The effect of fluorine on viscosities in the system Na2O-Al2O3-SiO2: implications for phonolites, trachytes and rhyolites

The effect of fluorine on melt viscosities of five compositions in the system Na2O-Al2O3- SiO2h as been investigateda t one atmospherea nd 1000-1600'Cb y concentric-cylinder viscometry. The compositions chosen were albite, jadeite and nepheline on the join NaAlOlSiO2 and two others of the join at 75 mole percent SiO2, one peralkaline and one peraluminous. All melt viscosities were independent of shear rate over two orders of magnitude, indicating Newtonian behavior. All viscosity-temperature relationships were Arrhenian within error. Fluorine reduces the viscosities and activation energies of all melts investigated. The viscosity-reducing power of fluorine increases with the SiO2 content of melts on the join NaAlO2-SiO2 and is a maximum at Na/Al (molar) = I for melts containing 75 mole percent SiO2. Fluorine and water have similar effects on aluminosilicate melt viscosities, probably due to depolymerization of these melts by replacement of Si-O-(Si, Al) bridges with Si-OH and Si-F bonds, respectively. Evidence from slag systems shows that fluorine also reduces the viscosity of depolymerized silicate melts. The viscous flow of phonolites, trachytes and rhyolites will be strongly afected by fluorine. It appears that fluorine contents of igneous rocks may be combined with water in calculation schemes for determining the viscosity of natural melts

Author response: Effects of orthostatic hypotension on cognition in Parkinson disease

OBJECTIVE: To investigate the relation between orthostatic hypotension (OH) and posture-mediated cognitive impairment in persons with Parkinson's disease (PD) without dementia. METHODS: There were 55 participants: 37 non-demented individuals with idiopathic PD, including 18 with OH (PDOH), and 19 without (PDWOH), and18 control participants (C). All participants completed neuropsychological tests in the supine and in the upright tilted position. Blood pressure was assessed in each posture using a standardized oscillometric cuff at the right brachial artery. RESULTS: The two PD groups performed similarly while supine, with a profile notable for executive dysfunction consisting of deficits in sustained attention, response inhibition, and semantic verbal fluency, as well as reduced verbal memory encoding and retention. When upright, these deficits were exacerbated and broadened to include additional cognitive functions in the PDOH group: deficits in phonemic verbal fluency, psychomotor speed, and both basic and complex aspects of auditory working memory. When group-specific supine scores were used as baseline anchors, both PD groups showed cognitive changes following tilt, though the PDOH group had a wider range of deficits in the executive functioning and memory domains and was the only group to show significant changes in visuospatial skills. CONCLUSIONS: Cognitive deficits in idiopathic PD have been widely reported, though assessments are typically performed in the supine position. While both PD groups had supine deficits that aligned with prior studies and clinical findings, we demonstrated that those with PD and orthostatic hypotension had transient, posture-mediated changes in excess of those found in PD without autonomic failure. These observed changes suggest an acute, reversible effect, and as orthostatic hypotension is a significant comorbid factor in PD, an independent target for clinical intervention. Further understanding of the effects of autonomic failure on cognition in other disorders is desirable, particularly in the context of neuroimaging studies and clinical assessments where data are collected only in the supine or seated positions. Identification of a distinct neuropsychological profile in PD with autonomic failure also has implications for functional activities of daily living and overall quality of life.Accepted manuscrip

Effects of orthostatic hypotension on cognition in Parkinson's disease

OBJECTIVE: To investigate the relation between orthostatic hypotension (OH) and posture-mediated cognitive impairment in Parkinson disease (PD) using a cross-sectional and within-group design. METHODS: Individuals without dementia with idiopathic PD included 18 with OH (PDOH) and 19 without OH; 18 control participants were also included. Neuropsychological tests were conducted in supine and upright-tilted positions. Blood pressure was assessed in each posture. RESULTS: The PD groups performed similarly while supine, demonstrating executive dysfunction in sustained attention and response inhibition, and reduced semantic fluency and verbal memory (encoding and retention). Upright posture exacerbated and broadened these deficits in the PDOH group to include phonemic fluency, psychomotor speed, and auditory working memory. When group-specific supine scores were used as baseline anchors, both PD groups showed cognitive changes following tilt, with the PDOH group exhibiting a wider range of deficits in executive function and memory as well as significant changes in visuospatial function. CONCLUSIONS: Cognitive deficits in PD have been widely reported with assessments performed in the supine position, as seen in both our PD groups. Here we demonstrated that those with PDOH had transient, posture-mediated changes in excess of those found in PD without OH. These observed changes suggest an acute, reversible effect. Understanding the effects of OH due to autonomic failure on cognition is desirable, particularly as neuroimaging and clinical assessments collect data only in the supine or seated positions. Identification of a distinct neuropsychological profile in PD with OH has quality of life implications, and OH presents itself as a possible target for intervention in cognitive disturbance.Accepted manuscriptAccepted manuscrip

