Qualitative System Identification from Imperfect Data

Experience in the physical sciences suggests that the only realistic means of understanding complex systems is through the use of mathematical models. Typically, this has come to mean the identification of quantitative models expressed as differential equations. Quantitative modelling works best when the structure of the model (i.e., the form of the equations) is known; and the primary concern is one of estimating the values of the parameters in the model. For complex biological systems, the model-structure is rarely known and the modeler has to deal with both model-identification and parameter-estimation. In this paper we are concerned with providing automated assistance to the first of these problems. Specifically, we examine the identification by machine of the structural relationships between experimentally observed variables. These relationship will be expressed in the form of qualitative abstractions of a quantitative model. Such qualitative models may not only provide clues to the precise quantitative model, but also assist in understanding the essence of that model. Our position in this paper is that background knowledge incorporating system modelling principles can be used to constrain effectively the set of good qualitative models. Utilising the model-identification framework provided by Inductive Logic Programming (ILP) we present empirical support for this position using a series of increasingly complex artificial datasets. The results are obtained with qualitative and quantitative data subject to varying amounts of noise and different degrees of sparsity. The results also point to the presence of a set of qualitative states, which we term kernel subsets, that may be necessary for a qualitative model-learner to learn correct models. We demonstrate scalability of the method to biological system modelling by identification of the glycolysis metabolic pathway from data

Testing metallicity indicators at z~1.4 with the gravitationally lensed galaxy CASSOWARY 20

We present X-shooter observations of CASSOWARY 20 (CSWA 20), a star-forming (SFR ~6 Msol/yr) galaxy at z=1.433, magnified by a factor of 11.5 by the gravitational lensing produced by a massive foreground galaxy at z=0.741. We analysed the integrated physical properties of the HII regions of CSWA 20 using temperature- and density-sensitive emission lines. We find the abundance of oxygen to be ~1/7 of solar, while carbon is ~50 times less abundant than in the Sun. The unusually low C/O ratio may be an indication of a particularly rapid timescale of chemical enrichment. The wide wavelength coverage of X-shooter gives us access to five different methods for determining the metallicity of CSWA 20, three based on emission lines from HII regions and two on absorption features formed in the atmospheres of massive stars. All five estimates are in agreement, within the factor of ~2 uncertainty of each method. The interstellar medium of CSWA 20 only partially covers the star-forming region as viewed from our direction; in particular, absorption lines from neutrals and first ions are exceptionally weak. We find evidence for large-scale outflows of the interstellar medium (ISM) with speeds of up 750 km/s, similar to the values measured in other high-z galaxies sustaining much higher rates of star formation.Comment: 18 pages, 11 figures, accepted for publication in MNRA

First-principles study of (BiScO3){1-x}-(PbTiO3){x} piezoelectric alloys

We report a first-principles study of a class of (BiScO3)_{1-x}-(PbTiO3)_x (BS-PT) alloys recently proposed by Eitel et al. as promising materials for piezoelectric actuator applications. We show that (i) BS-PT displays very large structural distortions and polarizations at the morphotropic phase boundary (MPB) (we obtain a c/a of ~1.05-1.08 and P_tet of ~1.1 C/m^2); (ii) the ferroelectric and piezoelectric properties of BS-PT are dominated by the onset of hybridization between Bi/Pb-6p and O-2p orbitals, a mechanism that is enhanced upon substitution of Pb by Bi; and (iii) the piezoelectric responses of BS-PT and Pb(Zr_{1-x}Ti_x)O3 (PZT) at the MPB are comparable, at least as far as the computed values of the piezoelectric coefficient d_15 are concerned. While our results are generally consistent with experiment, they also suggest that certain intrinsic properties of BS-PT may be even better than has been indicated by experiments to date. We also discuss results for PZT that demonstrate the prominent role played by Pb displacements in its piezoelectric properties.Comment: 6 pages, with 3 postscript figures embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/ji_bi/index.htm

Eight Weeks of Combined Exercise Training Induced Improvements in Insulin Sensitivity is Associated with Improvement in Aerobic Capacity, but not with Improvement in Strength.

