Mile-a-minute Weed, (Polygonum perfoliatum L.), an Invasive Vine in Natural and Disturbed Sites

Polygonum perfoliatum L. (Polygonaceae) or mile-a-minute weed, from eastern Asia, has been spreading through wild and disturbed areas of the mid-Atlantic United States. It has a wide ecological amplitude and is found on stream banks, moist thickets, roadsides, nurseries, wood-piles, clearings, and ditches. Polygonum perfoliatum presents serious problems for reforestation because it thrives where forests are clear-cut. A southward direction of spread indicates that the species will probably proliferate in at least some southern states. Mechanical control is not likely to be completely effective because seeds are often left behind. No appropriate biocontrols are known. The plant poses a threat to natural and restored ecosystems because of its capacity to grow rapidly and overgrow other species. It is expected to cover large areas unless it is controlled

Consumption Rates, Evacuation Rates and Diets of Pygmy Killifish, Leptolucania ommata, and Mosquitofish, Gambusia affinis in the Okefenokee Swamp

I studied feeding dynamics of Leptolucania ommata and Gambusia affinis in the Okefenokee Swamp. Both fishes mainly ate insect larvae (such as Chironomidae) and Cladocera. Evacuation rates ranged from 0.143 (L. ommala in winter) to 0.279/hour (L. ommala in summer). Daily food consumption (dry weight) ranged from 24.2 (L. ommata in winter) to 148.3 mg/g/day (G. affinis in summer). Maximum consumption by both species was estimated at 26.31 mg/t m2 / day, in summer. These values are consistent with other observations supporting a hypothesis that invertebrate prey production is substantial in these blackwater wetlands

A Review of the Biology of Giant Salvinia

Giant salvinia (Salviniaceae) is a potentially serious aquatic weed that is native to Brazil. It has been reported in more than 20 countries, but is not established in the U.S. at this time. Mitchell and Tur (1975) reported that three years after the formation of the Kariba Reservoir in Africa, giant salvinia blanketed 21.5% or 1003 km2 of the reservoir surface area. Creagh (199111992) wrote, A single small plant may grow to form a thick mat covering more than 100 sq. km. in just three months - choking lakes and waterways, reducing populations of aquatic plants and animals and in some countries threatening the livelihoods of ... thousands of people . Dense mats of giant salvinia. interfere with rice cultivation, clog fishing nets, and disrupt access to water for humans, livestock, and wildlife (Mitchell 1979), and recreation, transportation, irrigation, hydroelectric generation, and flood control are also hampered (Holm et al. 1977). Thick mats of giant salvinia form large floating islands which support secondary and tertiary colonizing plants and fill in waterbodies (Thomas 1979). Common names of S. molesta include giant salvinia, African pyle, and Kariba weed (Mitchell and Thomas 1972). These names allude to this species\u27 relatively large size and to its successful invasion of Lake Kariba and other waters of Africa. The plant was originally reported as a form of S. auriculata Aubl. It was later reclassified as S. molesta, based on details of the male sporocarps (Mitchell 1972). This review reports on the pertinent scientific literature concerning giant salvinia

Testing the Capital Asset Pricing Model Efficiently Under Elliptical Symmetry: A Semiparametric Approach

We develop new tests of the capital asset pricing model (CAPM) that take account of and are valid under the assumption that the distribution generating returns is elliptically symmetric; this assumption is necessary and sufficient for the validity of the CAPM. Our test is based on semiparametric efficient estimation procedures for a seemingly unrelated regression model where the multivariate error density is elliptically symmetric, but otherwise unrestricted. The elliptical symmetry assumption allows us to avert the curse of dimensionality problem that typically arises in multivariate semiparametric estimation procedures, because the multivariate elliptically symmetric density function can be written as a function of a scalar transformation of the observed multivariate data. The elliptically symmetric family includes a number of thick-tailed distributions and so is potentially relevant in financial applications. Our estimated betas are lower than the OLS estimates, and our parameter estimates are much less consistent with the CAPM restrictions than the corresponding OLS estimates. Nous développons de nouveaux tests du modèle d'évaluation des actifs financiers (" CAPM ") qui tiennent compte de, et sont valides sous, l'hypothèse que les retours des actifs découlent d'un loi de probabilité elliptiquement symétrique. Cette hypothèse est nécessaire et suffisante pour la validité du CAPM. Notre test utilise un estimateur des paramètres du modèle qui a l'efficacité semiparamétrique quand on a un modèle de régression apparemment sans relation et qui a des erreurs qui suivent une loi elliptiquement symétrique. L'hypothèse de la symétrie elliptique nous permet d'éviter le problème d'estimer non-paramétriquement une fonction de haute dimension parce qu'on peut écrire la densité d'une loi elliptique comme une fonction d'une transformation unidimensionnelle de la variable aléatoire multidimensionnelle. La famille des lois elliptiquement symétriques inclue plusieurs lois leptokurtiques, donc elle est pertinente à des applications financières. Les bêtas obtenus avec notre estimateur sont plus bas que ceux qui sont obtenus en utilisant des moindres carrés, et sont moins compatibles avec le CAPM.Adaptive estimation, capital asset pricing model, elliptical symmetry, semiparametric efficiency

The Magic Flute: a condensed and simplified arrangement for junior high school.

