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At least 451 records · Page 25Linked to original sources

PubMed2000

Detection of intracranial aneurysms with unenhanced and echo contrast enhanced transcranial power Doppler.

OBJECTIVE: To assess transcranial power Doppler and the effect of an intravenous ultrasonic contrast agent for detecting intracranial aneurysms in patients admitted with a subarachnoid haemorrhage METHODS: 203 patients with subarachnoid haemorrhage were examined with the operator blind to the results of the admission CT and subsequent digital subtraction angiogram (DSA). In 98 cases patients were imaged using unenhanced transcranial power Doppler, and in 105 cases, patients were imaged both using unenhanced and echo contrast enhanced (Levovist, Schering AG) transcranial power Doppler. RESULTS: DSA detected 168 intracranial aneurysms in 128 patients (24 patients had multiple lesions) and 75 patients had an aneurysm negative DSA. There was agreement between DSA and transcranial power Doppler in 87 intracranial aneurysms of which 20 were only detected after infusion of contrast agent. Without contrast infusion, transcranial power Doppler showed a sensitivity of 40% and specificity of 91%. A significant increase in detection was noted when using a contrast agent (chi(2) = 9.49, p<0.001). With a contrast study the sensitivity increase to 55% with a specificity of 83%. Intracranial aneurysm detection by transcranial power Doppler was significantly dependent on position using a contrast infusion (chi(2) = 15.87, p<0.05). A positive correlation was also found between the size of intracranial aneurysms measured by transcranial power Doppler and DSA (r = 0.55, p<0.05). The transcranial power Doppler sensitivity and specificity increased with larger aneurysms and reached 100% for intracranial aneurysms greater than 12 mm diameter. Detection by transcranial power Doppler was also dependent on morphology (chi(2) = 14.46, p<0.001). CONCLUSIONS: The detection of intracranial aneurysm by transcranial power Doppler is dependent on aneurysm location, size, and morphology and is enhanced with the use of an intravenous contrast agent.

Adult↗

PubMed1996

Power versus conventional color Doppler sonography: comparison in the depiction of vasculature in liver tumors.

PURPOSE: To compare power and conventional color Doppler sonography in the depiction of the intratumoral vasculature of hemangiomas, hepatocellular carcinomas (HCCs), and metastases of the liver. MATERIALS AND METHODS: Thirty-two patients with liver tumors (12 hemangiomas, 11 HCCs, and nine metastases) were prospectively evaluated with power and conventional color Doppler sonography by using a 2-4-MHz convex probe with 2-MHz Doppler frequency. Power Doppler sonography was performed with a 75%-88% gain. Conventional color Doppler sonography was performed with a 55%-75% gain and a pulse repetition frequency of 700 Hz. Power Doppler signals and color Doppler signals interrogated in one plane were analyzed by two radiologists, who subjectively rated power Doppler sonography as superior, equal, or inferior to color Doppler sonography. RESULTS: Overall, power Doppler sonography was superior to color Doppler sonography in 18 patients and equal in 14 (P < .01). In hemangiomas, power Doppler sonography was superior to color Doppler sonography in 10 patients and equal in two (P < .01). In HCCs, power Doppler sonography was superior to color Doppler sonography in four patients and equal in seven (P > .05). In metastases, power Doppler sonography was superior to color Doppler sonography in four patients and equal in five (P < .05). CONCLUSION: Power Doppler sonography is more sensitive than color Doppler sonography in the depiction of the vasculature of liver tumors, particularly in hemangiomas.

Adult↗

PubMed2000

Nonpalpable breast lesions: evaluation with power Doppler US and a microbubble contrast agent-initial experience.

