Near infrared spectroscopy in detecting delayed cerebral ischemia in subarachnoid hemorrhage patients

Thesis (M.A.)--Boston UniversityBackground: Aneurysmal subarachnoid hemorrhage (aSAH) affects 30,000 Americans each year. Delayed cerebral ischemia caused by cerebral vasospasm is a complication that occurs in approximately 30% of aSAH patients and is a major cause of morbidity and mortality (Hijdra et al., 1986; Roos et al., 2000). The only two established screening methods for vasospasm, transcranial doppler (TCD) and CT angiography (CTA), have their own shortcomings (Jan van Gijn, Kerr, & Rinkel). Studies have shown that TCD has a 63% sensitivity and 52% specificity in detecting vasospasm (Carrera et al., 2009). Furthermore, TCDs require skilled technicians to insonate the cerebral blood vessels thereby explaining why TCDs can only be performed once per day. While CTA is highly specific and sensitive in detecting vasospasm, it requires the use of contrast dye which and carries the risk of contrast nephropathy. Near Infrared Spectroscopy (NIRS), however, is an FDA approved imaging technique that has been used in carotid endarterectomy surgeries to monitor for cerebral ischemia. It is a non-invasive technique and can take continuous, 24-hour measurements of cortical oxygenation. Additionally, NIRS does not require a trained technician to operate, nor does it confer any risk of nephropathy. Also, it is markedly cheaper than the other methods of detection mentioned here because there is no other cost other than the purchase of the machine and the disposable sensors. [TRUNCATED

The Effects of Blade Fillets on Aerodynamic Performance of a High Pressure Ratio Centrifugal Compressor

In most cases of aerodynamic design of centrifugal compressors, the effects of impeller blade fillets on performance are not considered in the process, but could be estimated later from some limited studies. As one of numerical investigations for the effects in centrifugal compressors, the Krain backswept impeller was modeled with and without blade fillets on the hub. A vaneless diffuser and impeller tip clearances were included in the steady state analysis using a commercial CFD code. Over the range of flows at design speed, the case with blade fillets showed a slight drop in the pressure ratio, the efficiency, the choke flow and the range of operation, relative to the case of clean blades. A more detailed look into three-dimensional flow structure inside the impeller shows that a small scraping vortex, developed in the case of clean blades at the corner of the hub pressure surface, disappears in the case with blade fillets due to a local flow acceleration produced by the fillet. As a result of balancing forces acting in the impeller passage, it was observed that the shroud passage vortex in the case with blade fillets grows toward the impeller exit with a higher vortex core than that in the case of clean blades, which means that there are more wake flows with blade fillets, leading to aerodynamic performance drops

Intermediate long wave equation in negative Sobolev spaces

We study the intermediate long wave equation (ILW) in negative Sobolev spaces. In particular, despite the lack of scaling invariance, we identify the regularity $s = -\frac 12$ as the critical regularity for ILW with any depth parameter, by establishing the following two results. (i) By viewing ILW as a perturbation of the Benjamin-Ono equation (BO) and exploiting the complete integrability of BO, we establish a global-in-time a priori bound on the $H^s$-norm of a solution to ILW for $- \frac 12 < s < 0$. (ii) By making use of explicit solutions, we prove that ILW is ill-posed in $H^s$ for $s < - \frac 12$. Our results apply to both the real line case and the periodic case.Comment: 15 page

Metacognitive Performance, the Tip-of-Tongue Experience, Is Not Disrupted in Parkinsonian Patients

The present study investigated whether a form of metamemory, the tip-of-tongue phenomenon (TOT), was affected in patients with Parkinson's disease (PD). The PD patient (n = 22), age-matched elderly control (n = 22), and college student control (n = 46) groups were compared on a motor timing task and TOT measures. Motor timing was assessed using a cued hand-clapping task, whereas TOT was assessed using general knowledge questions. The results indicated that motor timing was significantly impaired in the PD group relative to both control groups. However, all of the TOT metacognitive measures: frequency, strength, and accuracy were statistically equivalent between the PD patients and elderly control groups, both of whom showed significantly better memory performance than college controls. These findings demonstrate that TOT metamemory is not compromised in PD patients, and that further insight into TOT mechanisms in PD may prove helpful in developing novel intervention strategies to enhance memory and general cognitive functions in these patients

