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PubMed2005

Prediction of kinetics and kinematics of running animals using an analytical approximation to the planar spring-mass system.

The spring-mass model is often used to describe bouncing gaits. Although at first inspection the mechanical system appears simple, the solution to the motion cannot be derived easily. An analytical solution would provide a fast and intuitive method to determine the kinetic and kinematics of the centre of mass of terrestrial animals during over-ground steady state locomotion. Here, an analytical approximation using sine wave simplifications for the motion is presented. The analytical solution was almost indistinguishable from the numerical solution across initial leg angles of 17.5-30 degrees ; percentage differences between the analytical solution and the numerical solution were less than 1% for total mechanical energy, centre of mass position, total limb compression and centre of mass velocity and less than 2% different for resultant limb force and vertical acceleration of the centre of mass. The solution matched the relationship between stance time and speed collected from a trotting racehorse and accurately characterised previously published biological data. This study has shown that a simple analytical solution can predict the kinetics and kinematics of a spring-mass system over the range of biologically relevant sweep angles and horizontal velocities, and could be used to further understanding of limb deployment and gait selection. Using this analytical solution not only the force profile but also the changes in mechanical energy can be calculated from easily observed morphological and kinematic data.

Animals↗
PubMed1980

The difference in protection efficiency between earplugs and earmuffs. An investigation performed at a workplace.

The hearing thresholds of shipyard workers have been measured with a Békésy sweep audiometer. The number of employees at different workplaces is so large that it is possible to select groups of workers of specified ages who have been employed by the shipyard for many years. These workers have used either earplugs of earmuffs for 5--10 years and have also been working all the time in almost the same noise environment. Three ways of investigation have been used to observe differences in the hearing levels between 'plug-men' and 'muff-men'. All three show a greater hearing impairment for 'muff-men' than for 'plug-men'. Under certain conditions earplugs provide the most effective protection although the attenuation is higher for earmuffs than for earplugs.

Adult↗
PubMed2006

Genotype-by-environment interactions influencing the emergence of rpoS mutations in Escherichia coli populations.

Polymorphisms in rpoS are common in Escherichia coli. rpoS status influences a trade-off between nutrition and stress resistance and hence fitness across different environments. To analyze the selective pressures acting on rpoS, measurement of glucose transport rates in rpoS+ and rpoS bacteria was used to estimate the role of F(nc), the fitness gain due to improved nutrient uptake, in the emergence of rpoS mutations in nutrient-limited chemostat cultures. Chemostats with set atmospheres, temperatures, pH's, antibiotics, and levels of osmotic stress were followed. F(nc) was reduced under anaerobiosis, high osmolarity, and with chloramphenicol, consistent with a reduced rate of rpoS enrichment in these conditions. F(nc) remained high, however, with alkaline pH and low temperature but rpoS sweeps were diminished. Under these conditions, F(sp), the fitness reduction due to lowered stress protection, became significant. We also estimated whether the fitness need for the gene was related to its regulation. No consistent pattern emerged between the level of RpoS and the loss of rpoS function in particular environments. This dissection allows an unprecedented view of the genotype-by-environment interactions controlling a mutational sweep and shows that both F(nc) and F(sp) are influenced by individual stresses and that additional factors contribute to selection pressure in some environments.

Bacterial Proteins↗
PubMed2006

A new approach for the detection of a nonfluorescent compound by CE-resonance Raman spectroscopy based on the sweeping-MEKC mode.

A CE-resonance Raman spectroscopy (CE-RRS) method based on MEKC and sweeping-MEKC modes is described. A nonfluorescent compound, malachite green (MG), and a doubled Nd:YAG laser (532 nm, 300 mW) were selected as model compound and light source, respectively. In order to carry out a quantitative analysis of MG, a monochromator (effective bandwidth, 0.4 nm) was used to collect the specific Raman line at 1616 cm(-1) (N-phi and C-C stretch, corresponding to 582 nm when the wavelength of the exciting source was 532 nm). As a result, the LOD for MG was 10 ppm, based on the MEKC/RRS mode. This could be improved to 5 ppb when the sweeping-MEKC/RRS mode was applied. Furthermore, with the addition of nano-size silver colloids to the CE buffer the detection limits can be further improved, but the data obtained with surface-enhanced resonance Raman spectroscopy (SERRS) are less useful for quantitative purposes.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2003

On-line preconcentration strategies for trace analysis of metabolites by capillary electrophoresis.

