How many subjects are needed in a longitudinal birth cohort study?

One of the first decisions that needs to be taken when planning a birth cohort concerns the size of the study. This in turn will depend on the research questions to be answered and thence whether environmental exposures and outcomes are measured on a continuum or as dichotomous variables. Here we describe ways in which different birth cohorts have addressed this issue and explore the advantages of smaller detailed studies over larger less-detailed studies.     

Selection of Single Nucleotide Polymorphisms for Association Studies in Candidate Genes

Comparison of polymorphic sites such as single nucleotide polymorphisms (SNPs) within a gene between cases and controls may be useful for establishing a role of this gene in disease susceptibility. The approach includes two steps: the first step is the discovery of the different SNPs within the candidate gene and the second step is the association testing per se that can be done on the entire set of sites discovered or on a subset of these sites only. Selecting a subset of sites may increase the power to detect the association with the candidate gene since a smaller number of tests would then be performed. We proposed a strategy to select sites within a candidate gene and applied it on the Genetic Analysis Workshop 12 candidate gene data. Using these selected sites, we detected an association with candidate genes 1 and 6. © 2001 Wiley‐Liss, Inc.     

Multidimensional analysis of metabolism contributions involved in running track tests

It is difficult to interpret the training induced changes in middle-distance running, since numerous aerobic and anaerobic determinants of the performance are interdependent. Several aerobic and anaerobic tests are available but their results, particularly those from anaerobic tests, may be discordant, not providing univocal interpretation of training. The purpose of this study is to use a multidimensional approach to distinguish aerobic and anaerobic capacities assessed by two running tests on a track: the maximal anaerobic running test (MART) and V(O2max) tests. Eleven runners carried out two maximal tests on a synthetic track before and after a 4-week training period: (i) a maximal test to determine V(O2max), the velocity associated with V(O2max) (vV(O2max)) and the velocity at the lactate threshold (v(LT)), (ii) a maximal anaerobic running test to estimate anaerobic capacity. An all-out test run at v(LT)+50% of the difference between v(LT) and vV(O2max), known to be affected by both aerobic and anaerobic energy production, was used to test this approach. A principal components analysis (PCA) shows that two components (i.e., aerobic and anaerobic) explained 79% of the variation in the physiological variables. The PCA suggests that V(O2max) and MART tests assess the aerobic and the anaerobic capacities, respectively. In contrast, the performance in the all-out test is affected by both aerobic and anaerobic energy production. The PCA shows that v(LT) and DeltaP (difference between the maximal power of the MART and V(O2max)) are clear markers of the long-term endurance and the anaerobic capacity, respectively. This multidimensional approach can be a useful way to disentangle the aerobic and anaerobic components of track tests.     

A treadmill test of sprint running

Anaerobic power is characterized by a high degree of specificity regarding both the recruited muscles as well as the recruitment pattern. The popular Wingate Anaerobic Test (WAnT) is a cycling test that does not satisfy the need for a running-specific anaerobic test. We describe such a test, using a novel type of a commercially available treadmill (BRL 1800, Gymrol, France). The ergometer is equipped with a torque motor to neutralize the frictional resistance of the treadmill belt, and a hip-belt harness connected to a horizontal rod. Force applied to the harness is monitored by a strain gauge mounted on the rod, while vertical movement is monitored by a potentiometer at the posterior fixed end of the rod. These, in conjunction with the treadmill belt speed, enable the computation of horizontal and vertical power as well as the combined total output. Power is calculated both as 'peak' power (highest 2.5 s segment) and 'mean' power (20 s duration). Preliminary results of young athletes were generally consistent with the expected age-related changes in anaerobic power. Values obtained on the anaerobic treadmill were always higher than the corresponding WAnT values previously obtained in comparable age groups. The higher values were probably due to the larger muscle mass involved and the shorter peak and mean power durations (2.5 and 20 s versus 5 and 30 s in the WAnT, respectively). This test should enable not only running-specific anaerobic power monitoring but also the characterization of the relationship between the horizontal and vertical components of that power.     

使用电力载波技术实现中央控制电子钟

本文应用电力载波技术，实现远端时钟的中央控制。系统通过电力载波芯片从电力线上收发控制信号，中央控制端发送的时钟校准信号到电力线网络，接人网络的远端时钟接收到校准信号后，由微处理器解析数据调整受控端时钟显示，从而实现时钟的中央控制。     

医疗设备开关电源的维修

介绍了阿洛卡SSD2000开关电源的工作原理和常见故障的检修方法。     

The effects of THA on scopolamine and nucleus basalis lesion-induced EEG slowing

The effectiveness of THA (an anticholinesterae) on scopolamine (0.4 mg/kg) and nucleus basalis (NB) lesion-induced change in neocortical spectral electroencephalography (EEG) were investigated. Scopolamine increased the amplitudes of all the spectral components in waking-immobility. In the movement-related EEG spectral values, only the alpha power was increased. THA 7.5 mg/kg, but not THA 3 mg/kg, could reverse scopolamine-induced amplitude change. NB lesioning increased delta and theta amplitudes, but decreased beta amplitude. Delta amplitude was increased during movement recordings in NB-lesioned rats. THA 7.5 mg/kg and pilocarpine 10 mg/kg, but not THA 3 mg/kg, could partially reverse the increase of delta and theta amplitudes induced by NB lesions. However, the beta power decrease could not be restored with cholinomimetics. This study demonstrates that quantitative EEG activity analysis may reflect the THA-induced restoration of the function of the cholinergic nucleus basalis.     

High-quality recording of bioelectric events

A multichannel instrumentation amplifier, developed to be used in a miniature universal eight-channel amplifier module, is described. After discussing the specific properties of a bioelectric recording, the difficulties of meeting the demanded specifications with a design based on operational amplifiers are reviewed. Because it proved impossible to achieve the demanded combination of low noise and low power consumption using commercially available operational amplifiers, an amplifier equipped with an input stage with discrete transistors was developed. A new design concept was used to expand the design to a multichannel version with an equivalent input noise voltage of 0·35 μV RMS in a bandwidth of 0·1–100 Hz and a power consumption of 0·6 mW per channel. The results of this study are applied to miniature, universal, eight-channel amplifier modules, manufactured with thick-film production techniques. The modules can be coupled to satisfy the demand for a multiple of eight channels. The low power consumption enables the modules to be used in all kinds of portable and telemetry measurement systems and simplifies the power supply in stationary measurement systems.