Motion Resolution Research Articles

僧帽弁形成後のＳＡＭの自然消失の１例

僧帽弁形成後のＳＡＭの自然消失の１例

What Counts as Fraud? An Empirical Study of Motions to Dismiss Under the Private Securities Litigation Reform Act

This article presents the findings of a study of the resolution of motions to dismiss securities fraud lawsuits since the passage of the Private Securities Litigation Reform Act in 1995. Our sample consists of decisions on motions to dismiss in securities class actions by district and appellate courts in the Second and Ninth Circuits for cases filed after the passage of the Reform Act to the end of 2001. These circuits are the leading circuits for the filing of securities class actions and are generally recognized as representing two ends of the securities class action spectrum. Post-PSLRA, the Second Circuit applies the least restrictive pleading standard to securities claims and the Ninth Circuit applies the most restrictive. We find some evidence that the Ninth Circuit's post-PSLRA reputation as being a tougher venue in which to win securities fraud class actions is born out by a significantly higher dismissal rate. The differences between the two circuits are also reflected in factors that correlate with dismissal. For example, allegations of violations of accounting principles other than revenue recognition correlate negatively with dismissal in the Second Circuit. This coefficient, however, is insignificant in our regressions for the Ninth Circuit. Allegations of revenue recognition violations are insignificant in both circuits, whether or not the issuer has been forced to restate those revenues. The circuits part ways on other factors as well: the Second Circuit is significantly less likely to dismiss cases with allegations of false forward-looking statements, a surprising result given the stringent standards for such statements imposed by the PSLRA. The Ninth Circuit is significantly less likely to dismiss complaints with allegations of '33 Act violations and the Second Circuit is more likely to dismiss cases brought by the Milberg Weiss firm. When it comes to insider trading, however, the two circuits are both skeptical and the allegations correlate with dismissal in both circuits.

Fast measurement of intracardiac pressure differences with 2D breath-hold phase-contrast MRI.

Intracardiovascular blood pressure differences can be derived from velocity images acquired with phase-contrast (PC) MRI by evaluating the Navier-Stokes equations. Pressure differences within a slice of interest can be calculated using only the in-plane velocity components from that slice. This rapid exam is proposed as an alternative to the lengthy 3D velocity imaging exams. Despite their good spatial coverage, the 3D exams are prone to artifacts and errors from respiratory motion and insufficient temporal resolution, and are unattractive in the clinical setting due to their excessive scan times (>10 min of free breathing). The proposed single-slice approach requires only one or two breath-holds of acquisition time, and the velocity data can be processed for the calculation of pressure differences online with immediate feedback. The impact of reducing the pressure difference calculation to two dimensions is quantified by comparison with 3D data sets for the case of blood flow within the cardiac chambers. The calculated pressure differences are validated using high-fidelity pressure transducers both in a pulsatile flow phantom and in vivo in a dog model. There was excellent agreement between the transducer and PC-MRI results in all of the studies.

A moving unstructured staggered mesh method for the simulation of incompressible free-surface flows

A new moving staggered mesh discretization for the numerical simulation of incompressible flow problems involving free-surfaces is presented. The method uses the staggered mesh to obtain speed and conservation properties. Mesh motion provides a high quality mesh in the interior and detailed resolution of the free-surface motion on the surface. Mesh flipping allows for optimal mesh connectivity to be maintained. The method uses an exact projection procedure which reduces the number of unknowns as well as satisfying the continuity constraint without solving a pressure Poisson equation. The implementation of surface tension forces in the staggered mesh framework is discussed. The resulting method is tested against analytical solutions for liquid sloshing and free-surface channel flow. It is also demonstrated on the cases of droplet collision, three-dimensional sloshing, and turbulence next to a free-surface.

On the relationship between dynamic visual and auditory processing and literacy skills; results from a large primary-school study.