PURPOSE: To evaluate power Doppler ultrasonography (US) performed with a microbubble US contrast agent in the differentiation of nonpalpable breast lesions. MATERIALS AND METHODS: Fifty nonpalpable breast lesions in 50 patients were prospectively evaluated with power Doppler US before and after injection of the contrast agent SH U 508A. Lesion vascularity and the morphology of vessels on US scans were analyzed and were correlated with histologic results. RESULTS: Surgical excision revealed 22 cancers and 28 benign lesions. At nonenhanced power Doppler US, eight (36%) of 22 cancers and four (14%) of 28 benign lesions were vascular. At contrast agent-enhanced power Doppler US, 21 (95%) cancers and six (21%) benign lesions were vascular (P <.001). Irregular vessels were seen in three cancers and one benign lesion at nonenhanced power Doppler US and in 11 cancers and one benign lesion at contrast-enhanced power Doppler US. By using the presence of vascularity in the mass as the diagnostic criterion for malignancy, the sensitivity, specificity, and positive and negative predictive values of power Doppler US changed from 36%, 86%, 67%, and 63%, respectively, to 95%, 79%, 78%, and 96% after contrast agent injection. CONCLUSION: Contrast-enhanced power Doppler US was superior to nonenhanced power Doppler US in the demonstration and characterization of tumor vascularity in nonpalpable breast lesions. Contrast-enhanced power Doppler US may be useful for the differentiation between nonpalpable breast cancers and benign tumors.

Adult↗

PubMed1988

A constant-load ergometer for measuring peak power output and fatigue.

A constant-load cycle ergometer was constructed that allows maximal power output to be measured for each one-half pedal revolution during brief, high-intensity exercise. To determine frictional force, an electronic load cell was attached to the resistance strap and the ergometer frame. Dead weights were attached to the strap's free end. Flywheel velocity was recorded by means of a magnetic switch and two magnets placed on the pedal sprocket. Pedaling resulted in magnetically activated switch closures, which produced two electronic pulses per pedal revolution. Pulses and load cell output were recorded (512 Hz), digitized, and stored on disk via microcomputer. Power output was later computed for each pair of adjacent pulses, representing average power per one-half pedal revolution. Power curves generated for each subject were analyzed for peak power output (the highest one-half pedal revolution average), time to peak power, power fatigue rate and index, average power, and total work. Thirty-eight males performed two 15-s tests separated by 15 min (n = 16) or 48 h (n = 22). Peak power output ranged from 846.0 to 1,289.1 W. Intraclass correlation analysis revealed high test-retest reliability for all parameters recorded on the same or different days (R = 0.91-0.97). No significant differences (P greater than 0.05) were noted between parameter means of the first and second tests. These results indicate that the ergometer described provides a means for conveniently and reliably assessing short-term power output and fatigue.

Ergonomics↗

PubMed2005

Power and sample size calculations for genetic case/control studies using gene-centric SNP maps: application to human chromosomes 6, 21, and 22 in three populations.

Power and sample size calculations are critical parts of any research design for genetic association. We present a method that utilizes haplotype frequency information and average marker-marker linkage disequilibrium on SNPs typed in and around all genes on a chromosome. The test statistic used is the classic likelihood ratio test applied to haplotypes in case/control populations. Haplotype frequencies are computed through specification of genetic model parameters. Power is determined by computation of the test's non-centrality parameter. Power per gene is computed as a weighted average of the power assuming each haplotype is associated with the trait. We apply our method to genotype data from dense SNP maps across three entire chromosomes (6, 21, and 22) for three different human populations (African-American, Caucasian, Chinese), three different models of disease (additive, dominant, and multiplicative) and two trait allele frequencies (rare, common). We perform a regression analysis using these factors, average marker-marker disequilibrium, and the haplotype diversity across the gene region to determine which factors most significantly affect average power for a gene in our data. Also, as a 'proof of principle' calculation, we perform power and sample size calculations for all genes within 100 kb of the PSORS1 locus (chromosome 6) for a previously published association study of psoriasis. Results of our regression analysis indicate that four highly significant factors that determine average power to detect association are: disease model, average marker-marker disequilibrium, haplotype diversity, and the trait allele frequency. These findings may have important implications for the design of well-powered candidate gene association studies. Our power and sample size calculations for the PSORS1 gene appear consistent with published findings, namely that there is substantial power (>0.99) for most genes within 100 kb of the PSORS1 locus at the 0.01 significance level.

Black or African American↗

PubMedDate not supplied

A regression model for correcting intraocular lens power after refractive surgery independent of preoperative data.

