The utility of preoperative six-minute-walk distance in lung transplantation

RATIONALE The use of 6-minute-walk distance (6MWD) as an indicator of exercise capacity to predict postoperative survival in lung transplantation has not previously been well studied. OBJECTIVES To evaluate the association between 6MWD and postoperative survival following lung transplantation. METHODS Adult, first time, lung-only transplantations per the United Network for Organ Sharing database from May 2005 to December 2011 were analyzed. Kaplan-Meier methods and Cox proportional hazards modeling were used to determine the association between preoperative 6MWD and post-transplant survival after adjusting for potential confounders. A receiver operating characteristic curve was used to determine the 6MWD value that provided maximal separation in 1-year mortality. A subanalysis was performed to assess the association between 6MWD and post-transplant survival by disease category. MEASUREMENTS AND MAIN RESULTS A total of 9,526 patients were included for analysis. The median 6MWD was 787 ft (25th-75th percentiles = 450-1,082 ft). Increasing 6MWD was associated with significantly lower overall hazard of death (P < 0.001). Continuous increase in walk distance through 1,200-1,400 ft conferred an incremental survival advantage. Although 6MWD strongly correlated with survival, the impact of a single dichotomous value to predict outcomes was limited. All disease categories demonstrated significantly longer survival with increasing 6MWD (P ≤ 0.009) except pulmonary vascular disease (P = 0.74); however, the low volume in this category (n = 312; 3.3%) may limit the ability to detect an association. CONCLUSIONS 6MWD is significantly associated with post-transplant survival and is best incorporated into transplant evaluations on a continuous basis given limited ability of a single, dichotomous value to predict outcomes.

Retention in care during the first 3 years of antiretroviral therapy for women in Malawi's option B+ programme: an observational cohort study

Background Studies of Malawi's option B+ programme for HIV-positive pregnant and breastfeeding women have reported high loss to follow-up during pregnancy and at the start of antiretroviral therapy (ART), but few data exist about retention during breastfeeding and after weaning. We examined loss to follow-up and retention in care in patients in the option B+ programme during their first 3 years on ART. Methods We analysed two data sources: aggregated facility-level data about patients in option B+ who started ART between Oct 1, 2011, and June 30, 2012, at 546 health facilities; and patient-level data from 20 large facilities with electronic medical record system for HIV-positive women who started ART between Sept 1, 2011, and Dec 31, 2013, under option B+ or because they had WHO clinical stages 3 or 4 disease or had CD4 counts of less than 350 cells per μL. We used facility-level data to calculate representative estimates of retention and loss to follow-up. We used patient-level data to study temporal trends in retention, timing of loss to follow-up, and predictors of no follow-up and loss to follow-up. We defined patients who were more than 60 days late for their first follow-up visit as having no follow-up and patients who were more than 60 days late for a subsequent visit as being lost to follow-up. We calculated proportions and cumulative probabilities of patients who had died, stopped ART, had no follow-up, were lost to follow-up, or were retained alive on ART for 36 months. We calculated odds ratios and hazard ratios to examine predictors of no follow-up and loss to follow-up. Findings Analysis of facility-level data about patients in option B+ who had not transferred to a different facility showed retention in care to be 76·8% (20 475 of 26 658 patients) after 12 months, 70·8% (18 306 of 25 849 patients) after 24 months, and 69·7% (17 787 of 25 535 patients) after 36 months. Patient-level data included 29 145 patients. 14 630 (50·2%) began treatment under option B+. Patients in option B+ had a higher risk of having no follow-up and, for the first 2 years of ART, higher risk of loss to follow-up than did patients who started ART because they had CD4 counts less than 350 cells per μL or WHO clinical stage 3 or 4 disease. Risk of loss to follow-up during the third year was low and similar for patients retained for 2 years. Retention rates did not change as the option B+ programme matured. Interpretation Our data suggest that pregnant and breastfeeding women who start ART immediately after they are diagnosed with HIV can be retained on ART through the option B+ programme, even after many have stopped breastfeeding. Interventions might be needed to improve retention in the first year on ART in option B+. Funding Bill & Melinda Gates Foundation, Partnerships for Enhanced Engagement in Research Health, and National Institute of Allergy and Infectious Diseases.

Sand geochemistry on sediment core CRP-3 from the Ross Sea, Antarctica

A total of 167 samples distubuted throughout the CRP-3 drillhole from 5.77 to 787.68 mbsf and representing fine to coarse sandstones have been analysed by X-ray fluorescence spectrometry (XRF) Bulk sample geochemistry (major and trace elements) indicates a dominant provenance of detritus from the Ferrar Supergroup in the uppermost 200 mbsf of the core. A markedly increased contribution from the Beacon sandstones is recognized below 200 mbsf and down to 600 mbsf. In the lower part of CRP-3, down to 787.68 mbsf, geochemical evidence for influxes of Ferrar materials is again recorded. On the basis of preliminary magnetostratigraphic data reported for the lower 447 mbsf of the drillhole, we tentatively evaluated the main periodicities modulating the geochemical records. Our results identify a possible influence of the precession, obliquity and long-eccentricity astronomical components (21, 41, and 400 ky frequency bands) on the deposition mechanisms of the studied glaciomarine sediments.

