Automorphisms of Partially Commutative Groups II: Combinatorial Subgroups

We define several "standard" subgroups of the automorphism group Aut(G) of a partially commutative (right-angled Artin) group and use these standard subgroups to describe decompositions of Aut(G). If C is the commutation graph of G, we show how Aut(G) decomposes in terms of the connected components of C: obtaining a particularly clear decomposition theorem in the special case where C has no isolated vertices. If C has no vertices of a type we call dominated then we give a semi-direct decompostion of Aut(G) into a subgroup of locally conjugating automorphisms by the subgroup stabilising a certain lattice of "admissible subsets" of the vertices of C. We then characterise those graphs for which Aut(G) is a product (not necessarily semi-direct) of two such subgroups.Comment: 7 figures, 63 pages. Notation and definitions clarified and typos corrected. 2 new figures added. Appendix containing details of presentation and proof of a theorem adde

High-Pressure Viscosity of Biodiesel, Diesel, and Biodiesel-Diesel Blends: Experimental Data and Modeling

Biodiesel was produced in excess of one billion gallons in the United States last year. It is sold as B100 (neat) and as a variety of blends. It is well known as a renewable fuel that reduces net carbon dioxide production, and other harmful emissions. Because much of the recent experimentation has involved biodiesel simply as a “drop in” fuel, its full, beneficial potential has not been reached. The ability to understand, model and predict important physical property behavior of current and potential fuels can lead to increased diesel engine performance, reduce harmful emissions further, and even improve fuel perception. High-pressure viscosity has been identified as one of the most important fuel properties of diesel fuel due to vehicle injectors creating pressures thousands of times greater than atmospheric. High-pressure viscosity measurements were performed for common biodiesels like those produced from soy and canola oils, but more exotic feedstocks like coconut and jatropha were also tested. Measurements were performed on dozens of fuels for temperatures between 278.15 and 373.15 K and pressures up to 131 MPa. Fuels were found to vary significantly from their ambient viscosities, and some were found to be more than 700 percent of their initial viscosity at the highest pressure tested. Blends were typically found to increase in viscosity with increasing blend fraction of biodiesel, however, this trend was shown to vary at low temperature and high pressure. Possible pressure freezing was found to occur for all biodiesel samples and for several high-percentage biodiesel blends at 283.15 K. Empirical models were developed as functions of temperature, pressure and blend percentage and were typically within the 95% confidence interval of the instrument

How to Optimally Constrain Galaxy Assembly Bias: Supplement Projected Correlation Functions with Count-in-cells Statistics

Most models for the connection between galaxies and their haloes ignore the possibility that galaxy properties may be correlated with halo properties other than mass, a phenomenon known as galaxy assembly bias. Yet, it is known that such correlations can lead to systematic errors in the interpretation of survey data. At present, the degree to which galaxy assembly bias may be present in the real Universe, and the best strategies for constraining it remain uncertain. We study the ability of several observables to constrain galaxy assembly bias from redshift survey data using the decorated halo occupation distribution (dHOD), an empirical model of the galaxy--halo connection that incorporates assembly bias. We cover an expansive set of observables, including the projected two-point correlation function $w_{\mathrm{p}}(r_{\mathrm{p}})$, the galaxy--galaxy lensing signal $\Delta \Sigma(r_{\mathrm{p}})$, the void probability function $\mathrm{VPF}(r)$, the distributions of counts-in-cylinders $P(N_{\mathrm{CIC}})$, and counts-in-annuli $P(N_{\mathrm{CIA}})$, and the distribution of the ratio of counts in cylinders of different sizes $P(N_2/N_5)$. We find that despite the frequent use of the combination $w_{\mathrm{p}}(r_{\mathrm{p}})+\Delta \Sigma(r_{\mathrm{p}})$ in interpreting galaxy data, the count statistics, $P(N_{\mathrm{CIC}})$ and $P(N_{\mathrm{CIA}})$, are generally more efficient in constraining galaxy assembly bias when combined with $w_{\mathrm{p}}(r_{\mathrm{p}})$. Constraints based upon $w_{\mathrm{p}}(r_{\mathrm{p}})$ and $\Delta \Sigma(r_{\mathrm{p}})$ share common degeneracy directions in the parameter space, while combinations of $w_{\mathrm{p}}(r_{\mathrm{p}})$ with the count statistics are more complementary. Therefore, we strongly suggest that count statistics should be used to complement the canonical observables in future studies of the galaxy--halo connection.Comment: Figures 3 and 4 show the main results. Published in Monthly Notices of the Royal Astronomical Societ

