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At least 865 records · Page 48Linked to original sources
PubMed2004

Speed rather than distance: a novel graded treadmill test to assess claudication.

OBJECTIVE: To evaluate a new treadmill test, determining pain threshold speed (PTS) for use in assessment and measuring rehabilitation of patients with intermittent claudication. METHODS AND DESIGN: Twenty-nine patients with claudication were evaluated, and the ankle-brachial index (ABI) was assessed. PTS was determined with a treadmill protocol based on level walking, low starting speed, and progressive increments at a predetermined distance up to the onset of pain. Repeatability and equivalence with a time-based protocol were verified. PTS was compared to pain-free walking distance, 6-minute walking distance, and ABI. RESULTS: PTS was measured in all patients (3.6+/-1.1 km/h). Repeatability and equivalence between established tests were demonstrated. PTS showed a significant correlation with pain-free walking distance (r=0.833; P=0.0001), with 6-minute walking distance (r=0.724; P=0.005), and with ABI in the more ischemic limb (r=0.641; P=0.0001). CONCLUSIONS: PTS is a reliable parameter that correlates well with other established measures. It is useful for determining the degree of functional handicap and for designing and guiding rehabilitation protocols.

Aged↗
PubMed2005

Comparison of injuries caused by the pistols Tokarev, Makarov and Glock 19 at firing distances of 10, 15 and 25cm.

Firings at cloth targets and at human skin from autopsy material were performed from the pistols 7.62 mm Tokarev (TT), 9 mm Makarov (PM) and 9 x 19 mm Glock 19 with common ammunition. The differences were in the soot deposit pattern, the degree of scorching of the synthetic fibres on the edges of the entrance hole and in the findings of the soot and the gunpowder particles. The results were similar on the cloth and on the skin targets. In the case of the TT and the PM, the soot deposit patterns reminded of a blossom or shafts of rays or fans, or the bullet wipe had four narrow and four wide sections regarding the number of lands and grooves. The TT left a large amount of soot and many gunpowder particles and caused the melting of the synthetic fibres on the edges of the entrance hole, producing a defect of the material 0.1-0.3 cm in diameter and defects of textile fibres around the entrance hole. In the skin the TT caused many intraepithelial tears, folds of the epidermis and recesses of the epidermis containing soot. Firings from the PM and the Glock 19 caused the melting only of the ends of individual synthetic fibres on the edges of the entrance hole. The PM left a large amount of soot and only a few gunpowder particles. The Glock 19 gave the least soot and the greatest number of gunpowder particles and also caused tears and recesses in the epidermis. Only in the case of the Glock 19, hexagonal or polygonal zones were seen in the soot deposit pattern. The differences in the soot pattern were more distinct at the firing distance of 10 cm. By increasing the distance from 10 to 15 cm, the intensity of soot diminished and began to disappear at 25cm, but remained more visible in the case of the TT. The gunpowder particles could be found in the epidermis and deeper in both layers of the dermis at all distances fired from the TT and the Glock 19. In the case of firings from the PM, at the distance 10 cm some of the gunpowder particles had penetrated into the dermis and most of them were in the upper layer of the dermis. At the firing distance of 15 and 25 cm, the gunpowder particles were only on and in the stratum corneum.

Firearms↗
PubMed2005

Distance correction in the electrocardiographic estimation of left ventricular mass.

Assessment of the left ventricular mass (LVM) from electrocardiograms may be improved by the addition of clinical variables into a multivariate equation. As the heart-thorax distance may affect the results, its relationships with electrocardiographic and clinical data have been evaluated in a group of 220 subjects (53 +/- 15 years, 126 female, 175 without demonstrated heart disease) who were assessed for echocardiographic LVM and heart-thorax distance. Sokolow, Cornell, and total QRS voltage indexes were obtained. Multiple regression equations with LVM as the dependent variable were fit, with an ECG index, body mass index (BMI), age, and gender as the independent predictors. Each of the 3 ECG indexes, BMI, age, and sex was shown to be independent predictors of LVM, with the ECG and BMI contributing with most of the explanatory power. When added to the model, the distance from the interventricular septum to the precordium (septal-LVD) was not a predictor of LVM, but when BMI was withdrawn, septal-LVD became an independent predictor of LVM (P < .001). This was not observed when septal-LVD was substituted for any other clinical or ECG variable, thus suggesting that septal-LVD accounts for information contained in BMI but not in the remaining variables. In addition, the distance from the center of LV to the precordium (mid-LVD) achieved significance as an independent LVM predictor, although the coefficient of multiple determination (R) practically did not change. Almost identical results are obtained when LVM is indexed for body surface area. Body mass index supplies virtually all the information contained in the heart-thorax distance.

