1,473 research outputs found
Comment on "Fisheries Management"
No full textThe recent article by O’Leary et al. (2011) raises an important question about the relationship between science and those who manage fisheries. They contend that fishery managers do not give due cognisance to scientific advice and consistently set Total Allowable Catches (TACs) above values advised by scientists (which they define as ‘‘political adjustment’’). The authors claim that the consequence of this is that there is a high probability of stock collapse in the next 40 years. They use a simulation model to argue that this probability may exceed 80% at the mean level of political adjustment adopted by managers, depending on the degree of environmental variability and life history strategy of the fish
Sewing the Body of Christ : Eucharist wafer souvenirs stitched into fifteenth-century manuscripts, primarily in the Netherlands
No full textBooks of hours in the fifteenth century occupied several social and devotional roles. People used them to store small objects, including metal badges. Although the cultural practice of sewing in badges was widespread in the late Middle Ages, nearly all of the badges were removed (by later collectors). This article examines the practice by considering needle holes and offsets in the soft parchment, which indicate the shape of the badges and where they were attached. Noting that vast majority of metal offsets in books of hours are round, the author posits that these were not impressed by pilgrims’ badges, as is often repeated in the scholarly literature, but rather by tokens that commemorate having taken the Eucharist. The round badges are the same size and shape and bear the same imagery as host wafers. Owners stitched such badges into their books’ margins at locations relevant to Eucharistic piety. When they were sewn into books, Eucharist badges reconfigured the book as a shrine that recorded a votary’s pursuit of Communion.Peer reviewe
Interview with Lakshmi Raj Sharma, Author of The Tailor’s Needle
No full textInterview with Indian writer Lakshmi Raj Sharma, author of 'The Tailor's needle
Evaluating the effect of real-time closures on cod targeting
No full textAbstract
Needle, C. L., and Catarino, R. 2011. Evaluating the effect of real-time closures on cod targeting. – ICES Journal of Marine Science, 68: 1647–1655. Under its Conservation Credits scheme to reduce cod mortality, the Scottish Government has implemented a system of real-time closures (RTCs) since 2008. These are relatively small, temporarily closed areas (50–225 square nautical miles per RTC, closed for 21 d) that are triggered by high cod catches. An important step in evaluating their effectiveness is to determine the response of vessels to RTCs, because the conservation benefit would be reduced if vessels moved to areas of greater cod abundance following closures. Abundance indices from research-vessel surveys and commercial-vessel observer trips are combined to create a time- and space-dependent relative cod-importance index (RCII). Vessel monitoring system data from Scottish vessels fishing during 2008/2009 are used to construct RCII profiles for each vessel, which are then used to determine whether the areas to which vessels move have a higher or a lower RCII, and how far away they move when an RTC is activated. We show that the RCII of the areas moved to tends to be lower than that of the RTC and that vessels travel farther when moving away from a closure than when moving back after reopening. Although not conclusive, this result indicates that RTCs may impact beneficially on cod mortality.</jats:p
Wasp-inspired needle insertion with low net push force
No full textThis paper outlines the development of a four-part needle prototype inspired by the ovipositor of parasitic wasps. In the wasp ovipositor, three longitudinal segments called valves move reciprocally to gain depth in the substrate. It has been suggested that serrations located along the wasp ovipositor induce a friction difference between moving and anchoring valves that is needed for this reciprocal motion. Such an anchoring mechanism may not be desired in a medical setting, as serrations can induce tissue damage. Our aim was to investigate whether a multipart needle can penetrate tissue phantom material with near-zero net push force while using needle parts devoid of surface gripping textures or serrations. Accordingly, a four-part needle prototype was developed and tested in gelatine substrates. The performance of the prototype was assessed in terms of the degree of slipping of the needle with respect to the gelatine, with less slip implying better performance. Slip decreased with decreasing gelatine concentration and increasing offset between the needle parts. Motion through gelatine was achieved with a maximum push force of 0.035 N. This study indicates the possibility of needle propagation into a substrate with low net push force and without the need of serrations on the needle surface.Accepted Author ManuscriptMedical Instruments & Bio-Inspired Technolog
Needle deflection in tissue