Three hundred and fifty randomly selected primary school children completed a psychometric and psychophysical test battery to ascertain relationships between reading ability and sensitivity to dynamic visual and auditory stimuli. The first analysis examined whether sensitivity to visual coherent motion and auditory frequency resolution differed between groups of children with different literacy and cognitive skills. For both tasks, a main effect of literacy group was found in the absence of a main effect for intelligence or an interaction between these factors. To assess the potential confounding effects of attention, a second analysis of the frequency discrimination data was conducted with performance on catch trials entered as a covariate. Significant effects for both the covariate and literacy skill was found, but again there was no main effect of intelligence, nor was there an interaction between intelligence and literacy skill. Regression analyses were conducted to determine the magnitude of the relationship between sensory and literacy skills in the entire sample. Both visual motion sensitivity and auditory sensitivity to frequency differences were robust predictors of children's literacy skills and their orthographic and phonological skills.

Diagnosis and Management of Cervicogenic Headache and Local Cervical Syndrome with Multiple Pain Generators

Numerous pain generators can be responsible for cervicogenic headache and pain in both the cervical and thoracic regions. A 45-year-old female presented in the clinic with a 20-year history of cervicogenic and migraine headaches, accompanied by a prolonged history of local cervical and interscapular pain. The cervicogenic symptoms were attributed to secondary discrelated changes in the cervical spine, as evidenced by specific provocation behaviors and segmental limitation patterns. The patient was educated regarding the presenting problems, and ergonomic changes were initiated. The limitations were addressed with joint-specific mobilization techniques, accompanied by specific home exercises. The patient demonstrated initial rapid improvements that were characterized by reduced symptoms and increased motion, followed by gradual full motion recovery and resolution of cervicogenic symptoms. This recovery pattern suggests the efficacy of manual techniques in the management of cervicogenic headaches and local cervical syndrome, even in the context of rather prolonged symptoms.

Design of low-power silicon articulated microrobots

We are creating a class of autonomous low-power silicon articulated microrobots fabricated on a 1 cm2 silicon die and mounted with actuators, a controller, and a solar array. By taking advantage of the high force-density of electrostatic actuators in the micro scale, low-power actuators can be made for microrobots. A micromotor with an energy efficiency of 4%, that uses CMOS-compatible supply voltage, and has a motion resolution of 2 μm has been demonstrated in a volume of 0.015 mm3. Articulated two degrees-of-freedom legs with built-in mechanical couplings have been fabricated in a commercial micromachining foundry (MUMPs) and successfully assembled. Lowpower CMOS electronics will be used to control the robot locomotion and a solar array chip will be used to power the microrobot.

Spherical episodic ejection of material from a young star

The exact processes by which interstellar matter condenses to form young stars are of great interest, in part because they bear on the formation of planets like our own from the material that fails to become part of the star. Theoretical models suggest that ejection of gas during early phases of stellar evolution is a key mechanism for removing excess angular momentum, thereby allowing material to drift inwards towards the star through an accretion disk. Such ejections also limit the mass that can be accumulated by the stellar core. To date, these ejections have been observed to be bipolar and highly collimated, in agreement with theory. Here we report observations at very high angular resolution of the proper motions of an arc of water-vapour masers near a very young, massive star in Cepheus. We find that the arc of masers can be fitted to a circle with an accuracy of one part in a thousand, and that the structure is expanding. Only a sphere will always produce a circle in projection, so our observations strongly suggest that the perfectly spherical ejection of material from this star took place about 33 years earlier. The spherical symmetry of the ejecta and its episodic nature are very surprising in the light of present theories.

How the CO in myoglobin acquired its bend: lessons in interpretation of crystallographic data.