Spatial patterns and intensity of the surface storm tracks in CMIP5 models

Author Posting. © American Meteorological Society, 2017. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 30 (2017): 4965-4981, doi:10.1175/JCLI-D-16-0228.1.To improve the understanding of storm tracks and western boundary current (WBC) interactions, surface storm tracks in 12 CMIP5 models are examined against ERA-Interim. All models capture an equatorward displacement toward the WBCs in the locations of the surface storm tracks’ maxima relative to those at 850 hPa. An estimated storm-track metric is developed to analyze the location of the surface storm track. It shows that the equatorward shift is influenced by both the lower-tropospheric instability and the baroclinicity. Basin-scale spatial correlations between models and ERA-Interim for the storm tracks, near-surface stability, SST gradient, and baroclinicity are calculated to test the ability of the GCMs’ match reanalysis. An intermodel comparison of the spatial correlations suggests that differences (relative to ERA-Interim) in the position of the storm track aloft have the strongest influence on differences in the surface storm-track position. However, in the North Atlantic, biases in the surface storm track north of the Gulf Stream are related to biases in the SST. An analysis of the strength of the storm tracks shows that most models generate a weaker storm track at the surface than 850 hPa, consistent with observations, although some outliers are found. A linear relationship exists among the models between storm-track amplitudes at 500 and 850 hPa, but not between 850 hPa and the surface. In total, the work reveals a dual role in forcing the surface storm track from aloft and from the ocean surface in CMIP5 models, with the atmosphere having the larger relative influence.JFB was partially supported by the NOAA Climate Program Office’s Modeling, Analysis, Predictions, and Projections program (Grant NA15OAR4310094). Y-OK was supported by NSF Division of Atmospheric and Geospace Science Climate and Large-scale Dynamics Program (AGS-1355339), NASA Physical Oceanography Program (NNX13AM59G), and DOE Office of Biological and Environmental Research Regional and Global Climate Modeling Program (DE-SC0014433). RJS was supported by DOE Office of Biological and Environmental Research (DE-SC0006743) and NSF Directorate for Geosciences Division of Ocean Sciences (1419584),2017-10-0

Soluble factors from neocortical astrocytes enhance neuronal differentiation of neural progenitor cells from adult rat hippocampus on micropatterned polymer substrates

Rat adult hippocampal progenitor cells (AHPCs) are self-renewing, multipotent neural progenitors that have the ability to differentiate into neurons and glia. Previously, we demonstrated that coculture of AHPCs with postnatal day two, type 1 cortical astrocytes on laminin-coated micropatterned polymer substrates facilitates selective neuronal differentiation of the AHPCs 1. Under this condition, multi-dimensional cell-cell and/or cell-extracellular matrix interactions, as well as possible soluble factors released from astrocytes provided spatial and temporal control selectively enhancing neuronal differentiation and neurite alignment on topographically different regions of the same substrate. To investigate the potential role of astrocyte-derived soluble factors as cues involved in neuronal differentiation, a non-contact co-culture system was used. Under control conditions, approximately 14% of the AHPCs were immunoreactive (IR) for the neuronal marker, class III β-tubulin (TUJ1-IR). When co-cultured in physical contact with astrocytes, neuronal differentiation increased significantly to about 25%, consistent with our previous results. Moreover, under non-contact co-culture conditions using Transwell insert cultures, neuronal differentiation was dramatically increased to approximately 64%. Furthermore, neurite outgrowth from neuronal cell bodies was considerably greater on the patterned substrate, compared to the non-patterned planar substrate under non-contact co-culture conditions. Taken together, our results demonstrate that astrocyte-derived soluble factors provide cues for specific neuronal differentiation of AHPCs cultured on micropatterned substrates. In addition, a suppressive influence on neuronal differentiation appears to be mediated by contact with co-cultured astrocytes. These results provide important insights into mechanisms for controlling neural progenitor/stem cell differentiation and facilitate development of strategies for CNS repair