抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

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Principles Of Fluorescence Spectroscopy

Photoplethysmography and its application in clinical physiological measurement

Foot plantar pressure is the pressure field that acts between the foot and the support surface during everyday locomotor activities. Information derived from such pressure measures is important in gait and posture research for diagnosing lower limb problems, footwear design, sport biomechanics, injury prevention and other applications. This paper reviews foot plantar sensors characteristics as reported in the literature in addition to foot plantar pressure measurement systems applied to a variety of research problems. Strengths and limitations of current systems are discussed and a wireless foot plantar pressure system is proposed suitable for measuring high pressure distributions under the foot with high accuracy and reliability. The novel system is based on highly linear pressure sensors with no hysteresis.

Foot plantar pressure measurement system: a review.

Eye tracking has a long history in medical and psychological research as a tool for recording and studying human visual behavior. Real-time gaze-based text entry can also be a powerful means of communication and control for people with physical disabilities. Following recent technological advances and the advent of affordable eye trackers, there is a growing interest in pervasive attention-aware systems and interfaces that have the potential to revolutionize mainstream human-technology interaction. In this chapter, we provide an introduction to the state-of-the art in eye tracking technology and gaze estimation. We discuss challenges involved in using a perceptual organ, the eye, as an input modality. Examples of real life applications are reviewed, together with design solutions derived from research results. We also discuss how to match the user requirements and key features of different eye tracking systems to find the best system for each task and application.

Eye Tracking and Eye-Based Human–Computer Interaction

A measurement method to measure biopotentials with a passive LC resonator is presented. The sensor consists of an LC resonance circuit where the capacitive component is a varactor and the biopotential electrodes are connected over the varactor ends. This induces a change in the varactor capacitance which can be measured over an inductive link as modified reflected impedance. The sensor itself dissipates virtually no energy at all but of course, some energy is lost in form of resistive losses in the sensor wires and components. The sensor is inexpensive to manufacture and since it is a totally passive device, it is very suitable for implantable applications. Two different measurement methods to sense the reflected impedance are also presented: a slope detector and a phase locked detector. Measurement results from human ECG are discussed that are measured with the both suggested measurement methods. The sensor is proven to be suitable for biopotential measurements with some limitations regarding the movements between the sensor and the receiver device. The properties and performance of the two different measurement devices are discussed. The measurement range, i.e. distance between the sensor and the measurement coils was approximately 5 cm in air for the both measurement devices. However, it seems that the phase locked measurement device suits better to the measurements than the slope detector since its signal-to-noise ratio remains almost constant throughout the measurement range (distance).

Totally passive wireless biopotential measurement sensor by utilizing inductively coupled resonance circuits

A system for unobtrusive night-time electrocardiogram (EKG) and heart rate variability (HRV) monitoring as well as data analysis methods are presented, comparing bed sheet HR and HRV values with corresponding parameters obtained by a reference measurement. Our system uses eight embroidered textile electrodes attached laterally to a bed sheet for measuring bipolar contact EKG from multiple channels. The electrodes are arranged in a line so that at least two adjacent electrodes make sufficient skin contact. The focus of the signal processing development has been on selecting the best measurement channel for further analysis and minimizing the amount of incorrectly detected R-peaks. The test measurements were performed with four healthy men without previously known cardiac disorders and one who frequently had premature ventricular contractions (ectopic beats). For healthy test subjects, an average of 94.9% heartbeat detection coverage was achieved with the system during 29 measurement nights (in total 213.8 h of data). In most cases, the quality of the signal obtained from bed sheet electrodes is good enough for the computer-assisted cardiac arrhythmia detection. Applications for EKG derived RR-interval data include the calculation of HRV parameters that can be utilized in sleep quality analysis and other wellness-related topics as well as sleep apnoea detection.

Night-Time EKG and HRV Monitoring With Bed Sheet Integrated Textile Electrodes

A light-weight, wearable, wireless gaze tracker with integrated selection command source for human-computer interaction is introduced. The prototype system combines head-mounted, video-based gaze tracking with capacitive facial movement detection that enable multimodal interaction by gaze pointing and making selections with facial gestures. The system is targeted mainly to disabled people with limited mobility over their hands. The hardware was made wireless to remove the need to take off the device when moving away from the computer, and to allow future use in more mobile contexts. The algorithms responsible for determining the eye and head orientations to map gaze direction to on-screen coordinates are presented together with the one to detect movements from the measured capacitance signal. Point-and-click experiments were conducted to assess the performance of the multimodal system. The results show decent performance in laboratory and office conditions. The overall point-and-click accuracy in the multimodal experiments is comparable to the errors in previous research on head-mounted, single modality gaze tracking that does not compensate for changes in head orientation.

A Wearable, Wireless Gaze Tracker with Integrated Selection Command Source for Human‐Computer Interaction

A head cap made of fabric for measuring EOG and facial EMG signals is presented. Reusable and easy to use electrodes, embroidered of silver coated thread, are integrated into the cap. A two-way wireless data transmission link operating at license free 2.4 GHz frequency band is used for transferring the 16-bit measurement data, sampled with 1 kHz frequency from six channels at maximum, to the receiver device connected to a PC. Tailored PC software is used for displaying the signals and controlling the measurement parameters. The measurement system is intended for recording facial expressions during human emotion studies but it can also be utilized in computer user interface control. The paper shows preliminary results from EOG and facial EMG measurements

Wireless Head Cap for EOG and Facial EMG Measurements

A capacitive facial movement detection method designed for human-computer interaction is presented. Some point-and-click interfaces use facial electromyography for clicking. The presented method provides a contactless alternative. Electrodes with no galvanic coupling to the face are used to form electric fields. Changes in the electric fields due to facial movements are detected by measuring capacitances between the electrodes. A prototype device for measuring a capacitance signal affected by frowning and lifting eyebrows was constructed. A commercial integrated circuit for capacitive touch sensors is used in the measurement. The applied movement detection algorithm uses an adaptive approach to provide operation capability in noisy and dynamic environments. Experimentation with 10 test subjects proved that, under controlled circumstances, the movements are detected with good efficiency, but characterizing the movements into frowns and eyebrow lifts is more problematic. Integration with a two-dimensional (2D) pointing solution and further experiments are still required.

Jarmo Verho

Papers

Totally passive wireless biopotential measurement sensor by utilizing inductively coupled resonance circuits

Night-Time EKG and HRV Monitoring With Bed Sheet Integrated Textile Electrodes

A Wearable, Wireless Gaze Tracker with Integrated Selection Command Source for Human‐Computer Interaction

Wireless Head Cap for EOG and Facial EMG Measurements

Capacitive facial movement detection for human-computer interaction to click by frowning and lifting eyebrows : Assistive technology ()