All relevant key techniques involved in photogrammetric vision metrology for fully automatic 3D measurement of large-scale structure are studied. A new kind of coded target consisting of circular retroreflective discs is designed, and corresponding detection and recognition algorithms based on blob detection and clustering are presented. Then a three-stage strategy starting with view clustering is proposed to achieve automatic network orientation. As for matching of noncoded targets, the concept of matching path is proposed, and matches for each noncoded target are found by determination of the optimal matching path, based on a novel voting strategy, among all possible ones. Experiments on a fixed keel of airship have been conducted to verify the effectiveness and measuring accuracy of the proposed methods. As science and technology develop, more and more large-scale structures come into our lives, such as bridges, tunnels, airplanes, airships, wind turbine blades, and antennas. To ensure safety and prevent potential accidents and disasters, it is necessary to conduct mechanical testing and dimensional quality monitoring for these large-scale structures, which require automatic three-dimensional measurement with high metric precision.Deformation measurement of large-scale structures constitutes a 3D coordinate measuring problem involving large measurement ranges and high measuring accuracy. Compared to other measuring means such as strain gauge method , 2, survNonexpert user oriented vision metrology systems are well established in industrial metrology –13, thouUsually, in order to facilitate image measurement, retroreflective targets and highly controlled illumination conditions are employed in vision metrology, and together with the usage of coded target system –17, fullIn this paper, we focus on photogrammetric vision metrology for fully automatic 3D measurement of large-scale structure; all relevant key techniques involved are studied, such as coded target, network orientation, and matching of noncoded target. All will be described in the following sections detailedly.x, and the world point is denoted by a homogeneous 4-vector X; then the Pinhole Imaging Model can be simply expressed bya is an arbitrary scale factor. K is a 3 × 3 upper triangular calibration matrix, holding the intrinsic parameters. R is a 3 × 3 rotation matrix and t is a 3-vector representing the translation vector; R and t together denote the rigid body transformation between the view and the world coordinate system. The 3 × 4 matrix P = K[R | t] is the projection matrix.The image point is denoted by a homogeneous 3-vector P is projected to x and x′, respectively, on view S and S′, obviously, P, x, x′, and two optical centers C and C′ are in the same spatial plane π, this is the well-known coplanarity or epipolar constraint, which is encoded in the 3 × 3 fundamental matrix F , slightly different from what is stated in 2.1; the coordinate system of view S, which is C-XYZ, is now the world coordinate system. Let [t]× denote the skew symmetric matrix:F isK and K′ are the calibration matrices of view S and S′, respectively.The relative pose between view F can be considered without knowledge of the calibration matrices [K and K′ are known, which means view S and S′ are calibrated; image points can be normalizedx and x′, respectively; then the epipolar constraint  and , respectively, and the last one represents the point on X-axis with coordinates .There are two kinds of circular points in the designed coded target; one is reference points; there are 4 of them in total, and they together establish the two-dimensional target coordinate system i, j), and each one of them represents one binary bit k; the presence and absence of it represent the status 1 and 0 of this binary bit, respectively. If there are m coding points at most per column, in other words, the X coordinate i is not more than m, then the relationship between the binary bit k and the coordinates  is given byn, the total amount of binary bits encoded by the designed coded target is m × n; then the overall coding capacity is 2m×n, which means 2m×n instances of coded target with different coding information can be derived, for m and n are chosen arbitrarily; thus, theoretically, there is no upper limit to the coding capacity of the designed coded target.The other kind is coding points; they are located in positions with positive integer coordinates  and , respectively; according to  NLoG;blob clustering based on image distance between two points; the clusters containing only single blob are determined to be noncoded targets, whereas the clusters containing the required amount of blobs are treated as potential coded targets in succeeding recognition process;coded target recognition based on geometric characteristics and coding principle of the designed coded target; potential coded targets cannot be diagnosed until all constraints are met in this recognition process.Detection of coded and noncoded targets in this paper is carried out mainly in the following four steps:σ is the scale parameter; and the detection of blobs with multiple scales is to detect scale-space maxima/minima, which are points that are simultaneously local maxima/minima with respect to both space and scale [The blob detector adopted in this paper is the well-known scale invariant  NLoG, which is given as follows:nd scale , 27.As stated before, a coded target is imaged as a group of blobs, whereas a noncoded one is imaged as one single blob, which means the blobs within a coded target distributes much denser than blobs of multiple noncoded targets do; this will not change as long as the distribution density of multiple noncoded targets in space does not exceed the one of points within a coded target, and the depths of noncoded targets, relative to camera, do not vary too much from the one of a coded target. Thus, simple blob clustering based on image distance between two points can be conducted to distinguish between coded and noncoded targets.r denotes the adjacent area of each blob; if a blob is within this adjacent area of another blob, then these two blobs are adjacent to each other and can be clustered into the same cluster. As you can see, there are no other blobs within the adjacent area of each noncoded target, so the cluster of each noncoded target contains only its own blob.The blob clustering process is demonstrated in a first, blob b will be added into cluster next, for it is within the adjacent area of blob a, and then come blobs c and d; clustering will keep going until no more adjacent blobs are found.Let us check out step by step how clustering works out for coded target; if it starts at blob This blob clustering process, like the view clustering process which is going to be described in the succeeding section, is a standard recursive process; they both can be implemented by the recursive routine shown in After clustering, clusters containing only single blob are determined to be noncoded targets directly, and clusters containing reasonable amount of blobs are determined to be potential coded targets, since a true coded target contains at least 4 reference points and limited amount of coding points. If a cluster contains unreasonable amount of blobs, blobs within it will be sentenced to be noncoded targets as well.recognition of reference points;decoding.As stated before, coded target recognition is based on geometric characteristics and coding principle of the designed coded target; potential coded targets coming from blob clustering cannot be diagnosed until all constraints are met in this recognition process. Coded target recognition is carried out mainly in the following two steps:O of the target coordinate system. As shown in O is much bigger than any of the other blobs, so it can be located simply by finding the blob with the biggest size. Naturally, radius can be considered; it is a measure of blob size, and it is readily acquired in blob detection stage, but radius alone cannot ensure clear distinction between the origin O and other blobs, since the radius difference between two blobs may be smaller than the scale resolution in blob detection, which is the scale step between two NLoG templates; thus, more robust method is needed. In this paper, the grayscale sum of pixels within blob radius, in other words, the grayscale weighted area, is used to make a clear distinction of the origin O from other blobs; the blob with the biggest grayscale weighted area is determined to be the origin O.The first thing to do is to determine which blob is the origin x, y1, and y2, have their own geometric characteristics; the angle between segments Oy1 and Ox equals the angle between Oy2 and Ox, which is both α0 as shown in αi formed by any other two blobs toward origin O; based on these, x, y1, and y2 are determined in this paper by finding angle α0.The rest three reference points, x, y), and its target coordinates  is a projective transformation; however, 4 pairs of correspondences between image and target generated by 4 reference points are unable to solve this projective transformation, since there are 3 reference points which are collinear, which are O, y1, and y2, respectively. Fortunately, when target depth, relative to camera, is far greater than target size, as is usually the case in practice, the relationship between  and  approximates to an affine transformation Ha:Ha; thus, the recognized 4 reference points in Ha.Technically, the relationship between the image coordinates of a coding point, which is  of each coding point can be computed according to  represents the total amount of observations in view