2,205 research outputs found
Most Black Holes Are Born Very Slowly Rotating
The age of gravitational-wave astronomy has begun, and black hole (BH) mergers detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) are providing novel constraints on massive star evolution. A major uncertainty in stellar theory is the angular momentum (AM) transport within the star that determines its core rotation rate and the resulting BH's spin. Internal rotation rates of low-mass stars measured from asteroseismology prove that AM transport is efficient, suggesting that massive stellar cores may rotate slower than prior expectations. We investigate AM transport via the magnetic Tayler instability, which can largely explain the rotation rates of low-mass stars and white dwarfs. Implementing an updated AM transport prescription into models of high-mass stars, we compute the spins of their BH remnants. We predict that BHs born from single stars rotate very slowly, with a ~ 10^(â2), regardless of initial rotation rate, possibly explaining the low Ï_(eff) of most BH binaries detected by LIGO thus far. A limited set of binary models suggests slow rotation for many binary scenarios as well, although homogeneous evolution and tidal spin-up of post-common-envelope helium stars can create moderate or high BH spins. We make predictions for the values of Ï_(eff) in future LIGO events, and we discuss implications for engine-powered transients
Polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene, intakes of folate and related B vitamins and colorectal cancer : a case-control study in a population with relatively low folate intake
Peer reviewedPublisher PD
Frost Formation in Evaporator Fins with Embedded Negative Stiffness Structures
Frosting in the evaporator leads to an increase in thermal resistance and reduced airflow, resulting in decreased performance. Traditional thermal defrosting strategies lead to significant energy penalties. Novel shape morphing evaporator fins embedded with multistable structures offer the opportunity for faster defrosting and large energy savings while keeping the capital cost low. This type of morphing fins enables a mechanical defrosting approach that is more effective for higher densities and thicknesses of frost. However, there is a need to better understand frost formation in these structures. In this study, we use a modeling and experimental approach to understand frosting on shape morphing fins. An experimental setup was developed that is capable of frost formation at different conditions and testing various defrosting strategies. Leveraging this, we formed frost at various conditions on both an angled shape morphing fin and a flat fin and performed comparisons between model predictions and measurements
Distortion of the acoustic peaks in the CMBR due to a primordial magnetic field
In this paper we study the effect of a magnetic field on the fluctuation
spectrum of the cosmic microwave background. We find that upcoming measurements
might give interesting bounds on large scale magnetic fields in the early
Universe. If the effects are seen, it might be possible to establish the
presence of different fields in different patches of the sky. Absence of any
effect, will provide by one order of magnitude a better limit for a primordial
field, now given by nucleosynthesis.Comment: 10 pages, 2 .ps figures included, extra reference added and
typographical errors correcte
Tree species composition, growing space and management in Hong Kongâs commercial sky gardens
Sky gardens, a type of above-ground urban green space, have been increasingly welcomed and installed in cities. However, few studies have assessed tree planting, management and health in high-rise greenery. This study investigated tree species composition, planting space design and management, and their relationships with tree health in sky gardens in 15 commercial sky gardens with 480 trees in Hong Kong. We assessed the differences between old and new sites regarding tree species, height, crown diameter, and health. We also evaluated selected planting and management factors, including planter type, distance to neighbor trees, root-growth obstacles, canopy barriers, canopy overlap and topping history. Tree species selection in commercial sky gardens was substantially different from public and private residential green spaces. Older sky gardens had more palm trees by species and tree counts. Newer gardens had increased adoption of broadleaf and conifer species with high ornamental value and compact form but fewer native tree species and lower species diversity. The widely planted Ficus spp. had created long-term management issues. Trees were often densely planted, particularly in newer sky gardens. The common practice of topping indicates poor species selection and mismanagement. Planter types with insufficient growing space had dampened tree health. Our findings reveal the trend of tree species adoption, narrower planting spaces and wider adoption of the sunken planter. Improvements in species selection, growing space design and management practices could promote healthy, stable and safe trees in sky gardens with contributions to biodiversity and other ecosystem services
Cisplatin Induces Cytotoxicity through the Mitogen-Activated Protein Kinase Pathways ana Activating Transcription Factor 3
AbstractThe mechanisms underlying the proapoptotic effect of the chemotherapeutic agent, cisplatin, are largely undefined. Understanding the mechanisms regulating cisplatin cytotoxicity may uncover strategies to enhance the efficacy of this important therapeutic agent. This study evaluates the role of activating transcription factor 3 (ATF3) as a mediator of cisplatin-induced cytotoxicity. Cytotoxic doses of cisplatin and carboplatin treatments consistently induced ATF3 expression in five tumor-derived cell lines. Characterization of this induction revealed a p53, BRCA1, and integrated stress response-independent mechanism, all previously implicated in stress-mediated ATF3 induction. Analysis of mitogenactivated protein kinase (MAPK) pathway involvement in ATF3 induction by cisplatin revealed a MAPK-dependent mechanism. Cisplatin treatment combined with specific inhibitors to each MAPK pathway (c-Jun N-terminal kinase, extracellularsignal-regulated kinase, and p38) resulted in decreasedATF3 induction at the protein level. MAPK pathway inhibition led to decreased ATF3 messenger RNA expression and reduced cytotoxic effects of cisplatin as measured by the 3-(4,5-dimethylthiazol-2-ylF2,5-diphenyltetrazolium bromide cell viability assay. In A549 lung carcinoma cells, targeting ATF3 with specific small hairpin RNA also attenuated the cytotoxic effects of cisplatin. Similarly, ATF3-/murine embryonic fibroblasts (MEFs) were shown to be less sensitive to cisplatin-induced cytotoxicity compared with ATF3+/+ MEFs. This study identifies cisplatin as a MAPK pathway-dependent inducer of ATF3, whose expression influences cisplatinâs cytotoxic effects
DiLogics: Creating Web Automation Programs With Diverse Logics
Knowledge workers frequently encounter repetitive web data entry tasks, like
updating records or placing orders. Web automation increases productivity, but
translating tasks to web actions accurately and extending to new specifications
is challenging. Existing tools can automate tasks that perform the same logical
trace of UI actions (e.g., input text in each field in order), but do not
support tasks requiring different executions based on varied input conditions.
We present DiLogics, a programming-by-demonstration system that utilizes NLP to
assist users in creating web automation programs that handle diverse
specifications. DiLogics first semantically segments input data to structured
task steps. By recording user demonstrations for each step, DiLogics
generalizes the web macros to novel but semantically similar task requirements.
Our evaluation showed that non-experts can effectively use DiLogics to create
automation programs that fulfill diverse input instructions. DiLogics provides
an efficient, intuitive, and expressive method for developing web automation
programs satisfying diverse specifications
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