ENSO feedbacks and their relationships with the mean state in a flux adjusted ensemble

The El Niño Southern Oscillation (ENSO) is governed by a combination of amplifying and damping ocean–atmosphere feedbacks in the equatorial Pacific. Here we quantify these feedbacks in a flux adjusted HadCM3 perturbed physics ensemble under present day conditions and a future emissions scenario using the Bjerknes Stability Index (BJ index). Relationships between feedbacks and both the present day biases and responses under climate change of the mean equatorial Pacific climate are investigated. Despite minimised mean sea surface temperature biases through flux adjustment, the important dominant ENSO feedbacks still show biases with respect to observed feedbacks and inter-ensemble diversity. The dominant positive thermocline and zonal advective feedbacks are found to be weaker in ensemble members with stronger mean zonal advection. This is due to a weaker sensitivity of the thermocline slope and zonal surface ocean currents in the east Pacific to surface wind stress anomalies. A drier west Pacific is also found to be linked to weakened shortwave and latent heat flux damping, suggesting a link between ENSO characteristics and the hydrological cycle. In contrast to previous studies using the BJ index that find positive relationships between the index and ENSO amplitude, here they are weakly or negatively correlated, both for present day conditions and for projected differences. This is caused by strong thermodynamic damping which dominates over positive feedbacks, which alone approximate ENSO amplitude well. While the BJ index proves useful for individual linear feedback analysis, we urge caution in using the total linear BJ index alone to assess the reasons for ENSO amplitude biases and its future change in models

Why the South Pacific Convergence Zone is diagonal

During austral summer, the majority of precipitation over the Pacific Ocean is concentrated in the South Pacific Convergence Zone (SPCZ). The surface boundary conditions required to support the diagonally (northwest-southeast) oriented SPCZ are determined through a series of experiments with an atmospheric general circulation model. Continental configuration and orography do not have a significant influence on SPCZ orientation and strength. The key necessary boundary condition is the zonally asymmetric component of the sea surface temperature (SST) distribution. This leads to a strong subtropical anticyclone over the southeast Pacific that, on its western flank, transports warm moist air from the equator into the SPCZ region. This moisture then intensifies (diagonal) bands of convection that are initiated by regions of ascent and reduced static stability ahead of the cyclonic vorticity in Rossby waves that are refracted toward the westerly duct over the equatorial Pacific. The climatological SPCZ is comprised of the superposition of these diagonal bands of convection. When the zonally asymmetric SST component is reduced or removed, the subtropical anticyclone and its associated moisture source is weakened. Despite the presence of Rossby waves, significant moist convection is no longer triggered; the SPCZ disappears. The diagonal SPCZ is robust to large changes (up to +/-6 degC) in absolute SST (i.e. where the SST asymmetry is preserved). Extreme cooling (change less than -6 degC) results in a weaker and more zonal SPCZ, due to decreasing atmospheric temperature, moisture content and convective available potential energy

Multidecadal ENSO amplitude variability in a 1000-yr simulation of a coupled global climate model: Implications for observed ENSO variability

The amplitude of the El Niño-Southern Oscillation (ENSO) can vary naturally over multidecadal time scales and can be influenced by climate change. However, determining the mechanism for this variation is difficult because of the paucity of observations over such long time scales. Using a 1000-yr integration of a coupled global climate model and a linear stability analysis, it is demonstrated that multidecadal modulation of ENSO amplitude can be driven by variations in the governing dynamics. In this model, the modulation is controlled by the underlying thermocline feedback mechanism, which in turn is governed by the response of the oceanic thermocline slope across the equatorial Pacific to changes in the overlying basinwide zonal winds. Furthermore, the episodic strengthening and weakening of this coupled interaction is shown to be linked to the slowly varying background climate. In comparison with the model statistics, the recent change of ENSO amplitude in observations appears to be still within the range of natural variability. This is despite the apparent warming trend in the mean climate. Hence, this study suggests that it may be difficult to infer a climate change signal from changes in ENSO amplitude alone, particularly given the presently limited observational data. © 2013 American Meteorological Society

