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Small-angle X-ray scattering measurements were made on samples of CaO—MgO—SiO2 as CaO-MgO-SiO2 glass in which met astable amorphous phase separation had been induced by heat treatment. Glass rods drawn from a melt of composition 30.5% CaO, 8.0% MgO, 61.5% SiO2 (by weight) at 1400°C were heat treated for 1, 2, 10, and 15hr at 825°C. X-ray scattering intensities of heat-treated and non-heat-treated samples were measured using an apparatus based on Kratky collimation geometry and equipped with a pulse height analyzer. Particle sizes were calculated from the radii of gyration which were determined from plots of log intensity vs, θ2, according to the method of Guinier. The data show a growth with time of the dispersed spheres from 350 to 1880 Å in diameter and correspond to the growth rate for diffusion-controlled growth of a sphere. Electron micrographs of identical samples prepared concurrently are presented. Inhomogeneity sizes obtained by the two methods are in very good agreement. Results obtained using the Kratky system in conjunction with a pulse height analyzer are compared with those obtained when a slit collimation system and balanced filter monochronmtization were used to study the same sample.
Herbicide resistance is ‘wicked’ in nature; therefore, results of the many educational efforts to encourage diversification of weed control practices in the United States have been mixed. It is clear that we do not sufficiently understand the totality of the grassroots obstacles, concerns, challenges, and specific solutions needed for varied crop production systems. Weed management issues and solutions vary with such variables as management styles, regions, cropping systems, and available or affordable technologies. Therefore, to help the weed science community better understand the needs and ideas of those directly dealing with herbicide resistance, seven half-day regional listening sessions were held across the United States between December 2016 and April 2017 with groups of diverse stakeholders on the issues and potential solutions for herbicide resistance management. The major goals of the sessions were to gain an understanding of stakeholders and their goals and concerns related to herbicide resistance management, to become familiar with regional differences, and to identify decision maker needs to address herbicide resistance. The messages shared by listening-session participants could be summarized by six themes: we need new herbicides; there is no need for more regulation; there is a need for more education, especially for others who were not present; diversity is hard; the agricultural economy makes it difficult to make changes; and we are aware of herbicide resistance but are managing it. The authors concluded that more work is needed to bring a community-wide, interdisciplinary approach to understanding the complexity of managing weeds within the context of the whole farm operation and for communicating the need to address herbicide resistance.
Seven half-day regional listening sessions were held between December 2016 and April 2017 with groups of diverse stakeholders on the issues and potential solutions for herbicide-resistance management. The objective of the listening sessions was to connect with stakeholders and hear their challenges and recommendations for addressing herbicide resistance. The coordinating team hired Strategic Conservation Solutions, LLC, to facilitate all the sessions. They and the coordinating team used in-person meetings, teleconferences, and email to communicate and coordinate the activities leading up to each regional listening session. The agenda was the same across all sessions and included small-group discussions followed by reporting to the full group for discussion. The planning process was the same across all the sessions, although the selection of venue, time of day, and stakeholder participants differed to accommodate the differences among regions. The listening-session format required a great deal of work and flexibility on the part of the coordinating team and regional coordinators. Overall, the participant evaluations from the sessions were positive, with participants expressing appreciation that they were asked for their thoughts on the subject of herbicide resistance. This paper details the methods and processes used to conduct these regional listening sessions and provides an assessment of the strengths and limitations of those processes.
There is no consensus as to whether magnetic resonance imaging (MRI) should be used as part of the initial clinical evaluation of patients with first-episode psychosis (FEP).
(a) To assess the logistical feasibility of routine MRI; (b) to define the clinical significance of radiological abnormalities in patients with FEP.
Radiological reports from MRI scans of two FEP samples were reviewed; one comprised 108 patients and 98 healthy controls recruited to a research study and the other comprised 241 patients scanned at initial clinical presentation plus 66 healthy controls.
In the great majority of patients, MRI was logistically feasible. Radiological abnormalities were reported in 6% of the research sample and in 15% of the clinical sample (odds ratio (OR) = 3.1, 95% CI 1.26–7.57, χ2(1) = 6.63, P = 0.01). None of the findings necessitated a change in clinical management.
Rates of neuroradiological abnormalities in FEP are likely to be underestimated in research samples that often exclude patients with organic abnormalities. However, the majority of findings do not require intervention.
