A brief introduction to the model microswimmer {\it Chlamydomonas reinhardtii}

The unicellular biflagellate green alga {\it Chlamydomonas reinhardtii} has been an important model system in biology for decades, and in recent years it has started to attract growing attention also within the biophysics community. Here we provide a concise review of some of the aspects of {\it Chlamydomonas} biology and biophysics most immediately relevant to physicists that might be interested in starting to work with this versatile microorganism.Comment: 16 pages, 7 figures. To be published as part of EPJ S

Microalgae scatter off solid surfaces by hydrodynamic and contact forces

Interactions between microorganisms and solid boundaries play an important role in biological processes, such as egg fertilization, biofilm formation, and soil colonization, where microswimmers move within a structured environment. Despite recent efforts to understand their origin, it is not clear whether these interactions can be understood as being fundamentally of hydrodynamic origin or hinging on the swimmer’s direct contact with the obstacle. Using a combination of experiments and simulations, here we study in detail the interaction of the biflagellate green alga Chlamydomonas reinhardtii, widely used as a model puller microorganism, with convex obstacles, a geometry ideally suited to highlight the different roles of steric and hydrodynamic effects. Our results reveal that both kinds of forces are crucial for the correct description of the interaction of this class of flagellated microorganisms with boundaries

Microalgae Scatter off Solid Surfaces by Hydrodynamic and Contact Forces

Interactions between microorganisms and solid boundaries play an important role in biological processes, such as egg fertilization, biofilm formation, and soil colonization, where microswimmers move within a structured environment. Despite recent efforts to understand their origin, it is not clear whether these interactions can be understood as being fundamentally of hydrodynamic origin or hinging on the swimmer's direct contact with the obstacle. Using a combination of experiments and simulations, here we study in detail the interaction of the biflagellate green alga Chlamydomonas reinhardtii, widely used as a model puller microorganism, with convex obstacles, a geometry ideally suited to highlight the different roles of steric and hydrodynamic effects. Our results reveal that both kinds of forces are crucial for the correct description of the interaction of this class of flagellated microorganisms with boundaries.We acknowledge the support of a Ph.D. studentship from the Engineering and Physical Sciences Research Council (MC), the Spanish Ministry of Economy and Competitiveness Grant No. FIS2013-48444-C2-1-P, and the subprogram Ramón y Cajal (IT)Peer Reviewe

Fracture of high-density polyethylene used for bleach bottles

High-density polyethylene (HDPE) can be blow-molded and used for the production of bottles for aggressive products. These products can interact both chemically and physically with the polymer constituting these containers, leading to a decrease in the performance of the material and undermining the structural integrity of the component. A fracture mechanics approach was adopted to evaluate the Environmental Stress Cracking Resistance (ESCR) of two HDPE commercial grades used for bleach containers; two different solutions, with and without sodium hypochlorite (the main ingredient of commercial bleach solutions), were considered as aggressive environments. Size effects were studied using different test configurations and loading histories in air. The correlation between the stress intensity factor and the initiation time was found. A clear effect of the aggressive solutions on the fracture resistance of the two HDPEs was observed, irrespective of the presence of sodium hypochlorite; the effect therefore has to be ascribed to other bleach components

Recycle Glass

Increasing the circularity of flat glass does not only mean to collect glass cullet from internal and pre- consumer processes. It also means to use glass cullet from the post- consumer applications, such as residential or commercial buildings. The flat glass industry is currently in a transformation phase to reduce its CO2 emissions. To produce Low Carbon Glass with reduced carbon emissions generated during the production of float glass, a holistic approach is applied. Among these, one of the pillars is the increased use of cullet. Cullet comes from different sources: internal cullet, pre- and post- consumer cullet. In order to be able to use cullet in float glass production, it must be of high quality. Since there are a large number of architectural glass products and glass types, it is essential to collect and sort in the most adequate wa

Microbial narrow-escape is facilitated by wall interactions

Cells have evolved efficient strategies to probe their surroundings and navigate through complex environments. From metastatic spread in the body to swimming cells in porous materials, escape through narrow constrictions - a key component of any structured environment connecting isolated microdomains - is one ubiquitous and crucial aspect of cell exploration. Here, using the model microalgae Chlamydomonas reinhardtii, we combine experiments and simulations to achieve a tractable realization of the classical Brownian narrow-escape problem in the context of active confined matter. Our results differ from those expected for Brownian particles or leaking chaotic billiards and demonstrate that cell-wall interactions substantially modify escape rates and, under generic conditions, expedite spread dynamics.</p

Noćni život i cijepljenje protiv bolesti COVID-19: Terenska studija na uzorku mladih Talijana u noćnome izlasku tijekom ljeta 2021. godine

