Data Compression in the Petascale Astronomy Era: a GERLUMPH case study

As the volume of data grows, astronomers are increasingly faced with choices on what data to keep -- and what to throw away. Recent work evaluating the JPEG2000 (ISO/IEC 15444) standards as a future data format standard in astronomy has shown promising results on observational data. However, there is still a need to evaluate its potential on other type of astronomical data, such as from numerical simulations. GERLUMPH (the GPU-Enabled High Resolution cosmological MicroLensing parameter survey) represents an example of a data intensive project in theoretical astrophysics. In the next phase of processing, the ~27 terabyte GERLUMPH dataset is set to grow by a factor of 100 -- well beyond the current storage capabilities of the supercomputing facility on which it resides. In order to minimise bandwidth usage, file transfer time, and storage space, this work evaluates several data compression techniques. Specifically, we investigate off-the-shelf and custom lossless compression algorithms as well as the lossy JPEG2000 compression format. Results of lossless compression algorithms on GERLUMPH data products show small compression ratios (1.35:1 to 4.69:1 of input file size) varying with the nature of the input data. Our results suggest that JPEG2000 could be suitable for other numerical datasets stored as gridded data or volumetric data. When approaching lossy data compression, one should keep in mind the intended purposes of the data to be compressed, and evaluate the effect of the loss on future analysis. In our case study, lossy compression and a high compression ratio do not significantly compromise the intended use of the data for constraining quasar source profiles from cosmological microlensing.Comment: 15 pages, 9 figures, 5 tables. Published in the Special Issue of Astronomy & Computing on The future of astronomical data format

Superbursts from Strange Stars

Recent models of carbon ignition on accreting neutron stars predict superburst ignition depths that are an order of magnitude larger than observed. We explore a possible solution to this problem, that the compact stars in low mass X-ray binaries that have shown superbursts are in fact strange stars with a crust of normal matter. We calculate the properties of superbursts on strange stars, and the resulting constraints on the properties of strange quark matter. We show that the observed ignition conditions exclude fast neutrino emission in the quark core, for example by the direct Urca process, which implies that strange quark matter at stellar densities should be in a color superconducting state. For slow neutrino emission in the quark matter core, we find that reproducing superburst properties requires a definite relation between three poorly constrained properties of strange quark matter: its thermal conductivity, its slow neutrino emissivity and the energy released by converting a nucleon into strange quark matter.Comment: 4 pages, submitted to Ap. J. Let

Fabrication and Characterization of Quad-Component Bioinspired Hydrogels to Model Elevated Fibrin Levels in Central Nervous Tissue Scaffolds

Multicomponent interpenetrating polymer network (mIPN) hydrogels are promising tissue-engineering scaffolds that could closely resemble key characteristics of native tissues. The mechanical and biochemical properties of mIPNs can be finely controlled to mimic key features of target cellular microenvironments, regulating cell-matrix interactions. In this work, we fabricated hydrogels made of collagen type I (Col I), fibrin, hyaluronic acid (HA), and poly (ethylene glycol) diacrylate (PEGDA) using a network-by-network fabrication approach. With these mIPNs, we aimed to develop a biomaterial platform that supports the in vitro culture of human astrocytes and potentially serves to assess the effects of the abnormal deposition of fibrin in cortex tissue and simulate key aspects in the progression of neuroinflammation typically found in human pathologies such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and tissue trauma. Our resulting hydrogels closely resembled the complex modulus of AD human brain cortex tissue (~7.35 kPa), promoting cell spreading while allowing for the modulation of fibrin and hyaluronic acid levels. The individual networks and their microarchitecture were evaluated using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Human astrocytes were encapsulated in mIPNs, and negligible cytotoxicity was observed 24 h after the cell encapsulation

Cooling of the Cassiopeia A neutron star and the effect of diffusive nuclear burning

The study of how neutron stars cool over time can provide invaluable insights into fundamental physics such as the nuclear equation of state and superconductivity and superfluidity. A critical relation in neutron star cooling is the one between observed surface temperature and interior temperature. This relation is determined by the composition of the neutron star envelope and can be influenced by the process of diffusive nuclear burning (DNB). We calculate models of envelopes that include DNB and find that DNB can lead to a rapidly changing envelope composition which can be relevant for understanding the long-term cooling behavior of neutron stars. We also report on analysis of the latest temperature measurements of the young neutron star in the Cassiopeia A supernova remnant. The 13 Chandra observations over 18 years show that the neutron star's temperature is decreasing at a rate of 2-3 percent per decade, and this rapid cooling can be explained by the presence of a proton superconductor and neutron superfluid in the core of the star.Comment: 7 pages, 7 figures; to appear in the AIP Conference Proceedings of the Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy (January 3-7, 2019, Xiamen, China