Analysis of low concentrations of metabolites is required for new fields of biological research, such as metabolomics. In this review, recent work in our laboratory aimed at developing improved strategies for on-line sample preconcentration of metabolites by capillary electrophoresis (CE) is presented. Dynamic pH junction, sweeping and dynamic pH junction-sweeping represent three complementary methods for electrokinetic focusing of large volumes of sample directly on-capillary. Focusing selectivity and focusing efficiency are two factors that can be used to assess the suitability of each method for different classes of metabolites. Buffer properties can be selected to enhance the focusing of specific types of metabolites based on knowledge of the analyte physicochemical properties. The application of on-line preconcentration CE for trace analysis of metabolites in real samples of interest, such as biological fluids and cellular extracts, is also demonstrated. Under optimum conditions, up to three orders of magnitude increase in concentration sensitivity can be realized for several classes of metabolites, including catecholamines, purines, nucleosides, nucleotides, amino acids, steroids and coenzymes. Recent work on hyphenating on-line preconcentration with multiplexed CE is highlighted as a promising platform for sensitive and high-throughput analyses of metabolites.

Electrophoresis, Capillary↗
PubMed1998

Verotoxin-producing Escherichia coli (VTEC) infection in randomly selected population of Ilam Province (Iran).

In a randomly selected population, 2,008 fecal samples were screened for presence of Verotoxin producing Escherichia coli (VTEC) by colony sweep polymyxin-B extraction method. Non-sorbitol fermentation (NSF) phenotype and slide agglutination with O157: H7 antisera were used for screening and detection of this serotype. Ninety-eight (4.9%) fecal samples were found to be VTEC-positives and none of them belonged to the O157: H7 serotype. In rural areas, most individuals carrying VTEC isolates were asymptomatic, whereas in urban areas, a significant association was found between VTEC isolation and diarrhoea (p < 0.01).

Adolescent↗
PubMed1985

Calculated T1 images derived from a partial saturation-inversion recovery pulse sequence with adiabatic fast passage.

Calculated T1 images of the head and abdomen have been obtained using an alternating partial saturation-inversion recovery pulse sequence. Timing parameters were adjusted to yield optimum T1 contrast-to-noise ratio for this sequence for the range of T1 studied. Adiabatic fast passage (AFP) was implemented for the nonselective inverting pulse, to reduce the sensitivity of the measurement to RF and static field inhomogeneity. A nonlinear frequency sweep was used to improve the efficiency of the AFP pulse. The effect on the T1 calculation of slice selection during the pi/2 pulses was also determined and corrected for in the image reconstruction algorithm. The T1's determined by this method show a standard deviation of less than 10%, and good agreement with the literature.

Abdomen↗
PubMed2001

Age-related temporal processing speed deterioration in auditory cortex.

A common problem among the elderly is a difficulty in discriminating speech sounds. One factor that may contribute to this is a deterioration in the ability to process dynamic aspects of speech such as formant transitions. For the aging auditory system, this deterioration in temporal processing speed may be manifest as a deficit in encoding time-varying sounds that contain rapidly changing frequencies such as formant transitions. The primary goal of this study was to explore the neural basis of the effects of aging on temporal processing speed. To this end, single units were recorded from the auditory cortex of young and aged rats in response to frequency-modulated (FM) sweeps that changed from trial to trial in both direction and speed. Results showed that the majority of cells recorded from young rats responded most vigorously to fast and medium speeds. By contrast, the majority of units recorded from aged animals responded best to slow speeds. For preferred direction of FM sweep, similar results were observed for both age groups, namely, approximately half of the units exhibited a direction-selective response. The results of the present study demonstrate an age-related decrease in the rate of change of frequency that can be processed by the auditory cortex.

