Pair Of Jaws Research Articles

Stylet jaws of Chrysopetalidae (Annelida)

ABSTRACTMicro-CT imaging elucidates jaw and pharynx structure in 14 nominal taxa belonging to Chrysopetalinae, Dysponetinae and Calamyzinae (Chrysopetalidae: Annelida). Systematic evaluation of chrysopetalid jaw form in each taxon is used to compare inter-generic relationships within and between each subfamily and with other polychaete families possessing lateral pairs of jaws. Jaw morphology proves diagnostic at all levels including agreement with current molecular phylogenetic analyses of the Chrysopetalidae. The greatest diversity of pharynx and jaw form, associated with sensory body characters, is found amongst taxa of the epibenthic Chrysopetalinae. It is hypothesized that the paired stylet jaws interlock to pierce prey tissue, and, in concert with a highly muscular pharynx, suck out prey fluids that pass down the internal groove of the stylets. Three generic groups are identified based on congruence of jaw form, and novel buccal structures are revealed in some taxa: a pharyngeal calcareous ‘ring’ and extensive pharyngeal glands. A continuum across free-living and facultative symbiont lifestyles is represented across all Chrysopetalinae. Dysponetinae comprises free-living, very small individuals that exhibit a meiofaunal lifestyle. All species possess one type of simple, tanned rod-like stylet jaws and certain simplified body structures. Calamyzinae species possess polyphyletic jaw forms and grades of radically simplified sensory morphologies. Free-living, bacteriovore calamyzins inhabit extreme chemosynthetic habitats and lack jaws, or possess modified jaws composed of an anterior platelet and posterior grooved jaw, present in the larvae and lost in the adult. New observations of an ectoparasitic Calamyzinae include details of a specialized mouth opening and stylet jaw present in a species that exhibits cryptic coloration, while grooved jaws are revealed for the first time in an obligate symbiont calamyzin. The grooved jaw form is considered a non-homoplasious synapomorphy that supports the monophyly of the family Chrysopetalidae.

Capture of Prey, Feeding, and Functional Anatomy of the Jaws in Velvet Worms (Onychophora).

Onychophorans are carnivorous, terrestrial invertebrates that occur in tropical and temperate forests of the Southern Hemisphere and around the Equator. Together with tardigrades, onychophorans are regarded as one of the closest relatives of arthropods. One of the most peculiar features of onychophorans is their hunting and feeding behavior. These animals secrete a sticky slime, which is ejected via a pair of slime-papillae, to entangle the prey. After the prey has been immobilized, its cuticle is punctured using a pair of jaws located within the mouth. These jaws constitute internalized appendages of the second body segment and are innervated by the deutocerebrum; thus, they are homologous to the chelicerae of chelicerates, and to the (first) antennae of myriapods, crustaceans, and insects. The jaws are also serial homologs of the paired claws associated with each walking limb of the trunk. The structure of the jaws is similar in representatives of the two major onychophoran subgroups, the Peripatidae and Peripatopsidae. Each jaw is characterized by an outer and an inner blade; while the outer blade consists only of a large principal tooth and up to three accessory teeth, the inner blade bears numerous additional denticles. These denticles are separated from the remaining part of the inner jaw by a diastema and a soft membrane only in peripatids. The onychophoran jaws are associated with large apodemes and specialized muscles that enable their movement. In contrast to the mandibles of arthropods, the onychophoran jaws are moved along, rather than perpendicular to, the main axis of the body. Our elemental analysis reveals an increased incorporation of calcium at the tip of each blade, which might provide rigidity, whereas there is no evidence for incorporation of metal or prominent mineralization. Stability of the jaw might be further facilitated by the cone-in-cone organization of its cuticle, as each blade consists of several stacked, cuticular elements. In this work, we summarize current knowledge on the jaws of onychophorans, which are a characteristic feature of these animals.