Thesis (M.M.E.)--Boston Universit

Residual influence of macronutrient enrichment on the aquatic food web of an Okefenokee Swamp abandoned bird rookery

We present evidence for residual nutrient enrichment of diverse components of a blackwater marsh, by a biotic component of the ecosystem itself. Thousands of nesting white ibis (Eudocimus albus) that foraged over a 20-km radius fertilized a rookery with guano within Okefenokee Swamp. Georgia. USA. One to two yr after the birds abandoned it. this marsh showed continued enrichment effects. Elevated available phosphorus in sediments, as measured by equilibrium phosphate concentration, contributed to enhanced biomass of phytoplankton in the overlying water column. Planktivorous fish were greater in biomass than at reference sites. Experimental phosphorus and nitrogen fertilization of enclosures at a reference site (at levels representing residual enrichment after birds had left) caused zooplankton biomass to increase significantly. These results demonstrate that this blackwater ecosystem was macronutrient limited, and manifested residual enrichment effects of wading birds on sediments, and a positive effect of sediments on phytoplankton. Results also suggest further indirect positive effects of birds on higher trophic levels (zooplankton and fish), via macronutrient transfers

Comparison of Three Methods for Sampling Fishes and Macroinvertebrates in a Vegetated Wetland

Three methods of sampling fishes, two seining methods and a drop trap method, were evaluated in heavily vegetated freshwater habitats. The portable drop trap method, which utilized a 1 x 1 m-sq. trap, collected significantly more macroinvertebrates and fish per unit area than did the seining methods. The meter square drop trap offered the additional advantages of a greater number of animals per unit effort and an integrated sample of vegetation, macroinvertebrates and fish in a given area. A 90% (s.d.= 7.4%) recovery of tagged fishes released into the traps in different habitats showed the m2 drop trap to be a highly reliable and effective sampling method for fish in vegetated wetlands

Effects of biogenic and simulated nutrient enrichment on fish and other components of Okefenokee Swamp marshes

Biogenic and simulated nutrient enrichment increased levels of various ecological components of Okefenokee Swamp marshes. Fertilization by wading birds and an artificial experimental source increased stores of phosphorus in diverse links of the food web. Simulation modeling lent support to the hypothesis that birds mediated such changes that persisted after they abandoned this ecosystem. To simulate nutrient enrichment from birds, I placed pots of enriched agar inside clear enclosures. In the laboratory, pots released a mean of 45 mg NH\sb4-N d\sp{-1} and 11 mg PO\sb4-P d\sp{-1} into water. In the marsh, mesocosms containing pots had higher stocks of zooplankton (primarily Diaphanosoma brachyurum) than controls. These results demonstrate that simulation of enrichment remaining after birds left can cause significant effects on zooplankton primary consumers in the marshes. Evidence was presented for residual enrichment by a biotic component of the ecosystem itself, the birds. One to two years after they abandoned the marsh, it showed continued nutrient effects. Elevated available phosphorus in sediments contributed to enhanced levels of phytoplankton. Planktivorous fish were greater in biomass than at reference sites. These results and the zooplankton data suggest residual enrichment effects of birds on sediments, and indirectly on plankton and fish. I measured the trophic transfer to Leptolucania ommata and Gambusia affinis, in situ. Both fishes ate mainly insect larvae (such as Chironomidae) and Cladocera. Consumption by both species in summer (26.31 mg m\sp{-2} d\sp{-1}) supports a hypothesis that invertebrate prey production must be substantial in such blackwater marshes. Trophic model dynamics were checked by seasonal data before, during and after simulated nutrient input from birds. The model reasonably estimates effects of enrichment on benthic detritus, aquatic macrophytes and phytoplankton, and conservatively estimates the increase of zooplankton and fish. Simulated levels decreased after simulated abandonment, and the decreases generally followed field trends. The model indicates that nesting birds can have considerable effects on aspects of an ecosystem not normally associated with them. On the applied side, wetlands have been suggested for natural sewage treatment. Results described here indicate a sizeable capacity to buffer pulses of sewage nutrients, by time-delayed release

Intraoperative electrocochleographic characteristics of auditory neuropathy spectrum disorder in cochlear implant subjects

Auditory neuropathy spectrum disorder (ANSD) is characterized by an apparent discrepancy between measures of cochlear and neural function based on auditory brainstem response (ABR) testing. Clinical indicators of ANSD are a present cochlear microphonic (CM) with small or absent wave V. Many identified ANSD patients have speech impairment severe enough that cochlear implantation (CI) is indicated. To better understand the cochleae identified with ANSD that lead to a CI, we performed intraoperative round window electrocochleography (ECochG) to tone bursts in children (n = 167) and adults (n = 163). Magnitudes of the responses to tones of different frequencies were summed to measure the “total response” (ECochG-TR), a metric often dominated by hair cell activity, and auditory nerve activity was estimated visually from the compound action potential (CAP) and auditory nerve neurophonic (ANN) as a ranked “Nerve Score”. Subjects identified as ANSD (45 ears in children, 3 in adults) had higher values of ECochG-TR than adult and pediatric subjects also receiving CIs not identified as ANSD. However, nerve scores of the ANSD group were similar to the other cohorts, although dominated by the ANN to low frequencies more than in the non-ANSD groups. To high frequencies, the common morphology of ANSD cases was a large CM and summating potential, and small or absent CAP. Common morphologies in other groups were either only a CM, or a combination of CM and CAP. These results indicate that responses to high frequencies, derived primarily from hair cells, are the main source of the CM used to evaluate ANSD in the clinical setting. However, the clinical tests do not capture the wide range of neural activity seen to low frequency sounds