Role of immune serum in the killing of Helicobacter pylori by macrophages

Background: Helicobacter pylori infection can lead to the development of gastritis, peptic ulcers and gastric cancer, which makes this bacterium an important concern for human health. Despite evoking a strong immune response in the host, H. pylori persists, requiring complex antibiotic therapy for eradication. Here we have studied the impact of a patient’s immune serum on H. pylori in relation to macrophage uptake, phagosome maturation, and bacterial killing. Materials and Methods: Primary human macrophages were infected in vitro with both immune serum-treated and control H. pylori. The ability of primary human macrophages to kill H. pylori was characterized at various time points after infection. H. pylori phagosome maturation was analyzed by confocal immune fluorescence microscopy using markers specific for H. pylori, early endosomes (EEA1), late endosomes (CD63) and lysosomes (LAMP-1). Results: Immune serum enhanced H. pylori uptake into macrophages when compared to control bacteria. However, a sufficient inoculum remained for recovery of viable H. pylori from macrophages, at 8 hours after infection, for both the serum-treated and control groups. Both serum-treated and control H. pylori phagosomes acquired EEA1 (15 minutes), CD63 and LAMP-1 (30 minutes). These markers were then retained for the rest of an 8 hour time course. Conclusions: While immune sera appeared to have a slight positive effect on bacterial uptake, both serum-treated and control H. pylori were not eliminated by macrophages. Furthermore, the same disruptions to phagosome maturation were observed for both serum-treated and control H. pylori. We conclude that to eliminate H. pylori, a strategy is required to restore the normal process of phagosome maturation and enable effective macrophage killing of H. pylori, following a host immune response.Stacey Keep, Glenn Borlace, Ross Butler and Doug Brook

Extreme swings of the South Pacific Convergence Zone and the different types of El Niño events

There have been three extreme equatorward swings of the South Pacific Convergence Zone (SPCZ) during the satellite era. These zonal SPCZ (zSPCZ) events coincided with an El Niño of different magnitude and spatial pattern, in which strong anomalous warming reduced the off-equatorial-to-equatorial meridional sea surface temperature (SST) gradient near the dateline, enabling convection to shift equatorward. It is not known, given the short observational record, how and whether different types of El Niño are associated with zSPCZ events. Using perturbed physics ensembles experiments in which SST biases are reduced, we find that zSPCZ events are concurrent with notable eastern Pacific (EP) warming. Central Pacific warming alone is rarely able to produce a swing, even as the climate warms under a CO2 increase scenario. Only El Niño events with strong EP warming can shift the convective zone. Such co-occurring events are found to increase in frequency under greenhouse warming. Key Points Extreme swings of the SPCZ occur with El Niño eastern Pacific warming Extreme El Niño is not required to induce an extreme swing of the SPCZ Extreme swings occur more often with EP-type El Niño under greenhouse warming ©2014. American Geophysical Union. All Rights Reserved

Outcomes of acinetobacter peritonitis in peritoneal dialysis patients: a multicenter registry analysis

Acinetobacter is a rare but important cause of peritonitis in peritoneal dialysis (PD) patients. As the complication has not been comprehensively evaluated previously, the present study examined the outcomes of Acinetobacter peritonitis in a large, national cohort of PD patients.The study included all episodes of peritonitis in Australia from January 2004 to December 2014 using Australia and New Zealand Dialysis and Transplant Registry (ANZDATA) data. The primary outcome was peritonitis cure and secondary outcomes were catheter removal, hemodialysis transfer, recurrent/relapsing peritonitis, peritonitis-related hospitalization, and death. Outcomes were compared using multivariable logistic regression.Overall, 5,367 patients experienced 11,122 episodes of peritonitis across 51 centers in Australia. Of these, 228 (4.2%) patients experienced 253 (2.3%) episodes of Acinetobacter peritonitis (176 episodes were due to Acinetobacter alone and 77 involved co-infection with other organisms). Of the 176 solitary Acinetobacter episodes, 131(74%) achieved cure with antibiotics alone. Compared with Acinetobacter, significantly lower odds of peritonitis cure were observed for Pseudomonas (adjusted odds ratio [AOR] 0.24, 95% confidence interval [CI]: 0.16 - 0.36), other gram-negative organisms (AOR 0.54, 95% CI 0.37 - 0.77), fungi (AOR 0.02, 95% CI 0.01 - 0.03), and polymicrobial organisms (AOR 0.36, 95% CI 0.25 - 0.51), whilst similar odds of cure were observed for Staphylococcus (AOR 0.73, 95% CI 0.50 - 1.06), other gram-positive organisms (AOR 1.32,95% CI 0.93 - 1.89), culture-negative (AOR 1.19, 95% CI 0.82 -1.71), and other organisms (AOR 0.72, 95% CI 0.49 - 1.07). The odds of catheter removal and hemodialysis transfer were higher with Pseudomonas, other gram-negative, fungal, and polymicrobial peritonitis than with Acinetobacter peritonitis. The odds of death were also higher with Pseudomonas and fungal peritonitis than with Acinetobacter peritonitis. Treatment of Acinetobacter peritonitis with gentamicin, ciprofloxacin, or ceftazidime achieved comparable outcomes.Outcomes of Acinetobacter peritonitis were favorable compared with most other forms of organism-specific peritonitis. Commonly used antibiotics covering gram-negative bacteria achieved comparable outcomes in Acinetobacter peritonitis.Htay Htay, Yeoungjee Cho, Elaine M. Pascoe, Carmel Hawley, Philip A. Clayton, Monique Borlace, Sunil V. Badve, Kamal Sud, Neil Boudville, Stephen P. McDonald and David W. Johnso

