481 research outputs found
Electron-positron generation by irradiating various metallic materials with laser-accelerated electrons
No full textWe examined electron–positron pair production in solid iron, zinc, tungsten, and lead targets irradiated by a laser-accelerated electron beam generated with a 100 TW laser. These targets were assessed at the target thickness of 0.5, 1.25, and 2.0 radiation lengths for each material. Using a 0.75-T-magnetic spectrometer, we measured the electron and positron yields and spectra, producing 3 × 108 positrons per shot with a peak leptonic density of 4 × 1012 cm−3. These experimental results agree very well with Monte Carlo simulations conducted with the simulation code Geant4. Importantly, our findings show that normalizing the target thickness to each material's radiation length results in consistent electron and positron yields across the materials, effectively reducing discrepancies due to material differences. © 2023 The Author(s)11Nsciescopu
Reliability−based topology optimization frameworks for the design of structures subjected to random excitations
No full textEmbargo set by: Seth Robbins for item 95486
Lift date: 2018-11-10T18:43:22Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 95486 on 2018-11-11T10:15:32Z.Structural optimization aims to provide structural designs that allow for the best performance while satisfying given design constraints. Among various applications of structural optimization, topology optimization based on mathematical programming and finite element analysis has recently gained great attention in research community as well as in applied structural engineering fields. One of the most fundamental requirements on building structures is to withstand various uncertain loads such as earthquake ground motions, wind loads and ocean waves. The design of structures, therefore, needs to ensure safe and reliable operations of structures over a prolonged period of time during which they may be exposed to various randomness of excitations caused by hazardous events. As such, significant amount of time and financial resources are invested to control the dynamic response of a structure under random vibrations caused by natural hazards or operations of non-structural components. In this regard, topology optimization of structures with stochastic response constraints is of great importance and consideration in industrial applications. This thesis discusses the development of structural optimization frameworks for a wide spectrum of deterministic and probabilistic constraints in engineering and investigate numerical applications.
First, the efficient optimization framework for statics and dynamics problems is investigated. In many incidences, expensive computational cost and labor hours are so prohibitive that optimization processes become impractical or inapplicable. In order to alleviate the computational burden in dynamic topology optimization, the multiresolution topology optimization approach is adopted. Based on the polygonal finite element method and multiresolution topology optimization techniques, a method of polygonal multiresolution topology optimization for statics and dynamics problems is developed. This development provides methods to discretize complicated geometries and reduce computational cost to obtain topology results of high-resolutions.
Despite rapid technological advances, incorporating stochastic response of structures into topology optimization is considered a relatively new field of research mainly due to computational challenges. In order to overcome such technical challenges in this field, a new method is introduced for incorporating random vibration theories into topology optimization using a discrete representation method for stochastic processes. Furthermore, a novel formulation is developed for sensitivity analysis of stochastic responses in order to use gradient-based optimization algorithms for the proposed topology optimization employing the discrete representation method.
To assess the reliability of a structure subjected to random excitations, the probability of the occurrence of at least one failure event over a time interval, i.e. the first passage probability, often needs to be evaluated. In this thesis, a new method is proposed to incorporate probabilistic constraints on the first passage probability into structural design and topology optimization. To obtain the first passage probability effectively during each iteration, the failure event is described as a series system event consisting of failure events defined at discrete time points, and the system failure probability is obtained with the sequential compounding method. A new sensitivity formulation is developed employing the sequential compounding method to facilitate the use of gradient-based optimizers for the proposed method.
