Head-on Approach Research Articles

Collision avoidance behaviours of luggage-laden pedestrians

Understanding how pedestrians move and avoid collisions is essential for ensuring safety in crowded environments. In this study, we conducted detailed experiments, focusing on variables such as movement type (walking and running), encounter angles (90 and 180 degrees), and pedestrian characteristics. We analyzed a total of 168 trajectories to gain insights into the collision avoidance strategies employed by luggage-laden pedestrians. Our study highlights the significant impact of luggage on the minimum avoidance distance in vertical encounters, while head-on approaches show limited influence. We use the minimum predicted distance to evaluate time avoidance time, with particular focus on the presence of luggage as a pivotal determinant. Furthermore, we conduct a comprehensive categorization on pedestrian behaviors when carrying luggage, taking into account their speed and trajectory. Our findings reveal distinct strategies adopted by luggage-laden pedestrians when avoiding from the left and right sides. Interestingly, pedestrians employ more efficient conflict mitigation tactics when interacting with luggage-laden individuals approaching from the left compared to the right side. These insights are valuable for optimizing crowd management strategies, particularly in transportation hubs with luggage-laden crowds.

The influence of whalewatching on the behaviour of migrating gray whales (Eschrichtius robustus) in Todos Santos Bay and surrounding waters, Baja California, Mexico

This study investigated the influence of whalewatching boats on the behaviour of gray whales on their migratory route in Todos Santos Bay, near the port of Ensenada, Baja California, Mexico. The objectives were: (1) to compare the swimming direction and velocity of whales in the presence and absence of whalewatching vessels, and when other boats were fishing, cruising or drifting; and (2) to contribute scientific data to the improvement of whalewatching regulations for Todos Santos Bay and surrounding waters. During the winters of 1998 and 1999, theodolite tracking was undertaken from a lighthouse tower located on northern Todos Santos Island. During both years, the migration corridor was about 2.5km wide at the Todos Santos Islands; this is relatively narrow compared to other shore stations along the northern coast (USA). Sightings were separated into northbound or southbound migration routes and the variability of whale swimming direction was analysed by circular statistics. During the southbound migration, whale swimming direction was not different in the presence or absence of whalewatching vessels and other boats. This variable, however, was statistically different during the northbound migration both with whalewatching vessels (p = 0.007) and with other boats (p = 0.02). Whale swimming velocity showed significant differences without boats and with whalewatching boats during both migrations (northbound, p = 0.04; southbound, p < 0.001). Analysis of velocity in the absence and presence of other boats did not yield significant differences for either of the migrations. In addition, a head-on approach by whalewatching boats changed the whales’ swimming direction (p = 0.05) and velocity (p = 0.015) significantly when compared with an approach towards the rear or flanks. Although Mexican whalewatching law is explicit concerning manoeuvres around whale groups, an additional suggestion is made here to prevent unintentional head-on approaches.

Killing in the Name of Islam? Assessing the Tunisian Approach to Criminalising Takfir and Incitement to Religious Hatred against International and Regional Human Rights Instruments

ABSTRACT The rise of political Islam since the 1970s and the lack of a robust political alternative during the Arab Spring have paved the way for the widespread issuance of accusations of unbelief or takfir against individuals, groups of people, or institutions. These pronouncements fit into the broader context of radical Islamist ideologies spread by systematic hate propaganda, and when the two converge they constitute instigation to murder. The need to address this phenomenon has arisen in states with substantive Muslim populations in order to protect essential human rights. Tunisia has chosen a head-on approach by criminalising accusations of unbelief and incitement to religious hatred and loathing as terrorist offences. While this approach can be seen as an encroachment upon the right to freedom of expression, it has to be balanced against states' positive obligations in protecting competing human rights. Drawing on the jurisprudence of the Human Rights Committee of the ICCPR and the African Commission of the ACHPR as well as literature in the field of human rights, this paper demonstrates the interrelation between the right to life, freedom from fear, security of the person, and the right to dignity, as well as their violations through unfettered takfirism.

A Theology of Interreligious Relations

A Theology of Interreligious Relations

Testing a key assumption of using drones as frightening devices: Do birds perceive drones as risky?