In this study, we described rates of COVID vaccination, attitudes towards COVID prevention behaviours, and perceived risk in relation to different areas of personal well-being and substance use during the pandemic, in a sample of 16- to 25-year-olds (N = 411). The participants completed a short self-report questionnaire, while they were spending their 2021 summer nightlife in a crowded city venue. Results showed that 64% of respondents reported being vaccinated. Among the unvaccinated participants, those who were unwilling to be vaccinated agreed less with prevention rules and felt more at risk for drug use and for chances of getting or maintaining a job, when compared to both vaccinated peers and to peers who were unvaccinated but positively intentioned to vaccinate. Overall, the present findings confirm that youth felt at risk for their well-being during the pandemic and further reveal that young people who are reluctant to vaccinate deserve more attention. Vaccination campaigns need to be strengthened in social contexts, where chances of getting a job or keeping it are lower, while the risk of drug use is higher.U ovome smo istraživanju opisali stope cijepljenja protiv bolesti COVID-19, stavove prema ponašanjima važnima za prevenciju te bolesti i percipirani rizik u odnosu na različita područja osobne dobrobiti i zlouporabe droga tijekom pandemije na uzorku sudionika u dobi od 16 do 25 godina (N = 411). Sudionici su ispunili kratki upitnik samoprocjene za vrijeme noćnoga izlaska tijekom ljeta 2021. godine na gradskoj lokaciji gdje je vladala velika gužva. Rezultati su pokazali da je 64 % sudionika izjavilo da je cijepljeno. Među necijepljenim sudionicima oni koji se nisu željeli cijepiti manje su bili suglasni s pravilima prevencije, osjećali su se više izloženima riziku zlouporabe droga i smatrali su da je manja vjerojatnost da dobiju ili zadrže posao u usporedbi s cijepljenim vršnjacima i vršnjacima koji su bili necijepljeni, ali s pozitivnim namjerama za cijepljenje. Zaključno, sadašnji nalazi potvrđuju da su mladi tijekom pandemije osjećali da im je ugrožena dobrobit te da mladi koji se nerado cijepe zaslužuju više pažnje. Potrebno je pojačati kampanje za promociju cijepljenja u društvenim kontekstima gdje je vjerojatnost za dobivanje ili zadržavanje posla manja, a rizik od zlouporabe droga veći

Nightlife and COVID Vaccinations: A Field Study on an Italian Sample of Party Youth in summer 2021

In this study, we described rates of COVID vaccination, attitudes towards COVID prevention behaviours, and perceived risk in relation to different areas of personal well-being and substance use during the pandemic, in a sample of 16- to 25-year-olds (N = 411). The participants completed a short self-report questionnaire, while they were spending their 2021 summer nightlife in a crowded city venue. Results showed that 64% of respondents reported being vaccinated. Among the unvaccinated participants, those who were unwilling to be vaccinated agreed less with prevention rules and felt more at risk for drug use and for chances of getting or maintaining a job, when compared to both vaccinated peers and to peers who were unvaccinated but positively intentioned to vaccinate. Overall, the present findings confirm that youth felt at risk for their well-being during the pandemic and further reveal that young people who are reluctant to vaccinate deserve more attention. Vaccination campaigns need to be strengthened in social contexts, where chances of getting a job or keeping it are lower, while the risk of drug use is higher

Entre la libertad y la constricción: el dilema de la agorafobia.

This study aimed to empirically test the clinical theory, common to different psychotherapeutic approaches, that agoraphobia is psychologically linked to the semantics of freedom. The hypothesis was that personal constructs of “free-constrained” and associated meanings are predominant for people suffering from agoraphobia. Participants and method. The Repertory Grid Technique (Kelly, 1955) was carried out with 30 agoraphobic patients to elicit their personal constructs. A group of 30 of patients suffering from other psychological disease was used as a control group. Participants’ constructs were grouped into semantic categories using hermeneutic criteria and the data compared using appropriate statistical techniques. Results: The constructs of agoraphobic group were found to be significantly more connected to the semantics of freedom than those of the control Group. The empirical data seems to confirm the hypothesis. These results and their limitations are discussed in the light of their possible clinical applications and of methodological and epistemological issues raising from the study.El objetivo de la presente investigación es someter a examen empírico la tesis clínica, común a diferentes enfoques psicoterapéuticos, sobre la conexión entre agorafobia y semántica de la libertad, planteando la hipótesis que los constructos personales relacionados con la esfera de la “libertad-constricción” son predominantes en los pacientes agorafóbicos. Método y participantes. La técnica de la rejilla de repertorio (Kelly, 1955) ha sido aplicada a 30 pacientes agorafóbicos, a fin de elicitar sus constructos personales más significativos. Como “grupo de control” han sido utilizados otros 30 pacientes que sufren otras psicopatologías. Los constructos personales de los dos grupos de pacientes han sido categorizados según criterios hermenéuticos y comparados mediante pruebas estadísticos. Los resultados corroboran la hipótesis formulada: entre los pacientes agorafóbicos existe una significativa prevalencia de los constructos relativos a la semántica de la libertad, mientras que esto no se da en el grupo de control. Dichos resultados y sus limitaciones se ponen en discusión a la luz de sus posibles aplicaciones clínicas y de cuestiones epistemológicas y metodológicas más amplias inherentes a la investigación

Nightlife and COVID Vaccinations: A Field Study on an Italian Sample of Party Youth in summer 2021

In this study, we described rates of COVID vaccination, attitudes towards COVID prevention behaviours, and perceived risk in relation to different areas of personal well-being and substance use during the pandemic, in a sample of 16- to 25-year-olds (N = 411). The participants completed a short self-report questionnaire, while they were spending their 2021 summer nightlife in a crowded city venue. Results showed that 64% of respondents reported being vaccinated. Among the unvaccinated participants, those who were unwilling to be vaccinated agreed less with prevention rules and felt more at risk for drug use and for chances of getting or maintaining a job, when compared to both vaccinated peers and to peers who were unvaccinated but positively intentioned to vaccinate. Overall, the present findings confirm that youth felt at risk for their well-being during the pandemic and further reveal that young people who are reluctant to vaccinate deserve more attention. Vaccination campaigns need to be strengthened in social contexts, where chances of getting a job or keeping it are lower, while the risk of drug use is higher