Shelf-ocean exchange and hydrography west of the Antarctic Peninsula: A review

The West Antarctic Peninsula (WAP) is a highly productive marine ecosystem where extended periods of change have been observed in the form of glacier retreat, reduction of sea-ice cover and shifts in marine populations, among others. The physical environment on the shelf is known to be strongly influenced by the Antarctic Circumpolar Current flowing along the shelf slope and carrying warm, nutrient-rich water, by cold waters flooding into the northern Bransfield Strait from the Weddell Sea, by an extensive network of glaciers and ice shelves, and by strong seasonal to inter-annual variability in sea-ice formation and air–sea interactions, with significant modulation by climate modes like El Niño–Southern Oscillation and the Southern Annular Mode. However, significant gaps have remained in understanding the exchange processes between the open ocean and the shelf, the pathways and fate of oceanic water intrusions, the shelf heat and salt budgets, and the long-term evolution of the shelf properties and circulation. Here, we review how recent advances in long-term monitoring programmes, process studies and newly developed numerical models have helped bridge these gaps and set future research challenges for the WAP system

The genetics of resistance to grapevine fanleaf virus in Vitis vinifera

Two wild Vitis vinifera accessions from the Middle East previously found to be resistant to grapevine fanleaf virus (GFV) were selfed and also crossed to a GFV-susceptible female cultivar. Five seedling populations of 60 plants each were established. A micrografting procedure was developed for screening the seedlings whereby single-node seedling stem segments were cleft-grafted go GFV-infected stocks in vitro. After 8 weeks, scion tissue was scored phenotypically and assayed by ELISA to measure virus titer. Resistance to GFV appears to segregate as a recessive trait controlled by at least two genes

Acoustic characterization of crack damage evolution in sandstone deformed under conventional and true triaxial loading

We thank the Associate Editor, Michelle Cooke, and the reviewers, Ze'ev Reches and Yves Guéguen, for useful comments which helped to improve the manuscript. We thank J.G. Van Munster for providing access to the true triaxial apparatus at KSEPL and for technical support during the experimental program. We thank R. Pricci for assistance with technical drawings of the apparatus. This work was partly funded by NERC award NE/N002938/1 and by a NERC Doctoral Studentship, which we gratefully acknowledge. Supporting data are included in a supporting information file; any additional data may be obtained from J.B. (e-mail: [email protected]).Peer reviewedPublisher PD

Sources of resistance to grapevine fanleaf virus (GFV) in Vitis species

A diverse array of Vitis germplasm was screened to identify sources of resistance to grapevine fanleaf virus (GFV). The 173 accessions screened included Vitis species, cultivars, and interspecific hybrids. Since Vitis vinifera and GFV are thought to have a common origin in the Middle East, particular attention was paid to this species - 27 Middle Eastern vinifera accessions and 9 vinifera cultivars were surveyed. In addition, North American accessions of 24 Euvitis species and 2 Muscadinia species were tested, including cultivars of rotundifolia, as were accessions of 5 Asian species. The interspecific hybrids included 3 vinifera x rotundifolia (VR) hybrids known to be resistant to the feeding of Xiphinema index, the nematode vector of GFV. The vines to be tested were approach grafted to infected Cabernet Sauvignon vines and subsequently screened for the presence of the virus by ELISA. 3 GFV-resistant accessions were identified - a Middle Eastern vinifera, rotundifolia cv. Bountiful, and one of the VR hybrids. Several vinifera accessions (including some cultivars) previously reported to be GFV-resistant were susceptible in this study. These results suggest that two forms of GFV resistance, hast plant resistance and nonhost resistance, exist in Vitis germplasm

Genetic transformation of Vitis vinifera L. cvs Thompson Seedless and Chardonnay with the pear PGIP and GFP encoding genes

Transgenic plants of Vitis vinifera L. cvs. Chardonnay and Thompson Seedless expressing the β-glucuronidase gene (GUS) and either the pear polygalacturonase inhibiting protein gene (PGIP) or the green fluorescent protein gene (GFP) were produced via somatic embryogenesis. Various media and culture conditions were tested in order to develop an efficient transformation method. Best results were obtained when embryogenic callus was initiated from anthers cultured on PIV medium and maintained in PT medium. Embryogenic lines of the rootstocks Saint George, 110 Richter and Freedom and from inflorescence primordia of Chardonnay and 110 Richter were also established using the same media. Inoculation with 109 cells·ml-1 Agrobacterium resulted in a higher number of selected calli than cultures inoculated with 107 or 108 cells·ml-1. Plants were regenerated in a modified WP medium from up to 46 % of the selected callus. Approximately 80 % of the lines expressed GUS and either PGIP or GFP but a low correlation was found between β-glucuronidase and polygalacturonase inhibiting protein activities.

Mortality Differences Between Traditional Medicare and Medicare Advantage: A Risk-Adjusted Assessment Using Claims Data.