Abstract Wildlife managers have recently suggested the use of unmanned aircraft systems or drones as nonlethal hazing tools to deter birds from areas of human-wildlife conflict. However, it remains unclear if birds perceive common drone platforms as threatening. Based on field studies assessing behavioral and physiological responses, it is generally assumed that birds perceive less risk from drones than from predators. However, studies controlling for multiple confounding effects have not been conducted. Our goal was to establish the degree to which the perception of risk by birds would vary between common drone platforms relative to a predator model when flown at different approach types. We evaluated the behavioral responses of individual Red-winged Blackbirds (Agelaius phoeniceus) to 3 drone platforms: a predator model, a fixed-wing resembling an airplane, and a multirotor, approaching either head-on or overhead. Blackbirds became alert earlier (by 13.7 s), alarm-called more frequently (by a factor of 12), returned to forage later (by a factor of 4.7), and increased vigilance (by a factor of 1.3) in response to the predator model compared with the multirotor. Blackbirds also perceived the fixed-wing as riskier than the multirotor, but less risky than the predator model. Overhead approaches mostly failed to elicit flight in blackbirds across all platform types, and no blackbirds took flight in response to the multirotor at either overhead or head-on approaches. Our findings demonstrate that birds perceived drones with predatory characteristics as riskier than common drone models (i.e. fixed-wing and multirotor platforms). We recommend that drones be modified with additional stimuli to increase perceived risk when used as frightening devices, but avoided if used for wildlife monitoring.

Experimental characterization of collision avoidance in pedestrian dynamics.

In the present paper, the avoidance behavior of pedestrians was characterized by controlled experiments. Several conflict situations were studied considering different flow rates and group sizes in crossing and head-on configurations. Pedestrians were recorded from above, and individual two-dimensional trajectories of their displacement were recovered after image processing. Lateral swaying amplitude and step lengths were measured for free pedestrians, obtaining similar values to the ones reported in the literature. Minimum avoidance distances were computed in two-pedestrian experiments. In the case of one pedestrian dodging an arrested one, the avoidance distance did not depend on the relative orientation of the still pedestrian with respect to the direction of motion of the first. When both pedestrians were moving, the avoidance distance in a perpendicular encounter was longer than the one obtained during a head-on approach. It was found that the mean curvature of the trajectories was linearly anticorrelated with the mean speed. Furthermore, two common avoidance maneuvers, stopping and steering, were defined from the analysis of the acceleration and curvature in single trajectories. Interestingly, it was more probable to observe steering events than stopping ones, also the probability of simultaneous steering and stopping occurrences was negligible. The results obtained in this paper can be used to validate and calibrate pedestrian dynamics models.

Sharks modulate their escape behavior in response to predator size, speed and approach orientation

Escape responses are often critical for surviving predator–prey interactions. Nevertheless, little is known about how predator size, speed and approach orientation impact escape performance, especially in larger prey that are primarily viewed as predators. We used realistic shark models to examine how altering predatory behavior and morphology (size, speed and approach orientation) influences escape behavior and performance in Squalus acanthias, a shark that is preyed upon by apex marine predators. Predator models induced C-start escape responses, and increasing the size and speed of the models triggered a more intense response (increased escape turning rate and acceleration). In addition, increased predator size resulted in greater responsiveness from the sharks. Among the responses, predator approach orientation had the most significant impact on escapes, such that the head-on approach, as compared to the tail-on approach, induced greater reaction distances and increased escape turning rate, speed and acceleration. Thus, the anterior binocular vision in sharks renders them less effective at detecting predators approaching from behind. However, it appears that sharks compensate by performing high-intensity escapes, likely induced by the lateral line system, or by a sudden visual flash of the predator entering their field of view. Our study reveals key aspects of escape behavior in sharks, highlighting the modulation of performance in response to predator approach.

