Targeted vaccination and the speed of SARS-CoV-2 adaptation

The limited supply of vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) raises the question of targeted vaccination. Many countries have opted to vaccinate older and more sensitive hosts first to minimize the disease burden. However, what are the evolutionary consequences of targeted vaccination? We clarify the consequences of different vaccination strategies through the analysis of the speed of viral adaptation measured as the rate of change of the frequency of a vaccine-adapted variant. We show that such a variant is expected to spread faster if vaccination targets individuals who are likely to be involved in a higher number of contacts. We also discuss the pros and cons of dose-sparing strategies. Because delaying the second dose increases the proportion of the population vaccinated with a single dose, this strategy can both speed up the spread of the vaccine-adapted variant and reduce the cumulative number of deaths. Hence, strategies that are most effective at slowing viral adaptation may not always be epidemiologically optimal. A careful assessment of both the epidemiological and evolutionary consequences of alternative vaccination strategies is required to determine which individuals should be vaccinated first.

Modelling the effect of the interaction between vaccination and non-pharmaceutical measures on COVID-19 incidence

Since December 2019, the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly from Wuhan (China) across the globe, affecting more than 200 countries by mid-2021, with over 190 M reported cases and around 4 M fatalities. During the first year of the pandemic, affected countries implemented a variety of non-pharmaceutical interventions to control virus transmission. In December 2020, countries started administering several authorised vaccines under a limited supply scenario. In this context, a SEIR-type continuous-time deterministic disease model was developed to explore the effect of vaccination in terms of vaccination rate and efficacy, together with varying non-pharmaceutical protection measures, on disease incidence in the initial phase of vaccination. For this, the model incorporates (i) a protection measure including low (self-protection), medium (mobility limitation), high (closure of indoor facilities) and very high (lockdown) protection levels, (ii) quarantine for confirmed cases, and (iii) vaccination rate and efficacy of four type of vaccines (Pfizer, Moderna, Astra Zeneca or Janssen). The model was verified and evaluated using the response timeline and vaccination strategies and rates in the Basque Country (N. Spain). Once the model performance was validated, different initial phase (when 30% of the population is vaccinated) vaccination scenarios were simulated, including (i) a realistic vaccine limited supply scenario, and (ii) four potential full vaccine supply scenarios where a unique vaccine type is administered. The Pfizer scenario resulted in the lowest prevalence of infection and cumulative mortality, particularly for low- and medium-level protection rates. However, regardless of the administered vaccine, a high-level protection scenario is the most effective to control the virus transmission and disease mortality in the studied initial phase of vaccination. The model here, which is based on this example, could be easily applied to other regions or countries, modifying the strategies implemented and initial conditions.

Eucalyptus plantation and its integrated supply chain in pulp and paper mill

Nowadays, demand of the pulp and paper production increases quickly. That increasing demand has led to demanding of eucalyptus plantation. That is why eucalyptus plantation has rapidly expanded and became the most planted tree species across the world over the last century. Not only because its unique characteristics, increasing of eucalyptus plantation also happened because its growing gives a socio-economic benefits, industrial benefits, and environmental impacts. However, increasing demand of eucalyptus certainly make availability of eucalyptus being determined, known as limited supply chain. Due to the increasing demand and limited supply chain, the eucalyptus wood supply should managed, by integrated the supply chain well. In this research study, the supply chain of eucalyptus wood for pulp and paper industry was diagnosed and divided into three degree, there are direct supply chain, extended supply chain, and ultimate supply chain. Four main stakeholders in this chain identified consisted of the eucalyptus seedling developers and sellers, the suppliers, the distribution centers, and the pulp and paper production plants.

Bundling Decisions for Selling Multiple Items in Online Auctions

Fueled by the widespread use of the internet, more and more ordinary people have now become merchandise sellers who sell their own possessions, such as antique collections and limited souvenirs, to buyers who are interested in such goods via online auctions. This study examines the decision making related to the bidding strategies used in online auctions by both sellers and buyers. When selling goods for which there is a limited supply, sellers consider whether to sell the single homogenous items in multiple, simultaneous auctions or all the items in a single auction. Moreover, when selling heterogeneous but associated goods, sellers may decide to bundle the items for sale or not with an aim of increasing the potential buyers’ willingness to make a purchase. We investigate the effects that various factors related to the bidding strategies used in online auctions, such as the base price and duration of the auction determined by the seller and the bidding price decided by the buyer, have on the seller’s profit, and the utilities of both parties are considered to derive the equilibrium solutions. This study contributes to the literature by proposing an online auction framework that focuses more on individual sellers selling a limited quantity of items with an aim to establish a favorable online auction for both sellers and buyers and earn more profits for sellers. The results show that the base prices and direct purchase prices should be unestablished to achieve the most attractive characteristics of online auctions, which would encourage more buyers to freely place bids. As a result, the bidding items would have more chances to be eventually obtained by the buyer who places the highest bid, which, thus, maximizes the seller’s profit.

