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Dark matter electron interactions in detector materials
Get PDFDark Matter (DM) makes up 85% of the matter content of the universe, and its gravitational effects are seen on scales ranging from that of cosmology to that of galactic astrophysics. The nature of DM is, however, unknown. Studying DM in the lab is key to understanding its nature. For decades, experiments have been attempting to do this through searches for DM induced nuclear recoils. These have not been found, and a possible reason for this is that the hypothetical DM particle is too light to induce nuclear recoils. Therefore, in the last decade experiments have been built to study DM through electron recoils instead. As the electron is 4 orders of magnitude lighter than the nucleus, electron recoils can be induced by DM down to 4 orders of magnitude lighter than the lightest DM particle probeable with nuclear recoils.In order to understand current and upcoming results from experiments searching for DM induced electron recoils, a theoretical understanding of DM electron scatterings in detector materials is needed. This requires input both from dark matter and material physics, and so far DM electron interactions have only been studied within the dark photon model. In the dark photon model, the DM-electron scattering takes a relatively simple form, and the material responds to the scattering through a single "response function".\ua0Relaxing the assumption of the dark photon model, and instead applying Non-Relativistic Effective Theory approach, we calculate the expected detector signature for a wide range of DM models in Silicon and Germanium. In the papers of this thesis, we find that in contrast to the single response function produced by the dark photon model, the material can respond with 7 different response functions. These novel response functions we show to generically arise in a wide range of DM-electron interactions. As such, the papers of this thesis vastly extends the forms of DM-electron interactions that can be studied in Silicon and Germanium based experiments. These interactions made studyable by the works underlying this thesis are not fringe cases, but generically arise in a wide range of models. To illustrate this we consider a range of simplified models with a DM particle with spin 0, spin 1/2 and spin 1
The Corruption of Co-Design: Political and Social Conflicts in Participatory Design Thinking
No full textDesigners are often depicted as social change agents that serve the good in the world. Similarly, co-design tends to be described as a democratic mode of creativity that is somehow beyond reproach. But is change a virtue in itself, and do participatory practices always produce socially beneficial outcomes?Such questions are becoming more pressing as co-design has emerged as a dominant practice in planning and urban design, while also informing corporate management and public administration. In this book, Otto von Busch and Karl Palm\ue5s suggest that designers tend to overemphasize the place of ideals in design, leaving them ill-equipped to deal with a social world of power-wielding and zero-sum games. Seeking to reorient the concerns of the Scandinavian tradition of participatory design, they suggest that co-design processes are rife with betrayals, decay, and corruption, and that designerly empathy has morphed into a new form of cunning statecraft.In putting forward Realdesign as an alternative conception of design practice, von Busch and Palm\ue5s ask: What hard lessons about the social must today’s designers learn from realists like Machiavelli?Table of Contents1. Introduction: The Problems of Participatory Design\ua0 2. The Realist Challenge: Power and Possibilities\ua0 3. Betrayal: Post-political Participation\ua0 4. Corruption: Design and Decay\ua0 5. Cunning: M\ueatis and Designerly Statecraft\ua0 6. Hypocrisy: of virtue and vice\ua0 7. Closing Propositions: After Empathy, Realdesig
Architectural Knitted Windbreaks for Improved Wind Comfort in the City: A Wind Tunnel Study of Custom-Designed Porous Textile Screens
Get PDFThere is a need to shield from the wind to improve pedestrian comfort in urban environments. Perforated windbreaks, such as fences, vegetation or textile nets, have proven to be an efficient solution, whereas knitted textiles have not yet been explored. The purpose of this study was to evaluate the capacity of knitted textile windbreaks to reduce wind velocities, to inform further research and promote wider architectural applications. Five custom-knitted textile prototypes, representing fragments of textile windbreaks, were tested in a wind tunnel and compared against a perforated and a nonperforated solid board. Forces on the models, as well as upstream and downstream velocities, were measured. The results indicate that the optimal optical porosity of knitted windbreaks should be around 10%, which differs from the porosity for perforated windbreaks recommended by prior studies. Moreover, it was observed that a textile windbreak knitted using the drop-stitch technique efficiently reduces the wind, while not generating a large drag force. Furthermore, the drag coefficient for the knitted windbreak is reduced with increased windspeed. With this, the presented study demonstrates that knitted structures exposed to wind influence have the functional potential of becoming efficient windbreaks, thus improving wind comfort and aesthetic user experience in the urban space