Adult↗
PubMed2006

Rangeland dynamics of southern Ethiopia: (2). Assessment of woody vegetation structure in relation to land use and distance from water in semi-arid Borana rangelands.

The structure and advancement of woody vegetation was studied in a semi-arid rangeland of southern Ethiopia under three land-use systems (communal land, a government ranch and a traditional grazing reserve enclosure) and along a distance gradient (near, middle and far) from water sources. A total of 54 woody plant species were identified. Based on the subjective opinions of the pastoralists, 85% of the identified woody plants have forage values to livestock. Cadaba farinsoa, Ormocarpum trichocarpum, Rhus natalensis, Acacia brevispica, Cordia gharaf and Hibiscus sparseaculeatus were reported to have fair to good palatability. Tree equivalent (TE) density of all woody plants combined was greater (P <0.01) in the government ranch (1) 188 TE ha(-1)) and the communal land (1083 TE ha(-1)) than in the traditional grazing reserve (419 TE ha(-1)), whereas this did not vary significantly (P >0.05) along the distance gradient from water. The most important encroaching woody plant species in the study areas were in descending order: Commiphora africana, Acacia drepanolobium, A. brevispica, Acacia. tortilis, Grewia tembensis and Lannea floccosa. The density of individual encroaching woody plant species along the distance gradient from water was not consistent. All encroaching woody species had the highest TE density in the communal land. The prevalence of these species followed the pattern of intensity of use within the communal grazing area. Most of the woody species had the highest abundance in the height class >0-2m regardless of land use and distance gradient from water. This study investigated the advance of severe woody encroachment in the communal and government sites as well as along the distance gradient from water. Some of the important contributing factors that can be suggested are heavy grazing pressure (in both the communal and government sites), expansion of cultivation and reduced mobility of livestock due to settlement of the pastoralists in the communal land.

Conservation of Natural Resources↗
PubMed2004

Rotational-resonance distance measurements in multi-spin systems.

It is demonstrated that internuclear distances can be evaluated from rotational-resonance (RR) experiments in uniformly (13)C-labelled compounds. The errors in the obtained distances are less than 10% without the need to know any parameters of the spin system except the isotropic chemical shifts of all spins. We describe the multi-spin system with a simple fictitious spin-1/2 model. The influence of the couplings to the passive spins (J and dipolar coupling) is described by an empirical constant offset from the rotational-resonance condition. Using simulated data for a three-spin system, we show that the two-spin model describes the rotational-resonance transfer curves well as long as none of the passive spins is close to a rotational-resonance condition with one of the active spins. The usability of the two-spin model is demonstrated experimentally using a sample of acetylcholine perchlorate with labelling schemes of various levels of complexity. Doubly-, triply-, and fully labelled compounds lead to strongly varying RR polarization-transfer curves but the evaluated distances using the two-spin model are identical within the expected error limits and coincide with the distance from the X-ray structure. Rotational-resonance distance measurements in fully labelled compounds allow, in particular, the measurement of weak couplings in the presence of strong couplings.

Journal Article↗
PubMed2006

Optimal flight initiation distance.

