In remote sensing applications, Optimal Estimation (OE) retrievals are sometimes compared to independent OE retrievals of the same process. This intercomparison is often done in instrument ...validation, where retrievals are compared with data from a separate validation instrument, and it is sometimes done in data assimilation, where data from multiple instruments need to be adjusted to the “same footing.” In these cases, the two different retrievals are compared using an adjustment that is colloquially known as the averaging kernel correction. A general misconception in the existing literature is that this averaging kernel correction removes any bias introduced by prior misspecification by either (or both) of the two comparative OE retrievals. In this paper, we will analytically show that this is not the case and the averaging kernel correction process implicitly “shifts” both OE retrievals to a common comparison prior. We will also show that there is generally a non-zero bias that is proportional to the difference between this comparison prior mean and the true (but unobserved) mean state, which has large implications for retrieval validation and data assimilation in remote sensing. Finally, to better characterize OE retrievals and retrieval intercomparisons, we will make some recommendations for mitigating this prior-induced bias in intercomparison of OE retrievals.
Aquaporin-4 (AQP4) channels play an important role in brain water homeostasis. Water transport across plasma membranes has a critical role in brain water exchange of the normal and the diseased ...brain. AQP4 channels are implicated in the pathophysiology of hydrocephalus, a disease of water imbalance that leads to CSF accumulation in the ventricular system. Many molecular aspects of fluid exchange during hydrocephalus have yet to be firmly elucidated, but review of the literature suggests that modulation of AQP4 channel activity is a potentially attractive future pharmaceutical therapy. Drug therapy targeting AQP channels may enable control over water exchange to remove excess CSF through a molecular intervention instead of by mechanical shunting. This article is a review of a vast body of literature on the current understanding of AQP4 channels in relation to hydrocephalus, details regarding molecular aspects of AQP4 channels, possible drug development strategies, and limitations. Advances in medical imaging and computational modeling of CSF dynamics in the setting of hydrocephalus are summarized. Algorithmic developments in computational modeling continue to deepen the understanding of the hydrocephalus disease process and display promising potential benefit as a tool for physicians to evaluate patients with hydrocephalus.
Sports-related concussions (SRCs) are traumatic events that affect up to 3.8 million athletes per year. The initial diagnosis and management is often instituted on the field of play by coaches, ...athletic trainers, and team physicians. SRCs are usually transient episodes of neurological dysfunction following a traumatic impact, with most symptoms resolving in 7-10 days; however, a small percentage of patients will suffer protracted symptoms for years after the event and may develop chronic neurodegenerative disease. Rarely, SRCs are associated with complications, such as skull fractures, epidural or subdural hematomas, and edema requiring neurosurgical evaluation. Current standards of care are based on a paradigm of rest and gradual return to play, with decisions driven by subjective and objective information gleaned from a detailed history and physical examination. Advanced imaging techniques such as functional MRI, and detailed understanding of the complex pathophysiological process underlying SRCs and how they affect the athletes acutely and long-term, may change the way physicians treat athletes who suffer a concussion. It is hoped that these advances will allow a more accurate assessment of when an athlete is truly safe to return to play, decreasing the risk of secondary impact injuries, and provide avenues for therapeutic strategies targeting the complex biochemical cascade that results from a traumatic injury to the brain.
Optimal Estimation (OE) methods can simultaneously estimate surface and atmospheric properties from remote Visible/Shortwave imaging spectroscopy. Simultaneous solutions can improve retrieval ...accuracy with principled uncertainty quantification for hypothesis testing. While OE has been validated under benign atmospheric conditions, future global missions will observe environments with high aerosol and water vapor loadings. This work addresses the gap with diverse scenes from NASA's Next Generation Airborne Visible Infrared Imaging Spectrometer (AVIRIS-NG) India campaign. We refine atmospheric models to represent variable aerosol optical depths and properties. We quantify retrieval accuracy and information content for both reflectance and aerosols over different surface types, comparing results to in situ and remote references. Additionally, we assess uncertainty of maximum a posteriori solutions using linearized estimates as well as sampling-based inversions that more completely characterize posterior uncertainties. Principled uncertainty quantification can combine multiple spacecraft data products while preventing local environmental biases in future global investigations.
