The linewidth of a non-Markovian atom laser

We present a fully quantum mechanical treatment of a single mode atom laser including pumping and output coupling. By ignoring atom-atom interactions, we have solved this model without making the Born-Markov approximation. We find substantially less gain narrowing than is predicted under that approximation.Comment: 4 pages, 1 encapsulated postscript figur

Practice pointer: Using the new UK-WHO growth charts

The new UK growth charts for children aged 0-4 years (designed using data from the new WHO standards) describe the optimal pattern of growth for all children, rather than the prevailing pattern in the UK (as with previous charts). The new charts are suitable for all ethnic groups and set breast feeding as the norm. UK children match the new charts well for length and height, but after age 6 months fewer children will be below the 2nd centile for weight or show weight faltering, and more will be above the 98th centile. The new charts look different: they have a separate preterm section, no lines between 0 and 2 weeks, and the 50th percentile is no longer emphasised. The charts give clear instructions on gestational correction, and there is a new chart for infants born before 32 weeks’ gestation. The instructions advise on when and how to measure and when a measurement or growth pattern is outside the normal range. The charts include a “look-up” tool for determining the body mass index centile from height and weight centiles without calculation and aid for predicting adult height. The charts and supporting educational materials can be downloaded from www.growthcharts.rcpch.ac.u

Onset and Evolution of Southern Annular Mode-Like Changes at Centennial Timescale

The Southern Westerly Winds (SWW) are the surface expression of geostrophic winds that encircle the southern mid-latitudes. In conjunction with the Southern Ocean, they establish a coupled system that not only controls climate in the southern third of the world, but is also closely connected to the position of the Intertropical Convergence Zone and CO2 degassing from the deep ocean. Paradoxically, little is known about their behavior since the last ice age and relationships with mid-latitude glacier history and tropical climate variability. Here we present a lake sediment record from Chilean Patagonia (51°S) that reveals fluctuations of the low-level SWW at mid-latitudes, including strong westerlies during the Antarctic Cold Reversal, anomalously low intensity during the early Holocene, which was unfavorable for glacier growth, and strong SWW since ∼7.5 ka. We detect nine positive Southern Annular Mode-like events at centennial timescale since ∼5.8 ka that alternate with cold/wet intervals favorable for glacier expansions (Neoglaciations) in southern Patagonia. The correspondence of key features of mid-latitude atmospheric circulation with shifts in tropical climate since ∼10 ka suggests that coherent climatic shifts in these regions have driven climate change in vast sectors of the Southern Hemisphere at centennial and millennial timescales.Fil: Moreno, P.I.. Universidad de Chile; ChileFil: Vilanova, Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Villa-Martínez, R.. Universidad de Magallanes; ChileFil: Dunbar, R.B.. University of Stanford; Estados UnidosFil: Mucciarone, D.A.. University of Stanford; Estados UnidosFil: Kaplan, M.R.. Columbia University; Estados UnidosFil: Garreaud, R.D.. Universidad de Chile; ChileFil: Rojas, M.. Universidad de Chile; ChileFil: Moy, C.M.. University of Otago; Nueva ZelandaFil: De Pol-Holz, R.. Universidad de Magallanes; ChileFil: Lambert, F.. Pontificia Universidad Católica de Chile; Chil

Regional conditions cause contrasting behaviour in U-isotope fractionation in black shales: Constraints for global ocean palaeo-redox reconstructions

The U-isotope system is a well-established palaeo-redox proxy that potentially constrains the global extent of marine anoxia during average as well as extreme redox events throughout Earth's history. A typical archive that forms underneath a reducing water column and acts as an intense U sink is organic-rich black shale. However, the degree to which black shale archives reflect the marine U-isotope signature is not well understood because U-isotope fractionation between U(VI)-bearing seawater and U(IV)-bearing black shales may vary as a function of local environmental conditions. Here, we present a combination of U-isotope and elemental concentration datasets, supported by a complementary Mo-isotope record, for the Furlo sedimentary section in Marche–Umbria, Italy and interrogate the combined systematics to unravel the mechanisms controlling the U-isotope fractionation factor between black shales and ambient seawater. We examine black shales deposited before and during Oceanic Anoxic Event 2 (OAE 2), which was one of the most extreme climatic perturbations of the Mesozoic Era that took place around the Cenomanian–Turonian boundary (Late Cretaceous, c. 94 Ma). The results of this study show that the U-isotope signature in the black shales deposited before OAE 2 was controlled by different mechanisms than the U-isotope ratios recorded in black shales deposited during OAE 2, with both stratigraphic intervals likely influenced by local environmental conditions. Probable local environmental changes include increased U reduction associated with biomass at or above the sediment–water interface and varying dissolved hydrogen sulphide concentrations in the water column and sediment. The overall results of this study confirm that black shales are a highly complex archive for U-isotope studies of past oceanic redox conditions, due to the sensitivity of the U-isotope fractionation mechanism to local environmental conditions, which are difficult to constrain. We propose the application of a ∆238Ushale-seawater of 0.6 ± 0.1 ‰ to black shale records deposited under locally constant euxinic conditions at non-restricted settings

Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the Last Glacial Termination

Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000–11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well-known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records, making it difficult to assess relationships between Antarctic ice-sheet (AIS) dynamics, climate change and sea level. Here we present results from a highly-resolved ‘horizontal ice core’ from the Weddell Sea Embayment, which records millennial-scale AIS dynamics across this extensive region. Counterintuitively, we find AIS mass-loss across the full duration of the Antarctic Cold Reversal (ACR; 14,600–12,700 yrs ago), with stabilisation during the subsequent millennia of atmospheric warming. Earth-system and ice-sheet modelling suggests these contrasting trends were likely Antarctic-wide, sustained by feedbacks amplified by the delivery of Circumpolar Deep Water onto the continental shelf. Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise

Content and performance of the MiniMUGA genotyping array: A new tool to improve rigor and reproducibility in mouse research

The laboratory mouse is the most widely used animal model for biomedical research, due in part to its well-annotated genome, wealth of genetic resources, and the ability to precisely manipulate its genome. Despite the importance of genetics for mouse research, genetic quality control (QC) is not standardized, in part due to the lack of cost-effective, informative, and robust platforms. Genotyping arrays are standard tools for mouse research and remain an attractive alternative even in the era of high-throughput whole-genome sequencing. Here, we describe the content and performance of a new iteration of the Mouse Universal Genotyping Array (MUGA), MiniMUGA, an array-based genetic QC platform with over 11,000 probes. In addition to robust discrimination between most classical and wild-derived laboratory strains, MiniMUGA was designed to contain features not available in other platforms: (1) chromosomal sex determination, (2) discrimination between substrains from multiple commercial vendors, (3) diagnostic SNPs for popular laboratory strains, (4) detection of constructs used in genetically engineered mice, and (5) an easy-to-interpret report summarizing these results. In-depth annotation of all probes should facilitate custom analyses by individual researchers. To determine the performance of MiniMUGA, we genotyped 6899 samples from a wide variety of genetic backgrounds. The performance of MiniMUGA compares favorably with three previous iterations of the MUGA family of arrays, both in discrimination capabilities and robustness. We have generated publicly available consensus genotypes for 241 inbred strains including classical, wild-derived, and recombinant inbred lines. Here, we also report the detection of a substantial number of XO and XXY individuals across a variety of sample types, new markers that expand the utility of reduced complexity crosses to genetic backgrounds other than C57BL/6, and the robust detection of 17 genetic constructs. We provide preliminary evidence that the array can be used to identify both partial sex chromosome duplication and mosaicism, and that diagnostic SNPs can be used to determine how long inbred mice have been bred independently from the relevant main stock. We conclude that MiniMUGA is a valuable platform for genetic QC, and an important new tool to increase the rigor and reproducibility of mouse research

Designing new UK-WHO growth charts: implications for health staff use and understanding of charts and growth monitoring

New pre-school UK charts have been produced incorporating the new World Health Organization growth standards based on healthy breastfed infants. This paper describes the process by which the charts and evidence-based instructions were designed and evaluated, and what it revealed about professional understanding of charts and growth monitoring. A multidisciplinary expert group drew on existing literature, new data analyses and parent focus groups as well as two series of chart-plotting workshops for health staff. The first series explored possible design features and general chart understanding. The second evaluated an advanced prototype with instructions, using plotting and interpretation of three separate scenarios on the old charts, compared with the new charts. The first plotting workshops (46 participants) allowed decisions to be made about the exact chart format, but it also revealed widespread confusion about use of adjustment for gestation and the plotting of birthweight. In the second series (78 participants), high levels of plotting inaccuracy were identified on both chart formats, with 64% of respondents making at least one major mistake. Significant neonatal weight loss was poorly recognized. While most participants recognized abnormal and normal growth patterns, 13–20% did not. Many respondents had never received any formal training in chart use. Growth charts are complex clinical tools that are, at present, poorly understood and inconsistently used. The importance of clear guidelines and formal training has now been recognized and translated into supporting educational materials (free to download at http://www.growthcharts.rcpch.ac.uk)

Plio-Pleistocene ocean circulation changes in the GOA and its impacts on the carbon and nitrogen cycles and the CIS development

The modern Gulf of Alaska (GOA) is a high nutrient low chlorophyll (HNLC) region, estimated to be important for nutrient cycling and CO2 exchange. Little is known of the GOA evolution over the Pliocene and Pleistocene as well as its impact on the Cordilleran Ice Sheet (CIS) development, when other evidence for changing North Pacific circulation has emerged. We analysed IODP Expedition 341 Site U1417 sediments, which extend through the Plio-Pleistocene transition (4-1.7 Ma), focussing on productivity-related biomarkers (alkenones, brassicasterol), siliceous microfossils and bulk carbon and nitrogen stable isotopes. Our results show two dominant water column regimes: one characterised by high silica and low organic matter preservation, containing microorganism remains from a mix of habitats (4-3.7 Ma) and a second characterised by low biogenic silica and increased organic matter preservation of microorganisms from dominantly open ocean habitats (3.33-3.32 Ma and 2.8-1.66 Ma). An increase of phytoplankton diversity (3.7-3.35 Ma, 3.19-2.82 Ma) characterises the two transitions of water column conditions, from oxygenated to reductive, that we attribute to a change from ocean mixing to strong stratified conditions with some occasional mixing. The biogeochemical changes in the GOA follow 400 and 100 kyr eccentricity cycles which are also reflected in changes in the CIS. We conclude that the CIS expansion created HNLC conditions in the GOA during the Mid Piacenzian Warm Period (MPWP) and the early Pleistocene. In turn, positive feedbacks increased marine productivity export, atmospheric CO2 drawdown and further CIS expansion