Mathematical model of a moment-less arch.

This paper presents a mathematical model for predicting the geometrical shapes of rigid, two-pin, moment-less arches of constant cross section. The advancement of this work lies in the inclusion of arch self-weight and the ability to produce moment-less arch forms for any span/rise ratio, and any ratio of uniformly distributed load per unit span, w, to uniformly distributed arch weight per unit arch length, q. The model is used to derive the shapes of two classical 'moment-less' arch forms: parabolic and catenary, prior to demonstrating a general case, not restricted by the unrealistic load assumptions (absence of q, in the case of a parabolic form, or no w, in the case of a catenary arch). Using the same value of span/rise ratio, and w/q>1, the behaviour of the moment-less and parabolic arches under permanent loading, (w+q), is analysed. Results show the former to be developing much lower stresses than its parabolic rival, even when there are relatively small differences in the two geometries; for a medium span/rise ratio of 4 and w/q=2, differences in the parabolic and moment-less arch geometries would, in practical terms, be viewed as insignificant, but the stresses in them are different.

Silent aspiration and recovery from dysphagia in a case of bickerstaff brainstem encephalitis.

Bickerstaff brainstem encephalitis (BBE) is a rare inflammatory demyelinating disease with rapid progression typically followed by complete recovery. Reports of dysphagia in this population are limited and general. The purpose of this article is to heighten awareness of the potential for silent aspiration in patients with BBE. This article details the nature of dysphagia during the recovery phase of BBE and includes findings from serial videofluoroscopic swallowing evaluations. In addition, it shows the impact of cognitive impairment on the ability to eat safely. Early instrumental swallowing evaluation, close monitoring, and conservative management are essential to ensure safety in patients recovering from BBE.

Development of neutron radioscopy for the inspection of CF188 flight control surfaces.

Neutron radioscopy, using a cooled charged coupled device (CCD) camera and a neutron-sensitive scintillation screen, was developed at the SLOWPOKE-2 Facility at the Royal Military College (RMC) to detect water ingress into the composite layers and the aluminium honeycomb core in flight control surfaces on the CF188 Hornet aircraft. The response of the CCD camera system was tested at different neutron fluxes utilising the SLOWPOKE-2 at RMC and the Breazeale Nuclear Reactor at Pennsylvania State University.

Parasitic wasps learn and report diverse chemicals with unique conditionable behaviors.

Parasitoids exploit numerous chemical cues to locate hosts and food. Whether they detect and learn chemicals foreign to their natural history has not been explored. We show that the parasitoid Microplitis croceipes can associate, with food or hosts, widely different chemicals outside their natural foraging encounters. When learned chemicals are subsequently detected, this parasitoid manifests distinct behaviors characteristic with expectations of food or host, commensurate with prior training. This flexibility of parasitoids to rapidly link diverse chemicals to resource needs and subsequently report them with recognizable behaviors offers new insights into their foraging adaptability, and provides a model for further dissection of olfactory learning related processes.

Plant production of volatile semiochemicals in response to insect-derived elicitors.

An increase in the release of volatile compounds by plants in response to insect feeding is triggered by interaction of elicitors in the oral secretions of insect herbivores with damaged plant tissues. This herbivore damage triggers de novo biosynthesis of volatile plant metabolites derived from several different biochemical pathways. Natural enemies of herbivores use these volatile semiochemicals to locate their hosts. Although some volatile compounds are released from storage in plants immediately whenever damage to cells or glands occurs, the induced compounds are only synthesized and released during the light period. This often results in a delay between feeding damage and release of volatiles. Plants release the induced compounds from undamaged as well as damaged leaves. Thus, damage to only a few leaves results in a systemic response and release of volatiles by the entire plant. We propose that plants respond differently to individual herbivore species at least in part due to the composition of insect elicitors that come in contact with the plant. Specialist parasitoids can differentiate the volatile blends released due to damage by hosts from those resulting from non-host damage as well as from mechanical damage, thereby facilitating host location for the parasitoid. Elicitors in the oral secretions of beet armyworm caterpillars have been identified and synthesized.

A total system approach to sustainable pest management.