Finally, the conventional filter effects are investigated in reliability-based topology optimization using the elastic formulation of the ground structure method. In addition, an optimization scheme employing the discrete filter is proposed to ensure that optimized solutions satisfy the probabilistic constraints and global equilibrium. In addition, the single-loop approach is incorporated to enhance the computational efficiency of the proposed RBTO method.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-08-01The student, Junho Chun, accepted the attached license on 2016-07-14 at 13:46.The student, Junho Chun, submitted this Dissertation for approval on 2016-07-14 at 14:36.This Dissertation was approved for publication on 2016-07-15 at 09:10.DSpace SAF Submission Ingestion Package generated from Vireo submission #9934 on 2016-11-10 at 12:25:23Made available in DSpace on 2016-11-10T18:43:01Z (GMT). No. of bitstreams: 3
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Previous issue date: 2016-07-1
Optimization of peripheral blood volume for in silico reconstitution of the human B-cell receptor repertoire
No full textB cells recognize antigens via membrane-expressed B-cell receptors (BCR) and antibodies. Similar human BCR sequences are frequently found at a significantly higher frequency than that theoretically calculated. Patients infected with SARS-CoV2 and HIV or with autoimmune diseases share very similar BCRs. Therefore, in silico reconstitution of BCR repertoires and identification of stereotypical BCR sequences related to human pathology have diagnostic potential. Furthermore, monitoring changes of clinically significant BCR sequences and isotype conversion has prognostic potential. For BCR repertoire analysis, peripheral blood (PB) is the most convenient source. However, the optimal human PB volume for in silico reconstitution of the BCR repertoire has not been studied in detail. Here, we sampled 5, 10, and 20 mL PB from the left arm and 40 mL PB from the right arm of two volunteers, reconstituted in silico PB BCR repertoires, and compared their composition. In both volunteers, PB sampling over 20 mL resulted in slight increases in functional unique sequences (FUSs) or almost no increase in repertoire diversity. All FUSs with a frequency above 0.08% or 0.03% in the 40 mL PB BCR repertoire were detected even in the 5 mL PB BCR repertoire from each volunteer. FUSs with a higher frequency were more likely to be found in BCR repertoires from reduced PB volume, and those coexisting in two repertoires showed a statistically significant correlation in frequency irrespective of sampled anatomical site. The correlation was more significant in higher-frequency FUSs. These observations support the potential of BCR repertoire analysis for diagnosis.N
Neutron yield scaling law in laser-cluster fusion experiments
No full textWe present a scaling law ( Y ∼ E β ) of fusion neutron yields (Y) for laser pulse energy (E) in laser-cluster fusion experiments. We compare the available neutron yield data from previous deuterium cluster fusion experiments with those calculated using the cylindrical fusion plasma model. The calculated neutron yields are shown as functions of the incident laser pulse energy, average number density, and ion temperature. Although the deuterium-deuterium fusion reactivity is known to increase rapidly with ion temperature, the neutron yield shows a modest increase above ∼10 keV for a given laser pulse energy. We find the scaling exponent β approaching 1.0 as the ion temperature increases from 1 keV to 100 keV. We explain the observed temperature dependence of β by examining the temperature dependence of the beam-beam and beam-target fusion neutron yields separately. Our scaling law differs from previously reported scaling laws from individual experiments, but it shows an excellent agreement with the scaling law determined by the maximum neutron yields of individual experiments. © 2023 The Author(s). Published on behalf of IAEA by IOP Publishing Ltd.11Nsciescopu
Effective Combination Immunotherapy through Vessel Normalization Using a Cancer-Targeting Antiangiogenic Peptide–Antibody Hybrid
No full text© 2022 Wiley-VCH GmbH.Although cancer immunotherapy using immune checkpoint blockade (ICB) has changed the paradigm for treating patients with certain cancers, its therapeutic benefits are limited to approximately one-fourth of patients, highlighting the potential for combining immunotherapy with another therapeutic modality. Here, a treatment regimen that combines a cancer-targeting antiangiogenic agent that inhibits angiogenesis within the tumor and ICB to improve therapeutic outcome is reported. The cancer-targeting antiangiogenic modality is constructed as a hybrid complex, designated HyPEPEDB-VEGF, comprising a cotinine-labeled bispecific peptide targeting both extra domain B of fibronectin (EDB) and vascular endothelial growth factor (VEGF) and an anticotinine antibody (Abcot). The resulting HyPEPEDB-VEGF specifically bound to EDB-overexpressing CT26 murine colorectal cancer cells and inhibited VEGF-induced proliferation of human umbilical vascular endothelial cells. Upon intraperitoneal injection, HyPEPEDB-VEGF preferentially accumulates in CT26 syngeneic tumors and inhibits tumor growth in a dose-dependent manner. Furthermore, the combination of HyPEPEDB-VEGF with an anti-PD-1 antibody (αPD-1) in conjunction with dose optimization of the two modalities leads to substantial inhibition of tumor growth without loss of body weight due to vascular normalization within the tumor. These findings suggest that the combination of cancer-specific antiangiogenic therapy using HyPEPEDB-VEGF together with ICB may be a feasible approach for effective cancer therapy.N