ik.A matching path is defined as follows:x15, finds four matches in view 6, resulting in four separate paths; then we continue to find matches in view 7 for those four points. Since the point 1 in view 6, which is x16, can find two different matches in view 7, a previous path now splits into two, resulting in five separate paths in total, which areThe process of finding possible matching paths for a given image point is demonstrated in Fba is the fundamental matrix between view a and view b, then the epipolar line lja in view b, as shown in xja is the point j in view a. In short, lja is an epipolar line induced by xja.Given that As the process described above continues, the amount of matching paths will be expected to increase, but if the amount of paths remains one eventually, image points contained in the only matching path will naturally be determined to be matched or the voting strategy, which is described in the next section, will step in.The novel voting strategy proposed in this paper is still based on epipolar constraint; if image points contained in a matching path are really matched, epipolar constraint should be met between all N-choose-2 points; thus, we can determine whether a path is the real one simply by checking if all the N-choose-2 cases in it meet the epipolar constraint. However, due to error, probably not all the cases are qualified, so in practice it is reasonable to choose the path with most qualified cases instead of all qualified cases as the optimal matching path, which contains points really matched.xjk1ik1 and xjk2ik2 are, respectively, the k1th and k2th points in the path, and the function check is given as follows:xjk1ik1, Fik1ik2xjk2ik2) is the distance between point xjk1ik1 and the epipolar line Fik1ik2xjk2ik2 and d is some certain distance threshold, as explained in k1th point is close enough to the epipolar line in view ik1 induced by the k2th point, the path gets one vote.The vote that a matching path can get is given byxjk1ik1, xjk2ik2) and check, respectively, so if all N-choose-2 cases in a path meet the epipolar constraint, this path will get a unanimous vote, which is w(w − 1).Apparently, each N-choose-2 case has two votes to give, which is check(Taking the three images shown in The main types of airship are nonrigid blimps, semirigid airship, and rigid airship. Unlike the nonrigid blimps, semirigid airship usually has a fixed keel besides internal pressure, which runs the length of the ship along the bottom of the hull, as shown in A designed keel structure in a practical semi-airship is shown in Figures In order to ensure safety and prevent potential structural failure in extreme conditions like storm, it is necessary to conduct mechanical testing and high-precision dimensional quality monitoring for this designed keel structure before the airship is put into use.The proposed methods in this paper have been applied to this mechanical testing, and results are shown in the following figures. The reference frame is established by the three points on the chessboard shown in There are 18 images which are taken under one working condition; some of these images are shown in In order to verify the measuring accuracy, vertical deformations of one node under different load and internal pressure conditions are measured by total station besides our automatic vision metrology as true values, and the deviations of our measurement results from the true values are given in In this paper, all relevant key techniques involved in photogrammetric vision metrology for fully automatic 3D measurement of large-scale structure are studied. A new kind of coded target consisting of circular retroreflective discs is designed, and corresponding detection and recognition algorithms based on blob detection and clustering are presented. Then a three-stage strategy starting with view clustering is proposed to achieve automatic network orientation. As for matching of noncoded targets, the concept of matching path is proposed, and matches for each noncoded target are found by determination of the optimal matching path, based on a novel voting strategy, among all possible ones. Experiments on a fixed keel of airship have been conducted to verify the effectiveness and measuring accuracy of the proposed methods.Future work will mainly focus on developing new blob clustering method that is more adaptive to coded targets in different depths, and improved method that is less sensitive to starting point should be developed for finding all possible matching paths, since, in current way, different starting points may lead to different amount of points within the optimal paths with some matched points missed.


Flying in a small piston-engine plane bears little resemblance to flying in a commercial jet. There are no lines at the airport, no baggage checks, and often less legroom once you duck inside the cabin. You can feel every bump in the tarmac as the plane heads down the runway, every rumble of the engine. Once you are aloft there’s no denying the improbability of flight; the low cruising altitude offers detailed views of the land passing below. The experience is more like traveling in an airborne car than in the insulated cocoon of an airliner. For passengers like this writer, it’s also much more fun.,There’s another less obvious difference. Unlike commercial jets, which use kerosene-based jet fuel, piston-engine aircraft still mostly run on leaded aviation gasoline, or avgas. In fact, avgas is one of the few fuels in the United States that still contain lead,,,Lead is a well-documented neurotoxicant that is particularly harmful to children, who are typically exposed when they ingest or inhale lead-containing dust in the home. In recent years, serious harm to cognitive and behavioral functions including intelligence, attention, and motor skills has been demonstrated in children with much less lead in their blood than previously thought to cause harm,,,Still, a great deal of progress has been made in reducing lead exposure. Today, the mean blood lead level among U.S. children is 1.2 µg/dL, down from 15 µg/dL in 1976–1980.But unlike automobile gasoline, lead in avgas has remained unreg-ulated.“Lead is like the magic elixir for detonation prevention. There’s really no other chemical that precludes detonation like lead does,” says Peter White, head of the new Fuels Program Office in the Federal Aviation Administration (FAA), which the agency established in fall 2012 to identify an unleaded alternative to 100LL.There are nearly 20,000 airports across the United States, the majority of them small facilities dedicated to so-called general aviation—civilian, noncommercial flight with private or corporate planes, flying schools, sightseeing tours, and the like. The general-aviation fleet includes a diverse menagerie of aircraft built over many decades, from airplanes to experimental craft.Seventy-one percent of the fleet, about 159,000 aircraft,,,,,3, two-thirds of the NAAQS limit of 0.15 µg/m3. This prompted the EPA to note that airports have the potential to push ambient lead concentrations above the NAAQS, even as the agency now considers whether that standard itself should be lowered.Monitoring studies have shown that lead in the air on and surrounding five North American airports exceeds background levels.While a little less than half of lead emissions from piston-engine aircraft linger near airports, the remainder disperses far and wide during flight, according to the EPA.The EPA considers general-aviation pilots and frequent fliers to have the greatest risk of exposure to lead from avgas. But the general public may also be affected. In 2010 the agency estimated that 16 million people live and 3 million children attend school within a kilometer of lead-emitting airports. This population contains a disproportionate percentage of low-income and minority residents, groups already facing an increased risk of lead exposure.In the only study of its kind, published in 2011, Duke University researchers assessed the relationship between child blood lead levels and residential proximity to airports in six North Carolina counties. They found that children living within 500 m of airports where avgas was used had blood lead levels averaging 4.4% higher than children living more than 2,000 m away. Lead exposure decreased in children living within 500–1,000 m of the airports and declined to background levels further away.Though small, the average increase was enough to push some children in the study above the CDC reference value of 5 µg/dL, according to Marie Lynn Miranda, the study’s lead author, who is now dean of the School of Natural Resources and Environment at the University of Michigan. And while the airports were not conclusively implicated as the source of the excess lead, Miranda says it’s important to reduce any small sources of lead even in the face of bigger ones like deteriorating lead-based paint, imported products, and some drinking water sources. “While lead in aviation gasoline is not in my top three priorities for childhood lead exposure, it is a source of a known neurotoxicant,” she says. “The more we study lead, the more we understand that even very low levels of exposure cause adverse effects.”The increase potentially attributable to avgas in Miranda’s study could be much higher than the average in certain subgroups of children, says David Bellinger, a professor of neurology at Harvard Medical School, who studies how neurotoxicants affect brain development. While praising the study, Bellinger says he would like to see further research clarifying how such factors as flight paths and prevailing winds might