Aging↗
PubMed2004

Towards an ideal rowing technique for performance : the contributions from biomechanics.

At international standard, sculling (two oars) and rowing (one oar) are competed on-water over 2000 m. Race time is the critical measure of performance and is determined from mean skiff velocity during a race. Although a high proportion of race training is completed on-water, rowing ergometers are commonly used for performance testing, technique coaching, crew selection or for training during poor weather. Rowing biomechanics research has aimed to identify characteristics of successful sculling and sweep rowing strokes; however, biomechanical predictors of 2000 m rowing performance are indistinct in the literature. If specific biomechanical parameters distinguish between ability levels and successful or unsuccessful techniques, these attributes can be considered when modifying technique or predicting future rowing performance. The kinematics and kinetics of the sculling and rowing movements have been described on ergometers, on-water and for novice and elite male and female rowers, but there is limited research on the ideal technique or how a rower's anthropometry or boat set-up could help improve/optimise their rowing performance. Currently viewing the technique and providing verbal feedback is the primary tool used by a coach to help improve a rower's technique and performance. The greater use of customised telemetered sensors on the rowing skiff can assist the coach and biomechanist with judging when performance (skiff velocity) improves with some form of intervention.

Anthropometry↗
PubMed2006

Amperometric immunosensor for nonylphenol determination based on peroxidase indicating reaction.

Novel immunosensor for nonylphenol (NP) determination has been developed by immobilization of specific antibodies together with horseradish peroxidase on the surface of carbon screen-printed electrode. The signal of the immunosensor is generated by the involvement of NP accumulated in the peroxidase oxidation of mediator (Methylene Blue, hydroquinone or iodide). This results in the increase of the signal recorded by linear-sweep voltammetry. The sensitivity of the detection depends on the nature of mediator, its concentration and incubation period. Cross-selectivity of the response toward readily oxidized phenolic compounds has been determined. The immunosensor developed makes it possible to detect from 20 microgL(-1) to 44 mgL(-1) of NP with detection limit 10 microgL(-1) of NP.

Animals↗
PubMed2003

Metabolic and ventilatory parameters of four activities of daily living accomplished with arms in COPD patients.

STUDY OBJECTIVE: The upper limbs are involved in the activities of daily living (ADLs). Normal subjects usually perform such activities without noticing the energy cost, but patients with COPD report tiredness when performing them. This study was designed to assess the metabolic and ventilatory demands in patients with COPD during the performance of four ADLs involving the upper limbs. DESIGN: The patients were tested on two different days. Oxygen uptake (O(2)), carbon dioxide output (CO(2)), minute ventilation (E), and heart rate were measured while performing four ADLs for 5 min each: sweeping, erasing a blackboard, lifting pots, and replacing lamps. PARTICIPANTS: Ten normal, young, male subjects (mean age, 27.9 years) were selected for testing the reproducibility of the methods, and 9 male patients with COPD (FEV(1), 32.5%; mean age, 58.9 years) entered the study. MEASUREMENTS AND RESULTS: The tests were reproducible for both groups. Patients with COPD presented a significant increase (p < 0.05) in O(2) (mean, 50.2% of maximum O(2)) and in E (mean, 55.7% of maximum voluntary ventilation [MVV]) in relation to initial resting conditions for all four activities. CONCLUSIONS: We conclude that when performing these four activities, patients with moderate-to-severe COPD present a high O(2), which may explain the tiredness reported by them during simple activities involving the upper limbs; the high E/MVV may be associated to dyspnea.

Activities of Daily Living↗
PubMed2002

Measurement of energy cost of selected household and farm activities performed by rural women.