A lifestyle compromised of predominantly sedentary behavior is a risk factor that promotes the development of metabolic syndrome. It has been demonstrated that individuals with blunted insulin sensitivity (IS) and metabolic flexibility (MF) tend to be more prone to develop the disease. An increase in physical activity is recommended in order to prevent cardiovascular disease and type 2 diabetes mellitus. PURPOSE: to determine whether healthy, sedentary, normoglycemic, Mexican American men without a family history of type 2 diabetes are able to improve IS and MF after participating in a combined (aerobic/resistance) exercise intervention. METHODS: Subjects (n=6; 21.83±0.8 years; BMI 28.92 ± 1.6 kg/m2), participated in 8 weeks of combined exercise training three times per week (35 minutes of aerobic training & 45 minutes of resistance training/session). Upper body 1 repetition maximum (1RM) was measured using the flat barbell bench press and lower body 1RM was measured using a back leg strength dynamometer. IS was assessed using the hyperinsulinemic euglycemic clamp (clamp). Insulin dose administered to each subject was set 80mU/m2/min. MF was assessed by determining change in RQ (ΔRQ) at the steady state of the clamp compared to RQ measured at baseline/resting. Participants were provided with standard diet 5 days before pre and post intervention testing in order to control for the effects of diet on insulin sensitivity. Body composition was measured using dual x-ray absorptiometry. RESULTS: IS improved significantly after the 8 weeks of combined exercise training (3.18±0.35 to 3.75±0.34 mg/kg EMBS/min, p=0.05). There was no significant improvement in MF (0.06±0.02 to 0.08±0.02 ∆RER, p=0.19). Body weight significantly increased (3.76%; 81.06±5.38 to 84.11±5.67 kg, p=0.01) with no change in fat mass and a trend to increase in fat free mas (2.8%; 55.92±2.77 to 57.5±2.38 kg, p=0.1). Upper body strength significantly increased (168.3±26.57 to 195±26.04 lb., p=0.001). Lower body strength increased (356.7±46.52 to 428.3±34.51 lb., p=0.02).VO2 max improved significantly (3.90±0.14 to 4.19±0.16 L/min, p=0.037). Improvement in IS was associated with an increase in VO2max (r=0.92, p=0.008) but not with the improvement in strength. Improvement in MF was significantly correlated with fasting glucose (r=-0.83, p=0.04), and an increase in lean mass (r=0.82, p=0.04). CONCLUSION: 8 weeks of combined exercise improves insulin sensitivity in healthy, sedentary, normoglycemic Hispanic men. Improvement in insulin sensitivity is associated with improvement in aerobic fitness but not gain in upper and lower body strength

24 hours of Electrical Pulse Stimulation upregulates GLUT4 and AMPK protein content in human myotubes

Electrical pulse stimulation (EPS), an in vitro exercise mimetic, has been shown to increase mitochondrial and lipid content in cultured human myotubes. We have recently shown that myotubes retain certain in vivo characteristics of the donors. Purpose: We aimed to examine the EPS-induced adaptations in relation to Glucose Transporter Type 4 (GLUT4) and 5’Adenosine Monophosphate-activated Protein Kinase (AMPK) content using human myotubes. Additionally, we examined if the duration of EPS as well as cell harvest times (immediate vs. 24hrs. after the cessation of EPS) plays a role in EPS induced changes in GLUT4 and AMPK content. Methods: EPS was applied to myotubes 24 and 48 hr. (single bipolar pulses of 1 Hz for 2 ms; 30V) and were harvested at two different time points: immediately after (early harvest) and 24hr after (late harvest) the end of stimulation. Total GLUT4 and AMPK content were measured by western immunoblotting. Results: GLUT4 content was ~ 1.7 fold higher after 24 hr. early harvest and ~2.1 fold higher after 48 hr. late harvest stimulation. Total AMPK content was ~3.2 fold higher after 24 hr. early harvest stimulation and ~1.4 fold higher after 48 hr. late harvest stimulation. There was a ~0.6 fold decrease in AMPK after 24 hr. late harvest stimulation. Conclusion: These findings suggest that 24Hr of EPS stimulation upregulates GLUT4 and AMPK protein content. Duration and harvesting time (a reflection of post-exercise recovery) with regards to EPS treatment is a key factor leading to GLUT4 and AMPK content adaptations to exercise in human myotubes

Validation of Quasi-Invariant Ice Cloud Radiative Quantities with MODIS Satellite-Based Cloud Property Retrievals

Similarity relations applied to ice cloud radiance calculations are theoretically analyzed and numerically validated. If t(1v) and t(1vg) are conserved where t is optical thickness, v the single-scattering albedo, and g the asymmetry factor, it is possible that substantially different phase functions may give rise to similar radiances in both conservative and non-conservative scattering cases, particularly in the case of large optical thicknesses. In addition to theoretical analysis, this study uses operational ice cloud optical thickness retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) Level 2 Collection5 (C5) and Collection 6 (C6) cloud property products to verify radiative similarity relations. It is found that, if the MODIS C5 and C6 ice cloud optical thickness values are multiplied by their respective (1wg)factors, the resultant products referred to as the effective optical thicknesses become similar with their ratio values around unity. Furthermore, the ratios of the C5 and C6 ice cloud effective optical thicknesses display an angular variation pattern similar to that of the corresponding ice cloud phase function ratios. The MODIS C5 and C6 values of ice cloud similarity parameter, defined as [(1w)(1(exp. 1/2)wg)]12, also tend to be similar