affect exposure patterns (which Miranda says she is planning).Bellinger points out that although such low levels of lead exposure may not affect any one child in obvious ways—it’s hard to notice the loss of a few IQ points—the effects can add up for the population as a whole. In April 2012 he published a study calculating the cumulative deficit of IQ points among U.S. children aged 0–5 years that were attributable to a variety of chemical exposures and medical conditions. Lead exposure overall accounted for a nationwide loss of nearly 23 million IQ points, a figure exceeded only by the loss attributable to preterm birth.Pressure has been mounting to do something about the lead in avgas since 2003. That’s when Bluewater Network, a non-profit organization that later merged with the environ-mental group Friends of the Earth (FoE), first wrote to the EPA arguing that leaded avgas endangers public health and welfare. In 2006 FoE petitioned the EPA to either officially declare that it does endanger public health by making a so-called “endangerment finding” that would require regulating it under the Clean Air Act, or else conduct the research necessary to make that determination. In April 2010 the agency issued an Advance Notice of Proposed Rulemaking, which described existing data and planned research and requested comment and further information on the subject, but took no further action.,In March 2012 FoE sued to force the agency to decide whether to make an endangerment finding. Four months later the EPA responded, stating it is conducting monitoring and modeling studies to clarify the effect of lead emissions from airports across the nation and to determine how big a role they play in areas failing to meet the NAAQS.“We feel like there’s enough evidence already that [leaded avgas] is harmful,” says Marcie Keever, FoE’s legal director. “It doesn’t seem to us and many members of the public who live on the fence line of these airports that there is a question that we need to move toward phasing lead out of avgas.” An EPA spokesperson was unable to make agency scientists or policy staff available for comment.Meanwhile, in 2011 another environmental group called the Center for Environmental Health (CEH) sued several avgas producers and suppliers under California’s unique Safe Drinking Water and Toxic Enforcement Act (a.k.a. Proposition 65) for failing to warn residents near 25 airports about lead emissions. In response to advance notices from CEH, a group of avgas sup-pliers filed a suit of their own, claiming that federal law preempted the use of Proposition 65 against avgas. If CEH’s suit were to succeed, they claimed, it would effectively shut down the sale of avgas in the state and ground 37,000 general-aviation aircraft. A federal court dismissed the suppliers’ suit, but CEH’s Proposition 65 action remains pending.The lawsuits and the potential for regulation combined with concerns about rising avgas prices, declining use of piston-engine aircraft that burn the fuel, and the future of TEL supplies, which come from a single manufacturer, convinced the aviation industry that the time had come to find an alternative to 100LL, says Rob Hackman, vice president of regulatory affairs at the Aircraft Owners and Pilots Association (AOPA). AOPA, along with the National Air Transportation Association (NATA) and other aviation and petroleum trade groups joined together in the General Aviation Avgas Coalition. In a 2010 comment submitted to the EPA contending a lack of data to support an endangerment finding, the coalition nonetheless asserted its commitment to “an unleaded future.”Hackman says the general-aviation industry recognizes that a new type of fuel is necessary and is devoting extensive research to develop it. In fact, it has been trying for more than two decades, with the petroleum industry, to remove lead from avgas. For most of that time they insisted that only a “silver-bullet replacement” fuel would do—one usable by every avgas-burning aircraft and fully compatible with existing fuel supply networks, says Hackman. Those criteria proved to be unattainable.Dozens of promising blends have been examined in full-scale engine testing, but none could satisfy all the performance requirements of 100LL.The industry now accepts that 100LL’s replacement will require tradeoffs and is searching for the least-disruptive alternative, Hackman says. That won’t happen quickly, though. In 2011 the FAA announced its intent to make an unleaded fuel available by 2018.The FAA has adopted many of the committee’s recommendations and opened the Fuels Program Office to oversee certification of a new fuel. The agency also currently allocates about $2 million per year for research and development—though that’s a fraction of what the committee requested. The process is open-ended, says the FAA’s White. At a minimum he says the agency expects to certify a version of the current 100LL fuel with the lead removed (resulting in a reduced rating of 91–94 octane), which would satisfy a good chunk of the piston-engine fleet. The FAA also plans to evaluate what modifications would enable high-performance engines to burn a lead-free version of 100LL, albeit with a potential loss in performance.Another option would be to slowly phase the lead out of avgas while developing any necessary engine modifications in tandem. Yet another would be to find a way to make more than one fuel available at airports that would satisfy the low- and high-performance segments of the fleet separately.Some observers argue that this latter solution has been right under the industry’s nose all along. The majority of the U.S. piston-engine fleet—around 75% is the number generally accepted by the industry, according to White—does not require high-octane avgas at all. Most of these aircraft can run quite happily on ordinary unleaded automobile gasoline, provided it does not contain ethanol. This fuel, often called autogas or mogas, also has the advantages of being cheap and produced in vast quantities, compared with 100LL avgas.Although most older piston-engine aircraft aren’t factory-certified to run on mogas, owners of some 60,000 aircraft—about one-third of the piston-engine fleet—have already procured the certificates and accompanying fuel-cap stickers that are required for tanking up with mogas, according to Kent Misegades, a North Carolina–based recreational pilot and cofounder of the Aviation Fuel Club, which advocates for access to mogas. Furthermore, he says, nearly all of the latest generation of piston engines come factory-certified to operate on mogas.Although gasoline without ethanol is increasingly rare, the biggest barrier to using mogas is that only a handful of U.S. airports offer it, Misegades says. “They want to create some new boutique fuel for these specialized, high-performance engines that are hardly made,” he says of the FAA’s committee. “You could make a big dent in the lead emissions literally within a year by getting more mogas onto the field,” something he says most small European general-aviation airports already do. In October 2012 U.S. congressman Henry Waxman , the ranking member of the House Energy and Commerce Committee, made a similar case in a letter to the FAA.White agrees that increasing use of mogas is a good idea, but he says the high-performance aircraft that cannot currently burn it tend to fly more than the less-demanding aircraft that can, and actually consume about 70% of the avgas used, according to unpublished industry estimates. Moreover, the market—not the FAA—dictates what fuels are available, and fuel suppliers believe the market does not support the costs associated with making mogas or any other fuel available alongside 100LL avgas at airports, according to Michael France, director of regulatory affairs at NATA, who served on the FAA committee. The market for avgas is so small, he explains, that most general-aviation airports and their fuel suppliers balk at the cost of adding fuel tanks and other equipment needed to offer a second fuel. “We support a process that identifies the replacement fuel that works best for everyone, and a two-grade solution similar to how the auto industry transitioned is really unworkable in aviation,” France says.One illustration of the market’s sway is that in 2011 the FAA approved a fuel for use in all piston-engine aircraft with a maximum lead content 19% lower than that of 100LL. The new fuel is called 100VLL, for “very low lead.” White says some 100LL on the market actually meets the new 100VLL standard; in fact, data from 89 samples of 100LL indicate that on average the avgas being sold only slightly exceeds the 100VLL standard. Yet even though lower-lead avgas is already being used by the piston-engine aircraft fleet without complaint, White says he is unaware of any 100VLL being sold separately because there isn’t any specific demand for it. There also is no legal requirement to provide it.“We can approve fuels, we can certify aircraft and engines to operate on those fuels—we’ve done that before,” says White. “How do we get over the hurdle of getting the market to make that fuel available at the airports? That’s really our big challenge.”Of course, an endangerment finding by EPA would do just that. Currently, at least one federal agency, the aviation and petroleum industries, and environmental groups all seem to agree that leaded avgas’s days are numbered. What remains to be hashed out is how to go about replacing it, how quickly to proceed, and whether the industry can come up with a solution before the EPA decides whether to regulate. For now, the process appears to be a long-haul flight.


