Circulation, retention, and mixing of waters within the Weddell-Scotia Confluence, Southern Ocean:The role of stratified Taylor columns

The waters of the Weddell-Scotia Confluence (WSC) lie above the rugged topography of the South Scotia Ridge in the Southern Ocean. Meridional exchanges across the WSC transfer water and tracers between the Antarctic Circumpolar Current (ACC) to the north and the subpolar Weddell Gyre to the south. Here, we examine the role of topographic interactions in mediating these exchanges, and in modifying the waters transferred. A case study is presented using data from a free-drifting, intermediate-depth float, which circulated anticyclonically over Discovery Bank on the South Scotia Ridge for close to 4 years. Dimensional analysis indicates that the local conditions are conducive to the formation of Taylor columns. Contemporaneous ship-derived transient tracer data enable estimation of the rate of isopycnal mixing associated with this column, with values of O(1000 m2/s) obtained. Although necessarily coarse, this is of the same order as the rate of isopycnal mixing induced by transient mesoscale eddies within the ACC. A picture emerges of the Taylor column acting as a slow, steady blender, retaining the waters in the vicinity of the WSC for lengthy periods during which they can be subject to significant modification. A full regional float data set, bathymetric data, and a Southern Ocean state estimate are used to identify other potential sites for Taylor column formation. We find that they are likely to be sufficiently widespread to exert a significant influence on water mass modification and meridional fluxes across the southern edge of the ACC in this sector of the Southern Ocean

Ignition of fuel–air mixtures from a hot circular cylinder

Ignition of hydrogen–air, ethylene–air and n-hexane–air mixtures from a horizontally and vertically oriented heated circular cylinder was studied experimentally in a wide range of equivalence ratio. Initial pressure and temperature were 101.3 kPa and 296 K, respectively. The cylinder with outer diameter 10 mm and heated length 10 mm was designed for high temperature uniformity. Two-color pyrometry measured the surface temperature; Time-resolved Mach–Zehnder interferometry acquired ignition dynamics, gas temperature fields and heat transfer characteristics. Ignition from the horizontal cylinder occurred at temperatures between 960 K and 1100 K for hydrogen, between 1060 K and 1110 K for ethylene, and between 1150 K and 1190 K for n-hexane. Vertical cylinder orientation increased ignition thresholds by 50–110 K for ethylene and n-hexane, whereas only little variation was observed for hydrogen. Infinite-fringe interferograms visualized the ignition dynamics and identified the most favorable ignition locations, which coincided with locations of lowest wall heat flux (largest thermal boundary layer thickness) and long residence time. Gas temperature fields were obtained by post-processing the interferograms, resolving the temporal and spatial development of thermal boundary layers and enabling local heat transfer analysis. The convective pattern around a horizontal cylinder features distinctly shallow temperature gradients, i.e., low heat flux, at the cylinder top due to thermal plume formation, which promotes ignition compared to the vertical cylinder. An analytical scaling model for ignition from hot surfaces was evaluated to determine the sensitivity of ignition threshold to heat transfer variations, and to reveal the influence of chemical mixture properties. This analysis predicts a particularly low sensitivity for hydrogen–air mixtures at temperatures near the extended second explosion limit, and a larger sensitivity of ethylene–air and n-hexane–air mixtures, which is in accordance with the experiments

The sensitivity of southeast pacific heat distribution to local and remote changes in ocean properties