Decisions regarding flight initiation distance have received scant theoretical attention. A graphical model by Ydenberg and Dill (1986. The economics of fleeing from predators. Adv. Stud. Behav. 16, 229-249) that has guided research for the past 20 years specifies when escape begins. In the model, a prey detects a predator, monitors its approach until costs of escape and of remaining are equal, and then flees. The distance between predator and prey when escape is initiated (approach distance = flight initiation distance) occurs where decreasing cost of remaining and increasing cost of fleeing intersect. We argue that prey fleeing as predicted cannot maximize fitness because the best prey can do is break even during an encounter. We develop two optimality models, one applying when all expected future contribution to fitness (residual reproductive value) is lost if the prey dies, the other when any fitness gained (increase in expected RRV) during the encounter is retained after death. Both models predict optimal flight initiation distance from initial expected fitness, benefits obtainable during encounters, costs of escaping, and probability of being killed. Predictions match extensively verified predictions of Ydenberg and Dill's (1986) model. Our main conclusion is that optimality models are preferable to break-even models because they permit fitness maximization, offer many new testable predictions, and allow assessment of prey decisions in many naturally occurring situations through modification of benefit, escape cost, and risk functions.

Animals↗
PubMed2005

Rapid foot and calf compression increases walking distance in patients with intermittent claudication: results of a randomized study.

OBJECTIVE: The aim of our pilot study was to determine the usefulness of rapid, high-pressure, intermittent pneumatic calf and foot compression (IPCFC) in patients with stable intermittent claudication, with reference to the end points of improvement in initial claudication distance (ICD) (distance at which patient feels pain or discomfort in the legs), and improvement in absolute claudication distance (ACD) (distance at which patient stops walking because the pain or discomfort becomes severe). METHODS: Thirty male patients presenting with stable, intermittent claudication (ACD between 50 and 150 meters on treadmill testing at 3.8 km/h, 10 degrees gradient) were recruited into this pilot study from a single center. Fifteen patients were randomized to treatment with IPCFC (applied for 1 hour twice daily in the sitting position) and were also advised to have daily exercise, and 15 patients served as controls, who were advised exercise alone. All patients received aspirin and had resting and postexercise ankle/brachial index (ABI) measured at enrollment along with ICD and ACD on treadmill testing (3.8 km/h, 10 degrees gradient). The mean age, baseline ICD, and ACD of the treatment and control groups were 70.4 +/- 7 years and 70.7 +/- 9 years, 55.8 +/- 15 meters and 68.4 +/- 17 meters, and 86.7 +/- 19 meters and 103.9 +/- 27 meters, respectively. Both groups were equally matched for risk factors, including smoking, type II diabetes mellitus, and hypercholesterolemia. IPCFC was applied. The study protocol included follow-up visits at 1, 2, 3, 4, 6, and 12 months with the ABI, ICD and ACD being measured at every visit. RESULTS: The percent change from baseline for ICD and ACD for each patient visit and the mean +/- standard deviation (SD), standard error (SE), and median were calculated for the control and treatment groups. The percent change from baseline measurements (mean +/- SD) for ICD and ACD in the control group at 4, 6, and 12 months were 2.2 +/- 18 and 2.3 +/- 18, 2.9 +/- 17 and 5.2 +/- 20, and 3.6 +/- 18 and 5.8 +/- 20, respectively. In contrast, the changes in ICD and ACD at 4, 6, and 12 months in the treatment group were 137.1 +/- 128 (P < .01) and 84.3 +/- 82 (P < .01), 140.6 +/- 127 (P < .01) and 96.4 +/- 106 (P = .01), and 150.8 +/- 124 (P <0.01) and 101.2 +/- 104 (P <0.01), respectively. Although the ABI showed a slight increase in the treatment group, these differences were not statistically significant. CONCLUSIONS: The results of this pilot study show that IPCFC improves walking distance in patients with stable intermittent claudication. A significant increase in ICD and ACD was seen at 4 and 6 months of treatment, respectively, and the improvement was sustained at 1 year. The combination of IPCFC with other treatment such as risk-factor modification and daily exercise may prove useful in patients with peripheral arterial occlusive disease. It may be a useful first line of therapy in patients with disabling claudication who are unfit for major reconstructive surgery. Improved walking on long-term follow-up and experience from different centers may establish a role for this treatment modality in the future.

