CONTINUOUS MONITORING OF THE GALVANIC SKIN RESPONSE

poster abstractGalvanic Skin Response (GSR) is an objective measurement of the electrical conductance of the skin. GSR is tightly correlated with peripheral sweat rate, which in turn is associated with many clinical conditions. These conditions include, but are not limited to, menopausal “hot flashes”, diabetic hypoglycemic and hyperglycemic episodes, and various cancers. The objective quantification of GSR can be a valuable clinical tool in evaluating the effectiveness of clinical interventions for these and other conditions. Current methods of monitoring GSR are not well suited to implementation outside of the clinical setting. The goal of this research is to develop a reliable portable device for real-time ambulatory monitoring of GSR. In order to get accurate and consistent readings, electrodes must be attached to the patient with a lasting and non-irritating electrically conductive gel with suitable impedance characteristics. Development of such a device requires consideration of many physiological factors. The distribution and density of sweat glands must be considered to determine a location for the device on the body that will yield measurable GSR without interfering with the patient’s daily activities. We are in the process of evaluating the electrical impedance of electrode and gel combinations presently used in the Carpenter lab. Quantification of the frequency dependent loading profile of the electrode-gel interface will improve the measurement accuracy of the GSR. The ionic composition of sweat and the sweat rate must be evaluated to ensure that the integrity of the interface between the body and the device is maintained throughout the monitoring period. 1Department of Biomedical Engineering, Purdue School of Engineering and Technology, Indiana University-Purdue University Indianapolis, IN 46204 2Center for Enhancing Quality of Life, Indiana University School of Nursing, IUPUI, Indianapolis, IN 4620

Discovery of a candidate protoplanetary disk around the embedded source IRc9 in Orion

We report the detection of spatially-extended mid-infrared emission around the luminous embedded star IRc9 in OMC-1, as seen in 8.8, 11.7, and 18.3 micron images obtained with T-ReCS on Gemini South. The extended emission is asymmetric, and the morphology is reminiscent of warm dust disks around other young stars. The putative disk has a radius of roughly 1.5 arcsec (700 AU), and a likely dust mass of almost 10 Earth masses. The infrared spectral energy distribution of IRc9 indicates a total luminosity of about 100 Lsun, implying that it shall become an early A-type star when it reaches the main sequence. Thus, the candidate disk around IRc9 may be a young analog of the planetary debris disks around Vega-like stars and the disks of Herbig Ae stars, and may provide a laboratory in which to study the earliest phases of planet formation. A disk around IRc9 may also add weight to the hypothesis that an enhanced T Tauri-like wind from this star has influenced the molecular outflow from the OMC-1 core.Comment: 7 pages, 2 figs, Accepted by ApJ Letter

Automated Quantitative Analysis of Nerve Fiber Conduction Velocity

poster abstractThe baroreflex (BRX) is essential for reliable autonomic control of arterial blood pressure. Central to BRX function is a rapid, negative feedback control of heart rate. Arterial pressure sensors known as baroreceptors (BR) encode heart rate and blood pressure information into patterns of neural discharge that is conveyed to the central nervous system via a network of sensory afferent nerve fibers. These BR fibers are broadly classified as myelinated A-fibers with diameters in the range of 1-10 μm and unmyelinated Cfibers with diameters typically less than 1 μm. Fiber diameter and conduction velocity are related with the large A-fibers being much faster (> 10 m/sec) than the smaller diameter C-fibers (< 1 m/sec). Recently, our lab has documented an additional phenotype of myelinated BR afferents termed Ah-fibers that are notably present in female; but only rarely observed in male rats. In response to an electrical stimulus, the nerve fibers produce a compound action potential (CAP) that propagates away from the stimulation site. The CAP of each fiber type is observable in the evoked waveform on account of the differing conduction velocities. As Ah-fibers have conduction velocities in the range of 10 m/sec - 2 m/sec, the resulting CAP is clearly separated in time from the faster A-fibers and much slower C-fibers. Root-mean-square analysis of these distinct time segments provides a quantitative measure of the total signal energy from each of the A-, Ah-, and C-type fibers. This project sought to create MATLAB scripts that would import nerve recording files from both male and female rats and automate the energy analysis in an efficient and reliable manner. Doing so not only facilitates the analysis of these large data files, but also reduces the possibility for biases and errors that can occur during a manual measurement of nerve activity