Increase in Mitochondrial content after Electrical Pulse Stimulation is dependent on duration of stimulation

Increase in Mitochondrial content after Electrical Pulse Stimulation is dependent on duration of stimulation Daniel Conde B.S.1, Jeffrey D. Covington Ph.D.2, Cecilia Gamboa3 George A. King Ph.D.1, Arild C. Rustan Ph.D.4, Sudip Bajpeyi Ph.D.1. 1 Department of Kinesiology, University of Texas at El Paso, TX; 2Louisiana State University Health Sciences Center, New Orleans, LA; 3Clinical Laboratory Sciences, University of Texas at El Paso; 4Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway. Skeletal Muscle Metabolism Laboratory; Kinesiology; University of Texas at El Paso; El Paso, TX Category: Masters Advisor / Mentor: Bajpeyi, Sudip ([email protected]) ABSTRACT We have previously shown that human skeletal muscle myotubes cultured in vitro, retain in vivo characteristics of the donors. Recent studies indicate that electrical pulse stimulation (EPS) can be used as an exercise mimetic in a cell culture model, and could be beneficial to understand molecular mechanisms underlying exercise training. Purpose: The purpose of this study was to compare acute, moderate and long duration EPS treatments on mitochondrial and lipid content in cultured myotubes. Methods: EPS stimulation was applied to human myotubes cultured from sedentary donors under three conditions: Acute (bipolar pulses of 100 Hz for 200 ms every 5th second; 30V for 60 min) and chronic stimulation (single bipolar pulses of 2 ms; 30V, 1Hz continuously for 24 h or 48 h). Mitochondrial and lipid contents were measured by primary antibody for complex IV and bodipy green dye, respectively, using immunohistochemistry techniques. Fluoroskan ascent microplate reader was used to quantify fluorescence signals. OXPHOS proteins were measured using western immunoblotting. Results: There was no change in lipid or mitochondrial content as assessed by immunohistochemistry after acute EPS stimulation. Chronic stimulation resulted in a significant increase in the mitochondrial content after 24 h (from 0.183 ± 0.02 AU to 0.350 ± 0.03 AU; p=0.008) and 48 h (from 0.290 ± 0.01 AU to 0.337 ± 0.01 AU; p=0.02) of continuous EPS stimulation. OXPHOS proteins increased after 48 h of EPS. There was also a significant increase in lipid content after 48 h of EPS stimulation (from 0.210 ± 0.01 AU to 0.256 ± 0.01 AU; p=0.02). Conclusion: These findings suggest that 48 h of chronic EPS results in an increase in both mitochondrial and lipid contents in human myotubes. The concomitant increase in lipid and mitochondrial content after exercise mimetic EPS stimulation supports the elevated level of intramyocellular lipid and mitochondrial content evident in endurance trained athletes

X-ray reflection in a sample of X-ray bright Ultraluminous X-ray sources

We apply a reflection-based model to the best available XMM-Newton spectra of X-ray bright UltraLuminous X-ray (ULX) sources (NGC 1313 X-1, NGC 1313 X-2, M 81 X-6, Holmberg IX X-1, NGC 5408 X-1 and Holmberg II X-1). A spectral drop is apparent in the data of all the sources at energies 6-7 keV. The drop is interpreted here in terms of relativistically-blurred ionized reflection from the accretion disk. A soft-excess is also detected from these sources (as usually found in the spectra of AGN), with emission from O K and Fe L, in the case of NGC 5408 X-1 and Holmberg II X-1, which can be understood as features arising from reflection of the disk. Remarkably, ionized disk reflection and the associated powerlaw continuum provide a good description of the broad-band spectrum, including the soft-excess. There is no requirement for thermal emission from the inner disk in the description of the spectra. The black holes of these systems must then be highly spinning, with a spin close to the maximum rate of a maximal spinning black hole. The results require the action of strong light bending in these sources. We suggest that they could be strongly accreting black holes in which most of the energy is extracted from the flow magnetically and released above the disc thereby avoiding the conventional Eddington limit.Comment: Accepted for publication in MNRA

Hinge for Use in a Tension Stiffened and Tendon Actuated Manipulator

A tension stiffened and tendon actuated manipulator is provided performing robotic-like movements when acquiring a payload. The manipulator design can be adapted for use in-space, lunar or other planetary installations as it is readily configurable for acquiring and precisely manipulating a payload in both a zero-g environment and in an environment with a gravity field. The manipulator includes a plurality of link arms, a hinge connecting adjacent link arms together to allow the adjacent link arms to rotate relative to each other and a cable actuation and tensioning system provided between adjacent link arms. The cable actuation and tensioning system includes a spreader arm and a plurality of driven and non-driven elements attached to the link arms and the spreader arm. At least one cable is routed around the driven and non-driven elements for actuating the hinge