WorldWideScience

Sample records for minimizes tissue artefacts

  1. Minimizing the self-heating artefacts due to the microwave irradiation of thermocouples.

    Science.gov (United States)

    Dunscombe, P B; Constable, R T; McLellan, J

    1988-01-01

    The self-heating of metallic thermocouples in therapeutic microwave fields has long been recognized as a source of temperature artefacts in clinical hyperthermia dosimetry. We examine several techniques by which the probe and tissue heating artefacts resulting from self-heating may be quantitatively assessed, and discuss these in the context of their applicability to clinical hyperthermia.

  2. [Tissue artefacts by the use of overheated forceps for paraffin embedding (author's transl)].

    Science.gov (United States)

    Müller, K M

    1980-05-01

    Histologic work-up of tissue specimens, especially from endoscopic biopsies, requires the use of fine forceps for orientation and dressing in fluid paraffin during the embedding procedure. These forceps are usually preheated over an open flame. If, however, smaller tissue particles are handled with overheated forceps, arteficial alterations may occur which are apt to hamper or falsify the histologic evaluation of the prepared section. Some typical tissue artefacts due to the handling with overheated forceps, are demonstrated with slides from liver biopsies. Recent experiences with an auxiliary instrument for paraffin embedding (Histostat of Vogel, designed by Ciplea) are reported. The forceps are kept at stable temperatures by immersion in fluid paraffin during the embedding procedure, thus excluding almost completely the risk of tissue artefacts by handling with overheated forceps.

  3. Minimally destructive DNA extraction from archaeological artefacts made from whale baleen

    DEFF Research Database (Denmark)

    Sinding, Mikkel Holger Strander; Gilbert, M. Thomas P.; Grønnow, Bjarne

    2012-01-01

    Here we demonstrate the successful extraction and amplification of target species DNA from artefacts made of whale baleen collected from excavations of past palaeo-Eskimo and Inuit cultures in Greenland. DNA was successfully extracted and amplified from a single baleen bristle of 1.5 cm length...... dated based on archaeological context to the period of the Saqqaq culture, more than 4000 years ago and following decades of storage at room temperature at the National Museum. The results reveal ancient baleen in archaeological material as a potential source of DNA that can be used for population...

  4. Artefacts in histopathology.

    Science.gov (United States)

    Chatterjee, Shailja

    2014-09-01

    Histopathology is the science of slide analysis for the diagnostic and research purposes. However, sometimes the presence of certain artefacts in a microscopic section can result in misinterpretations leading to diagnostic pitfalls that can result in increased patient morbidity. This article reviews the common artefacts encountered during slide examination alongside the remedial measures which can be undertaken to differentiate between an artefact and tissue constituent.

  5. Artefacts in histopathology

    Directory of Open Access Journals (Sweden)

    Shailja Chatterjee

    2014-01-01

    Full Text Available Histopathology is the science of slide analysis for the diagnostic and research purposes. However, sometimes the presence of certain artefacts in a microscopic section can result in misinterpretations leading to diagnostic pitfalls that can result in increased patient morbidity. This article reviews the common artefacts encountered during slide examination alongside the remedial measures which can be undertaken to differentiate between an artefact and tissue constituent.

  6. Effect of various upper limb multibody models on soft tissue artefact correction: A case study.

    Science.gov (United States)

    Naaim, Alexandre; Moissenet, Florent; Duprey, Sonia; Begon, Mickaël; Chèze, Laurence

    2017-01-31

    Soft tissue artefacts (STA) introduce errors in joint kinematics when using cutaneous markers, especially on the scapula. Both segmental optimisation and multibody kinematics optimisation (MKO) algorithms have been developed to improve kinematics estimates. MKO based on a chain model with joint constraints avoids apparent joint dislocation but is sensitive to the biofidelity of chosen joint constraints. Since no recommendation exists for the scapula, our objective was to determine the best models to accurately estimate its kinematics. One participant was equipped with skin markers and with an intracortical pin screwed in the scapula. Segmental optimisation and MKO for 24-chain models (including four variations of the scapulothoracic joint) were compared against the pin-derived kinematics using root mean square error (RMSE) on Cardan angles. Segmental optimisation led to an accurate scapula kinematics (1.1°≤RMSE≤3.3°) even for high arm elevation angles. When MKO was applied, no clinically significant difference was found between the different scapulothoracic models (0.9°≤RMSE≤4.1°) except when a free scapulothoracic joint was modelled (1.9°≤RMSE≤9.6°). To conclude, using MKO as a STA correction method was not more accurate than segmental optimisation for estimating scapula kinematics.

  7. Surface marker cluster translation, rotation, scaling and deformation: Their contribution to soft tissue artefact and impact on knee joint kinematics.

    Science.gov (United States)

    Benoit, D L; Damsgaard, M; Andersen, M S

    2015-07-16

    When recording human movement with stereophotogrammetry, skin deformation and displacement (soft tissue artefact; STA) inhibits surface markers' ability to validly represent the movement of the underlying bone. To resolve this issue, the components of marker motions which contribute to STA must be understood. The purpose of this study is to describe and quantify which components of this marker motion (cluster translation, rotation, scaling and deformation) contribute to STA during the stance phase of walking, a cutting manoeuvre, and one-legged hops. In vivo bone pin-based tibio-femoral kinematics of six healthy subjects were used to study skin marker-based STA. To quantify how total cluster translation, rotation, scaling and deformation contribute to STA, a resizable and deformable cluster model was constructed. STA was found to be greater in the thigh than the shank during all three movements. We found that the non-rigid (i.e. scaling and deformation) movements contribute very little to the overall amount of error, rendering surface marker optimisation methods aimed at minimising this component superfluous. The results of the current study indicate that procedures designed to account for cluster translation and rotation during human movement are required to correctly represent the motion of body segments, however reducing marker cluster scaling and deformation will have little effect on STA.

  8. Perfusion systems that minimize vascular volume fraction in engineered tissues.

    Science.gov (United States)

    Truslow, James G; Tien, Joe

    2011-06-01

    This study determines the optimal vascular designs for perfusing engineered tissues. Here, "optimal" describes a geometry that minimizes vascular volume fraction (the fractional volume of a tissue that is occupied by vessels) while maintaining oxygen concentration above a set threshold throughout the tissue. Computational modeling showed that optimal geometries depended on parameters that affected vascular fluid transport and oxygen consumption. Approximate analytical expressions predicted optima that agreed well with the results of modeling. Our results suggest one basis for comparing the effectiveness of designs for microvascular tissue engineering.

  9. Soft tissue artefacts of the human back: comparison of the sagittal curvature of the spine measured using skin markers and an open upright MRI.

    Directory of Open Access Journals (Sweden)

    Roland Zemp

    Full Text Available Soft tissue artefact affects the determination of skeletal kinematics. Thus, it is important to know the accuracy and limitations of kinematic parameters determined and modelled based on skin marker data. Here, the curvature angles, as well as the rotations of the lumbar and thoracic segments, of seven healthy subjects were determined in the sagittal plane using a skin marker set and compared to measurements taken in an open upright MRI scanner in order to understand the influence of soft tissue artefact at the back. The mean STA in the flexed compared to the extended positions were 10.2±6.1 mm (lumbar/9.3±4.2 mm (thoracic and 10.7±4.8 mm (lumbar/9.2±4.9 mm (thoracic respectively. A linear regression of the lumbar and thoracic curvatures between the marker-based measurements and MRI-based measurements resulted in coefficients of determination, R2, of 0.552 and 0.385 respectively. Skin marker measurements therefore allow for the assessment of changes in the lumbar and thoracic curvature angles, but the absolute values suffer from uncertainty. Nevertheless, this marker set appears to be suitable for quantifying lumbar and thoracic spinal changes between quasi-static whole body postural changes.

  10. [Artefacts of confocal microscopy].

    Science.gov (United States)

    Vekshin, N L; Frolov, M S

    2014-01-01

    Typical artefacts caused by using confocal fluorescent microscopy while studying living cells are considered. The role of light scattering, mobility, staining, local concentrations, etc. is discussed.

  11. Bioinspired Nanoparticulate Medical Glues for Minimally Invasive Tissue Repair.

    Science.gov (United States)

    Lee, Yuhan; Xu, Chenjie; Sebastin, Monisha; Lee, Albert; Holwell, Nathan; Xu, Calvin; Miranda Nieves, David; Mu, Luye; Langer, Robert S; Lin, Charles; Karp, Jeffrey M

    2015-11-18

    Delivery of tissue glues through small-bore needles or trocars is critical for sealing holes, affixing medical devices, or attaching tissues together during minimally invasive surgeries. Inspired by the granule-packaged glue delivery system of sandcastle worms, a nanoparticulate formulation of a viscous hydrophobic light-activated adhesive based on poly(glycerol sebacate)-acrylate is developed. Negatively charged alginate is used to stabilize the nanoparticulate surface to significantly reduce its viscosity and to maximize injectability through small-bore needles. The nanoparticulate glues can be concentrated to ≈30 w/v% dispersions in water that remain localized following injection. With the trigger of a positively charged polymer (e.g., protamine), the nanoparticulate glues can quickly assemble into a viscous glue that exhibits rheological, mechanical, and adhesive properties resembling the native poly(glycerol sebacate)-acrylate based glues. This platform should be useful to enable the delivery of viscous glues to augment or replace sutures and staples during minimally invasive procedures.

  12. Negotiating meaning through artefacts

    DEFF Research Database (Denmark)

    Tavella, Elena

    2015-01-01

    This research contributes to the domain of strategy making, specifically to unpacking the complexity of sociomateriality in strategy discourse. Scholars have emphasized the potential of artefacts to enhance sensemaking during strategizing. However there is a lack of insight into how artefacts...... and conversational aspects are linked at the micro‑level of discourse, also how artefacts and sensemaking shape one another. This research addresses this gap by empirically analyzing strategy discourse within a facilitated modelling workshop. Considering strategizing as a socially constructed activity, the author...... analyzes a workshop transcript to assess the extent to which stakeholders’ appropriation of artefacts supports them in engaging in negotiation of meaning with action implications. Moreover, how artefacts and negotiation of meaning shape one another is identified. The data suggest that appropriating...

  13. Artefacts: a diagnostic dilemma - a review.

    Science.gov (United States)

    Rastogi, Varun; Puri, Naveen; Arora, Swati; Kaur, Geetpriya; Yadav, Lalita; Sharma, Rachna

    2013-10-01

    The significance of proper handling of biopsy specimens is important and obvious for any histopathological diagnosis. Accuracy of tissue diagnosis by the pathologists is heavily dependent upon the competence of histotechnologists. The aim of a good histopathological technique is to produce microscopic preparation of tissues, usually stained, that represents as closely as possible, their structures in life. But this is not always possible and some sort of tissue morphology is bound to be seen. The ability of oral pathologists in interpreting a biopsy correctly is directly proportional not only to the quality, but also to the quantity of the specimen. There are many ways through which the exact interpretation of tissue specimen becomes compromised and the major pitfall is the presence of artefacts. These artefacts may occur during surgical removal, fixation, processing, embedding, microtomy and staining procedures. It is therefore important to identify the common occurring artefacts during interpretation of oral biopsies.

  14. Measuring femoral lesions despite CT metal artefacts: a cadaveric study

    NARCIS (Netherlands)

    Malan, D.F.; Botha, C.P.; Kraaij, G.; Joemai, R.M.S.; Van der Heide, H.J.L.; Nelissen, R.G.H.H.; Valstar, E.R.

    2011-01-01

    Objective Computed tomography is the modality of choice for measuring osteolysis but suffers from metal-induced artefacts obscuring periprosthetic tissues. Previous papers on metal artefact reduction (MAR) show qualitative improvements, but their algorithms have not found acceptance for clinical app

  15. Symbol: artefact and model

    DEFF Research Database (Denmark)

    Galle, Per

    2000-01-01

    In preparation of an analysis of product modelling in terms of communication, this report presents a brief analysis of symbols; that is, the entities by means of which communication takes place. Symbols are defined in such a way as to admit artefacts and models (the latter including linguistic...

  16. Artefacts that talk

    DEFF Research Database (Denmark)

    Hasse, Cathrine

    2013-01-01

    The article takes up the notion of artefacts as tools and signs and discusses how socially assistive robots impact professional work life and professional identities as multistable active change agents. It argues for a multistable understanding of tools as signs, building on a combination of post...

  17. Symbol: artefact and model

    DEFF Research Database (Denmark)

    Galle, Per

    2000-01-01

    In preparation of an analysis of product modelling in terms of communication, this report presents a brief analysis of symbols; that is, the entities by means of which communication takes place. Symbols are defined in such a way as to admit artefacts and models (the latter including linguistic...

  18. Artefacts in CBCT: a review

    Science.gov (United States)

    Schulze, R; Heil, U; Groβ, D; Bruellmann, DD; Dranischnikow, E; Schwanecke, U; Schoemer, E

    2011-01-01

    Artefacts are common in today's cone beam CT (CBCT). They are induced by discrepancies between the mathematical modelling and the actual physical imaging process. Since artefacts may interfere with the diagnostic process performed on CBCT data sets, every user should be aware of their presence. This article aims to discuss the most prominent artefacts identified in the scientific literature and review the existing knowledge on these artefacts. We also briefly review the basic three-dimensional (3D) reconstruction concept applied by today's CBCT scanners, as all artefacts are more or less directly related to it. PMID:21697151

  19. Minimalism

    CERN Document Server

    Obendorf, Hartmut

    2009-01-01

    The notion of Minimalism is proposed as a theoretical tool supporting a more differentiated understanding of reduction and thus forms a standpoint that allows definition of aspects of simplicity. This book traces the development of minimalism, defines the four types of minimalism in interaction design, and looks at how to apply it.

  20. Evaluation of minimal disseminated disease in cryopreserved ovarian tissue from bone and soft tissue sarcoma patients.

    Science.gov (United States)

    Dolmans, M M; Iwahara, Y; Donnez, J; Soares, M; Vaerman, J L; Amorim, C A; Poirel, H

    2016-10-01

    What is the risk of finding malignant cells in cryopreserved ovarian tissue from sarcoma patients? Minimal disseminated disease (MDD) was not detected in frozen-thawed ovarian tissue from 26 patients by any of the sensitive methods applied. In case of leukemia, the risk of malignant cell transmission through the graft is well known and widely documented. However, for bone cancer, like Ewing sarcoma or osteosarcoma, only a small number of case reports, have been published. These cancers often affect prepubertal girls, in whom ovarian tissue cryopreservation and transplantation is the only option to preserve fertility. The presence of malignant cells in cryopreserved ovarian tissue from patients with bone/soft tissue sarcoma was investigated with disease-specific markers for each patient, using immunohistochemistry (IHC), FISH and real-time quantitative RT-PCR (qPCR), with the original tumor serving as a positive control. Forty-eight sarcoma patients were enrolled in the study, 12 of whom subsequently died. In each case, tissue from the primary tumor was investigated in order to identify markers (immunohistochemical and/or molecular) to analyze the ovarian tissue case by case. Ovarian tissue from osteosarcoma (n = 15), liposarcoma (n = 1) and undifferentiated sarcoma (n = 5) patients could not be evaluated, as no specific markers were detected by FISH or sensitive IHC in any of their primary tumoral tissue. One patient with Li-Fraumeni syndrome was also excluded from the study. IHC analyses were therefore performed on ovarian tissue from 26 patients and qPCR on 19. The primary tumors involved were Ewing sarcoma family of tumors (n = 14), rhabdomyosarcoma (n = 7), synovial sarcoma (n = 2), clear cell sarcoma (n = 2) and a malignant peripheral nerve sheath tumor (n = 1). MDD was not detected in any of the 26 analyzed samples using sensitive techniques in this largest reported series, even from patients who subsequently died and/or those who presented

  1. Measuring femoral lesions despite CT metal artefacts: a cadaveric study

    Energy Technology Data Exchange (ETDEWEB)

    Malan, Daniel F. [Leiden University Medical Center, Department of Orthopaedics, Leiden (Netherlands); Delft University of Technology, Department of Mediamatics, EEMCS, P.O. Box 5031, Delft (Netherlands); Botha, Charl P. [Delft University of Technology, Department of Mediamatics, EEMCS, P.O. Box 5031, Delft (Netherlands); Leiden University Medical Center, Department of Radiology, Leiden (Netherlands); Kraaij, Gert; Heide, Huub J.L. van der; Nelissen, Rob G.H.H. [Leiden University Medical Center, Department of Orthopaedics, Leiden (Netherlands); Joemai, Raoul M.S. [Leiden University Medical Center, Department of Radiology, Leiden (Netherlands); Valstar, Edward R. [Leiden University Medical Center, Department of Orthopaedics, Leiden (Netherlands); Delft University of Technology, Department of Biomechanical Engineering, Delft (Netherlands)

    2012-05-15

    Computed tomography is the modality of choice for measuring osteolysis but suffers from metal-induced artefacts obscuring periprosthetic tissues. Previous papers on metal artefact reduction (MAR) show qualitative improvements, but their algorithms have not found acceptance for clinical applications. We investigated to what extent metal artefacts interfere with the segmentation of lesions adjacent to a metal femoral implant and whether metal artefact reduction improves the manual segmentation of such lesions. We manually created 27 periprosthetic lesions in 10 human cadaver femora. We filled the lesions with a fibrotic interface tissue substitute. Each femur was fitted with a polished tapered cobalt-chrome prosthesis and imaged twice - once with the metal, and once with a substitute resin prosthesis inserted. Metal-affected CTs were processed using standard back-projection as well as projection interpolation (PI) MAR. Two experienced users segmented all lesions and compared segmentation accuracy. We achieved accurate delineation of periprosthetic lesions in the metal-free images. The presence of a metal implant led us to underestimate lesion volume and introduced geometrical errors in segmentation boundaries. Although PI MAR reduced streak artefacts, it led to greater underestimation of lesion volume and greater geometrical errors than without its application. CT metal artefacts impair image segmentation. PI MAR can improve subjective image appearance but causes loss of detail and lower image contrast adjacent to prostheses. Our experiments showed that PI MAR is counterproductive for manual segmentation of periprosthetic lesions and should be used with care. (orig.)

  2. Material culture - artefacts and daily life

    DEFF Research Database (Denmark)

    Roesdahl, Else; Verhaeghe, Frans

    2011-01-01

    A survey of main groups of medieval portable artefacts, with a focus on north-western and central Europe (including Scandinavia), and a discussion of methods and interpretations in artefact studies......A survey of main groups of medieval portable artefacts, with a focus on north-western and central Europe (including Scandinavia), and a discussion of methods and interpretations in artefact studies...

  3. A fiber optic approach for in vivo minimally invasive study of tissue optical properties

    Science.gov (United States)

    Ilev, Ilko K.; Waynant, Ronald W.; Byrnes, Kimberly R.; Anders, Juanita

    2004-06-01

    Based on a fiber-optic approach, we present a fundamental in vivo study of optical properties and light transmission characteristics of single and multiple tissue layers and blood in a Sprague Dawley rat model. In our experiments, we utilize either coherent laser sources with various energy and spectral characteristics or incoherent light sources in a broadband spectral range covering the visible and near-infrared (from 400 nm to 1200 nm). The measurement techniques are based on a simple minimally invasive fiber-optic light delivery system that provides an effective method for homogeneously and precisely controlling the light irradiation of the tissue medium as well as being a highly sensitive detector of the tissue's scattered light. The delivery-sensor probes are placed into different tissue layers (skin, sub-cutaneous connective and deep connective tissue, back muscle, bone and spinal cord) and blood, and broadband spectral transmission characteristics of these media are measured in vivo. The transmission spectra are analyzed in order to determine the specificity of interaction of different tissues with light. The main goal is to determine the most effective coherent or incoherent light sources and their optimal parameters that might be used for minimally invasive therapeutic and optical diagnostics techniques.

  4. Transforming Artefacts into Digital Heritage

    DEFF Research Database (Denmark)

    Otto, Ton; Hardy, Dianna

    2016-01-01

    This paper deals with the possibilities and challenges of the digitisation of artefacts. It argues that artefacts are complex phenomena that consist of the material objects as well as the various forms of categorization and documentation that are connected with the objects. Digitalisation presents...... a genuine transformation of the artefacts that opens up new possibilities of use. These include providing access to and facilitating the reappropriation of cultural knowledge stored elsewhere, maintaining and developing a living digital cultural heritage, and gathering, sharing and transferring knowledge...... that is available within Aboriginal communities. In this paper we examine different types of digital repositories and we assess their suitability for use by Aboriginal communities. We classify a number of institutional archiving systems and analyse in some detail two interactive systems that were specifically...

  5. Static jaw collimation settings to minimize radiation dose to normal brain tissue during stereotactic radiosurgery

    Energy Technology Data Exchange (ETDEWEB)

    Han, Eun Young, E-mail: eyhan@uams.edu [Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR (United States); Zhang Xin; Yan Yulong; Sharma, Sunil; Penagaricano, Jose [Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR (United States); Moros, Eduardo [Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL (United States); Corry, Peter [Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR (United States)

    2012-01-01

    At University of Arkansas for Medical Sciences (UAMS) intracranial stereotactic radiosurgery (SRS) is performed by using a linear accelerator with an add-on micromultileaf collimator (mMLC). In our clinical setting, static jaws are automatically adapted to the furthest edge of the mMLC-defined segments with 2-mm (X jaw) and 5-mm (Y jaw) margin and the same jaw values are applied for all beam angles in the treatment planning system. This additional field gap between the static jaws and the mMLC allows additional radiation dose to normal brain tissue. Because a radiosurgery procedure consists of a single high dose to the planning target volume (PTV), reduction of unnecessary dose to normal brain tissue near the PTV is important, particularly for pediatric patients whose brains are still developing or when a critical organ, such as the optic chiasm, is near the PTV. The purpose of this study was to minimize dose to normal brain tissue by allowing minimal static jaw margin around the mMLC-defined fields and different static jaw values for each beam angle or arc. Dose output factors were measured with various static jaw margins and the results were compared with calculated doses in the treatment planning system. Ten patient plans were randomly selected and recalculated with zero static jaw margins without changing other parameters. Changes of PTV coverage, mean dose to predefined normal brain tissue volume adjacent to PTV, and monitor units were compared. It was found that the dose output percentage difference varied from 4.9-1.3% for the maximum static jaw opening vs. static jaw with zero margins. The mean dose to normal brain tissue at risk adjacent to the PTV was reduced by an average of 1.9%, with negligible PTV coverage loss. This dose reduction strategy may be meaningful in terms of late effects of radiation, particularly in pediatric patients. This study generated clinical knowledge and tools to consistently minimize dose to normal brain tissue.

  6. Breast tissue classification in digital tomosynthesis images based on global gradient minimization and texture features

    Science.gov (United States)

    Qin, Xulei; Lu, Guolan; Sechopoulos, Ioannis; Fei, Baowei

    2014-03-01

    Digital breast tomosynthesis (DBT) is a pseudo-three-dimensional x-ray imaging modality proposed to decrease the effect of tissue superposition present in mammography, potentially resulting in an increase in clinical performance for the detection and diagnosis of breast cancer. Tissue classification in DBT images can be useful in risk assessment, computer-aided detection and radiation dosimetry, among other aspects. However, classifying breast tissue in DBT is a challenging problem because DBT images include complicated structures, image noise, and out-of-plane artifacts due to limited angular tomographic sampling. In this project, we propose an automatic method to classify fatty and glandular tissue in DBT images. First, the DBT images are pre-processed to enhance the tissue structures and to decrease image noise and artifacts. Second, a global smooth filter based on L0 gradient minimization is applied to eliminate detailed structures and enhance large-scale ones. Third, the similar structure regions are extracted and labeled by fuzzy C-means (FCM) classification. At the same time, the texture features are also calculated. Finally, each region is classified into different tissue types based on both intensity and texture features. The proposed method is validated using five patient DBT images using manual segmentation as the gold standard. The Dice scores and the confusion matrix are utilized to evaluate the classified results. The evaluation results demonstrated the feasibility of the proposed method for classifying breast glandular and fat tissue on DBT images.

  7. Artefacts and the performance of an exhibition

    DEFF Research Database (Denmark)

    Svabo, Connie

    2008-01-01

    The article explores the role of mediating artefacts in children's encounters with a museum of natural history. Using actor network theory it explores how a specific artefact shapes the way users relate to exhibited objects and how the artefact guides users' movements in the exhibition. The media...

  8. Static jaw collimation settings to minimize radiation dose to normal brain tissue during stereotactic radiosurgery.

    Science.gov (United States)

    Han, Eun Young; Zhang, Xin; Yan, Yulong; Sharma, Sunil; Penagaricano, Jose; Moros, Eduardo; Corry, Peter

    2012-01-01

    At the University of Arkansas for Medical Sciences (UAMS) intracranial stereotactic radiosurgery (SRS) is performed by using a linear accelerator with an add-on micromultileaf collimator (mMLC). In our clinical setting, static jaws are automatically adapted to the furthest edge of the mMLC-defined segments with 2-mm (X jaw) and 5-mm (Y jaw) margin and the same jaw values are applied for all beam angles in the treatment planning system. This additional field gap between the static jaws and the mMLC allows additional radiation dose to normal brain tissue. Because a radiosurgery procedure consists of a single high dose to the planning target volume (PTV), reduction of unnecessary dose to normal brain tissue near the PTV is important, particularly for pediatric patients whose brains are still developing or when a critical organ, such as the optic chiasm, is near the PTV. The purpose of this study was to minimize dose to normal brain tissue by allowing minimal static jaw margin around the mMLC-defined fields and different static jaw values for each beam angle or arc. Dose output factors were measured with various static jaw margins and the results were compared with calculated doses in the treatment planning system. Ten patient plans were randomly selected and recalculated with zero static jaw margins without changing other parameters. Changes of PTV coverage, mean dose to predefined normal brain tissue volume adjacent to PTV, and monitor units were compared. It was found that the dose output percentage difference varied from 4.9-1.3% for the maximum static jaw opening vs. static jaw with zero margins. The mean dose to normal brain tissue at risk adjacent to the PTV was reduced by an average of 1.9%, with negligible PTV coverage loss. This dose reduction strategy may be meaningful in terms of late effects of radiation, particularly in pediatric patients. This study generated clinical knowledge and tools to consistently minimize dose to normal brain tissue.

  9. Gaze-contingent soft tissue deformation tracking for minimally invasive robotic surgery.

    Science.gov (United States)

    Mylonas, George P; Stoyanov, Danail; Deligianni, Fani; Darzi, Ara; Yang, Guang-Zhong

    2005-01-01

    The introduction of surgical robots in Minimally Invasive Surgery (MIS) has allowed enhanced manual dexterity through the use of microprocessor controlled mechanical wrists. Although fully autonomous robots are attractive, both ethical and legal barriers can prohibit their practical use in surgery. The purpose of this paper is to demonstrate that it is possible to use real-time binocular eye tracking for empowering robots with human vision by using knowledge acquired in situ. By utilizing the close relationship between the horizontal disparity and the depth perception varying with the viewing distance, it is possible to use ocular vergence for recovering 3D motion and deformation of the soft tissue during MIS procedures. Both phantom and in vivo experiments were carried out to assess the potential frequency limit of the system and its intrinsic depth recovery accuracy. The potential applications of the technique include motion stabilization and intra-operative planning in the presence of large tissue deformation.

  10. Flexible shape-memory scaffold for minimally invasive delivery of functional tissues

    Science.gov (United States)

    Montgomery, Miles; Ahadian, Samad; Davenport Huyer, Locke; Lo Rito, Mauro; Civitarese, Robert A.; Vanderlaan, Rachel D.; Wu, Jun; Reis, Lewis A.; Momen, Abdul; Akbari, Saeed; Pahnke, Aric; Li, Ren-Ke; Caldarone, Christopher A.; Radisic, Milica

    2017-10-01

    Despite great progress in engineering functional tissues for organ repair, including the heart, an invasive surgical approach is still required for their implantation. Here, we designed an elastic and microfabricated scaffold using a biodegradable polymer (poly(octamethylene maleate (anhydride) citrate)) for functional tissue delivery via injection. The scaffold’s shape memory was due to the microfabricated lattice design. Scaffolds and cardiac patches (1 cm × 1 cm) were delivered through an orifice as small as 1 mm, recovering their initial shape following injection without affecting cardiomyocyte viability and function. In a subcutaneous syngeneic rat model, injection of cardiac patches was equivalent to open surgery when comparing vascularization, macrophage recruitment and cell survival. The patches significantly improved cardiac function following myocardial infarction in a rat, compared with the untreated controls. Successful minimally invasive delivery of human cell-derived patches to the epicardium, aorta and liver in a large-animal (porcine) model was achieved.

  11. Reduction of metallic coil artefacts in computed tomography body imaging: effects of a new single-energy metal artefact reduction algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Kidoh, Masafumi; Utsunomiya, Daisuke; Ikeda, Osamu; Tamura, Yoshitaka; Oda, Seitaro; Yuki, Hideaki; Nakaura, Takeshi; Hirai, Toshinori; Yamashita, Yasuyuki [Kumamoto University, Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto (Japan); Funama, Yoshinori [Kumamoto University, Department of Medical Physics, Faculty of Life Sciences, Kumamoto (Japan); Kawano, Takayuki [Kumamoto University Graduate School, Department of Neurosurgery, Faculty of Life Sciences Research, Kumamoto (Japan)

    2016-05-15

    We evaluated the effect of a single-energy metal artefact reduction (SEMAR) algorithm for metallic coil artefact reduction in body imaging. Computed tomography angiography (CTA) was performed in 30 patients with metallic coils (10 men, 20 women; mean age, 67.9 ± 11 years). Non-SEMAR images were reconstructed with iterative reconstruction alone, and SEMAR images were reconstructed with the iterative reconstruction plus SEMAR algorithms. We compared image noise around metallic coils and the maximum diameters of artefacts from coils between the non-SEMAR and SEMAR images. Two radiologists visually evaluated the metallic coil artefacts utilizing a four-point scale: 1 = extensive; 2 = strong; 3 = mild; 4 = minimal artefacts. The image noise and maximum diameters of the artefacts of the SEMAR images were significantly lower than those of the non-SEMAR images (65.1 ± 33.0 HU vs. 29.7 ± 10.3 HU; 163.9 ± 54.8 mm vs. 10.3 ± 19.0 mm, respectively; P < 0.001). Better visual scores were obtained with the SEMAR technique (3.4 ± 0.6 vs. 1.0 ± 0.0, P < 0.001). The SEMAR algorithm significantly reduced artefacts caused by metallic coils compared with the non-SEMAR algorithm. This technique can potentially increase CT performance for the evaluation of post-coil embolization complications. (orig.)

  12. Minimally invasive proximal interphalangeal joint arthrodesis using a locking compression plate and tissue engineering in horses: A pilot study

    OpenAIRE

    SEO, Jong-Pil; Yamaga, Takashi; TSUZUKI, Nao; YAMADA, Kazutaka; HANEDA, Shingo; Furuoka, Hidefumi; Tabata, Yasuhiko; SASAKI, Naoki

    2014-01-01

    This pilot study assessed the efficacy of 2 minimally invasive techniques for proximal interphalangeal (PIP) joint arthrodesis in horses. The PIP joints of both forelimbs (n = 6) were stabilized with locking compression plates (LCP) using a minimally invasive technique (LCP technique). Subsequently, for 1 randomly selected PIP joint of each horse, surgical drilling (SurD) was performed and tissue engineering (TE) was applied (LCP/SurD/TE technique). Minimally invasive PIP joint arthrodesis wi...

  13. A review of medical robotics for minimally invasive soft tissue surgery.

    Science.gov (United States)

    Dogangil, G; Davies, B L; Rodriguez y Baena, F

    2010-01-01

    This paper provides an overview of recent trends and developments in medical robotics for minimally invasive soft tissue surgery, with a view to highlight some of the issues posed and solutions proposed in the literature. The paper includes a thorough review of the literature, which focuses on soft tissue surgical robots developed and published in the last five years (between 2004 and 2008) in indexed journals and conference proceedings. Only surgical systems were considered; imaging and diagnostic devices were excluded from the review. The systems included in this paper are classified according to the following surgical specialties: neurosurgery; eye surgery and ear, nose, and throat (ENT); general, thoracic, and cardiac surgery; gastrointestinal and colorectal surgery; and urologic surgery. The systems are also cross-classified according to their engineering design and robotics technology, which is included in tabular form at the end of the paper. The review concludes with an overview of the field, along with some statistical considerations about the size, geographical spread, and impact of medical robotics for soft tissue surgery today.

  14. Minimally invasive soft tissue release of foot and ankle contracture secondary to stroke.

    Science.gov (United States)

    Boffeli, Troy J; Collier, Rachel C

    2014-01-01

    Lower extremity contracture associated with stroke commonly results in a nonreducible, spastic equinovarus deformity of the foot and ankle. Rigid contracture deformity leads to gait instability, pain, bracing difficulties, and ulcerations. The classic surgical approach for stroke-related contracture of the foot and ankle has been combinations of tendon lengthening, tendon transfer, osteotomy, and joint fusion procedures. Recovery after traditional foot and ankle reconstructive surgery requires a period of non-weightbearing that is not typically practical for these patients. Little focus has been given in published studies on minimally invasive soft tissue release of contracture. We present the case of a 61-year-old female with an equinovarus foot contracture deformity secondary to stroke. The patient underwent Achilles tendon lengthening, posterior tibial tendon Z lengthening, and digital flexor tenotomy of each toe with immediate weightbearing in a walking boot, followed by transition to an ankle-foot orthosis. The surgical principles and technique tips are presented to demonstrate our minimally invasive approach to release of foot and ankle contracture secondary to stroke. The main goal of this approach is to improve foot and ankle alignment for ease of bracing, which, in turn, will improve gait, reduce the risk of falls, decrease pain, and avoid the development of pressure sores. Copyright © 2014 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

  15. Dosimetric impact of a CT metal artefact suppression algorithm for proton, electron and photon therapies.

    Science.gov (United States)

    Wei, Jikun; Sandison, George A; Hsi, Wen-Chien; Ringor, Michael; Lu, Xiaoyi

    2006-10-21

    Accurate dose calculation is essential to precision radiation treatment planning and this accuracy depends upon anatomic and tissue electron density information. Modern treatment planning inhomogeneity corrections use x-ray CT images and calibrated scales of tissue CT number to electron density to provide this information. The presence of metal in the volume scanned by an x-ray CT scanner causes metal induced image artefacts that influence CT numbers and thereby introduce errors in the radiation dose distribution calculated. This paper investigates the dosimetric improvement achieved by a previously proposed x-ray CT metal artefact suppression technique when the suppressed images of a patient with bilateral hip prostheses are used in commercial treatment planning systems for proton, electron or photon therapies. For all these beam types, this clinical image and treatment planning study reveals that the target may be severely underdosed if a metal artefact-contaminated image is used for dose calculations instead of the artefact suppressed one. Of the three beam types studied, the metal artefact suppression is most important for proton therapy dose calculations, intermediate for electron therapy and least important for x-ray therapy but still significant. The study of a water phantom having a metal rod simulating a hip prosthesis indicates that CT numbers generated after image processing for metal artefact suppression are accurate and thus dose calculations based on the metal artefact suppressed images will be of high fidelity.

  16. Organisational learning is crystallised into artefacts

    DEFF Research Database (Denmark)

    Bertelsen, Olav Wedege

    1996-01-01

    In this note I understand organisational learning in terms of manifest crystallisation of collective experience into artefacts, and I attempt to integrate an engineering and an emancipatory perspective. A Danish music festival serves as an example.......In this note I understand organisational learning in terms of manifest crystallisation of collective experience into artefacts, and I attempt to integrate an engineering and an emancipatory perspective. A Danish music festival serves as an example....

  17. Minimal and inducible regulation of tissue factor pathway inhibitor-2 in human gliomas.

    Science.gov (United States)

    Konduri, Santhi D; Osman, Francis Ali; Rao, Chilukuri N; Srinivas, Harish; Yanamandra, Niranjan; Tasiou, Anastasia; Dinh, Dzung H; Olivero, William C; Gujrati, Meena; Foster, Donald C; Kisiel, Walter; Kouraklis, Gregory; Rao, Jasti S

    2002-01-31

    Tissue factor pathway inhibitor-2 (TFPI-2), a serine protease inhibitor abundant in the extra cellular matrix, is highly expressed in non-invasive cells but undetectable levels in highly invasive human glioma cells. The mechanisms responsible for its transcriptional regulation are not well elucidated. In this study, we made several deletion constructs from a 3.6 kb genomic fragment from Hs683 cells containing the 5'-flanking region of the TFPI-2 gene, transiently transfected with these constructs into non-invasive (Hs683) and highly invasive (SNB19) human glioma cells, and assessed their expression by using a luciferase reporter gene. Three constructs showed high promoter activity (pTF5, -670 to +1; pTF6, -312 to +1; pTF2, -1511 to +1). Another construct, pTF8 (-81 to +1), showed no activity. PTF9, a variant of pTF5 in which a further 231 bp fragment (-312 to -81) was deleted, from the [-670 to +1] pTF5 region, also showed no promoter activity. Hence, (-312 to -81) this region is essential for the transcription of TFPI-2 in glioma cells. Sequencing of this promoter region revealed that it has a high G+C content, contains potential SP1 and AP1 binding motifs, and lacks canonical TATA and CAAT boxes immediately upstream of the major transcriptional initiation site, although CAAT boxes were found about -3000 bp upstream of the transcription start site. We also found a strong repressor in the region between -927 to -1181, upstream of the major transcriptional initiation site, followed by positive elements or enhancers between -1511 to -1181. These positive elements masked the silencer effect. Finally TFPI-2 was induced in Hs683 cells transfected with the pTF6 construct (-312 to +1) and stimulated with phorbol-12-myristate-13-acetate (PMA). We conclude that the -312 to +1 region is critical for the minimal and inducible regulation of TFPI-2 in non-invasive (Hs683) and highly invasive (SNB19) human glioma cell lines.

  18. Minimally invasive proximal interphalangeal joint arthrodesis using a locking compression plate and tissue engineering in horses: a pilot study.

    Science.gov (United States)

    Seo, Jong-pil; Yamaga, Takashi; Tsuzuki, Nao; Yamada, Kazutaka; Haneda, Shingo; Furuoka, Hidefumi; Tabata, Yasuhiko; Sasaki, Naoki

    2014-11-01

    This pilot study assessed the efficacy of 2 minimally invasive techniques for proximal interphalangeal (PIP) joint arthrodesis in horses. The PIP joints of both forelimbs (n = 6) were stabilized with locking compression plates (LCP) using a minimally invasive technique (LCP technique). Subsequently, for 1 randomly selected PIP joint of each horse, surgical drilling (SurD) was performed and tissue engineering (TE) was applied (LCP/SurD/TE technique). Minimally invasive PIP joint arthrodesis with LCP demonstrated low postoperative infection rates. Gross and histological evaluations revealed considerable destruction of the articular cartilage in the LCP/SurD/TE-treated joints. In contrast, almost no destruction of the cartilage was observed in the LCP-treated joints. Our results suggest that the LCP technique alone is not sufficient for PIP joint arthrodesis and that the LCP/SurD/TE technique may be useful for PIP joint arthrodesis in horses.

  19. A novel suturing approach for tissue displacement within minimally invasive periodontal plastic surgery.

    Science.gov (United States)

    Ronco, Vincent; Dard, Michel

    2016-08-01

    This paper describes a novel suturing approach that achieves harmonious and atraumatic soft tissue displacement in periodontal plastic surgery and soft tissue management around implants. The technique relies on a combination of horizontal and vertical mattress that are anchored at the splinted incisal contact points.

  20. A novel suturing approach for tissue displacement within minimally invasive periodontal plastic surgery

    OpenAIRE

    Ronco, Vincent; Dard, Michel

    2016-01-01

    Key Clinical Message This paper describes a novel suturing approach that achieves harmonious and atraumatic soft tissue displacement in periodontal plastic surgery and soft tissue management around implants. The technique relies on a combination of horizontal and vertical mattress that are anchored at the splinted incisal contact points.

  1. Explicating the Sustainable Design of Technical Artefacts

    DEFF Research Database (Denmark)

    Vissonova, Karina

    2016-01-01

    that despite the ambiguities, there are discernible necessary and sufficient conditions by which the design may qualify as the sustainable kind. My claims are constructed based on two assumptions: the first being the presence of side effects of the design of technical artefacts, and the second being the values......Sustainable design of technical artefacts is referred to as if it were a kind of design with some specific characteristics. However, in design research and practice alike, there appears to be a lack of shared conceptions of what such a design might entail. Furthermore, we have no clear grounds...... for evaluating what makes the sustainable design solutions permissible. The lack of shared conceptions is largely due to ambiguities associated with the notion of sustainability. In response to these challenges, the aim of my study is to offer a definition of sustainable design of technical artefacts. I argue...

  2. Innovative optical microsystem for static and dynamic tissue diagnosis in minimally invasive surgical operations

    Science.gov (United States)

    Ahmadi, Roozbeh; Packirisamy, Muthukumaran; Dargahi, Javad

    2012-08-01

    During conventional surgical tasks, surgeons use their tactile perception in their finger tips to sense the degree of softness of biological tissues to identify tissue types and to feel for any abnormalities. However, in robotic-assisted surgical systems, surgeons are unable to sense this information because only surgical tools interact with tissues. In order to provide surgeons with such useful tactile perception, therefore, a tactile sensor is required that is capable of simultaneously measuring contact force and resulting tissue deformation. Accordingly, this paper discusses the design, prototyping, testing, and validation of an innovative tactile sensor that is capable of measuring the degree of softness of soft objects such as tissues under both static and dynamic loading conditions and which is also magnetic resonance compatible and electrically passive. These unique characteristics of the proposed sensor would also make it a practical choice for use in robotic-assisted surgical platforms. The prototype version of this sensor was developed by using optical micro-systems technology and, thus far, experimental test results performed on the prototyped sensor have validated its ability to measure the relative softness of artificial tissues.

  3. Model output: fact or artefact?

    Science.gov (United States)

    Melsen, Lieke

    2015-04-01

    As a third-year PhD-student, I relatively recently entered the wonderful world of scientific Hydrology. A science that has many pillars that directly impact society, for example with the prediction of hydrological extremes (both floods and drought), climate change, applications in agriculture, nature conservation, drinking water supply, etcetera. Despite its demonstrable societal relevance, hydrology is often seen as a science between two stools. Like Klemeš (1986) stated: "By their academic background, hydrologists are foresters, geographers, electrical engineers, geologists, system analysts, physicists, mathematicians, botanists, and most often civil engineers." Sometimes it seems that the engineering genes are still present in current hydrological sciences, and this results in pragmatic rather than scientific approaches for some of the current problems and challenges we have in hydrology. Here, I refer to the uncertainty in hydrological modelling that is often neglected. For over thirty years, uncertainty in hydrological models has been extensively discussed and studied. But it is not difficult to find peer-reviewed articles in which it is implicitly assumed that model simulations represent the truth rather than a conceptualization of reality. For instance in trend studies, where data is extrapolated 100 years ahead. Of course one can use different forcing datasets to estimate the uncertainty of the input data, but how to prevent that the output is not a model artefact, caused by the model structure? Or how about impact studies, e.g. of a dam impacting river flow. Measurements are often available for the period after dam construction, so models are used to simulate river flow before dam construction. Both are compared in order to qualify the effect of the dam. But on what basis can we tell that the model tells us the truth? Model validation is common nowadays, but validation only (comparing observations with model output) is not sufficient to assume that a

  4. Minimizing Postsampling Degradation of Peptides by a Thermal Benchtop Tissue Stabilization Method.

    Science.gov (United States)

    Segerström, Lova; Gustavsson, Jenny; Nylander, Ingrid

    2016-04-01

    Enzymatic degradation is a major concern in peptide analysis. Postmortem metabolism in biological samples entails considerable risk for measurements misrepresentative of true in vivo concentrations. It is therefore vital to find reliable, reproducible, and easy-to-use procedures to inhibit enzymatic activity in fresh tissues before subjecting them to qualitative and quantitative analyses. The aim of this study was to test a benchtop thermal stabilization method to optimize measurement of endogenous opioids in brain tissue. Endogenous opioid peptides are generated from precursor proteins through multiple enzymatic steps that include conversion of one bioactive peptide to another, often with a different function. Ex vivo metabolism may, therefore, lead to erroneous functional interpretations. The efficacy of heat stabilization was systematically evaluated in a number of postmortem handling procedures. Dynorphin B (DYNB), Leu-enkephalin-Arg(6) (LARG), and Met-enkephalin-Arg(6)-Phe(7) (MEAP) were measured by radioimmunoassay in rat hypothalamus, striatum (STR), and cingulate cortex (CCX). Also, simplified extraction protocols for stabilized tissue were tested. Stabilization affected all peptide levels to varying degrees compared to those prepared by standard dissection and tissue handling procedures. Stabilization increased DYNB in hypothalamus, but not STR or CCX, whereas LARG generally decreased. MEAP increased in hypothalamus after all stabilization procedures, whereas for STR and CCX, the effect was dependent on the time point for stabilization. The efficacy of stabilization allowed samples to be left for 2 hours in room temperature (20°C) without changes in peptide levels. This study shows that conductive heat transfer is an easy-to-use and efficient procedure for the preservation of the molecular composition in biological samples. Region- and peptide-specific critical steps were identified and stabilization enabled the optimization of tissue handling and opioid

  5. The design stance and its artefacts

    NARCIS (Netherlands)

    Vermaas, P.E.; Carrara, M.; Borgo, S.; Garbacz, P.

    2011-01-01

    In this paper we disambiguate the design stance as proposed by Daniel C. Dennett, focusing on its application to technical artefacts. Analysing Dennett’s work and developing his approach towards interpreting entities, we show that there are two ways of spelling out the design stance, one that presup

  6. Artefact Correction in MRI Temperature Mapping

    NARCIS (Netherlands)

    Shmatukha, A.V.

    2007-01-01

    The thesis describes techniques that can be used to reduce or eliminate artefacts arising due to magnetic field disturbances and/or motion in temperature maps obtained by the Proton Resonance Frequency Shift (PRFS) method of MRI temperature mapping. The first chapter describes a hardware modificatio

  7. The design stance and its artefacts

    NARCIS (Netherlands)

    Vermaas, P.E.; Carrara, M.; Borgo, S.; Garbacz, P.

    2011-01-01

    In this paper we disambiguate the design stance as proposed by Daniel C. Dennett, focusing on its application to technical artefacts. Analysing Dennett’s work and developing his approach towards interpreting entities, we show that there are two ways of spelling out the design stance, one that presup

  8. Artefacts: Minecraft meets Collaborative Interactive Evolution

    DEFF Research Database (Denmark)

    Patrascu, Cristinel; Risi, Sebastian

    2016-01-01

    does not only allow players to collaborate by building larger structures from evolved objects but also to continue evolution of others’ artefacts. Results from playtests on three different game iterations indicate that players generally enjoy playing the game and are able to discover a wide variety...

  9. Artefact Correction in MRI Temperature Mapping

    NARCIS (Netherlands)

    Shmatukha, A.V.

    2007-01-01

    The thesis describes techniques that can be used to reduce or eliminate artefacts arising due to magnetic field disturbances and/or motion in temperature maps obtained by the Proton Resonance Frequency Shift (PRFS) method of MRI temperature mapping. The first chapter describes a hardware

  10. Minimizing Nitrate Reduction during Kjeldahl Digestion of Plant Tissue Extracts and Stem Exudates : APPLICATION TO N STUDIES.

    Science.gov (United States)

    Pace, G M; Mackown, C T; Volk, R J

    1982-01-01

    From 10 to 60% of the nitrate present in plant tissue extracts and stem exudates of corn (Zea mays L.) was found to be reduced during Kjeldahl digestion, even in the absence of added reducing agents. This reduction is of particular concern in [(15)N]nitrate assimilation studies, because it results in an overestimate of nitrate reduction. To overcome this problem, a method was developed for removing nitrate prior to Kjeldahl digestion, thereby preventing nitrate reduction. The procedure utilizes hydrogen peroxide for partial oxidation of organic matter in order to minimize the nitration of organic compounds. The free nitrates are then volatilized as nitric acid from concentrated sulfuric acid at 95 degrees C. When the proposed method was used as a pretreatment to Kjeldahl digestion, less than 0.5% of the applied nitrate was recovered in the reduced nitrogen fraction of plant tissue extracts and stem exudates.

  11. 3D artefact for concurrent scale calibration in Computed Tomography

    DEFF Research Database (Denmark)

    Stolfi, Alessandro; De Chiffre, Leonardo

    2016-01-01

    A novel artefact for calibration of the scale in 3D X-ray Computed Tomography (CT) is presented. The artefact comprises a carbon fibre tubular structure on which a number of reference ruby spheres are glued. The artefact is positioned and scanned together with the workpiece inside the CT scanner ...

  12. [Hard dental tissue minimal-invasive preparation using contemporary polymer rotating instruments and laser].

    Science.gov (United States)

    Beloica, Milos; Vulićević, Zoran R; Mandinić, Zoran; Radović, Ivana; Jovicić, Olivera; Carević, Momir; Tekić, Jasmina

    2014-01-01

    Goal of contemporary dentistry is to decrease the patient's discomfort during treatment. Dentists aim to achieve maximum with the newly developed dental materials as well as with new cavity preparation techniques in the shortest time span. Since the development of the first constructed borer (drilling machine) for caries removal, the preparation techniques have considerably changed. The progress of dental materials as well as the cavity preparation techniques has led us to contemporary carbide tungsten and diamond borers that are used with obligatory water cooling. The innovation within this field represents newly developed polymer borers that can detect the difference between carious lesions and healthy tooth structure. In this way the cavity preparation may be performed without damaging dental healthy tissue. This is possible owing to their hardness which is lower than the hardness of intact dentin. Polymer borer preparation is painless with less vibration, while the increase in temperature is negligible. Lasers have been used in clinical dentistry since 1980s so it can be said that they represent a new technology. The function of lasers is based on ablation which requires water. Erbium lasers have shown the highest potential with their ability to produce effective ablation of hard dental tissues. Laser application in dentistry requires special training as well as some protective measures. Laser advantages, compared to traditional preparation techniques, involve the absence of vibration, painless preparation, possibility of preparation without anesthetic and easier patient's adjustment to dental intervention which is of importance, especially in pediatric dentistry.

  13. Automatic macroscopic density artefact removal in a Nissl-stained microscopic atlas of whole mouse brain.

    Science.gov (United States)

    Ding, W; Li, A; Wu, J; Yang, Z; Meng, Y; Wang, S; Gong, H

    2013-08-01

    Acquiring a whole mouse brain at the micrometer scale is a complex, continuous and time-consuming process. Because of defects caused by sample preparation and microscopy, the acquired image data sets suffer from various macroscopic density artefacts that worsen the image quality. We have to develop the available preprocessing methods to improve image quality by removing the artefacts that effect cell segmentation, vascular tracing and visualization. In this study, a set of automatic artefact removal methods is proposed for images obtained by tissue staining and optical microscopy. These methods significantly improve the complicated images that contain various structures, including cells and blood vessels. The whole mouse brain data set with Nissl staining was tested, and the intensity of the processed images was uniformly distributed throughout different brain areas. Furthermore, the processed image data set with its uniform brightness and high quality is now a fundamental atlas for image analysis, including cell segmentation, vascular tracing and visualization.

  14. Hard dental tissue minimal-invasive preparation using contemporary polymer rotating instruments and laser

    Directory of Open Access Journals (Sweden)

    Beloica Miloš

    2014-01-01

    Full Text Available Goal of contemporary dentistry is to decrease the patient’s discomfort during treatment. Dentists aim to achieve maximum with the newly developed dental materials as well as with new cavity preparation techniques in the shortest time span. Since the development of the first constructed borer (drilling machine for caries removal, the preparation techniques have considerably changed. The progress of dental materials as well as the cavity preparation techniques has led us to contemporary carbide tungsten and diamond borers that are used with obligatory water cooling. The innovation within this field represents newly developed polymer borers that can detect the difference between carious lesions and healthy tooth structure. In this way the cavity preparation may be performed without damaging dental healthy tissue. This is possible owing to their hardness which is lower than the hardness of intact dentin. Polymer borer preparation is painless with less vibration, while the increase in temperature is negligible. Lasers have been used in clinical dentistry since 1980s so it can be said that they represent a new technology. The function of lasers is based on ablation which requires water. Erbium lasers have shown the highest potential with their ability to produce effective ablation of hard dental tissues. Laser application in dentistry requires special training as well as some protective measures. Laser advantages, compared to traditional preparation techniques, involve the absence of vibration, painless preparation, possibility of preparation without anesthetic and easier patient’s adjustment to dental intervention which is of importance, especially in pediatric dentistry. [Projekat Ministarstva nauke Republike Srbije, br. 46009

  15. Optical clearing of vaginal tissues, ex vivo, for minimally invasive laser treatment of female stress urinary incontinence

    Science.gov (United States)

    Chang, Chun-Hung; Myers, Erinn M.; Kennelly, Michael J.; Fried, Nathaniel M.

    2017-01-01

    Near-infrared laser energy in conjunction with applied tissue cooling is being investigated for thermal remodeling of the endopelvic fascia during minimally invasive treatment of female stress urinary incontinence. Previous computer simulations of light transport, heat transfer, and tissue thermal damage have shown that a transvaginal approach is more feasible than a transurethral approach. However, results were suboptimal, and some undesirable thermal insult to the vaginal wall was still predicted. This study uses experiments and computer simulations to explore whether application of an optical clearing agent (OCA) can further improve optical penetration depth and completely preserve the vaginal wall during subsurface treatment of the endopelvic fascia. Several different mixtures of OCA's were tested, and 100% glycerol was found to be the optimal agent. Optical transmission studies, optical coherence tomography, reflection spectroscopy, and computer simulations [including Monte Carlo (MC) light transport, heat transfer, and Arrhenius integral model of thermal damage] using glycerol were performed. The OCA produced a 61% increase in optical transmission through porcine vaginal wall at 37°C after 30 min. The MC model showed improved energy deposition in endopelvic fascia using glycerol. Without OCA, 62%, 37%, and 1% of energy was deposited in vaginal wall, endopelvic fascia, and urethral wall, respectively, compared with 50%, 49%, and 1% using OCA. Use of OCA also resulted in 0.5-mm increase in treatment depth, allowing potential thermal tissue remodeling at a depth of 3 mm with complete preservation of the vaginal wall.

  16. Innovation cascades: artefacts, organization and attributions.

    Science.gov (United States)

    Lane, David A

    2016-03-19

    Innovation cascades inextricably link the introduction of new artefacts, transformations in social organization, and the emergence of new functionalities and new needs. This paper describes a positive feedback dynamic, exaptive bootstrapping, through which these cascades proceed, and the characteristics of the relationships in which the new attributions that drive this dynamic are generated. It concludes by arguing that the exaptive bootstrapping dynamic is the principal driver of our current Innovation Society.

  17. Computer Simulation of Multidimensional Archaeological Artefacts

    Directory of Open Access Journals (Sweden)

    Vera Moitinho de Almeida

    2012-11-01

    Our project focuses on the Neolithic lakeside site of La Draga (Banyoles, Catalonia. In this presentation we will begin by providing a clear overview of the major guidelines used to capture and process 3D digital data of several wooden artefacts. Then, we shall present the use of semi-automated relevant feature extractions. Finally, we intend to share preliminary computer simulation issues.

  18. Artefacting reliability in QEEG topographic maps.

    Science.gov (United States)

    Lawson, J Stuart; Galin, Howard; Adams, Susan J; Brunet, Donald G; Criollo, Margarita; MacCrimmon, Duncan J

    2003-05-01

    To quantify the extent of disagreement among expert artefactors, to compare their results with a 'minimalist' approach where only gross artefacts were removed, and to relate the result to frequency and to cranial location. Raw QEEG records for 12 subjects were artefacted by 6-expert, and one 'minimalist', artefactor. Standard errors (SEs) of measurement were computed for each of 20 1.2 Hz frequency bins in each of 20 electrode positions. SEs declined with frequency. SEs associated with the 'minimalist' were comparable to those of the experts. The high SEs in delta were confined to the frontal and frontotemporal regions. SEs were small and uniform over the cranium for frequencies greater than 5.2 Hz. Artefactor unreliability is a serious problem in the delta band because of disagreement on eye movement artefacts. The success of the 'minimalist' suggests that automated methodologies may be a feasible alternative to the use of expert technicians. A novel statistical procedure proves helpful in elucidating the sources of artefactor error and points to possible remedies.

  19. Fine-needle aspiration and core needle biopsy: An update on 2 common minimally invasive tissue sampling modalities.

    Science.gov (United States)

    VanderLaan, Paul A

    2016-12-01

    Fine-needle aspiration (FNA) and core needle biopsy (CNB) represent 2 of the most common minimally invasive tissue sampling modalities. Although similar in many ways, there are significant differences in the collection, processing, interpretation, and suitability for ancillary testing that exist between FNA and CNB. This review provides a brief overview of the strengths and weaknesses of FNA compared with CNB, as well as an update regarding the landscape of recently published studies that investigate the organ-specific comparative performance metrics of FNA and CNB. A current understanding of the benefits and limitations of FNA and CNB will help the cytopathologist and the clinician alike to select the right procedure for the right patient at the right time. Cancer Cytopathol 2016;124:862-870. © 2016 American Cancer Society. © 2016 American Cancer Society.

  20. A study of artefacts in simultaneous PET and MR imaging using a prototype MR compatible PET scanner.

    Science.gov (United States)

    Slates, R B; Farahani, K; Shao, Y; Marsden, P K; Taylor, J; Summers, P E; Williams, S; Beech, J; Cherry, S R

    1999-08-01

    We have assessed the possibility of artefacts that can arise in attempting to perform simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) using a small prototype MR compatible PET scanner (McPET). In these experiments, we examine MR images for any major artefacts or loss in image quality due to inhomogeneities in the magnetic field, radiofrequency interference or susceptibility effects caused by operation of the PET system inside the MR scanner. In addition, possible artefacts in the PET images caused by the static and time-varying magnetic fields or radiofrequency interference from the MR system were investigated. Biological tissue and a T2-weighted spin echo sequence were used to examine susceptibility artefacts due to components of the McPET scanner (scintillator, optical fibres) situated in the MR field of view. A range of commonly used MR pulse sequences was studied while acquiring PET data to look for possible artefacts in either the PET or MR images. Other than a small loss in signal-to-noise using gradient echo sequences, there was no significant interaction between the two imaging systems. Simultaneous PET and MR imaging of simple phantoms was also carried out in different MR systems with field strengths ranging from 0.2 to 4.7 T. The results of these studies demonstrate that it is possible to acquire PET and MR images simultaneously, without any significant artefacts or loss in image quality, using our prototype MR compatible PET scanner.

  1. The materiality of materials and artefacts used in science classrooms

    DEFF Research Database (Denmark)

    Cowie, Bronwen; Otrel-Cass, Kathrin; Moreland, Judy

    materials as natural objects in this world and artefacts as manmade objects. We are aware that in a classroom material objects and artefacts shape, and are shaped by classroom practice through the way they selectively present scientific explanations. However, materials and artefacts have no intrinsic...... such as fossils, plant samples and artefacts like test tubes, worksheets and digital tools along with written inscriptions produced during interactions and that served as artefacts in subsequent interactions (Roehl, 2012). Data sources Data were generated via classroom observation using video, student work sample....... d) Artefacts as an adjunct to talk. The use of sets of cards or actual objects. Students changed the position of the cards/ objects as a dynamic visual representation of consensus thinking. Significance The teachers in our study did not view materials as being neutral objects but thought about means...

  2. The Role of Artefact Theories in Design

    DEFF Research Database (Denmark)

    Andreasen, Mogens Myrup

    1998-01-01

    This positioning paper reflects personal experiences and considerations related to design research and theories. The multiple object of design theory is pointed out and the possible research questions related to these multiple aspects. The complexity leads to need for simplification, linking...... together and unification, but we also need a metric: what is a good theory? An important theory dimension in synthesis is the artefact theory, leading to the question of a design language. Such a language might be the core of a universal design theory....

  3. Optical artefact characterization and correction in volumetric scintillation dosimetry

    Science.gov (United States)

    Robertson, Daniel; Hui, Cheukkai; Archambault, Louis; Mohan, Radhe; Beddar, Sam

    2014-01-01

    The goals of this study were (1) to characterize the optical artefacts affecting measurement accuracy in a volumetric liquid scintillator detector, and (2) to develop methods to correct for these artefacts. The optical artefacts addressed were photon scattering, refraction, camera perspective, vignetting, lens distortion, the lens point spread function, stray radiation, and noise in the camera. These artefacts were evaluated by theoretical and experimental means, and specific correction strategies were developed for each artefact. The effectiveness of the correction methods was evaluated by comparing raw and corrected images of the scintillation light from proton pencil beams against validated Monte Carlo calculations. Blurring due to the lens and refraction at the scintillator tank-air interface were found to have the largest effect on the measured light distribution, and lens aberrations and vignetting were important primarily at the image edges. Photon scatter in the scintillator was not found to be a significant source of artefacts. The correction methods effectively mitigated the artefacts, increasing the average gamma analysis pass rate from 66% to 98% for gamma criteria of 2% dose difference and 2 mm distance to agreement. We conclude that optical artefacts cause clinically meaningful errors in the measured light distribution, and we have demonstrated effective strategies for correcting these optical artefacts.

  4. Deviations in delineated GTV caused by artefacts in 4DCT

    DEFF Research Database (Denmark)

    Persson, Gitte Fredberg; Nygaard, Ditte Eklund; Brink, Carsten;

    2010-01-01

    Four-dimensional computed tomography (4DCT) is used for breathing-adapted radiotherapy planning. Irregular breathing, large tumour motion or interpolation of images can cause artefacts in the 4DCT. This study evaluates the impact of artefacts on gross tumour volume (GTV) size.......Four-dimensional computed tomography (4DCT) is used for breathing-adapted radiotherapy planning. Irregular breathing, large tumour motion or interpolation of images can cause artefacts in the 4DCT. This study evaluates the impact of artefacts on gross tumour volume (GTV) size....

  5. Investigating effects of different artefact types on motor imagery BCI

    DEFF Research Database (Denmark)

    Frølich, Laura; Winkler, Irene; Muller, Klaus-Robert

    2015-01-01

    Artefacts in recordings of the electroencephalogram (EEG) are a common problem in Brain-Computer Interfaces (BCIs). Artefacts make it difficult to calibrate from training sessions, resulting in low test performance, or lead to artificially high performance when unintentionally used for BCI contro...

  6. Emergent Artefacts of Ethnography and Processual Engagements of design

    DEFF Research Database (Denmark)

    Wallace, Jamie

    2012-01-01

    Relating to processes of design and creativity, the use of artefacts are contrasted between two different disciplines. Pointing to possible challenges, the study considers how collaborative innovation depends upon the interplay between entwined and emergent artefact worlds and their related skill...

  7. An Artefact suppressing fast-recovery myoelectric amplifier

    NARCIS (Netherlands)

    Thorsen, R.

    1999-01-01

    An amplifier for recording myoelectric signals using surface electrodes has been developed. The special features are suppression of stimulation artefacts and motion artefacts from electrodes. It is designed for recording of myoelectric signals from a muscle that is being stimulated with short impuls

  8. Enhancing Professional Learning Communities through Knowledge Artefacts in Mainland China

    Science.gov (United States)

    Qiao, Xuefeng; Yu, Shulin

    2016-01-01

    This qualitative case study examines the perspectives and experiences of seven Chinese primary teachers on the integration of shared knowledge artefacts into teaching in professional learning communities. The analysis of the semi-structured interviews and observation data revealed that using knowledge artefacts, such as preview sheets, flowing…

  9. GIS as an Artefact in Geography Education: Some Future Challenges

    DEFF Research Database (Denmark)

    Madsen, Lene Møller; Winsløw, Carl

    2007-01-01

    Geographers have always used a variety of physical artefacts e.g. a pluviometer, a map, or a globe as tools to perform their profession. Each of these artefacts has in different ways shaped our ways of being and becoming geographers. Not only have they shaped how we learn but also what we learn. ...

  10. Re-scripting interactive artefacts with feminine values

    DEFF Research Database (Denmark)

    Rasmussen, Majken Kirkegaard; Petersen, Marianne Graves

    2012-01-01

    This paper takes up the challenge, of developing value-centred interaction design as an approach to avoiding stereotypic presumptions about femininity when designing artefacts. We suggest that utilizing a feminine value perspective to design artefacts can create a richer profusion of ways to view...

  11. CT metal artefact reduction of total knee prostheses using angled gantry multiplanar reformation.

    Science.gov (United States)

    Lewis, Mark; Toms, Andoni P; Reid, Karen; Bugg, William

    2010-08-01

    This study was designed to determine whether or not acquiring CT images of total knee prostheses by using an angled gantry and multiplanar reformation can reduce beam hardening artefact. A CT phantom was created with a total knee prosthesis suspended in gelatine with a known attenuation. CT data was acquired with a gantry angled at 0 degrees, 5 degrees, 10 degrees and 15 degrees in both craniocaudal oblique planes. Axial images where then reformatted from these datasets. Two independent observers selected regions of interest to measure the mean and standard deviation (SD) of attenuation in the gelatine for all reformatted axial images. Artefact was measured as SD of the background attenuation and areas under the curve of SD for each gantry angle acquisition were compared. Inter-observer reliability was excellent (ICC=0.89, CI 0.875-0.908). The most accurate mean attenuation values for tissues around a TKR were obtained with a CT gantry using 10 degrees to 15 degrees anteroinferior to posterosuperior angulation. The smallest area under the curve for SD of attenuation for the whole prosthesis, and the femoral component in isolation, was obtained with a 5 degrees gantry angle in the same direction. The smallest area under the curve for the tibial component in isolation occurred with a gantry angle of 15 degrees. We conclude that acquiring CT data with a gantry angle can reduce metal artefact around a TKR. Optimal overall metal artefact reduction can be achieved with a small angle from anteroinferior to posterosuperior. Further selective artefact reduction around the tibial component can be achieved with larger angles.

  12. The materiality of materials and artefacts used in science classrooms

    DEFF Research Database (Denmark)

    Cowie, Bronwen; Otrel-Cass, Kathrin; Moreland, Judy

    and ends of artefacts/ materials. They explored artefacts/materials and how they could be used and through this exemplified materiality in the objects. More deliberate and focused attention to what constitutes materiality can support collaboration and communication to support and enhance learning...... materials as natural objects in this world and artefacts as manmade objects. We are aware that in a classroom material objects and artefacts shape, and are shaped by classroom practice through the way they selectively present scientific explanations. However, materials and artefacts have no intrinsic...... and constrain forms of action and insights that are likely to “emerge” (Wells, 2003). Methods The study's teachers considered that students enjoy and benefit from “hands–on” learning activities and many commented that tasks and interactions incorporated the use of materials. These included material objects...