Contrary to the expectation of chemists, the first X-ray structures of carbon monoxide bound to myoglobin (Mb) showed a highly distorted Fe-C-O bond system. These results appeared to support the idea of a largely steric mechanism for discrimination by the protein against CO binding, a lethal act for the protein in terms of its physiological function. The most recent independently determined high-resolution structures of Mb-CO have allowed the 25 year old controversy concerning the mode of CO binding to be resolved. The CO is now seen to bind in a roughly linear fashion without substantial bending, consistent with chemical expectations and spectroscopic measurements. Access to deposited diffraction data prompted a reevaluation of the sources of the original misinterpretation. A series of careful refinements of models against the data at high (1.1 A) and modest resolutions (1.5 A) have been performed in anisotropic versus isotropic modes. The results suggest that the original artifact was a result of lower quality crystals combined with anisotropic motion and limited resolution of the diffraction data sets. This retrospective analysis should serve as a caution for all researchers using structural tools to draw far-reaching biochemical conclusions.

ROTATIONAL VIBRATION MEASUREMENTS USING LASER DOPPLER VIBROMETRY: COMPREHENSIVE THEORY AND PRACTICAL APPLICATION

This paper builds on a previous study of the velocity sensed by a single laser vibrometer beam incident on a target in an arbitrary direction to predict the velocity sensed by multiple laser beams with arbitrary orientations. The usefulness of parallel beam arrangements is demonstrated and a concise new theory for the difference velocity sensitivity for two parallel beams is presented. Parallel beam arrangements for virtually unambiguous measurement of torsional vibration are presented along with arrangements that allow measurement of the pitch and yaw vibration to be derived. Resolution of individual pitch and yaw motions is shown not to be possible by any geometrical arrangement of the beams but a post-processing technique that enables the genuine pitch and yaw vibrations to be estimated from the measurements of the pitch and yaw vibration sets is demonstrated and validated experimentally in the laboratory. Measurements of pitch and yaw vibration are, for the first time, obtained from the crank-shaft of a running diesel engine, enabling identification of the first natural frequency of the crank-shaft in bending.

Conservative chiropractic care of lateral epicondylitis

Objective: To discuss the management of a patient with lateral epicondylitis refractory to previous medical and conservative interventions. Clinical Features: A 45-year-old woman had difficulty in supinating her left elbow because of pain from activities at work. Standard tests demonstrated and reproduced pain at the lateral epicondyle with resisted extension of the wrist and fingers. Intervention and Outcome: Specific joint manipulation for relief of lateral epicondylitis was performed. Immobilization of the elbow joint after manipulation was accomplished by means of a sugar tong plaster splint. Follow-up joint manipulation with a progressive rehabilitation program was effective in providing relief of symptoms. Conclusion: Resolution of pain and limited elbow motion was demonstrated after Mills' manipulation. (J Manipulative Physiol Ther 2000;23:619-22)

The effect of contraction and twist on myocardial PET and SPECT image resolution: a mathematical phantom study

Motion of the heart blurs cardiac PET and SPECT images. A mathematical phantom was constructed that models the contractile and non-uniform twisting motions of the left ventricular myocardium as the heart beats. The phantom was used to estimate the effect of normal heart motion on ECT image resolution and quantitation in regions of interest (ROIs). The movement of mid-myocardial points was tracked, from which motion blurring was computed. Clinical PET resolution of 7 mm was degraded to 10-12 mm FWHM in the direction of motion and clinical SPECT resolution of 14 mm to 15-16 mm FWHM. Contractile motion was greater near the base and twisting motion was greater near the apex. The blur due to both motions was equivalent to 7-10 mm FWHM Gaussian smoothing in the direction of motion. Activity weight coefficients characterized how activity in source model ROIs contributed to activity in short and long axis ROIs. The effect of contraction was dependent on whether the ROIs were from short or long axis slices and on the ROI location. The activity weights for short axis slices showed the effect of twist in blurring activity to adjacent angular sectors. This effect was not seen for constant thickness long axis slices because the angular range of the slices was greater, particularly near the apex. The contrast of perfusion defects in short axis ROIs was decreased by cardiac twist. A mathematical heart phantom that models contractile and twisting motions is useful for investigating the effect of these motions on cardiac ECT studies.

Single kinesin molecules studied with a molecular force clamp.

