Optimizing Vaccine Allocation at Different Points in Time during an Epidemic

For current pandemic influenza H1N1, vaccine production started in the early summer, and vaccination started in the fall. In most countries, by the time vaccination started, the second wave of H1N1 was already under way. With limited supplies of vaccine, it might be a good strategy to vaccinate the high-transmission groups earlier in the epidemic, but it might be a better use of resources to protect instead the high-risk groups later on. We develop a deterministic epidemic model with two age-groups (children and adults) and further subdivide each age group in low and high risk. We compare optimal vaccination strategies started at various points in time in two different settings: a population in the United States (US) where children account for 24% of the population, and a population in Senegal, where children make up for the majority of the population, 55%. For each of these populations, we minimize mortality and we find an optimal vaccination vector that gives us the best vaccine allocation given a starting vaccination date and vaccine coverage level. We find that there is a switch in the optimal vaccination strategy at some time point just before the peak of the epidemic. For instance, with 25% vaccine coverage, it is better to protect the high-transmission groups before this point, but it is optimal to protect the most vulnerable groups afterward

UNE APPROCHE SOCIO-INSTITUTIONNELLE DE LA PSYCHODYNAMIQUE DU TRAVAIL

En este artículo se presenta una propuesta de comprensión e intervención de las problemáticas psico-biológicas emergentes en empresas grandes y en instituciones de salud pública, a partir de un abordaje psicodinámico del trabajo fundamentado en una epistemología de los sistemas complejos de Piaget. Para lograr este cometido, se exponen dos casos de empresas que vivieron una intervención, a partir del modelo propuesto por el autor, destacando la importancia que tiene reconocer tanto los aspectos estructurales de una determinada realidad laboral, como también los procesos subjetivos de los trabajadores, directivos y clientes que componen una determinada organización. Concretamente, y en términos epistemológicos, el modelo realiza: procesos de validación y demostración de las problemáticas en tensión, a partir una concepción metodológica positivista; estudia la relación subjetividad/actividad/empresa, con lo cual se permite estudiar e intervenir no solo contextos menores sino también empresas de tamaño grande; desarrolla un paradigma operativo denominado campanas concéntricas, que integra las diferentes formas de análisis del problema de forma sintética. De esta manera, se hace un valioso aporte al campo de la psicodinámica del trabajo, buscando generar críticas, nuevas aproximaciones y soluciones ante los problemas que dicho campo interviene. Palabras clave: psicodinámica del trabajo; subjetividad; epistemología de los sistemas complejos; empresa.  This article presents a proposal for understanding and intervention of emerging psychobiological problems in large companies and in public health institutions, based on a psychodynamic approach to work based on an epistemology of complex systems of Piaget. In order to achieve this task, two cases of companies that lived an intervention are exposed, based on the model proposed by the author, highlighting the importance of recognizing both the structural aspects of a given labor reality and the subjective processes of workers, Managers and clients that make part of a particular organization. Specifically, and in epistemological terms, the model realizes: processes of validation and demonstration of the problems in tension, from a positivist methodological conception; Studies the relationship subjectivity / activity / company, which allows to study and intervene not only smaller contexts but also large companies; Develops an operational paradigm called concentric bells, which integrates the different ways of analyzing the problem in a synthetic way. In this way, a valuable contribution is made to the field of psychodynamic of work, seeking to generate criticism, new approaches and solutions to the problems that this field intervenes.   Key words: Psychodynamic of work; subjectivity; epistemology of complex systems; company.  Nesse artigo apresenta-se uma proposta de compreensão e intervenção das problemáticas de Psicobiologias emergentes em grandes empresas e em instituições de saúde pública, a partir de uma abordagem Psicodinâmica do Trabalho fundamentado em uma epistemologia dos sistemas complexos de Piaget. Para alcançar essa obrigação, apresentam-se dois casos de empresas que passaram uma intervenção, a partir do modelo proposto pelo autor, destacando a importância que tem reconhecer tanto os aspectos estruturais de uma determinada realidade laboral, como também os processos subjetivos dos trabalhadores, diretores e clientes que compõem uma determinada organização. Concretamente, e em termos epistemológicos, o modelo realiza: processos de validação e demonstração das problemáticas em pressão, a partir de uma concepção metodológica positivista; estuda a relação subjetividade/atividade/empresa, na qual se permite estudar e intervir não somente contextos menores senão também empresas grandes; desenvolve um paradigma operativo denominado campanhas concêntricas, que integra as diferentes formas de análise do problema de forma sintética. Dessa maneira, faz-se uma valiosa contribuição no campo da Psicodinâmica do Trabalho, buscando gerar críticas, novas aproximações e soluções perante os problemas cujo esse campo participa.   Palavras Chave: psicodinâmica do trabalho; subjetividade; epistemologia dos sistemas complexos; empresa.                                Dans cet article, nous présentons une proposition de compréhension et de l'intervention des problèmes émergents Psicobiologias dans les grandes entreprises et les institutions de santé publique, d'un psychodynamique du travail à la terre approcher une épistémologie de Piaget systèmes complexes. Pour parvenir à cette exigence, nous présentons deux cas d'entreprises qui ont une intervention du modèle proposé par l'auteur, en soulignant l'importance de reconnaître les aspects structurels d'une réalité particulière du travail, ainsi que les travailleurs des processus subjectifs, les directeurs et les clients qui composent une organisation particulière. Plus précisément, et en termes épistémologiques, le modèle effectue: la validation et la démonstration des problèmes de pression, d'une conception méthodologique positiviste; la subjectivité des études de relation / activité / entreprise, dans laquelle il permet d'étudier et d'intervenir non seulement plus petits mais aussi grands contextes d'affaires; développe un paradigme d'exploitation appelé campagnes concentriques, intégrant différentes formes d'analyse du problème synthétiquement. Ainsi, il est une contribution précieuse dans le domaine de la psychodynamique du travail, cherchant à susciter des critiques, de nouvelles approches et des solutions aux problèmes que ce pays participe. Mots-clés: psychodynamique du travail; la subjectivité; épistémologie des systèmes complexes; société