Charge-neutral, GeV-scale electron-positron pair beams produced using bremsstrahlung gamma rays
No full textAbstract Matter-antimatter plasmas, such as electron-positron pair plasmas, are frequently observed in various astrophysical phenomena. In laboratory settings, electron-positron pairs have often been generated using high-Z converters irradiated by either direct laser pulses or laser-driven electron beams. Here we generate charge-neutral electron-positron beams with energies in the GeV range, utilizing bremsstrahlung gamma rays. Specifically, intense high-energy gamma rays produced electron-positron pair particles in a lead converter via the Bethe-Heitler process. The produced pair beams exhibited neutrality across all converter thicknesses throughout the energy spectrum spanning from 10 MeV to 1.8 GeV. Pairs with energies surpassing 1 GeV constituted up to 26% of the total kinetic energy within the spectrum. The experimental results were in good agreement with our Geant4 Monte Carlo simulations. These GeV-scale neutral pair particle beams have potential applications for understanding energetic astrophysical phenomena and high-energy particle physics
The C. elegans regulatory factor X (RFX) DAF-19M module: A shift from general ciliogenesis to cell-specific ciliary and behavioral specialization
No full text© 2022 The Author(s)Cilia are important for the interaction with environments and the proper function of tissues. While the basic structure of cilia is well conserved, ciliated cells have various functions. To understand the distinctive identities of ciliated cells, the identification of cell-specific proteins and its regulation is essential. Here, we report the mechanism that confers a specific identity on IL2 neurons in Caenorhabditis elegans, neurons important for the dauer larva-specific nictation behavior. We show that DAF-19M, an isoform of the sole C. elegans RFX transcription factor DAF-19, heads a regulatory subroutine, regulating target genes through an X-box motif variant under the control of terminal selector proteins UNC-86 and CFI-1 in IL2 neurons. Considering the conservation of DAF-19M module in IL2 neurons for nictation and in male-specific neurons for mating behavior, we propose the existence of an evolutionarily adaptable, hard-wired genetic module for distinct behaviors that share the feature recognizing the environment.N
ELTD1 as a multi-focal target for malignant gliomas: Preclinical studies
No full text© 2021 The Author(s). Published by Oxford University Press, the Society for Neuro-Oncology and the European Association of Neuro-Oncology.Background: Glioblastoma (GBM) is the most aggressive malignant primary brain tumor in adults. These high-grade gliomas undergo unregulated vascular angiogenesis, migration and cell proliferation allowing the tumor cells to evade cell-cycle checkpoints and apoptotic pathways. The Epidermal growth factor, latrophilin, and seven transmembrane domain-containing 1 on chromosome 1 (ELTD1) is an angiogenic biomarker that is highly expressed in malignant gliomas. Novel treatments targeting ELTD1 with monovalent monoclonal (mmAb) and single chain variable fragment (scFv) antibodies were effective in increasing animal survival, decreasing tumor volume and normalizing the vasculature. Due to the success of our antibody treatments on angiogenesis, this study sought to determine if our anti-ELTD1 treatments affected other aspects of tumorigenesis (cell proliferation, migration, and apoptosis) in a G55 glioma xenograft preclinical mouse model. Methods: Tumor tissue from untreated, mmAb and scFv anti-ELTD1 treated animals was used to quantify the positivity levels of human mitochondrial antibody, c-MET and Ki-67 for cellular proliferation, migratory markers CD44v6, TRPM8, and BMP2, and cleaved caspase 3 to assess apoptotic activity. Results: This approach demonstrated that our anti-ELTD1 treatments directly affected and decreased the human tumor cells within the tumor region. Additionally, there was a significant decrease in both cellular proliferation and migration due to anti-ETLD1 therapy. Lastly, anti-ELTD1 treatments successfully increased apoptotic activity within the tumor region. Conclusion: Our data suggest that anti-ELTD1 therapies would be effective against malignant gliomas by having a multi-focal effect and targeting all four aspects of tumorigenesis.N
Natural and engineered surfaces for enhanced phase change heat transfer