Multilevel Dual Active Bridge Leakage Inductance Selection for Various DC-Link Voltage Spans
Get PDFThe leakage inductance of the transformer in a dual active bridge (DAB) dc–dc converter directly impacts the ac current waveforms and the power factor; thus, it can be considered a design requirement for the transformer. In the existing literature, a choice is made to either ensure soft switching in nominal power or to minimize the RMS current of the transformer. The inductance is typically obtained using optimization procedures. Implementing these optimizations is time-consuming, which can be avoided if a closed-form equation is derived for the optimum leakage inductance. In this paper, analytical formulas are derived to estimate the desired leakage inductance such that the highest RMS value of the current in the operation region of a DAB is kept to its minimum value. The accuracy and sensitivity of the analytical solutions are evaluated. It is shown that in a large design domain, the solution for the YY-connected MFT has a less than 3% error compared to the results obtained from an optimization engine. As an example of the importance of selecting the leakage inductance correctly, it is shown that for 11% deviations in the dc link voltages, a 10% deviation from the desired leakage inductance value can cause 2% higher RMS currents in the converter
Experimental and simulated distribution and interaction of water in cellulose esters with alkyl chain substitutions
Get PDFThis study investigated the effect of the average length of substituted side chains in different cellulose esters on water sorption and the water association mechanism. For this purpose, a set of esters with a similar total degree of substitution was selected: cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Dynamic vapor sorption was used to determine the effect of the side chain length on sorption, desorption, and the occurrence of water clustering. Since water association in the structure was of interest, molecular dynamics simulations were performed on cellulose acetate and cellulose acetate propionate. This study showed that cellulose acetate appears to be water-sensitive and experiences hysteresis upon water sorption, which was attributed to structural changes. The simulations also showed that water is screened out by the side chains and forms intermolecular hydrogen bonds, primarily to the carbonyl oxygen rather than the residual hydroxyl groups
Concluding destructive investigation of a nine-year-old marine-exposed cracked concrete panel
Get PDFThis study undertaken on a nine-year-old cracked concrete panel further investigates the impact of cracks on the corrosion performance of conventional steel reinforcement in marine-exposed concrete to explain observed monitoring data. The present data covers seven 1.80 m long (12.6 m) reinforcing bars embedded in good quality concrete (w/b = 0.40 and cover >75 mm). Each bar was crossed by two horizontal cracks (surface crack widths 0.20–0.30 mm). The investigation showed no corrosion on the surface of the reinforcing bars, in either cracked or uncracked areas. Two of the seven reinforcing bars were instrumented in the vicinity of the cracks. Extensive corrosion was found in the interior of all instrumented parts of these bars. This may explain the monitoring data despite the lack of corrosion on the exterior surface of the two instrumented rebars. However, with no other weaknesses, the remaining conventional rebars showed no impact from the cracks
Combined metabolic activators improve cognitive functions in Alzheimer’s disease patients: a randomised, double-blinded, placebo-controlled phase-II trial
Get PDFBackground: Alzheimer’s disease (AD) is associated with metabolic abnormalities linked to critical elements of neurodegeneration. We recently administered\ua0combined metabolic activators (CMA) to the AD rat model and observed that CMA improves the AD-associated histological parameters in the animals. CMA promotes mitochondrial fatty acid uptake from the cytosol, facilitates fatty acid oxidation in the mitochondria, and alleviates oxidative stress. Methods: Here, we designed a randomised, double-blinded, placebo-controlled phase-II clinical trial and studied the effect of CMA administration on the global metabolism of AD patients. One-dose CMA included 12.35\ua0g L-serine (61.75%), 1\ua0g nicotinamide riboside (5%), 2.55\ua0g\ua0N-acetyl-L-cysteine (12.75%), and 3.73\ua0g L-carnitine tartrate (18.65%). AD patients received one dose of CMA or placebo daily during the first 28\ua0days and twice daily between day 28 and day 84. The primary endpoint was the difference in the cognitive function and daily living activity scores between the placebo and the treatment arms. The secondary aim of this study was to evaluate the safety and tolerability of CMA. A comprehensive plasma metabolome and proteome analysis was also performed to evaluate the efficacy of the CMA in AD patients. Results: We showed a significant decrease of AD Assessment Scale-cognitive subscale (ADAS-Cog) score on day 84 vs day 0 (P = 0.00001, 29% improvement) in the CMA group. Moreover, there was a significant decline (P = 0.0073) in ADAS-Cog scores (improvement of cognitive functions) in the\ua0CMA compared to the placebo group in patients with higher ADAS-Cog scores. Improved cognitive functions in AD patients were supported by the relevant alterations in the hippocampal volumes and cortical thickness based on imaging analysis. Moreover, the plasma levels of proteins and metabolites associated with NAD + and glutathione metabolism were significantly improved after CMA treatment. Conclusion: Our results indicate that treatment of AD patients with CMA can lead to enhanced cognitive functions and improved clinical parameters associated with phenomics, metabolomics, proteomics and imaging analysis. Trial registration\ua0ClinicalTrials.gov NCT04044131 Registered 17 July 2019, https://clinicaltrials.gov/ct2/show/NCT04044131
