Theory and practice of a portable photosynthesis instrument

Abstract. Theory and practice of non-steady-state portable photosynthesis instruments (LI-6000 and 6200, LI-COR Inc., Nebraska, U.S.A.) are presented. Mass balance equations for the time dependence of H₂O and CO₂ mol fractions within the leaf chamber were used to describe instrument function. Measurements for each run were fitted to an exponential function to estimate average rates of CO₂ assimilation and transpiration during the measurement period. Stomatal conductances and intercellular CO₂ mol fractions were also computed. Linear data analysis used in the LI-6200 produced similar results for assimilation rates, stomatal conductances and intercellular CO₂ concentrations compared to a more rigorous nonlinear analysis, provided humidity within the chamber was kept constant during the measurement period. Instrument performance for CO₂ fluxes was confirmed by injecting pure CO₂ at steady rates from a microsyringe into the chamber. Miniature evaporimeters were designed to check H₂O flux measurements. Significant discrepancies were observed between LI-6200 estimates of H₂O fluxes and direct measurement and errors were attributed to adsorption desorption of water vapour on chamber walls or to leaks. The leaf chamber should be stored at humidities and temperatures similar to those during measurement conditions for maximum reliability of results.     

The use of natural language to communicate the perception of vibrotactile stimuli

This study explores the subjective use of adjectives to verbally communicate vibrotactile stimulation across multiple frequencies. In total, nine different vibrotactile stimulus frequencies (10–300?Hz) were utilized, and subjective evaluation methods, which involved adjectives, were used to assess the sensory representations of the participants (18 healthy male participants; mean age, 22.9 years; standard deviation, 3.5). Sensory terms such as ‘slow,’ ‘protruding,’ and ‘thick’ were used as representative expressions to describe low-frequency (10–100?Hz) vibrotactile stimulations, while ‘fast,’ ‘shallow,’ and ‘tickly’ were used to describe high-frequency (225–300?Hz) vibrotactile stimulations. At the frequencies of 150 and 200?Hz, no characteristic word was found because there was no difference in subjective evaluation scores from other low or high frequencies. The results suggest that vibrotactile stimulation at different frequencies induce diverse sensory representations, owing to not only the motion and shape of the stimuli but also the subjective responses of the perceivers. The results of this study could be utilized in developing affective haptic devices in the future.     

Validation of a portable EMG device to assess muscle activity during free-living situations

Portable amplifiers that record electromyograms (EMGs) for longer than four hours are commonly priced over $20,000 USD. This cost, and the technical challenges associated with recording EMGs during free-living situations, typically restrict EMG use to laboratory settings. A low-cost system (μEMG; OT Bioelecttronica, 100€), using specialized concentric bipolar electrodes, has been developed specifically for free-living situations. The purpose of this study was to validate the μEMG system by comparing EMGs from μEMG with a laboratory-based alternative (Telemyo 900; Noraxon USA, Inc.). Surface EMGs from biceps brachii (BB) and tibialis anterior (TA) of ten subjects were recorded simultaneously with both systems as subjects performed maximal voluntary contractions (MVCs), submaximal contractions at 25%, 50%, and 75% MVC, seven simulated activities of daily living (ADLs), and >60 min of simulated free-living inside the laboratory. In general, EMG parameters (e.g., average full-wave rectified EMG amplitude) derived from both systems were not significantly different for all outcome variables, except there were small differences across systems in baseline noise and absolute EMG amplitudes during MVCs. These results suggest that μEMG is a valid approach to the long-term recording of EMG.     

Accuracy and precision of a wrist movement when vibrotactile prompts inform movement speed

Abstract

Purpose: This study investigated the effect of movement speed on task accuracy and precision when participants were provided temporally oriented vibrotactile prompts. Materials and methods: Participants recreated a simple wrist flexion/extension movement at fast and slow speeds based on target patterns conveyed via vibrating motors affixed to the forearm. Each participant was given five performance-blinded trials to complete the task at each speed. Movement accuracy (root mean square error) and precision (standard deviation) were calculated for each trial in both the spatial and temporal domains. Results: 28 participants completed the study. Results showed temporal accuracy and precision improved with movement speed (both: fast?>?slow, p?<?0.01), while all measures improved across trials (temporal accuracy and precision: trial 1?<?all other trials, p?<?0.05; spatial accuracy: trial 1 and 2?<?all other trials, p?<?0.05; spatial precision: trial 1?<?all other trials, p?<?0.05). Conclusions: Overall, temporal and spatial results indicate participants quickly recreated and maintained the desired pattern regardless of speed. Additionally, movement speed seems to influence movement accuracy and precision, particularly within the temporal domain. These results highlight the potential of vibrotactile prompts in rehabilitation paradigms aimed at motor re-education.     

