1,164 research outputs found

    Recent Advances in Terrestrial Lidar Applications in Geotechnical Earthquake Engineering

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    During the past five years, geotechnical earthquake engineering and ground deformation research has benefited from the advent of terrestrial LIDAR technology, a revolutionary tool for characterizing fine-scale changes in topography. For ground deformation research, LIDAR is particularly useful for characterizing the dimensions of failures and for monitoring subtle deformations through time. Tripod mounted LIDAR systems have accuracies of approximately 0.4-2.0 cm, and can illuminate targets up to one kilometer away from the sensor. During several minutes of LIDAR scanning, millions of survey position points are collected and processed into an ultra-high resolution terrain model. During earthquake reconnaissance efforts, the detailed failure morphologies of landslides and liquefaction sites can be measured remotely and in a way that is either impractical or impossible by conventional survey means. The ultra-high resolution imagery of the complex surface morphology of ground failures allows the exploration and visualization of damage on a computer in orientations and scales not previously possible. Detailed understanding of the ground surface morphology allows for better numerical modeling of potential failure modes, deformation patterns, and morphologies. Finally, LIDAR allows for the permanent archiving of 3-D terrain models. In this paper, we present the evaluation of the accuracy, bias and dispersion of LIDAR data under controlled experimental conditions. Field applications of LIDAR-damage visualization and analysis are presented from data gathered during the 2004 Niigata Chuetsu (M6.6) earthquake and the 2007-2008 PARI-Ishikari, Hokkaido blast-liquefaction experiment

    Predicting tensile properties of Ti-6Al-4V produced via directed energy deposition

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    Advanced manufacturing approaches, including additive manufacturing (i.e., ā€œ3D printingā€) of metallic structures requires a change to qualification strategies. One approach, informed qualification, integrates modeling strategies to make predictions of material characteristics, including the prediction of tensile properties for given chemistries and microstructures. In this work, constitutive equations are developed and presented that can predict the yield strength of additively manufactured Ti-6Al-4V subjected to one of three different heat-treatments: a stress relief anneal in the Ī±+Ī² phase field; a hot isostatic press treatment in the Ī±+Ī² phase field; and a Ī²-anneal. The equations are nominally identical, though different strengthening mechanisms are active according to subtle microstructural differences. To achieve an equation that can predict the yield strength of the material, it is also necessary to include an assessment of dramatic reduction in the tensile strength due to texture (i.e., a ā€œknock-downā€ effect). This has been experimentally measured, and included in this paper. The resulting predictions of yield strength are generally within 5% of their experimentally measured values

    Predicting the tensile properties of additively manufactured Ti-6Al-4V via electron beam deposition

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    Additively manufactured materials are gaining wide attention owing to the manufacturing benefits as it results in near net shape components. It is well known that the manufacturing processes affects the performance of the components via microstructural features and the mechanical properties. There is an urgent need to understand the processing-structure-property-performance relationship for the materials manufactures via such innovative techniques. Strategies are needed to quantify and modify the mechanical properties. This study assists to design and tailor the process parameters based on the final properties required. Current work predicts the yield strength of additively manufactured Ti-6Al-4V with different post heat treatments. A thermal model predicted by ABAQUS is fed into an implementation of Langmuir equation that predicts the chemistry which is then used in a phenomenological equation predicting the yield strength. The model is confirmed via experiments showing less than 2% deviation from the predicated properties. A statistical model gives design allowables that have an uncertainty of less than 1 ksi

    CyberKnife(Ā® )radiosurgery in the treatment of complex skull base tumors: analysis of treatment planning parameters

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    BACKGROUND: Tumors of the skull base pose unique challenges to radiosurgical treatment because of their irregular shapes, proximity to critical structures and variable tumor volumes. In this study, we investigate whether acceptable treatment plans with excellent conformity and homogeneity can be generated for complex skull base tumors using the Cyberknife(Ā® )radiosurgical system. METHODS: At Georgetown University Hospital from March 2002 through May 2005, the CyberKnife(Ā® )was used to treat 80 patients with 82 base of skull lesions. Tumors were classified as simple or complex based on their proximity to adjacent critical structures. All planning and treatments were performed by the same radiosurgery team with the goal of minimizing dosage to adjacent critical structures and maximizing target coverage. Treatments were fractionated to allow for safer delivery of radiation to both large tumors and tumors in close proximity to critical structures. RESULTS: The CyberKnife(Ā® )treatment planning system was capable of generating highly conformal and homogeneous plans for complex skull base tumors. The treatment planning parameters did not significantly vary between spherical and non-spherical target volumes. The treatment parameters obtained from the plans of the complex base of skull group, including new conformity index, homogeneity index and percentage tumor coverage, were not significantly different from those of the simple group. CONCLUSION: Our data indicate that CyberKnife(Ā® )treatment plans with excellent homogeneity, conformity and percent target coverage can be obtained for complex skull base tumors. Longer follow-up will be required to determine the safety and efficacy of fractionated treatment of these lesions with this radiosurgical system

    Ex vivo promoter analysis of antiviral heat shock cognate 70B gene in Anopheles gambiae