  13. In vitro artefact assessment of a new MR-compatible microwave antenna and a standard MR-compatible radiofrequency ablation electrode for tumour ablation

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Ruediger; Rempp, Hansjoerg; Eibofner, Frank; Kessler, David-Emanuel; Weiss, Jakob; Nikolaou, Konstantin; Clasen, Stephan [Eberhard Karls University, Department of Diagnostic and Interventional Radiology, Tuebingen (Germany); Blumenstock, Gunnar [Eberhard Karls University, Department of Clinical Epidemiology and Applied Biometry, Tuebingen (Germany); Pereira, Philippe L. [SLK-Kliniken Heilbronn GmbH, Department of Radiology, Minimally Invasive Therapies, and Nuclear Medicine, Heilbronn (Germany)

    2016-03-15

    To evaluate and compare artefact configuration and diameters in a magnetic resonance (MR)-compatible prototype microwave (MW) applicator and a standard MR-compatible radiofrequency (RF) applicator for MR-guided tumour ablation. Both applicators were tested in a phantom study at 1.5T with three sequences: T1-weighted three-dimensional volume interpolated breath-hold examination (VIBE), T1-weighted fast low angle shot (FLASH), T2-weighted turbo spin echo (TSE). Applicator orientation to main magnetic field (B{sub 0}) and slice orientation were varied. Needle tip location error (TLE) was assessed, and artefact diameters were calculated. Influence of imaging parameters on artefacts was assessed with analysis of variance (ANOVA) and post hoc testing. MW applicator: the shaft artefact diameter measured 2.3 +/- 0.8 mm. Tip artefact diameter and length measured 2.2 ± 0.8 mm and 2.4 ± 1.3 mm, respectively. A prominent oval artefact (diameter: 16.5 +/- 1.8 mm, length: 19.1 +/- 2.5 mm) appeared close to the tip. TLE: -.3 +/- 0.6 mm. RF applicator: shaft and tip diameter measured 8.9 +/- 4.7 mm and 9.0 +/-.0 mm, respectively. TLE: -0.1 +/- 0.8 mm. Minimal artefacts were measured with RF applicator orientation parallel to B{sub 0} (P < 0.0001), whereas no such influence was found for MW applicator. For both applicators, significantly large artefacts were measured with T1 FLASH (P = 0.03). The MW applicator's artefact is satisfactory and seems useable for MR-guided ablation procedures. (orig.)

  14. Suppression of high-density artefacts in x-ray CT images using temporal digital subtraction with application to cryotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Baissalov, R.; Sandison, G.A.; Rewcastle, J.C. [Department of Medical Physics, Tom Baker Cancer Center, Calgary, Canada, T2N 4N2 2 Department of Physics and Astronomy, University of Calgary, Calgary T2N 2N4 (Canada); Donnelly, B.J. [Department of Surgery, Tom Baker Cancer Center, Calgary, Canada, T2N 4N2 4 Department of Surgery, Foothills Hospital, Calgary T2N 2T7 (Canada); Saliken, J.C. [Department of Surgery, Tom Baker Cancer Center, Calgary T2N 4N2 (Canada); Department of Diagnostic Imaging, Foothills Hospital, Calgary T2N 2T7 (Canada); McKinnon, J.G. [Department of Surgery, Foothills Hospital, Calgary T2N 2T7 (Canada); Muldrew, K. [Department of Surgery, Faculty of Medicine, University of Calgary, Calgary T2N 2T7 (Canada)

    2000-05-01

    Image guidance in cryotherapy is usually performed using ultrasound. Although not currently in routine clinical use, x-ray CT imaging is an alternative means of guidance that can display the full 3D structure of the iceball, including frozen and unfrozen regions. However, the quality of x-ray CT images is compromised by the presence of high-density streak artefacts. To suppress these artefacts we applied temporal digital subtraction (TDS). This TDS method has the added advantage of improving the grey-scale contrast between frozen and unfrozen tissue in the CT images. Two sets of CT images were taken of a phantom material, cryoprobes and a urethral warmer (UW) before and during the cryoprobe freeze cycle. The high-density artefacts persisted in both image sets. TDS was performed on these two image sets using the corresponding mask image of unfrozen material and the same geometrical configuration of the cryoprobes and the UW. The resultant difference image had a significantly reduced artefact content. Thus TDS can be used to significantly suppress or eliminate high-density CT streak artefacts without reducing the metallic content of the cryoprobes. In vivo study needs to be conducted to establish the utility of this TDS procedure for CT assisted prostate or liver cryotherapy. Applying TDS in x-ray CT guided cryotherapy will facilitate estimation of the number and location of all frozen and unfrozen regions, potentially making cryotherapy safer and less operator dependent. (author)

  15. Filling defect artefacts in magnetic resonance urography

    Energy Technology Data Exchange (ETDEWEB)

    Girish, G.; Chooi, W.K.; Morcos, S.K. [Department of Diagnostic Imaging, Northern General Hospital, Sheffield Teaching Hospitals NHS Trust, S5 7AU, Sheffield (United Kingdom)

    2004-01-01

    The aim of this study was to determine the prevalence of filling defect artefacts (FDA) in magnetic resonance urography (MRU). Retrospectively, we assessed MRU examinations of 45 patients with neurogenic bladder dysfunction (21 men, 24 women; mean age 35 years, age range 18-71 years). The MRU was performed 30 min after intramuscular injection of 20 mg frusemide using heavily T2-weighted fast-spin-echo techniques [axial, thick coronal slab, coronal maximum intensity projection (MIP) images] with fat saturation. The images were reviewed by two observers to determine the presence of filling defects and dilatation of pelvicalyceal system and ureters. The filling defects were classified into central, eccentric and complete. Clinical course and plain films were reviewed to determine significance of the detected filling defects. True filling defects were observed in 5 patients (11%) and all due to stones seen on the plain radiograph of the abdomen. Filling defects artefacts (FDAs) were seen in 23 patients (51%; 17 pelvicalyceal system, 17 upper third of ureters, 7 mid ureters and 1 distal ureter). No stones were seen on the plain radiograph of these patients and they had a favourable clinical course for over 24 months. The true filling defects were large in size, eccentric in position and seen in more than one sequence of the MRU examination (axial, n=5; slab, n=5; and MIP, n=4). Four (80%) of the patients with true defects and 21 (91%) of those with FDAs had dilatation of the pelvicalyceal system and ureters. The FDAs were small in size, centrally placed (74%) and always seen in axial images, rarely in slab images (2 cases) and not seen in MIP images. Artefactual filling defects can be seen in MRU examinations. The cause of the FDAs is not fully explained and could be secondary to turbulent and fast flow of the urine. Some of the FDAs seen in the calyces could be due to the tips of the papillae. Awareness of such defects obviates misinterpretation and prevents

  16. Artefact specification, design, and production as a process of communication

    DEFF Research Database (Denmark)

    Galle, Per

    1999-01-01

    for the success of communication carry over to the artefact production process. The purpose of the analysis is to provide a conceptual background for the study of various aspects of artefact production, such as design, or the development of computer-based tools for collaborative design, product modelling......The co-operative process of specifying, designing, and producing an artefact is analysed in terms of communication among the agents involved. By way of introduction, I offer a brief analysis of communication in general, outlining conditions for its success, while avoiding simplistic assumptions...

  17. Dramatic reduction of sequence artefacts from DNA isolated from formalin-fixed cancer biopsies by treatment with uracil- DNA glycosylase.

    Science.gov (United States)

    Do, Hongdo; Dobrovic, Alexander

    2012-05-01

    Non-reproducible sequence artefacts are frequently detected in DNA from formalinfixed and paraffin-embedded (FFPE) tissues. However, no rational strategy has been developed for reduction of sequence artefacts from FFPE DNA as the underlying causes of the artefacts are poorly understood. As cytosine deamination to uracil is a common form of DNA damage in ancient DNA, we set out to examine whether treatment of FFPE DNA with uracil-DNA glycosylase (UDG) would lead to the reduction of C>T (and G>A) sequence artefacts. Heteroduplex formation in high resolution melting (HRM)-based assays was used for the detection of sequence variants in FFPE DNA samples. A set of samples that gave false positive HRM results for screening for the E17K mutation in exon 4 of the AKT1 gene were chosen for analysis. Sequencing of these samples showed multiple non-reproducible C:G>T:A artefacts. Treatment of the FFPE DNA with UDG prior to PCR amplification led to a very marked reduction of the sequence artefacts as indicated by both HRM and sequencing analysis, indicating that uracil lesions are the major cause of sequence artefacts. Similar results were shown for the BRAF V600 region in the same sample set and EGFR exon 19 in another sample set. UDG treatment specifically suppressed the formation of artefacts in FFPE DNA as it did not affect the detection of true KRAS codon 12 and true EGFR exon 19 and 20 mutations. We conclude that uracil in FFPE DNA leads to a significant proportion of sequence artefacts. These can be minimised by a simple UDG pretreatment which can be readily carried out, in the same tube, as the PCR immediately prior to commencing thermal cycling. HRM is a convenient way of monitoring both the degree of damage and the effectiveness of the UDG treatment. These findings have immediate and important implications for cancer diagnostics where FFPE DNA is used as the primary genetic material for mutational studies guiding personalised medicine strategies and where simple

  18. Digital correction of motion artefacts in microscopy image sequences collected from living animals using rigid and nonrigid registration.

    Science.gov (United States)

    Lorenz, K S; Salama, P; Dunn, K W; Delp, E J

    2012-02-01

    Digital image analysis is a fundamental component of quantitative microscopy. However, intravital microscopy presents many challenges for digital image analysis. In general, microscopy volumes are inherently anisotropic, suffer from decreasing contrast with tissue depth, lack object edge detail and characteristically have low signal levels. Intravital microscopy introduces the additional problem of motion artefacts, resulting from respiratory motion and heartbeat from specimens imaged in vivo. This paper describes an image registration technique for use with sequences of intravital microscopy images collected in time-series or in 3D volumes. Our registration method involves both rigid and nonrigid components. The rigid registration component corrects global image translations, whereas the nonrigid component manipulates a uniform grid of control points defined by B-splines. Each control point is optimized by minimizing a cost function consisting of two parts: a term to define image similarity, and a term to ensure deformation grid smoothness. Experimental results indicate that this approach is promising based on the analysis of several image volumes collected from the kidney, lung and salivary gland of living rodents.

  19. An Artefact suppressing fast-recovery myoelectric amplifier

    OpenAIRE

    1999-01-01

    An amplifier for recording myoelectric signals using surface electrodes has been developed. The special features are suppression of stimulation artefacts and motion artefacts from electrodes. It is designed for recording of myoelectric signals from a muscle that is being stimulated with short impulses. The artifact suppression is achieved by using fast-recovery instrumentation amplifiers and having a nonlinear feedback loop for automatic compensation of changes in DC-offset

  20. Mesenchymal stem cell isolation from human umbilical cord tissue: understanding and minimizing variability in cell yield for process optimization.

    Science.gov (United States)

    Iftimia-Mander, Andreea; Hourd, Paul; Dainty, Roger; Thomas, Robert J

    2013-10-01

    Human tissue banks are a potential source of cellular material for the nascent cell-based therapy industry; umbilical cord (UC) tissue is increasingly privately banked in such facilities as a source of mesenchymal stem cells for future therapeutic use. However, early handling of UC tissue is relatively uncontrolled due to the clinical demands of the birth environment and subsequent transport logistics. It is therefore necessary to develop extraction methods that are robust to real-world operating conditions, rather than idealized operation. Cell yield, growth, and differentiation potential of UC tissue extracted cells was analyzed from tissue processed by explant and enzymatic digestion. Variability of cell yield extracted with the digestion method was significantly greater than with the explant method. This was primarily due to location within the cord tissue (higher yield from placental end) and time delay before tissue processing (substantially reduced yield with time). In contrast, extraction of cells by explant culture was more robust to these processing variables. All cells isolated showed comparable proliferative and differentiation functionality. In conclusion, given the challenge of tightly controlled operating conditions associated with isolation and shipping of UC tissue to banking facilities, explant extraction of cells offers a more robust and lower-variability extraction method than enzymatic digestion.

  1. Pulmonary MRA: Differentiation of pulmonary embolism from truncation artefact

    Energy Technology Data Exchange (ETDEWEB)

    Bannas, Peter [University of Wisconsin-Madison, Department of Radiology, Madison, WI (United States); University Hospital Hamburg-Eppendorf, Department of Radiology, Hamburg (Germany); Schiebler, Mark L.; Motosugi, Utaroh; Francois, Christopher J. [University of Wisconsin-Madison, Department of Radiology, Madison, WI (United States); Reeder, Scott B. [University of Wisconsin-Madison, Department of Radiology, Madison, WI (United States); University of Wisconsin-Madison, Department of Biomedical Engineering, Madison, WI (United States); University of Wisconsin-Madison, Department of Medical Physics, Madison, WI (United States); University of Wisconsin-Madison, Department of Medicine, Madison, WI (United States); Nagle, Scott K. [University of Wisconsin-Madison, Department of Radiology, Madison, WI (United States); University of Wisconsin-Madison, Department of Medical Physics, Madison, WI (United States); University of Wisconsin-Madison, Department of Pediatrics, Madison, WI (United States)

    2014-08-15

    Truncation artefact (Gibbs ringing) causes central signal drop within vessels in pulmonary magnetic resonance angiography (MRA) that can be mistaken for emboli, reducing diagnostic accuracy for pulmonary embolism (PE). We propose a quantitative approach to differentiate truncation artefact from PE. Twenty-eight patients who underwent pulmonary computed tomography angiography (CTA) for suspected PE were recruited for pulmonary MRA. Signal intensity drops within pulmonary arteries that persisted on both arterial-phase and delayed-phase MRA were identified. The percent signal loss between the vessel lumen and central drop was measured. CTA served as the reference standard for presence of pulmonary emboli. A total of 65 signal intensity drops were identified on MRA. Of these, 48 (74 %) were artefacts and 17 (26 %) were PE, as confirmed by CTA. Truncation artefacts had a significantly lower median signal drop than PE on both arterial-phase (26 % [range 12-58 %] vs. 85 % [range 53-91 %]) and delayed-phase MRA (26 % [range 11-55 %] vs. 77 % [range 47-89 %]), p < 0.0001 for both. Receiver operating characteristic (ROC) analyses revealed a threshold value of 51 % (arterial phase) and 47 % signal drop (delayed phase) to differentiate between truncation artefact and PE with 100 % sensitivity and greater than 90 % specificity. Quantitative signal drop is an objective tool to help differentiate truncation artefact and pulmonary embolism in pulmonary MRA. (orig.)

  2. Inner ear tissue preservation by rapid freezing: improving fixation by high-pressure freezing and hybrid methods.

    Science.gov (United States)

    Bullen, A; Taylor, R R; Kachar, B; Moores, C; Fleck, R A; Forge, A

    2014-09-01

    In the preservation of tissues in as 'close to life' state as possible, rapid freeze fixation has many benefits over conventional chemical fixation. One technique by which rapid freeze-fixation can be achieved, high pressure freezing (HPF), has been shown to enable ice crystal artefact-free freezing and tissue preservation to greater depths (more than 40 μm) than other quick-freezing methods. Despite increasingly becoming routine in electron microscopy, the use of HPF for the fixation of inner ear tissue has been limited. Assessment of the quality of preservation showed routine HPF techniques were suitable for preparation of inner ear tissues in a variety of species. Good preservation throughout the depth of sensory epithelia was achievable. Comparison to chemically fixed tissue indicated that fresh frozen preparations exhibited overall superior structural preservation of cells. However, HPF fixation caused characteristic artefacts in stereocilia that suggested poor quality freezing of the actin bundles. The hybrid technique of pre-fixation and high pressure freezing was shown to produce cellular preservation throughout the tissue, similar to that seen in HPF alone. Pre-fixation HPF produced consistent high quality preservation of stereociliary actin bundles. Optimising the preparation of samples with minimal artefact formation allows analysis of the links between ultrastructure and function in inner ear tissues. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

  3. Denoising and artefact reduction in dynamic flat detector CT perfusion imaging using high speed acquisition: first experimental and clinical results.

    Science.gov (United States)

    Manhart, Michael T; Aichert, André; Struffert, Tobias; Deuerling-Zheng, Yu; Kowarschik, Markus; Maier, Andreas K; Hornegger, Joachim; Doerfler, Arnd

    2014-08-21

    Flat detector CT perfusion (FD-CTP) is a novel technique using C-arm angiography systems for interventional dynamic tissue perfusion measurement with high potential benefits for catheter-guided treatment of stroke. However, FD-CTP is challenging since C-arms rotate slower than conventional CT systems. Furthermore, noise and artefacts affect the measurement of contrast agent flow in tissue. Recent robotic C-arms are able to use high speed protocols (HSP), which allow sampling of the contrast agent flow with improved temporal resolution. However, low angular sampling of projection images leads to streak artefacts, which are translated to the perfusion maps. We recently introduced the FDK-JBF denoising technique based on Feldkamp (FDK) reconstruction followed by joint bilateral filtering (JBF). As this edge-preserving noise reduction preserves streak artefacts, an empirical streak reduction (SR) technique is presented in this work. The SR method exploits spatial and temporal information in the form of total variation and time-curve analysis to detect and remove streaks. The novel approach is evaluated in a numerical brain phantom and a patient study. An improved noise and artefact reduction compared to existing post-processing methods and faster computation speed compared to an algebraic reconstruction method are achieved.

  4. Denoising and artefact reduction in dynamic flat detector CT perfusion imaging using high speed acquisition: first experimental and clinical results

    Science.gov (United States)

    Manhart, Michael T.; Aichert, André; Struffert, Tobias; Deuerling-Zheng, Yu; Kowarschik, Markus; Maier, Andreas K.; Hornegger, Joachim; Doerfler, Arnd

    2014-08-01

    Flat detector CT perfusion (FD-CTP) is a novel technique using C-arm angiography systems for interventional dynamic tissue perfusion measurement with high potential benefits for catheter-guided treatment of stroke. However, FD-CTP is challenging since C-arms rotate slower than conventional CT systems. Furthermore, noise and artefacts affect the measurement of contrast agent flow in tissue. Recent robotic C-arms are able to use high speed protocols (HSP), which allow sampling of the contrast agent flow with improved temporal resolution. However, low angular sampling of projection images leads to streak artefacts, which are translated to the perfusion maps. We recently introduced the FDK-JBF denoising technique based on Feldkamp (FDK) reconstruction followed by joint bilateral filtering (JBF). As this edge-preserving noise reduction preserves streak artefacts, an empirical streak reduction (SR) technique is presented in this work. The SR method exploits spatial and temporal information in the form of total variation and time-curve analysis to detect and remove streaks. The novel approach is evaluated in a numerical brain phantom and a patient study. An improved noise and artefact reduction compared to existing post-processing methods and faster computation speed compared to an algebraic reconstruction method are achieved.

  5. A minimal peach type II chlorophyll a/b-binding protein promoter retains tissue-specificity and light regulation in tomato

    Directory of Open Access Journals (Sweden)

    Scorza Ralph

    2007-08-01

    Full Text Available Abstract Background Promoters with tissue-specificity are desirable to drive expression of transgenes in crops to avoid accumulation of foreign proteins in edible tissues/organs. Several photosynthetic promoters have been shown to be strong regulators of expression of transgenes in light-responsive tissues and would be good candidates for leaf and immature fruit tissue-specificity, if expression in the mature fruit were minimized. Results A minimal peach chlorophyll a/b-binding protein gene (Lhcb2*Pp1 promoter (Cab19 was isolated and fused to an uidA (β-glucuronidase [GUS] gene containing the PIV2 intron. A control vector carrying an enhanced mas35S CaMV promoter fused to uidA was also constructed. Two different orientations of the Cab19::GUS fusion relative to the left T-DNA border of the binary vector were transformed into tomato. Ten independent regenerants of each construct and an untransformed control line were assessed both qualitatively and quantitatively for GUS expression in leaves, fruit and flowers, and quantitatively in roots. Conclusion The minimal CAB19 promoter conferred GUS activity primarily in leaves and green fruit, as well as in response to light. GUS activity in the leaves of both Cab19 constructs averaged about 2/3 that observed with mas35S::GUS controls. Surprisingly, GUS activity in transgenic green fruit was considerably higher than leaves for all promoter constructs; however, in red, ripe fruit activities were much lower for the Cab19 promoter constructs than the mas35S::GUS. Although GUS activity was readily detectable in flowers and roots of mas35S::GUStransgenic plants, little activity was observed in plants carrying the Cab19 promoter constructs. In addition, the light-inducibility of the Cab19::GUS constructs indicated that all the requisite cis-elements for light responsiveness were contained on the Cab19 fragment. The minimal Cab19 promoter retains both tissue-specificity and light regulation and can be used to

  6. Minimally invasive surgery using intraoperative electron-beam radiotherapy for the treatment of soft tissue sarcoma of the extremities with tendon involvement.

    Science.gov (United States)

    Matsumine, Akihiko; Tsujii, Masaya; Nakamura, Tomoki; Asanuma, Kunihiro; Matsubara, Takao; Kakimoto, Takuya; Yada, Yuki; Takada, Akinori; Ii, Noriko; Nomoto, Yoshihito; Sudo, Akihiro

    2016-08-12

    When a soft tissue sarcoma (STS) is located at the distal part of an extremity and involves the tendon, a wide excision usually causes severe functional disability. We therefore developed a minimally invasive surgical technique using intraoperative electron-beam radiotherapy (IOERT) to reduce the incidence of post-operative functional disability in patients with peri-/intra-tendinous STS. We assessed the clinical outcomes of the novel minimally invasive surgery. The study population included five patients who received treatment for distal extremity STSs. After elevating the tumor mass, including the tendon and nerve from the tumor bed with a wide margin, a lead board was inserted beneath the tumor mass to shield the normal tissue. IOERT (25-50 Gy) was then applied, and the tumor excised with care taken to maintain the continuity of the tendon. In a desmoid patient, local recurrence was observed outside the irradiated field. No cases of neuropathy or bone necrosis were observed. The mean limb function score was excellent in all patients. None of the high-grade sarcoma patients had local recurrence or distant metastasis. Although the current study is only a pilot study with a small number of patients, it shows that this minimally invasive procedure has the potential to become a standard treatment option for selected patients. H17-250 (registered 2 November 2005) and H25-250 (modified from H17-250, registered 5 December 2013).

  7. Metal artefact reduction in gemstone spectral imaging dual-energy CT with and without metal artefact reduction software

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Young Han; Song, Ho-Taek; Kim, Sungjun; Suh, Jin-Suck [Yonsei University College of Medicine, Department of Radiology, Research Institute of Radiological Science, Medical Convergence Research Institute, and Severance Biomedical Science Institute, Seoul (Korea, Republic of); Park, Kwan Kyu [Yonsei University College of Medicine, Department of Orthopaedic Surgery, Seoul (Korea, Republic of)

    2012-06-15

    To assess the usefulness of gemstone spectral imaging (GSI) dual-energy CT (DECT) with/without metal artefact reduction software (MARs). The DECTs were performed using fast kV-switching GSI between 80 and 140 kV. The CT data were retro-reconstructed with/without MARs, by different displayed fields-of-view (DFOV), and with synthesised monochromatic energy in the range 40-140 keV. A phantom study of size and CT numbers was performed in a titanium plate and a stainless steel plate. A clinical study was performed in 26 patients with metallic hardware. All images were retrospectively reviewed in terms of the visualisation of periprosthetic regions and the severity of beam-hardening artefacts by using a five-point scale. The GSI-MARs reconstruction can markedly reduce the metal-related artefacts, and the image quality was affected by the prosthesis composition and DFOV. The spectral CT numbers of the prosthesis and periprosthetic regions showed different patterns on stainless steel and titanium plates. Dual-energy CT with GSI-MARs can reduce metal-related artefacts and improve the delineation of the prosthesis and periprosthetic region. We should be cautious when using GSI-MARs because the image quality was affected by the prosthesis composition, energy (in keV) and DFOV. The metallic composition and size should be considered in metallic imaging with GSI-MARs reconstruction. circle Metal-related artefacts can be troublesome on musculoskeletal computed tomography (CT). circle Gemstone spectral imaging (GSI) with dual-energy CT (DECT) offers a novel solution circle GSI and metallic artefact reduction software (GSI-MAR) can markedly reduce these artefacts. circle However image quality is influenced by the prosthesis composition and other parameters. circle We should be aware about potential overcorrection when using GSI-MARs. (orig.)

  8. A minimal set of tissue-specific hypomethylated CpGs constitute epigenetic signatures of developmental programming.

    Directory of Open Access Journals (Sweden)

    Alejandro Colaneri

    Full Text Available BACKGROUND: Cell specific states of the chromatin are programmed during mammalian development. Dynamic DNA methylation across the developing embryo guides a program of repression, switching off genes in most cell types. Thus, the majority of the tissue specific differentially methylated sites (TS-DMS must be un-methylated CpGs. METHODOLOGY AND PRINCIPAL FINDINGS: Comparison of expanded Methyl Sensitive Cut Counting data (eMSCC among four tissues (liver, testes, brain and kidney from three C57BL/6J mice, identified 138,052 differentially methylated sites of which 23,270 contain CpGs un-methylated in only one tissue (TS-DMS. Most of these CpGs were located in intergenic regions, outside of promoters, CpG islands or their shores, and up to 20% of them overlapped reported active enhancers. Indeed, tissue-specific enhancers were up to 30 fold enriched in TS-DMS. Testis showed the highest number of TS-DMS, but paradoxically their associated genes do not appear to be specific to the germ cell functions, but rather are involved in organism development. In the other tissues the differentially methylated genes are associated with tissue-specific physiological or anatomical functions. The identified sets of TS-DMS quantify epigenetic distances between tissues, generated during development. We applied this concept to measure the extent of reprogramming in the liver of mice exposed to in utero or early postnatal nutritional stress. Different protocols of food restriction reprogrammed the liver methylome in different but reproducible ways. CONCLUSION AND SIGNIFICANCE: Thus, each identified set of differentially methylated sites constituted an epigenetic signature that traced the developmental programing or the early nutritional reprogramming of each exposed mouse. We propose that our approach has the potential to outline a number of disease-associated epigenetic states. The composition of differentially methylated CpGs may vary with each situation, behaving

  9. The Application of Minimally Invasive Devices with Nanostructured Surface Functionalization: Antisticking Behavior on Devices and Liver Tissue Interface in Rat

    Directory of Open Access Journals (Sweden)

    Li-Hsiang Lin

    2015-01-01

    Full Text Available This study investigated the thermal injury and adhesion property of a novel electrosurgery of liver using copper-doped diamond-like carbon (DLC-Cu surface treatment. It is necessary to reduce the thermal damage of surrounding tissues for clinical electrosurgeries. The surface morphologies of stainless steel (SS coated with DLC (DLC-Cu-SS films were characterized by scanning electron microscopy (SEM and transmission electron microscopy (TEM. Bionic liver models were reconstructed using magnetic resonance imaging (MRI to simulate electrosurgery. Cell cytotoxicity assays showed that the DLC-Cu thin film was nontoxic. The temperature of tissue decreased significantly with use of the electrosurgical device with nanostructured DLC-Cu films and increased with increasing thickness of the films. Thermography revealed that the surgical temperature in the DLC-Cu-SS electrosurgical device was significantly lower than that in the untreated device in the animal model. Moreover, compared to the SS electrosurgical device, the DLC-Cu-SS electrosurgical device caused a relatively small injury area and lateral thermal effect. The results indicate that the DLC-Cu-SS electrosurgical device decreases excessive thermal injury and ensures homogeneous temperature transformation in the tissues.

  10. Detection and correction of probe-level artefacts on microarrays

    Directory of Open Access Journals (Sweden)

    Petri Tobias

    2012-05-01

    Full Text Available Abstract Background A recent large-scale analysis of Gene Expression Omnibus (GEO data found frequent evidence for spatial defects in a substantial fraction of Affymetrix microarrays in the GEO. Nevertheless, in contrast to quality assessment, artefact detection is not widely used in standard gene expression analysis pipelines. Furthermore, although approaches have been proposed to detect diverse types of spatial noise on arrays, the correction of these artefacts is mostly left to either summarization methods or the corresponding arrays are completely discarded. Results We show that state-of-the-art robust summarization procedures are vulnerable to artefacts on arrays and cannot appropriately correct for these. To address this problem, we present a simple approach to detect artefacts with high recall and precision, which we further improve by taking into account the spatial layout of arrays. Finally, we propose two correction methods for these artefacts that either substitute values of defective probes using probeset information or filter corrupted probes. We show that our approach can identify and correct defective probe measurements appropriately and outperforms existing tools. Conclusions While summarization is insufficient to correct for defective probes, this problem can be addressed in a straightforward way by the methods we present for identification and correction of defective probes. As these methods output CEL files with corrected probe values that serve as input to standard normalization and summarization procedures, they can be easily integrated into existing microarray analysis pipelines as an additional pre-processing step. An R package is freely available from http://www.bio.ifi.lmu.de/artefact-correction.

  11. The role of action knowledge in the comprehension of artefacts--a PET study

    DEFF Research Database (Denmark)

    Gerlach, Christian; Law, I; Gade, A

    2002-01-01

    and two naming tasks divided by category (natural objects vs artefacts). The left PMv (BA 6/44) was more activated by the categorization task for artefacts than by the categorization task for natural objects and the naming task for artefacts. However, the left PMv was not associated with the contrast...... between the naming task for artefacts and the naming task for natural objects nor with the processing of artefacts in general. If the PMv does mediate action knowledge, these results suggest that action knowledge does not contribute directly to the comprehension of artefacts but may support...

  12. Minimal Pairs: Minimal Importance?

    Science.gov (United States)

    Brown, Adam

    1995-01-01

    This article argues that minimal pairs do not merit as much attention as they receive in pronunciation instruction. There are other aspects of pronunciation that are of greater importance, and there are other ways of teaching vowel and consonant pronunciation. (13 references) (VWL)

  13. GIS as an Artefact in Geography Education: Some Future Challenges

    DEFF Research Database (Denmark)

    Madsen, Lene Møller; Winsløw, Carl

    2007-01-01

    is the introduction of Geographical Information Systems (GIS). In this paper we explain and examine the theory of instrumental genesis in order to analyse the interplay between artefacts (such as GIS) and geographical knowledge. Based on a study of first year university students in Denmark we argue that this theory...... can be used to inform our understanding of the actual and potential roles of GIS in the education of geographers. Our conclusion is that there is a need to recognise GIS as an artefact interwoven with the professional development of becoming a geographer and to start researching the challenges...

  14. The total number of tissue blocks per centimetre of tumor significantly correlated with the risk of distant metastasis in patients with minimally invasive follicular thyroid carcinoma.

    Science.gov (United States)

    Lang, Brian Hung-Hin; Shek, Tony W H; Wu, Arnold L H; Wan, Koon Yat

    2017-02-01

    Given that careful histological examination plays a pivotal role in follicular thyroid carcinoma categorization, we hypothesize that the number of blocks taken at initial specimen review may be associated with survival outcomes of patients initially diagnosed with minimally invasive follicular thyroid carcinoma. A total of 162 patients with confirmed minimally invasive follicular thyroid carcinoma were analyzed. The number of tissue blocks taken from each patient was recorded and the number of blocks per each centimeter of tumor was calculated. A multivariate analysis was conducted to identify independent factors for distant metastasis-free survival. After a mean follow-up of 197.88 ± 155.39 months, 7 (4.3%) patients developed distant metastasis during follow-up (group II). Relative to those who remained disease-free (group I), group II were significantly older at initial operation (p = 0.022), had larger tumors (p = 0.002) and fewer number of blocks taken/cm of tumor (p = 0.001). However, after adjusting for age at initial operation and tumor size, total number of tissue blocks taken/cm of tumor was the only independent determinant for distant metastasis-free survival (p = 0.049). The 10-year distant metastasis-free survival was significantly better in those who had ≥ 4 blocks/cm of tumor (n = 82) than those with ≤ 3 block/cm of tumor (n = 80) (100 vs. 84.7%, p = 0.005, by log rank). Although our study was not able to identify the precise cause for the association between the total number of tissue blocks taken/cm of tumor and distant metastasis-free survival, our data support a more liberal approach in taking tissue blocks on thyroid nodules especially those showing well-differentiated follicular cell differentiation.

  15. Evaluation of a prototype correction algorithm to reduce metal artefacts in flat detector computed tomography of scaphoid fixation screws

    Energy Technology Data Exchange (ETDEWEB)

    Filli, Lukas; Finkenstaedt, Tim; Andreisek, Gustav; Guggenberger, Roman [University Hospital of Zurich, Department of Diagnostic and Interventional Radiology, Zurich (Switzerland); Marcon, Magda [University Hospital of Zurich, Department of Diagnostic and Interventional Radiology, Zurich (Switzerland); University of Udine, Institute of Diagnostic Radiology, Department of Medical and Biological Sciences, Udine (Italy); Scholz, Bernhard [Imaging and Therapy Division, Siemens AG, Healthcare Sector, Forchheim (Germany); Calcagni, Maurizio [University Hospital of Zurich, Division of Plastic Surgery and Hand Surgery, Zurich (Switzerland)

    2014-12-15

    The aim of this study was to evaluate a prototype correction algorithm to reduce metal artefacts in flat detector computed tomography (FDCT) of scaphoid fixation screws. FDCT has gained interest in imaging small anatomic structures of the appendicular skeleton. Angiographic C-arm systems with flat detectors allow fluoroscopy and FDCT imaging in a one-stop procedure emphasizing their role as an ideal intraoperative imaging tool. However, FDCT imaging can be significantly impaired by artefacts induced by fixation screws. Following ethical board approval, commercially available scaphoid fixation screws were inserted into six cadaveric specimens in order to fix artificially induced scaphoid fractures. FDCT images corrected with the algorithm were compared to uncorrected images both quantitatively and qualitatively by two independent radiologists in terms of artefacts, screw contour, fracture line visibility, bone visibility, and soft tissue definition. Normal distribution of variables was evaluated using the Kolmogorov-Smirnov test. In case of normal distribution, quantitative variables were compared using paired Student's t tests. The Wilcoxon signed-rank test was used for quantitative variables without normal distribution and all qualitative variables. A p value of < 0.05 was considered to indicate statistically significant differences. Metal artefacts were significantly reduced by the correction algorithm (p < 0.001), and the fracture line was more clearly defined (p < 0.01). The inter-observer reliability was ''almost perfect'' (intra-class correlation coefficient 0.85, p < 0.001). The prototype correction algorithm in FDCT for metal artefacts induced by scaphoid fixation screws may facilitate intra- and postoperative follow-up imaging. (orig.)

  16. Contextualising the Curriculum through local floodplain artefacts at ...

    African Journals Online (AJOL)

    school practitioners, educational administrators or university teacher .... 2002), yet artefacts are critically important for the success of further learning in ... School managers at Lealui Basic School (i.e. the head teacher and deputy head teacher) .... elements are faced with extinction owing to various factors and, therefore, ...

  17. Students' Conscious Unknowns about Artefacts and Natural Objects

    Science.gov (United States)

    Vaz-Rebelo, Piedade; Fernandes, Paula; Morgado, Julia; Monteiro, António; Otero, José

    2016-01-01

    This study attempts to characterise what 7th- and 12th-grade students believe they do not know about artefacts and natural objects, as well as the dependence of what is unknown on a knowledge of these objects. The students were asked to make explicit through questioning what they did not know about a sample of objects. The unknowns generated were…

  18. The earliest securely-dated hominin artefact in Anatolia?

    NARCIS (Netherlands)

    Maddy, D.; Schreve, D.; Demir, T.; Veldkamp, A.; Wijbrans, J. R.; van Gorp, W.; van Hinsbergen, D. J. J.; Dekkers, M. J.; Scaife, R.; Schoorl, J. M.; Stemerdink, C.; van der Schriek, T.

    2015-01-01

    Anatolia lies at the gateway from Asia into Europe and has frequently been favoured as a route for Early Pleistocene hominin dispersal. Although early hominins are known to have occupied Turkey, with numerous finds of Lower Palaeolithic artefacts documented, the chronology of their dispersal has lit

  19. Students' Conscious Unknowns about Artefacts and Natural Objects

    Science.gov (United States)

    Vaz-Rebelo, Piedade; Fernandes, Paula; Morgado, Julia; Monteiro, António; Otero, José

    2016-01-01

    This study attempts to characterise what 7th- and 12th-grade students believe they do not know about artefacts and natural objects, as well as the dependence of what is unknown on a knowledge of these objects. The students were asked to make explicit through questioning what they did not know about a sample of objects. The unknowns generated were…

  20. Matter(s) of interest: artefacts, spacing and timing

    NARCIS (Netherlands)

    Schwanen, T.

    2007-01-01

    This paper argues that time-geography can make a contribution to contemporary 'rematerialized' geographies, because the interconnections among social processes, human corporeality and inanimate material artefacts within the landscape were among Hägerstrand's central concerns. Time-geography needs

  1. Towards Weyl fermions on the lattice without artefacts

    CERN Document Server

    Hasenfratz, Peter

    2008-01-01

    In spite of the breakthrough in non-perturbative chiral gauge theories during the last decade, the present formulation has stubborn artefacts. Independently of the fermion representation one is confronted with unwanted CP violation and infinitely many undetermined weight factors. Renormalization group identifies the culprit. We demonstrate the procedure on Weyl fermions in a real representation.

  2. Replica calibration artefacts for optical 3D scanning of micro parts

    DEFF Research Database (Denmark)

    De Chiffre, Leonardo; Carmignato, S.; Cantatore, Angela

    2009-01-01

    This work deals with development of calibration artefacts produced by using hard replica materials, achieving high quality geometrical reproduction of suitable reference artefacts, high stability, and high surface cooperativeness. An investigation was carried out using a replica material for dental...

  3. Artefacts in 1H NMR-based metabolomic studies on cell cultures.

    Science.gov (United States)

    Madhu, Basetti; Dadulescu, Madalina; Griffiths, John

    2015-04-01

    , alanine, fructose, and fumarate signals that appear in the (1)H NMR spectrum of the unused (pure) medium originate from FBS. Plastic Petri dishes from five different manufacturers gave rise to essentially identical artefactual peaks. Use of a pH indicator to assist neutralisation introduced still more artefactual signals in the aromatic region, as well as methanol and ethanol signals. Methanol and acetonitrile extracts also contained artefacts arising from the plasticware, although the amounts were less than in the perchloric acid extracts. Finally, we provide suggestions for minimizing these artefacts. The best practice would be to run a "null" extraction with every batch of cellular metabolomics experiments to test for contamination and to provide a "background" spectrum.

  4. Quantitative image analysis for the detection of motion artefacts in coronary artery computed tomography

    NARCIS (Netherlands)

    Kristanto, Wisnumurti; van Ooijen, Peter M.; Dikkers, Riksta; Greuter, Marcel J.; Zijlstra, Felix; Oudkerk, Matthijs

    2010-01-01

    Multi detector-row CT (MDCT), the current preferred method for coronary artery disease assessment, is still affected by motion artefacts. To rule out motion artefacts, qualitative image analysis is usually performed. Our study aimed to develop a quantitative image analysis for motion artefacts detec

  5. NOTE: Suppression of high-density artefacts in x-ray CT images using temporal digital subtraction with application to cryotherapy

    Science.gov (United States)

    Baissalov, R.; Sandison, G. A.; Donnelly, B. J.; Saliken, J. C.; McKinnon, J. G.; Muldrew, K.; Rewcastle, J. C.

    2000-05-01

    Image guidance in cryotherapy is usually performed using ultrasound. Although not currently in routine clinical use, x-ray CT imaging is an alternative means of guidance that can display the full 3D structure of the iceball, including frozen and unfrozen regions. However, the quality of x-ray CT images is compromised by the presence of high-density streak artefacts. To suppress these artefacts we applied temporal digital subtraction (TDS). This TDS method has the added advantage of improving the grey-scale contrast between frozen and unfrozen tissue in the CT images. Two sets of CT images were taken of a phantom material, cryoprobes and a urethral warmer (UW) before and during the cryoprobe freeze cycle. The high-density artefacts persisted in both image sets. TDS was performed on these two image sets using the corresponding mask image of unfrozen material and the same geometrical configuration of the cryoprobes and the UW. The resultant difference image had a significantly reduced artefact content. Thus TDS can be used to significantly suppress or eliminate high-density CT streak artefacts without reducing the metallic content of the cryoprobes. In vivo study needs to be conducted to establish the utility of this TDS procedure for CT assisted prostate or liver cryotherapy. Applying TDS in x-ray CT guided cryotherapy will facilitate estimation of the number and location of all frozen and unfrozen regions, potentially making cryotherapy safer and less operator dependent.

  6. Sex determination of baleen whale artefacts

    DEFF Research Database (Denmark)

    Sinding, Mikkel Holger Strander; Tervo, Outi M.; Grønnow, Bjarne

    2016-01-01

    Abstract Methods to determine the sex from tissue samples of mammals include the amplification of Y chromosome specific regions, which should only amplify from males, or amplification of homologous regions of the X and Y chromosome containing XY specific SNPs. A disadvantage of the first approach...... is that PCR failure can be misinterpreted as the identification of a female. The latter approach is proposed to identify PCR failure through non-amplification of the X homologue, which should be present in both sexes. This method is therefore potentially more suitable for molecular sexing of degraded DNA...... with a high probability of PCR failure, such as for example, ancient DNA samples. Here, we investigate the validity of this assumption regarding the use of XY homologue PCR assays for molecular sexing of ancient DNA. We tested a primer set targeting the ZFX/ZFY alleles using ancient DNA extracts from 100...

  7. Temperature measurement artefacts of thermocouples and fluoroptic probes during laser irradiation at 810 nm.

    Science.gov (United States)

    Reid, A D; Gertner, M R; Sherar, M D

    2001-06-01

    This study examined the artefact induced in temperature measurements made with thermocouples and Luxtron fluoroptic probes in the presence of infrared radiation. Localized heating was created using a continuous-wave, 810 nm diode laser system emitting 2.0 W from a cylindrical diffusing optical fibre, in air, water and an agar-albumin phantom. The temperature was measured every 1.0 s for 10 to 150 s, with both a thermocouple and a Luxtron fluoroptic probe at distances of 2, 3, 4, 5, 6 and 7 mm from the cylindrical diffusing tip. In all cases, the fluoroptic probe recorded a higher temperature than the thermocouple during laser irradiation. The difference in measured temperatures between the Luxtron probe and the thermocouple ranged from 1.6 degrees C to 18.8 degrees C in air, from 0.3 degrees C to 10.2 degrees C in water, and from 1.4 degrees C to 10.1 degrees C in phantom, depending on the distance of the probe from the laser source. The results suggest that in the presence of laser irradiation, self-heating of the Luxtron probe induces a significant artefact in temperature measurements at distances less than 4 mm from the source fibre. As a result, fluoroptic probes may not be suitable for monitoring tissue temperature for treatments when laser irradiation is present if sensors are located close to the fibre tip (<4 mm).

  8. Avoiding artefacts during electron microscopy of silver nanomaterials exposed to biological environments.

    Science.gov (United States)

    Chen, S; Goode, A E; Skepper, J N; Thorley, A J; Seiffert, J M; Chung, K F; Tetley, T D; Shaffer, M S P; Ryan, M P; Porter, A E

    2016-02-01

    Electron microscopy has been applied widely to study the interaction of nanomaterials with proteins, cells and tissues at nanometre scale. Biological material is most commonly embedded in thermoset resins to make it compatible with the high vacuum in the electron microscope. Room temperature sample preparation protocols developed over decades provide contrast by staining cell organelles, and aim to preserve the native cell structure. However, the effect of these complex protocols on the nanomaterials in the system is seldom considered. Any artefacts generated during sample preparation may ultimately interfere with the accurate prediction of the stability and reactivity of the nanomaterials. As a case study, we review steps in the room temperature preparation of cells exposed to silver nanomaterials (AgNMs) for transmission electron microscopy imaging and analysis. In particular, embedding and staining protocols, which can alter the physicochemical properties of AgNMs and introduce artefacts thereby leading to a misinterpretation of silver bioreactivity, are scrutinized. Recommendations are given for the application of cryogenic sample preparation protocols, which simultaneously fix both particles and diffusible ions. By being aware of the advantages and limitations of different sample preparation methods, compromises or selection of different correlative techniques can be made to draw more accurate conclusions about the data.

  9. Light scattering artefacts in a funnel phantom using optical CT

    Energy Technology Data Exchange (ETDEWEB)

    Bosi, Stephen G [Department of Radiation Oncology, Prince of Wales Hospital, Sydney (Australia); Brown, Saxby; Baldock, Clive [Institute of Medical Physics, School of Physics, University of Sydney Australia (Australia); Sarabipour, Sarvenaz [Department of Nuclear Medicine and Radiobiology, University of Sherbrooke (Canada); De Deene, Yves [Radiotherapy Department, Ghent University Hospital (Belgium)], E-mail: c.baldock@physics.usyd.edu.au

    2009-05-01

    A gelatin phantom containing a funnel-shaped region of high opacity (or optical density OD) was used to examine light-scattering induced artefacts in a cone-beam optical CT scanner used for gel dosimetry. To correctly simulate polymer gel dosimeters, the opacity was introduced by adding a colloidal scatterer to the gelatin. In line profiles of OD taken from 3-D reconstructions of the funnel, those profiles with a long pathlength through high OD regions exhibited a 'dishing' artefact, while those of short pathlength exhibited the opposite effect - 'doming'. These phenomena are accounted for by a model that includes the effect of stray, scattered light.

  10. Deviations in delineated GTV caused by artefacts in 4DCT

    DEFF Research Database (Denmark)

    Persson, Gitte Fredberg; Nygaard, Ditte Eklund; Brink, Carsten;

    2010-01-01

    BACKGROUND AND PURPOSE: Four-dimensional computed tomography (4DCT) is used for breathing-adapted radiotherapy planning. Irregular breathing, large tumour motion or interpolation of images can cause artefacts in the 4DCT. This study evaluates the impact of artefacts on gross tumour volume (GTV......) size. MATERIAL AND METHODS: In 19 4DCT scans of patients with peripheral lung tumours, GTV was delineated in all bins. Variations in GTV size between bins in each 4DCT scan were analysed and correlated to tumour motion and variations in breathing signal amplitude and breathing signal period. End......-expiration GTV size (GTVexp) was considered as reference for GTV size. Intra-session delineation error was estimated by re-delineation of GTV in eight of the 4DCT scans. RESULTS: In 16 of the 4DCT scans the maximum deviations from GTVexp were larger than could be explained by delineation error. The deviations...

  11. Investigation on a Roman copper alloy artefact from Pompeii (Italy).

    Science.gov (United States)

    Baraldi, Pietro; Baraldi, Cecilia; Ferrari, Giorgia; Foca, Giorgia; Marchetti, Andrea; Tassi, Lorenzo

    2006-01-01

    A selection of samples, obtained from a particular copper-alloy domestic artefact of Roman style from Pompeii, has been analysed by using different techniques (IR, Raman, SEM-EDX, FAAS), in order to investigate the chemical nature and composition of the metals utilised for such manufacturing pieces. The surface analysis of the bright red metallic microfragments conducted by different analytical techniques, emphasises the presence of pure unalloyed copper and confirms the absence of other metallic species on the upper layers. On the contrary, the mapping analysis of the section of the laminar metal of the investigated sample shows a consistent enrichment in tin content. Finally, destructive analysis by FAAS confirms that the artefact looks like a bronze metal alloy, with a medium Sn content of about 6.5%.

  12. Multiple height calibration artefact for 3D microscopy

    DEFF Research Database (Denmark)

    De Chiffre, Leonardo; Carli, Lorenzo; Eriksen, Rasmus Solmer

    2011-01-01

    to 3D techniques at the micrometer and nanometer scale, e.g. 3D SEM, confocal microscopes etc. Two different series of samples were fabricated using EDM with three steps of 2–5–7μm, and 20–50–70μm, respectively, from a 3mm diameter carbide wire. The artefact steps were calibrated on a stylus instrument...

  13. Artefacts in geometric phase analysis of compound materials

    Energy Technology Data Exchange (ETDEWEB)

    Peters, Jonathan J.P., E-mail: j.j.p.peters@warwick.ac.uk [Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom); Beanland, Richard; Alexe, Marin [Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom); Cockburn, John W.; Revin, Dmitry G.; Zhang, Shiyong Y. [Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Sanchez, Ana M., E-mail: a.m.sanchez@warwick.ac.uk [Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom)

    2015-10-15

    The geometric phase analysis (GPA) algorithm is known as a robust and straightforward technique that can be used to measure lattice strains in high resolution transmission electron microscope (TEM) images. It is also attractive for analysis of aberration-corrected scanning TEM (ac-STEM) images that resolve every atom column, since it uses Fourier transforms and does not require real-space peak detection and assignment to appropriate sublattices. Here it is demonstrated that, in ac-STEM images of compound materials with compositionally distinct atom columns, an additional geometric phase is present in the Fourier transform. If the structure changes from one area to another in the image (e.g. across an interface), the change in this additional phase will appear as a strain in conventional GPA, even if there is no lattice strain. Strategies to avoid this pitfall are outlined. - Highlights: • GPA is shown to produce incorrect strains when applied to images of compound materials. • A mathematical description is laid out for why GPA can produce artefacts. • The artefact is demonstrated using experimental and simulated data. • A ‘rule’ is set to avoid this artefact in GPA.

  14. Removing Ocular Movement Artefacts by a Joint Smoothened Subspace Estimator

    Directory of Open Access Journals (Sweden)

    Ronald Phlypo

    2007-01-01

    Full Text Available To cope with the severe masking of background cerebral activity in the electroencephalogram (EEG by ocular movement artefacts, we present a method which combines lower-order, short-term and higher-order, long-term statistics. The joint smoothened subspace estimator (JSSE calculates the joint information in both statistical models, subject to the constraint that the resulting estimated source should be sufficiently smooth in the time domain (i.e., has a large autocorrelation or self predictive power. It is shown that the JSSE is able to estimate a component from simulated data that is superior with respect to methodological artefact suppression to those of FastICA, SOBI, pSVD, or JADE/COM1 algorithms used for blind source separation (BSS. Interference and distortion suppression are of comparable order when compared with the above-mentioned methods. Results on patient data demonstrate that the method is able to suppress blinking and saccade artefacts in a fully automated way.

  15. Sub-Nyquist artefacts and sampling moiré effects.

    Science.gov (United States)

    Amidror, Isaac

    2015-03-01

    Sampling moiré effects are well known in signal processing. They occur when a continuous periodic signal g(x) is sampled using a sampling frequency f s that does not respect the Nyquist condition, and the signal-frequency f folds over and gives a new, false low frequency in the sampled signal. However, some visible beating artefacts may also occur in the sampled signal when g(x) is sampled using a sampling frequency f s which fully respects the Nyquist condition. We call these phenomena sub-Nyquist artefacts. Although these beating effects have already been reported in the literature, their detailed mathematical behaviour is not widely known. In this paper, we study the behaviour of these phenomena and compare it with analogous results from the moiré theory. We show that both sampling moirés and sub-Nyquist artefacts obey the same basic mathematical rules, in spite of the differences between them. This leads us to a unified approach that explains all of these phenomena and puts them under the same roof. In particular, it turns out that all of these phenomena occur when the signal-frequency f and the sampling frequency f s satisfy f≈(m/n)f s with integer m, n, where m/n is a reduced integer ratio; cases with n=1 correspond to true sampling moiré effects.

  16. Investigation of the viscous heating artefact arising from the use of thermocouples in a focused ultrasound field.

    Science.gov (United States)

    Morris, Hugh; Rivens, Ian; Shaw, Adam; Haar, Gail Ter

    2008-09-07

    Accurate temperature measurements in therapeutic ultrasound fields are necessary for understanding damage mechanisms, verification of thermal modelling and calibration of non-invasive clinical thermometry. However, artefactual heating, primarily due to viscous forces which result from motion relative to the surrounding tissue, occurs when metal thermocouples are used in an ultrasound field. The magnitude and time dependence of this artefact has been characterized by comparison with novel thin-film thermocouples (TFTs) at 1-2 cm focal depths in fresh degassed ex vivo bovine liver. High-intensity focused ultrasound exposures (1.7 MHz; free-field spatial-peak temporal-average intensities 40-600 W cm(-2)) were used. Subtraction of the TFT data from that obtained for other thermocouples yielded the time dependence of the viscous heating artefact. This was found to be intensity independent up to 600 W cm(-2) (below the threshold for cavitation and lesion formation) and remained significant at radial distances out to the first side lobe in the focal plane. The contribution of viscous heating to cooling was also found to be significant for at least 5 s after the end of insonation. The ratio of viscous artefact to absorptive heating after 5 s was: 1.76 +/- 0.07 for a fine-wire, 0.45 +/- 0.07 and 1.93 +/- 0.07 for two different sheathed-wires and 0.24 +/- 0.07 for a needle thermocouple.

  17. Development, implementation and evaluation of a dedicated metal artefact reduction method for interventional flat-detector CT.

    Science.gov (United States)

    Prell, D; Kalender, W A; Kyriakou, Y

    2010-12-01

    The purpose of this study was to develop, implement and evaluate a dedicated metal artefact reduction (MAR) method for flat-detector CT (FDCT). The algorithm uses the multidimensional raw data space to calculate surrogate attenuation values for the original metal traces in the raw data domain. The metal traces are detected automatically by a three-dimensional, threshold-based segmentation algorithm in an initial reconstructed image volume, based on twofold histogram information for calculating appropriate metal thresholds. These thresholds are combined with constrained morphological operations in the projection domain. A subsequent reconstruction of the modified raw data yields an artefact-reduced image volume that is further processed by a combining procedure that reinserts the missing metal information. For image quality assessment, measurements on semi-anthropomorphic phantoms containing metallic inserts were evaluated in terms of CT value accuracy, image noise and spatial resolution before and after correction. Measurements of the same phantoms without prostheses were used as ground truth for comparison. Cadaver measurements were performed on complex and realistic cases and to determine the influences of our correction method on the tissue surrounding the prostheses. The results showed a significant reduction of metal-induced streak artefacts (CT value differences were reduced to below 22 HU and image noise reduction of up to 200%). The cadaver measurements showed excellent results for imaging areas close to the implant and exceptional artefact suppression in these areas. Furthermore, measurements in the knee and spine regions confirmed the superiority of our method to standard one-dimensional, linear interpolation.

  18. Persuasiveness, Personalization & Productive Workplace Practices with IT-Knowledge Artefacts

    DEFF Research Database (Denmark)

    Fischer, Louise Harder; Pries-Heje, Lene

    2016-01-01

    The workplace is getting increasingly globalized, virtualized and networked. At the same time, work itself has become discrete, autonomous and complex. In a fast changing world, the individual knowledge worker and his interactions becomes the new locus of value creation. Management promote...... work. We see a possible way forward for improving workplace practices with IT-knowledge artefact based applications, by combining new insight of how different personality traits prefer different knowledge sharing processes with new insight on personalizing persuasive technology. We explore new research...

  19. Plasma cleaning and analysis of archeological artefacts from Sipan

    Energy Technology Data Exchange (ETDEWEB)

    Saettone, E A O [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, CEP 05508-900 (Brazil); Matta, J A S da [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, CEP 05508-900 (Brazil); Alva, W [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, CEP 05508-900 (Brazil); Chubaci, J F O [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, CEP 05508-900 (Brazil); Fantini, M C A [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, CEP 05508-900 (Brazil); Galvao, R M O [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, CEP 05508-900 (Brazil); Kiyohara, P [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, CEP 05508-900 (Brazil); Tabacniks, M H [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, CEP 05508-900 (Brazil)

    2003-04-07

    A novel procedure using plasma sputtering in an electron-cyclotron-resonance device has been applied to clean archeological MOCHE artefacts, unearthed at the Royal Tombs of Sipan. After successful cleaning, the pieces were analysed by a variety of complementary techniques, namely proton-induced x-ray emission, Rutherford backscattering spectroscopy, x-ray diffraction, electron microscopy, and inductively coupled plasma mass spectroscopy. With these techniques, it has been possible to not only determine the profiles of the gold and silver surface layers, but also to detect elements that may be relevant to explain the gilding techniques skillfully developed by the metal smiths of the MOCHE culture.

  20. CT artefact reduction by signal to thickness calibration function shaping

    Energy Technology Data Exchange (ETDEWEB)

    Vavrik, Daniel, E-mail: daniel.vavrik@utef.cvut.cz [Institute of Experimental and Applied Physics of the Czech Technical University in Prague, Horska 3a/22, 128 00 Prague 2 (Czech Republic); Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences, Prosecka 76, 190 00 Prague 9 (Czech Republic)

    2011-05-15

    It is frequently a task to calibrate the radiogram intensity in reference to the object thickness/density value. This knowledge is important when the radiographic densitometry, thickness measurements or precise computed tomography are required. Often aluminum is used as calibrating material and processed radiogram of the real object is evaluated as aluminum equivalent. This approach is qualitatively convenient for transmission radiograms; however, certain secondary artefacts remain in CT reconstructions. Fortunately the calibration function can be shaped using only one or two known thickness values of the object investigated. The shaped calibration function obtained produces the right signal to thickness relationship and CT quality is improved when it is applied.

  1. Indigenous african artefacts: Can they serve as tangible programming objects?

    CSIR Research Space (South Africa)

    Smith, Adrew C

    2010-05-01

    Full Text Available that can be applied to computer programming. Section 5 proposes a programming environment which exploits these findings and section 6 discusses proposed future work. Section 7 concludes. 2. Background A number of factors should be taken into account... Environments [6]. 2.1 Abstract Tangible Objects Heijboer and van den Hoven conducted a study to determine to what level a physical artefact can be abstracted and still be interpreted correctly in the context for which it was designed [4]. They concluded...

  2. Metabolic cold adaptation of polar fish based on measurements of aerobic oxygen consumption: fact or artefact? Artefact!

    DEFF Research Database (Denmark)

    Steffensen, John Fleng

    2002-01-01

    a considerably elevated resting oxygen consumption, or standard metabolic rate, compared with oxygen consumption values of tropical or temperate fish extrapolated to similar low polar temperatures. Recent experiments on arctic and Antarctic fish, however, do not show elevated resting aerobic oxygen consumption......Whether metabolic cold adaptation in polar fish, based on measurements of aerobic standard metabolic rate, is a fact or an artefact has been a dispute since Holeton asked the question in 1974. So far polar fish had been considered to be metabolically cold adapted because they were reported to have...

  3. fMRI Artefact Rejection and Sleep Scoring Toolbox

    Directory of Open Access Journals (Sweden)

    Yves Leclercq

    2011-01-01

    Full Text Available We started writing the “fMRI artefact rejection and sleep scoring toolbox”, or “FAST”, to process our sleep EEG-fMRI data, that is, the simultaneous recording of electroencephalographic and functional magnetic resonance imaging data acquired while a subject is asleep. FAST tackles three crucial issues typical of this kind of data: (1 data manipulation (viewing, comparing, chunking, etc. of long continuous M/EEG recordings, (2 rejection of the fMRI-induced artefact in the EEG signal, and (3 manual sleep-scoring of the M/EEG recording. Currently, the toolbox can efficiently deal with these issues via a GUI, SPM8 batching system or hand-written script. The tools developed are, of course, also useful for other EEG applications, for example, involving simultaneous EEG-fMRI acquisition, continuous EEG eye-balling, and manipulation. Even though the toolbox was originally devised for EEG data, it will also gracefully handle MEG data without any problem. “FAST” is developed in Matlab as an add-on toolbox for SPM8 and, therefore, internally uses its SPM8-meeg data format. “FAST” is available for free, under the GNU-GPL.

  4. The origin of emeralds embedded in archaeological artefacts in Slovenia

    Directory of Open Access Journals (Sweden)

    Albina Kržič

    2013-06-01

    Full Text Available Roman gold jewellery, which was excavated in Ptuj (Poetovio and consists of a necklace, earrings and a braceletwith embedded emeralds, is part of the Slovenian archaeological artefacts collections. Crystallographic characteristics,inclusions, luminous phenomena and geological characteristics were determined in order to establish theorigin of the emeralds. Chemical composition of the emeralds was determined non-destructively using the methodsof proton-induced X-rays and gamma rays (PIXE/PIGE. The results were compared with reference emeraldsfrom Habachtal in Austria and with green beryls from the Ural Mts. Literature data for emeralds from Egypt andmodern-day Afghanistan area were used to interpret the results. Specifically, these sites were known for emeraldsbeing mined for jewellery in Roman times. It was assumed that emeralds from archaeological artefacts originatedfrom Habachtal in Austria, given that this site was the nearest to the place where found. But the emeralds fromthe necklace and earrings in fact came from Egyptian deposits. The origin of emeralds from the bracelet could nothave been determined absolutely reliably due to the lack of comparative materials; they may originate from a site inmodern-day Afghanistan or from Egypt, but certainly not from the same site as the previously mentioned emeraldsin the necklace and earrings.

  5. Iterative metal artefact reduction in CT: can dedicated algorithms improve image quality after spinal instrumentation?

    Science.gov (United States)

    Aissa, J; Thomas, C; Sawicki, L M; Caspers, J; Kröpil, P; Antoch, G; Boos, J

    2017-05-01

    To investigate the value of dedicated computed tomography (CT) iterative metal artefact reduction (iMAR) algorithms in patients after spinal instrumentation. Post-surgical spinal CT images of 24 patients performed between March 2015 and July 2016 were retrospectively included. Images were reconstructed with standard weighted filtered back projection (WFBP) and with two dedicated iMAR algorithms (iMAR-Algo1, adjusted to spinal instrumentations and iMAR-Algo2, adjusted to large metallic hip implants) using a medium smooth kernel (B30f) and a sharp kernel (B70f). Frequencies of density changes were quantified to assess objective image quality. Image quality was rated subjectively by evaluating the visibility of critical anatomical structures including the central canal, the spinal cord, neural foramina, and vertebral bone. Both iMAR algorithms significantly reduced artefacts from metal compared with WFBP (palgorithms led to an improvement in visualisation of soft-tissue structures (median iMAR-Algo1=3; interquartile range [IQR]:1.5-3; iMAR-Algo2=4; IQR: 3.5-4) and bone structures (iMAR-Algo1=3; IQR:3-4; iMAR-Algo2=4; IQR:4-5) compared to WFBP (soft tissue: median 2; IQR: 0.5-2 and bone structures: median 2; IQR: 1-3; palgorithms reduced artefacts compared with WFBP, however, the iMAR algorithm with dedicated settings for large metallic implants was superior to the algorithm specifically adjusted to spinal implants. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

  6. X-ray CT high-density artefact suppression in the presence of bones

    Energy Technology Data Exchange (ETDEWEB)

    Wei Jikun [School of Health Sciences, 550 Stadium Mall Drive, West Lafayette, IN 47907-2051 (United States); Chen Laigao [BioImaging Center of Emphasis, Pfizer Global Research and Development, 2800 Plymouth RD, Ann Arbor, MI 48105 (United States); Sandison, George A [School of Health Sciences, 550 Stadium Mall Drive, West Lafayette, IN 47907-2051 (United States); Liang Yun [Department of Radiology, Indiana University Medical School, Indianapolis, IN 46202 (United States); Xu, Lisa X [School of Mechanical Engineering, 585 Purdue Mall, West Lafayette, IN 47907-2040 (United States)

    2004-12-21

    This paper presents a novel method of reducing x-ray CT high-density artefacts generated by metal objects when abundant bone structures are present in the region of interest. This method has an advantage over previously proposed methods since it heavily suppresses the metal artefacts without introducing extra bone artefacts. The method of suppression requires that bone pixels are isolated and segmented by thresholding. Then artificial CT numbers are assigned to the bone pixels so that their projection profiles are smooth and thus can be properly simulated by a polynomial interpolation. The projection profile of the metal object is then removed to fully suppress the artefacts. The resulting processed profile is fed to a reconstruction routine and the previously preserved bone pixels added back. The new method utilizes two important features of the CT image with metal artefacts: (a) metal and bone pixels are not severely affected by the high-density artefacts and (b) the high-density artefacts can be located in specific projection channels in the profile domain, although they are spread out in the image domain. This suppression method solves the problem of CT image artefacts arising from metal objects in the body. It has the potential to greatly improve diagnostic CT imaging in the presence of these objects and treatment planning that utilizes CT for patients with metal applicators (e.g., brachytherapy for cervix cancer and prostate cryotherapy)

  7. Inertia artefacts and their effect on the parameterisation of keyboard reaction forces.

    Science.gov (United States)

    Asundi, Krishna; Johnson, Peter W; Dennerlein, Jack T

    2009-10-01

    Reaction force measurements collected during typing on keyboard trays contain inertia artefacts due to dynamic movements of the supporting work surface. To evaluate the effect of these artefacts, vertical forces and accelerations were measured while nine volunteers touch-typed on a rigid desk and a compliant keyboard tray. Two signal processing methods were evaluated: 1) low pass filtering with 20 Hz cut-off; 2) inertial force cancellation by subtracting the accelerometer signal. High frequency artefacts in the force signal, present on both surfaces, were eliminated by low pass filtering. Low frequency artefacts, present only when subjects typed on the keyboard tray, were attenuated by subtracting the accelerometer signal. Attenuation of these artefacts altered the descriptive statistics of the force signal by as much as 7%. For field measurements of typing force, reduction of low frequency artefacts should be considered for making more accurate comparisons across groups using work surfaces with different compliances. Direct measures of physical risk factors in the workplace can improve understanding of the aetiology of musculoskeletal disorders. Findings from this study characterise inertia artefacts in typing force measures and provide a method for eliminating them. These artefacts can add variability to measures, masking possible differences between subject groups.

  8. Influence of metallic dental implants and metal artefacts on dose calculation accuracy

    Energy Technology Data Exchange (ETDEWEB)

    Maerz, Manuel; Koelbl, Oliver; Dobler, Barbara [Regensburg University Medical Center, Department of Radiotherapy, Regensburg (Germany)

    2014-10-31

    Metallic dental implants cause severe streaking artefacts in computed tomography (CT) data, which inhibit the correct representation of shape and density of the metal and the surrounding tissue. The aim of this study was to investigate the impact of dental implants on the accuracy of dose calculations in radiation therapy planning and the benefit of metal artefact reduction (MAR). A second aim was to determine the treatment technique which is less sensitive to the presence of metallic implants in terms of dose calculation accuracy. Phantoms consisting of homogeneous water equivalent material surrounding dental implants were designed. Artefact-containing CT data were corrected using the correct density information. Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans were calculated on corrected and uncorrected CT data and compared to 2-dimensional dose measurements using GafChromic trademark EBT2 films. For all plans the accuracy of dose calculations is significantly higher if performed on corrected CT data (p = 0.015). The agreement of calculated and measured dose distributions is significantly higher for VMAT than for IMRT plans for calculations on uncorrected CT data (p = 0.011) as well as on corrected CT data (p = 0.029). For IMRT and VMAT the application of metal artefact reduction significantly increases the agreement of dose calculations with film measurements. VMAT was found to provide the highest accuracy on corrected as well as on uncorrected CT data. VMAT is therefore preferable over IMRT for patients with metallic implants, if plan quality is comparable for the two techniques. (orig.) [German] Zahnimplantate aus Metall verursachen in Computertomographiedaten (CT) streifenfoermige Artefakte. Diese verhindern eine korrekte Zuordnung von Form und Dichteeigenschaften des Metalls und des umgebenden Gewebes. Ziel dieser Studie war es, den Einfluss von Zahnimplantaten auf die Genauigkeit der Dosisberechnung in der

  9. Laryngeal mask airway (LMA) artefact resulting in MRI misdiagnosis

    Energy Technology Data Exchange (ETDEWEB)

    Schieble, Thomas [University of Medicine and Dentistry of New Jersey, Department of Anesthesiology, New Jersey Medical School, Newark, NJ (United States); Maimonides Medical Center, Department of Anesthesiology, Brooklyn, NY (United States); Patel, Anuradha; Davidson, Melissa [University of Medicine and Dentistry of New Jersey, Department of Anesthesiology, New Jersey Medical School, Newark, NJ (United States)

    2008-03-15

    We report a 7-year-old child who underwent brain MRI for a known seizure disorder. The technique used for general anesthesia included inhalation induction followed by placement of a laryngeal mask airway (LMA) for airway maintenance. Because the reviewing radiologist was unfamiliar with the use of an LMA during anesthesia, and because the attending anesthesiologist did not communicate his technique to the radiologist, an MRI misdiagnosis was reported because of artefact created by the in situ LMA. As a result of this misdiagnosis the child was subjected to unnecessary subsequent testing to rule out a reported anatomic abnormality induced by the LMA. Our case illustrates the need for coordination of patient care among hospital services. (orig.)