During these years, Burchfield absorbed such diverse influences as Chinese scroll paintings; the works of Hiroshige, Hokusai, and Aubrey Beardsley; and Russian ballet designs by Léon Bakst. But “The greatest inspiration to me was Henry G. Keller… not only a good painter but also a good teacher…. He made you feel as though art was the most important thing in the world, and you couldn't do better than to be an artist if you had the aptitude for it.” Keller said that his student’s “inability to see form” and his “virtually complete concentration on two-dimensional pattern amounted almost to genius.”A scholarship in 1916 to the national Academy of Design in New York City did not appeal, as Burchfield dropped out of the program after 1 day. But during his brief stay in the city, he met art critic and instructor Mary Mowbray-Clarke, who showed his works at her gallery, the Sunwise Turn Book shop, launching his career as a leading artist. Later, he was to describe 1917 as his “golden year.” This period and up to 1918 was also his most prolific. This was too a time of war, so he joined the army. “I was made a sergeant and I had a half a dozen men under me, and we were doing camouflage. And I was happy making the designs for camouflage.”After this brief career in the military, he returned to Salem, where he continued to paint around his work as accountant in an auto parts company. When a better opportunity came up, he moved to Buffalo, New York, to work as designer for H. M. Birge and Sons, “the finest wallpaper firm in the country.” “I had to make a living somehow…. I knew it would be years before I could hope to make any money out of painting.” It was 1929 and his work was shown in the prestigious Montross Gallery when he made the decision to devote all his time to painting.Burchfield felt most comfortable with the medium of watercolor. “I use a dry paper and what is called a dry brush, which isn’t dry, of course, in that it has the minimum amount of water in it, and I stand them up… just as a man painting an oil painting, except that you are using different materials.” Of his technique, he said, “I like to advance and retreat, just like a man writing a book. I doubt that very few of them ever sit down and leave a paragraph as it first comes into their head. They work over it, delete things and add things…. A picture has a life and direction of its own, and the artist has to find out which way the picture wants to go and follow …. It sounds like doubletalk, but it’s true.”Camouflage design, on this month’s cover, one of two surviving studies from Burchfield’s military days, is a mix of abstract and realistic elements and like all his work reaches for more than meets the eye. At home with modern camouflage, he built on art invented by those like him, who studied nature. American naturalist and artist Abbott Handerson Thayer (1849–1921), sometimes referred to as the father of camouflage because of his pioneering research on protective coloration in nature, laid out basic principles: the color of a camouflaged object must match its background. Strong patterns work better than delicate ones because they interfere with how we read the outline of a form. A dark strip at the top and a white splash underneath disrupt our expectations of how an object will appear (countershading).Crude forms have been used in warfare since antiquity. Shakespeare knew camouflage. In Macbeth, at the wood of Birnam, Malcolm said, “Let every soldier hew him down a bough / And bear’t before him: thereby shall we shadow / The numbers of our host and make discovery /Err in report of us.” And then, “As I did stand my watch upon the hill, / I look’d toward Birnam, and anon, methought, / The wood began to move.”C’est nous qui avons fait ça,’ he said.”Thayer’s ideas were quickly put to military and artistic use. And when the United States entered World War I, several artists, Burchfield among them, became involved, producing various patterns, initially representational then boldly abstract. When cubism swept the art scene, obliterating the distinction between an object and its background, it influenced military camouflage designs. In The Autobiography of Alice B. Toklas, Gertrude Stein described an evening in 1915, when she and Toklas were strolling with Picasso and his mistress Eva Gouel. “All of a sudden down the street came some big cannon, the first any of us had seen painted, that is, camouflaged. Pablo stopped, he was spell-bound. ‘Near the end of his life, Burchfield went back to the paintings of his golden year, his time most inspired by nature. He pasted them into new works, seamlessly expanding and absorbing them into larger creations incorporating the most profound discoveries of his later artistic career. These masterpieces, the culmination of his love for nature, seem to complete his desire to become one with it.Camouflage design with its graceful curves, flat patterns, and strong colors over linear designs is a perfect portrait of natural elements, overlapping and filled with movement, light, or heat, the underpinnings as well as the surface of nature, and most of all, its mystery and intrigue.The merger between art and nature sensed by camouflage artists has broad applicability in disease emergence, where the borders, geographic and biologic, blend as smoothly and seamlessly as in art. Burchfield’s A look at the ecologic dynamics, meteorologic variables, and transmission cycles, along with human travel and vector control of malaria alone as it reemerges around the world, attests to Burchfield’s acute understanding of complexity underneath the surface. In Ecuador, the railway inadvertently provided transportation of the vector and parasite to higher elevations. In other parts of the world, dengue virus activity, a major cause of illness in travelers, is increasing and, until an effective vaccine is licensed, will likely remain a threat to military troops operating where the disease is endemic. Recent outbreaks in Hawaii, Texas, and Florida resulted in recommendations on public health response, including such vector control activities as spraying for adult mosquitoes and eliminating standing water around homes. In Veneto Italy, surveillance to identify cases of West Nile fever, imported dengue and chikungunya infections in travelers also highlighted, among other measures, the need for vector control. But, while artists and the military have managed to fool human enemies by camouflage, we have yet to adequately fool mosquito and other vectors of disease.


They were constructed as studio aids to achieve a more expressive use of the human figure and free me from the choreographer’s understanding of the body.”A native of Wales, Hicks-Jenkins spent the first 25 years of his working life as stage designer, choreographer, and theater director. The figures in Gothic Bohemian paintings in the National Gallery in Prague reminded him of the population on his own studio walls. He saw in these figures a kind of “postural distortion,” affirming his notion that “This is not about flesh and the corporeal body.”He was born in Newport and showed early artistic talent, which he cultivated in London at the Rambert Dance Company and The Italia Conti Academy. He traveled widely in Europe and America, touring with dance and theater troops, but settled back in Wales in the 1980s to focus on his love of painting. His studio, the “battery,” he shares with Pipistrelle bats, which “roost in the roof space above and make frequent forays to pepper my paintings with their droppings. I don’t mind. I enjoy their company.”Hicks-Jenkins’ painting has been described as figurative, a term now encompassing any form of modern art characterized by references to the real world. “I am not at all captivated by ‘likeness’ or the capturing of it. Most of the figures in my paintings are of ‘types’ rather than specific, identifiable sitters.”He has experimented with various styles, using elements from them in his own work, which is always changing. “I continue to lay myself open to the currents that carry me in new directions.... Every time I reach a point where skill becomes even close to practiced and reliable, I feel the urge to derail the train.”mimesis, an imitation of nature. These puppets, reminiscent of animation figures, distract him from the usual objects of observation, enabling him to concentrate on “Inventing dynamic though often anatomically impossible arrangements of limbs that a live model quite simply couldn’t provide” and to fill space. “They’ve been crucial too in helping me flatten out and pile up shapes…. The paintings become almost like collages.”Hicks-Jenkins’ artistic talent was nourished by his years in the theater. “The stage is a revealing space, much like a painting. All the attention is focused on the limited area, and everything within it becomes more important.” The stage is a rich source of compositional elements. “I’ve developed a technique of making three-dimensional, articulated paper maquettes as part of my preparation for painting at the easel. These fragile little works are pieced together quickly from thin card, cut, and then worked in frottage, monoprint, conté crayon, and acrylic. The puppets are held together with hidden, brass paper fasteners.” He uses maquettes “not as convenient stand-ins for people” but to resolve a common dilemma of the artist pursuing an independent creation, an idea, instead of The creative effort of imagining and inventing codes and other means of communication goes back to prehistoric times and may be the factor distinguishing humans from other animals. We search for such codes throughout the millennia, trying to decipher human history. Many of the messages we find are from the visual arts, which appeal to the senses as well as the intellect. Mental and visual communications are integrated by details or cues to make characters or situations recognizable without captions. To this end, art often resorts to iconography, a tradition of communicating through images. In this tradition, recurrent figures may be portrayed with the same facial features or clothing, despite changing eras or styles. They may be painted in certain colors or be accompanied by recognized objects or animals. Once the subject becomes identifiable, other elements may be added that elevate the meaning from historical to universal.The Prophet Fed by a Raven, on this month’s cover, contains elements of iconography placed in a contemporary setting and filled with timeless universal themes. The clues point to well-loved prophet Elias  of the Old Testament, an elusive figure of swift foot and obscure origins. The artist placed him on a ledge, as “He dwelled in the clefts of the torrents or in the caves of mountains” and lived the life of “a true son of the desert.” “Nothing was too high for him, and when he was laid on sleep his body prophesied.” He was “as fire, and his word burnt like a torch.” He appeared abruptly on the historical scene, delivered his message against the corruption of his age, lived off charity under conditions of drought and famine, and vanished to the east of the Jordan, where legend has it, ravens “brought him bread and flesh in the evening, and he drank of the torrent.”Like many