In situ spatiotemporal measurements of the detailed azimuthal substructure of the substorm current wedge

The substorm current wedge (SCW) is a fundamental component of geomagnetic substorms. Models tend to describe the SCW as a simple line current flowing into the ionosphere toward dawn and out of the ionosphere toward dusk, linked by a westward electrojet. We use multispacecraft observations from perigee passes of the Cluster 1 and 4 spacecraft during a substorm on 15 January 2010, in conjunction with ground-based observations, to examine the spatial structuring and temporal variability of the SCW. At this time, the spacecraft traveled east-west azimuthally above the auroral region. We show that the SCW has significant azimuthal substructure on scales of 100 km at altitudes of 4000-7000 km. We identify 26 individual current sheets in the Cluster 4 data and 34 individual current sheets in the Cluster 1 data, with Cluster 1 passing through the SCW 120-240 s after Cluster 4 at 1300-2000 km higher altitude. Both spacecraft observed large-scale regions of net upward and downward field-aligned current, consistent with the large-scale characteristics of the SCW, although sheets of oppositely directed currents were observed within both regions. We show that the majority of these current sheets were closely aligned to a north-south direction, in contrast to the expected east-west orientation of the preonset aurora. Comparing our results with observations of the field-aligned current associated with bursty bulk flows (BBFs), we conclude that significant questions remain for the explanation of SCW structuring by BBF-driven "wedgelets." Our results therefore represent constraints on future modeling and theoretical frameworks on the generation of the SCW.

KEY POINTS

The substorm current wedge (SCW) has significant azimuthal structureCurrent sheets within the SCW are north-south alignedThe substructure of the SCW raises questions for the proposed wedgelet scenario.

Understanding the contribution of neural and physiological signal variation to the low repeatability of emotion-induced BOLD responses

Previous studies have reported low repeatability of BOLD activation measures during emotion processing tasks. It is not clear, however, whether low repeatability is a result of changes in the underlying neural signal over time, or due to insufficient reliability of the acquired BOLD signal caused by noise contamination. The aim of this study was to investigate the influence of “cleaning” the BOLD signal, by correcting for physiological noise and for differences in BOLD responsiveness, on measures of repeatability.

Fifteen healthy volunteers were scanned on two different occasions, performing an emotion provocation task with faces (neutral, 50% fearful, 100% fearful) followed by a breath-hold paradigm to provide a marker of BOLD responsiveness. Repeatability of signal distribution (spatial repeatability) and repeatability of signal amplitude within two regions of interest (amygdala and fusiform gyrus) were estimated by calculating the intraclass correlation coefficient (ICC).

Significant repeatability of signal amplitude was only found within the right amygdala during the perception of 50% fearful faces, but disappeared when physiological noise correction was performed. Spatial repeatability was higher within the fusiform gyrus than within the amygdala, and better at the group level than at the participant level. Neither physiological noise correction, nor consideration of BOLD responsiveness, assessed through the breath-holding, increased repeatability.

The findings lead to the conclusion that low repeatability of BOLD response amplitude to emotional faces is more likely to be explained by the lack of stability in the underlying neural signal than by physiological noise contamination. Furthermore, reported repeatability might be a result of repeatability of task-correlated physiological variation rather than neural activity. This means that the emotion paradigm used in this study might not be useful for studies that require the BOLD response to be a stable measure of emotional processing, for example in the context of biomarkers.

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We investigated repeatability of BOLD responses during a widely used emotion task.

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Repeatability of signal amplitude was low in the amygdala and in the fusiform gyrus.

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Spatial repeatability was higher within the fusiform gyrus than within the amygdala.

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Physiological noise correction did not improve any of the repeatability measures.

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The BOLD response to this emotion task might not be useful as a biomarker.

Prenatal diagnosis using combined quantitative fluorescent polymerase chain reaction and array comparative genomic hybridization analysis as a first-line test: results from over 1000 consecutive cases

OBJECTIVES

First, to assess the performance of a prenatal diagnostic service using quantitative fluorescent polymerase chain reaction (QF-PCR) and array comparative genomic hybridization (aCGH) as first-line investigations. Second, to determine the incidence of copy number variants (CNVs) by indication for testing, with particular reference to ultrasound and biochemical parameters measured in combined first-trimester screening.

METHODS

All patients undergoing invasive prenatal testing at a specialist prenatal screening service in Sydney, Australia, were included in the study. All samples underwent QF-PCR and targeted aCGH.

RESULTS

Of 1049 cases, CNVs were reported in 156 (14.9%). Preliminary QF-PCR identified abnormalities in 104 of these cases. Of the remaining 52 cases, 20 could have been detected on karyotype testing, leaving 32 cases (3.1%) with CNVs only detectable by aCGH, of which 13 (1.2%) were pathogenic. Variants of unknown significance (VOUS) were seen in only three cases. Fetal structural abnormalities identified in the first trimester were the group most likely to be associated with pathogenic CNVs (11.8%).

