Are microbial biosurfactants actually only surfactants?

The term biosurfactants refers to a complex mixture of metabolites with surface-active properties produced by specific microorganisms. However, nowadays trends moves towards isolation, screening and purifying single biocompatible, biodegradable biosurfactants with high commercialization potential. Current legislation limiting petrochemicals combined with environmentally concerned consumers did not only stimulate research and development but it also promoted large-scale production of this class of molecules. However, recent data recorded on single congeners question the actual pertinence of using the word ''biosurfactant'' associated to these molecules. By evaluating the accepted characteristics of surfactants and comparing them to the actual self-assembly and bulk properties in water of molecules traditionally called ''biosurfactants'', this opinion paper aims at showing that the term ''biosurfactant'' can be somewhat reductive when applied to specific individual compounds produced by fermentation. The use of a more generic term, like bioamphiphile could probably be more pertinent and appropriate for consideration in the future.Comment: Current Opinion in Colloid & Interface Science, In pres

Housing for Returning Offenders in the United States

In the United States, individuals returning home from prison face serious obstacles securing affordable, stable housing. Without appropriate housing, applying for jobs, obtaining needed social services, and successfully reintegrating to their communities becomes nearly impossible. Furthermore, a lack of stable housing is a predictor for recidivism and homelessness, which places pressure on municipal budgets. Because no one agency or level of government sees housing for returning offenders as its responsibility, there has been little action on or attention to this problem. In this article, I first review the literature describing the barriers returning offenders face in securing housing, including legal prohibitions, limited family support, and fragmented social service delivery. Then, I examine policy models to address these problems in Washington State, New York City, and Ohio. Based on the results of these programs, I conclude with policy recommendations, including removing barriers to public housing based on past offending, search assistance programs for returning offenders, improving coordination across the criminal justice system and post-release service providers, and revitalizing neighborhoods that support high levels of returning offenders.https://deepblue.lib.umich.edu/bitstream/2027.42/136592/1/Baccile_HousingForReturningOffendersInTheUnitedStates.pd

Sviluppo di procedure per l'analisi di sistemi di controllo per MCI mediante strumenti Hardware in the loop

Questa tesi, realizzata durante una attività di stage svolta presso Ferrari S.p.A., ha come oggetto lo sviluppo di procedure automatiche finalizzate alla verifica dei software utilizzati dalle unità di controllo per motori a combustione interna (ECU), attraverso sistemi di simulazione Hardware in the loop. Il compito di questi programmi, creati nel linguaggio Python, è monitorare il comportamento sia delle funzioni diagnostiche della ECU, sia di evoluzioni dei software di controllo. Nel primo caso sono stati simulati guasti nei collegamenti tra la centralina e gli attuatori ed è stata verificata la presenza di codici di errore, la cui memorizzazione da parte delle unità di controllo è resa obbligatoria dalle normative On Board Diagnostic. Nel secondo caso lo scopo dei programmi è effettuare un confronto tra una release software, già validata e deliberata per il raggiungimento delle migliori caratteristiche in termini di emissioni e prestazioni, e le sue successive evoluzioni. Questi paragoni sono stati realizzati considerando da un lato i principali parametri di attuazione motoristici, ad esempio anticipo di accensione e posizione della valvola a farfalla, e dall’altro le curve di coppia e potenza erogate dal motore in funzione del regime di rotazione

Advanced materials from microbial fermentation : the case of glycolipids and nanocellulose

