The Mass, Orbit, and Tidal Evolution of the Quaoar-Weywot System

Here we present new adaptive optics observations of the Quaoar-Weywot system. With these new observations we determine an improved system orbit. Due to a 0.39 day alias that exists in available observations, four possible orbital solutions are available with periods of $\sim11.6$, $\sim12.0$, $\sim12.4$, and $\sim12.8$ days. From the possible orbital solutions, system masses of $1.3-1.5\pm0.1\times10^{21}$ kg are found. These observations provide an updated density for Quaoar of 2.7-5.0{g cm^{-3}}. In all cases, Weywot's orbit is eccentric, with possible values $\sim0.13-0.16$. We present a reanalysis of the tidal orbital evolution of the Quoaor-Weywot system. We have found that Weywot has probably evolved to a state of synchronous rotation, and have likely preserved their initial inclinations over the age of the Solar system. We find that for plausible values of the effective tidal dissipation factor tides produce a very slow evolution of Weywot's eccentricity and semi-major axis. Accordingly, it appears that Weywot's eccentricity likely did not tidally evolve to its current value from an initially circular orbit. Rather, it seems that some other mechanism has raised its eccentricity post-formation, or Weywot formed with a non-negligible eccentricity.Comment: Accepted to Icarus, Nov. 8 201

Prevalence and predictors of postdischarge antibiotic use following mastectomy

OBJECTIVESurvey results suggest that prolonged administration of prophylactic antibiotics is common after mastectomy with reconstruction. We determined utilization, predictors, and outcomes of postdischarge prophylactic antibiotics after mastectomy with or without immediate breast reconstruction.DESIGNRetrospective cohort.PATIENTSCommercially insured women aged 18–64 years coded for mastectomy from January 2004 to December 2011 were included in the study. Women with a preexisting wound complication or septicemia were excluded.METHODSPredictors of prophylactic antibiotics within 5 days after discharge were identified in women with 1 year of prior insurance enrollment; relative risks (RR) were calculated using generalized estimating equations.RESULTSOverall, 12,501 mastectomy procedures were identified; immediate reconstruction was performed in 7,912 of these procedures (63.3%). Postdischarge prophylactic antibiotics were used in 4,439 procedures (56.1%) with immediate reconstruction and 1,053 procedures (22.9%) without immediate reconstruction (P&lt;.001). The antibiotics most commonly prescribed were cephalosporins (75.1%) and fluoroquinolones (11.1%). Independent predictors of postdischarge antibiotics were implant reconstruction (RR, 2.41; 95% confidence interval [CI], 2.23–2.60), autologous reconstruction (RR, 2.17; 95% CI, 1.93–2.45), autologous reconstruction plus implant (RR, 2.11; 95% CI, 1.92–2.31), hypertension (RR, 1.05; 95% CI, 1.00–1.10), tobacco use (RR, 1.07; 95% CI, 1.01–1.14), surgery at an academic hospital (RR, 1.14; 95% CI, 1.07–1.21), and receipt of home health care (RR, 1.11; 95% CI, 1.04–1.18). Postdischarge prophylactic antibiotics were not associated with SSI after mastectomy with or without immediate reconstruction (bothP&gt;.05).CONCLUSIONSProphylactic postdischarge antibiotics are commonly prescribed after mastectomy; immediate reconstruction is the strongest predictor. Stewardship efforts in this population to limit continuation of prophylactic antibiotics after discharge are needed to limit antimicrobial resistance.Infect Control Hosp Epidemiol2017;38:1048–1054</jats:sec

Low-energy quenching of positronium by helium

Very low-energy scattering of orthopositronium by helium has been investigated for simultaneous study of elastic cross section and pick-off quenching rate using a model exchange potential. The present calculational scheme, while agrees with the measured cross section of Skalsey et al, reproduces successfully the parameter ^ 1Z_{\makebox{eff}}, the effective number of electrons per atom in a singlet state relative to the positron. Together with the fact that this model potential also leads to an agreement with measured medium energy cross sections of this system, this study seems to resolve the long-standing discrepancy at low energies among different theoretical calculations and experimental measurements.Comment: 4 latex pages, 3 postscript figure