A nutritional study was carried out on 30 rural, low-income women, aged 25 to 35 years, in the village of Dhandra, Ludhiana District, Punjab, India, to measure the energy cost of selected household and farm activities. The mean weight, mid-upper-arm circumference, and triceps skinfold thickness were below the reference standards. A negative energy balance among the subjects indicated their poor energy status. The energy costs of selected household and farm activities were assessed by the Caltrac personal activity computer. The energy costs of household activities--making dough, making chapatis, grinding masala, hand pumping, washing utensils, sweeping, mopping, washing the floor, mud pasting, and washing clothes--were 0.0306, 0.0281, 0.0595, 0.0337, 0.0266, 0.0424, 0.0530, 0.0331, 0.0634, and 0.0453 kcal/kg/min, respectively. The energy costs of farm activities--collecting fodder, chaffing fodder, milking, making dung cakes, picking sag, harvesting wheat, bundling wheat, picking paddy, brooming paddy, and separating paddy--were 0.0472, 0.0372, 0.0530, 0.0270, 0.0337, 0.0623, 0.0374, 0.0411, 0.0370, and 0.0744 kcal/kg/min, respectively. All selected activities were categorized as light, except for grinding masala, mopping, mud pasting, harvesting wheat, separating paddy, and milking, which were categorized as moderate on the basis of Food and Agriculture Organization (FAO) physical activity ratios. The Caltrac gave lower values for the energy costs of most of the activities. Although it is simpler and less costly, the Caltrec must be calibrated against methods of measuring oxygen consumption for similar activities.

Adult↗
PubMed2006

[Selective determination of dopamine in the presence of high concentration of ascorbic acid with L-cysteine modified glassy carbon electrodes].

OBJECTIVE: To establish an assay system for determination of dopamine (DA) in the presence of ascorbic acid (AA) with L-cysteine modified glassy carbon electrode. METHODS: L-cysteine was modified onto glassy carbon electrode electrochemically, and with this modified electrode, dopamine was determined by linear sweep stripping voltammetry. RESULTS: L-cysteine polymer-modified electrode had strong catalytic effect towards the electrochemical oxidation of DA. The modified electrode showed good properties in determination of DA with coexisting AA. Under selected conditions, the linearity of DA was in the range of 2.0 x 10(-7) - 1.0 x 10(-4) mol/L with the detection limit of 2.0 x 10(-8) mol/L. The stability, reliability and recovery of this L-cysteine-modified electrode based on electrochemical method were also satisfactory. CONCLUSION: L-cysteine-modified electrode can avoid the interference by AA for determination of DA.

Ascorbic Acid↗
PubMed2006

Self-selected exercise intensity during household/garden activities and walking in 55 to 65-year-old females.

This study determined whether some of the more vigorous household and garden tasks (sweeping, window cleaning, vacuuming and lawn mowing) were performed at a moderate intensity (3-6 METs or metabolic equivalents) by a representative sample of 50, 55 to 65-year-old women (X +/- SD; 59.3 +/- 3.1 years, 161.5 +/- 5.2 cm, 69.4 +/- 12.4 kg, 38.4 +/- 7.3% BF). Data collection was conducted in a standardised laboratory environment and in the subjects' homes. Energy expenditure during self-perceived moderate paced walking around a quadrangle was also used as a marker of exercise intensity. Energy expenditure measured via indirect calorimetry was also predicted from: HR, CSA accelerometer counts, Quetelet's index and the Borg rating of perceived exertion. Ninety-six percent of the subjects walked at an intensity of >or= 3.0 METs. Except for vacuuming in the laboratory (X = 2.9 METs; P = 0.19), the intensity of each of the other activities was significantly (P or= 3.0 METs when the four household/garden activities were performed in the subjects' homes. These activities therefore have the potential to contribute to the 30 min day(-1) of moderate intensity physical activity required to confer health benefits but there was much inter-individual variability in the intensity at which these tasks were performed. Random intercept regression analyses yielded prediction equations with 95% confidence intervals of +/- 0.80 and +/- 0.84 METs for the laboratory and home based equations, respectively. Considering the means for the five activities ranged from 2.9 to 5.5 METs, these 95% confidence intervals lack predictive precision at the individual level. Nevertheless, the laboratory and home-based equations predicted with correct classification rates of 89 and 90%, respectively, whether energy expenditure was < 3.0 or >or= 3.0 METs.

