83 research outputs found
Generalised sifting in black-box groups
We present a generalisation of the sifting procedure introduced originally by
Sims for computation with finite permutation groups, and now used for many
computational procedures for groups, such as membership testing and finding
group orders. Our procedure is a Monte Carlo algorithm, and is presented and
analysed in the context of black-box groups. It is based on a chain of subsets
instead of a subgroup chain. Two general versions of the procedure are worked
out in detail, and applications are given for membership tests for several of
the sporadic simple groups.
Our major objective was that the procedures could be proved to be Monte Carlo
algorithms, and their costs computed. In addition we explicitly determined
suitable subset chains for six of the sporadic groups, and we implemented the
algorithms involving these chains in the {\sf GAP} computational algebra
system. It turns out that sample implementations perform well in practice. The
implementations will be made available publicly in the form of a {\sf GAP}
package
Enthalpy of formation of yeâelimite and ternesite
Calcium sulfoaluminate clinkers containing yeâelimite (Ca4Al6O12(SO4)) and ternesite (Ca5(SiO4)2SO4) are being widely investigated as components of calcium sulfoaluminate cement clinkers. These may become low energy replacements for Portland cement. Conditional thermodynamic data for yeâelimite and ternesite (enthalpy of formation) have been determined experimentally using a combination of techniques: isothermal conduction calorimetry, X-ray powder diffraction and thermogravimetric analysis. The enthalpies of formation of yeâelimite and ternesite at 25 °C were determined to be â 8523 and â 5993 kJ molâ1, respectively
Suspicion of respiratory tract infection with multidrug-resistant Enterobacteriaceae: epidemiology and risk factors from a Paediatric Intensive Care Unit
Observing many researchers using the same data and hypothesis reveals a hidden universe of uncertainty
This study explores how researchersâ analytical choices affect the reliability of scientific findings. Most discussions of reliability problems in science focus on systematic biases. We broaden the lens to emphasize the idiosyncrasy of conscious and unconscious decisions that researchers make during data analysis. We coordinated 161 researchers in 73 research teams and observed their research decisions as they used the same data to independently test the same prominent social science hypothesis: that greater immigration reduces support for social policies among the public. In this typical case of social science research, research teams reported both widely diverging numerical findings and substantive conclusions despite identical start conditions. Researchersâ expertise, prior beliefs, and expectations barely predict the wide variation in research outcomes. More than 95% of the total variance in numerical results remains unexplained even after qualitative coding of all identifiable decisions in each teamâs workflow. This reveals a universe of uncertainty that remains hidden when considering a single study in isolation. The idiosyncratic nature of how researchersâ results and conclusions varied is a previously underappreciated explanation for why many scientific hypotheses remain contested. These results call for greater epistemic humility and clarity in reporting scientific findings
Gewichtssprung und IL-8 : PrÀdiktive Kombination zur Diagnose der nekrotisierenden Enterokolitis?
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