The combined application of the contrast-to-noise index and 80 kVp for cardiac CTA scanning before atrial fibrillation ablation reduces radiation dose exposure.

INTRODUCTION: To compare the radiation dose, diagnostic accuracy, and the resultant ablation procedures using 80 and 120-kVp cardiac computed tomography angiography (CCTA) protocols with the same contrast-to-noise ratio in patients scheduled for atrial fibrillation (AF) ablation. METHODS: This retrospective study was performed following institutional review board approval. We divided 140 consecutive patients who had undergone CCTA using a 64-MDCT scanner into two equal groups. Standard deviation (SD) of the CT number was set at 25 Hounsfield units (HU) for the 120-kVp protocol. To facilitate a reduction in radiation dose it was set at 40 HU for the 80 kVp protocol. We compared the two protocols with respect to the radiation dose, the diagnostic accuracy for detecting left atrial appendage (LAA) thrombi, matching for surface registration, and the resultant ablation procedures. RESULTS: At 120 kVp, the dose length product (DLP) was 2.2 times that at 80 kVp (1269.0 vs 559.0 mGy cm, p < 0.01). The diagnostic accuracy for thrombus detection was 100% using both protocols. There was no difference between the two protocols with respect to matching for surface registration. The protocols did not differ with respect to the subsequent time required for the ablation procedures and the ablation fluoroscopy time, and the radiation dose (p = 0.54, 0.33, and 0.32, respectively). CONCLUSION: For the same CNR, the DLP at 80 kVp (559.0 mGy cm) was 56% of that delivered at 120 kVp (1269.0 mGy cm). There was no reduction in diagnostic accuracy. IMPLICATIONS FOR PRACTICE: Maintaining CNR allows for a reduction in the radiation dose without reducing the image quality.

Asymmetric Phosphorus Incorporation in Homoepitaxial P-Doped (111) Diamond Revealed by Photoelectron Holography.

Diamond has two crystallographically inequivalent sites in the unit cell. In doped diamond, dopant occupation in the two sites is expected to be equal. Nevertheless, preferential dopant occupation during growth under nonequilibrium conditions is of fundamental importance, for example, to enhance the properties of nitrogen-vacancy (N-V) centers; therefore, this is a promising candidate for a qubit. However, the lack of suitable experimental techniques has made it difficult to study the crystal- and chemical-site-resolved local structures of dopants. Here, we confirm the identity of two chemical sites with asymmetric dopant incorporation in the diamond structure, via the photoelectron holography (PEH) of heavily phosphorus (P)-doped diamond prepared by chemical vapor deposition. One is substitutionally incorporated P with preferential site occupations and the other can be attributed to a PV split vacancy complex with preferential orientation. The present study shows that PEH is a valuable technique to study the local structures around dopants with a resolution of crystallographically inequivalent but energetically equivalent sites/orientations. Such information provides strategies to improve the properties of dopant related-complexes in which alignment is crucial for sensing of magnetic field or quantum spin register using N-V centers in diamond.

Electronic structure of K-doped picene film on HOPG.

We have performed potassium (K)-doping dependent photoemission (PES) measurements of picene film on highly oriented pyrolytic graphite (HOPG). K-doping dependent valence band PES data exhibits a shift of the valence band to a higher binding energy, indicative of the charge transfer from the K atoms to the picene film. K-doping dependent PES spectra near the Fermi level (E F) show the appearance and disappearance of a Fermi edge, indicating the metallic properties of the film at certain K concentrations. High-resolution PES spectrum at the lowest measured temperature does not show an opening of the superconducting gap, requesting further studies to explore the superconducting properties of the K-doped picene film. The results will be discussed by comparison with previous and recent spectroscopic studies.

Preliminary study for the assessment of physical activity using a triaxial accelerometer with a gyro sensor on the upper limbs of subjects with paraplegia driving a wheelchair on a treadmill.

