Some infections may be sustained in the human population by persistent transmission among patients in healthcare facilities, including patients colonized with multi-drug-resistant organisms posing a major health threat. A nuanced understanding of facility characteristics that contribute to crossing a threshold for self-sustaining outbreak potential may be crucial to designing efficient interventions for lowering regional disease burden and preventing high-risk infections. Using a mathematical model, we define the facility basic reproduction number R0, where a single facility can sustain an outbreak without ongoing importation under the threshold condition R0 > 1. We define R0 for a general model with heterogeneous patient susceptibility and transmissibility and with generic length-of-stay assumptions, and we provide a software package for numerical calculation of user-defined examples. We estimate R0 using published data for carbapenemase-producing Enterobacteriaceae (CPE) in long-term acute-care hospitals (LTACHs) and the effects of interventions on R0, including surveillance, pathogen reduction treatments, and length-of-stay reduction. In a simple model, R0 is directly proportional to the sum of the mean and variance-to-mean ratio of the length-of-stay distribution. In intervention models, R0 depends on the moment-generating function of the length-of-stay distribution. From the CPE data, we estimated R0 = 1.24 (95% CI: 1.04, 1.45) prior to intervention. Weekly surveillance with 50% transmission reduction of detected patients alone could have reduced R0 to 0.85 (0.72, 0.98), with additional reduction if detected patients could be decolonized. Reducing the mean length of stay does not necessarily reduce R0 if the variance-to-mean ratio is not also reduced. We conclude that R0 > 1 conditions plausibly exist in LTACHs, where CPE outbreaks could be sustained by patients who acquire colonization and subsequently transmit to other patients during the same hospital stay. Our findings illuminate epidemiological mechanisms producing those conditions and their relationship to interventions that could efficiently improve population health.

Petascale simulations compute at resolutions ranging into billions of cells and write terabytes of data for visualization and analysis. Interactive visualization of this time series is a desired step before starting a new run. The I/O subsystem and associated network often are a significant impediment to interactive visualization of time-varying data, as they are not configured or provisioned to provide necessary I/O read rates. In this paper, we propose a new I/O library for visualization applications: VisIO. Visualization applications commonly use N-to-N reads within their parallel enabled readers which provides an incentive for a shared-nothing approach to I/O, similar to other data-intensive approaches such as Hadoop. However, unlike other data-intensive applications, visualization requires: (1) interactive performance for large data volumes, (2) compatibility with MPI and POSIX file system semantics for compatibility with existing infrastructure, and (3) use of existing file formats and their stipulated data partitioning rules. VisIO, provides a mechanism for using a non-POSIX distributed file system to provide linear scaling of I/O bandwidth. In addition, we introduce a novel scheduling algorithm that helps to co-locate visualization processes on nodes with the requested data. Testing using VisIO integrated into Para View was conducted using the Hadoop Distributed File System (HDFS) on TACC's Longhorn cluster. A representative dataset, VPIC, across 128 nodes showed a 64.4% read performance improvement compared to the provided Lustre installation. Also tested, was a dataset representing a global ocean salinity simulation that showed a 51.4% improvement in read performance over Lustre when using our VisIO system. VisIO, provides powerful high-performance I/O services to visualization applications, allowing for interactive performance with ultra-scale, time-series data.

We present a new approach to handling the demanding I/O workload incurred during checkpoint writes encountered in High Performance Computing. Prior efforts to improve performance have been bound by issues such as hard drive limitations, and the network. Our research surpasses this limitation by providing a method to: (1) write checkpoint data to a high-speed, non-volatile buffer, and (2) asynchronously write this data to permanent storage while resuming computation. This removes the hard drive from the critical data path because our I/O node based buffers isolate the compute nodes from the storage servers. This solution is feasible because of industry declines in cost for high-capacity, non-volatile storage technologies. Testing was conducted using a standardized HPC benchmark on a test bed cluster at Los Alamos National Laboratory. Results show a definitive speedup factor for select workloads over writing directly to a typical global parallel file system; the Panasas ActiveScale File System.

The proliferation of wireless-enabled portable computing devices has spurred a growing need for efficient and powerful networking protocols. The key challenge in the development of robust wireless networking protocols is an ability to conduct effective and efficient evaluation of the protocol in order to ensure its successful working in real-world settings. We proposed MiNT-2, a fresh re-design of the original MiNT framework developed at Stony Brook University. One of the fundamental requirements of MiNT-2 is to provide location awareness of all the nodes within the network. In this paper, we demonstrate the use of radio-frequency identification (RFID) technology in order to carry out localization of the mobile nodes within the system. We also demonstrate the application of the localization system of constructing different scenarios for wireless protocols evaluation.

With the emergence of data-intensive applications, recent years have seen a fast-growing volume of I/O traffic propagated through the local I/O interconnect bus. This raises up a question for storage servers on how to resolve such a potential bottleneck. In this paper, we present a hierarchical data cache architecture called DCA to effectively slash local interconnect traffic and thus boost the storage server performance. A popular iSCSI storage server architecture is chosen as an example. DCA is composed of a read cache in NIC called NIC cache and a read/write unified cache in host memory called helper cache. The NIC cache services most portions of read requests without fetching data via the PCI bus, while the helper cache (1) supplies some portions of read requests per partial NIC cache hit, (2) directs cache placement for NIC cache, and (3) absorbs most transient writes locally. We develop a novel state-locality-aware cache placement algorithm called SLAP to improve the NIC cache hit ratio for mixed read and write workloads. To demonstrate the effectiveness of DCA, we develop a DCA prototype system and evaluate it with an open source iSCSI implementation under representative storage server workloads. Experimental results showed that DCA can boost iSCSI storage server throughput by up to 121 percent and reduce the PCI traffic by up to 74 percent compared with an iSCSI target without DCA.

Software reconfigurability of air interfaces, the actual reconfiguration processes and the procurement of reconfiguration software are posing substantial threats to the system integrity of wireless communication system. These threats are investigated and reported, and mechanisms to ensure secure reconfiguration procedures are described. The security mechanisms documented form part of the MVCE reconfiguration management architecture (RMA).

Aspects of the security services in the CCITT draft 1988 X.400 recommendations for message handling systems are examined. A brief introduction to relevant cryptographic concepts is followed by a description of how some of the security services can be provided. Key management, as defined within the CCITT draft X.500 recommendations for directory services, and as referenced by the X.400 recommendations, is also described. A discussion of certain limitations of the current X.400 security architecture is included.>