Sow Preference for Types of Flooring in Farrowing Crates

A preference-testing apparatus was used to provide sows with continuous access to three identical farrowing crates, each with a different type of flooring. The crates radiated from a central hub area sufficiently large for sows to enter or leave any crate freely. In exp. 1, nine sows from a concrete-floored gestation room were offered crates over concrete, plastic-coated rod, and galvanized metal rod. In exp. 2, sows were pre-exposed for a period of 1 wk to one of the three floors before entry into the preference testing apparatus. Video recording was used to determine sow position from 3 d before to 13 d after farrowing in exp. 1 and for a 3-d period before and 3-d period after farrowing in exp. 2. In exp. 1, sows showed a strong preference (P \u3c 0.05) for the concrete floor before farrowing, but this preference had diminished by the final week.in the apparatus (P ≈ 0.16). In exp. 2, sows pre-exposed to metal or plastic-coated flooring made more voluntary use of these products, but the metal floor was strongly avoided during and immediately after farrowing. Overall, concrete seemed to be a preferred floor material for sows at farrowing

Preference by Sows for a Partially Enclosed Farrowing Crate

A preference testing apparatus was designed to give sows continuous access to three farrowing crates with different degrees of visual enclosure. A ‘fully enclosed\u27 crate had solid black panels on the sides and top of the crate, a ‘solid-sided’ crate had the side panels only and an ‘open crate’ had no solid panels over the crate\u27s tubular framework. The crates radiated from a central area sufficient for sows to enter or leave any crate freely. Video recording was used to determine sow position from 3 days before to 6 days after farrowing. The results indicated that younger sows (second or third panty) preferred the enclosure offered by the solid side panels during and for several days after farrowing (P \u3c 0.05). Older sows, which had previously farrowed a number of times in an open crate, had no clear preference. A solid panel overhead did not improve, and may have reduced, the acceptance of a crate with solid sides. It is concluded that less experienced sows prefer a degree of enclosure on the sides of the farrowing crate, but that this preference largely disappears with repeated experience of open crates

Sow Preference for Farrowing-Crate Width

A preference-testing apparatus was designed to provide sows with continuous access to three farrowing crates of different widths. The crates radiated from a central hub area sufficiently large for sows to enter or leave any crate freely. In exp. 1, nine sows were offered crates of 450-, 600- and 750-mm width at standing height. In exp. 2, 12 sows were offered widths of 450, 750 and 1200 mm, the largest being of sufficient width for the sow to turn around. Video recording was used to determine sow position from 3 d before to 6 d after farrowing. In exp. 1, sows showed a preference for the widest crate of 750 mm during and after farrowing (P \u3c 0.05) but not before. ln exp. 2, the 1200-mm width was preferred before, during and after farrowing (P \u3c 0.005) over the widths that were too narrow to permit turning. Sufficient space for turning appears to be preferred by sows around the time of farrowing

Preference Tests of Ramp Designs for Young Pigs

Preference experiments were used to identify features of ramp design that influence the voluntary use of ramps by young pigs. In seven experiments, groups of pigs, aged 7-8 wk, were given free access to four different ramps simultaneously. The animals\u27 behavior was monitored to identify the amount of time spent on the ramps and the number of pigs that failed to use specific designs. Slope, in the range of 20-32° from the horizontal, had a major influence on the pigs\u27 behavior, with the shallower slopes attracting more use than steep ones. Pigs preferred ramps with angle-iron cleats (cross-laid on the ramps to provide foot-holds) spaced every 50 or 100 mm rather than 200 or 300 mm. Cleat height, in the range of 10-40 mm, had little effect. Pigs showed a slight preference for ramps with solid or open (wire mesh) side walls, compared to ramps partially enclosed by a railing. Reduced width (510 vs. 710 mm) was not a major impediment to ramp use, although the narrow ramps were used somewhat less, by a degree proportional to their smaller width. Level of illumination (up to 1200 lx) had no major effect. A staircase composed of 20 small steps was used at least as readily as a ramp of similar slope, but staircase designs with fewer, larger steps were not preferred. The results suggest that a ramp sloped at 20-24°, with cleats cross-laid every 50-100 mm, would provide a feasible design with good acceptance by young pigs, either for loading pigs or for two-level housing systems

Initial Test of a Farrowing Crate with Inward-Sloping Sides

A farrowing crate was designed with sides spaced well apart (1150 mm) at the sow\u27s standing height but angled inward near the floor to restrict the sow\u27s lying area and to prevent the sow from dropping suddenly onto one side. Survival and body-weight data were collected for 20 farrowings in the prototype crate and for 18-20 farrowings in each of 3 other crate types. No significant differences were found in stillbirth rate, other deaths to 14 days, or average piglet weight gains, but gains were somewhat more variable in one of the conventional designs which interfered with the piglets\u27 access to the teats. The principle of inward-sloping crate sides may provide a less restrictive alternative to conventional farrowing crates, but large-scale testing is needed