OBJECTIVE: This study aimed to examine whether, on the basis of the relationship between sensors attached on the upper limbs and energy expenditure (EE) at the time of wheelchair propulsion, there are differences in the measurement of EE depending on the sensor attachment site and whether addition of the angular velocity information to the acceleration value is advantageous. We also aimed to clarify the variables used to estimate EE as well as the estimated error. SETTING: Laboratory of the National Hospital Organization Murayama Medical Center, Japan. METHODS: Six male subjects with spinal cord injuries participated in the study. Each wore sensors at the wrist and the middle upper arm on both sides while driving a wheelchair on a treadmill at three levels: very, very light; very light; and fairly light. Triaxial acceleration, triaxial angular velocity and EE were measured during driving. We analyzed the correlation between EE and acceleration, angular velocity and synthesized values of acceleration and angular velocity at each location using regression, multiple regression and Bland-Altman analyses. RESULTS: The determination coefficients between EE and the acceleration, angular velocity and synthesized values of acceleration and angular velocity varied from 0.68 to 0.87 at each location. The mean difference between the measured and estimated EE varied from 0.0028 (s.d., 0.0027) kcal min(-1) kg(-1) on the right upper arm. CONCLUSION: These findings suggest that combining the synthesized values of angular velocity and acceleration of the motion sensors on the upper limbs might reflect EE during a wheelchair driving activity on a treadmill.

Estimation of the kinetic-optimized stimulus intensity envelope for drop foot gait rehabilitation.

The purpose of present study is to estimate the optimal stimulus intensity envelope for drop foot rehabilitation based on a kinetic perspective. The voluntary and electric-stimulated elicited dorsiflexion torque responses of 11 healthy subjects were measured. During dorsiflexion, we recorded the tibialis anterior (TA) electromyography (EMG) or the stimulation intensity at four angles of the ankle joint. From these measurements, we derived two approximate equations that estimate dorsiflexion produced by either voluntary contraction or by electrical stimulation using a sigmoid function and a stepwise-regression analysis. We then tested the predictive capability of the model using Pearson correlation. Both equations indicated high correlation coefficients. Finally, we derived a relation between the TA EMG amplitude and stimulation intensity. From the obtained equation, we determined the optimal stimulus amplitude. We assume that the derived stimulus intensity envelope, calculated from EMG amplitude and angle of ankle joint, satisfies kinetic demand.

A novel signal processing method using system identification for underwater surface electromyography.

PURPOSE: Currently, to record underwater surface electromyography (EMG), electrodes are covered with waterproof tape. For short-term measurement, waterproof tape prevents electrical leakage. However, during long-term measurement, water or sweat can contact the electrodes, changing the measurement conditions and gradually affecting the EMG data. The purpose of present study was to devise a novel method for prolonged underwater EMG recording, which estimate dry-land EMG from underwater EMG recorded by non-waterproofed electrodes using system identification techniques. METHOD: One healthy male participated in this study. System identification was used to convert underwater EMG signals to the estimated dry-land signals. Transfer functions were derived using two pairs of surface recording electrodes on the same muscle in parallel. System input was the EMG recorded using non-waterproofed electrodes; the output was the signal recorded underwater using waterproofed electrodes (supposed to be the same as dry-land signals). To examine the validity of the present method, three experiments were conducted. RESULT: There was a high positive correlation between the estimated dry-land EMG based on the non-waterproofed electrodes and the EMG obtained using waterproofed electrodes. To test the validity of long-term recording using the novel method, the estimated dry-land EMG signals were measured during 30 minutes of underwater stepping and were stable. CONCLUSION: The novel method using non-waterproofed electrodes with system identification techniques eliminated the effect of changes in measurement conditions and appears effective for long-term, underwater surface EMG recording.

Interplay of superconductivity and rattling phenomena in beta-pyrochlore KOs2O6 studied by photoemission spectroscopy.

The electronic structure near the Fermi level (EF) of the beta-pyrochlore superconductor KOs2O6 is studied using laser-excited ultrahigh-resolution photoemission spectroscopy. The superconducting gap clearly opens across the superconducting transition (Tc=9.6 K), with the strong electron-phonon coupling value of 2Delta(0)/k B Tc>or=4.56. A fitting analysis identifies clear anomalies at Tp=7.5 K in the temperature dependencies of the superconducting gap size and the quasiparticle relaxation lifetime. These anomalies and the fine spectral structures arising from phonons suggest that the existence of the rattling behavior of K ions significantly affects the superconductivity in KOs2O6.

NMR observation of rattling phonons in the pyrochlore superconductor KOs2O6.

We report nuclear magnetic resonance studies on the beta-pyrochlore oxide superconductor KOs2O6. The nuclear relaxation at the K sites is entirely caused by fluctuations of the electric field gradient, which we ascribe to highly anharmonic low frequency oscillation (rattling) of K ions. A phenomenological analysis shows a crossover from overdamped to underdamped behavior of the rattling phonons with decreasing temperature and its sudden sharpening below the superconducting transition temperature T(c). Suppression of the Hebel-Slichter peak in the relaxation rate at the O sites below T(c) also indicates strong electron-phonon coupling.

