A method to synchronise video cameras using the audio band

This paper proposes and evaluates a novel method for synchronisation of video cameras using the audio band. The method consists in generating and transmitting an audio signal through radio frequency for receivers connected to the microphone input of the cameras and inserting the signal in the audio band. In a software environment, the phase differences among the video signals are calculated and used to interpolate the synchronous 2D projections of the trajectories. The validation of the method was based on: (1) Analysis of the phase difference changes as a function of time of two video signals. (2) Comparison between the values measured with an oscilloscope and by the proposed method. (3) Estimation of the improvement in the accuracy in the measurements of the distance between two markers mounted on a rigid body during movement applying the method. The results showed that the phase difference changes in time slowly (0.150 ms/min) and linearly, even when the same model of cameras are used. The values measured by the proposed method and by oscilloscope showed equivalence (R2=0.998), the root mean square of the difference between the measurements was 0.10 ms and the maximum difference found was 0.31 ms. Applying the new method, the accuracy of the 3D reconstruction had a statistically significant improvement. The accuracy, simplicity and wide applicability of the proposed method constitute the main contributions of this work.     

Three-dimensional electrogoniometric gait recording

Gait recordings of twenty healthy subjects were made on a treadmill and on level ground by means of a light-weight computerised electrogoniometer. The angular excursions in three planes were recorded simultaneously with regard to hip, knee and ankle joints in both legs. Determinations of the mean values and dispersions were then made. In order to establish the reliability of the method tests and retests were performed. Also its validity was checked by comparing the goniometric recordings with concomitant measurements obtained by other methods. The reliability and validity of the method was found to be satisfactory. Apart from flexion of the hip and knee joints during stance phase (i.e. a difference of 2 and 2.4 degrees respectively), no difference was ascertained between walking on a treadmill and walking on level ground.     

Synchronisation of cancer cell lines of human origin using methotrexate

U937 human histiocytic lymphoma cell line and SW626 ovarian carcinoma line of human origin were synchronised using very low, nontoxic concentrations (0.04-0.08 microM for 16-24 h) of methotrexate (MTX) under standard culture conditions. Satisfactory synchrony was achieved to study S phase events. Various kinetic behaviours and biological properties of the synchronised cells are considered for characterisation of the system. MTX-synchronisation was compared with that induced by aphidicolin (APC) alone and by serum deprivation and APC. In some cancer cell lines MTX appears to be the best choice for obtaining highly synchronised cell populations without cytotoxicity or physiological perturbations.     

Heat production as a cell cycle monitoring parameter

A microcalorimetric method was applied to define the cell cycle by measuring heat production of mouse breast cancer cell line, FM3A. FM3A cells, were synchronised at the Go phase and produced 13.0 mu Watts (W) per 1 X 10(6) cells. Although the number of cells in fresh medium remained unchanged during the following 24 hour, a dramatic increase of heat production was observed and maximum heat (46.2 mu W) was produced by the cells at 24 hours when the cell cycle was presumably at the G2 phase. At 26 hours, although cell number increased, heat production decreased. Since the cells were not treated in any manner, this microcalorimetric method of measuring the cell cycle by monitoring heat production can be a very useful tool.     

Analysis of single-molecule mechanical recordings: application to acto-myosin interactions

Several laboratories have now developed methods to make single-molecule mechanical recordings from interacting pairs of biological molecules. The mechanical work done (product of force and distance) by a single biomolecular interaction is usually of the same order as thermal energy. Recordings made from non-processive, intermittently interacting, molecular motors such as acto-myosin therefore contain a large background of thermal noise. We have applied Page's test to analyse mechanical interactions between muscle myosin II's and F-actin recorded using an optical tweezers based single-molecule mechanical transducer. We compare Page's test with other variance-based methods and find it to be a robust method for analysing both simulated and real data sets. We discuss some of the problems associated with automatic detection of transient mechanical events in noisy data signals, and show that if the start and end points of individual events are known accurately then the events may be synchronised and combined to give more detailed information about different mechanical states.     

