Quintic threefolds and Fano elevenfolds

The derived category of coherent sheaves on a general quintic threefold is a central object in mirror symmetry. We show that it can be embedded into the derived category of a certain Fano elevenfold. Our proof also generates related examples in different dimensions.Comment: V1: 12 pages. V2: added reference to work of Iliev and Manivel. V3: persistent sign error corrected. Other minor changes following referee's suggestions. To appear in Crell

Arctic Cloud Radiative Forcing in Contemporary Atmospheric Reanalyses

Arctic clouds play an important role in modifying the surface energy balance. In the Arctic, clouds are thought to influence the underlying sea ice cover through changing downwelling longwave radiative fluxes to the surface and through the selective reflection of the shortwave flux in summer. Atmospheric reanalyses are generally thought to have a poor representation of cloud processes at high latitudes, although the representation of trends over the perennial Arctic sea ice pack is less well known. Here, atmospheric energy fluxes are examined at the top of the atmosphere from contemporary reanalyses in comparison to satellite measurements from the CERES-EBAF version 4.1 product. The principal reanalyses examined are the NASA MERRA-2, the ECMWF ERA5 and ERA-Interim, the JRA-55, and the regional Arctic System Reanalysis version 2. In agreement with previous observation-based studies, changes with time in the shortwave cloud radiative forcing in reanalyses are found to be negligible despite strong trends in the absorbed shortwave. Over the full satellite period, there is large disagreement in the seasonality of longwave cloud forcing trends. These trends are reduced during the CERES-EBAF observing period (2003-present). An examination of these trends with respect to sea ice cover changes in each of the reanalyses is conducted

Structure, placement and modelling

The nature of hierarchical design tools for VLSI implementation is explored in terms of the "Caltech Structured Design Philosophy" as interpreted by Rowson in his doctoral thesis [Rowson]. One obvious implication of this thesis is the desirability of tools for leaf and composition cell design. This thesis describes one such tool targeted at the composition cell design problem. It is intended to be used in the architectual phases of a design and allows structural (interface specification), physical (floor planing), and behavioral (simulation modelling) descriptions to be written down, integrated, and tested. One biproduct of this process is the generation of a comprehensive design document from which workbooks can be generated automatically. The later sections describe a hierarchical simulator and how it fits into the step-wise refinement process of design. The most important considerations in the design of this simulator were ease of expression and the provision of enough generality to allow the specification of any VLSI structure. Simulation takes place in a time axis/delay environment and uses a system in which nodes may take one of four values or states. This allows a high level simulation in which physical devices are replaced by register transfer type operations. Data is altered and moved around using flow control mechanisms, logical and mathematical operations, and various means of specifying delay. Though not necessary or typical it is possible to model actual devices as ideal switches using these techniques. It is a multi-model simulation because simulation can occur at any level of design abstraction. Several examples are given including the modelling of the GR2 stack data microprocessor which was recently fabricated in NMOS

Status, Party and the American Negro

http://deepblue.lib.umich.edu/bitstream/2027.42/50810/1/25.pd

Parsimonious and efficient assessment of health-related quality of life in osteoarthritis research: validation of the Assessment of Quality of Life (AQoL) instrument

BACKGROUND: The Assessment of Quality of Life (AQoL) utility instrument was psychometrically developed for the general population. This study aimed to explore its potential as an osteoarthritis (OA) outcome measure. METHODS: WOMAC, Lequesne index, SF-36, Visual analogue scales and the AQoL were administered to 222 people with OA. The ability of each questionnaire to detect differences between groups was based on (i) self-rated health (SRH) and, (ii) differences between people on an orthopedic waiting list (WL) vs people with OA in the community (C). Comparisons included effect size, relative efficiency and receiver operator characteristic curves. RESULTS: All instruments detected differences between groups; however no one instrument exhibited superior efficiency. The AQoL demonstrated strong psychometric properties. CONCLUSION: The AQoL has equivalent performance to comparator questionnaires commonly used in OA research and would be a useful adjunct to well-established disease specific scales. The AQoL has important advantages; brevity (12 items), facilitates comparisons between disease groups, and delivers a utility score that can be used in health economic evaluations