Green chemistry is a recent discipline ruled by twelve founding principles, which include, among others, atom economy, the prevention of pollution via environmentally friendly chemical synthesis methods, such as, for example, the choice of an aqueous medium over organic solvents, but also the development of chemicals and materials derived from plant biomass. In this context, microbial synthesis is a tool to supplant, in some notable cases, syntheses by a standard organic chemistry approach. More recently, attention has begun to be given to the microbial synthesis of polymeric sugars, such as dextran or cellulose, or lipids, such as amphiphilic glycolipids. Although the microbial production of glycosylated compounds can be traced back by several decades, the development of green chemistry is encouraging teams of multidisciplinary researchers to focus on production, diversification, and applications of this class of compounds, thus going beyond the community of researchers in microbiology, historically interested in the development of fermentation products from microorganisms. This article develops the above-mentioned theme by focusing on nanocellulose, representing an important glycosylated polymer, and on biosurfactants, in regards of the glycosylated lipids. The choice of these two systems is justified by the strong development of nanocellulose-based materials but also by the need to replace in part the “conventional” surfactants, a significant source of CO2 emissions worldwide. The main classes of molecules, the classical methods of synthesis, their properties and some examples of notorious applications are presented

Measuring the bending rigidity of microbial glucolipid (biosurfactant) bioamphiphile self-assembled structures by neutron spin-echo (NSE): interdigitated vesicles, lamellae and fibers

Bending rigidity, k, is classically measured for lipid membranes to characterize their nanoscale mechanical properties as a function of composition. Widely employed as a comparative tool, it helps understanding the relationship between the lipid's molecular structure and the elastic properties of its corresponding bilayer. Widely measured for phospholipid membranes in the shape of giant unilamellar vesicles (GUVs), bending rigidity is determined here for three self-assembled structures formed by a new biobased glucolipid bioamphiphile, rather associated to the family of glycolipid biosurfactants than phospholipids. In its oleyl form, glucolipid G-C18:1 can assemble into vesicles or crystalline fibers, while in its stearyl form, glucolipid G-C18:0 can assemble into lamellar gels. Neutron spin-echo (NSE) is employed in the q-range between 0.3 nm-1 (21 nm) and 1.5 nm-1 (4.1 nm) with a spin-echo time in the range of up to 500 ns to characterize the bending rigidity of three different structures (Vesicle suspension, Lamellar gel, Fiber gel) solely composed of a single glucolipid. The low (k= 0.30 $\pm$ 0.04 kbT) values found for the Vesicle suspension and high values found for the Lamellar (k= 130 $\pm$ 40 kbT) and Fiber gels (k= 900 $\pm$ 500 kbT) are unusual when compared to most phospholipid membranes. By attempting to quantify for the first time the bending rigidity of self-assembled bioamphiphiles, this work not only contributes to the fundamental understanding of these new molecular systems, but it also opens new perspectives in their integration in the field of soft materials

Primary and Secondary Hydration Forces between Interdigitated Membranes Composed of Bolaform Microbial Glucolipids

To better understand lipid membranes in living organisms, the study of intermolecular forces using the osmotic pressure technique applied to model lipid membranes has constituted the ground knowledge in the field since four decades. However, the study of intermolecular forces in lipid systems other than phospholipids, like glycolipids, has gained a certain interest only recently. Even in this case, the work generally focus on the study of membrane glycolipids, but little is known on new forms of non-membrane functional compounds, like pH-responsive bolaform glycolipids. This works explores, through the osmotic stress method involving an adiabatic humidity chamber coupled to neutron diffraction, the short-range (< 2 nm) intermolecular forces of membranes entirely composed of interdigitated glucolipids. Experiments are performed at pH 6, when the glucolipid is partially negatively charged and for which we explore the effect of low (16 mM) and high (100 mM) ionic strength. We find that this system is characterized by primary and secondary hydration regimes, respectively insensitive and sensitive to ionic strength and with typical decay lengths of λ_H1= 0.37 ± 0.12 nm and λ_H2=1.97 ± 0.78 nm

