1,355 research outputs found

    Two-Photon Direct Frequency Comb Spectroscopy of Rubidium

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    Precision spectroscopy measurements have contributed significantly to our understanding of the fundamental structure of atoms. Here we present an experiment involving a new precision spectroscopic technique using a femtosecond optical frequency comb to excite two-photon transitions in rubidium. A femtosecond optical frequency comb is an ultrashort, pulsed laser with tens of thousands of frequencies, equally spaced in frequency-space. These frequencies can be used to excite atoms to specific transitions. The frequency comb is a versatile instrument that can avoid many of the experimental uncertainties that are associated with other spectroscopic techniques. The specific technique we use is called velocity selective resonance, and it is used to eliminate Doppler broadening in our spectra. In addition, the setup could be cheaply and easily altered to study different atoms or systems. In this experiment, we study this new precision measurement technique of using an optical frequency comb for spectroscopy

    Two-Photon Direct Frequency Comb Spectroscopy of Rubidium

    Get PDF
    Precision spectroscopy measurements have contributed significantly to our understanding of the fundamental structure of atoms. Here we present an experiment involving a new precision spectroscopic technique using a femtosecond optical frequency comb to excite two-photon transitions in rubidium. A femtosecond optical frequency comb is an ultrashort, pulsed laser with tens of thousands of frequencies, equally spaced in frequency-space. These frequencies can be used to excite atoms to specific transitions. The frequency comb is a versatile instrument that can avoid many of the experimental uncertainties that are associated with other spectroscopic techniques. The specific technique we use is called velocity selective resonance, and it is used to eliminate Doppler broadening in our spectra. In addition, the setup could be cheaply and easily altered to study different atoms or systems. In this experiment, we study this new precision measurement technique of using an optical frequency comb for spectroscopy

    PW-laser produced MeV proton beams stopped in WDM plasmas (H, He, Ar, N, Xe)

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    Physical processes involved in the interaction of ion beams in Warm Dense Matter (WDM) (i.e. 1-100 eV. 0.01-100 g/cc) is fundamental to the understanding of condensed matter, solidstate physics, fusion sciences, and astrophysical phenomena..

    Angiogenesis and Its Role in the Tumour Microenvironment: A Target for Cancer Therapy

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    The process of angiogenesis refers to the growth of new blood vessels from existing ones. Tumours can produce factors in the micro-environment which act on blood vessels to promote angiogenesis. It is therefore considered to be fundamental in tumour progression and metastatic dissemination. This neovascularization can be regulated by numerous endogenous factors in the tumour micro-environment. As a result, anti-angiogenic therapies have been developed in the hope of targeting this process to reduce tumour growth and progression. However, only a proportion of patients respond to therapy, indicating the presence of treatment resistance in some. In this chapter, we aim to highlight the process of angiogenesis and to review pivotal evidence for the use of anti-angiogenic therapies thus far (alone and in combination with other agents). Finally, we will illustrate recent evidence for the discovery of biomarkers for anti-angiogenic therapies and potential mechanisms of resistance to such agents

    IT Outsourcing Success in Healthcare Industry: Build Your Capabilities on Multiple Fronts within the Institutional Framework

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    In this manuscript we report the findings from an in-depth case study about the factors that determine IT outsourcing success in the healthcare industry. Healthcare organizations in Taiwan are faced with increasing institutional pressures in the forms of hospital accreditation systems and national insurance program requirements. We found that organizations appeared to have adopted similar outsourcing practices under institutional pressures. However, whether or not an organization could successfully implement an outsourcing decision depends on the organization’s IT capabilities, governance capabilities, and capabilities to manage its relationship with the vendor. Research implications of these results are discussed

    MCRAGE: Synthetic Healthcare Data for Fairness

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    In the field of healthcare, electronic health records (EHR) serve as crucial training data for developing machine learning models for diagnosis, treatment, and the management of healthcare resources. However, medical datasets are often imbalanced in terms of sensitive attributes such as race/ethnicity, gender, and age. Machine learning models trained on class-imbalanced EHR datasets perform significantly worse in deployment for individuals of the minority classes compared to samples from majority classes, which may lead to inequitable healthcare outcomes for minority groups. To address this challenge, we propose Minority Class Rebalancing through Augmentation by Generative modeling (MCRAGE), a novel approach to augment imbalanced datasets using samples generated by a deep generative model. The MCRAGE process involves training a Conditional Denoising Diffusion Probabilistic Model (CDDPM) capable of generating high-quality synthetic EHR samples from underrepresented classes. We use this synthetic data to augment the existing imbalanced dataset, thereby achieving a more balanced distribution across all classes, which can be used to train an unbiased machine learning model. We measure the performance of MCRAGE versus alternative approaches using Accuracy, F1 score and AUROC. We provide theoretical justification for our method in terms of recent convergence results for DDPMs with minimal assumptions.Comment: Keywords: synthetic electronic health records, conditional denoising diffusion probabilistic model, healthcare AI, tabular data, fairness, synthetic data. This paper is the result of work completed at the 2023 Emory University Department of Mathematics REU/RET program under the direction of Project Advisor Dr. Xi Yuanzhe. This work is sponsored by NSF DMS 205101

    Cause Event Representations for Happiness and Surprise

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    PACLIC 23 / City University of Hong Kong / 3-5 December 200

    Are Emotions Enumerable or Decomposable? And its Implications for Emotion Processing

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    PACLIC 23 / City University of Hong Kong / 3-5 December 200

    An Integrated Approach to Heterogeneous Data for Information Extraction

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    PACLIC 23 / City University of Hong Kong / 3-5 December 200
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