Determination of optimal system parameters to measure bending property of fabric based on the CHES-FY system

The main content of the paper is to determine the optimal system parameters to measure bending property of fabric based on the Comprehensive Handle Evaluation System for Fabric and Yarn (CHES-FY). Four system parameters of the CHES-FY system were selected, including space distance between a pair of jaws, space distance between Bi-U-shaped pins, vertical distance between a pair of jaws and Bi-U-shaped pins, and diameter of Bi-U-shaped pins. In order to both determine the sequence of significant influences of the four system parameters on bending property, and to determine the optimal values of the four parameters to measure bending property of fabric, the Orthogonal design method was adopted to set the four system parameters as four factors and to assign four levels to each factor. Correlations were conducted between bending property and the featured indices (slope and peak value) from the pulling-out force and displacement curves recorded by the CHES-FY system. Comparing results show that the featured indices have good relations with both bending rigidity and bending length measured by FAST-2 meter as well as drape coefficient. Range values and average values are used to assess the significant relation of both factors and factor’s levels with bending property of fabric. The sequence of significant influences of the four system parameters on bending property are diameter of Bi-U-shaped pins, space distance between Bi-U-shaped pins, vertical distance between a pair of jaws and Bi-U-shaped pins, and space distance between a pair of jaws. Moreover, the optimal parameters’ levels are also obtained to better measure bending property of fabric. It indicates that the optimal system parameters of the CHES-FY system are a highly effective combination in evaluating bending property of fabric.

Control of Shape Memory Alloy Actuated Gripper using Pulse-Width Modulation

End effectors like grippers find wide applications in robotic systems. Direct drive actuators like Shape Memory Alloys (SMAs) produce seemingly large linear or rotational movements of a modular actuator upon electrical heating. Mechanical work thus generated by SMAs can be harnessed to develop gripping systems with minimal moving parts. This article presents a simplest gripper actuated by SMA wire. The mechanical structure of the gripper is comprised of a pair of jaws (one movable) and an actuation means (a SMA wire and a counteracting torsion spring) for the movable jaw. Open loop and closed loop performance of the gripper are experimentally evaluated to manipulate objects of various sizes. In order to control the position of the devised gripper, a model is estimated from open loop data using system identification technique. Accurate and precise position tracking control is achieved using Pulse Width Modulation (PWM) technique.

SU-E-T-557: Dosimetric Evaluation of Elekta-XiO Superposition Convolution Algorithm for Siemens MultiLeaf Collimators

Purpose: Elekta-XiO treatment planning system(TPS) uses the same machine layout to simulate both two level jaw system Linacs like Siemens and three level jaw system like Varian Linacs. The purpose of this study is to perform a systematic investigation of the dose calculated from TPS using superposition convolution algorithm and compare that to the measurements for these two types of Linacs. Method and Materials: Siemens Primus and Artiste accelerators with multi-leaf collimators as lower jaws and Varian Trilogy accelerators with tertiary multileaf collimators were used in this study. A series of specially-designed T-shaped MLC fields with different field-aperture-opening-ratios(FAOR) and several clinically used 3DCRT MLC-blocked fields were calculated using the XiO superposition convolution and Clarkson methods. These plans were delivered on the respective Linacs and measurements were compared to the calculations. Several TMR based dose calculations were performed as independent checks on both superposition convolution and Clarkson methods. Monte Carlo simulations were performed to verify the dose calculation and to study the sources of scattering contribution. Results: A larger discrepancy was found between the dose calculated by XiO using superposition convolution algorithm and the dose measured for the Siemens Linacs than Varian Linacs. An average difference of 1.8% between Siemens and Varian Linacs was found for the situation of FAOR >0.33, possibly resulted from modeling the non-existant lower jaws for Siemens Linacs in the XiO convolution algorithm. TMR based dose calculations using a combined collimator scatter and phantom scatter factors with a XiO back-projected-blocked equivalent square(BES) can estimate the delivered dose accurately(0.12% of measured values) including extreme cases for Siemens(FAOR<0.33). Conclusions: A correction of magnitude of 1.8% should be applied to Linacs that use MLCs to replace a pair of jaws in the XiO superposition convolution algorithm when FAOR is >0.33. For FAOR<0.33, the algorithm cannot predict the delivered doses accurately.

