Shock Arrives Research Articles

The Effects of Macroeconomic Shocks: Household Financial Distress Matters

Abstract When a macroeconomic shock arrives, variation in household balance sheet health (captured by the presence of financial distress, or “FD”) leads to differential access to credit and hence a distribution in consumption responses. As we document, though, over the past two recessions, households in prior FD also experienced macroeconomic shocks more intensely than others, leading to a distribution of shock severity. Quantifying the importance of each dimension of heterogeneity (FD or shock severity) for consumption requires a structural model. We find that heterogeneity in FD matters more for shaping the responses of individual and aggregate consumption to shocks. (JEL D31, E21, E44, G11, G12, G21)

Learning from implementation of a COVID case management desk guide and training: a pilot study in Sierra Leone

BackgroundWhen the COVID pandemic hit the world, there was need for applied guides and training materials to support frontline health care staff to manage patients effectively and safely and to educate themselves and communities. This article reports on the development and piloting of such a set of materials in Sierra Leone, which were based on international evidence but adapted to the local context. Reflecting on this experience, including community and health system barriers and enablers, is important to prepare for future regional shocks.MethodsThis study, in Bombali district in 2020, piloted user-friendly COVID guides for frontline health workers (the intervention), which was evaluated using facility checklists (pre and post training), routine data analysis and 32 key informant interviews.ResultsKey informants at district, hospital and community health centre levels identified gains from the training and desk guides, including improved diagnosis, triaging, infection prevention and management of patients. They also reported greater confidence to share messages on protection with colleagues and community members, which was needed to encourage continued use of essential services during the pandemic. However, important barriers were also revealed, including the lack of testing facilities, which reduced the sense of urgency, as few cases were identified. Actions based on the Ebola experience, such as setting up testing and isolation centres, which the community avoided, were not appropriate to COVID. Stigma and fear were important factors, although these were reduced with outreach activities. Supplies of essential medicines and personal protective equipment were also lacking.ConclusionThis pilot study demonstrated the relevance and importance of guides adapted to the context, which were able to improve the confidence of health staff to manage their own and the community’s fears in the face of a new pandemic and improve their skills. Previous epidemics, particularly Ebola, complicated this by both creating structures that could be revitalised but also assumptions and behaviours that were not adapted to the new disease. Our study documents positive adaptations and resilience by health staff but also chronic system weaknesses (particularly for medicines, supplies and equipment) which must be urgently addressed before the next shock arrives.

Reliability modeling: combining self-healing characteristics and dynamic failure thresholds

ABSTRACT The failure threshold of a product is not always constant when affected by random shocks. Thus, this paper establishes a reliability model that combines dynamic failure threshold and self-healing characteristics, which are subjected to the competing failure process. Soft failure is caused by degradation exceeding the soft failure threshold, and hard failure occurs because of random shocks. Degradation consists of natural degradation and a degradation increment caused by shocks. The failure thresholds and degradation rate will also be affected by random shocks. Moreover, the self-healing characteristics in the degradation process, together with the degradation increment, will affect the whole degradation process. When the random shock arrives, the soft and hard failure thresholds will change simultaneously. Based on the above factors, the corresponding analytical expressions of reliability models under different shock models are derived. To confirm the effectiveness of the proposed model, an example of micro-engine is used to verify the constructed reliability model. The influences of self-healing and dynamic thresholds in micro-engines on reliability are studied. The effects of self-healing and thresholds on the models are analyzed, which can provide study basis for the maintenance and replacement of product.

Returning to school after COVID-19 closures: Who is missing in Malawi?

During the early stages of the COVID-19 pandemic, almost all countries implemented school closures to prevent disease transmission. However, prolonged closures can put children at risk of leaving school permanently, a decision that can reduce their long-term potential and income. This study investigated the extent to which the COVID-19 pandemic and associated school closures reduced school attendance in Malawi, a low-income African country. We used longitudinal data from a cohort of adolescents interviewed before (2017/18; at age 10–16) and after (2021; at age 13–20) the pandemic school closures. Of those students who had been attending school prior to school closures, we find that 86% returned when schools re-opened. Dropouts were more pronounced among older girls: over 30% of those aged 17–19 did not return to school. This resulted in further lowering the gender parity index to the greater disadvantage of girls. We also found that students already lagging behind in school were more likely to dropout. Thus, our data suggest that the COVID-19 pandemic has magnified gender inequalities in schooling, at least partially erasing recent progress towards inclusive education. Urgent investments are needed to find and re-enroll lost students now, and to create more resilient and adaptable educational systems before the next pandemic or other negative shock arrives.