Effect of voluntary contraction with electrical stimulation to antagonist muscle on agonist H-reflex.

OBJECTIVE: Hybrid exercise (HE) was designed to use the force generated by an electrically stimulated antagonist to provide resistance to a volitionally contracting agonist. The purpose of this study was to measure and compare the soleus H-reflex before and after HE or conventional resistance exercise (CRE). METHODS: The experiments were carried out in 18 healthy subjects (5 men and 13 women; 19-30 yr), who were divided into 2 groups of 9 for each protocol (HE or CRE). The exercise sessions lasted for 15 consecutive minutes. The soleus Hmax/Mmax was measured before and after the HE or the CRE. RESULTS: In the HE group, although there was no significant difference, the soleus Hmax/Mmax after the exercise increased compared with before the exercise (54.7 +/- 10.2% to 59.0 +/- 14.5%). On the other hand, the soleus Hmax/Mmax decreased in the CRE group (61.8 +/- 14.9% to 55.7 +/- 16.1%). In the rate of change of the soleus Hmax/Mmax, the result for the HE group was significantly higher than in the CRE group (108.0 +/- 11.7% and 89.1 +/- 8.0%, respectively) (p < 0.001). CONCLUSION: Our results show a clear difference of the neurophysiological mechanism between HE and CRE. Thus, HE might not be an alternative method for CRE.

Thermal conductivity of the pyrochlore superconductor KOs2O6: strong electron correlations and fully gapped superconductivity.

To elucidate the nature of the superconducting ground state of the geometrically frustrated pyrochlore KOs2O6 (Tc=9.6 K), the thermal conductivity was measured down to low temperatures (approximately Tc/100). We found that the quasiparticle mean free path is strikingly enhanced below a transition at Tp=7.8 K, indicating enormous electron inelastic scattering in the normal state. In magnetic fields, the conduction at T-->0 K is nearly constant up to approximately 0.4Hc2, in contrast with the rapid growth expected for superconductors with an anisotropic gap. This unambiguously indicates a fully gapped superconductivity, in contrast with previous studies. These results highlight that KOs2O6 is unique among superconductors with strong electron correlations.

Disorder of phase-related modulation of soleus H-reflex during hip movement in stroke patients.

PURPOSE: The soleus H-reflex during passive hip movement was measured to clarify the modulation of excitability of the soleus monosynaptic reflex during locomotion-like movement in spastic stroke patients. METHOD: The experiment was performed in five patients with spastic hemiparesis. The hip joint was moved passively ranging from 0 to 40 degrees. The knee joint was fixed at full extension and the ankle joint was fixed at the mid-position. During the movement, the soleus M-wave and soleus H-reflex were measured. RESULTS: Flexion caused a decrease in the soleus H-reflex, whereas extension caused an increase symmetrically for both the static and dynamic conditions. In addition, the lowest value was observed at the end of the flexion phase during fast movement. CONCLUSION: These findings indicate that the phase-related modulation of soleus H-reflex during hip movement is partially disordered in stroke patients.

Anomalous pressure dependence of the superconducting transition temperature of beta-pyrochlore AOs2O6 oxides.

High-pressure effects on the superconducting transitions of beta-pyrochlore oxide superconductors AOs(2)O(6) (A = Cs,Rb,K) are studied by measuring resistivity under high pressures up to 10 GPa. The superconducting transition temperature T(c) first increases with increasing pressure in every compound and then exhibits a broad maximum at 7.6 K (6 GPa), 8.2 K (2 GPa), and 10 K (0.6 GPa) for A = Cs, Rb, and K, respectively. Finally, the superconductivity is suppressed completely at a critical pressure near 7 GPa and 6 GPa for A = Rb and K and probably above 10 GPa for A = Cs. Characteristic changes in the coefficient A of the T(2) term in resistivity and residual resistivity are observed, both of which are synchronized with the corresponding change in T(c).

Post-activation depression of the soleus H-reflex in stroke patients.

