North Atlantic climate far more predictable than models imply.

Quantifying signals and uncertainties in climate models is essential for the detection, attribution, prediction and projection of climate change1-3. Although inter-model agreement is high for large-scale temperature signals, dynamical changes in atmospheric circulation are very uncertain4. This leads to low confidence in regional projections, especially for precipitation, over the coming decades5,6. The chaotic nature of the climate system7-9 may also mean that signal uncertainties are largely irreducible. However, climate projections are difficult to verify until further observations become available. Here we assess retrospective climate model predictions of the past six decades and show that decadal variations in North Atlantic winter climate are highly predictable, despite a lack of agreement between individual model simulations and the poor predictive ability of raw model outputs. Crucially, current models underestimate the predictable signal (the predictable fraction of the total variability) of the North Atlantic Oscillation (the leading mode of variability in North Atlantic atmospheric circulation) by an order of magnitude. Consequently, compared to perfect models, 100 times as many ensemble members are needed in current models to extract this signal, and its effects on the climate are underestimated relative to other factors. To address these limitations, we implement a two-stage post-processing technique. We first adjust the variance of the ensemble-mean North Atlantic Oscillation forecast to match the observed variance of the predictable signal. We then select and use only the ensemble members with a North Atlantic Oscillation sufficiently close to the variance-adjusted ensemble-mean forecast North Atlantic Oscillation. This approach greatly improves decadal predictions of winter climate for Europe and eastern North America. Predictions of Atlantic multidecadal variability are also improved, suggesting that the North Atlantic Oscillation is not driven solely by Atlantic multidecadal variability. Our results highlight the need to understand why the signal-to-noise ratio is too small in current climate models10, and the extent to which correcting this model error would reduce uncertainties in regional climate change projections on timescales beyond a decade.

The Future of Neurocritical Care Research: Proceedings and Recommendations from the Fifth Neurocritical Care Research Network Conference.

The Fifth Neurocritical Care Research Network (NCRN) Conference held in Boca Raton, Florida, in September of 2018 was devoted to challenging the current status quo and examining the role of the Neurocritical Care Society (NCS) in driving the science and research of neurocritical care. The aim of this in-person meeting was to set the agenda for the NCS's Neurocritical Care Research Central, which is the overall research arm of the society. Prior to the meeting, all 103 participants received educational content (book and seminar) on the 'Blue Ocean Strategy®,' a concept from the business world which aims to identify undiscovered and uncontested market space, and to brainstorm innovative ideas and methods with which to address current challenges in neurocritical care research. Three five-member working groups met at least four times by teleconference prior to the in-person meeting to prepare answers to a set of questions using the Blue Ocean Strategy concept as a platform. At the Fifth NCRN Conference, these groups presented to a five-member jury and all attendees for open discussion. The jury then developed a set of recommendations for NCS to consider in order to move neurocritical care research forward. We have summarized the topics discussed at the conference and put forward recommendations for the future direction of the NCRN and neurocritical care research in general.

Diffusional Kurtosis along the Corticospinal Tract in Adult Normal Pressure Hydrocephalus.

BACKGROUND AND PURPOSE: Normal Pressure Hydrocephalus is a reversible form of dementia characterized by enlarged ventricles, which can deform and cause disruptions to adjacent white matter fibers. The purpose of this work was to examine how diffusion and kurtosis parameters vary along the corticospinal tract and determine where along this path microstructure is compromised in patients diagnosed with normal pressure hydrocephalus. We hypothesized that disruption of the corticospinal tract from ventricular enlargement can be measured using diffusion MR imaging and this will be quantified in periventricular regions. MATERIALS AND METHODS: We developed a method to analyze diffusion parameters at discrete points along neural tracts. We then used diffusion MR imaging data from patients with Alzheimer disease and healthy controls to compare whether diffusion along the corticospinal tract differs from that of patients with normal pressure hydrocephalus. RESULTS: We found that diffusion parameters can differentiate patients with normal pressure hydrocephalus from those with Alzheimer disease and healthy controls: Axial diffusion, axial kurtosis, and the axonal water fraction were found to differ significantly across groups (P < .05) in an area located close to the superior internal capsule and corona radiata but below the cortex. CONCLUSIONS: A lower axonal water fraction indicates a lower axonal density in the corticospinal tract, which may indicate permanent damage. Lower axial kurtosis may imply that axons are being more aligned due to compression.

Recent Progress in Understanding and Predicting Atlantic Decadal Climate Variability.