Polarization in the ELAIS-N1 LOFAR deep field
Get PDFThe physical characteristics of cosmic magnetic fields are encoded in the po- larization properties of the extragalactic radio sources. Linearly polarized radiation undergoes Faraday rotation as it crosses a magneto-ionic medium; the rotation of the polarization angle of the signal is equal to its wavelength squared times the Rotation Measure (RM), that is proportional to the line- of-sight integral of the product of the magnetic field component along the line of sight and the density of thermal electrons. Mapping the values of the RM across the sky provides a mean to constrain cosmic magnetic fields. For this purpose, statistical studies of the properties of polarized radio sources spread over cosmological distances are essential.The advantage of low radio-frequency observations over higher-frequency ones is the better precision on the inferred RM values. On the other hand, at low radio-frequency observations are more affected by depolarization, which affect the detection rate. Indeed, the population of faint polarized extragalac- tic sources at low radio frequencies is still mostly unknown.In this context, the LOw Frequency ARray (LOFAR) plays an important role because of sensitivity, angular resolution and precision on the inferred RM values that can be achieved through low-frequency broad-band polarimetry, allowing us to study the polarized radio emission at frequencies around 150 MHz.In our work, we developed a new method to combine polarimetric obser- vations with slightly different frequency configurations, and we applied this method to the European Large Area ISO Survey-North 1 (ELAIS-N1) deep field, one of the deepest of the LOFAR Two-Meter Sky Survey (LoTSS) Deep Fields so far, at 114.9–177.4 MHz. We imaged an area of 25 deg2 at 6-arcsec of resolution in which, through stacking of 19 8-hour-long epochs, detected 1.28 sources per square degrees, the highest number density of polarized sources ever found at low radio frequencies. We compared our results with other RM catalogs and we quantified the depolarization properties of sources detected also at 1.4 GHz. We also modeled the source counts in polarization from the source counts in total flux density.This work dealt with technical and theoretical challenges inherent to the observation and interpretation of polarimetric data and represents a step in solving complex issues that modern radio astronomy is facing due the large amounts of data generated by new-generation radio-interferometers
Examining the orbital decay targets KELT-9 b, KELT-16 b, and WASP-4 b, and the transit-timing variations of HD 97658 b,
Get PDFContext. Tidal orbital decay is suspected to occur for hot Jupiters in particular, with the only observationally confirmed case of this being WASP-12 b. By examining this effect, information on the properties of the host star can be obtained using the so-called stellar modified tidal quality factor Q′∗, which describes the efficiency with which the kinetic energy of the planet is dissipated within the star. This can provide information about the interior of the star. Aims. In this study, we aim to improve constraints on the tidal decay of the KELT-9, KELT-16, and WASP-4 systems in order to find evidence for or against the presence of tidal orbital decay. With this, we want to constrain the Q′∗ value for each star. In addition, we aim to test the existence of the transit timing variations (TTVs) in the HD 97658 system, which previously favoured a quadratic trend with increasing orbital period. Methods. Making use of newly acquired photometric observations from CHEOPS (CHaracterising ExOplanet Satellite) and TESS (Transiting Exoplanet Survey Satellite), combined with archival transit and occultation data, we use Markov chain Monte Carlo (MCMC) algorithms to fit three models to the data, namely a constant-period model, an orbital-decay model, and an apsidal-precession model. Results. We find that the KELT-9 system is best described by an apsidal-precession model for now, with an orbital decay trend at over 2 σ being a possible solution as well. A Keplerian orbit model with a constant orbital period provides the best fit to the transit timings of KELT-16 b because of the scatter and scale of their error bars. The WASP-4 system is best represented by an orbital decay model at a 5 σ significance, although apsidal precession cannot be ruled out with the present data. For HD 97658 b, using recently acquired transit observations, we find no conclusive evidence for a previously suspected strong quadratic trend in the data