Abstract
Many COVID-19 vaccines are proving to be highly effective to prevent severe disease and to diminish infections. Their uneven geographical distribution favors the appearance of new variants ...of concern, as the highly transmissible Delta variant, affecting particularly non-vaccinated people. It is important to device reliable models to analyze the spread of the different variants. A key factor is to consider the effects of vaccination as well as other measures used to contain the pandemic like social behaviour. The stochastic geographical model presented here, fulfills these requirements. It is based on an extended compartmental model that includes various strains and vaccination strategies, allowing to study the emergence and dynamics of the new COVID-19 variants. The model conveniently separates the parameters related to the disease from the ones related to social behavior and mobility restrictions. We applied the model to the United Kingdom by using available data to fit the recurrence of the currently prevalent variants. Our computer simulations allow to describe the appearance of periodic waves and the features that determine the prevalence of certain variants. They also provide useful predictions to help planning future vaccination boosters. We stress that the model could be applied to any other country of interest.
In recent years, the need for more efficient machining processes has notably increased, both in terms of productivity and eco-efficiency. In this paper, the use of combined techniques based on ...cryogenic cooling and minimum quantity of lubrication is proposed and compared with other near-to-dry coolant alternatives. To evaluate the success of the proposed technique, technical feasibility on the one hand and ecological footprint on the other should be analyzed. Results show that this combined solution implies a tool life improvement (more than 50%) and the possibility of increasing the cutting speed (more than 30%) comparing with dry machining. Moreover, cutting forces and surface integrity are maintained or even improved in comparison with conventional techniques. From an ecological point of view, a life cycle assessment was performed providing a comparison of the different alternatives proposed. Results show that the combination of cryogenic and minimum quantity of lubrication techniques is the key to success, reaching a balance between technical and environmental issues. Stand-alone systems (no combined ones) do not provide a complete solution. Cooling without lubrication or vice versa is not enough when machining these materials.
•A review of the most recent cryogenic machining technologies is presented.•A combined CryoMQL process is analyzed for turning AISI 304.•Process performance was compared using multiple lubri-coolant techniques.•LCA is performed to validate the eco-efficiency of the proposed solution.
In a world being hit by waves of COVID-19, vaccination is a light on the horizon. However, the roll-out of vaccination strategies and their influence on the pandemic are still open questions. In ...order to compare the effect of various strategies proposed by the World Health Organization and other authorities, a previously developed SEIRS stochastic model of geographical spreading of the virus is extended by adding a compartment for vaccinated people. The parameters of the model were fitted to describe the pandemic evolution in Argentina, Mexico and Spain to analyze the effect of the proposed vaccination strategies. The mobility parameters allow to simulate different social behaviors (e.g. lock-down interventions). Schemes in which vaccines are applied homogeneously in all the country, or limited to the most densely-populated areas, are simulated and compared. The second strategy is found to be more effective. Moreover, under the current global shortage of vaccines, it should be remarked that immunization is enhanced when mobility is reduced. Additionally, repetition of vaccination campaigns should be timed considering the immunity lapse of the vaccinated (and recovered) people. Finally, the model is extended to include the effect of isolation of detected positive cases, shown to be important to reduce infections.
In this work we present some experiments which can be performed in college or on the first courses of university to acquire knowledge about resonant acoustical phenomena in closed cavities in a ...tangible way, through experiments based on the photoacoustic effect in gases. This phenomenon consists in the generation of acoustic waves after optical excitation of an absorbing gas and further local heating of the non-absorbing surrounding gas by energy exchange through collisions between molecules of both species. Simple experiments, performed with daily live elements, can be very useful for teachers and students to get in touch with the phenomenon of acoustic resonances with the addition of concepts about light-matter interaction. The setups consist of the resonant cavity, the illumination source and the signal detection-acquisition scheme. In this paper a closed glass test tube is used as the resonant cavity and is filled with a mixture of nitrogen dioxide and air. The illumination is performed by a pulsed power LED modulated at different resonant frequencies of the cavity. A microphone inside the tube is connected to an oscilloscope which displays the photoacoustic signal. The LED is moved along the tube showing how different resonant modes can be excited.