An integrative approach to engineering data and automatic project coordination

A new approach to integration of automation environments is necessary in order to overcome some fundamental limitations of current methods. The most common request for integration comes when an organization finds itself with many design systems and representations most of which cannot communicate directly. Solutions to this problem have required either a proliferation of translations between systems, or the provision of a central data base with which all applications must communicate. Another aspect of integration is the provision of mechanisms which keep track of the status of design. The working - release method along with version control techniques is well known but does not directly address the compatability issue and provides only a partial solution to status keeping. Another approach to integration is to exploit the underlying structure of an engineering project. This method can result in improvement in both realms of integration described above. The potential results of such an approach include the following, each of which is described in this paper. Firstly, this approach provides a new mechanism ~or providing design team independence and a better definition of design team responsibility. Secondly, the concept of inter-verification is introduced as a way of providing a continuum of representations which can be kept consistent through the project structure. Thirdly, automatic conflict detection and coordination mechanisms can be implemented, eliminating much of the delay usually associated with design changes. The final portion of this paper indicates some of the other areas influenced by the use of project structure in the computational environment. This includes, subdivision of verification processes, documentation systems, external object integration and automatic design systems

Model simulation of impacts of transient surface wetness on summer rainfall in the US Midwest during drought and flood years

Surface moisture availability has been hypothesized by various investigators to provide additional negative (positive) feedback on rainfall during summer drought (flood) conditions in the Midwest. In this note, we report on a preliminary numerical modeling effort in which the impact of transient changes in surface wetness an summer rainfall events in the midwestern United States during two recent drought and flood years is assessed. It was found that during the drought of 1988, hypothetical temporary extreme moistening of the surface resulted in large relative increases in simulated rainfall, often by as much as a factor of 2. However, from an agricultural perspective these large relative changes in rainfall might not necessarily have translated into meaningful increases since the original absolute rainfall amounts were quite small. In the flood year of 1993, an assumed transient drying of the surface resulted in relative decreases in simulated rainfall by as much as 30%–40%. This relative decrease in rainfall did, however, translate into a discernible drop in the absolute rainfall

Influences of Model Parameterization Schemes on the Response of Rainfall to Soil Moisture in the Central United States

The sensitivities of soil moisture impacts on summer rainfall in the central United States to different commonly used cumulus parameterization and surface flux schemes are examined using the PSU-NCAR MMS under different atmospheric and soil moisture conditions. The cumulus convection schemes used are the Kuo and Grell parameterization schemes, while the surface-moisture flux schemes used are the aerodynamic formulation and the Simple Biosphere (SiB) Model. Results show that a transient increase in soil moisture enhanced total rainfall over the simulation domain. The increase in soil moisture enhanced local rainfall when the lower atmosphere was thermally unstable and relatively dry, but it decreased the rainfall when the atmosphere was humid and lacked sufficient thermal forcing to initiate deep convection. Soil moisture impacts were noticeably stronger for the Kuo scheme, which simulated lighter peak rainfall, than those for the Grell scheme, which simulated heavier peak rainfall. The greater sensitivity to soil moisture exhibited by the Kuo scheme than either the Grell or explicit scheme implies that it exaggerated the role of soil moisture. This difference was related to how each scheme partitioned rainfall between convective and stable forms, and possibly to each scheme\u27s closure assumptions. Adding details to the surface-moisture flux schemes had a secondary influence on soil moisture impacts on rainfall within a 24-h period

The dynamical zeta function for commuting automorphisms of zero-dimensional groups

For a Zd-action α by commuting homeomorphisms of a compact metric space, Lind introduced a dynamical zeta function that generalizes the dynamical zeta function of a single transformation. In this article, we investigate this function when α is generated by continuous automorphisms of a compact abelian zero-dimensional group. We address Lind’s conjecture concerning the existence of a natural boundary for the zeta function and prove this for two significant classes of actions, including both zero entropy and positive entropy examples. The finer structure of the periodic point counting function is also examined and, in the zero entropy case, we show how this may be severely restricted for subgroups of prime index in Zd. We also consider a related open problem concerning the appearance of a natural boundary for the dynamical zeta function of a single automorphism, giving further weight to the Pólya–Carlson dichotomy proposed by Bell and the authors