Chameleons communicate with complex colour changes during contests: different body regions convey different information

Many animals display static coloration (e.g. of feathers or fur) that can serve as a reliable sexual or social signal, but the communication function of rapidly changing colours (as in chameleons and cephalopods) is poorly understood. We used recently developed photographic and mathematical modelling tools to examine how rapid colour changes of veiled chameleons Chamaeleo calyptratus predict aggressive behaviour during male-male competitions. Males that achieved brighter stripe coloration were more likely to approach their opponent, and those that attained brighter head coloration were more likely to win fights; speed of head colour change was also an important predictor of contest outcome. This correlative study represents the first quantification of rapid colour change using organism-specific visual models and provides evidence that the rate of colour change, in addition to maximum display coloration, can be an important component of communication. Interestingly, the body and head locations of the relevant colour signals map onto the behavioural displays given during specific contest stages, with lateral displays from a distance followed by directed, head-on approaches prior to combat, suggesting that different colour change signals may evolve to communicate different information (motivation and fighting ability, respectively).

Cuito Cuanavale - Wie het werklik Gewen? 'n Strategiese en Operasionele Ontleding

The Angolan campaign of 1987- '88 came as the culmination of a long and bitter war between South Africa and Swapo. Although South Africa's underlying intention was to limit Swapo's guerilla war to the territory of Ovambo, this could only succeed if the Angolan rebel movement Unita could continue covering the southeastern part of Angola. It was, therefore, in South Africa's interest to prevent Unita from being removed from the equation by the massive MPLA offensive of late winter and spring 1987. This was the basic reason for the county’s intervention with Operation Modulêr. The operation was, however, run with excessive operational control from Pretoria. Instead of allowing the officers on the ground a classic Liddell Hartian indirect approach by marching northwards west of the Cuito river to cut the advancing MPLA forces from their logistical hinterland and dislocating their offensive by attacking them from behind, Pretoria forced them into a direct head-on approach east of the river. The reason was to keep the South African involvement secret or, at the very least  'plausibly deniable' - a naïve expectation. This did indeed result in a spectacular South African tactical victory at the Lomba River, where the MPLA offensive was decisively beaten back. But thereafter the South African forces were forced into a series of frontal attacks on increasingly well prepared MPLA defensive positions, including three final attacks on well fortified positions at Tumpo, which were beaten back, resulting in a subsequent stalemate. The stalemate was then brilliantly broken by Cuban forces, who marched to the southwestern Namibian border, threatening to cut the South Africans off at Tumpo, or alternatively to invade Namibia. The campaign is analysed in the light of military theory, especially the ideas of Clausewitz and Liddell Hart. The conclusion is that the MPLA lost badly, that South Africa reached its strategic objectives but did badly operationally, and that Cuba came out of the affair with flying colours.

Hurricane and Flood Preparedness for Aboveground Storage Tanks

Abstract In 2005 Hurricanes Katrina and Rita cased over ten major (> 100,000 gallons) oil spills and medium (> 10,000 gallons) oil spills in coastal areas of Texas and Louisiana. The volume for these spills was approximately eight (8) million gallons, which is just over half the volume of the Exxon Valdez event (1989). After these natural disasters caused such an environmental impact, the Federal Region 6- Regional Response Team (RRT) Executive Committee charged the Science and Technology Chair to form a committee to investigate these situations and make recommendations. The committee included representatives from several federal and state agencies, including: US Environmental Protection Agency (USEPA), US Coast Guard (USCG), US Department of Energy (USDOE), National Oceanic and Atmospheric Administration (NOAA) and Texas General Land Office (GLO). It also included several representatives from the involved industry. The committee then decided to take a head-on approach by tasking each member to focus on h...

Potential energy calculations for various water dimer configurations

Intermolecular potential energy curves are presented and analyzed for three different water dimer structures: the normal hydrogen-bonded structure (Cs); a weakly hydrogen-bonded structure (C1) thought to be important in encounters of hydrated ions in aqueous solution; and a repulsive configuration (C2h) characterized by a head-on approach of hydrogen atoms (OH … HO). Results are based on ab initio calculations [SCF and CI (at the MP2 level), with and without counterpoise (CP) correction for basis set superposition error (BSSE)] and also a recent semiempirical effective pair potential (RWK2). The CP corrections have a significant effect on the location and depth of the potential wells for the hydrogen-bonded structures, even when CI and extended basis sets are employed.