AbstractThe Southern Ocean features ventilation pathways that transport surface waters into the subsurface thermocline on time scales from decades to centuries, sequestering anomalies of heat and carbon away from the atmosphere and thereby regulating the rate of surface warming. Despite its importance for climate sensitivity, the factors that control the distribution of heat along these pathways are not well understood. In this study, we use an observationally constrained, physically consistent global ocean model to examine the sensitivity of heat distribution in the recently ventilated subsurface Pacific (RVP) sector of the Southern Ocean to changes in ocean temperature and salinity. First, we define the RVP using numerical passive tracer release experiments that highlight the ventilation pathways. Next, we use an ensemble of adjoint sensitivity experiments to quantify the sensitivity of the RVP heat content to changes in ocean temperature and salinity. In terms of sensitivities to surface ocean properties, we find that RVP heat content is most sensitive to anomalies along the Antarctic Circumpolar Current (ACC), upstream of the subduction hotspots. In terms of sensitivities to subsurface ocean properties, we find that RVP heat content is most sensitive to basin-scale changes in the subtropical Pacific Ocean, around the same latitudes as the RVP. Despite the localized nature of mode water subduction hotspots, changes in basin-scale density gradients are an important controlling factor on heat distribution in the southeast Pacific.</jats:p

Modeling interannual dense shelf water export in the region of the Mertz Glacier Tongue (1992-2007)

1] Ocean observations around the Australian-Antarctic basin show the importance of coastal latent heat polynyas near the Mertz Glacier Tongue (MGT) to the formation of Dense Shelf Water (DSW) and associated Antarctic Bottom Water (AABW). Here, we use a regional ocean/ice shelf model to investigate the interannual variability of the export of DSW from the Adélie (west of the MGT) and the Mertz (east of the MGT) depressions from 1992 to 2007. The variability in the model is driven by changes in observed surface heat and salt fluxes. The model simulates an annual mean export of DSW through the Adélie sill of about 0.07 ± 0.06 Sv. From 1992 to 1998, the export of DSW through the Adélie (Mertz) sills peaked at 0.14 Sv (0.29 Sv) during July to November. During periods of mean to strong polynya activity (defined by the surface ocean heat loss), DSW formed in the Adélie depression can spread into the Mertz depression via the cavity under the MGT. An additional simulation, where ocean/ice shelf thermodynamics have been disabled, highlights the fact that models without ocean/ice shelf interaction processes will significantly overestimate rates of DSW export. The melt rates of the MGT are 1.2 ± 0.4 m yr−1 during periods of average to strong polynya activity and can increase to 3.8 ± 1.5 m/yr during periods of sustained weak polynya activity, due to the increased presence of relatively warmer water interacting with the base of the ice shelf. The increased melting of the MGT during a weak polynya state can cause further freshening of the DSW and ultimately limits the production of AABW

Equality, value pluralism and relevance: Is luck egalitarianism in one way good, but not all things considered?

Some luck egalitarians argue that justice is just one value among others and is thus not necessarily what we should strive for in order to make the world better. Yet, by focusing on only one dimension of what matters – luck equality – it proves very difficult to draw political implications in cases where several values are in tension. We believe that normative political philosophy must have the ambitionto guide political action. Hence, in this paper we make a negative and a positive point. Negatively, we argue that the inability to offer recommendations on what to strive for potentially weakens Kasper Lippert-Rasmussen’s account of luck egalitarianism. In order not to be irrelevant for political practice, a more serviceable version of luck egalitarianism that would allow for all-things-considered judgments is needed. Positively, we examine two possible routes toward such a view. One would be to stick to pluralism, but to discuss possible clashes and find a rule of regulation in each case. Another would consist in giving up value pluralism by identifying an over-arching value or principle that would arbitrate between different values. We suggest that Lippert-Rasmussen’s foundation of equality carries the potential for such an overarching principle.Political Philosophy and Ethic

The missing link: Predicting connectomes from noisy and partially observed tract tracing data