Fluctuations du taux d'AMP cyclique et des activites adenylate cyclase et AMP cyclique-phosphodiesterase dans les cultures synchrones d'un procaryote, Nocardia restricta

Cultures of Nocardia restricta, a prokaryote from the group of Actinomycetes, can be synchronised by diluting, in a fresh growth medium, cells already in stationary phase. The synchronisation of the cultures is monitored by examining the synchrony of DNA replication.In these synchronised cultures, the intracellular cyclic AMP level exhibits rythmic oscillations with a period equal to the generation time of the culture. There is only one peak per generation. The average ratio of maximum to minimum concentrations is at least 3.Cyclic AMP accumulates also in the medium with a step pattern. It appears in the medium during maximum production of cyclic AMP in the cell.The specific activity of adenylate cyclase (EC 4.6.1.1) measured in the 30 000 × g pellet of cell-free extracts also oscillates and correlates well with fluctuations in the cyclic AMP level. At the end of exponential growth, cyclic-AMP phosphodiesterase (EC 3.1.4.17) is detectable in the cells. The specific activity of this enzyme measured in the 30 000 × g supernatant of cell-free extracts shows also an oscillating pattern.To our knowledge it is the first time that such oscillations in the metabolism of cyclic AMP are described among prokaryotes. It is now possible to look at a link between this phenomenon and the cell cycle of the organism.     

Quantifying Plant Colour and Colour Difference as Perceived by Humans Using Digital Images

Human perception of plant leaf and flower colour can influence species management. Colour and colour contrast may influence the detectability of invasive or rare species during surveys. Quantitative, repeatable measures of plant colour are required for comparison across studies and generalisation across species. We present a standard method for measuring plant leaf and flower colour traits using images taken with digital cameras. We demonstrate the method by quantifying the colour of and colour difference between the flowers of eleven grassland species near Falls Creek, Australia, as part of an invasive species detection experiment. The reliability of the method was tested by measuring the leaf colour of five residential garden shrub species in Ballarat, Australia using five different types of digital camera. Flowers and leaves had overlapping but distinct colour distributions. Calculated colour differences corresponded well with qualitative comparisons. Estimates of proportional cover of yellow flowers identified using colour measurements correlated well with estimates obtained by measuring and counting individual flowers. Digital SLR and mirrorless cameras were superior to phone cameras and point-and-shoot cameras for producing reliable measurements, particularly under variable lighting conditions. The analysis of digital images taken with digital cameras is a practicable method for quantifying plant flower and leaf colour in the field or lab. Quantitative, repeatable measurements allow for comparisons between species and generalisations across species and studies. This allows plant colour to be related to human perception and preferences and, ultimately, species management.     

Oscillatory interactions between sensorimotor cortex and the periphery

Field potential recordings from motor cortex show oscillations in the beta-band (approximately 20 Hz), which are coherent with similar oscillations in the activity of contralateral contracting muscles. Recent findings have revised concepts of how this activity might be generated in the cortex, suggesting it could achieve useful computation. Other evidence shows that these oscillations engage not just motor structures, but also return from muscle to the central nervous system via feedback afferent pathways. Somatosensory cortex has strong beta-band oscillations, which are synchronised with those in motor cortex, allowing oscillatory sensory reafference to be interpreted in the context of the oscillatory motor command which produced it.     

Detecting determinism in short time series, with an application to the analysis of a stationary EEG recording

We have developed a new method for detecting determinism in a short time series and used this method to examine whether a stationary EEG is deterministic or stochastic. The method is based on the observation that the trajectory of a time series generated from a differentiable dynamical system behaves smoothly in an embedded phase space. The angles between two successive directional vectors in the trajectory reconstructed from a time series at a minimum embedding dimension were calculated as a function of time. We measured the irregularity of the angle variations obtained from the time series using second-order difference plots and central tendency measures, and compared these values with those from surrogate data. The ability of the proposed method to distinguish between chaotic and stochastic dynamics is demonstrated through a number of simulated time series, including data from Lorenz, R?ssler, and Van der Pol attractors, high-dimensional equations, and 1/f noise. We then applied this method to the analysis of stationary segments of EEG recordings consisting of 750 data points (6-s segments) from five normal subjects. The stationary EEG segments were not found to exhibit deterministic components. This method can be used to analyze determinism in short time series, such as those from physiological recordings, that can be modeled using differentiable dynamical processes.     

