FDTD-ANT User Manual

This manual explains the theory and operation of the finite-difference time domain code FDTD-ANT developed by Analex Corporation at the NASA Lewis Research Center in Cleveland, Ohio. This code can be used for solving electromagnetic problems that are electrically small or medium (on the order of 1 to 50 cubic wavelengths). Calculated parameters include transmission line impedance, relative effective permittivity, antenna input impedance, and far-field patterns in both the time and frequency domains. The maximum problem size may be adjusted according to the computer used. This code has been run on the DEC VAX and 486 PC's and on workstations such as the Sun Sparc and the IBM RS/6000

Designs for the ATDRSS tri-band reflector antenna

Two approaches to design a tri-band reflector antenna for the Advanced TDRSS are examined. Two reflector antenna configurations utilizing frequency selective surfaces for operation in three frequency bands, S, Ku, and Ka, are proposed. Far-field patterns and the antenna feed losses were computed for each configuration. An offset-fed single reflector antenna configuration was adapted for conceptual spacecraft design. CADAM drawings were completed and a 1/13th scale model of the spacecraft was constructed

Color Variation in the Caribbean Crab Platypodiella spectabilis (Herbst, 1794) (Decapoda, Brachyura, Xanthidae)

The use of color in brachyuran crab systematics, and in particular the use of subtle color differences to suggest or differentiate cryptic or morphologically similar species, is now well documented (e.g., see Campbell and Mahon 1974 for species of Leptograpsus, Williams and Felder 1989 for species of Menippe, Zimmerman and Felder 1991 for species of Sesarma). Less clearly understood is why color patterns and intensities can sometimes vary appreciably within a species, even within narrowly restricted geographic regions. An appreciation of color patterns is critical to correctly identifying species for conservation and resource management purposes, yet often color patterns and ranges are unreported, causing confusion and sometimes misidentifications. Here we document a wide range of color patterns in a small Caribbean xanthid crab based on specimens collected in essentially the same habitat at the same time of year

Artificial Reef Matrix Structures (Arms): An Inexpensive and Effective Method for Collecting Coral Reef-Associated Invertebrates

Collecting reef-associated invertebrates usually involves disturbance of the reef area, often damaging the habitat and sometimes damaging live corals. We introduce a nondestructive, inexpensive, and effective method for collecting coral reef-associated invertebrates using approximations of small coral heads constructed of concrete, PVC pipes, nylon cleaning pads, and other materials easily obtainable in most tropical (coral-rich) countries. An example showing the effectiveness of the method is presented based on fieldwork in the eastern Caribbean

The Stomatopod Alachosquilla floridensis (Manning, 1962) (Crustacea, Stomatopoda, Nannosquillidae) Reported from Guana Island, British Virgin Islands, with Observations on Color

Although color pattern can vary among and within species of the Crustacea, it can also be a conservative feature that can be very helpful in field identifications. This is often the case in the Crustacea Decapoda, where sibling species can be detected by subtle differences in color (e.g., Williams and Felder 1989, Zimmerman and Felder 1991, Knowlton and Mills 1992). Stomatopods are among the most colorful crustaceans when living. Many species show a great deal of variability (Manning 1969, Camp 1973), and knowledge of this coloration is often key to their identification in the field and in the lab (Schotte and Manning 1993). As part of an ongoing survey of the marine invertebrate fauna of Guana Island, British Virgin Islands, we collected 2 large (45 mm and 48 mm TL) females, and one male specimen (30 mm TL) of the rarely reported stomatopod species Alachosquilla floridensis (Manning 1962). To our knowledge, the species has been reported previously in the literature only 4 times (see Schotte and Manning 1993). These reports are based on a total of 8 specimens. Previous distribution records for the species include Lake Worth Inlet, Florida; Virgin Gorda, US Virgin Islands; Isla Marguerita, Venezuela; Bahia, Brazil; and Saint Giles Island and London Bridge Rock, Tobago, West Indies (Manning 1969, Schotte and Manning 1993)

First Record and Habitat Notes for the Genus Lightiella (Crustacea, Cephalocarida, Hutchinsoniellidae) from the British Virgin Islands