  10. THE A (H1N1 INFLUENZA. SYMBOLIC DIMENSIONS OF A PANDEMIC ARTEFACT

    Directory of Open Access Journals (Sweden)

    Andrés G. Seguel

    2013-01-01

    Full Text Available The aim of the present paper is to present the symbolic features that are exposed by the concept of artefact in the context of a pandemic alarm, such as the A (H1N1 influenza. The symbolic qualities entailed by the notion of artefact are well-known within the Social Sciences: Sociology, Anthropology, Archaeology, and Linguistics. The artefact is basically not an object, but an action aimed at designing, simulating or creating a simile by means of material, technological or linguistic structures. The purpose of the present work is to unveil the symbolic dimensions that are activated by the A (H1N1 influenza as a Pandemic Artefact: a the assumption of separating information from matter; b the need for a material support to enable the exchange; c the sociological reflexivity of the artefact and its agency; d the arbitrariness of its social use, that detaches it from the design as intention.

  11. Analytical artefacts in the speciation of arsenic in clinical samples

    Energy Technology Data Exchange (ETDEWEB)

    Slejkovec, Zdenka [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia)], E-mail: zdenka.slejkovec@ijs.si; Falnoga, Ingrid [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Goessler, Walter [Institute of Chemistry - Analytical Chemistry, Karl-Franzens University Graz, Universitaetsplatz 1, Graz (Austria); Elteren, Johannes T. van [National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana (Slovenia); Raml, Reingard [Institute of Chemistry - Analytical Chemistry, Karl-Franzens University Graz, Universitaetsplatz 1, Graz (Austria); Podgornik, Helena; Cernelc, Peter [University Medical Centre Ljubljana, Zaloska 7, 1000 Ljubljana (Slovenia)

    2008-01-21

    Urine and blood samples of cancer patients, treated with high doses of arsenic trioxide were analysed for arsenic species using HPLC-HGAFS and, in some cases, HPLC-ICPMS. Total arsenic was determined with either flow injection-HGAFS in urine or radiochemical neutron activation analysis in blood fractions (in serum/plasma, blood cells). The total arsenic concentrations (during prolonged, daily/weekly arsenic trioxide therapy) were in the {mu}g mL{sup -1} range for urine and in the ng g{sup -1} range for blood fractions. The main arsenic species found in urine were As(III), MA and DMA and in blood As(V), MA and DMA. With proper sample preparation and storage of urine (no preservation agents/storage in liquid nitrogen) no analytical artefacts were observed and absence of significant amounts of alleged trivalent metabolites was proven. On the contrary, in blood samples a certain amount of arsenic can get lost in the speciation procedure what was especially noticeable for the blood cells although also plasma/serum gave rise to some disappearance of arsenic. The latter losses may be attributed to precipitation of As(III)-containing proteins/peptides during the methanol/water extraction procedure whereas the former losses were due to loss of specific As(III)-complexing proteins/peptides (e.g. cysteine, metallothionein, reduced GSH, ferritin) on the column (Hamilton PRP-X100) during the separation procedure. Contemporary analytical protocols are not able to completely avoid artefacts due to losses from the sampling to the detection stage so that it is recommended to be careful with the explanation of results, particularly regarding metabolic and pharmacokinetic interpretations, and always aim to compare the sum of species with the total arsenic concentration determined independently.

  12. Prospective ECG triggering reduces prosthetic heart valve-induced artefacts compared with retrospective ECG gating on 256-slice CT.

    NARCIS (Netherlands)

    Symersky, P.; Habets, J.; Westers, P.; Mol, B.A. de; Prokop, M.; Budde, R.P.

    2012-01-01

    OBJECTIVES: Multidetector computed tomography (MDCT) has diagnostic value for the evaluation of prosthetic heart valve (PHV) dysfunction but it is hampered by artefacts. We hypothesised that image acquisition using prospective triggering instead of retrospective gating would reduce artefacts related

  13. Optimization of metal artefact reduction (MAR) sequences for MRI of total hip prostheses

    Energy Technology Data Exchange (ETDEWEB)

    Toms, A.P., E-mail: andoni.toms@nnuh.nhs.u [Department of Radiology, Norfolk and Norwich University Hospital Trust, Norwich, Norfolk NR4 7UY (United Kingdom); Smith-Bateman, C.; Malcolm, P.N.; Cahir, J. [Department of Radiology, Norfolk and Norwich University Hospital Trust, Norwich, Norfolk NR4 7UY (United Kingdom); Graves, M. [University Department of Radiology, Addenbrooke' s Hospital, Cambridge (United Kingdom)

    2010-06-15

    Aim: To describe the relative contribution of matrix size and bandwidth to artefact reduction in order to define optimal sequence parameters for metal artefact reduction (MAR) sequences for MRI of total hip prostheses. Methods and materials: A phantom was created using a Charnley total hip replacement. Mid-coronal T1-weighted (echo time 12 ms, repetition time 400 ms) images through the prosthesis were acquired with increasing bandwidths (150, 300, 454, 592, and 781 Hz/pixel) and increasing matrixes of 128, 256, 384, 512, 640, and 768 pixels square. Signal loss from the prosthesis and susceptibility artefact was segmented using an automated tool. Results: Over 90% of the achievable reduction in artefacts was obtained with matrixes of 256 x 256 or greater and a receiver bandwidth of approximately 400 Hz/pixel or greater. Thereafter increasing the receiver bandwidth or matrix had little impact on reducing susceptibility artefacts. Increasing the bandwidth produced a relative fall in the signal-to-noise ratio (SNR) of between 49 and 56% for a given matrix, but, in practice, the image quality was still satisfactory even with the highest bandwidth and largest matrix sizes. The acquisition time increased linearly with increasing matrix parameters. Conclusion: Over 90% of the achievable metal artefact reduction can be realized with mid-range matrices and receiver bandwidths on a clinical 1.5 T system. The loss of SNR from increasing receiver bandwidth, is preferable to long acquisition times, and therefore, should be the main tool for reducing metal artefact.

  14. Automatic removal of manually induced artefacts in ultrasound images of thyroid gland.

    Science.gov (United States)

    Narayan, Nikhil S; Marziliano, Pina; Hobbs, Christopher G L

    2013-01-01

    Manually induced artefacts, like caliper marks and anatomical labels, render an ultrasound (US) image incapable of being subjected to further processes of Computer Aided Diagnosis (CAD). In this paper, we propose a technique to remove these artefacts and restore the image as accurately as possible. The technique finds application as a pre-processing step when developing unsupervised segmentation algorithms for US images that deal with automatic estimation of the number of segments and clustering. The novelty of the algorithm lies in the image processing pipeline chosen to automatically identify the artefacts and is developed based on the histogram properties of the artefacts. The algorithm was able to successfully restore the images to a high quality when it was executed on a dataset of 18 US images of the thyroid gland on which the artefacts were induced manually by a doctor. Further experiments on an additional dataset of 10 unmarked US images of the thyroid gland on which the artefacts were simulated using Matlab showed that the restored images were again of high quality with a PSNR > 38 dB and free of any manually induced artefacts.

  15. A standardized evaluation of artefacts from metallic compounds during fast MR imaging.

    Science.gov (United States)

    Murakami, Shumei; Verdonschot, Rinus G; Kataoka, Miyoshi; Kakimoto, Naoya; Shimamoto, Hiroaki; Kreiborg, Sven

    2016-10-01

    Metallic compounds present in the oral and maxillofacial regions (OMRs) cause large artefacts during MR scanning. We quantitatively assessed these artefacts embedded within a phantom according to standards set by the American Society for Testing and Materials (ASTM). Seven metallic dental materials (each of which was a 10-mm(3) cube embedded within a phantom) were scanned [i.e. aluminium (Al), silver alloy (Ag), type IV gold alloy (Au), gold-palladium-silver alloy (Au-Pd-Ag), titanium (Ti), nickel-chromium alloy (NC) and cobalt-chromium alloy (CC)] and compared with a reference image. Sequences included gradient echo (GRE), fast spin echo (FSE), gradient recalled acquisition in steady state (GRASS), a spoiled GRASS (SPGR), a fast SPGR (FSPGR), fast imaging employing steady state (FIESTA) and echo planar imaging (EPI; axial/sagittal planes). Artefact areas were determined according to the ASTM-F2119 standard, and artefact volumes were assessed using OsiriX MD software (Pixmeo, Geneva, Switzerland). Tukey-Kramer post hoc tests were used for statistical comparisons. For most materials, scanning sequences eliciting artefact volumes in the following (ascending) order FSE-T1/FSE-T2 < FSPGR/SPGR < GRASS/GRE < FIESTA < EPI. For all scanning sequences, artefact volumes containing Au, Al, Ag and Au-Pd-Ag were significantly smaller than other materials (in which artefact volume size increased, respectively, from Ti < NC < CC). The artefact-specific shape (elicited by the cubic sample) depended on the scanning plane (i.e. a circular pattern for the axial plane and a "clover-like" pattern for the sagittal plane). The availability of standardized information on artefact size and configuration during MRI will enhance diagnosis when faced with metallic compounds in the OMR.

  16. Exploring Preferences and Non-use Values for Hidden Archaeological Artefacts

    DEFF Research Database (Denmark)

    Lundhede, Thomas; Bille, Trine; Hasler, Berit

    2013-01-01

    This paper presents a choice experiment study of a proposed wetland restoration project which aims to preserve archaeological artefacts from Stone Age villages which are presently buried within the topsoil. Wetland restoration can avoid destruction of the artefacts due to agricultural cultivation...... is for ensuring permanent protection of archaeological artefacts, rather than biological diversity and recreational opportunities. The results are discussed in relation to the Prospect Theory: people value a loss of cultural heritage higher than a gain of new cultural goods or services. This insight is of general...

  17. Exploring preferences and non-use values for hidden archaeological artefacts

    DEFF Research Database (Denmark)

    Lundhede, Thomas; Bille, Trine; Hasler, Berit

    2013-01-01

    This paper presents a choice experiment study of a proposed wetland restorationproject which aims to preserve archaeological artefacts from Stone Age villages which are presently buried within the topsoil. Wetland restoration can avoid destruction of the artefacts due to agricultural cultivation...... is for ensuring permanent protection of archaeological artefacts, rather than biological diversity and recreational opportunities. The results are discussed in relation to the Prospect Theory:people value a loss of cultural heritage higher than a gain of new cultural goods or services. This insight is of general...

  18. Cell respiration under hypoxia: facts and artefacts in mitochondrial oxygen kinetics.

    Science.gov (United States)

    Scandurra, Francesca M; Gnaiger, Erich

    2010-01-01

    When oxygen supply to tissues is limiting, mitochondrial respiration and ATP production are compromised. To assess the bioenergetic consequences under normoxia and hypoxia, quantitative evaluation of mitochondrial oxygen kinetics is required. Using high-resolution respirometry, the "apparent K (m)" for oxygen or p (50) of respiration in 32D cells was determined at 0.05 +/- 0.01 kPa (0.4 mmHg, 0.5 microM, 0.25% air saturation). Close agreement with p (50) of isolated mitochondria indicates that intracellular gradients are small in small cells at routine activity. At intracellular p (O2) respiration is limited by >2% with a p (50) of 0.05 kPa. Over-estimation of p (50) at 0.4 kPa (3 mmHg) would imply significant (>17%) oxygen limitation of respiration under intracellular normoxia. Based on a critical review, we conclude that p (50) ranges from 0.01 to 0.10 kPa in mitochondria and small cells in the absence of inhibitors of cytochrome c oxidase, whereas experimental artefacts explain the controversial >200-fold range of p (50) in the literature on mitochondrial oxygen kinetics.

  19. Motion artefact detection in structured illumination microscopy for live cell imaging.

    Science.gov (United States)

    Förster, Ronny; Wicker, Kai; Müller, Walter; Jost, Aurélie; Heintzmann, Rainer

    2016-09-19

    The reconstruction process of structured illumination microscopy (SIM) creates substantial artefacts if the specimen has moved during the acquisition. This reduces the applicability of SIM for live cell imaging, because these artefacts cannot always be recognized as such in the final image. A movement is not necessarily visible in the raw data, due to the varying excitation patterns and the photon noise. We present a method to detect motion by extracting and comparing two independent 3D wide-field images out of the standard SIM raw data without needing additional images. Their difference reveals moving objects overlaid with noise, which are distinguished by a probability theory-based analysis. Our algorithm tags motion-artefacts in the final high-resolution image for the first time, preventing the end-user from misinterpreting the data. We show and explain different types of artefacts and demonstrate our algorithm on a living cell.

  20. A framework to evaluate the educational potential of a digital artefact for math learning

    Directory of Open Access Journals (Sweden)

    Chiappini Giampaolo

    2015-12-01

    Full Text Available This article provides a methodology with two potential applications: to prove useful to maths teachers for analysing and evaluating the educational potential of different digital artefacts and to help designers of maths learning artefacts to evaluate their design during the implementation phase. The educational potential of an artefact is considered as an entity determined by actions and representations structure available within the artefact, the interpretation and behaviour of who uses it and the features of the activity in which it is used. The proposed methodology is based on the notions of affordance, narrative and cycle of expansive learning. The methodology has been applied on AlNuSet, a system designed for supporting the teaching and learning of algebra by means of modalities of interaction that are of visual, spatial and motor nature.

  1. Automatic detection of EEG artefacts arising from head movements using EEG and gyroscope signals.

    Science.gov (United States)

    O'Regan, Simon; Faul, Stephen; Marnane, William

    2013-07-01

    Contamination of EEG signals by artefacts arising from head movements has been a serious obstacle in the deployment of automatic neurological event detection systems in ambulatory EEG. In this paper, we present work on categorizing these head-movement artefacts as one distinct class and on using support vector machines to automatically detect their presence. The use of additional physical signals in detecting head-movement artefacts is also investigated by means of support vector machines classifiers implemented with gyroscope waveforms. Finally, the combination of features extracted from EEG and gyroscope signals is explored in order to design an algorithm which incorporates both physical and physiological signals in accurately detecting artefacts arising from head-movements.

  2. ECG movement artefacts can be greatly reduced with the aid of a movement absorbing device

    DEFF Research Database (Denmark)

    Harrison, Adrian Paul; Wandall, Kirsten; Thorball, Jørgen

    2007-01-01

    Accurate ECG signal analysis can be confounded by electric lead, and/or electrode movements varying in origin from, for example, hiccups, tremor or patient restlessness. ECG signals recorded using either a conventional electrode holder or with the aid of an electrode holder capable of absorbing...... movement artefacts, were measured on a healthy human subject. Results show a greatly improved stability of the ECG signal recorded using an electrode holder capable of absorbing movement artefacts during periods of lead disturbance, and highlight the movement artefacts that develop when the recording lead...... of a conventional ECG electrode holder is tugged or pulled during theperiod of monitoring. It is concluded that the new design of ECG electrode holder will not only enable clearer signal recordings for clinical assessment, but will reduce the ECG artefacts associated with the transportation of patients, and may...

  3. Settings and artefacts relevant in colour/power Doppler ultrasound in rheumatology.

    Science.gov (United States)

    Torp-Pedersen, S T; Terslev, L

    2008-02-01

    The paper explains the most important parameters for the use of colour and power Doppler in rheumatology. Recommendations for machine settings are given. The commonly encountered artefacts and their importance for image interpretation are explained.

  4. Removal of BCG artefact from concurrent fMRI-EEG recordings based on EMD and PCA.

    Science.gov (United States)

    Javed, Ehtasham; Faye, Ibrahima; Malik, Aamir Saeed; Abdullah, Jafri Malin

    2017-08-24

    Simultaneous electroencephalography (EEG) and functional magnetic resonance image (fMRI) acquisitions provide better insight into brain dynamics. Some artefacts due to simultaneous acquisition pose a threat to the quality of the data. One such problematic artefact is the ballistocardiogram (BCG) artefact. We developed a hybrid algorithm that combines features of empirical mode decomposition (EMD) with principal component analysis (PCA) to reduce the BCG artefact. The algorithm does not require extra electrocardiogram (ECG) or electrooculogram (EOG) recordings to extract the BCG artefact. The method was tested with both simulated and real EEG data of 11 participants. From the simulated data, the similarity index between the extracted BCG and the simulated BCG showed the effectiveness of the proposed method in BCG removal. On the other hand, real data were recorded with two conditions, i.e. resting state (eyes closed dataset) and task influenced (event-related potentials (ERPs) dataset). Using qualitative (visual inspection) and quantitative (similarity index, improved normalized power spectrum (INPS) ratio, power spectrum, sample entropy (SE)) evaluation parameters, the assessment results showed that the proposed method can efficiently reduce the BCG artefact while preserving the neuronal signals. Compared with conventional methods, namely, average artefact subtraction (AAS), optimal basis set (OBS) and combined independent component analysis and principal component analysis (ICA-PCA), the statistical analyses of the results showed that the proposed method has better performance, and the differences were significant for all quantitative parameters except for the power and sample entropy. The proposed method does not require any reference signal, prior information or assumption to extract the BCG artefact. It will be very useful in circumstances where the reference signal is not available. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Cultural camouflage--a critical study of how artefacts are camouflaged and mental health policy subverted.

    Science.gov (United States)

    Berlin, Johan M; Carlström, Eric D

    2015-01-01

    This study identifies hidden artefacts in a public organisation. In contrast to earlier studies, it focuses on artefacts as concealing rather than conveying meaning. Negligent behaviour caused by an unpopular culture was recognised in five psychiatric wards at a Swedish university hospital. Data comprising observations (87 h) and interviews (n = 60) were collected over a period of 48 months (2008-2011). Four different items used in everyday work representing a deeper meaning of the organisation were identified during the observations. The items selected were work attire, nametags, keys and restraint beds. These were considered particularly promising when it came to the aim of the study, namely, to find out how artefacts are camouflaged. The observations and the interviews revealed that these were controversial and contested artefacts in the organisation. The study uses the term 'cultural camouflage' for behaviour that ignores and consciously conceals symbols that have negative values. This concept contrasts with previous research that shows how artefacts are emphasised and how they contribute to the character of the activity in a transparent way. Conservative and backward-looking behaviour among staff provided one explanation as to why artefacts were concealed. Another was the need to establish harmonious internal interactions. Copyright © 2013 John Wiley & Sons, Ltd.

  6. Evaluation of metal artefact reduction in cone-beam computed tomography images of different dental materials.

    Science.gov (United States)

    Queiroz, Polyane Mazucatto; Oliveira, Matheus Lima; Groppo, Francisco Carlos; Haiter-Neto, Francisco; Freitas, Deborah Queiroz

    2017-05-23

    The aim of this study is to evaluate the efficacy of metal artefact reduction (MAR) in different dental materials with Picasso Trio cone-beam computed tomography (CBCT) scanner. Three imaging phantoms were custom-made of acrylic resin. Each phantom presented three cylinders of the same material: dental amalgam alloy, gutta-percha or aluminium-copper alloy. CBCT scans were performed on Picasso Trio unit with and without MAR, and artefact expression (standard deviation of grey values) was obtained and compared by Kruskal-Wallis and Student-Newman-Keuls (post hoc) (α = 0.05). Significant reduction of artefact expression (p  0.05) was observed with or without MAR when gutta-percha was scanned. MAR was effective in reducing artefacts arising from dental alloys on CBCT images. Dental materials of high atomic number and density are widely used in dentistry and can produce artefact that compromise CBCT image. The present study demonstrated that metal artefact reduction algorithm is an effective tool to improve image quality.

  7. Social Analysis in Development Interventions: Policy Artefact or Constructive Transformation?

    Directory of Open Access Journals (Sweden)

    SUSANNA PRICE

    2012-02-01

    Full Text Available Recently attention has focused on the role of social researchers in the processes of construction and transmission of knowledge about global poverty and its reduction. This paper examines some of the formative efforts by pioneering social researchers in development institutions to step into the realm of policy making to construct processes for project preparation and management through social analysis. Before 1970 development planners invoked ‘social' or ‘human' factors only as an excuse to explain away project failures - they designed and implemented development projects in the absence of any strategies or regulatory frameworks for managing their social impacts. Recognizing that project investments represent induced change and constitute a social process in themselves, pioneering social researchers constructed policies and procedures to introduce sociological content and method into the project cycle and so re-order social outcomes. Were such constructs merely policy artefacts? Even as the constructs helped to shift the statements of the development discourse towards ‘people oriented' poverty reduction, new modalities appeared which tested the limits of the agreed methods. Institutions may forget, neglect, contest or re-write the documents if in perceived conflict with the institutional ‘core business'. Yet those pioneering efforts created institutional space for, and understanding of, social analysis, with a measure of flow-on international recognition. Tracking social analysis in several international institutions and in a significant emerging economy, China, this paper highlights not only a history full of lessons to be learned where social analysis is not practiced systematically but also outlines some future challenges.

  8. Minimally invasive periodontal therapy.

    Science.gov (United States)

    Dannan, Aous

    2011-10-01

    Minimally invasive dentistry is a concept that preserves dentition and supporting structures. However, minimally invasive procedures in periodontal treatment are supposed to be limited within periodontal surgery, the aim of which is to represent alternative approaches developed to allow less extensive manipulation of surrounding tissues than conventional procedures, while accomplishing the same objectives. In this review, the concept of minimally invasive periodontal surgery (MIPS) is firstly explained. An electronic search for all studies regarding efficacy and effectiveness of MIPS between 2001 and 2009 was conducted. For this purpose, suitable key words from Medical Subject Headings on PubMed were used to extract the required studies. All studies are demonstrated and important results are concluded. Preliminary data from case cohorts and from many studies reveal that the microsurgical access flap, in terms of MIPS, has a high potential to seal the healing wound from the contaminated oral environment by achieving and maintaining primary closure. Soft tissues are mostly preserved and minimal gingival recession is observed, an important feature to meet the demands of the patient and the clinician in the esthetic zone. However, although the potential efficacy of MIPS in the treatment of deep intrabony defects has been proved, larger studies are required to confirm and extend the reported positive preliminary outcomes.

  9. First pregnancies, live birth, and in vitro fertilization outcomes after transplantation of frozen-banked ovarian tissue with a human extracellular matrix scaffold using robot-assisted minimally invasive surgery.

    Science.gov (United States)

    Oktay, Kutluk; Bedoschi, Giuliano; Pacheco, Fernanda; Turan, Volkan; Emirdar, Volkan

    2016-01-01

    Ovarian tissue cryopreservation is an experimental fertility preservation method and the transplantation techniques are still evolving. We attempted to improve the technique with the utility of a human decellularized extracellular tissue matrix (ECTM) scaffold, robot-assisted minimally invasive surgery, and perioperative pharmacological support. We prospectively studied 2 subjects with hemophagocytic lymphohistiocytosis (patient A) and non-Hodgkin lymphoma (patient B) who underwent ovarian tissue cryopreservation at the age of 23 years, before receiving preconditioning chemotherapy for hematopoietic stem cell transplantation. Both experienced ovarian failure postchemotherapy and we transplanted ovarian cortical tissues to the contralateral menopausal ovary 7 and 12 years later, using a human ECTM scaffold and robotic assistance. The ECTM scaffold tissue compatibility was shown in preclinical studies. Patients also received estrogen supplementation and baby aspirin preoperatively to aid in the revascularization process. Ovarian follicle development was observed approximately 10 (patient A) and 8 (patient B) weeks after ovarian tissue transplantation. Following 8 and 7 cycles of in vitro fertilization, 9 and 10 day-3 embryos were cryopreserved (patients A and B, respectively). While the baseline follicle-stimulating hormone (range 3.6-15.4 mIU/mL) levels near normalized by 7 months and remained steady postovarian transplantation in patient A, patient B showed improved but elevated follicle-stimulating hormone levels throughout (range 21-31 mIU/mL). Highest follicle yield was achieved 14 (8 follicles; patient A) and 11 (6 follicles; patient B) months postintervention. Patient A experienced a chemical pregnancy after the third frozen embryo transfer attempt. She then conceived following her first fresh in vitro fertilization embryo transfer and the pregnancy is currently ongoing. Patient B conceived after the first frozen embryo transfer attempt and delivered a

  10. Real-Time Measurement of the Tool-Tissue Interaction in Minimally Invasive Abdominal Surgery: The First Step to Developing the Next Generation of Smart Laparoscopic Instruments.

    Science.gov (United States)

    Barrie, Jenifer; Jayne, David G; Neville, Anne; Hunter, Louise; Hood, Adrian J; Culmer, Peter R

    2016-10-01

    Introduction Analysis of force application in laparoscopic surgery is critical to understanding the nature of the tool-tissue interaction. The aim of this study is to provide real-time data about manipulations to abdominal organs. Methods An instrumented short fenestrated grasper was used in an in vivo porcine model, measuring force at the grasper handle. Grasping force and duration over 5 small bowel manipulation tasks were analyzed. Forces required to retract gallbladder, bladder, small bowel, large bowel, and rectum were measured over 30 seconds. Four parameters were calculated-T(hold), the grasp time; T(close), time taken for the jaws to close; F(max), maximum force reached; and F(rms), root mean square force (representing the average force across the grasp time). Results Mean F(max) to manipulate the small bowel was 20.5 N (±7.2) and F(rms) was 13.7 N (±5.4). Mean T(close) was 0.52 seconds (±0.26) and T(hold) was 3.87 seconds (±1.5). In individual organs, mean F(max) was 49 N (±15) to manipulate the rectum and 59 N (±13.4) for the colon. The mean F(max) for bladder and gallbladder retraction was 28.8 N (±7.4) and 50.7 N (±3.8), respectively. All organs exhibited force relaxation, the F(rms) reduced to below 25 N for all organs except the small bowel, with a mean F(rms) of less than 10 N. Conclusion This study has commenced the process of quantifying tool-tissue interaction. The static measurements discussed here should evolve to include dynamic measurements such as shear, torque, and retraction forces, and be correlated with evidence of histological damage to tissue.

  11. Minimally Invasive Surgery for Axillary Osmidrosis Using a Combination of Subcutaneous Tissue Removal and a 1,444-nm Nd:YAG Laser.

    Science.gov (United States)

    Lee, Sang Geun; Ryu, Hwa Jung; Kim, Il-Hwan

    2014-12-01

    Many treatment modalities have been developed for axillary osmidrosis. It is well known that the surgical treatment has the best results. However, there is a high possibility of side effects. The 1,444-nm lipolysis laser has been recently introduced to remove the apocrine glands. So far, subdermal coagulation treatment with a 1,444-nm Nd:YAG laser may be the least invasive and most effective therapy for axillary osmidrosis. However, according to our previous experience, the recurrence rate was 20%~30%. This emphasizes the need for combination of surgical method and non-surgical method and we combined subcutaneous tissue removal and photothermocoagulation with a 1,444-nm Nd:YAG laser. Three patients for bilateral axillary osmidrosis were enrolled. After an incision of about one-third the length of the widest transverse diameter, the apocrine glands were separated from the skin. And then apocrine glands within the marked area were destroyed by irradiation with a 1,444-nm Nd:YAG laser thereafter. All patients exhibited no relapse of axillary osmidrosis and were satisfied with the treatment results. A combination of subcutaneous tissue removal and Interstitial laser photothermocoagulation with a 1,444-nm Nd:YAG laser could be an effective treatment for mild to moderate axillary osmidrosis.

  12. Minimal cosmography

    CERN Document Server

    Piazza, Federico

    2015-01-01

    The minimal requirement for cosmography - a nondynamical description of the universe - is a prescription for calculating null geodesics, and timelike geodesics as a function of their proper time. In this paper, we consider the most general linear connection compatible with homogeneity and isotropy, but not necessarily with a metric. A light-cone structure is assigned by choosing a set of geodesics representing light rays. This defines a "scale factor" and a local notion of distance, as that travelled by light in a given proper time interval. We find that the velocities and relativistic energies of free-falling bodies decrease in time as a consequence of cosmic expansion, but at a rate that can be different than that dictated by the usual metric framework. By extrapolating this behavior to photons redshift, we find that the latter is in principle independent of the "scale factor". Interestingly, redshift-distance relations and other standard geometric observables are modified in this extended framework, in a w...

  13. Minimal cosmography

    Science.gov (United States)

    Piazza, Federico; Schücker, Thomas

    2016-04-01

    The minimal requirement for cosmography—a non-dynamical description of the universe—is a prescription for calculating null geodesics, and time-like geodesics as a function of their proper time. In this paper, we consider the most general linear connection compatible with homogeneity and isotropy, but not necessarily with a metric. A light-cone structure is assigned by choosing a set of geodesics representing light rays. This defines a "scale factor" and a local notion of distance, as that travelled by light in a given proper time interval. We find that the velocities and relativistic energies of free-falling bodies decrease in time as a consequence of cosmic expansion, but at a rate that can be different than that dictated by the usual metric framework. By extrapolating this behavior to photons' redshift, we find that the latter is in principle independent of the "scale factor". Interestingly, redshift-distance relations and other standard geometric observables are modified in this extended framework, in a way that could be experimentally tested. An extremely tight constraint on the model, however, is represented by the blackbody-ness of the cosmic microwave background. Finally, as a check, we also consider the effects of a non-metric connection in a different set-up, namely, that of a static, spherically symmetric spacetime.

  14. Quality Enhancement and Nerve Fibre Layer Artefacts Removal in Retina Fundus Images by Off Axis Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Giancardo, Luca [ORNL; Meriaudeau, Fabrice [ORNL; Karnowski, Thomas Paul [ORNL; Li, Yaquin [University of Tennessee, Knoxville (UTK); Tobin Jr, Kenneth William [ORNL; Chaum, Edward [University of Tennessee, Knoxville (UTK)

    2011-01-01

    Retinal fundus images acquired with non-mydriatic digital fundus cameras are a versatile tool for the diagnosis of various retinal diseases. Because of the ease of use of newer camera models and their relative low cost, these cameras are employed worldwide by retina specialists to diagnose diabetic retinopathy and other degenerative diseases. Even with relative ease of use, the images produced by these systems sometimes suffer from reflectance artefacts mainly due to the nerve fibre layer (NFL) or other camera lens related reflections. We propose a technique that employs multiple fundus images acquired from the same patient to obtain a single higher quality image without these reflectance artefacts. The removal of bright artefacts, and particularly of NFL reflectance, can have great benefits for the reduction of false positives in the detection of retinal lesions such as exudate, drusens and cotton wool spots by automatic systems or manual inspection. If enough redundant information is provided by the multiple images, this technique also compensates for a suboptimal illumination. The fundus images are acquired in straightforward but unorthodox manner, i.e. the stare point of the patient is changed between each shot but the camera is kept fixed. Between each shot, the apparent shape and position of all the retinal structures that do not exhibit isotropic reflectance (e.g. bright artefacts) change. This physical effect is exploited by our algorithm in order to extract the pixels belonging to the inner layers of the retina, hence obtaining a single artefacts-free image.

  15. Comparison of CT and MRI artefacts from coils and vascular plugs used for portal vein embolization

    Energy Technology Data Exchange (ETDEWEB)

    Geisel, Dominik, E-mail: dominik.geisel@charite.de [Department of Diagnostic and Interventional Radiology, Charité, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin (Germany); Gebauer, Bernhard [Department of Diagnostic and Interventional Radiology, Charité, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin (Germany); Malinowski, Maciej; Stockmann, Martin [Department of General, Visceral and Transplantation Surgery, Charité, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin (Germany); Denecke, Timm [Department of Diagnostic and Interventional Radiology, Charité, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin (Germany)

    2014-04-15

    Purpose: To retrospectively analyze the degree of artefacts in CT and MRI scans caused by coils and vascular plugs used for portal vein embolization (PVE). Materials and methods: All patients who underwent PVE between July 2011 and December 2012 and received either plug or coil embolization additional to particle embolization were retrospectively analyzed. Artefacts causes by embolization materials were measured in CT and MRI scans following PVE. Results: The sum of the artefact diameters caused from coils was significantly higher in CT (188.3 ± 26.1 mm) than in MRI T1 (50.5 ± 6.5 mm) or T2 imaging (39.5 ± 9.7 mm) (P < 0.05). In MRI, the diameter in T1 and T2 sequences did not differ significantly (P = 0.977). The sum of the artefact diameters from vascular plugs in MRI T1 sequences (62.5 ± 8.7 mm) was significantly higher than in CT (46.6 ± 4.8 mm; P < 0.05) and MRI T2 sequences (52.8 ± 3.8 mm; P < 0.05). Conclusion: PVE with particles and vascular plug causes significantly fewer artefacts than PVE with particles and coils on CT scans following embolization, which can be important in the event of vascular complications or in follow-up scans, should the patient become unresectable.

  16. Issues relating to the subtraction phase in EOG artefact correction of the EEG.

    Science.gov (United States)

    Croft, Rodney J; Barry, Robert J

    2002-06-01

    An important method for removing the effect of ocular artefact from the EEG is 'EOG correction'. This method estimates the proportion of ocular artefact that is in the EEG, and removes it by subtraction. To date, EOG correction research has focused on problems relating to the estimation of the correction coefficients. Using both mathematical rationale and empirical data, this paper addresses issues relating to the subtraction phase, such as the magnitude of error that can be expected due to EOG correction. Using ERP methodology, principal component and regression analyses, it is shown that the N1P2 complex propagates forward to the horizontal and radial (but not vertical) electrooculograms (EOG), and it is shown mathematically that this will result in EOG-correction error. Assuming an accurate estimate of ocular contamination of the EEG, maximal subtraction-phase error of the N1P2 complex was found to be a prefrontal attenuation of 15-22%, decreasing to central and occipital enhancements of 3-4% and 13-14%, respectively. The magnitude of this subtraction-phase error is compared to between-subject ERP variability and to error associated with EOG rejection (omitting data contaminated by ocular artefact). It is argued that such EOG correction error is small relative to both artefact rejection procedures and to normal variability found in ERP studies, and that it is less pernicious than artefact rejection procedures.

  17. Motion artefact reduction of the photoplethysmographic signal in pulse transit time measurement.

    Science.gov (United States)

    Foo, J Y A; Wilson, S J; Williams, G R; Harris, M; Cooper, D M

    2004-12-01

    Motion artefact is a common occurrence that contaminates photoplethysmographic (PPG) measurements. To extract timing information from signals during artefact is challenging. PPG signal is very sensitive to artefacts and can be used in applications like, pulse transit time (PTT) as part of the polysomnographic studies. A correlation cancellation or signal processing approach is implemented with the adaptive cancelling filter concept and a triaxial accelerometry. PPG signals obtained from a Masimo (Reference) pulse oximeter is used as reference to compare with the reconstructed PPG signals. Different hands are used for each PPG source, one stationary while the other involves typical movements during sleep. A second Masimo pulse oximeter is used to register intensity of timing errors on commercial PPG signals. 108 PTT measurements are recorded in three different movements with PTT estimates from unprocessed PPG signals showing 35.51+/-27.42%, Masimo 50.02+/-29.40% and reconstructed 4.32+/-3.59% difference against those from the Reference PPG. The triaxial accelerometry can be used to detect the presence of artefact on PPG signals. This is useful in PTT measurements when signal contaminated with artefacts are required for further analysis, especially after and during arousals in sleep. The suggested filtering model can then reconstruct these corrupted PPG signals.

  18. Minimally Invasive Dentistry

    Science.gov (United States)

    ... to your desktop! more... What Is Minimally Invasive Dentistry? Article Chapters What Is Minimally Invasive Dentistry? Minimally ... techniques. Reviewed: January 2012 Related Articles: Minimally Invasive Dentistry Minimally Invasive Veneers Dramatically Change Smiles What Patients ...

  19. A minimally invasive method of piscine tissue collection and an analysis of long-term field-storage conditions for samples

    Directory of Open Access Journals (Sweden)

    Smalley John V

    2006-05-01

    Full Text Available Abstract Background The acquisition of high-quality DNA for use in phylogenetic and molecular population genetic studies is a primary concern for evolutionary and genetic researchers. Many non-destructive DNA sampling methods have been developed and are used with a variety of taxa in applications ranging from genetic stock assessment to molecular forensics. Results The authors have developed a field sampling method for obtaining high-quality DNA from sunfish (Lepomis and other freshwater fish that employs a variation on the buccal swab method and results in the collection of DNA suitable for PCR amplification and polymorphism analysis. Additionally, since the circumstances of storage are always a concern for field biologists, the authors have tested the potential storage conditions of swabbed samples and whether those conditions affect DNA extraction and PCR amplification. It was found that samples stored at room temperature in the dark for over 200 days could still yield DNA suitable for PCR amplification and polymorphism detection. Conclusion These findings suggest that valuable molecular genetic data may be obtained from tissues that have not been treated or stored under optimal field conditions. Furthermore, it is clear that the lack of adequately low temperatures during transport and long term storage should not be a barrier to anyone wishing to engage in field-based molecular genetic research.

  20. Preliminary Results of Ocular Artefacts Identification in EEC Series by Neural Network

    Directory of Open Access Journals (Sweden)

    M. Kofronova

    1996-06-01

    Full Text Available The human electroencephalogram (EEG, is record of the electrical activity of the brain and contains useful diagnostic information on a variety of neurological disorders. Normal EEG signal are usually registered from electrodes placed on the scalp, and are often very small in amplitude, of 20 µV. The EEG, like all biomedical signals, is very susceptible to a variety of large signal contamination or artefacts (signals of other than brain activity which reduce its clinical usefulness. For example, blinking or moving eyes produces large electrical potentials around the eyes called the electrooculogram (EOG. The EOG spreads across the scalp to contaminate the EEG, when it is referred to as an ocular artefact (OA. This paper includes method of identification portion of the EEG record where ocular artefact appears and classification its type by neural network.

  1. An Evaluation View of an Ensemble Artefact for Decision Support using Action Design Research

    Directory of Open Access Journals (Sweden)

    Dale MacKrell

    2016-11-01

    Full Text Available This paper investigates the integration of content, context and process (CCP into the Action Design Research (ADR framework to account for the interplay of organisational issues in artefact design and development. The investigation is conducted through a case study in which successive ICT student teams incrementally build, over several semesters, a tailored, low cost business intelligence (BI system as an ensemble artefact for an organisation in the not-for-profit (NFP sector. During project development, CCP’s human-centred approach to evaluation complements ADR’s more prescribed technology-driven software testing. The integration of CCP into ADR as an evaluation view offers an holistic approach to assessing an ensemble artefact. The resultant conceptual framework is presented as a model with an explication of unexpected design and research outcomes.

  2. METHODOLOGY TO CREATE DIGITAL AND VIRTUAL 3D ARTEFACTS IN ARCHAEOLOGY

    Directory of Open Access Journals (Sweden)

    Calin Neamtu

    2016-12-01

    Full Text Available The paper presents a methodology to create 3D digital and virtual artefacts in the field of archaeology using CAD software solution. The methodology includes the following steps: the digitalization process, the digital restoration and the dissemination process within a virtual environment. The resulted 3D digital artefacts have to be created in files formats that are compatible with a large variety of operating systems and hardware configurations such as: computers, graphic tablets and smartphones. The compatibility and portability of these 3D file formats has led to a series of quality related compromises to the 3D models in order to integrate them on in a wide variety of application that are running on different hardware configurations. The paper illustrates multiple virtual reality and augmented reality application that make use of the virtual 3D artefacts that have been generated using this methodology.

  3. Problem Solving of Low Data Throughput on Mobile Devices by Artefacts Prebuffering

    Directory of Open Access Journals (Sweden)

    Krejcar Ondrej

    2009-01-01

    Full Text Available The paper deals with a problem of low data throughput on wirelessly connected mobile devices and a possibility to solve this problem by prebuffering of selected artefacts. The basics are in determining the problem parts of a mobile device and solve the problem by a model of data prebuffering-based system enhancement for locating and tracking users inside the buildings. The framework uses a WiFi network infrastructure to allow the mobile device determine its indoor position. User location is used for data prebuffering and for pushing information from a server to PDAs. All server data are saved as artefacts with its indoor position information. Accessing prebuffered data on a mobile device can significantly improve a response time needed to view large multimedia data. The solution was tested on a facility management information system built on purpose with a testing collection of about hundred large size artefacts.

  4. What Then Happens When Interaction is Not Possible: The Virtuosic Interpretation of Ergodic Artefacts

    Directory of Open Access Journals (Sweden)

    Miguel Carvalhais

    2015-11-01

    Full Text Available Procedural systems allow unique modes of authorship and singular aesthetic experiences. As creators and users of these systems, we need to be aware that their aesthetic potential is not solely defined by interaction but that interpretation, and the capacity to understand and simulate the processes taking place within these artefacts is highly significant. This paper argues that although direct interaction is usually the most discernible component in the relationship between ergodic artefacts and their users, ergodicity does not necessarily imply interaction. Non-interactive procedural artefacts may allow the development of ergodic experiences through interpretation, and the probing of the system by its reader through simulations. We try to set the grounds for designing towards virtuosic interpretation, an activity that we may describe as the ergodic experience developed by means of mental simulation through the development of theories of systems.

  5. ASPECTS OF BIODETERIORATION OF LAPIDEOUS SUBMERGED ARTEFACTS: 3D METHODOLOGIES APPLICATION

    Directory of Open Access Journals (Sweden)

    S. Ricci

    2015-04-01

    Full Text Available Submerged stone archaeological artefacts are bioeroded by endolithic microbiota (cyanobacteria, algae and fungi and macroborers (Porifera, Bivalvia and Sipuncula. Optical microscope and SEM observations permit to analyse the bioerosion traces and to identify bioeroders. Data obtained with these techniques cannot be used to estimate volumes of material bioeroded. This aspect require the need to collect three-dimensional, close-range data from artefact. In this work we illustrate two 3D imaging techniques used to study bioerosion phenomena of underwater Cultural Heritage. In particular Digital Video Microscope permit the elaboration of 3D images, which are widely employed for close-range acquisitions. Underwater Laser Scanner documents the in situ degradation of submerged artefacts. This research aims to sensitize specialist figures in the study 3D offering a starting point for future collaborations that could lead to interesting results.

  6. Aspects of Biodeterioration of Lapideous Submerged Artefacts: 3d Methodologies Application

    Science.gov (United States)

    Ricci, S.; Antonelli, F.; Sacco Perasso, C.

    2015-04-01

    Submerged stone archaeological artefacts are bioeroded by endolithic microbiota (cyanobacteria, algae and fungi) and macroborers (Porifera, Bivalvia and Sipuncula). Optical microscope and SEM observations permit to analyse the bioerosion traces and to identify bioeroders. Data obtained with these techniques cannot be used to estimate volumes of material bioeroded. This aspect require the need to collect three-dimensional, close-range data from artefact. In this work we illustrate two 3D imaging techniques used to study bioerosion phenomena of underwater Cultural Heritage. In particular Digital Video Microscope permit the elaboration of 3D images, which are widely employed for close-range acquisitions. Underwater Laser Scanner documents the in situ degradation of submerged artefacts. This research aims to sensitize specialist figures in the study 3D offering a starting point for future collaborations that could lead to interesting results.

  7. The effect of head size∕shape, miscentering, and bowtie filter on peak patient tissue doses from modern brain perfusion 256-slice CT: how can we minimize the risk for deterministic effects?

    Science.gov (United States)

    Perisinakis, Kostas; Seimenis, Ioannis; Tzedakis, Antonis; Papadakis, Antonios E; Damilakis, John

    2013-01-01

    To determine patient-specific absorbed peak doses to skin, eye lens, brain parenchyma, and cranial red bone marrow (RBM) of adult individuals subjected to low-dose brain perfusion CT studies on a 256-slice CT scanner, and investigate the effect of patient head size∕shape, head position during the examination and bowtie filter used on peak tissue doses. The peak doses to eye lens, skin, brain, and RBM were measured in 106 individual-specific adult head phantoms subjected to the standard low-dose brain perfusion CT on a 256-slice CT scanner using a novel Monte Carlo simulation software dedicated for patient CT dosimetry. Peak tissue doses were compared to corresponding thresholds for induction of cataract, erythema, cerebrovascular disease, and depression of hematopoiesis, respectively. The effects of patient head size∕shape, head position during acquisition and bowtie filter used on resulting peak patient tissue doses were investigated. The effect of eye-lens position in the scanned head region was also investigated. The effect of miscentering and use of narrow bowtie filter on image quality was assessed. The mean peak doses to eye lens, skin, brain, and RBM were found to be 124, 120, 95, and 163 mGy, respectively. The effect of patient head size and shape on peak tissue doses was found to be minimal since maximum differences were less than 7%. Patient head miscentering and bowtie filter selection were found to have a considerable effect on peak tissue doses. The peak eye-lens dose saving achieved by elevating head by 4 cm with respect to isocenter and using a narrow wedge filter was found to approach 50%. When the eye lies outside of the primarily irradiated head region, the dose to eye lens was found to drop to less than 20% of the corresponding dose measured when the eye lens was located in the middle of the x-ray beam. Positioning head phantom off-isocenter by 4 cm and employing a narrow wedge filter results in a moderate reduction of signal-to-noise ratio

  8. The effect of head size/shape, miscentering, and bowtie filter on peak patient tissue doses from modern brain perfusion 256-slice CT: How can we minimize the risk for deterministic effects?

    Energy Technology Data Exchange (ETDEWEB)

    Perisinakis, Kostas; Seimenis, Ioannis; Tzedakis, Antonis; Papadakis, Antonios E.; Damilakis, John [Department of Medical Physics, Faculty of Medicine, University of Crete, P.O. Box 2208, Heraklion 71003, Crete (Greece); Medical Diagnostic Center ' Ayios Therissos,' P.O. Box 28405, Nicosia 2033, Cyprus and Department of Medical Physics, Medical School, Democritus University of Thrace, Panepistimioupolis, Dragana 68100, Alexandroupolis (Greece); Department of Medical Physics, University Hospital of Heraklion, P.O. Box 1352, Heraklion 71110, Crete (Greece); Department of Medical Physics, Faculty of Medicine, University of Crete, P.O. Box 2208, Heraklion 71003, Crete (Greece)

    2013-01-15

    Purpose: To determine patient-specific absorbed peak doses to skin, eye lens, brain parenchyma, and cranial red bone marrow (RBM) of adult individuals subjected to low-dose brain perfusion CT studies on a 256-slice CT scanner, and investigate the effect of patient head size/shape, head position during the examination and bowtie filter used on peak tissue doses. Methods: The peak doses to eye lens, skin, brain, and RBM were measured in 106 individual-specific adult head phantoms subjected to the standard low-dose brain perfusion CT on a 256-slice CT scanner using a novel Monte Carlo simulation software dedicated for patient CT dosimetry. Peak tissue doses were compared to corresponding thresholds for induction of cataract, erythema, cerebrovascular disease, and depression of hematopoiesis, respectively. The effects of patient head size/shape, head position during acquisition and bowtie filter used on resulting peak patient tissue doses were investigated. The effect of eye-lens position in the scanned head region was also investigated. The effect of miscentering and use of narrow bowtie filter on image quality was assessed. Results: The mean peak doses to eye lens, skin, brain, and RBM were found to be 124, 120, 95, and 163 mGy, respectively. The effect of patient head size and shape on peak tissue doses was found to be minimal since maximum differences were less than 7%. Patient head miscentering and bowtie filter selection were found to have a considerable effect on peak tissue doses. The peak eye-lens dose saving achieved by elevating head by 4 cm with respect to isocenter and using a narrow wedge filter was found to approach 50%. When the eye lies outside of the primarily irradiated head region, the dose to eye lens was found to drop to less than 20% of the corresponding dose measured when the eye lens was located in the middle of the x-ray beam. Positioning head phantom off-isocenter by 4 cm and employing a narrow wedge filter results in a moderate reduction of

  9. A cell shrinkage artefact in growth plate chondrocytes with common fixative solutions: importance of fixative osmolarity for maintaining morphology

    Directory of Open Access Journals (Sweden)

    MY Loqman

    2010-05-01

    Full Text Available The remarkable increase in chondrocyte volume is a major determinant in the longitudinal growth of mammalian bones. To permit a detailed morphological study of hypertrophic chondrocytes using standard histological techniques, the preservation of normal chondrocyte morphology is essential. We noticed that during fixation of growth plates with conventional fixative solutions, there was a marked morphological (shrinkage artifact, and we postulated that this arose from the hyper-osmotic nature of these solutions. To test this, we fixed proximal tibia growth plates of 7-day-old rat bones in either (a paraformaldehyde (PFA; 4%, (b glutaraldehyde (GA; 2% with PFA (2% with ruthenium hexamine trichloride (RHT; 0.7%, (c GA (2% with RHT (0.7%, or (d GA (1.3% with RHT (0.5% and osmolarity adjusted to a ‘physiological’ level of ~280mOsm. Using conventional histological methods, confocal microscopy, and image analysis on fluorescently-labelled fixed and living chondrocytes, we then quantified the extent of cell shrinkage and volume change. Our data showed that the high osmolarity of conventional fixatives caused a shrinkage artefact to chondrocytes. This was particularly evident when whole bones were fixed, but could be markedly reduced if bones were sagittally bisected prior to fixation. The shrinkage artefact could be avoided by adjusting the osmolarity of the fixatives to the osmotic pressure of normal extracellular fluids (~280mOsm. These results emphasize the importance of fixative osmolarity, in order to accurately preserve the normal volume/morphology of cells within tissues.

  10. Reducing beam hardening effects and metal artefacts using Medipix3RX: With applications from biomaterial science

    CERN Document Server

    Rajendran, K; de Ruiter, N J A; Chernoglazov, A I; Panta, R K; Butler, A P H; Butler, P H; Bell, S T; Anderson, N G; Woodfield, T B F; Tredinnick, S J; Healy, J L; Bateman, C J; Aamir, R; Doesburg, R M N; Renaud, P F; Gieseg, S P; Smithies, D J; Mohr, J L; Mandalika, V B H; Opie, A M T; Cook, N J; Ronaldson, J P; Nik, S J; Atharifard, A; Clyne, M; Bones, P J; Bartneck, C; Grasset, R; Schleich, N; Billinghurst, M

    2014-01-01

    This paper discusses methods for reducing beam hardening effects using spectral data for biomaterial applications. A small-animal spectral scanner operating in the diagnostic energy range was used. We investigate the use of photon-processing features of the Medipix3RX ASIC in reducing beam hardening and associated artefacts. A fully operational charge summing mode was used during the imaging routine. We present spectral data collected for metal alloy samples, its analysis using algebraic 3D reconstruction software and volume visualisation using a custom volume rendering software. Narrow high energy acquisition using the photon-processing detector revealed substantial reduction in beam hardening effects and metal artefacts.

  11. Reduction of metal artefacts in musculoskeletal imaging; Reduktion von Metallartefakten in der muskuloskelettalen Bildgebung

    Energy Technology Data Exchange (ETDEWEB)

    Sutter, Reto; Dietrich, Tobias [Universitaetsklinik Balgrist, Zuerich (Switzerland). Radiologie

    2016-06-15

    Joint replacement and other orthopaedic implants are utilized in many patients with musculoskeletal disorders. While these operations commonly show a good clinical result, a substantial number of patients need to undergo postoperative imaging during follow-up. The presence of orthopaedic implants induces severe metal artefacts at MRI and CT. We review several basic methods and advanced techniques for reducing metal artefacts at MRI and CT in order to enable a diagnostic examination in patients with metal implants. With the use of these techniques, MRI and CT are important and reliable modalities to examine patients with joint replacement and orthopaedic implants.

  12. Head and neck imaging with PET and PET/CT: artefacts from dental metallic implants

    Energy Technology Data Exchange (ETDEWEB)

    Goerres, Gerhard W.; Hany, Thomas F.; Kamel, Ehab; von Schulthess, Gustav K.; Buck, Alfred [Division of Nuclear Medicine, Department of Radiology, University Hospital Zurich (Switzerland)

    2002-03-01

    Germanium-68 based attenuation correction (PET{sub Ge68}) is performed in positron emission tomography (PET) imaging for quantitative measurements. With the recent introduction of combined in-line PET/CT scanners, CT data can be used for attenuation correction. Since dental implants can cause artefacts in CT images, CT-based attenuation correction (PET{sub CT}) may induce artefacts in PET images. The purpose of this study was to evaluate the influence of dental metallic artwork on the quality of PET images by comparing non-corrected images and images attenuation corrected by PET{sub Ge68} and PET{sub CT}. Imaging was performed on a novel in-line PET/CT system using a 40-mAs scan for PET{sub CT} in 41 consecutive patients with high suspicion of malignant or inflammatory disease. In 17 patients, additional PET{sub Ge68} images were acquired in the same imaging session. Visual analysis of fluorine-18 fluorodeoxyglucose (FDG) distribution in several regions of the head and neck was scored on a 4-point scale in comparison with normal grey matter of the brain in the corresponding PET images. In addition, artefacts adjacent to dental metallic artwork were evaluated. A significant difference in image quality scoring was found only for the lips and the tip of the nose, which appeared darker on non-corrected than on corrected PET images. In 33 patients, artefacts were seen on CT, and in 28 of these patients, artefacts were also seen on PET imaging. In eight patients without implants, artefacts were seen neither on CT nor on PET images. Direct comparison of PET{sub Ge68} and PET{sub CT} images showed a different appearance of artefacts in 3 of 17 patients. Malignant lesions were equally well visible using both transmission correction methods. Dental implants, non-removable bridgework etc. can cause artefacts in attenuation-corrected images using either a conventional {sup 68}Ge transmission source or the CT scan obtained with a combined PET/CT camera. We recommend that the

  13. Origin and compensation of imaging artefacts in localization-based super-resolution microscopy.

    Science.gov (United States)

    Erdélyi, M; Sinkó, J; Kákonyi, R; Kelemen, A; Rees, E; Varga, D; Szabó, G

    2015-10-15

    Interpretation of high resolution images provided by localization-based microscopy techniques is a challenge due to imaging artefacts that can be categorized by their origin. They can be introduced by the optical system, by the studied sample or by the applied algorithms. Some artefacts can be eliminated via precise calibration procedures, others can be reduced only below a certain value. Images studied both theoretically and experimentally are qualified either by pattern specific metrics or by a more general metric based on fluorescence correlation spectroscopy.

  14. A Comparative Performance Analysis of FDM Machines Based on a Calibration Artefact

    DEFF Research Database (Denmark)

    D'Angelo, Greta; Nielsen, Jakob Skov; Rasmussen, Jeppe

    2014-01-01

    During the past ten years Additive Manufacturing (AM) technologies have been constantly developing in terms of materials and processes. This allows the use of the AM not only during the preproduction but also for the manufacturing of final components for commercial use [1], [2]. However one...... and there are no standards to compare them with. To overcome this problem, a method to evaluate the performance of AM machine tools based on the printing of an artefact and the subsequent measuring of its features is proposed and shown. This paper shows a validation of the method by means of a laser interferometer....... Furthermore, different AM machines are tested using the printed artefact....

  15. Intraosseous secondary calcium salt crystal deposition: an artefact of acid decalcification.

    Science.gov (United States)

    Keen, C E; Crocker, P R; Brady, K; Buk, S J; Levison, D A

    1995-08-01

    We previously observed, in decalcificated bone specimens, intraosseous crystal deposits with morphological and analytical similarity to calcium pyrophosphate dihydrate. We have now been able, by a combination of more detailed morphological studies of these and similar cases, and by infrared spectroscopy in three cases, to show that this is, in fact deposition of the secondary calcium salts brushite and monetite, occurring as an artefact during formic acid decalcification. Our earlier postulate of bone as an additional primary crystallization site for calcium pyrophosphate dihydrate is effectively disproved. This artefact deserves wider recognition.

  16. Automatic artefact removal in a self-paced hybrid brain- computer interface system

    Directory of Open Access Journals (Sweden)

    Yong Xinyi

    2012-07-01

    Full Text Available Abstract Background A novel artefact removal algorithm is proposed for a self-paced hybrid brain-computer interface (BCI system. This hybrid system combines a self-paced BCI with an eye-tracker to operate a virtual keyboard. To select a letter, the user must gaze at the target for at least a specific period of time (dwell time and then activate the BCI by performing a mental task. Unfortunately, electroencephalogram (EEG signals are often contaminated with artefacts. Artefacts change the quality of EEG signals and subsequently degrade the BCI’s performance. Methods To remove artefacts in EEG signals, the proposed algorithm uses the stationary wavelet transform combined with a new adaptive thresholding mechanism. To evaluate the performance of the proposed algorithm and other artefact handling/removal methods, semi-simulated EEG signals (i.e., real EEG signals mixed with simulated artefacts and real EEG signals obtained from seven participants are used. For real EEG signals, the hybrid BCI system’s performance is evaluated in an online-like manner, i.e., using the continuous data from the last session as in a real-time environment. Results With semi-simulated EEG signals, we show that the proposed algorithm achieves lower signal distortion in both time and frequency domains. With real EEG signals, we demonstrate that for dwell time of 0.0s, the number of false-positives/minute is 2 and the true positive rate (TPR achieved by the proposed algorithm is 44.7%, which is more than 15.0% higher compared to other state-of-the-art artefact handling methods. As dwell time increases to 1.0s, the TPR increases to 73.1%. Conclusions The proposed artefact removal algorithm greatly improves the BCI’s performance. It also has the following advantages: a it does not require additional electrooculogram/electromyogram channels, long data segments or a large number of EEG channels, b it allows real-time processing, and c it reduces signal distortion.

  17. Radiographic artefact due to a faulty lead rubber shield

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, G. E-mail: gunasekarankumar@hotmail.com; Kamath, V.; Murali, S.R.; Temperley, D

    2003-05-01

    Radiographic examination is one of the commonest investigations performed in the field of Orthopaedics. There are several pitfalls to be kept in mind while interpreting radiographs in Orthopaedics. Bony or soft tissue lesions can be mimicked by anatomical variations, superimposition of soft tissues, inappropriate radiographic exposure and presence of external radio-opaque substances, to name a few. We present a case, where a faulty lead rubber shield mimicked a fracture of distal end of humerus. Early identification of these abnormalities can avoid distress to and unnecessary investigations of the patient.

  18. Minimally Invasive Parathyroidectomy

    Directory of Open Access Journals (Sweden)

    Lee F. Starker

    2011-01-01

    Full Text Available Minimally invasive parathyroidectomy (MIP is an operative approach for the treatment of primary hyperparathyroidism (pHPT. Currently, routine use of improved preoperative localization studies, cervical block anesthesia in the conscious patient, and intraoperative parathyroid hormone analyses aid in guiding surgical therapy. MIP requires less surgical dissection causing decreased trauma to tissues, can be performed safely in the ambulatory setting, and is at least as effective as standard cervical exploration. This paper reviews advances in preoperative localization, anesthetic techniques, and intraoperative management of patients undergoing MIP for the treatment of pHPT.

  19. The establishment of an in vitro gene bank in Dianthus spiculifolius Schur and D. glacialis ssp. gelidus (Schott Nym. et Kotschy Tutin: I. The initiation of a tissue collection and the characterization of the cultures in minimal growth conditions

    Directory of Open Access Journals (Sweden)

    Mihaela Holobiuc

    2009-12-01

    Full Text Available In the last decades the plants have to cope with the warming of the climate. As a consequence of this process more than half of the plant species could become vulnerable or threatened until 2080. Romania has a high plant diversity, with endemic and endangered plant species, the measures of biodiversity conservation being necessary. The integrated approach of biodiversity conservation involves both in situ and ex situ strategies. Among ex situ methods of conservation, besides the traditional ones (including field and botanic collection and seed banks, in vitro tissues techniques offer a viable alternative. The germplasm collections can efficiently preserve the species (of economic, scientific and conservative importance, in the same time being a source of plant material for international exchanges and for reintroduction in the native habitats.The "in vitro gene banking" term refers to in vitro tissues cultures from many accessions of a target species and involves the collection of plant material from field or from native habitats, the elaboration of sterilization, micropropagation and maintaining protocols. These collections have to be maintained in optimal conditions, morphologically and genetically characterized. The aim of our work was to characterize the response of the plant material to the minimal in vitro growth protocol for medium-term cultures achievement as a prerequisite condition for an active gene bank establishment in two rare Caryophyllaceae taxa: Dianthus spiculifolius and D. glacialis ssp. gelidus. Among different factors previously tested for medium-term preservation in Dianthus genus, mannitol proved to be more efficient for minimal cultures achievement. In vitro, the cultures were evaluated concerning their growth, regenerability and enzyme activity (POX, SOD, CAT as a response to the preservation conditions in the incipient phase of the initiation of the in vitro collection. The two species considered in this study showed a

  20. Human-competitive evolution of quantum computing artefacts by Genetic Programming.

    Science.gov (United States)

    Massey, Paul; Clark, John A; Stepney, Susan

    2006-01-01

    We show how Genetic Programming (GP) can be used to evolve useful quantum computing artefacts of increasing sophistication and usefulness: firstly specific quantum circuits, then quantum programs, and finally system-independent quantum algorithms. We conclude the paper by presenting a human-competitive Quantum Fourier Transform (QFT) algorithm evolved by GP.

  1. Student Engagement with Artefacts and Scientific Ideas in a Laboratory and a Concept-Mapping Activity

    Science.gov (United States)

    Mikael Hamza, Karim; Wickman, Per-Olof

    2013-09-01

    The purpose of this study is to use a comparative approach to scrutinize the common assumption that certain school science activities are theoretical and therefore particularly suited for engaging students with scientific ideas, whereas others are practical and, thus, not equally conducive to engagement with scientific ideas. We compared two school science activities, one (laboratory work) that is commonly regarded as focusing attention on artefacts that may distract students from central science concepts and the other (concept mapping) that is thought to make students focus directly on these concepts. We observed students in either a laboratory activity about real galvanic cells or a concept-mapping activity about idealized galvanic cells. We used a practical epistemology analysis to compare the two activities regarding students' actions towards scientific ideas and artefacts. The comparison revealed that the two activities, despite their alleged differences along the theory-practice scale, primarily resulted in similar student actions. For instance, in both activities, students interacted extensively with artefacts and, to a lesser extent, with scientific ideas. However, only occasionally did students establish any explicit continuity between artefacts and scientific ideas. The findings indicate that some of the problems commonly considered to be unique for school science practical work may indeed be a feature of school science activities more generally.

  2. Discovering new information from historical artefacts. Using electromagnetic radiation and charged particles as a probe

    Science.gov (United States)

    Macková, A.; Šmit, Ž.; Giuntini, L.

    2016-06-01

    Archaeological artefacts included in cultural heritage contribute to the knowledge of our roots, which may help us to learn about our future. Although the connection between ancient times and nuclear technology seems farfetched, this paper will try to show how nuclear radiation of various kinds can be irreplaceable in the elemental composition analysis of an archaeological find.

  3. Children, Multimedia Content and Technological Artefacts: An Exploratory Study Using Text Analysis Tools

    Science.gov (United States)

    Mazzoni, Elvis; Nicolò, Enrico; Sapio, Bartolomeo

    2015-01-01

    Purpose: This paper aims to investigate the user experience of young people with video content accessed through different technological artefacts. Design/methodology/approach: To this purpose, an essay has been assigned to the pupils of two lower secondary school classes (mean age 12 years) to know their diverse types of usage of multimedia…

  4. Beyond tokenistic participation: using representational artefacts to enable meaningful public participation in health service design.

    Science.gov (United States)

    Morrison, Cecily; Dearden, Andy

    2013-10-01

    A number of recent policies promote public participation in health service design. Yet, a growing literature has articulated a gap between policy aims and actual practice resulting in public participation becoming tokenistic. Drawing on theory from participatory design, we argue that choosing appropriate artefacts to act as representations can structure discussions between public participants and health professionals in ways that both groups find meaningful and valid. Through a case study of a service improvement project in outpatient services for older people, we describe three representational artefacts: emotion maps, stories, and tracing paper, and explain how they helped to mediate interactions between public participants and health professionals. We suggest that using such representational artefacts can provide an alternative approach to participation that stands in contrast to the current focus on the professionalisation of public participants. We conclude that including participatory designers in projects, to chose or design appropriate representational artefacts, can help to address the policy-practice gap of including public participants in health service design.

  5. Registration concepts for the just-in-time artefact correction by means of virtual computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Kasperl, St.; Franz, M. [Fraunhofer Development Center for X-ray Technology EZRT, a cooperative dept. of the Fraunhofer Institutes IZFP Saarbrucken and IIS Erlangen, Furth (Germany)

    2007-07-01

    This article deals with the enhancement of accuracy in CT by just-in-time correction of artefacts (beam hardening, scattered radiation) caused by the interaction of X-rays with matter. The so called EAR method needs for simulation a registration of the object. Therefore the article presents two different registration concepts. (authors)

  6. 3D Dose reconstruction: Banding artefacts in cine mode EPID images during VMAT delivery

    Science.gov (United States)

    Woodruff, H. C.; Greer, P. B.

    2013-06-01

    Cine (continuous) mode images obtained during VMAT delivery are heavily degraded by banding artefacts. We have developed a method to reconstruct the pulse sequence (and hence dose deposited) from open field images. For clinical VMAT fields we have devised a frame averaging strategy that greatly improves image quality and dosimetric information for three-dimensional dose reconstruction.

  7. Musculoskeletal colour/power Doppler in sports medicine: image parameters, artefacts, image interpretation and therapy

    DEFF Research Database (Denmark)

    Boesen, M I; Boesen, Mikael; Kønig, Merete Juhl

    2011-01-01

    guidelines and recommendations are based on personal experience since no evidence in literature exists. The basic technical background of Doppler ultrasound and typical artefacts will be discussed, in order to understand and interpret the Doppler result. Recommendations for the Doppler settings are given...

  8. From Governing through Data to Governmentality through Data: Artefacts, Strategies and the Digital Turn

    Science.gov (United States)

    Souto-Otero, Manuel; Beneito-Montagut, Roser

    2016-01-01

    The article argues that current discussions about governance through data in education can be fruitfully extended through: (1) the establishment of connections with wider debates about the role of commensuration processes and governmentality in the recreation of education systems; (2) greater emphasis on the "artefacts" through which…

  9. Persistent Artefacts in an Online Classroom: The Value of a Dynamic Learning Archive

    Science.gov (United States)

    Berry, Stuart C.