PURPOSE: To find a method of calculating intraocular lens (IOL) power that may be independent of preoperative data in eyes that have previously undergone myopic laser in situ keratomileusis (LASIK). METHODS: In 148 eyes of 75 patients, before and 6 months after LASIK, IOL power was calculated with SRK/T formula utilizing the spherical equivalent as the desired target refraction. Assuming that LASIK does not alter the crystalline lens refractive properties, IOL calculation error (CER) was estimated with this formula: CER = [pre-LASIK IOL power]/[post-LASIK IOL power]. Then the authors used postoperative biometry and Orbscan II corneal topography data in multiple regression models to find the best variables to predict the CER. Predicted amount of error which is calculated independent of preoperative data could be used to correct the post-LASIK calculated IOL: [corrected post-LASIK IOL power] = CER x [post-LASIK IOL power]. RESULTS: A regression model with these predictors was found: axial length in millimeters (L), radius of the anterior corneal surface best fitted sphere in millimeters divided by radius of the posterior corneal surface best fitted sphere in millimeters (AntBFS/PostBFS), corneal central 5 millimeters mean power in diopters divided by corneal central 3 millimeters mean power in diopters (mean 5 mm/mean 3 mm), the post-LASIK IOL power, and the post-LASIK simulated K reading. The model R square was 0.88. CONCLUSIONS: There is correlation between post-LASIK biometry values and IOL power correction factor. This study presents a new model for further investigation.

Adult↗

PubMed2005

Differences in codon bias cannot explain differences in translational power among microbes.

BACKGROUND: Translational power is the cellular rate of protein synthesis normalized to the biomass invested in translational machinery. Published data suggest a previously unrecognized pattern: translational power is higher among rapidly growing microbes, and lower among slowly growing microbes. One factor known to affect translational power is biased use of synonymous codons. The correlation within an organism between expression level and degree of codon bias among genes of Escherichia coli and other bacteria capable of rapid growth is commonly attributed to selection for high translational power. Conversely, the absence of such a correlation in some slowly growing microbes has been interpreted as the absence of selection for translational power. Because codon bias caused by translational selection varies between rapidly growing and slowly growing microbes, we investigated whether observed differences in translational power among microbes could be explained entirely by differences in the degree of codon bias. Although the data are not available to estimate the effect of codon bias in other species, we developed an empirically-based mathematical model to compare the translation rate of E. coli to the translation rate of a hypothetical strain which differs from E. coli only by lacking codon bias. RESULTS: Our reanalysis of data from the scientific literature suggests that translational power can differ by a factor of 5 or more between E. coli and slowly growing microbial species. Using empirical codon-specific in vivo translation rates for 29 codons, and several scenarios for extrapolating from these data to estimates over all codons, we find that codon bias cannot account for more than a doubling of the translation rate in E. coli, even with unrealistic simplifying assumptions that exaggerate the effect of codon bias. With more realistic assumptions, our best estimate is that codon bias accelerates translation in E. coli by no more than 60% in comparison to microbes with very little codon bias. CONCLUSIONS: While codon bias confers a substantial benefit of faster translation and hence greater translational power, the magnitude of this effect is insufficient to explain observed differences in translational power among bacterial and archaeal species, particularly the differences between slowly growing and rapidly growing species. Hence, large differences in translational power suggest that the translational apparatus itself differs among microbes in ways that influence translational performance.

Bacterial Physiological Phenomena↗

PubMed2006

The effects of powered ankle-foot orthoses on joint kinematics and muscle activation during walking in individuals with incomplete spinal cord injury.

