Effects of Compton scattering on the neutron star radius constraints in rotation-powered millisecond pulsars

The aim of this work is to study the possible effects and biases on the radius constraints for rotation-powered millisecond pulsars when using Thomson approximation to describe electron scattering in the atmosphere models, instead of using exact formulation for Compton scattering. We compare the differences between the two models in the energy spectrum and angular distribution of the emitted radiation. We also analyse a self-generated synthetic phase-resolved energy spectrum, based on Compton atmosphere and the most X-ray luminous rotation-powered millisecond pulsars observed by the Neutron star Interior Composition ExploreR (NICER). We derive constraints for the neutron star parameters using both the Compton and Thomson models. The results show that the method works by reproducing the correct parameters with the Compton model. However, biases are found in size and the temperature of the emitting hot spot, when using the Thomson model. The constraints on the radius are still not significantly changed, and therefore the Thomson model seems to be adequate if we are interested only in the radius measurements using NICER.Comment: 6 pages, 9 figures, published in A&

Estimate of convection-diffusion coefficients from modulated perturbative experiments as an inverse problem

The estimate of coefficients of the Convection-Diffusion Equation (CDE) from experimental measurements belongs in the category of inverse problems, which are known to come with issues of ill-conditioning or singularity. Here we concentrate on a particular class that can be reduced to a linear algebraic problem, with explicit solution. Ill-conditioning of the problem corresponds to the vanishing of one eigenvalue of the matrix to be inverted. The comparison with algorithms based upon matching experimental data against numerical integration of the CDE sheds light on the accuracy of the parameter estimation procedures, and suggests a path for a more precise assessment of the profiles and of the related uncertainty. Several instances of the implementation of the algorithm to real data are presented.Comment: Extended version of an invited talk presented at the 2012 EPS Conference. To appear in Plasma Physics and Controlled Fusio

To Reframe a Constitution: Public Service in a Consumptive State

This normative analysis builds upon Ulrich Beck\u27s world risk society theory to argue that the United States is making a shift of revolutionary proportions from an administrative state to a consumptive state. Public administration theory is assessed for its ability to address a consumptive state\u27s unprecedented dynamics, e.g., accelerating technoscientific development and mega-hazards such as global warming. Qualitative evidence suggests that the field\u27s adaptability has been limited by a continued, if generally unacknowledged, embrace of obsolete normative commitments such as to a politics-technoscience dichotomy, contempocentrism, and overconsumption. The sustainability movement, a discourse coalition with roots largely outside public administration, is presented as having the greatest potential of transcending the field\u27s limitations if it avoids cooptation by a technocratic mindset. Institutional implications of knowledge production are critiqued and reforms suggested. A new school of thought is sketched - sustainable public service - that imports sustainability principles into public administration educatio

Bayesian parameter constraints for neutron star masses and radii using X-ray timing observations of accretion-powered millisecond pulsars

We present a Bayesian method to constrain the masses and radii of neutron stars (NSs) using the information encoded in the X-ray pulse profiles of accreting millisecond pulsars. We model the shape of the pulses using "oblate Schwarzschild" approximation, which takes into account the deformed shape of the star together with the special and general relativistic corrections to the photon trajectories and angles. The spectrum of the radiation is obtained from an empirical model of Comptonization in a hot slab in which a fraction of seed blackbody photons is scattered into a power-law component. By using an affine-invariant Markov chain Monte Carlo ensemble sampling method, we obtain posterior probability distributions for the different model parameters, especially for the mass and the radius. To test the robustness of our method, we first analyzed self-generated synthetic data with known model parameters. Similar analysis was then applied for the observations of SAX J1808.4-3658 by the Rossi X-ray Timing Explorer (RXTE). The results show that our method can reproduce the model parameters of the synthetic data, and that accurate constraints for the radius can be obtained using the RXTE pulse profile observations if the mass is a priori known. For a mass in the range 1.5-1.8 Msun, the radius of the NS in SAX J1808.4-3658 is constrained between 9 and 13 km. If the mass is accurately known, the radius can be determined with an accuracy of 5% (68% credibility). For example, for the mass of 1.7 Msun the equatorial radius is Req = 11.9+0.5 -0.4 km. Finally, we show that further improvements can be obtained when the X-ray polarization data from the Imaging X-ray Polarimeter Explorer will become available.Comment: 16 pages, 9 figures, published in A&

Modeling heat transfer from quench protection heaters to superconducting cables in Nb3Sn magnets