    2016-01-01

    This paper summarizes a multi-year research project that examines the use and value of visible and persistent artefacts within an online learning environment. This study is framed within elements of a business management theory. Changes to an online learning environment are documented as well as an examination of the impact of these changes on the…

  10. Mediation of Artefacts, Tools and Technical Objects: An International and French Perspective

    Science.gov (United States)

    Impedovo, Maria Antonietta; Andreucci, Colette; Ginestié, Jacques

    2017-01-01

    In this article we present a review of literature on the concept of Artefact, Tool and Technical Object in the light of sociocultural approach. Particular attention is given to present and discuss the French research tradition on the Technical Object and Technological education. The aim is to give a broad perspective to explore the mediation…

  11. Mediation of Artefacts, Tools and Technical Objects: An International and French Perspective

    Science.gov (United States)

    Impedovo, Maria Antonietta; Andreucci, Colette; Ginestié, Jacques

    2017-01-01

    In this article we present a review of literature on the concept of Artefact, Tool and Technical Object in the light of sociocultural approach. Particular attention is given to present and discuss the French research tradition on the Technical Object and Technological education. The aim is to give a broad perspective to explore the mediation…

  12. Skin movement artefact assessment and compensation in the estimation of knee-joint kinematics.

    Science.gov (United States)

    Lucchetti, L; Cappozzo, A; Cappello, A; Della Croce, U

    1998-11-01

    In three dimensional (3-D) human movement analysis using close-range photogrammetry, surface marker clusters deform and rigidly move relative to the underlying bone. This introduces an important artefact (skin movement artefact) which propagates to bone position and orientation and joint kinematics estimates. This occurs to the extent that those joint attitude components that undergo small variations result in totally unreliable values. This paper presents an experimental and analytical procedure, to be included in a subject-specific movement analysis protocol, which allows for the assessment of skin movement artefacts and, based on this knowledge, for their compensation. The effectiveness of this procedure was verified with reference to knee-joint kinematics and to the artefacts caused by the hip movements on markers located on the thigh surface. Quantitative validation was achieved through experimental paradigms whereby prior reliable information on the target joint kinematics was available. When position and orientation of bones were determined during the execution of a motor task, using a least-squares optimal estimator, but the rigid artefactual marker cluster movement was not dealt with, then knee joint translations and rotations were affected by root mean square errors (r.m.s.) up to 14 mm and 6 degrees, respectively. When the rigid artefactual movement was also compensated for, then r.m.s errors were reduced to less than 4 mm and 3 degrees, respectively. In addition, errors originally strongly correlated with hip rotations, after compensation, lost this correlation.

  13. From Governing through Data to Governmentality through Data: Artefacts, Strategies and the Digital Turn

    Science.gov (United States)

    Souto-Otero, Manuel; Beneito-Montagut, Roser

    2016-01-01

    The article argues that current discussions about governance through data in education can be fruitfully extended through: (1) the establishment of connections with wider debates about the role of commensuration processes and governmentality in the recreation of education systems; (2) greater emphasis on the "artefacts" through which…

  14. 3D Visualization of Cultural Heritage Artefacts with Virtual Reality devices

    Science.gov (United States)

    Gonizzi Barsanti, S.; Caruso, G.; Micoli, L. L.; Covarrubias Rodriguez, M.; Guidi, G.

    2015-08-01

    Although 3D models are useful to preserve the information about historical artefacts, the potential of these digital contents are not fully accomplished until they are not used to interactively communicate their significance to non-specialists. Starting from this consideration, a new way to provide museum visitors with more information was investigated. The research is aimed at valorising and making more accessible the Egyptian funeral objects exhibited in the Sforza Castle in Milan. The results of the research will be used for the renewal of the current exhibition, at the Archaeological Museum in Milan, by making it more attractive. A 3D virtual interactive scenario regarding the "path of the dead", an important ritual in ancient Egypt, was realized to augment the experience and the comprehension of the public through interactivity. Four important artefacts were considered for this scope: two ushabty, a wooden sarcophagus and a heart scarab. The scenario was realized by integrating low-cost Virtual Reality technologies, as the Oculus Rift DK2 and the Leap Motion controller, and implementing a specific software by using Unity. The 3D models were implemented by adding responsive points of interest in relation to important symbols or features of the artefact. This allows highlighting single parts of the artefact in order to better identify the hieroglyphs and provide their translation. The paper describes the process for optimizing the 3D models, the implementation of the interactive scenario and the results of some test that have been carried out in the lab.

  15. Artefacts and power corrections revisiting the MOM Z_psi and Z_V

    CERN Document Server

    Boucaud, P; Leroy, J P; Le Yaouanc, A; Micheli, J; Moutarde, H; Pène, O; Rodríguez-Quintero, J; Boucaud, Ph.

    2006-01-01

    We extract the power corrections due to the A^2 condensate in the overlap quark propagator (vector part of the inverse propagator Z_psi). The results are consistent with the previous gluon analysis. The role of artefacts is extensively discussed.

  16. Prospective ECG triggering reduces prosthetic heart valve-induced artefacts compared with retrospective ECG gating on 256-slice CT

    Energy Technology Data Exchange (ETDEWEB)

    Symersky, Petr [Academic Medical Center, Department of Cardiothoracic Surgery, Amsterdam (Netherlands); Habets, Jesse; Budde, Ricardo P.J. [University Medical Center Utrecht, Department of Radiology, Utrecht (Netherlands); Westers, Paul [University Medical Center Utrecht, Department of Biostatistics, Julius Center for Health Sciences and Primary Care, Utrecht (Netherlands); Mol, Bas A.J.M. de [Academic Medical Center, Department of Cardiothoracic Surgery, Amsterdam (Netherlands); University of Technology Eindhoven, Department of Biomedical Engineering, Eindhoven (Netherlands); Prokop, Mathias [Radboud University Nijmegen Medical Center, Department of Radiology, Nijmegen (Netherlands)

    2012-06-15

    Multidetector computed tomography (MDCT) has diagnostic value for the evaluation of prosthetic heart valve (PHV) dysfunction but it is hampered by artefacts. We hypothesised that image acquisition using prospective triggering instead of retrospective gating would reduce artefacts related to pulsating PHV. In a pulsatile in vitro model, a mono- and bileaflet PHV were imaged using 256 MDCT at 60, 75 and 90 beats per minute (BPM) with either retrospective gating (120 kV, 600 mAs, pitch 0.2, CTDI{sub vol} 39.8 mGy) or prospective triggering (120 kV, 200 mAs, CTDI{sub vol} 13.3 mGy). Two thresholds (>175 and <-45HU), derived from the density of surrounding structures, were used for quantification of hyper- and hypodense artefacts. Image noise and artefacts were compared between protocols. Prospective triggering reduced hyperdense artefacts for both valves at every BPM (P = 0.001 all comparisons). Hypodense artefacts were reduced for the monoleaflet valve at 60 (P = 0.009), 75 (P = 0.016) and 90 BPM (P = 0.001), and for the bileaflet valves at 60 (P = 0.001), 90 (P = 0.001) but not at 75 BPM (P = 0.6). Prospective triggering reduced image noise at 60 (P = 0.001) and 75 (P < 0.03) but not at 90 BPM. Compared with retrospective gating, prospective triggering reduced most artefacts related to pulsating PHV in vitro. circle Computed tomographic images are often degraded by prosthetic heart valve-induced artefacts circle Prospective triggering reduces prosthetic heart valve-induced artefacts in vitro circle Artefact reduction at 90 beats per minute occurs without image noise reduction circle Prospective triggering may improve CT image quality of moving hyperdense structures. (orig.)

  17. Modelling of polysomnographic respiratory measurements for artefact detection and signal restoration.

    Science.gov (United States)

    Rathnayake, S I; Abeyratne, U R; Hukins, C; Duce, B

    2008-09-01

    Polysomnography (PSG), which incorporates measures of sleep with measures of EEG arousal, air flow, respiratory movement and oxygenation, is universally regarded as the reference standard in diagnosing sleep-related respiratory diseases such as obstructive sleep apnoea syndrome. Over 15 channels of physiological signals are measured from a subject undergoing a typical overnight PSG session. The signals often suffer from data losses, interferences and artefacts. In a typical sleep scoring session, artefact-corrupted signal segments are visually detected and removed from further consideration. This is a highly time-consuming process, and subjective judgement is required for the job. During typical sleep scoring sessions, the target is the detection of segments of diagnostic interest, and signal restoration is not utilized for distorted segments. In this paper, we propose a novel framework for artefact detection and signal restoration based on the redundancy among respiratory flow signals. We focus on the air flow (thermistor sensors) and nasal pressure signals which are clinically significant in detecting respiratory disturbances. The method treats the respiratory system and other organs that provide respiratory-related inputs/outputs to it (e.g., cardiovascular, brain) as a possibly nonlinear coupled-dynamical system, and uses the celebrated Takens embedding theorem as the theoretical basis for signal prediction. Nonlinear prediction across time (self-prediction) and signals (cross-prediction) provides us with a mechanism to detect artefacts as unexplained deviations. In addition to detection, the proposed method carries the potential to correct certain classes of artefacts and restore the signal. In this study, we categorize commonly occurring artefacts and distortions in air flow and nasal pressure measurements into several groups and explore the efficacy of the proposed technique in detecting/recovering them. The results we obtained from a database of clinical

  18. The influence of metal artefacts on the range of ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Jaekel, Oliver; Reiss, Petra [German Cancer Research Center - Deutsches Krebsforschungszentrum, Division for Medical Physics in Radiotherapy (E040), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany)

    2007-02-07

    The influence of artefacts due to metal implants on the range of ion beams is investigated, using a geometrically well-defined head and pelvic phantom together with inserts from steel, titanium and tungsten. The ranges along various beam paths including artefacts were calculated from the TPS and compared to known calculations for phantoms without any insert. In the head phantom, beams intersecting the streak artefacts lead to errors in the range of around or below 1%, which is mainly due to a cancellation of various effects. Beams through the metal or close to it show an underestimation of 3.5% of the range for tungsten. For the pelvic phantom, a large underestimation of the range is observed for a lateral path through the metal insert. In the case of tungsten and steel, range errors of -5% and -18% are observed, respectively. Such beam paths are typically used for pelvic tumours in radiotherapy with ion beams. For beams in the anterior-posterior direction through the inserts, an overestimation of ion ranges of up to 3% for titanium and 8% for steel is expected, respectively. Beam paths outside the metal insert show a large cancellation for the lateral beams (leading to errors of around 1% only) and somewhat higher errors for anterior-posterior beams (around 3% for titanium and 6% for steel). The analysis of CT data of patients with dental implants of gold as compared to patients with healthy teeth also showed a significant effect of the artefacts on the distribution of HU in the data, namely a redistribution of HU to higher and lower values as compared to patients with healthy teeth. The corresponding mean range variation was a 2.5% reduction in the data with artefacts as compared to the data without artefacts. It is concluded that beam paths through metal implants should generally be avoided in proton and ion therapy. In this case, the underestimation of ion range due to artefacts alone may amount to 3% for dental fillings and up to 5% and 18% for hip prosthesis

  19. Correction of step artefact associated with MRI scanning of long bones.

    Science.gov (United States)

    Rathnayaka, Kanchana; Cowin, Gary; Schuetz, Michael A; Sahama, Tony; Schmutz, Beat

    2013-07-01

    3D models of long bones are being utilised for a number of fields including orthopaedic implant design. Accurate reconstruction of 3D models is of utmost importance to design accurate implants to allow achieving a good alignment between two bone fragments. Thus for this purpose, CT scanners are employed to acquire accurate bone data exposing an individual to a high amount of ionising radiation. Magnetic resonance imaging (MRI) has been shown to be a potential alternative to computed tomography (CT) for scanning of volunteers for 3D reconstruction of long bones, essentially avoiding the high radiation dose from CT. In MRI imaging of long bones, the artefacts due to random movements of the skeletal system create challenges for researchers as they generate inaccuracies in the 3D models generated by using data sets containing such artefacts. One of the defects that have been observed during an initial study is the lateral shift artefact occurring in the reconstructed 3D models. This artefact is believed to result from volunteers moving the leg during two successive scanning stages (the lower limb has to be scanned in at least five stages due to the limited scanning length of the scanner). As this artefact creates inaccuracies in the implants designed using these models, it needs to be corrected before the application of 3D models to implant design. Therefore, this study aimed to correct the lateral shift artefact using 3D modelling techniques. The femora of five ovine hind limbs were scanned with a 3T MRI scanner using a 3D vibe based protocol. The scanning was conducted in two halves, while maintaining a good overlap between them. A lateral shift was generated by moving the limb several millimetres between two scanning stages. The 3D models were reconstructed using a multi threshold segmentation method. The correction of the artefact was achieved by aligning the two halves using the robust iterative closest point (ICP) algorithm, with the help of the overlapping

  20. Soft tissue damage after minimally invasive THA

    NARCIS (Netherlands)

    van Oldenrijk, J.; Hoogland, P.V.J.M.; Tuijthof, G.J.M.; Corveleijn, R.; Noordenbos, T.W.H.; Schafroth, M.U.

    2010-01-01

    Methods 5 surgeons each performed a total hip arthroplasty on 5 fresh frozen cadaver hips, using either a MIS anterior, MIS anterolateral, MIS 2-incision, MIS posterior, or lateral transgluteal approach. Postoperatively, the hips were dissected and muscle damage color-stained. We measured proportion

  1. Soft tissue damage after minimally invasive THA

    NARCIS (Netherlands)

    van Oldenrijk, J.; Hoogland, P.V.J.M.; Tuijthof, G.J.M.; Corveleijn, R.; Noordenbos, T.W.H.; Schafroth, M.U.

    2010-01-01

    Methods 5 surgeons each performed a total hip arthroplasty on 5 fresh frozen cadaver hips, using either a MIS anterior, MIS anterolateral, MIS 2-incision, MIS posterior, or lateral transgluteal approach. Postoperatively, the hips were dissected and muscle damage color-stained. We measured proportion

  2. What is minimally invasive dentistry?

    Science.gov (United States)

    Ericson, Dan

    2004-01-01

    Minimally Invasive Dentistry is the application of "a systematic respect for the original tissue." This implies that the dental profession recognizes that an artifact is of less biological value than the original healthy tissue. Minimally invasive dentistry is a concept that can embrace all aspects of the profession. The common delineator is tissue preservation, preferably by preventing disease from occurring and intercepting its progress, but also removing and replacing with as little tissue loss as possible. It does not suggest that we make small fillings to restore incipient lesions or surgically remove impacted third molars without symptoms as routine procedures. The introduction of predictable adhesive technologies has led to a giant leap in interest in minimally invasive dentistry. The concept bridges the traditional gap between prevention and surgical procedures, which is just what dentistry needs today. The evidence-base for survival of restorations clearly indicates that restoring teeth is a temporary palliative measure that is doomed to fail if the disease that caused the condition is not addressed properly. Today, the means, motives and opportunities for minimally invasive dentistry are at hand, but incentives are definitely lacking. Patients and third parties seem to be convinced that the only things that count are replacements. Namely, they are prepared to pay for a filling but not for a procedure that can help avoid having one.

  3. Artefacts in multimodal imaging of titanium, zirconium and binary titanium-zirconium alloy dental implants: an in vitro study.

    Science.gov (United States)

    Smeets, Ralf; Schöllchen, Maximilian; Gauer, Tobias; Aarabi, Ghazal; Assaf, Alexandre T; Rendenbach, Carsten; Beck-Broichsitter, Benedicta; Semmusch, Jan; Sedlacik, Jan; Heiland, Max; Fiehler, Jens; Siemonsen, Susanne

    2017-02-01

    To analyze and evaluate imaging artefacts induced by zirconium, titanium and titanium-zirconium alloy dental implants. Zirconium, titanium and titanium-zirconium alloy implants were embedded in gelatin and MRI, CT and CBCT were performed. Standard protocols were used for each modality. For MRI, line-distance profiles were plotted to quantify the accuracy of size determination. For CT and CBCT, six shells surrounding the implant were defined every 0.5 cm from the implant surface and histogram parameters were determined for each shell. While titanium and titanium-zirconium alloy induced extensive signal voids in MRI owing to strong susceptibility, zirconium implants were clearly definable with only minor distortion artefacts. For titanium and titanium-zirconium alloy, the MR signal was attenuated up to 14.1 mm from the implant. In CT, titanium and titanium-zirconium alloy resulted in less streak artefacts in comparison with zirconium. In CBCT, titanium-zirconium alloy induced more severe artefacts than zirconium and titanium. MRI allows for an excellent image contrast and limited artefacts in patients with zirconium implants. CT and CBCT examinations are less affected by artefacts from titanium and titanium-zirconium alloy implants compared with MRI. The knowledge about differences of artefacts through different implant materials and image modalities might help support clinical decisions for the choice of implant material or imaging device in the clinical setting.

  4. BLADE sequences in transverse T2-weighted MR imaging of the cervical spine. Cut-off for artefacts?

    Energy Technology Data Exchange (ETDEWEB)

    Finkenzeller, T. [Hospital Nuremberg Sued (Germany). Inst. of Radiology and Neuroradiology; Wendl, C.M.; Stroszczynski, C.; Fellner, C. [University Hospital Regensburg (Germany). Inst. of Radiology; Lenhart, S. [Klinikum Weiden (Germany). Radiology and Neuroradiology; Schuierer, G. [Center of Neuroradiology, Regensburg (Germany). Inst. of Neuroradiology

    2015-02-15

    The BLADE (PROPELLER) technique reduces artefacts in imaging of the cervical spine in sagittal orientation, but till now failed to do so in axial orientation, because here it increased through plane CSF-flow artefacts, which spoiled the benefit of BLADE artefact reduction 'in plane'. The aim of this study was to compare a BLADE sequence with optimised measurement parameters in axial orientation to T2-TSE. Both sequences were compared in 58 patients with 31 discal, 16 bony and 11 spinal cord lesions. Image sharpness, reliability of spinal cord depiction, CSF flow artefacts and lesion detection were evaluated by 3 independent observers. Additionally the observers were asked which sequence they would prefer for diagnostic workup. Statistical evaluations were performed using sign and {sub X}2 test. BLADE was significantly superior concerning image sharpness, spinal cord depiction and overall lesion detection. BLADE was rated better for most pathologies, for bony lesions the differences compared with TSE were statistically significant. Regarding CSF-flow artefacts both sequences showed no difference. All readers preferred BLADE in side by side reading. An optimised axial T2 BLADE sequence decreases the problems of increased through plane CSF-flow artefacts in this orientation. By reducing various other artefacts it yields better image quality and has the potential to reduce the number of non-diagnostic examinations especially in uncooperative patients.

  5. First pass cable artefact correction for cardiac C-arm CT imaging.

    Science.gov (United States)

    Haase, C; Schäfer, D; Kim, M; Chen, S J; Carroll, J D; Eshuis, P; Dössel, O; Grass, M

    2014-07-21

    Cardiac C-arm CT imaging delivers a tomographic region-of-interest reconstruction of the patient's heart during image guided catheter interventions. Due to the limited size of the flat detector a volume image is reconstructed, which is truncated in the cone-beam (along the patient axis) and the fan-beam (in the transaxial plane) direction. To practically address this local tomography problem correction methods, like projection extension, are available for first pass image reconstruction. For second pass correction methods, like metal artefact reduction, alternative correction schemes are required when the field of view is limited to a region-of-interest of the patient. In classical CT imaging metal artefacts are corrected by metal identification in a first volume reconstruction and generation of a corrected projection data set followed by a second reconstruction. This approach fails when the metal structures are located outside the reconstruction field of view. When a C-arm CT is performed during a cardiac intervention pacing leads and other cables are frequently positioned on the patients skin, which results in propagating streak artefacts in the reconstruction volume. A first pass approach to reduce this type of artefact is introduced and evaluated here. It makes use of the fact that the projected position of objects outside the reconstruction volume changes with the projection perspective. It is shown that projection based identification, tracking and removal of high contrast structures like cables, only detected in a subset of the projections, delivers a more consistent reconstruction volume with reduced artefact level. The method is quantitatively evaluated based on 50 simulations using cardiac CT data sets with variable cable positioning. These data sets are forward projected using a C-arm CT system geometry and generate artefacts comparable to those observed in clinical cardiac C-arm CT acquisitions. A C-arm CT simulation of every cardiac CT data set without

  6. Reducing motion artefacts in diffusion-weighted MRI of the brain: efficacy of navigator echo correction and pulse triggering

    Energy Technology Data Exchange (ETDEWEB)

    Dietrich, O.; Heiland, S.; Benner, T.; Sartor, K. [Dept. of Neuroradiology, University of Heidelberg Medical School, Heidelberg (Germany)

    2000-02-01

    Diffusion-weighted MRI (DWI) is extremely sensitive to motion of the object being examined. Pulse triggering and navigator echo correction are methods for reducing motion artefacts which can be combined with conventional DWI sequences. Implementation of these methods in imaging sequences with a readout of one, three, or five echoes is presented and imaging results compared in a study of five healthy volunteers. As an objective measure for motion-induced image artefacts, the ''artefacticity'' of an image is defined. Pulse triggering and navigator echo correction significantly improve image quality and provide a technique for high-quality DWI on standard imagers without improved gradient hardware. (orig.)

  7. Novel artefact removal algorithms for co-registered EEG/fMRI based on selective averaging and subtraction.

    Science.gov (United States)

    de Munck, Jan C; van Houdt, Petra J; Gonçalves, Sónia I; van Wegen, Erwin; Ossenblok, Pauly P W

    2013-01-01

    Co-registered EEG and functional MRI (EEG/fMRI) is a potential clinical tool for planning invasive EEG in patients with epilepsy. In addition, the analysis of EEG/fMRI data provides a fundamental insight into the precise physiological meaning of both fMRI and EEG data. Routine application of EEG/fMRI for localization of epileptic sources is hampered by large artefacts in the EEG, caused by switching of scanner gradients and heartbeat effects. Residuals of the ballistocardiogram (BCG) artefacts are similarly shaped as epileptic spikes, and may therefore cause false identification of spikes. In this study, new ideas and methods are presented to remove gradient artefacts and to reduce BCG artefacts of different shapes that mutually overlap in time. Gradient artefacts can be removed efficiently by subtracting an average artefact template when the EEG sampling frequency and EEG low-pass filtering are sufficient in relation to MR gradient switching (Gonçalves et al., 2007). When this is not the case, the gradient artefacts repeat themselves at time intervals that depend on the remainder between the fMRI repetition time and the closest multiple of the EEG acquisition time. These repetitions are deterministic, but difficult to predict due to the limited precision by which these timings are known. Therefore, we propose to estimate gradient artefact repetitions using a clustering algorithm, combined with selective averaging. Clustering of the gradient artefacts yields cleaner EEG for data recorded during scanning of a 3T scanner when using a sampling frequency of 2048 Hz. It even gives clean EEG when the EEG is sampled with only 256 Hz. Current BCG artefacts-reduction algorithms based on average template subtraction have the intrinsic limitation that they fail to deal properly with artefacts that overlap in time. To eliminate this constraint, the precise timings of artefact overlaps were modelled and represented in a sparse matrix. Next, the artefacts were disentangled with

  8. The microbe-free plant: fact or artefact?

    Directory of Open Access Journals (Sweden)

    Laila P. Pamela Partida-Martinez

    2011-12-01

    Full Text Available Plant-microbe interactions are ubiquitous. Plants are often colonized by pathogens but even more commonly engaged in neutral or mutualistic interactions with microbes: below-ground microbial plant associates are mycorrhizal fungi, Rhizobia and rhizosphere bacteria, above-ground plant parts are colonized by bacterial and fungal endophytes and by microbes in the phyllosphere. We emphasize here that a completely microbe-free plant is an exotic exception rather than the biologically relevant rule. The complex interplay of such microbial communities with the host plant affects plant nutrition, growth rate, resistance to biotic and abiotic stress, and plant survival and distribution. The mechanisms involved reach from nutrient acquisition, the production of plant hormones or direct antibiosis to effects on host resistance genes or interactions at higher trophic levels. Plant-associated microbes are heterotrophic and cause costs to their host plant, whereas the benefits depend on the environment. Thus, the outcome of the interaction is highly context-dependent. Considering the microbe-free plant as the ‘normal’ or control stage significantly impairs research into important phenomena such as (1 phenotypic and epigenetic plasticity, (2 the ‘normal’ ecological outcome of a given interaction and (3 the evolution of plants. For the future, we suggest cultivation-independent screening methods using direct PCR from plant tissue of more than one fungal and bacterial gene to collect data on the true microbial diversity in wild plants. The patterns found could be correlated to host species and environmental conditions, in order to formulate testable hypotheses on the biological roles of plant endophytes in nature. Experimental approaches should compare different host-endophyte combinations under various environmental conditions and study at the genetic, transcriptional and physiological level the parameters that shift the interaction along the mutualism

  9. Modelling optical scattering artefacts for varying pathlength in a gel dosimeter phantom.

    Science.gov (United States)

    Bosi, Stephen G; Brown, Saxby; Sarabipour, Sarvenaz; De Deene, Yves; Baldock, Clive

    2009-01-21

    A gelatin phantom containing an optically scattering funnel-shaped region of elevated optical density (OD) was used to examine light-scattering-induced artefacts in a cone-beam optical CT scanner used for gel dosimetry. To simulate polymer gel dosimeters, the opacity was introduced by adding a colloidal scatterer to the gelatin. Scatter results in an underestimate of OD (hence dose). In line profiles of OD taken from 3D reconstructions of the funnel, those profiles with a long pathlength through high OD regions exhibited a 'dishing' (or 'cupping') artefact, while those of short pathlength exhibited the opposite effect-'doming'. These phenomena are accounted for by a model that includes the effect of stray, scattered light.

  10. Modelling optical scattering artefacts for varying pathlength in a gel dosimeter phantom

    Energy Technology Data Exchange (ETDEWEB)

    Bosi, Stephen G [Department of Radiation Oncology, Prince of Wales Hospital, Randwick, NSW 2031 (Australia); Brown, Saxby; Sarabipour, Sarvenaz; Baldock, Clive [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia); De Deene, Yves [Division of Radiotherapy, University Hospital of Ghent, de Pintelaan 185, 9000 Ghent (Belgium)], E-mail: s.bosi@physics.usyd.edu.au

    2009-01-21

    A gelatin phantom containing an optically scattering funnel-shaped region of elevated optical density (OD) was used to examine light-scattering-induced artefacts in a cone-beam optical CT scanner used for gel dosimetry. To simulate polymer gel dosimeters, the opacity was introduced by adding a colloidal scatterer to the gelatin. Scatter results in an underestimate of OD (hence dose). In line profiles of OD taken from 3D reconstructions of the funnel, those profiles with a long pathlength through high OD regions exhibited a 'dishing' (or 'cupping') artefact, while those of short pathlength exhibited the opposite effect-'doming'. These phenomena are accounted for by a model that includes the effect of stray, scattered light.

  11. Artefacts in Neutron CT - Their effects and how to Reduce some of Them

    Science.gov (United States)

    Schillinger, Burkhard; Grazzi, Francesco

    Neutron computed tomography relies on plain mathematical projections of the sample onto an ideal detector to reconstruct a three-dimensional model of the sample. However, several effects disturb this assumption, like buildup of afterglow on the scintillation screen, degradation of the screen during the measurement, background by neutrons scattered in the sample, and edge effects by reflection and refraction on sample edges and surfaces. Calculating a correct mathematical correction, e.g. using a point spread function, requires a lot of a priori knowledge about the sample and the detection system and cannot be given universally. This publication describes the observation of artefacts in neutron imaging and gives physical arguments for simple mathematical corrections to reduce, but not fully remove these artefacts in the reconstructed image. Often, awareness of these error sources is even more important than full removal.

  12. Titanium plate artefact mimicking popliteal artery dissection on digital subtraction CT angiography.

    Science.gov (United States)

    Woodacre, Timothy; Wienand-Barnett, Sophie

    2013-04-05

    Titanium plates used for the internal fixation of long bone fractures cause significant artefact on CT scans but have not been reported to affect digital subtraction CT angiography. We present a patient with clinical suspicion of popliteal artery injury following a high tibial osteotomy. The osteotomy was stabilised with a titanium locking plate. During the digital subtraction process used to produce reconstruction CT angiography, removal of artefact caused by the titanium plate produced CT images mimicking the appearance of a popliteal artery dissection. The imaging inaccuracy was realised prior to the patient undergoing further intervention. We highlight the potential error caused by titanium plates on digital subtraction CT angiography and recommend careful analysis of such images prior to further treatment.

  13. The fourth dimension of tool use: temporally enduring artefacts aid primates learning to use tools.

    Science.gov (United States)

    Fragaszy, D M; Biro, D; Eshchar, Y; Humle, T; Izar, P; Resende, B; Visalberghi, E

    2013-11-19

    All investigated cases of habitual tool use in wild chimpanzees and capuchin monkeys include youngsters encountering durable artefacts, most often in a supportive social context. We propose that enduring artefacts associated with tool use, such as previously used tools, partly processed food items and residual material from previous activity, aid non-human primates to learn to use tools, and to develop expertise in their use, thus contributing to traditional technologies in non-humans. Therefore, social contributions to tool use can be considered as situated in the three dimensions of Euclidean space, and in the fourth dimension of time. This notion expands the contribution of social context to learning a skill beyond the immediate presence of a model nearby. We provide examples supporting this hypothesis from wild bearded capuchin monkeys and chimpanzees, and suggest avenues for future research.

  14. The brain-artefact interface (BAI): a challenge for archaeology and cultural neuroscience.

    Science.gov (United States)

    Malafouris, Lambros

    2010-06-01

    Cultural neuroscience provides a new approach for understanding the impact of culture on the human brain (and vice versa) opening thus new avenues for cross-disciplinary collaboration with archaeology and anthropology. Finding new meaningful and productive unit of analysis is essential for such collaboration. But what can archaeological preoccupation with material culture and long-term change contribute to this end? In this article, I introduce and discuss the notion of the brain-artefact interface (BAI) as a useful conceptual bridge between neuroplastisty and the extended mind. I argue that a key challenge for archaeology and cultural neuroscience lies in the cross-disciplinary understanding of the processes by which our plastic enculturated brains become constituted within the wider extended networks of non-biological artefacts and cultural practices that delineate the real spatial and temporal boundaries of the human cognitive map.

  15. Corrosion of archaeological iron artefacts compared to modern iron at the waterlogged site Nydam, Denmark

    DEFF Research Database (Denmark)

    Matthiesen, Henning; Hilbert, Lisbeth Rischel; Gregory, David;

    2004-01-01

    loss, corrosion potential, electrochemical impedance spectroscopy and electrical resistivity. 3) Measurements of environmental parameter such as water level, redox potential, oxygen concentration, soil pH, and the concentration of a range of dissolved species in the pore water. This presentation shows...... focuses solely on the iron objects. A three-pronged approach has been used in the studies in Nydam: Studies of the excavated artefacts, including the compositon of corrosion products and a mapping of their exact state of preservation. 2) Use of modern iron samples placed in the soil for studies of weight...... some of the results obtained during the seven years of studies at the site. It is demonstrated how the three pronged approach is useful in understanding not only the current corrosion rate and threats against the artefacts but also the corrosion history, i.e. when were the deterioration patterns...

  16. The surface of cultural heritage artefacts: physicochemical investigations for their knowledge and their conservation.

    Science.gov (United States)

    Aucouturier, Marc; Darque-Ceretti, Evelyne

    2007-10-01

    This tutorial review intends to show, through demonstrative examples chosen from the recent literature, how surface characterisation conducted by modern investigation methods leads to very rich information on a cultural heritage artefact's history, fabrication techniques and conservation state. Application of surface science to conservation science is of great help for the definition of a conservation and restoration policy for museum and archaeological objects. A brief description of the investigation methods is given, together with relevant references for more detailed information.

  17. Diamond-like carbon coatings for the protection of metallic artefacts: effect on the aesthetic appearance

    Science.gov (United States)

    Faraldi, Federica; Angelini, Emma; Caschera, Daniela; Mezzi, Alessio; Riccucci, Cristina; Caro, Tilde De

    2014-03-01

    Plasma-enhanced chemical vapour deposition (PECVD) is an environmentally friendly process used to deposit a variety of nano-structured coatings for the protection or the surface modification of metallic artefacts like the SiO2-like films that have been successfully tested on ancient silver, bronze and iron artefacts as barriers against aggressive agents. This paper deals with the preliminary results of a wider investigation aimed to the development of eco-sustainable coatings for the protection of Cu and Ag-based artefacts of archaeological and historic interest. Diamond-like carbon (DLC) coatings have been deposited by PECVD in different experimental conditions, in a capacitively coupled asymmetric plasma reactor, placing the substrates either on electrically powered electrode (cathodic mode) or grounded electrode (anodic mode) with and without hydrogen addition in the gas mixture. The final goal is to develop a coating with good protective effectiveness against aggressive atmospheres and contemporarily with negligible effects on the aesthetic appearance of the artefacts. The evaluation of possible colour changes of the surface patinas, due to coating process, was performed by optical microscopy and colorimetric measurements. Furthermore, to evaluate the reversibility of the thin DLC layer, an etching treatment in oxygen plasma has been successfully carried out and optimized. The chemical-physical characterization of the deposited DLC coatings was performed by means of the combined use of micro-Raman and XPS spectroscopies. The results show that the DLC films obtained in the anodic mode, may be proposed as a viable alternative to polymeric coatings for the protection of metallic ancient objects.

  18. Respiratory motion artefacts in dynamic liver MRI: a comparison using gadoxetate disodium and gadobutrol

    Energy Technology Data Exchange (ETDEWEB)

    Luetkens, Julian A.; Kupczyk, Patrick A.; Doerner, Jonas; Willinek, Winfried A.; Schild, Hans H.; Kukuk, Guido M. [University of Bonn, Department of Radiology, Bonn (Germany); Fimmers, Rolf [University of Bonn, Department of Medical Biometry, Informatics, and Epidemiology, Bonn (Germany)

    2015-11-15

    Our aim was to retrospectively evaluate the occurrence of respiratory motion artefacts in patients undergoing dynamic liver magnetic resonance (MR) either with gadoxetate disodium or gadobutrol. Two hundred and thirty liver MR studies (115 with gadobutrol, 115 with gadoxetate disodium) were analysed. Respiratory motion artefacts on dynamic 3D T1-weighted MR images (pre-contrast, arterial, venous, and late-dynamic phase) were assessed using a five-point rating scale. Severe motion was defined as a score ≥ 4. Mean motion scores were compared with the Mann-Whitney-U-test. The chi-squared-test was used for dichotomous comparisons. Mean motion scores for gadoxetate disodium and gadobutrol showed no relevant differences for each phase of the dynamic contrast series (pre-contrast: 1.85 ± 0.70 vs. 1.88 ± 0.57, arterial: 1.85 ± 0.81 vs. 1.87 ± 0.74, venous: 1.82 ± 0.67 vs. 1.74 ± 0.64, late-dynamic: 1.75 ± 0.62 vs. 1.79 ± 0.63; p = 0.469, 0.557, 0.382 and 0.843, respectively). Severe motion artefacts had a similar incidence using gadoxetate disodium and gadobutrol (11/460 [2.4 %] vs. 7/460 [1.5 %]; p = 0.341). Gadoxetate disodium is associated with equivalent motion scores compared to gadobutrol in dynamic liver MRI. In addition, both contrast agents demonstrated a comparable and acceptable rate of severe respiratory motion artefacts. (orig.)

  19. In vitro axial preload application during spine flexibility testing: towards reduced apparatus-related artefacts.

    Science.gov (United States)

    Cripton, P A; Bruehlmann, S B; Orr, T E; Oxland, T R; Nolte, L P

    2000-12-01

    Presently, there is little consensus about how, or even if, axial preload should be incorporated in spine flexibility tests in order to simulate the compressive loads naturally present in vivo. Some preload application methods are suspected of producing unwanted "artefact" forces as the specimen rotates and, in doing so, influencing the resulting kinematics. The objective of this study was to quantitatively compare four distinct types of preload which have roots in contemporary experimental practice. The specific quantities compared were the reaction moments and forces resulting at the intervertebral disc and specimen kinematics. The preload types incorporated increasing amounts of caudal constraint on the preload application vector ranging from an unconstrained dead-load arrangement to an apparatus that allowed the vector to follow rotations of the specimen. Six human cadaveric spine segments were tested (1-L1/L2, 3-L2/L3, 1-L3/L4 and 1-L4/L5). Pure moments were applied to the specimens with each of the four different types of compressive preload. Kinematic response was measured using an opto-electronic motion analysis system. A six-axis load cell was used to measure reaction forces and moments. Artefact reaction moments and shear forces were significantly affected by preload application method and magnitude. Unconstrained preload methods produced high artefact moments and low artefact shear forces while more constrained methods did the opposite. A mechanical trade-off is suggested by our results, whereby unwanted moment can only be prevented at the cost of shear force production. When comparing spine flexibility studies, caution should be exercised to ensure preload was applied in a similar manner for all studies. Unwanted moments or forces induced as a result of preload application method may render the comparison of two seemingly similar studies inappropriate.

  20. Anoxic survival potential of bivalves: (arte)facts.

    Science.gov (United States)

    de Zwaan, Albertus; Babarro, Jose M F; Monari, Marta; Cattani, Otello

    2002-03-01

    that proliferation of anaerobic pathogenic bacteria, firmly associated with the bivalves, is a main cause of death besides lack of oxygen. Bacterial damage is probably caused by injury of the tissues of the clams and not by the release of noxious compounds to the medium.

  1. Composition and microstructure of Roman metallic artefacts of Southwestern Iberian Peninsula

    Science.gov (United States)

    Valério, P.; Voráčová, E.; Silva, R. J. C.; Araújo, M. F.; Soares, A. M. M.; Arruda, A. M.; Pereira, C.

    2015-10-01

    The Roman invasion introduces new alloys and metallurgical practices in Iberian Peninsula. The southwestern end of this region has many evidences of connections with the Roman World, but there are no studies about the manufacture and use of copper-based artefacts during this period. Therefore, a set of about 20 ornaments, tools and small attachments recovered at the Roman sites of Monte Molião and Cidade das Rosas was studied by an analytical approach combining micro-EDXRF, optical microscopy, SEM-EDS and Vickers microhardness testing. The artefact composition shows a good correlation with function, namely pure copper for nails and rivets, low-tin bronze (2-6 wt% Sn) for basic tools, high-tin bronze (14 wt% Sn) for fibulae and high-lead bronze (19 wt% Pb) for a decorated jug handle. The manufacture also depends on function because most artefacts were subjected to thermomechanical processing, except the ornaments that would not benefit from post-casting work. Brass and gunmetal were only present in the site with a later chronology. A metallurgy visibly ruled by economical, aesthetical and technological concerns reinforces the evidences about the total integration of Southwestern Iberian Peninsula in the Roman World, but further studies will be essential to determine the evolution of copper-based alloys in Lusitania under Roman influence.

  2. Evaluation of efficacy of metal artefact reduction technique using contrast media in Computed Tomography

    Science.gov (United States)

    Yusob, Diana; Zukhi, Jihan; Aziz Tajuddin, Abd; Zainon, Rafidah

    2017-05-01

    The aim of this study was to evaluate the efficacy of metal artefact reduction using contrasts media in Computed Tomography (CT) imaging. A water-based abdomen phantom of diameter 32 cm (adult body size) was fabricated using polymethyl methacrylate (PMMA) material. Three different contrast agents (iodine, barium and gadolinium) were filled in small PMMA tubes and placed inside a water-based PMMA adult abdomen phantom. The orthopedic metal screw was placed in each small PMMA tube separately. These two types of orthopedic metal screw (stainless steel and titanium alloy) were scanned separately. The orthopedic metal crews were scanned with single-energy CT at 120 kV and dual-energy CT at fast kV-switching between 80 kV and 140 kV. The scan modes were set automatically using the current modulation care4Dose setting and the scans were set at different pitch and slice thickness. The use of the contrast media technique on orthopedic metal screws were optimised by using pitch = 0.60 mm, and slice thickness = 5.0 mm. The use contrast media can reduce the metal streaking artefacts on CT image, enhance the CT images surrounding the implants, and it has potential use in improving diagnostic performance in patients with severe metallic artefacts. These results are valuable for imaging protocol optimisation in clinical applications.

  3. An Introduction To Multi-Battery Factor Analysis: Overcoming Method Artefacts.

    Directory of Open Access Journals (Sweden)

    Gavin T L Brown

    2007-05-01

    Full Text Available Examination of participants' responses to factor or scale scores provides useful insights, but analysis of such scores from multiple measures or batteries is sometimes confounded by methodological artefacts. This paper provides a short primer into the use of multi-trait, multi-method (MTMM correlational analysis and multi-battery factor analysis (MBFA. The principles of both procedures are outlined and a case study is provided from the author's research into 233 teachers' responses to 22 scale scores drawn from five batteries. The batteries were independently developed measures of teachers' thinking about the nature and purpose of assessment, teaching, learning, curriculum, and teacher efficacy. Detailed procedures for using Cudeck's (1982 MBFACT software are provided. Both MTMM and MBFA analyses identified an appropriate common trait across the five batteries, whereas joint factor analysis of the 22 scale scores confounded the common trait with a battery or method artefact. When researchers make use of multiple measures, they ought to take into account the impact of method artefacts when analyzing scale scores from multiple batteries. The multi-battery factor analysis procedure and MBFACT software provide a robust procedure for exploring how scales inter-relate.

  4. Studies on artefacts induced in the specimen preparation routines of electron microscopy characterization

    Science.gov (United States)

    Monikandan, V. V.; Joseph, M. A.; Rajendrakumar, P. K.

    2016-09-01

    Artefacts are induced during the preparation of specimens for electron microscopic characterization. The present work is a study of the artefacts induced on worn surfaces and wear debris specimens of AA6061-B4C-Gr hybrid composites. The worn surfaces are prepared using routines such as Focused Ion Beam (FIB) milling and ion milling. Apart from these routines, a novel trial is made to prepare the worn surface using femtosecond laser machining. The wear debris is pelletized and sectioned using ultramicrotome. In femtosecond laser machining, FIB milling and ion milling operations, melting and re-solidification of ablated debris, re-deposition and melting of sputtered debris and formation of the amorphous layer, respectively are the major artefacts that diminish the accuracy of the inferences made on the microstructural characteristics of the specimen. In ultramicrotomy, knife marks, tearing of sections and absence of wear debris distribution reduce the effectiveness of the routine, making it impossible to derive any substantial inference from the micrographs.

  5. Synchronizing the transcranial magnetic pulse with electroencephalographic recordings effectively reduces inter-trial variability of the pulse artefact

    DEFF Research Database (Denmark)

    Tomasevic, Leo; Takemi, Mitsuaki; Siebner, Hartwig Roman

    2017-01-01

    BACKGROUND: Electroencephalography (EEG) can capture the cortical response evoked by transcranial magnetic stimulation (TMS). The TMS pulse provokes a large artefact, which obscures the cortical response in the first milliseconds after TMS. Removing this artefact remains a challenge. METHODS: We...... were tested at 10 and 20 kHz using the head phantom. We also tested the effect of a soft sheet placed between the stimulation coil and recording electrodes in both human and melon. RESULTS & CONCLUSION: Synchronizing TMS and data acquisition markedly reduced trial-to-trial variability of the pulse......-to-trial variability renders it possible to create an artefact template for off-line filtering. Template-based subtraction of the artefact from the EEG signals is a prerequisite to effectively recover the immediate physiological response in the stimulated cortex and inter-connected areas....

  6. Gradient Artefact Correction and Evaluation of the EEG Recorded Simultaneously with fMRI Data Using Optimised Moving-Average

    Directory of Open Access Journals (Sweden)

    José L. Ferreira

    2016-01-01

    Full Text Available Over the past years, coregistered EEG-fMRI has emerged as a powerful tool for neurocognitive research and correlated studies, mainly because of the possibility of integrating the high temporal resolution of the EEG with the high spatial resolution of fMRI. However, additional work remains to be done in order to improve the quality of the EEG signal recorded simultaneously with fMRI data, in particular regarding the occurrence of the gradient artefact. We devised and presented in this paper a novel approach for gradient artefact correction based upon optimised moving-average filtering (OMA. OMA makes use of the iterative application of a moving-average filter, which allows estimation and cancellation of the gradient artefact by integration. Additionally, OMA is capable of performing the attenuation of the periodic artefact activity without accurate information about MRI triggers. By using our proposed approach, it is possible to achieve a better balance than the slice-average subtraction as performed by the established AAS method, regarding EEG signal preservation together with effective suppression of the gradient artefact. Since the stochastic nature of the EEG signal complicates the assessment of EEG preservation after application of the gradient artefact correction, we also propose a simple and effective method to account for it.

  7. Gradient Artefact Correction and Evaluation of the EEG Recorded Simultaneously with fMRI Data Using Optimised Moving-Average

    Science.gov (United States)

    Wu, Yan; Besseling, René M. H.; Lamerichs, Rolf; Aarts, Ronald M.

    2016-01-01

    Over the past years, coregistered EEG-fMRI has emerged as a powerful tool for neurocognitive research and correlated studies, mainly because of the possibility of integrating the high temporal resolution of the EEG with the high spatial resolution of fMRI. However, additional work remains to be done in order to improve the quality of the EEG signal recorded simultaneously with fMRI data, in particular regarding the occurrence of the gradient artefact. We devised and presented in this paper a novel approach for gradient artefact correction based upon optimised moving-average filtering (OMA). OMA makes use of the iterative application of a moving-average filter, which allows estimation and cancellation of the gradient artefact by integration. Additionally, OMA is capable of performing the attenuation of the periodic artefact activity without accurate information about MRI triggers. By using our proposed approach, it is possible to achieve a better balance than the slice-average subtraction as performed by the established AAS method, regarding EEG signal preservation together with effective suppression of the gradient artefact. Since the stochastic nature of the EEG signal complicates the assessment of EEG preservation after application of the gradient artefact correction, we also propose a simple and effective method to account for it. PMID:27446943

  8. Reduced artefacts and improved assessment of hyperintense brain lesions with BLADE MR imaging in patients with neurofibromatosis type 1

    Energy Technology Data Exchange (ETDEWEB)

    Kalle, Thekla von; Fabig-Moritz, Claudia; Mueller-Abt, Peter; Zieger, Michael; Winkler, Peter [Department of Paediatric Radiology, Stuttgart (Germany); Blank, Bernd [Haematology and Immunology, Department of Paediatric Oncology, Stuttgart (Germany); Wohlfarth, Katrin [Siemens Healthcare Sector, Erlangen (Germany)

    2009-11-15

    Assessment of small brain lesions in children is often compromised by pulsation, flow or movement artefacts. MRI with a rotating blade-like k-space covering (BLADE, PROPELLER) can compensate for these artefacts. We compared T2-weighted FLAIR images that were acquired with different k-space trajectories (conventional Cartesian and BLADE) to evaluate the impact of BLADE technique on the delineation of small or low-contrast brain lesions. The subject group comprised 26 children with neurofibromatosis type 1 (NF 1), who had been routinely scanned at 1.5 T for optic pathway gliomas with both techniques and who had the typical hyperintense brain lesions seen in NF 1. Four experienced radiologists retrospectively compared unlabelled 4-mm axial images with respect to the presence of artefacts, visibility of lesions, quality of contour and contrast. Both techniques were comparable in depicting hyperintense lesions as small as 2 mm independent of contrast and edge definition. Pulsation and movement artefacts were significantly less common with BLADE k-space trajectory. In 7 of 26 patients (27%), lesions and artefacts were rated as indistinguishable in conventional FLAIR, but not in BLADE FLAIR images. BLADE imaging significantly improved the depiction of lesions in T2-W FLAIR images due to artefact reduction especially in the posterior fossa. (orig.)

  9. Comparison and Combination of Dual-Energy- and Iterative-Based Metal Artefact Reduction on Hip Prosthesis and Dental Implants.

    Science.gov (United States)

    Bongers, Malte N; Schabel, Christoph; Thomas, Christoph; Raupach, Rainer; Notohamiprodjo, Mike; Nikolaou, Konstantin; Bamberg, Fabian

    2015-01-01

    To compare and combine dual-energy based and iterative metal artefact reduction on hip prosthesis and dental implants in CT. A total of 46 patients (women:50%,mean age:63±15years) with dental implants or hip prostheses (n = 30/20) were included and examined with a second-generation Dual Source Scanner. 120kV equivalent mixed-images were derived from reconstructions of the 100/Sn140kV source images using no metal artefact reduction (NOMAR) and iterative metal artefact reduction (IMAR). We then generated monoenergetic extrapolations at 130keV from source images without IMAR (DEMAR) or from source images with IMAR, (IMAR+DEMAR). The degree of metal artefact was quantified for NOMAR, IMAR, DEMAR and IMAR+DEMAR using a Fourier-based method and subjectively rated on a five point Likert scale by two independent readers. In subjects with hip prosthesis, DEMAR and IMAR resulted in significantly reduced artefacts compared to standard reconstructions (33% vs. 56%; for DEMAR and IMAR; respectively, pdental implants only IMAR showed a significant reduction of artefacts whereas DEMAR did not (71%, vs. 8% pprosthesis: 47%, dental implants 18%; both pdental implants, compared to a dual energy based method. The combination of DE-source images with IMAR and subsequent monoenergetic extrapolation provides an incremental benefit compared to both single methods.

  10. Compressed sensing for reduction of noise and artefacts in direct PET image reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Richter, Dominik; Israel, Ina; Schneider, Magdalena; Samnick, Samuel [Wuerzburg Univ. (Germany). Dept. of Nuclear Medicine; Basse-Luesebrink, Thomas C.; Kampf, Thomas; Jakob, Peter M. [Wuerzburg Univ. (Germany). Dept. of Experimental Physics 5; Fischer, Andre [Wuerzburg Univ. (Germany). Inst. of Radiology

    2014-03-01

    Aim: Image reconstruction in positron emission tomography (PET) can be performed using either direct or iterative methods. Direct reconstruction methods need a short reconstruction time. However, for data containing few counts, they often result in poor visual images with high noise and reconstruction artefacts. Iterative reconstruction methods such as ordered subset expectation maximization (OSEM) can lead to overestimation of activity in cold regions distorting quantitative analysis. The present work investigates the possibilities to reduce noise and reconstruction artefacts of direct reconstruction methods using compressed sensing (CS). Materials and methods: Raw data are generated either using Monte Carlo simulations using GATE or are taken from PET measurements with a Siemens Inveon small-animal PET scanner. The fully sampled dataset was reconstructed using filtered backprojection (FBP) and reduced in Fourier space by multiplication with an incoherently undersampled sampling pattern, followed by an additional reconstruction with CS. Different sampling patterns are used and an average of the reconstructions is taken. The images are compared to the results of an OSEM reconstruction and quantified using signal-to-noise ratio (SNR). Results: The application of the proposed CS post-processing technique clearly improves the image contrast. Dependent on the undersampling factor, noise and artefacts are reduced resulting in an SNR that is increased up to 3.4-fold. For short acquisition times with low count statistics the SNR of the CS reconstructed image exceeds the SNR of the OSEM reconstruction. Conclusion: Especially for low count data, the proposed CS-based post-processing method applied to FBP reconstructed PET images enhances the image quality significantly. (orig.)

  11. Planning Uncertainty: Creating an Artefact Density Index for North Yorkshire, England

    Directory of Open Access Journals (Sweden)

    Nick Boldrini

    2007-04-01

    Full Text Available Portable antiquities (sometimes known as small finds or chance finds are often recorded within most Historic Environment Records to a spurious level of precision. For example, finds located only within a parish, or general area, are often mapped within GIS systems to exact points. Similarly, finds known only to the nearest kilometre square are usually mapped in the bottom left-hand corner of the square in GIS. While such mappings can be taken into account to some extent when trying to assess the archaeological potential of an area, the degree to which the records may give distorted views of the archaeological potential of an area may not be fully appreciated. This may mean that the full archaeological impacts of development may not be taken into account during development control decision making. This article looks at an alternative method for mapping such finds in order to produce an Artefact Density Index for areas, which more usefully reflects the pattern of activities across the landscape. The Artefact Density Index (ADI was divided to reflect broad archaeological periods (e.g. Roman, medieval etc., as well as broad artefact types (e.g. weapons, tools etc.. The ADI was based on combining weighted values for finds types, with the weight reflecting the precision of the location of the finds (i.e. finds recorded only at parish level will be given less weight than those recorded more precisely. An ADI was developed for a sub-area of the North Yorkshire County Council HER area, and also incorporated data from the Portable Antiquities scheme as a case study for the project.

  12. An x-ray CT polymer gel dosimetry prototype: I. Remnant artefact removal.

    Science.gov (United States)

    Jirasek, A; Carrick, J; Hilts, M

    2012-05-21

    In this study a new x-ray CT polymer gel dosimetry (PGD) filtering technique is presented for the removal of (i) remnant ring and streak artefacts, and (ii) 'structured' noise in the form of minute, intrinsic gel density fluctuations. It is shown that the noise present within x-ray CT PGD images is not purely stochastic (pixel by pixel) in nature, but rather is 'structured', and hence purely stochastic-based noise-removal filters fail in removing this significant, unwanted noise component. The remnant artefact removal (RAR) technique is based on a class of signal stripping (i.e. baseline-estimation) algorithms typically used in the estimation of unwanted non-uniform baselines underlying spectral data. Here the traditional signal removal algorithm is recast, whereby the 'signal' that is removed is the structured noise and remnant artefacts, leaving the desired polymer gel dose distribution. The algorithm is extended to 2D and input parameters are optimized for PGD images. RAR filter results are tested on (i) synthetic images with measured gel background images added, in order to accurately represent actual noise present in PGD images, and (ii) PGD images of a three-field gel irradiation. RAR results are compared to a top-performing noise filter (adaptive mean, AM), used in previous x-ray CT PGD studies. It is shown that, in all cases, the RAR filter outperforms the AM filter, particularly in cases where either (i) a low-dose gel image has been acquired or (ii) the signal-to-noise ratio of the PG image is low, as in the case when a low number of image averages are acquired within a given experiment. Guidelines for the implementation of the RAR filter are given.

  13. Musculoskeletal colour/power Doppler in sports medicine: image parameters, artefacts, image interpretation and therapy

    DEFF Research Database (Denmark)

    Boesen, M I; Boesen, Mikael; Kønig, Merete Juhl;

    2010-01-01

    This review article discusses the aspects of sports medicine where musculoskeletal Doppler ultrasound has valuable contribution in diagnosis and/or treatment of some of the typical musculoskeletal sports injuries. Also, conditions where the Doppler ultrasound has no value are discussed. Some...... guidelines and recommendations are based on personal experience since no evidence in literature exists. The basic technical background of Doppler ultrasound and typical artefacts will be discussed, in order to understand and interpret the Doppler result. Recommendations for the Doppler settings are given...... in relevant sections. Ultrasound guided treatments where the Doppler result is used as a guide are mentioned and discussed....

  14. Development of Focused Ion Beam technique for high speed steel 3D-SEM artefact fabrication

    DEFF Research Database (Denmark)

    Carli, Lorenzo; MacDonald, A. Nicole; De Chiffre, Leonardo

    2009-01-01

    The work describes preliminary manufacture by grinding, followed by machining on a Focused Ion Beam (FIB), of a high speed steel step artefact for 3D-SEM calibration. The FIB is coupled with a SEM in the so called dual beam instrument. The milling capabilities of FIB were checked from a qualitati...... point of view, using the dual beam SEM imaging, and quantitatively using a reference stylus instrument, to establish traceability. A triangular section having a depth of about 10 μm was machined, where the 50 μm curvature radius due to grinding was reduced to about 2 μm by FIB milling...

  15. The fission-track analysis: An alternative technique for provenance studies of prehistoric obsidian artefacts

    CERN Document Server

    Bellot-Gurlet, L; Dorighel, O; Oddone, M; Poupeau, G; Yegingil, Z

    1999-01-01

    Comparison of fission-track parameters - age and track densities - is an alternative tool for correlating obsidian artefacts with their potential natural sources. This method was applied by different fission-track groups in various regions and results were compared with those obtained using the more popular provenance identification techniques based on chemical composition studies. Hundreds of analyses prove that fission-track dating is a complementary technique which turns out to be very useful, specially when the chemical composition does not fully discriminate different sources. Archaeologically significant results were obtained applying the fission-track analysis in various regions of earth.

  16. The use of radiation in the study of cultural heritage artefacts

    Science.gov (United States)

    Creagh, Dudley; Otieno-Alego, Vincent; Treasure, Alana; Kubik, Maria; Hallam, David

    2017-08-01

    Patrons of art galleries and museums, tourists visiting historic buildings, and sightseers viewing archaeological sites are generally unaware of the extent to which science and technology has contributed to the value of what they see. Many countries rely on cultural tourism to generate national wealth. The use of radiation of many kinds to assist in the conservation/restoration of cultural heritage artefacts is described in this paper. In particular, the paper will describe studies of the pigments used in historic Australian Indigenous art, the degradation of manuscripts written using iron-gall inks, the protection of statues against corrosion and the selection of lubricants for use in old machinery.

  17. Increasingly minimal bias routing

    Energy Technology Data Exchange (ETDEWEB)

    Bataineh, Abdulla; Court, Thomas; Roweth, Duncan

    2017-02-21

    A system and algorithm configured to generate diversity at the traffic source so that packets are uniformly distributed over all of the available paths, but to increase the likelihood of taking a minimal path with each hop the packet takes. This is achieved by configuring routing biases so as to prefer non-minimal paths at the injection point, but increasingly prefer minimal paths as the packet proceeds, referred to herein as Increasing Minimal Bias (IMB).

  18. Avoidance of harvesting and sampling artefacts in hydraulic analyses: a protocol tested on Malus domestica.

    Science.gov (United States)

    Beikircher, Barbara; Mayr, Stefan

    2016-06-01

    A prerequisite for reliable hydraulic measurements is an accurate collection of the plant material. Thereby, the native hydraulic state of the sample has to be preserved during harvesting (i.e., cutting the plant or plant parts) and preparation (i.e., excising the target section). This is particularly difficult when harvesting has to be done under transpiring conditions. In this article, we present a harvesting and sampling protocol designed for hydraulic measurements on Malus domestica Borkh. and checked for possible sampling artefacts. To test for artefacts, we analysed the percentage loss of hydraulic conductivity, maximum specific conductivity and water contents of bark and wood of branches, taking into account conduit length, time of day of harvesting, different shoot ages and seasonal effects. Our results prove that use of appropriate protocols can avoid artefactual embolization or refilling even when the xylem is under tension at harvest. The presented protocol was developed for Malus but may also be applied for other angiosperms with similar anatomy and refilling characteristics.

  19. Space invaders - A netnographic study of how artefacts in nursing home environments exercise disciplining structures.

    Science.gov (United States)

    Salzmann-Erikson, Martin

    2016-06-01

    This study aims to present culturally situated artefacts as depicted in nursing home environments and to analyse the underlying understandings of disciplining structures that are manifested in these kinds of places. Our personal geographies are often taken for granted, but when moving to a nursing home, geographies are glaringly rearranged. The study design is archival and cross-sectional observational, and the data are comprised of 38 photographs and 13 videos showing environments from nursing homes. The analysis was inspired by the methodological steps in Roper's and Shapira's description of conducting ethnography. The results are presented in four categories: (i) public areas, (ii) orderliness, (iii) staff's places and (iv) devices. The rearrangement of geography implies a degrading of agency and loss of authority over one's place. The places should be understood in their relation to the agents and their temporarily claims upon them. The material and immaterial artefacts, that is the items, people and behaviours, transform the nursing staff into 'space invaders'. Future inquiries may take into consideration the ways that space invasion in participative space intersect and construct the identities of the agents it invades upon.

  20. Calibration artefacts in radio interferometry. III. Phase-only calibration and primary beam correction

    CERN Document Server

    Grobler, T G; Wijnholds, S J; Kenyon, J S; Smirnov, O M

    2016-01-01

    This is the third installment in a series of papers in which we investigate calibration artefacts. Calibration artefacts (also known as ghosts or spurious sources) are created when we calibrate with an incomplete model. In the first two papers of this series we developed a mathematical framework which enabled us to study the ghosting mechanism itself. An interesting concomitant of the second paper was that ghosts appear in symmetrical pairs. This could possibly account for spurious symmetrization. Spurious symmetrization refers to the appearance of a spurious source (the anti-ghost) symmetrically opposite an unmodelled source around a modelled source. The analysis in the first two papers indicates that the anti-ghost is usually very faint, in particular when a large number of antennas are used. This suggests that spurious symmetrization will mainly occur at an almost undetectable flux level. In this paper, we show that phase-only calibration produces an anti-ghost that is $N$-times (where $N$ denotes the numb...

  1. Myocardial first-pass perfusion imaging with hybrid-EPI: frequency-offsets and potential artefacts

    Directory of Open Access Journals (Sweden)

    Ferreira Pedro F

    2012-06-01

    Full Text Available Abstract Background First-pass myocardial perfusion is often imaged with a tailored hybrid centric interleaved echo-planar-imaging sequence, providing rapid image acquisition with good contrast enhancement. The centric interleaved phase-encode order minimises the effective time-of-echo but it is sensitive to frequency-offsets. This short article aims to show possible artefacts that might originate with this sequence, in the context of first-pass perfusion imaging, when frequency-offsets are present. Non-uniform magnitude modulation effects were also analysed. Methods Numerical and phantom simulations were used to illustrate the effects of frequency-offsets and non-uniform magnitude modulation with this sequence in a typical perfusion protocol. In vivo data was post-processed to analyse the h-EPI’s sensitivity to the frequency-offsets. Results The centric phase-order was shown to be highly sensitive to frequency-offsets due to its symmetrical phase slope. Resulting artefacts include blurring, and splitting of the image into two identical copies along the phase-encode direction. It was also shown that frequency-offsets can introduce signal loss and ghosting of the right ventricle signal into the myocardium. The in vivo results were confirmed by numerical and phantom simulations. Magnitude modulation effects were found to be small. Conclusions Imaging first-pass myocardial perfusion with an hybrid centric echo-planar-imaging sequence can be corrupted with ghosting and splitting of the image due to frequency-offsets.

  2. Explorative Materiality and Knowledge. The Role of Creative Exploration and Artefacts in Design Research

    Directory of Open Access Journals (Sweden)

    Kristina Niedderer

    2013-08-01

    Full Text Available Juxtaposing the nature of design and the foundations of research in the traditional science and humanities disciplines puts their differences into sharp relief. The comparison highlights the key characteristics of design – its creative and experiential nature – which any design research must take into account, as well as the theoretical foundations of research. The aim of this article is to develop an understanding of the ontological, epistemological and methodological issues of design research, and to offer a framework that can embrace equally the notions of creativity and experiential knowledge, and of academic rigour. Furthermore,the potential roles of the design process and artefact within research are examined within this theoretical framework, which suggests that design processes and artefacts can – if appropriately framed – play an important partin the research process, facilitating an approach commensurate with the aims ofdesign enquiry. A case study of the Niedderer’s own work serves to illustratethe balance and integration of theory and (creative practice within the research process, and how this integration can enable a multi-layered contribution to the theoretical and practical advancement of the field.

  3. The Study of Prehistoric Artefacts in National Context: Belgian Archaeologists and the Problem of Ancient Stone Implements

    Directory of Open Access Journals (Sweden)

    Matthew R. Goodrum

    2013-09-01

    Full Text Available During the early nineteenth century European archaeologists were formulating new ideas about the significance of ancient stone artefacts. Some, such as Christian Thomsen in Copenhagen, believed that in Scandinavia, a Stone Age had preceded the Bronze and Iron Ages. In France some excavations had retrieved stone artefacts from deep levels of peat and cave deposits that suggested that these objects were of very great antiquity. While the collection and study of stone artefacts occurred across much of Europe, there were regional variations in their interpretation. Assisted by local institutions and motivated by patriotism, Belgian archaeologists who participated in this research, had much in common with their colleagues elsewhere in Europe, but the nature of local archaeological sites and the ideas of local researchers had an impact on the development and contributions of Belgian prehistoric archaeology.

  4. Electron tomography based on a total variation minimization reconstruction technique

    Energy Technology Data Exchange (ETDEWEB)

    Goris, B., E-mail: bart.goris@ua.ac.be [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Van den Broek, W. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Batenburg, K.J. [Centrum Wiskunde and Informatica, Science Park 123, NL-1098XG Amsterdam (Netherlands); Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium); Heidari Mezerji, H.; Bals, S. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium)

    2012-02-15

    The 3D reconstruction of a tilt series for electron tomography is mostly carried out using the weighted backprojection (WBP) algorithm or using one of the iterative algorithms such as the simultaneous iterative reconstruction technique (SIRT). However, it is known that these reconstruction algorithms cannot compensate for the missing wedge. Here, we apply a new reconstruction algorithm for electron tomography, which is based on compressive sensing. This is a field in image processing specialized in finding a sparse solution or a solution with a sparse gradient to a set of ill-posed linear equations. Therefore, it can be applied to electron tomography where the reconstructed objects often have a sparse gradient at the nanoscale. Using a combination of different simulated and experimental datasets, it is shown that missing wedge artefacts are reduced in the final reconstruction. Moreover, it seems that the reconstructed datasets have a higher fidelity and are easier to segment in comparison to reconstructions obtained by more conventional iterative algorithms. -- Highlights: Black-Right-Pointing-Pointer A reconstruction algorithm for electron tomography is investigated based on total variation minimization. Black-Right-Pointing-Pointer Missing wedge artefacts are reduced by this algorithm. Black-Right-Pointing-Pointer The reconstruction is easier to segment. Black-Right-Pointing-Pointer More reliable quantitative information can be obtained.

  5. Investigating the effect of modifying the EEG cap lead configuration on the gradient artefact in simultaneous EEG-fMRI

    Directory of Open Access Journals (Sweden)

    Karen J Mullinger

    2014-07-01

    Full Text Available EEG data recorded during simultaneous fMRI are contaminated by large voltages generated by time-varying magnetic field gradients. Correction of the resulting gradient artefact (GA generally involves low-pass filtering to attenuate the high-frequency voltage fluctuations of the GA, followed by subtraction of a GA template produced by averaging over repeats of the artefact waveforms. This average artefact subtraction (AAS process relies on the EEG amplifier having a large enough dynamic range to characterise the artefact voltages and on invariance of the artefact waveform over repeated image acquisitions. Saturation of the amplifiers and changes in subject position can leave unwanted residual GA after AAS. Previous modelling work suggested that modifying the lead layout and the exit position of the cable bundle on the EEG cap could reduce the GA amplitude.Here, we used simulations and experiments to evaluate the effect of modifying the lead paths on the magnitude of the GA and on the residual artefact after AAS. The modelling work showed that for wire paths following great circles, the smallest overall GA occurs when the leads converge at electrode Cz. The performance of this new cap design was compared with a standard cap in experiments on a spherical agar phantom and human subjects. Using gradient pulses applied separately along the three Cartesian axes, we found that the GA due to the foot-head gradient was most significantly reduced relative to a standard cap for the phantom, whereas the anterior-posterior GA was most attenuated for human subjects. In addition, there was an overall 37% reduction in the RMS GA amplitude produced by a standard EPI sequence when comparing the two caps on the phantom. In contrast, the subjects showed an 11% increase in the average RMS of the GA. This work shows that the optimal design reduces the GA on a spherical phantom however; these gains are not translated to human subjects, probably due to the differences in

  6. Influence of pulse sequence parameters at 1.5 T and 3.0 T on MRI artefacts produced by metal-ceramic restorations.

    Science.gov (United States)

    Cortes, A R G; Abdala-Junior, R; Weber, M; Arita, E S; Ackerman, J L

    2015-01-01

    Susceptibility artefacts from dental materials may compromise MRI diagnosis. However, little is known regarding MRI artefacts of dental material samples with the clinical shapes used in dentistry. The present phantom study aims to clarify how pulse sequences and sequence parameters affect MRI artefacts caused by metal-ceramic restorations. A phantom consisting of nickel-chromium metal-ceramic restorations (i.e. dental crowns and fixed bridges) and cylindrical reference specimens immersed in agar gel was imaged in 1.5 and 3.0 T MRI scanners. Gradient echo (GRE), spin echo (SE) and ultrashort echo time (UTE) pulse sequences were used. The artefact area in each image was automatically calculated from the pixel values within a region of interest. Mean values for similar pulse sequences differing in one parameter at a time were compared. A comparison between mean artefact area at 1.5 and 3.0 T, and from GRE and SE was also carried out. In addition, a parametric correlation between echo time (TE) and artefact area was performed. A significant correlation was found between TE and artefact area in GRE images. Higher receiver bandwidth significantly reduced artefact area in SE images. UTE images yielded the smallest artefact area at 1.5 T. In addition, a significant difference in mean artefact area was found between images at 1.5 and 3.0 T field strengths (p = 0.028) and between images from GRE and SE pulse sequences (p = 0.005). It is possible to compensate the effect of higher field strength on MRI artefacts by setting optimized pulse sequences for scanning patients with metal-ceramic restorations.

