1,333 research outputs found
Surveillance Lessons from First-wave Pandemic (H1N1) 2009, Northern California, USA
After the appearance of pandemic (H1N1) 2009 in April 2009, influenza activity was monitored within the Kaiser Permanente Northern California division by using laboratory, pharmacy, telephone calls, and utilization (services patients received) data. A combination of testing and utilization data showed a pattern of disease activity, but this pattern may have been affected by public perception of the epidemic
Gaining access to customers' resources through relationship bonds
In order to get good access to a buyer's resources, which contribute to relationship value creation, a seller needs to put resources into the relationship, and the bonds between the buyer and seller need to be strong. This paper reports on a preliminary study that assesses how the expected level of input of resources by sellers into business-to-business buyer-seller relationships and the strength of relationship bonds affects sellers' access to their buyers' resources. The paper's focus is on access to the buyer's less imitable intangible resources, such as downstream market knowledge, which provide long-term competitive advantage. Based on extant literature and interviews with managers, the study proposes a model which includes relationship bonds as a mediator of the effect of seller's resource input on their access to their buyers' resources. The study applies structural equation modeling to survey data to test this model and finds support for it
S=1 kagom\'e Ising model with triquadratic interactions, single-ion anisotropy and magnetic field: exact phase diagrams
We consider a S=1 kagom\'e Ising model with triquadratic interactions around
each triangular face of the kagom\'e lattice, single-ion anisotropy and an
applied magnetic field. A mapping establishes an equivalence between the
magnetic canonical partition function of the model and the grand canonical
partition function of a kagom\'e lattice-gas model with localized
three-particle interactions. Since exact phase diagrams are known for
condensation in the one-parameter lattice-gas model, the mapping directly
provides the corresponding exact phase diagrams of the three-parameter S=1
Ising model. As anisotropy competes with interactions, results include the
appearance of confluent singularities effecting changes in the topology of the
phase diagrams, phase boundary curves (magnetic field vs temperature) with
purely positive or negative slopes as well as intermediate cases showing
nonmonotonicity, and coexistence curves (magnetization vs temperature) with
varying shapes and orientations, in some instances entrapping a homogeneous
phase.Comment: 14 pages plus 11 figures; to be published in Physica
Possible chiral phase transition in two-dimensional solid He
We study a spin system with two- and four-spin exchange interactions on the
triangular lattice, which is a possible model for the nuclear magnetism of
solid He layers. It is found that a novel spin structure with scalar chiral
order appears if the four-spin interaction is dominant. Ground-state properties
are studied using the spin-wave approximation. A phase transition concerning
the scalar chirality occurs at a finite temperature, even though the
dimensionality of the system is two and the interaction has isotropic spin
symmetry. Critical properties of this transition are studied with Monte Carlo
simulations in the classical limit.Comment: 4 pages, Revtex, 4 figures, to appear in Phys.Rev.Let
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FABRICATE AND TEST AN ADVANCED NON-POLLUTING TURBINE DRIVE GAS GENERATOR
In September 2000 the Department of Energy's National Energy Technology Laboratory (DOE/NETL) contracted with Clean Energy Systems, Inc. (CES) of Sacramento, California to design, fabricate, and test a 20 MW{sub t} (10 MW{sub e}) gas generator. Program goals were to demonstrate a non-polluting gas generator at temperatures up to 3000 F at 1500 psi, and to demonstrate resulting drive gas composition, comprising steam and carbon dioxide substantially free of pollutants. Following hardware design and fabrication, testing, originally planned to begin in the summer of 2001, was delayed by unavailability of the contracted test facility. CES designed, fabricated, and tested the proposed gas generator as originally agreed. The CES process for producing near-zero-emissions power from fossil fuels is based on the near-stoichiometric combustion of a clean gaseous fuel with oxygen in the presence of recycled water, to produce a high-temperature, high-pressure turbine drive fluid comprising steam and carbon dioxide. Tests demonstrated igniter operation over the prescribed ranges of pressure and mixture ratios. Ignition was repeatable and reliable through more than 100 ignitions. Injector design ''A'' was operated successfully at both low power ({approx}20% of rated power) and at rated power ({approx}20 MW{sub t}) in more than 95 tests. The uncooled gas generator configuration (no diluent injectors or cooldown chambers installed) produced drive gases at temperatures approaching 3000 F and at pressures greater than 1550 psia. The fully cooled gas generator configuration, with cooldown chambers and injector ''A'', operated consistently at pressures from 1100 to 1540 psia and produced high pressure, steam-rich turbine drive gases at temperatures ranging from {approx}3000 to as low as 600 F. This report includes description of the intended next steps in the gas generator technology demonstration and traces the anticipated pathway to commercialization for the gas generator technology developed in this program
Patterns of pneumococcal vaccination and revaccination in elderly and non-elderly adults: a Vaccine Safety Datalink study
