Assessment of the quality of ACE-FTS stratospheric ozone data

For the past 17 years, the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) instrument on the Canadian SCISAT satellite has been measuring profiles of atmospheric ozone. The latest two operational versions of the level 2 ozone data are versions 3.6 and 4.1. This technical note characterizes how both products compare with correlative data from other limb-sounding satellite instruments, namely MAESTRO, MLS, OSIRIS, SABER, and SMR. In general, v3.6, with respect to the other instruments, exhibits a smaller bias (which is on the order of ~3 %) in the middle stratosphere than v4.1 (~2–9 %), however the bias exhibited in the v4.1 data tends to be more stable, i.e. not changing significantly over time in any altitude region. In the lower stratosphere, v3.6 has a positive bias of about 3–5 % that is stable to within ±1 % dec−1, and v4.1 has a bias on the order of −1 to +5 % and is also stable to within ±1 % dec−1. In the middle stratosphere, v3.6 has a positive bias of ~3 % with a significant negative drift on the order of 0.5–2.5 % dec−1, and v4.1 has a positive bias of 2–9 % that is stable to within ±0.5 % dec−1. However, the v4.1 bias in the middle stratosphere is reduced to 0–5 % after being corrected for field-of-view modelling errors. In the upper stratosphere, v3.6 has a positive bias that increases with altitude up to ~16 % and a significant negative drift on the order of 2–3 % dec−1, and v4.1 has a positive bias that increases with altitude up to ~15 % and is stable to within ±1 % dec−1.

Patients with Ventromedial Prefrontal Lesions Show an Implicit Approach Bias to Angry Faces

Damage to the ventromedial PFC (VMPFC) can cause maladaptive social behavior, but the cognitive processes underlying these behavioral changes are still uncertain. Here, we tested whether patients with acquired VMPFC lesions show altered approach–avoidance tendencies to emotional facial expressions. Thirteen patients with focal VMPFC lesions and 31 age- and gender-matched healthy controls performed an implicit approach–avoidance task in which they either pushed or pulled a joystick depending on stimulus color. Whereas controls avoided angry faces, VMPFC patients displayed an incongruent response pattern characterized by both increased approach and reduced avoidance of angry facial expressions. The approach bias was stronger in patients with higher self-reported impulsivity and disinhibition and in those with larger lesions. We further used linear ballistic accumulator modeling to investigate latent parameters underlying approach–avoidance decisions. Controls displayed negative drift rates when approaching angry faces, whereas VMPFC lesions abolished this pattern. In addition, VMPFC patients had weaker response drifts than controls during avoidance. Finally, patients showed reduced drift rate variability and shorter nondecision times, indicating impulsive and rigid decision-making. Our findings thus suggest that VMPFC damage alters the pace of evidence accumulation in response to social signals, eliminating a default, protective avoidant bias and facilitating a dysfunctional approach behavior.

Negative drift of sedation depth in critically ill patients receiving constant minimum alveolar concentration of isoflurane, sevoflurane, or desflurane: a randomized controlled trial