Solder interconnect reliability under drop impact loading conditions using High-speed Cold Bump Pull

The use of microelectronic components in mobile appliances is constantly increasing. Appliances like mobile phones, PDA’s and navigation systems contain more and more functionality and smaller microelectronic components. Dropping an appliance during its lifespan is very common and the product is required to survive this. The drop however, generates significant forces and vibrations on the internal assembly of the product. The performance of a microelectronic component under drop conditions has thus become an important reliability parameter. Assessing the solder interconnect quality by means of drop impact testing, as standardized by e.g. JEDEC, during normal production requires considerable amounts of time and effort. Besides this, the repeatability of the drop impact test is low and introduces elaborate and time-consuming analysis of the results after testing. Already many researchers have investigated new test techniques capable of replacing the drop impact test. In the CBP test the solder bump is pulled in vertical direction from the die using a small pair of jaws. In this test, by varying the pull speed several different strain rates can be applied to the solder bump. In our research a correlation between the drop impact test and Cold Bump Pull test is investigated. This can be divided into three parts. First by investigating the Cold Bump Pull test apparatus for uncontrolled parameters that might introduce a bias or spread in the results. Secondly by means of modeling the Cold Bump Pull test to investigate solder bump deformation and solder bump loading during pull off. Finally in a comparison the differences and similarities between the two tests are briefly discussed and some observations concerning the solder joint performance are presented.

Twice bitten

The toothy visage of a moray eel is a fearsome sight. The discovery that morays can thrust a second pair of jaws out from their throat to wolf down prey whole increases their predatory reputation still further.

A scaleless scale worm: Molecular evidence for the phylogenetic placement of Pisione remota (Pisionidae, Annelida)

Pisionidae is a group of interstitial worms whose phylogentic affinities have been enigmatic. They have been allied to different Phyllodocida taxa. Although originally associated with Glyceridae and Phyllodocidae, they are more recently considered to be related to scale worms. Scale worms are a well-defined taxon, Aphroditiformia, within Annelida due to the unique possession of dorsal scales called elytra. Pisionidae lack elytra but they have been grouped with scale worms because they possess two pairs of jaws with venom glands, also found in Glyceridae. Determining the phylogenetic position of Pisionidae is important for understanding if features such as elytra and venomous jaws are evolutionarily labile in annelid history. Therefore, we explored 18S rDNA and Cytochrome c Oxidase subunit I data from several Aphroditiformia, Pisionidae, and other Phyllodocida to determine the phylogenetic placement of Pisionidae. Maximum likelihood and Bayesian inference of separate and combined data sets were conducted. All analyses support a derived position of Pisionidae within Aphroditiformia, close to Pholoidae and Sigalionidae. The loss of elytra in Pisionidae is probably due to adaptation for interstitial life. Furthermore, the results reject a monophyletic Aphroditoidea comprising Acoetidae, Aphroditidae, Eulepethidae and Polynoidae. Thus, the possession of only simple chaetae is either symplesiomorphic or convergent.

Slip and damage properties of jaws of laparoscopic graspers

The optimal jaws of laparoscopic graspers can be used to manipulate the tissue properly with minimal damage. The criteria jaws should satisfy are investigated. The cecum of pigs was clamped between 13 pairs of jaws differing in size and profile. Various pinch and pull forces were applied. At 5 N pull force, the minimally required pinch force to prevent slip and the pinch force that is maximally allowable without causing damage were obtained. With increasing size of the jaws, the contact area with the tissue increases. With increasing contact area, the pinch force leading to tissue damage was increased from 15 to 37 N. A profile of the jaws decreased the pinch force needed to prevent slip of tissue from 22 to 3 N. An optimal jaw possesses a large contact area to prevent tissue damage and a slight profile to prevent tissue slip.

Architecture of RNA polymerase II and implications for the transcription mechanism.

A backbone model of a 10-subunit yeast RNA polymerase II has been derived from x-ray diffraction data extending to 3 angstroms resolution. All 10 subunits exhibit a high degree of identity with the corresponding human proteins, and 9 of the 10 subunits are conserved among the three eukaryotic RNA polymerases I, II, and III. Notable features of the model include a pair of jaws, formed by subunits Rpb1, Rpb5, and Rpb9, that appear to grip DNA downstream of the active center. A clamp on the DNA nearer the active center, formed by Rpb1, Rpb2, and Rpb6, may be locked in the closed position by RNA, accounting for the great stability of transcribing complexes. A pore in the protein complex beneath the active center may allow entry of substrates for polymerization and exit of the transcript during proofreading and passage through pause sites in the DNA.

