Simulating spatial and temporal variation of corn canopy temperature during an irrigation cycle

The canopy air temperature difference (delta T) which provides an index for scheduling irrigation was examined. The Monteith transpiration equation was combined with both uptake from a single layered root zone and change in internal storage of the plant and the continuity equation for water flux in the soil plant atmosphere system was solved. The model indicates that both daily total transpiration and soil induced depression of plant water potential may be inferred from mid-day delta T. It is suggested that for the soil plant weather data used in the simulation, either a mid day spatial variability of about 0.8K in canopy temperatures or a field averaged delta T of 2 to 4K may be a suitable criterion for irrigation scheduling

A Mathematical Theory of Stochastic Microlensing II. Random Images, Shear, and the Kac-Rice Formula

Continuing our development of a mathematical theory of stochastic microlensing, we study the random shear and expected number of random lensed images of different types. In particular, we characterize the first three leading terms in the asymptotic expression of the joint probability density function (p.d.f.) of the random shear tensor at a general point in the lens plane due to point masses in the limit of an infinite number of stars. Up to this order, the p.d.f. depends on the magnitude of the shear tensor, the optical depth, and the mean number of stars through a combination of radial position and the stars' masses. As a consequence, the p.d.f.s of the shear components are seen to converge, in the limit of an infinite number of stars, to shifted Cauchy distributions, which shows that the shear components have heavy tails in that limit. The asymptotic p.d.f. of the shear magnitude in the limit of an infinite number of stars is also presented. Extending to general random distributions of the lenses, we employ the Kac-Rice formula and Morse theory to deduce general formulas for the expected total number of images and the expected number of saddle images. We further generalize these results by considering random sources defined on a countable compact covering of the light source plane. This is done to introduce the notion of {\it global} expected number of positive parity images due to a general lensing map. Applying the result to microlensing, we calculate the asymptotic global expected number of minimum images in the limit of an infinite number of stars, where the stars are uniformly distributed. This global expectation is bounded, while the global expected number of images and the global expected number of saddle images diverge as the order of the number of stars.Comment: To appear in JM

The Arabidopsis mutant feronia disrupts the female gametophytic control of pollen tube reception

Reproduction in angiosperms depends on communication processes of the male gametophyte (pollen) with the female floral organs (pistil, transmitting tissue) and the female gametophyte (embryo sac). Pollen-pistil interactions control pollen hydration, germination and growth through the stylar tissue. The female gametophyte is involved in guiding the growing pollen tube towards the micropyle and embryo sac. One of the two synergids flanking the egg cell starts to degenerate and becomes receptive for pollen tube entry. Pollen tube growth arrests and the tip of the pollen tube ruptures to release the sperm cells. Failures in the mutual interaction between the synergid and the pollen tube necessarily impair fertility. But the control of pollen tube reception is not understood. We isolated a semisterile, female gametophytic mutant from Arabidopsis thaliana, named feronia after the Etruscan goddess of fertility, which impairs this process. In the feronia mutant, embryo sac development and pollen tube guidance were unaffected in all ovules, although one half of the ovules bore mutant female gametophytes. However, when the pollen tube entered the receptive synergid of a feronia mutant female gametophyte, it continued to grow, failed to rupture and release the sperm cells, and invaded the embryo sac. Thus, the feronia mutation disrupts the interaction between the male and female gametophyte required to elicit these processes. Frequently, mutant embryo sacs received supernumerary pollen tubes. We analysed feronia with synergid-specific GUS marker lines, which demonstrated that the specification and differentiation of the synergids was normal. However, GUS expression in mutant gametophytes persisted after pollen tube entry, in contrast to wild-type embryo sacs where it rapidly decreased. Apparently, the failure in pollen tube reception results in the continued expression of synergid-specific genes, probably leading to an extended expression of a potential pollen tube attractant

Three-manifold invariant from functional integration

We give a precise definition and produce a path-integral computation of the normalized partition function of the abelian U(1) Chern-Simons field theory defined in a general closed oriented 3-manifold. We use the Deligne-Beilinson formalism, we sum over the inequivalent U(1) principal bundles over the manifold and, for each bundle, we integrate over the gauge orbits of the associated connection 1- forms. The result of the functional integration is compared with the abelian U(1) Reshetikhin-Turaev surgery invariant

