Biochemical and Genetic Studies of Beclin 1 Function in Autophagy

Beclin 1 is a mammalian autophagy protein and has important functions in development, tumor suppression and neurodegeneration. Beclin 1 exists in a protein complex with Vps34, which is a class III phosphatidylinositol (PtdIns) 3-kinase and mediates multiple vesicle trafficking pathways including autophagy and endocytosis. However the precise role of Beclin 1 in autophagy regulation is not well understood and information is lacking regarding the function of Beclin 1 in neuronal development and degeneration. In a study that combines mouse genetics and biochemistry, three novel Beclin 1 interaction proteins Atg14L (yeast Atg14-like), Rubicon (RUN domain and cysteine-rich domain containing, Beclin 1-interacting protein) and Nrbf2 were identified from mouse tissues. Gel filtration and co-immunoprecipitation show that these proteins co-exist in one large in vivo protein complex, from which multiple sub-complexes may be generated. Functional assays reveal that Atg14L positively regulates Vps34/PtdIns3K kinase activity and autophagy while Rubicon shows negative regulatory effects. Moreover, Beclin 1 and Atg14L synergistically promote autophagosome biogenesis while over-expression of Rubicon causes formation of aberrant late endosomes/early lysosomes and blocks autophagosome maturation. Therefore Atg14L and Rubicon regulate autophagy in opposite directions and at different steps, possibly through forming distinctive complexes with Beclin 1 and mediating Vps34/PtdIns3K kinase activity. Meanwhile, to study the function of Beclin 1 in neuronal development and degeneration, targeted deletion of beclin 1 was performed in pyramidal cells of the hippocampus and the cerebral cortex and in cerebellar Purkinje cells. Consequently, the deletion leads to rapid and severe degeneration in these cells. In degenerating pyramidal cells, there is intracellular protein accumulation that may have resulted from impaired autophagy, and activation of apoptotic pathway is also observed. In Purkinje cells, electron microscopy studies show a large number of aberrant electron dense structures and they are closely associated with intracellular membranes. Meanwhile, immuno-staining shows that deletion of beclin 1 induces localization change of PtdIns(3)P, the product of Vps34/PtdIns3K. Therefore it is suggested that Beclin 1 is critical for normal neuronal development and that its deletion not only results in impaired autophagy but also may induce abnormal membrane and vesicle trafficking, possibly due to disrupted regulation of Vps34/PtdIns3K

On Primordial Perturbations of Test Scalar Fields

The primordial perturbations of test scalar fields not affecting the evolution of background may be very interesting since they can be transferred to the curvature perturbations by some mechanisms, and thus under certain condition can be responsible for the structure formation of observable universe. In this brief report we study the primordial perturbations of test scalar fields in various (super)accelerated expanding backgrounds.Comment: 4 pages, no figures, clarifications and refs. added, typos corrected, to publish in PR

Cavity-based architecture to preserve quantum coherence and entanglement

Quantum technology relies on the utilization of resources, like quantum coherence and entanglement, which allow quantum information and computation processing. This achievement is however jeopardized by the detrimental effects of the environment surrounding any quantum system, so that finding strategies to protect quantum resources is essential. Non-Markovian and structured environments are useful tools to this aim. Here we show how a simple environmental architecture made of two coupled lossy cavities enables a switch between Markovian and non-Markovian regimes for the dynamics of a qubit embedded in one of the cavity. Furthermore, qubit coherence can be indefinitely preserved if the cavity without qubit is perfect. We then focus on entanglement control of two independent qubits locally subject to such an engineered environment and discuss its feasibility in the framework of circuit quantum electrodynamics. With up-to-date experimental parameters, we show that our architecture allows entanglement lifetimes orders of magnitude longer than the spontaneous lifetime without local cavity couplings. This cavity-based architecture is straightforwardly extendable to many qubits for scalability.Comment: 12 pages, 9 figures, 1 table. To appear on Nature Scientific Report

Multi-stage Suture Detection for Robot Assisted Anastomosis based on Deep Learning

In robotic surgery, task automation and learning from demonstration combined with human supervision is an emerging trend for many new surgical robot platforms. One such task is automated anastomosis, which requires bimanual needle handling and suture detection. Due to the complexity of the surgical environment and varying patient anatomies, reliable suture detection is difficult, which is further complicated by occlusion and thread topologies. In this paper, we propose a multi-stage framework for suture thread detection based on deep learning. Fully convolutional neural networks are used to obtain the initial detection and the overlapping status of suture thread, which are later fused with the original image to learn a gradient road map of the thread. Based on the gradient road map, multiple segments of the thread are extracted and linked to form the whole thread using a curvilinear structure detector. Experiments on two different types of sutures demonstrate the accuracy of the proposed framework.Comment: Submitted to ICRA 201