Dosimetric comparison of an integrated multileaf-collimator versus a conventional collimator

The dosimetric characteristics of both a conventional GE collimator (CC) and a GE multileaf collimator (MLC) are compared for different photon beam energies. The integrated GE MLC consists of 32 pairs of tungsten leaves, replacing the lower pair of jaws of the conventional collimator. Measurements were performed with the conventional collimator before this collimator was replaced by the MLC. All parts of the accelerator except the collimator remained the same. Leakage and transmission measurements show good agreement with the manufacturer's specification, stating a leakage between leaves of less than 1% for all energies and a transmission through leaves of less than 0.5%. The dosimetric characteristics of both collimators are very similar for square and rectangular fields. No significant change in beam quality, beam attenuation and depth of maximum dose could be detected within the measurement accuracy. The MLC output ratio variation is smaller than the one measured with the CC. The penumbra difference in the Y direction is less than 0.5 mm at a depth of 5 cm in phantom; in the X direction the penumbra is 1 mm larger for the MLC due to the rounded leaf fronts. As the two leaf banks replace the lower pair of collimator jaws the distance from the collimator end to the isocentre is similar for the two collimators, therefore the MLC does not reduce the flexibility of the treatment unit. For symmetrical and regular collimator settings the MLC can be treated as the CC.

A formalism to calculate the output ratio in a mini-phantom for a GE multileaf collimator

A GE multileaf collimator (MLC) has been recently installed on a Saturne 43 and is used with 6, 18 and 25 MV photon beams. In the integrated GE MLC the lower pair of jaws in the X direction is replaced by 32 pairs of computer controlled opposed tungsten leaves. The influence of each set of leaves on the output ratio is smaller than the influence of the jaws it replaces (8% instead of 10%). For irregular fields it is necessary to evaluate the influence on the output ratio of each independent leaf. It is assumed that each leaf and each jaw have an independent influence on the output ratio. According to this assumption leaf correction functions are derived from measurements as a function of their X position. A second-order correction (less than 1%) has to be applied for the jaw positions. The output ratio in a mini-phantom for a given irregular field can be calculated by the product of the 64 leaf and two jaw correction factors. The formalism is applied to symmetric square and rectangular fields, asymmetric and irregular fields. For all fields checked, the calculated and the measured output ratios agree within 1%. Furthermore the simple formula suggested by Vadash and Bjärngard for square field sizes equivalent to rectangular fields can be used with a good accuracy with an A value of 1.6 for the three energies used. The proposed formalism to calculate the output ratio in a mini-phantom is restricted to fields including the collimator axis with a minimum distance of 2 cm between any leaf and the collimator axis.

Using the field edge correction (FEC) method to generate accurate POCRs and OCRs for asymmetric fields.

Dose planning programs originally intended for use with symmetric fields have been adapted for use with asymmetric fields. An accurate representation of the change in primary beam quality with off-axis distance and depth is essential for accurate dose calculation and is usually represented in the computer as a primary radiation profile or primary off-center ratio (POCR). The original field edge correction (FEC) method described by Cadman [Med. Phys. 22, 457 (1995)] to determine POCRs has been extended to allow accurate POCR values to be obtained to an off-axis distance defined by the corners of the largest field, typically at an off-axis distance of 28.3 cm. This technique requires only routine symmetric field measurements including beam profiles, TMRs, and collimator and phantom scatter factors. The POCRs obtained using the FEC technique were used to generate off-center ratios (OCRs) using the boundary factor technique of Chui et al. [Med. Phys. 15, 92 (1988)]. Excellent agreement with measured values was obtained for cross-beam OCRs using a 10 x 10-cm2 field defined by a single set of asymmetric jaws with a field center offset of 15 cm and for diagonal OCRs using a 20 x 20-cm2 field with each pair of jaws in a half-blocked configuration.