of Hicks-Jenkins’ works, Basic elements aside, the artist departs from iconography. The raven is true enough to form in its shaggy throat feathers, wedge-shaped tail, slender figure, narrow wings, and long, thin “fingers” at the wingtips. But it defies traditional color for flaming red and seems far more fiery than the prophet. The remote mountain backdrop is telescoped and manipulated into the top of the composition, placed within reach, virtually inside the window frame. Perched solidly on the edge, the bird turns one sharp eye toward its charge, Bowie knife of a beak parted as if in conversation with the figure slouched enigmatically in the foreground.The raven, among the most intelligent of birds, is a frequent visitor in the arts where, as in life, it has a contradictory presence, signaling both life and death. Stately and handsome in its shiny uniform coat―black down to the legs, eyes, and beak―it is graceful and inquisitive. Despite its unsavory reputation as an indiscriminate eater, it struts, soars, and glides confidently in virtually all environments and around humans and other animals. “I have no interest in expressions of the stories where the nature of the wild is perverted from its true self,” the artist says about his portrayal of animals. “For me the true miracle of relationships that break the usual mold is that the animal moderates its behavior because it’s moved to.”The Prophet Fed by a Raven, the bird breaks from ‘likeness’ to become a type, emblematic not only of what can happen between prophets and birds but of all animal–human interactions. In many of these, the roles are often reversed, as in this painting, where the bird takes care of the prophet living in the wild. Sometimes, the raven becomes the prophet, as in the case of West Nile virus spread in North America, when dying birds of the crow family, including ravens, foretold human infection in the New World. But ravens are not alone. With many infections emerging first in animals in remote and underprivileged settings, surveillance of animal health can forecast disease risks to humans. In Sri Lanka, field veterinarians used mobile phones to report animal health information, confirming that this type of animal population surveillance can work in isolated areas with limited resources. While the prophet–raven platform has changed with the times, the universal human–animal interface and its zoonotic consequences, including disease transmission, remain unchanged.In


But there are other dimensions of his legacy on both the personal and professional levels that I will explore, and hopefully extend, in my presentation. Alex’s professional life was a model of perseverance from which we all can learn. He earned his PhD some 20 years after changing course from an intended career as a schoolteacher. Throughout this time he garnered a reputation for moderation, friendship, mentorship, generosity, and collaborative work that is a model of how research should be conducted. All this was achieved against a backdrop of personal health challenges that would have caused many lesser individuals to abandon professional activities altogether. Alex Stacoff’s professional passion was to understand the biomechanics of the foot and shoe during locomotion. He used both classical and novel methods, the later including bone pin-mounted targets, magnetic resonance imaging kinematics, and fluoroscopy. He expressed an early interest in learning from barefoot running [Alex Stacoff was a Swiss biomechanics researcher and a key member of the small group of scientists who founded the International Foot and Ankle Biomechanics Community (i-FAB) in 2007. He was an active participant at the first i-FAB Congress in September 2008, but he died tragically while running, only three weeks later, at the young age of 58 years. The fact that a flourishing i-FAB is now holding its 3 running  and I wi


So that everything before that was just getting ready, and after that I was in some strange way altered, really,” said Katherine Anne Porter about her nearly fatal encounter with the Spanish flu. “It took me a long time to go out and live in the world again.” Years later, in a thinly disguised autobiographical novel, she laid out not just her own traumatic run-in with death, the pale rider, but also a rare literary account of the 1918 flu pandemic in the United States and the unprecedented human loss.now or I’ll put her on the sidewalk.” “They can’t get an ambulance, and there aren’t any beds. And we can’t find a doctor or nurse. They’re all busy.” “It’s as bad as anything can be … all the theaters and nearly all the shops and restaurants are closed, and the streets have been full of funerals all day and ambulances all night.” “Two cherry flavored pills,” “orange juice and ice cream,” “coffee in a thermos bottle.” “The men are dying like flies out there …. This funny new disease. Simply knocks you into a cocked hat.”For her recollection of the pandemic, Porter had to rely on fragments of memory before her illness and after her recovery. These fragments involved the landlady; her beloved fiancé Adam; and fatal flu in Denver, Colorado, during World War I, which killed many young men needed for battle. “I tell you, they must come for her Porter wakes up from her illness to find that Adam, “tall and heavily muscled in the shoulders, narrow in the waist and flanks,” handsome Adam with “his eyes pale tan with orange flecks in them, and his hair the color of a haystack when you turn the weathered top back to the clear straw beneath,” Adam, who had “never had a pain in his life that he [could] remember,” had died.Porter, the consummate storyteller, used words to express the devastating effects of illness on her life. Across the world, in Austria, Egon Schiele, whose self-portrait graces this month’s cover, in similar circumstances, found no comfort in words, despite his own poetic nature. When his wife was dying of the flu, he was unable to articulate his feelings. In a letter to his mother, he coolly speculated that Edith would probably not survive. But he used art to express his devastation. He made several sketches of his wife during the last 2 days of her life. In these sketches, the lines were fluid and sensitive, the colors subdued, the format understated. All these features, a departure from his usual provocative style, reflected the emotional stability found in his life with Edith. His last work was a portrait of his wife, who died the following day. She was 6 months pregnant. He died 3 days later.Even before his fatal encounter with the flu, Schiele was acquainted with adversity. His early years were marred by a troubled relationship with his mother, poor academic performance, and the loss of his father, a provincial railroad stationmaster, to tertiary syphilis, when Egon was 14 years old. “I don’t know whether there is anyone else at all who remembers my noble father with such sadness.” The elder Schiele had kept his condition from his 17-year-old bride, Egon’s mother. Her first three babies were stillborn. The fourth child died at age 10 of meningitis, a complication of late-onset congenital syphilis. Egon was the first boy to survive. “I shall be the fruit which after its decay will leave behind eternal life; therefore how great must be your joy―to have borne me?” Egon wrote to his mother. His penchant for grandiosity and certain physical features in his early self-portraits led some to wonder whether he might have also been infected.Schiele lived his life at an accelerated pace. He started to draw as a child and was enrolled in the Vienna Academy of Fine Arts at age 16. He became a protégé of Gustav Klimt, a strong early influence. Once when asked if young Schiele’s drawings showed talent, Klimt responded, “Much too much.” The gifted but troublesome student would soon go off on his own and form the New Artists group. Later, when Klimt was struck down by the flu, Schiele made several portraits of him on his deathbed.Schiele went on to serve in the military; to have high-profile love affairs; get arrested and be thrown in jail; and before his own untimely death, make a proper and by all accounts promising marriage. All along, he grew as an artist and achieved an expressionist style focused on feelings and their interpretation. He was drawn to the unconventional and controversial, and his hundreds of self-portraits were penetrating and disquieting. His exaggerated lines, unrealistic shapes, and intense colors invoked human situations with a candor that many found disturbing. During his brief career he created more than 3000 works on paper, some 300 paintings. Despite the edginess, his artistic reputation grew, he was offered commissions, and his work sold well.Self-Portrait with Physalis, probably his best-known self-portrait, shows him at the peak of his creativity in 1912, his most productive year, when his expressionist style had matured. Clues for interpreting a self-portrait can also be drawn from facial expressions, gestures, and props within the painting—what the artist allows us to see. In this self-portrait, the arms and body are severely cropped, only the cocked head and shoulders are shown. The one-eyed stare challenges the viewer. So do the pursed lips. This is a laconic composition, though a theatrical one, what with its intensely colored lampion fruit and dreamy sentimentality. Despite the scattered character clues, there is one thing we will never know from Schiele’s Self-Portrait with Physalis, and that is what would have happened if he had not died at age 28 of pandemic flu.In interpreting any self-portrait, it is tempting to draw clues from the artist’s life. During his short career, Schiele was alienated and vulnerable and in the midst of World War I and pandemic flu. When the pandemic ended, which took away even her “decrepit hound and silver kitten,” there was, Porter wrote, a “dazed silence.” The “Great Pandemic” claimed more lives in a short time than any other disease in history, yet because it was intertwined with the “Great War,” the horror of it in human terms may not have been adequately chronicled. Some have called it the “forgotten pandemic”—but not those who work in public health.Many strides have been made in flu prevention and control since 1918: better understanding of the virus, its distribution in nature, its presence in animals and birds, some of its virulence factors, how it mutates, how it is distributed in tissues, how it is transmitted. We now have prevention programs, vaccines, and antiviral drugs. But many still die, and the threat of another pandemic lurks.Dramatic tension captured in literature and art prevents us from forgetting the dead and the grave pandemics of history. Schiele did his part by immortalizing the faces of his beloved persons—very much like Porter, who in her version of the spiritual “Pale Horse, Pale Rider,” she contends that death takes away the singer’s lover, mother, siblings, and eventually over the course of several verses the entire family, “But not the singer, not yet,” “Death always leaves one singer to mourn.” That’s to ensure remembrance, which applies as well in public health, where to prevent the next pandemic, it pays to remember and study the past ones.