Nanosecond laser texturing for high friction applications

AbstractA nanosecond pulsed Nd:YAG fibre laser with wavelength of 1064nm was used to texture several different steels, including grade 304 stainless steel, grade 316 stainless steel, Cr–Mo–Al ‘nitriding’ steel and low alloy carbon steel, in order to generate surfaces with a high static friction coefficient. Such surfaces have applications, for example, in large engines to reduce the tightening forces required for a joint or to secure precision fittings easily. For the generation of high friction textures, a hexagonal arrangement of laser pulses was used with various pulse overlaps and pulse energies. Friction testing of the samples suggests that the pulse energy should be high (around 0.8mJ) and the laser pulse overlap should be higher than 50% in order to achieve a static friction coefficient of more than 0.5. It was also noted that laser processing increases the surface hardness of samples which appears to correlate with the increase in friction. Energy-Dispersive X-ray spectroscopy (EDX) measurements indicate that this hardness is caused by the formation of hard metal-oxides at the material surface

Mixed-conducting oxygen permeable ceramic membranes for the carbon dioxide reforming of methane

This is the published version. Copyright 2007 Royal Society of ChemistryDue to the high economic, environmental, and safety costs associated with pure oxygen, mixed-conducting oxygen-permeable ceramic membranes are being explored as an alternative oxygen source for hydrocarbon conversion reactors. This work reports a dramatic improvement in catalyst performance when an oxygen-permeable SrFeCo0.5Ox ceramic membrane is used in conjunction with a conventional powder Pt/ZrO2 catalyst for the CO2 reforming of CH4. Experiments comparing catalyst performance with up to 2% co-fed oxygen to catalyst performance with oxygen from the ceramic membrane demonstrated a conversion three times higher with the membrane than with any amount of co-fed oxygen. The results suggest that membrane oxygen is more beneficial for catalyst activity and stability than molecular gas-phase oxygen

Do Patients Taking Warfarin Experience Delays to Theatre, Longer Hospital Stay, and Poorer Survival After Hip Fracture?

BACKGROUND: Patients sustaining a fractured neck of the femur are typically of advanced age with multiple comorbidities. As a consequence, the proportion of these patients receiving warfarin therapy is approximately 10%. There are currently few studies investigating outcomes in this subset of patients. QUESTIONS/PURPOSES: The purpose of this study was to assess the association between warfarin therapy and time to surgery, length of hospital stay, and survival in patients sustaining a fractured neck of the femur. METHODS: Data for 2036 patients admitted to our center between July 2009 and July 2014 with a fractured neck of the femur were extracted from the National Hip Fracture Database. Fifty-seven patients received no surgical treatment and were excluded from analysis. Multivariable ordinary least squares regression was performed to test the association between warfarin treatment on time to surgery and length of stay, and Cox proportional hazards to test followup survival. Variables included in the regression model were age, sex, American Society of Anesthesiologists (ASA) score, admission Abbreviated Mental Test Score (AMTS), fracture type, operation type, and premorbid Work Ability Index (WAI). One hundred fifty-two of 1979 surgically treated patients (8%) were receiving warfarin therapy at the time of admission. RESULTS: After controlling for age, sex, ASA score, AMTS, fracture type, operation type, and WAI, we found that patients taking warfarin were less likely to go to surgery by 36 hours (odds ratio [OR], 0.20; 95% CI, 0.14-0.30), and less likely to go to surgery by 48 hours (OR, 0.17; 95% CI, 0.11-0.24). Patients taking warfarin had a longer length of stay (median, 15 days; interquartile range [IQR], 12-22 days) compared with patients not taking warfarin (median, 13 days; IQR, 9-20 days; p < 0.001). Survival analysis to June 2015 showed a higher mortality for patients taking warfarin (12-month survival, 66% vs 76%; hazard ratio, 1.57; 95% CI, 1.21-2.04; p < 0.001). CONCLUSIONS: After controlling for multiple prognostic factors such as age, ASA score, AMTS, and WAI, warfarin therapy at the time of injury is associated with increased time to surgery, length of stay, and decreased survival. This study highlights the need to view warfarin therapy as a 'red flag' in patients presenting with a fractured neck of the femur. Preoperatively, prompt warfarin reversal together with adequate investigation and optimization of the patient should ensure timely, safe surgery. Early involvement of the anesthesia team should ensure an appropriate level of postoperative care for these patients. LEVEL OF EVIDENCE: Level III, therapeutic study.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s11999-016-5056-

Defining and Exploring Animal Sentience

One of the commentaries on the target article notes that animal sentience is difficult to define operationally. This response to the commentaries develops a working, usable definition of animal sentience and examines the relationships between animal emotions and sentience