Direct Approach to Atomistic Ab Initio Studies of Precipitate Growth in Alloys

AbstractA dramatic gain in the knowledge of precipitate formation, composition, and evolution in alloys has been achieved in the recent years with improvement of transmission electron microscopy techniques for direct structural imaging [1]. A detailed understanding of the microstructure is often essential for control and manipulation of materials properties: an important example for metals is the significant hardening of Al alloys by particular precipitates from a sequence strongly dependent on alloying element concentration and the treatment of the material [2]. The wealth of experimental information provides a playground for theory in the context of elucidating precipitate growth mechanisms and influence on the host material. A head-on approach to atomistic modelling of these phenomena using an ab initio based scheme is conventionally deemed highly desired but impractical. The basic argument is that the system of any reasonably sized (i.e. realistic) and well isolated microstructure will simply contain too many atoms. We will challenge this conventional view: it is argued that most of the atoms of the above mentioned system do not play an active role in the growth discussion, hence need not be included in the modelling. Subsequently, a model system is presented which offers a highly accurate description of the interface between the host lattice and a microstructure of an arbitrary size, for the case where this interface is coherent and compositionally abrupt. When used in conjunction with other approaches already available, this model system offers a direct approach to atomistic ab initio studies of microstructure growth. A general introduction to the modelling scheme will be presented, with the particular application being the main hardening precipitate β'' in the Al-Mg-Si alloy. [1] K. W. Urban, Nature Mater. 8, 260 (2009). [2] C. D. Marioara, S. J. Andersen, H. W. Zandbergen, and R. Holmestad, Metal. Mater. Trans. A 36A, 691 (2005).

Swimming kinematics and hydrodynamic imaging in the blind Mexican cave fish (Astyanax fasciatus)

Blind Mexican cave fish (Astyanax fasciatus) lack a functioning visual system, and are known to use self-generated water motion to sense their surroundings; an ability termed hydrodynamic imaging. Nearby objects distort the flow field created by the motion of the fish. These flow distortions are sensed by the mechanosensory lateral line. Here we used image processing to measure detailed kinematics, along with a new behavioural technique, to investigate the effectiveness of hydrodynamic imaging. In a head-on approach to a wall, fish reacted to avoid collision with the wall at an average distance of only 4.0+/-0.2 mm. Contrary to previous expectation, there was no significant correlation between the swimming velocity of the fish and the distance at which they reacted to the wall. Hydrodynamic imaging appeared to be most effective when the fish were gliding with their bodies held straight, with the proportion of approaches to the wall that resulted in collision increasing from 11% to 73% if the fish were beating their tails rather than gliding as they neared the wall. The swimming kinematics of the fish were significantly different when swimming beside a wall compared with when swimming away from any walls. Blind cave fish frequently touched walls when swimming alongside them, indicating that they use both tactile and hydrodynamic information in this situation. We conclude that although hydrodynamic imaging can provide effective collision avoidance, it is a short-range sense that may often be used synergistically with direct touch.

Using Time-To-Contact information to assess potential collision modulates both visual and temporal prediction networks

Accurate estimates of the time-to-contact (TTC) of approaching objects are crucial for survival. We used an ecologically valid driving simulation to compare and contrast the neural substrates of egocentric (head-on approach) and allocentric (lateral approach) TTC tasks in a fully factorial, event-related fMRI design. Compared to colour control tasks, both egocentric and allocentric TTC tasks activated left ventral premotor cortex/frontal operculum and inferior parietal cortex, the same areas that have previously been implicated in temporal attentional orienting. Despite differences in visual and cognitive demands, both TTC and temporal orienting paradigms encourage the use of temporally predictive information to guide behaviour, suggesting these areas may form a core network for temporal prediction. We also demonstrated that the temporal derivative of the perceptual index tau (tau-dot) held predictive value for making collision judgements and varied inversely with activity in primary visual cortex (V1). Specifically, V1 activity increased with the increasing likelihood of reporting a collision, suggesting top–down attentional modulation of early visual processing areas as a function of subjective collision. Finally, egocentric viewpoints provoked a response bias for reporting collisions, rather than no-collisions, reflecting increased caution for head-on approaches. Associated increases in SMA activity suggest motor preparation mechanisms were engaged, despite the perceptual nature of the task.