  7. Peering through the glare: using dual-energy CT to overcome the problem of metal artefacts in bone radiology

    Energy Technology Data Exchange (ETDEWEB)

    Coupal, Tyler M. [McMaster University, Michael G. DeGroote School of Medicine, Hamilton, ON (Canada); Mallinson, Paul I.; McLaughlin, Patrick; Nicolaou, Savvas; Munk, Peter L.; Ouellette, Hugue [Vancouver General Hospital, Radiology Department, Vancouver, BC (Canada)

    2014-05-15

    Imaging of patients with large metal implants remains one of the most difficult endeavours for radiologists. This article reviews the theory of dual-energy CT (DECT) and its ability to reduce metal artefact, thus enhancing the diagnostic value of musculoskeletal imaging. The strengths, weaknesses, and alternative applications of DECT, as well as areas requiring further research, will also be reviewed. Currently, DECT stands as the frontier for metal artefact reduction in musculoskeletal imaging. DECT requires no additional radiation and provides significantly enhanced image acquisition. When considered along with its other capabilities, DECT is a promising new tool for musculoskeletal and trauma radiologists. (orig.)

  8. Locally minimal topological groups

    OpenAIRE

    Außenhofer, Lydia; Chasco, María Jesús; Dikranjan, Dikran; Domínguez, Xabier

    2009-01-01

    A Hausdorff topological group $(G,\\tau)$ is called locally minimal if there exists a neighborhood $U$ of 0 in $\\tau$ such that $U$ fails to be a neighborhood of zero in any Hausdorff group topology on $G$ which is strictly coarser than $\\tau.$ Examples of locally minimal groups are all subgroups of Banach-Lie groups, all locally compact groups and all minimal groups. Motivated by the fact that locally compact NSS groups are Lie groups, we study the connection between local minimality and the ...

  9. Reduction of artefacts caused by hip implants in CT-based attenuation-corrected PET images using 2-D interpolation of a virtual sinogram on an irregular grid

    NARCIS (Netherlands)

    Abdoli, Mehrsima; de Jong, Johan R.; Pruim, Jan; Dierckx, Rudi A. J. O.; Zaidi, Habib

    2011-01-01

    Purpose Metallic prosthetic replacements, such as hip or knee implants, are known to cause strong streaking artefacts in CT images. These artefacts likely induce over-or underestimation of the activity concentration near the metallic implants when applying CT-based attenuation correction of positron

  10. On minimal round functions

    NARCIS (Netherlands)

    Khimshiashvili, G.; Siersma, D.

    2001-01-01

    We describe the structure of minimal round functions on closed surfaces and three-folds. The minimal possible number of critical loops is determined and typical non-equisingular round function germs are interpreted in the spirit of isolated line singularities. We also discuss a version of Lusternik-

  11. Bronze Age metal artefacts found on Cyprus - metal from Anatolia and the Western Mediterranean

    Directory of Open Access Journals (Sweden)

    Stos-Gale, Zofia A.

    2010-12-01

    Full Text Available Hundreds of Bronze Age metal artefacts excavated on archaeological sites in Cyprus have been analysed for their lead isotope and elemental composition in the Isotrace Laboratory, University of Oxford, in the years 1982-2002. In parallel, but in particular after 1995, hundreds of samples of minerals and slags collected from the mines and smelting sites around the Troodos Mountains were also analysed. Most of the results were published in various articles over the years, but the interpretation of some of the lead isotope data needs a current revision in view of new research conducted in Spain, Sardinia and southern France. It has been known that the lead isotope data for metal artefacts from the Cypriot Bronze Age sites shows that not all of the copper is consistent with origin from the Cypriot ores. In addition, the lead and silver artefacts found there must have been imported, because there are no lead or silver ores on Cyprus. The re-evaluation of the data shows that about 11 % of the analysed metal artefacts are consistent with the origin from the deposits in the Aegean and Turkey, while about 14 % with sources in the Western Mediterranean. This paper discusses in detail the current interpretation of the research into the sources of imported metal found in the Bronze Age context on Cyprus.

    Cientos de objetos de metal de la Edad del Bronce excavados en yacimientos de Chipre han sido analizados para conocer su composición elemental y sus isótopos de plomo en el Isotrace Laboratory de la Universidad de Oxford entre los años 1982 y 2002. Especialmente con posterioridad a 1995 cientos de muestras de minerales y escorias recogidas de minas y sitios de reducción de minerales localizadas en el entorno de las montañas de Troodos también fueron analizadas. La mayoría de los resultados fueron publicados en varios artículos a lo largo del tiempo, pero la interpretación de algunos análisis de isótopos de plomo necesitan de una revisión a

  12. Archaeometric study of artefacts from firing places of Longola-Poggiomarino protohystoric settlement site (Naples, Italy)

    Science.gov (United States)

    Balassone, G.; di Maio, G.; Barca, D.; Mormone, A.

    2009-04-01

    The Longola-Poggiomarino protohistoric village was discovered at west of Naples (southern Italy) in the year 2000, during the construction of a purification plant. It is located nearby the harbour of the Roman town of Pompeii and its age spans from the late Middle Bronze Age to the 6th century B.C., when the site was definitely abandoned (Cicirelli et al., 2006). This is a noteworthy discovery in southern Italy and in Europe, due to the peculiarity of its riverine location and the way in which it was constructed. In fact the village was built on many artificial small islands surrounded by a navigable canal network; hence it is surnamed "The prehistoric Venice". It is characterized by numerous evidences of human activities, like houses, pirogues, numerous objects and some handicraft working areas, where artefacts for domestic artisan and ornamental use were made (Salari et al., 2006). A great abundance of ceramics and metallic objects (made of diversified materials like lead, bronze, iron and gold) has been found, pointing to several distinct working/smelting sites throughout the village (Balassone et al., 2009). In these working sites, fair evidences of heating have been detected on several materials. In this work we characterized the compositional features of fifteen samples coming from firing places found at Longola, by means of a multi-analytical approach. Likely use of these findings could be coverings of burnt pavements, bricks or heat resistant vessel. The research aim is to contribute to the scenario reconstruction of this archaeological site by the knowledge of some production techniques, firing temperatures and provenance of raw materials. The microstructural features and modal mineralogy of the findings were determined by optical microscopy. X-ray diffraction, SEM-EDS and FTIR spectroscopy were used to determine and characterize overall mineral constituents and their quantitative composition. Representative findings were also analyzed for their whole

  13. Interaction of pulse laser radiation of 532 nm with model coloration layers for medieval stone artefacts

    Energy Technology Data Exchange (ETDEWEB)

    Colson, J. [University of Vienna, Department of Physical Chemistry, A-1090 Vienna (Austria); Nimmrichter, J. [Austrian Federal Office for the Care of Monuments, Department for Conservation and Restoration, Arsenal, Objekt 15, Tor 4, A-1030 Vienna (Austria); Kautek, W., E-mail: wolfgang.kautek@univie.ac.at [University of Vienna, Department of Physical Chemistry, A-1090 Vienna (Austria)

    2014-05-01

    Multilayer polychrome coatings on medieval and Renaissance stone artefacts represent substantial challenges in laser cleaning. Therefore, polychromic models with classical pigments, minium (Pb{sub 2}{sup 2+}Pb{sup 4+}O{sub 4}), zinc white (ZnO), and lead white ((PbCO{sub 3}){sub 2}·Pb(OH){sub 2}) in an acrylic binder, were irradiated with a Q-switched Nd:YAG laser emitting at 532 nm. The studied medieval pigments exhibit strongly varying incubation behaviours directly correlated to their band gap energies. Higher band gaps beyond the laser photon energy of 2.3 eV require more incubative generation of defects for resonant transitions. A matching of the modification thresholds after more than four laser pulses was observed. Laser cleaning with multiple pulsing should not exceed ca. 0.05 J/cm{sup 2} when these pigments coexist in close spatial proximity.

  14. The material variance of the Dead Sea Scrolls: On texts and artefacts

    Directory of Open Access Journals (Sweden)

    Eibert Tigchelaar

    2016-05-01

    Full Text Available What does a sacred text look like? Are religious books materially different from other books? Does materiality matter? This article deals with three different aspects of material variance attested amongst the Dead Sea Scrolls, Ancient Jewish religious text fragments, of which were found in the Judean Desert. I suggest that the substitution of the ancient Hebrew script by the everyday Aramaic script, also for Torah and other religious texts, was intentional and programmatic: it enabled the broader diffusion of scriptures in Hellenistic and Roman Judea. The preponderant use of parchment for religious texts rather than papyrus may be a marker of identity. The many small scrolls which contained only small parts of specific religious books (Genesis, Psalms may have been produced as religious artefacts which express identity in the period when Judaism developed into a religion of the book. Keywords: Dead Sea Scrolls; Judaism; Manuscripts

  15. Neutral particle lithography: a simple solution to charge-related artefacts in ion beam proximity printing

    Energy Technology Data Exchange (ETDEWEB)

    Wolfe, J C; Craver, B P [Department of Electrical and Computer Engineering and Nanosystem Manufacturing Center, University of Houston, Houston, TX 77204-4005 (United States)

    2008-01-21

    Neutral particle lithography (NPL) is a high resolution, proximity exposure technique where a broad beam of energetic neutral atoms floods a stencil mask and transmitted beamlets transfer the mask pattern to resist on a substrate. It preserves the advantages of ion beam lithography, including extremely large depth-of-field, sub-5 nm resist scattering, and the near absence of diffraction, yet is intrinsically immune to charge-related artefacts including line-edge roughness and pattern placement errors due to charge accumulation on the mask and substrate. This paper reviews the principles of NPL, surveys recent advances in the field and discusses applications involving insulating substrates, large proximity gaps or ultra-small features where the approach has particular advantages.

  16. The characterization of artefacts of cultural heritage significance using physical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Creagh, D.C. [Cultural Heritage Research Centre, Division of Science and Design, University of Canberra, Canberra ACT 2601 (Australia)]. E-mail: dcreagh@bigpond.net.eu

    2005-12-15

    All societies attempt to preserve their cultural heritage because it is this that gives them their identity. How artefacts are identified as being of significance to society, and how to preserve these for posterity, depend on the sophistication of those societies, their wealth, and the determination of members of the societies to preserve their past. If conservation or restoration measures are being undertaken complex analytical experiments must be undertaken beforehand to ensure that the work is being undertaken in an appropriate manner. These investigations may employ electromagnetic (IR, VIS, UV, X-ray, {gamma}-ray) or particulate (electron, proton, neutron, and ion beams) radiation. The use of many of these techniques is described in this paper in experiments on Australian Aboriginal bark paintings, a suit of armour belonging to a famous Australian outlaw, and the degradation of colour motion picture film.

  17. A detector combining quantum and thermal primary radiometric standards in the same artefact

    Science.gov (United States)

    White, M.; Gran, J.; Tomlin, N.; Lehman, J.

    2014-12-01

    We present the concept of a dual-mode primary standard cryogenic detector, utilizing a predictable quantum efficient silicon photodiode, and demonstrate the behaviour of the detector from room temperature down to 30 K. The detector absorbs visible radiation generating either heat or photocurrent, dependent on the selected mode of operation. In effect, this detector links optical power to fundamental constants through the two different routes of operation in the one artefact. Forward biasing of the photodiode is used in lieu of resistive heating to provide the electrical substitution power. The detector has a thermal time constant of 50 s and a sensitivity of 1.39 K mW-1. Using an LED source, we measure equivalence between the two modes of operation of 1.5% at 50 K, limited principally by our knowledge of the wavelength of the emitted radiation of the source.

  18. EVALUATING AND REFINING THE ‘ENTERPRISE ARCHITECTURE AS STRATEGY’ APPROACH AND ARTEFACTS

    Directory of Open Access Journals (Sweden)

    M. De Vries

    2012-01-01

    Full Text Available

    ENGLISH ABSTRACT: Enterprise Architecture (EA is a new discipline that has emerged from the need to create a holistic view of an enterprise, and thereby to discover business/IT integration and alignment opportunities across enterprise structures. Previous EA value propositions that merely focus on IT cost reductions will no longer convince management to invest in EA. Today, EA should enable business strategy in the organisation to create value. This resides in the ability to do enterprise optimisation through process standardisation and integration. In order to do this, a new approach is required to integrate EA into the strategy planning process of the organisation.
    This article explores the use of three key artefacts – operating models, core diagrams, and an operating maturity assessment as defined by Ross, Weill & Robertson [1] – as the basis of this new approach. Action research is applied to a research group to obtain qualitative feedback on the practicality of the artefacts.

    AFRIKAANSE OPSOMMING: Ondernemingsargitektuur (OA is ’n nuwe dissipline wat ontstaan het uit die behoefte om ’n holistiese perspektief van ’n onderneming te skep om sodoende besigheid/IT-integrasie en - belyningsgeleenthede regoor ondernemingstrukture te ontdek. Vorige OA waardeaanbiedings wat hoofsaaklik gefokus het op IT kostebesparings sal bestuur nie meer kan oorreed om in OA te belê nie. Vandag behoort OA bevoegdheid te gee aan ondernemingstrategie om werklik waarde te skep. Hierdie bevoegdheid lê gesetel in ondernemingsoptimering deur middel van prosesstandaardisasie en -integrasie. ’n Nuwe benadering word benodig ten einde OA te integreer met die strategiese beplanningsproses van die organisasie.
    Hierdie artikel ondersoek die gebruik van drie artefakte – operasionele modelle, kerndiagramme, en operasionele volwassenheidsassessering soos gedefinieer deur Ross, Weill & Robertson [1] – as die basis van hierdie nuwe benadering

  19. Protection of metal artefacts with the formation of metal-oxalates complexes by Beauveria bassiana.

    Directory of Open Access Journals (Sweden)

    Edith eJoseph

    2012-01-01

    Full Text Available Several fungi present high tolerance to toxic metals and some are able to transform metals into metal-oxalate complexes. In this study, the ability of Beauveria bassiana to produce copper oxalates was evaluated in vitro. Growth performance was tested on various copper-containing media. B. bassiana proved highly resistant to copper, tolerating concentrations of up to 20 g.L-1, and precipitating copper oxalates on all media tested. Chromatographic analyses showed that this species produced oxalic acid as sole metal chelator. The production of metal-oxalates can be used in the restoration and conservation of archaeological and modern metal artefacts. The production of copper-oxalates was confirmed directly using metallic pieces (both archaeological and modern. The conversion of corrosion products into copper oxalates was demonstrated as well. In order to assess whether the capability of B. bassiana to produce metal-oxalates could be applied to other metals, iron and silver were tested as well. Iron appears to be directly sequestered in the wall of the fungal hyphae forming oxalates and probably goethite. However, the formation of a homogeneous layer on the object is not yet optimal. Silver nitrate was extracellularly reduced into nanoparticles of elemental silver by an unknown mechanism. The production of copper oxalates is immediately applicable for the conservation of copper-based artefacts. For iron and silver this is not yet the case. However, the vast ability of B. bassiana to transform toxic metals using different immobilization mechanisms seems to offer considerable possibilities for industrial applications, such as the bioremediation of contaminated soils or the green synthesis of chemicals.

  20. A novel approach for removing the hook effect artefact from Electrical Bioimpedance spectroscopy measurements

    Science.gov (United States)

    Buendia, R.; Seoane, F.; Gil-Pita, R.

    2010-04-01

    Very often in Electrical Bioimpedance (EBI) spectroscopy measurements the presence of stray capacitances creates a measurement artefact commonly known as Hook Effect. Such an artefact creates a hook-alike deviation of the EBI data noticeable when representing the measurement on the impedance plane. Such Hook Effect is noticeable at high frequencies but it also causes a data deviation at lower measurement frequencies. In order to perform any accurate analysis of the EBI spectroscopy data, the influence of the Hook Effect must be removed. An established method to compensate the hook effect is the well known Td compensation, which consists on multiplying the obtained spectrum, Zmeas(ω) by a complex exponential in the form of exp[jωTd]. Such a method cannot correct entirely the Hook Effect since the hook-alike deviation occurs a broad frequency range in both magnitude and phase of the measured impedance, and by using a scalar value for Td. First a scalar only modifies the phase of the measured impedance and second, a single value can truly corrects the Hook Effect only at a single frequency. In addition, the process to select a value for the scalar Td by an iterative process with the aim to obtain the best Cole fitting lacks solid scientific grounds. In this work the Td compensation method is revisited and a modified approach for correcting the Hook Effect including a novel method for selecting the correcting values is proposed. The initial validation results confirm that the proposed method entirely corrects the Hook Effect at all frequencies.

  1. Quantitative assessment of chemical artefacts produced by propionylation of histones prior to mass spectrometry analysis.

    Science.gov (United States)

    Soldi, Monica; Cuomo, Alessandro; Bonaldi, Tiziana

    2016-07-01

    Histone PTMs play a crucial role in regulating chromatin structure and function, with impact on gene expression. MS is nowadays widely applied to study histone PTMs systematically. Because histones are rich in arginine and lysine, classical shot-gun approaches based on trypsin digestion are typically not employed for histone modifications mapping. Instead, different protocols of chemical derivatization of lysines in combination with trypsin have been implemented to obtain "Arg-C like" digestion products that are more suitable for LC-MS/MS analysis. Although widespread, these strategies have been recently described to cause various side reactions that result in chemical modifications prone to be misinterpreted as native histone marks. These artefacts can also interfere with the quantification process, causing errors in histone PTMs profiling. The work of Paternoster V. et al. is a quantitative assessment of methyl-esterification and other side reactions occurring on histones after chemical derivatization of lysines with propionic anhydride [Proteomics 2016, 16, 2059-2063]. The authors estimate the effect of different solvents, incubation times, and pH on the extent of these side reactions. The results collected indicate that the replacement of methanol with isopropanol or ACN not only blocks methyl-esterification, but also significantly reduces other undesired unspecific reactions. Carefully titrating the pH after propionic anhydride addition is another way to keep methyl-esterification under control. Overall, the authors describe a set of experimental conditions that allow reducing the generation of various artefacts during histone propionylation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. The concept of minimally invasive dentistry.

    Science.gov (United States)

    Ericson, Dan

    2007-01-01

    This paper reviews Minimally Invasive Dentistry (MID) from a day-to-day dentistry perspective, focusing mostly on cariology and restorative dentistry, even though it embraces many aspects of dentistry. The concept of MID supports a systematic respect for the original tissue, including diagnosis, risk assessment, preventive treatment, and minimal tissue removal upon restoration. The motivation for MID emerges from the fact that fillings are not permanent and that the main reasons for failure are secondary caries and filling fracture. To address these flaws, there is a need for economical re-routing so that practices can survive on maintaining dental health and not only by operative procedures.

  3. Automated correction of spin-history related motion artefacts in fMRI : Simulated and phantom data

    NARCIS (Netherlands)

    Muresan, Lucian; Renken, Remco; Roerdink, Jos B.T.M.; Duifhuis, Hendrikus

    2005-01-01

    This paper concerns the problem of correcting spin-history artefacts in fMRI data. We focus on the influence of through-plane motion on the history of magnetization. A change in object position will disrupt the tissue’s steady-state magnetization. The disruption will propagate to the next few acquir

  4. A (not so) dangerous method: pXRF vs. EPMA-WDS analyses of copper-based artefacts

    DEFF Research Database (Denmark)

    Orfanou, Vana; Rehren, Thilo

    2015-01-01

    Analysis of metal objects with portable and handheld X-ray fluorescence spectrometry has become increasingly popular in recent years. Here, methodological concerns that apply to non-destructive, surface examination with XRF instruments of ancient metal artefacts are discussed based on the compara...

  5. Correction of motion artefacts and pseudo colour visualization of multispectral light scattering images for optical diagnosis of rheumatoid arthritis

    Science.gov (United States)

    Minet, Olaf; Scheibe, Patrick; Beuthan, Jürgen; Zabarylo, Urszula

    2010-02-01

    State-of-the-art image processing methods offer new possibilities for diagnosing diseases using scattered light. The optical diagnosis of rheumatism is taken as an example to show that the diagnostic sensitivity can be improved using overlapped pseudo-coloured images of different wavelengths, provided that multispectral images are recorded to compensate for any motion related artefacts which occur during examination.

  6. Working with Artefacts: Gestures, Drawings and Speech in the Construction of the Mathematical Meaning of the Visual Pyramid

    Science.gov (United States)

    Maschietto, Michela; Bartolini Bussi, Maria G.

    2009-01-01

    This paper reports a part of a study on the construction of mathematical meanings in terms of development of semiotic systems (gestures, speech in oral and written form, drawings) in a Vygotskian framework, where artefacts are used as tools of semiotic mediation. It describes a teaching experiment on perspective drawing at primary school (fourth…

  7. The Role of Cultural Artefacts in Play as Tools to Mediate Learning in an Intercultural Preschool Programme

    Science.gov (United States)

    Hennig, Kelly; Kirova, Anna

    2012-01-01

    Starting with the research question "What is the role of play as a means of genuine inclusion of home language and cultural traditions in an intercultural early learning programme?", the article focuses on the role of cultural artefacts in a programme in which the majority of the children were refugees from Africa. The sociocultural theory of…

  8. The usefulness of ultrasound colour-Doppler twinkling artefact for detecting urolithiasis compared with low dose nonenhanced computerized tomography

    DEFF Research Database (Denmark)

    Winkel, Rikke Rass; Kalhauge, Anna; Fredfeldt, Knud-Erik

    2012-01-01

    This prospective study evaluates the usefulness of the twinkling artefact (TA) seen on colour-Doppler ultrasound (US) in diagnosing urolithiasis. US and standard computed tomography (CT) were performed blinded on 105 patients. B-mode US and colour-Doppler used separately and in combination showed...

  9. Minimally invasive paediatric cardiac surgery.

    Science.gov (United States)

    Bacha, Emile; Kalfa, David

    2014-01-01

    The concept of minimally invasive surgery for congenital heart disease in paediatric patients is broad, and has the aim of reducing the trauma of the operation at each stage of management. Firstly, in the operating room using minimally invasive incisions, video-assisted thoracoscopic and robotically assisted surgery, hybrid procedures, image-guided intracardiac surgery, and minimally invasive cardiopulmonary bypass strategies. Secondly, in the intensive-care unit with neuroprotection and 'fast-tracking' strategies that involve early extubation, early hospital discharge, and less exposure to transfused blood products. Thirdly, during postoperative mid-term and long-term follow-up by providing the children and their families with adequate support after hospital discharge. Improvement of these strategies relies on the development of new devices, real-time multimodality imaging, aids to instrument navigation, miniaturized and specialized instrumentation, robotic technology, and computer-assisted modelling of flow dynamics and tissue mechanics. In addition, dedicated multidisciplinary co-ordinated teams involving congenital cardiac surgeons, perfusionists, intensivists, anaesthesiologists, cardiologists, nurses, psychologists, and counsellors are needed before, during, and after surgery to go beyond apparent technological and medical limitations with the goal to 'treat more while hurting less'.

  10. FT-Raman and FT-Infrared investigations of archaeological artefacts from Foeni Neolithic site (Banat, Romania

    Directory of Open Access Journals (Sweden)

    Simona Cîntă Pînzaru

    2008-08-01

    Full Text Available An impressive collection of chert artefacts from the Foeni Neolithic archaeological site (Timiş County, Banat region, Romania is hosted by the Banat Museum in Timişoara. A representative set of seven specimens was non-destructively investigated using FT-Raman and ATR-FT-IR spectroscopy. The research was carried out for checking if these readily-available, non-destructive, fast, and cheap methods, which do not require preliminary sample preparation could provide significant information for characterizing the mineral composition of chert artefacts. Based on vibrational data, it was confirmed that the raw material was represented by microcrystalline quartz and moganite, with local concentrations of accessory minerals (calcite, dolomite, and clay minerals. In spite of their wide macroscopic heterogeneity (colour, transparency, based on single point FT-Raman measurements the chert artefacts could not be assigned to distinctive groups of raw silica materials, in order to provide specific arguments for provenance studies. However, the presence of specific accessory minerals (dolomite, illite pointed to distinctive genetic conditions in the case of one lithic material. Sets of measurements (mapping are required for statistically characterizing each artefact specimen. IR data were less significant, due to the rough surface texture of the specimens in contact with the ZnSe crystal of the ATR-FT-IR module. However, illite was identified based solely on its contribution to the IR spectrum. This pioneering study on chert artefacts from Romania based on optical spectroscopic methods shows that there are good premises for a systematic investigation of highly-valuable museum collections, in particular in terms of chert geology.

  11. Minimal change disease

    Science.gov (United States)

    ... get worse You develop new symptoms, including side effects from the medicines used to treat the disorder Alternative Names Minimal change nephrotic syndrome; Nil disease; Lipoid nephrosis; Idiopathic nephrotic syndrome of childhood Images ...

  12. Minimal Orderings Revisited

    Energy Technology Data Exchange (ETDEWEB)

    Peyton, B.W.

    1999-07-01

    When minimum orderings proved too difficult to deal with, Rose, Tarjan, and Leuker instead studied minimal orderings and how to compute them (Algorithmic aspects of vertex elimination on graphs, SIAM J. Comput., 5:266-283, 1976). This paper introduces an algorithm that is capable of computing much better minimal orderings much more efficiently than the algorithm in Rose et al. The new insight is a way to use certain structures and concepts from modern sparse Cholesky solvers to re-express one of the basic results in Rose et al. The new algorithm begins with any initial ordering and then refines it until a minimal ordering is obtained. it is simple to obtain high-quality low-cost minimal orderings by using fill-reducing heuristic orderings as initial orderings for the algorithm. We examine several such initial orderings in some detail.

  13. Minimal Markov Models

    CERN Document Server

    Gonzalez-Lopez, Jesus E Garcia Veronica A

    2010-01-01

    In this work we introduce a new and richer class of finite order Markov chain models and address the following model selection problem: find the Markov model with the minimal set of parameters (minimal Markov model) which is necessary to represent a source as a Markov chain of finite order. Let us call $M$ the order of the chain and $A$ the finite alphabet, to determine the minimal Markov model, we define an equivalence relation on the state space $A^{M}$, such that all the sequences of size $M$ with the same transition probabilities are put in the same category. In this way we have one set of $(|A|-1)$ transition probabilities for each category, obtaining a model with a minimal number of parameters. We show that the model can be selected consistently using the Bayesian information criterion.

  14. Ruled Laguerre minimal surfaces

    KAUST Repository

    Skopenkov, Mikhail

    2011-10-30

    A Laguerre minimal surface is an immersed surface in ℝ 3 being an extremal of the functional ∫ (H 2/K-1)dA. In the present paper, we prove that the only ruled Laguerre minimal surfaces are up to isometry the surfaces ℝ (φλ) = (Aφ, Bφ, Cφ + D cos 2φ) + λ(sin φ, cos φ, 0), where A,B,C,D ε ℝ are fixed. To achieve invariance under Laguerre transformations, we also derive all Laguerre minimal surfaces that are enveloped by a family of cones. The methodology is based on the isotropic model of Laguerre geometry. In this model a Laguerre minimal surface enveloped by a family of cones corresponds to a graph of a biharmonic function carrying a family of isotropic circles. We classify such functions by showing that the top view of the family of circles is a pencil. © 2011 Springer-Verlag.

  15. Minimal intervention dentistry - a new frontier in clinical dentistry.

    Science.gov (United States)

    Mm, Jingarwar; Nk, Bajwa; A, Pathak

    2014-07-01

    Minimally invasive procedures are the new paradigm in health care. Everything from heart bypasses to gall bladder, surgeries are being performed with these dynamic new techniques. Dentistry is joining this exciting revolution as well. Minimally invasive dentistry adopts a philosophy that integrates prevention, remineralisation and minimal intervention for the placement and replacement of restorations. Minimally invasive dentistry reaches the treatment objective using the least invasive surgical approach, with the removal of the minimal amount of healthy tissues. This paper reviews in brief the concept of minimal intervention in dentistry.

  16. Persistent Artefacts in an Online Classroom: The Value of a Dynamic Learning Archive | Artefacts persistants dans une salle de classe en ligne : la valeur d’une archive dynamique de l’apprentissage

    Directory of Open Access Journals (Sweden)

    Stuart C. Berry

    2016-04-01

    Full Text Available This paper summarizes a multi-year research project that examines the use and value of visible and persistent artefacts within an online learning environment. This study is framed within elements of a business management theory. Changes to an online learning environment are documented as well as an examination of the impact of these changes on the learning process. The study also shows the impact of learner engagement with artefacts over the life of multiple iterations of a course within this socially networked online learning space. Two significant outcomes emerged: 1. How the use of a socially networked online learning environment can offer a rich and supportive place for teaching and learning; and 2. That students in this study support the inclusion of an archive containing artefacts from learners in prior iterations of a course. The connection between the inclusion of this archive and the impact of a socially networked online learning environment will be demonstrated throughout. Cet article résume un projet de recherche sur plusieurs années, examinant l’utilisation et la valeur des artefacts visibles et persistants au sein d’un environnement d’apprentissage en ligne. Cette étude a été structurée selon des éléments d’une théorie de la gestion des affaires. Les modifications à l’environnement d’apprentissage en ligne sont documentées, ainsi que l’examen de l’incidence de ces modifications sur le processus d’apprentissage. L’étude montre aussi l’impact de l’engagement de l’apprenant avec les artefacts sur plusieurs itérations d’un cours dans un espace d’apprentissage en ligne doté de réseaux sociaux. Deux résultats importants ont émergé : 1. un espace d’apprentissage en ligne doté de réseaux sociaux peut offrir un endroit riche et soutenant pour l’enseignement et l’apprentissage; et 2. les étudiants dans cette étude sont favorables à l’inclusion d’une archive rassemblant les

  17. On the feasibility of establishing the provenance of Australian Aboriginal artefacts using synchrotron radiation X-ray diffraction and proton-induced X-ray emission

    Science.gov (United States)

    Creagh, D. C.; Kubik, M. E.; Sterns, M.

    2007-09-01

    Museums and galleries in Australia have extensive collections of Aboriginal artefacts in their custody. In particular, the National Museum of Australia and the National Gallery of Australia are custodians of works of very considerable significance, in both cultural and financial terms. Art fraud can occur, documentation relating to artefacts can be mislaid, or the artefacts can be incorrectly filed. Because of this, it has become essential to establish protocols for the objective determination of the provenance of artefacts through scientific tests. For the work reported here we are concerned with the comparison of very small quantities of materials, paint scrapings from artefacts. Scrapings from artefacts of unknown provenance are compared with those from artefacts of known provenance, and the database established using an extended set of analytical techniques by Kubik. We describe here our use of synchrotron radiation X-ray diffraction (SR-XRD) to determine the mineral phase compositions of very small amounts of pigment material (<50 μg), and the use of PIXE to give their atomic compositions to a threshold level of 1 ppm for similar masses of material.

  18. Towards a Knowledge Communication Perspective on Designing Artefacts Supporting Knowledge Work

    Directory of Open Access Journals (Sweden)

    Niclas Eberhagen

    2015-02-01

    Full Text Available The designing of computer-based artefacts to support knowledge work is far from a straightforward rational process. Characteristics of knowledge work have a bearing upon how developers (or designers, together with users, come to approach and capture the rich and tacit knowing of the practice. As all knowledge work is about the production of knowledge, transforming it, so is the design practice for developing artefacts to occupy space within that same practice. There is a need for providing a conceptual language to better reflect the nature of this design work that goes beyond those dressed in the managerial (or rational language of planned activities and deliverables. Towards this end, a conceptual frame is presented that makes several important aspects of the design practice visible. The frame brings together both nature of design work and characteristics of knowledge work to extend the frame of knowledge in user-developer communication of Kensing and Munk-Madsen. Thereby, providing a means to focus attention and dress debate on what situated designing is. By using explicit concepts, such as types knowledge domains embedded in the design situation, the transitional paths between them, and design engagements, it arms practitioners with specific linguistic constructs to direct attention and efforts in planning and organizing development undertakings.Purpose – the purpose of this work is to present and argue for a perspective on designing of computer-based artefacts supporting knowledge work. This is done to inform practitioners, directing their attention and dressing debate, and providing a conceptual language to better capture design activities in planning and organizing development undertakings.Design/Methodology/Approach – The approach presented in this article is conceptual in so far that a model or frame providing linguistic constructs is constructed and argued, building upon scholarly work of knowledge communication and drawing upon

  19. Locally minimal topological groups

    CERN Document Server

    enhofer, Lydia Au\\ss; Dikranjan, Dikran; Domínguez, Xabier

    2009-01-01

    A Hausdorff topological group $(G,\\tau)$ is called locally minimal if there exists a neighborhood $U$ of 0 in $\\tau$ such that $U$ fails to be a neighborhood of zero in any Hausdorff group topology on $G$ which is strictly coarser than $\\tau.$ Examples of locally minimal groups are all subgroups of Banach-Lie groups, all locally compact groups and all minimal groups. Motivated by the fact that locally compact NSS groups are Lie groups, we study the connection between local minimality and the NSS property, establishing that under certain conditions, locally minimal NSS groups are metrizable. A symmetric subset of an abelian group containing zero is said to be a GTG set if it generates a group topology in an analogous way as convex and symmetric subsets are unit balls for pseudonorms on a vector space. We consider topological groups which have a neighborhood basis at zero consisting of GTG sets. Examples of these locally GTG groups are: locally pseudo--convex spaces, groups uniformly free from small subgroups (...

  20. Adaptive Alternating Minimization Algorithms

    CERN Document Server

    Niesen, Urs; Wornell, Gregory

    2007-01-01

    The classical alternating minimization (or projection) algorithm has been successful in the context of solving optimization problems over two variables or equivalently of finding a point in the intersection of two sets. The iterative nature and simplicity of the algorithm has led to its application to many areas such as signal processing, information theory, control, and finance. A general set of sufficient conditions for the convergence and correctness of the algorithm is quite well-known when the underlying problem parameters are fixed. In many practical situations, however, the underlying problem parameters are changing over time, and the use of an adaptive algorithm is more appropriate. In this paper, we study such an adaptive version of the alternating minimization algorithm. As a main result of this paper, we provide a general set of sufficient conditions for the convergence and correctness of the adaptive algorithm. Perhaps surprisingly, these conditions seem to be the minimal ones one would expect in ...

  1. Minimal E$_{0}$-semigroups

    CERN Document Server

    Arveson, W

    1995-01-01

    It is known that every semigroup of normal completely positive maps of a von Neumann can be ``dilated" in a particular way to an E_0-semigroup acting on a larger von Neumann algebra. The E_0-semigroup is not uniquely determined by the completely positive semigroup; however, it is unique (up to conjugacy) provided that certain conditions of {\\it minimality} are met. Minimality is a subtle property, and it is often not obvious if it is satisfied for specific examples even in the simplest case where the von Neumann algebra is \\Cal B(H). In this paper we clarify these issues by giving a new characterization of minimality in terms projective cocycles and their limits. Our results are valid for semigroups of endomorphisms acting on arbitrary von Neumann algebras with separable predual.

  2. Trapeziometacarpal osteoarthrosis: clinical results and sonographic evaluation of the interposed tissue after trapeziectomy and first metacarpal suspension by external minifixation at a minimal two-year follow-up.

    Science.gov (United States)

    Putterie, G; Créteur, V; Mouraux, D; Robert, C; El-Kazzi, W; Schuind, F

    2014-02-01

    Among the surgical options to treat trapeziometacarpal osteoarthrosis, trapeziectomy has been criticized as unable to prevent postoperative collapse of the thumb, causing painful scapho-metacarpal impingement. The implantation of an external minifixator between the first and the second metacarpals for sufficient time has been proposed to maintain the postoperative space created by the bone resection to allow the development of a resistant interposed fibrous tissue. Nineteen patients (16 women, 3 men, mean age 64.5 years) were evaluated at 3.3 years of follow-up after an unilateral trapeziectomy and first metacarpal suspension by external minifixation. Eighty-four percent of the patients were very satisfied with the operation. The mean DASH score was 27.7%, the pain 1.7/10 (Visual Analogue Scale), the opening angle of the first web 58.3° and the Kapandji opposition score 9.5/10. Sonography demonstrated the existence of a strong fibrotic interposed tissue, preventing scapho-metacarpal impingement. The mean height of the trapeziectomy space (8.4mm) was maintained upon active pinch and maximal traction on the thumb. A significant atrophy of thenar muscles was also demonstrated, except for the Abductor pollicis brevis. In conclusion, total trapeziectomy with external minifixation provides acceptable clinical results, stabilizes the base of the thumb and prevents scapho-metacarpal impingement. The study brings also important new information about the nature of the interposed tissue in the trapezial space and about the state of the thenar muscles after trapeziectomy.

  3. The characterisation of non-evaporable getters by Auger electron spectroscopy Analytical potential and artefacts

    CERN Document Server

    Scheuerlein, C; Taborelli, M

    2002-01-01

    The surfaces of getter materials are particularly difficult to analyse because of their high chemical reactivity. The results obtained can be strongly influenced by the experimental set-up and procedures. In this paper the experimental influence on the Auger electron spectroscopy results is discussed, based on the measurements of more than 100 different non-evaporable getter (NEG) materials. There are four typical changes in the Auger electron spectra when a NEG becomes activated. The oxygen peak intensity decreases, the shape of the metal peaks changes, the carbon peak shape changes shape and intensity and a chlorine peak occurs. All these changes are affected by instrumental artefacts. The Zr-MNV peak shape changes occurring during the reduction of ZrO2 are well suited to determine the onset of NEG activation, while the slope with which the O-KLL peak intensity decreases in a certain temperature range is a better criterion for the determination of the temperature at which activation is complete. The O-KLL i...

  4. Dark-field electron holography for the mapping of strain in nanostructures: correcting artefacts and aberrations

    Energy Technology Data Exchange (ETDEWEB)

    Hytch, M J; Houdellier, F; Snoeck, E; Huee, F, E-mail: hytch@cemes.f [CEMES-CNRS, 29 rue Jeanne Marvig, 31055 Toulouse (France)

    2010-07-01

    We present details of the new electron holographic dark-field technique (HoloDark) for mapping strain in nanostructures. A diffracted beam emanating from an unstrained region of crystal is interfered (with the aid of an electrostatic biprism) with a diffracted beam from the strained region of interest. Geometric phase analysis (GPA) of the holographic fringes determines the relative deformation of the two crystalline lattices. Strain can be measured to high precision, with nanometre spatial resolution and for micron fields of view. Experiments are carried out on the SACTEM-Toulouse, a Tecnai F20 (FEI) equipped with imaging aberration corrector (CEOS), field-emission gun and rotatable biprism (FEI). We operate the microscope in free-lens control with the main objective lens switched off and using the corrector transfer lenses as a Lorentz lens. We will present measurements of strain in test nanostructures and show how artefacts from thickness variations can be removed. Finally, we show our first results using a recently developed aberration-corrected Lorentz mode (CEOS).

  5. Supporting BPMN choreography with system integration artefacts for enterprise process collaboration

    Science.gov (United States)

    Nie, Hongchao; Lu, Xudong; Duan, Huilong

    2014-07-01

    Business Process Model and Notation (BPMN) choreography modelling depicts externally visible message exchanges between collaborating processes of enterprise information systems. Implementation of choreography relies on designing system integration solutions to realise message exchanges between independently developed systems. Enterprise integration patterns (EIPs) are widely accepted artefacts to design integration solutions. If the choreography model represents coordination requirements between processes with behaviour mismatches, the integration designer needs to analyse the routing requirements and address these requirements by manually designing EIP message routers. As collaboration scales and complexity increases, manual design becomes inefficient. Thus, the research problem of this paper is to explore a method to automatically identify routing requirements from BPMN choreography model and to accordingly design routing in the integration solution. To achieve this goal, recurring behaviour mismatch scenarios are analysed as patterns, and corresponding solutions are proposed as EIP routers. Using this method, a choreography model can be analysed by computer to identify occurrences of mismatch patterns, leading to corresponding router selection. A case study demonstrates that the proposed method enables computer-assisted integration design to implement choreography. A further experiment reveals that the method is effective to improve the design quality and reduce time cost.

  6. The scope and limits of overimitation in the transmission of artefact culture.

    Science.gov (United States)

    Lyons, Derek E; Damrosch, Diana H; Lin, Jennifer K; Macris, Deanna M; Keil, Frank C

    2011-04-12

    Children are generally masterful imitators, both rational and flexible in their reproduction of others' actions. After observing an adult operating an unfamiliar object, however, young children will frequently overimitate, reproducing not only the actions that were causally necessary but also those that were clearly superfluous. Why does overimitation occur? We argue that when children observe an adult intentionally acting on a novel object, they may automatically encode all of the adult's actions as causally meaningful. This process of automatic causal encoding (ACE) would generally guide children to accurate beliefs about even highly opaque objects. In situations where some of an adult's intentional actions were unnecessary, however, it would also lead to persistent overimitation. Here, we undertake a thorough examination of the ACE hypothesis, reviewing prior evidence and offering three new experiments to further test the theory. We show that children will persist in overimitating even when doing so is costly (underscoring the involuntary nature of the effect), but also that the effect is constrained by intentionality in a manner consistent with its posited learning function. Overimitation may illuminate not only the structure of children's causal understanding, but also the social learning processes that support our species' artefact-centric culture.

  7. In situ structural characterisation of non stable phases involved in atmospheric corrosion of ferrous heritage artefacts

    Energy Technology Data Exchange (ETDEWEB)

    Burger, E.; Perrin, S. [CEA Saclay, DEN, DPC, SCCME, LECA, F-91191 Gif Sur Yvette (France); Burger, E.; Neff, D.; Faiz, H.; Dillmann, P. [CEA Saclay, UMR CEA CNRS, UMR 3299, IRAMIS, SIS2M, LAPA, F-91191 Gif Sur Yvette (France); Legrand, L. [Univ Evry, CNRS, LAMBE UMR8587, F-91025 Evry (France); Faiz, H. [Nancy Univ, Inst Jean Lamour, UMR CNRS 7198, Nancy (France); L' Hostis, V. [CEA Saclay, DEN, DPC, SCCME, LECBA, F-91191 Gif Sur Yvette (France); Dillmann, P. [CNRS, IRAMAT, LMC, UMR 5060, F-91191 Gif Sur Yvette (France)

    2010-07-01

    The prediction of very long term corrosion of iron and low alloy steel in atmospheric conditions or in hydraulic binder media is a crucial issue for the conservation and restoration of heritage artefacts. For both media, the typical iron corrosion product layers (CPL) can be described as a matrix of goethite ({alpha}-FeOOH) crossed by marbling of reactive phases: maghemite (gamma-Fe{sub 2}O{sub 3}), ferri-hydrite (Fe{sub 5}HO{sub 8}.4H{sub 2}O), feroxyhyte ({delta}-FeOOH), etc. The aim of the experiments presented here is to bring new insights on the role that the maghemite could potentially play in the mechanisms of corrosion. For that purpose, electrochemical reductions have been coupled with in situ Raman microspectroscopy. These experiments enable the authors to propose a hypothesis of local mechanisms in the specific case of marbling of maghemite connected to the metallic substrate. These local mechanisms could drastically influence the global corrosion rate. (authors)

  8. Barrier SiO2-like coatings for archaeological artefacts preservation

    Science.gov (United States)

    Prochazka, M.; Blahova, L.; Krcma, F.

    2016-10-01

    Thin film chemical vapour deposition technique has been used for more than 50 years. Introducing organo-silicones as precursors, e.g. hexamethyldisiloxane (HMDSO) or tetraethyl orthosilicate (TEOS), brought new possibilities to this method. Barrier properties of thin films have become an important issue, especially for army and emergency services as well as for food and drink manufacturers. Our work is focused on protective HMDSO thin films for encapsulating cleaned archaeological artefacts, preventing the corrosion from destroying these historical items.Thin films are deposited via plasma enhanced chemical vapour deposition (PECVD) technique using low pressure capacitively coupled pasma in flow regime. Oxygen transmission rate (OTR) measurement was chosen as the most important one for characterization of barrier properties of deposited thin films. Lowest OTR reached for 50 nm thin film thickness was 120 cm3 m-2 atm-1 day-1. Samples were also analyzed by Fourier Transform Infrared spectrometry (FTIR) to determine their composition. Optical emission spectra and thin film thickness were measured during the deposition process. We optimized the deposition parameters for barrier layers by implementation of pulsed mode of plasma and argon plasma pre-treatment into the process.

  9. Resonant Mie scattering in infrared spectroscopy of biological materials--understanding the 'dispersion artefact'.

    Science.gov (United States)

    Bassan, Paul; Byrne, Hugh J; Bonnier, Franck; Lee, Joe; Dumas, Paul; Gardner, Peter

    2009-08-01

    Infrared spectroscopic cytology is potentially a powerful clinical tool. However, in order for it to be successful, practitioners must be able to extract reliably a pure absorption spectrum from a measured spectrum that often contains many confounding factors. The most intractable problem to date is the, so called, dispersion artefact which most prominently manifests itself as a sharp decrease in absorbance on the high wavenumber side of the amide I band in the measured spectrum, exhibiting a derivative-like line shape. In this paper we use synchrotron radiation FTIR micro-spectroscopy to record spectra of mono-dispersed poly(methyl methacrylate) (PMMA) spheres of systematically varying size and demonstrate that the spectral distortions in the data can be understood in terms of resonant Mie scattering. A full understanding of this effect will enable us to develop strategies for deconvolving the scattering contribution and recovering the pure absorption spectrum, thus removing one of the last technological barriers to the development of clinical spectroscopic cytology.

  10. Registers of Artefacts of Creation—From the Late Medieval Period to the 19th Century

    Directory of Open Access Journals (Sweden)

    Chris Dent

    2014-06-01

    Full Text Available This paper offers a new perspective on the “development” of the intellectual property regimes in the United Kingdom. The system put in place under the 1875 Trade Marks Act may be seen as the last of a sequence of earlier “technologies” that sought to administer the creative endeavours of (sections of the English population. Prior to the trade mark registration (that included examination there was the registration of designs that did not require examination but was necessary for the protection of the right. In the eighteenth century, patent specifications were lodged with the Crown via a process that was much more involved than that was instituted for designs in the nineteenth century. Before that, books had to be enrolled with the Stationers’ Company before they could be printed. And, in what may be seen as an earlier attempt at the centralised regulation of artefacts of expression, the Rolls of Arms (maintained by the King of Arms was repository of coats of arms for English nobility. An exploration of these different technologies of regulation, in their socio-political context, will offer new insight into the antecedents, and limits, of the registration systems that are now common across the intellectual property world.

  11. Evaluation of reconstruction errors and identification of artefacts for JET gamma and neutron tomography

    Energy Technology Data Exchange (ETDEWEB)

    Craciunescu, Teddy, E-mail: teddy.craciunescu@jet.uk; Tiseanu, Ion; Zoita, Vasile [National Institute for Laser, Plasma and Radiation Physics, Magurele-Bucharest (Romania); Murari, Andrea [Consorzio RFX, Padova (Italy); Kiptily, Vasily; Sharapov, Sergei [CCFE Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Lupelli, Ivan [CCFE Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); University of Rome “Tor Vergata,” Roma (Italy); Fernandes, Ana [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa (Portugal); Collaboration: EUROfusion Consortium, JET, Culham Science Centre, Abingdon OX14 3DB (United Kingdom)

    2016-01-15

    The Joint European Torus (JET) neutron profile monitor ensures 2D coverage of the gamma and neutron emissive region that enables tomographic reconstruction. Due to the availability of only two projection angles and to the coarse sampling, tomographic inversion is a limited data set problem. Several techniques have been developed for tomographic reconstruction of the 2-D gamma and neutron emissivity on JET, but the problem of evaluating the errors associated with the reconstructed emissivity profile is still open. The reconstruction technique based on the maximum likelihood principle, that proved already to be a powerful tool for JET tomography, has been used to develop a method for the numerical evaluation of the statistical properties of the uncertainties in gamma and neutron emissivity reconstructions. The image covariance calculation takes into account the additional techniques introduced in the reconstruction process for tackling with the limited data set (projection resampling, smoothness regularization depending on magnetic field). The method has been validated by numerically simulations and applied to JET data. Different sources of artefacts that may significantly influence the quality of reconstructions and the accuracy of variance calculation have been identified.

  12. Achieving Closed-Loop Control Simulation of Human-Artefact Interaction: A Comparative Review

    Directory of Open Access Journals (Sweden)

    Wilhelm Frederik van der Vegte

    2011-01-01

    Full Text Available To include user interactions in simulations of product use, the most common approach is to couple human subjects to simulation models, using hardware interfaces to close the simulation-control loop. Testing with virtual human models could offer a low-cost addition to evaluation with human subjects. This paper explores the possibilities for coupling human and artefact models to achieve fully software-based interaction simulations. We have critically reviewed existing partial solutions to simulate or execute control (both human control and product-embedded control and compared solutions from literature with a proof-of-concept we have recently developed. Our concept closes all loops, but it does not rely on validated algorithms to predict human decision making and low-level human motor control. For low-level control, validated solutions are available from other approaches. For human decision making, however, validated algorithms exist only to predict the timing but not the reasoning behind it. To identify decision-making schemes beyond what designers can conjecture, testing with human subjects remains indispensable.

  13. Comparative Laser Spectroscopy Diagnostics for Ancient Metallic Artefacts Exposed to Environmental Pollution

    Directory of Open Access Journals (Sweden)

    Łukasz Ciupiński

    2010-05-01

    Full Text Available Metal artworks are subjected to corrosion and oxidation processes due to reactive agents present in the air, water and in the ground that these objects have been in contact with for hundreds of years. This is the case for archaeological metals that are recovered from excavation sites, as well as artefacts exposed to polluted air. Stabilization of the conservation state of these objects needs precise diagnostics of the accrued surface layers and identification of original, historical materials before further protective treatments, including safe laser cleaning of unwanted layers. This paper presents analyses of the chemical composition and stratigraphy of corrosion products with the use of laser induced breakdown spectroscopy (LIBS and Raman spectroscopy. The discussion of the results is supported by material studies (SEM-EDS, XRF, ion-analyses. The tests were performed on several samples taken from original objects, including copper roofing from Wilanów Palace in Warsaw and Karol Poznański Palace in Łódź, bronze decorative figures from the Wilanów Palace gardens, and four archaeological examples of old jewellery (different copper alloys. Work has been performed as a part of the MATLAS project in the frames of EEA and Norway Grants (www.matlas.eu and the results enable the comparison of the methodology and to elaborate the joint diagnostic procedures of the three project partner independent laboratories.

  14. Comparative Laser Spectroscopy Diagnostics for Ancient Metallic Artefacts Exposed to Environmental Pollution

    Science.gov (United States)

    Ciupiński, Łukasz; Fortuna-Zaleśna, Elżbieta; Garbacz, Halina; Koss, Andrzej; Kurzydłowski, Krzysztof J.; Marczak, Jan; Mróz, Janusz; Onyszczuk, Tomasz; Rycyk, Antoni; Sarzyński, Antoni; Skrzeczanowski, Wojciech; Strzelec, Marek; Zatorska, Anna; Żukowska, Grażyna Z.

    2010-01-01

    Metal artworks are subjected to corrosion and oxidation processes due to reactive agents present in the air, water and in the ground that these objects have been in contact with for hundreds of years. This is the case for archaeological metals that are recovered from excavation sites, as well as artefacts exposed to polluted air. Stabilization of the conservation state of these objects needs precise diagnostics of the accrued surface layers and identification of original, historical materials before further protective treatments, including safe laser cleaning of unwanted layers. This paper presents analyses of the chemical composition and stratigraphy of corrosion products with the use of laser induced breakdown spectroscopy (LIBS) and Raman spectroscopy. The discussion of the results is supported by material studies (SEM-EDS, XRF, ion-analyses). The tests were performed on several samples taken from original objects, including copper roofing from Wilanów Palace in Warsaw and Karol Poznański Palace in ŁódŸ, bronze decorative figures from the Wilanów Palace gardens, and four archaeological examples of old jewellery (different copper alloys). Work has been performed as a part of the MATLAS project in the frames of EEA and Norway Grants (www.matlas.eu) and the results enable the comparison of the methodology and to elaborate the joint diagnostic procedures of the three project partner independent laboratories. PMID:22399915

  15. Raman study of diamond-based abrasives, and possible artefacts in detecting UHP microdiamond

    Science.gov (United States)

    Nasdala, Lutz; Steger, Simon; Reissner, Claudia

    2016-11-01

    Raman spectral characteristics of a range of diamond-based abrasives (powders and sprays) and drilling and cutting tools, originating from preparation laboratories worldwide, are presented. Some abrasives show strong broadening of the main diamond band [FWHM (full width at half band-maximum) > 5 cm- 1] accompanied by strong band-downshift (ν˜ = 1316-1330 cm- 1). Others are characterised by moderate band broadening (FWHM = 1.8-5 cm- 1) at rather regular band position (ν˜ = 1331-1333 cm- 1). In addition we found that a ;fresh; abrasive and its used analogue may in some cases show vast differences in their Raman spectra. The Raman parameters of diamond-based abrasives overlap widely with Raman parameters of UHP (ultra-high pressure) microdiamond. It is hence impossible to assign diamond detected in a geological specimen to either an introduced artefact or a genuine UHP relict, from the Raman spectrum alone. Raman is an excellent technique for the detection of minute amounts of diamond; however it does not provide conclusive evidence for the identification of UHP microdiamond. The latter requires thorough verification, for instance by optical microscopy or, if doubts cannot be dispelled, transmission electron microscopy.

  16. Minimal constrained supergravity

    Directory of Open Access Journals (Sweden)

    N. Cribiori

    2017-01-01

    Full Text Available We describe minimal supergravity models where supersymmetry is non-linearly realized via constrained superfields. We show that the resulting actions differ from the so called “de Sitter” supergravities because we consider constraints eliminating directly the auxiliary fields of the gravity multiplet.

  17. Logarithmic Superconformal Minimal Models

    CERN Document Server

    Pearce, Paul A; Tartaglia, Elena

    2013-01-01

    The higher fusion level logarithmic minimal models LM(P,P';n) have recently been constructed as the diagonal GKO cosets (A_1^{(1)})_k oplus (A_1^{(1)})_n / (A_1^{(1)})_{k+n} where n>0 is an integer fusion level and k=nP/(P'-P)-2 is a fractional level. For n=1, these are the logarithmic minimal models LM(P,P'). For n>1, we argue that these critical theories are realized on the lattice by n x n fusion of the n=1 models. For n=2, we call them logarithmic superconformal minimal models LSM(p,p') where P=|2p-p'|, P'=p' and p,p' are coprime, and they share the central charges of the rational superconformal minimal models SM(P,P'). Their mathematical description entails the fused planar Temperley-Lieb algebra which is a spin-1 BMW tangle algebra with loop fugacity beta_2=x^2+1+x^{-2} and twist omega=x^4 where x=e^{i(p'-p)pi/p'}. Examples are superconformal dense polymers LSM(2,3) with c=-5/2, beta_2=0 and superconformal percolation LSM(3,4) with c=0, beta_2=1. We calculate the free energies analytically. By numerical...

  18. Prostate resection - minimally invasive

    Science.gov (United States)

    ... invasive URL of this page: //medlineplus.gov/ency/article/007415.htm Prostate resection - minimally invasive To use ... into your bladder instead of out through the urethra ( retrograde ... on New Developments in Prostate Cancer and Prostate Diseases. Evaluation and treatment of lower ...

  19. Anatomical studies of timber and EPMA analysis of brass artefacts collected from steam engine shipwreck of Minicoy Island, Lakshadweep, India

    Digital Repository Service at National Institute of Oceanography (India)

    Tripati, S.; Shukla, S.R.; Som, V.; Sundaresh; Khedekar, V.; Shashikala, S.; Sharma, S.K.

    CURRENT SCIENCE, VOL. 104, NO. 10, 25 MAY 2013 1282 Anatomical studies of timber and EPMA analysis of brass artefacts collected from steam engine shipwreck of Minicoy Island, Lakshadweep, India The maritime activity of India is datable... on 17 November 1862. The weather was stormy and cloudy on the early Figure 1. Location of shipwrecks off Minicoy Island and other Islands of Lakshadweep. SCIENTIFIC CORRESPONDENCE CURRENT SCIENCE, VOL. 104, NO. 10, 25 MAY 2013 1283 morning...

  20. SU-E-J-158: Audiovisual Biofeedback Reduces Image Artefacts in 4DCT: A Digital Phantom Study

    Energy Technology Data Exchange (ETDEWEB)

    Pollock, S; Kipritidis, J; Lee, D; Keall, P [University of Sydney, Sydney (Australia); Bernatowicz, K [Paul Scherrer Institute, Psi, Aargau (Switzerland)

    2015-06-15

    Purpose: Irregular breathing motion has a deleterious impact on 4DCT image quality. The breathing guidance system: audiovisual biofeedback (AVB) is designed to improve breathing regularity, however, its impact on 4DCT image quality has yet to be quantified. The purpose of this study was to quantify the impact of AVB on thoracic 4DCT image quality by utilizing the digital eXtended Cardiac Torso (XCAT) phantom driven by lung tumor motion patterns. Methods: 2D tumor motion obtained from 4 lung cancer patients under two breathing conditions (i) without breathing guidance (free breathing), and (ii) with guidance (AVB). There were two breathing sessions, yielding 8 tumor motion traces. This tumor motion was synchronized with the XCAT phantom to simulate 4DCT acquisitions under two acquisition modes: (1) cine mode, and (2) prospective respiratory-gated mode. Motion regularity was quantified by the root mean square error (RMSE) of displacement. The number of artefacts was visually assessed for each 4DCT and summed up for each breathing condition. Inter-session anatomic reproducibility was quantified by the mean absolute difference (MAD) between the Session 1 4DCT and Session 2 4DCT. Results: AVB improved tumor motion regularity by 30%. In cine mode, the number of artefacts was reduced from 61 in free breathing to 40 with AVB, in addition to AVB reducing the MAD by 34%. In gated mode, the number of artefacts was reduced from 63 in free breathing to 51 with AVB, in addition to AVB reducing the MAD by 23%. Conclusion: This was the first study to compare the impact of breathing guidance on 4DCT image quality compared to free breathing, with AVB reducing the amount of artefacts present in 4DCT images in addition to improving inter-session anatomic reproducibility. Results thus far suggest that breathing guidance interventions could have implications for improving radiotherapy treatment planning and interfraction reproducibility.

  1. Synergistic effects of additives to benzotriazole solutions applied as corrosion inhibitors to archaeological copper and copper alloy artefacts.

    OpenAIRE

    Golfomitsou, S.

    2006-01-01

    Benzotriazole (BTA) is a corrosion inhibitor extensively used for the stabilisation of active corrosion of archaeological copper and copper alloys. However, BTA often fails to effectively retard corrosion when applied on heavily corroded artefacts. Although there are numerous studies about its mode of action on clean copper, there is no comprehensive understanding about the way it is bonded to corroded copper. This thesis aimed to understand and compare BTA and its mode of action on clean and...

  2. Apneic oxygenation for elimination of respiratory motion artefact in an intubated patient undergoing helical chest computed tomography angiography.

    Directory of Open Access Journals (Sweden)

    Ioannis Pneumatikos

    2008-10-01

    Full Text Available Respiratory motion artifact in intubated and mechanically ventilated patients often reduces the quality of helical computed tomography pulmonary angiography (CTPA. Apneic oxygenation is a well established intra-operative technique that allows adequate oxygenation for short periods (up to 10 min in sedated and paralyzed patients. We describe the use of the apneic oxygenation for elimination of respiratory motion artefact in an intubated patient undergoing helical chest computed tomography angiography.

  3. Pitfalls and artefacts in performance and interpretation of contrast-enhanced MR angiography of the lower limbs

    Energy Technology Data Exchange (ETDEWEB)

    Malcolm, P.N., E-mail: paul.malcolm@nnuh.nhs.u [Department of Radiology, Norfolk and Norwich University Hospital, Norwich (United Kingdom); Craven, P. [Department of Radiology, Pilgrim Hospital, United Lincolnshire Hospitals NHS Trust, Boston (United Kingdom); Klass, D. [Department of Radiology, Norfolk and Norwich University Hospital, Norwich (United Kingdom)

    2010-08-15

    Peripheral contrast-enhanced MR angiography is widely used for anatomical imaging of the arterial system of the lower limb. There are several pitfalls in the planning, acquisition, and interpretation of these studies that can result in the loss of important diagnostic information, as well as artefacts that can be misinterpreted as disease entities. This review illustrates the range of these potential sources of error and how to avoid them.

  4. Value of monoenergetic dual-energy CT (DECT) for artefact reduction from metallic orthopedic implants in post-mortem studies

    Energy Technology Data Exchange (ETDEWEB)

    Filograna, Laura [University of Zurich, Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, Zurich (Switzerland); Catholic University of Rome, School of Medicine, University Hospital ' ' A. Gemelli' ' , Department of Radiological Sciences, Rome (Italy); Magarelli, Nicola; Leone, Antonio; Bonomo, Lorenzo [Catholic University of Rome, School of Medicine, University Hospital ' ' A. Gemelli' ' , Department of Radiological Sciences, Rome (Italy); Guggenberger, Roman; Winklhofer, Sebastian [University Hospital Zurich, Institute of Diagnostic and Interventional Radiology, Zurich (Switzerland); Thali, Michael John [University of Zurich, Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, Zurich (Switzerland)

    2015-09-15

    The aim of this ex vivo study was to assess the performance of monoenergetic dual-energy CT (DECT) reconstructions to reduce metal artefacts in bodies with orthopedic devices in comparison with standard single-energy CT (SECT) examinations in forensic imaging. Forensic and clinical impacts of this study are also discussed. Thirty metallic implants in 20 consecutive cadavers with metallic implants underwent both SECT and DECT with a clinically suitable scanning protocol. Extrapolated monoenergetic DECT images at 64, 69, 88, 105, 120, and 130 keV and individually adjusted monoenergy for optimized image quality (OPTkeV) were generated. Image quality of the seven monoenergetic images and of the corresponding SECT image was assessed qualitatively and quantitatively by visual rating and measurements of attenuation changes induced by streak artefact. Qualitative and quantitative analyses showed statistically significant differences between monoenergetic DECT extrapolated images and SECT, with improvements in diagnostic assessment in monoenergetic DECT at higher monoenergies. The mean value of OPTkeV was 137.6 ± 4.9 with a range of 130 to 148 keV. This study demonstrates that monoenergetic DECT images extrapolated at high energy levels significantly reduce metallic artefacts from orthopedic implants and improve image quality compared to SECT examination in forensic imaging. (orig.)

  5. Magnetic resonance imaging acquisition techniques intended to decrease movement artefact in paediatric brain imaging: a systematic review

    Energy Technology Data Exchange (ETDEWEB)

    Woodfield, Julie [University of Edinburgh, Child Life and Health, Edinburgh (United Kingdom); Kealey, Susan [Western General Hospital, Department of Neuroradiology, Edinburgh (United Kingdom)

    2015-08-15

    Attaining paediatric brain images of diagnostic quality can be difficult because of young age or neurological impairment. The use of anaesthesia to reduce movement in MRI increases clinical risk and cost, while CT, though faster, exposes children to potentially harmful ionising radiation. MRI acquisition techniques that aim to decrease movement artefact may allow diagnostic paediatric brain imaging without sedation or anaesthesia. We conducted a systematic review to establish the evidence base for ultra-fast sequences and sequences using oversampling of k-space in paediatric brain MR imaging. Techniques were assessed for imaging time, occurrence of movement artefact, the need for sedation, and either image quality or diagnostic accuracy. We identified 24 relevant studies. We found that ultra-fast techniques had shorter imaging acquisition times compared to standard MRI. Techniques using oversampling of k-space required equal or longer imaging times than standard MRI. Both ultra-fast sequences and those using oversampling of k-space reduced movement artefact compared with standard MRI in unsedated children. Assessment of overall diagnostic accuracy was difficult because of the heterogeneous patient populations, imaging indications, and reporting methods of the studies. In children with shunt-treated hydrocephalus there is evidence that ultra-fast MRI is sufficient for the assessment of ventricular size. (orig.)

  6. Magnetic resonance imaging acquisition techniques intended to decrease movement artefact in paediatric brain imaging: a systematic review.

    Science.gov (United States)

    Woodfield, Julie; Kealey, Susan

    2015-08-01

    Attaining paediatric brain images of diagnostic quality can be difficult because of young age or neurological impairment. The use of anaesthesia to reduce movement in MRI increases clinical risk and cost, while CT, though faster, exposes children to potentially harmful ionising radiation. MRI acquisition techniques that aim to decrease movement artefact may allow diagnostic paediatric brain imaging without sedation or anaesthesia. We conducted a systematic review to establish the evidence base for ultra-fast sequences and sequences using oversampling of k-space in paediatric brain MR imaging. Techniques were assessed for imaging time, occurrence of movement artefact, the need for sedation, and either image quality or diagnostic accuracy. We identified 24 relevant studies. We found that ultra-fast techniques had shorter imaging acquisition times compared to standard MRI. Techniques using oversampling of k-space required equal or longer imaging times than standard MRI. Both ultra-fast sequences and those using oversampling of k-space reduced movement artefact compared with standard MRI in unsedated children. Assessment of overall diagnostic accuracy was difficult because of the heterogeneous patient populations, imaging indications, and reporting methods of the studies. In children with shunt-treated hydrocephalus there is evidence that ultra-fast MRI is sufficient for the assessment of ventricular size.

