An Analysis of Diversity in Freshwater Mussels (Bivalvia: Unionidae) of the Cuyahoga and Rocky River Watersheds (Ohio, USA) Based on the 16S rRNA Gene

The continued loss of freshwater unionid mussel species in the Great Lakes region, and particularly from Lake Erie, raises the question of how much phylogenetic and genetic variation remain in the watershed. The introduction of molecular markers into population biology offers one reproducible technique for assessing this variation. A fragment of the 16S rRNA gene of mitochondrial DNA has previously been used to infer phylogenetic relationships in the family Unionidae. Therefore, we reanalyzed these published molecular data with the addition of 12 species from the Cuyahoga and Rocky rivers in northeast Ohio. Both rivers drain to Lake Erie. The species assessed were Pyganodon grandis, Lasmigona complanata, Lasmigona compressa, Lampsilis radiata luteola, Fusconaia flava, Potamilus alatus, Strophitus undulatus, and Toxolasma parvus, for which published data were unavailable, and northern specimens of four wide ranging species, Lasmigona costata, Leptodea fragilis, Utterbackia imbecillis, and Quadrula quadrula. The resulting phylogenetic tree remained consistent with the accepted major taxonomic divisions in the Unionidae, and it indicates that these rivers still contain a phylogenetically diverse assemblage. However, the most abundant species all are members of the Anodontinae. Intraspecific variation in these unionid species was low, even where results were compared to published sequences on individuals from distant watersheds. One exception was a unique haplotype of Q. quadrula that differed at more base sites than is generally found for many congeneric species

A Study of the Unionidae of Tinkers Creek, Ohio

We present data on freshwater mussel (Mollusca: Bivalvia: Unionidae) distributions for Tinkers Creek, a small Ohio stream that previously had not been surveyed for its unionid fauna. The distribution of these mussels was mapped against the changing habitat of the stream, with special attention paid to two zones of human manipulation, a wastewater treatment plant and a stretch of the river where the bed was relocated to enable development. At least five unionid species live in Tinkers Creek. These are Pyganodon grandis, Lampsilis radiata luteola, Fusconaiajlava, Lasmigona costata, and Lasmigona compressa. Fresh shells suggested the presence of three others: Strophitus undulatus, Toxolasma parvus, and Alasmidonta marginata. The region of Tinkers Creek where the mussels are most common extends through Twinsburg, Ohio, and upstream to a waterfall just below the confluence with Pond Brook. Relocation of the river channel eliminated mussels from a 0.5 km stretch in eastern Twinsburg. Furthermore, the impact of effluent from a wastewater treatment plant was minor, at most. Mussel diversity diminished from five to three species commonly found below this facility. A change in river habitat to faster flow, however, provided an alternate explanation for this faunal change. The most striking difference was the replacement of Lasmigona costata, a species usually found in medium and large rivers, by L. compressa, a species common in small streams and headwaters

A Study of the Unionidae of Tinkers Creek, Ohio

We present data on freshwater mussel (Mollusca: Bivalvia: Unionidae) distributions for Tinkers Creek, a small Ohio stream that previously had not been surveyed for its unionid fauna. The distribution of these mussels was mapped against the changing habitat of the stream, with special attention paid to two zones of human manipulation, a wastewater treatment plant and a stretch of the river where the bed was relocated to enable development. At least five unionid species live in Tinkers Creek. These are Pyganodon grandis, Lampsilis radiata luteola, Fusconaiajlava, Lasmigona costata, and Lasmigona compressa. Fresh shells suggested the presence of three others: Strophitus undulatus, Toxolasma parvus, and Alasmidonta marginata. The region of Tinkers Creek where the mussels are most common extends through Twinsburg, Ohio, and upstream to a waterfall just below the confluence with Pond Brook. Relocation of the river channel eliminated mussels from a 0.5 km stretch in eastern Twinsburg. Furthermore, the impact of effluent from a wastewater treatment plant was minor, at most. Mussel diversity diminished from five to three species commonly found below this facility. A change in river habitat to faster flow, however, provided an alternate explanation for this faunal change. The most striking difference was the replacement of Lasmigona costata, a species usually found in medium and large rivers, by L. compressa, a species common in small streams and headwaters