Solar radiation over and under sea ice and photographic quantification of Ice algal aggregates during the POLARSTERN cruise ARK-XXVII/3 (IceArc) in summer 2012

The ice cover of the Arctic Ocean has been changing dramatically in the last decades and the consequences for the sea-ice associated ecosystem remain difficult to assess. Algal aggregates underneath sea ice have been described sporadically but the frequency and distribution of their occurrence is not well quantified. We used upward looking images obtained by a remotely operated vehicle (ROV) to derive estimates of ice algal aggregate biomass and to investigate their spatial distribution. During the IceArc expedition (ARK-XXVII/3) of RV Polarstern in late summer 2012, different types of algal aggregates were observed floating underneath various ice types in the Central Arctic basins. Our results show that the floe scale distribution of algal aggregates in late summer is very patchy and determined by the topography of the ice underside, with aggregates collecting in dome shaped structures and at the edges of pressure ridges. The buoyancy of the aggregates was also evident from analysis of the aggregate size distribution. Different approaches used to estimate aggregate biomass yield a wide range of results. This highlights that special care must be taken when upscaling observations and comparing results from surveys conducted using different methods or on different spatial scales.

Solar irradiance over and under seasonal land-fast sea ice off Barrow, Alaska, in 2010

The amount of solar radiation transmitted through Arctic sea ice is determined by the thickness and physical properties of snow and sea ice. Light transmittance is highly variable in space and time since thickness and physical properties of snow and sea ice are highly heterogeneous on variable time and length scales. We present field measurements of under-ice irradiance along transects under undeformed land-fast sea ice at Barrow, Alaska (March, May, and June 2010). The measurements were performed with a spectral radiometer mounted on a floating under-ice sled. The objective was to quantify the spatial variability of light transmittance through snow and sea ice, and to compare this variability along its seasonal evolution. Along with optical measurements, snow depth, sea ice thickness, and freeboard were recorded, and ice cores were analyzed for chlorophyll a and particulate matter. Our results show that snow cover variability prior to onset of snow melt causes as much relative spatial variability of light transmittance as the contrast of ponded and white ice during summer. Both before and after melt onset, measured transmittances fell in a range from one third to three times the mean value. In addition, we found a twentyfold increase of light transmittance as a result of partial snowmelt, showing the seasonal evolution of transmittance through sea ice far exceeds the spatial variability. However, prior melt onset, light transmittance was time invariant and differences in under-ice irradiance were directly related to the spatial variability of the snow cover.

Particulate and phytoplankton absorption during POLARSTERN cruises ANT-XXVI/3 and ANT-XXVIII/3

The euphotic depth (Zeu) is a key parameter in modelling primary production (PP) using satellite ocean colour. However, evaluations of satellite Zeu products are scarce. The objective of this paper is to investigate existing approaches and sensors to estimate Zeu from satellite and to evaluate how different Zeu products might affect the estimation of PP in the Southern Ocean (SO). Euphotic depth was derived from MODIS and SeaWiFS products of (i) surface chlorophyll-a (Zeu-Chla) and (ii) inherent optical properties (Zeu-IOP). They were compared with in situ measurements of Zeu from different regions of the SO. Both approaches and sensors are robust to retrieve Zeu, although the best results were obtained using the IOP approach and SeaWiFS data, with an average percentage of error (E) of 25.43% and mean absolute error (MAE) of 0.10 m (log scale). Nevertheless, differences in the spatial distribution of Zeu-Chla and Zeu-IOP for both sensors were found as large as 30% over specific regions. These differences were also observed in PP. On average, PP based on Zeu-Chla was 8% higher than PP based on Zeu-IOP, but it was up to 30% higher south of 60°S. Satellite phytoplankton absorption coefficients (aph) derived by the Quasi-Analytical Algorithm at different wavelengths were also validated and the results showed that MODIS aph are generally more robust than SeaWiFS. Thus, MODIS aph should be preferred in PP models based on aph in the SO. Further, we reinforce the importance of investigating the spatial differences between satellite products, which might not be detected by the validation with in situ measurements due to the insufficient amount and uneven distribution of the data.

(Table 1) Paleomagnetic of ODP Leg 126 sites

A paleomagnetic study was made on the deep-marine sediments and volcanic rocks drilled by Ocean Drilling Program Leg 126 in the Izu-Bonin forearc region (Sites 787, 792, and 793). This study evaluates the sense and amount of the tectonic drift and rotation associated with the evolution of the Philippine Sea Plate and the Izu-Bonin Arc. Alternating-field and thermal demagnetization experiments show that most of the samples have stable remanence and are suitable for paleomagnetic studies. Paleomagnetic declinations were recovered by two methods of core orientation, one of which uses a secondary viscous magnetization vector of each specimen as an orientation standard, and the other of which is based on the data of downhole microresistivity measurement obtained by using a formation microscanner. Oligocene to early Miocene samples show 10° to 14° shallower paleolatitudes than those of the present. Middle Miocene to early Oligocene samples show progressive clockwise deflections (up to ~80°) in declination with time. These results suggest large northward drift and clockwise rotation of the Izu-Bonin forearc region since early Oligocene time. Considering previous paleomagnetic results from the other regions in the Philippine Sea, this motion may reflect large clockwise rotation of the whole Philippine Sea Plate over the past 40 m.y.