  7. Design of a Biomimetic Skin for an Octopus-Inspired Robot - Part Ⅱ: Development of the Skin Artefact

    Institute of Scientific and Technical Information of China (English)

    Jinping Hou,; Richard H. C. Bonser; George Jeronimidis

    2011-01-01

    In order to develop skin aetefact for an octopus-inspired robot arm, which is designed to be able to elongate 60% of its original length, silicone rubber and knitted nylon sheet were selected to manufacture an artificial skin, due to their higher elastic strain and high flexibility. Tensile and scissors cutting tests were conducted to characterise the matrix and reinforcing materials and the skin artefact. Material properties of the individual and the composite materials were compared with the measured properties of real octopus skin presented in Part Ⅰ. The Young's modulus of the skin should be below 20 MPa and the elastic strain range should be over 60%. The fracture toughness should be at least 0.9 kJ·m-2. Tubes made of the skin artefact filled with liquid were tested to study volume change under deformation. Finite element analysis model was developed to simulate the material and arm structure under tensile loading. Results show that the skin artefact developed has similar mechanical properties as the real octopus skin and satisfies all the design specifications of the OCTOPUS robot.

  8. Evaluation of a metal artefact reduction tool on different positions of a metal object in the FOV.

    Science.gov (United States)

    Queiroz, Polyane M; Santaella, Gustavo M; da Paz, Thais D J; Freitas, Deborah Q

    2017-03-01

    To evaluate the action of a metal artefact reduction (MAR) tool when artefact-generator metal object is at different positions in the field of view (FOV). A cylindrical utility wax phantom, with a metal alloy sample inside, was made. The phantom was positioned centrally and peripherally in the FOV for image acquisition, with and without the MAR tool activation. The standard deviation values (image noise levels) from areas around the metal sample and the control area were obtained. The numbers were compared by Student's t-test (α = 0.05). When the tool was activated, a significant difference of image noise was observed for central and peripheral positioning, for both control area (p = 0.0012) and metal area (p = 0.03), and a smaller level of noise was observed for images with phantoms in central positioning. A decrease in image noise with the tool activated was found only in phantoms with the metal object positioned centrally in the FOV. For the MAR tool to be effective, the artefact-generator object needs to be in the central region of the FOV.

  9. Checking the homogeneity of gold artefacts of the final bronze age found in Roca Vecchia, Italy by proton induced X-ray emission

    Energy Technology Data Exchange (ETDEWEB)

    Butalag, K. [Department of Engineering of Innovation, University of Lecce, via per Monteroni, Ed. Stecca, 73100 Lecce (Italy); Demortier, G. [Department of Engineering of Innovation, University of Lecce, via per Monteroni, Ed. Stecca, 73100 Lecce (Italy); Quarta, G. [Department of Engineering of Innovation, University of Lecce, via per Monteroni, Ed. Stecca, 73100 Lecce (Italy)]. E-mail: gianluca.quarta@unile.it; Muscogiuri, D. [Department of Engineering of Innovation, University of Lecce, via per Monteroni, Ed. Stecca, 73100 Lecce (Italy); Maruccio, L. [Department of Engineering of Innovation, University of Lecce, via per Monteroni, Ed. Stecca, 73100 Lecce (Italy); Calcagnile, L. [Department of Engineering of Innovation, University of Lecce, via per Monteroni, Ed. Stecca, 73100 Lecce (Italy); Pagliara, C. [Department of Cultural Heritage, University of Lecce, 73100 Lecce (Italy); Maggiulli, G. [Department of Cultural Heritage, University of Lecce, 73100 Lecce (Italy); Mazzotta, C. [Department of Cultural Heritage, University of Lecce, 73100 Lecce (Italy)

    2005-10-15

    Seven gold artefacts found in the same cultural and chronological context in the archaeological site of Roca Vecchia, Southern Italy, have been analyzed in air by proton induced X-ray emission at CEDAD, the AMS-IBA facility of the University of Lecce, Italy. The age of the artefacts has been also indirectly determined by carrying out AMS radiocarbon analyses on short lived organic materials archaeologically associated with the studied objects. The measurements confirmed that the artefacts were formed by a native alloy with a gold concentration ranging from 83.10 to 88.51 wt%. The compositional homogeneity of the artefacts seems to confirm the hypothesis of a common metalworking and origin of the raw materials.

  10. Artefacts induced by coiled intracranial aneurysms on 3.0-Tesla versus 1.5-Tesla MR angiography--An in vivo and in vitro study.

    Science.gov (United States)

    Schaafsma, Joanna D; Velthuis, Birgitta K; Vincken, Koen L; de Kort, Gerard A P; Rinkel, Gabriel J E; Bartels, Lambertus W

    2014-05-01

    To compare metal-induced artefacts from coiled intracranial aneurysms on 3.0-Tesla and 1.5-Tesla magnetic resonance angiography (MRA), since concerns persist on artefact enlargement at 3.0Tesla. We scanned 19 patients (mean age 53; 16 women) with 20 saccular aneurysms treated with coils only, at 1.5 and 3.0Tesla according to standard clinical 3D TOF-MRA protocols containing a shorter echo-time but weaker read-out gradient at 3.0Tesla in addition to intra-arterial digital subtraction angiography (IA-DSA). Per modality two neuro-radiologists assessed the occlusion status, measured residual flow, and indicated whether coil artefacts disturbed this assessment on MRA. We assessed relative risks for disturbance by coil artefacts, weighted kappa's for agreement on occlusion levels, and we compared remnant sizes. For artefact measurements, a coil model was created and scanned with the same protocols followed by 2D MR scans with variation of echo-time and read-out gradient strength. Coil artefacts disturbed assessments less frequently at 3.0Tesla than at 1.5Tesla (RR: 0.3; 95%CI: 0.1-0.8). On 3.0-Tesla MRA, remnants were larger than on 1.5-Tesla MRA (difference: 0.7mm; 95%CI: 0.3-1.1) and larger than on IA-DSA (difference: 1.0mm; 95%CI: 0.6-1.5) with similar agreement on occlusion levels with IA-DSA for both field strengths (κ 0.53; 95%CI: 0.23-0.84 for 1.5-Tesla MRA and IA-DSA; κ 0.47; 95%CI: 0.19-0.76 for 3.0-Tesla MRA and IA-DSA). Coil model artefacts were smaller at 3.0Tesla than at 1.5Tesla. The echo-time influenced artefact size more than the read-out gradient. Artefacts were not larger, but smaller at 3.0Tesla because a shorter echo-time at 3.0Tesla negated artefact enlargement. Despite smaller artefacts and larger remnants at 3.0Tesla, occlusion levels were similar for both field strengths. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  11. A Single Bout of Fasting (24 h Reduces Basal Cytokine Expression and Minimally Impacts the Sterile Inflammatory Response in the White Adipose Tissue of Normal Weight F344 Rats

    Directory of Open Access Journals (Sweden)

    Kristin J. Speaker

    2016-01-01

    Full Text Available Sterile inflammation occurs when inflammatory proteins are increased in blood and tissues by nonpathogenic states and is a double-edged sword depending on its cause (stress, injury, or disease, duration (transient versus chronic, and inflammatory milieu. Short-term fasting can exert a host of health benefits through unknown mechanisms. The following experiment tested if a 24 h fast would modulate basal and stress-evoked sterile inflammation in plasma and adipose. Adult male F344 rats were either randomized to ad libitum access to food or fasted for 24 h prior to 0 (control, 10, or 100, 1.5 mA-5 s intermittent, inescapable tail shocks (IS. Glucose, nonesterified free fatty acids (NEFAs, insulin, leptin, and corticosterone were measured in plasma and tumor necrosis factor- (TNF- α, interleukin- (IL- 1β, IL-6, and IL-10 in plasma, and subcutaneous, intraperitoneal, and visceral compartments of white adipose tissue (WAT. In control rats, a 24 h fast reduced all measured basal cytokines in plasma and visceral WAT, IL-1β and IL-6 in subcutaneous WAT, and IL-6 in intraperitoneal WAT. In stressed rats (IS, fasting reduced visceral WAT TNF-α, subcutaneous WAT IL-1β, and plasma insulin and leptin. Short-term fasting may thus prove to be a useful dietary strategy for reducing peripheral inflammatory states associated with visceral obesity and chronic stress.

  12. Body physique and heart rate variability determine the occurrence of stair-step artefacts in 64-slice CT coronary angiography with prospective ECG-triggering.

    Science.gov (United States)

    Husmann, Lars; Herzog, Bernhard A; Burkhard, Nina; Tatsugami, Fuminari; Valenta, Ines; Gaemperli, Oliver; Wyss, Christophe A; Landmesser, Ulf; Kaufmann, Philipp A

    2009-07-01

    The purpose of this study was to describe and characterize the frequency and extent of stair-step artefacts in computed tomography coronary angiography (CTCA) with prospective electrocardiogram (ECG)-triggering and to identify their determinants. One hundred and forty three consecutive patients (55 women, mean age 57 +/- 13 years) underwent 64-slice CTCA using prospective ECG-triggering. Occurrence of stair-step artefacts in CTCA of the thoracic wall and the coronary arteries was determined and maximum offset was measured. If stair-step artefacts occurred in both cases, a difference between thoracic wall and coronary artery offset of 0.6 mm or greater was attributed to additional motion of the heart. Mean effective radiation dose was 2.1 +/- 0.7 mSv (range 1.0-3.5 mSv). Eighty-nine patients (62%) had stair-step artefacts in CTCA of the coronary arteries (mean offset of 1.7 +/- 1.1 mm), while only 77 patients had thoracic wall stair-step artefacts (mean offset of 1.0 +/- 0.3 mm; significantly different, P < 0.001). Stair-step artefacts in CTCA of the thoracic wall were determined by BMI and weight (P < 0.01), while artefacts in CTCA of the coronary arteries were associated with heart rate variability (P < 0.05). Stair-step artefacts in CTCA with prospective ECG-triggering are determined by (a) motion of the entire patient during table travel, particularly in large patients and (b) by motion of the heart, particularly when heart rates are variable.

  13. On the artefactual parasitic eubacteria clan in conditioned logdet phylogenies: heterotachy and ortholog identification artefacts as explanations

    Directory of Open Access Journals (Sweden)

    Bryant David

    2010-11-01

    Full Text Available Abstract Background Phylogenetic reconstruction methods based on gene content often place all the parasitic and endosymbiotic eubacteria (parasites for short together in a clan. Many other lines of evidence point to this parasites clan being an artefact. This artefact could be a consequence of the methods used to construct ortholog databases (due to some unknown bias, the methods used to estimate the phylogeny, or both. We test the idea that the parasites clan is an ortholog identification artefact by analyzing three different ortholog databases (COG, TRIBES, and OFAM, which were constructed using different methods, and are thus unlikely to share the same biases. In each case, we estimate a phylogeny using an improved version of the conditioned logdet distance method. If the parasites clan appears in trees from all three databases, it is unlikely to be an ortholog identification artefact. Accelerated loss of a subset of gene families in parasites (a form of heterotachy may contribute to the difficulty of estimating a phylogeny from gene content data. We test the idea that heterotachy is the underlying reason for the estimation of an artefactual parasites clan by applying two different mixture models (phylogenetic and non-phylogenetic, in combination with conditioned logdet. In these models, there are two categories of gene families, one of which has accelerated loss in parasites. Distances are estimated separately from each category by conditioned logdet. This should reduce the tendency for tree estimation methods to group the parasites together, if heterotachy is the underlying reason for estimation of the parasites clan. Results The parasites clan appears in conditioned logdet trees estimated from all three databases. This makes it less likely to be an artefact of database construction. The non-phylogenetic mixture model gives trees without a parasites clan. However, the phylogenetic mixture model still results in a tree with a parasites clan

  14. Minimal hepatic encephalopathy.

    Science.gov (United States)

    Zamora Nava, Luis Eduardo; Torre Delgadillo, Aldo

    2011-06-01

    The term minimal hepatic encephalopathy (MHE) refers to the subtle changes in cognitive function, electrophysiological parameters, cerebral neurochemical/neurotransmitter homeostasis, cerebral blood flow, metabolism, and fluid homeostasis that can be observed in patients with cirrhosis who have no clinical evidence of hepatic encephalopathy; the prevalence is as high as 84% in patients with hepatic cirrhosis. Physician does generally not perceive cirrhosis complications, and neuropsychological tests and another especial measurement like evoked potentials and image studies like positron emission tomography can only make diagnosis. Diagnosis of minimal hepatic encephalopathy may have prognostic and therapeutic implications in cirrhotic patients. The present review pretends to explore the clinic, therapeutic, diagnosis and prognostic aspects of this complication.

  15. Minimal triangulations of simplotopes

    CERN Document Server

    Seacrest, Tyler

    2009-01-01

    We derive lower bounds for the size of simplicial covers of simplotopes, which are products of simplices. These also serve as lower bounds for triangulations of such polytopes, including triangulations with interior vertices. We establish that a minimal triangulation of a product of two simplices is given by a vertex triangulation, i.e., one without interior vertices. For products of more than two simplices, we produce bounds for products of segments and triangles. Our analysis yields linear programs that arise from considerations of covering exterior faces and exploiting the product structure of these polytopes. Aside from cubes, these are the first known lower bounds for triangulations of simplotopes with three or more factors. We also construct a minimal triangulation for the product of a triangle and a square, and compare it to our lower bound.

  16. Minimal Composite Inflation

    DEFF Research Database (Denmark)

    Channuie, Phongpichit; Jark Joergensen, Jakob; Sannino, Francesco

    2011-01-01

    We investigate models in which the inflaton emerges as a composite field of a four dimensional, strongly interacting and nonsupersymmetric gauge theory featuring purely fermionic matter. We show that it is possible to obtain successful inflation via non-minimal coupling to gravity, and that the u......We investigate models in which the inflaton emerges as a composite field of a four dimensional, strongly interacting and nonsupersymmetric gauge theory featuring purely fermionic matter. We show that it is possible to obtain successful inflation via non-minimal coupling to gravity......, and that the underlying dynamics is preferred to be near conformal. We discover that the compositeness scale of inflation is of the order of the grand unified energy scale....

  17. Wetting and Minimal Surfaces

    CERN Document Server

    Bachas, C; Wiese, K J; Bachas, Constantin; Doussal, Pierre Le; Wiese, Kay Joerg

    2006-01-01

    We study minimal surfaces which arise in wetting and capillarity phenomena. Using conformal coordinates, we reduce the problem to a set of coupled boundary equations for the contact line of the fluid surface, and then derive simple diagrammatic rules to calculate the non-linear corrections to the Joanny-de Gennes energy. We argue that perturbation theory is quasi-local, i.e. that all geometric length scales of the fluid container decouple from the short-wavelength deformations of the contact line. This is illustrated by a calculation of the linearized interaction between contact lines on two opposite parallel walls. We present a simple algorithm to compute the minimal surface and its energy based on these ideas. We also point out the intriguing singularities that arise in the Legendre transformation from the pure Dirichlet to the mixed Dirichlet-Neumann problem.

  18. Minimal Walking Technicolor

    DEFF Research Database (Denmark)

    Frandsen, Mads Toudal

    2007-01-01

    I report on our construction and analysis of the effective low energy Lagrangian for the Minimal Walking Technicolor (MWT) model. The parameters of the effective Lagrangian are constrained by imposing modified Weinberg sum rules and by imposing a value for the S parameter estimated from the under...... the underlying Technicolor theory. The constrained effective Lagrangian allows for an inverted vector vs. axial-vector mass spectrum in a large part of the parameter space....

  19. On Minimal Constraint Networks

    CERN Document Server

    Gottlob, Georg

    2011-01-01

    In a minimal binary constraint network, every tuple of a constraint relation can be extended to a solution. It was conjectured that computing a solution to such a network is NP complete. We prove this conjecture true and show that the problem remains NP hard even in case the total domain of all values that may appear in the constraint relations is bounded by a constant.

  20. The relieving pain and numbness effects of minimally invasive therapy of soft tissue combined with traction chiropractic on the treatment of cervical spondylotic radiculopathy%软组织微创配合牵引下整脊对神经根型颈椎病的镇痛止麻效果

    Institute of Scientific and Technical Information of China (English)

    沈彤; 尹伦辉; 章瑛; 梁伟坚; 敖晓龙; 谌凌燕; 何巍

    2013-01-01

    Objective To observe the effect of relieving pain and numbness of minimally invasive therapy of soft tissue combined with traction chiropractic in the treatment of cervical spondylotic radiculopathy.Methods 60 patients were randomly divided into a minimally invasive therapy of soft tissue combined with traction chiropractic treatment group and minimally invasive therapy of soft tissue combined with pure traction control group with 30 cases in each group.Traction chiropractic and pure traction were all carried out for 9 times.Minimally invasive therapy of soft tissue was carried out for 3 times.The scores of the symptoms and signs of the pain on neck、shoulder and arm,neck tenderness and numbness were compared between two groups before and after treatment and on the 3rd month after treatment.Results The scores of the symptoms and signs of two groups were all improved as compared with those before treatment (P < 0.05),but the total effect in treatment group improved more than those in the conrtrol group(P < 0.05).Conclusion Minimally invasive therapy of soft tissue combined with traction chiropractic is a safe method in relieving the symptoms of the pain on neck,shoulder and arm,neck tenderness and numbness.%目的 观察软组织微创配合牵引下整脊对神经根型颈椎病的镇痛止麻效果.方法 选60例合格的神经根型颈椎病患者,随机分为软组织微创配合牵引下整脊治疗组及软组织微创配合单纯牵引对照组各30例.牵引下整脊及单纯牵引各治疗9次,软组织微创治疗3次.分析治疗前后及随访3个月后两组颈肩臂疼痛、颈部压痛及麻木症状体征积分的变化.结果 两组治疗后及随访3个月后症状体征积分均有改善(P<0.05),治疗组的症状体征积分改善优于对照组(P<0.05).结论 软组织微创配合牵引下整脊在减轻神经根型颈椎病颈肩臂疼痛、颈部压痛及麻木症状方面疗效显著,操作安全.

  1. Identifying scientific artefacts in biomedical literature: the Evidence Based Medicine use case.

    Science.gov (United States)

    Hassanzadeh, Hamed; Groza, Tudor; Hunter, Jane

    2014-06-01

    Evidence Based Medicine (EBM) provides a framework that makes use of the current best evidence in the domain to support clinicians in the decision making process. In most cases, the underlying foundational knowledge is captured in scientific publications that detail specific clinical studies or randomised controlled trials. Over the course of the last two decades, research has been performed on modelling key aspects described within publications (e.g., aims, methods, results), to enable the successful realisation of the goals of EBM. A significant outcome of this research has been the PICO (Population/Problem-Intervention-Comparison-Outcome) structure, and its refined version PIBOSO (Population-Intervention-Background-Outcome-Study Design-Other), both of which provide a formalisation of these scientific artefacts. Subsequently, using these schemes, diverse automatic extraction techniques have been proposed to streamline the knowledge discovery and exploration process in EBM. In this paper, we present a Machine Learning approach that aims to classify sentences according to the PIBOSO scheme. We use a discriminative set of features that do not rely on any external resources to achieve results comparable to the state of the art. A corpus of 1000 structured and unstructured abstracts - i.e., the NICTA-PIBOSO corpus - is used for training and testing. Our best CRF classifier achieves a micro-average F-score of 90.74% and 87.21%, respectively, over structured and unstructured abstracts, which represents an increase of 25.48 percentage points and 26.6 percentage points in F-score when compared to the best existing approaches.

  2. Ambient aerosol chlorine concentrations and artefacts during the MEGAPOLI Paris campaigns

    Science.gov (United States)

    Furger, Markus; Visser, Suzanne; Slowik, Jay; Crippa, Monica; Poulain, Laurent; Sciare, Jean; Flechsig, Uwe; Prévôt, André; Baltensperger, Urs

    2015-04-01

    Trace elements, especially those that are toxic, can affect the environment in significant ways. Studying them is advantageous with respect to a refinement of source apportionment when measured with high time resolution and appropriate size segregation. This approach is especially useful in urban environments with numerous time-variant emission sources distributed across a relatively narrow space. Two field campaigns took place in the framework of the MEGAPOLI project in Paris, France: one in the summer of 2009 (1-31 July), the other in the winter of 2010 (11 Jan - 10 Feb). Rotating drum impactors (RDI) were operated at an urban and a suburban site in each campaign. The RDI segregated the aerosols into three size ranges (PM10-2.5, PM2.5-1.0 and PM1.0-0.3) and sampled with 2-hour time resolution. The samples were analyzed with synchrotron radiation-induced X-ray fluorescence spectrometry (SR-XRF) at the synchrotron facility of the Paul Scherrer Institute (SLS), where a broad range of elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn) was analyzed for each size range. Time series of the analyzed elements for the different sites and campaigns were prepared to characterize the aerosol trace element composition and temporal behavior for different weather situations and urban environments. Quality assurance was performed partly by intercomparison with independent measurements. An exceptional behavior was observed for chlorine (Cl), where periods with zero RDI concentration alternated with periods of normal load. Zero concentrations were not observed in particle-into-liquid (PILS) measurements. This identifies the observed behavior as a RDI sampling artefact. Nevertheless, the non-zero periods of Cl concentrations are still a gain in information compared to conventional sampling techniques, mainly due to the high time resolution.

  3. Impact of metal artefacts due to EEG electrodes in brain PET/CT imaging

    Science.gov (United States)

    Lemmens, Catherine; Montandon, Marie-Louise; Nuyts, Johan; Ratib, Osman; Dupont, Patrick; Zaidi, Habib

    2008-08-01

    The goal of this study is to investigate the impact of electroencephalogram (EEG) electrodes on the visual quality and quantification of 18F-FDG PET images in neurological PET/CT examinations. For this purpose, the scans of 20 epilepsy patients with EEG monitoring were used. The CT data were reconstructed with filtered backprojection (FBP) and with a metal artefact reduction (MAR) algorithm. Both data sets were used for CT-based attenuation correction (AC) of the PET data. Also, a calculated AC (CALC) technique was considered. A volume of interest (VOI)-based analysis and a voxel-based quantitative analysis were performed to compare the different AC methods. Images were also evaluated visually by two observers. It was shown with simulations and phantom measurements that from the considered AC methods, the MAR-AC can be used as the reference in this setting. The visual assessment of PET images showed local hot spots outside the brain corresponding to the locations of the electrodes when using FBP-AC. In the brain, no abnormalities were observed. The quantitative analysis showed a very good correlation between PET-FBP-AC and PET-MAR-AC, with a statistically significant positive bias in the PET-FBP-AC images of about 5-7% in most brain voxels. There was also good correlation between PET-CALC-AC and PET-MAR-AC, but in the PET-CALC-AC images, regions with both a significant positive and negative bias were observed. EEG electrodes give rise to local hot spots outside the brain and a positive quantification bias in the brain. However, when diagnosis is made by mere visual assessment, the presence of EEG electrodes does not seem to alter the diagnosis. When quantification is performed, the bias becomes an issue especially when comparing brain images with and without EEG monitoring.

  4. Living archaeology: artefacts of specific nest site fidelity in wild chimpanzees.

    Science.gov (United States)

    Stewart, F A; Piel, A K; McGrew, W C

    2011-10-01

    Savanna chimpanzees are known to re-use areas of the landscape for sleep, and patterns of chimpanzee sleeping site re-use are proposed as a referential model for early hominin archaeological site formation. We recorded the prevalence of deformed but healed branches and remnants of dead branches found around fresh nests at the savanna site of Issa in Ugalla, Tanzania. These old nest scars were found in 79% of 112 beds. We also randomly selected potential nesting locations for a subset of 32 beds within the same trees, and found nest scars in only 19% of these "control" locations. We then monitored 275 nests for up to 19 months for decay, regeneration of new branches, and re-use. Of these 275 nest locations, 24% were re-used within the first nine months of monitoring, and most re-use occurred when the nest had already decayed and was not easily visible from the ground. After 18 months, the proportion of specific nest positions re-used increased to 48%. This fidelity is likely a result of the creation of ideally-shaped support structures and supple new growth for mattress material with successive use of nest locations. We propose that specific nest site re-use may not be a direct product of environmental determination, but a result of "niche construction" through formation of good building sites within trees. Environmental modification through construction behaviour may have influenced both chimpanzee and early hominin ranging, and thus leaves behind recognisable patterns of artefact deposition across the landscape. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Minimal E6 unification

    Science.gov (United States)

    Susič, Vasja

    2016-06-01

    A realistic model in the class of renormalizable supersymmetric E6 Grand Unified Theories is constructed. Its matter sector consists of 3 × 27 representations, while the Higgs sector is 27 +27 ¯+35 1'+35 1' ¯+78 . An analytic solution for a Standard Model vacuum is found and the Yukawa sector analyzed. It is argued that if one considers the increased predictability due to only two symmetric Yukawa matrices in this model, it can be considered a minimal SUSY E6 model with this type of matter sector. This contribution is based on Ref. [1].

  6. Minimal Higgs inflation

    CERN Document Server

    Maity, Debaprasad

    2016-01-01

    In this paper we propose two simple minimal Higgs inflation scenarios through a simple modification of the Higgs potential, as opposed to the usual non-minimal Higgs-gravity coupling prescription. The modification is done in such a way that it creates a flat plateau for a huge range of field values at the inflationary energy scale $\\mu \\simeq (\\lambda)^{1/4} \\alpha$. Assuming the perturbative Higgs quartic coupling, $\\lambda \\simeq {\\cal O}(1)$, for both the models inflation energy scale turned out to be $\\mu \\simeq (10^{14}, 10^{15})$ GeV, and prediction of all the cosmologically relevant quantities, $(n_s,r,dn_s^k)$, fit extremely well with observations made by PLANCK. Considering observed central value of the scalar spectral index, $n_s= 0.968$, our two models predict efolding number, $N = (52,47)$. Within a wide range of viable parameter space, we found that the prediction of tensor to scalar ratio $r (\\leq 10^{-5})$ is far below the current experimental sensitivity to be observed in the near future. The ...

  7. Heroin-associated anthrax with minimal morbidity.

    Science.gov (United States)

    Black, Heather; Chapman, Ann; Inverarity, Donald; Sinha, Satyajit

    2017-03-08

    In 2010, during an outbreak of anthrax affecting people who inject drugs, a heroin user aged 37 years presented with soft tissue infection. He subsequently was found to have anthrax. We describe his management and the difficulty in distinguishing anthrax from non-anthrax lesions. His full recovery, despite an overall mortality of 30% for injectional anthrax, demonstrates that some heroin-related anthrax cases can be managed predominately with oral antibiotics and minimal surgical intervention.

  8. Logarithmic superconformal minimal models

    Science.gov (United States)

    Pearce, Paul A.; Rasmussen, Jørgen; Tartaglia, Elena

    2014-05-01

    The higher fusion level logarithmic minimal models {\\cal LM}(P,P';n) have recently been constructed as the diagonal GKO cosets {(A_1^{(1)})_k\\oplus (A_1^ {(1)})_n}/ {(A_1^{(1)})_{k+n}} where n ≥ 1 is an integer fusion level and k = nP/(P‧- P) - 2 is a fractional level. For n = 1, these are the well-studied logarithmic minimal models {\\cal LM}(P,P')\\equiv {\\cal LM}(P,P';1). For n ≥ 2, we argue that these critical theories are realized on the lattice by n × n fusion of the n = 1 models. We study the critical fused lattice models {\\cal LM}(p,p')_{n\\times n} within a lattice approach and focus our study on the n = 2 models. We call these logarithmic superconformal minimal models {\\cal LSM}(p,p')\\equiv {\\cal LM}(P,P';2) where P = |2p - p‧|, P‧ = p‧ and p, p‧ are coprime. These models share the central charges c=c^{P,P';2}=\\frac {3}{2}\\big (1-{2(P'-P)^2}/{P P'}\\big ) of the rational superconformal minimal models {\\cal SM}(P,P'). Lattice realizations of these theories are constructed by fusing 2 × 2 blocks of the elementary face operators of the n = 1 logarithmic minimal models {\\cal LM}(p,p'). Algebraically, this entails the fused planar Temperley-Lieb algebra which is a spin-1 Birman-Murakami-Wenzl tangle algebra with loop fugacity β2 = [x]3 = x2 + 1 + x-2 and twist ω = x4 where x = eiλ and λ = (p‧- p)π/p‧. The first two members of this n = 2 series are superconformal dense polymers {\\cal LSM}(2,3) with c=-\\frac {5}{2}, β2 = 0 and superconformal percolation {\\cal LSM}(3,4) with c = 0, β2 = 1. We calculate the bulk and boundary free energies analytically. By numerically studying finite-size conformal spectra on the strip with appropriate boundary conditions, we argue that, in the continuum scaling limit, these lattice models are associated with the logarithmic superconformal models {\\cal LM}(P,P';2). For system size N, we propose finitized Kac character formulae of the form q^{-{c^{P,P';2}}/{24}+\\Delta ^{P,P';2} _{r

  9. Reduction of artefacts caused by hip implants in CT-based attenuation-corrected PET images using 2-D interpolation of a virtual sinogram on an irregular grid

    Energy Technology Data Exchange (ETDEWEB)

    Abdoli, Mehrsima; Jong, Johan R. de; Pruim, Jan; Dierckx, Rudi A.J.O. [University of Groningen, Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, Groningen (Netherlands); Zaidi, Habib [University of Groningen, Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, Groningen (Netherlands); Geneva University Hospital, Division of Nuclear Medicine and Molecular Imaging, Geneva (Switzerland); Geneva University, Geneva Neuroscience Center, Geneva (Switzerland)

    2011-12-15

    Metallic prosthetic replacements, such as hip or knee implants, are known to cause strong streaking artefacts in CT images. These artefacts likely induce over- or underestimation of the activity concentration near the metallic implants when applying CT-based attenuation correction of positron emission tomography (PET) images. Since this degrades the diagnostic quality of the images, metal artefact reduction (MAR) prior to attenuation correction is required. The proposed MAR method, referred to as virtual sinogram-based technique, replaces the projection bins of the sinogram that are influenced by metallic implants by a 2-D Clough-Tocher cubic interpolation scheme performed in an irregular grid, called Delaunay triangulated grid. To assess the performance of the proposed method, a physical phantom and 30 clinical PET/CT studies including hip prostheses were used. The results were compared to the method implemented on the Siemens Biograph mCT PET/CT scanner. Both phantom and clinical studies revealed that the proposed method performs equally well as the Siemens MAR method in the regions corresponding to bright streaking artefacts and the artefact-free regions. However, in regions corresponding to dark streaking artefacts, the Siemens method does not seem to appropriately correct the tracer uptake while the proposed method consistently increased the uptake in the underestimated regions, thus bringing it to the expected level. This observation is corroborated by the experimental phantom study which demonstrates that the proposed method approaches the true activity concentration more closely. The proposed MAR method allows more accurate CT-based attenuation correction of PET images and prevents misinterpretation of tracer uptake, which might be biased owing to the propagation of bright and dark streaking artefacts from CT images to the PET data following the attenuation correction procedure. (orig.)

  10. Image artefact propagation in motion estimation and reconstruction in interventional cardiac C-arm CT.

    Science.gov (United States)

    Müller, K; Maier, A K; Schwemmer, C; Lauritsch, G; De Buck, S; Wielandts, J-Y; Hornegger, J; Fahrig, R

    2014-06-21

    The acquisition of data for cardiac imaging using a C-arm computed tomography system requires several seconds and multiple heartbeats. Hence, incorporation of motion correction in the reconstruction step may improve the resulting image quality. Cardiac motion can be estimated by deformable three-dimensional (3D)/3D registration performed on initial 3D images of different heart phases. This motion information can be used for a motion-compensated reconstruction allowing the use of all acquired data for image reconstruction. However, the result of the registration procedure and hence the estimated deformations are influenced by the quality of the initial 3D images. In this paper, the sensitivity of the 3D/3D registration step to the image quality of the initial images is studied. Different reconstruction algorithms are evaluated for a recently proposed cardiac C-arm CT acquisition protocol. The initial 3D images are all based on retrospective electrocardiogram (ECG)-gated data. ECG-gating of data from a single C-arm rotation provides only a few projections per heart phase for image reconstruction. This view sparsity leads to prominent streak artefacts and a poor signal to noise ratio. Five different initial image reconstructions are evaluated: (1) cone beam filtered-backprojection (FDK), (2) cone beam filtered-backprojection and an additional bilateral filter (FFDK), (3) removal of the shadow of dense objects (catheter, pacing electrode, etc) before reconstruction with a cone beam filtered-backprojection (cathFDK), (4) removal of the shadow of dense objects before reconstruction with a cone beam filtered-backprojection and a bilateral filter (cathFFDK). The last method (5) is an iterative few-view reconstruction (FV), the prior image constrained compressed sensing combined with the improved total variation algorithm. All reconstructions are investigated with respect to the final motion-compensated reconstruction quality. The algorithms were tested on a mathematical

  11. Natural minimal dark matter

    CERN Document Server

    Fabbrichesi, Marco

    2015-01-01

    We show how the Higgs boson mass is protected from the potentially large corrections due to the introduction of minimal dark matter if the new physics sector is made supersymmetric. The fermionic dark matter candidate (a 5-plet of $SU(2)_L$) is accompanied by a scalar state. The weak gauge sector is made supersymmetric and the Higgs boson is embedded in a supersymmetric multiplet. The remaining standard model states are non-supersymmetric. Non vanishing corrections to the Higgs boson mass only appear at three-loop level and the model is natural for dark matter masses up to 15 TeV--a value larger than the one required by the cosmological relic density. The construction presented stands as an example of a general approach to naturalness that solves the little hierarchy problem which arises when new physics is added beyond the standard model at an energy scale around 10 TeV.

  12. Minimal Mirror Twin Higgs

    CERN Document Server

    Barbieri, Riccardo; Harigaya, Keisuke

    2016-01-01

    In a Mirror Twin World with a maximally symmetric Higgs sector the little hierarchy of the Standard Model can be significantly mitigated, perhaps displacing the cutoff scale above the LHC reach. We show that consistency with observations requires that the Z2 parity exchanging the Standard Model with its mirror be broken in the Yukawa couplings. A minimal such effective field theory, with this sole Z2 breaking, can generate the Z2 breaking in the Higgs sector necessary for the Twin Higgs mechanism, and has constrained and correlated signals in invisible Higgs decays, direct Dark Matter Detection and Dark Radiation, all within reach of foreseen experiments. For dark matter, both mirror neutrons and a variety of self-interacting mirror atoms are considered. Neutrino mass signals and the effects of a possible additional Z2 breaking from the vacuum expectation values of B-L breaking fields are also discussed.

  13. Minimal Hepatic Encephalopathy

    Directory of Open Access Journals (Sweden)

    Laura M Stinton

    2013-01-01

    Full Text Available Minimal hepatic encephalopathy (MHE is the earliest form of hepatic encephalopathy and can affect up to 80% of cirrhotic patients. By definition, it has no obvious clinical manifestation and is characterized by neurocognitive impairment in attention, vigilance and integrative function. Although often not considered to be clinically relevant and, therefore, not diagnosed or treated, MHE has been shown to affect daily functioning, quality of life, driving and overall mortality. The diagnosis of MHE has traditionally been achieved through neuropsychological examination, psychometric tests or the newer critical flicker frequency test. A new smartphone application (EncephalApp Stroop Test may serve to function as a screening tool for patients requiring further testing. In addition to physician reporting and driving restrictions, medical treatment for MHE includes non-absorbable disaccharides (eg, lactulose, probiotics or rifaximin. Liver transplantation may not result in reversal of the cognitive deficits associated with MHE.

  14. Minimally extended SILH

    Energy Technology Data Exchange (ETDEWEB)

    Chala, Mikael [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Valencia Univ. (Spain). Dept. de Fisica Teorica y IFIC; Durieux, Gauthier; Matsedonskyi, Oleksii [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Grojean, Christophe [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Humboldt-Univ. Berlin (Germany). Inst. fuer Physik; Lima, Leonardo de [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Univ. Estadual Paulista, Sao Paulo (Brazil). Inst. de Fisica Teorica

    2017-03-15

    Higgs boson compositeness is a phenomenologically viable scenario addressing the hierarchy problem. In minimal models, the Higgs boson is the only degree of freedom of the strong sector below the strong interaction scale. We present here the simplest extension of such a framework with an additional composite spin-zero singlet. To this end, we adopt an effective field theory approach and develop a set of rules to estimate the size of the various operator coefficients, relating them to the parameters of the strong sector and its structural features. As a result, we obtain the patterns of new interactions affecting both the new singlet and the Higgs boson's physics. We identify the characteristics of the singlet field which cause its effects on Higgs physics to dominate over the ones inherited from the composite nature of the Higgs boson. Our effective field theory construction is supported by comparisons with explicit UV models.

  15. Resource Minimization Job Scheduling

    Science.gov (United States)

    Chuzhoy, Julia; Codenotti, Paolo

    Given a set J of jobs, where each job j is associated with release date r j , deadline d j and processing time p j , our goal is to schedule all jobs using the minimum possible number of machines. Scheduling a job j requires selecting an interval of length p j between its release date and deadline, and assigning it to a machine, with the restriction that each machine executes at most one job at any given time. This is one of the basic settings in the resource-minimization job scheduling, and the classical randomized rounding technique of Raghavan and Thompson provides an O(logn/loglogn)-approximation for it. This result has been recently improved to an O(sqrt{log n})-approximation, and moreover an efficient algorithm for scheduling all jobs on O((OPT)^2) machines has been shown. We build on this prior work to obtain a constant factor approximation algorithm for the problem.

  16. The Fundamentals Regarding the Usage of the Concept of Interface for the Modeling of the Software Artefacts

    Directory of Open Access Journals (Sweden)

    Dorin Bocu

    2016-03-01

    Full Text Available This paper presents the conceptual foundations of a software system’s solution modelling activity, which is formally based on two essential concepts: the artefact and the interface. This  modelling activity envisions  two  objectives: the  explicit emphasis on the  interfaces’ importance in the software engineering, and the preparation of the  framework inside which  the  loop structure-behaviour can be formalized considering the inherent benefits for the  modelling activity in  general, and  for  the  modelling activity automation in particular.

  17. Exploring young children’s artefact engagements as premises for creating purposeful intergenerational knowledge of digitalized everyday life

    DEFF Research Database (Denmark)

    Chimirri, Niklas Alexander

    as reflecting actual and seemingly unavoidable current transformations of the everyday life of adults and children across all societal practices, rendering the political wish to strengthening the digital media literacy of its ‘future citizens’ comprehensible, the ways in which digitalization is promoted......The presentation takes its point of departure in a major current expression of the top-down steering rationale in Danish Early Childhood Education and Care, namely the process of digitalization of childcare institutions. While the promotion of using digital artefacts in childcare can be seen...

  18. Dynamic miniature lighting system with low correlated colour temperature and high colour rendering index for museum lighting of fragile artefacts

    DEFF Research Database (Denmark)

    Thorseth, Anders; Corell, Dennis Dan; Poulsen, Peter Behrensdorff

    2013-01-01

    Illumination of fragile and irreplaceable historical objects exhibited to the public presents challenges with regards to: good colour rendering, low photochemical degradation of sensitive materials and general energy consumption. We present a dynamic tri-colour LED lighting system for illumination...... of historical artefacts in display cases at museums and other exhibitions, which can replace 3-5 Watt incandescent light bulbs with a correlated colour temperature (CCT) from 2000 K to 2400 K. The solution decreases the energy consumption by up to 80 %, while maintaining colour rendering indices (Ra) above 90...

  19. Minimally invasive procedures on the lumbar spine

    Science.gov (United States)

    Skovrlj, Branko; Gilligan, Jeffrey; Cutler, Holt S; Qureshi, Sheeraz A

    2015-01-01

    Degenerative disease of the lumbar spine is a common and increasingly prevalent condition that is often implicated as the primary reason for chronic low back pain and the leading cause of disability in the western world. Surgical management of lumbar degenerative disease has historically been approached by way of open surgical procedures aimed at decompressing and/or stabilizing the lumbar spine. Advances in technology and surgical instrumentation have led to minimally invasive surgical techniques being developed and increasingly used in the treatment of lumbar degenerative disease. Compared to the traditional open spine surgery, minimally invasive techniques require smaller incisions and decrease approach-related morbidity by avoiding muscle crush injury by self-retaining retractors, preventing the disruption of tendon attachment sites of important muscles at the spinous processes, using known anatomic neurovascular and muscle planes, and minimizing collateral soft-tissue injury by limiting the width of the surgical corridor. The theoretical benefits of minimally invasive surgery over traditional open surgery include reduced blood loss, decreased postoperative pain and narcotics use, shorter hospital length of stay, faster recover and quicker return to work and normal activity. This paper describes the different minimally invasive techniques that are currently available for the treatment of degenerative disease of the lumbar spine. PMID:25610845

  20. Evaluation of a completely automated tissue-sectioning machine for paraffin blocks.

    Science.gov (United States)

    Onozato, Maristela L; Hammond, Stephen; Merren, Mark; Yagi, Yukako

    2013-02-01

    Tissue-sectioning automation can be a resourceful tool in processing anatomical pathology specimens. The advantages of an automated system compared with traditional manual sectioning are the invariable thickness, uniform orientation and fewer tissue-sectioning artefacts. This short report presents the design of an automated tissue-sectioning device and compares the sectioned specimens with normal manual tissue sectioning performed by an experienced histology technician. The automated system was easy to use, safe and the sectioned material showed acceptable quality with well-preserved morphology and tissue antigenicity. It is expected that the turnaround time will be improved in the near future.

  1. Metal artefact suppression at 3 T MRI: comparison of MAVRIC-SL with conventional fast spin echo sequences in patients with Hip joint arthroplasty

    Energy Technology Data Exchange (ETDEWEB)

    Kretzschmar, Martin; Nardo, Lorenzo; Han, Misung M.; Heilmeier, Ursula; Sam, Craig; Joseph, Gabby B.; Krug, Roland; Link, Thomas M. [University of California San Francisco, Musculoskeletal Quantitative Imaging Research Group, Department of Radiology and Biomedical Imaging, San Francisco, CA (United States); Koch, Kevin M. [Medical Collage of Wisconsin, Departments of Biophysics and Radiology, Milwaukee, WI (United States)

    2015-08-15

    The aim of our study was to evaluate the clinical feasibility and diagnostic value of a new MRI metal artefact reduction pulse sequence called MAVRIC-SL in a 3 T MRI environment. Two MAVRIC-SL sequences obtained in 61 patients with symptomatic total hip replacement were compared with standard FSE-STIR sequences optimized for imaging around metal. Artefact size was measured on the slice of greatest extent. Image quality, fat saturation, image distortion, visibility of anatomical structures, and detectability of joint abnormalities were visually assessed and graded on qualitative scales. Differences between MAVRIC-SL and FSE sequences were tested with the Wilcoxon signed-rank test. MAVRIC-SL sequences at 3 T showed significantly smaller metal artefacts compared to FSE-STIR sequences (p < 0.0001). The general image quality of MAVRIC-SL sequences was reduced with regard to spatial resolution, noise and contrast (p = 0.001), and fat saturation (p < 0.0001). The reduction of artefact size and image distortion significantly improved visualization of joint anatomy (p < 0.0001) and diagnostic confidence regarding implant-associated abnormalities (p = 0.0075 to <0.0001). Although the image quality of MAVRIC-SL sequences is limited at 3 T, its clinical application is feasible and provides important additional diagnostic information for the workup of patients with symptomatic hip replacement through substantially reduced metal artefacts. (orig.)

  2. Minimal Log Gravity

    CERN Document Server

    Giribet, Gaston

    2014-01-01

    Minimal Massive Gravity (MMG) is an extension of three-dimensional Topologically Massive Gravity that, when formulated about Anti-de Sitter space, accomplishes to solve the tension between bulk and boundary unitarity that other models in three dimensions suffer from. We study this theory at the chiral point, i.e. at the point of the parameter space where one of the central charges of the dual conformal field theory vanishes. We investigate the non-linear regime of the theory, meaning that we study exact solutions to the MMG field equations that are not Einstein manifolds. We exhibit a large class of solutions of this type, which behave asymptotically in different manners. In particular, we find analytic solutions that represent two-parameter deformations of extremal Banados-Teitelboim-Zanelli (BTZ) black holes. These geometries behave asymptotically as solutions of the so-called Log Gravity, and, despite the weakened falling-off close to the boundary, they have finite mass and finite angular momentum, which w...

  3. Minimal dilaton model

    Directory of Open Access Journals (Sweden)

    Oda Kin-ya

    2013-05-01

    Full Text Available Both the ATLAS and CMS experiments at the LHC have reported the observation of the particle of mass around 125 GeV which is consistent to the Standard Model (SM Higgs boson, but with an excess of events beyond the SM expectation in the diphoton decay channel at each of them. There still remains room for a logical possibility that we are not seeing the SM Higgs but something else. Here we introduce the minimal dilaton model in which the LHC signals are explained by an extra singlet scalar of the mass around 125 GeV that slightly mixes with the SM Higgs heavier than 600 GeV. When this scalar has a vacuum expectation value well beyond the electroweak scale, it can be identified as a linearly realized version of a dilaton field. Though the current experimental constraints from the Higgs search disfavors such a region, the singlet scalar model itself still provides a viable alternative to the SM Higgs in interpreting its search results.

  4. Minimal log gravity

    Science.gov (United States)

    Giribet, Gaston; Vásquez, Yerko

    2015-01-01

    Minimal massive gravity (MMG) is an extension of three-dimensional topologically massive gravity that, when formulated about anti-de Sitter space, accomplishes solving the tension between bulk and boundary unitarity that other models in three dimensions suffer from. We study this theory at the chiral point, i.e. at the point of the parameter space where one of the central charges of the dual conformal field theory vanishes. We investigate the nonlinear regime of the theory, meaning that we study exact solutions to the MMG field equations that are not Einstein manifolds. We exhibit a large class of solutions of this type, which behave asymptotically in different manners. In particular, we find analytic solutions that represent two-parameter deformations of extremal Bañados-Teitelboim-Zanelli black holes. These geometries behave asymptotically as solutions of the so-called log gravity, and, despite the weakened falling off close to the boundary, they have finite mass and finite angular momentum, which we compute. We also find time-dependent deformations of Bañados-Teitelboim-Zanelli that obey Brown-Henneaux asymptotic boundary conditions. The existence of such solutions shows that the Birkhoff theorem does not hold in MMG at the chiral point. Other peculiar features of the theory at the chiral point, such as the degeneracy it exhibits in the decoupling limit, are discussed.

  5. Minimal distances between SCFTs

    Energy Technology Data Exchange (ETDEWEB)

    Buican, Matthew [Department of Physics and Astronomy, Rutgers University,Piscataway, NJ 08854 (United States)

    2014-01-28

    We study lower bounds on the minimal distance in theory space between four-dimensional superconformal field theories (SCFTs) connected via broad classes of renormalization group (RG) flows preserving various amounts of supersymmetry (SUSY). For N=1 RG flows, the ultraviolet (UV) and infrared (IR) endpoints of the flow can be parametrically close. On the other hand, for RG flows emanating from a maximally supersymmetric SCFT, the distance to the IR theory cannot be arbitrarily small regardless of the amount of (non-trivial) SUSY preserved along the flow. The case of RG flows from N=2 UV SCFTs is more subtle. We argue that for RG flows preserving the full N=2 SUSY, there are various obstructions to finding examples with parametrically close UV and IR endpoints. Under reasonable assumptions, these obstructions include: unitarity, known bounds on the c central charge derived from associativity of the operator product expansion, and the central charge bounds of Hofman and Maldacena. On the other hand, for RG flows that break N=2→N=1, it is possible to find IR fixed points that are parametrically close to the UV ones. In this case, we argue that if the UV SCFT possesses a single stress tensor, then such RG flows excite of order all the degrees of freedom of the UV theory. Furthermore, if the UV theory has some flavor symmetry, we argue that the UV central charges should not be too large relative to certain parameters in the theory.

  6. Far-reaching geometrical artefacts due to thermal decomposition of polymeric coatings around focused ion beam milled pigment particles.

    Science.gov (United States)

    Rykaczewski, K; Mieritz, D G; Liu, M; Ma, Y; Iezzi, E B; Sun, X; Wang, L P; Solanki, K N; Seo, D-K; Wang, R Y

    2016-06-01

    Focused ion beam and scanning electron microscope (FIB-SEM) instruments are extensively used to characterize nanoscale composition of composite materials, however, their application to analysis of organic corrosion barrier coatings has been limited. The primary concern that arises with use of FIB to mill organic materials is the possibility of severe thermal damage that occurs in close proximity to the ion beam impact. Recent research has shown that such localized artefacts can be mitigated for a number of polymers through cryogenic cooling of the sample as well as low current milling and intelligent ion beam control. Here we report unexpected nonlocalized artefacts that occur during FIB milling of composite organic coatings with pigment particles. Specifically, we show that FIB milling of pigmented polysiloxane coating can lead to formation of multiple microscopic voids within the substrate as far as 5 μm away from the ion beam impact. We use further experimentation and modelling to show that void formation occurs via ion beam heating of the pigment particles that leads to decomposition and vaporization of the surrounding polysiloxane. We also identify FIB milling conditions that mitigate this issue.

  7. DNA from keratinous tissue

    DEFF Research Database (Denmark)

    Bengtsson, Camilla F.; Olsen, Maja E.; Brandt, Luise Ørsted

    2011-01-01

    Keratinous tissues such as nail, hair, horn, scales and feather have been used as a source of DNA for over 20 years. Particular benefits of such tissues include the ease with which they can be sampled, the relative stability of DNA in such tissues once sampled, and, in the context of ancient...... genetic analyses, the fact that sampling generally causes minimal visual damage to valuable specimens. Even when freshly sampled, however, the DNA quantity and quality in the fully keratinized parts of such tissues is extremely poor in comparison to other tissues such as blood and muscle – although little...... systematic research has been undertaken to characterize how such degradation may relate to sample source. In this review paper we present the current understanding of the quality and limitations of DNA in two key keratinous tissues, nail and hair. The findings indicate that although some fragments of nuclear...

  8. Sex determination of baleen whale artefacts : Implications for ancient DNA use in zooarchaeology

    NARCIS (Netherlands)

    Sinding, Mikkel Holger S; Tervo, Outi M.; Grønnow, Bjarne; Gulløv, Hans Christian; Toft, Peter A.; Bachmann, Lutz; Fietz, Katharina; Rekdal, Silje L.; Christoffersen, Mads F.; Heide-Jørgensen, Mads Peter; Olsen, Morten Tange; Foote, Andrew D.

    2016-01-01

    Methods to determine the sex from tissue samples of mammals include the amplification of Y chromosome specific regions, which should only amplify from males, or amplification of homologous regions of the X and Y chromosome containing XY specific SNPs. A disadvantage of the first approach is that PCR

  9. On stable compact minimal submanifolds

    CERN Document Server

    Torralbo, Francisco

    2010-01-01

    Stable compact minimal submanifolds of the product of a sphere and any Riemannian manifold are classified whenever the dimension of the sphere is at least three. The complete classification of the stable compact minimal submanifolds of the product of two spheres is obtained. Also, it is proved that the only stable compact minimal surfaces of the product of a 2-sphere and any Riemann surface are the complex ones.

  10. Global Analysis of Minimal Surfaces

    CERN Document Server

    Dierkes, Ulrich; Tromba, Anthony J

    2010-01-01

    Many properties of minimal surfaces are of a global nature, and this is already true for the results treated in the first two volumes of the treatise. Part I of the present book can be viewed as an extension of these results. For instance, the first two chapters deal with existence, regularity and uniqueness theorems for minimal surfaces with partially free boundaries. Here one of the main features is the possibility of 'edge-crawling' along free parts of the boundary. The third chapter deals with a priori estimates for minimal surfaces in higher dimensions and for minimizers of singular integ

  11. Minimal surfaces for architectural constructions

    Directory of Open Access Journals (Sweden)

    Velimirović Ljubica S.

    2008-01-01

    Full Text Available Minimal surfaces are the surfaces of the smallest area spanned by a given boundary. The equivalent is the definition that it is the surface of vanishing mean curvature. Minimal surface theory is rapidly developed at recent time. Many new examples are constructed and old altered. Minimal area property makes this surface suitable for application in architecture. The main reasons for application are: weight and amount of material are reduced on minimum. Famous architects like Otto Frei created this new trend in architecture. In recent years it becomes possible to enlarge the family of minimal surfaces by constructing new surfaces.

  12. On minimal artinian modules and minimal artinian linear groups

    Directory of Open Access Journals (Sweden)

    Leonid A. Kurdachenko

    2001-01-01

    minimal artinian linear groups. The authors prove that in such classes of groups as hypercentral groups (so also, nilpotent and abelian groups and FC-groups, minimal artinian linear groups have precisely the same structure as the corresponding irreducible linear groups.

  13. Human presence in the central Netherlands during early MIS 6 (∼170-190 Ka): Evidence from early Middle Palaeolithic artefacts in ice-pushed Rhine-Meuse sediments

    NARCIS (Netherlands)

    Balen, R.T. van; Busschers, F.S.

    2010-01-01

    Part of the gravelly deposits of a combined Rhine-Meuse river of Middle Pleistocene age in the central Netherlands contains early Middle Palaeolithic artefacts. Although not in their original position, a significant part of these artefacts is hardly abraded, indicating limited fluvial transport. The

  14. The material science of minimally invasive esthetic restorations.

    Science.gov (United States)

    Nový, Brian B; Fuller, Cameron E

    2008-01-01

    The term esthetic dentistry usually conjures up mental images of porcelain crowns and veneers. To some dentists, the term minimally invasive dentistry evokes thoughts of observing early lesions, and postponing treatment until lesions are closer to the pulp. (The World Congress of Minimally Invasive Dentistry defines minimally invasive dentistry as those techniques which respect health, function, and esthetics of oral tissue by preventing disease from occurring, or intercepting its progress with minimal tissue loss.) It would seem these two niches within dentistry are on opposite ends of the spectrum; however, composite resin and glass ionomer restorative materials unite these two ideologies. Understanding the limitations, benefits, and science behind each material allows clinicians to produce highly esthetic restorations that can resist future decay, internally remineralize the tooth, and help protect adjacent teeth from cariogenic attack.

  15. Abeta mediated diminution of MTT reduction--an artefact of single cell culture?

    Directory of Open Access Journals (Sweden)

    Raik Rönicke

    Full Text Available The 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyl-tetrazoliumbromide (MTT reduction assay is a frequently used and easily reproducible method to measure beta-amyloid (Abeta toxicity in different types of single cell culture. To our knowledge, the influence of Abeta on MTT reduction has never been tested in more complex tissue. Initially, we reproduced the disturbed MTT reduction in neuron and astroglia primary cell cultures from rats as well as in the BV2 microglia cell line, utilizing four different Abeta species, namely freshly dissolved Abeta (25-35, fibrillar Abeta (1-40, oligomeric Abeta (1-42 and oligomeric Abeta (1-40. In contrast to the findings in single cell cultures, none of these Abeta species altered MTT reduction in rat organotypic hippocampal slice cultures (OHC. Moreover, application of Abeta to acutely isolated hippocampal slices from adult rats and in vivo intracerebroventricular injection of Abeta also did not influence the MTT reduction in the respective tissue. Failure of Abeta penetration into the tissue cannot explain the differences between single cells and the more complex brain tissue. Thus electrophysiological investigations disclosed an impairment of long-term potentiation (LTP in the CA1 region of hippocampal slices from rat by application of oligomeric Abeta (1-40, but not by freshly dissolved Abeta (25-35 or fibrillar Abeta (1-40. In conclusion, the experiments revealed a glaring discrepancy between single cell cultures and complex brain tissue regarding the effect of different Abeta species on MTT reduction. Particularly, the differential effect of oligomeric versus other Abeta forms on LTP was not reflected in the MTT reduction assay. This may indicate that the Abeta oligomer effect on synaptic function reflected by LTP impairment precedes changes in formazane formation rate or that cells embedded in a more natural environment in the tissue are less susceptible to damage by Abeta, raising cautions against the

  16. Not all that glitters is gold - Electron microscopy study on uptake of gold nanoparticles in Daphnia magna and related artefacts

    DEFF Research Database (Denmark)

    Jensen, Louise Helene Søgaard; Skjolding, Lars Michael; Thit, Amalie

    2016-01-01

    techniques are used to investigate internalization of 10 nm gold nanoparticles in Daphnia magna gut lumen and gut epithelial cells upon 24h exposure and outline potential artefacts, i.e. high contract precipitates from sample preparation related to these techniques. Light sheet microscopy confirmed...... accumulation of gold nanoparticles in the gut lumen. Scanning transmission electron microscopy and elemental analysis revealed gold nanoparticles attached to the microvilli of gut cells. Interestingly, the peritrophic membrane appeared to act as a semipermeable barrier between the lumen and the gut epithelium......, permitting only single particles through. Structures resembling nanoparticles were also observed inside gut cells. As elemental analysis could not verify these to be gold they were likely artifacts from the preparation, such as osmium and iron. Importantly, gold nanoparticles were in fact found inside...

  17. Nanoparticles of Sr(OH){sub 2}: synthesis in homogeneous phase at low temperature and application for cultural heritage artefacts

    Energy Technology Data Exchange (ETDEWEB)

    Ciliberto, E.; Condorelli, G.G.; La Delfa, S.; Viscuso, E. [Universita di Catania, Dipartimento di Scienze Chimiche, Catania (Italy)

    2008-07-15

    This paper concerns the synthesis and the characterization of nanometer particles of Sr(OH){sub 2}, a moderately high water soluble hydroxide (Ksp=3.2 x 10{sup -4} at 25 C). The reported process yields strontium hydroxide nanoparticles starting from low cost raw materials in aqueous medium (homogeneous phase) at low temperature (below 100 C) by chemical precipitation from salt solutions, involving very simple operational steps and avoiding the use of organic solvents. Observations by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron dispersive X-Ray (EDX) and Fourier transform infrared spectroscopy (FTIR) indicate that the particles are well-crystallized and have nanometer dimensions ({proportional_to}30 nm in diameter). Moreover, experimental evidence shows the potential use of this material for the protection and the consolidation of wall paintings (frescoes), paper, stone, wood and other artistic artefacts. (orig.)

  18. Dynamic miniature lighting system with low correlated colour temperature and high colour rendering index for museum lighting of fragile artefacts

    DEFF Research Database (Denmark)

    Thorseth, Anders; Corell, Dennis Dan; Poulsen, Peter Behrensdorff

    2013-01-01

    Illumination of fragile and irreplaceable historical objects exhibited to the public presents challenges with regards to: good colour rendering, low photochemical degradation of sensitive materials and general energy consumption. We present a dynamic tri-colour LED lighting system for illumination...... of historical artefacts in display cases at museums and other exhibitions, which can replace 3-5 Watt incandescent light bulbs with a correlated colour temperature (CCT) from 2000 K to 2400 K. The solution decreases the energy consumption by up to 80 %, while maintaining colour rendering indices (Ra) above 90...... and important special colour rendering indices R9 between 50 and 90, while decreasing the level of harmful short wavelength radiation by between 20 - 30 %....

  19. A multi-channel opto-electronic sensor to accurately monitor heart rate against motion artefact during exercise.

    Science.gov (United States)

    Alzahrani, Abdullah; Hu, Sijung; Azorin-Peris, Vicente; Barrett, Laura; Esliger, Dale; Hayes, Matthew; Akbare, Shafique; Achart, Jérôme; Kuoch, Sylvain

    2015-10-12

    This study presents the use of a multi-channel opto-electronic sensor (OEPS) to effectively monitor critical physiological parameters whilst preventing motion artefact as increasingly demanded by personal healthcare. The aim of this work was to study how to capture the heart rate (HR) efficiently through a well-constructed OEPS and a 3-axis accelerometer with wireless communication. A protocol was designed to incorporate sitting, standing, walking, running and cycling. The datasets collected from these activities were processed to elaborate sport physiological effects. t-test, Bland-Altman Agreement (BAA), and correlation to evaluate the performance of the OEPS were used against Polar and Mio-Alpha HR monitors. No differences in the HR were found between OEPS, and either Polar or Mio-Alpha (both p > 0.05); a strong correlation was found between Polar and OEPS (r: 0.96, p heart rate.

  20. Provenance analysis of Roman stone artefacts from sedimentary rocks from the archaeological site near Mošnje, NW Slovenia

    Directory of Open Access Journals (Sweden)

    Snježana Miletić

    2016-08-01

    Full Text Available This study deals with the macroscopic and microfacies characterisation of Roman stone artefacts excavated in 2006 from a Roman villa rustica near Mošnje (NW Slovenia with the aim of defiing their provenance. A total of 28 representative fids (querns, mortars, whetstones, tooled and rounded stones, a fragment of stone slab, mosaic tesserae and two architectural elements - one with a relief made of clastic and carbonate sedimentary rocks were examined. Comparison was made with rock samples taken from quarries and gravel bars close to the archaeological site, as well as from larger distance to the site. The majority of artefact sampled is composed of Upper Palaeozoic quartz sandstones, which are found as pebbles in gravel bars close to the archaeological site; while 2 samples were from Quaternary coarse grained clastic rocks which can be found in local glacio-flvial sediments. Other fids were made of four different Mesozoic shallow-water limestones which outcrop in different areas of Central and SW Slovenia. The nearest Lower Jurassic biopelmicritic limestones are found at the western periphery of Ljubljana in Podutik. Cretaceous miliolid limestones and biocalcarenitic limestones with rudists are common in the successions of the Dinaric Carbonate Platform in SW Slovenia (for example, on the Trieste-Komen Plateau, NE Italy and SW Croatia. This indicates that the limestones for architectural elements, stone mortars and tesserae were brought to Mošnje from distant locations. Smaller stone tools are likely to have been made at the location of the archaeological site from material gathered locally, mostly pebbles from clastic rocks, which were accessible and suitable for tooling.

  1. Blasphemy As Violence: Trying to Understand the Kind of Injury That Can Be Inflicted by Acts and Artefacts That Are Construed As Blasphemy

    NARCIS (Netherlands)

    Baumgartner, C.

    2013-01-01

    This article suggests an understanding of blasphemy as violence that enables us to identify various kinds of injury that can be inflicted by blasphemous acts and artefacts. Understanding blasphemy as violence can take three forms: physical violence, indirect intersubjective violence, and

  2. ICA-based muscle artefact correction of EEG data: what is muscle and what is brain? Comment on McMenamin et al.

    Science.gov (United States)

    Olbrich, Sebastian; Jödicke, Johannes; Sander, Christian; Himmerich, Hubertus; Hegerl, Ulrich

    2011-01-01

    Independent component analysis (ICA)-based muscle artefact correction has become a popular tool within electroencephalographic (EEG) research. As a comment on the article by McMenamin et al. (2010), we want to address three issues concerning the claimed lack of sensitivity and specificity of this method. The under- or overestimation of myogenic and neurogenic signals after ICA-based muscle artefact correction reported by McMenamin et al. might be explainable in part by a) insufficient temporal independence of myogenic and neurogenic components when exploring more than one condition, b) wrong classification of myogenic or neurogenic components by human raters and c) differences of neuronal mass activity during tensed or relaxed-muscle conditions. Our own data show only significant differences regarding intracortical alpha band EEG-source estimates for contrasts between clean EEG data and artificially contaminated EEG data at group-analysis level but not between clean data and data after ICA-based correction. ICA-based artefact correction already provides a powerful tool for muscle artefact rejection. More research is needed for determining reliable criteria to delineate myogenic from neurogenic components.

  3. The effect of metal artefact reduction on CT-based attenuation correction for PET imaging in the vicinity of metallic hip implants : a phantom study

    NARCIS (Netherlands)

    Harnish, Roy; Prevrhal, Sven; Alavi, Abass; Zaidi, Habib; Lang, Thomas F.

    2014-01-01

    To determine if metal artefact reduction (MAR) combined with a priori knowledge of prosthesis material composition can be applied to obtain CT-based attenuation maps with sufficient accuracy for quantitative assessment of F-18-fluorodeoxyglucose uptake in lesions near metallic prostheses. A custom h

  4. Reduction of CT beam hardening artefacts of ethylene vinyl alcohol copolymer by variation of the tantalum content: evaluation in a standardized aortic endoleak phantom

    Energy Technology Data Exchange (ETDEWEB)

    Treitl, Karla M.; Scherr, Michael; Foerth, Monika; Braun, Franziska; Maxien, Daniel; Treitl, Marcus [Hospitals of the Ludwig-Maximilians-University of Munich, Institute for Clinical Radiology, Munich (Germany)

    2014-10-16

    Our aim was to develop an aortic stent graft phantom to simulate endoleak treatment and to find a tantalum content (TC) of ethylene-vinyl-alcohol-copolymer that causes fewer computed tomography (CT) beam hardening artefacts, but still allows for fluoroscopic visualization. Ethylene-vinyl-alcohol-copolymer specimens of different TC (10-50 %, and 100 %) were injected in an aortic phantom bearing a stent graft and endoleak cavities with simulated re-perfusion. Fluoroscopic visibility of the ethylene-vinyl-alcohol-copolymer specimens was analyzed. In addition, six radiologists analyzed endoleak visibility, and artefact intensity of ethylene-vinyl-alcohol-copolymer in CT. Reduction of TC significantly decreased CT artefact intensity of ethylene-vinyl-alcohol-copolymer and increased visibility of endoleak re-perfusion (p < 0.000). It also significantly decreased fluoroscopic visibility of ethylene-vinyl-alcohol-copolymer (R = 0.883, p ≤ 0.01), and increased the active embolic volumes prior to visualization (Δ ≥ 40 μl). Ethylene-vinyl-alcohol-copolymer specimens with a TC of 45-50 % exhibited reasonable visibility, a low active embolic volume and a tolerable CT artefact intensity. The developed aortic stent graft phantom allows for a reproducible simulation of embolization of endoleaks. The data suggest a reduction of the TC of ethylene-vinyl-alcohol-copolymer to 45 -50 % of the original, to interfere less with diagnostic imaging in follow-up CT examinations, while still allowing for fluoroscopic visualization. (orig.)

  5. Er,CR:YSGG lasers induce fewer dysplastic-like epithelial artefacts than CO2 lasers: an in vivo experimental study on oral mucosa.

    Science.gov (United States)

    González-Mosquera, A; Seoane, J; García-Caballero, L; López-Jornet, P; García-Caballero, T; Varela-Centelles, P

    2012-09-01

    Our aim was to assess wounds made by lasers (CO(2) and Er,Cr:YSGG) for their epithelial architectural changes and width of damage. We allocated 60 Sprague-Dawley(®) rats into groups: glossectomy by CO(2) laser at 3 different wattages (n=10 in each); glossectomy by Er,Cr:YSGG laser at two different emissions (n=10 in each), and a control group (n=10). Histological examination assessed both prevalence and site of thermal artefacts for each group. Both lasers (CO(2) and Er,Cr:YSGG) caused the same type of cytological artefacts. The 3W Er,Cr:YSGG laser produced the fewest cytological artefacts/specimen, and was significantly different from the other experimental groups: 3W CO(2) laser (95% CI=0.8 to 1.0); the 6W CO(2) laser (95% CI=0.1 to 2.0) and the 10W CO(2) laser (95% CI=1.1 to 3.0). CO(2) lasers (3-10W) generate epithelial damage that can simulate dysplastic changes with cytological atypia that affects mainly the basal and suprabasal layers. Irradiation with Er,CR:YSGG laser (2-4W) produces significantly fewer cellular artefacts and less epithelial damage, which may be potentially useful for biopsy of oral mucosa.