Unsettled Economic, Environmental, and Health Issues of Ammonia for Automotive Applications

Ammonia has been previously trialed as an automotive fuel; however, it was hardly competitive with fossil fuels in terms of cost, energy density, and practicality. However, due to climate change, those practical and cost-related parameters have finally become secondary deciding factors in fuel selection. Ammonia is safer than most fuels and it offers superior energy densities compared to compressed or liquefied hydrogen. It is believed that ammonia might be an ultimate clean fuel choice and an extension to the emerging hydrogen economy. Unsettled Economic, Environmental, and Health Issues of Ammonia for Automotive Applications examines the major unsettled issues of using ammonia as a clean automotive fuel alternative, including the lack of regulations and standards for automotive applications, technology readiness, safety perception, and presently limited supply. While ammonia as a fuel is still in its infancy, identifying and addressing these challenges early could enable a safe and smooth transition.

Innovative Solutions to Overcome the Health Services Crisis within the Covid-19 Era

The outbreak of the SARS-CoV-2 pandemic has fundamentally changed the natural course of activity of all economic sectors worldwide, as well as the healthcare sector which was deeply influenced. This paper analyzes the relationship between the increased demand for health services during the pandemic and the limited supply of healthcare using the transversal method for some European Union (EU) states.

A QPTAS for ɛ-Envy-Free Profit-Maximizing Pricing on Line Graphs

We consider the problem of pricing edges of a line graph so as to maximize the profit made from selling intervals to single-minded customers. An instance is given by a set E of n edges with a limited supply for each edge, and a set of m clients, where each client specifies one interval of E she is interested in and a budget B j which is the maximum price she is willing to pay for that interval. An envy-free pricing is one in which every customer is allocated an (possibly empty) interval maximizing her utility. Grandoni and Rothvoss (SIAM J. Comput. 2016) proposed a polynomial-time approximation scheme ( PTAS ) for the unlimited supply case with running time ( nm ) O ((1/ɛ) 1/ɛ ) , which was extended to the limited supply case by Grandoni and Wiese (ESA 2019). By utilizing the known hierarchical decomposition of doubling metrics , we give a PTAS with running time ( nm ) O (1/ ɛ 2 ) for the unlimited supply case. We then consider the limited supply case, and the notion of ɛ-envy-free pricing in which a customer gets an allocation maximizing her utility within an additive error of ɛ. For this case, we develop an approximation scheme with running time ( nm ) O (log 5/2 max e H e /ɛ 3 ) , where H e = B max ( e )/ B min ( e ) is the maximum ratio of the budgets of any two customers demanding edge e . This yields a PTAS in the uniform budget case, and a quasi-PTAS for the general case. The best approximation known, in both cases, for the exact envy-free pricing version is O (log c max ), where c max is the maximum item supply. Our method is based on the known hierarchical decomposition of doubling metrics, and can be applied to other problems, such as the maximum feasible subsystem problem with interval matrices.

Features of cascading disk-gear extrusion of plastics

The relevant task of today is to improve the installations for thermostat extrusion, in order to increase the indicators of resource/energy efficiency. The study of the features peculiar to the loading and melting area (LMA) and the elimination of shortcomings can significantly reduce the energy costs of the process. To achieve high-quality results in cascading disk-gear extrusion, the main methods of the dispersion melting of thermoplastic granules are analyzed, taking into account all the features of the physical model of the extrusion process. The dispersion model of melting is achieved by observing a limited supply of raw materials to the loading area. This ensures the intensification of the process and significantly reduces the total length of the LMA. In this case, the length of the area with the most filled channel directly depends on the resistance of the disk zone. With increasing resistance, the polymer stopper moves to the loading neck. The polymer is gradually compacted, and each leakage of the LMA is periodically filled. From the rotating disk heated to 107 oC, samples of the polymer were removed and cut into separate sections. Previously, to facilitate the process of visual research, the polymer was colored with 0.5% blue pigment. The results of the analysis confirmed the performance of the proposed physical model for the processes occuring in the disk-gear extruder. As a result, it is possible to calculate the time over which the granules stay in the LMA and the length of the screw cutting in this area, depending on the performance. Taking into account all the features of the disk-gear extrusion process allows creating an upgraded productive, resource-efficient installation and implementing it into practice.