PURPOSE OF REVIEW: Recent Atlantic climate prediction studies are an exciting new contribution to an extensive body of research on Atlantic decadal variability and predictability that has long emphasized the unique role of the Atlantic Ocean in modulating the surface climate. We present a survey of the foundations and frontiers in our understanding of Atlantic variability mechanisms, the role of the Atlantic Meridional Overturning Circulation (AMOC), and our present capacity for putting that understanding into practice in actual climate prediction systems. RECENT FINDINGS: The AMOC-or more precisely, the buoyancy-forced thermohaline circulation (THC) that encompasses both overturning and gyre circulations-appears to underpin decadal timescale prediction skill in the subpolar North Atlantic in retrospective forecasts. Skill in predicting more wide-ranging climate variations, including those over land, is more limited, but there are indications this could improve with more advanced models. SUMMARY: Preliminary successes in the field of initialized Atlantic climate prediction confirm the climate relevance of low-frequency Atlantic Ocean dynamics and suggest that useful decadal climate prediction is a realizable goal.

Temporal flow velocity profile in the descending aorta in coarctation.

The temporal blood flow velocity profile in the descending aorta at the diaphragm was investigated using pulsed Doppler echocardiography in patients with documented coarctation of the aorta and in control patients. The ratio of peak systolic to peak diastolic frequency shift, an angle-independent index of pulsatility derived from the Doppler curve, proved to be an excellent indicator of aortic arch obstruction in the absence of a patent ductus arteriosus. Control groups included patients with a systemic right ventricle, systemic ventricular dysfunction and aortic stenosis, to determine if these conditions would confound the test. None of these factors were found to influence significantly the frequency shift ratio. However, the Doppler curves in six patients with interrupted aortic arch or severe coarctation, whose descending aorta was supplied by way of a large patent ductus arteriosus, were similar to those seen in control patients. Two indexes of wave transmission velocity, the rate of acceleration and the time to peak velocity, discriminated less effectively between patients with coarctation and the control patients, particularly those with aortic stenosis. After surgery for coarctation, the Doppler indexes and contour of the Doppler curve discriminated completely between patients with and without residual coarctation.

Two-dimensional echocardiographic diagnosis of pulmonary artery sling in infancy.

The vascular anomaly in which the left pulmonary artery arises from the right pulmonary artery and passes posteriorly and leftward between the trachea and the esophagus is termed a pulmonary artery sling. Two-dimensional echocardiograms were performed in five infants with this anomaly and successfully identified it in four, including one patient with truncus arteriosus communis. The subxiphoid long-axis sweep was useful in identifying the origin and initial course of the left pulmonary artery, and short-axis subxiphoid views showed both its origin from the right pulmonary artery and its initial posterior course. Angulation toward the cardiac apex displayed the right pulmonary artery in cross section anteriorly and the left pulmonary artery in cross section posteriorly. A transducer orientation midway between the subxiphoid long- and short-axis positions was helpful in distinguishing a large right upper lobe branch of the right pulmonary artery from a pulmonary artery sling. The precordial short-axis plane displayed the origin and initial posterior and leftward course of the left pulmonary artery, while the bifurcation of the main pulmonary artery, usually easily seen in this view, could not be demonstrated. Two-dimensional echocardiography offers a rapid, noninvasive diagnosis of pulmonary artery sling in infants.

Primary surgical closure of ventricular septal defect in the first year of life: results in 128 infants.

Between January 1973 and July 1981, 128 patients less than 1 year of age with failure to thrive, congestive heart failure or pulmonary artery hypertension underwent primary repair of a ventricular septal defect. The hospital mortality rate was 7.8% (10 of 128), and the late mortality rate was 2.3% (3 of 128). Mortality was highest among younger infants with preexisting respiratory problems or a hemodynamically significant residual lesion postoperatively. Complications included a large residual shunt in eight (6.2%), transient neurologic problems in five (3.9%) and persistent complete heart block in three (2.3%). Lung biopsy specimens obtained from 49 patients showed pulmonary vascular abnormalities in all. Complete right bundle branch block developed in 74 (64%) and bifascicular block appeared in 11 (9%). Recatheterization in 70 patients (55%) showed normal pulmonary artery pressures in all but 2 patients with a large residual shunt. Complete closure of the defect had been achieved in 49 (70%), and a hemodynamically insignificant shunt remained in 19 (27%). Patients without significant hemodynamic residua were asymptomatic and tended to accelerate in growth after surgery.

Effect of application force on noninvasive measurements of intracranial pressure.

Application of the Ladd fiberoptic sensor to the anterior fontanel of the human newborn has been used as a method for monitoring intracranial pressure noninvasively. This study measures the effect of varying the force with which the sensor is applied to the fontanel. The Ladd sensor readings of five preterm human infants were continuously monitored while sensor application force was increased in a stepwise manner. The Ladd sensor readings for each infant varied with the force applied. In one infant sensor application was gradually increased while direct measurements of lumbar CSF pressure were made. Ladd sensor readings in this infant increased with increasing application force, while lumbar CSF pressure remained unchanged. It is concluded that readings obtained with the Ladd sensor applied to the anterior fontanel of the human infant depend on the force with which the sensor is applied. The effect of application force must be taken into account if noninvasive measurements of intracranial pressure are to be made with the Ladd device.