Hybrid Amperometric and Potentiometric Sensing Based on a CMOS ISFET Array

Potentiometry and amperometry are some of the most important techniques for electroanalytical applications. Integrating these two techniques on a single chip using CMOS technology paves the way for more analysis and measurement of chemical solutions. In this paper, we describe the integration of electrode transducers (amperometry) on an ion imager based on an ISFET array (potentiometry). In particular, this integration enables the spatial representation of the potential distribution of active electrodes in a chemical solution under investigation

Automated Analysis of a Nematode Population-based Chemosensory Preference Assay

The nematode, Caenorhabditis elegans' compact nervous system of only 302 neurons underlies a diverse repertoire of behaviors. To facilitate the dissection of the neural circuits underlying these behaviors, the development of robust and reproducible behavioral assays is necessary. Previous C. elegans behavioral studies have used variations of a "drop test", a "chemotaxis assay", and a "retention assay" to investigate the response of C. elegans to soluble compounds. The method described in this article seeks to combine the complementary strengths of the three aforementioned assays. Briefly, a small circle in the middle of each assay plate is divided into four quadrants with the control and experimental solutions alternately placed. After the addition of the worms, the assay plates are loaded into a behavior chamber where microscope cameras record the worms' encounters with the treated regions. Automated video analysis is then performed and a preference index (PI) value for each video is generated. The video acquisition and automated analysis features of this method minimizes the experimenter's involvement and any associated errors. Furthermore, minute amounts of the experimental compound are used per assay and the behavior chamber's multi-camera setup increases experimental throughput. This method is particularly useful for conducting behavioral screens of genetic mutants and novel chemical compounds. However, this method is not appropriate for studying stimulus gradient navigation due to the close proximity of the control and experimental solution regions. It should also not be used when only a small population of worms is available. While suitable for assaying responses only to soluble compounds in its current form, this method can be easily modified to accommodate multimodal sensory interaction and optogenetic studies. This method can also be adapted to assay the chemosensory responses of other nematode species

Insurance-induced moral hazard: a dynamic model of within-year medical care decision making under uncertainty

Insurance-induced moral hazard may lead individuals to overconsume medical care. Many studies estimate this overconsumption using models that aggregate medical care decisions up to the annual level. Using employer-employee matched data from the Medical Expenditure Panel Survey (MEPS), I estimate the effect of moral hazard on medical care expenditure using a dynamic model of within-year medical care consumption that allows for endogenous health transitions, variation in medical care prices, and individual uncertainty within a health insurance year. I then calculate moral hazard effects under a second set of conditions that are consistent with the assumptions of most annual decision-making models. The within-year decision-making model produces a moral hazard effect that is 24% larger than the alternative model. I also provide evidence of heterogeneous moral hazard effects, particularly between insured and uninsured individuals, and discuss related policy implications. The dissertation concludes with a counterfactual policy simulation that implements the individual mandate provision of the 2010 Patient Protection and Affordable Care Act. I find that full implementation of the individual mandate decreases the percentage of uninsured individuals in the population being analyzed from 11.8% to 6.0% and increases average medical care expenditure 77% among the newly insured.Doctor of Philosoph

Triceps Surae Short Latency Stretch Reflexes Contribute to Ankle Stiffness Regulation during Human Running

During human running, short latency stretch reflexes (SLRs) are elicited in the triceps surae muscles, but the function of these responses is still a matter of controversy. As the SLR is primarily mediated by Ia afferent nerve fibres, various methods have been used to examine SLR function by selectively blocking the Ia pathway in seated, standing and walking paradigms, but stretch reflex function has not been examined in detail during running. The purpose of this study was to examine triceps surae SLR function at different running speeds using Achilles tendon vibration to modify SLR size. Ten healthy participants ran on an instrumented treadmill at speeds between 7 and 15 km/h under 2 Achilles tendon vibration conditions: no vibration and 90 Hz vibration. Surface EMG from the triceps surae and tibialis anterior muscles, and 3D lower limb kinematics and ground reaction forces were simultaneously collected. In response to vibration, the SLR was depressed in the triceps surae muscles at all speeds. This coincided with short-lasting yielding at the ankle joint at speeds between 7 and 12 km/h, suggesting that the SLR contributes to muscle stiffness regulation by minimising ankle yielding during the early contact phase of running. Furthermore, at the fastest speed of 15 km/h, the SLR was still depressed by vibration in all muscles but yielding was no longer evident. This finding suggests that the SLR has greater functional importance at slow to intermediate running speeds than at faster speeds

The effects of prospective mate quality on investments in healthy body weight among single women

This paper examines how a single female's investment in healthy body weight is affected by the quality of single males in her marriage market. A principle concern in estimation is the presence of market-level unobserved heterogeneity that may be correlated with changes in single male quality. To address this concern, we employ a differencing strategy that normalizes the exercise behaviors of single women to those of their married counterparts. Our main results suggest that when potential mate quality in a marriage market decreases, single black women invest less in healthy body weight. For example, we find that a ten percentage point increase in the proportion of low quality single black males leads to a 5% to 10% decrease in vigorous exercise taken by single black females. No significant response is found for single white women. These results highlight the relationship between male and female human capital acquisition that is driven by participation in the marriage market. Our results suggest that programs designed to improve the economic prospects of single males may yield positive externalities in the form of improved health behaviors, such as more exercise, particularly for single black females