CONCLUSIONS

Combining QF-PCR and aCGH is an effective first-tier prenatal testing regime that does not require conventional karyotyping. The incidence of VOUS in this study was very low owing to appropriate aCGH targeting and specific reporting criteria that reduced the number of potentially difficult counseling encounters. Pathogenic CNVs are positively correlated with the presence of fetal structural abnormalities, but not with enlarged nuchal translucency or abnormal first-trimester serology results.

Quality of fracture risk assessment in post-fracture care in Ontario, Canada

As fracture risk assessment is a basis for treatment decisions, accurate risk assessments on bone mineral density (BMD) reports are important. Over 50 % of sampled BMD reports for Ontarians with fracture histories underestimated fracture risk by a single category. Risk assessments in Ontario may not accurately inform treatment recommendations.

INTRODUCTION

The shifting emphasis on fracture risk assessment as a basis for treatment recommendations highlights the importance of ensuring that accurate fracture risk assessments are present on reading specialists' BMD reports. This study seeks to determine the accuracy of fracture risk assessments on a sample of BMD reports from 2008 for individuals with a history of fracture and produced by a broad cross section of Ontario's imaging laboratories.

METHODS

Forty-eight BMD reports for individuals with documented history of fragility fracture were collected as part of a cluster randomized trial. To compute fracture risk, risk factors, and BMD T-scores from reports were abstracted using a standardized template and compared to the assessments on the reports. Cohen's kappa was used to score agreement between the research team and the reading specialists.

RESULTS

The weighted kappa was 0.21, indicating agreement to be at the margin of "poor to fair." More than 50 % of the time, reported fracture risks did not reflect fracture history and were therefore underestimated by a single category. Over 30 % of the reports containing a "low" fracture risk assessment were assessed as "moderate" fracture risk by the research team, given fracture history. Over 20 % of the reports with a "moderate" fracture risk were assessed as "high" by the research team, given fracture history.

CONCLUSIONS

This study highlights the high prevalence of fracture risk assessments that are underestimated. This has implications in terms of fracture risk categorization that can negatively affect subsequent follow-up care and treatment recommendations.

Qutenza patch--our early experience

Qutenza is a high potency capsaicin topical patch which has been recommended for the treatment of peripheral neuropathic pain. The aim of this study was to assess our selected patients' response to Qutenza application. All patients had their dynamic pain score recorded prior to application and were asked to fill in a standardised questionnaire for three months post application. Patients were also asked to document any changes to the character of their pain, changes in sleep, activities of daily living and mood as well as any changes to their medication usage. 21 patients had Qutenza applied in a 5 month period. 17 patients completed the questionnaire in a 5 month period. We found that the mean overall reduction in pain score at 3 months was 32.7%. 8 of our patients (47%) reported improved sleep, activities of daily living and mood. 6 patients (35%) reported a reduction in medication use, while 7 (41%) reported an improvement in the character of their pain.

Does Courvoisier's sign stand the test of time?

AIM

To investigate the validity of Courvoisier's sign, in the age of cross-sectional imaging and image analysis software by objectively measuring gallbladder volumes at magnetic resonance cholangiopancreatography (MRCP) in patients with and without biliary obstruction and to assess whether gallbladder volume is more significantly increased in patients with gallstone-related rather than non-gallstone-related biliary obstruction.

MATERIALS AND METHODS

All MCRP investigations that were performed at a tertiary hepatobiliary centre over a 2-year period were analysed. The information recorded included the presence or absence of gallbladder stones as well as the presence and type of common bile duct (CBD) disease. Gallbladder volume was calculated from MRCP studies using image analysis software.

RESULTS

Three hundred and ninety-four of 645 examined MRCPs (61.1%) were eligible for analysis. A statistically significant difference in mean gallbladder volume existed between the summated obstructive and non-obstructive groups (p < 0.001). In addition, a significant difference existed in mean gallbladder volume between those with CBD stones and non-gallstone CBD obstruction (p = 0.03).

CONCLUSION

A significant difference was observed in gallbladder volumes in the group with biliary obstruction from choledocholithiasis compared with the group with biliary obstruction from other causes. Thus, objective measurement of gallbladder volume from modern cross-sectional imaging studies appears to validate Courvoisier's sign as a valuable clinical sign, which could be applied to modern imaging studies in distinguishing different causes of biliary obstruction in the jaundiced patient.

Biochemical assessment of canine body cavity effusions using three bench-top analysers

OBJECTIVES

To assess the performance of three bench-top chemistry instruments for the analysis of canine effusions. Acceptable results were compared with those obtained by a reference chemistry analyser.

METHODS

Total protein, albumin, creatinine and bilirubin concentrations were measured in 74 effusions using the VetScanVS2, VetTest8008 and SpotchemEZ analysers. Cholesterol and triglyceride concentrations were also measured by the VetTest and Spotchem. Results were analysed using Westgard's error analysis, Spearman's correlation, Bland-Altman plots and Deming regression. Results were considered acceptable when observed total error (TE(obs) ) was less than allowable total error (TE(A) ).