On a microcanonical relation between continuous and discrete spin models

A relation between a class of stationary points of the energy landscape of continuous spin models on a lattice and the configurations of a Ising model defined on the same lattice suggests an approximate expression for the microcanonical density of states. Based on this approximation we conjecture that if a O(n) model with ferromagnetic interactions on a lattice has a phase transition, its critical energy density is equal to that of the n = 1 case, i.e., a system of Ising spins with the same interactions. The conjecture holds true in the case of long-range interactions. For nearest-neighbor interactions, numerical results are consistent with the conjecture for n=2 and n=3 in three dimensions. For n=2 in two dimensions (XY model) the conjecture yields a prediction for the critical energy of the Berezinskij-Kosterlitz-Thouless transition, which would be equal to that of the two-dimensional Ising model. We discuss available numerical data in this respect.Comment: 5 pages, no figure

Invasive Species Management Programs in Alaska: A Survey of Statewide Expenditures, 2007–11

Invasive species have already reduced biodiversity, damaged the environment, threatened human health, and created economic losses worldwide. Alaska, by contrast, had relatively few invasive species for most of the 20th century. But increased population and development in recent years have brought an influx of non-native species. However, the problem remains in its infancy, and Alaska still has the opportunity to take advantage of cost-effective management, given appropriate coordination among government agencies and private groups. To help improve such coordination and increase public understanding about this issue, the authors collected data on spending to manage invasive species in Alaska between 2007 and 2011. Such spending increased from $4.7 million in 2007 to$6.9 million in 2010, and it totaled $29 million over the entire study period. Federal agencies paid 84$5 million), northern pike that were eating juvenile salmon in lakes of Southcentral Alaska ($2.7 million), and European rabbits that were destroying bird habitat in southwestern Alaska ($0.8 million). Overall, research accounted for 24%, monitoring for 20%, eradication for 20%, administration and planning for 11%, and other spending for 25% of total expenditures. The number of jobs in managing invasive species increased over the study period, as did volunteer efforts, which may suggest increasing public awareness about this issue in Alaska. Les espèces envahissantes ont déjà eu pour effet de réduire la biodiversité, de nuire à l’environnement, de menacer la santé de l’être humain et d’engendrer des pertes économiques partout dans le monde. Malgré tout, pendant la quasi-totalité du XXe siècle, relativement peu d’espèces envahissantes ont atteint l’Alaska. Cela dit, l’augmentation de la population et les travaux d’aménagement qui ont eu cours dans la région ces dernières années ont apporté une panoplie de plantes non indigènes. Cependant, puisque le problème n’en est qu’à ses débuts, il n’est pas trop tard pour l’Alaska de profiter d’une gestion économique qui serait le fruit d’une coordination adéquate entre les organismes gouvernementaux et des groupes privés. Afin de faciliter cette coordination et d’aider les gens à mieux comprendre cet enjeu, les auteurs ont recueilli des données sur les sommes affectées à la gestion des espèces envahissantes en Alaska entre 2007 et 2011. Ces dépenses sont passées de 4,7 millions de dollars en 2007 à 6,9 millions de dollars en 2010. Pendant toute la période visée par l’étude, elles ont totalisé 29 millions de dollars. Les organismes fédéraux ont affecté 84 % de cette somme et les organismes sans but lucratif ont affecté 9 % du total, tandis que l’État de l’Alaska a versé 5 % du total, les gouvernements locaux, 2%, et des particuliers, moins de 1 %. La plus grande partie des fonds affectés à la lutte des espèces envahissantes (79 %) visait les plantes et les animaux terrestres, bien que les fonds injectés dans la lutte des espèces marines et des organismes envahissants d’eau douce aient augmenté pendant la période. Les dépenses les plus importantes visaient l’éradication des rats de Norvège qui tuaient les populations d’oiseaux sur une île aléoutienne (5 millions de dollars), du brochet du Nord qui mangeait le saumon juvénile des lacs du centre-sud de l’Alaska (2,7 millions de dollars), et des lapins d’Europe qui détruisaient l’habitat de la faune avienne dans le sud-ouest de l’Alaska (0,8 million de dollars). Dans l’ensemble, les dépenses se sont réparties comme suit : 24 % pour les travaux de recherche, 20 % pour la surveillance, 20 % pour l’éradication, 11 % pour l’administration et la planification, et 25 % pour des dépenses diverses. Au cours de la période visée par l’étude, le nombre d’emplois consacré à la lutte des espèces envahissantes s’est accru, comme cela a été le cas du travail accompli par des bénévoles, ce qui laisse entendre que le grand public est de plus en plus conscient de cet enjeu en Alaska.Mots clés : espèces envahissantes, Alaska, enquête sur les dépenses, gestion des ressources, écolo-économi