The Venus Flytrap as a model for a biomimetic material with built-in sensors and actuators

In the present paper a model is presented for the dynamic response of a family (Droseraceae) of carnivorous plants such as the Venus Flytrap ( Dionaea Muscipula Ellis) and the Waterwheel Plant ( Aldrovanda Vesiculosa) to external dynamic disturbances. The goal of the present investigation is to apply such modelling to the molecular design of biomimetic materials with sensors and actuators. In modelling the dynamic response of such plants (or their flowers, to be exact) to external disturbances it is worth noting that these plants are capable of trapping and capturing their prey, usually small insects and flies, by the stimulation of a number of built-in trigger hairs or whisker-type sensors, which may be electro-elastic. The trapping and capturing action is quite muscular in the sense that, for example in the case of the Venus Flytrap, the flower, which is in the form of twin-lobed leaf blades closes quite quickly, upon stimulation of its trigger hairs, to trap the prey. These petals or valves are normally held ajar like an open spring trap. A victim entering the compass of the valves trips a trigger mechanism, whereupon the valves snap together with often surprising speed like a pair of jaws, and the victim is securely held within. The Venus Flytrap and Waterwheel Plant are closely related, though the former is terrestrial while the latter is aquatic. They belong to the same family as the Sundews (Droseraceae). The purpose of the present paper is to present a model for such intelligent structures with built-in sensors and muscular actuators in the hope of being able to fabricate similar intelligent materials (biomimetics) and intelligent structures for practical applications. Another remarkable property of the Venus Flytrap is that it is indeed possible to spring the trap without touching the trigger hairs — by repeated rubbing or scratching of the surface of the lobes for example — but the insect always does so by touching one or more trigger hairs. Based on a number of experimental observations in our laboratory we present a model for sensing and actuation of the Venus Flytrap. Our model is based on redistribution of ions and in particular Ca 2+ and H + ions in the tissue volumes. Generation of action potential simulation of trigger whiskers creates an ionic membrane type depolarization wave that propagates throughout the flower tissues.

A method for implementing dynamic photon beam intensity modulation using independent jaws and a multileaf collimator

A mathematical model is derived for digitally controlled linear accelerators to deliver a desired photon intensity distribution by combining collimator motion and machine dose rate variations. It shows that, at any instant, the quotient of the machine dose rate and the speed of collimator motion is proportional to the gradient of the desired in-air photon fluence distribution. The model is applicable for both independently controlled collimator jaws and multileaf collimators and can be implemented by controlling different parameters to accommodate linear accelerators from different manufacturers. For independent jaws, each pair of jaws creates photon fluence variations along the direction of the jaw movement. For multileaf collimators, where each leaf is independently controlled, any two-dimensional (2D) photon fluence distribution can be delivered. The model has been implemented for wedged isodose distributions using independent jaws, and 2D intensity modulation using a multileaf collimator. One-dimensional (1D) wedged isodose distributions are created by moving an independent jaw at constant speed while varying machine dose rate. 2D intensity modulation has been implemented using a 'dynamic stepping' scheme, which controls the leaf progression during irradiation at constant machine dose rate. With this automated delivery scheme, the beam delivery time for dynamic intensity modulation, which depends on the complexity of the desired intensity distribution, approaches that of conventional beam modifiers. This paper shows the derivation of the model, its application, and the authors' delivery scheme. Examples of 1D dynamic wedges and 2D intensity modulations will be given to illustrate the versatility of the model, the simplicity of its application, and the efficiency of beam delivery. These features make this approach practical for delivering conformal therapy treatments.

A Technique for Treating Local Breast Cancer Using a Single set-up Point and Asymmetric Collimation

Using both pairs of asymmetric jaws of a linear accelerator local-regional breast cancer may be treated from a single set-up point. This point is placed at the abutment of the supraclavicuhu fields with the medial and lateral tangential fields. Positioning the jaws to create a half-beam superiorly permits treatment of the supraclavicular field. Positioning both jaws asymmetrically at midline to define a single beam in the inferoanterior quadrant permits treatment of the breast from medial and lateral tangents. The highest possible matching accuracy between the supraclavicular and tangential fields is inherently provided by this technique. For treatment of all fields at 100 cm source to axis distance (SAD) the lateral placement and depth of the set-up point may be determined by simulation and simple trigonometry. We elaborate on the clinical procedure. For the technologists treatment of all fields from a single set-up point is simple and efficient. Since the tissue at the superior border of the tangential fields is generally firmer than in mid-breast, greater accuracy in day-to-day set-up is permitted. This technique eliminates the need for table angles even when tangential fields only are planned. Because of half-beam collimation the limit to the tangential field length is 20 cm. Means will be suggested to overcome this limitation in the few cases where it occurs. Another modification is suggested for linear accelerators with only one independent pair of jaws.