RESULTS

VetScan error analysis revealed acceptable results for total protein (TE(obs) =1.11, TE(A) =4.7) and creatinine (TE(obs) =42.2, TE(A) =78.1). Correlation was fair for protein (r(s) =0.66) and creatinine (r(s) =0.76), but poor and not significant for bilirubin (r(s) =0.01, P=0.08), precluding error analysis. VetTest error analysis was acceptable for creatinine only (TE(obs) =5.55, TE(A) =25.5). Correlation was good (r(s) =0.81). The difference plot revealed a bias (95% confidence interval) of -1.5 (-37 to 40) and four outliers. The Spotchem did not generate a precise arithmetic value in most (56.9 to 73.6%) samples, precluding further analysis.

CLINICAL SIGNIFICANCE

Acceptable results were obtained for total protein (VetScan) and creatinine [Vetscan, Vettest (with good correlation)]. The Spotchem is of limited value in canine effusion analysis.

Rare structural variation of synapse and neurotransmission genes in autism

Autism spectrum disorders (ASDs) comprise a constellation of highly heritable neuropsychiatric disorders. Genome-wide studies of autistic individuals have implicated numerous minor risk alleles but few common variants, suggesting a complex genetic model with many contributing loci. To assess commonality of biological function among rare risk alleles, we compared functional knowledge of genes overlapping inherited structural variants in idiopathic ASD subjects relative to healthy controls. In this study we show that biological processes associated with synapse function and neurotransmission are significantly enriched, with replication, in ASD subjects versus controls. Analysis of phenotypes observed for mouse models of copy-variant genes established significant and replicated enrichment of observable phenotypes consistent with ASD behaviors. Most functional terms retained significance after excluding previously reported ASD loci. These results implicate several new variants that involve synaptic function and glutamatergic signaling processes as important contributors of ASD pathophysiology and suggest a sizable pool of additional potential ASD risk loci.

Performance characteristics of two automated solid-phase red cell adherence systems for pretransfusion antibody screening: a cautionary tale

Out institution has implemented two instruments, the Galileo and the Echo, that use different solid-phase red cell adherence assays for antibody screening in pretransfusion compatibility testing.During the initial implementation of these two instruments, we noticed very different problems: falsely positive results on the Galileo, and falsely negative results and lack of reproducibility on the Echo. Comparison of falsely positive antibody screen results from approximately equivalent numbers of samples run on the Galileo and samples tested by standard manual tube technique using low-ionic-strength saline enhancement showed a false-positive rate of 1.4 percent on the Galileo (defined as a positive screen with a negative panel). Testing using the Echo identified four cases of falsely negative antibody screens, (defined as a negative screen on a patient sample subsequently shown to be positive by the same method). In addition, we note a lack of reproducibility on the Echo, which emphasizes the importance of replicate testing during validation of automated antibody screening platforms.

The relationship between lung function impairment and quantitative computed tomography in chronic obstructive pulmonary disease

OBJECTIVES

To determine the relationship between lung function impairment and quantitative computed tomography (CT) measurements of air trapping and emphysema in a population of current and former heavy smokers with and without airflow limitation.

METHODS

In 248 subjects (50 normal smokers; 50 mild obstruction; 50 moderate obstruction; 50 severe obstruction; 48 very severe obstruction) CT emphysema and CT air trapping were quantified on paired inspiratory and end-expiratory CT examinations using several available quantification methods. CT measurements were related to lung function (FEV(1), FEV(1)/FVC, RV/TLC, Kco) by univariate and multivariate linear regression analysis.

RESULTS

Quantitative CT measurements of emphysema and air trapping were strongly correlated to airflow limitation (univariate r-squared up to 0.72, p < 0.001). In multivariate analysis, the combination of CT emphysema and CT air trapping explained 68-83% of the variability in airflow limitation in subjects covering the total range of airflow limitation (p < 0.001).

CONCLUSIONS

The combination of quantitative CT air trapping and emphysema measurements is strongly associated with lung function impairment in current and former heavy smokers with a wide range of airflow limitation.

Obstetric outcome with low molecular weight heparin therapy during pregnancy

This was a prospective study of women attending a combined haematology/obstetric antenatal clinic in the National Maternity Hospital (2002-2008). Obstetric outcome in mothers treated with low molecular weight heparin (LMWH) was compared to the general obstetric population of 2006. There were 133 pregnancies in 105 women. 85 (63.9%) received prophylactic LMWH and 38 (28.6%) received therapeutic LMWH in pregnancy. 10 (7.5%) received postpartum prophylaxis only. The perinatal mortality rate was 7.6/1000 births. 14 (11.3%) women delivered preterm which is significantly higher than the hospital population rate (5.7%, p<0.05). Despite significantly higher labour induction rates (50% vs 29.2% p<0.01), there was no difference in CS rates compared to the general hospital population (15.4% vs 18.9%, NS). If carefully managed, these high-risk women can achieve similar vaginal delivery rates as the general obstetric population.