Quorum Sensing as a long-range interaction for bacteria growth and bioluminescence

We study the role of Quorum Sensing (QS) in the growth of bacterial colonies and in the bioluminescence produced. These two phenomena are both regulated by QS and the experimental data show a non-trivial correlation between them. It is also known that the specific bacterial substrate potentially modifies the behavior of the colony. In the specific case of the bioluminescent gram-negative bacterium, Vibrio harveyi, we propose a three-autoinducer model in which QS is described in terms of long-range interaction between charged objects placed on a regular network and playing the role of bacteria. The charges spread in the network through fictitious non-linear electrostatic interactions. QS is monitored by analyzing the current flowing within the network. The model parameters are determined by comparing the simulations with the data present in the literature and related to liquid cultures. New colony growth measurements are then performed on Vibrio campbelli (a member of the clade Harveyi) grown on hydroxyapatite (HA) substrates relevant for biomedical applications. Growth on the substrate differs from growth in liquid culture, although the observed bioluminescence is similar. We exploit our model to understand the differences between colonies in liquid culture and on substrate in terms of the relative role and cooperation of the three autoinducers.Comment: 8 pages, 5 figure

Mixing enhancement induced by viscoelastic micromotors in microfluidic platforms

Fine manipulation of fluid flows at the microscale has a tremendous impact on mass transport phenomena of chemical and biological processes inside microfluidic platforms. Fluid mixing in the laminar flow regime at low Reynolds number is poorly effective due to the inherently slow diffusive mechanism. As a strategy to enhance mixing and prompt mass transport, here, we focus on polyelectrolyte multilayer capsules (PMCs), embodying a catalytic polyoxometalate, as microobjects to create elastic turbulence and as micromotors to generate chaotic flows by fuel-fed propulsions. The effects of the elastic turbolence and of the artificial propulsion on some basic flow parameters, such as pressure and volumetric flow rate, are studied by a microfluidic set-up including pressure and flow sensors. Numerical-handling and physical models of the experimental data are presented and discussed to explain the measured dependence of the pressure drop on the flow rate in presence of the PMCs. As a practical outcome of the study, a strong decrease of the mixing time in a serpentine microreactor is demonstrated. Unlike our previous reports dealing with capillarity flow studies, the present paper relies on hydrodynamic pumping experiments, that allow us to both develop a theoretical model for the understanding of the involved phenomena and demonstrate a successful microfluidic mixing application. All of this is relevant in the perspective of developing microobject-based methods to overcome microscale processes purely dominated by diffusion with potential improvements of mass trasport in microfluidic platforms. \ua9 2019 Elsevier B.V

Thermal neutron conversion by high purity 10B-enriched layers: PLD-growth, thickness-dependence and neutron-detection performances

Neutron applications and detection are of paramount importance in industry, medicine, scientific research, homeland security, production of extreme UV optics and so on. Neutron detection requires a converter element that, as a result of its interaction with neutrons, produces reaction products (mainly charged particles) whose detection can be correlated with the neutron flux. Reduced availability and increased cost of the most used converter element, 3He, have triggered research efforts for alternative materials, proper deposition methods and new detector architectures. 10B converter is a valid alternative to 3He thanks to its high thermal neutron cross section and relatively high Q value. In this paper we report on the room temperature Pulsed Laser Deposition (PLD) of high quality and uniform 10B films with the expected density, different thickness values (0.5, 1.0, 1.2, 1.5 and 2.0 μm) and uniform thickness over a circular area of about 30 mm in diameter. Additionally, they are adherent to the substrate with a negligible presence of contaminants. The conversion properties of such 10B coatings coupled to a Si solid state detector are studied upon exposure to a neutron flux from an Am-Be neutron source (2.2·106 n/s). The experimental results, compared with spectra simulated by using a GEANT4 code, present a good agreement and efficiencies of the order of a few percent

broadband visible light emission from nominally undoped and hbox cr 3 doped garnet nanopowders

Synthetic garnet nanopowders of Y 3 Al 5 O 12 (YAG) and Gd 3 Ga 5 O 12 (GGG) were produced, and the occurrence of a broadband bright visible emission by nominally undoped YAG and GGG and Cr 3+ doped GGG, depending on the environment pressure, as well as exciting on the pumping power, was demonstrated. The results indicate that high-intensity infrared laser irradiation in samples not only leads to heating (melting effects) but also produces visible broadband emission. Low pressure of the powders' environment favors the white light emission by lowering the threshold pumping power. A hypothesis on the nature of the emission is presented

Pengetahuan Remaja tentang Polycystic Ovary Syndrome (PCOS)

Polycystic Ovary Syndrome (PCOS) merupakan gangguan hormonal yang terjadi pada wanita usia subur. Wanita yang mengidap PCOS memiliki banyak kista kecil yang terletak di sepanjang tepi ovarium, hal ini dapat menyebabkan tidak terjadinya ovulasi sehingga akan menyulitkan wanita untuk mendapatkan keturunan. Tujuan penelitian ini adalah Untuk mengetahui pengetahuan remaja putri tentang PCOS. Metode Penelitian ini menggunakan jenis penelitian literature review dengan menggunakan teknik rapid review atau ulasan cepat yaitu bentuk sintesis bukti yang dapat memberikan informasi lebih tepat waktu. Hasil dari penelitian ini didapatkan 10artikel yang memenuhi kriteria inklusi. bahwa diperlukan tingkat kesadaran diri dan pengetahuan yang baik tentang Polycystic Ovary Syndrome (PCOS) terutama pada remaja. Karena deteksi dini PCOS bisa dilakukan jika perempuan perempuan mengetahui tanda gejala PCOS sehingga salah satu upaya yang bisa dilakukan supaya perempuan usia subur bisa aware adalah dengan memberikan informasi kepada remaja putri mengenai PCOS

