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KURVS: the outer rotation curve shapes and dark matter fractions of z ∼1.5 star-forming galaxies
Full text linkWe present first results from the KMOS Ultra-deep Rotation Velocity Survey (KURVS), aimed at studying the outer rotation curves shape and dark matter content of 22 star-forming galaxies at z ∼1.5. These galaxies represent \u27typical\u27 star-forming discs at z ∼1.5, being located within the star-forming main sequence and stellar mass-size relation with stellar masses 9.5 ≤ log(M*/M⊙) ≤ 11.5. We use the spatially resolved H α emission to extract individual rotation curves out to 4 times the effective radius, on average, or ∼10-15 kpc. Most rotation curves are flat or rising between three and six disc scale radii. Only three objects with dispersion-dominated dynamics (vrot/σ0 ∼0.2) have declining outer rotation curves at more than 5σ significance. After accounting for seeing and pressure support, the nine rotation-dominated discs with vrot/σ0 ≥ 1.5 have average dark matter fractions of at the effective radius, similar to local discs. Together with previous observations of star-forming galaxies at cosmic noon, our measurements suggest a trend of declining dark matter fraction with increasing stellar mass and stellar mass surface density at the effective radius. Measurements of simulated EAGLE galaxies are in quantitative agreement with observations up to log, and overpredict the dark matter fraction of galaxies with higher mass surface densities by a factor of ∼3. We conclude that the dynamics of typical rotationally-supported discs at z ∼1.5 is dominated by dark matter from effective radius scales, in broad agreement with cosmological models. The tension with observations at high stellar mass surface density suggests that the prescriptions for baryonic processes occurring in the most massive galaxies (such as bulge growth and quenching) need to be reassessed
Integrating InP MMICs and Silicon Micromachined Waveguides for sub-THz Systems
No full textA novel co-designed transition from InP monolithic microwave integrated circuits to silicon micromachined waveguides is presented. The transition couples a microstrip line to a substrate waveguide sitting on top of a vertical waveguide. The silicon part of the transition consists of a top and a bottom chip, fabricated in a very low-loss silicon micromachined waveguide technology using silicon on insulator wafers. The transition has been designed, fabricated and characterized for 220-330 GHz in a back-to-back configuration. Measured insertion loss is 3-6 dB at 250-300 GHz, and return loss is in excess of 5 dB
Fast, Verified Computation for Candle
Full text linkThis paper describes how we have added an efficient function for computation to the kernel of the Candle interactive theorem prover. Candle is a CakeML port of HOL Light which we have, in prior work, proved sound w.r.t. the inference rules of the higher-order logic. This paper extends the original implementation and soundness proof with a new kernel function for fast computation. Experiments show that the new computation function is able to speed up certain evaluation proofs by several orders of magnitude
CO enhancement by magnetohydrodynamic waves. Striations in the Polaris Flare
No full textContext. The formation of molecular gas in interstellar clouds is a slow process, but can be enhanced by gas compression. Magneto-hydrodynamic (MHD) waves can create compressed quasi-periodic linear structures, referred to as striations. Striations are observed at the column densities at which the transition from atomic to molecular gas takes place. Aims: We explore the role of MHD waves in the CO chemistry in regions with striations within molecular clouds. Methods: We targeted a region with striations in the Polaris Flare cloud. We conducted a CO J = 2−1 survey in order to probe the molecular gas properties. We used archival starlight polarization data and dust emission maps in order to probe the magnetic field properties and compare against the CO morphological and kinematic properties. We assessed the interaction of compressible MHD wave modes with CO chemistry by comparing their characteristic timescales. Results: The estimated magnetic field is 38-76 \ub5G. In the CO integrated intensity map, we observe a dominant quasiperiodic intensity structure that tends to be parallel to the magnetic field orientation and has a wavelength of approximately one parsec. The periodicity axis is ~17\ub0 off from the mean magnetic field orientation and is also observed in the dust intensity map. The contrast in the CO integrated intensity map is ~2.4 times higher than the contrast of the column density map, indicating that CO formation is enhanced locally. We suggest that a dominant slow magnetosonic mode with an estimated period of 2.1-3.4 Myr and a propagation speed of 0.30-0.45 km s−1 is likely to have enhanced the formation of CO, hence created the observed periodic pattern. We also suggest that within uncertainties, a fast magnetosonic mode with a period of 0.48 Myr and a velocity of 2.0 km s−1 could have played some role in increasing the CO abundance. Conclusions: Quasiperiodic CO structures observed in striation regions may be the imprint of MHD wave modes. The Alfv\ue9nic speed sets the dynamical timescales of the compressible MHD modes and determines which wave modes are involved in the CO chemistry
Joint User Localization and Location Calibration of A Hybrid Reconfigurable Intelligent Surface
No full textThe recent research in the emerging technology of reconfigurable intelligent surfaces (RISs) has identified its high potential for localization and sensing. However, to accurately localize a user placed in the area of influence of an RIS, the RIS location needs to be known a priori and its phase profile is required to be optimized for localization. In this paper, we study the problem of the joint localization of a hybrid RIS (HRIS) and a user, considering that the former is equipped with a single reception radio-frequency (RF) chain enabling simultaneous tunable reflections and sensing via power splitting. Focusing on the downlink of a multi-antenna base station, we present a multi-stage approach for the estimation of the HRIS position and orientation as well as the user position. Our simulation results, including comparisons with the Cram\ue9r-Rao lower bounds, demonstrate the efficiency of the proposed localization approach, while showcasing that there exists an optimal HRIS power splitting ratio for the desired multi-parameter estimation problem