No full textIntroduction: One of the factors that contribute to the total needle-targeting error in medical procedures is needle deflection, which can lead to e.g. hemorrhage, prolonged intervention time and decreased treatment efficiency. This deflection can be defined as the deviation of the needle from its suspected straight insertion path. In this study, we focused on the effect of tissue heterogeneity on needle deflection. We hypothesized that needle deflection would be bigger for insertions into heterogeneous than homogeneous specimens, due to an unequal force distribution on the needle. Method: the inner needle of a 18Gauge trocar needle with triangular tip was inserted (5mm/s) multiple times at several positions into 4 gelatin-, 4 animal liver-, and 2 human liver specimens. Deflection in X- and Y-direction was measured using sliding gauges and axial forces acting on the needle were captured using a force sensor mounted onto the needle hub. Axial force analysis was used to give a rough estimation of the mechanical properties of the specimens. Results: Results show an increase in magnitude and variance for needle insertions into the liver specimens (Animal: Mean = 1.01mm, SD = 0.54, Human: Mean = 0.83mm, SD = 0.48) compared with those into gelatin specimens (Mean = 0.59mm, SD = 0.26mm). Differences between the median and maximal needle tip forces for insertions into gelatin were almost zero (Mean = 0.08, SD = 0.04N), whereas those differences were bigger for insertions into tissue specimens (Mean = 0.58, SD = 0.23N), indicating the homogeneous nature of gelatin and heterogeneous nature of tissue. Discussion: The results obtained in this study suggest that heterogeneity causes the needle to deflect from its straight path. Both magnitude and variance of needle deflection are bigger for insertions into heterogeneous tissue specimens than into homogeneous gelatin specimens. A suggestion for future research is to study the effect of pathologic tissue on needle deflection, as this type of tissue is known for being more heterogeneous than healthy tissue.BioMechanical EngineeringMechanical, Maritime and Materials Engineerin
Ovipositor-inspired steerable needle: design and preliminary experimental evaluation
No full textFlexible steerable needles have the potential to allow surgeons to reach deep targets inside the human body with higher accuracy than rigid needles do. Furthermore, by maneuvering around critical anatomical structures, steerable needles could limit the risk of tissue damage. However, the design of a thin needle (e.g., diameter under 2 mm) with a multi-direction steering mechanism is challenging. The goal of this paper is to outline the design and experimental evaluation of a biologically inspired needle with a diameter under 2 mm that advances through straight and curved trajectories in a soft substrate without being pushed, without buckling, and without the need of axial rotation. The needle design, inspired by the ovipositor of parasitoid wasps, consisted of seven Nickel Titanium wires and had a total diameter of 1.2 mm. The motion of the needle was tested in gelatin phantoms. Forward motion of the needle was evaluated based on the lag between the actual and the desired insertion depth of the needle. Steering was evaluated based on the radius of curvature of a circle fitted to the needle centerline and on the ratio of the needle deflection from the straight path to the insertion depth. The needle moved forward inside the gelatin with a lag of 0.21 (single wire actuation) and 0.34 (double wire actuation) and achieved a maximum curvature of 0.0184 cm-1and a deflection-to-insertion ratio of 0.0778. The proposed biologically inspired needle design is a relevant step towards the development of thin needles for percutaneous interventions.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Medical Instruments & Bio-Inspired Technolog
Development of a Novel Needle Guide Tool for Percutaneous Interventions with an Omnidirectional Steerable Needle during Real-Time US-Guidance
No full textRadiofrequency ablation (RFA) is a localized thermalintervention technique with the purpose to destroy small tumours (< 3 cm) byheating the tumour tissue. Due to various challenges with targeting andvisualisation during RFA, the clinical need of steerable needles is present forradiologists. Helwig, B.P. developed a new omnidirectional steerableneedle for this purpose. However, this needle is not yet ready forimplementation in the operation room (OR) because no clinical testing isperformed in vivo. Therefore, the aim of this thesis is to develop a novelneedle guide tool for percutaneous interventions with an omnidirectionalsteerable needle during real-time US-guidance. In order to examine the visibility of the steerable needle,an experimental study has been conducted. The steerable needle has a promisingvisibility in Polyvinyl alcohol and is expected to be well visible duringultrasound guided interventions. The developed needle guide tool is calledUShift and provides both the benefits of needle guided puncturing and free-handpuncturing. Which are for free-hand puncturing: freedom of movement of boththe probe and needle during puncturing and for needle guided puncturing: a shorter procedure time, reduced needle manipulation and improvedneedle visualisation. A user test is performed to verify how the needle guide isperforming compared to the currently used needle guide while hypothetical usingthe Omnidirectional steerable needle. The difference between the two puncturetechniques is 0,9 seconds, the UShift is 23% faster. In conclusion, thisproject resulted in a novel needle guide tool that can be used in combinationwith the omnidirectional steerable needle during percutaneous interventions.The UShift has great benefits compared to currently used needle guides and istherefore stated as innovative. More gain is to be expected through future researchconcerning production methods, material options, the cost-effectiveness andother application fields of the UShift.Biomedical Engineerin
Needle-Tissue Interaction by Experiment
