Polaron Physics in Optical Lattices

We investigate the effects of a nearly uniform Bose-Einstein condensate (BEC) on the properties of immersed trapped impurity atoms. Using a weak-coupling expansion in the BEC-impurity interaction strength, we derive a model describing polarons, i.e., impurities dressed by a coherent state of Bogoliubov phonons, and apply it to ultracold bosonic atoms in an optical lattice. We show that, with increasing BEC temperature, the transport properties of the impurities change from coherent to diffusive. Furthermore, stable polaron clusters are formed via a phonon-mediated off-site attraction.Comment: 4 pages, 4 figure

Enhancing surgical performance in cardiothoracic surgery with innovations from computer vision and artificial intelligence: a narrative review

When technical requirements are high, and patient outcomes are critical, opportunities for monitoring and improving surgical skills via objective motion analysis feedback may be particularly beneficial. This narrative review synthesises work on technical and non-technical surgical skills, collaborative task performance, and pose estimation to illustrate new opportunities to advance cardiothoracic surgical performance with innovations from computer vision and artificial intelligence. These technological innovations are critically evaluated in terms of the benefits they could offer the cardiothoracic surgical community, and any barriers to the uptake of the technology are elaborated upon. Like some other specialities, cardiothoracic surgery has relatively few opportunities to benefit from tools with data capture technology embedded within them (as is possible with robotic-assisted laparoscopic surgery, for example). In such cases, pose estimation techniques that allow for movement tracking across a conventional operating field without using specialist equipment or markers offer considerable potential. With video data from either simulated or real surgical procedures, these tools can (1) provide insight into the development of expertise and surgical performance over a surgeon’s career, (2) provide feedback to trainee surgeons regarding areas for improvement, (3) provide the opportunity to investigate what aspects of skill may be linked to patient outcomes which can (4) inform the aspects of surgical skill which should be focused on within training or mentoring programmes. Classifier or assessment algorithms that use artificial intelligence to ‘learn’ what expertise is from expert surgical evaluators could further assist educators in determining if trainees meet competency thresholds. With collaborative efforts between surgical teams, medical institutions, computer scientists and researchers to ensure this technology is developed with usability and ethics in mind, the developed feedback tools could improve cardiothoracic surgical practice in a data-driven way

Phylogeny and adaptive evolution of the brain-development gene microcephalin (MCPH1) in cetaceans.

BACKGROUND: Representatives of Cetacea have the greatest absolute brain size among animals, and the largest relative brain size aside from humans. Despite this, genes implicated in the evolution of large brain size in primates have yet to be surveyed in cetaceans. RESULTS: We sequenced ~1240 basepairs of the brain development gene microcephalin (MCPH1) in 38 cetacean species. Alignments of these data and a published complete sequence from Tursiops truncatus with primate MCPH1 were utilized in phylogenetic analyses and to estimate ω (rate of nonsynonymous substitution/rate of synonymous substitution) using site and branch models of molecular evolution. We also tested the hypothesis that selection on MCPH1 was correlated with brain size in cetaceans using a continuous regression analysis that accounted for phylogenetic history. Our analyses revealed widespread signals of adaptive evolution in the MCPH1 of Cetacea and in other subclades of Mammalia, however, there was not a significant positive association between ω and brain size within Cetacea. CONCLUSION: In conjunction with a recent study of Primates, we find no evidence to support an association between MCPH1 evolution and the evolution of brain size in highly encephalized mammalian species. Our finding of significant positive selection in MCPH1 may be linked to other functions of the gene.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Role of runoff and interflow in chemical transport for claypan soils