ROLE OF SWEAT GLAND PHYSIOLOGY IN OBJECTIVE GALVANIC SKIN RE-SPONSE MEASUREMENT

poster abstractFor the purpose of studying sweat in response to hot flashes, a type of thermal sweating, the process of extensive literature review performed in this particular project focused primarily on the eccrine sweat glands. Of the three categories of sweat glands, eccrine sweat glands account for the ma-jority of the sweat glands on the human body, existing over almost the en-tire body surface, and contributing to thermal sweating. Thermal sweating occurs as a means for the human body to regulate temperature (Johnson 1996). There are approximately 1.6 to 5 million eccrine sweat glands dis-tributed over the surface of the human body. Sweat gland density varies across different regions of the body, with the highest density on the palms of hands and soles of feet, while the lowest sweat gland density of 64 sweat glands per square centimeter is found on the back (Wilke et al., 2007). Wa-ter comprises approximately 99% of eccrine sweat, with the remaining com-pounds consisting mostly of varying amounts of sodium, potassium, calcium, and magnesium (Groscurth, 2002). The Galvanic Skin Response is an objec-tive measure of skin conductance that has been linked with the peripheral sweat rate (Carpenter et al., 2005). Importance has been put upon the po-tential clinical significance of using the Galvanic Skin Response to objectively enumerate the influence and effectiveness of interventions for health related issues in which sweating is a substantial symptom (Tataryn et al., 1981). One of the objectives of this research is to determine the effect that various sweat gland physiological factors, such as density, ionic composition, and sweat rate, may have on the accuracy of different Galvanic Skin Response measurement techniques and devices. 1Center for Enhancing Quality of Life, Indiana University School of Nursing, IUPUI, Indian-apolis, IN 4620

Analysis of Heart Rate Variability in Male and Female Rats

poster abstractHeart disease is the leading cause of death in the United States. Quantitative measures of cardiovascular function are often essential to effective clinical interventions. The QRS complex is one such measure widely used by cardiologists. These analyses can involve subtle changes in the magnitude and time course of the QRS complex, to differences in the timing between successive heart beats. Electrocardiograms (ECG) are continuous recordings of the QRS complex at various locations across the body surface and provide a comprehensive measurement of the electrical activity of the heart. Knowledge obtained from investigating ECG signal characteristics can help the cardiologist diagnose possible health or cardiac abnormalities such as arrhythmias and can provide objective measures of heart health following injury such as myocardial infarction. Heart rate variability (HRV) can also serve as a reliable indicator of heart health and has been shown to be a strong indicator of mortality and morbidity following myocardial infarction. Unfortunately, very little is known concerning the neurophysiological mechanisms underlying HRV beyond the broader impact of the autonomic nervous system and associated neurocirculatory reflexes. In this research project, we first implemented several established methods for quantifying HRV in male and female rats such as calculating the power spectral density of a long time series of HRV measures, and calculating the standard deviation of the averages of all beat-to-beat intervals in the recording. These measures compared well to those in the literature supporting the accuracy and reliability of the Matlab scripts created to process these data. Simultaneous recordings of the QRS complex and femoral arterial pressure (BP) provided the opportunity to determine how well BP recordings could be used to quantify HRV. In addition, HRV measurements were compared across populations of male and normal, cycling (OVI) and ovariectomized (OVX) female rats in order to determine if HRV is sexually dimorphic. Mentors: John H. Schild, Grace Santa Cruz Chavez, Department of Biomedical Engineering, Purdue School of Engineering and Technology, IUPUI, Indianapolis, I

