Chemical flux analysis of low-temperature plasma-enhanced oxidation of methane and hydrogen in argon

Plasma can be used to enhance the reactivity of combustible mixtures at low temperatures. In this article, the chemical pathways predicted by three different reaction mechanisms are investigated for the low-temperature oxidation of hydrogen and methane. To validate our model and the reaction mechanisms, the numerical results are compared against experimental results in a diluted flow reactor. Our model with all three reaction mechanisms predicts trends similar to those observed in the experiments. Moreover, all predicted quantities show reasonable quantitative agreement with the experiments. Flux analysis is used to identify the main pathways of oxidation at different temperatures. Three different modes, each active in a different temperature range, are identified in the oxidation of hydrogen. When the temperature is increased, these modes become increasingly self-sustained. Similarly, three different pathways are identified in the oxidation of methane. Below 1000K, methane quickly removes hydroxyl radicals from the radical pool, inhibiting self-sustained oxidation. From our analysis, we conclude that plasma provides activation of the low-temperature chemistry by the generation of radicals

Are the orthostatic fluid shifts to the calves augmented in autonomic failure?

In autonomic failure (AF), blood pressure (BP) falls upon standing which is commonly ascribed to defective vasoconstriction and excessive pooling. Observations on the amount of pooling in AF are contradictory. We evaluated pooling using strain-gauge plethysmography (SGP) during head-up tilt (HUT) with a parachute harness fixed to the tilt table to avoid muscle tension in the lower limbs and thus to maximise pooling. 23 healthy subjects and 12 patients with AF were tilted for 5 min. BP and calf volume changes, as measured by SGP, were measured continuously. Multiple regression analysis was used to examine the effect of AF on orthostatic fluid shifts after adjustment for potential confounders. Patients did not differ from controls with respect to the increase of calf volume after 5 min HUT. The acute (0-1 min) and the prolonged (1-5 min) phases of calf volume responses to HUT were also similar between patients and controls. No correlation was found between the degree of orthostatic hypotension and the orthostatic calf volume change in AF. In one patient an additional measurement was made before rising from bed in the early morning demonstrating a greater albeit small increase of calf volume upon HUT. Orthostatic fluid shifts at the level of the calf in AF are not augmented during the course of the day despite marked hypotension. However, a small increase of pooling may be expected when the patient first gets out of bed in the morning probably due to the absence of oedema.Paroxysmal Cerebral Disorder

Contagion as Domino Effect in Global Stock Markets

This paper shows that stock market contagion operates through a domino effect, where small crashes evolve into more severe crashes. Using a novel unifying framework we model the occurrence of local, regional and global crashes in terms of past occurrences of these different crashes and financial variables. We find convincing evidence that global crashes do not occur abruptly but are preceded by local and regional crashes. Additionally, interest rates, bond returns and volatility affect the probabilities of different crash types, indicating interdependence. We show that in forecasting global crashes our model outperforms a binomial model for global crashes only

Time Variation in Asset Return Dependence: Strength or Structure?

The dependence between asset returns varies. Its strength can become stronger or weaker. Also, its structure can change, for example, when asymmetries related to bull and bear markets become more or less pronounced. To analyze these different types of variations, we develop a model that separately accommodates these changes. It combines a mixture of structurally different copulas with time variation. Our model shows both types of changes in the dependence between several equity market returns. Ignoring them leads to biases in risk measures. An underestimation of Value-at-Risk by maximum 15% occurs exactly when most harmful, during crisis periods

Managing psychogenic pseudosyncope: Facts and experiences

Psychogenic pseudosyncope (PPS) is a common cause of apparent transient loss of conscious­ness (TLOC) with a dramatic impact on the quality of life. This review aims to give an overview of the definition, incidence, etiology, diagnosis, treatment, and prognosis of PPS based on a combination of literature data and personal experience. The limited literature on the subject suggests that PPS is relatively common but insufficiently recognized. PPS is probably similar to psychogenic nonepiteptic seizures (PNES), in which a long delay to diagnosis worsens the prognosis. A detailed history is of paramount importance for the diagnosis. The key feature in the history of patients with PPS is the occurrence of frequent, long attacks of apparent TLOC with closed eyes. The diagnosis is certain when a typical event is recorded during a tilt-table test with simultaneous blood pressure (BP), heart rate and video-electroencephalographic re­cordings. Home video and BP recording during an attack can be very useful. The diagnosis should be communicated to the patient in a way that is clear, understandable and does not cause offense. Although treatment options have not been investigated formally, the literature on PNES suggests that cognitive behavioral therapy is beneficial