Fine-grained precursors dominate the micrometeorite flux

We optically classified 5682 micrometeorites (MMs) from the 2000 South Pole collection into textural classes, imaged 2458 of these MMs with a scanning electron microscope, and made 200 elemental and eight isotopic measurements on those with unusual textures or relict phases. As textures provide information on both degree of heating and composition of MMs, we developed textural sequences that illustrate how fine-grained, coarse-grained, and single mineral MMs change with increased heating. We used this information to determine the percentage of matrix dominated to mineral dominated precursor materials (precursors) that produced the MMs. We find that at least 75% of the MMs in the collection derived from fine-grained precursors with compositions similar to CI and CM meteorites and consistent with dynamical models that indicate 85% of the mass influx of small particles to Earth comes from Jupiter family comets. A lower limit for ordinary chondrites is estimated at 2–8% based on MMs that contain Na-bearing plagioclase relicts. Less than 1% of the MMs have achondritic compositions, CAI components, or recognizable chondrules. Single mineral MMs often have magnetite zones around their peripheries. We measured their isotopic compositions to determine if the magnetite zones demarcate the volume affected by atmospheric exchange during entry heating. Because we see little gradient in isotopic composition in the olivines, we conclude that the magnetites are a visual marker that allows us to select and analyze areas not affected by atmospheric exchange. Similar magnetite zones are seen in some olivine and pyroxene relict grains contained within MMs

Protocol for Future Amino Acid Analyses of Samples Returned by the Stardust Mission

We have demonstrated that LC-ToF-MS coupled with UV fluorescence detection is a powerful tool for the detection of amino acids in meteorite extracts. Using this new analytical technique we were able to identify the extraterrestrial amino acid AIB extracted from fifteen 20 micron sized Murchison meteorite grains. We found that the amino acid contamination levels in Stardust aerogels was much lower than the levels observed in the Murchison meteorite. In addition, the alpha-dialkyl amino acids AIB and isovaline which are the most abundant amino acids in Murchison were not detected in the aerogel above blank levels. We are currently integrating LIF detection capability to our existing nanoflow LC-ToF-MS for enhanced sensitivity required for the analysis of amino acids in Stardust samples

Submicrometer Organic Grains: Widespread Constituents of the Early Solar System

Primitive meteorites and interplanetary dust particles (IDPs) contain remants of interstellar organic matter, marked by anomalous H and N isotopic ratios. These isotopic anomalies are attributed to mass fractionation during chemical reactions at cryogenic temperatures (10-100K) in a cold molecular cloud. Significant variations in the chemistry and isotopic compositions of organic compounds within and between these samples suggest varying histories of alteration and dilution of the presolar components. Recent studies have reported large H and N isotopic anomalies preserved in sub-m organic inclusions in both meteorites and IDPs. In the Tagish Lake meteorite, the largest H and N isotopic anomalies are associated with sub-m, hollow organic globules. The common physical, chemical, and isotopic characteristics of these globules suggest that they formed before being incorporated into their parent meteorite. These organic globules probably originated as organic ice coatings that formed on preexisting ice or mineral grains in a cold molecular cloud. Radiation driven photochemistry may have processed them into refractory organic grains. This model implies that submicrometer organic grains were widely distributed throughout the solar nebula during the epoch of planet formation. Submicrometer organic particles were detected by the Giotto and Vega encounters with comet Halley, termed CHON particles based on their major element chemistry. The first direct samples of cometary dust (comet Wild-2) were returned by the Stardust spacecraft in January 2006. These samples exhibit widely varying, fine grained mineralogy similar to anhydrous IDPs, including submicrometer carbonaceous grains. The submicrometer organic grains from comet Wild-2 exhibit H and N isotopic anomalies of similar magnitude to those commonly observed in primitive meteorites and IDPs. Isotopically anomalous, submicrometer organic grains have now been observed in meteorites, IDPs, the Oort-cloud comet Halley, and the Kuiper-belt comet Wild-2, suggesting that such grains were prevalent throughout the protoplanetary disk