Fate of moderate and large secundum type atrial septal defect associated with isolated coarctation in infants.

A moderate to large secundum atrial septal defect associated with isolated coarctation in infancy is likely to close spontaneously. Nine of 12 defects, including 4 defects > or =8 mm in at least 1 dimension, had either closed or were believed to be hemodynamically insignificant at follow-up, supporting the strategy of a lateral thoracotomy approach to coarctation and deferral of atrial surgery.

Measurement of systemic and pulmonary blood flow and QP/QS ratio using Doppler and two-dimensional echocardiography.

A noninvasive method for measuring systemic and pulmonary blood flow using Doppler velocimetry combined with 2-dimensional (2-D) echocardiography has been developed. High correlations were found between Fick- and Doppler-derived indexed measurements of systemic and pulmonary flow as well as the pulmonary to systemic flow ratio in 33 patients undergoing cardiac catheterization (systemic flow [n = 28], r = 0.78; pulmonary flow [n = 21], r = 0.88; Qp/Qs ratio [n = 24], r = 0.85). The random errors of the 2 methods were not significantly different. Outflow tract obstruction, semilunar valve regurgitation, and patent ductus arteriosus were the only lesions in which limitations to the use of this method were encountered. We anticipate that this method will be of use in initial and serial evaluations of adult and pediatric patients with low cardiac output or intracardiac shunts.

Accuracy of prospective two-dimensional echocardiographic evaluation of left ventricular outflow tract in complete transposition of the great arteries.

Thirty-two consecutive infants with transposition of the great arteries (TGA) and ventricular septal defect underwent subxiphoid 2-dimensional echocardiography (2-D echo). Two independent observers prospectively evaluated each echocardiogram for the presence or absence of left ventricular (LV) outflow tract obstruction, whether outflow obstruction was dynamic or fixed, or both, and the precise anatomic type of fixed obstruction. Compared with the LV-to-pulmonary artery gradient determined at cardiac catheterization, 2-D echo yielded low false-negative (7 to 13%) and false-positive (0 to 6%) rates for diagnosing the presence or absence of LV outflow tract obstruction. Moreover, the false-negative cases were only minor errors, because the measured LV-pulmonary artery gradients proved to be less than 25 mm Hg. Compared with the long-axial oblique LV angiogram, 2-D echo yielded no false-negative results in detection of outflow tract obstruction, which was at least partly fixed. Compared with autopsy/surgical observation, 2-D echo made no significant errors in delineating the exact anatomic type of fixed obstruction. The diagnostic accuracy of 2-D echo in detecting and characterizing LV outflow tract obstruction limits the need for "routine" cardiac catheterization before repair in infants with TGA and intact ventricular septum. Furthermore, because certain types of fixed LV outflow tract obstruction are difficult for the surgeon to visualize and alleviate, precise knowledge of the anatomic type of fixed obstruction influences the choice among Rastelli, intraatrial baffle and arterial switch procedures in patients with TGA and ventricular septal defect.

Perinatal and postnatal chest sonography.

Sonography is the primary method used to image the fetal chest. Many significant congenital anomalies such as pleural effusion, congenital diaphragmatic hernia, cystic adenomatoid malformation, pulmonary sequestration, and congenital heart disease can be detected during early prenatal sonography. Fetal sonography also permits accurate assessment of the severity of these processes, allowing for parental counseling and optimal planning of postnatal care. After birth, sonography is the primary method for evaluating cardiac anatomy and diagnosing congenital heart disease. Sonography also serves as a useful adjunct to plain film radiology and other modalities in evaluation of the mediastinum, diaphragm, pleura, and chest wall.

Self-reported factors that affect glycemic control in college students with type 1 diabetes.

PURPOSE: This study examined the self-reported impact of different factors on the overall diabetes care of college students with type 1 diabetes. METHODS: An 18-item questionnaire was mailed to 164 students with type 1 diabetes attending college away from home; results from 42 students fulfilled study criteria and were analyzed. Metabolic control was assessed by relative changes in glycosylated hemoglobin (HbA1c) levels from medical records. RESULTS: HbA1c levels did not change significantly between high school and college, yet most college students reported that diabetes was more difficult to manage in college. Commonly reported barriers to diabetes control included diet, irregular schedules, lack of parental involvement, peer pressure, drugs and alcohol, fear of hypoglycemia, and finances. Factors identified as improving diabetes control were an increased sense of responsibility, increased frequency of blood glucose testing, exercise, contact with healthcare providers, fear of hyperglycemia, and knowledge of the results of the Diabetes Control and Complications Trial. Many students reported testing their blood more frequently and taking more injections than in high school; most were on intensive insulin regimens. CONCLUSIONS: Despite the perception that diabetes management was more difficult in college, metabolic control was maintained during college, possibly due to a more intensive treatment approach.