Heliospheric Compression Due to Recent Nearby Supernova Explosions

The widespread detection of 60Fe in geological and lunar archives provides compelling evidence for recent nearby supernova explosions within ∼100 pc at 3 and 7 Myr ago. The blasts from these explosions had a profound effect on the heliosphere. We perform new calculations to study the compression of the heliosphere due to a supernova blast. Assuming a steady but non-isotropic solar wind, we explore a range of properties appropriate for supernova distances inspired by recent 60Fe data, and for a 20 pc supernova proposed to account for mass extinctions at the end-Devonian period. We examine the locations of the termination shock decelerating the solar wind and the heliopause that marks the boundary between the solar wind and supernova material. Pressure balance scaling holds, consistent with studies of other astrospheres. Solar wind anisotropy does not have an appreciable effect on shock geometry. We find that supernova explosions at 50 pc (95 pc) lead to heliopause locations at 16 au (23 au) when the forward shock arrives. Thus, the outer solar system was directly exposed to the blast, but the inner planets—including Earth—were not. This finding reaffirms that the delivery of supernova material to Earth is not from the blast plasma itself, but likely is from supernova dust grains. After the arrival of the forward shock, the weakening supernova blast will lead to a gradual rebound of the heliosphere, taking ∼few 100 kyr to expand beyond 100 au. Prospects for future work are discussed.

Angiotensin II for the emergency physician

Refractory hypotension is one of the most common and difficult clinical problems faced by acute care clinicians, and it poses a particularly large problem to the emergency physician when a...

Improvement of proton acceleration via collisionless shock acceleration by laser-foil interaction with an external magnetic field

Effects of the external intense axial magnetic field on collisionless shock acceleration (CSA) are investigated by using two-dimensional particle-in-cell simulations. Proton beams accelerated by CSA show different properties when left-hand circularly polarized (LHCP) or right-hand circularly polarized (RHCP) lasers are individually applied to a foil target with or without the magnetic field. It can be attributed to the difference of the dispersion relationship for the laser propagating in a plasma. Protons achieve more efficient acceleration when magnetized plasma is irradiated by the RHCP laser compared with the LHCP laser. Furthermore, the effect of different amplitudes of the magnetic field is studied numerically. It shows that the induced electrostatic charge-separation field arises deep in the target with huge strength of the magnetic field. Protons in the upstream are accelerated before the shock arrives, leading to less efficient acceleration. As a result, an appropriate magnetic field should be applied to enhance the CSA regime.

Escaping Damocles' Sword: Endogenous Climate Shocks in a Growing Economy

Climate economics has been criticized for ignoring uncertainty, catastrophic changes, and tipping points (Stern 2016). The present paper addresses these issues. We consider multiple climate shocks which are recurring, random, uninsurable, and potentially large. The associated damages and the hazard rate are endogenously driven by the stock of greenhouse gases. We provide closed-form solutions for the optimal climate policy and the growth rate of the economy. The optimal path is characterized by a constant growth rate of consumption and of the capital stock until a shock arrives, triggering a downward jump in both variables. The mitigation policy consists of a simple and intuitive rule which requires spending a constant fraction of output on emissions abatement. In a quantitative assessment we show that under favorable conditions the abatement expenditure represents 0.5% of output, equivalent to $37 per ton carbon. Under less favorable conditions with respect to abatement technology and damages, coupled with a relative risk aversion which exceeds unity, the abatement propensity increases to 2.9%, equivalent to $212 per ton carbon, and it jumps to a striking 10% in the pessimistic scenario involving severe shocks and a possible crossing of a tipping point.