Identification of a threshold level to assess essential derivation in durum wheat

Essentially derived varieties (EDV) are considered to be those that are obtained from an original variety by means of methods that do not substantially modify its genetic structure, and whose characteristics are therefore derived from the original. The identification of EDV requires the definition of a threshold value of genetic similarity between the new and the original variety that if exceeded would suggest derivation. Although protocols for estimating genetic similarities based on molecular markers have been proposed for EDV identification in some species, no information was available for durum wheat (Triticum durum). A set of 60 genotypes (F8 or F9 lines and their parents) representing different levels of relatedness were profiled using 14 (later reduced to 13 by excluding the most deviant one) amplified fragment length polymorphism (AFLP) primer combinations and 109 simple sequence repeat (SSR) loci evenly distributed in the genome. For both marker types, an EDV threshold was calculated according to the “tail principle” on the distributions of Jaccard similarities among the subset of 39 independent genotypes. For all pairs of closely related lines branched in advanced generations (F7–F8), or for all but one pairs of lines deriving from the same F4 family, similarities exceeded the thresholds for both marker types, indicating a very good agreement in showing cases of suspected derivation. Compared to SSR markers, AFLP markers appear more suitable for assessing essential derivation because of their superior cost-efficiency. Based on 13 AFLP primer combinations, a threshold of 0.96 Jaccard similarity is proposed, below which a variety should be considered to be independently derived.     

Sucrose acceptance threshold: a way to measure sugar perception in ants

Variation in the perception of sweet taste is a well-known phenomenon in the animal kingdom. Well-established protocols for measuring sucrose responsiveness in non-social insects and honeybees have made it possible to understand many aspects of their biology and behaviour. Ants are also advanced social insects that present a plethora of life histories with diverse strategies and behaviours; however, a universal paradigm possible to measure this response in different ant species has not yet been developed. Here, we present a protocol for measuring the sucrose acceptance threshold (SAT) under controlled conditions in harnessed ants with different feeding habits. By testing the response to antennal and palp sucrose stimulation and using the occurrence of licking as the response, we developed a non-ambiguous evaluation that allowed easy detection of threshold changes. The results showed that the response to both antennal and palp stimulation varied widely among species. Some species licked in response to antennal stimulation while others did so in response to palp stimulation. Using the appropriate kind of stimulation, we tested the SAT protocol in ants of different genera and ants of the same species with different levels of sugar reserve. The differences detected in both cases imply that the protocol is appropriate for measuring and detecting variations in sugar perception in ants.     

Q-cgi: new techniques to assess variation in perception applied to facial attractiveness

We present novel methods for assessing variation in the perception of subjective cues based on a fusion of Q-methodology with computer graphics techniques. Participants first Q-sort face stimuli based upon a subjective quality; a randomization-based statistic is then calculated to test whether groups of participants differ in their perception. Computer graphics are then used to extract and illustrate the differences in the manner which participants sorted so that the differences can be quantified. As a demonstration, the technique is applied to investigate the effects of prospective relationship duration and of sexual restrictiveness on the characteristics which participants find attractive in photographs of opposite-sex faces. Results show that in a naturally varying set of faces, female participants prefer facial cues related to masculinity for short-term relationships, whereas characteristics related to positive personality attributes are preferred for long-term relationships. For short-term relationships, male participants appear to prefer more feminine, youthful faces. Preferences of individuals with less restricted sexual strategy paralleled short-term preferences in that more feminine female faces and more masculine male faces were preferred.     

The threshold of perception of angular acceleration as a function of duration

The threshold for rotation about the yaw axis was determined for constant acceleration stimuli as a function of their duration in the range from 3 to 25 s. From the torsion-swing model the following theoretical equation can be derived: 1 $$a_{{\text{thr}}} = {C \mathord{\left/ {\vphantom {C {\left[ {1 - \exp \left( { - {{t_s } \mathord{\left/ {\vphantom {{t_s } {\tau _1 }}} \right. \kern-\nulldelimiterspace} {\tau _1 }}} \right)} \right]}}} \right. \kern-\nulldelimiterspace} {\left[ {1 - \exp \left( { - {{t_s } \mathord{\left/ {\vphantom {{t_s } {\tau _1 }}} \right. \kern-\nulldelimiterspace} {\tau _1 }}} \right)} \right]}}$$ , where a _thr=acceleration amplitude at threshold, t _s =duration of the acceleration, τ₁=time constant, C=threshold for very long stimuli. According to this formula the Mulder product (i.e. the product of the threshold acceleration amplitude and the duration of the stimulus) is constant for durations up to 0.3 τ₁. The best fit of this theoretical function to the somatosensory data is found for τ₁=14.5 s, and C=0.22⁰/s ². The time within the Mulder product is constant (about 5s) is doubtless due to the mechanics of the semicircular canals. For the oculogyral data a lower value of τ₁ is found. We do not have any explanation for this lower value.     

