The Cognitive Basis for Sentence Planning Deficits in Discourse Following Traumatic Brain Injury

Recent analyses of the language produced by individuals with traumatic brain injury place increasing emphasis on within-sentence patterns as well as those between sentences. Discussions of production deficits within sentences following TBI have questioned whether these problems involve the implementation of well-formed sentence frames or whether they represent a more fundamental linguistic disturbance in computing sentence structure. This study used online methods to investigate whether problems with sentence planning for discourse after TBI are associated with impaired language functioning or other cognitive processes. The results demonstrated that sentence planning deficits were associated with short-term memory span and attentional processing

Towards Predicting Patient-Specific Flow-Diverter Treatment Outcomes for Bifurcation Aneurysms: From Implantation Rehearsal to Virtual Angiograms

Despite accounting for the majority of all cerebral aneurysm cases, bifurcation aneurysms present many challenges to standard endovascular treatment techniques. This study examines the treatment of bifurcation aneurysms endovascularly with flow-diverting stents and presents an integrative computational modeling suite allowing for rehearsing all aspects of the treatment. Six bifurcation aneurysms are virtually treated with 70% porosity flow-diverters. Substantial reduction (>50%) in aneurysm inflow due to device deployment is predicted in addition to reductions in peak and average aneurysm wall shear stress to values considered physiologically normal. The subsequent impact of flow-diverter deployment on daughter vessels that are jailed by the device is investigated further, with a number of simulations conducted with increased outlet pressure conditions at jailed vessels. Increased outlet pressures at jailed daughter vessels are found to have little effect on device-induced aneurysm inflow reduction, but large variation (13-86%) is seen in the resulting reduction in daughter vessel flow rate. Finally, we propose a potentially powerful approach for validation of such models, by introducing an angiographic contrast model, with contrast transport modeled both before and after virtual treatment. Virtual angiograms and contrast residence curves are created, which offer unique clinical relevance and the potential for future in vivo verification of simulated results

An FFAG Transport Line for the PAMELA Project

The PAMELA project to design an accelerator for hadron therapy using non-scaling Fixed Field Alternating Gradient (NS-FFAG) magnets requires a transport line and gantry to take the beam to the patient. The NS-FFAG principle offers the possibility of a gantry much smaller, lighter and cheaper than conventional designs, with the added ability to accept a wide range of fast changing energies. This paper will build on previous work to investigate a transport line which could be used for the PAMELA project. The design is presented along with a study and optimisation of its acceptance

Effects of Elevated pCO2 and Irradiance on Growth, Photosynthesis and Calcification in Halimeda discoidea

Ocean acidification (OA) effects on photophysiology and calcification were examined in Halimeda discoidea, a calcifying macroalga that produces tropical reef sediments. Photosynthetic parameters, including maximum photosynthetic rate (Pmax), photosynthetic efficiency (α) and compensating irradiance (Ic) were determined in short-term assays on live thalli after a 10 d exposure to 4 levels of CO2 partial pressures (pCO2; 491, 653, 982 and 1201 µatm) under saturating (300 µmol photons m-2 s-1) and sub-saturating (90 µmol photons m-2 s-1) irradiance in an aquaria study. Morphology of aragonite crystals produced in segments formed on adult thalli was characterized using scanning electron microscopy (SEM). Further, we examined crystal morphology and changes in inorganic content of non-living segments exposed to elevated (1201 µatm) and ambient pCO2 for 27 d to assess OA effects on carbonate sediments generated from H. discoidea. Even though Pmax was higher under elevated pCO2, this photophysiological response did not result in higher calcification rates. Based on crystal measurements and SEM imagery, aragonite crystals within new segments were indistinguishable across pCO2 and irradiance treatments. Under high irradiance, new segments showed a greater investment in organic versus inorganic production. Non-living segments contained narrower crystals after 27 d exposure to elevated pCO2 relative to controls, but differences were small (0.03 µm) and did not contribute significantly to changes in normalized biomass or inorganic content. Based on these results, H. discoidea will likely produce new calcified segments with intact aragonite crystals under year 2100 pCO2 levels at high and low irradiance, while aragonite crystals of the sediment may produce thinner needle carbonate muds

Hot DQ White Dwarfs: Something Different

We present a detailed analysis of all the known Hot DQ white dwarfs in the Fourth Data Release of the Sloan Digital Sky Survey (SDSS) recently found to have carbon dominated atmospheres. Our spectroscopic and photometric analysis reveals that these objects all have effective temperatures between ~18,000 and 24,000 K. The surface composition is found to be completely dominated by carbon, as revealed by the absence of Hbeta and HeI 4471 lines (or determination of trace amount in a few cases). We find that the surface gravity of all objects but one seems to be ''normal'' and around log g = 8.0 while one is likely near log g = 9.0. The presence of a weak magnetic field is directly detected by spectropolarimetry in one object and is suspected in two others. We propose that these strange stars could be cooled down versions of the weird PG1159 star H1504+65 and form a new family of hydrogen and helium deficient objects following the post-AGB phase. Finally, we present the results of full nonadiabatic calculations dedicated specifically to each of the Hot DQ that show that only SDSS J142625.70+575218.4 is expected to exhibit luminosity variations. This result is in excellent agreement with recent observations by Montgomery et al. who find that J142625.70+575218.4 is the only pulsator among 6 Hot DQ white dwarfs surveyed in February 2008.Comment: 33 pages, 7 figures, accepted for publication in Ap