Could widespread use of antiviral treatment curb the COVID-19 pandemic? A modeling study

Background: Despite the development of safe and effective vaccines, effective treatments for COVID-19 disease are still urgently needed. Several antiviral drugs have shown to be effective in reducing progression of COVID-19 disease. Methods: In the present work, we use an agent-based mathematical model to assess the potential population impact of the use of antiviral treatments in four countries with different demographic structure and current levels of vaccination coverage: Kenya, Mexico, United States (US) and Belgium. We analyzed antiviral effects on reducing hospitalization and death, and potential antiviral effects on reducing transmission. For each country, we varied daily treatment initiation rate (DTIR) and antiviral effect in reducing transmission (AVT). Results: Irrespective of location and AVT, widespread antiviral treatment of symptomatic adult infections (20% DTIR) prevented the majority of COVID-19 deaths, and recruiting 6% of all adult symptomatic infections daily reduced mortality by over 20% in all countries. Furthermore, our model projected that targeting antiviral treatment to the oldest age group (65 years old and older, DTIR of 20%) can prevent over 30% of deaths. Our results suggest that early antiviral treatment (as soon as possible after inception of infection) is needed to mitigate transmission, preventing 50% more infections compared to late treatment (started 3 to 5 days after symptoms onset). Our results highlight the synergistic effect of vaccination and antiviral treatment: as the vaccination rate increases, antivirals have a larger relative impact on population transmission. Finally, our model projects that even in highly vaccinated populations, adding antiviral treatment can be extremely helpful to mitigate COVID-19 deaths. Conclusions: These results suggest that antiviral treatments can become a strategic tool that, in combination with vaccination, can significantly reduce COVID-19 hospitalizations and deaths and can help control SARS-CoV-2 transmission

Infrared, UV/VIS and Raman Spectroscopy of Comet Wild-2 Samples Returned by the Stardust Mission

Results from the preliminary examination of Stardust samples obtained using various spectroscopic methods will be presented

Nature and evolution of the dominant carbonaceous matter in interplanetary dust particles: effects of irradiation and identification with a type of amorphous carbon

Aims.Interplanetary dust particle (IDP) matter probably evolved under irradiation in the interstellar medium (ISM) and the solar nebula. Currently IDPs are exposed to irradiation in the Solar System. Here the effects of UV and proton processing on IDP matter are studied experimentally. The structure and chemical composition of the bulk of carbon matter in IDPs is characterized. Methods: .Several IDPs were further irradiated in the laboratory using ultraviolet (UV) photons and protons in order to study the effects of such processing. By means of infrared and Raman spectroscopy, IDPs were also compared to different materials that serve as analogs of carbon grains in the dense and diffuse ISM. Results: .The carbonaceous fraction of IDPs is dehydrogenated by exposure to hard UV photons or 1 MeV protons. On the other hand, proton irradiation at lower energies (20 keV) leads to an efficient hydrogenation of the carbonaceous IDP matter. The dominant type of carbon in IDPs, observed with Raman and infrared spectroscopy, is found to be either a form of amorphous carbon (a-C) or hydrogenated amorphous carbon (a-C:H), depending on the IDP, consisting of aromatic units with an average domain size of 1.35 nm (5-6 rings in diameter), linked by aliphatic chains. Conclusions: .The D- and 15N-enrichments associated to an aliphatic component in some IDPs are probably the result of chemical reactions at cold temperatures. It is proposed that the amorphous carbon in IDPs was formed by energetic processing (UV photons and cosmic rays) of icy grains, maybe during the dense cloud stage, and more likely on the surface of the disk during the T Tauri phase of our Sun. This would explain the isotopic anomalies and morphology of IDPs. Partial annealing, 300-400°C, is required to convert an organic residue from ice photoprocessing into the amorphous carbon with low heteroatom content found in IDPs. Such annealing might have occurred as the particles approached the Sun and/or during atmospheric entry heating