BACKGROUND: Powered lower limb orthoses could reduce therapist labor during gait rehabilitation after neurological injury. However, it is not clear how patients respond to powered assistance during stepping. Patients might allow the orthoses to drive the movement pattern and reduce their muscle activation. The goal of this study was to test the effects of robotic assistance in subjects with incomplete spinal cord injury using pneumatically powered ankle-foot orthoses. METHODS: Five individuals with chronic incomplete spinal cord injury (ASIA C-D) participated in the study. Each subject was fitted with bilateral ankle-foot orthoses equipped with artificial pneumatic muscles to power ankle plantar flexion. Subjects walked on a treadmill with partial bodyweight support at four speeds (0.36, 0.54, 0.72 and 0.89 m/s) under three conditions: without wearing orthoses, wearing orthoses unpowered (passively), and wearing orthoses activated under pushbutton control by a physical therapist. Subjects also attempted a fourth condition wearing orthoses activated under pushbutton control by them. We measured joint angles, electromyography, and orthoses torque assistance. RESULTS: A therapist quickly learned to activate the artificial pneumatic muscles using the pushbuttons with the appropriate amplitude and timing. The powered orthoses provided approximately 50% of peak ankle torque. Ankle angle at stance push-off increased when subjects walked with powered orthoses versus when they walked with passive-orthoses (ANOVA, p < 0.05). Ankle muscle activation amplitudes were similar for powered and passive-orthoses conditions except for the soleus (approximately 13% lower for powered condition; p < 0.05). Two of the five subjects were able to control the orthoses themselves using the pushbuttons. The other three subjects found it too difficult to coordinate pushbutton timing. Orthoses assistance and maximum ankle angle at push-off were smaller when the subject controlled the orthoses compared to when the therapist-controlled the orthoses (p < 0.05). Muscle activation amplitudes were similar between the two powered conditions except for tibialis anterior (approximately 31% lower for therapist-controlled; p < 0.05). CONCLUSION: Mechanical assistance from powered ankle-foot orthoses improved ankle push-off kinematics without substantially reducing muscle activation during walking in subjects with incomplete spinal cord injury. These results suggest that robotic plantar flexion assistance could be used during gait rehabilitation without promoting patient passivity.

Journal Article↗

PubMed1992

The influence of temperature on power output of scup red muscle during cyclical length changes.

To gain insight into how temperature affects locomotory performance, we measured power output of scup red muscle during oscillatory length changes at 10 degrees C and 20 degrees C. When we optimized work loop parameters, we found that maximum power was 27.9 W kg-1 at 20 degrees C and 12.8 W kg-1 at 10 degrees C, giving a Q10 of 2.29. Maximum power was generated at a higher oscillation frequency at 20 degrees C (5 Hz) than at 10 degrees C (2.5 Hz), and the Q10 for power output at a given oscillation frequency ranged from about 1 at 1 Hz to about 5 at 7.5 Hz. An analysis of the results in terms of crossbridge kinetics suggests that the higher power output at 20 degrees C is associated with both a higher Vmax (i.e. more power per cycling crossbridge) and faster activation and relaxation (i.e. a greater number of cycling crossbridges). To obtain a more realistic understanding of the functional importance of temperature effects on muscle, we imposed on isolated muscle in vivo length changes and oscillation frequencies (measured during previous experiments on swimming scup) and the in vivo stimulus duty cycle (measured from electromyograms in this study). At 20 degrees C, muscle bundles tested under these in vivo conditions produced nearly maximal power, suggesting that the muscle works optimally during locomotion and, thus, important contractile parameters have been adjusted to produce maximum mechanical power at the oscillation frequencies and length changes needed during swimming. At 10 degrees C, muscle bundles tested under in vivo conditions produced much less power than was obtained during the 'optimized' work loop experiments discussed above. Furthermore, although 'optimized' work loop experiments showed that maximum power output occurs at 2.5 Hz, scup do not appear to swim with such a low tailbeat frequency. Although the reason for these apparent discrepancies at 10 degrees C are not known, it shows that simple extrapolation from isolated muscle to the whole animal, without knowledge of how the muscle is actually used in vivo, can be misleading.

Animals↗

PubMed1997

Maximum speed and mechanical power output in lizards.

The goal of the present study was to test the hypothesis that maximum running speed is limited by how much mechanical power the muscular system can produce. To test this hypothesis, two species of lizards, Coleonyx variegatus and Eumeces skiltonianus, sprinted on hills of different slopes. According to the hypothesis, maximum speed should decrease on steeper uphill slopes but mechanical power output at maximum speed should be independent of slope. For level sprinting, the external mechanical power output was determined from force platform data. For uphill sprinting, the mechanical power output was approximated as the power required to lift the center of mass vertically. When the slope increased from level to 40 degrees uphill, maximum speed decreased by 28% in C. variegatus and by 16% in E. skiltonianus. At maximum speed on a 40 degrees uphill slope in both species, the mechanical power required to lift the body vertically was approximately 3.9 times greater than the external mechanical power output at maximum speed on the level. Because total limb mass is small in both species (6-16% of body mass) and stride frequency is similar at maximum speed on all slopes, the internal mechanical power output is likely to be small and similar in magnitude on all slopes. I conclude that the muscular system is capable of producing substantially more power during locomotion than it actually produces during level sprinting. Thus, the capacity of the muscular system to produce power does not limit maximum running speed.