Constructive feedback is an essential element of the educational process, helping trainees reach their maximum potential and increasing their skill level. Video-based feedback has been described as highly effective in various educational contexts. The present study aimed to evaluate the feasibility and acceptability of video-based, on-ward supervision for final year students in a clinical context with real patients.Nine final year medical students  and eight patients  participated in the pilot study. Final year students performed routine medical procedures at bedside on internal medicine wards at the University of Heidelberg Medical Hospital. Students were filmed and were under supervision. After performing the procedures, an oral feedback loop was established including student, patient and supervisor feedback on communicative and procedural aspects of skills performed. Finally, students watched their video, focusing on specific teachable moments mentioned by the supervisor. Written evaluations and semi-structured interviews were conducted that focused on the benefits of video-based, on-ward supervision. Interviews were analysed qualitatively, using open coding to establish recurring themes and overarching categories to describe patients’ and students’ impressions. Descriptive, quantitative analysis was used for questionnaire data.n = 6), physical examination (n = 1), IV cannulation (n = 1), and ECG recording (n = 1). The video-based, on-ward supervision was well accepted by patients and students. Supervisor feedback was rated as highly beneficial, with the video material providing an additional opportunity to focus on crucial aspects and to further validate the supervisor’s feedback. Students felt the video material would be less beneficial without the supervisor’s feedback. The setting was rated as realistic, with filming not influencing behaviour.Supervised, self-chosen skills included history taking (Video-based, on-ward supervision may be a powerful tool for improving clinical medical education. However, it should be regarded as an additional tool in combination with supervisors’ oral feedback. Acceptance was high in both students and patients. Further research should address possibilities of efficiently combining and routinely establishing these forms of feedback in medical education. To ensure a smooth transition from university to clinical practice, workplace learning is of the utmost importance , 2. In GSome innovative models have begun to emerge to address these limitations in final year medical education, for example, establishing educational wards offering the supervised treatment of real patients –16. HoweTo acquire clinical competencies, feedback is seen as a central factor supporting individual learning processes . Here, iWhile the overall aim of the present study was to develop and establish a video-based, on-ward supervision model, our study sought to (1) evaluate the feasibility and acceptability of video-based, on-ward supervision via the assessment of process, resources, management and scientific factors; and, (2) assess whether video-based, on-ward supervision was perceived as beneficial by participating final year students.We used Ericsson’s model of deliberate practice as the conceptual framework for our approach . EricssoThe present study was a pilot study using a mixed-method approach , involviIn German medical school programmes, the sixth year is also known as the final year. Final year students must complete one term of internal medicine, one term of surgery and one elective term . All final year students working in internal medicine departments at the University of Heidelberg Medical Hospital between December 2013 and March 2014, were invited to participate in video-based, on-ward supervision by e-mail and during lectures. Students were informed that participation was voluntary, and that nonparticipation would have no influence on other aspects of their final year medical programme or grades.One experienced supervising doctor, a 4th year internal medicine resident (JG), specially trained in medical student education and who was not the supervising ward physician, observed all participating students’ patient admissions and performance of procedural skills at bedside. Following this observation, the supervising doctor provided the students with structured feedback following a supervisor manual based on methods by Roos et al. .All patients were internal medicine inpatients at the University of Heidelberg Medical Hospital. Preferably, participating patients were located on the ward in which the student worked.n = 6); 2) a complete internist’s physical examination (n = 1); 3) IV cannulation (n = 1); and, 4) performing an ECG recording (n = 1). When possible, patients were initially invited to participate by the student and in exceptional circumstances by the responsible supervisor . Supervision was conducted in the patient’s room on the ward. Patients with language difficulties, dementia, or psychological instability were excluded from participation.The procedure of the present study is presented in Table The supervisor was specifically trained in the supervision of final year medical students during clinical on-ward procedures and to provide professional, structured feedback. During supervision, the supervisor provided students with standardised instructions and outlined expectations, for example, the respectful treatment of patients during all contact. For history taking, a complete history of the patient was expected following the standard University of Heidelberg procedure . StudentA Rollei Movieline SD-23  camera was used to record the performance of clinical skills. It was placed in the corner of the patient’s room facing the patient’s bed, without showing a neighbouring patient in the same room. The camera was operated by the chief investigator (JG), with occasional assistance by a second team member (RS). The camera position was only adapted during the supervision of manual skills (for example the use of the camera zoom during IV cannulation) to show some aspects of the skill in more detail. Field notes were taken by the supervisor during each session to record relevant positive or improvable procedural or communicative aspects. These aspects were then discussed fully in the feedback loop.After completion of the supervised procedure, a standardised feedback loop was performed. Feedback itself was not filmed. First, the student gave self-reflective feedback including the setting , and the procedure . This was followed by the patient’s oral feedback, addressing the setting and a subjective assessment of the student’s performance. Finally, the supervisor gave the student oral feedback regarding the setting, the student’s behaviour, and their performance of the technical skill. Most of the supervisor’s feedback was given in the patient’s room in their presence. If necessary, any major professional issues were addressed outside the patient’s room. Before watching the video, the supervisor identified specific issues requiring focus. A quiet room on the ward was chosen for students to view their videos. In most cases, viewing was undertaken in the presence of the supervisor, who did not comment during the video. After watching the video, the student was asked whether he/she was able to relate to the supervisor’s feedback and whether new aspects not initially identified had been observed.For pre-assessment, a questionnaire was administered seeking information on baseline characteristics  as well as assessing students familiarity with the required skills  during their studies in a) controlled  or b) real conditions. Finally, students were asked to self-assess each of the four skills regarding their feeling of preparedness for entry into their profession. Self-assessment was on a 7-point Likert scale .After watching the video, students completed an evaluation form specifically addressing the benefits of video-based supervision. Responses were on a 6-point Likert scale that deliberately avoided a neutral score; ensuring participants rated their intervention experience in terms of a ‘forced choice’. The questionnaire consisted of 13 items (statements about the benefit of the video-based supervision and the experienced feedback), rated individually on a scale from 1 to 6 .The interview procedure followed the consolidated criteria for reporting qualitative research (COREQ) checklist  and the Individual, face-to-face interviews were conducted with all participating students. Interviews lasted approximately 20 min and were conducted by a trained interviewer who was supervised by an experienced tutor. The interviews were semi-structured –50 with Patients were asked to provide feedback via a post-assessment questionnaire. This questionnaire used a similar structure to that administered to the students , and comprised seven items addressing the patients’ feelings during the supervision, their willingness to participate in future and their opinion on how important video-based, on-ward supervision was for final year students.The content analysis followed grounded theory principles . First, Descriptive quantitative data were managed with Microsoft Excel 2010  and presented as mean ± standard deviation (SD) and median with interquartile range as applicable. A 7-point Likert scale was used to evaluate students’ abilities before the video-based supervision and a 6-point Likert scale was used post-supervision to assess patients’ and students’ opinions of the supervision.We adopted ethical principles according to the 2013 World Medical Association Declaration of Helsinki: ethical principles for medical research involving human subjects. The study protocol was approved by the Ethics Committee of the University of Heidelberg. Students’ refusal to participate had no impact on subsequent evaluations or other assessments in the curriculum. Patients were advised they could refuse to participate without having to provide a reason or fear negative effects. Final year medical students and patients who were willing to participate gave written informed consent before participating in the study.Nine final year medical students  consented to participate in the present pilot study on a voluntary basis . Eight students had studied medicine at the University of Heidelberg, and one at the University of Mainz. All participating students had previous experience of being filmed during their studies as part of communication training with standardised patients at our faculty .Eight internal medicine patients consented to participate in the study . One patient was willing to participate twice, meaning one participating student took the patient’s history and another student performed a physical examination on the same patient an hour later.Students self-reported feeling most confident about placing peripheral intravenous portals, taking histories and executing a physical examination, whereas they self-reported being less confident about case presentations Table .Table 2SAcceptance ratings of the video-based, on-ward supervision are presented in Table The qualitative analysis of the interviews covered four categories incorporating nine themes, as defined below Table .Table 4OAll students preferred a quiet environment without disturbances from telephones, incoming staff or visitors, stating ‘nobody entered the room, no one disturbed us; that was good’, and ‘[therefore] I was relaxed, and I had the feeling that the patient was relaxed as