No full textPhase change of water is a ubiquitous process that occurs throughout nature and in a wide range of engineering systems. Over the last century, many researchers have studied the effect of surface wettability on the enhancement of phase change heat transfer. Interestingly, interfacial phenomena tailored for the manipulation of water can be found in nature. Many natural plant and insect surfaces have evolved to repel or attract water in order to adapt to external evolutionary pressures and to help them survive. This dissertation focuses on nature-inspired surfaces with desirable wettability characteristics that can enhance phase change heat transfer. We begin by investigating the wettability of natural surfaces to understand why and how hydrophobicity is achieved. We reveal that hydrophobicity of cicada wings, stemming from both chemistry and structure, is governed by life history and reproductive strategy, rather than habitat. We utilize the knowledge of natural surface chemistries to develop hydrophobic materials for environmentally friendly superhydrophobic coatings. Furthermore, we answer a key scientific controversy regarding the wettability of rare earth oxides by conclusively showing that hydrophobicity is driven by hydrocarbon adsorption. The findings were leveraged to design, develop, and demonstrate a novel concepts of condensation heat transfer capable of enhancing performance of state-of-the-art sytems by leveraging thin film condensation and jumping-droplet induced localized hot spot cooling.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-08-01The student, Junho Oh, accepted the attached license on 2019-07-10 at 17:05.The student, Junho Oh, submitted this Dissertation for approval on 2019-07-10 at 17:10.This Dissertation was approved for publication on 2019-07-12 at 13:04.DSpace SAF Submission Ingestion Package generated from Vireo submission #14252 on 2019-11-26 at 14:03:44Made available in DSpace on 2019-11-26T20:59:44Z (GMT). No. of bitstreams: 3
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Previous issue date: 2019-07-12Embargo set by: Seth Robbins for item 113078
Lift date: 2021-11-26T20:59:54Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 113078 on 2021-11-27T10:15:37Z
NSC and the value of flexibility : a case study of implementation and analysis of a mega-scale project
No full textThesis (S.M. in Real Estate Development)--Massachusetts Institute of Technology, Dept. of Architecture, Center for Real Estate, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 74-75).In the modern real estate industry, mega-scale developments have been a notable feature. The distinctiveness of these projects is that they are enormous in scale and thus require many years to develop. Unlike regular sized projects, they have greater opportunities to alter strategies, plans or designs during the multiple years of development. This provides the developer with alternative options to mitigate potential risks or seize upside opportunities. The "Real options" theory is especially applicable for valuation and decisionmaking of mega-scale real estate development projects. Relying on the dynamic decisions of the developer, for example, the project can proceed, be delayed or be abandoned. Either way, the developer can avoid downside risks and attain a more optimal value for the project. The New Songdo City (NSC) project in South Korea is an archetype of the mega-scale development phenomenon. "New Songdo City" is a massive city development project on 1,415 acres of reclaimed land in Incheon, near Seoul. The project features innovative and valuable aspects that are milestones for the real estate industry. Not only is NSC of megascale and multi-phase, but it is highly international in nature (foreign lead developer and architect, much foreign capital, and aimed at international world-class occupants). It also features imaginative conceptual planning, local and international developer partnership and sophisticated investment and financing techniques. The project highlights the importance of the interaction of local circumstances and other participants, helping to avoid risks and enhance the future values of the project. New Songdo City thus provides an excellent laboratory to explore both the broader strategic and historical development of a Mega-Project and also the applicability of modern, cutting- edge analytical tools for valuing flexibility in project design and implementation.(cont.) This thesis seeks to explore both of these aspects, including an in-depth review of the history and strategic prospects for the project as well as a specific quantitative model focusing on the value of phasing in the project. The quantitative model is innovative in that, while previous literature has developed classical economics-based real options models of NSC, this is the first application of the "engineering-based approach" advocated by Professor de Neufville and the MIT Engineering Systems Division. This approach allows the model to be more transparent and user-friendly to decision-makers, assisting the valuation of flexibility in the project in a manner more supportive for practitioners.by Junho Lee and Jeehyun Oh.S.M.in Real Estate Developmen
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