On-chip pressure measurements and channel deformation after oil absorption

Microfluidic channels moulded from the soft polymer poly(dimethylsiloxane) (PDMS) are widely used as a platform for mimicking biological environments, and can be used for the simulation of fluid filled structures such as blood and lung vessels. The control of pressure and flow rate within these structures is vital to mimic physiological conditions. The flexibility of PDMS leads to pressure-induced deformation under flow, leading to variable flow profiles along a device. Here, we investigate the change in Young’s modulus of microfluidic channels due to infiltration of mineral oil, a PDMS permeable fluid, and how this affects the resulting pressure profile using a novel pressure measurement method. We found a 53% decrease in Young’s modulus of PDMS due to mineral oil absorption over the course of 3 h accounted for lower internal pressure and larger channel deformation compared to fresh PDMS at a given flow rate. Confocal fluorescence microscopy used to image channel profiles before and after the introduction of mineral oil showed a change in pressure-induced deformation after infiltration of the oil. Atomic force microscopy (AFM) nanoindentation was used to measure Young’s modulus of PDMS before (2.80±0.032.80±0.03 MPa) and after (1.32±0.041.32±0.04 MPa) mineral oil absorption. Raman spectroscopy showed the infiltration of mineral oil into PDMS from channel walls and revealed the diffusion coefficient of mineral oil in PDMS

Surface energy and nucleation modes

Deposition is a manufacturing process in which a precursor material is delivered to a surface on which it reorganizes by interplay between thermodynamics and kinetics. The evolution of the microstructure of the deposit (layers with thicknesses between a few atomic layers and several micrometers [films] or nanostructure distributions or nanostructured films) is highly dependent on the physical conditions (i.e., the deposition technique and parameters) under which deposition takes place, apart from the choice of materials. Understanding the mechanisms underlying the structural and morphological evolution of a growing deposit is essential to being able to tailor the properties and performances of functional materials at the atomic scale depending on the deposition approach. In this chapter a comprehensive overview to the classical theory of growth will be given, with a focus on the importance of kinetic factors and processes as well as the growth manipulations enabled by a prototypal far-from-equilibrium deposition technique, such as pulsed laser depositio

Nanophosphors-based white light sources

Miniaturization requests and progress in nanofabrication are prompting worldwide interest in nanophosphors as white-emission mercury-free lighting sources. By comparison with their bulk counterparts, nanophosphors exhibit reduced concentration quenching effects and a great potential to enhance luminescence effciency and tunability. In this paper, the physics of the nanophoshors is overviewed with a focus on the impact of spatial confinement and surface-to-volume ratio on the luminescence issue, as well as rare earth-activated multicolor emission for white light (WL) output. In this respect, the prominently practiced strategies to achieve WL emission are single nanophosphors directly yielding WL by means of co-doping and superposition of the individual red, green, and blue emissions from different nanophosphors. Recently, a new class of effcient broadband WL emitting nanophosphors has been proposed, i.e., nominally un-doped rare earth free oxide (yttrium oxide, Y2O3) nanopowders and Cr transition metal-doped garnet nanocrystals. In regard to this unconventional WL emission, the main points are: it is strictly a nanoscale phenomenon, the presence of an emitting center may favor WL emission without being necessary for observing it, and, its inherent origin is still unknown. A comparison between such an unconventional WL emission and the existing literature is presented to point out its novelty and superior lighting performances

Realistic absorption coefficient of each individual film in a multilayer architecture

A spectrophotometric strategy, termed multilayer-method (ML-method), is presented and discussed to realistically calculate the absorption coefficient of each individual layer embedded in multilayer architectures without reverse engineering, numerical refinements and assumptions about the layer homogeneity and thickness. The strategy extends in a non-straightforward way a consolidated route, already published by the authors and here termed basic-method, able to accurately characterize an absorbing film covering transparent substrates. The ML-method inherently accounts for non-measurable contribution of the interfaces (including multiple reflections), describes the specific film structure as determined by the multilayer architecture and used deposition approach and parameters, exploits simple mathematics, and has wide range of applicability (high-to-weak absorption regions, thick-to-ultrathin films). Reliability tests are performed on films and multilayers based on a well-known material (indium tin oxide) by deliberately changing the film structural quality through doping, thickness-tuning and underlying supporting-film. Results are found consistent with information obtained by standard (optical and structural) analysis, the basic-method and band gap values reported in the literature. The discussed example-applications demonstrate the ability of the ML-method to overcome the drawbacks commonly limiting an accurate description of multilayer architectures

Realistic reflectance spectrum of thin films covering a transparent optically thick substrate

A spectrophotometric strategy is presented and discussed for calculating realistically the reflectance spectrum of an absorbing film deposited over a thick transparent or semi-transparent substrate. The developed route exploits simple mathematics, has wide range of applicability (high-to-weak absorption regions and thick-to-ultrathin films), rules out numerical and curve-fitting procedures as well as model-functions, inherently accounts for the non-measurable contribution of the film-substrate interface as well as substrate backside, and describes the film reflectance spectrum as determined by the experimental situation (deposition approach and parameters). The reliability of the method is tested on films of a well-known material (indium tin oxide) by deliberately changing film thickness and structural quality through doping. Results are found consistent with usual information yielded by reflectance, its inherent relationship with scattering processes and contributions to the measured total reflectance