<p>Abstract</p> <p>Background</p> <p>Pneumococcal polysaccharide vaccine (PPV) is recommended for all adults 65 years of age and older and for younger adults with high-risk conditions. While data from national surveys provide information on the proportion of adults 65 years of age and older reporting ever receipt of PPV they do not collect more detailed information, such as age at vaccination or the total number of vaccinations received. In addition, there is relatively little information available on PPV coverage in younger adults with chronic conditions. To assess contemporary patterns of pneumococcal vaccination and revaccination of adults, we conducted a cross-sectional study of adults enrolled in medical care organizations (MCOs) participating in the Vaccine Safety Datalink project.</p> <p>Methods</p> <p>The study population included 1.5 million adults 25 years of age and older enrolled in the four participating MCOs on December 1, 2006. PPVs administered to members of the study population prior to that date were identified from computerized immunization registries maintained by the MCOs.</p> <p>Results</p> <p>Among the general population of adults 25 through 64 years of age, vaccine coverage increased from 2% in the 25–29 year old age-group to 26% in the 60–64 year old age-group. In all age-groups, coverage was substantially higher in persons defined as having a chronic high risk condition. This was particularly true for diabetes mellitus, with vaccine coverage of over 50% in the lower age-groups and 75% in those 60–64 years of age. Among adults 65 years of age and older, 82% had received at least one PPV and 18% had received two or more PPVs.</p> <p>Conclusion</p> <p>We found higher levels of PPV coverage among adults 65 years of age and older and among younger adults with diabetes mellitus than reported by national surveys and for those groups PPV coverage approached the <it>Healthy People 2010 </it>national objectives. These results suggest that achieving those objectives for PPV is possible and that high vaccination coverage may be facilitated by vaccine tracking and reminder systems.</p
Yang-Lee and Fisher Zeros of Multisite Interaction Ising Models on the Cayley-type Lattices
A general analytical formula for recurrence relations of multisite
interaction Ising models in an external magnetic field on the Cayley-type
lattices is derived. Using the theory of complex analytical dynamics on the
Riemann sphere, a numerical algorithm to obtain Yang-Lee and Fisher zeros of
the models is developed. It is shown that the sets of Yang-Lee and Fisher zeros
are almost always fractals, that could be associated with Mandelbrot-like sets
on the complex magnetic field and temperature planes respectively.Comment: 9 pages, 3 figures; with minor correction
Application of the small punch test to determine the fatigue properties of additive manufactured aerospace alloys
Additive layer manufacturing (ALM) processes are becoming increasingly prevalent in the aerospace industry as design engineers look to profit from the numerous advantages that these advanced techniques can offer. However, given the safety critical nature and arduous operating conditions to which these components will be exposed to whilst in service, it is essential that the mechanical properties of such structures are fully understood. Transient microstructures are a typical characteristic of ALM components and resulting from the thermal cycles that occur during the build operation. Those microstructures make any mechanical assessment an involved procedure when assessing the process variables for any given parameter set. A useful mechanical test technique is small-scale testing, in particular, the small punch (SP) test. SP testing is capable of localised sampling of a larger scale component and presents an attractive option to mechanically assess complex parts with representative geometries, that would not be possible using more conventional uniaxial test approaches. This paper will present the recent development of a small-scale testing methodology capable of inducing fatigue damage and a series of novel tests performed on different variants of Ti-6Al-4V
Lessons Learned From Efforts To Restore Oyster Populations In Maryland And Virginia, 1990 To 2007
A century-long decline of the fishery for the Eastern oyster Crassostrea virginica (Gmelin, 1791) in Maryland and Virginia stimulated numerous efforts by federal, state, and nongovernmental agencies to restore oyster populations, with limited success. To learn from recent efforts, we analyzed records of restoration and monitoring activities undertaken between 1990 and 2007 by 12 such agencies. Of the 1,037 oyster bars (reefs, beds, or grounds) for which we obtained data, 43% experienced both restoration and monitoring, with the remaining experiencing either restoration or monitoring only. Restoration activities involved adding substrate (shell), transplanting hatchery or wild seed (juvenile oysters), bar cleaning, and bagless dredging. Of these, substrate addition and transplanting seed were common actions, with bar cleaning and bagless dredging relatively uncommon. Limited monitoring efforts, a lack of replicated postrestoration sampling, and the effects of harvest on some restored bars hinders evaluations of the effectiveness of restoration activities. Future restoration activities should have clearly articulated objectives and be coordinated among agencies and across bars, which should also be off limits to fishing. To evaluate restoration efforts, experimental designs should include replication, quantitative sampling, and robust sample sizes, supplemented by pre- and postrestoration monitoring
Reconciling founder variant multiplicity of HIV-1 infection with the rate of CD4+ decline
HIV-1 transmission precipitates a stringent genetic bottleneck, with 75% of new infections initiated by a single genetic variant. Where multiple variants initiate infection, recipient set point viral load (SpVL) and the rate of CD4+ 4 T cell decline may be elevated, but these findings remain inconsistent. Here, we summarised the evidence for this phenomenon, then tested whether previous studies possessed sufficient statistical power to reliably identify a true effect of multiple variant infection associating with higher SpVL. Next, we combined models of HIV-1 transmission, heritability and disease progression to understand whether available data suggest a faster CD4+ T cell decline would be expected to associate with multiple variant infection, without an explicit dependency between the two. We found that most studies had insufficient power to identify a true significant difference, prompting an explanation for previous inconsistencies. Next, our model framework revealed we would not expect to observe a positive association between multiple variant infections and faster CD4+ T cell decline, in the absence of an explicit dependency. Consequently, while empirical evidence may be consistent with a positive association between multiple variant infection and faster CD4+ T cell decline, further investigation is required to establish a causal basis for this association
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