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PubMed1991

Nonlinearity of indexes of left ventricular performance: effects on estimation of slope and diameter axis intercepts.

The slope and diameter axis intercept (D0) of the linear indexes end-systolic pressure-diameter relation (ESPDR), maximum of the first derivative of left ventricular pressure (dP/dtmax)-end-diastolic diameter relation (dP/dtmax-Ded), and dimensional preload-recruitable stroke work relation (PRDSW) are used to describe left ventricular performance. We tested the hypothesis that nonlinearity in these indexes would preclude accurate estimation of slope and D0. In nine pentobarbital-anesthetized dogs, right heart bypass was used to obtain a wide range of pressure-minor axis diameter (sonomicrometry) points from which the three indexes were derived. For ESPDR and dP/dtmax-Ded, a nonlinear fit (y = ax2 + bx + c) approximated the data better than a linear fit, with significant nonlinearity toward the diameter axis (a = -10.28 +/- 3.42 and -111.2 +/- 26.2, respectively, P less than 0.05). Although linear D0 was significantly less than nonlinear D0, this difference was overcome by the diameter intercept at a midrange value of end-systolic pressure or dP/dtmax. PRDSW demonstrated no significant nonlinearity (a = -4.40 +/- 3.53, P = 0.86) but extrapolation to D0 demonstrated linear and nonlinear differences. We conclude that 1) ESPDR and dP/dtmax-Ded demonstrate significant nonlinearity, while PRDSW is well-approximated by a linear fit over a large range of data points; and 2) extrapolation of D0 is inaccurate in all three indexes, while a midrange intercept is independent of the model used to fit the data. Left ventricular performance may be more accurately described by linear slope and midrange diameter intercept over comparable ranges of data.

Animals↗
PubMed2005

Anticipating the effects of gravity when intercepting moving objects: differentiating up and down based on nonvisual cues.

Intercepting an object requires a precise estimate of its time of arrival at the interception point (time to contact or "TTC"). It has been proposed that knowledge about gravitational acceleration can be combined with first-order, visual-field information to provide a better estimate of TTC when catching falling objects. In this experiment, we investigated the relative role of visual and nonvisual information on motor-response timing in an interceptive task. Subjects were immersed in a stereoscopic virtual environment and asked to intercept with a virtual racket a ball falling from above or rising from below. The ball moved with different initial velocities and could accelerate, decelerate, or move at a constant speed. Depending on the direction of motion, the acceleration or deceleration of the ball could therefore be congruent or not with the acceleration that would be expected due to the force of gravity acting on the ball. Although the best success rate was observed for balls moving at a constant velocity, we systematically found a cross-effect of ball direction and acceleration on success rate and response timing. Racket motion was triggered on average 25 ms earlier when the ball fell from above than when it rose from below, whatever the ball's true acceleration. As visual-flow information was the same in both cases, this shift indicates an influence of the ball's direction relative to gravity on response timing, consistent with the anticipation of the effects of gravity on the flight of the ball.

Attention↗
PubMed2006

Use of the Sequential Intercept Model as an approach to decriminalization of people with serious mental illness.

The Sequential Intercept Model provides a conceptual framework for communities to use when considering the interface between the criminal justice and mental health systems as they address concerns about criminalization of people with mental illness. The model envisions a series of points of interception at which an intervention can be made to prevent individuals from entering or penetrating deeper into the criminal justice system. Ideally, most people will be intercepted at early points, with decreasing numbers at each subsequent point. The interception points are law enforcement and emergency services; initial detention and initial hearings; jail, courts, forensic evaluations, and forensic commitments; reentry from jails, state prisons, and forensic hospitalization; and community corrections and community support. The model provides an organizing tool for a discussion of diversion and linkage alternatives and for systematically addressing criminalization. Using the model, a community can develop targeted strategies that evolve over time to increase diversion of people with mental illness from the criminal justice system and to link them with community treatment.

Cooperative Behavior↗
PubMed2006

Echolocating bats use a nearly time-optimal strategy to intercept prey.

