5,094 research outputs found

    Practical quantum key distribution over a 48-km optical fiber network

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    The secure distribution of the secret random bit sequences known as "key" material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is a new technique for secure key distribution with single-photon transmissions: Heisenberg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non-orthogonal photon states to generate shared key material over multi-kilometer optical fiber paths and over line-of-sight links. In both cases, key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. Here we report the most recent results of our optical fiber experiment in which we have performed quantum key distribution over a 48-km optical fiber network at Los Alamos using photon interference states with the B92 and BB84 quantum key distribution protocols.Comment: 13 pages, 7 figures, .pdf format submitted to Journal of Modern Optic

    Manacled to Identity: Cosmopolitanism, Class, and ‘The Culture Concept’ in Stephen Crane

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    This article begins with a close reading of Stephen Crane’s short story ‘Manacled’ from 1900, which situates this rarely considered short work within the context of contemporary debates about realism. I then proceed to argue that many of the debates raised by the tale have an afterlife in our own era of American literary studies, which has frequently focused on questions of ‘identity’ and ‘culture’ in its reading of realism and naturalism to the exclusion of the importance of cosmopolitan discourses of diffusion and exchange across national borders. I then offer a brief reading of Crane’s novel George’s Mother, which follows Walter Benn Michaels in suggesting that the recent critical attention paid to particularities of cultural difference in American studies have come to conflate ideas of class and social position with ideas of culture in ways that have ultimately obscured the presence of genuine historical inequalities in US society. In order to challenge this critical commonplace, I situate Crane’s work within a history of transatlantic cosmopolitanism associated with the ideas of Franz Boas and Matthew Arnold to demonstrate the ways in which Crane’s narratives sought out an experience of the universal within their treatments of the particular

    Insight Into the Molecular Mechanisms for Microcystin Biodegradation in Lake Erie and Lake Taihu

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    Microcystins are potent hepatotoxins that are frequently detected in fresh water lakes plagued by toxic cyanobacteria. Microbial biodegradation has been referred to as the most important avenue for removal of microcystin from aquatic environments. The biochemical pathway most commonly associated with the degradation of microcystin is encoded by the mlrABCD (mlr) cassette. The ecological significance of this pathway remains unclear as no studies have examined the expression of these genes in natural environments. Six metatranscriptomes were generated from microcystin-producing Microcystis blooms and analyzed to assess the activity of this pathway in environmental samples. Seventy-eight samples were collected from Lake Erie, United States/Canada and Lake Tai (Taihu), China, and screened for the presence of mlr gene transcripts. Read mapping to the mlrcassette indicated transcripts for these genes were absent, with only 77 of the collective 3.7 billion reads mapping to any part of the mlr cassette. Analysis of the assembled metatranscriptomes supported this, with only distantly related sequences identified as mlrABC-like. These observations were made despite the presence of microcystin and over 500,000 reads mapping to the mcy cassette for microcystin production. Glutathione S-transferases and alkaline proteases have been previously hypothesized to be alternative pathways for microcystin biodegradation, and expression of these genes was detected across space and time in both lakes. While the activity of these alternative pathways needs to be experimentally confirmed, they may be individually or collectively more important than mlr genes in the natural environment. Importantly, the lack of mlr expression could indicate microcystin biodegradation was not occurring in the analyzed samples. This study raises interesting questions about the ubiquity, specificity and locality of microcystin biodegradation, and highlights the need for the characterization of relevant mechanisms in natural communities to understand the fate of microcystin in the environment and risk to public health

    Association between HbA1c and the development of cystic fibrosis‐related diabetes

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    Aims To examine HbA1c as a predictor of risk for future development of cystic fibrosis‐related diabetes and to assess the association with the development of retinopathy in people with cystic fibrosis‐related diabetes. Methods A 7‐year retrospective longitudinal study was conducted in 50 adults with cystic fibrosis, comparing oral glucose tolerance test results with HbA1c values in predicting the development of cystic fibrosis‐related diabetes. Retinal screening data were also compared with HbA1c measurements to assess microvascular outcome. Results An HbA1c value ≥37 mmol/mol (5.5%; hazard ratio 3.49, CI 1.5–8.1) was significantly associated with the development of dysglycaemia, as defined by the oral glucose tolerance test over a 7‐year period. Severity of diabetic retinopathy was associated with a higher HbA1c and longer duration of cystic fibrosis‐related diabetes. Conclusion There is a link between HbA1c level and the future development of dysglycaemia in cystic fibrosis based on oral glucose tolerance test, as well as microvascular outcomes. Although current guidance does not advocate the use of HbA1c as a diagnostic tool in cystic fibrosis‐related diabetes, it may be of clinical use in determining individuals at risk of future development of cystic fibrosis‐related diabetes

    Practical quantum cryptography for secure free-space communications

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    Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics and information-theoretically secure post-processing methods. An adversary can neither successfully tap the quantum transmissions, nor evade detection, owing to Heisenberg's uncertainty principle. In this paper we describe the theory of quantum cryptography, and the most recent results from our experimental free-space system with which we have demonstrated for the first time the feasibility of quantum key generation over a point-to-point outdoor atmospheric path in daylight. We achieved a transmission distance of 0.5 km, which was limited only by the length of the test range. Our results provide strong evidence that cryptographic key material could be generated on demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on orbit. We present a feasibility analysis of surface-to-satellite quantum key generation.Comment: 12 pages, 4 figure

    Adapting an intervention to address barriers to pain management in hospice: Formative research to inform EMPOWER-D for dementia caregivers

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    BACKGROUND: Nearly half of more than 1.7 million older Americans who receive hospice care each year have a primary or comorbid diagnosis of dementia. Pain is often undertreated in this patient population owing to myriad factors, including unmet informational needs among family caregivers. OBJECTIVE: We sought to inform the adaptation of a pain education intervention for hospice family caregivers to the context of dementia by eliciting feedback on the educational content covered in adapted intervention materials. DESIGN: We conducted a multimethod, formative research study to inform the adaptation of an existing, evidence-based intervention. SETTING/SUBJECTS: The study included a purposively recruited sample ( MEASUREMENTS: Participants quantitatively rated the importance of each of the eight pain concerns presented in the adapted intervention materials (1 = not important to 3 = very important) and provided qualitative feedback via Zoom interview on the acceptability, clinical accuracy, and potential benefits of the adapted content. We analyzed quantitative data via descriptive statistics and qualitative data via content analysis. RESULTS: Participants rated the adapted educational content as highly important (range CONCLUSIONS: Findings support the continued development and testing of the adapted intervention
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