•We validate Optimal Estimation (OE) atmospheric correction for challenging conditions.•Linearized and MCMC estimates provide rigorous uncertainty quantification.•OE with aerosol and H2O vapor estimation significantly improves reflectance accuracy.•Retrieved aerosol properties are consistent with in-situ and remote space-based data.
BACKGROUND:Steroid administration is part of a standard treatment regimen in metastatic spinal cord compression, though the appropriate dose, duration, efficacy, and risks remain controversial.
...OBJECTIVE:To analyze the risk of preoperative steroid use on 30-d mortality in surgical metastatic spinal tumors with dissemination disease using a large multicenter national database.
METHODS:Adult patients who underwent surgical treatment for metastatic spine tumors between 2005 and 2014 were identified in the American College of Surgeons National Surgical Quality Improvement Program database. Demographic, preoperative risk factors, operative information, and postoperative events were extracted. Multivariate logistical regression modeling was used to investigate the association with preoperative steroid use with the outcome of interest, 30-d mortality. Other independent risk factors associated with 30-d mortality were also identified.
RESULTS:Five hundred fifty-two patients underwent surgical treatment of spinal metastases with disseminated cancer present at time of surgery. Independent risk factors of 30-d mortality included prolonged steroid use (odds ratio OR 2.48, 95% confidence interval CI1.22–5.04, P = .012), dependent functional status (OR 2.91, 95% CI1.68–5.04, P < .001), history of bleeding disorder (OR 2.80, 95% CI1.16–6.74, P = .021), history of smoking (OR 2.26, 95% CI1.11–4.61, P = .024), preoperative transfusions (OR 2.91, 95% CI1.02–8.29, P = .049), and preoperative infection/sepsis (OR 2.67, 95% CI1.18–6.08, P = .02). Our model demonstrates very strong predictive capabilities, with an area under the receiver operating characteristic curve of 0.7447.
CONCLUSION:Steroid use is associated with a significant increased risk of 30-d mortality in surgical metastatic spine tumor patients with disseminated disease. These findings warrant further investigation in controlled experimental environments.
The grand challenge of producing hydrometeorological estimates every time and everywhere has motivated the fusion of sparse observations with dense numerical models, with a particular interest on ...discharge in river modeling. Ensemble methods are largely preferred as they enable the estimation of error properties, but at the expense of computational load and generally with underestimations. These imperfect stochastic estimates motivate the use of correction methods, that is, error localization and inflation, although the physical justifications for their optimality are limited. The purpose of this study is to use one of the simplest forms of data assimilation when applied to river modeling and reveal the underlying mechanisms impacting its performance. Our framework based on assimilating daily averaged in situ discharge measurements to correct daily averaged runoff was tested over a 4-yr case study of two rivers in Texas. Results show that under optimal conditions of inflation and localization, discharge simulations are consistently improved such that the mean values of Nash–Sutcliffe efficiency are enhanced from −11.32 to 0.55 at observed gauges and from −12.24 to −1.10 at validation gauges. Yet, parameters controlling the inflation and the localization have a large impact on the performance. Further investigations of these sensitivities showed that optimal inflation occurs when compensating exactly for discrepancies in the magnitude of errors while optimal localization matches the distance traveled during one assimilation window. These results may be applicable to more advanced data assimilation methods as well as for larger applications motivated by upcoming river-observing satellite missions, such as NASA’s Surface Water and Ocean Topography mission.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
10.
It is time to rethink EMS Hobbs, Jonathan
Veterinary record,
10/2020, Letnik:
187, Številka:
9
Journal Article
Recenzirano
Personally, I found it invaluable and I certainly would not have been ready for practice without the exposure to clinical cases and the chances to practise crucial manual skills that I was afforded. ......as an experienced clinician, I also thoroughly enjoy teaching the next crop of vets – watching someone gain a new skill or piece of knowledge and develop over their time with us in practice is incredibly rewarding. Having an external student come for a two-week placement after hot-footing it from another practice two weeks prior, and university before that, provides a substantial risk to both the health of my staff and our practice finances.
PDF