No full textMedical needles may not be very popular among patients, but they are exceptionally versatile instruments that have found their way into virtually every clinical intervention imaginable. However, despite their versatility, needles can be very difficult to use, and there is much room for improvement. Improvements can be realized by optimization of needle geometry, by the development of training facilities for clinicians, imaging modalities and needle-based sensors, by development of needle-steering mechanisms and path planning methods, or even by fully automating the needle insertion process. These approaches all rely on a proper understanding of the mechanical interaction between needle and soft-tissue. Ideally, insight into needle-tissue interaction mechanics should follow from the development and refinement of theoretical models based on experimental observation. The development of theoretical models has received a lot of attention in the literature, but our inability to collect useful and reliable experimental data remains an important obstacle. For this reason, the present thesis deals with the experimental study of needle-tissue interaction. The goal of the thesis is to provide insight into needle-tissue interaction mechanics based on experimental observation. To achieve this goal we measure the axial component of the external force acting on the needle during interaction with tissue, and we observe the position of the needle relative to the surrounding tissue. The first part of the thesis provides a basis for experimentation. This includes a survey of literature related to needle-tissue interaction force measurements. The intention of this survey is to gather existing experimental evidence regarding the influence of different factors, such as needle type, tissue type, and insertion speed, on the axial force. Based on this survey, a data model is constructed that describes the interrelations between the different aspects of needle-tissue interaction experiments. This data model enables the detailed encoding of experimental equipment, conditions, design, and results, and can be used as the blueprint for a database for experimental needle-tissue interaction data. The second part of the thesis presents two examples of relatively well-controlled experiments involving artificial specimens. These examples illustrate what happens at the tip of a needle during puncture of a membrane. The first experiment involves the use of high speed video to investigate the relation between axial force and needle tip geometry. The second experiment presents a follow-up study that investigates the influence of needle coating (lubrication) on the axial force during membrane puncture. The last part of the thesis presents two examples of experiments involving biological tissue. The first example is an exploratory study aimed at the characterization of forces during needle insertion into the kidney of a human cadaver. This is done with the help of synchronized ultrasound visualization. The second example is concerned with needle insertion into isolated porcine kidneys, intended to achieve a more detailed characterization of forces for different anatomical structures inside the kidney. This experiment uses synchronized ultrasound visualization with the ultrasound probe moving along with the needle. The thesis contributes to the field of needle-tissue interaction mechanics by providing an overview of available knowledge concerning needle-tissue interaction forces, and by providing a framework for structuring and expanding this knowledge. The thesis provides some insight by illustrating how needle reuse, needle coating, and specimen boundary conditions influence specific force metrics in artificial specimens. In addition, the thesis provides a first impression of the variability encountered during needle insertion into human cadaverous kidneys, and it provides a multivariate stochastic model of membrane puncture forces in porcine kidneys that can be used to simulate puncture events. However, the most important contribution consists of a set of tools for gathering, analyzing, and disseminating experimental needle-tissue interaction data.BioMechanical EngineeringMechanical, Maritime and Materials Engineerin
Applicability of the needle penetrometer: The upper strength limit, effects of saturation, different needle types and the F/d relation
No full textIn this study the applicability of the needle penetrometer is investigated. The needle penetrometer is a device which gives an indication of the Uniaxial Compressive Strength(UCS) by pushing a needle in a rock and measuring both the penetration depth and the applied force. More specific; research has been done to different needle types, the upper strength limit of the needle penetrometer, the effect of saturation and the relation between the force and the penetration depth. These limits were tested and found with multiple different needles and on multiple different samples. As far as the needles concerned, the Chenille 22 needle is a very good replacement for the Maruto needle. The upper strength limit of the needle penetrometer depends on the needle that is used and the strength of the rock. The average upper limit is around 10 MPa. The cause of this is that there are deviations at the upper strength limit. These deviations make the results of harder rocks less reliable, such as a non-linear penetration rate when gradually putting more pressure on the needle . Saturated rocks are weaker than their dry counterparts. The last conclusion in this study is that the needle penetrometer isn`t the right tool to acquire the data necessary to conclude anything meaningful about the F/d relation, other than that the relation seems to be linear. Since the spread of the acquired data is too wide.Section Geo-EngineeringGeoscience & EngineeringCivil Engineering and Geoscience
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