced. Based on this mini trap scheme, it is possible to realize a chip-size atom trap array for quantum information processing.

Characterization and management of the commercial sector of the Pohnpei coral reef fishery, Micronesia

Commercial coral reef fisheries in Pohnpei (Micronesia) extract approximately 1,521 kg of reef fish daily (*500 MT year -1 ) from 152 km 2 of surrounding reef. More than 153 species were represented during sur- veys, with 25 species very common or common within combined-gear catch. Acanthurids contributed the greatest to catch volume, with bluespine unicornfish, Naso uni- cornis, and orangespine unicornfish, Naso lituratus, among the most frequently observed herbivores. Nighttime spearfishing was the dominant fishing method and inner lagoon areas were primarily targeted. A seasonal sales ban (March-April), intended to reduce pressure on reproduc- tively active serranids, significantly increased the capture volume of other families. Catch was significantly greater during periods of low lunar illumination, suggesting higher fishing success or greater effort, or both. The marketed catch was dominated by juveniles and small adults, based on fishes of known size at sexual maturity. Artificially depressed market prices appear to be catalyzing (potential or realized) overfishing by increasing the volume of fish needed to offset rising fuel prices. These results support the need for comprehensive fisheries management that pro- duces sustainable fishing and marketing practices and promotes shared management and enforced responsibilities between communities and the state. To be effective, management should prohibit nighttime spearfishing.

Continuous loading ofS01calcium atoms into an optical dipole trap

We demonstrate an efficient scheme for continuous trap loading based upon spatially selective optical pumping. We discuss the case of $^{1}$S$_{0}$ calcium atoms in an optical dipole trap (ODT), however, similar strategies should be applicable to a wide range of atomic species. Our starting point is a reservoir of moderately cold ($\approx 300 \mu$K) metastable $^{3}$P$_{2}$-atoms prepared by means of a magneto-optic trap (triplet-MOT). A focused 532 nm laser beam produces a strongly elongated optical potential for $^{1}$S$_{0}$-atoms with up to 350 $\mu$K well depth. A weak focused laser beam at 430 nm, carefully superimposed upon the ODT beam, selectively pumps the $^{3}$P$_{2}$-atoms inside the capture volume to the singlet state, where they are confined by the ODT. The triplet-MOT perpetually refills the capture volume with $^{3}$P$_{2}$-atoms thus providing a continuous stream of cold atoms into the ODT at a rate of $10^7 $s$^{-1}$. Limited by evaporation loss, in 200 ms we typically load $5 \times 10^5$ atoms with an initial radial temperature of 85 $\mu$K. After terminating the loading we observe evaporation during 50 ms leaving us with $10^5$ atoms at radial temperatures close to 40 $\mu$K and a peak phase space density of $6.8 \times 10^{-5}$. We point out that a comparable scheme could be employed to load a dipole trap with $^{3}$P$_{0}$-atoms.

Mirror magneto-optical trap exploiting hexapole-compensated magnetic field

A mirror magneto-optical trap (MOT) that exploits a hexapole-compensated magnetic field was developed and used in the experimental surface trapping of neutral atoms. A pair of subsidiary wires, which was placed near the main current-carrying wire, was designed to improve the uniformity of the quadrupole magnetic field and thus increased the effective capture volume of our mirror-MOT. In the experiment, the number of $^{87}\mathrm{Rb}$ atoms captured with our mirror-MOT was approximately twice that captured with a conventional mirror-MOT.