Activities of Daily Living↗
PubMed2025

Efficient detection and characterization of targets of natural selection using transfer learning.

Natural selection leaves detectable patterns of altered spatial diversity within genomes, and identifying affected regions is crucial for understanding species evolution. Recently, machine learning approaches applied to raw population genomic data have been developed to uncover these adaptive signatures. Convolutional neural networks (CNNs) are particularly effective for this task, as they handle large data arrays while maintaining element correlations. However, shallow CNNs may miss complex patterns due to their limited capacity, while deep CNNs can capture these patterns but require extensive data and computational power. Transfer learning addresses these challenges by utilizing a deep CNN pre-trained on a large dataset as a feature extraction tool for downstream classification and evolutionary parameter prediction. This approach reduces extensive training data generation requirements and computational needs while maintaining high performance. In this study, we developed TrIdent, a tool that uses transfer learning to enhance detection of adaptive genomic regions from image representations of multilocus variation. We evaluated TrIdent across various genetic, demographic, and adaptive settings, in addition to unphased data and other confounding factors. TrIdent demonstrated improved detection of adaptive regions compared to recent methods using similar data representations. We further explored model interpretability through class activation maps and adapted TrIdent to infer selection parameters for identified adaptive candidates. Using whole-genome haplotype data from European and African populations, TrIdent effectively recapitulated known sweep candidates and identified novel cancer, and other disease-associated genes as potential sweeps.

Journal Article↗
PubMed1994

Processing of frequency-modulated sounds in the cat's anterior auditory field.

1. Single-neuron activity was recorded from the anterior auditory field (AAF) in the cortex of gas-anesthetized cats. 2. Tone bursts and broad-band complex sounds were used for auditory stimulation. Responses to frequency-modulated (FM) sounds, in particular, were studied systematically. 3. Linear FM sweeps were centered around the best frequency (BF) of a neuron and had an excursion large enough to cover its whole frequency tuning range. Rate and direction of change of the FM sweeps were varied. 4. In 69% of the FM responses, a peak was found at an instantaneous frequency that corresponded to the BF in the pure-tone response. Thirty-three percent of the units had multiple maxima in their FM response. These secondary maxima were not always reflected in the pure-tone response of the same neurons. 5. The vast majority of AAF neurons showed one of two types of selectivity for FM rate. Depending on the criterion, almost half of the cells (46%) preferred fast changes of > 200 Hz/ms (high-pass) in both FM directions. Forty-eight percent of all neurons showed band-pass behavior with a clear preference in the middle range of FM rates in one or both directions. Low-pass or all-pass neurons made up only a small proportion (4 and 1%, respectively) of AAF neurons. 6. When both directions of an FM sweep (low-to-high and high-to-low-frequency) were tested, 66% of the neurons clearly were selective for one direction. This selectivity was not present necessarily at the preferred FM rate. In general, FM direction selectivity was most pronounced at slower FM rates. 7. The selectivity of AAF neurons for the rate and direction of FM sounds makes these neurons suitable for the detection and analysis of communication sounds, which often contain FM components with a particular sweep rate and direction.

Animals↗
PubMed1981

Auditory-nerve fiber responses to frequency-modulated tones.

Discharge patterns of cat auditory-nerve fibers were obtained in response to frequency-modulated (FM) tones. The rate and direction of frequency change and the sound-pressure level of the sweep tones were systematically varied, and aspects of the discharge patterns were compared to aspects of the discharge patterns elicited by pure tones. Increases in SPL broaden the frequency range over which the fiber responds, as is the case with pure-tone stimuli. Increases in the rate of frequency change have little effect on frequency selectivity for the rates tested. In general, the pure-tone response area is a good predictor of the response area to FM. Although approximately equal numbers of spikes are elicited by ascending and descending sweeps, the discharge patterns differ slightly; for each direction of frequency change, the FM response area is shifted in the direction of the earliest-occurring frequencies. Most of this shift can be accounted for by neural adaptation. This asymmetry is small, relative to those observed in the central nervous system.

Acoustic Stimulation↗