Administration, Oral↗
PubMed2006

The distance-saturation product predicts mortality in idiopathic pulmonary fibrosis.

INTRODUCTION: The 6-min walk test (6MWT) has prognostic value in various pulmonary disorders including idiopathic pulmonary fibrosis (IPF). We determined the individual prognostic accuracy of distance walked and oxygen saturation during the 6MWT in patients with IPF. We defined a new composite index, the distance-saturation product (DSP), which is the product of distance walked and lowest oxygen saturation during the 6-min walk test. We compared the performance of the DSP to the individual 6MWT parameters in predicting mortality. METHODS: We evaluated pulmonary function tests, 6-min walk parameters and the DSP between survivors and non-survivors. The ability of each measure to discriminate outcomes was determined by receiver operator curves. RESULTS: 81 patients (48 survivors, 33 non-survivors) were included. Pulmonary function tests were similar and did not correlate with survival. Desaturation was greater (89.4% versus 83.7%, P<0.001) and distance walked was lower (406.9 versus 181.3m, P = 0.005) in non-survivors. The DSP was significantly lower among non-survivors (364.8 versus 153.5m%, P < 0.001) and predicted mortality more accurately than either individual 6MWT component (P = 0.035 versus desaturation, P=0.040 versus distance). A DSP <200 m% was associated with a seven-fold greater risk of 12-month mortality and an 18.0% shorter median survival compared with a DSP > 200 m% (P < 0.001). DISCUSSION: Each component of the 6-min walk independently predicted mortality in IPF with greater accuracy than spirometry. However, a composite of both parameters, the DSP, provides slightly greater accuracy and represents a novel measure for assessing survival in patients with IPF.

Exercise Test↗
PubMed2006

Endobronchial ultrasonography with distance for peripheral pulmonary lesions.

BACKGROUND: We assessed the effectiveness of applying the distance from the orifice of the bronchus to visualized peripheral pulmonary lesion (PPL) under endobronchial ultrasonography (EBUS) to transbronchial biopsy (TBB), as an alternative to EBUS with a guide sheath (GS) and fluoroscopy. PATIENTS AND METHODS: From October 2004 to July 2005, a total of 158 consecutive patients with solitary PPLs, which were not visualized under flexible video bronchoscopy, were received EBUS for advanced localization subsequently. One hundred and thirteen of 158 patients with solitary PPLs which were visualized on EBUS image were included in this prospective study and randomly divided into two groups for TBB using different methods. In group EBUS-D (57 patients) the distance from the bronchial orifice to pulmonary lesion was measured, then the biopsy forceps were advanced to this measured distance and biopsy followed. In group EBUS (56 patients) the biopsy forceps were advanced regardless of distance. The diagnostic yields were then compared. RESULTS: TBBs in group EBUS-D patients had a significantly higher diagnostic yield (45/57, 78.9%) than group EBUS patients (32/56, 57.1%) [P=0.013]. Size and location of lesion, duration of EBUS, diagnosis of malignancy, and whether the probe was located within the lesion on EBUS image did not differ between these two groups. Mild bleeding occurred in three patients in group EBUS-D and two in group EBUS. One group EBUS patient had a self-limited pneumothorax. CONCLUSIONS: Measuring and applying the distance between the orifice of bronchus and the lesion could increase the diagnostic yield of EBUS-guided TBBs for PPLs.

Adult↗
PubMedDate not supplied

Travel distance, age, and sex as factors in follow-up visit compliance in the post-gastric bypass population.