Hay una necesidad a nivel mundial de dispositivos compactos, de bajo costo y con alta sensibilidad y selectividad para monitoreo de aguas y análisis médicos y biológicos. La mayoría de los equipos ...del mercado adecuados para este tipo de aplicaciones son de dimensiones grandes y/o costos excesivos. Otro tipo de métodos requieren pre-tratamientos de las muestras haciendo que el análisis consuma mucho tiempo. En este trabajo se muestra el diseño de un sistema de lente térmica compacto y de bajo costo para monitoreo de aguas. El dispositivo consta de dos láseres compactos (punteros) con longitudes de onda de excitación de 405nm y 532 nm, modulados a baja frecuencia (4 y 7 Hz respectivamente), lo cual permite una medición diferencial en tiempo real. Además, posee un diodo rojo como haz de prueba cuyo haz atraviesa la muestra en forma colineal con los haces de excitación y una pequeña fracción de su luz es colectada por una fibra óptica de 200 μm, que la guía a un fotodiodo. La señal del detector es digitalizada por una placa Arduino y enviada a una PC para ser analizada. El procesamiento se realiza en tiempo real aplicando una transformada rápida de Fourier para diferenciar las señales provenientes de ambas fuentes de excitación. Se implementó un sistema de inyección en flujo que permite agilizar las mediciones. En este trabajo se muestra el funcionamiento del sistema haciendo uso de colorantes de baja toxicidad.
The market of turning tools is coped majority by hard metal tools with CVD coating. However, availability of tools with sharp cutting edges is essential in light turning of small parts. In this ...context, PVD process is optimum for obtaining sharp edges. Therefore, a methodology is presented to evaluate the performance of PVD advanced tools for turning of difficult to machine materials. Four coatings were tested: AlTiSiN (nACo®), AlCrSiN (nACRo®), AlTiN and TiAlCrN. The analysis was developed carrying out wear tests and analyzing different signals such as cutting forces, EDX analysis of inserts, part roughness and insert image analysis. Results indicate that the best coatings for turning of difficult to machine materials as austenitic stainless steels are nACo® and AlTiN coatings, since they offer the best performance. Several factors demonstrate it: better tool flank wear evolution, less tangential cutting force or lower part roughness.
Due to rising worldwide industrial competitiveness the machining sector is compelled to improve day by day. In this way, CO2 cryogenic machining is presented as alternative to conventional hard ...turning. So, in the tests carried out in this research, dry and CO2 cryogenic hard turning with two types of inserts were compared. The variables measured were tool life, superficial roughness and the piece microstructure. The results show an increase of tool life over 60%, a similar superficial roughness and, when positive insert is used, the absence of the white layer.
Objectives
To explore differences in the vaginal microbiome between preterm and term deliveries.
Design
Nested case–control study in 3D cohort (design, develop, discover).
Setting
Quebec, Canada.
...Sample
Ninety‐four women with spontaneous preterm birth as cases 17 early (<34 weeks) and 77 late (34–36 weeks) preterm birth and 356 women as controls with term delivery (≥37 weeks).
Methods
To assess the vaginal microbiome by sequencing the V4 region of the 16S ribosomal RNA (rRNA) gene in swabs self‐collected during early pregnancy.
Main outcome measures
Comparison of relative abundance of bacterial operational taxonomic units and oligotypes and identifying vaginal community state types (CSTs) in early or late spontaneous preterm and term deliveries.
Results
Lactobacillus gasseri/ Lactobacillus johnsonii (coefficient −5.36, 95% CI −8.07 to −2.65), Lactobacillus crispatus (99%)/ Lactobacillus acidophilus (99%) (−4.58, 95% CI −6.20 to −2.96), Lactobacillus iners (99%)/ Ralstonia solanacearum (99%) (−3.98, 95% CI −6.48 to −1.47) and Bifidobacterium longum/ Bifidobacterium breve (−8.84, 95% CI −12.96 to −4.73) were associated with decreased risk of early but not late preterm birth. Six vaginal CSTs were identified: four dominated by Lactobacillus; one with presence of bacterial vaginosis‐associated bacteria (Gardnerella vaginalis, Atopobium vaginae and Veillonellaceae bacterium) (CST IV); and one with nondominance of Lactobacillus (CST VI). CST IV was associated with increased risk of early (4.22, 95% CI 1.24–24.85) but not late (1.63, 95% CI 0.68–5.04) preterm birth, compared with CST VI.
Conclusions
Lactobacillus gasseri/L. johnsonii, L. crispatus/L. acidophilus, L. iners/R. solanacearum and B. longum/B. breve may be associated with decreased risk of early preterm birth. A bacterial vaginosis‐related vaginal CST versus a CST nondominated by Lactobacillus may be associated with increased risk of early preterm birth.
Tweetable
Largest study of its kind finds certain species of vaginal Lactobacillus + Bifidobacterium may relate to lower risk of preterm birth.
Tweetable
Largest study of its kind finds certain species of vaginal Lactobacillus + Bifidobacterium may relate to lower risk of preterm birth.
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