Students supported: 2 Student AssistantsNo-tillage systems have been found to increase water runoff for some soils. This is a major concern because this increased runoff has the potential for increasing the runoff of dissolved herbicides in the spring since these chemicals are not incorporated into the soil with no-tillage systems. This study was conducted to evaluate the effects of seven longterm crop and tillage systems on runoff and saturated hydraulic conductivity. The study was conducted near Kingdom City, Missouri on a Mexico silt loam (fine, montmorillonitic, mesic Udollic Ochraqualf). Runoff records from 1983 through 1993 were collected. The seven treatments consisted of no-tillage (NT), moldboard plow (MP), and chisel plow (CP) continuous corn (Zea mays L.) and continuous soybean (Glycine max L.) and fallow (F). Saturated hydraulic conductivity (Ksat), bulk density, organic matter, and water content were determined on soil cores removed from two interrow positions (trafficked and non-trafficked) and two soil depths (0 - 125 mm, 125 - 150 mm). Tillage had a small but significant effect on runoff, Ksat, bulk density, water content at sampling, and organic matter. The Fallow treatment produced the lowest values of Ksat (0.2 mm/h), bulk density (1.3 g cm^-3), and organic matter content (0.9 percent) for the surface 125 mm, as compared to the NT, MB and CP treatments. No differences in Ksat were found (p=0.587) among NT, MP and CP tillage treatments. Complex interaction effects of tillage vs. wheel traffic (p=0.039) and tillage vs. depth (p=0.003) suggested that tillage effects on Ksat vary with interrow position and soil depth. The NT (0.301 mm mm^-3) had significantly higher field volumetric water content than MP (0.285 mm mm^-3) and CP (0.282 mm mm^-3), when averaged across crops. Plots planted to corn had greater water content (0.297 mm mm^-3) compared to soybean plots (0.281 mm mm^-3). Runoff under F was the highest in each year from 1983 to 1993. The greatest amount of runoff occurred during Period 4 (harvest to planting). Runoff was lowest during Period 1 and 2. No-tillage had significantly higher runoff than MP and CP treatments during Period 4, spring (p=0.006); Period 4, fall (p=0.011 ); Fallow period (p=0.005); and Period 1 and 2 (p=0.021). Cumulative runoff with NT was significantly (p=0.001) higher compared to MP and CP, except from 1991 to 1993 in which differences were not significant (p=0.374). Corn produced lower runoff rates than soybean at the 0.05 level in Period 4, fall. Increased runoff in NT was attributed to higher water content and subsequently lower infiltration for this soil which had a nearly impermeable subsurface argillic horizon.Project # G-2029-02 Agreement # 14-08-0001-G-2029-0

Chlordane movement during rainfall

Indoor rainfall simulation experiments were conducted to quantify the mass of technical chlordane leaving an experimental soil box in runoff, splash and leachate. The initial mass of technical chlordane was uniformly distributed throughout the soil at concentrations equal to those recommended for termite control around basement and foundation walls. Two silt loam soils and one sandy soil were studied. The mass of chlordane in runoff adsorbed to organic matter was estimated to be 16 times the mass of chlordane in runoff adsorbed to clay. For a soil with a clay-to-organic-matter ratio as high as 66, the mass of chlordane in runoff appears to be predominantly a function of clay content. For a soil with a clay-to-organic-matter ratio as low as 2 to 5, the mass of chlordane in runoff appears to be predominantly a function of organic matter content. An increase in rainfall intensity from 51 to 102 mm/hr increased chlordane mass in runoff by 300 to 500 percent. This increase in rainfall intensity increased the chlordane-to-sediment mass ratio in the runoff by 7 to 18 percent. The chlordane mass in runoff was 5 to 9 times as great as the mass of bromide in runoff. The chlordane mass in splash was 25 percent of the chlordane mass in runoff. Only the sandy soil at the higher rainfall intensity produced leachate. The chlordane mass in this leachate during the rainfall period was 37 percent of the chlordane mass in runoff and 264 percent of the chlordane mass in splash. The total chlordane mass which left the soil box by runoff, splash and leachate was equivalent to 4 to 44 mg per square foot of treated surface. This amounted to 0.03 to 0.31 percent of the original chlordane mass applied to the experimental soil box. This could potentially occur from previous legal surface applications in agriculture and turf management, from more recent illegal surface applications in agriculture and turf management, from proper use (according to label directions) as a subsurface termiticide but where depth of untreated cover soil was insufficient, from improper use as a subsurface termiticide where treated soil remained uncovered at the surface or from disturbance by new construction of large areas treated in previous years. This type of horizontal movement of chlordane and other organochlorine pesticides has been documented. Bennett et al. (1974) measured 70 ppb of gamma chlordane in the top five inches of soil located 10 feet away from a foundation wall treated 21 years earlier. Lichtenstein (1958) found higher concentrations of the organochlorine insecticides aldrin, lindane and DDT on the downslope side than on the upslope side of treated test plots. Similarly, Peach et al. (1973) found surface movement of aldrin, lindane and heptachlor toward points of lower elevation in a sloping field. Haan (1971) conducted laboratory rainfall-runoff experiments following surface treatment with aldrin, dieldrin and DDT and found that sediment carried more than twice as much pesticide mass as the water. Wauchope (1978) reviewed the literature on pesticide losses in runoff water from agricultural fields. He found that organochlorine pesticides lose about 1 percent of the total mass applied to the field through runoff. This compared to other commercial pesticides which lose 0.5 percent or less unless severe rainfall conditions occur within 2 weeks after application. Another important consideration is the mass of pesticide located within a few millimeters of the soil surface. Investigators have found that it is this zone from which pesticides are released during rainfall. Sharpley (1985) studied 5 soils and found the depth of this zone to range from 2 to 4 mm for 4 percent slopes under 50 mm/hr rainfall intensity to 13 to 37 mm for 20 percent slopes under 160 mm/hr rainfall intensity.Project # G-1432-04 Agreement # 14-08-0001-G-1423-0