BACKGROUND: There is no consensus regarding the optimal rate of follow-up in the post-bariatric surgery patient population. METHODS: The records of all patients who underwent laparoscopic Roux-en-Y gastric bypass from 2001 to 2003 were reviewed. Using patient zip codes, travel distances were calculated between the patients' places of residence and our clinic. Patients were then assigned to 1 of 3 cohorts according to the following distances: (1) < 50 miles, (2) 50 to 100 miles, and (3) > 100 miles. Patient compliance with follow-up appointments at 3 weeks, 3 months, 6 months, 9 months, and 12 months was analyzed. Linear trends were identified using the Mantel-Haenszel test. Age and sex were analyzed as possible predictors of compliance using the chi(2) test. P values < .05 were considered statistically significant. RESULTS: The study group comprised 150 patients (127 females and 23 males). The 3 cohorts contained 115, 21, and 14 patients, respectively. All patients in each cohort were compliant with the 3-week follow-up appointment. Although there were differences in compliance between cohorts at each of the remaining appointments, only the 9-month (70.3% vs 61.9% vs 35.7%) visit showed statistical significance (P = .035). The 6-month visit trended toward significance (85.2% vs 76.2% vs 64.3%; P = .088). Males were more likely to be compliant with the 12-month follow-up (P = .040). When controlling for sex, travel distance was also a predictor of compliance at this follow-up visit (P = .024). Age was not predictive of compliance (P = .827). CONCLUSION: Based on our findings, we conclude that travel distance from the clinic does not significantly affect compliance at the initial follow-up, 3-month, and 12-month appointments. However, distance does tend to affect compliance at the 6-month appointment and significantly affects compliance at the 9-month appointment. Males are more likely to be compliant at the 12 month follow-up visit. We must continue to strive for 100% follow-up in our post-bariatric surgery patients.

Adult↗
PubMed2006

The correlation between root canal patterns and interorificial distance in mandibular first molars.

OBJECTIVES: The aim of this study was to investigate the relationship of the distance between mesiobuccal (MB) and mesiolingual (ML) orifices (interorificial distances) in the pulp chamber floor and the degree of canal curvature in the mandibular first molars. STUDY DESIGN: In this in vitro study, 102 extracted teeth were radiographed in both buccolingual (CV) and mesiodistal (PV) directions and then grouped according to the Vertucci classification. The interorificial distance was measured by the stereomicroscope method. RESULTS: The interorificial distance was significantly higher in type IV compared to type II (P= .016). In the logistic regression analysis, the increase in the degree of primary canal curvature of the ML in CV was a predictive factor for increase in the primary curvature of ML in PV (P = .01). CONCLUSION: The interorificial distance in the pulp chamber floor and primary curvatures in CV were found to be key factors for evaluation of root canal patterns in PV.

Analysis of Variance↗
PubMed2004

Tip to substrate distances in STM imaging of biomolecules.

STM images of single biomolecules adsorbed on conductive substrates do not reproduce the expected physical height, which generally appears underestimated. This may cause the tip to interfere with the soft biological sample during the imaging scans. Therefore, a key requirement to avoid invasive STM imaging is the knowledge, and the control, of the initial tip to substrate distance. This is connected to the setting of the tunnelling current and applied voltage, which define a tunnelling resistance. The height of the STM tip was measured by calibrating the tunnelling resistance, as a function of its vertical displacement until establishing a mechanical contact. At a tunnelling resistance of 4 x 10(9)Omega, distances of about 3 and 6 nm are estimated when flat Au substrates are imaged in water and in air, respectively. On such a ground, the relevance of the starting tip-substrate distance in determining a non-invasive imaging has been investigated for a plastocyanin mutant chemisorbed on Au(111) electrodes. At tunnelling distances sufficient to overcome the physical height of the imaged biomolecules, their lateral dimensions are found to be consistent with the crystallography, whereas they are significantly broadened for smaller distances.

Animals↗
PubMed2005

Two wrongs make a right: linear increase of accuracy of visually-guided manual pointing, reaching, and height-matching with increase in hand-to-body distance.