Kinesin is a two-headed, ATP-driven motor protein that moves processively along microtubules in discrete steps of 8 nm, probably by advancing each of its heads alternately in sequence. Molecular details of how the chemical energy stored in ATP is coupled to mechanical displacement remain obscure. To shed light on this question, a force clamp was constructed, based on a feedback-driven optical trap capable of maintaining constant loads on single kinesin motors. The instrument provides unprecedented resolution of molecular motion and permits mechanochemical studies under controlled external loads. Analysis of records of kinesin motion under variable ATP concentrations and loads revealed several new features. First, kinesin stepping appears to be tightly coupled to ATP hydrolysis over a wide range of forces, with a single hydrolysis per 8-nm mechanical advance. Second, the kinesin stall force depends on the ATP concentration. Third, increased loads reduce the maximum velocity as expected, but also raise the apparent Michaelis-Menten constant. The kinesin cycle therefore contains at least one load-dependent transition affecting the rate at which ATP molecules bind and subsequently commit to hydrolysis. It is likely that at least one other load-dependent rate exists, affecting turnover number. Together, these findings will necessitate revisions to our understanding of how kinesin motors function.

Dual mode control of a system with friction

The stick-slip friction system is known to exhibit very different macro and microscopic behaviors. For large movements, the system exhibits the familiar stick-slip friction characteristics; and for very fine movements, the elastic deformation seems to prevail. While there have been tremendous efforts to understand the stick-slip friction mechanism, most people would agree that the complexity of the friction characteristics prevents the establishment, of a simple mathematical model. Thus, the controller design cannot be solely dependent on a friction model. In the paper, a robust controller is developed so that it achieves ultimate boundedness in both the macro and micro motion regions. As a result, the controller is capable of controlling the system across the macro movement range and achieves precision positioning in the micro motion resolution. Comparisons with existing controllers also show that the proposed controller easily achieves a better performance.

Path Planning of Space Manipulators to Reduce Spacecraft Attitude Disturbances.

Motions of a space manipulator cause dynamic disturbances to the spacecraft attitude. This paper proposes a method of path planning for space manipulators to reduce such dynamic disturbances. The method is based on the concept of the Enhanced Disturbance Map where the direction of joint movements that causes zero disturbance to the spacecraft attitude is given in the joint space. In this paper, this approach is applied to the path planning of space manipulators. The proposed method determines the direction of small joint movements at each step that causes zero atteitude disturbance and moves the end effector toward a desired position. The path planning algorithms are presented first for the case of non-redundandant DOF space manipulators and, then, for redundant DOF space manipulators. The present method also avoids the singular points in the joint space by means of the singularity low-sensitive motion resolution method. Results of numerical simulations are presented for a two-link planner space manipulator system and for a three-link redundant system.

An Investigation of Key Factors Affecting Solder Microdroplet Deposition

This paper combines a theoretical model with experimental measurements to elucidate the role of key operating parameters affecting solder microdroplet deposition in the electronics manufacturing industry. The experimental investigation is used to evaluate the final deposit (bump) shapes and trends predicted by the model. The effects of substrate temperature, material composition, layer thickness, and thermal contact resistance (including surface oxidation) are delineated. Solder-deposit shape comparisons between experiments and modeling suggest that the value of thermal contact resistance may change with process parameters, and is probably dependent on the solder phase. It is established that inferences regarding the overall shape or solidification times of solder bumps using limited modeling trends should be made only after careful consideration of the substrate composition, accurate representation of the thermal contact resistance, and adequate resolution of the fluid dynamical oscillatory motion and its effects on solidification rates. It is shown that modeling tools can be used in conjunction with experiments to promote our fundamental understanding of the transport processes in the complex solder jetting technology.