Animals↗

PubMed2002

Muscle designed for maximum short-term power output: quail flight muscle.

Take-off in birds at high speeds and steep angles of elevation requires a high burst power output. The mean power output of the pectoralis muscle of blue-breasted quail (Coturnix chinensis) during take-off is approximately 400 W kg(-1) muscle, as determined using two independent methods. This burst power output is much higher than has been measured in any other cyclically contracting muscle. The power output of muscle is determined by the interactions between the physiological properties of the muscle, the stimulation regime imposed by the central nervous system and the details of the strain cycle, which are determined by the reciprocal interaction between the muscle properties and the environmental load. The physiological adaptations that enable a high power output to be achieved are those that allow the muscle to develop high stresses whilst shortening rapidly. These characteristics include a high myofibrillar density, rapid twitch contraction kinetics and a high maximum intrinsic velocity of shortening. In addition, several features of the strain cycle increase the power output of the quail pectoralis muscle. First, the muscle operates at a mean length shorter than the plateau of the length/force relationship. Second, the muscle length trajectory is asymmetrical, with 70 % of the cycle spent shortening. The asymmetrical cycle is expected to increase the power output substantially. Third, subtle deviations in the velocity profile improve power output compared with a simple asymmetrical cycle with constant lengthening and shortening rates. The high burst power outputs found in the flight muscles of quail and similar birds are limited to very brief efforts before fatigue occurs. This strong but short flight performance is well-suited to the rapid-response anti-predation strategy of these birds that involves a short flight coupled with a subsequent sustained escape by running. These considerations serve as a reminder that the maximum power-producing capacities of muscles need to be considered in the context of the in vivo situation within which the muscles operate.

Animals↗

PubMed2006

Sex differences in single muscle fiber power in older adults.

PURPOSE: This study was conducted to determine whether differences in power at the single muscle fiber level contribute to sex differences in whole muscle power production in the elderly. METHODS: A total of 16 sedentary older persons (10 women, 6 men), mean age 72 yr, had percutaneous needle biopsy of musculus vastus lateralis. Chemically skinned single muscle fibers were activated with Ca for maximal isometric force measurement (Po). The slack test was performed to determine maximal unloaded shortening velocity (Vo). Force-velocity and power curves were generated via a series of isotonic contractions, allowing measurement of peak power and specific power. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to determine myosin heavy chain composition of single muscle fibers. Whole muscle strength, velocity, and power were measured for knee extension and double leg press. RESULTS: Men had greater whole muscle strength, power, and velocity compared with women. Studied were 274 type I and 33 type IIa single fibers. No significant sex differences were found for fiber size, Po, specific force, Vo, power, or specific power in type I or IIa fibers. CONCLUSIONS: Single muscle fiber quality in older women is equivalent to that in older men and can not explain the differences seen in whole muscle strength, power, or function.

Aged↗

PubMed2006

Power output during stage racing in professional road cycling.

PURPOSE: The aim of the study was to evaluate the power output during a multistage professional road race using direct power measurements and to compare these results with the performance measurements using competition heart rate recordings. METHODS: Six professional road cyclists performed an incremental cycling test during which peak power output, power output, and heart rate at the lactate threshold (LT) and at a lactate increase of 1 mM above the LT (LT + 1) were assessed. During a six-stage road race competition, power output was measured directly (SRM crankset). To analyze the time spent at different intensities during competition, the amount of competition time spent below LT (zone 1), between the LT and LT + 1 (zone 2), and above LT + 1 (zone 3) determined during laboratory testing were calculated for power output and heart rate. RESULTS: During the five mass start stages, a mean power output of 220 +/- 22 W (3.1 +/- 0.2 W x kg(-1)) with a mean heart rate of 142 +/- 5 bpm was measured. Average power output during an uphill time trial was 392 +/- 60 W (5.5 +/- 0.4 W x kg(-1)) with a mean heart rate of 169 +/- 3 bpm. For the mass start stages, the average distribution of exercise time spent in different intensities calculated for power output and heart rate was 58 versus 38% for zone 1, 14 versus 38% for zone 2, and 28 versus 24% for zone 3. CONCLUSION: Most of the competition time during the mass start stages was spent at intensities near the LT. Compared with power output, heart rate measurement underestimated the time spent at intensity zones 1 and 3, and overestimated the time spent in zone 2.