Acquisition of food in many animal species depends on the pursuit and capture of moving prey. Among modern humans, the pursuit and interception of moving targets plays a central role in a variety of sports, such as tennis, football, Frisbee, and baseball. Studies of target pursuit in animals, ranging from dragonflies to fish and dogs to humans, have suggested that they all use a constant bearing (CB) strategy to pursue prey or other moving targets. CB is best known as the interception strategy employed by baseball outfielders to catch ballistic fly balls. CB is a time-optimal solution to catch targets moving along a straight line, or in a predictable fashion--such as a ballistic baseball, or a piece of food sinking in water. Many animals, however, have to capture prey that may make evasive and unpredictable maneuvers. Is CB an optimum solution to pursuing erratically moving targets? Do animals faced with such erratic prey also use CB? In this paper, we address these questions by studying prey capture in an insectivorous echolocating bat. Echolocating bats rely on sonar to pursue and capture flying insects. The bat's prey may emerge from foliage for a brief time, fly in erratic three-dimensional paths before returning to cover. Bats typically take less than one second to detect, localize and capture such insects. We used high speed stereo infra-red videography to study the three dimensional flight paths of the big brown bat, Eptesicus fuscus, as it chased erratically moving insects in a dark laboratory flight room. We quantified the bat's complex pursuit trajectories using a simple delay differential equation. Our analysis of the pursuit trajectories suggests that bats use a constant absolute target direction strategy during pursuit. We show mathematically that, unlike CB, this approach minimizes the time it takes for a pursuer to intercept an unpredictably moving target. Interestingly, the bat's behavior is similar to the interception strategy implemented in some guided missiles. We suggest that the time-optimal strategy adopted by the bat is in response to the evolutionary pressures of having to capture erratic and fast moving insects.

Animals↗
PubMed2005

Hitting a moving target: perception and action in the timing of rapid interceptions.

Different interceptive tasks and modes of interception (hitting or capturing) do not necessarily involve similar control processes. Control based on preprogramming of movement parameters is possible for actions with brief movement times but is now widely rejected; continuous perceptuomotor control models are preferred for all types of interception. The rejection of preprogrammed control and acceptance of continuous control is evaluated for the timing of rapidly executed, manual hitting actions. It is shown that a preprogrammed control model is capable of providing a convincing account of observed behavior patterns that avoids many of the arguments that have been raised against it. Prominent continuous perceptual control models are analyzed within a common framework and are shown to be interpretable as feedback control strategies. Although these models can explain observations of on-line adjustments to movement, they offer only post hoc explanations for observed behavior patterns in hitting tasks and are not directly supported by data. It is proposed that rapid manual hitting tasks make up a class of interceptions for which a preprogrammed strategy is adopted--a strategy that minimizes the role of visual feedback. Such a strategy is effective when the task demands a high degree of temporal accuracy.

Attention↗
PubMed1999

Analysis of recent empirical challenges to an account of interceptive timing.

How do we perceive how long it will be before we reach a certain place when running, driving, or skiing? How do we perceive how long it will be before a moving object reaches us or will arrive at a place where it can be hit or caught? These are questions of how we temporally coordinate our actions with a dynamic environment so as to control collision events. Much of the theoretical work on the control of these interceptive actions has been united in supposing that (1) timing is functionally separable from positioning and the two are controlled using different types of information; (2) timing is controlled using special-purpose time-to-arrival information; (3) the time-to-arrival information used for the timing of fast interceptive actions is a first-order approximation to the actual time-to-arrival, which does not take accelerations into account. Challenges to each of these suppositions have recently emerged, suggesting that a complete rethinking of how interceptions are controlled may be necessary. These challenges are analyzed in detail and it is shown that they are readily accommodated by a recent theory of interceptive timing based on the points just noted.

Humans↗
PubMedDate not supplied

The intercept method: a novel method for establishing consistency of M-wave recruitment curves.

The stability of the M-wave is an important component of experimental H-reflex methodology. Despite this importance, there is inconsistency in H-reflex literature on the most valid method of M-wave stability analysis. Further, there is currently no specific method for establishing the stability of an M-wave recruitment curve across various trials within an experiment. Therefore, the aim of this study was to investigate the most appropriate method of M-wave stability analysis for use with the recruitment curve methodology. Twenty-five healthy subjects participated in the study. Four M-wave recruitment curve recordings were made in various static positions that imposed stretch on the posterior structures of the back and leg. Four methods of post-data collection M-wave stability analysis were compared. Although on visual inspection, there was clear evidence of marked alterations to the M-wave recruitment curves between trials in some subject's data, analysis of variance of the Ms/p and Mmax found no significant difference. Evaluation of the percent deviation in Mmax found nine subjects with greater than ten percent deviation in their maximum M-wave across the four trials. The intercept method that utilises analysis of the 95% confidence interval of the intercept of the M-wave recruitment curve slope, excluded eight subjects that demonstrated variation. Comparison of the percent deviation and the intercept method revealed that the intercept method was the most appropriate method for M-wave stability analysis in conjunction with the recruitment curve methodology.