A Short-term Memory Treatment Appraoch to the Repetition Deficit in Conduction Aphasia

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Once is not Enough: Thoughts on Replication in Functional Analysis Research in Aphasia

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Virtual flow-diverter treatment planning: The effect of device placement on bifurcation aneurysm haemodynamics

Bifurcation aneurysms account for a large fraction of cerebral aneurysms and often present morphologies that render traditional endovascular treatments, such as coiling, challenging and problematic. Flow-diverter stents offer a potentially elegant treatment option for such aneurysms, but clinical use of these devices remains controversial. Specifically, the deployment of a flow-diverter device in a bifurcation entails jailing one or more potentially vital vessels with a low-porosity mesh designed to restrict the flow. When multiple device placement configurations exist, the most appropriate clinical decision becomes increasingly opaque. In this study, three bifurcation aneurysm geometries were virtually treated by flow-diverter device. Each aneurysm was selected to offer two possible device deployment positions. Flow-diverters similar to commercially available designs were deployed with a fast-deployment algorithm before transient and steady state computational fluid dynamics simulations were performed. Reductions in aneurysm inflow, mean wall shear stress and maximum wall shear stress, all factors often linked with aneurysm treatment outcome, were compared for different device configurations in each aneurysm. In each of the three aneurysms modelled, a particular preferential device placement was shown to offer superior performance with the greatest reduction in the flow metrics considered. In all the three aneurysm geometries, substantial variations in inflow reduction (up to 25.3%), mean wall shear stress reduction (up to 14.6%) and maximum wall shear stress reduction (up to 12.1%) were seen, which were all attributed to device placement alone. Optimal device placement was found to be non-trivial and highly aneurysm specific; in only one-third of the simulated geometries, the best overall performance was achieved by deploying a device in the daughter vessel with the highest flow rate. Good correspondence was seen between transient results and steady state computations that offered a significant reduction in simulation run time. If accurate steady state computations are combined with the fast-deployment algorithm used, the modest run time and corresponding hardware make a virtual treatment pipeline in the clinical setting a meaningful possibility

Difficulty linking macro- and microlinguistic processes for narrative production following TBI

Substantial evidence has accumulated over the past 35 years suggesting deficient intersentential cohesion in the narrative discourse of many individuals with traumatic brain injury (TBI). Since Mentis and Prutting (1987) reported significantly fewer cohesive ties in the narratives of brain-injured versus normal speakers, a number of reports have replicated and expanded upon these findings (e.g., Coelho, Liles, & Duffy, 1995; Davis & Coelho, 2004; Hartley & Jensen, 1991; Liles, Coelho, Duffy, & Zalagans, 1989; Marini et al., 2011). At the same time, several studies have not found evidence of deficient intersentential cohesion in these adults (Coelho, 2002; Glosser & Deser, 1991; Hough & Barrow, 2003). It can be said then that the narratives produced by at least some speakers with TBI tend to show less adequate intersentential cohesion than that observed in normal speakers (Cannizzaro & Coelho, 2012; Coelho, 2007). Variable microlinguistic impairment has also been observed in narrative discourse following TBI. Sentences produced by speakers with TBI have been reported to include more lexical and syntactic errors, increased mazes, more frequent pausing, and greater reductions in content when compared to normal speakers (Ellis & Peach, 2009; Glosser & Deser, 1991; Hartley & Jensen, 1991; Peach, 2013; Peach & Schaude, 1986; Stout, Yorkston, & Pimenthal, 2000). Such narratives also tend to be less efficient (i.e., lengthier and containing more words per maze) (Erlich, 1988; Hartley & Jensen, 1991; Stout et al., 2000) and less complex (Coelho, Grela, Corso, Gamble, & Feinn, 2005; Peach, Shapiro, Rubin, & Schaude, 1990) than those produced by normal speakers. Nonetheless, other studies have not found few, if any, such microlinguistic disturbances in speakers with TBI (Hough & Barrow, 2003; Marini et al., 2011). It has been suggested that brain injury produces a dissociation between the macrolinguistic and microlinguistic components of narrative production (Glosser & Deser, 1991; Hough & Barrow, 2003) and thus, that the processing of discourse and the processing of sentences are based on different cognitive devices (Consentino, Adornetti, & Ferretti, 2013). Alternatively, it might be that the macrolinguistic structure of narratives produced by brain injured speakers is affected by their microlinguistic impairments (see, e.g., Boyle, 2011; Christiansen, 1995). Given the variable patterns that have been observed in the narratives of speakers with TBI, it may be that narrative production following TBI is the result of an effortful interaction between macrolinguistic and microlinguistic processes rather than dissociation of separate cognitive mechanisms. However, few studies exist that attempt to establish the connections between these different levels of language. As a result, there is little information available to describe how specific changes at either level may influence the processing of narrative discourse. Armstrong (2000) has suggested that cohesion analysis is one of the few methods which directly attempts to link the macro- and microlinguistic aspects of discourse. This study therefore investigated the relationship between intersentential cohesion and microlinguistic impairments in discourse produced by speakers with severe traumatic brain injury (TBI)