Adult↗

PubMed2006

Power spectral analysis of finger plethysmographic waveform in patients with coronary artery disease and after coronary artery bypass graft surgery.

BACKGROUND: The aim of the present study was to assess the clinical significance of spectral analysis of plethysmographic waveform in patients with coronary artery disease (CAD) and after coronary artery bypass graft (CABG) surgery. METHODS AND RESULTS: The study group comprised 26 healthy subjects, 15 CAD patients, and 24 CAD patients after CABG. Finger plethysmographic waveforms from both right and left index fingers were recorded and analyzed using power spectral analysis. The total power of the right pulse was found to be higher than that of left pulse in the 3 groups of subjects. In CABG patients, the total power of both pulses was increased, the right-to-left ratio of bilateral total power was decreased, and the power of the harmonics of the right pulse shifted from high-frequency to low-frequency. The normalized power of the 4th harmonic of the left pulse and of the 3rd and 4th harmonics of right pulse decreased, whereas that of the 1st harmonic of right pulse increased in CABG patients. Several harmonics correlated significantly to some heart rate variability measures in both controls and CAD patients, but not in CABG patients. CONCLUSIONS: The increase in the total power of both pulses, the shift of the normalized power of harmonics of the right pulse from high- to low-frequency, and the decrease in the right-to-left ratio of the total power of both pulses are the 3 significant changes in the power spectra of the pulses in CAD patients after CABG. The plethysmographic waveform of normal controls and CAD patients may be modulated by the autonomic nervous system, and in CAD patients the CABG surgery may have diminished the effect of autonomic nervous modulation on the pulse waveforms.

Aged↗

PubMedDate not supplied

Clinical implications of power Doppler three-dimensional ultrasonography.

Power Doppler ultrasonography displays an estimate of the entire power contained in that part of the received radiofrequency ultrasound signal for which a phase shift corresponding to the motion of the target is detected. In contrast, conventional color Doppler imaging displays Doppler frequency shift information. Few reports have been published on the clinical utility of three-dimensional power Doppler ultrasonography in vascular patients. This study analyzed our experience of the clinical utility of this technology. Fifty-three patients selected out of 281 who were referred to our vascular laboratory underwent both conventional color duplex ultrasonography and power Doppler ultrasonography for the following indications: the question of subtotal versus total arterial occlusion, tortuous artery with limited imaging on color duplex ultrasonography, the presence of significant disease by Doppler ultrasonography with limited imaging, deep-lying arteries with an obscure orifice (e.g., renal artery), and heavily calcified arteries. The power Doppler ultrasonography portion of the examination was considered of positive diagnostic value if the final impression was different from that of conventional color duplex ultrasonography. A positive diagnostic value was achieved in 22 of 29 (76%) carotid artery examinations, 10 of 14 (71%) peripheral artery examinations, 4 of 5 (80%) renal artery examinations, and 3 of 5 (60%) aortoiliac examinations. Overall, positive diagnostic value was achieved by adding power Doppler ultrasonography in 39 of 53 patients (74%). Five of six patients (83%) who were felt to have carotid occlusion by color duplex ultrasonography were confirmed to have subtotal occlusion by power Doppler ultrasonography. Similarly, 6 of 8 patients (75%) with questionable subtotal versus total peripheral arterial occlusion by color duplex ultrasonography were confirmed to have subtotal occlusion by power Doppler ultrasonography. Four of five patients' (80%) renal examinations had a positive diagnostic value, which included three patients in whom the orifice of renal arteries was not seen by color duplex ultrasonography. Three-dimensional power Doppler ultrasonography can be more readily applied to clinical practice. Power Doppler ultrasonography is capable of defining the severity or extent of vascular disease, particularly in differentiating subtotal from total arterial occlusion.

Arterial Occlusive Diseases↗

PubMed2006

2 Gbit/s 0.5 microm complementary metal-oxide semiconductor optical transceiver with event-driven dynamic power-on capability.