Adult↗
PubMed2004

Two interceptive approaches to palatally displaced canines: a prospective longitudinal study.

This study evaluated the effectiveness of two interceptive approaches to palatally displaced canines (PDCs), ie, extraction of the deciduous canines alone and in association with the use of a cervical pull headgear. The prospective longitudinal design of the investigation included 46 subjects with PDC (62 maxillary canines) who were randomly assigned to one of three groups (1) a group that underwent the extraction of the deciduous canine only, (2) a group that received in addition the use of a cervical pull headgear, and (3) an untreated control group. Panoramic radiographs were evaluated at initial observation (T1) and after an average period of 18 months (T2). Cervical vertebral maturation was assessed on lateral cephalograms at T1. Successful or unsuccessful canine eruption was assessed 48 months after T1. The between-group statistical comparisons were performed on the T1-T2 changes in the diagnostic parameters on panoramic radiographs, the prevalence rates of successful canine eruption, and the amount of time for canine eruption. The removal of the deciduous canine as an isolated measure to intercept palatal displacement of maxillary canines showed a prevalence rate of 50% success, which was not significantly greater than the success rate in untreated controls. The use of a headgear in addition to the extraction of the deciduous canine induced successful eruption in 80% of the cases, with a significant improvement in the measures for intraosseous canine position. There was no significant difference between the two interceptive approaches in the time required for canine eruption.

Cephalometry↗
PubMed1981

Need for interceptive intervention for malocclusion in 6-year-old Finnish children.

The need for interceptive intervention for malocclusion was studied in a sample of 839 Finnish children aged 6 years. The children had participated in an organized preventive orthodontic program, and nearly 10% of them had received preventive or interceptive orthodontic treatment at the age of 3-5 years (stage I of the preventive orthodontic program of the author). Orthodontic intervention was estimated to be needed for 5.9% of the children due to crossbite of the permanent central incisors, to crossbite or scissors-bite of the permanent first molars, to ectopic eruption of the permanent first molars, to numerical variation of the permanent incisors, or to functional open bite. The need for further inspection in order to follow-up development of the dentition was noted in 2.7% of the children. The indications occasioning this consideration were initial severe crowding, extreme incisal overjet, and early loss of the primary mandibular canines. The relatively low prevalence rates seemed to indicate advantageous results of the preventive and interceptive orthodontic measures.

Child↗
PubMed1999

The palatally displaced maxillary canine. A retrospective comparison between an interceptive and a corrective treatment group.

The purpose of this retrospective study was to analyze palatally displaced maxillary canines referred for specialist treatment compared with those successfully treated by the general practitioner by interceptive extraction of either the primary canine or the primary canine and primary first molar. Special interest was focused on chronological age, dental age and dental maturity as well as the position of the canine at the time of recognition and referral. The Interceptive Treatment group consisted of 50 consecutive cases from computerized records, median age 11.7 years (range 8.9-14.11 years). The Corrective Treatment group comprised 47 consecutive cases, median age 14.1 years (range 11.1-18.0 years), referred to the Department of Orthodontics. Information was obtained by assessing the patient charts and radiographs. The results show that age at the time of recognition and referral is the most important factor for the final outcome while the position of the canine concerning angle alpha and sector S is a compromising factor. The results suggest that about one third of the Corrective Treatment group might have had a reasonably good chance of the canine's erupting without corrective treatment if they had been diagnosed and treated with interceptive extraction of the primary canine at an earlier age.

Adolescent↗
PubMed2003

Preventive and interceptive orthodontic demand for malocclusion.

