生物质谱仪高速数据采集系统设计

目的 研制一种采样频率为2 GHz的高速数据采集系统,以满足生物质谱仪对飞行时间的精确测量要求.方法 采用ALTERA STRATIXⅢ系列FPGA作为主控芯片, 配合采样频率可达2 GHz、分辨率为12 bit的高性能ADC芯片,同时外扩512 MB DDR3 SDRAM用于数据缓存,并通过千兆以太网与上位机进行数据交互;此外,在高速数据采集板卡布线和制板时,采用多种方式有效保证信号完整性.结果 对数据采集板卡输入250 MHz高频信号进行2 GHz数据采集,并对采样结果进行数据分析,得到高速数据采集系统的SNR为44.6639,ENOB为7.1,满足设计要求.结论 基于ADC技术的高速数据采集系统是生物质谱数据测量分析的一种快速可靠的路径和方法.     

Pathological changes in rabbit retina and its relationship with glutamic Acid after injuries from high-speed bullets

Purpose:To observe the pathological changes in rabbit retinas and the measure of glutamic acid levels in the vitreous body after suffering from high-speed bullet injuries.Methods:Rabbits eyeball contusion models were established with high-speed bullets,i.e,the rabbits eyes were shot with a fixed air rifle at a speed of 90 m/s.(using plastic bullets,weighing 0.201 g,on average).Retinal tissues treated with HE staining and were prepared for light microscopy examination and glutamate levels were tested at different time points after the injury.Results:Edema,exudation,hemorrhage,and rupture were evident in rabbit retinas following bullet injuries.Meanwhile,glutamate levels gradually increased as time proceeded.Conclusion:Visual impairment is related with retinal damages after high-speed bullet injuries.Increased glutamate concentration serves as a potential factor for aggravating retinal injuries.     

Relationship between visual span and reading performance in age-related macular degeneration

PURPOSE: Visual-span profiles are plots of letter-recognition accuracy as a function of letter position left and right of the point of fixation. Legge, Mansfield, and Chung [Legge, G. E., Mansfield, J. S., & Chung, S. T. L. (2001). Psychophysics of reading-XX. Linking letter recognition to reading speed in central and peripheral vision. Vision Research, 41(6), 725-743] proposed that reduced size of the visual span is a spatial factor limiting reading speed in patients with age-related macular degeneration (AMD). We have recently shown that a temporal property of letter recognition--the exposure time required for a high level of accuracy--is also a factor limiting reading speed in AMD [Cheong, A. M. Y., Legge, G. E., Lawrence, M. G., Cheung, S. H., & Ruff, M. (2007). Relationship between slow visual processing and reading speed in people with macular degeneration. Vision Research, 47, 2943-2965]. We measured the visual-span profiles of AMD subjects and assessed the relationship of the spatial and temporal properties of these profiles to reading speed. METHODS: Thirteen AMD subjects and 11 age-matched normals were tested. Visual-span profiles were measured by using the trigram letter-recognition method described by Legge et al. (2001). Each individual's temporal threshold for letter recognition (80% accuracy criterion) was used as the exposure time for measuring the visual-span profile. Size of the visual span was computed as the area under the profile in bits of information transmitted. The information transfer rate in bits per second was defined as the visual-span size in bits divided by the exposure time in sec. RESULTS: AMD visual-span sizes were substantially smaller (median of 23.9 bits) than normal visual-span sizes in central vision (median of 40.8 bits, p<.01). For the nine AMD subjects with eccentric fixation, the visual-span sizes (median of 20.6 bits) were also significantly smaller than visual spans of normal controls at 10 degrees below fixation in peripheral vision (median of 29.0 bits, p=.01). Information transfer rate for the AMD subjects (median of 29.5 bits/s) was significantly slower than that for the age-matched normals at both central and peripheral vision (median of 411.7 and 290.5 bits/s respectively, ps<.01). Information transfer rates were more strongly correlated with reading speed than the size of the visual span, and explained 36% of the variance in AMD reading speed. CONCLUSION: Both visual-span size and information transfer rate were significantly impaired in the AMD subjects compared with age-matched normals. Information transfer rate, representing the combined effects of a reduced visual span and slower temporal processing of letters, was a better predictor of reading speed in AMD subjects than was the size of the visual span.     