Multimodal nocturnal seizure detection in children with epilepsy:A prospective, multicenter, long-term, in-home trial

Objective: There is a pressing need for reliable automated seizure detection in epilepsy care. Performance evidence on ambulatory non-electroencephalography-based seizure detection devices is low, and evidence on their effect on caregiver's stress, sleep, and quality of life (QoL) is still lacking. We aimed to determine the performance of NightWatch, a wearable nocturnal seizure detection device, in children with epilepsy in the family home setting and to assess its impact on caregiver burden. Methods: We conducted a phase 4, multicenter, prospective, video-controlled, in-home NightWatch implementation study (NCT03909984). We included children aged 4–16 years, with ≥1 weekly nocturnal major motor seizure, living at home. We compared a 2-month baseline period with a 2-month NightWatch intervention. The primary outcome was the detection performance of NightWatch for major motor seizures (focal to bilateral or generalized tonic–clonic [TC] seizures, focal to bilateral or generalized tonic seizures lasting &gt;30 s, hyperkinetic seizures, and a remainder category of focal to bilateral or generalized clonic seizures and "TC-like" seizures). Secondary outcomes included caregivers' stress (Caregiver Strain Index [CSI]), sleep (Pittsburgh Quality of Sleep Index), and QoL (EuroQol five-dimension five-level scale). Results: We included 53 children (55% male, mean age = 9.7 ± 3.6 years, 68% learning disability) and analyzed 2310 nights (28 173 h), including 552 major motor seizures. Nineteen participants did not experience any episode of interest during the trial. The median detection sensitivity per participant was 100% (range = 46%–100%), and the median individual false alarm rate was.04 per hour (range = 0–.53). Caregiver's stress decreased significantly (mean total CSI score = 8.0 vs. 7.1, p =.032), whereas caregiver's sleep and QoL did not change significantly during the trial. Significance: The NightWatch system demonstrated high sensitivity for detecting nocturnal major motor seizures in children in a family home setting and reduced caregiver stress.</p

Mixing in Shallow Cumulus Clouds Studied by Lagrangian Particle Tracking

Mixing between shallow cumulus clouds and their environment is studied using large-eddy simulations. The origin of in-cloud air is studied by two distinct methods: 1) by analyzing conserved variable mixing diagrams (Paluch diagrams) and 2) by tracing back cloud-air parcels represented by massless Lagrangian particles that follow the flow. The obtained Paluch diagrams are found to be similar to many results in the literature, but the source of entrained air found by particle tracking deviates from the source inferred from the Paluch analysis. Whereas the classical Paluch analysis seems to provide some evidence for cloud-top mixing, particle tracking shows that virtually all mixing occurs laterally. Particle trajectories averaged over the entire cloud ensemble also clearly indicate the absence of significant cloud-top mixing in shallow cumulus clouds

Mixing in Shallow Cumulus Clouds Studied by Lagrangian Particle Tracking

Mixing between shallow cumulus clouds and their environment is studied using large-eddy simulations. The origin of in-cloud air is studied by two distinct methods: 1) by analyzing conserved variable mixing diagrams (Paluch diagrams) and 2) by tracing back cloud-air parcels represented by massless Lagrangian particles that follow the flow. The obtained Paluch diagrams are found to be similar to many results in the literature, but the source of entrained air found by particle tracking deviates from the source inferred from the Paluch analysis. Whereas the classical Paluch analysis seems to provide some evidence for cloud-top mixing, particle tracking shows that virtually all mixing occurs laterally. Particle trajectories averaged over the entire cloud ensemble also clearly indicate the absence of significant cloud-top mixing in shallow cumulus clouds

The pathophysiology of vasovagal syncope: novel insights

The pathophysiology of vasovagal syncope (VVS) is reviewed, focusing on hemodynamic aspects. Much more is known about orthostatic than about emotional VVS, probably because the former can be studied using a tilt table test (TTT). Recent advances made it possible to quantify the relative contributions of the three factors that control blood pressure: heart rate (HR), stroke volume (SV) and total peripheral resistance (TPR). Orthostatic VVS starts with venous pooling, reflected in a decrease of SV. This is followed by cardioinhibition (CI), which is a decrease of HR that accelerates the ongoing decrease of BP, making the start of CI a literal as well as fundamental turning point.The role of hormonal and other humoral factors, respiration and of psychological influences is reviewed in short, leading to the conclusion that a multidisciplinary approach to the study of the pathophysiology of VVS may yield new insights.Paroxysmal Cerebral Disorder

Tilt table testing in neurology and clinical neurophysiology

Paroxysmal Cerebral Disorder