well’. One student also said that ‘switching the telephone [’s ring tone] off would have helped because [the] phone ringing [during history taking] distracts me’. Interaction with patients at eye level was regarded as optimal, and sitting next to each other was preferred to sitting opposite.As the intervention took place in patients’ rooms on medical wards, students found the context to be highly realistic: For example, ‘It felt like it usually feels when routinely performing an ECG recording in the same surroundings’. The supervisor’s choice of patients was considered to be more realistic than students choosing the patients themselves, as they would have had to first obtain permission . One student noted that ‘the patient knew beforehand what my task was and that I am not his attending physician. That probably changed our relationship [that is to the patient], as the patient behaved more like an actor due to the more artificial situation’. The students preferred real patients to actors because ‘actors are fine, but by using real patients, you can draw a better comparison to how it really feels [to perform medical skills on a daily basis]’. Another student noted ‘an actual patient usually has a more profound story to tell than an actor, who specifically prepared for one situation by learning the symptoms by heart’, and ‘They [the actors] sometimes even help you’. Compared with working with a patient already admitted and simply repeating history taking, having to actually admit a patient on the ward also increased the realism of the situation: ‘you have to perform [the history taking] properly, otherwise you will have to go back to the patient to ask the questions you forgot, which I don’t like’.Students were familiar with the situation, having already experienced being filmed in previous classes. Most students stated they had generally performed skills according to their usual daily routine, but possibly with more diligence and dedication, for example, asking for more details during history taking owing to being filmed. It was agreed that being supervised might have also influenced their behaviour, regardless of the camera. One student commented ‘I made more comments [than usual] for the camera [while doing the physical examination], which were of no interest for the patient’. However, other students felt quite the opposite with the camera running, reporting they were less communicative and more focused on important subjects. A student stated critically that he thought ‘it is very difficult to be unbiased whilst videotaping, especially when it comes to behaviour [which will be different owing to being filmed]’ , and another commented ‘It felt 80 % realistic, but you had more time than usual for performing the skills’.As students were aware of being filmed, they were able to cope with and largely ignore the presence of the supervisor and camera. One student noted that she ‘realised [she] occasionally looked into the camera instead of facing the patient’. However, not all students liked the feeling of being filmed, possibly experiencing a sense of embarrassment when later observing their behaviour on film. Another student was indirectly distracted by the camera, as the patient kept looking into the camera instead of talking to her during history taking.Most students reported they felt confident about communicating during history taking, physical examination and IV cannulation, stating they were able to build good and trusting relationships with their patient.Nevertheless, video-based supervision was found to be helpful, as some aspects that were not perceived or addressed by the supervisor, were detected by the students themselves while watching the video. One student realised that she had ‘used her hands too much while talking, like some kind of sign language’ , concluding that she should ‘get rid of that habit’.Generally, students reported they felt confident in the technique and framework of history taking. Some students ‘did not note making any mistakes’ , or ‘forgot [to ask] some things, but overall, … found it [history taking] to be pretty good’. One student thought he ‘knew the general sequence in history taking’ , but there were ‘specific gaps of knowledge’ regarding the patient’s suspected diagnosis. Another stated that ‘more preparation [reading the case history] beforehand’ would have been beneficial. Most students began with an open question for their patient and followed with more specific questions. One student observed that ‘sometimes, when you let the patient talk, you will find out what you want without having to dig deeper’.The patient’s layperson perspective was seen as beneficial, highlighting ‘some aspects [the students] didn’t think of before’. One patient, for example, said they had no interest in being informed about the technical details of ECGs, when the student had not realised that they had given detailed information when performing the ECG. However, feedback from the actual patients was considered less beneficial than that from specifically trained actors. Although, one student stated: ‘To be able to perform these skills on actual patients [under supervision] is more valuable’. Nevertheless, feedback from patients was considered useful, but ‘not as useful as the supervisor’s feedback’.The supervisor’s feedback was generally perceived as beneficial, especially in regard to procedural technical skills, as this provided a frank analysis from a different and expert perspective. One student thought that ‘generally, the feedback from the supervisor [was] more helpful [than video-based supervision]’. Overall, students preferred receiving the supervisor’s feedback before watching the video, as they could then focus their attention on important points: ‘I find the combination [that is the supervisor’s feedback plus video-based feedback] very helpful. The patient’s feedback is likely to bring less in the specific situations, but the supervisor’s feedback in combination with the video feedback is very helpful, I think’. Another student stated that sequential feedback was ‘helpful, especially as you got it [the supervisor’s feedback] right after [patient contact], and then watched the video, because then I realised that the feedback was really justified and it helped a lot, yes’.Video-based feedback was mostly positively received by students: ‘I self-reflect [upon my actions] a lot, but I experienced [my performance] in a different way thanks to the video’. However, most students felt it was only beneficial as an addition to the previous oral feedback from the supervisor. Sequential feedback was regarded as the most beneficial, that is first receiving feedback from the supervisor and then watching the video: ‘the video backs the supervisor’s feedback up, it is a tool for self-reflection, but without the supervisor’s oral feedback, it wouldn’t have helped much’. However, the video was not only considered beneficial for the evaluation of procedural technical skills, but also for communicative skills, with one student stating, ‘I usually do not see my body language’. Another student said, ‘sometimes, I cut my sentences off, finishing them half a minute later, with a long period of silence in between’, concluding that ‘[I] should speak more clearly and slowly, and let the patient finish her sentences’.Not all aspects of the video-based supervision were seen positively. Some students felt uncertain about the benefit of filming procedures during on-ward supervision, feeling that the additional study of the video material ‘did not help that much because I do not know in which way it will influence my behaviour in future’; and ‘The problem is, I would not change anything [when performing the skill again] due to the video’.In addition, students expressed a desire for the evaluation of more complex procedures through future video-based supervision, such as placing central venous catheters.The patients’ ratings regarding their participation and subjective impressions are presented in Table To our knowledge, the present pilot study is the first to describe an innovative approach for video-based, on-ward supervision. The implementation of this method in an on-ward setting was well accepted by both students and patients. Our analysis of the process of video-based, on-ward supervision and its determinants highlighted that participating students found sequential feedback most beneficial, as watching the video after hearing the supervisor’s feedback gave them opportunity to self-reflect on their performance. However, students considered the supervisor’s feedback the most beneficial element of supervision. In terms of feasibility, video-based, on-ward supervision was a viable supervision method. However, additional resources are required to implement video-based, on-ward supervision as part of the educational routine, such as acquiring the necessary equipment and personnel to manage and coordinate the process, thus ensuring a beneficial one-on-one learning experience.On-ward supervision has already proven to be well accepted in preliminary work  and is aOverall, the patients perceived the video-based supervision as valuable support for students. Although patients rarely reported personally benefiting from the supervision, they were happy to participate and did not perceive participation as a burden. This was an interesting finding, especially in view of the fact that little is known about the perceived burden for real patients participating in bedside teaching . FinallySome limitations of our study should be noted. Firstly, our study is limited by the small number of participants, possibly due to participation being voluntary, which may lead to biases in our analysis. As described by Schmidt and Bordage, the present study is a descriptive pilot study , which dOur study found that video-based, on-ward supervision with individualised feedback was successful in improving the development of clinical skills of final year medical students. To determine the added value of filming patient interactions, future research should aim to objectively assess the added benefit to the supervision programme , 53 when