Orthodontic unit, University College Hospital, Ibadan is young and in need of baseline data for effective planning. The main aim of this study was to determine the nature of orthodontic demands in the unit that could benefit from preventive and interceptive treatment so as to enhance treatment planning, teaching and further research. Consecutive patients who presented for treatment in the Unit between May 1997 and November 1999 were included in the study. The patients aged 5-19 years with mean age of 8.8 +/- 0.82 years. One hundred and twenty-one (60.5%) of the orthodontic cases that presented for treatment needed one form of preventive and interceptive treatment or the other such as extraction of retained primary teeth, use of upper removable orthodontic appliances to correct teeth in cross bite, extraction of erupted supernumerary teeth and fabrication of oral habit breaking appliances such as goal post appliance. Ninety-three (76.9%) of these children had retained primary anterior teeth while 9.1% had proclination of maxillary anterior teeth with moderate spacing. Based on dental history and clinical examination, nine (7.4%) children were involved with oral habits, seven (5.8%) and one (0.8%) had anterior crossbite and supernumerary teeth, respectively. The remaining 39.5% needed full-blown orthodontic treatments. No sex predilection was found in relation to the various needs (P > 0.05). We suggest a need for more emphasis on preventive and interceptive orthodontic treatment in our environment due to the relatively high prevalence ofthese presenting needs.

Adolescent↗
PubMed2005

Need for interceptive intervention for malocclusion in handicapped children in Lagos, Nigeria.

Orthodontic care for handicapped children in Nigeria has generally been neglected. There is a need for baseline data for effective planning of orthodontic services for this population group. The purpose of this study was to determine the need for interceptive orthodontic intervention in handicapped children in Lagos, Nigeria. The sample consisted of 106 handicapped children, 60 boys and 46 girls who were 7-10 years old, selected from 5 special schools in Lagos. Overall, forty-nine (46.2%) of the children had a need for interceptive orthodontic treatment. Orthodontic intervention was needed in 20.7% of the children due to crossbite of the anterior and lateral segments. Extraction was indicated in 4.7% of the children with retained primary teeth and in 1.9% of children with erupted supernumerary teeth. Orthodontic treatment or education was needed in 16.1% of the children due to oral habits. Three(2.8%) of the children presented with proclination of the maxillary anterior teeth with moderate spacing. In 10.4% of the children, there was a need for further inspection in order to follow-up the development of the occlusion. This study has revealed a significant need for interceptive orthodontic treatment among handicapped children in Lagos, Nigeria. Appropriate policy action and strategies to improve oral health education and provide publicly funded programmes will be required.

Age Distribution↗
PubMed1984

Interception of lymphatic drainage by Nd:YAG laser irradiation in rat urinary bladder.

Lymphatic drainage can be demonstrated by colloidal indian ink injection. A small intramural indian ink spot in the bladder dome is separated from the rest of the rat urinary bladder by encircling transmural Neodymium-YAG (Nd:YAG) laser irradiation. In untreated animals there is an ink flow via the lymphatic vessels to the regional lymph nodes within several hours. In treated animals, after laser irradiation, the indian ink remains in the bladder dome and a penetration of the irradiated area cannot be found by macroscopic and histologic examination. Indian ink will be found in the regional lymph nodes after the ninth day of absorption of the coagulation necrosis and recanalisation of the intercepted lymphatics. Evidence for the interception of the lymphatic drainage is demonstrated by the distinctly delayed ink flow and the injected ink's remaining in the irradiated area. From this, we conclude that Nd:YAG laser irradiation is especially suitable for tumor coagulation, since simultaneous interception of lymphatic drainage will inhibit the spreading of tumor cells.

Animals↗
PubMed2006

Interception of the radicals produced in electrophilic fluorination with radical traps (Tempo, Dmpo) studied by electrospray ionization mass spectrometry.

The interaction of the nitroxide radical traps (Tempo and Dmpo) and radicals produced in the electrophilic fluorination of olefins (styrene and alpha-methylstyrene) and Selectfluor (1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octanebis(tetrafluoroborate) (F-TEDA-BF(4)) (1)) was investigated by electrospray ionization mass spectrometry (ESI-MS). Tempo succeeded in intercepting the radical cationic intermediates and the radical adduct ions were detected at m/z 260 (for styrene) and m/z 274 (for alpha-methylstyrene). Dmpo could also intercept the fluorine radical and radical adduct ions were detected at m/z 131, 132 and 152. The interception of the radical cationic intermediates and fluorine radical is good evidence for the presence of a single-electron transfer mechanism in the electrophilic fluorination.

Fluorine↗
PubMed2001

Predictive elements in ocular interception and tracking of a moving target by untrained cats.