Our understanding of the wiring map of the brain, known as the connectome, has increased greatly in the last decade, mostly due to technological advancements in neuroimaging techniques and improvements in computational tools to interpret the vast amount of available data. Despite this, with the exception of the C. elegans roundworm, no definitive connectome has been established for any species. In order to obtain this, tracer studies are particularly appealing, as these have proven highly reliable. The downside of tract tracing is that it is costly to perform, and can only be applied ex vivo. In this paper, we suggest that instead of probing all possible connections, hitherto unknown connections may be predicted from the data that is already available. Our approach uses a 'latent space model' that embeds the connectivity in an abstract physical space. Regions that are close in the latent space have a high chance of being connected, while regions far apart are most likely disconnected in the connectome. After learning the latent embedding from the connections that we did observe, the latent space allows us to predict connections that have not been probed previously. We apply the methodology to two connectivity data sets of the macaque, where we demonstrate that the latent space model is successful in predicting unobserved connectivity, outperforming two baselines and an alternative model in nearly all cases. Furthermore, we show how the latent spatial embedding may be used to integrate multimodal observations (i.e. anterograde and retrograde tracers) for the mouse neocortex. Finally, our probabilistic approach enables us to make explicit which connections are easy to predict and which prove difficult, allowing for informed follow-up studies

Contralateral breast cancer risk is influenced by the age at onset in BRCA1-associated breast cancer

BRCA1/2 mutation carriers diagnosed with breast cancer have a strongly elevated life-time risk of developing a contralateral tumour. We studied the contralateral breast cancer risk in 164 patients from 83 families with a proven BRCA1 mutation in relation to the age at diagnosis of the first primary breast cancer. In the actuarial outcomes after 10 years’ follow-up, 40% of the 124 BRCA1-patients diagnosed with breast cancer < 50 years had developed contralateral breast cancer, vs 12% of the 40 patients > 50 years at first diagnosis (Plogrank= 0.02). These data suggest that age at diagnosis of the first tumour should be taken into account when prophylactic mastectomy in BRCA1-patients is considered. © 2000 Cancer Research Campaig

Митрополит Андрей Шептицький на владичому престолі (1889-1900 рр.) в Станіславові

Актуальність проблеми, зв’язок її з важливими науковими та практичними завданнями полягає в тому, що призначення Андрея Шептицького ЧСВВ третім Станіславівським Єпископом різко змінило подальший розвиток Станіславівської Української Греко-Католицької Єпархії. Як зазначає д-р Г.Лужницький, “після такого науковця, як Єпископ Ю.Пелеш, та хворого і розчарованого ідеаліста, яким був Юліан Куїловський, молодий, повний ініціативи, Кир Андрей Шептицький був Божою благодаттю нової і ще не зорганізованої як слід Станіславівської Єпархії”

Reproducibility of the lung anatomy under Active Breathing Coordinator control: Dosimetric consequences for scanned proton treatments.

Purpose/Objective The treatment of moving targets with scanning proton beams is challenging. By controlling lung volumes, Active Breathing Control (ABC) assists breath-holding for motion mitigation. The delivery of proton treatment fractions often exceeds feasible breath-hold durations, requiring high breath-hold reproducibility. Therefore, we investigated dosimetric consequences of anatomical reproducibility uncertainties in the lung under ABC, evaluating robustness of scanned proton treatments during breath-hold. Material/Methods T1-weighted MRIs of five volunteers were acquired during ABC, simulating image acquisition during four subsequent breath-holds within one treatment fraction. Deformation vector fields obtained from these MRIs were used to deform 95% inspiration phase CTs of 3 randomly selected non-small-cell lung cancer patients (Figure 1). Per patient, an intensity-modulated proton plan was recalculated on the 3 deformed CTs, to assess the dosimetric influence of anatomical breath-hold inconsistencies. Results Dosimetric consequences were negligible for patient 1 and 2 (Figure 1). Patient 3 showed a decreased volume (95.2%) receiving 95% of the prescribed dose for one deformed CT. The volume receiving 105% of the prescribed dose increased from 0.0% to 9.9%. Furthermore, the heart volume receiving 5 Gy varied by 2.3%. Figure 2 shows dose volume histograms for all relevant structures in patient 3. Conclusion Based on the studied patients, our findings suggest that variations in breath-hold have limited effect on the dose distribution for most lung patients. However, for one patient, a significant decrease in target coverage was found for one of the deformed CTs. Therefore, further investigation of dosimetric consequences from intra-fractional breath-hold uncertainties in the lung under ABC is needed