The most common assumption in evolutionary game theory is that players should adopt a strategy that warrants the highest payoff. However, recent studies indicate that the spatial selection for cooperation is enhanced if an appropriate fraction of the population chooses the most common rather than the most profitable strategy within the interaction range. Such conformity might be due to herding instincts or crowd behavior in humans and social animals. In a heterogeneous population where individuals differ in their degree, collective influence, or other traits, an unanswered question remains who should conform. Selecting conformists randomly is the simplest choice, but it is neither a realistic nor the optimal one. We show that, regardless of the source of heterogeneity and game parametrization, socially the most favorable outcomes emerge if the masses conform. On the other hand, forcing leaders to conform significantly hinders the constructive interplay between heterogeneity and coordination, leading to evolutionary outcomes that are worse still than if conformists were chosen randomly. We conclude that leaders must be able to create a following for network reciprocity to be optimally augmented by conformity. In the opposite case, when leaders are castrated and made to follow, the failure of coordination impairs the evolution of cooperation. Unlike interactions among bacteria, plants or viruses12357891112131415Since social interactions are traditionally described by models entailing networks171819202223243034353839Here we wish to extend the scope of evolutionary games41424344454748495051525354555657585960616263x is initially designated either as cooperator (C) or defector (D) with equal probability. Each instance of the game involves a pairwise interaction where mutual cooperation yields the reward R, mutual defection leads to punishment P, and the mixed choice gives the cooperator the sucker’s payoff S and the defector the temptation T. We predominantly consider the weak prisoner’s dilemma, such that T > 1, R = 1 and P = S = 0, but we also consider the true prisoner’s dilemma where S < 0.We consider evolutionary social dilemmas on either the scale-free or the Erdős-Rényi random network (see Methods for details), or on interaction networks with a uniform degree distributions, such as the random regular graph and the square lattice, where each player x acquires its payoff Πx by playing the game with all its neighbors. Next, player x randomly chooses one neighbor y, who then also acquires its payoff Πy in the same way as previously player x. To avoid payoff-related effects that are due to heterogeneous interaction topologiesx adopts the strategy sy from player y with a probability determined by the Fermi functionThe standard Monte Carlo simulation procedure comprises the following elementary steps. First, according to a random sequential update protocol, a randomly selected player K = 0.1 quantifies the uncertainty related to the strategy adoption process2270where ρ of the population as being conformity-driven, which influences the strategy adoption rule. Instead of x is a conformist, we useTo introduce conformity, we designate a fraction sx within the interaction range of player x, while kh is one half of the degree of player x. By using x is most likely to adopt the strategy that is, at the time, the most common in its neighborhood. As in K = 0.1 introduces some uncertainty to the process, such that it is not completely impossible for a conformist to adopt a strategy that is in the minority among its neighbors. If, however, the number of cooperators and defectors in the neighborhood is equal, the conformity-driven player will change its strategy with probability 1/2. We also emphasize that, in this study, a conformist uses only local information. In particular, a conformity-driven player simply tends to follow the majority in its local neighborhood. An alternative approach might entail a conformist having available global information about the whole population and act accordingly. In such a case, however, the global information may likely suppress the vital importance of local information stemming from the direct neighbors. Due to several open questions and options on implementation, we leave it to future studies to determine the merits of global conformity.where ρ of the population that act as conformists. We consider and compare several different options. The simplest option is to assign conformists uniformly at random, which we use as the benchmark case. Secondly, on heterogeneous interaction networks, such as scale-free and Erdős-Rényi random networks, we use the degree kx of each player, whereby the probability to be designated as a conformist can be either kx/kmax or 1 − kx/kmax for degree-related or inversely-degree-related assignment, respectively. In the former case, high-degree players, i.e., the hubs or leaders, most certainly end up as conformists, while in the latter case low-degree players, i.e., the masses or the periphery, are the most likely conformists. Thirdly, again of relevance on heterogeneous networks, we use the concept of collective influence of players to distinguish themCIx at depth 1 for every player x  or inversely-w-related (1 − wx) assignment of conformity, such that the leaders or the masses are preferentially considered as conformists, respectively.A key consideration in this paper is which players make up the fraction fC) in the stationary state depends on the fraction ρ of the whole population that is made up of conformist players. As stated in the Introduction, these players do not aspire to maximal payoffs as is traditionally assumed in evolutionary games, but rather, they prefer to adopt the most common strategy within their interaction range. As we have reported infC as the fraction of conformists increases, but this is just a simple consequence of the fact that we reach a strategy neutral state at ρ = 1.We begin by presenting the main results on scale-free networks in On the other hand, if conformists are preferentially selected from low-degree players, i.e., from the masses, then an even higher level of cooperation in the stationary state is attainable, indicating an optimization of the aforementioned interplay. This result is intuitive and understandable, because high-degree players are naturally in a position to influence a large neighborhood, and the effectiveness of this influence is facilitated further if the neighborhood is made up predominantly of conformist players. This interplay of heterogeneity  and coordination  ultimately leads to large homogenous groups or clusters competing in the population, which in the long-run reveals the benefits of cooperation by virtue of network reciprocity. Naturally, this argument fails if leaders are made to conform because they then become unable to capitalize on their central position within the network. In the latter case, the coordination becomes less efficient, because players having the capacity to search for a more successful strategy are unable to lead others, which ultimately hinders the successful evolution of cooperation.T − S range.These details of the described macroscopic dynamics are generally valid and apply regardless of the properties of the interaction network and game parametrization. Indeed, as indicated by the results presented in Previous research has also shown that, when we normalize payoffs on heterogeneous interaction network, we destroy the heterogeneity among players, which drastically weakens the positive impact of enhanced network reciprocity7273w to wx ∈  interval, as show in the inset of wx ≈ 1. In this context the former players are the masses, while the later players are the more influential leaders. Evidently, we can select conformist preferably among the high-w players , either way precluding the observation of notable differences. In the intermediate region, however, we can see that higher cooperation levels can be obtained if conformity-driven players are chosen from low-w group. In other words, it is better to allow leaders to search for higher individual payoffs, and in parallel, we should encourage the masses to conform. If we reverse these roles, leaders loose their ability to lead, which ultimately weakens network reciprocity.However, it is also possible to verify the above described conclusion directly if we distinguish players on regular networks or lattices, of course not by means of their degree or collective influence (because everybody has the same), but by means of their diverse capacities to pass strategy to the neighbors. In the latter case we apply a player specific prefactor  high in  or amongs low in . As expeWe have studied the evolution of cooperation in social dilemmas where a fraction of the population aspires to conform rather than to maximize payoff. Thus, instead of choosing the strategy that is performing best in terms of payoff, conformists simply choose the strategy that is most prevalent in their interaction range. We have confirmed that, in general, conformity promotes cooperation by enhancing network reciprocityWhat we have focused on specifically in the present paper is the fact that individuals within a population will typically be different in terms of the influence they are able to exert on others. The question then becomes who should conform if the goal is a socially desirable evolutionary outcome with ample cooperation. Should it be leaders, i.e., players with the highest degree, collective influence, or teaching activity, or should it be the masses, i.e., players with the lowest of these properties? Is it beneficial for the society if leaders tend to follow the masses? Using the simplest alternative, which is to assign conformists randomly regardless of their rank, as the benchmark, we have shown that leaders should not be conformists in evolutionary social dilemmas. Socially most favorable outcomes emerge only if the masses conform. This result is both intuitive as well as easily understandable in terms of the macroscopic dynamics that conditions it. In particular, we have argued that forcing the leaders to conform significantly hinders the constructive interplay between heterogeneity and coordination. Leaders must be able to create a following, which ultimately results in homogenous groups or clusters competing in the population. This competition is then swayed in favor of cooperators by the virtue of network reciprocity, which is further enhanced by smooth(er) interfaces that emerge due to the coordination of conformists. If, on the contrary, the leaders are made to follow, an unnatural coordination emerges – the masses are expected to drive cooperation, but their limited interaction range and related weakness preclude this – which ultimately hinders the successful evolution of cooperation.Our results suggest that conformity might have had an evolutionary origin in that it promotes prosocial behavior. Although payoff maximization is surely an apt description of interactions among simpler forms of life, the preference to conform might also be a good heuristic in social decision making as it can help to avoid punishment or earn a rewardk〉 = 4, or heterogeneous graphs including Erdős-Rényi random networks with average degree 〈k〉 = 6, or Barabási-Albert scale-free networks with an average degree 〈k〉 = 4. For the generation of the latter, we implement the standard growth and preferential attachment algorithm, as described inAs the interaction network, we use either homogeneous networks with a uniform degree distribution, such as the square lattice with periodic boundary conditions or random regular graphs with the same average degree 〈N elementary steps described above when introducing evolutionary games with conformists, which are repeated consecutively, thus giving a chance to every player to change its strategy once on average. All simulation results are obtained on networks typically comprising N = 104 –105 players. We determine the fraction of cooperators fC in the stationary state after a sufficiently long relaxation time lasting up to 105 MCS. To further improve accuracy, the final results are averaged over up to 5000 independent realizations, including the generation of scale-free and Erdős-Rényi networks, as well as random initial strategy distributions, for each set of parameter values.In terms of the simulation procedure, we note that each full Monte Carlo step (MCS) consists of ρ of the population is done only once at the start of the simulation or if conformity is assigned to players at each instance of the game anew.We also note that the results are independent of whether the assignment of conformity to the fraction How to cite this article: Szolnoki, A. and Perc, M. Leaders should not be conformists in evolutionary social dilemmas. Sci. Rep. 6, 23633; doi: 10.1038/srep23633 (2016).