Synchronisation of Giardia lamblia: identification of cell cycle stage-specific genes and a differentiation restriction point

The intestinal parasite Giardia lamblia undergoes cell differentiations that entail entry into and departure from the replicative cell cycle. The pathophysiology of giardiasis depends directly upon the ability of the trophozoite form to replicate in the host upper small intestine. Thus, cell proliferation is tightly linked to disease. However, studies of cell cycle regulation in Giardia have been hampered by the inability to synchronise cultures. Here we report that Giardia isolates of the major human genotypes A and B can be synchronised using aphidicolin, a mycotoxin that reversibly inhibits replicative DNA polymerases in eukaryotic cells. Aphidicolin arrests Giardia trophozoites in the early DNA synthesis (S) phase of the cell cycle. We identified a set of cell cycle orthologues in the Giardia genome using bioinformatic analyses and showed that synchronised parasites express these genes in a cell cycle stage-specific manner. The synchronisation method also showed that during encystation, exit from the ordinary cell cycle occurs preferentially in G(2) and defines a restriction point for differentiation. Synchronisation opens up possibilities for further molecular and cell biological studies of chromosome replication, mitosis and segregation of the complex cytoskeleton in Giardia.     

Acute effect of static and dynamic stretching on hip dynamic range of motion during instep kicking in professional soccer players

The purpose of this study was to examine the effects of static and dynamic stretching within a pre-exercise warm-up on hip dynamic range of motion (DROM) during instep kicking in professional soccer players. The kicking motions of dominant legs were captured from 18 professional adult male soccer players (height: 180.38 ± 7.34 cm; mass: 69.77 ± 9.73 kg; age: 19.22 ± 1.83 years) using 4 3-dimensional digital video cameras at 50 Hz. Hip DROM at backward, forward, and follow-through phases (instep kick phases) after different warm-up protocols consisting of static, dynamic, and no-stretching on 3 nonconsecutive test days were captured for analysis. During the backswing phase, there was no difference in DROM after the dynamic stretching compared with the static stretching relative to the no-stretching method. There was a significant difference in DROM after the dynamic stretching compared with the static stretching relative to the no-stretching method during (a) the forward phase with p < 0.03, (b) the follow-through phase with p < 0.01, and (c) all phases with p < 0.01. We concluded that professional soccer players can perform a higher DROM of the hip joint during the instep kick after dynamic stretching incorporated in warm-ups, hence increasing the chances of scoring and injury prevention during soccer games.     

Cytosolic phospholipase A(2) activity during the ongoing cell cycle

Cytosolic phospholipase A(2) (cPLA(2)) is of special interest because it selectively releases arachidonic acid from membrane phospholipids. Arachidonic acid has been implicated to play an important role in various cellular responses. Recently arachidonic acid release and prostaglandin synthesis have been shown to be cell cycle dependent and therefore the activity of cPLA(2) during the ongoing cell cycle was investigated, using the mitotic shake off method for cell synchronisation. cPLA(2) activity was high in mitotic cells and decreased rapidly in the early G1 phase. A strong increase in activity was measured following the G1/S transition in both neuroblastoma and Chinese hamster ovary cells. The changes in activity were not due to a difference in cPLA(2) expression but due to phosphorylation of cPLA(2). Phosphorylation of cPLA(2) occurs through MAPK since the use of a specific MAPK kinase inhibitor and serum depletion of synchronised cells inhibited cPLA(2) activity.     

Phase-averaged characterization of respiratory sinus arrhythmia pattern

A method for the accurate time-domain characterization of respiratory sinus arrhythmia (RSA) pattern is presented and applied to two groups of healthy subjects to lay the baseline of RSA patterns and to underlay their features: response to standing, stability in successive recordings, and individuality of the shape of RSA pattern. RSA pattern is evaluated by selective averaging of heart rate (HR) changes from multiple respiratory cycles over the respiratory phase and represents the complete modulating function of HR by respiration. The RSA pattern is evaluated with free respiration and even in cases of severe arrhythmia. Estimation error is 6-8% in magnitude, phase resolution is 0.2 rad, and sensitivity margin for respiratory-related HR variability (HRV) components is 1%. RSA magnitude, phase lag, and expiration-to-inspiration time ratio are derived in addition to the entire pattern. In a group of 10 healthy young adults, a phase lag difference of 11.4 +/- 8.5% (mean +/- SD, P < 0.004) was observed between supine and standing postures, possibly ascribed to breathing mechanics. A second group of 15 healthy young adults at supine rest showed stability of the RSA pattern in successive recordings (several weeks apart) as well as individuality among subjects. This may suggest a nonscalar individual long-term index for cardiorespiratory coupling. The method is complementary to the existing statistical and spectral methods. It allows the complete characterization of the primary RSA components and may provide new insight into the effects of vagal activity and changes in clinical conditions.     