We use a recently developed quench protection heater modeling tool for an analysis of heater delays in superconducting high-field Nb3Sn accelerator magnets. The results suggest that the calculated delays are consistent with experimental data, and show how the heater delay depends on the main heater design parameters.Comment: 8 pages, Contribution to WAMSDO 2013: Workshop on Accelerator Magnet, Superconductor, Design and Optimization; 15 - 16 Jan 2013, CERN, Geneva, Switzerlan

Kinematic Constraints on Formation of Bound States of Cosmic Strings - Field Theoretical Approach

Superstring theory predicts the potential formation of string networks with bound states ending in junctions. Kinematic constraints for junction formation have been derived within the Nambu-Goto thin string approximation. Here we test these constraints numerically in the framework of the Abelian-Higgs model in the Type-I regime and report on good agreement with the analytical predictions. We also demonstrate that strings can effectively pass through each other when they meet at speeds slightly above the critical velocity permitting bound state formation. This is due to reconnection effects that are beyond the scope of the Nambu-Goto approximation.Comment: 6 pages, 12 eps figures - matches the published versio

The “Open Innovation” paradigm: A contingency perspective

The “open innovation” model is currently being touted as a superior path for achieving long-term success. Rather than relying on their own, limited resources for research and development in the traditional, closed invention system, firms are encouraged to share knowledge across firm boundaries to enhance their innovative potential. Yet, such sharing may also have adverse consequences by reducing the rarity of a firm’s inventions. This paper accordingly attempts to identify and analyze the parameters that determine whether open or closed types of innovation management are most appropriate for a given firm. Following a contingency perspective, we examine these determinants as various internal and external constraints (situational factors). More specifically, applying concepts related to absorptive capacity, complementary resources, game theory and others, we derive testable propositions and provide case study evidence regarding the value generating properties of open innovation.Peer Reviewe

Homekasvuston mittaaminen ioniliikkuvuusspektrometrillä

Tiivistelmä. Tässä diplomityössä tutkittiin, soveltuuko ioniliikkuvuusspektrometria homeen tunnistukseen sisäilmaa mittaamalla. Mikrobiologisille epäpuhtauksille altistumisella on todettu olevan terveysvaikutuksia. Tästä syystä on tärkeää havaita mahdolliset epäpuhtaudet sisäilmasta. Tutkimusta varten kehitettiin mittausjärjestelmä ja testattiin differentiaalista ioniliikkuvuusspektrometriä ja sen käyttöä sisäilma-anturina. Työssä käsiteltiin anturin teoriaa sähkötekniikan ja elektroniikan näkökulmasta. Aikaisempien tutkimusten perusteella selvitettiin homeiden aineenvaihduntatuotteista sellaisia yhdisteitä, joiden avulla homeita voitaisiin tunnistaa sisäilmaa mittaamalla. Tutkimuksen kohteena oli Stachybotrys chartarum-home, jota kasvatettiin kipsilevyllä mittauksia varten. Työssä testattiin anturin ja mittasysteemin kykyä tunnistaa aineenvaihduntatuotteita. Alustavien tulosten perusteella vaikuttaa siltä, että differentiaalista ioniliikkuvuusspektrometria voidaan käyttää tunnistamaan aktiivinen mikrobikasvusto kipsilevyltä. Työssä käytetyn mittausjärjestelmän näytteenottoa tulee jatkokehittää. Tämä työ antaa pohjan ioniliikkuvuusspektrometriin perustuvan mittajärjestelmän jatkokehittämiselle homekasvuston havaitsemiseen.Mold detection with ion mobility spectrometry. Abstract. The suitability of ion mobility spectrometry was investigated in this thesis for detection of molds by measuring indoor air. Exposure to microbial pollutants have been associated with health effects. It is important to detect potential contaminants for that reason. A measurement system was developed and differential ion mobility spectrometry was tested as an indoor air quality sensor. The sensor theory was explored from the perspective of electrical engineering. Based on previous studies, metabolic compounds that could be used to identify molds by measuring indoor air was investigated. The subject of the study was Stachybotrys chartarum-mold and it was cultivated on a plasterboard for test measurements. The ability of the sensor and measuring system to detect metabolic products was tested in the work. Based on preliminary results, differential ion mobility spectrometer can be used to detect microbial growth on plasterboard. The sampling of the measurement system used in the work must be further developed. This thesis provides a basis for the further development of a measurement system based on ion mobility spectrometry for detecting mold growth