Developing a theory-based instrument to assess the impact of continuing professional development activities on clinical practice: a study protocol

Background

Continuing professional development (CPD) is one of the principal means by which health professionals (i.e. primary care physicians and specialists) maintain, improve, and broaden the knowledge and skills required for optimal patient care and safety. However, the lack of a widely accepted instrument to assess the impact of CPD activities on clinical practice thwarts researchers' comparisons of the effectiveness of CPD activities. Using an integrated model for the study of healthcare professionals' behaviour, our objective is to develop a theory-based, valid, reliable global instrument to assess the impact of accredited CPD activities on clinical practice.

Methods

Phase 1: We will analyze the instruments identified in a systematic review of factors influencing health professionals' behaviours using criteria that reflect the literature on measurement development and CPD decision makers' priorities. The outcome of this phase will be an inventory of instruments based on social cognitive theories. Phase 2: Working from this inventory, the most relevant instruments and their related items for assessing the concepts listed in the integrated model will be selected. Through an e-Delphi process, we will verify whether these instruments are acceptable, what aspects need revision, and whether important items are missing and should be added. The outcome of this phase will be a new global instrument integrating the most relevant tools to fit our integrated model of healthcare professionals' behaviour. Phase 3: Two data collections are planned: (1) a test-retest of the new instrument, including item analysis, to assess its reliability and (2) a study using the instrument before and after CPD activities with a randomly selected control group to explore the instrument's mere-measurement effect. Phase 4: We will conduct individual interviews and focus groups with key stakeholders to identify anticipated barriers and enablers for implementing the new instrument in CPD practice. Phase 5: Drawing on the results from the previous phases, we will use consensus-building methods to develop with the decision makers a plan to implement the new instrument.

Discussion

This project proposes to give stakeholders a theory-based global instrument to validly and reliably measure the impacts of CPD activities on clinical practice, thus laying the groundwork for more targeted and effective knowledge-translation interventions in the future.

     

The auditory sensory epithelium: the instrument of sound perception

The auditory sensory epithelium is the specialized region of the cochlear epithelium that transduces sound. It is composed of a highly ordered, repeated array of mechanosensory hair cells and nonsensory supporting cells that run along the length of the cochlea. On the apical surface of the hair cells is a specialized structure called the hair bundle that deflects in response to sound vibration, resulting in depolarization of the hair cell and neurotransmitter release. Formation of the auditory sensory epithelium during embryogenesis involves strict control of both cell proliferation and cell patterning. Misregulation of these events can lead to congenital hearing loss, and damage to the auditory sensory epithelium during adult life can lead to adult-onset deafness. This paper reviews recent data on the formation of the auditory sensory epithelium during embryogenesis, the identification of components of the sound transduction apparatus, and advances in the treatment of hearing impairment.     

Optical-geometrical parameters and perception threshold of the fragmented contour figures

The thresholds of recognition of line drawings of common objects were measured using the Gollin-test procedure, in which separate random line fragments are displayed cumulatively up to the point of recognition. It was shown that the mean percentage of contour displayed at threshold recognition for different images was always about 12.5%, despite inter-subject variability between 5% and 25%. The comparative and spatial-frequency analysis of the geometrical parameters of images was carried out for different levels of fragmentation (before threshold, at threshold, and for the complete contour). The magnitude information of the Fourier domain image of figures was characterized by maximum at low and high levels of fragmentation, but at recognition threshold fragmentation it was characterized by minimum variability.     

Considerations in the construction of an instrument to assess attitudes regarding critical illness gene variation research

Clinical studies conducted in intensive care units are associated with logistical and ethical challenges. Diseases investigated are precipitous and life-threatening, care is highly technological, and patients are often incapacitated and decision-making is provided by surrogates. These investigations increasingly involve collection of genetic data. The manner in which the exigencies of critical illness impact attitudes regarding genetic data collection is unstudied. Given interest in understanding stakeholder preferences as a foundation for the ethical conduct of research, filling this knowledge gap is timely. The conduct of opinion research in the critical care arena is novel. This brief report describes the development of parallel patient/surrogate decision-maker quantitative survey instruments for use in this environment. Future research employing this instrument or a variant of it with diverse populations promises to inform research practices in critical illness gene variation research.     