Graffiti : interações sociais através da semiótica visual

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Comunicação, Programa de Pós-Graduação em Comunicação, 2017.O objetivo desse trabalho de pesquisa é investigar de que maneira se dá a relação entre o objeto de estudo graffiti e a sociedade, com recorte geográfico nas cidades de Brasília e São Paulo. Para tal estudo serão analisados, em primeiro lugar, o objeto em si, desde sua origem e caminhos percorridos até o momento atual, em específico de acordo com o olhar social. Em segundo, o contexto das cidades de Brasília e São Paulo com relação a seus comportamentos sociais que podem interferir na vivência com o objeto. E por último, a metodologia semiótica visual apresentada nas categorias de pessoa, espaço e tempo. De modo a uma melhor elucidação do assunto, serão feitas as montagens de esquemas, desde o quadrado semiótico abordado por Landowski (1992) até esquemas autorais. Ademais, partindo da teoria do plano da expressão e plano do conteúdo de Oliveira (2004), faz-se necessária a montagem de um sistema analítico que possibilita o acesso ao significado dos registros fotográficos dos graffitis, entendendo assim que o acesso ao significado é a resposta da problemática proposta.The objective of this research is to investigate how the relationship between the object of graffiti study and society, with geographic cut in the cities of Brasília and São Paulo. For this study, will be analyzed, first, the object in itself, from its origin and paths traveled until the present moment, in specific according to the social gaze. Second, the context of the cities of Brasília and São Paulo in relation to their social behaviors that can interfere in the experience with the object. And finally, the visual semiotic methodology presented in the categories of person, space and time. In order to better elucidate the subject, schema assemblies will be made, from the semiotic square approached by Landowski (1992) to authorial schemes. In addition, starting from the theory of the plane of the expression and plan of the content of Oliveira (2004), it is necessary to set up an analytical system that allows access to the meaning of photographic records of graffiti. Understanding that access to meaning is the answer to the problematic proposal

Self-assembly mechanism of pH-responsive glycolipids : micelles, fibers, vesicles, and bilayers

A set of four structurally related glycolipids are described: two of them have one glucose unit connected to either stearic or oleic acid, and two other ones have a diglucose headgroup (sophorose) similarly connected to either stearic or oleic acid. The self-assembly properties of these compounds, poorly known, are important to know due to their use in various fields of application from cleaning to cosmetics to medical. At basic pH, they all form mainly small micellar aggregates. At acidic pH, the oleic and stearic derivatives of the monoglucose form, respectively, vesicles and bilayer, while the same derivatives of the sophorose headgroup form micelles and twisted ribbons. We use pH-resolved in situ small angle X-ray scattering (SAXS) under synchrotron radiation to characterize the pH-dependent mechanism of evolution from micelles to the more complex aggregates at acidic pH. By pointing out the importance of the COO-/COOH ratio, the melting temperature, T-m, of the lipid moieties, hydration of the glycosidic headgroup, the packing parameter, membrane rigidity, and edge stabilization, we are now able to draw a precise picture of the full self-assembly mechanism. This work is a didactical illustration of the complexity of the self-assembly process of a stimuli-responsive amphiphile during which many concomitant parameters play a key role at different stages of the process

Sophorolipids-functionalized iron oxide nanoparticles

International audienceFunctional iron oxide nanoparticles (NP) have been synthesized in a one and a two-step method using a natural functional glycolipid belonging to the family of sophorolipids (SL). These compounds, whose open acidic form is highly suitable for nanoparticle stabilization, are readily obtained by a fermentation process of the yeast Candida bombicola (polymorph Starmerella bombicola) in large amounts. The final carbohydrate coated iron oxide nanoparticles represent interesting potentially biocompatible materials for biomedical applications. According to the synthesis strategy, magnetic properties can eventually be tuned, thus putting in evidence the direct effect of the glycolipid on the final material's structure (maghemite and ferrihydrite have been obtained here). A combination of FT-IR, Dynamic Light Scattering (DLS) and UV-Vis experiments shows that SL complex the nanoparticle surface via their accessible COOH group thus forming stable colloids, whose hydrodynamic diameter mostly varies between 10 nm and 30 nm, both in water and in KCl-containing (0.01 M and 2 M) solutions. The materials can stand multiple filtration steps (up to 10) at different extents, where the largest recorded average aggregate size is 100 nm. In general, materials synthesized at T = 80 °C display better stability and smaller size distribution than those obtained at room temperature