  6. The social construction of facts and artefacts: or How the sociology of science and the sociology of technology might benefit each other

    NARCIS (Netherlands)

    Pinch, Trevor J.; Bijker, Wiebe E.

    1984-01-01

    The need for an integrated social constructivist approach towards the study of science and technology is outlined. Within such a programme both scientific facts and technological artefacts are to be understood as social constructs. Literature on the sociology of science, the science-technology

  7. The effect of metal artefact reduction on CT-based attenuation correction for PET imaging in the vicinity of metallic hip implants : a phantom study

    NARCIS (Netherlands)

    Harnish, Roy; Prevrhal, Sven; Alavi, Abass; Zaidi, Habib; Lang, Thomas F.

    To determine if metal artefact reduction (MAR) combined with a priori knowledge of prosthesis material composition can be applied to obtain CT-based attenuation maps with sufficient accuracy for quantitative assessment of F-18-fluorodeoxyglucose uptake in lesions near metallic prostheses. A custom

  8. Minimal massive 3D gravity

    NARCIS (Netherlands)

    Bergshoeff, Eric; Hohm, Olaf; Merbis, Wout; Routh, Alasdair J.; Townsend, Paul K.

    2014-01-01

    We present an alternative to topologically massive gravity (TMG) with the same 'minimal' bulk properties; i.e. a single local degree of freedom that is realized as a massive graviton in linearization about an anti-de Sitter (AdS) vacuum. However, in contrast to TMG, the new 'minimal massive gravity'

  9. Uniqueness of PL Minimal Surfaces

    Institute of Scientific and Technical Information of China (English)

    Yi NI

    2007-01-01

    Using a standard fact in hyperbolic geometry, we give a simple proof of the uniqueness of PL minimal surfaces, thus filling in a gap in the original proof of Jaco and Rubinstein. Moreover, in order to clarify some ambiguity, we sharpen the definition of PL minimal surfaces, and prove a technical lemma on the Plateau problem in the hyperbolic space.

  10. Guidelines for mixed waste minimization

    Energy Technology Data Exchange (ETDEWEB)

    Owens, C.

    1992-02-01

    Currently, there is no commercial mixed waste disposal available in the United States. Storage and treatment for commercial mixed waste is limited. Host States and compacts region officials are encouraging their mixed waste generators to minimize their mixed wastes because of management limitations. This document provides a guide to mixed waste minimization.

  11. Influenza SIRS with Minimal Pneumonitis.

    Science.gov (United States)

    Erramilli, Shruti; Mannam, Praveen; Manthous, Constantine A

    2016-01-01

    Although systemic inflammatory response syndrome (SIRS) is a known complication of severe influenza pneumonia, it has been reported very rarely in patients with minimal parenchymal lung disease. We here report a case of severe SIRS, anasarca, and marked vascular phenomena with minimal or no pneumonitis. This case highlights that viruses, including influenza, may cause vascular dysregulation causing SIRS, even without substantial visceral organ involvement.

  12. Minimal changes in health status questionnaires: distinction between minimally detectable change and minimally important change

    Directory of Open Access Journals (Sweden)

    Knol Dirk L

    2006-08-01

    Full Text Available Abstract Changes in scores on health status questionnaires are difficult to interpret. Several methods to determine minimally important changes (MICs have been proposed which can broadly be divided in distribution-based and anchor-based methods. Comparisons of these methods have led to insight into essential differences between these approaches. Some authors have tried to come to a uniform measure for the MIC, such as 0.5 standard deviation and the value of one standard error of measurement (SEM. Others have emphasized the diversity of MIC values, depending on the type of anchor, the definition of minimal importance on the anchor, and characteristics of the disease under study. A closer look makes clear that some distribution-based methods have been merely focused on minimally detectable changes. For assessing minimally important changes, anchor-based methods are preferred, as they include a definition of what is minimally important. Acknowledging the distinction between minimally detectable and minimally important changes is useful, not only to avoid confusion among MIC methods, but also to gain information on two important benchmarks on the scale of a health status measurement instrument. Appreciating the distinction, it becomes possible to judge whether the minimally detectable change of a measurement instrument is sufficiently small to detect minimally important changes.

  13. Minimal Webs in Riemannian Manifolds

    DEFF Research Database (Denmark)

    Markvorsen, Steen

    2008-01-01

    are of instrumental importance for the applications. We apply these properties to show that minimal webs in ambient Riemannian spaces share several analytic and geometric properties with their smooth (minimal submanifold) counterparts in such spaces. In particular we use appropriate versions of the divergence......)$ into Riemannian manifolds $(N^{n}, h)$. Such immersions we call {\\em{minimal webs}}. They admit a natural 'geometric' extension of the intrinsic combinatorial discrete Laplacian. The geometric Laplacian on minimal webs enjoys standard properties such as the maximum principle and the divergence theorems, which...... theorems together with the comparison techniques for distance functions in Riemannian geometry and obtain bounds for the first Dirichlet eigenvalues, the exit times and the capacities as well as isoperimetric type inequalities for so-called extrinsic $R-$webs of minimal webs in ambient Riemannian manifolds...

  14. Waste minimization handbook, Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    Boing, L.E.; Coffey, M.J.

    1995-12-01

    This technical guide presents various methods used by industry to minimize low-level radioactive waste (LLW) generated during decommissioning and decontamination (D and D) activities. Such activities generate significant amounts of LLW during their operations. Waste minimization refers to any measure, procedure, or technique that reduces the amount of waste generated during a specific operation or project. Preventive waste minimization techniques implemented when a project is initiated can significantly reduce waste. Techniques implemented during decontamination activities reduce the cost of decommissioning. The application of waste minimization techniques is not limited to D and D activities; it is also useful during any phase of a facility`s life cycle. This compendium will be supplemented with a second volume of abstracts of hundreds of papers related to minimizing low-level nuclear waste. This second volume is expected to be released in late 1996.

  15. Reducing the effects of metal artefact using high keV monoenergetic reconstruction of dual energy CT (DECT) in hip replacements

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Mark [Norfolk and Norwich University Hospital, Norwich (United Kingdom); Norwich Radiology Academy, Norwich (United Kingdom); Reid, Karen [Norfolk and Norwich University Hospital, Norwich (United Kingdom); Toms, Andoni P. [Norfolk and Norwich University Hospital and University of East Anglia, Norwich (United Kingdom)

    2013-02-15

    The aim of this study was to determine whether high keV monoenergetic reconstruction of dual energy computed tomography (DECT) could be used to overcome the effects of beam hardening artefact that arise from preferential deflection of low energy photons. Two phantoms were used: a Charnley total hip replacement set in gelatine and a Catphan 500. DECT datasets were acquired at 100, 200 and 400 mA (Siemens Definition Flash, 100 and 140 kVp) and reconstructed using a standard combined algorithm (1:1) and then as monoenergetic reconstructions at 10 keV intervals from 40 to 190 keV. Semi-automated segmentation with threshold inpainting was used to obtain the attenuation values and standard deviation (SD) of the streak artefact. High contrast line pair resolution and background noise were assessed using the Catphan 500. Streak artefact is progressively reduced with increasing keV monoenergetic reconstructions. Reconstruction of a 400 mA acquisition at 150 keV results in reduction in the volume of streak artefact from 65 cm{sup 3} to 17 cm{sup 3} (74 %). There was a decrease in the contrast to noise ratio (CNR) at higher tube voltages, with the peak CNR seen at 70-80 keV. High contrast spatial resolution was maintained at high keV values. Monoenergetic reconstruction of dual energy CT at increasing theoretical kilovoltages reduces the streak artefact produced by beam hardening from orthopaedic prostheses, accompanied by a modest increase in heterogeneity of background image attenuation, and decrease in contrast to noise ratio, but no deterioration in high contrast line pair resolution. (orig.)

  16. Algorithms that eliminate the effects of calibration artefact and trial-imposed offsets of Masimo oximeter in BOOST-NZ trial.

    Science.gov (United States)

    Zahari, Marina; Lee, Dominic Savio; Darlow, Brian Alexander

    2016-10-01

    The displayed readings of Masimo pulse oximeters used in the Benefits Of Oxygen Saturation Targeting (BOOST) II and related trials in very preterm babies were influenced by trial-imposed offsets and an artefact in the calibration software. A study was undertaken to implement new algorithms that eliminate the effects of offsets and artefact. In the BOOST-New Zealand trial, oxygen saturations were averaged and stored every 10 s up to 36 weeks' post-menstrual age. Two-hundred and fifty-seven of 340 babies enrolled in the trial had at least two weeks of stored data. Oxygen saturation distribution patterns corresponding with a +3 % or -3 % offset in the 85-95 % range were identified together with that due to the calibration artefact. Algorithms involving linear and quadratic interpolations were developed, implemented on each baby of the dataset and validated using the data of a UK preterm baby, as recorded from Masimo oximeters with the original software and a non-offset Siemens oximeter. Saturation distributions obtained were compared for both groups. There were a flat region at saturations 85-87 % and a peak at 96 % from the lower saturation target oximeters, and at 93-95 and 84 % respectively from the higher saturation target oximeters. The algorithms lowered the peaks and redistributed the accumulated frequencies to the flat regions and artefact at 87-90 %. The resulting distributions were very close to those obtained from the Siemens oximeter. The artefact and offsets of the Masimo oximeter's software had been addressed to determine the true saturation readings through the use of novel algorithms. The implementation would enable New Zealand data be included in the meta-analysis of BOOST II trials, and be used in neonatal oxygen studies.

  17. Transdermal Photopolymerization for Minimally Invasive Implantation

    Science.gov (United States)

    Elisseeff, J.; Anseth, K.; Sims, D.; McIntosh, W.; Randolph, M.; Langer, R.

    1999-03-01

    Photopolymerizations are widely used in medicine to create polymer networks for use in applications such as bone restorations and coatings for artificial implants. These photopolymerizations occur by directly exposing materials to light in "open" environments such as the oral cavity or during invasive procedures such as surgery. We hypothesized that light, which penetrates tissue including skin, could cause a photopolymerization indirectly. Liquid materials then could be injected s.c. and solidified by exposing the exterior surface of the skin to light. To test this hypothesis, the penetration of UVA and visible light through skin was studied. Modeling predicted the feasibility of transdermal polymerization with only 2 min of light exposure required to photopolymerize an implant underneath human skin. To establish the validity of these modeling studies, transdermal photopolymerization first was applied to tissue engineering by using "injectable" cartilage as a model system. Polymer/chondrocyte constructs were injected s.c. and transdermally photopolymerized. Implants harvested at 2, 4, and 7 weeks demonstrated collagen and proteoglycan production and histology with tissue structure comparable to native neocartilage. To further examine this phenomenon and test the applicability of transdermal photopolymerization for drug release devices, albumin, a model protein, was released for 1 week from photopolymerized hydrogels. With further study, transdermal photpolymerization potentially could be used to create a variety of new, minimally invasive surgical procedures in applications ranging from plastic and orthopedic surgery to tissue engineering and drug delivery.

  18. Superspace geometry and the minimal, non minimal, and new minimal supergravity multiplets

    Energy Technology Data Exchange (ETDEWEB)

    Girardi, G.; Grimm, R.; Mueller, M.; Wess, J.

    1984-11-01

    We analyse superspace constraints in a systematic way and define a set of natural constraints. We give a complete solution of the Bianchi identities subject to these constraints and obtain a reducible, but not fully reducible multiplet. By additional constraints it can be reduced to either the minimal nonminimal or new minimal multiplet. We discuss the superspace actions for the various multiplets.

  19. Locally minimal topological groups 1

    OpenAIRE

    Chasco, María Jesús; Dikranjan, Dikran N.; Außenhofer, Lydia; Domínguez, Xabier

    2015-01-01

    The aim of this paper is to go deeper into the study of local minimality and its connection to some naturally related properties. A Hausdorff topological group ▫$(G,tau)$▫ is called locally minimal if there exists a neighborhood ▫$U$▫ of 0 in ▫$tau$▫ such that ▫$U$▫ fails to be a neighborhood of zero in any Hausdorff group topology on ▫$G$▫ which is strictly coarser than ▫$tau$▫. Examples of locally minimal groups are all subgroups of Banach-Lie groups, all locally compact groups and all mini...

  20. Minimal flows and their extensions

    CERN Document Server

    Auslander, J

    1988-01-01

    This monograph presents developments in the abstract theory of topological dynamics, concentrating on the internal structure of minimal flows (actions of groups on compact Hausdorff spaces for which every orbit is dense) and their homomorphisms (continuous equivariant maps). Various classes of minimal flows (equicontinuous, distal, point distal) are intensively studied, and a general structure theorem is obtained. Another theme is the ``universal'' approach - entire classes of minimal flows are studied, rather than flows in isolation. This leads to the consideration of disjointness of flows, w

  1. Factors of psychological distress: clinical value, measurement substance, and methodological artefacts.

    Science.gov (United States)

    Böhnke, J R; Croudace, T J

    2015-04-01

    Psychometric models and statistical techniques are cornerstones of research into latent structures of specific psychopathology and general mental health. We discuss "pivot points" for future research efforts from a psychometric epidemiology perspective, emphasising sampling and selection processes of both indicators that guide data collection as well as samples that are confronted with them. First, we discuss how a theoretical model of psychopathology determines which empirical indicators (questions, diagnoses, etc.) and modelling methods are appropriate to test its implications. Second, we deal with how different research designs introduce different (co-)variances between indicators, potentially leading to a different understanding of latent structures. Third, we discuss widening the range of statistical models available within the "psychometrics class": the inclusion of categorical approaches can help to enlighten the debate on the structure of psychopathology and agreement on a minimal set of models might lead to greater convergence between studies. Fourth, we deal with aspects of methodology that introduce spurious (co-)variance in latent structure analysis (response styles, clustered data) and differential item functioning to gather more detailed information and to guard against over-generalisation of results, which renders assessments unfair. Building on established insights, future research efforts should be more explicit about their theoretical understanding of psychopathology and how the analysis of a given indicator-respondent set informs this theoretical model. A coherent treatment of theoretical assumptions, indicators, and samples holds the key to building a comprehensive account of the latent structures of different types of psychopathology and mental health in general.

  2. Sludge minimization technologies - an overview

    Energy Technology Data Exchange (ETDEWEB)

    Oedegaard, Hallvard

    2003-07-01

    The management of wastewater sludge from wastewater treatment plants represents one of the major challenges in wastewater treatment today. The cost of the sludge treatment amounts to more that the cost of the liquid in many cases. Therefore the focus on and interest in sludge minimization is steadily increasing. In the paper an overview is given for sludge minimization (sludge mass reduction) options. It is demonstrated that sludge minimization may be a result of reduced production of sludge and/or disintegration processes that may take place both in the wastewater treatment stage and in the sludge stage. Various sludge disintegration technologies for sludge minimization are discussed, including mechanical methods (focusing on stirred ball-mill, high-pressure homogenizer, ultrasonic disintegrator), chemical methods (focusing on the use of ozone), physical methods (focusing on thermal and thermal/chemical hydrolysis) and biological methods (focusing on enzymatic processes). (author)

  3. Minimally invasive surgery. Future developments.

    OpenAIRE

    1994-01-01

    The rapid development of minimally invasive surgery means that there will be fundamental changes in interventional treatment. Technological advances will allow new minimally invasive procedures to be developed. Application of robotics will allow some procedures to be done automatically, and coupling of slave robotic instruments with virtual reality images will allow surgeons to perform operations by remote control. Miniature motors and instruments designed by microengineering could be introdu...

  4. Cost minimization and asset pricing

    OpenAIRE

    Robert G. Chambers; John Quiggin

    2005-01-01

    A cost-based approach to asset-pricing equilibrium relationships is developed. A cost function induces a stochastic discount factor (pricing kernel) that is a function of random output, prices, and capital stockt. By eliminating opportunities for arbitrage between financial markets and the production technology, firms minimize the current cost of future consumption. The first-order conditions for this cost minimization problem generate the stochastic discount factor. The cost-based approach i...

  5. Influenza SIRS with minimal pneumonitis

    Directory of Open Access Journals (Sweden)

    Shruti Erramilli

    2016-08-01

    Full Text Available While systemic inflammatory response syndrome (SIRS, is a known complication of severe influenza pneumonia, it has been reported very rarely in patients with minimal parenchymal lung disease. We here report a case of severe SIRS, anasarca and marked vascular phenomena with minimal or no pneumonitis. This case highlights that viruses, including influenza, may cause vascular dysregulation causing SIRS, even without substantial visceral organ involvement.

  6. Practical pathology perspectives for minimally invasive hyperthermic medical devices

    Science.gov (United States)

    Coad, James E.

    2011-03-01

    Currently, hyperthermic-based minimally invasive medical devices are available for the treatment of dysfunctional and neoplastic tissues in a variety of organ systems. These therapies employ a spectrum of modalities for delivering heat energy to the targeted tissue, including radiofrequency/microwave, high intensity focused ultrasound, conductive/convective sources and others. While differences in energy transfer and organ systems exist, hyperthermic treatment sites show a spectrum of changes that intimately correlate with the thermal history generated in the tissue (temperature-time dependence). As a result, these hyperthermic medical technologies can be viewed using a "gradient" approach. First, the thermal applications themselves can be globally categorized along a high-dose ablation to low-dose ablation to lowdose non-ablative rejuvenating slope. Second, the resultant tissue changes can be viewed along a decreasing thermal dose gradient from thermally/heat-fixed tissue necrosis to coagulative tissue necrosis to partial tissue necrosis (transition zone) to subtle non-necrotizing tissue changes. Finally, a gradient of cellular and structural protein denaturation is present, especially within the transition zone and adjacent viable tissue region. A hyperthermic treatment's location along these gradients depends more on the overall thermal history it generates than the amount of energy it deposits into the tissue. The features of these gradients are highlighted to provide a better understanding of hyperthermic device associated tissue changes and their associated healing responses.

  7. [Metal artefact on head and neck cone-beam CT images].

    Science.gov (United States)

    Kovacs, Miklós; Fejérdy, Pál; Dobó, Nagy Csaba

    2008-10-01

    There are only a few factors, where the properties of the CBCT is inferior compared to conventional CT. One of these properties is the low contrast resolution, which has an importance in the discrimination of different soft tissues. Another difference is the image quality degrading effect by metal objects. This latter factor has much higher importance in head and neck region CBCT application. The metal artifact is closely related to other types of artifacts, like beam-hardening and x-ray photon scattering artifacts. In some of the cases, metal artifacts can be avoided by the proper adjustment of the scanning parameters, but sometimes the problem overgrows the possibilities. The current pre- and post-processing algorithms used for the correction of different artifacts can improve the image quality, but these algorithms are not the ultimate solution to the problem. The introduction of iterative reconstruction algorithms into the CBCT market will effectively reduce the most CT artifacts, however, the spread of this algorithms are set back because of the insufficient computational power of today's PCs. Another advantage of the use of iterative algorithms is that the patient dose could be significantly reduced.

  8. A Multi-Channel Opto-Electronic Sensor to Accurately Monitor Heart Rate against Motion Artefact during Exercise

    Directory of Open Access Journals (Sweden)

    Abdullah Alzahrani

    2015-10-01

    Full Text Available This study presents the use of a multi-channel opto-electronic sensor (OEPS to effectively monitor critical physiological parameters whilst preventing motion artefact as increasingly demanded by personal healthcare. The aim of this work was to study how to capture the heart rate (HR efficiently through a well-constructed OEPS and a 3-axis accelerometer with wireless communication. A protocol was designed to incorporate sitting, standing, walking, running and cycling. The datasets collected from these activities were processed to elaborate sport physiological effects. t-test, Bland-Altman Agreement (BAA, and correlation to evaluate the performance of the OEPS were used against Polar and Mio-Alpha HR monitors. No differences in the HR were found between OEPS, and either Polar or Mio-Alpha (both p > 0.05; a strong correlation was found between Polar and OEPS (r: 0.96, p < 0.001; the bias of BAA 0.85 bpm, the standard deviation (SD 9.20 bpm, and the limits of agreement (LOA from −17.18 bpm to +18.88 bpm. For the Mio-Alpha and OEPS, a strong correlation was found (r: 0.96, p < 0.001; the bias of BAA 1.63 bpm, SD 8.62 bpm, LOA from −15.27 bpm to +18.58 bpm. These results demonstrate the OEPS to be capable of carrying out real time and remote monitoring of heart rate.

  9. The Structure of Artefacts of Management Control in the Innovation Process: Does Exist Association with the Strategic Profile?

    Directory of Open Access Journals (Sweden)

    Fábio Frezatti

    2015-01-01

    Full Text Available This study investigates what is the role of strateg ic profiles and management control instruments in organisations’ innovation process. B ased in a survey using structural equation modelling (121 companies, we confirm that analyser , defender e prospector profiles are associated with strategic planning, balanced scorec ard (BSC and rolling forecast. The reactor type is associated with lower use of artefacts. Our results confirm the linkage between incremental innovation and strategic planning and b etween radical innovation and BSC. These findings reflect the alignment between strate gic types, the availability of instruments and intensity of innovation, which is useful inform ation with which to understand organisations and their market activities. This pap er bring information about specific management control instruments existence and the im pact for the intensity of the innovation that is relevant for management and must stimulate organizations to be consistent in the cases that the strategic profile is a clear long term def inition or see the possibility of change when it is not the desired one.

  10. Spectral performance of SKA Log-periodic Antennas I: mitigating spectral artefacts in SKA1-LOW 21 cm cosmology experiments

    Science.gov (United States)

    de Lera Acedo, Eloy; Trott, Cathryn M.; Wayth, Randall B.; Fagnoni, Nicolas; Bernardi, Gianni; Wakley, Brett; Koopmans, Léon V. E.; Faulkner, Andrew J.; bij de Vaate, Jan Geralt

    2017-08-01

    This paper is the first in a series of papers describing the impact of antenna instrumental artefacts on the 21 cm cosmology experiments to be carried out by the low frequency instrument (SKA1-LOW) of the Square Kilometre Array telescope (SKA), i.e. the Cosmic Dawn (CD) and the Epoch of Reionization (EoR). The smoothness of the passband response of the current log-periodic antenna being developed for the SKA1-LOW is analysed using numerical electromagnetic simulations. The amplitude variations over the frequency range are characterized using low-order polynomials defined locally, in order to study the impact of the passband smoothness in the instrument calibration and CD/EoR Science. A solution is offered to correct a fast ripple found at 60 MHz during a test campaign at the SKA site at the Murchison Radio-astronomy Observatory, Western Australia in 2015 September with a minor impact on the telescope's performance and design. A comparison with the Hydrogen Epoch of Reionization Array antenna is also shown demonstrating the potential use of the SKA1-LOW antenna for the delay-spectrum technique to detect the EoR.

  11. On artefact-free reconstruction of low-energy (30–250 eV) electron holograms

    Energy Technology Data Exchange (ETDEWEB)

    Latychevskaia, Tatiana, E-mail: tatiana@physik.uzh.ch; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

    2014-10-15

    Low-energy electrons (30–250 eV) have been successfully employed for imaging individual biomolecules. The most simple and elegant design of a low-energy electron microscope for imaging biomolecules is a lensless setup that operates in the holographic mode. In this work we address the problem associated with the reconstruction from the recorded holograms. We discuss the twin image problem intrinsic to inline holography and the problem of the so-called biprism-like effect specific to low-energy electrons. We demonstrate how the presence of the biprism-like effect can be efficiently identified and circumvented. The presented sideband filtering reconstruction method eliminates the twin image and allows for reconstruction despite the biprism-like effect, which we demonstrate on both, simulated and experimental examples. - Highlights: • Radiation damage-free imaging of individual biomolecules. • Elimination of the twin image in inline holograms. • Circumventing biprism-like effect in low-energy electron holograms. • Artefact-free reconstructions of low-energy electron holograms.

  12. The usefulness of ultrasound colour-Doppler twinkling artefact for detecting urolithiasis compared with low dose nonenhanced computerized tomography.

    Science.gov (United States)

    Winkel, Rikke Rass; Kalhauge, Anna; Fredfeldt, Knud-Erik

    2012-07-01

    This prospective study evaluates the usefulness of the twinkling artefact (TA) seen on colour-Doppler ultrasound (US) in diagnosing urolithiasis. US and standard computed tomography (CT) were performed blinded on 105 patients. B-mode US and colour-Doppler used separately and in combination showed 55% sensitivity and 99% specificity (positive predictive value [PPV] 67% and negative predictive value [NPV] 98%). Of CT verified stones, 61% were ≤3 mm. TAs were present in 74% of the B-mode stones (43% of all CT verified stones). Patients with CT verified stone disease had significantly more TAs in other foci than the stone(s) found on CT, suggestive of microlithiasis. In conclusion, colour-Doppler TA is a helpful supplement for detecting urolithiasis when CT is contraindicated. In addition, US can be valuable in monitoring stones left to pass without intervention if they have presented a TA. CT, US and US with colour-Doppler TA can be useful as complementary techniques for detecting stones.

  13. Identification of the earliest collagen- and plant-based coatings from Neolithic artefacts (Nahal Hemar cave, Israel).

    Science.gov (United States)

    Solazzo, Caroline; Courel, Blandine; Connan, Jacques; van Dongen, Bart E; Barden, Holly; Penkman, Kirsty; Taylor, Sheila; Demarchi, Beatrice; Adam, Pierre; Schaeffer, Philippe; Nissenbaum, Arie; Bar-Yosef, Ofer; Buckley, Michael

    2016-08-09

    Mortuary practices in human evolution record cognitive, social changes and technological innovations. The Neolithic Revolution in the Levant was a watershed in this domain that has long fascinated the archaeological community. Plaster modelled skulls are well known at Jericho and several other Neolithic sites, and in Nahal Hemar cave (Israel, ca. 8200 -7300 cal. BC) excavations yielded six unique human skulls covered with a black organic coating applied in a net pattern evoking a headdress. This small cave was used as storage for paraphernalia in the semi-arid area of the Judean desert and the dry conditions preserved other artefacts such as baskets coated with a similar dark substance. While previous analysis had revealed the presence of amino acids consistent with a collagen signature, in the present report, specific biomarkers were characterised using combined proteomic and lipid approaches. Basket samples yielded collagen and blood proteins of bovine origin (Bos genus) and a large sequence coverage of a plant protein charybdin (Charybdis genus). The skull residue samples were dominated by benzoate and cinnamate derivatives and triterpenes consistent with a styrax-type resin (Styrax officinalis), thus providing the earliest known evidence of an odoriferous plant resin used in combination with an animal product.

  14. Minimally Invasive Video-Assisted versus Minimally Invasive Nonendoscopic Thyroidectomy

    Directory of Open Access Journals (Sweden)

    Zdeněk Fík

    2014-01-01

    Full Text Available Minimally invasive video-assisted thyroidectomy (MIVAT and minimally invasive nonendoscopic thyroidectomy (MINET represent well accepted and reproducible techniques developed with the main goal to improve cosmetic outcome, accelerate healing, and increase patient’s comfort following thyroid surgery. Between 2007 and 2011, a prospective nonrandomized study of patients undergoing minimally invasive thyroid surgery was performed to compare advantages and disadvantages of the two different techniques. There were no significant differences in the length of incision to perform surgical procedures. Mean duration of hemithyroidectomy was comparable in both groups, but it was more time consuming to perform total thyroidectomy by MIVAT. There were more patients undergoing MIVAT procedures without active drainage in the postoperative course and we also could see a trend for less pain in the same group. This was paralleled by statistically significant decreased administration of both opiates and nonopiate analgesics. We encountered two cases of recurrent laryngeal nerve palsies in the MIVAT group only. MIVAT and MINET represent safe and feasible alternative to conventional thyroid surgery in selected cases and this prospective study has shown minimal differences between these two techniques.

  15. Minimizing Costs Can Be Costly

    Directory of Open Access Journals (Sweden)

    Rasmus Rasmussen

    2010-01-01

    Full Text Available A quite common practice, even in academic literature, is to simplify a decision problem and model it as a cost-minimizing problem. In fact, some type of models has been standardized to minimization problems, like Quadratic Assignment Problems (QAPs, where a maximization formulation would be treated as a “generalized” QAP and not solvable by many of the specially designed softwares for QAP. Ignoring revenues when modeling a decision problem works only if costs can be separated from the decisions influencing revenues. More often than we think this is not the case, and minimizing costs will not lead to maximized profit. This will be demonstrated using spreadsheets to solve a small example. The example is also used to demonstrate other pitfalls in network models: the inability to generally balance the problem or allocate costs in advance, and the tendency to anticipate a specific type of solution and thereby make constraints too limiting when formulating the problem.

  16. Minimal Marking: A Success Story

    Directory of Open Access Journals (Sweden)

    Anne McNeilly

    2014-11-01

    Full Text Available The minimal-marking project conducted in Ryerson’s School of Journalism throughout 2012 and early 2013 resulted in significantly higher grammar scores in two first-year classes of minimally marked university students when compared to two traditionally marked classes. The “minimal-marking” concept (Haswell, 1983, which requires dramatically more student engagement, resulted in more successful learning outcomes for surface-level knowledge acquisition than the more traditional approach of “teacher-corrects-all.” Results suggest it would be effective, not just for grammar, punctuation, and word usage, the objective here, but for any material that requires rote-memory learning, such as the Associated Press or Canadian Press style rules used by news publications across North America.

  17. Debriefing the Land:The Use of Non-immersive Virtual Reality Technologies to Record, Navigate and Analyse Artefact-rich Landscapes

    Directory of Open Access Journals (Sweden)

    Brian Larkman

    2000-09-01

    Full Text Available This article discusses ways of perceiving subtle features within landscapes and of transposing them into hypermedia. It sets out to examine the problems encountered when navigating, recording, and analysing forms of landscape-related artefacts such as prehistoric 'monuments', land art, sculpture parks, and landscaped gardens. In particular, techniques for examining and recording both the local properties - including texture, form, weathering, and construction techniques - and the wider properties such as relationship of artefacts to their site, topography, inter-visibility etc., are considered. As a pilot study, Apple Computer's QuickTimeVR technology has been used to record several representative landscapes, including some of the prehistoric carved rock art of Yorkshire and Northumberland, with particular reference to inter-visibility between sites. The recordings are examined with reference to the local and wider properties of the sites and the landscapes that contain them to determine how successfully the technique captures their features for remote viewing.

  18. Fps1p channel is the mediator of the major part of glycerol passive diffusion in Saccharomyces cerevisiae : artefacts and re-definitions

    OpenAIRE

    Oliveira, Rui Pedro Soares de; Lages, Fernanda; Graça, Magda Maria Couto da Silva; Lucas, Cândida

    2003-01-01

    Glycerol has been shown to cross Saccharomyces cerevisiae plasma membrane (1) through a H+/symport detected in cells grown on non-fermentable carbon sources, (2) by passive diffusion and (3) through the constitutive Fps1p channel. This has been named a facilitator, for mediating glycerol low affinity transport of the facilitated diffusion type. We present experimental evidence that this kinetics is an artefact created by glycerol kinase activity. Instead, the channel is shown to mediate the m...

  19. How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment.

    Science.gov (United States)

    Bernáth, Balázs; Farkas, Alexandra; Száz, Dénes; Blahó, Miklós; Egri, Adám; Barta, András; Akesson, Susanne; Horváth, Gábor

    2014-06-01

    Vikings routinely crossed the North Atlantic without a magnetic compass and left their mark on lands as far away as Greenland, Newfoundland and Baffin Island. Based on an eleventh-century dial fragment artefact, found at Uunartoq in Greenland, it is widely accepted that they sailed along chosen latitudes using primitive Sun compasses. Such instruments were tested on sea and proved to be efficient hand-held navigation tools, but the dimensions and incisions of the Uunartoq find are far from optimal in this role. On the basis of the sagas mentioning sunstones, incompatible hypotheses were formed for Viking solar navigation procedures and primitive skylight polarimetry with dichroic or birefringent crystals. We describe here a previously unconceived method of navigation based on the Uunartoq artefact functioning as a 'twilight board', which is a combination of a horizon board and a Sun compass optimized for use when the Sun is close to the horizon. We deduced an appropriate solar navigation procedure using a twilight board, a shadow-stick and birefringent crystals, which bring together earlier suggested methods in harmony and provide a true skylight compass function. This could have allowed Vikings to navigate around the clock, to use the artefact dial as a Sun compass during long parts of the day and to use skylight polarization patterns in the twilight period. In field tests, we found that true north could be appointed with such a medieval skylight compass with an error of about ±4° when the artificially occluded Sun had elevation angles between +10° and -8° relative to the horizon. Our interpretation allows us to assign exact dates to the gnomonic lines on the artefact and outlines the schedule of the merchant ships that sustained the Viking colony in Greenland a millennium ago.

  20. How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment

    Science.gov (United States)

    Bernáth, Balázs; Farkas, Alexandra; Száz, Dénes; Blahó, Miklós; Egri, Ádám; Barta, András; Åkesson, Susanne; Horváth, Gábor

    2014-01-01

    Vikings routinely crossed the North Atlantic without a magnetic compass and left their mark on lands as far away as Greenland, Newfoundland and Baffin Island. Based on an eleventh-century dial fragment artefact, found at Uunartoq in Greenland, it is widely accepted that they sailed along chosen latitudes using primitive Sun compasses. Such instruments were tested on sea and proved to be efficient hand-held navigation tools, but the dimensions and incisions of the Uunartoq find are far from optimal in this role. On the basis of the sagas mentioning sunstones, incompatible hypotheses were formed for Viking solar navigation procedures and primitive skylight polarimetry with dichroic or birefringent crystals. We describe here a previously unconceived method of navigation based on the Uunartoq artefact functioning as a ‘twilight board’, which is a combination of a horizon board and a Sun compass optimized for use when the Sun is close to the horizon. We deduced an appropriate solar navigation procedure using a twilight board, a shadow-stick and birefringent crystals, which bring together earlier suggested methods in harmony and provide a true skylight compass function. This could have allowed Vikings to navigate around the clock, to use the artefact dial as a Sun compass during long parts of the day and to use skylight polarization patterns in the twilight period. In field tests, we found that true north could be appointed with such a medieval skylight compass with an error of about ±4° when the artificially occluded Sun had elevation angles between +10° and −8° relative to the horizon. Our interpretation allows us to assign exact dates to the gnomonic lines on the artefact and outlines the schedule of the merchant ships that sustained the Viking colony in Greenland a millennium ago. PMID:24910520

  1. X-ray fluorescence microscopy artefacts in elemental maps of topologically complex samples: Analytical observations, simulation and a map correction method

    Science.gov (United States)

    Billè, Fulvio; Kourousias, George; Luchinat, Enrico; Kiskinova, Maya; Gianoncelli, Alessandra

    2016-08-01

    XRF spectroscopy is among the most widely used non-destructive techniques for elemental analysis. Despite the known angular dependence of X-ray fluorescence (XRF), topological artefacts remain an unresolved issue when using X-ray micro- or nano-probes. In this work we investigate the origin of the artefacts in XRF imaging of topologically complex samples, which are unresolved problems in studies of organic matter due to the limited travel distances of low energy XRF emission from the light elements. In particular we mapped Human Embryonic Kidney (HEK293T) cells. The exemplary results with biological samples, obtained with a soft X-ray scanning microscope installed at a synchrotron facility were used for testing a mathematical model based on detector response simulations, and for proposing an artefact correction method based on directional derivatives. Despite the peculiar and specific application, the methodology can be easily extended to hard X-rays and to set-ups with multi-array detector systems when the dimensions of surface reliefs are in the order of the probing beam size.

  2. Investigation of ternary and quaternary high-temperature fixed-point cells, based on platinum-carbon-X, as blind comparison artefacts

    Science.gov (United States)

    Dong, W.; Machin, G.; Bloembergen, P.; Lowe, D.; Wang, T.

    2016-11-01

    Extensive studies of platinum-carbon eutectic alloy based high temperature fixed point cells have shown that this alloy has extremely good metrological potential as a temperature reference. However, it’s possible adoption as an accepted reference standard means that its eutectic temperature value will soon be agreed with an uncertainty less than most radiation thermometry scales at that temperature. Thus it will lack credibility if used as a future scale comparison artefact. To avoid this, the fixed-point cell can be deliberately doped with an impurity to change its transition temperature by an amount sufficient to test the accuracy of the scales of the institutes, involved in the comparison. In this study dopants of palladium and iridium were added to platinum-carbon to produce ternary alloy and quaternary alloy fixed-point cells. The stability of these artefacts was demonstrated and the fixed-point cells were used to compare the ITS-90 scales of NIM and NPL. It was found that the fixed point temperatures could be changed by an appreciable amount while retaining the stability and repeatability required for comparison artefacts.

  3. Minimal Flavor Constraints for Technicolor

    DEFF Research Database (Denmark)

    Sakuma, Hidenori; Sannino, Francesco

    2010-01-01

    We analyze the constraints on the the vacuum polarization of the standard model gauge bosons from a minimal set of flavor observables valid for a general class of models of dynamical electroweak symmetry breaking. We will show that the constraints have a strong impact on the self-coupling and mas...

  4. Dubin's Minimal Linkage Construct Revisited.

    Science.gov (United States)

    Rogers, Donald P.

    This paper contains a theoretical analysis and empirical study that support the major premise of Robert Dubin's minimal-linkage construct-that restricting communication links increases organizational stability. The theoretical analysis shows that fewer communication links are associated with less uncertainty, more redundancy, and greater…

  5. Minimal Surfaces for Hitchin Representations

    DEFF Research Database (Denmark)

    Li, Qiongling; Dai, Song

    2016-01-01

    Given a reductive representation $\\rho: \\pi_1(S)\\rightarrow G$, there exists a $\\rho$-equivariant harmonic map $f$ from the universal cover of a fixed Riemann surface $\\Sigma$ to the symmetric space $G/K$ associated to $G$. If the Hopf differential of $f$ vanishes, the harmonic map is then minimal...

  6. Acquiring minimally invasive surgical skills

    NARCIS (Netherlands)

    Hiemstra, Ellen

    2012-01-01

    Many topics in surgical skills education have been implemented without a solid scientific basis. For that reason we have tried to find this scientific basis. We have focused on training and evaluation of minimally invasive surgical skills in a training setting and in practice in the operating room.

  7. On Minimal Norms on Mn

    Directory of Open Access Journals (Sweden)

    Madjid Mirzavaziri

    2007-01-01

    norms ‖⋅‖1 and ‖⋅‖2 on ℂn such that N(A=max{‖Ax‖2:‖x‖1=1, x∈ℂn} for all A∈ℳn. This may be regarded as an extension of a known result on characterization of minimal algebra norms.

  8. Implications of minimally invasive therapy

    NARCIS (Netherlands)

    Banta, H.D.; Schersten, T.; Jonsson, E.

    1993-01-01

    The field of minimally invasive therapy (MIT) raises many important issues for the future of health care. It seems inevitable that MIT will replace much conventional surgery. This trend is good for society and good for patients. The health care system, however, may find the change disruptive. The

  9. Surgical efficacy of minimally invasive thoracic discectomy.

    Science.gov (United States)

    Elhadi, Ali M; Zehri, Aqib H; Zaidi, Hasan A; Almefty, Kaith K; Preul, Mark C; Theodore, Nicholas; Dickman, Curtis A

    2015-11-01

    We aimed to determine the clinical indications and surgical outcomes for thoracoscopic discectomy. Thoracic disc disease is a rare degenerative process. Thoracoscopic approaches serve to minimize tissue injury during the approach, but critics argue that this comes at the cost of surgical efficacy. Current reports in the literature are limited to small institutional patient series. We systematically identified all English language articles on thoracoscopic discectomy with at least two patients, published from 1994 to 2013 on MEDLINE, Science Direct, and Google Scholar. We analyzed 12 articles that met the inclusion criteria, five prospective and seven retrospective studies comprising 545 surgical patients. The overall complication rate was 24% (n=129), with reported complications ranging from intercostal neuralgia (6.1%), atelectasis (2.8%), and pleural effusion (2.6%), to more severe complications such as pneumonia (0.8%), pneumothorax (1.3%), and venous thrombosis (0.2%). The average reported postoperative follow-up was 20.5 months. Complete resolution of symptoms was reported in 79% of patients, improvement with residual symptoms in 10.2%, no change in 9.6%, and worsening in 1.2%. The minimally invasive endoscopic approaches to the thoracic spine among selected patients demonstrate excellent clinical efficacy and acceptable complication rates, comparable to the open approaches. Disc herniations confined to a single level, with small or no calcifications, are ideal for such an approach, whereas patients with calcified discs adherent to the dura would benefit from an open approach.

  10. [Theory and practice of minimally invasive endodontics].

    Science.gov (United States)

    Jiang, H W

    2016-08-01

    The primary goal of modern endodontic therapy is to achieve the long-term retention of a functional tooth by preventing or treating pulpitis or apical periodontitis is. The long-term retention of endodontically treated tooth is correlated with the remaining amount of tooth tissue and the quality of the restoration after root canal filling. In recent years, there has been rapid progress and development in the basic research of endodontic biology, instrument and applied materials, making treatment procedures safer, more accurate, and more efficient. Thus, minimally invasive endodontics(MIE)has received increasing attention at present. MIE aims to preserve the maximum of tooth structure during root canal therapy, and the concept covers the whole process of diagnosis and treatment of teeth. This review article focuses on describing the minimally invasive concepts and operating essentials in endodontics, from diagnosis and treatment planning to the access opening, pulp cavity finishing, root canal cleaning and shaping, 3-dimensional root canal filling and restoration after root canal treatment.

  11. Minimally invasive approach of panfacial fractures

    Directory of Open Access Journals (Sweden)

    Yudi Wijaya

    2017-08-01

    Full Text Available Background. Panfacial fractures involves fractures of several bones of face. They are associated with malocclusion, dish face deformity, enopthalmos, diplopia, cerebrospinal fluid leak and soft tissue injuries. Purpose. The purpose of this paper is to present a case of minimizing surgical wound and morbidity. Case. A 40 year old female presented with severe maxillofacial injuries caused by motor vehicle collisions about 5 days prior to admission. The assessment of the patient is mild head injury, panfacial fractures, lacerated wound at face,  rupture of globe of occular sinistra. An open reduction and internal fixation  (ORIF and enucleation of globe occular sinistra was performed.  Intraoral vestibular incision is made in the upper and lower vestibular region. Mucoperiosteal flap elevation of vestibular will exposure of the anterior maxilla and mandibular fractures. Intermaksilary fixation within 3 week and restore aesthetic with prosthesis fitting eyeball and denture. Discusion. The goal of  treatment of  panfacial fracture is to restore both the functions and pre-injury 3-dimensional facial contours. To achieve this goal two common  sequences of management of Panfacial fractures are proposed, “Bottom up and inside out” or “Top down and outside in”. Other sequences exist but there are variations of these two major approaches. Conclusion. A minimally invasive approach to  the fracture site is an alternative method  to manage panfacial fracture with a simple, effective and lower complication rate.

  12. Tissue tests

    NARCIS (Netherlands)

    Sonneveld, C.; Voogt, W.

    2009-01-01

    Tissue tests are widely used in horticulture practice and have in comparison with soil or substrate testing advantages as well disadvantages in comparison with soil testing. One of the main advantages of tissue tests is the certainty that analysed nutrients in plant tissues are really present in the

  13. Tissue tests

    NARCIS (Netherlands)

    Sonneveld, C.; Voogt, W.

    2009-01-01

    Tissue tests are widely used in horticulture practice and have in comparison with soil or substrate testing advantages as well disadvantages in comparison with soil testing. One of the main advantages of tissue tests is the certainty that analysed nutrients in plant tissues are really present in the

  14. Neural tissue-spheres

    DEFF Research Database (Denmark)

    Andersen, Rikke K; Johansen, Mathias; Blaabjerg, Morten

    2007-01-01

    maintained their neurogenic potential throughout 77 days of propagation, while the ability of anterior NTS to generate neurons severely declined from day 40. The present procedure describes isolation and long-term expansion of forebrain SVZ tissue with potential preservation of the endogenous cellular......By combining new and established protocols we have developed a procedure for isolation and propagation of neural precursor cells from the forebrain subventricular zone (SVZ) of newborn rats. Small tissue blocks of the SVZ were dissected and propagated en bloc as free-floating neural tissue......-spheres (NTS) in EGF and FGF2 containing medium. The spheres were cut into quarters when passaged every 10-15th day, avoiding mechanical or enzymatic dissociation in order to minimize cellular trauma and preserve intercellular contacts. For analysis of regional differences within the forebrain SVZ, NTS were...

  15. Harm minimization among teenage drinkers

    DEFF Research Database (Denmark)

    Jørgensen, Morten Hulvej; Curtis, Tine; Christensen, Pia Haudrup

    2007-01-01

    AIM: To examine strategies of harm minimization employed by teenage drinkers. DESIGN, SETTING AND PARTICIPANTS: Two periods of ethnographic fieldwork were conducted in a rural Danish community of approximately 2000 inhabitants. The fieldwork included 50 days of participant observation among 13......-16-year-olds (n = 93) as well as 26 semistructured interviews with small self-selected friendship groups of 15-16-year-olds (n = 32). FINDINGS: The teenagers participating in the present study were more concerned about social than health risks. The informants monitored their own level of intoxication....... In regulating the social context of drinking they relied on their personal experiences more than on formalized knowledge about alcohol and harm, which they had learned from prevention campaigns and educational programmes. CONCLUSIONS: In this study we found that teenagers may help each other to minimize alcohol...

  16. On the Hopcroft's minimization algorithm

    CERN Document Server

    Paun, Andrei

    2007-01-01

    We show that the absolute worst case time complexity for Hopcroft's minimization algorithm applied to unary languages is reached only for de Bruijn words. A previous paper by Berstel and Carton gave the example of de Bruijn words as a language that requires O(n log n) steps by carefully choosing the splitting sets and processing these sets in a FIFO mode. We refine the previous result by showing that the Berstel/Carton example is actually the absolute worst case time complexity in the case of unary languages. We also show that a LIFO implementation will not achieve the same worst time complexity for the case of unary languages. Lastly, we show that the same result is valid also for the cover automata and a modification of the Hopcroft's algorithm, modification used in minimization of cover automata.

  17. A Minimally Symmetric Higgs Boson

    CERN Document Server

    Low, Ian

    2014-01-01

    Models addressing the naturalness of a light Higgs boson typically employ symmetries, either bosonic or fermionic, to stabilize the Higgs mass. We consider a setup with the minimal amount of symmetries: four shift symmetries acting on the four components of the Higgs doublet, subject to the constraints of linearly realized SU(2)xU(1) electroweak symmetry. Up to terms that explicitly violate the shift symmetries, the effective lagrangian can be derived, irrespective of the spontaneously broken group G in the ultraviolet, and is universal in all models where the Higgs arises as a pseudo-Nambu-Goldstone boson (PNGB). Very high energy scatterings of vector bosons could provide smoking gun signals of a minimally symmetric Higgs boson.

  18. Early outcome of minimally invasive mitral valve surgery

    Directory of Open Access Journals (Sweden)

    Shawky Fareed

    2016-08-01

    Conclusion: Right anterolateral mini-thoracotomy minimally invasive technique provides excellent exposure of the mitral valve, even with a small atrium and offers a better cosmetic lateral scar which is less prone to keloid formation. In addition, minimally invasive right anterolateral mini-thoracotomy is as safe as median sternotomy for mitral valve surgery, with fewer complications and postoperative pain, less ICU and hospital stay, fast recovery to work with no movement restriction after surgery. It should be used as an initial approach for mitral valve surgery. Furthermore, it was believed that less spreading of the incision, no interference with the diaphragm and less tissue dissection might improve outcomes, particularly respiratory function.

  19. Consistency of trace norm minimization

    CERN Document Server

    Bach, Francis

    2007-01-01

    Regularization by the sum of singular values, also referred to as the trace norm, is a popular technique for estimating low rank rectangular matrices. In this paper, we extend some of the consistency results of the Lasso to provide necessary and sufficient conditions for rank consistency of trace norm minimization with the square loss. We also provide an adaptive version that is rank consistent even when the necessary condition for the non adaptive version is not fulfilled.

  20. Principle of minimal work fluctuations.

    Science.gov (United States)

    Xiao, Gaoyang; Gong, Jiangbin

    2015-08-01

    Understanding and manipulating work fluctuations in microscale and nanoscale systems are of both fundamental and practical interest. For example, in considering the Jarzynski equality 〈e-βW〉=e-βΔF, a change in the fluctuations of e-βW may impact how rapidly the statistical average of e-βW converges towards the theoretical value e-βΔF, where W is the work, β is the inverse temperature, and ΔF is the free energy difference between two equilibrium states. Motivated by our previous study aiming at the suppression of work fluctuations, here we obtain a principle of minimal work fluctuations. In brief, adiabatic processes as treated in quantum and classical adiabatic theorems yield the minimal fluctuations in e-βW. In the quantum domain, if a system initially prepared at thermal equilibrium is subjected to a work protocol but isolated from a bath during the time evolution, then a quantum adiabatic process without energy level crossing (or an assisted adiabatic process reaching the same final states as in a conventional adiabatic process) yields the minimal fluctuations in e-βW, where W is the quantum work defined by two energy measurements at the beginning and at the end of the process. In the classical domain where the classical work protocol is realizable by an adiabatic process, then the classical adiabatic process also yields the minimal fluctuations in e-βW. Numerical experiments based on a Landau-Zener process confirm our theory in the quantum domain, and our theory in the classical domain explains our previous numerical findings regarding the suppression of classical work fluctuations [G. Y. Xiao and J. B. Gong, Phys. Rev. E 90, 052132 (2014)].

  1. Risk minimization and portfolio diversification

    OpenAIRE

    Farzad Pourbabaee; Minsuk Kwak; Traian A. Pirvu

    2014-01-01

    We consider the problem of minimizing capital at risk in the Black-Scholes setting. The portfolio problem is studied given the possibility that a correlation constraint between the portfolio and a financial index is imposed. The optimal portfolio is obtained in closed form. The effects of the correlation constraint are explored; it turns out that this portfolio constraint leads to a more diversified portfolio.

  2. Outcomes After Minimally Invasive Esophagectomy

    Science.gov (United States)

    Luketich, James D.; Pennathur, Arjun; Awais, Omar; Levy, Ryan M.; Keeley, Samuel; Shende, Manisha; Christie, Neil A.; Weksler, Benny; Landreneau, Rodney J.; Abbas, Ghulam; Schuchert, Matthew J.; Nason, Katie S.

    2014-01-01

    Background Esophagectomy is a complex operation and is associated with significant morbidity and mortality. In an attempt to lower morbidity, we have adopted a minimally invasive approach to esophagectomy. Objectives Our primary objective was to evaluate the outcomes of minimally invasive esophagectomy (MIE) in a large group of patients. Our secondary objective was to compare the modified McKeown minimally invasive approach (videothoracoscopic surgery, laparoscopy, neck anastomosis [MIE-neck]) with our current approach, a modified Ivor Lewis approach (laparoscopy, videothoracoscopic surgery, chest anastomosis [MIE-chest]). Methods We reviewed 1033 consecutive patients undergoing MIE. Elective operation was performed on 1011 patients; 22 patients with nonelective operations were excluded. Patients were stratified by surgical approach and perioperative outcomes analyzed. The primary endpoint studied was 30-day mortality. Results The MIE-neck was performed in 481 (48%) and MIE-Ivor Lewis in 530 (52%). Patients undergoing MIE-Ivor Lewis were operated in the current era. The median number of lymph nodes resected was 21. The operative mortality was 1.68%. Median length of stay (8 days) and ICU stay (2 days) were similar between the 2 approaches. Mortality rate was 0.9%, and recurrent nerve injury was less frequent in the Ivor Lewis MIE group (P < 0.001). Conclusions MIE in our center resulted in acceptable lymph node resection, postoperative outcomes, and low mortality using either an MIE-neck or an MIE-chest approach. The MIE Ivor Lewis approach was associated with reduced recurrent laryngeal nerve injury and mortality of 0.9% and is now our preferred approach. Minimally invasive esophagectomy can be performed safely, with good results in an experienced center. PMID:22668811

  3. Minimal Length, Measurability and Gravity

    Directory of Open Access Journals (Sweden)

    Alexander Shalyt-Margolin

    2016-03-01

    Full Text Available The present work is a continuation of the previous papers written by the author on the subject. In terms of the measurability (or measurable quantities notion introduced in a minimal length theory, first the consideration is given to a quantum theory in the momentum representation. The same terms are used to consider the Markov gravity model that here illustrates the general approach to studies of gravity in terms of measurable quantities.

  4. Optimizing Processes to Minimize Risk

    Science.gov (United States)

    Loyd, David

    2017-01-01

    NASA, like the other hazardous industries, has suffered very catastrophic losses. Human error will likely never be completely eliminated as a factor in our failures. When you can't eliminate risk, focus on mitigating the worst consequences and recovering operations. Bolstering processes to emphasize the role of integration and problem solving is key to success. Building an effective Safety Culture bolsters skill-based performance that minimizes risk and encourages successful engagement.

  5. BDD Minimization for Approximate Computing

    OpenAIRE

    Soeken, Mathias; Grosse, Daniel; Chandrasekharan, Arun; Drechsler, Rolf

    2016-01-01

    We present Approximate BDD Minimization (ABM) as a problem that has application in approximate computing. Given a BDD representation of a multi-output Boolean function, ABM asks whether there exists another function that has a smaller BDD representation but meets a threshold w.r.t. an error metric. We present operators to derive approximated functions and present algorithms to exactly compute the error metrics directly on the BDD representation. An experimental evaluation demonstrates the app...

  6. Torsional Rigidity of Minimal Submanifolds

    DEFF Research Database (Denmark)

    Markvorsen, Steen; Palmer, Vicente

    2006-01-01

    We prove explicit upper bounds for the torsional rigidity of extrinsic domains of minimal submanifolds $P^m$ in ambient Riemannian manifolds $N^n$ with a pole $p$. The upper bounds are given in terms of the torsional rigidities of corresponding Schwarz symmetrizations of the domains in warped...... for the torsional rigidity are actually attained and give conditions under which the geometric average of the stochastic mean exit time for Brownian motion at infinity is finite....

  7. Reservoir Operation to Minimize Sedimentation

    Directory of Open Access Journals (Sweden)

    Dyah Ari Wulandari

    2013-10-01

    Full Text Available The Wonogiri Reservoir capacity decreases rapidly, caused by serious sedimentation problems. In 2007, JICA was proposed a sediment storage reservoir with a new spillway for the purpose of sediment flushing / sluicing from The Keduang River. Due to the change of reservoir storage and change of reservoir system, it requires a sustainable reservoir operation technique. This technique is aimed to minimize the deviation between the input and output of sediments. The main objective of this study is to explore the optimal Wonogiri reservoir operation by minimizing the sediment trap. The CSUDP incremental dynamic programming procedure is used for the model optimization.  This new operating rules will also simulate a five years operation period, to show the effect of the implemented techniques. The result of the study are the newly developed reservoir operation system has many advantages when compared to the actual operation system and the disadvantage of this developed system is that the use is mainly designed for a wet hydrologic year, since its performance for the water supply is lower than the actual reservoir operations.Doi: 10.12777/ijse.6.1.16-23 [How to cite this article:  Wulandari, D.A., Legono, D., and Darsono, S., 2014. Reservoir Operation to Minimize Sedimentation. International Journal of Science and Engineering, 5(2,61-65. Doi: 10.12777/ijse.6.1.16-23] Normal 0 false false false EN-US X-NONE X-NONE

  8. Minimal lepton flavor violating realizations of minimal seesaw models

    CERN Document Server

    Sierra, Diego Aristizabal; Kamenik, Jernej F

    2012-01-01

    We study the implications of the global U(1)R symmetry present in minimal lepton flavor violating implementations of the seesaw mechanism for neutrino masses. In the context of minimal type I seesaw scenarios with a slightly broken U(1)R, we show that, depending on the R-charge assignments, two classes of generic models can be identified. Models where the right-handed neutrino masses and the lepton number breaking scale are decoupled, and models where the parameters that slightly break the U(1)R induce a suppression in the light neutrino mass matrix. We show that within the first class of models, contributions of right-handed neutrinos to charged lepton flavor violating processes are severely suppressed. Within the second class of models we study the charged lepton flavor violating phenomenology in detail, focusing on mu to e gamma, mu to 3e and mu to e conversion in nuclei. We show that sizable contributions to these processes are naturally obtained for right-handed neutrino masses at the TeV scale. We then ...

  9. Minimal families of curves on surfaces

    KAUST Repository

    Lubbes, Niels

    2014-11-01

    A minimal family of curves on an embedded surface is defined as a 1-dimensional family of rational curves of minimal degree, which cover the surface. We classify such minimal families using constructive methods. This allows us to compute the minimal families of a given surface.The classification of minimal families of curves can be reduced to the classification of minimal families which cover weak Del Pezzo surfaces. We classify the minimal families of weak Del Pezzo surfaces and present a table with the number of minimal families of each weak Del Pezzo surface up to Weyl equivalence.As an application of this classification we generalize some results of Schicho. We classify algebraic surfaces that carry a family of conics. We determine the minimal lexicographic degree for the parametrization of a surface that carries at least 2 minimal families. © 2014 Elsevier B.V.

  10. Resection of an Occipital-Cervical Junction Schwannoma through a modified minimally invasive approach: Technical Note

    Directory of Open Access Journals (Sweden)

    Michael Feldman

    2015-01-01

    Conclusion: In properly selected patients, minimally invasive approaches to the OCJ for resection of mass lesions are feasible, provide adequate visualization of tumor and surrounding structures, and may even be preferable given the lower morbidity of a smaller incision and minimal soft tissue dissection.

  11. Minimally invasive PCNL-MIP.

    Science.gov (United States)

    Zanetti, Stefano Paolo; Boeri, Luca; Gallioli, Andrea; Talso, Michele; Montanari, Emanuele

    2017-01-01

    Miniaturized percutaneous nephrolithotomy (mini-PCNL) has increased in popularity in recent years and is now widely used to overcome the therapeutic gap between conventional PCNL and less-invasive procedures such as shock wave lithotripsy (SWL) or flexible ureterorenoscopy (URS) for the treatment of renal stones. However, despite its minimally invasive nature, the superiority in terms of safety, as well as the similar efficacy of mini-PCNL compared to conventional procedures, is still under debate. The aim of this chapter is to present one of the most recent advancements in terms of mini-PCNL: the Karl Storz "minimally invasive PCNL" (MIP). A literature search for original and review articles either published or e-published up to December 2016 was performed using Google and the PubMed database. Keywords included: minimally invasive PCNL; MIP. The retrieved articles were gathered and examined. The complete MIP set is composed of different sized rigid metallic fiber-optic nephroscopes and different sized metallic operating sheaths, according to which the MIP is categorized into extra-small (XS), small (S), medium (M) and large (L). Dilation can be performed either in one-step or with a progressive technique, as needed. The reusable devices of the MIP and vacuum cleaner efect make PCNL with this set a cheap procedure. The possibility to shift from a small to a larger instrument within the same set (Matrioska technique) makes MIP a very versatile technique suitable for the treatment of almost any stone. Studies in the literature have shown that MIP is equally effective, with comparable rates of post-operative complications, as conventional PCNL, independently from stone size. MIP does not represent a new technique, but rather a combination of the last ten years of PCNL improvements in a single system that can transversally cover all available techniques in the panorama of percutaneous stone treatment.

  12. Social work and artefacts

    DEFF Research Database (Denmark)

    Høybye-Mortensen, Line Matilde

    2015-01-01

    artefakter. Det empiriske materiale består af 30 kvalitative interview med sagsbehandlere foretaget i forbindelse med en undersøgelse af beslutningsinstrumenter, der bruges i ældresektoren, jobcentre og i udredningen af udsatte børn og unge i danske kommuner. Analyserne viser, at sagsbehandlerne er optaget...

  13. Social influence by artefacts

    OpenAIRE

    Bauer, Martin W.

    2008-01-01

    A review of the paradigms of social influence – suggestion, imitation, normalization, conformity, compliance, conversion – leads me to diagnose a triple malaise: the shrinkage of paradigms to cognitive dual-processing theories of information; the dominant methodology of laboratory experiments falls short of the reality of (mass) communication; and the focus of social influence on inter-subjectivity is only half of the story. I will suggest two extensions of social influence theory to include ...

  14. Minimal dispersion refractive index profiles.

    Science.gov (United States)

    Feit, M D

    1979-09-01

    The analogy between optics and quantum mechanics is exploited by considering a 2-D quantum system whose Schroedinger equation is closely related to the wave equation for light propagation in an optical fiber. From this viewpoint, Marcatili's condition for minimal-dispersion-refractive-index profiles, and the Olshansky- Keck formula for rms pulse spreading in an alpha-profile fiber may be derived without recourse to the WKB approximation. Besides affording physical insight into these results, the present approach points out a possible limitation in their application to real fibers.

  15. Minimal sets of Reidemeister moves

    CERN Document Server

    Polyak, Michael

    2009-01-01

    It is well known that any two diagrams representing the same oriented link are related by a finite sequence of Reidemeister moves O1, O2 and O3. Depending on orientations of fragments involved in the moves, one may distinguish 4 different versions of each of the O1 and O2 moves, and 8 versions of the O3 move. We introduce a minimal generating set of oriented Reidemeister moves, which includes two moves of types O1 and O2, and only one move of type O3. We then consider other sets of moves and show that only few of them generate all Reidemeister moves.

  16. About the ZOOM minimization package

    Energy Technology Data Exchange (ETDEWEB)

    Fischler, M.; Sachs, D.; /Fermilab

    2004-11-01

    A new object-oriented Minimization package is available for distribution in the same manner as CLHEP. This package, designed for use in HEP applications, has all the capabilities of Minuit, but is a re-write from scratch, adhering to modern C++ design principles. A primary goal of this package is extensibility in several directions, so that its capabilities can be kept fresh with as little maintenance effort as possible. This package is distinguished by the priority that was assigned to C++ design issues, and the focus on producing an extensible system that will resist becoming obsolete.

  17. Prepulse minimization in KALI-5000

    Science.gov (United States)

    Kumar, D. Durga Praveen; Mitra, S.; Senthil, K.; Sharma, Vishnu K.; Singh, S. K.; Roy, A.; Sharma, Archana; Nagesh, K. V.; Chakravarthy, D. P.

    2009-07-01

    A pulse power system (1 MV, 50 kA, and 100 ns) based on Marx generator and Blumlein pulse forming line has been built for generating high power microwaves. The Blumlein configuration poses a prepulse problem and hence the diode gap had to be increased to match the diode impedance to the Blumlein impedance during the main pulse. A simple method to eliminate prepulse voltage using a vacuum sparkgap and a resistor is given. Another fundamental approach of increasing the inductance of Marx generator to minimize the prepulse voltage is also presented. Experimental results for both of these configurations are given.

  18. Risk minimization through portfolio replication

    Science.gov (United States)

    Ciliberti, S.; Mã©Zard, M.

    2007-05-01

    We use a replica approach to deal with portfolio optimization problems. A given risk measure is minimized using empirical estimates of asset values correlations. We study the phase transition which happens when the time series is too short with respect to the size of the portfolio. We also study the noise sensitivity of portfolio allocation when this transition is approached. We consider explicitely the cases where the absolute deviation and the conditional value-at-risk are chosen as a risk measure. We show how the replica method can study a wide range of risk measures, and deal with various types of time series correlations, including realistic ones with volatility clustering.

  19. Tissue types (image)

    Science.gov (United States)

    There are 4 basic types of tissue: connective tissue, epithelial tissue, muscle tissue, and nervous tissue. Connective tissue ... and binds them together (bone, blood, and lymph tissues). Epithelial tissue provides a covering (skin, the linings of ...

  20. Next-to-Minimal SOFTSUSY

    CERN Document Server

    Allanach, B C; Tunstall, Lewis C; Voigt, A; Williams, A G

    2013-01-01

    We describe an extension to the SOFTSUSY program that provides for the calculation of the sparticle spectrum in the Next-to-Minimal Supersymmetric Standard Model (NMSSM), where a chiral superfield that is a singlet of the Standard Model gauge group is added to the Minimal Supersymmetric Standard Model (MSSM) fields. Often, a $\\mathbb{Z}_{3}$ symmetry is imposed upon the model. SOFTSUSY can calculate the spectrum in this case as well as the case where general $\\mathbb{Z}_{3}$ violating (denoted as $\\,\\mathbf{\\backslash}\\mkern-11.0mu{\\mathbb{Z}}_{3}$) terms are added to the soft supersymmetry breaking terms and the superpotential. The user provides a theoretical boundary condition for the couplings and mass terms of the singlet. Radiative electroweak symmetry breaking data along with electroweak and CKM matrix data are used as weak-scale boundary conditions. The renormalisation group equations are solved numerically between the weak scale and a high energy scale using a nested iterative algorithm. This paper se...

  1. Risk minimization by experimental mechanics

    Energy Technology Data Exchange (ETDEWEB)

    1992-01-01

    Experimental mechanics has to undertake new functions to confirm theoretical perceptions and to check results of numerical analysis, because such results are dependent on the validity of assumptions and suppositions which generally are necessary to enable mathematical analysis of complex problems. Methods of experimental mechanics have become essential to design structures and products of a large variety to save raw materials and energy, to improve safety against failure and reliability of products, structures and even complex technical systems. Experimental methods are applied in system identification of complex structures. They are developed also as tools for supervising operating systems, machinery and installations as well as engineering structures, in order to get reliable informations on the life-time, to guarantee a higher degree of safety and to minimize risks. Therefore, methods of experimental mechanics are quite essential in developing strategies of riskmanagement. The contributions to this report are dealing with new theoretical perceptions, practical applications and experiences according to the objectives of the international symposium on 'Risk Minimization by Experimental Mechanics'. (orig.).

  2. Noise Tolerance under Risk Minimization

    CERN Document Server

    Manwani, Naresh

    2011-01-01

    In this paper we explore the problem of noise tolerant learning of classifiers. We formulate the problem as follows. We assume that there is an ${\\bf unobservable}$ training set which is noise-free. The actual training set given to the learning algorithm is obtained from this ideal data set by corrupting the class label of each example where the probability that the class label on an example is corrupted is a function of the feature vector of the example. This would account for almost all kinds of noisy data one may encounter in practice. We say that a learning method is noise tolerant if the classifiers learnt with the ideal noise-free data and with noisy data have the same classification accuracy on the noise-free data. In this paper we analyze the noise tolerant properties of risk minimization, which is a generic method for learning classifiers. We consider different loss functions such as 0-1 loss, hinge loss, exponential loss, squared error loss etc. We show that the risk minimization under 0-1 loss func...

  3. Concentrator design to minimize LCOE

    Science.gov (United States)

    McDonald, Mark; Horne, Steve; Conley, Gary

    2007-09-01

    The Levelized Cost of Energy (LCOE) takes into account more than just the cost of power output. It encompasses product longevity, performance degradation and the costs associated with delivering energy to the grid tie point. Concentrator optical design is one of the key components to minimizing the LCOE, by affecting conversion efficiency, acceptance angle and the amount of energy concentrated on the receiver. Optical systems for concentrators, even those at high concentrations ( >350X) can be designed by straightforward techniques, and will operate under most circumstances. Adding requirements for generous acceptance angles, non-destructive off-axis operation, safety and high efficiency however, complicate the design. Furthermore, the demands of high volume manufacturing, efficient logistics, minimal field commissioning time and low cost lead to quite complicated, system level design trade-offs. The technology which we will discuss features an array of reflective optics, scaled to be fabricated by techniques used in the automotive industry. The design couples a two-element imaging system to a non-imaging total internal reflection tertiary in a very compact design, with generous tolerance margins. Several optical units are mounted in a housing, which protects the optics and assists with dissipating waste heat. This paper outlines the key elements in the design of SolFocus concentrator optics, and discusses tradeoffs and experience with various design approaches.