A hand-operated, 180° rotating-scoop sediment sampler

A hand-operated, rotating-scoop sediment sampler (HORS) has been developed for coarse-grained, shallow-marine sediment. Design of the 10 kg HORS was inspired by the 60 kg, winch-operated Shipek sampler which also has a 180° rotating scoop. At one-sixth of the Shipek mass, the HORS typically collects about one-sixth as much sediment. The HORS is recommended only if a winch is unavailable for a Shipek grab sampler. Grab samplers without a 180° rotating scoop rely on one or two pairs of jaws which close toward the center along arcs of 90°. These center-closing devices commonly fail to sample coarse sediment because a large grain, e.g. a shell fragment, impedes closure and allows the sample to escape during ascent. Center-closing jaws which meet rather than overlap eventually fail to meet completely because of wear along the jaw edge or misalignment. All grab samplers, including rotating-scoop types, may induce some loss of the finest fraction and so are best reserved for reconnaissance work. The sampler described herein has facilitated reconnaissance of the modern equivalent of oolitic ironstone in the southeastern Caribbean.

A technique for treating local breast cancer using a single set-up point and asymmetric collimation

Using both pairs of asymmetric jaws of a linear accelerator local-regional breast cancer may be treated from a single set-up point. This point is placed at the abutment of the supraclavicular fields with the medial and lateral tangential fields. Positioning the jaws to create a half-beam superiorly permits treatment of the supraclavicular field. Positioning both jaws asymmetrically at midline to define a single beam in the inferoanterior quadrant permits treatment of the breast from medial and lateral tangents. The highest possible matching accuracy between the supraclavicular and tangential fields is inherently provided by this technique. For treatment of all fields at 100 cm source to axis distance (SAD) the lateral placement and depth of the set-up point may be determined by simulation and simple trigonometry. We elaborate on the clinical procedure. For the technologists treatment of all fields from a single set-up point is simple and efficient. Since the tissue at the superior border of the tangential fields is generally firmer than in mid-breast, greater accuracy in day-to-day set-up is permitted. This technique eliminates the need for table angles even when tangential fields only are planned. Because of half-beam collimation the limit to the tangential field length is 20 cm. Means will be suggested to overcome this limitation in the few cases where it occurs. Another modification is suggested for linear accelerators with only one independent pair of jaws.

Characteristics of Mevatron 77 15-MV photon beam.

The characteristics of 15-MV photon beam of Mevatron 77 have been examined with respect to clinical parameters. Some of the characteristics of this 15-MV photon beam are different from those of similar machines used in radiotherapy. The tissue-maximum ratio values have been determined experimentally for SAD 100 cm and percentage depth dose values have been determined from tissue-maximum ratio data. It is found that the experimentally determined PDD values for SSD 80, 100, and 120 cm are within +/- 1% of the calculated data. The scatter-maximum ratio data have been calculated from the experimentally determined zero area attenuation coefficient and tissue-maximum ratio data and are presented as function of depth and radii of circular fields. The relative dose factors have been determined both for square and rectangular fields. The relative dose factor for rectangular fields depends on the two pairs of jaws differently and the maximum difference is about 1.5%. The flatness and symmetry are within the specifications set by the manufacturer.

An adjustable collimator for neutron therapy

Describes a system of adjustable collimators installed on the fast neutron beam (16 MeVd on Be) from the MRC Cyclotron at Hammersmith Hospital. A vertical section through the midplane of the collimators is shown. They consist of pairs of jaws moving in two planes at right angles to each other. The jaws defining the vertical extent of the field are divided into two sections, one near the target and the other acting as a trimmer. In the other plane there is only a single pair. The edges project back to the outside of the target, an area of 2 cm*2 cm. The outer end of the trimmer is at 100 cm from the target. At the treatment distance of 135 cm the field size is set by limit switches between 3 cm*3 cm and 20 cm*20 cm. The jaws can be rotated through +or-50 degrees so that the field can be inclined at any desired angle. The drives to the pairs of jaws and to the rotation of the collimator use DC stepper motors. These, together with the appropriate electronic control circuitry, provide precise and rapid positioning of the jaws.