Waves in consumption with interdependence among consumers

International audienc

Relativistic central--field Green's functions for the RATIP package

From perturbation theory, Green's functions are known for providing a simple and convenient access to the (complete) spectrum of atoms and ions. Having these functions available, they may help carry out perturbation expansions to any order beyond the first one. For most realistic potentials, however, the Green's functions need to be calculated numerically since an analytic form is known only for free electrons or for their motion in a pure Coulomb field. Therefore, in order to facilitate the use of Green's functions also for atoms and ions other than the hydrogen--like ions, here we provide an extension to the Ratip program which supports the computation of relativistic (one--electron) Green's functions in an -- arbitrarily given -- central--field potential \rV(r). Different computational modes have been implemented to define these effective potentials and to generate the radial Green's functions for all bound--state energies $E < 0$. In addition, care has been taken to provide a user--friendly component of the Ratip package by utilizing features of the Fortran 90/95 standard such as data structures, allocatable arrays, or a module--oriented design.Comment: 20 pages, 1 figur

The Major Veins of Mesomorphic Leaves Revisited: Tests for Conductive Overload in Acer saccharum (Aceraceae) and Quercus rubra (Fagaceae)

Many leaves survive the severing of their major veins in apparently excellent health. According to the classical explanation, the leaf minor veins provide "conductive overload," an excess of parallel conductive paths, rendering the major veins hydraulically dispensable. Whether such an excess of conductive paths exists has important implications for vascular design and for leaf response to vascular damage. We subjected leaves of Acer saccharum and Quercus rubra to cutting treatments that disrupted the major vein system and determined leaf survival, stomatal conductance (g), quantum yield of photosystem II (Phi(PSII)), and leaf hydraulic conductance (K-leaf). For A. saccharum, the cuts led to the death of distal lamina. For Q. rubra, however, the treated leaves typically remained apparently healthy. Despite their appearance, the treated Q. rubra leaves had a strongly reduced K-leaf,K- relative to control leaves, and g and Phi(PSII) were reduced distal to the cuts, respectively, by 75-97% and 48-76%. Gas exchange proximal to the cuts was unaffected, indicating the independence of lamina regions and their local stomata. Analogous results were obtained with excised Q. rubra leaves. These studies demonstrate an indispensable, vital role of the major veins in conducting water throughout the lamina.Organismic and Evolutionary Biolog

Supporting Father Involvement: An Intervention with Community and Child Welfare–Referred Couples

Objective: To expand the evidence base of the Supporting Father Involvement (SFI) intervention to include child welfare families. Background: Taking a preventive father-inclusive approach, SFI aims to strengthen coparenting, parent–child relationships, and child outcomes. This study replicates 4 prior iterations of the program using the same 32-hour curriculum facilitated by clinically trained staff, case managers, and onsite child care and family meals. Method: Participants (N = 239) included low-income (median = $24,000) coparenting pairs, typically mothers and fathers/father figures, half of whom were Mexican American, with toddlers (median age \u3c 3 years). Questionnaires assessing multiple family domains were administered verbally over an 18-month period. Intervention effectiveness was tested through a randomized control trial with immediate treatment or waitlist–control groups using a moderated mediator structural equation model. Results: The model explained 49% to 56% of the variance in children\u27s problem behaviors (intervention and autoregressive effects). The intervention reduced couple conflict, which reduced anxious and harsh parenting, leading to better child outcomes. The intervention was equally effective for community and child welfare–referred families and family dynamics pathways were similar across conditions. Conclusion: With its intentional outreach and inclusion of fathers, SFI offers an effective intervention for lower risk child welfare–involved families. Implications: Results argue for the utility of treating community and child welfare parents in mixed-gender prevention groups that focus on strengthening multiple levels of family relationships

Samuel D. Gross, M.D. (1805-1884): an innovator, even in death.

Dr. Samuel Gross\u27 contributions to the field of surgery are well known and range from numerous clinical advances to pioneering scholarship and professional activities. Dr. Gross was ceaselessly ambitious and even remarked in his autobiography that his ‘‘conviction has always been that is far better for a man to wear out than to rust out.’’1 It is through this frame of motivation that Dr. Gross lived his life

Future Needs for Tribo-Corrosion Research and Testing

Tribo-corrosion is an emerging interdisciplinary subject that spans from basic research on the behavior of surfaces in mechanical contact in chemically active surroundings to the test methods needed to quantify its effects, and from the selection of materials for bio-implants to the minimization of surface degradation and wastage in advanced energy conversion systems. Such a diverse field brings with it many challenges in understanding, testing, standardization, and application to engineering practice. This paper summarizes a panel discussion and participant survey held at the Third International Symposium on Tribo-Corrosion in Atlanta, Georgia, USA, in April 2012. It reflects a sense of agreement on many of the key scientific challenges in the field and the fact that tribo-corrosion is still in its infancy in terms of broad industry recognition, education, and the ability of those who conduct tribo-corrosion research to connect their laboratory results and theories to applications. Some sub-fields, notably the bio-tribo-corrosion of medical implants, have witnessed active international research efforts, but the engineering community in many other important areas of technology may not yet be aware of the field despite numerous tribo-corrosion problems that may exist within their purview

Iron Dynamics in a Gas-Water-Sediment Microcosm

Iron dynamics in eutrophic systems were studied in the laboratory utilizing gas-water-Sediment phase sealed microcosms. Sediments from Hyrum Reservoir (2.4 percent iron by weight) were placed in the dark to simulate the hypolimnetic regions of a eutrophic impoundment. Iron both chemically and physically was readily available to microorganisms of the aqueous phase because iron in these systems was soluble. In the light microcosms, which simulated shallow littoral regions of eutrophic impoundments, iron was found in higher aqueous phase concentrations than was predicted chemically and physically; this was rationalized through biological mechanisms. The experiment was conducted in two phases: Phase I lasted 189 days (0 and 0.300 mg NO3–N/1 inputs) and phase II lated 175 days (10mg NO3-N/1 imput). Average light microcosm effluent iron concentrations increased from 0.092 mg FE/1 (Phase I) to 0.246 mg Fe/1 (Phase II) given higher inorganic nitrogen inputs. In Phase II, when nitrogen input into the microcosms ceased (nitrogen perturbations, day 115), aqueous phase iron concentrations in the dark microcosms increased dramatically (0.011 to 0.624 mg Fe/1)