Configuration Control of a Mobile Dexterous Robot: Real-Time Implementation and Experimentation

This article describes the design and implementation of a real- time control system with multiple modes of operation for a mobile, dexterous manipulator. The manipulator under study is a kinematically redundant seven-degree-of-freedom arm from Robotics Research Corporation, mounted on a one-degree-of- freedom motorized platform. The manipulator-plus-platform system has two degrees-of-redundancy for the basic task of end-effector placement and orientation. The redundancy reso lution is achieved by accomplishing two additional tasks using the configuration-control technique. The system allows a choice of arm-angle control or collision avoidance for the seventh task, and elbow-angle control or platform placement for the eighth task. In addition, joint-limit avoidance tasks are auto matically invoked when any of the manipulator joints approach their limits. The system is robust to singularities, and the user is capable of assigning weighting factors to end-effector mo tion, joint-limit avoidance, and redundancy resolution tasks. The motion-control algorithms are executed at 1.1 ms on two MC68040 processors in a VME-bus environment running the VxWorks real-time operating system. The article describes the hardware and software components of the manipulator- control system. Experimental results on real-time control of the Robotics Research arm are also presented.

Visual acuity for moving objects in first- and second-order neurons of the fly compound eye.

The early stages of visual systems contain a variety of components that limit both the spatial resolution and the temporal resolution of vision. When an animal sees a moving object, or moves relative to its environment, both spatial and temporal factors contribute to its ability to resolve the movement. In the present work we have combined currently available knowledge about the early stages of fly vision (optical system, photoreceptors, and large monopolar cells) to predict the resolution of the first two cell layers to moving point objects. These calculations included recent measurements of nonlinear light responses. Because background light level has a strong effect on the temporal behavior of these early visual layers, we examined the effects of light level on motion resolution. We also studied the effect of position within the eye, which is known to affect the static resolution of vision. Our results indicate that responses in large monopolar cells to moving point objects are maximal at angular velocities of 100-200 degrees/s. The resolution of point objects by both these early stages of the visual system is similar from stationary to an angular velocity of approximately 200 degrees/s. Above this, resolution deteriorates approximately linearly with velocity.

Femtosecond molecular dynamics of tautomerization in model base pairs.

Hydrogen bonds commonly lend robustness and directionality to molecular recognition processes and supramolecular structures. In particular, the two or three hydrogen bonds in Watson-Crick base pairs bind the double-stranded DNA helix and determine the complementarity of the pairing. Watson and Crick pointed out, however, that the possible tautomers of base pairs, in which hydrogen atoms become attached to the donor atom of the hydrogen bond, might disturb the genetic code, as the tautomer is capable of pairing with different partners. But the dynamics of hydrogen bonds in general, and of this tautomerization process in particular, are not well understood. Here we report observations of the femtosecond dynamics of tautomerization in model base pairs (7-azaindole dimers) containing two hydrogen bonds. Because of the femtosecond resolution of proton motions, we are able to examine the cooperativity of formation of the tautomer (in which the protons on each base are shifted sequentially to the other base), and to determine the characteristic timescales of the motions in a solvent-free environment. We find that the first step occurs on a timescale of a few hundred femtoseconds, whereas the second step, to form the full tautomer, is much slower, taking place within several picoseconds; the timescales are changed significantly by replacing hydrogen with deuterium. These results establish the molecular basis of the dynamics and the role of quantum tunnelling.

Simultaneous temporal resolution of cardiac and respiratory motion in MR imaging.

To evaluate a magnetic resonance (MR) imaging method that allows for simultaneous resolution of both the cardiac and respiratory cycles. Conventional and phase-contrast cine sequences were modified to provide additional resolution of the respiratory cycle. Data were collected in 11 healthy volunteers during MR imaging of the heart and portal vein. The imaging time was increased over that of a conventional cine acquisition by a factor equal to the number of frames in the respiratory cycle. Data were compared with those from comparable sequences in which only one motion cycle was resolved. In the heart, motion due to cardiac dynamics was separated from respiration-induced excursions. The extent of motion could be measured, and artifacts were minimized. Changes in flow rate as a function of both motion cycles were resolved and quantified in both the portal vein and superior vena cava. This method allows for simultaneous resolution of cardiac and respiratory motion cycles and helps provide a more physiologic view of the effects of cardiac and respiratory variations.