Frog stomach enteric plexuses in culture: isolation, morphological characterization and bioelectrical recordings

We have succeeded in the isolation, culture and morphological characterization of Rana ridibunda stomach enteric plexuses. We have furthermore obtained intra and extracellular bioelectric recordings from the explants in culture. The culture medium used (Eagle MEM), the collagenase digestion and the general culture conditions followed are similar to those applied to mammal enteric plexus explant cultures. The most striking difference is that the solutions were diluted to 70% in order to maintain the osmolar conditions required by the amphibian cells. Acetylcholinesterase, osmium tetroxide-zinc iodide- and para-formaldehyde-induced fluorescence methods reveal similar morphological images from the perivascular fibre plexuses. The different cell types observed by phase contrast light microscopy from the myenteric explants in culture have been identified by comparison with those revealed by the acetylcholinesterase method. The prevailing neurons show piramidal somas; other neurons are bipolar with oval somas and a third type shows oval somas tightly aligned, following sinusoidal courses. The intra and extracellular bioelectric recordings from the explants in culture show that the culture conditions we have applied preserve the electrophysiological properties of the neuronal membranes. These preliminary recordings will allow us to undertake the synaptic characterization of the gastrointestinal neurotransmitters in frogs.     

A combined stereo-photogrammetry and underwater-video system to study group composition of dolphins

One reason for the paucity of knowledge of dolphin social structure is the difficulty of measuring individual dolphins. In Hector’s dolphins, Cephalorhynchus hectori, total body length is a function of age, and sex can be determined by individual colouration pattern. We developed a novel system combining stereo-photogrammetry and underwater-video to record dolphin group composition. The system consists of two downward-looking single-lens-reflex (SLR) cameras and a Hi8 video camera in an underwater housing mounted on a small boat. Bow-riding Hector’s dolphins were photographed and video-taped at close range in coastal waters around the South Island of New Zealand. Three-dimensional, stereoscopic measurements of the distance between the blowhole and the anterior margin of the dorsal fin (BH-DF) were calibrated by a suspended frame with reference points. Growth functions derived from measurements of 53 dead Hector’s dolphins (29 female : 24 male) provided the necessary reference data. For the analysis, the measurements were synchronised with corresponding underwater-video of the genital area. A total of 27 successful measurements (8 with corresponding sex) were obtained, showing how this new system promises to be potentially useful for cetacean studies. Received: 5 January 1999 / Accepted: 29 June 1999     

Quantifying spatial and temporal variation of North Pacific fin whale (Balaenoptera physalus) acoustic behavior

In order to help develop hypotheses of connectivity among North Pacific fin whales, we examine recordings from 10 regions collected in the spring and fall. We develop a Random Forest model to classify fin whale note types that avoids manual note classification errors. We also present a method that objectively quantifies the note and pattern composition of recordings. We find that fin whale recordings near Hawaii have distinctive patterns, similar to those found in other regions in the central North Pacific, suggesting potential migration pathways. Our results are consistent with previous studies that suggest there may be two different populations utilizing the Chukchi Sea and central Aleutians in the fall and mix to some degree in the southern Bering Sea. Conversely, we found little difference between spring and fall recordings in the eastern Gulf of Alaska, suggesting some residency of whales in this region. This is likely due to fine scale similarities of calls among the inshore regions of British Columbia, while offshore areas are being utilized by whales traveling from various distant areas. This study shows how our novel approach to characterize recordings is an objective and informative way to standardize spatial and temporal comparisons of fin whale recordings.     