A fundamental shift to a total system approach for crop protection is urgently needed to resolve escalating economic and environmental consequences of combating agricultural pests. Pest management strategies have long been dominated by quests for "silver bullet" products to control pest outbreaks. However, managing undesired variables in ecosystems is similar to that for other systems, including the human body and social orders. Experience in these fields substantiates the fact that therapeutic interventions into any system are effective only for short term relief because these externalities are soon "neutralized" by countermoves within the system. Long term resolutions can be achieved only by restructuring and managing these systems in ways that maximize the array of "built-in" preventive strengths, with therapeutic tactics serving strictly as backups to these natural regulators. To date, we have failed to incorporate this basic principle into the mainstream of pest management science and continue to regress into a foot race with nature. In this report, we establish why a total system approach is essential as the guiding premise of pest management and provide arguments as to how earlier attempts for change and current mainstream initiatives generally fail to follow this principle. We then draw on emerging knowledge about multitrophic level interactions and other specific findings about management of ecosystems to propose a pivotal redirection of pest management strategies that would honor this principle and, thus, be sustainable. Finally, we discuss the potential immense benefits of such a central shift in pest management philosophy.

Microbial interactions with catheter material.

The use of central venous catheters to deliver parenteral nutrition therapy is often complicated by infection. The original source of these infections has been debated but it appears that organisms colonizing the skin or those contaminating the catheter hub are most often responsible. Before forming a biofilm, an organism must first successfully attach to a surface. To do this, microbes have evolved strategies that allow them to adhere to surfaces and evade forces that would favor their detachment. Once a biofilm is formed on a catheter, the organisms are relatively safe from a host immune response and antibiotics. In this review, what is known about these interactions is discussed.

How caterpillar-damaged plants protect themselves by attracting parasitic wasps.

Parasitic and predatory arthropods often prevent plants from being severely damaged by killing herbivores as they feed on the plants. Recent studies show that a variety of plants, when injured by herbivores, emit chemical signals that guide natural enemies to the herbivores. It is unlikely that herbivore-damaged plants initiate the production of chemicals solely to attract parasitoids and predators. The signaling role probably evolved secondarily from plant responses that produce toxins and deterrents against herbivores and antibiotics against pathogens. To effectively function as signals for natural enemies, the emitted volatiles should be clearly distinguishable from background odors, specific for prey or host species that feed on the plant, and emitted at times when the natural enemies forage. Our studies on the phenomena of herbivore-induced emissions of volatiles in corn and cotton plants and studies conducted by others indicate that (i) the clarity of the volatile signals is high, as they are unique for herbivore damage, produced in relatively large amounts, and easily distinguishable from background odors; (ii) specificity is limited when different herbivores feed on the same plant species but high as far as odors emitted by different plant species and genotypes are concerned; (iii) the signals are timed so that they are mainly released during the daytime, when natural enemies tend to forage, and they wane slowly after herbivory stops.

The chemistry of eavesdropping, alarm, and deceit.

Arthropods that prey on or parasitize other arthropods frequently employ those chemical cues that reliably indicate the presence of their prey or hosts. Eavesdropping on the sex pheromone signals emitted to attract mates allows many predators and parasitoids to find and attack adult insects. The sex pheromones are also useful signals for egg parasitoids since eggs are frequently deposited on nearby plants soon after mating. When the larval stages of insects or other arthropods are the targets, a different foraging strategy is employed. The larvae are often chemically inconspicuous, but when they feed on plants the injured plants respond by producing and releasing defensive chemicals. These plant chemicals may also serve as "alarm signals" that are exploited by predators and parasitoids to locate their victims. There is considerable evidence that the volatile "alarm signals" are induced by interactions of substances from the herbivore with the damaged plant tissue. A very different strategy is employed by several groups of spiders that remain stationary and send out chemical signals that attract prey. Some of these spiders prey exclusively on male moths. They attract the males by emitting chemicals identical to the sex pheromones emitted by female moths. These few examples indicate the diversity of foraging strategies of arthropod predators and parasitoids. It is likely that many other interesting chemically mediated interactions between arthropod hunters and their victims remain to be discovered. Increased understanding of these systems will enable us to capitalize on natural interactions to develop more ecologically sound, environmentally safe methods for biological control of insect pests of agriculture.

Host-specific recognition kairomone for the parasitoidMicroplitis croceipes (Cresson).