Medicare Advantage (MA) has grown rapidly since the Affordable Care Act; nearly one-third of Medicare beneficiaries now choose MA. An assessment of the comparative value of the 2 options is confounded by an apparent selection bias favoring MA, as reflected in mortality differences. Previous assessments have been hampered by lack of access to claims diagnosis data for the MA population. An indirect comparison of mortality as an outcome variable was conducted by modeling mortality on a traditional fee-for-service (FFS) Medicare data set, applying the model to an MA data set, and then evaluating the ratio of actual-to-predicted mortality in the MA data set. The mortality model adjusted for clinical conditions and demographic factors. Model development considered the effect of potentially greater coding intensity in the MA population. Further analysis calculated ratios for subpopulations. Predicted, risk-adjusted mortality was lower in the MA population than in FFS Medicare. However, the ratio of actual-to-predicted mortality (0.80) suggested that the individuals in the MA data set were less likely to die than would be predicted had those individuals been enrolled in FFS Medicare. Differences between actual and predicted mortality were particularly pronounced in low income (dual eligibility), nonwhite race, high morbidity, and Health Maintenance Organization (HMO) subgroups. After controlling for baseline clinical risk as represented by claims diagnosis data, mortality differences favoring MA over FFS Medicare persisted, particularly in vulnerable subgroups and HMO plans. These findings suggest that differences in morbidity do not fully explain differences in mortality between the 2 programs

Secondary Shear Waves From Source Boreholes

The purpose of this paper is to synthesize the most important results of the thesis work of Meredith (1990) concerning radiation from seismic sources in boreholes. Previous studies of radiation from sources in boreholes have been far-field studies and have neglected the explicit contribution of the borehole. In general, this is fine for P-wave radiation and for S-wave radiation into high velocity rocks. However, tube waves "leak" shear conical waves (Mach waves) which propagate when the tube wave velocity is greater than the shear wave velocity of the surrounding medium. These Mach waves are of high amplitude because of the dominance of the tube wave and radiate away from the borehole in a fixed conical shape. The shape of the cone is dependent on the shear wave velocity of the medium and the tube wave velocity. This paper defines the conditions under which these Mach waves exist and thoroughly describes them in a physical sense and less so in a mathematical sense. Finally, the relationship of Mach waves to data sets is examined and how Mach waves may be confused with receiver borehole tube waves. To keep the presentation simple, radiation from axial or torsional sources or radiation from empty boreholes is omitted in this paper but fully addressed in Meredith (1990).Massachusetts Institute of Technology. Full Waveform Acoustic Logging Consortiu

Modelling Of Downhole Seismic Sources II: An Analysis Of The Heelan/Brekhovskikh Results And Comparison Of Point Source Radiation To Radiation From Boreholes

The work of Heelan (1952, 1953a,b) was one of the first studies of wave propagation from a cylindrical boundary. Heelan attempted to model the radiation emanating from a cylindrical shot hole filled with dynamite. To do so he applied a constant stress to a finite length of an empty infinite cylindrical cavity embedded in an infinite elastic, homogeneous medium. The stresses he considered were axial, torsional, and radial stresses. The radial and axial stresses were required to be proportional to each other and of the same duration. To date Heelan's work has been referenced in over 100 articles and 15 different journals including recent works (Paulsson, 1988) . His results have also been compared with results from the reciprocity theorem (White, 1953, 1960) and played an integral part of important books including those by Brekhovskikh (1960, 1980) and White (1965, 1983). His fundamental contributions were the description of shear wave lobes, the famous four-leaved rose, generated from a radial source in a borehole and that the radiation patterns for an axial source and a torsional source in a borehole have the same geometries as the point axial and torsional sources in infinite media. Despite the importance of this work, Heelan's results have been criticized by Jordan (1962) who dismissed the work as mathematically unsound and Abo-Zena (1977) who devoted an appendix of his 1977 paper to criticizing Heelan's results. The main point of contention has been the use of contour analysis in his first paper (Heelan, 1953a). Although Heelan's work did not include a fluid-filled borehole which is a crucial omission for our purposes, his work may nonetheless be seen as a starting point for the modelling of downhole seismic sources. For instance, Lee and Balch (1982) developed radiation patterns for fluid boreholes which were simple extensions of Heelan's results. Additionally, one particular application of Heelan's theory is in the preliminary development of downhole seismic Sources that often require dry holes until the electronics can be properly shielded. For that reason, an exhaustive examination of the mathematics and physics that went into Heelan's first paper was undertaken to determine if his formulation was correct. The fundamental basis of Heelan's work was a variant of the Sommerfeld integral, an integral of cylindrical waves, in which he unfortunately did not specify the contour. To overcome this obstacle of an unknown contour a parallel method suggested by Brekhovskikh (1960, 1980) was implemented. Brekhovskikh used the Weyl integral, an integral over plane waves, to duplicate Heelan's results for the radial and torsional stresses. However he does no justification of the extensive algebra or analysis involved and does not include the effects of axial stress. Thus in this paper, we have completed and elucidated the work that Brekhovskikh initiated and moreover indirectly verified that Heelan's results were correct. Additionally, we found that Abo-Zena's and Heelan's initial formulations were equivalent. The only difference was in a reversal of the separation of variables procedure necessary to replicate this work and also in Abo-Zena's USe of the Laplace transform where Heelan used the Fourier transform. However, Abo-Zena's results do extend Heelan's by allowing the source function to vary over the distance in which it is applied. The far field results of Abo-Zena and Heelan are equivalent (White, 1983) only if a 1/μ correction is applied to Abo-Zena's results. The first half of this paper is very involved mathematically but much of the algebra is relegated to Appendix A. Having verified that Heelan's results were correct we then proceed to compare Heelan's results with well established point source representations known in the literature (White, 1983) and also with radiation patterns from point sources and stress sources in a fluid-filled borehole (Lee and Balch, 1982). These comparisons will help us isolate the propagation effects of the fluid and the geometrical effect of the borehole. One unique aspect to our approach will be the consideration of radiation from boreholes surrounded by varying lithologies instead of just the Poisson solid as is commonly done. The lithologies to be considered include a soft sediment (Pierre shale) and two more indurated sediments, Berea sandstone and Solenhofen limestone. By following this approach we show that the effect on the radiation magnitude can be substantial due to changes in lithology in addition to isolating the relative effects of the borehole and the fluid.Massachusetts Institute of Technology. Full Waveform Acoustic Logging Consortiu