The crustacean class Cephalocarida, as currently understood, is comprised of five genera and ten species (Hessler and Elofsson 1996, Hessler and Wakabara 2000). Although in some instances numerous specimens have been collected in a single locale (e.g., the nearly 120 specimens of Lightiella incisa Gooding, 1963 from Puerto Rico studied by Sanders and Hessler (1964), and the numerous specimens of Hutchinsoniella macracantha Sanders, 1955 now known from Buzzards Bay, Massachusetts, see Hessler and Sanders 1973:193), most reports are based on very few specimens. For example, the original description of the genus Hutchinsoniella Sanders, 1955 was based on only eight specimens from Long Island Sound, New York (Sanders 1955); the genus Sandersiella was originally described by Shiino (1965) on the basis of only one specimen from Japan; the genus Chiltoniella Knox and Fenwick, 1977 was based on two specimens from New Zealand (Knox and Fenwick 1977), and the genus Lightiella Jones, 1961 was based on seven specimens from San Francisco Bay (Jones 1961). Lightiella moniotae was described for a single individual from New Caledonia (Cals and Delamare-Deboutteville 1970); Sandersiella calmani for two specimens from Peru (Hessler and Sanders 1973); and Sandersiella bathyalis for two specimens from the deep ocean off southwest Africa (Hessler and Sanders 1973). The single eastern Caribbean record (Barbados) of a cephalocarid also was based on two specimens (Gooding 1963), although Gooding also discussed two specimens from Puerto Rico in that account. Cephalocarids are of such interest morphologically and phylogenetically, and are found so infrequently, that their presence anywhere is noteworthy. As part of an ongoing survey of the cryptic marine invertebrates of certain Caribbean islands, we obtained a single specimen of a cephalocarid from Guana Island, British Virgin Islands, that matches most closely the description by Gooding (1963) of L. incisa. The find is of interest not only because it is the first record for the far eastern Caribbean other than Gooding’s (1963) two type specimens from Barbados, but also because of the unusual habitat in which it was found

The Theory of Planned Behavior and the Earned Income Tax Credit

The Earned Income Tax Credit (EITC) seeks to reduce poverty and provide the resources necessary for an individual to become self-sufficient. The EITC achieves this annually by lifting millions of households above the poverty level through income supplementation. However, recent evidence suggests that the long-term upward economic mobility provided by the EITC in practice is limited. To investigate the factors associated with achieving this financial independence, this study utilized the Theory of Planned Behavior to determine if (a) attitudes—as measured by time preference and self-esteem, (b) subjective norms—as measured by education, parents’ poverty level or work status, and religiosity, and/or (c) perceived behavioral control—as measured by self-efficacy (perceived effectiveness in accomplishing tasks) were significant in moving beyond qualification standards of the EITC. Using data from the National Longitudinal Survey of Youth (NLSY79), the EITC utilization pattern of a sample of 178 individuals was investigated. Results reaffirmed the economic advantages of marriage, suggesting that, by protecting and support healthy marriages, financial therapists can actively contribute to improved financial outcomes. Results also indicated that individuals with a high degree of mastery (feeling in control) were more likely to experience economic improvement, as measured through movement above EITC qualification standards. This suggests that financial therapists should work to facilitate growth in personal mastery as a part of helping clients reach their financial goals

Handbook for Navigating through the Minneapolis Commercial Corridor Process.

A renewed interest in commercial corridors has emerged as neighborhoods in Minneapolis have identified areas needing revitalization. Planning and implementing a commercial corridor revitalization is complex and time-consuming. This 1996 handbook serves as a guide to the process. It supplies worksheets, flowcharts, and a glossary of terms and organizations. It identifies the important questions to ask, resources to consider, and issues to address. It outlines the process from creating a vision statement, to forming a planning team, to securing funding, and celebratin completion of the implementation.Sponsored by Neighborhood Planning for Community Revitalization, Center for Urban and Regional Affairs, University of Minnesota

Universality of low-energy scattering in (2+1) dimensions

We prove that, in (2+1) dimensions, the S-wave phase shift, $\delta_0(k)$, k being the c.m. momentum, vanishes as either $\delta_0 \to {c\over \ln (k/m)} or \delta_0 \to O(k^2)$ as $k\to 0$. The constant $c$ is universal and $c=\pi/2$. This result is established first in the framework of the Schr\"odinger equation for a large class of potentials, second for a massive field theory from proved analyticity and unitarity, and, finally, we look at perturbation theory in $\phi_3^4$ and study its relation to our non-perturbative result. The remarkable fact here is that in n-th order the perturbative amplitude diverges like $(\ln k)^n$ as $k\to 0$, while the full amplitude vanishes as $(\ln k)^{-1}$. We show how these two facts can be reconciled.Comment: 23 pages, Late