Structural and Spectroscopic Studies Shed Light on the Mechanism of Oxalate Oxidase

Oxalate oxidase (EC 1.2.3.4) catalyzes the conversion of oxalate and dioxygen to hydrogen peroxide and carbon dioxide. In this study, glycolate was used as a structural analogue of oxalate to investigate substrate binding in the crystalline enzyme. The observed monodentate binding of glycolate to the active site manganese ion of oxalate oxidase is consistent with a mechanism involving C-C bond cleavage driven by superoxide anion attack on a monodentate coordinated substrate. In this mechanism, the metal serves two functions: to organize the substrates (oxalate and dioxygen) and to transiently reduce dioxygen. The observed structure further implies important roles for specific active site residues (two asparagines and one glutamine) in correctly orientating the substrates and reaction intermediates for catalysis. Combined spectroscopic, biochemical, and structural analyses of mutants confirms the importance of the asparagine residues in organizing a functional active site complex.

A Fundamental Study on the Danger Territories for Pedestrians and Cyclists on Sidewalk

In this paper, the distances and the relative velocities were focused on as the factors of dangers that they feel in their near miss. The experiments and the analysis cleared the differences in their feeling and in the territories in which they feel the danger between pedestrians and cyclists. Each experiment was conducted for a pair of a pe-destrian and acyclists, which gave us the distances in which they feel danger as a result. The results were main-ly as follows: Pedestrians felt the danger earlier than cyclists in head-on approach. Cyclists felt it and avoided the pedestrian earlier.

Autoimmune TCR structure

A crooked T cell receptor (TCR)–MHC interaction may result in immune responses that are similarly skewed, based on findings from Michael Hahn, Kai Wucherpfennig, and colleagues (Dana-Farber Cancer Institute, Boston, MA). The TCR in question is associated with multiple sclerosis, suggesting that protective and autoimmune T cells recognize antigens differently. Figure An autoimmune TCR (left; red and yellow) sits off-center on its MHC (blue) and peptide (green) compared with a more conventional arrangement (right). A head-on approach has been seen in protective cases, in which the TCR sits directly atop the foreign peptide/MHC complex on an antigen-presenting cell. Now, the authors present the first crystal structure of an autoimmunity-generating complex—a TCR that binds to MHC presenting the myelin basic protein (MBP) peptide. This structure, derived from a TCR that was isolated from a multiple sclerosis patient, reveals a tilted complex in which the TCR contacted mostly the NH2-terminal portion of the MBP peptide. The hypervariable (rearranged) TCR loops created a much larger fraction of the contact surface with the MHC and peptide than in conventional arrangements. “It's the sequence diversity of TCRs that allows these unusual topologies,” says Wucherpfennig. The CD4 coreceptor, which is required for T cell function, was thus unusually positioned. If this odd geometry limits T cell activation in the thymus, the cell might evade negative selection (the removal of autoreactive T cells) and escape to the periphery. Escapees remain harmless unless they are activated, possibly by microbial peptides with some structural similarity to MBP. This kind of activation might be more likely since the TCR recognizes a smaller-than-normal section of the peptide. Reference: Hahn, M., et al. 2005. Nat. Immunol. 6:490–496. [PubMed]

Modification of Schooling Behavior in Larval Atherinid FishAtherina mochonby Heat Exposure of Eggs and Larvae

