1,273 research outputs found
Assessment of HY-8 and HEC-RAS Bridge Models for Large-Span Water-Encapsulating Structures
Current INDOT policy requires that culvert-like structures with spans greater than 20 ft be treated for purposes of hydraulic analysis as a bridge, and hence mandates the use of software such as HEC-RAS for predicting the headwater, rather than the culvert-specific software, HY-8. In this context, culvert-like structures are assumed to have a standard inlet geometry (e.g., such as those already modeled in HY-8) and a constant barrel geometry. The present study examines the technical basis of this policy, and whether the policy could be revised to allow the application of simpler culvert-hydraulics analysis and HY-8 to culvert-like structures with spans greater than 20 ft. Laboratory experiments were performed with model box culverts of span 1.5 ft and two streamwise lengths, 2.1 ft and 8 ft, and performance curves describing the variation of headwater with discharge were obtained. The effects of bed roughness, the presence or absence of a cover (if present, the rise was 0.5 ft), and a range of tailwater levels, were investigated. The laboratory observations were compared with predictions by HY-8 and HEC-RAS models, and the model performance assessed. In general, HY-8 predictions were found to be as good as, and in some cases superior to, the HEC-RAS predictions, for both long and short culvert-like structures. This was attributed to the empirical information in HY-8 being more tailored to the specific standardized geometry of culvert-like structures, and the automatic inclusion of roughness effects, whereas HEC-RAS, at least when used with default coefficients and settings, relied on generic coefficients and neglected roughness effects. It was therefore recommended that a change in INDOT policy allowing large-span culvert-like structures to be analyzed using conventional culvert hydraulics would be technically justified for problems where the structure could be considered in isolation and accurate input data are available
A Laboratory Study of Apron-Riprap Design for Small-Culvert Outlets
The present study investigated primarily the appropriate stone-sizing of on-grade riprap aprons, and more specifically whether the current INDOT design policy may be overly conservative especially within the context of smaller culverts. In the study, laboratory experiments were performed with two pipe diameters, D = 4.25 in (0.35 ft) and 5.75 in (0.48 ft), and four stone sizes, median diameters estimated to be d50 = 0.61 in, 1.22 in, 1.73 in, and 2.24 in, for a range of discharges and tailwater depths. Video records were made of the laboratory apron to detect stone-mobilization events, and stable and unstable cases were distinguished. Logistic regression was then applied to develop equations delineating the boundary between stable and unstable regions for different riprap size classes in terms of d50/D. These regression equations were then modified to ensure that they formed an ordered system in that each equation was more conservative than the next, to include a safety factor, and to set a minimum size for each size class consistent with the applicability of each equation. Procedures for applying the proposed equations are described.
Compared to the current INDOT design policy, the proposed approach typically predicts a smaller standard riprap class required for apron stability. In an application to a sample of actual culverts, the proposed approach, including the recommended safety factors, yielded a smaller required standard INDOT riprap class in 75% of cases, but, in a small number of cases with very low relative tailwater depths, did recommend a more conservative design. Of the other two main approaches to stone sizing for riprap aprons, the HEC-14 model was rather restricted in its range of application, but where applicable it was found to be somewhat more conservative in its stone-size recommendation, though in practice the recommended riprap class largely agreed with the proposed approach. The results of the other main approach, that due to Bohan (1970), were more erratic, with the maximum-tailwater equation being too lax and the minimum-tailwater equation being generally too stringent. Both the HEC-14 and the Bohan models tended to be less conservative than the proposed approach for larger values of d50/D.