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    <p>Abstract</p> <p>Background</p> <p>The <it>Anopheles gambiae </it>heat shock cognate gene (<it>hsc70B</it>) encodes a constitutively expressed protein in the <it>hsp70 </it>family and it functions as a molecular chaperone for protein folding. However, the expression of <it>hsc70B </it>can be further induced by certain stimuli such as heat shock and infection. We previously demonstrated that the <it>An. gambiae hsc70B </it>is induced during o'nyong-nyong virus (ONNV) infection and subsequently suppresses ONNV replication in the mosquito. To further characterize the inducibility of <it>hsc70B </it>by ONNV infection in <it>An. gambiae</it>, we cloned a 2.6-kb region immediately 5' upstream of the starting codon of <it>hsc70B </it>into a luciferase reporter vector (pGL3-Basic), and studied its promoter activity in transfected Vero cells during infection with o'nyong-nyong, West Nile and La Crosse viruses.</p> <p>Results</p> <p>Serial deletion analysis of the <it>hsc70B </it>upstream sequence revealed that the putative promoter is likely located in a region 1615ā€“2150 bp upstream of the <it>hsc70B </it>starting codon. Sequence analysis of this region revealed transcriptional regulatory elements for heat shock element-binding protein (HSE-bind), nuclear factor ĪŗB (NF-ĪŗB), dorsal (Dl) and fushi-tarazu (Ftz). Arbovirus infection, regardless of virus type, significantly increased the <it>hsc70B </it>promoter activity in transfected Vero cells.</p> <p>Conclusion</p> <p>Our results further validate the transcriptional activation of <it>hsc70B </it>during arbovirus infection and support the role of specific putative regulatory elements. Induction by three taxonomically distinct arboviruses suggests that the HSC70B protein may be expressed to cope with cellular stress imposed during infection.</p

    Treatment of malignant tumors of the skull base with multi-session radiosurgery

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    <p>Abstract</p> <p>Objective</p> <p>Malignant tumors that involve the skull base pose significant challenges to the clinician because of the proximity of critical neurovascular structures and limited effectiveness of surgical resection without major morbidity. The purpose of this study was to evaluate the efficacy and safety of multi-session radiosurgery in patients with malignancies of the skull base.</p> <p>Methods</p> <p>Clinical and radiographic data for 37 patients treated with image-guided, multi-session radiosurgery between January 2002 and December 2007 were reviewed retrospectively. Lesions were classified according to involvement with the bones of the base of the skull and proximity to the cranial nerves.</p> <p>Results</p> <p>Our cohort consisted of 37 patients. Six patients with follow-up periods less than four weeks were eliminated from statistical consideration, thus leaving the data from 31 patients to be analyzed. The median follow-up was 37 weeks. Ten patients (32%) were alive at the end of the follow-up period. At last follow-up, or the time of death from systemic disease, tumor regression or stable local disease was observed in 23 lesions, representing an overall tumor control rate of 74%. For the remainder of lesions, the median time to progression was 24 weeks. The median progression-free survival was 230 weeks. The median overall survival was 39 weeks. In the absence of tumor progression, there were no cranial nerve, brainstem or vascular complications referable specifically to CyberKnife<sup>Ā® </sup>radiosurgery.</p> <p>Conclusion</p> <p>Our experience suggests that multi-session radiosurgery for the treatment of malignant skull base tumors is comparable to other radiosurgical techniques in progression-free survival, local tumor control, and adverse effects.</p

    Label-Free Characterization of Organic Nanocarriers Reveals Persistent Single Molecule Cores For Hydrocarbon Sequestration

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    Self-assembled molecular nanostructures embody an enormous potential for new technologies, therapeutics, and understanding of molecular biofunctions. Their structure and function are dependent on local environments, necessitating in-situ/operando investigations for the biggest leaps in discovery and design. However, the most advanced of such investigations involve laborious labeling methods that can disrupt behavior or are not fast enough to capture stimuli-responsive phenomena. We utilize X-rays resonant with molecular bonds to demonstrate an in-situ nanoprobe that eliminates the need for labels and enables data collection times within seconds. Our analytical spectral model quantifies the structure, molecular composition, and dynamics of a copolymer micelle drug delivery platform using resonant soft X-rays. We additionally apply this technique to a hydrocarbon sequestrating polysoap micelle and discover that the critical organic-capturing domain does not coalesce upon aggregation but retains distinct single-molecule cores. This characteristic promotes its efficiency of hydrocarbon sequestration for applications like oil spill remediation and drug delivery. Such a technique enables operando, chemically sensitive investigations of any aqueous molecular nanostructure, label-free

    A comparative study of WASP-67b and HAT-P-38b from WFC3 data

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    Atmospheric temperature and planetary gravity are thought to be the main parameters affecting cloud formation in giant exoplanet atmospheres. Recent attempts to understand cloud formation have explored wide regions of the equilibrium temperature-gravity parameter space. In this study, we instead compare the case of two giant planets with nearly identical equilibrium temperature (TeqT_\mathrm{eq} āˆ¼1050ā€‰K\sim 1050 \, \mathrm{K}) and gravity (gāˆ¼10ā€‰mā€‰sāˆ’1)g \sim 10 \, \mathrm{m \, s}^{-1}). During HSTHST Cycle 23, we collected WFC3/G141 observations of the two planets, WASP-67 b and HAT-P-38 b. HAT-P-38 b, with mass 0.42 MJ_\mathrm{J} and radius 1.4 RJR_\mathrm{J}, exhibits a relatively clear atmosphere with a clear detection of water. We refine the orbital period of this planet with new observations, obtaining P=4.6403294Ā±0.0000055ā€‰dP = 4.6403294 \pm 0.0000055 \, \mathrm{d}. WASP-67 b, with mass 0.27 MJ_\mathrm{J} and radius 0.83 RJR_\mathrm{J}, shows a more muted water absorption feature than that of HAT-P-38 b, indicating either a higher cloud deck in the atmosphere or a more metal-rich composition. The difference in the spectra supports the hypothesis that giant exoplanet atmospheres carry traces of their formation history. Future observations in the visible and mid-infrared are needed to probe the aerosol properties and constrain the evolutionary scenario of these planets.Comment: 16 pages, 17 figures, 8 tables, accepted for publication in The Astronomical Journa
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