PURPOSE: We examined post-activation depression in 35 stroke patients and 10 healthy subjects, and investigated whether their clinical symptoms were correlated to post-activation depression. METHODS: Post-activation depression of the soleus H-reflex evoked by electrical stimulation of the common peroneal nerve with supramaximal intensity of motor response on the tibialis anterior muscle. RESULTS: Post-activation depression was decreased on the affected side of the stroke patients. There was a significant difference between the affected and unaffected sides of the patients with post-activation depression, but no difference between the unaffected sides of the patients and healthy subjects. The presence of ankle clonus and the decrease in post-activation depression were correlated. CONCLUSION: Decreased post-activation depression in stroke patients suggests that a mechanism other than postsynaptic inhibition, such as reciprocal Ia inhibition and Ib inhibition, and presynaptic inhibition, may contribute to the exaggerated stretch reflexes, in particular, the manifestation of clonus.

Passive movement of hip and knee joints decreases the amplitude of soleus H-reflex in stroke patients.

OBJECTIVES: The study aims to investigate the changes of the H-reflex in soleus (Sol-H-reflex) during hip and knee joint movements in stroke patients. METHODS: The experiments were carried out on five stroke patients with spastic hemiplegia (2 males and 3 females, 48 to 71 years old). Sol-H-reflexes were measured 200 times for each joint movement speed Stimulus was given at random intervals (4 to 5 seconds) during the joint movement. Two movement speeds were used to investigate the effects of movement speed. RESULTS: For both fast and slow movements, the amplitude of the Sol-H-reflex decreased in the middle flexion phase. In contrast, the amplitude of the Sol-H-reflex increased in the middle extension phase. For the fast movement, the Sol-H-reflex was smaller in only a small angle range during the flexion and extension phase in comparison to the slow movement. The Sol-H-reflex during the flexion phase was significantly smaller than during the extension phase at almost all angles for both speeds. The Sol-H-reflex for both speeds was smaller than the Sol-H-reflex at rest for the whole angle range. CONCLUSION: These results demonstrate the differential effects of Sol-H-reflex modulation in stroke patients when compared with normal subjects.

Changes of reflex size in upper limbs using wrist splint in hemiplegic patients.

We evaluated the effect of prolonged wrist extension on H reflex in the flexor carpi radialis (FCR) muscle and tendon jerk (T) reflex in the biceps brachii (BB) muscle of 17 chronic hemiplegic patients. H reflex of the FCR and T reflex of the BB were assessed every 5 minutes within 20 minutes during prolonged wrist extension and post-20 minutes after the extension. As a result, H reflex in the FCR was reduced by passive wrist stretch in 82% of the spastic limbs. The effect was larger in the higher spastic group. In 45% of the spastic limbs, T reflex in the BB also was reduced by passive wrist stretch. The inhibitory effects had a tendency to strengthen in accordance with the grade of muscle tone. We considered from these results, prolonged wrist extension generated inhibitory projections via probably group II afferents of the FCR in the homonym and in the transjoint in spastic limbs.

New method using multi-regression analysis on evoked electromyography during movement to adjust stimulation conditions.

A new method of stimulation of the lower extremities was devised that automatically adjusts the stimulation conditions at any angle of the knee joint. An M-wave is considered to indicate the stimulation conditions, because it is the waveform that results from direct stimulation to the axon of the alpha motor neuron. The present device adjusted the stimulation intensity, using multi-regression analysis to evoke an M-wave of preset amplitude. Participants included five people without any neuromuscular impairment. The subjects sat on a chair during the test. The hip joint was fixed at a flexion angle of 90 degrees, and the ankle joint was fixed at the midposition. During passive knee joint movement ranging from 0 degrees to 135 degrees, M-waves were measured. Electrodes were attached at the popliteal fossa and the patella to stimulate the tibial nerve. Ag-AgCl electrodes were put on the belly of the right soleus muscle for the M-wave measurement. The device was set to give M-waves close to the preset value, 10% Mmax. According to previous research, the allowable limit of M-wave amplitude deviations was reported to be about 5% Mmax. The M-wave amplitudes evoked by the device were in the allowable range (9.2 +/- 2.5% Mmax). The device enabled control of the M-wave amplitude over the entire range of motion of the joint. Using this device, it was possible to examine the excitability of the alpha motor neuron pool more precisely.

Photoemission study of YBa(2)Cu(3)O(y) thin films under light illumination.