On fine differentiability properties of horizons and applications to Riemannian geometry

We study fine differentiability properties of horizons. We show that the set of end points of generators of a n-dimensional horizon H (which is included in a (n+1)-dimensional space-time M) has vanishing n-dimensional Hausdorff measure. This is proved by showing that the set of end points of generators at which the horizon is differentiable has the same property. For 1\le k\le n+1 we show (using deep results of Alberti) that the set of points where the convex hull of the set of generators leaving the horizon has dimension k is ``almost a C^2 manifold of dimension n+1-k'': it can be covered, up to a set of vanishing (n+1-k)-dimensional Hausdorff measure, by a countable number of C^2 manifolds. We use our Lorentzian geometry results to derive information about the fine differentiability properties of the distance function and the structure of cut loci in Riemannian geometry.Comment: Latex2e, 13 pages in A4 forma

Power calculation for gravitational radiation: oversimplification and the importance of time scale

A simplified formula for gravitational-radiation power is examined. It is shown to give completely erroneous answers in three situations, making it useless even for rough estimates. It is emphasized that short timescales, as well as fast speeds, make classical approximations to relativistic calculations untenable.Comment: Three pages, no figures, accepted for publication in Astronomische Nachrichte

Regularity of higher codimension area minimizing integral currents

This lecture notes are an expanded version of the course given at the ERC-School on Geometric Measure Theory and Real Analysis, held in Pisa, September 30th - October 30th 2013. The lectures aim to explain the main steps of a new proof of the partial regularity of area minimizing integer rectifiable currents in higher codimension, due originally to F. Almgren, which is contained in a series of papers in collaboration with C. De Lellis (University of Zurich).Comment: This text will appear in "Geometric Measure Theory and Real Analysis", pp. 131--192, Proceedings of the ERC school in Pisa (2013), L. Ambrosio Ed., Edizioni SNS (CRM Series

Corrosion of a stainless steel waste heat recuperator

Waste heat recuperation has significant potential for saving energy in fossil-fuel-fired industrial furnaces. Preheating the air used to burn the fuel can significantly reduce fuel consumption. The US Department of Energy is contracting several high-temperature waste heat recuperation demonstrations with the objective of using successful efforts to stimulate the industrial utilization of these devices. One of the recuperator demonstration contracts has as an objective the successful operation of a concentric-shell radiation recuperator of a new design on aluminum-scrap-remelting furnaces. The design employs type 309 stainless steel reradiant inserts within the type 309 stainless steel inner shell to increase heat radiation to the recuperator partition, thereby increasing the heat exhanger's effectiveness. The first demonstration recuperator in this program was installed on a furnace fired with No. 2 oil and melting about 60 Mg (66 tons) of aluminum per 24-h day. The unit operated for about 30 d and provided air to the burner at 540/sup 0/C. during this period, a burner control misoperation provided very fuel-rich gases to the base of the recuperator. This fuel combined with safety dilution air at the recuperator base and burned within the recuperator. Also, during this period, air flow loss was detected at the burner. An inspection revealed that this was caused by failure of the partition wall separating the primary and secondary sides of the recuperator. Extensive corrosion of the partition wall and reradiant inserts was also observed. The recuperator was removed from the furnace for an analysis of the failure