Accuracy and precision of hind limb foot contact timings of horses determined using a pelvis-mounted inertial measurement unit

Gait analysis using small sensor units is becoming increasingly popular in the clinical context. In order to segment continuous movement from a defined point of the stride cycle, knowledge about footfall timings is essential. We evaluated the accuracy and precision of foot contact timings of a defined limb determined using an inertial sensor mounted on the pelvis of ten horses during walk and trot at different speeds and in different directions. Foot contact was estimated from vertical velocity events occurring before maximum sensor roll towards the contralateral limb. Foot contact timings matched data from a synchronised hoof mounted accelerometer well when velocity minimum was used for walk (mean (SD) difference of 15 (18)ms across horses) and velocity zero-crossing for trot (mean (SD) difference from -4 (14) to 12 (7)ms depending on the condition). The stride segmentation method also remained robust when applied to movement data of hind limb lame horses. In future, this method may find application in segmenting overground sensor data of various species.     

Central blood oxygen saturation vs crying in preterm newborns

Infant cry characteristics reflect the development and possibly the integrity of the central nervous system. This study evaluates the distress occurring during cry in preterm newborn infants, as related to decrease of central blood oxygenation. A recording system was developed, that allows synchronised, non-invasive monitoring of blood oxygenation and audio recordings of newborn infant's cry. Cry episodes were identified by an automatic system allowing further analysis of the changes induced by the cry episodes on the oxygen saturation level in the central nervous system. Specifically, decrease in the oxygenation level appears during a cry episode, followed by recovery of the oxygenation after the cry episode is over. In the present work we compare a group of preterm infants with a control group of full term newborns in order to detect possible differences between the two sets of patients.Results indicate that a similar decrease in oxygenation level occurs in both groups of patients, but the recovery time after the crying episode is more stable and rapid in full term newborns than in preterm ones. This could prove useful for clinicians and nurses in the prevention of developmental diseases for this class of patients.     

An adaptive neuro-fuzzy method (<Emphasis Type="Italic">ANFIS</Emphasis>) for estimating single-trial movement-related potentials

This study aims to recover transient, trial-varying evoked potentials (EPs), in particular the movement-related potentials (MRPs), embedded within the background cerebral activity at very low signal-to-noise ratios (SNRs). A new adaptive neuro-fuzzy technique will attempt to estimate movement-related potentials within multi-channel EEG recordings, enabling this method to completely adapt to each input sweep without system training procedures. We assume that one of the sensors is corrupted by noise deriving from other sensors via an unknown function that will be estimated. We will approach this problem by: (1) spatially decorrelating the sensors in the preprocessing phase, (2) choosing the most informative of the filtered channels that will permit the best MRP estimation (input-selection phase) and (3) training the neuro-fuzzy model to fit the noise over the chosen sensor and therefore estimating the buried MRP. We tested this framework with simulations to validate the analytical results before applying them to the real biological data. Whenever it is applied to biological data, this method improves the SNR by more than 12dB, even to very low SNRs. The processing method proposed here is likely to complement other estimation techniques and can be useful to process, enhance and analyse single-trial MRPs.     

Monitoring of Heart and Breathing Rates Using Dual Cameras on a Smartphone

Some smartphones have the capability to process video streams from both the front- and rear-facing cameras simultaneously. This paper proposes a new monitoring method for simultaneous estimation of heart and breathing rates using dual cameras of a smartphone. The proposed approach estimates heart rates using a rear-facing camera, while at the same time breathing rates are estimated using a non-contact front-facing camera. For heart rate estimation, a simple application protocol is used to analyze the varying color signals of a fingertip placed in contact with the rear camera. The breathing rate is estimated from non-contact video recordings from both chest and abdominal motions. Reference breathing rates were measured by a respiration belt placed around the chest and abdomen of a subject; reference heart rates (HR) were determined using the standard electrocardiogram. An automated selection of either the chest or abdominal video signal was determined by choosing the signal with a greater autocorrelation value. The breathing rate was then determined by selecting the dominant peak in the power spectrum. To evaluate the performance of the proposed methods, data were collected from 11 healthy subjects. The breathing ranges spanned both low and high frequencies (6–60 breaths/min), and the results show that the average median errors from the reflectance imaging on the chest and the abdominal walls based on choosing the maximum spectral peak were 1.43% and 1.62%, respectively. Similarly, HR estimates were also found to be accurate.