A water-extractable host recognition kairomone in frass of corn earworm,Helicoverpa zea Boddie (Lepidoptera: Noctuidae), host larvae stimulates antennation by females of the parasitoidMicroplitis croceipes Cresson (Braconidae: Hymenoptera). In addition, when the wasps contact water extracts of host frass they will subsequently fly in a flight tunnel to odor associated with the extract. Contact with water extracts of cowpea leaves or with water extracts of frass from larvae of nonhost beet armyworm, fall armyworm, or cabbage looper that were fed cowpea leaves does not stimulate antennation, nor do wasps fly to associated odors after contact with these substances. However, contact with the water extract of host frass in association with hexane extract of cowpea-fed nonhost frass will induce the wasps to subsequently fly to the hexane extract of the nonhost frass when it is used as an odor source in a flight tunnel. Thus the host-specific kairomone by whichM. croceipes recognizes the frass of its host is extractable with water. This substance plays a crucial role in the foraging behavior of this parasitoid by allowing it to recognize host frass and to learn to search for odors originating from plants on which the host is feeding.

Contact diode laser microvascular anastomosis.

Contact diode laser microvascular anastomosis appears to be a valuable technique for anastomosing small arteries and veins. Significantly less foreign body reaction and markedly decreased operative time has been shown to be a major advantage of using contact diode laser technology. The authors have found that contact diode laser anastomosis can be performed in vessels as small as 1 mm in size using a 200-microns flat tip synthetic sapphire probe. Light microscopy has shown a significant decrease in foreign body reaction at the level of the anastomosis using laser techniques as compared to standard vessel anastomosis with 10-0 nylon sutures. The role of fibronectin and changes in collagen associated with laser anastomosis were also explored. Light microscopic electron-microscopic results as well as biotin-avidin immunoperoxidase fibronectin studies will be discussed.

Chemically mediated associative learning: An important function in the foraging behavior ofMicroplitis croceipes (Cresson).

When experienced by contact with feces from hosts feeding on cowpeas, laboratory-reared females ofMicroplitis croceipes, a larval parasitoid ofHeliothis spp., orient and fly to odors of the same feces, whereas naive laboratory-reared females do not. Flight-tunnel studies revealed that associative learning occurs during female encounters with hosts and host products. When females antennate host feces, they learn to recognize the volatile odors associated with the feces. Females even can be conditioned to respond to novel and otherwise unattractive odors such as vanilla extract by exposure to these volatile substances in association with a water extract of the feces. They apparently link the volatile odors with a nonvolatile hostspecific recognition chemical found in the feces. The antennating stimulant, 13-methylhentriacontane, was found to be a valuable ingredient, apparently as a facilitator of the initial antennation and subsequent linkage of the volatiles to the nonvolatile host recognition cue.

Exploitation of herbivore-induced plant odors by host-seeking parasitic wasps.

Corn seedlings release large amounts of terpenoid volatiles after they have been fed upon by caterpillars. Artificially damaged seedlings do not release these volatiles in significant amounts unless oral secretions from the caterpillars are applied to the damaged sites. Undamaged leaves, whether or not they are treated with oral secretions, do not release detectable amounts of the terpenoids. Females of the parasitic wasp Cotesia marginiventris (Cresson) learn to take advantage of those plant-produced volatiles to locate hosts when exposed to these volatiles in association with hosts or host by-products. The terpenoids may be produced in defense against herbivores but may also serve a secondary function in attracting the natural enemies of these herbivores.

Semiochemicals for use with parasitoids: Status and future.

Allelochemicals are known to serve important roles at all steps in the host-searching sequence of parasitoids. We discuss the various roles of these allelochemics and the type of information needed to develop their use in pest control, which to date has been very limited. Rapid advancements are being made with respect to airborne chemicals and longer-range foraging behavior. Moreover, recent discoveries have shown that genetic diversity in parasitoid populations and phenotypic plasticity of individuals, together with their physiological state, often result in substantial variations in the response to chemical cues. Successful application of semiochemical-parasitoid systems will require management of these intrinsic parasitoid variables as well as management of the foraging environment. We illustrate emerging technology for such an application. For the immediate future, the development of this technology will allow us to: (1) define the genetic and phenotypic foraging profiles important to consistent and efficient parasitoid foraging, and (2) establish the proper propagation and release procedures and monitoring bioassays necessary to ensure appropriate behavioral and physiological qualities of released organisms. For the long term, we envision technology for comprehensively manipulating the pest/crop environment in ways that would provide foraging stimuli and other needs important to retention and efficiency of parasitoids.

Beneficial arthropod behavior mediated by airborne semiochemicals. IX. Differential response ofTrichogramma pretiosum, an egg parasitoid ofHeliothis zea, to various olfactory cues.