A solid-state,portable instrument for measurement of chlorophyll luminescence induction in plants

A newly developed compact instrument is described for the measurement of chlorophyll luminescence induction in plants. The instrument operates with a pulsed light emitting diode (LED) as light source and a photodiode as luminescence detector. A special emitter-detector geometry provides for high irradiance of the sample and efficient collection of luminescence by the detector. With insertion of appropriate filters the same probe is also suited for measuring prompt chlorophyll fluorescence. The instrument shows considerable flexibility with respect to pulse frequency, relative lengths of light/dark intervals and luminescence sampling periods. Due to a selective amplifier system only that part of luminescence is processed which is induced by the individual excitation pulses. By this approach, the problem of slow phase accumulation, encountered with conventional phosphoroscopes, is eliminated. Some examples are given for system operation, demonstrating satisfactory performance in measurements with intact leaves and isolated chloroplasts.     

Relationship between vibrotactile detection threshold in the Pacinian channel and complex mechanical modulus of the human glabrous skin

The goal of this study was to investigate the relationship between the psychophysical vibrotactile thresholds of the Pacinian (P) channel and the mechanical properties of the skin at the fingertip. Seven healthy adult subjects (age: 23–30) participated in the study. The mechanical stimuli were 250-Hz sinusoidal bursts and applied with cylindrical contactor probes of radii 1, 2, and 3.5?mm on three locations at the fingertip. The duration of each burst was 0.5?s (rise and fall time: 50?ms). The subjects performed a two-interval forced-choice task while the stimulus levels changed for tracking the threshold at 75% probability of detection. There were significant main effects of contactor radius and location (two-way ANOVA, values of p?<?0.001). The thresholds decreased as the contactor radius increased (i.e., spatial summation effect) at all locations. The thresholds were lowest near the whorl at the fingertip. Additionally, we measured the mechanical impedance (specifically, the storage and loss moduli) at the contact locations. The storage moduli did not change with the contactor location, but the loss moduli were lowest near the whorl. While the loss moduli decreased, the storage moduli increased (e.g., more springiness) as the contactor radius increased. There was moderate and barely significant correlation between the absolute thresholds and the storage moduli (r?=?0.650, p?=?0.058). However, the correlation between the absolute thresholds and the loss moduli was high and very significant (r?=?0.951, p?<?0.001). The results suggest that skin mechanics may be important for locally shaping psychophysical detection thresholds, which would otherwise be expected to be constant due to uniform Pacinian innervention density at the fingertip.     

Variability in vibration perception threshold among sites: a potential source of error in biothesiometry

Vibration perception threshold was measured with a biothesiometer by a single observer at both medial malleoli and both big toes in 110 diabetic patients aged 15-65 selected at random and in 64 non-diabetic subjects aged 20-65. The vibration perception threshold showed appreciable individual variation both between contralateral sites and between ipsilateral sites, differing by at least 30% between the big toes in 26 (24%) of the diabetic patients and 16 (25%) of the non-diabetic group. Variability between sites was significantly greater in the diabetics than the normal subjects. The vibration perception threshold exceeded published normal values at one or more sites in 22 of the diabetic patients but at all four sites in only four.The wide variability in vibration perception threshold among sites may be due to the tissue characteristics locally and, in diabetic patients, possibly to asymmetric neuropathy. Biothesiometer readings at single or unilateral sites may be unrepresentative or misleading.     

Influence of body size on the electric current perception threshold]

Although the threshold for electric current perception is of great importance for safety considerations and safety regulations, important aspects remain unsolved, e.g. the role of age or body size. In the present study measurements of the perception threshold were performed in 790 persons aged between 18 and 82 years randomly selected from the general population. For the first time, the composition and size of the sample were selected such as to allow extrapolation to the general population. The results reveal not only statistically significant gender differences in the perception threshold but also statistically significant relationships between perception threshold and body size. The assumption that the differences in body size between men and women are responsible for the gender-specific difference in electric current perception threshold was not confirmed in this study.     

An animal model to assess aversion to intra-oral capsaicin: increased threshold in mice lacking substance p.

Despite the widespread consumption of products containing chemicals that irritate the oral mucosa, little is known about the underlying neural mechanisms nor is there a corresponding animal model of oral irritation. We have developed a rodent model to assess aversion to capsaicin in drinking water, using a paired preference paradigm. This method was used to test the hypothesis that the neuromodulator substance P (SP) plays a role in the detection of intra-oral capsaicin. 'Knockout' (KO) mice completely lacking SP and neurokinin A due to a disruption of the preprotachykinin A gene and a matched population of wild-type (WT) mice had free access to two drinking bottles, one containing water and the other capsaicin at various concentrations. Both KO and WT mice showed a concentration-dependent aversion to capsaicin. KO mice consumed significantly more capsaicin than WT at a single near threshold (1.65 microM) concentration, indicating that SP plays a limited role in the detection and rejection of oral irritants.