Measurements were made of the accuracy of open-loop manual pointing and height-matching to a visual target whose elevation was perceptually mislocalized. Accuracy increased linearly with distance of the hand from the body, approaching complete accuracy at full extension; with the hand close to the body (within the midfrontal plane), the manual errors equaled the magnitude of the perceptual mislocalization. The visual inducing stimulus responsible for the perceptual errors was a single pitched-from-vertical line that was long (50 degrees), eccentrically-located (25 degrees horizontal), and viewed in otherwise total darkness. The line induced perceptual errors in the elevation of a small, circular visual target set to appear at eye level (VPEL), a setting that changed linearly with the change in the line's visual pitch as has been previously reported (pitch: -30 degrees topbackward to 30 degrees topforward); the elevation errors measured by VPEL settings varied systematically with pitch through an 18 degrees range. In a fourth experiment the visual inducing stimulus responsible for the perceptual errors was shown to induce separately-measured errors in the manual setting of the arm to feel horizontal that were also distance-dependent. The distance-dependence of the visually-induced changes in felt arm position accounts quantitatively for the distance-dependence of the manual errors in pointing/reaching and height matching to the visual target: The near equality of the changes in felt horizontal and changes in pointing/reaching with the finger at the end of the fully extended arm is responsible for the manual accuracy of the fully-extended point; with the finger in the midfrontal plane their large difference is responsible for the inaccuracies of the midfrontal-plane point. The results are inconsistent with the widely-held but controversial theory that visual spatial information employed for perception and action are dissociated and different with no illusory visual influence on action. A different two-system theory, the Proximal/Distal model, employing the same signals from vision and from the body-referenced mechanism with different weights for different hand-to-body distances, accounts for both the perceptual and the manual results in the present experiments.

Adaptation, Ocular↗
PubMed2006

Testosterone levels in women and men who are single, in long-distance relationships, or same-city relationships.

Research points to an association between testosterone (T) and partnering in some women and men, and this association has been interpreted as an effect of either relationship status (i.e. differences in relationship status lead to differences in T) or relationship orientation (i.e. T is associated with the likelihood of entering relationships). To address whether physical partner presence was associated with decreased T, we examined T levels in people (72 women; 49 men) who were single, in long-distance relationships, or in same-city relationships. No participants were using exogenous hormones, including hormonal contraceptives. Participants provided a saliva sample and responded to questions about their relationship status. Single men had higher T than long-distance and same-city partnered men, which supports the relationship orientation interpretation. In contrast, same-city partnered women had lower T than single women and women in long-distance relationships, which supports the relationship status interpretation. We conclude that physical partner presence is not necessary to see an association between partnering and hormones in men (since same-city and long-distance partnered men had similar T levels), but may be necessary in women (since same-city partnered women had lower T than long-distance partnered women).

Adolescent↗
PubMed2026

Integrating genomic distance analyses in the description of a new family, genus, and species of sponge-associated antipatharians (black corals).

Antipatharians (black corals) are among the least studied coral groups, with much of their diversity still undescribed. Here, we present an integrative morphological, phylogenomic and genomic distance study of deep-sea antipatharians sampled in high seas areas of the North Pacific Ocean and from New Zealand's Exclusive Economic Zone. These corals grow on hexactinellid sponges - a unique characteristic in the order Antipatharia. Using a dataset of ultra-conserved elements and exons, combined with morphological analyses, we reconstruct phylogenomic relationships and formally describe a new family (Eidikopathidae fam. nov.), a new genus (Eidikopathesgen. nov.), and two new species (E. korallispongiasp. nov., E. zealandkoralliasp. nov.). Morphologically, the new family is distinguished by a corallum consisting of a network of loose branches that fuse with the sponge skeletal framework. Phylogenomic analyses recovered consistent topologies with strong nodal support, corroborating the distinct evolutionary placement of this sponge-associated lineage. Pairwise genomic distances estimated using the Tamura-Nei model were concordant with patristic genomic distances, identifying Pteridopathidae as the genetically closest family to Eidikopathidae fam. nov., followed by Myriopathidae and Stylopathidae, which were recovered as sister families in the phylogeny. This pattern shows that genomic distance complements, rather than simply mirrors, tree topology by quantifying accumulated sequence divergence among lineages. Together, these results provide the first genomic distance framework for Antipatharia, offering a baseline for future systematic, evolutionary, and biodiversity studies on this fundamental shallow, mesophotic and deep-sea coral group.