Illegal Community Detection in Bitcoin Transaction Networks

Community detection is widely used in social networks to uncover groups of related vertices (nodes). In cryptocurrency transaction networks, community detection can help identify users that are most related to known illegal users. However, there are challenges in applying community detection in cryptocurrency transaction networks: (1) the use of pseudonymous addresses that are not directly linked to personal information make it difficult to interpret the detected communities; (2) on Bitcoin, a user usually owns multiple Bitcoin addresses, and nodes in transaction networks do not always represent users. Existing works on cluster analysis on Bitcoin transaction networks focus on addressing the later using different heuristics to cluster addresses that are controlled by the same user. This research focuses on illegal community detection containing one or more illegal Bitcoin addresses. We first investigate the structure of Bitcoin transaction networks and suitable community detection methods, then collect a set of illegal addresses and use them to label the detected communities. The results show that 0.06% of communities from daily transaction networks contain one or more illegal addresses when 2,313,344 illegal addresses are used to label the communities. The results also show that distance-based clustering methods and other methods depending on them, such as network representation learning, are not suitable for Bitcoin transaction networks while community quality optimization and label-propagation-based methods are the most suitable

Experiencias vividas en una prolongada relación entrenador-atleta. El caso de un atleta paralímpico

The purpose of the present study was to explore the lived experiences of one male Paralympic athlete who maintained a longstanding relationship with his coach. This case provides insight into how a coach can serve as a key supportive agent in enabling an athlete to thrive both in sport and in life. The athlete was interviewed on two separate occasions and an interpretative phenomenological analysis was conducted. The athlete discussed the consequences of an acute bout of meningitis experienced at four years of age that left him impaired. During adolescence and adulthood, the athlete experienced the death of his mother and sister as well as the challenges associated with him assuming his homosexuality. Throughout these ordeals, his coach acted as a constant support figure. The athlete attributed much weight to his coach’s trust, respect, and empathy in explaining the significant success he attained on the international stage. The recommendations offered focus on how coaches can support athletes when athletes are navigating tough challenges

KAJIAN KELIMPAHAN IKAN KARANG PADA EKOSISTEM TERUMBU KARANG UNTUK ZONA INTI DI KABUPATEN BELITUNG

The research was carried out in March 2014 in Belitung District aims to study the abundance of reef fish, and determine the suitability of the area on coral reef community. This research using the method of survey on six stations observations determined based on resource utilization activities around the station, primarily tourism activities. Analysis of the conformity analysis is used to determine the core zone of the area of coral reefs. Parameters in determining the suitability of the core zone includes the quality of the waters, index of ecological fish, the percentage coverage of the coral, the reef ecological index, and the existence of important economically as well as biodiversity and rare species. The results showed Underwater Visual Census (UVC) found an abundance of reef fish ranges between 61 – 448 individuals and 33 species in the entire station. Found 12 family Ambassidae, Blenniidae, i.e., Chaetodontidae, Gobiidae, Haemulidae, Labridae, Lutjanidae, Mullidae, Pomacanthidae, Pomacentridae, Scaridae, and Siganidae, conditions of coral reefs in the waters of the Belitung district included in the category are up to. The percentage of coverage of the coral reefs in the observation stations ranged between 37.37%-81.77%. The corresponding observation stations for the core zone is located on Pulau Begador, Batu Berlayar and Batu Garuda, while a very appropriate observation stations for the core zone is located on Pulau Lengkuas, Pulau Babi, and Batu Malang Penyu

Thermalisation time and specific heat of neutron stars crust

We discuss the thermalisation process of the neutron stars crust described by solving the heat transport equation with a microscopic input for the specific heat of baryonic matter. The heat equation is solved with initial conditions specific to a rapid cooling of the core. To calculate the specific heat of inner crust baryonic matter, i.e., nuclear clusters and unbound neutrons, we use the quasiparticle spectrum provided by the Hartree-Fock-Bogoliubov approach at finite temperature. In this framework we analyse the dependence of the crust thermalisation on pairing properties and on cluster structure of inner crust matter. It is shown that the pairing correlations reduce the crust thermalisation time by a very large fraction. The calculations show also that the nuclear clusters have a non-negligible influence on the time evolution of the surface temperature of the neutron star.Comment: 7 pages, 5 figures, submitted to Phys. Rev.