다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The dark energy plus cold dark matter ($\Lambda$CDM) cosmological model has been a demonstrably successful framework for predicting and explaining the large-scale structure of Universe and its evolution with time. Yet on length scales smaller than $\sim 1$ Mpc and mass scales smaller than $\sim 10^{11} M_{\odot}$, the theory faces a number of challenges. For example, the observed cores of many dark-matter dominated galaxies are both less dense and less cuspy than naively predicted in $\Lambda$CDM. The number of small galaxies and dwarf satellites in the Local Group is also far below the predicted count of low-mass dark matter halos and subhalos within similar volumes. These issues underlie the most well-documented problems with $\Lambda$CDM: Cusp/Core, Missing Satellites, and Too-Big-to-Fail. The key question is whether a better understanding of baryon physics, dark matter physics, or both will be required to meet these challenges. Other anomalies, including the observed planar and orbital configurations of Local Group satellites and the tight baryonic/dark matter scaling relations obeyed by the galaxy population, have been less thoroughly explored in the context of $\Lambda$CDM theory. Future surveys to discover faint, distant dwarf galaxies and to precisely measure their masses and density structure hold promising avenues for testing possible solutions to the small-scale challenges going forward. Observational programs to constrain or discover and characterize the number of truly dark low-mass halos are among the most important, and achievable, goals in this field over then next decade. These efforts will either further verify the $\Lambda$CDM paradigm or demand a substantial revision in our understanding of the nature of dark matter.

Small-Scale Challenges to the $\Lambda$CDM Paradigm.

心臓病診療プラクティス 16. 心不全を癒す

The dark energy plus cold dark matter (ΛCDM) cosmological model has been a demonstrably successful framework for predicting and explaining the large-scale structure of the Universe and its evolution with time. Yet on length scales smaller than ∼1 Mpc and mass scales smaller than ∼1011M⊙, the theory faces a number of challenges. For example, the observed cores of many dark matter–dominated galaxies are both less dense and less cuspy than naively predicted in ΛCDM. The number of small galaxies and dwarf satellites in the Local Group is also far below the predicted count of low-mass dark matter halos and subhalos within similar volumes. These issues underlie the most well-documented problems with ΛCDM: cusp/core, missing satellites, and too-big-to-fail. The key question is whether a better understanding of baryon physics, dark matter physics, or both is required to meet these challenges. Other anomalies, including the observed planar and orbital configurations of Local Group satellites and the tight baryonic...

Small-Scale Challenges to the ΛCDM Paradigm

We present an overview of scenarios where the observed Dark Matter (DM) abundance consists of Feebly Interacting Massive Particles (FIMPs), produced nonthermally by the so-called freeze-in mechanism. In contrast to the usual freeze-out scenario, frozen-in FIMP DM interacts very weakly with the particles in the visible sector and never attained thermal equilibrium with the baryon–photon fluid in the early Universe. Instead of being determined by its annihilation strength, the DM abundance depends on the decay and annihilation strengths of particles in equilibrium with the baryon–photon fluid, as well as couplings in the DM sector. This makes frozen-in DM very difficult but not impossible to test. In this review, we present the freeze-in mechanism and its variations considered in the literature (dark freeze-out and reannihilation), compare them to the standard DM freeze-out scenario, discuss several aspects of model building, and pay particular attention to observational properties and general testability o...

The dawn of FIMP Dark Matter : A review of models and constraints

We have developed a new micro-fabricated platform for the measurement of the specific heat of low heat capacity mg-sized metallic samples, such as superconductors, down to temperatures of as low as $10\,\mathrm{mK}$. It addresses challenging aspects of setups of this kind such as the thermal contact between sample and platform, the thermometer resolution, and an addenda heat capacity exceeding that of the samples of interest (typically $\mbox{nJ/K at }20\,\mbox{mK}$). The setup allows us to use the relaxation method, where the thermal relaxation following a well defined heat pulse is monitored to extract the specific heat. The sample platform ($5 \times 5\, \mathrm{mm^2}$) includes a micro-structured paramagnetic \underline{Ag}:Er temperature sensor, which is read out by a dc-SQUID via a superconducting flux transformer. In this way, a relative temperature precision of $30\,\mathrm{nK/\sqrt{Hz}}$ can be reached, while the addenda heat capacity falls well below $0.5\,\mathrm{nJ/K}$ for $T < 300\,\mathrm{mK}$. A gold-coated mounting area ($4.4 \times 3 \, \mathrm{mm^2}$) is included to improve the thermal contact between sample and platform.

Development of a novel calorimetry setup based on metallic paramagnetic temperature sensors

Non-destructive assay (NDA) of nuclear materials would benefit from gamma detectors with improved energy resolution in cases where line overlap in current Ge detectors limits NDA accuracy. We are developing metallic magnetic calorimeter gamma-detectors for this purpose by electroplating $$\sim $$
 150 
 $$\upmu $$
 m thick Au absorbers into microfabricated molds on top of Au:Er sensors. Initial tests under non-optimized conditions show an energy resolution of $$\sim $$
 200 eV FWHM at 60 keV. Monte Carlo simulations illustrate that this resolution is starting to be sufficient for direct detection of $$^{242}$$
 Pu in plutonium separated from spent nuclear fuel.

/pdf/development-of-mmc-gamma-detectors-for-nuclear-analysis-44hgpvoakj.pdf

Development of MMC Gamma Detectors for Nuclear Analysis

https://iopscience.iop.org/article/10.1088/1748-0221/14/08/P08012/pdf

Development of a beta spectrometry setup using metallic magnetic calorimeters

To reach ultra-low detection thresholds necessary to probe unprecedentedly low Dark Matter masses, target material alternatives and novel detector designs are essential. One such target material is superfluid ^44He which has the potential to probe so far uncharted light Dark Matter parameter space at sub-GeV masses. The new “Direct search Experiment for Light dark matter”, DELight, will be using superfluid helium as active target, instrumented with magnetic micro-calorimeters. It is being designed to reach sensitivity to masses well below 100 MeV in Dark Matter-nucleus scattering interactions.

/pdf/delight-a-direct-search-experiment-for-light-dark-matter-13g3nvzz.pdf

DELight: A Direct search Experiment for Light dark matter with superfluid helium

Metallic magnetic calorimeters are energy-dispersive cryogenic particle detectors providing an excellent energy resolution, a fast signal rise time, a high quantum efficiency as well as an almost ideal linear detector response. To surpass the present record resolution of 1.6 eV (FWHM) for 6 keV photons, we have started to develop integrated detectors for which the paramagnetic temperature sensor monitoring the temperature rise of the detector is integrated directly into the pickup loop of the superconducting quantum interference device. Due to the greatly enhanced magnetic flux coupling and consequently the reduced contribution of SQUID noise to the overall noise spectrum, this kind of devices should push the resolution to a value well below 1 eV. Here, we discuss the design and performance of a prototype 64 pixels metallic magnetic calorimeter based detector array with integrated detectors that rely on first-order parallel gradiometric SQUIDs with two meander-shaped pickup coils onto which planar temperature sensor made of Ag:Er are deposited.

Sebastian Kempf

Papers

Development of a novel calorimetry setup based on metallic paramagnetic temperature sensors

Development of MMC Gamma Detectors for Nuclear Analysis

Development of a beta spectrometry setup using metallic magnetic calorimeters

DELight: A Direct search Experiment for Light dark matter with superfluid helium

Towards Energy-Dispersive Particle Detection with sub-eV Energy Resolution: Metallic Magnetic Calorimeters with Direct Sensor Readout