An afferent explanation for sexual dimorphism in the aortic baroreflex of rat

Sex differences in baroreflex (BRx) function are well documented. Hormones likely contribute to this dimorphism, but many functional aspects remain unresolved. Our lab has been investigating a subset of vagal sensory neurons that constitute nearly 50% of the total population of myelinated aortic baroreceptors (BR) in female rats but less than 2% in male rats. Termed “Ah,” this unique phenotype has many of the nonoverlapping electrophysiological properties and chemical sensitivities of both myelinated A-type and unmyelinated C-type BR afferents. In this study, we utilize three distinct experimental protocols to determine if Ah-type barosensory afferents underlie, at least in part, the sex-related differences in BRx function. Electron microscopy of the aortic depressor nerve (ADN) revealed that female rats have less myelin (P < 0.03) and a smaller fiber cross-sectional area (P < 0.05) per BR fiber than male rats. Electrical stimulation of the ADN evoked compound action potentials and nerve conduction profiles that were markedly different (P < 0.01, n = 7 females and n = 9 males). Selective activation of ADN myelinated fibers evoked a BRx-mediated depressor response that was 3–7 times greater in female (n = 16) than in male (n = 17) rats. Interestingly, the most striking hemodynamic difference was functionally dependent upon the rate of myelinated barosensory fiber activation. Only 5–10 Hz of stimulation evoked a rapid, 20- to 30-mmHg reduction in arterial pressure of female rats, whereas rates of 50 Hz or higher were required to elicit a comparable depressor response from male rats. Collectively, our experimental results are suggestive of an alternative myelinated baroreceptor afferent pathway in females that may account for, at least in part, the noted sex-related differences in autonomic control of cardiovascular function

The Century Survey: A Deeper Slice of the Universe

The ``Century Survey'' (CS hereafter) is a complete redshift survey of a 1$^\circ$-wide strip. It covers 0.03 steradians to a limiting m$_R$ = 16.13. The survey is 98.4% complete and contains 1762 galaxies. Large-scale features in the survey are qualitatively similar to those in other surveys: there are large voids surrounded or nearly surrounded by thin dense regions which are sections of structures like (and including) the Great Wall. The survey crosses the classical Corona Borealis supercluster. The galaxy density enhancement associated with this system extends for \simgreat 100 h^{-1} Mpc (the Hubble constant is H$_0 = 100h$ km s$^{-1}$Mpc$^{-1}$). The Schechter (1976) luminosity function parameters for the CS are: $M^*_{CS} = -20.73 ^{+0.17}_{-0.18}$, $\alpha_{CS} = -1.17 ^{+0.19}_{-0.19}$, and $\phi^*_{CS} = 0.0250\pm0.0061$ Mpc$^{-3}$mag$^{-1}$. In concert with the ESO Key Program (\cite{vet97}; \cite{zuc97}) and the AUTOFIB (\cite{ell96}) surveys, the CS indicates that the absolute normalization of the luminosity function exceeds estimates based on shallower and/or sparser surveys.Comment: 19 pages, 3 figures, 1 plate. The plate is substituted by a color lineplot in the preprint. AASTeX. To appear in tje December 1997 Astronomical Journa

New Rotation Periods in the Pleiades: Interpreting Activity Indicators

We present results of photometric monitoring campaigns of G, K and M dwarfs in the Pleiades carried out in 1994, 1995 and 1996. We have determined rotation periods for 18 stars in this cluster. In this paper, we examine the validity of using observables such as X-ray activity and amplitude of photometric variations as indicators of angular momentum loss. We report the discovery of cool, slow rotators with high amplitudes of variation. This contradicts previous conclusions about the use of amplitudes as an alternate diagnostic of the saturation of angular momentum loss. We show that the X-ray data can be used as observational indicators of mass-dependent saturation in the angular momentum loss proposed on theoretical grounds