Stream Aggregation with Compressed Sliding Windows
Full text linkHigh performance stream aggregation is critical for many emerging applications that analyze massive volumes of data. Incoming data needs to be stored in a sliding window during processing, in case the aggregation functions cannot be computed incrementally. Updating the window with new incoming values and reading it to feed the aggregation functions are the two primary steps in stream aggregation. Although window updates can be supported efficiently using multi-level queues, frequent window aggregations remain a performance bottleneck as they put tremendous pressure on the memory bandwidth and capacity. This article addresses this problem by enhancing StreamZip, a dataflow stream aggregation engine that is able to compress the sliding windows. StreamZip deals with a number of data and control dependency challenges to integrate a compressor in the stream aggregation pipeline and alleviate the memory pressure posed by frequent aggregations. In addition, StreamZip incorporates a caching mechanism for dealing with skewed-key distributions in the incoming data stream. In doing so, StreamZip offers higher throughput as well as larger effective window capacity to support larger problems. StreamZip supports diverse compression algorithms offering both lossless and lossy compression to integers as well as floating-point numbers. Compared to designs without compression, StreamZip lossless and lossy designs achieve up to 7.5
7 and 22
7 higher throughput, while improving the effective memory capacity by up to 5
7 and 23
7, respectively
Filtration of Microcrystalline and Microfibrillated Cellulose: The impact of ions and electric field
Full text linkDewatering plays an essential role in the processing of microcrystalline cellulose (MCC) and microfibrillated cellulose (MFC), as their commercial attractiveness in many applications is limited by the high water content of the products. Filtration is the most common mechanical dewatering technique, but the filtration of these materials results in filter cakes with high filtration resistance. Therefore, the process needs to be modified to make a viable option; this thesis presents two types of such modifications. In one study, the electrostatic repulsive interactions between MCC particles were altered by the addition of NaCl (0.1-1.0 g/L) during dead-end filtration. The addition of ions resulted in the agglomeration of MCC, which was confirmed by focused beam reflectance measurements, and a reduction in the average as well as local filtration resistance.Electro-assisted filtration, in which an electric field is applied across part of the filter chamber, was used to dewater two types of MFC: one produced via 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation of dissolving pulp and one commercially available. Regardless of the MFC type, a clear improvement in the dewatering rate was observed when pressure and electric field were combined. This was also observed with molecular dynamic (MD) simulations, which related it to the electro-osmotic flow of water and the electrophoresis of the negatively charged MFC towards the anode.Filter cakes with a channelled structure were formed, which may have contributed to the accelerated dewatering rate. This structure was especially pronounced for the TEMPO-oxidised MFC, and it was found that the microfibrils were partially oriented in the direction of the electric field by studying the structures using X-ray scattering and scanning electron microscopy.After dewatering, a slight reduction in the water retention value and viscoelastic properties of the MFC was observed. This may be attributed to a reduction in the total surface area, plausibly due to aggregation of the microfibrils and/or reshaping of the microfibrils/fibril bundles
Substrate-Less Vertical Chip-to-Waveguide Transition for W-Band Array Antenna Integration
No full textThis paper presents a vertical transition from a high permittivity GaAs MMIC to rectangular waveguide using bondwires as a coupling structure. The transition is advantageous for the direct integration of any off-the-shelf chip into a waveguide antenna since no modification of the GSG-pad or additional substrate is needed. An EBG structure consisting of pins is used for the packaging of the chip in order to avoid field propagation in undesired directions. The simulations results show that the reflection coefficient is lower than -10 dB and the average insertion loss is better than 0.5 dB from around 87 to 101 GHz (14% relative bandwidth)
Nonadiabatic Nuclear-Electron Dynamics: A Quantum Computing Approach
No full textCoupled quantum electron-nuclear dynamics is oftenassociatedwith the Born-Huang expansion of the molecular wave functionand the appearance of nonadiabatic effects as a perturbation. On theother hand, native multicomponent representations of electrons andnuclei also exist, which do not rely on any a priori approximation.However, their implementation is hampered by prohibitive scaling.Consequently, quantum computers offer a unique opportunity for extendingtheir use to larger systems. Here, we propose a quantum algorithmfor simulating the time-evolution of molecular systems and apply itto proton transfer dynamics in malonaldehyde, described as a rigidscaffold. The proposed quantum algorithm can be easily generalizedto include the explicit dynamics of the classically described molecularscaffold. We show how entanglement between electronic and nucleardegrees of freedom can persist over long times if electrons do notfollow the nuclear displacement adiabatically. The proposed quantumalgorithm may become a valid candidate for the study of such phenomenawhen sufficiently powerful quantum computers become available