Background Intensive care unit (ICU) physicians have extended the minimum alveolar concentration (MAC) to deliver and monitor long-term volatile sedation in critically ill patients. There is limited evidence of MAC’s reliability in controlling sedation depth in this setting. We hypothesized that sedation depth, measured by the electroencephalography (EEG)-derived Narcotrend-Index (burst-suppression N_Index 0—awake N_Index 100), might drift downward over time despite constant MAC values. Methods This prospective single-centre randomized clinical study was conducted at a University Hospital Surgical Intensive Care Unit and included consecutive, postoperative ICU patients fulfilling the inclusion criteria. Patients were randomly assigned to receive uninterrupted inhalational sedation with isoflurane, sevoflurane, or desflurane. The end-expiratory concentration of the anaesthetics and the EEG-derived index were measured continuously in time-stamped pairs. Sedation depth was also monitored using Richmond-Agitation-Sedation-Scale (RASS). The paired t-test and linear models (bootstrapped or multilevel) have been employed to analyze MAC, N_Index and RASS across the three groups. Results Thirty patients were recruited (female/male: 10/20, age 64 ± 11, Simplified Acute Physiology Score II 30 ± 10). In the first 24 h, 21.208 pairs of data points (N_Index and MAC) were recorded. The median MAC of 0.58 ± 0.06 remained stable over the sedation time in all three groups. The t-test indicated in the isoflurane and sevoflurane groups a significant drop in RASS and EEG-derived N_Index in the first versus last two sedation hours. We applied a multilevel linear model on the entire longitudinal data, nested per patient, which produced the formula N_Index = 43 − 0.7·h (R2 = 0.76), showing a strong negative correlation between sedation’s duration and the N_Index. Bootstrapped linear models applied for each sedation group produced: N_Index of 43–0.9, 45–0.8, and 43–0.4·h for isoflurane, sevoflurane, and desflurane, respectively. The regression coefficient for desflurane was almost half of those for isoflurane and sevoflurane, indicating a less pronounced time-effect in this group. Conclusions Maintaining constant MAC does not guarantee stable sedation depth. Thus, the patients necessitate frequent clinical assessments or, when unfeasible, continuous EEG monitoring. The differences across different volatile anaesthetics regarding their time-dependent negative drift requires further exploration. Trial registration: NCT03860129.

Tail asymptotics for the area under the excursion of a random walk with heavy-tailed increments

We study the tail behaviour of the distribution of the area under the positive excursion of a random walk which has negative drift and heavy-tailed increments. We determine the asymptotics for tail probabilities for the area.

Negative Drift of Sedation Depth In Critically Ill Patients Receiving Constant Minimum Alveolar Concentration of Isoflurane, Sevoflurane, or Desflurane: A Randomized Controlled Trial

Background: Intensive care unit (ICU) physicians have extended the minimum alveolar concentration (MAC) to deliver and monitor long-term volatile sedation in critically ill patients. There is limited evidence of MAC’s reliability in controlling sedation depth in this setting. We hypothesized that sedation depth, measured by the electroencephalography (EEG)-derived Narcotrend-Index (burst-suppression N_Index 0 – awake N_Index 100), might drift downward over time despite constant MAC values.Methods: This prospective single-centre randomized clinical study was conducted at a University Hospital Surgical Intensive Care Unit and included consecutive, postoperative ICU patients fulfilling the inclusion criteria. Patients were randomly assigned to receive uninterrupted inhalational sedation with isoflurane, sevoflurane, or desflurane. The end-expiratory concentration of the anaesthetics and the EEG-derived index were measured continuously in time-stamped pairs. Sedation depth was also monitored using Richmond-Agitation-Sedation-Scale (RASS). The paired t-test and linear models (bootstrapped or multilevel) have been employed to analyze MAC, N_Index and RASS across the three groups. Results: Thirty patients were recruited (female/male: 10/20, age 64±11, Simplified Acute Physiology Score II 30±10). In the first 24 hours, 21.208 pairs of data points (N_Index and MAC) were recorded. The median MAC of 0.58±0.06 remained stable over the sedation time in all three groups. The t-test indicated in the isoflurane and sevoflurane groups a significant drop in RASS and EEG-derived N_Index in the first versus last two sedation hours. We applied a multilevel linear model on the entire longitudinal data, nested per patient, which produced the formula N_Index=43−0.7·hours (R2=0.76), showing a strong negative correlation between sedation’s duration and the N_Index. Bootstrapped linear models applied for each sedation group produced: N_Index of 43–0.9, 45–0.8, and 43–0.4·hours for isoflurane, sevoflurane, and desflurane, respectively. The regression coefficient for desflurane was almost half of those for isoflurane and sevoflurane, indicating a less pronounced time-effect in this group.Conclusions: Maintaining constant MAC does not guarantee stable sedation depth. Thus, the patients necessitate frequent clinical assessments or, when unfeasible, continuous EEG monitoring. The differences across different volatile anaesthetics regarding their time-dependent negative drift requires further exploration.Trial registration: NCT03860129.