Gait initiation is dependent on the function of the paretic trailing limb in individuals with stroke

The purposes of this study were to compare the gait initiation task between individuals with chronic stroke and age-matched healthy controls, to determine whether the observed differences between groups could be attributed to the presence of a stroke or to differences in gait initiation speed, and to establish the gait initiation variables that relate with a faster gait initiation speed. All subjects initiated gait at their preferred speed, while control subjects were also asked to initiate gait at a speed that was comparable to the stroke group. It was found that while many temporal and kinetic differences were observed between the two groups, most were simply due to differences in gait initiation speed. Two variables that remained different when speed was controlled were the magnitude of the antero-posterior impulse generated by the paretic limb when it was used as either the leading or trailing limb. Kinetic parameters of the trailing limb (i.e. peak antero-posterior force and impulse) were also found to correlate with the gait initiation speed for the non-paretic lead limb condition. The results suggest that the propulsive function of the paretic limb when used as the trailing limb is a key area to address in the rehabilitation of gait initiation for individuals with stroke.     

Early development of sensitivity to radial motion at different speeds

We examined the sensitivity of 2- and 3-month-old infants to radial expansion/contraction at various speeds. The stimuli comprised one radial motion pattern (expansion or contraction) and one translational motion pattern (up, down, left or right; counterbalanced across infants) placed side by side. The two patterns in each stimulus had the same speed. Three-month-old infants could discriminate between radiation and translation, even under relatively low speeds (5.31 and 2.66°/s), whereas discrimination between the two patterns by 2-month-old infants was very limited. Thus, the range of speeds at which infants can detect radial expansion/contraction changes extensively between 2 and 3 months of age. This change in radial motion sensitivity may reflect the development of cortical motion mechanisms in the dorsal pathway, which is specialised to detect radial motion.     

Athletic trainers' and physical therapists' perceptions of the effectiveness of psychological skills within sport injury rehabilitation programs

CONTEXT: Psychological skills are alleged to augment sport-injury rehabilitation; however, implementation of mental imagery within rehabilitation programs is limited. OBJECTIVE: To examine attitudes of athletic trainers (ATs) and physical therapists (PTs) on the effectiveness of mental imagery, goal setting, and positive self-talk to improve rehabilitation adherence and recovery speed of injured athletes. DESIGN: The ATs and PTs were contacted via electronic or physical mailings to complete a single administration survey that measured their beliefs about the effectiveness of psychological skills for increasing adherence and recovery speed of injured athletes undergoing rehabilitation. SETTING: Professional member databases of the National Athletic Trainers' Association and the American Physical Therapy Association. PATIENTS OR OTHER PARTICIPANTS: Of the 1000 ATs and 1000 PTs who were selected randomly, 309 ATs (age = 34.18 +/- 8.32 years, years in profession = 10.67 +/- 7.34) and 356 PTs (age = 38.58 +/- 7.51 years, years in profession = 13.18 +/- 6.17) responded. MAIN OUTCOME MEASURE(S): The Attitudes About Imagery (AAI) survey measures attitudes about psychological skills for enhancing adherence and recovery speed of injured athletes. The AAI includes demographic questions and 15 items on a 7-point Likert scale measuring attitudes about the effectiveness of mental imagery, self-talk, goal setting, and pain control on rehabilitation adherence and recovery speed of injured athletes. Test-retest reliability ranged from .60 to .84 and Cronbach alphas ranged from .65 to .90. We calculated 1-way analyses of variance to determine whether differences existed in attitudes as a result of the professionals' education, training experience, and interest. RESULTS: Mean differences were found on attitudes about effectiveness of psychological skills for those who reported formal training and those who reported interest in receiving formal training (P < .05). In addition, ATs held more positive attitudes than PTs on 9 of 15 AAI items (P < .05). CONCLUSIONS: Overall, ATs and PTs held positive attitudes on the effectiveness of psychological skills to augment the rehabilitation process. Clinical implications regarding the use of mental skills are discussed.     