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Electron dropout echoes induced by interplanetary shock: A statistical study

Abstract“Electron dropout echo” as indicated by repeated moderate dropout and recovery signatures of the flux of energetic electron in the outer radiation belt region has been investigated systematically. The electron moderate dropout and its echoes are usually found for higher‐energy (>300 keV) channel fluxes, whereas the flux enhancements are obvious for lower energy electrons simultaneously after the interplanetary shock arrives at the Earth's geosynchronous orbit. The electron dropout echo events are found to be usually associated with the interplanetary shocks arrival. The 104 dropout echo events have been found from 215 interplanetary shock events from 1998 to 2007 based on the Los Alamos National Laboratory satellite data. In analogy to substorm injections, these 104 events could be naturally divided into two categories: dispersionless (49 events) or dispersive (55 events) according to the energy dispersion of the initial dropout. It is found that locations of dispersionless events are distributed mainly in the duskside magnetosphere. Further, the obtained locations derived from dispersive events with the time‐of‐flight technique of the initial dropout regions are mainly located at the duskside as well. Statistical studies have shown that the effect of shock normal, interplanetary magnetic field Bz and solar wind dynamic pressure may be insignificant to these electron dropout events. We suggest that the ∼1 min electric field impulse induced by the interplanetary shock produces a more pronounced inward migration of electrons at the duskside, resulting in the observed duskside moderate dropout of electron flux and its consequent echoes.

Numerical studies on the formation process of Z-pinch dynamic hohlruams and key issues of optimizing dynamic hohlraum radiation

Dynamic hohlraum is a possible selection to drive inertial confinement fusion. Currently, the ~8 MA PTS facility in China has been completed, which provides a powerful experimental platform of relatively large drive current for researches of dynamic hohlraums and dynamic hohlraum driven inertial fusion. To understand the formation processes and the main characteristics of the dynamic hohlraum, and explore the most important issues affecting the optimization of hohlraum radiation, is not only fundamental in the research of dynamic hohlraums, especially for the experimental design, but also can provide a physical insight for the experimental diagnosis. In this paper the implosion dynamics of a tungsten wire-array Z-pinch embedded with a CH foam converter, especially the impaction interaction of the wire-array plasma with the converter plasma, is numerically investigated using a one-dimensional non-equilibrium radiation magnetohydrodynamic code. In simulations the tungsten plasma is assumed as a plasma shell with a width of 1 mm, and the CH converter plasma is assumed to be uniform with an initial temperature of 0.1 eV. The overall implosion is driven by an assumed current with a peak value of 8 MA and a rise time of 66.4 ns. It is shown that a local high pressure region, which is generated by the impaction of the tungsten plasma with the converter plasma, is crucial to launch the strongly radiating shock wave and to form the dynamic hohlraum. Due to the supersonic radiation transfer in the low opacity CH converter plasma, which is also produced in the high pressure region, there exists a hohlraum region inside the front of the shock wave, in which the radiation is high. At the same time, the plasma pressure is uniform in this hohlraum region, so the plasma will not be disturbed before the shock arrives. As the shock propagates to the axis, the hohlraum becomes small and the radiation temperature is also increased. Basically, the hohlraum radiation is determined by the detailed profiles of plasma conditions when the wire-array plasma impacts onto the CH converter plasma. And these profiles are determined by many factors, such as the drive current, initial masses and radii of the wire-array and the converter, as well as the material of the converter. When the drive current is fixed, the optimal wire-array can be determined. Firstly, the mass ratio of the wire-array to the CH converter is varied. Numerical calculations show that as this ratio is decreased, the shock velocity is increased and the radiation temperature is increased as well. Additionally, the time duration of the radiation pulse before the shock arrives at the axis is remarkably increased. It is also found that when this mass ratio is slightly lower than unity, for example 0.75, a relative optimal dynamic hohlraum can be produced. Secondly, if the mass ratio is fixed and the initial radius of the converter is decreased, it is found that the shock velocity is just slightly changed. However, the peak hohlraum radiation temperature is increased and the radiation pulse becomes remarkably narrow. A suitable radius ratio of the wire-array to the converter, neither too large to induce strong Magneto-Rayleigh-Taylor (MRT) instability nor too small to gain a small kinetic energy of the wire-array before impacting onto the converter surface, should be selected. In the future we will develop two-dimensional code to investigate the effect of MRT instability on the formation of dynamic hohlraums.