A secondary aim of the study was an examination of the velocity field downstream of the outlet, and the possible implications for scour downstream of the apron. Point velocity measurements were obtained for four cases, all with the same 4.25-in diameter pipe, three of which involved the largest (d50 = 2.2 in) stone, and one over a smooth bed. In the three cases with a stone apron, the apron extended a distance of ≈9D downstream of the outlet. In all four cases, substantial velocities (maximum velociites greater than 70% of than the average outlet velocity) were observed beyond 4D (which is the minimum specified by INDOT design guidelines) and even beyond 8D (which is the largest apron length specified in HEC-14). A comparison between rough-bed and smooth-bed results indicated a measurable effect on maximum velocity due to the rough apron, but the reduction in maximum velocity is still likely insufficient to prevent scour downstream of the apron in most practical cases even if the apron extends to 9D
Impaired nuclear import and viral incorporation of Vpr derived from a HIV long-term non-progressor
We previously reported an epidemiologically linked HIV-1 infected patient cohort in which a long-term non-progressor (LTNP) infected two recipients who then exhibited normal disease progression. Expression of patient-derived vpr sequences from each of the three cohort members in mammalian cells tagged with GFP revealed a significant reduction in Vpr nuclear import and virion incorporation uniquely from the LTNP, whereas Vpr from the two progressing recipients displayed normal localisation and virion incorporation, implying a link between efficient Vpr nuclear import and HIV disease progression. Importantly, an F72L point mutation in the LTNP was identified for the first time as being uniquely responsible for decreased Vpr nuclear import
MaGIC: a machine learning tool set and web application for monoallelic gene inference from chromatin
Background: A large fraction of human and mouse autosomal genes are subject to random monoallelic expression (MAE), an epigenetic mechanism characterized by allele-specific gene expression that varies between clonal cell lineages. MAE is highly cell-type specific and mapping it in a large number of cell and tissue types can provide insight into its biological function. Its detection, however, remains challenging. Results: We previously reported that a sequence-independent chromatin signature identifies, with high sensitivity and specificity, genes subject to MAE in multiple tissue types using readily available ChIP-seq data. Here we present an implementation of this method as a user-friendly, open-source software pipeline for monoallelic gene inference from chromatin (MaGIC). The source code for the MaGIC pipeline and the Shiny app is available at https://github.com/gimelbrantlab/magic Conclusion: The pipeline can be used by researchers to map monoallelic expression in a variety of cell types using existing models and to train new models with additional sets of chromatin marks.National Institutes of Health (U.S.) (award U54 HG007963
Parameterized Verification of Safety Properties in Ad Hoc Network Protocols
We summarize the main results proved in recent work on the parameterized
verification of safety properties for ad hoc network protocols. We consider a
model in which the communication topology of a network is represented as a
graph. Nodes represent states of individual processes. Adjacent nodes represent
single-hop neighbors. Processes are finite state automata that communicate via
selective broadcast messages. Reception of a broadcast is restricted to
single-hop neighbors. For this model we consider a decision problem that can be
expressed as the verification of the existence of an initial topology in which
the execution of the protocol can lead to a configuration with at least one
node in a certain state. The decision problem is parametric both on the size
and on the form of the communication topology of the initial configurations. We
draw a complete picture of the decidability and complexity boundaries of this
problem according to various assumptions on the possible topologies.Comment: In Proceedings PACO 2011, arXiv:1108.145
Patient safety in dentistry: development of a candidate 'never event' list for primary care
Introduction The 'never event' concept is often used in secondary care and refers to an agreed list of patient safety incidents that 'should not happen if the necessary preventative measures are in place'. Such an intervention may raise awareness of patient safety issues and inform team learning and system improvements in primary care dentistry.
Objective To identify and develop a candidate never event list for primary care dentistry.
Methods A literature review, eight workshops with dental practitioners and a modified Delphi with 'expert' groups were used to identify and agree candidate never events.
Results Two-hundred and fifty dental practitioners suggested 507 never events, reduced to 27 distinct possibilities grouped across seven themes. Most frequently occurring themes were: 'checking medical history and prescribing' (119, 23.5%) and 'infection control and decontamination' (71, 14%). 'Experts' endorsed nine candidate never event statements with one graded as 'extreme risk' (failure to check past medical history) and four as 'high risk' (for example, extracting wrong tooth).
Conclusion Consensus on a preliminary list of never events was developed. This is the first known attempt to develop this approach and an important step in determining its value to patient safety. Further work is necessary to develop the utility of this method
Real-world utilization of the pill-in-the-pocket method for terminating episodes of atrial fibrillation: data from the multinational Antiarrhythmic Interventions for Managing Atrial Fibrillation (AIM-AF) survey
AIMS: Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice. Episodes may stop spontaneously (paroxysmal AF); may terminate only via intervention (persistent AF); or may persist indefinitely (permanent AF) (see European and American guidelines, referenced below, for more precise definitions). Recently, there has been renewed interest in an approach to terminate AF acutely referred to as 'pill-in-the-pocket' (PITP). The PITP is recognized in both the US and European guidelines as an effective option using an oral antiarrhythmic drug for acute conversion of acute/recent-onset AF. However, how PITP is currently used has not been systematically evaluated. METHODS AND RESULTS: The recently published Antiarrhythmic Interventions for Managing Atrial Fibrillation (AIM-AF) survey included questions regarding current PITP usage, stratified by US vs. European countries surveyed, by representative countries within Europe, and by cardiologists vs. electrophysiologists. This manuscript presents the data from this planned sub-study. Our survey revealed that clinicians in both the USA and Europe consider PITP in about a quarter of their patients, mostly for recent-onset AF with minimal or no structural heart disease (guideline appropriate). However, significant deviations exist. See the Graphical abstract for a summary of the data. CONCLUSION: Our findings highlight the frequent use of PITP and the need for further physician education about appropriate and optimal use of this strategy
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