Animals↗
PubMed1996

Distance between Cys-201 in erythrocyte band 3 and the bilayer measured by single-photon radioluminescence.

Single-photon radioluminescence (SPR), the excitation of fluorophores by short-range beta-decay electrons, was developed for the measurement of submicroscopic distances. The cytoplasmic domain of band 3 (cdb3) is the primary, multisite anchorage for the erythrocyte skeleton. To begin to define the membrane arrangement of the highly asymmetrical cdb3 structure, the distance from the bilayer of Cys-201 next to the "hinge" of cdb3 was measured by both SPR and resonance energy transfer (RET). cdb3 was labeled at Cys-201 with fluorescein maleimide. For SPR measurements, the bilayer was labeled with [3H]oleic acid. The corrected cdb3-specific SPR signal was 98 +/- 2 cps microCi-1 [mumol band 3]-1. From this and the signal from a parallel sample in which 3H2O was substituted for [3H]oleic acid to create uniform geometry between 3H and the fluorophores, a Cys-201-to-bilayer separation of 39 +/- 7 A was calculated. Confirmatory distances of 40 and 43 A were obtained by RET between fluorescein on Cys-201 and eosin and rhodamine B lipid probes, respectively. This distance indicates that Cys-201 lies near band 3's vertical axis of symmetry and that the subdomain of cdb3 between the hinge and the membrane is not significantly extended. In addition, these results validate SPR as a measure of molecular distances in biological systems.

Anion Exchange Protein 1, Erythrocyte↗
PubMed2004

"Mind the gap": the size-distance dissociation in visual neglect is a cueing effect.

There is a growing body of evidence that the processes mediating the allocation of spatial attention within objects may be separable from those governing attentional distribution between objects. In the neglect literature, a related proposal has been made regarding the perception of (within-object) sizes and (between-object) distances. This proposal follows observations that, in size-matching and bisection tasks, neglect is more strongly expressed when patients are required to attend to the sizes of discrete objects than to the (unfilled) distances between objects. These findings are consistent with a partial dissociation between size and distance processing, but a simpler alternative must also be considered. Whilst a neglect patient may fail to explore the full extent of a solid stimulus, the estimation of an unfilled distance requires that both endpoints be inspected before the task can be attempted at all. The attentional cueing implicit in distance estimation tasks might thus account for their superior performance by neglect patients. We report two bisection studies that address this issue. The first confirmed, amongst patients with left visual neglect, a reliable reduction of rightward error for unfilled "gap" stimuli as compared with solid lines. The second study assessed the cause of this reduction, deconfounding the effects of stimulus type (lines vs. gaps) and attentional cueing, by applying an explicit cueing manipulation to line and gap bisection tasks. Under these matched cueing conditions, all patients performed similarly on line and gap bisection tasks, suggesting that the reduction of neglect typically observed for gap stimuli may be attributable entirely to cueing effects. We found no evidence that a spatial extent, once fully attended, is judged any differently according to whether it is filled or unfilled.

Adult↗
PubMed1991

Tendency-distance models of social cohesion in animal groups.

Although it has been assumed that attraction and repulsion between social individuals constitute a basis for group cohesion, there has been no systematic study of the possible ways in which these tendencies might vary with inter-individual distance (IID), or of associated implications for group structure. In this paper, a family of attraction/repulsion--distance functions is described. Computer simulation was used to examine the effects of each function on group cohesion, as reflected by mean values and variability in IID and group shape. Our results showed that: (a) all models led to stability in group structure, but differed significantly in terms of stable IID and group shape characteristics; (b) cohesion was best served by an upwardly convex behaviour--distance function in which maximum attraction equaled maximum repulsion (and the biological plausibility of this function is discussed); (c) group elongation and variability in mean IID were significantly positively correlated; (d) although dyads maintained an equilibrial separation distance, at which attraction balanced repulsion, in larger groups stable nearest neighbour distances were often less than the equilibrium distance; and (e) individuals needed to monitor and respond to only relatively few of their companions in order to avoid group fragmentation.

Animals↗