Growth and Mitigation Policies With Uncertain Climate Damage

We analyze an endogenously growing economy in which production generates greenhouse gas emissions leading to global temperature increase. Global warming causes stochastic climate shocks, modeled by the Poisson process, which destroy part of the economy's capital stock. Part of the output may be devoted to emissions abatement and thus damages from climate shocks may be reduced. We solve the model in closed form and show that the optimal path is characterized by a constant growth rate of consumption and capital stock until a shock arrives, triggering a downward jump in both variables. The magnitude of the jump depends on the Poisson arrival rate, abatement efficiency, damage intensity, and the elasticity of intertemporal consumption substitution. Optimum mitigation policy consists of spending a constant share of output on abatement, which is an increasing function of the Poisson arrival rate, the economy's productivity, polluting intensity of output, and the intensity of environmental damage. Optimum growth and abatement react sharply to changes in the arrival rate and the damage intensity, suggesting more stringent climate policies for a realistic world with uncertainty compared to the certainty-equivalent case. We extend the baseline model by adding climate-induced fluctuations around the growth trend and stock pollution effects, showing the robustness of our results.

Growth and Mitigation Policies with Uncertain Climate Damage

Climate physics predicts that the intensity of natural disasters will increase in the future due to climate change. One of the biggest challenges for economic modeling is the inherent uncertainty of climate events, which crucially aects consumption, investment,and abatement decisions. We present a stochastic model of a growing economy where natural disasters are multiple and random, with damages driven by the economy's polluting activity. We provide a closed-form solution and show that the optimal path is characterized by a constant growth rate of consumption and the capital stock untila shock arrives, triggering a downward jump in both variables. Optimum mitigation policy consists of spending a constant fraction of output on emissions abatement. This fraction is an increasing function of the arrival rate, polluting intensity of output, and the damage intensity of emissions. A sharp response of the optimum growth rate and the abatement share to changes in the arrival rate and the damage intensity justies more stringent climate policies as compared to the expectation-based scenario. We subsequently extend the baseline model by adding climate-induced uctuations around the growth trend and stock-pollution eects, demonstrating robustness of our results. In a quantitative assessment of our model we show that the optimal abatement expenditure at the global level may represent 0.9% of output, which is equivalent to a tax of $71 per ton carbon.

An extended extreme shock maintenance model for a deteriorating system

In this paper, we study a deteriorating system which is suffering random shocks from its environment. Assume that in the system's operating stage, whenever a shock arrives, it will do some damage to the system, but shocks with a “small” level of damage are harmless for the system, while shocks with a “large” level of damage may result in the system's failure. The system's deterioration is caused by both the external shocks and the internal load. In the external, the magnitude of the shock damage the system can bear is decreasing with respect to the number of repairs taken. In the internal, the consecutive repair time is increasing in the number of repairs taken. A replacement policy N , by which the system is replaced at the time of the N th failure, is adopted. An explicit expression of the long run average cost per unit time is derived, and an optimal policy N * for minimizing the long run average cost per unit time is determined analytically. A numerical example is also given.

A geometric-process maintenance model for a deteriorating system under a random environment

This paper studies a geometric-process maintenance-model for a deteriorating system under a random environment. Assume that the number of random shocks, up to time t, produced by the random environment forms a counting process. Whenever a random shock arrives, the system operating time is reduced. The successive reductions in the system operating time are statistically independent and identically distributed random variables. Assume that the consecutive repair times of the system after failures, form an increasing geometric process; under the condition that the system suffers no random shock, the successive operating times of the system after repairs constitute a decreasing geometric process. A replacement policy N, by which the system is replaced at the time of the failure N, is adopted. An explicit expression for the average cost rate (long-run average cost per unit time) is derived. Then, an optimal replacement policy is determined analytically. As a particular case, a compound Poisson process model is also studied.

Interaction of a Shock Wave with a Thermal Boundary Layer

The interaction of a plane shock wave with a thermal boundary layer has been studied experimentally in the shock tube and a theory developed for those cases in which the shock is sufficiently strong and the heating small enough for the shock to extend clear to the surface. The experiment involves a technique of sliding a hot plate into the shock tube just before the shock arrives. The time required for establishment of steady conditions has been determined and the theory tested with experiments using shocks up to a pressure ratio of 1.36 and surface temperatures up to 80°C. The observed shape of the shock and pressure distribution along the surface agree well with predictions. When the speed of sound a t the surface exceeds the shock velocity, pressure disturbances propagate ahead of the main wave and the total pressure rise extends over about two heated thicknesses. Finally, the possibility of extending the experimental results to more extreme conditions by an analogy with diffusion of gases is discussed.