A 2 Gb/s0.5 microm complementary metal-oxide semiconductor optical transceiver designed for board- or backplane level power-efficient interconnections is presented. The transceiver supports optical wake-on-link (OWL), an event-driven dynamic power-on technique. Depending on external events, the transceiver resides in either the active mode or the sleep mode and switches accordingly. The active-to-sleep transition shuts off the normal, gigabit link and turns on dedicated circuits to establish a low-power (approximately 1.8 mW), low data rate (less than 100 Mbits/s) link. In contrast the normal, gigabit link consumes over 100 mW. Similarly the sleep-to-active transition shuts off the low-power link and turns on the normal, gigabit link. The low-power link, sharing the same optical channel with the normal, gigabit link, is used to achieve transmitter/receiver pair power-on synchronization and greatly reduces the power consumption of the transceiver. A free-space optical platform was built to evaluate the transceiver performance. The experiment successfully demonstrated the event-driven dynamic power-on operation. To our knowledge, this is the first time a dynamic power-on scheme has been implemented for optical interconnects. The areas of the circuits that implement the low-power link are approximately one-tenth of the areas of the gigabit link circuits.

Journal Article↗

PubMed2000

A practice-based study of a power toothbrush: assessment of effectiveness and acceptance.

BACKGROUND: The greater effectiveness of the power toothbrush compared with a manual toothbrush is well-documented. Despite this, acceptance by dental professionals is still low. METHODS: This general practice study evaluated the effectiveness of a power toothbrush (Braun Oral-B Ultra Plaque Remover, Braun GmbH) in 16,903 patients, based on the clinical opinions of dental professionals in regard to patients' changing oral health status. In addition, a survey assessed the attitudes of dental professionals and patients toward the power toothbrush. RESULTS: The power toothbrush was considered by dental professionals to have had a positive effect on the oral health of 80.5 percent of their patients; the noticeable benefits with respect to a number of clinical criteria included plaque removal and improved gingival condition. Most patients in the study (88.9 percent) reported that they would continue using the power toothbrush once the study was completed. At the end of the study, many more dentists and hygienists considered the power toothbrush to be the most effective way of brushing, and almost 70 percent said that they would now be more likely to recommend a power toothbrush to their patients. CONCLUSIONS: The power toothbrush improved the oral health of patients in this practice-based study, and the number of dental professionals who said they would recommend a power toothbrush increased markedly during the study. CLINICAL IMPLICATIONS: Enabling dental professionals to evaluate the effect of a power toothbrush reinforces the findings from controlled clinical studies and increases their awareness of its potential to improve oral hygiene.

Adolescent↗

PubMed1997

Power versus color Doppler sonography of the normal cystic artery: implications for patients with acute cholecystitis.

OBJECTIVE: The purposes of this investigation were to compare prospectively the pattern and extent of cystic artery flow revealed by power Doppler sonography and color Doppler sonography in patients with normal gallbladders and to analyze the potential implications of these findings for power Doppler sonography in diagnosing acute cholecystitis. SUBJECTS AND METHODS: The cystic arteries of 142 patients (79 women and 63 men) with normal gallbladders were imaged with both power Doppler sonography and color Doppler sonography using 5-MHz transducers and settings optimized to reveal low-volume flow. The presence or absence of cystic artery flow and the anatomic extent of its visualization were recorded for each patient. RESULTS: Power Doppler sonography revealed flow in 73% of patients with normal gallbladders compared with 53% revealed by color Doppler sonography. Cystic artery flow within the distal fundal quartile was revealed by power Doppler sonography in 20% of patients and flow spanning greater than 50% of the anterior gallbladder wall was revealed by power Doppler sonography in 17% of patients. These findings differed from those of color Doppler sonography at a highly significant level (p < .0001, chi-square test). CONCLUSIONS: Power Doppler sonography is significantly more sensitive than color Doppler sonography for revealing cystic artery flow in patients with normal gallbladders. The flow patterns in patients with normal gallbladders obtained with power Doppler sonography overlap flow patterns previously reported as fairly specific criteria for diagnosing acute cholecystitis using color Doppler sonography, namely, flow within the distal fundal quartile and flow spanning greater than 50% of the anterior gallbladder wall. Accordingly, these color Doppler sonography criteria are not applicable to the diagnosis of acute cholecystitis with power Doppler sonography. Different power Doppler sonography criteria are necessary for the diagnosis of acute cholecystitis.

Acute Disease↗