We provide an assessment of the supraglacial water budget of a moulin basin on the western margin of the Greenland ice sheet for 15 days in August 2009. Meltwater production, the dominant input term to the 1.14 ± 0.06 km2 basin, was determined from in situ ablation measurements. The dominant water-output terms from the basin, accounting for 52% and 48% of output, respectively, were moulin discharge and drainage into crevasses. Moulin discharge exhibits large diurnal variability (0.017–0.54 m3 s−1) with a distinct late-afternoon peak at 16:45 local time. This lags peak meltwater production by ∼2.8 ± 4.2 hours. An Extreme Ice Survey time-lapse photography sequence complements the observations of moulin discharge. We infer, from in situ observations of moulin geometry, previously published borehole water heights and estimates of the temporal lag between meltwater production and observed local ice surface uplift (‘jacking’), that the transfer of surface meltwater to the englacial water table via moulins is nearly instantaneous (<30 min). We employ a simple crevasse mass-balance model to demonstrate that crevasse drainage could significantly dampen the surface meltwater fluctuations reaching the englacial system in comparison to moulin discharge. Thus, unlike crevasses, moulins propagate meltwater pulses to the englacial system that are capable of overwhelming subglacial transmission capacity, resulting in enhanced basal sliding.
Ice velocities observed in 2005/06 at three GPS stations along the Sermeq Avannarleq flowline, West Greenland, are used to characterize an observed annual velocity cycle. We attempt to reproduce this annual ice velocity cycle using a 1-D ice-flow model with longitudinal stresses coupled to a 1-D hydrology model that governs an empirical basal sliding rule. Seasonal basal sliding velocity is parameterized as a perturbation of prescribed winter sliding velocity that is proportional to the rate of change of glacier water storage. The coupled model reproduces the broad features of the annual basal sliding cycle observed along this flowline, namely a summer speed-up event followed by a fall slowdown event. We also evaluate the hypothesis that the observed annual velocity cycle is due to the annual calving cycle at the terminus. We demonstrate that the ice acceleration due to a catastrophic calving event takes an order of magnitude longer to reach CU/ETH (‘Swiss’) Camp (46 km upstream of the terminus) than is observed. The seasonal acceleration observed at Swiss Camp is therefore unlikely to be the result of velocity perturbations propagated upstream via longitudinal coupling. Instead we interpret this velocity cycle to reflect the local history of glacier water balance.
We apply a novel one-dimensional glacier hydrology model that calculates hydraulic head to the tidewater-terminating Sermeq Avannarleq flowline of the Greenland ice sheet. Within a plausible parameter space, the model achieves a quasi-steady-state annual cycle in which hydraulic head oscillates close to flotation throughout the ablation zone. Flotation is briefly achieved during the summer melt season along a ∼17 km stretch of the ∼50 km of flowline within the ablation zone. Beneath the majority of the flowline, subglacial conduit storage ‘closes’ (i.e. obtains minimum radius) during the winter and ‘opens’ (i.e. obtains maximum radius) during the summer. Along certain stretches of the flowline, the model predicts that subglacial conduit storage remains open throughout the year. A calculated mean glacier water residence time of ∼2.2 years implies that significant amounts of water are stored in the glacier throughout the year. We interpret this residence time as being indicative of the timescale over which the glacier hydrologic system is capable of adjusting to external surface meltwater forcings. Based on in situ ice velocity observations, we suggest that the summer speed-up event generally corresponds to conditions of increasing hydraulic head during inefficient subglacial drainage. Conversely, the slowdown during fall generally corresponds to conditions of decreasing hydraulic head during efficient subglacial drainage.
The objective of this investigation is the determination of absolute parallaxes and proper motions with respect to faint galaxies for three fields at mid galactic latitudes and one field near the south galactic pole. The three mid galactic latitude fields were photographed on a IIIa-J + GG385 plate/filter combination by van Altena at the prime focus of the KPNO 4-meter in the mid 1970s, while the south polar region was photographed on a IIIa-F + RG610 plate/filter combination by van Altena and C.E. Lopez (Univ. of San Juan, Argentina) at the prime focus of the CTIO 4-meter; all plates were hypersensitized by baking and exposed to the sky limit. In this paper we report on the progress of an investigation of the mid galactic latitude field at R.A. = 7h 07m 31s and Dec. = +7o 19.7′ (1950) which contains the faint binary white dwarf LP543-32/33. Preliminary measurements of selected stars in this field were made some time ago and a parallax of the white dwarf binary were published by van Altena and Mora (1977). Those measurements showed that the plates were of very high astrometric quality and that it would be possible to obtain accurate parallaxes for very faint stars.