  4. Studies on the strategies of minimizing radiation damage

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Hee Yong; Sohn, Young Sook

    1998-04-01

    We studied on the strategies of minimizing radiation damage in animal system. To this end we studied following areas of research (1) mechanisms involved in bone marrow damage after total body irradiation, (2) extraction of components that are useful in protecting hematopoietic system from radiation damage, (3) cell therapy approach in restoring the damaged tissue, (4) development of radioprotective chemical reagent, and (5) epidemiological study on the population that had been exposed to radiation.

  5. Looking for the Signal: A guide to iterative noise and artefact removal in X-ray tomographic reconstructions of porous geomaterials

    Science.gov (United States)

    Bruns, S.; Stipp, S. L. S.; Sørensen, H. O.

    2017-07-01

    X-ray micro- and nanotomography has evolved into a quantitative analysis tool rather than a mere qualitative visualization technique for the study of porous natural materials. Tomographic reconstructions are subject to noise that has to be handled by image filters prior to quantitative analysis. Typically, denoising filters are designed to handle random noise, such as Gaussian or Poisson noise. In tomographic reconstructions, noise has been projected from Radon space to Euclidean space, i.e. post reconstruction noise cannot be expected to be random but to be correlated. Reconstruction artefacts, such as streak or ring artefacts, aggravate the filtering process so algorithms performing well with random noise are not guaranteed to provide satisfactory results for X-ray tomography reconstructions. With sufficient image resolution, the crystalline origin of most geomaterials results in tomography images of objects that are untextured. We developed a denoising framework for these kinds of samples that combines a noise level estimate with iterative nonlocal means denoising. This allows splitting the denoising task into several weak denoising subtasks where the later filtering steps provide a controlled level of texture removal. We describe a hands-on explanation for the use of this iterative denoising approach and the validity and quality of the image enhancement filter was evaluated in a benchmarking experiment with noise footprints of a varying level of correlation and residual artefacts. They were extracted from real tomography reconstructions. We found that our denoising solutions were superior to other denoising algorithms, over a broad range of contrast-to-noise ratios on artificial piecewise constant signals.

  6. Iron corrosion in an anoxic soil: Comparison between thermodynamic modelling and ferrous archaeological artefacts characterised along with the local in situ geochemical conditions

    Energy Technology Data Exchange (ETDEWEB)

    Saheb, M.; Neff, D.; Michelin, A.; Dillmann, P. [CEA Saclay, CNRS, LAPA SIS2M, UMR3299, 91 - Gif-sur-Yvette (France); Saheb, M. [ANDRA, F-92298 Chatenay Malabry (France); Descostes, M. [CEA Saclay, DEN DANS DPC SECR, Lab Radionuclides Migrat Measurements and Modelling, 91 - Gif-sur-Yvette (France); Descostes, M. [Univ Evry, CEA, CNRS, UMR 8587, Evry (France); Dillmann, P. [CNRS, Inst Rech Archeomat, UMR 5060, F-75700 Paris (France)

    2010-07-01

    This article is part of an ongoing study on the long-term corrosion behaviour of ferrous archaeological artefacts. The aim of this study is to correlate the corrosion products formed on ancient artefacts in an anoxic medium to the environmental data using thermodynamic modelling. For this purpose, measurement campaigns have been conducted on the archaeological site of Glinet (16. century, High Normandy (Seine-Maritime), France) where the evolution of the pore water chemistry has been recorded for a period of one year. Three evolution steps have been distinguished after the oxidizing perturbation which was induced by the piezometers installation. The first step was related to an oxidizing environment in which pore water was in equilibrium with a Fe(III) precipitated phase: ferri-hydrite (FeOOH center dot 0.4 H{sub 2}O). The second step was considered as an intermediate step and Fe speciation had evolved; equilibrium was achieved between ferri-hydrite and a Fe(II) carbonate phase: siderite (Fe(II)CO{sub 3}). The last step of the evolution was related to a reducing stage where pore water was in equilibrium with magnetite (Fe(II, III){sub 3}O{sub 4}) and with chukanovite (Fe(II){sub 2}(OH){sub 2}CO{sub 3}). As these phases were present in the corrosion layers formed on the archaeological samples, it is possible to conclude that the thermodynamic approach was helpful in developing a better understanding of the effect of geochemical conditions on the composition and mineralogy of the corrosion products formed on archaeological artefacts. This work could be used as a reference for further corrosion studies, especially on long-term corrosion processes applied to nuclear waste disposal. (authors)

  7. Metallic artefact reduction with monoenergetic dual-energy CT: systematic ex vivo evaluation of posterior spinal fusion implants from various vendors and different spine levels

    Energy Technology Data Exchange (ETDEWEB)

    Guggenberger, R.; Winklhofer, S.; Andreisek, G.; Alkadhi, H.; Stolzmann, P. [University Hospital Zurich, Institute of Diagnostic and Interventional Radiology, Zurich (Switzerland); Osterhoff, G.; Wanner, G.A. [University Hospital Zurich, Department of Surgery, Division of Trauma Surgery, Zurich (Switzerland); Fortunati, M. [The Spine Center, Thun (Switzerland)

    2012-11-15

    To evaluate optimal monoenergetic dual-energy computed tomography (DECT) settings for artefact reduction of posterior spinal fusion implants of various vendors and spine levels. Posterior spinal fusion implants of five vendors for cervical, thoracic and lumbar spine were examined ex vivo with single-energy (SE) CT (120 kVp) and DECT (140/100 kVp). Extrapolated monoenergetic DECT images at 64, 69, 88, 105 keV and individually adjusted monoenergy for optimised image quality (OPTkeV) were generated. Two independent radiologists assessed quantitative and qualitative image parameters for each device and spine level. Inter-reader agreements of quantitative and qualitative parameters were high (ICC = 0.81-1.00, {kappa} = 0.54-0.77). HU values of spinal fusion implants were significantly different among vendors (P < 0.001), spine levels (P < 0.01) and among SECT, monoenergetic DECT of 64, 69, 88, 105 keV and OPTkeV (P < 0.01). Image quality was significantly (P < 0.001) different between datasets and improved with higher monoenergies of DECT compared with SECT (V = 0.58, P < 0.001). Artefacts decreased significantly (V = 0.51, P < 0.001) at higher monoenergies. OPTkeV values ranged from 123-141 keV. OPTkeV according to vendor and spine level are presented herein. Monoenergetic DECT provides significantly better image quality and less metallic artefacts from implants than SECT. Use of individual keV values for vendor and spine level is recommended. (orig.)

  8. Unicompartmental knee arthroplasty MRI: impact of slice-encoding for metal artefact correction MRI on image quality, findings and therapy decision

    Energy Technology Data Exchange (ETDEWEB)

    Agten, Christoph A.; Pfirrmann, Christian W.A.; Sutter, Reto [Balgrist University Hospital, Radiology Department, Zurich (Switzerland); University of Zurich, Faculty of Medicine, Zurich (Switzerland); Grande, Filippo del [Regional Hospital, Radiology, Lugano (Switzerland); Fucentese, Sandro F.; Blatter, Samuel [University of Zurich, Faculty of Medicine, Zurich (Switzerland); Balgrist University Hospital, Orthopedics, Zurich (Switzerland)

    2015-07-15

    To evaluate the impact of slice-encoding for metal artefact correction (SEMAC) on image quality, findings, and therapy decision in patients with unicompartmental knee arthroplasty (UKA). Forty-five painful UKAs were examined at 1.5T-MRI (STIR, proton-density(PD)-weighted sequence, each with SEMAC and high-bandwidth). Artefact size, image quality, anatomic depiction, and clinically relevant findings were compared between SEMAC and high-bandwidth (2 readers). In 30 patients, therapy decision was retrospectively assessed by two orthopaedic surgeons without MRI, with high-bandwidth-MRI, and with SEMAC-MRI. SEMAC reduced mean artefact size for STIR (11.8 cm{sup 2} vs. 37.7 cm{sup 2}) and PD (16.8 cm{sup 2} vs. 18.9 cm{sup 2}), p < 0.0005 for both comparisons. SEMAC showed more blurring than high-bandwidth, p < 0.0005. STIR-SEMAC revealed more bone marrow oedema (29 vs. 18 patients, p = 0.001, 30 vs. 13 patients, p < 0.0005, for reader 1 and 2 respectively). PD-SEMAC was worse in detecting meniscal lesions (6 missed, p = 0.031, 9 missed, p = 0.004, by reader 1 and 2 respectively) than PD-high-bandwidth. Revision-surgery was chosen in 12 and 11 patients without MRI (surgeon 1 and 2), with high-bandwidth-MRI in 15 and 14 patients, and with SEMAC-MRI in 19 and 14 patients. STIR-SEMAC was useful in detecting bone marrow oedema and influenced the orthopaedic surgeons' decisions towards surgery, while PD-SEMAC showed no clinical benefit. (orig.)

  9. Magnetic resonance-guided upper abdominal biopsies in a high-field wide-bore 3-T MRI system: feasibility, handling, and needle artefacts

    Energy Technology Data Exchange (ETDEWEB)

    Kuehn, Jens-Peter; Langner, Soenke; Hegenscheid, Katrin; Hosten, Norbert; Puls, Ralf [Ernst Moritz Arndt University of Greifswald, Department of Radiology, Greifswald (Germany); Evert, Matthias [Ernst Moritz Arndt University of Greifswald, Department of Pathology, Greifswald (Germany); Kickhefel, Antje [Siemens Healthcare, Erlangen (Germany)

    2010-10-15

    To investigate the feasibility and handling of abdominal MRI-guided biopsies in a 3-T MRI system. Over a 1-year period, 50 biopsies were obtained in 47 patients with tumours of the upper abdominal organs guided by 3-T MRI with a large-bore diameter of 70 cm. Lesions in liver (47), spleen (1) and kidney (2) were biopsied with a coaxial technique using a 16-G biopsy needle guided by a T1-weighted three-dimensional gradient recalled echo volumetric interpolated breath-hold examination (T1w-3D-GRE-VIBE) sequence. Sensitivity, specificity, accuracy, complication rate, interventional complexity, room/intervention time and needle artefacts were determined. A sensitivity of 0.93, specificity of 1.0 and accuracy of 0.94 were observed. Three patients required a rebiopsy. There was a minor complications rate of 13.6%, and no major complications were observed. Histopathology revealed 38 malignant lesions, and 3-month follow-up confirmed 9 benign lesions. Mean lesion diameter was 3.4 {+-} 3.1 cm (50% being smaller than 2 cm). Mean needle tract length was 10.8 {+-} 3.3 cm. Median room time was 42.0 {+-} 19.8 min and intervention time 9.3 {+-} 8.1 min. Needle artefact size was about 9-fold greater for perpendicular access versus access parallel to the main magnetic field. Biopsies of the upper abdomen can be performed with great technical success and easy handling because of the large-bore diameter. The MRI-guided biopsy needle had an acceptable susceptibility artefact at 3 T. However future research must aim to reduce the susceptibility effects of the biopsy systems. (orig.)

  10. Is metal artefact reduction mandatory in cardiac PET/CT imaging in the presence of pacemaker and implantable cardioverter defibrillator leads?

    Energy Technology Data Exchange (ETDEWEB)

    Ghafarian, Pardis [Shahid Beheshti University, Department of Radiation Medicine, Tehran (Iran, Islamic Republic of); Geneva University Hospital, Division of Nuclear Medicine, Geneva 4 (Switzerland); Tehran University of Medical Sciences, Research Center for Science and Technology in Medicine, Tehran (Iran, Islamic Republic of); Aghamiri, S.M.R. [Shahid Beheshti University, Department of Radiation Medicine, Tehran (Iran, Islamic Republic of); Ay, Mohammad R. [Tehran University of Medical Sciences, Research Center for Science and Technology in Medicine, Tehran (Iran, Islamic Republic of); Tehran University of Medical Sciences, Department of Medical Physics and Biomedical Engineering, Tehran (Iran, Islamic Republic of); Tehran University of Medical Sciences, Research Institute for Nuclear Medicine, Tehran (Iran, Islamic Republic of); Rahmim, Arman [Johns Hopkins University, Department of Radiology, Baltimore, MD (United States); Schindler, Thomas H. [Geneva University, Cardiovascular Center, Nuclear Cardiology, Geneva (Switzerland); Ratib, Osman [Geneva University Hospital, Division of Nuclear Medicine, Geneva 4 (Switzerland); Zaidi, Habib [Geneva University Hospital, Division of Nuclear Medicine, Geneva 4 (Switzerland); Geneva University, Geneva Neuroscience Center, Geneva (Switzerland)

    2011-02-15

    Cardiac PET/CT imaging is often performed in patients with pacemakers and implantable cardioverter defibrillator (ICD) leads. However, metallic implants usually produce artefacts on CT images which might propagate to CT-based attenuation-corrected (CTAC) PET images. The impact of metal artefact reduction (MAR) for CTAC of cardiac PET/CT images in the presence of pacemaker, ICD and ECG leads was investigated using both qualitative and quantitative analysis in phantom and clinical studies. The study included 14 patients with various leads undergoing perfusion and viability examinations using dedicated cardiac PET/CT protocols. The PET data were corrected for attenuation using both artefactual CT images and CT images corrected using the MAR algorithm. The severity and magnitude of metallic artefacts arising from these leads were assessed on both linear attenuation coefficient maps ({mu}-maps) and attenuation-corrected PET images. CT and PET emission data were obtained using an anthropomorphic thorax phantom and a dedicated heart phantom made in-house incorporating pacemaker and ICD leads attached at the right ventricle of the heart. Volume of interest-based analysis and regression plots were performed for regions related to the lead locations. Bull's eye view analysis was also performed on PET images corrected for attenuation with and without the MAR algorithm. In clinical studies, the visual assessment of PET images by experienced physicians and quantitative analysis did not reveal erroneous interpretation of the tracer distribution or significant differences when PET images were corrected for attenuation with and without MAR. In phantom studies, the mean differences between tracer uptake obtained without and with MAR were 10.16{+-}2.1% and 6.86{+-}2.1% in the segments of the heart in the vicinity of metallic ICD or pacemaker leads, and were 4.43{+-}0.5% and 2.98{+-}0.5% in segments far from the leads. Although the MAR algorithm was able to effectively improve

  11. Minimally invasive percutaneous posterior lumbar interbody fusion.

    Science.gov (United States)

    Khoo, Larry T; Palmer, Sylvain; Laich, Daniel T; Fessler, Richard G

    2002-11-01

    The wide exposure required for a standard posterior lumbar interbody fusion (PLIF) can cause unnecessary trauma to the lumbar musculoligamentous complex. By combining existing microendoscopic, percutaneous instrumentation and interbody technologies, a novel, minimally invasive, percutaneous PLIF technique was developed to minimize such iatrogenic tissue injury (MIP-PLIF). The MIP-PLIF technique was validated in three cadaveric torsos with six motion segments decompressed and fused. Preoperative variables measured from imaging included interpedicular distance, pedicular height and width, interspinous distance, lordosis, intervertebral height, Cobb angle, and foraminal height and volume. Using the METRx and MD spinal access systems (Medtronic Sofamor Danek, Memphis, TN), bilateral laminotomies were performed using a hybrid of microsurgical and microendoscopic techniques. The intervertebral disc spaces were then distracted and prepared with the Tangent (Medtronic Sofamor Danek) interbody instruments. Either a 10 or 12 by 22 mm interbody graft was then placed. Using the Sextant (Medtronic Sofamor Danek) system, percutaneous pedicle screw-rod fixation of the motion segment was completed. We then applied MIP-PLIF in three patients. For segments with preoperative intervertebral/foraminal height loss, MIP-PLIF was effective in restoring both heights in all cases. The amount of improvement (9.7 to 38% disc height increase; 7.7 to 29.9% foraminal height increase) varied directly with the size of the graft used and the original degree of disc and foraminal height loss. Segmental lordosis improved by 29% on average. Graft and screw placement was accurate in the cadavers, except for a single Grade 1 screw violation of one pedicle. The average operative time was 3.5 hours per level. In our three clinical cases, the MIP-PLIF procedure required a mean of 5.4 hours, estimated blood loss was 185 ml, and inpatient stay was 2.8 days, with no intravenous narcotic use after 2 days in

  12. Complications of minimally invasive cosmetic procedures: Prevention and management

    Directory of Open Access Journals (Sweden)

    Lauren L Levy

    2012-01-01

    Full Text Available Over the past decade, facial rejuvenation procedures to circumvent traditional surgery have become increasingly popular. Office-based, minimally invasive procedures can promote a youthful appearance with minimal downtime and low risk of complications. Injectable botulinum toxin (BoNT, soft-tissue fillers, and chemical peels are among the most popular non-invasive rejuvenation procedures, and each has unique applications for improving facial aesthetics. Despite the simplicity and reliability of office-based procedures, complications can occur even with an astute and experienced injector. The goal of any procedure is to perform it properly and safely; thus, early recognition of complications when they do occur is paramount in dictating prevention of long-term sequelae. The most common complications from BoNT and soft-tissue filler injection are bruising, erythema and pain. With chemical peels, it is not uncommon to have erythema, irritation and burning. Fortunately, these side effects are normally transient and have simple remedies. More serious complications include muscle paralysis from BoNT, granuloma formation from soft-tissue filler placement and scarring from chemical peels. Thankfully, these complications are rare and can be avoided with excellent procedure technique, knowledge of facial anatomy, proper patient selection, and appropriate pre- and post-skin care. This article reviews complications of office-based, minimally invasive procedures, with emphasis on prevention and management. Practitioners providing these treatments should be well versed in this subject matter in order to deliver the highest quality care.

  13. Laparoscopic colonic resection in inflammatory bowel disease: minimal surgery, minimal access and minimal hospital stay.

    LENUS (Irish Health Repository)

    Boyle, E

    2008-11-01

    Laparoscopic surgery for inflammatory bowel disease (IBD) is technically demanding but can offer improved short-term outcomes. The introduction of minimally invasive surgery (MIS) as the default operative approach for IBD, however, may have inherent learning curve-associated disadvantages. We hypothesise that the establishment of MIS as the standard operative approach does not increase patient morbidity as assessed in the initial period of its introduction into a specialised unit, and that it confers earlier postoperative gastrointestinal recovery and reduced hospitalisation compared with conventional open resection.

  14. Rituximab in Minimal Change Disease

    Directory of Open Access Journals (Sweden)

    Nima Madanchi

    2017-03-01

    Full Text Available Treatment with rituximab, a monoclonal antibody against the B-lymphocyte surface protein CD20, leads to the depletion of B cells. Recently, rituximab was reported to effectively prevent relapses of glucocorticoid-dependent or frequently relapsing minimal change disease (MCD. MCD is thought to be T-cell mediated; how rituximab controls MCD is not understood. In this review, we summarize key clinical studies demonstrating the efficacy of rituximab in idiopathic nephrotic syndrome, mainly MCD. We then discuss immunological features of this disease and potential mechanisms of action of rituximab in its treatment based on what is known about the therapeutic action of rituximab in other immune-mediated disorders. We believe that studies aimed at understanding the mechanisms of action of rituximab in MCD will provide a novel approach to resolve the elusive immune pathophysiology of MCD.

  15. Minimally packed phases in holography

    CERN Document Server

    Donos, Aristomenis

    2015-01-01

    We numerically construct asymptotically AdS black brane solutions of $D=4$ Einstein-Maxwell theory coupled to a pseudoscalar. The solutions are holographically dual to $d=3$ CFTs held at constant chemical potential and magnetic field that spontaneously break translation invariance leading to the spontaneous formation of abelian and momentum magnetisation currents flowing around the plaquettes of a periodic Bravais lattice. We analyse the three-dimensional moduli space of lattice solutions, which are generically oblique, and show that the free energy is minimised by the triangular lattice, associated with minimal packing of circles in the plane. The triangular structure persists at low temperatures indicating the existence of novel crystalline ground states.

  16. A minimally invasive smile enhancement.

    Science.gov (United States)

    Peck, Fred H

    2014-01-01

    Minimally invasive dentistry refers to a wide variety of dental treatments. On the restorative aspect of dental procedures, direct resin bonding can be a very conservative treatment option for the patient. When tooth structure does not need to be removed, the patient benefits. Proper treatment planning is essential to determine how conservative the restorative treatment will be. This article describes the diagnosis, treatment options, and procedural techniques in the restoration of 4 maxillary anterior teeth with direct composite resin. The procedural steps are reviewed with regard to placing the composite and the variety of colors needed to ensure a natural result. Finishing and polishing of the composite are critical to ending with a natural looking dentition that the patient will be pleased with for many years.

  17. Determining Knots by Minimizing Energy

    Institute of Scientific and Technical Information of China (English)

    Cai-Ming Zhang; Hui-Jian Han; Fuhua Frank Cheng

    2006-01-01

    A new method for determining knots to construct polynomial curves is presented. At each data point, a quadric curve which passes three consecutive points is constructed. The knots for constructing the quadric curve are determined by minimizing the internal strain energy, which can be regarded as a function of the angle. The function of the angle is expanded as a Taylor series with two terms, then the two knot intervals between the three consecutive points are defined by linear expression. Between the two consecutive points, there are two knot intervals, and the combination of the two knot intervals is used to define the final knot interval. A comparison of the new method with several existing methods is included.

  18. [MINIMALLY INVASIVE AORTIC VALVE REPLACEMENT].

    Science.gov (United States)

    Tabata, Minoru

    2016-03-01

    Minimally invasive aortic valve replacement (MIAVR) is defined as aortic valve replacement avoiding full sternotomy. Common approaches include a partial sternotomy right thoracotomy, and a parasternal approach. MIAVR has been shown to have advantages over conventional AVR such as shorter length of stay and smaller amount of blood transfusion and better cosmesis. However, it is also known to have disadvantages such as longer cardiopulmonary bypass and aortic cross-clamp times and potential complications related to peripheral cannulation. Appropriate patient selection is very important. Since the procedure is more complex than conventional AVR, more intensive teamwork in the operating room is essential. Additionally, a team approach during postoperative management is critical to maximize the benefits of MIAVR.

  19. Minimization over randomly selected lines

    Directory of Open Access Journals (Sweden)

    Ismet Sahin

    2013-07-01

    Full Text Available This paper presents a population-based evolutionary optimization method for minimizing a given cost function. The mutation operator of this method selects randomly oriented lines in the cost function domain, constructs quadratic functions interpolating the cost function at three different points over each line, and uses extrema of the quadratics as mutated points. The crossover operator modifies each mutated point based on components of two points in population, instead of one point as is usually performed in other evolutionary algorithms. The stopping criterion of this method depends on the number of almost degenerate quadratics. We demonstrate that the proposed method with these mutation and crossover operations achieves faster and more robust convergence than the well-known Differential Evolution and Particle Swarm algorithms.

  20. Minimally invasive aortic valve replacement

    DEFF Research Database (Denmark)

    Foghsgaard, Signe; Schmidt, Thomas Andersen; Kjaergard, Henrik K

    2009-01-01

    In this descriptive prospective study, we evaluate the outcomes of surgery in 98 patients who were scheduled to undergo minimally invasive aortic valve replacement. These patients were compared with a group of 50 patients who underwent scheduled aortic valve replacement through a full sternotomy....... The 30-day mortality rate for the 98 patients was zero, although 14 of the 98 mini-sternotomies had to be converted to complete sternotomies intraoperatively due to technical problems. Such conversion doubled the operative time over that of the planned full sternotomies. In the group of patients whose...... is an excellent operation in selected patients, but its true advantages over conventional aortic valve replacement (other than a smaller scar) await evaluation by means of randomized clinical trial. The "extended mini-aortic valve replacement" operation, on the other hand, is a risky procedure that should...

  1. The diagnostic utility of the minimal carcinoma triple stain in breast carcinomas.

    Science.gov (United States)

    Ross, Dara S; Liu, Yi-Fang; Pipa, Jennifer; Shin, Sandra J

    2013-01-01

    Pathologists are expected to accurately diagnose increasingly smaller breast carcinomas. Correct classification (ie, lobular vs ductal or in situ vs invasive) directly affects subsequent management, especially when the focus is near a surgical margin or present in a needle core biopsy and is further challenging if the lesion is morphologically ambiguous. We assessed the diagnostic utility of a multiplex, trichromogen immunostain of 3 commonly employed antibodies (CK7, p63, and E-cadherin) developed in our laboratory to evaluate these small lesions. Of the 147 specimens containing minimal (defined as ≤3 mm in size) invasive carcinoma, 81 also contained in situ carcinoma. In each case, the Minimal Carcinoma Triple Stain was prepared with a parallel H&E-stained slide. Observations of staining characteristics in the focus of interest were recorded. The Minimal Carcinoma Triple Stain was diagnostically useful in all but 1 case. In a case of invasive lobular carcinoma in an excisional biopsy, the Minimal Carcinoma Triple Stain stained only the surrounding breast tissue (appropriately) and not the focus of interest. Also, a subset of 29 of 81 excisional biopsies had minimal invasive carcinoma located 2 mm or less from the inked surgical margin, in which in all cases the Minimal Carcinoma Triple Stain was fully interpretable despite morphologic distortion due to concomitant cautery artifact and tissue disruption in some cases. The Minimal Carcinoma Triple Stain offers an accurate and tissue-conserving method to diagnose small, morphologically problematic foci of breast carcinoma while ideally leaving more tissue for additional adjunctive studies.

  2. Similar incidence of periprosthetic fluid collections after ceramic-on-polyethylene total hip arthroplasties and metal-on-metal resurfacing arthroplasties: results of a screening metal artefact reduction sequence-MRI study.

    Science.gov (United States)

    Bisseling, P; de Wit, B W K; Hol, A M; van Gorp, M J; van Kampen, A; van Susante, J L C

    2015-09-01

    Patients from a randomised trial on resurfacing hip arthroplasty (RHA) (n = 36, 19 males; median age 57 years, 24 to 65) comparing a conventional 28 mm metal-on-metal total hip arthroplasty (MoM THA) (n = 28, 17 males; median age 59 years, 37 to 65) and a matched control group of asymptomatic patients with a 32 mm ceramic-on-polyethylene (CoP) THA (n = 33, 18 males; median age 63 years, 38 to 71) were cross-sectionally screened with metal artefact reducing sequence-MRI (MARS-MRI) for pseudotumour formation at a median of 55 months (23 to 72) post-operatively. MRIs were scored by consensus according to three different classification systems for pseudotumour formation. Clinical scores were available for all patients and metal ion levels for MoM bearing patients. Periprosthetic lesions with a median volume of 16 mL (1.5 to 35.9) were diagnosed in six patients in the RHA group (17%), one in the MoM THA group (4%) and six in the CoP group (18%). The classification systems revealed no clear differences between the groups. Solid lesions (n = 3) were exclusively encountered in the RHA group. Two patients in the RHA group and one in the MoM THA group underwent a revision for pseudotumour formation. There was no statistically significant relationship between clinical scoring, metal ion levels and periprosthetic lesions in any of the groups. Periprosthetic fluid collections are seen on MARS-MRI after conventional CoP THA and RHA and may reflect a soft-tissue collection or effusion. Currently available MRI classification systems seem to score these collections as pseudotumours, causing an-overestimatation of the incidence of pseudotumours.

  3. Tissue Classification

    DEFF Research Database (Denmark)

    Van Leemput, Koen; Puonti, Oula

    2015-01-01

    Computational methods for automatically segmenting magnetic resonance images of the brain have seen tremendous advances in recent years. So-called tissue classification techniques, aimed at extracting the three main brain tissue classes (white matter, gray matter, and cerebrospinal fluid), are now...... well established. In their simplest form, these methods classify voxels independently based on their intensity alone, although much more sophisticated models are typically used in practice. This article aims to give an overview of often-used computational techniques for brain tissue classification...

  4. Macroscopic Fourier transform infrared scanning in reflection mode (MA-rFTIR), a new tool for chemical imaging of cultural heritage artefacts in the mid-infrared range.

    Science.gov (United States)

    Legrand, Stijn; Alfeld, Matthias; Vanmeert, Frederik; De Nolf, Wout; Janssens, Koen

    2014-05-21

    In this paper we demonstrate that by means of scanning reflection FTIR spectroscopy, it is possible to record highly specific distribution maps of organic and inorganic compounds from flat, macroscopic objects with cultural heritage value in a non-invasive manner. Our previous work involved the recording of macroscopic distributions of chemical elements or crystal phases from painted works of art based on respectively macroscopic X-ray fluorescence or X-ray powder diffraction analysis. The use of infrared radiation instead of X-rays has the advantage that more specific information about the nature and distribution of the chemical compounds present can be gathered. This higher imaging specificity represents a clear advantage for the characterization of painting and artist materials. It allows the distribution of metallo-organic compounds to be visualized and permits distinguishing between pigmented materials containing the same key metal. The prototype instrument allows the recording of hyperspectral datacubes by scanning the surface of the artefact in a contactless and sequential single-point measuring mode, while recording the spectrum of reflected infrared radiation. After the acquisition, spectral line intensities of individual bands and chemical distribution maps can be extracted from the datacube to identify the compounds present and/or to highlight their spatial distribution. Not only is information gained on the surface of the investigated artefacts, but also images of overpainted paint layers and, if present, the underdrawing may be revealed in this manner. A current major limitation is the long scanning times required to record these maps.

  5. Mini-Med School Planning Guide

    Science.gov (United States)

    National Institutes of Health, Office of Science Education, 2008

    2008-01-01

    Mini-Med Schools are public education programs now offered by more than 70 medical schools, universities, research institutions, and hospitals across the nation. There are even Mini-Med Schools in Ireland, Malta, and Canada! The program is typically a lecture series that meets once a week and provides "mini-med students" information on some of the…

  6. Robotic-assisted minimally invasive liver resection

    Directory of Open Access Journals (Sweden)

    Yao-Ming Wu

    2014-04-01

    Conclusion: Robotic assistance increased the percentage of minimally invasive liver resections and the percentage of major minimally invasive liver resections with comparable perioperative results. Robotic-assisted minimally invasive liver resection is feasible, but its role needs more accumulated experience to clarify.

  7. Minimally invasive technique for curettage of chondroblastoma using endoscopic technique.

    Science.gov (United States)

    Errani, C; Traina, F; Chehrassan, M; Donati, D; Faldini, C

    2014-11-01

    Chondroblastoma is a rare benign bone tumor. The treatment for chondroblastoma usually consists of curettage of the lesion and packing the tumor cavity with bone grafts or bone cement. However, chondroblastomas are known to recur in 10% to 20% of cases after excision, possibly because the incomplete removal of pathological tissue at surgery. We present a case of chondroblastoma in the distal femur treated by endoscopic curettage, which allowed a complete resection of tumor tissue and a minimal damage of the bone. The patient had relief of symptoms, rapid function restoration and no local recurrence. Endoscopic curettage is a promising new treatment for chondroblastoma. In fact, the extra-articular technique enters the tumor cavity via a tunnel drilled through the medullary canal, allowing to visualize possible residual tumor tissue or defects of the articular surface, without violating the joint and without taking away a much bigger cortical window.

  8. Medical waste: a minimal hazard.

    Science.gov (United States)

    Keene, J H

    1991-11-01

    Medical waste is a subset of municipal waste, and regulated medical waste comprises less than 1% of the total municipal waste volume in the United States. As part of the overall waste stream, medical waste does contribute in a relative way to the aesthetic damage of the environment. Likewise, some small portion of the total release of hazardous chemicals and radioactive materials is derived from medical wastes. These comments can be made about any generated waste, regulated or unregulated. Healthcare professionals, including infection control personnel, microbiologists, public health officials, and others, have unsuccessfully argued that there is no evidence that past methods of treatment and disposal of regulated medical waste constitute any public health hazard. Historically, discovery of environmental contamination by toxic chemical disposal has followed assurances that the material was being disposed of in a safe manner. Therefore, a cynical public and its elected officials have demanded proof that the treatment and disposal of medical waste (i.e., infectious waste) do not constitute a public health hazard. Existent studies on municipal waste provide that proof. In order to argue that the results of these municipal waste studies are demonstrative of the minimal potential infectious environmental impact and lack of public health hazard associated with medical waste, we must accept the following: that the pathogens are the same whether they come from the hospital or the community, and that the municipal waste studied contained waste materials we now define as regulated medical waste.(ABSTRACT TRUNCATED AT 250 WORDS)

  9. Robotic assisted minimally invasive surgery

    Directory of Open Access Journals (Sweden)

    Palep Jaydeep

    2009-01-01

    Full Text Available The term "robot" was coined by the Czech playright Karel Capek in 1921 in his play Rossom′s Universal Robots. The word "robot" is from the check word robota which means forced labor.The era of robots in surgery commenced in 1994 when the first AESOP (voice controlled camera holder prototype robot was used clinically in 1993 and then marketed as the first surgical robot ever in 1994 by the US FDA. Since then many robot prototypes like the Endoassist (Armstrong Healthcare Ltd., High Wycombe, Buck, UK, FIPS endoarm (Karlsruhe Research Center, Karlsruhe, Germany have been developed to add to the functions of the robot and try and increase its utility. Integrated Surgical Systems (now Intuitive Surgery, Inc. redesigned the SRI Green Telepresence Surgery system and created the daVinci Surgical System ® classified as a master-slave surgical system. It uses true 3-D visualization and EndoWrist ® . It was approved by FDA in July 2000 for general laparoscopic surgery, in November 2002 for mitral valve repair surgery. The da Vinci robot is currently being used in various fields such as urology, general surgery, gynecology, cardio-thoracic, pediatric and ENT surgery. It provides several advantages to conventional laparoscopy such as 3D vision, motion scaling, intuitive movements, visual immersion and tremor filtration. The advent of robotics has increased the use of minimally invasive surgery among laparoscopically naοve surgeons and expanded the repertoire of experienced surgeons to include more advanced and complex reconstructions.

  10. Against Explanatory Minimalism in Psychiatry.

    Science.gov (United States)

    Thornton, Tim

    2015-01-01

    The idea that psychiatry contains, in principle, a series of levels of explanation has been criticized not only as empirically false but also, by Campbell, as unintelligible because it presupposes a discredited pre-Humean view of causation. Campbell's criticism is based on an interventionist-inspired denial that mechanisms and rational connections underpin physical and mental causation, respectively, and hence underpin levels of explanation. These claims echo some superficially similar remarks in Wittgenstein's Zettel. But attention to the context of Wittgenstein's remarks suggests a reason to reject explanatory minimalism in psychiatry and reinstate a Wittgensteinian notion of levels of explanation. Only in a context broader than the one provided by interventionism is that the ascription of propositional attitudes, even in the puzzling case of delusions, justified. Such a view, informed by Wittgenstein, can reconcile the idea that the ascription mental phenomena presupposes a particular level of explanation with the rejection of an a priori claim about its connection to a neurological level of explanation.

  11. Minimal hepatic encephalopathy: A review.

    Science.gov (United States)

    Nardone, Raffaele; Taylor, Alexandra C; Höller, Yvonne; Brigo, Francesco; Lochner, Piergiorgio; Trinka, Eugen

    2016-10-01

    Minimal hepatic encephalopathy (MHE) is the earliest form of hepatic encephalopathy and can affect up to 80% of patients with liver cirrhosis. By definition, MHE is characterized by cognitive function impairment in the domains of attention, vigilance and integrative function, but obvious clinical manifestation are lacking. MHE has been shown to affect daily functioning, quality of life, driving and overall mortality. The diagnosis can be achieved through neuropsychological testing, recently developed computerized psychometric tests, such as the critical flicker frequency and the inhibitory control tests, as well as neurophysiological procedures. Event related potentials can reveal subtle changes in patients with normal neuropsychological performances. Spectral analysis of electroencephalography (EEG) and quantitative analysis of sleep EEG provide early markers of cerebral dysfunction in cirrhotic patients with MHE. Neuroimaging, in particular MRI, also increasingly reveals diffuse abnormalities in intrinsic brain activity and altered organization of functional connectivity networks. Medical treatment for MHE to date has been focused on reducing serum ammonia levels and includes non-absorbable disaccharides, probiotics or rifaximin. Liver transplantation may not reverse the cognitive deficits associated with MHE. We performed here an updated review on epidemiology, burden and quality of life, neuropsychological testing, neuroimaging, neurophysiology and therapy in subjects with MHE.

  12. Unoriented Minimal Type 0 Strings

    CERN Document Server

    Carlisle, J E; Carlisle, James E; Johnson, Clifford V

    2004-01-01

    We define a family of string equations with perturbative expansions that admit an interpretation as an unoriented minimal string theory with background D-branes and R-R fluxes. The theory also has a well-defined non-perturbative sector and we expect it to have a continuum interpretation as an orientifold projection of the non-critical type~0A string for \\hat{c}=0, the (2,4) model. There is a second perturbative region which is consistent with an interpretation in terms of background R-R fluxes. We identify a natural parameter in the formulation that we speculate may have an interpretation as characterizing the contribution of a new type of background D-brane. There is a non-perturbative map to a family of string equations which we expect to be the \\hat{c}=0 type 0B string. The map exchanges D-branes and R-R fluxes. We present the general structure of the string equations for the (2,4k) type 0A models.

  13. Cosine tuning minimizes motor errors.

    Science.gov (United States)

    Todorov, Emanuel

    2002-06-01

    Cosine tuning is ubiquitous in the motor system, yet a satisfying explanation of its origin is lacking. Here we argue that cosine tuning minimizes expected errors in force production, which makes it a natural choice for activating muscles and neurons in the final stages of motor processing. Our results are based on the empirically observed scaling of neuromotor noise, whose standard deviation is a linear function of the mean. Such scaling predicts a reduction of net force errors when redundant actuators pull in the same direction. We confirm this prediction by comparing forces produced with one versus two hands and generalize it across directions. Under the resulting neuromotor noise model, we prove that the optimal activation profile is a (possibly truncated) cosine--for arbitrary dimensionality of the workspace, distribution of force directions, correlated or uncorrelated noise, with or without a separate cocontraction command. The model predicts a negative force bias, truncated cosine tuning at low muscle cocontraction levels, and misalignment of preferred directions and lines of action for nonuniform muscle distributions. All predictions are supported by experimental data.

  14. Study of constrained minimal supersymmetry

    CERN Document Server

    Kane, G L; Roszkowski, Leszek; Wells, J D; Chris Kolda; Leszek Roszkowski; James D Wells

    1994-01-01

    Taking seriously phenomenological indications for supersymmetry, we have made a detailed study of unified minimal SUSY, including effects at the few percent level in a consistent fashion. We report here a general analysis without choosing a particular unification gauge group. We find that the encouraging SUSY unification results of recent years do survive the challenge of a more complete and accurate analysis. Taking into account effects at the 5-10% level leads to several improvements of previous results, and allows us to sharpen our predictions for SUSY in the light of unification. We perform a thorough study of the parameter space. The results form a well-defined basis for comparing the physics potential of different facilities. Very little of the acceptable parameter space has been excluded by LEP or FNAL so far, but a significant fraction can be covered when these accelerators are upgraded. A number of initial applications to the understanding of the SUSY spectrum, detectability of SUSY at LEP II or FNAL...

  15. Cationic gold staining of glomerular anionic sites in archived tissue, reprocessed from paraffin wax into LR gold resin.

    Science.gov (United States)

    Goode, N P; Shires, M; Aparicio, S R; Davison, A M

    1993-05-01

    Glomerular capillary wall anionic sites have been demonstrated by cationic gold staining of archived renal biopsy tissue (up to 10 years old), obtained from six patients, originally embedded in paraffin wax, and subsequently reprocessed into LR gold resin. The staining patterns at pH 2.5 and pH 7.0, demonstrating different glomerular basement membrane (GBM) anionic constituents, were compared in three patients from whom tissue directly processed into LR gold and reprocessed tissue was available. Ultrastructural preservation was poorer and shrinkage artefact greater in paraformaldehyde-lysine periodate (PLP) as opposed to formol saline-fixed reprocessed tissue. However, GBM anionic site expression was well preserved, or even enhanced (lamina rara externa, pH 7.0) in reprocessed tissue, using either fixative. Although it may not be possible to compare subtle changes in anionic site distribution in variously fixed and processed tissues, due to these artefacts, the technique enables retrospective study of charge status in archived material from disease groups in which there are distinct anionic site aberrations.

  16. Global regularity for minimal sets and counterexamples

    CERN Document Server

    Liang, Xiangyu

    2011-01-01

    We discuss the global regularity for 2 dimensional minimal sets, that is, whether all global minimal sets in $\\R^n$ are cones or not. Every minimal set looks like a minimal cone $C$ at infinity, hence the main point is to use the topological properties of a minimal set at large scale to control its topology at smaller scales. Such arguments depend on the cone $C$, thus we have to discuss them one by one. Recall that this is the idea to prove that 1-dimensional Almgren-minimal sets in $\\R^n$, and 2-dimensional Mumford-Shah minimal sets in $\\R^3$ are cones. In this article we discuss three types of 2-dimensional minimal sets: Almgren-minimal set in $\\R^3$ whose blow-in limit is a $\\T$ set; topological minimal sets in $\\R^4$ whose blow-in limit is a $\\T$ set; and Almgren minimal sets in $\\R^4$ whose blow-in limit is the union $P_\\theta$ of two almost orthogonal planes. For the first one we eliminate an existing potential counterexample that was proposed by several people, and show that a real counterexample shou...

  17. Minimal models of multidimensional computations.

    Directory of Open Access Journals (Sweden)

    Jeffrey D Fitzgerald

    2011-03-01

    Full Text Available The multidimensional computations performed by many biological systems are often characterized with limited information about the correlations between inputs and outputs. Given this limitation, our approach is to construct the maximum noise entropy response function of the system, leading to a closed-form and minimally biased model consistent with a given set of constraints on the input/output moments; the result is equivalent to conditional random field models from machine learning. For systems with binary outputs, such as neurons encoding sensory stimuli, the maximum noise entropy models are logistic functions whose arguments depend on the constraints. A constraint on the average output turns the binary maximum noise entropy models into minimum mutual information models, allowing for the calculation of the information content of the constraints and an information theoretic characterization of the system's computations. We use this approach to analyze the nonlinear input/output functions in macaque retina and thalamus; although these systems have been previously shown to be responsive to two input dimensions, the functional form of the response function in this reduced space had not been unambiguously identified. A second order model based on the logistic function is found to be both necessary and sufficient to accurately describe the neural responses to naturalistic stimuli, accounting for an average of 93% of the mutual information with a small number of parameters. Thus, despite the fact that the stimulus is highly non-Gaussian, the vast majority of the information in the neural responses is related to first and second order correlations. Our results suggest a principled and unbiased way to model multidimensional computations and determine the statistics of the inputs that are being encoded in the outputs.

  18. Screening cervical and oesophageal tissues using optical coherence tomography

    Science.gov (United States)

    Erry, Gavin R. G.; Bazant-Hegemark, Florian; Read, Mike D.; Stone, Nicholas

    2011-06-01

    Optical Coherence Tomography (OCT) is a technique that allows imaging tissue in three spatial dimensions. Such a technique makes it possible to examine the subsurface of the tissue. The depth of penetration into the tissue can be tailored by tuning the wavelength of the light source. While in some cases it is desirable to obtain deep penetration of the sample, when scanning for cancerous changes, it may only be necessary to penetrate the first few hundred micrometres. The use of a shorter wavelength, while decreasing the penetration depth, will improve the resolution of the instrument. While images from OCT systems contain speckle and other artefacts, there are methods of evaluating the information by using image processing techniques. Of particular interest is the scattering coefficient that can be derived from the OCT data. Using discriminant techniques on the scattering data (such as principal components analysis), gives a sensitive way of differentiating between changes in structure in the tissue. An extensive data collection was performed on cervical tissue using samples that ranged from normal to invasive cancer. The histopathology of each sample was gathered and was classified from normal to cancer. The scattering profiles of the data were averaged and gradient analysis was performed, showing that for small distances into the sample there is a significant difference between scattering profiles between cancerous and normal tissue. PCA was also performed on the data showing grouping into various stages of cancer.

  19. [Minimally invasive approaches to hip and knee joints for total joint replacement].

    Science.gov (United States)

    Rittmeister, M; König, D P; Eysel, P; Kerschbaumer, F

    2004-11-01

    The manuscript features the different minimally invasive approaches to the hip for joint replacement. These include medial, anterior, anterolateral, and posterior approaches. The concept of minimally invasive hip arthroplasty makes sense if it is an integral part of a larger concept to lower postoperative morbidity. Besides minimal soft tissue trauma, this concept involves preoperative patient education, preemptive analgesia, and postoperative physiotherapy. It is our belief that minimal incision techniques for the hip are not suited for all patients and all surgeons. The different minimally invasive approaches to the knee joint for implantation of a knee arthroplasty are described and discussed. There have been no studies published yet that fulfill EBM criteria. The data so far show that minimally invasive approaches and implantation techniques for total knee replacements lead to quicker rehabilitation of patients.

  20. Minimizing RF heating of conducting wires in MRI.

    Science.gov (United States)

    Yeung, Christopher J; Karmarkar, Parag; McVeigh, Elliot R

    2007-11-01

    Performing interventions using long conducting wires in MRI introduces the risk of focal RF heating at the wire tip. Comprehensive EM simulations are combined with carefully measured experimental data to show that method-of-moments EM field modeling coupled with heat transfer modeling can adequately predict RF heating with wires partially inserted into the patient-mimicking phantom. The effects of total wire length, inserted length, wire position in the phantom, phantom position in the scanner, and phantom size are examined. Increasing phantom size can shift a wire's length of maximum tip heating from about a half wave toward a quarter wave. In any event, with wires parallel to the scanner bore, wire tip heating is minimized by keeping the patient and wires as close as possible to the central axis of the scanner bore. At 1.5T, heating is minimized if bare wires are shorter than 0.6 m or between approximately 2.4 m and approximately 3.0 m. Heating is further minimized if wire insertion into phantoms equivalent to most aqueous soft tissues is less than 13 cm or greater than 40 cm (longer for fatty tissues, bone, and lung). The methods demonstrated can be used to estimate the absolute amount of heating in order to set RF power safety thresholds.

  1. Prevailing Trends in Haptic Feedback Simulation for Minimally Invasive Surgery.

    Science.gov (United States)

    Pinzon, David; Byrns, Simon; Zheng, Bin

    2016-08-01

    Background The amount of direct hand-tool-tissue interaction and feedback in minimally invasive surgery varies from being attenuated in laparoscopy to being completely absent in robotic minimally invasive surgery. The role of haptic feedback during surgical skill acquisition and its emphasis in training have been a constant source of controversy. This review discusses the major developments in haptic simulation as they relate to surgical performance and the current research questions that remain unanswered. Search Strategy An in-depth review of the literature was performed using PubMed. Results A total of 198 abstracts were returned based on our search criteria. Three major areas of research were identified, including advancements in 1 of the 4 components of haptic systems, evaluating the effectiveness of haptic integration in simulators, and improvements to haptic feedback in robotic surgery. Conclusions Force feedback is the best method for tissue identification in minimally invasive surgery and haptic feedback provides the greatest benefit to surgical novices in the early stages of their training. New technology has improved our ability to capture, playback and enhance to utility of haptic cues in simulated surgery. Future research should focus on deciphering how haptic training in surgical education can increase performance, safety, and improve training efficiency. © The Author(s) 2016.

  2. Tissue Classification

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, David Gerald [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-01-01

    The project began as a e ort to support InLight and Lumidigm. With the sale of the companies to a non-New Mexico entity, the project then focused on supporting a new company Medici Technologies. The Small Business (SB) is attempting to quantify glucose in tissue using a series of short interferometer scans of the nger. Each scan is produced from a novel presentation of the nger to the device. The intent of the project is to identify and, if possible, implement improved methods for classi cation, feature selection, and training to improve the performance of predictive algorithms used for tissue classi cation.

  3. Reconstruction of in-situ porosity and porewater compositions of low-permeability crystalline rocks: Magnitude of artefacts induced by drilling and sample recovery

    Science.gov (United States)

    Meier, D. B.; Waber, H. N.; Gimmi, T.; Eichinger, F.; Diamond, L. W.

    2015-12-01

    Geological site characterisation programmes typically rely on drill cores for direct information on subsurface rocks. However, porosity, transport properties and porewater composition measured on drill cores can deviate from in-situ values due to two main artefacts caused by drilling and sample recovery: (1) mechanical disruption that increases porosity and (2) contamination of the porewater by drilling fluid. We investigated the effect and magnitude of these perturbations on large drill core samples (12-20 cm long, 5 cm diameter) of high-grade, granitic gneisses obtained from 350 to 600 m depth in a borehole on Olkiluoto Island (SW Finland). The drilling fluid was traced with sodium-iodide. By combining out-diffusion experiments, gravimetry, UV-microscopy and iodide mass balance calculations, we successfully quantified the magnitudes of the artefacts: 2-6% increase in porosity relative to the bulk connected porosity and 0.9 to 8.9 vol.% contamination by drilling fluid. The spatial distribution of the drilling-induced perturbations was revealed by numerical simulations of 2D diffusion matched to the experimental data. This showed that the rims of the samples have a mechanically disrupted zone 0.04 to 0.22 cm wide, characterised by faster transport properties compared to the undisturbed centre (1.8 to 7.7 times higher pore diffusion coefficient). Chemical contamination was shown to affect an even wider zone in all samples, ranging from 0.15 to 0.60 cm, in which iodide enrichment was up to 180 mg/kgwater, compared to 0.5 mg/kgwater in the uncontaminated centre. For all samples in the present case study, it turned out that the magnitude of the artefacts caused by drilling and sample recovery is so small that no correction is required for their effects. Therefore, the standard laboratory measurements of porosity, transport properties and porewater composition can be taken as valid in-situ estimates. However, it is clear that the magnitudes strongly depend on site- and

  4. Reconstruction of in-situ porosity and porewater compositions of low-permeability crystalline rocks: Magnitude of artefacts induced by drilling and sample recovery.

    Science.gov (United States)

    Meier, D B; Waber, H N; Gimmi, T; Eichinger, F; Diamond, L W

    2015-12-01

    Geological site characterisation programmes typically rely on drill cores for direct information on subsurface rocks. However, porosity, transport properties and porewater composition measured on drill cores can deviate from in-situ values due to two main artefacts caused by drilling and sample recovery: (1) mechanical disruption that increases porosity and (2) contamination of the porewater by drilling fluid. We investigated the effect and magnitude of these perturbations on large drill core samples (12-20 cm long, 5 cm diameter) of high-grade, granitic gneisses obtained from 350 to 600 m depth in a borehole on Olkiluoto Island (SW Finland). The drilling fluid was traced with sodium-iodide. By combining out-diffusion experiments, gravimetry, UV-microscopy and iodide mass balance calculations, we successfully quantified the magnitudes of the artefacts: 2-6% increase in porosity relative to the bulk connected porosity and 0.9 to 8.9 vol.% contamination by drilling fluid. The spatial distribution of the drilling-induced perturbations was revealed by numerical simulations of 2D diffusion matched to the experimental data. This showed that the rims of the samples have a mechanically disrupted zone 0.04 to 0.22 cm wide, characterised by faster transport properties compared to the undisturbed centre (1.8 to 7.7 times higher pore diffusion coefficient). Chemical contamination was shown to affect an even wider zone in all samples, ranging from 0.15 to 0.60 cm, in which iodide enrichment was up to 180 mg/kg water, compared to 0.5 mg/kg water in the uncontaminated centre. For all samples in the present case study, it turned out that the magnitude of the artefacts caused by drilling and sample recovery is so small that no correction is required for their effects. Therefore, the standard laboratory measurements of porosity, transport properties and porewater composition can be taken as valid in-situ estimates. However, it is clear that the magnitudes strongly depend on site

  5. A virtual sinogram method to reduce dental metallic implant artefacts in computed tomography-based attenuation correction for PET

    NARCIS (Netherlands)

    Abdoli, Mehrsima; Ay, Mohammad Reza; Ahmadian, Alireza; Zaidi, Habib

    2010-01-01

    Objective Attenuation correction of PET data requires accurate determination of the attenuation map (mu map), which represents the spatial distribution of linear attenuation coefficients of different tissues at 511 keV. The presence of high-density metallic dental filling material in head and neck X

  6. Visualisation of the intact dura mater and brain surface in infant autopsies: a minimally destructive technique for the post-mortem assessment of head injury.

    Science.gov (United States)

    Cheshire, Emma C; Malcomson, Roger D G; Rutty, Guy N; James, Deryk S

    2015-03-01

    During the post-mortem examination of babies and young children, it is important to be able to visualise the brain and its coverings, particularly in cases where a head injury is likely to have occurred. In this paper, we present an improved method for removal of the calvarial bones in infant autopsies to enable viewing of the dura mater and brain. In contrast to the standard post-mortem procedure for observing and removing the brain, this novel technique is minimally disruptive, allowing the dura mater to remain undamaged. Specialised paediatric neurosurgical tools were used to remove the skull bones from 23 neonates, infants and young children during post-mortem examination. In 21 of our 23 cases, the calvarial bones were removed successfully with the dura mater remaining intact. In one case, there was a thickening of the dura mater which created a strong adherence of this membrane to the bone. In another case, the dura mater was slightly damaged due to the inexperience of the operator in using the neurosurgical tools. This method of calvarial bone removal reduces the degree of post-mortem artefact and enhances the ability to observe and photographically document autopsy findings, including the artefact-free detection of signs of injury such as epidural or subdural haematoma, and brain swelling. This technique has now become a routine practise in both of our units to remove the skull bones in infant/young children post-mortem examinations.

  7. Surgical technique for minimally invasive fibula fracture fixation.

    Science.gov (United States)

    Carlile, G S; Giles, N C L

    2011-09-01

    This paper describes a minimally invasive percutaneous technique for reduction and fixation of distal fibula fractures using plate osteosynthesis. We believe this technique benefits patients with poor quality soft tissue envelopes. So far a total of 25 patients have undergone percutaneous fixation, 22 females and 3 males. At no stage yet has a minimally invasive procedure been abandoned intra-operatively in favour of conversion to an open procedure. The mean age was 61.6 years (range 25-80 years). The mean time to surgery was 2.00 days (range 0-5) and mean time to discharge was 4.20 days (range 1-9). At a minimum of over 1 year's follow-up all fractures have healed, with no delayed unions or complications so far experienced.

  8. Application of minimally invasive surgery in traumatic brain injury

    Directory of Open Access Journals (Sweden)

    Liu Baiyun

    2014-12-01

    Full Text Available This article aims to expound the essence of minimally invasive surgery as well as when and how to use it in craniocerebral trauma surgery according to the characteristics of the disease. In neurosurgery, the importance of tissue protection should be from the inside to the outside, i.e. brain→dura→skull→scalp. In this article, I want to share my opinion and our team’s experience in terms of selecting surgical approaches and incision, surgical treatment of the skull, dura handling, intracranial operation and placement of drainage based on the above theory. I hope this will be helpful for trauma surgeons. Key words: Traumatic brain injuries; Large craniectomy; Surgical procedures, minimally invasive

  9. On o-minimal homotopy groups

    CERN Document Server

    Baro, Elias

    2008-01-01

    We work over an o-minimal expansion of a real closed field. The o-minimal homotopy groups of a definable set are defined naturally using definable continuous maps. We prove that any two semialgebraic maps which are definably homotopic are also semialgebraically homotopic. This result together with the study of semialgebraic homotopy done by H. Delfs and M. Knebusch allows us to develop an o-minimal homotopy theory. In particular, we obtain o-minimal versions of the Hurewicz theorems and the Whitehead theorem.

  10. Contemporary review of minimally invasive pancreaticoduodenectomy.

    Science.gov (United States)

    Dai, Rui; Turley, Ryan S; Blazer, Dan G

    2016-12-27

    To assess the current literature describing various minimally invasive techniques for and to review short-term outcomes after minimally invasive pancreaticoduodenectomy (PD). PD remains the only potentially curative treatment for periampullary malignancies, including, most commonly, pancreatic adenocarcinoma. Minimally invasive approaches to this complex operation have begun to be increasingly reported in the literature and are purported by some to reduce the historically high morbidity of PD associated with the open technique. In this systematic review, we have searched the literature for high-quality publications describing minimally invasive techniques for PD-including laparoscopic, robotic, and laparoscopic-assisted robotic approaches (hybrid approach). We have identified publications with the largest operative experiences from well-known centers of excellence for this complex procedure. We report primarily short term operative and perioperative results and some short term oncologic endpoints. Minimally invasive techniques include laparoscopic, robotic and hybrid approaches and each of these techniques has strong advocates. Consistently, across all minimally invasive modalities, these techniques are associated less intraoperative blood loss than traditional open PD (OPD), but in exchange for longer operating times. These techniques are relatively equivalent in terms of perioperative morbidity and short term oncologic outcomes. Importantly, pancreatic fistula rate appears to be comparable in most minimally invasive series compared to open technique. Impact of minimally invasive technique on length of stay is mixed compared to some traditional open series. A few series have suggested that initiation of and time to adjuvant therapy may be improved with minimally invasive techniques, however this assertion remains controversial. In terms of short-terms costs, minimally invasive PD is significantly higher than that of OPD. Minimally invasive approaches to PD show

  11. Minimally invasive esthetic therapy: a case report describing the advantages of a multidisciplinary approach.

    Science.gov (United States)

    Pinto, Rodrigo Carlos; Chambrone, Leandro; Colombini, Bella Luna; Ishikiriama, Sérgio Kiyoshi; Britto, Isabella Maria; Romito, Giuseppe Alexandre

    2013-05-01

    The decision-making process for the treatment of esthetic areas is based on the achievement of a healthy, harmonious, and pleasant smile. These conditions are directly associated with a solid knowledge of tooth anatomy and proportions, as well as the smile line, soft tissue morphology, and osseous architecture. To achieve these objectives, a multidisciplinary approach may be necessary to create long-term harmony between the final restoration and the adjacent teeth, and the health of the surrounding soft and hard tissues. This case report describes the application of a minimally invasive therapy on a 33-year-old woman seeking esthetic treatment. Minimally invasive periodontal plastic surgery associated with porcelain laminate veneers yielded satisfactory esthetics and minimal trauma to dental and periodontal tissues. Such a combined approach may be considered a viable option for the improvement of "white" and "red" esthetics.

  12. [Kimura's disease: an unrecognized cause of adult-onset nephrotic syndrome with minimal change disease].

    Science.gov (United States)

    Shehwaro, N; Langlois, A-L; Gueutin, V; Debchi, L; Charlotte, F; Rouvier, P; Rottembourg, J; Izzedine, H

    2014-02-01

    Kimura's disease (KD) is an angiolymphoid proliferative disorder of soft tissue with eosinophilia, with a predilection for head and neck regions in young Oriental men. Kidney disease is thought to be rare in KD. About a case of adult-onset nephrotic syndrome with minimal change disease, we comment Kimura's disease and its associated kidney damage. Kimura disease should be suspected and included in the diagnosis of adult-onset nephrotic syndrome with minimal change disease.

  13. Optimal Needle Grasp Selection for Automatic Execution of Suturing Tasks in Robotic Minimally Invasive Surgery

    OpenAIRE

    Liu, Taoming; Çavuşoğlu, M. Cenk

    2015-01-01

    This paper presents algorithms for optimal selection of needle grasp, for autonomous robotic execution of the minimally invasive surgical suturing task. In order to minimize the tissue trauma during the suturing motion, the best practices of needle path planning that are used by surgeons are applied for autonomous robotic surgical suturing tasks. Once an optimal needle trajectory in a well-defined suturing scenario is chosen, another critical issue for suturing is the choice of needle grasp f...

  14. Vacuum grasping as a manipulation technique for minimally invasive surgery

    Science.gov (United States)

    Goossens, R. H. M.; van Eijk, D. J.; de Hingh, I. H. J. T.; Jakimowicz, J. J.

    2010-01-01

    Background Laparoscopic surgery requires specially designed instruments. Bowel tissue damage is considered one of the most serious forms of lesion, specifically perforation of the bowel. Methods An experimental setting was used to manipulate healthy pig bowel tissue via two vacuum instruments. During the experiments, two simple manipulations were performed for both prototypes by two experienced surgeons. Each manipulation was repeated 20 times for each prototype at a vacuum level of 60 kPa and 20 times for each prototype at a vacuum level of 20 kPa. All the manipulations were macroscopically assessed by two experienced surgeons in terms of damage to the bowel. Results In 160 observations, 63 ecchymoses were observed. All 63 ecchymoses were classified as not relevant and negligible. No serosa or seromuscular damages and no perforations were observed. Conclusion Vacuum instruments such as the tested prototypes have the potential to be used as grasper instruments in minimally invasive surgery. PMID:20195640

  15. Minimization of Fuzzy Finite Generalized Automata

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Some concepts in Fuzzy Generalized Automata (FGA) are established. Then an important new algorithm which would calculate the minimal FGA is given. The new algorithm is composed of two parts: the first is called E-reduction which contracts equivalent states, and the second is called RE-reduction which removes retrievable states. Finally an example is given to illuminate the algorithm of minimization.

  16. The relative volume growth of minimal submanifolds

    DEFF Research Database (Denmark)

    Markvorsen, Steen; Palmer, V.

    2002-01-01

    The volume growth of certain well-defined subsets of minimal submanifolds in riemannian spaces are compared with the volume growth of balls and spheres ill space forms of constant curvature.......The volume growth of certain well-defined subsets of minimal submanifolds in riemannian spaces are compared with the volume growth of balls and spheres ill space forms of constant curvature....

  17. Minimal Exit Trajectories with Optimum Correctional Manoeuvres

    Directory of Open Access Journals (Sweden)

    T. N. Srivastava

    1980-10-01

    Full Text Available Minimal exit trajectories with optimum correctional manoeuvers to a rocket between two coplaner, noncoaxial elliptic orbits in an inverse square gravitational field have been investigated. Case of trajectories with no correctional manoeuvres has been analysed. In the end minimal exit trajectories through specified orbital terminals are discussed and problem of ref. (2 is derived as a particular case.

  18. Commercial considerations in tissue engineering.

    Science.gov (United States)

    Mansbridge, Jonathan

    2006-10-01

    Tissue engineering is a field with immense promise. Using the example of an early tissue-engineered skin implant, Dermagraft, factors involved in the successful commercial development of devices of this type are explored. Tissue engineering has to strike a balance between tissue culture, which is a resource-intensive activity, and business considerations that are concerned with minimizing cost and maximizing customer convenience. Bioreactor design takes place in a highly regulated environment, so factors to be incorporated into the concept include not only tissue culture considerations but also matters related to asepsis, scaleup, automation and ease of use by the final customer. Dermagraft is an allogeneic tissue. Stasis preservation, in this case cryopreservation, is essential in allogeneic tissue engineering, allowing sterility testing, inventory control and, in the case of Dermagraft, a cellular stress that may be important for hormesis following implantation. Although the use of allogeneic cells provides advantages in manufacturing under suitable conditions, it raises the spectre of immunological rejection. Such rejection has not been experienced with Dermagraft. Possible reasons for this and the vision of further application of allogeneic tissues are important considerations in future tissue-engineered cellular devices. This review illustrates approaches that indicate some of the criteria that may provide a basis for further developments. Marketing is a further requirement for success, which entails understanding of the mechanism of action of the procedure, and is illustrated for Dermagraft. The success of a tissue-engineered product is dependent on many interacting operations, some discussed here, each of which must be performed simultaneously and well.

  19. Energetic recovery in porcine grafts by minimally invasive liver oxygenation.

    Science.gov (United States)

    Minor, Thomas; Scott, William E; Rizzari, Michael D; Suszynski, Thomas M; Luer, Bastian; Efferz, Patrik; Papas, Klearchos K; Paul, Andreas

    2012-12-01

    Gaseous insufflation of oxygen via the venous vascular system has proven to be an effective tool for preventing anoxic tissue injury after extended time periods of ischemic liver preservation. Most experimental studies so far have been undertaken in rat models and include a series of pinpricks into postsinusoidal venules as an outlet for the insufflated gas. Here, we describe a simplified technique for minimally invasive liver oxygenation in porcine grafts, representing a hassle-free access to organ oxygenation without vascular lesions. We retrieved livers from Landrace pigs and cold-stored them in histidine-tryptophan-ketoglutarate solution. Subsequent to 18 h preservation, we treated some livers for an additional 2 h with gaseous oxygen, insufflated via silicone tubing inserted into the suprahepatic caval vein. Gas pressure was limited to 18 mm Hg. We occluded the infrahepatic caval vein with a bulldog clamp. Gas bubbles left the graft via the portal vein. We assessed liver integrity by energetic tissue status and by controlled in vitro reperfusion with autologous blood. Magnetic resonance imaging demonstrated homogeneous gas distribution in the persufflated tissue without major shunting. Biochemical analyses revealed effective and homogeneous restoration of energetic homeostasis in the ischemic graft before reperfusion. Sinusoidal endothelial clearance of hyaluronic acid was significantly improved upon reperfusion, as was hepatic arterial flow. Parenchymal enzyme loss was concordantly mitigated after minimally invasive liver oxygenation. Our results indicate that gaseous oxygen persufflation of the porcine liver is possible without tissue trauma, and significantly enhances post-preservation recovery of the graft. Copyright © 2012 Elsevier Inc. All rights reserved.

  20. Minimally invasive tethered cord release in children: A technical note

    Directory of Open Access Journals (Sweden)

    S. Kağan Başarslan

    2014-03-01

    Full Text Available Tethered cord release is commonly performed in pediatric neurosurgery. Nowadays, minimally invasive procedures are created growing interest due to its highly tolerable nature for surgery. It has been main purpose a minimal damaging on access route and maximum protection of normal structures in surgery. We present a surgical treatment of tethered cord syndrome, by which is provided the cord releasing unlike the many methods being applied with tissue removal. The main advantage of performing this surgery through 2 cm hole is to avoid removing ligamentum flavum and bony structure like lamina in addition to reduce the length of the incision and the related scar tissue. J Clin Exp Invest 2014; 5 (1: 115-117 Technical note: the patient was taken on the operating table in the sitting-prone position, and L5-S1 distance was determined by fluoroscopy. The skin and subcutaneous tissues was passed via a 2 cm vertical incision settled in 0.5 cm laterally from midline. L5-S1 distance and its covering ligamentum flavum are displayed by the guidance of L5 lamina. Williams’s retractor was placed in the distance after fetching microscope. The foregoing procedures are the same with microdiscectomic surgery. By a vertical incision made on the flavum, its both layer was lifted up and hanged with simple suture on the back tissue for a comfortable exposure of the Dura. Thecal sac was opened by 0.5 cm long vertical incision on the Dura after obtaining secure CSF drainage with the help of yellow-tipped syringe needle. With finding by a nerve hook, the phylum was burned and released securely. Then the Dura was sutured primarily for the closure by means of microsurgery instruments, and flavum was laid on it again.