We report the effects of short daily exposures to sublethal increases in water temperature during the egg and larval stages on the development of the schooling behavior of the little sand smelt Atherina mochon. The experiments were conducted to simulate the periodic exposure of different developmental stages to a transient thermal plume caused by the discharge of heated effluents into the spawning environment. Exposures were administered for eggs only, larvae only, and both eggs and larvae and consisted of nonlethal increases in water temperature from a 20°C acclimation temperature to 28.5°C over a period of 30 min, maintenance at 28.5°C for 15 min, and a gradual reduction to 20°C over 35 min. Heat treatments were administered to the egg-only and larvae-only groups for 10 consecutive days each; those administered at both the egg and larval stages were for 20 consecutive days. Behavioral testing of larval fish at 10, 15, 20, 25, 30, and 35 d posthatch showed significant modification or retardation of schooling behavior. There was an increase in number of approach–withdrawals (behavior that precedes parallel formation and involves the head-on approach of two fry and immediate veering away) as well as a decrease in parallel orientation (schooling), higher latency for the formation of the first schools, and shorter duration of the longest-persisting schools in most heat-exposed fish relative to the controls. Locomotor ability was diminished and schooling was unstable, with wide fish-to-fish distances and an absence of synchrony in the position and swimming speed of school members. These behaviors were indicative of a reduction in normal social interaction, in which fish swim close together and adjust to each other in a coordinated fashion. Additional research is required to determine whether subtle changes in schooling behavior are as important as immediate heat death to the survival of local fish populations.

Information used in detecting upcoming collision.

In four experiments we examined the nature of the information used in judging whether events would or would not give rise to a collision in the near future. Observers were tested in situations depicting approaches between two objects (lateral approaches) and approaches between an object and the point of observation (head-on approaches), with objects moving according to constant deceleration or sinusoidal deceleration patterns. Judgments were found to be based, to a large extent, on the (in)sufficiency of current deceleration to avoid upcoming collision, as specified optically by tau-dot (tau). However, the information specified by tau (tau), that is the current (first-order) time remaining until contact, was also found to play a significant role. We deduce that judgment of upcoming collision is based on the detection of tau and its evolution over time, suggesting that observers are sensitive to delta(tau) rather than to tau itself.

A Mechanistic Investigation of Alkene Epoxidation by Sterically Encumbered trans-Dioxoruthenium(VI) Porphyrins

The highly substituted dioxoruthenium(VI) porphyrins [RuVI(DPP)O2] (1a; H2DPP = 2,3,5,7,8,10,12,13,15,17,18,20-dodecaphenylporphyrin), [RuVI(TDCPP)O2] (1b; H2TDCPP = meso-tetrakis(2,6-dichlorophenyl)porphyrin), and [RuVI(TMOPP)O2] (1c; H2TMOPP = meso-tetrakis(2,4,6-trimethoxyphenyl)porphyrin) are competent oxidants for alkene epoxidation. The oxidations were carried out in a CH2Cl2/Hpz solution, and a paramagnetic bis(pyrazolato)ruthenium(IV) porphyrin, [RuIV(Por)(pz)2] (2; H2Por = H2DPP, H2TDCPP, H2TMOPP), was isolated and characterized. For the oxidation of cis-alkenes, stereoselectivity is dependent upon both the alkenes and the ruthenium oxidants, and it decreases in the order: cis-stilbene > cis-β-methylstyrene > cis-β-deuteriostyrene. The observation of inverse secondary KIE for the oxidation of β-d2-styrene [kH/kD = 0.87 (1a); 0.86 (1b)] but not for the α-deuteriostyrene oxidations suggests that the C−O bond formation is more advanced at the C(β) atom than at the C(α) atom of styrene, consistent with a nonconcerted mechanism. By consideration of spin delocalization and polar effects, the second-order rate constants for the oxidation of para-substituted styrenes by complexes 1a−c can linearly correlate with the carboradical substituent constants σmb and σJJ• (Jiang, X.-K. Acc. Chem. Res. 1997, 30, 283). This implies that the styrene oxidation by the dioxoruthenium(VI) porphyrins should involve rate-limiting generation of a benzylic radical intermediate, and the magnitude of |ρ•JJ/ρmb| > 1 suggests that the spin delocalization effect is more important than the polar effect in the epoxidation reactions. The spontaneous epoxidation of trans-β-methylstyrene by the sterically encumbered [RuVI(TDCPP)O2] and [RuVI(TMOPP)O2] complexes and the comparable ΔS‡ values for their reactions with trans-β-methylstyrene and styrene are incompatible with the “side-on approach” model; a “head-on approach” model is implicated.