Valuation of machinery and equipment subject to the Wiener degradation process

We propose a model describing the decrease in the market value of machines (depreciation) with age. Usually it is characterized by the percent good factor, i.e. the ratio of machine’s value to the value of similar new machinery item. Often, appraisers know about a used machinery item only by its age, but not its performance. Therefore, for the valuation of the machinery item of a known age, they have to use the mean (for machines of this age) of percent good factor. In the proposed model, the state of the machine is characterized by the intensity of the benefits it brings. In this case, the benefits from using the machine in a certain period are defined as the market value of the work performed by it minus operating costs. We describe the change in the intensity of benefits over time by the Wiener process with negative drift. This allows us to take into account the tendency for the performance of machine to deteriorate during operation. The market value of a machine is defined as the maximum mathematical expectation of the sum of discounted benefits from its use. It is shown that it corresponds to the moment the machine reaches a certain boundary state. The parameters of the Wiener process (drift and volatility) are expressed through the known characteristics of the machine's durability, namely the average value and the coefficient of variation of the service life. The dependences of the mean percent good factor of machines on the relative age (the ratio of age to the average service life) are found. It turned out that these dependencies are almost independent of the discount rate and average service life.

Lower Bounds for Non-Elitist Evolutionary Algorithms via Negative Multiplicative Drift

A decent number of lower bounds for non-elitist population-based evolutionary algorithms has been shown by now. Most of them are technically demanding due to the (hard to avoid) use of negative drift theorems — general results which translate an expected movement away from the target into a high hitting time. We propose a simple negative drift theorem for multiplicative drift scenarios and show that it can simplify existing analyses. We discuss in more detail Lehre's (PPSN 2010) negative drift in populations method, one of the most general tools to prove lower bounds on the runtime of non-elitist mutation-based evolutionary algorithms for discrete search spaces. Together with other arguments, we obtain an alternative and simpler proof of this result, which also strengthens and simplifies this method. In particular, now only three of the five technical conditions of the previous result have to be verified. The lower bounds we obtain are explicit instead of only asymptotic. This allows to compute concrete lower bounds for concrete algorithms, but also enables us to show that super-polynomial runtimes appear already when the reproduction rate is only a [Formula: see text] factor below the threshold. For the special case of algorithms using standard bit mutation with a random mutation rate (called uniform mixing in the language of hyper-heuristics), we prove the result stated by Dang and Lehre (PPSN 2016) and extend it to mutation rates other than [Formula: see text], which includes the heavytailed mutation operator proposed by Doerr, Le, Makhmara, and Nguyen (GECCO 2017). We finally use our method and a novel domination argument to show an exponential lower bound for the runtime of the mutation-only simple genetic algorithm on ONEMAX for arbitrary population size.

The Effect of War Risk on Managerial and Investor Behavior: Evidence from the Brussels Stock Exchange in the Pre-1914 Era

With two news-based measures on war, I document that managers mitigated war risk through dividend cuts, arguably to establish a war chest. Moreover, I find that companies postponed their initial public offerings and that foreign companies were more likely to delist after the onset of wars. Investors reacted negatively to the increase in war news coverage. There is evidence of mean-reversion after a threat of war and a negative drift following the start of war. Finally, I highlight the importance of proximity to military conflicts. In general, the evidence indicates that both managers and investors became more risk averse as a consequence of war news.

Credibility Dynamics and Disinflation Plans

We study the optimal design of a disinflation plan by a planner who lacks commitment. Having announced a plan, the Central banker faces a tradeoff between surprise inflation and building reputation, defined as the private sector's belief that the Central bank is committed to the plan. Some plans are harder to sustain: the planner recognizes that paving out future grounds with temptation leads the way for a negative drift of reputation in equilibrium. Plans that successfully create low inflationary expectations balance promises of lower inflation with dynamic incentives that make them more credible. When announcing the disinflation plan, the planner takes into account these anticipated interactions. We find that, even in the zero reputation limit, a gradual disinflation is preferred despite the absence of inflation inertia in the private economy.