Synthesis and characterisation of folic acid based lanthanide ion probes

Abstract not availableZhangli Du, Glenn N. Borlace, Robert D. Brooks, Ross N. Butler, Doug A. Brooks, Sally E. Plus

The association between peritoneal dialysis modality and peritonitis

BACKGROUND AND OBJECTIVES: There is conflicting evidence comparing peritonitis rates among patients treated with continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD). This study aims to clarify the relationship between peritoneal dialysis (PD) modality (APD versus CAPD) and the risk of developing PD-associated peritonitis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This study examined the association between PD modality (APD versus CAPD) and the risks, microbiology, and clinical outcomes of PD-associated peritonitis in 6959 incident Australian PD patients between October 1, 2003, and December 31, 2011, using data from the Australia and New Zealand Dialysis and Transplant Registry. Median follow-up time was 1.9 years. RESULTS: Patients receiving APD were younger (60 versus 64 years) and had fewer comorbidities. There was no association between PD modality and time to first peritonitis episode (adjusted hazard ratio [HR] for APD versus CAPD, 0.98; 95% confidence interval [95% CI], 0.91 to 1.07; P=0.71). However, there was a lower hazard of developing Gram-positive peritonitis with APD than CAPD, which reached borderline significance (HR, 0.90; 95% CI, 0.80 to 1.00; P=0.05). No statistically significant difference was found in the risk of hospitalizations (odds ratio, 1.12; 95% CI, 0.93 to 1.35; P=0.22), but there was a nonsignificant higher likelihood of 30-day mortality (odds ratio, 1.33; 95% CI, 0.93 to 1.88; P=0.11) at the time of the first episode of peritonitis for patients receiving APD. For all peritonitis episodes (including subsequent episodes of peritonitis), APD was associated with lower rates of culture-negative peritonitis (incidence rate ratio [IRR], 0.81; 95% CI, 0.69 to 0.94; P=0.002) and higher rates of gram-negative peritonitis (IRR, 1.28; 95% CI, 1.13 to 1.46; P=0.01). CONCLUSIONS: PD modality was not associated with a higher likelihood of developing peritonitis. However, APD was associated with a borderline reduction in the likelihood of a first episode of Gram-positive peritonitis compared with CAPD, and with lower rates of culture-negative peritonitis and higher rates of Gram-negative peritonitis. Peritonitis outcomes were comparable between both modalities.Patrick G. Lan, David W. Johnson, Stephen P. McDonald, Neil Boudville, Monique Borlace, Sunil V. Badve, Kamal Sud, Philip A. Clayto

Duration of hemodialysis following peritoneal dialysis cessation in Australia and New Zealand: proposal for a standardized definition of technique failure

BACKGROUND: Although technique failure is a key outcome in peritoneal dialysis (PD), there is currently no agreement on a uniform definition. We explored different definitions of PD technique failure using data from the Australia and New Zealand Dialysis and Transplant (ANZDATA) Registry. METHODS: We included 16,612 incident PD patients in Australia and New Zealand from January 1998 to December 2012. Different definitions of technique failure were applied according to the minimum number of days (30, 60, 90, 180, or 365) the patient received hemodialysis after cessation of PD. RESULTS: Median technique survival varied from 2.0 years with the 30-day definition to 2.4 years with the 365-day definition. For all definitions, the most common causes of technique failure were death, followed by infectious complications. The likelihood of a patient returning to PD within 12 months of technique failure was highest in the 30-day definition (24%), and was very small when using the 180- and 365-day definitions (3% and 0.8%, respectively). Patients whose technique failed due to mechanical reasons were the most likely to return to PD (46% within 12 months using the 30-day definition). CONCLUSIONS: Both 30- and 180-day definitions have clinical relevance but offer different perspectives with very different prognostic implications for further PD. Therefore, we propose that PD technique failure be defined by a composite endpoint of death or transfer to hemodialysis using both 30-day and 180-day definitions.Patrick G. Lan, Philip A. Clayton, David W. Johnson, Stephen P. McDonald, Monique Borlace, Sunil V. Badve, Kamal Sud and Neil Boudvill