Potential For Population Regulation Of The Zebra Mussel By Finfish And The Blue Crab In North American Estuaries

We conducted a series of descriptive and manipulative experiments aimed at quantifying the abundance, natural mortality, and effectiveness of predators in controlling the zebra mussel, Dreissena polymorpha, in the Hudson River Estuary. First, we measured distribution, abundance, and mortality rates of a zebra mussel population in the middle portion of the Hudson River Estuary, NY. Rocks were collected along a depth gradient in the field and sampled for the density and size structure of the resident mussels over the growth season. Next, we either allowed access (controls) or denied access (predator exclusion) to predators in field experiments with rocks harboring a known number of zebra mussels to estimate natural mortality. Finally, we conducted manipulative field experiments to test the effectiveness of the blue crab, Callinectes sapidus, at consuming zebra mussels by presenting similar rocks to crabs in field enclosures. Field sampling in June, July, and August 1993 indicated a dense (similar to 30,000 mussels/m(2)) population composed of a single cohort of 1 + year-class mussels. Sampling in August 1994 indicated a decline in D. polymorpha density. Mussel density increased dramatically with depth less than 2 m below the spring low tide mark. in cage experiments, blue crabs caused mortality rates that were an order of magnitude higher than those measured for the local predator guild, which was primarily composed of finfish. Localized extinctions of zebra mussels within one growth season were predicted in areas where blue crab densities approach 0.1 crabs/m(2)

Conversational discourse analysis: appropriate and useful sample sizes

The time required to transcribe and analyse lengthy conversation puts conversational discourse analysis (CDA) out of reach for most practising clinicians. However, standards have not been established for appropriate conversation sample size. Data are presented supporting the use of conversation samples 5-10 minutes when studying conversation repair, speaking rate, and utterance length. Ten minute samples adequately represented 'parent' conversations from which they were derived when measuring conversation repair for six of eight cases. For measuring speaking efficiency (length of utterance and speaking rate) 5 minutes was adequate for all eight cases. For variables occurring once per minute, 10 minute samples were adequate, and for variables occurring three times per minute, 5 minute samples were adequate

A comparative analysis of naming errors made by subjects with naming impairment following stroke, Alzheimer's disease, and traumatic brain injury.

In two studies, the naming errors of individuals with naming impairment following stroke, Alzheimer's dementia and traumatic brain injury (TEl) were compared. Study 1 compared the errors of mild to moderately naming impaired individuals following stroke (n= 20), AD (n = 20), and TEl (n = 20), who were given a confrontation naming test. An error analysis was used to determine whether patterns existed within or across groups. Although each of these groups showed patterns in their naming errors, the differences were subtle. The particular types of naming errors were distributed differently among the three groups. A more consistent finding was a trend in all three groups toward more semantic errors in those with mild naming impairment and fewer semantic error in those with more severe naming impairment. In the stroke and TEl groups there was a trend of more irrelevant errors in those with more severe naming impairment and fewer irrelevant errors 100 in those with mild naming impairment. In Study 2, four groups of individuals post-stroke were given the same naming test. These groups were labeled high comprehension fluent (n = 17), low comprehension fluent (n = 10), low comprehension nonfluent (n = 11), and high comprehension non fluent (n = 10). Few naming error differences were found between groups, and these few differences were subtle. However the pattern in Study 1 also occurred for the subjects in Study 2. Individuals with milder naming impairment had a high frequency of semantic errors across the four groups. Individuals with more severe naming impairment had a high frequency of irrelevant errors, across the four groups. In the naming error literature two main issues are addressed. First, are different populations of naming impaired individuals affected differentially or, alternatively, is the severity of naming impairment a more salient determinant of naming error pattern. For individuals with mild to moderate naming impairment, the results of the current study favor the latter conclusion

Conversation analysis as a dependent measure in communication therapy with four individuals with aphasia

This report documents the progress of four individuals with aphasia through a seven-week course of Conversation Partners Therapy using a conversation analysis (CA). The CA as used in this study reveals changes otherwise unavailable from more traditional testing methods. Four individuals with aphasia participated. Their treatment comprised a seven-week regimen of therapy which used a family member as a trained facilitator, with the speech-language pathologist serving as ‘coach’. Weekly conversation probes were later analysed to determine whether progress documented with formal measures was observable from conversation. In the two patients with more satisfactory progress with conventional testing, parallel changes were realised in the CA, particularly with measures of verbal output and use of conversation self-repair. In the two patients with less satisfactory progress, little change in verbal output was noted, and no change or a decrease in conversation self-repairs occurred. The analyses in this study led directly to modification of therapeutic goals and objectives for each conversational dyad. For example, when little or no change in verbal output was recorded, the conversational partner was trained to facilitate more elaborate utterances by the partner with aphasia

Success stories in aphasia

Success in living with aphasia is discussed in the context of two couples who describe themselves as leading successful poststroke lives. Excerpts of interviews with the couples highlight some of the more salient issues and how each couple has come to accept and even appreciate “aphasic life.