A Nonparametric Adaptive Nonlinear Statistical Filter

We use statistical learning methods to construct an adaptive state estimator for nonlinear stochastic systems. Optimal state estimation, in the form of a Kalman filter, requires knowledge of the system's process and measurement uncertainty. We propose that these uncertainties can be estimated from (conditioned on) past observed data, and without making any assumptions of the system's prior distribution. The system's prior distribution at each time step is constructed from an ensemble of least-squares estimates on sub-sampled sets of the data via jackknife sampling. As new data is acquired, the state estimates, process uncertainty, and measurement uncertainty are updated accordingly, as described in this manuscript.Comment: Accepted at the 2014 IEEE Conference on Decision and Contro

Non-disturbing quantum measurements

We consider pairs of quantum observables (POVMs) and analyze the relation between the notions of non-disturbance, joint measurability and commutativity. We specify conditions under which these properties coincide or differ---depending for instance on the interplay between the number of outcomes and the Hilbert space dimension or on algebraic properties of the effect operators. We also show that (non-)disturbance is in general not a symmetric relation and that it can be decided and quantified by means of a semidefinite program.Comment: Minor corrections in v

Loan supply in Germany during the financial crisis

Distinguishing pure supply effects from other determinants of price and quantity in the market for loans is a notoriously difficult problem. Using German data, we employ Bayesian vector autoregressive models with sign restrictions on the impulse response functions in order to enquire the role of loan supply and monetary policy shocks for the dynamics of loans to non-financial corporations. For the three quarters following the Lehman collapse, we find very strong negative loan supply shocks, while monetary policy was essentially neutral. Nevertheless, the historical decomposition shows a cumulated negative impact of loan supply shocks and monetary policy shocks on loans to non-financial corporations, due to the lagged effects of past loan supply and monetary policy shocks. However, these negative effects on loans to non-financial corporations are overcompensated by positive other shocks, which implies that loans developed more favorably than implied by the model, over the past few quarters. --Loan supply,Bayesian VAR,sign restrictions

Therapeutic Hypothermia after Out-of-Hospital Cardiac Arrest - implementation and clinical management

Background: With the publication of two randomized controlled trials (RCTs) in 2002, therapeutic hypothermia (TH) was re-introduced in postresuscitation care of comatose out-of-hospital cardiac arrest (OHCA) patients. Many issues, however, were unresolved, including implementation protocol, cooling technique, clinical management, implications of TH treatment on prognostic accuracy and therapeutic benefit in subgroups of OHCA excluded from the initial RCTs. Objectives: We wanted to study the implementation of therapeutic hypothermia into daily practice, provide information on clinical management, including differences in cooling techniques and test application in elderly OHCA patients excluded in earlier trials. Subjects: We evaluated the clinical management of adult comatose OHCA patients who were treated in our ICU (paper I and IV). In paper II we surveyed our intensive care nursing staff with regard to key nursing aspects of different cooling methods and devices. In paper III, ICU consultants were assessed on their prognostic approach in OHCA patients treated with TH. Methods: In paper I we retrospectively compared OHCA patients treated with TH with a historic control group of OHCA patients fulfilling the TH inclusion criteria. We collected Utstein template data, as well as data on ICU-and hospital length of stay (LOS), incidence of adverse events, and outcome at hospital discharge and after one year. In paper II an anonymous survey was conducted with our intensive care nursing (ICN) staff, assessing ease of application, hygiene, work load, noise level and visual patient monitoring of four different cooling methods. In paper III we used a semi-structured telephone interview to conduct a nation-wide survey of the prognostication approach of comatose OHCA patients involving timing, methods, involved specialties and rating of prognostic methods. In paper IV we retrospectively studied outcome variables in all adult OHCA patients treated with TH in our ICU over a six-year period, who fulfilled the Hypothermia After Cardiac Arrest study (HACA) criteria with exception of the upper age limit. Results: With our simple cooling protocol we achieved 100% implementation and successful attainment of target temperature (TT) in 89% of patients (paper I). However, it took median 7, 5 hours (1-10 h) to reach TT, which was maintained for median 10 hours (6-19h). Demographics, Utstein template data, ICU and hospital LOS did not differ significantly between the two groups. Insulin resistance and hypokalemia were significantly more frequent in the TH group, whereas seizures were observed more frequent in the normothermia group. The TH group showed significantly higher rates of survival to hospital discharge (59% vs. 32%, p = 0, 05). In paper IV we found that although older age influenced outcome, over half of OHCA patients older than 75 years showed favorable outcome at hospital discharge. The four cooling methods used in our department differed significantly regarding key nursing aspects (paper II). Our simple cooling method scored high regarding ease of application and noise level, but low in work load and hygiene. The CoolGard and ArticSun systems scored highest in work load and hygiene. Only 53% of ICNs were satisfied with their initial training and merely 10% felt adequately prepared at the time when TH was introduced. In paper III we found that even after introduction of TH, prognostication after OHCA was performed within 48 hours in the majority of patients. More than one specialty was involved, using mainly clinical neurological examination (100%), prehospital data (76%), cerebral computer tomography (CCT) (58%) and electroencephalography (EEG) (52%) findings. Somatosensory evoked potentials (SSEP) (8%), biochemical markers (8%) and magnetic resonance imaging (MRI) (8%) only played a minor role. Only one ICU used a standardized protocol. Conclusions: Our simple external cooling protocol could be rapidly implemented, was safe, cheap and feasible, but not optimal with regard to accurate temperature management (paper I). Key nursing elements differed significantly among available cooling methods (paper II). Even though age influences outcome, more than half of our OHCA population older than 75 years showed good outcome. The limitation of patient eligibility for TH treatment should not be based on age alone (paper IV). Despite frequent use of TH, prognostication after OHCA was executed early, mainly based on clinical examination, prehospital data, CCT and EEG results. SSEP seems to be underused and underrated, whereas the clinical accuracy of CCT, prehospital data and EEG seems to be overrated (paper III)

First Extragalactic Detection of Thermal Hydroxyl (OH) 18cm Emission in M31 Reveals Abundant CO-faint Molecular Gas

The most abundant interstellar molecule, molecular Hydrogen (H$_{2}$), is practically invisible in cold molecular clouds. Astronomers typically use carbon monoxide (CO) to trace the bulk distribution and mass of H$_{2}$ in our galaxy and many others. CO observations alone fail to trace a massive component of molecular gas known as "CO-dark" gas. We present an ultra sensitive pilot search for the 18cm hydroxyl (OH) lines in the Andromeda Galaxy (M31) with the 100m Robert C. Byrd Green Bank Telescope. We successfully detected the 1667 and 1665 MHz OH in faint emission. The 1665/1667 MHz line ratio is consistent with the characteristic 5:9 ratio associated with local thermodynamic equilibrium (LTE). To our knowledge, this is the first detection of non-maser 18cm OH emission in another galaxy. We compare our OH and HI observations with archival CO (1-0) observations. Our OH detection position overlaps with the previously discovered Arp Outer Arm in CO. Our best estimates show that the amount of H$_{2}$ traced by OH is 140% higher than the amount traced by CO in this sightline. We show that the amount of dark molecular gas implied by dust data supports this conclusion. We conclude that the 18cm OH lines hold promise as a valuable tool for mapping of the "CO-dark" and "CO-faint" molecular gas phase in nearby galaxies, especially with upcoming multi-beam, phased-array feed receivers on radio telescopes which will allow for drastically improved mapping speeds of faint signals.Comment: 15 pages, 6 figures, Submitted to ApJ, comments welcome