Macropore effects on pesticides transport to groundwater

The objective of this investigation was to evaluate the leaching and degradation characteristics of atrazine and bromide in a field of alluvial soils under irrigated, no-till management. The experimental site was 0.1 ha in size. The soils were Sarpy (mixed, mesic Typic Udipsamments) with the surface texture varying from silt loam to loamy sand. Atrazine was applied at 2.2 kg/ha after sorghum (Sorghum bicolor) was planted. Bromide was applied at 115 kg/ha five days later. Soil cores were extracted to a depth of 150 cm which were segmented into 7.5 cm increments and were analyzed for each of the chemicals separately. The dates for sampling were one week, one month, two months, three months, and four months after application of the chemicals. As a result 1134 and 3542 soil samples were extracted for atrazine and bromide analysis, respectively. Atrazine was detected within the 15 to 22.5 cm depth increment one week after application. These data suggest that some of the atrazine can move to depth of 20 cm after one week which is probably due to the presence of macropores (1-5 mm diameter holes) open to the soil surface which were present in this field under no-till management. Atrazine was detected at very low concentrations at two and four months after application. Although extreme variability in atrazine concentrations occurred, the variations were not explained totally by differences in soil texture. The data in this study indicate some potential, although small, for atrazine contamination of groundwater.Project # G-1432-03 Agreement # 14-08-0001-G-1423-0

Structural Properties, Order-Disorder Phenomena and Phase Stability of Orotic Acid Crystal Forms

Orotic acid (OTA) is reported to exist in the anhydrous (AH), monohydrate (Hy1) and dimethylsulfoxide monosolvate (SDMSO) forms. In this study we investigate the (de)hydration/desolvation behavior, aiming at an understanding of the elusive structural features of anhydrous OTA by a combination of experimental and computational techniques, namely, thermal analytical methods, gravimetric moisture (de)sorption studies, water activity measurements, X-ray powder diffraction, spectroscopy (vibrational, solid-state NMR), crystal energy landscape and chemical shift calculations. The Hy1 is a highly stable hydrate, which dissociates above 135°C and loses only a small part of the water when stored over desiccants (25°C) for more than one year. In Hy1, orotic acid and water molecules are linked by strong hydrogen bonds in nearly perfectly planar arranged stacked layers. The layers are spaced by 3.1 Å and not linked via hydrogen-bonds. Upon dehydration the X-ray powder diffraction and solid-state NMR peaks become broader indicating some disorder in the anhydrous form. The Hy1 stacking reflection (122) is maintained, suggesting that the OTA molecules are still arranged in stacked layers in the dehydration product. Desolvation of SDMSO, a non-layer structure, results in the same AH phase as observed upon dehydrating Hy1. Depending on the desolvation conditions different levels of order-disorder of layers present in anhydrous OTA are observed, which is also suggested by the computed low energy crystal structures. These structures provide models for stacking faults as intergrowth of different layers is possible. The variability in anhydrate crystals is of practical concern as it affects the moisture dependent stability of AH with respect to hydration

Artifacts and Original Intent: A Cross-Cultural Perspective on the Design Stance

How do people decide what category an artifact belongs to? Previous studies have suggested that adults and, to some degree, children, categorize artifacts in accordance with the design stance, a categorization system which privileges the designer’s original intent in making categorization judgments. However, these studies have all been conducted in Western, technologically advanced societies, where artifacts are mass produced. In this study, we examined intuitions about artifact categorization among the Shuar, a hunter-horticulturalist society in the Amazon region of Ecuador. We used a forced-choice method similar to previous studies, but unlike these studies, our scenarios involved artifacts that would be familiar to the Shuar. We also incorporated a community condition to examine the possible effect of community consensus on how artifacts are categorized. The same scenarios were presented to university student participants in the UK. Across populations and conditions, participants tended to categorize artifacts in terms of a creator’s intent as opposed to a differing current use. This lends support to the view that the design stance may be a universal feature of human cognition. However, we conclude with some thoughts on the limitations of the present method for studying artifact concepts