There were two major kinds of Pennsylvanian-age tropical swamps: coal swamps, represented by most coal seams, and clastic swamps, commonly associated with coal as roof shale or sandstone floras. Such environments were part of depositionally-complex lowlands that also included non-swamp habitats. In general, the Pennsylvanian-age coal and clastic swamps were dominated by non-seed (lower vascular, spore-producing) plants, and the mesic, non-swamp vegetation was characterized by seed-plant (pollen-producing) dominance. On occasion, some drier-site kinds of vegetation are preserved, providing a glimpse of other kinds of plants in the lowland regions of the tropical belt; among these are the earliest known conifers (Scott and Chaloner, 1983) in the Middle Pennsylvanian.
Our objective is to map dynamic provinces and investigate dynamic changes in Jakobshavn Isbræ, Greenland. We use an approach that combines structural glaciology and remote-sensing data analysis, facilitated by mathematical characterization of generalized spatial surface roughness that provides parameters related to ice dynamics, deformation and interaction of the ice with bed topography. The approach is applied to derive time series of elevation and roughness changes and to attribute changes during rapid retreat. Different dynamic types of fast- and slow-moving ice can be mapped from ICESat Geoscience Laser Altimeter System data (2003–09) and Airborne Topographic Mapper data, using spatial roughness characterization, validated with ASTER and bed-topographic data. Results of comparative analysis of elevation changes and roughness changes of Jakobshavn south ice stream indicate (1) surface lowering of 10–15 m a-1 between 2004 and 2009 and (2) no change in surface roughness and dynamic types. These findings are consistent with a front retreat as part of a fjord-glacier cycle or following warming of fjord water and with climatic warming, but not with an internal dynamic acceleration as a cause of the observed changes during rapid retreat. Relationships to changes in basal water pressure are discussed. All glaciodynamic changes appear to have initiated near the front and propagated up-glacier.
We agree with Bracken, Rose, and Church (2016) and others that a critical design feature of any 360° feedback process is accountability, where the goal is “creation of sustainable individual, group, and/or organizational change in behaviors valued by the organization” (p. 764). Though we acknowledge the important roles that the organization and raters play in holding leaders accountable for their development, the goal of our commentary is to expand on how the leader's boss and other key individuals can serve as powerful sources of accountability in the 360° feedback process and throughout a leader's development journey. We also want to note that although the Center for Creative Leadership (CCL) encourages leaders to share what they have learned from their 360° feedback with their bosses and other accountability partners (e.g., peers), it is the leader's choice as to whether he or she shares key feedback with others. This practice ensures confidentiality of the data, helping leaders trust the process and increasing the likelihood that individuals accept difficult feedback and use it for performance improvement (Fleenor, Taylor, & Chappelow, 2008; King & Santana, 2010).
We investigated the physiology of two closely related albatross species relative to their breeding strategy: black-browed albatrosses (Thalassarche melanophris) breed annually, while grey-headed albatrosses (T. chrysostoma) breed biennially. From observations of breeding fate and blood samples collected at the end of breeding in one season and feather corticosterone levels (fCort) sampled at the beginning of the next breeding season, we found that in both species some post-breeding physiological parameters differed according to breeding outcome (successful, failed, deferred). Correlations between post-breeding physiology and fCort, and links to future breeding decisions, were examined. In black-browed albatrosses, post-breeding physiology and fCort were not significantly correlated, but fCort independently predicted breeding decision the next year, which we interpret as a possible migratory carry-over effect. In grey-headed albatrosses, post-breeding triglyceride levels were negatively correlated with fCort, but only in females, which we interpret as a potential cost of reproduction. However, this potential cost did not carry-over to future breeding in the grey-headed albatrosses. None of the variables predicted future breeding decisions. We suggest that biennial breeding in the grey-headed albatrosses may have evolved as a strategy to buffer against the apparent susceptibility of females to negative physiological costs of reproduction. Future studies are needed to confirm this.