Three‐compartment T1 relaxation model for intracellular paramagnetic contrast agents

The goal of this work was to elaborate a model describing the effective longitudinal relaxation rate constant R₁ for ¹H₂O in three cellular compartments experiencing possible equilibrium water exchange, and to apply this model to explain the effective R₁ dependence on the overall concentration of a cell‐internalized Gd³⁺‐based contrast agent (CA). The model voxel comprises three compartments representing extracellular, cytoplasmic, and vesicular (e.g., endosomal, lysosomal) subcellular spaces. Relaxation parameters were simulated using a modified Bloch–McConnell equation including magnetization exchange between the three compartments. With the model, several possible scenarios for internalized CA distribution were evaluated. Relaxation parameters were calculated for contrast agent restricted to the cytoplasmic or vesicular compartments. The size or the number of CA‐loaded vesicles was varied. The simulated data were then separately fitted with empirical mono‐ and biexponential inversion recovery expressions. The voxel CA‐concentration dependencies of R₁ can be used to qualitatively and quantitatively understand a number of different experimental observations reported in the literature. Most important, the simulations reproduced the relaxivity “quenching” for cell‐internalized contrast agent that has been observed. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

The impact of fluctuations in boat velocity during the rowing cycle on race time

In competitive rowing, the fluctuations in boat velocity during the rowing cycle are associated with an increased water resistance of the boat as compared with a boat moving at a constant velocity. We aimed to quantify the influence of the increased water resistance on race time using a mathematical approximation, based on the increase in physiological power being proportional to the 2nd power of boat speed. Biomechanical data (oar force, rowing angle, boat velocity, and boat acceleration) were measured when eight elite coxless pair crews performed a rowing test with a stepwise increasing stroke rate (SR: 20, 24, 28, and 32 min⁻¹) that successively increased the mean boat speed. The results revealed a +4.59 s (SR 24.2) to +5.05 s (SR 31.5) 2000-m race-time difference compared with a boat hypothetically moving without velocity fluctuations. Velocity fluctuations were highly correlated with SR ( r =0.93) because the accelerations of the rowers' body mass and the mass of the counteracting boat increase with SR. The possibilities to reduce velocity fluctuations and therefore race time are limited. For elite rowers, race time may be slightly reduced by a moderate reduction in SR that is compensated by an increased force output for each stroke.     

Theory of Q‐ball imaging redux: Implications for fiber tracking

Q‐ball imaging is widely used to determine fiber directions for fiber tracking. In q‐ball imaging the directional dependence of water diffusion in tissue is described by Tuch's orientation distribution function (ODF); a different function, the q‐ball orientation distribution function, is measured using high angular resolution magnetic resonance diffusion imaging (HARDI). Tuch's ODF is assumed to be well approximated by the q‐ball ODF. In this study it is shown that: 1) the q‐ball ODF is not a good approximation to Tuch's ODF; 2) the properties of the q‐ball ODF depend strongly on q, the area of the diffusion sensitization gradients; and 3) the q‐ball ODF for a composite system is the weighted average of the q‐ball ODFs for each subsystem, but the weighting factor is the product of the percent composition and a renormalization factor. In addition, a derivation is presented of the q‐ball ODF for a system described by a Gaussian distribution and expressions are derived for both the dependence of the angular resolution on q and for the relation between the angular resolution and the signal loss. These findings might be useful in the design and interpretation of fiber‐tracking experiments. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.