Heterojunctions of Nb-doped SrTiO3 substrate and YBa(2)Cu(3)O(y) thin films show photoconductivity and photovoltaic effects due to photocarrier injection. Photocarrier injection is expected to be a new carrier doping method in strongly correlated systems instead of chemical substitution. We have studied the nature of photocarrier injection in YBa(2)Cu(3)O(y)/SrTiO(3):Nb using x-ray photoemission spectroscopy with pulsed laser excitation. The core-level spectra shift to higher binding energy by 0.78 eV under pulsed laser illumination at 30 Hz. The energy shift corresponds to the photovoltage, which arises at the interface. In addition, we have observed that the energy shift strongly depends on the frequency of the laser. The lifetime of the injected photoholes has been estimated to be 40 ms by analyzing the frequency dependence.

Effects of therapeutic passive exercise of hip and knee joints on the soleus H-reflex.

UNLABELLED: The effect of passive movement of a leg on alpha-motoneurons of the soleus was investigated while the ankle was immobilized. Electrophysiological parameters of the H-reflex were used. Nineteen fully informed volunteers with no history of neurological or internal disease participated in the study. The mean age across all the experiments was 20.9 years. Contributions to the modulation of the soleus H-reflex by hip and knee joint movements were analyzed in two tasks. These were the most general movement methods used in physical therapy. Soleus H-reflexes were measured six times per experiment. Stimulation intensity was set at the 1.1 x M-wave threshold. RESULTS: 1. In both exercises, H/M decreased as flexion progressed with fast or slow movement. The quadriceps femoris inhibited soleus muscle alpha-motoneurons in both experiments. 2. H/M increased on initiation of extension in the two-joint exercise. In the single-joint exercise, inhibition was retained through the extension phase during both fast and slow movements. Hamstring effects were strong during extension of the leg. 3. In both exercises, the H/M for fast movement was lower than for slow movement at all angles, indicative that H/M decreases with fast movement irrespective of the effects produced by the hip joint.

Fascicle arrangements of vastus lateralis and gastrocnemius muscles in highly trained soccer players and swimmers of both genders.

The thickness, fascicle angles of pennation, and fascicle length of the vastus lateralis (VL) and medial gastrocnemius (MG) muscles in highly trained soccer players and swimmers of both genders were determined from ulrasonograms to investigate whether the fascicle arrangements of the lower limb muscles in the athletes could be related to the requirements of the events, i. e., intensive muscular activities in the water versus on the ground. In comparisons between the two events, the soccer players tended to show shorter fascicles and greater fascicle angles, and the swimmers thicker muscles and longer fascicles, especially in VL. In both events, the males showed thicker muscles and greater fascicle angles than the females. In both VL and MG, the thickness, fascicle length and fascicle angle were related to each other in a right-angled triangle model, and so, most of the event- and/or gender-related differences observed in the fascicle angle depended on the difference in muscle thickness relative to fascicle length. The present data cannot answer the question of whether the athletes had muscles suited to their respective sports prior to beginning their sports or whether the muscles adapted specifically to the competitive and/or training styles. However, it might be assumed that the lower limb muscles for swimmers are suitable to perform rapid, powerful kick movements during competitive swims by having greater thickness and longer fascicle, i. e., priorities in both force production and shortening velocity, but those for soccer players do not show architectural profiles which can be related to intensive activity on the ground, except that the thickness values exceed the normal range.

Statistical test for peri-stimulus time histograms in assessing motor neuron activity.

The peri-stimulus time histogram is a valuable tool for evaluating neural connections in humans. To detect the degree to which a conditioning stimulus to a sensory nerve modulates motor neuron activity, a histogram of motor unit spike intervals after a conditioning stimulus is measured. This histogram allows the effect of the conditioning stimulus to be visualised. By comparison with a reference histogram of motor unit spike intervals after a sham stimulus, the noise caused by spontaneous firing sway can be removed. However, no valid statistical test has yet been developed to separate the physiological effect from the spontaneous sway and statistical noise. A computational method has been proposed to detect modulation caused by a conditioning stimulus. To clarify the effect of a conditioning stimulus, this new method used reference histograms to calculate a confidence interval. A simulated experiment demonstrated that about 2000 re-samplings were sufficient to estimate a confidence interval for a histogram with 1 ms bin width constructed from 300 triggers. Testing of the experimental data, measured from the tibialis anterior muscles during the elicitation of the excitatory spinal reflex, confirmed that significant peaks were produced at 30, 34, 35 and 38ms after the conditioning stimulus. These correspond appropriately to the delay of the spinal reflex.