We presented a mechanical target moving at constant velocity to awake, nontrained, head-restrained cats, in order to study how naive animals pursue objects moving at a high speed with their gaze. Eye movements were recorded while the target was moving in different directions at a constant velocity (20-80 degrees/s) through the center of the visual field. We observed two oculomotor strategies: cats either made an interception saccade (IS) toward the target but opposite to its motion, or tracked it in the direction of motion. They used the interception strategy more frequently when the gaze position error at the onset of target motion was large, and the tracking strategy when it was small. Interception was always achieved by single saccades, which were faster than tracking saccades (TS). During tracking, cats generated sequences of two to six saccades separated by "smooth" eye movements. Tracking quality varied considerably from trial to trial. When the level of motivation was high, cats would track the target at 80 degrees/s over up to 75% of the oculomotor range, with relatively small position errors. We compared ISs and TSs with respect to their metric properties and timing. The amplitudes of ISs positively correlated with position error existing 100 ms before saccade onset, but saccade vectors were directed to a point ahead of the target along the target's track. We conclude that, in programming the ISs, target motion is used to predict the future target position so as to assure a spatial lead of the gaze at the saccade end, instead of attempting a precise capture of the target. The amplitude of TSs did not depend on preceding position errors. TSs were usually small at the onset of the first saccade, as if cats would wait till the target arrived near the line of sight. A majority of primary TSs were initiated before the target arrived near the direction of gaze. Thus they had a direction, opposite to the position error sampled 100 ms before the saccade, but the same as the direction of target motion. Prediction of the future target position from its velocity vector should therefore contribute to the programming of TSs. In addition, we observed that TSs were faster when they were initiated with a spatial lag relative to the target and they were slower if there was a spatial lead or target velocity was reduced. Such a modulation appears to be analogous to the predictive correction of the saccade amplitude during smooth pursuit in primates. Considering strong visual motion sensitivity and motor properties of output neurons of the superior colliculus, it is likely that, in cats, the colliculus makes a major contribution to the integration of eye movement-related and target motion-related signals.

Animals↗
PubMed1994

Intercept studies, clinical trials, and cluster experiments: to whom can we extrapolate?

While sample surveys rely on an explicit theory of the relationship between a sample and its reference population, many nonsurvey-based designs lack a clear relationship to the population to which inferences are to be drawn. For example, in order to be applicable to large populations, intercept studies--which include observational studies of migrant populations and randomized studies such as mall intercepts--must make implicit or explicit assumptions about the probability of finding members of the population. In conducting clinical trials, constraints imposed by the research often lead large segments of the population to have zero probability of observation. Although such experiments generally conduct research at only a few sites, investigators usually intend to apply their results quite broadly. This paper compares intercept studies and clinical trials with particular emphasis on inference to a population for which the probabilities of being observed are unknown, unreliable, or very small.

Adult↗
PubMed2006

Prospective strategies underlie the control of interceptive actions.

The purpose of this study was to test whether a constant bearing angle strategy could account for the displacement regulations produced by a moving observer when attempting to intercept a ball following a curvilinear path. The participants were asked to walk through a virtual environment and to change, if (deemed) necessary, their walking speed so as to intercept a moving ball that followed either a rectilinear or a curvilinear path. The results showed that ball path curvature did indeed influence the participants' displacement kinematics in a way that was predicted by adherence to a constant bearing angle strategy mode of control. Velocity modifications were found to be proportional to the magnitude of target curvature with opposing curvatures giving rise to mirror displacement velocity changes. The role of prospective strategies in the control of interceptive action is discussed.

Adult↗
PubMed2000

Target velocity effects on manual interception kinematics.

Participants generated manual interception movements toward a target cursor that moved across a computer screen. The target reached its peak velocity either during the first third, at the midpoint, or during the last third of the movement. In Experiment 1 the view of the target was available for either the first 316, 633, 950, or 1267 ms, after which it disappeared. Results showed that for all viewing conditions, the timing of the interception velocity was related to the temporal properties of the target's trajectory. In Experiment 2, when the portion of the target trajectory that was viewed was reversed (such that participants did not see the first 316, 633, 950, or 1267 ms of the trajectory, but instead saw only the later portions of the trajectory), there was no clear relationship between the target trajectory and the timing of the aiming trajectory. These results suggest that participants use visual information early in the target's trajectory to form a representation of the target motion that is used to facilitate manual interception.

Adult↗