The behavior ofTrichogramma pretiosum Nixon wasps when exposed to different olfactory cues was studied in a wind tunnel. Compared to clean air, the sex pheromone of its hostHeliothis zea (Boddie) increased wasp residence times, walking times, and path lengths on a platform and decreased walking velocity. If wasps were released on top of a glass rod above a platform, the odor caused the wasps to land shortly after takeoff. In addition, a clear dose effect with regard to total residence and walking times was found. These responses were not elicited by three dosages of the sex pheromone ofSpodoptera frugiperda (J.E. Smith) or by a blend of saturated acetates. These results correspond with the observation thatH. zea is a common field host ofT. pretiosum, whereas eggs ofS. frugiperda are rarely attacked by this parasitoid.

How contact foraging experiences affect preferences for host-related odors in the larval parasitoidCotesia marginiventris (Cresson) (Hymenoptera: Braconidae).

Responses of individual females of the parasitoidCotesia marginiventris to the odors of four different complexes of host larvae feeding on leaves were observed in a four-arm olfactometer. The plant-host complexes were composed of fall armyworm (FAW) larvae or cabbage looper (CL) larvae feeding on either corn or cotton seedlings. Prior to testing, each female was given a brief foraging experience on a plant-host complex and was then exposed to the odors of the same complex in the olfactometer. The experienced females responded to familiar odors in a dose-related manner, and these responses were virtually identical to all four complexes. Preferences for the odors of one of two plant-host complexes were tested in dual choice situations. Generally, FAW odors were preferred over CL odors and corn odors over cotton odors. A short foraging experience significantly affected the females' odor preferences in favor of the odors released by the experienced complex. Additional experiments revealed that neither longer bouts of experience nor bouts that included ovipositions resulted in a stronger change in preference. Experience affected preference in combinations where only the host species was varied as well as in combinations where only the plant species was varied. The results, therefore, strongly indicate that both the plants and the hosts somehow are involved in the production and/or release of the semiochemicals that attractC. marginiventris.

Craniofacial resection for large tumors of the paranasal sinuses.

Large tumors of the paranasal sinuses can be removed thoroughly with a craniofacial approach that provides for good visualization. With this approach, some tumors previously considered inoperable may be removed and in some cases cured. We report three cases of tumors managed by means of a craniofacial procedure. One case involved an extensive inverting papilloma of the ethmoid sinus that invaded the orbit and coursed over the globe around the optic nerve. The second patient had a large squamous cell carcinoma of the paranasal sinuses that involved the cribriform plate, dura, and a portion of frontal lobe. The third case involved a meningioma that invaded the sphenoid wing, orbit, pterygomaxillary space, and infratemporal fossa. The craniofacial surgical technique and adjunctive therapies are discussed.

Beneficial arthropod behavior mediated by airborne semiochemicals : VI. flight responses of femaleMicroplitis croceipes (CRESSON), a braconid endoparasitoid ofHeliothis spp., to varying olfactory stimulus conditions created with a turbulent jet.

Odor-mediated host-searching by femaleMicroplitis croceipes, a braconid endoparasitoid of larvalHeliothis species, was studied in a flight tunnel. Volatiles emitted by third-instarH. zea feeding on cowpea seedling leaves were released and carried with the wind, resulting either in an irregularly shaped plume, or injected with high velocity, resulting in a conically shaped jet plume. Flight maneuvers ofM. croceipes had a higher stereotype in jet plumes compared to irregularly shaped plumes. Variation in odor concentration in jet plumes due to intermittent feeding of the host larvae did not affect the number of flights. At the levels employed, odor concentration did not alter the rate of upwind progress in jet plumes. Because air velocity inside a jet increases in the upwind direction,M. crocepies regulates its ground-speed during its approach to the odor source.

Beneficial arthropod behavior mediated by airborne semiochemicals. II. Olfactometric studies of host location by the parasitoidMicroplitis croceipes (Cresson) (Hymenoptera: Braconidae).

The response ofMicroplitis croceipes (Cresson) to odors from a plant-host complex was investigated using a four-choice olfactometer. Female, but not male, parasitoids responded in a dose-dependent fashion to volatiles from the plant-host complex and oviposition experience enhanced this response. Female age had no apparent effect on the response. Both artificially damaged leaves and frass elicited positive responses but of lower magnitude than those elicited by the plant-host complex. Volatiles collected from the plant-host complex placed on filter paper also elicited positive responses by female parasitoids.