Harnessing non-Markovian quantum memory by environmental coupling

Controlling the non-Markovian dynamics of open quantum systems is essential in quantum information technology since it plays a crucial role in preserving quantum memory. Albeit in many realistic scenarios the quantum system can simultaneously interact with composite environments, this condition remains little understood, particularly regarding the effect of the coupling between environmental parts. We analyze the non-Markovian behavior of a qubit interacting at the same time with two coupled single-mode cavities which in turn dissipate into memoryless or memory-keeping reservoirs. We show that increasing the control parameter, that is the two-mode coupling, allows for triggering and enhancing a non-Markovian dynamics for the qubit starting from a Markovian one in absence of coupling. Surprisingly, if the qubit dynamics is non-Markovian for zero control parameter, increasing the latter enables multiple transitions from non-Markovian to Markovian regimes. These results hold independently on the nature of the reservoirs. This work highlights that suitably engineering the coupling between parts of a compound environment can efficiently harness the quantum memory, stored in a qubit, based on non-Markovianity.Comment: 8 pages, 5 figures. To appear in Phys. Rev.

Universal adversarial perturbations for multiple classification tasks with quantum classifiers

Quantum adversarial machine learning is an emerging field that studies the vulnerability of quantum learning systems against adversarial perturbations and develops possible defense strategies. Quantum universal adversarial perturbations are small perturbations, which can make different input samples into adversarial examples that may deceive a given quantum classifier. This is a field that was rarely looked into but worthwhile investigating because universal perturbations might simplify malicious attacks to a large extent, causing unexpected devastation to quantum machine learning models. In this paper, we take a step forward and explore the quantum universal perturbations in the context of heterogeneous classification tasks. In particular, we find that quantum classifiers that achieve almost state-of-the-art accuracy on two different classification tasks can be both conclusively deceived by one carefully-crafted universal perturbation. This result is explicitly demonstrated with well-designed quantum continual learning models with elastic weight consolidation method to avoid catastrophic forgetting, as well as real-life heterogeneous datasets from hand-written digits and medical MRI images. Our results provide a simple and efficient way to generate universal perturbations on heterogeneous classification tasks and thus would provide valuable guidance for future quantum learning technologies

Quantifying the Impacts of the Recent Economic Crisis on a Local Tourism Industry and Economy system

The purpose of this study is to explore the accuracy issue of the Input-Output model in quantifying the impacts of the 2007 economic crisis on a local tourism industry and economy. Though the model has been extensively used in the tourism impact analysis, its estimation accuracy is rarely verified empirically. The Metro Orlando area in Florida is investigated as a case study, and the visitor expenditure change between 2007 and 2008 is taken as the direct shock. The total impacts are assessed in terms of output and employment, and are compared with the actual data. This study finds that there are surprisingly large discrepancies among the estimated and actual results, and the Input-Output model tends to overestimate the negative impacts. By investigating the local economic activities during the study period, this study made some explorative efforts in explaining such discrepancies. Theoretical and practical implications are then suggeste

Developing a Parasocial Relationship with Hotel Brands on Facebook: Will Millennials Differ from GenXers?

Facebook, particularly its brand page, is becoming one of the most powerful tool for relationship building and customer engagement for hospitality companies. As the social media marketing practices evolve in the hospitality industry, the industry starts to realize the importance of customer participation behaviors based on relationship quality rather than quantity of interactions and the rising significance of the Millennials generation. To respond to this trend, this study pursues an empirical investigation of the antecedents for consumer-hotel brand relationship on Facebook, and the potential differences between Millennials and non-Millennials, particularly the GenXers. It also examines the potential varying relational consequences on consumers\u27 online participation behaviors and brand loyalty between these two groups. More specifically, this study positions Facebook as an innovative communication medium, and applies the “parasocial relationship” framework in mediated communication literature as an overarching theoretical guide. Five social-media related factors are included to explain the psychological mechanisms of consumer’s parasocial relationship with brands: utilitarian benefits, hedonic benefits, perceived self-disclosure, perceived interactivity, and perceived information overload. This study also investigates the effects of parasocial relationship on Facebook users’ online participation behaviors with brands and their offline brand loyalty. The hypothesized model is tested with multi-group SEM modelling. Practical and theoretical implications are also discussed in the study