Bipolar polaron pair recombination in P3HT/PCBM solar cells

The unique properties of organic semiconductors make them versatile base materials for many applications ranging from light emitting diodes to transistors. The low spin-orbit coupling typical for carbon-based materials and the resulting long spin lifetimes give rise to a large influence of the electron spin on charge transport which can be exploited in spintronic devices or to improve solar cell efficiencies. Magnetic resonance techniques are particularly helpful to elucidate the microscopic structure of paramagnetic states in semiconductors as well as the transport processes they are involved in. However, in organic devices the nature of the dominant spin-dependent processes is still subject to considerable debate. Using multi-frequency pulsed electrically detected magnetic resonance (pEDMR), we show that the spin-dependent response of P3HT/PCBM solar cells at low temperatures is governed by bipolar polaron pair recombination involving the positive and negative polarons in P3HT and PCBM, respectively, thus excluding a unipolar bipolaron formation as the main contribution to the spin-dependent charge transfer in this temperature regime. Moreover the polaron-polaron coupling strength and the recombination times of polaron pairs with parallel and antiparallel spins are determined. Our results demonstrate that the pEDMR pulse sequences recently developed for inorganic semiconductor devices can very successfully be transferred to the study of spin and charge transport in organic semiconductors, in particular when the different polarons can be distinguished spectrally

Changes in the Freshwater Mussel (Bivalvia: Unionidae) Fauna of the Cuyahoga River, Ohio, Since Late Prehistory

We provide new information from archaeological samples on the historical freshwater mussel fauna (Mollusca: Bivalvia: Unionoidea) of the Cuyahoga River (South Park site: occupied between ca. A.D. 950 and 1650) and Black River (White Fort site, occupation centered at ca. A.D. 1350), northeast Ohio. Data from these prehi storic sites are compared with information on extant mussel populations of the Cuyahoga River published between 1890 and 2000. The high representation at both archaeological sites of the species Actinonaias ligamentina, Elliptio dilatata, and Ptychobranchus fasciolaris suggests that these were· among the important clean water species in northeast Ohio prior to European settlement. By comparison, the modem mussel fauna of the lower Cuyahoga River (between Cleveland and Akron) contains none of these relatively abundant species, or any of the species represented in the archaeological material. The modern fauna of the lower river was established during the 20\u27 century. This fauna is a low diversity assemblage of pollution tolerant species represented by rare live individuals. The modem mussel fauna of the upper Cuyahoga River (between Akron and the source) suggests that the upper and lower reaches are effectively isolated from each other. Published records indicate little change in the fauna during the last three quarters of the 20\u27 century. Nevertheless, overall diversity, although substantially higher than that of the lower river, is considerably lower than that of the Grand River, which is located to the east of the Cuyahoga. Overall, the mussel fauna of the Cuyahoga River has changed greatly over time, most notably in terms of losses in diversity of clean water species and overall abundance

Portable Apparatus for Electrochemical Sensing of Ethylene

A small, lightweight, portable apparatus based on an electrochemical sensing principle has been developed for monitoring low concentrations of ethylene in air. Ethylene has long been known to be produced by plants and to stimulate the growth and other aspects of the development of plants (including, notably, ripening of fruits and vegetables), even at concentrations as low as tens of parts per billion (ppb). The effects are magnified in plant-growth and -storage chambers wherein ethylene can accumulate. There is increasing recognition in agriculture and related industries that it is desirable to monitor and control ethylene concentrations in order to optimize the growth, storage, and ripening of plant products. Hence, there are numerous potential uses for the present apparatus in conjunction with equipment for controlling ethylene concentrations. The ethylene sensor is of a thick-film type with a design optimized for a low detection limit. The sensor includes a noble metal sensing electrode on a chip and a hydrated solid-electrolyte membrane that is held in contact with the chip. Also located on the sensor chip are a counter electrode and a reference electrode. The sensing electrode is held at a fixed potential versus the reference electrode. Detection takes place at active-triple-point areas where the sensing electrode, electrolyte, and sample gas meet. These areas are formed by cutting openings in the electrolyte membrane. The electrode current generated from electrochemical oxidation of ethylene at the active triple points is proportional to the concentration of ethylene. An additional film of the solid-electrolyte membrane material is deposited on the sensing electrode to increase the effective triple-point areas and thereby enhance the detection signal. The sensor chip is placed in a holder that is part of a polycarbonate housing. When fully assembled, the housing holds the solid-electrolyte membrane in contact with the chip (see figure). The housing includes a water reservoir for keeping the solid-electrolyte membrane hydrated. The housing also includes flow channels for circulating a sample stream of air over the chip: ethylene is brought to the sensing surface predominately by convection in this sample stream. The sample stream is generated by a built-in sampling pump. The forced circulation of sample air contributes to the attainment of a low detection limit