Multiwell cartridge with integrated array of amorphous silicon photosensors for chemiluminescence detection: development,characterization and comparison with cooled-CCD luminograph

We propose a disposable multiwell microcartridge with integrated amorphous silicon photosensors array for bio- and chemiluminescence-based bioassays, where the enzymatic reactions and the detection unit are coupled on the same glass substrate. Each well, made in a polydimethylsiloxane (PDMS) unit, hosts an enzymatic reaction that is monitored by one photosensor of the array. Photosensors were characterized in terms of their dark current background noise and response to different wavelengths of visible light in order to determine their suitability as detection devices for chemical luminescent phenomena. Calibration curves of the photosensors’ response to different luminescent systems were then evaluated by using the chemiluminescent reactions catalyzed by alkaline phosphatase and horseradish peroxidase and the bioluminescent reaction catalyzed by firefly luciferase. Limits of detection in the order of attomoles for chemiluminescence enzymes and femtomoles for luciferase and sensitivities in the range between 0.007 and 0.1 pA pmol^?1 L were reached. We found that, without the need of cooling systems, the analytical performances of the proposed cartridge are comparable with those achievable with state-of-the-art thermoelectrically cooled charge-coupled device-based laboratory instrumentation. In addition, thanks to the small amount of generated output data, the proposed device allows the monitoring of long-lasting reactions with significant advantages in terms of data-storage needs, transmission bandwidth, ease of real-time signal processing and limited power consumption. Based on these results, the operation in model bioanalytical assays exploiting luminescent reactions was tested demonstrating that a-Si:H photosensors arrays, when integrated with PDMS microfluidic units, provide compact, sensitive and potentially low-cost microdevices for chemiluminescence and bioluminescence-based bioassays with a wide range of possible applications for in-field and point-of-care bio-analyses.     

Sustainable Materials and their Contribution to the Sustainable Development Goals (SDGs): A Critical Review Based on an Italian Example

The Sustainable Development Goals (SDGs) have been proposed to give a possible future to humankind. Due to the multidimensional characteristic of sustainability, SDGs need research activities with a multidisciplinary approach. This work aims to provide a critical review of the results concerning sustainable materials obtained by Italian researchers affiliated to the National Interuniversity Consortium of Materials Science and Technology (INSTM) and their contribution to reaching specific indicators of the 17 SDGs. Data were exposed by using the Web of Science (WoS) database. In the investigated period (from 2016 to 2020), 333 works about sustainable materials are found and grouped in one of the following categories: chemicals (33%), composites (11%), novel materials for pollutants sequestration (8%), bio-based and food-based materials (10%), materials for green building (8%), and materials for energy (29%). This review contributes to increasing the awareness of several of the issues concerning sustainable materials but also to encouraging the researchers to focus on SDGs’ interconnections. Indeed, the mapping of the achievements can be relevant to the decision-makers to identify the opportunities that materials can offer to achieve the final goals. In this frame, a “Sustainable Materials Partnership for SDGs” is envisaged for more suitable resource management in the future.     

Characterization of silver sulfadiazine-loaded solid lipid nanoparticles by thermal analysis

The aim of this study is the solid-state characterization of solid lipid nanoparticles (SLN) based on Compritol^® 888 (C888) and Lutrol^® F68 (F68), loaded with silver sulfadiazine (AgSD), used to develop sponge-like dressings to treat chronic skin ulcers such as decubitis and leg ulcers. Silver compounds like AgSD, in fact, are used to prevent and/or to treat wound colonization that could impair healing, also in the case of antibiotic-resistant bacteria. Thermal analysis, with support from powder X-ray diffractometry and Fourier transform infrared spectroscopy, is used to characterize lipid and drug bulk, unloaded and drug-loaded SLN. In particular, differential scanning calorimetry is used to investigate the degree of crystallinity and the solid-state modification of lipid, two parameters correlated to drug incorporation and drug release rates. The solid-state characterization demonstrates AgSD entrapment in C888 as a core enclosed into F68 shell. AgSD SLN are also stored at different temperatures 25 and 37 °C, respectively, to study the effect of storage conditions, that induce an increase of the lipid crystallinity index correlated to drug release from the lipid matrix.     

Nanoscale Imaging and Stabilization of Silica Nanospheres in Liquid Phase Transmission Electron Microscopy

Liquid phase transmission electron microscopy (LP‐TEM) is a novel and highly promising technique for the in situ study of important nanoscale processes, in particular the synthesis and modification of various nanostructures in a liquid. Destabilization of the samples, including reduction, oxidation, or dissolution by interactions between electron beam, liquid, and sample, is still one of the main challenges of this technique. This work focuses on amorphous silica nanospheres and the phenomena behind their reshaping and dissolution in LP‐TEM. It is proposed that silica degradation is primarily the result of reducing radical formation in the liquid phase and the subsequent accelerated hydroxylation of the silica, while alterations in silica solid structure, pH, and oxidizing species formation had limited influence. Furthermore, the presence of water vapor instead of liquid water also results in degradation of silica. Most importantly however, it is shown that the addition of scavengers for reducing radicals significantly improved amorphous silica stability during LP‐TEM imaging. Devising such methods to overcome adverse effects in LP‐TEM is of the utmost importance for further development and implementation of this technique in studies of nanoscale processes in liquid.     

Three dimensional thermoelastic analysis of a semi infinite solid with arbitrary heat supply

Summary This paper is devoted to the determination of the three dimensional steady state temperature, strains and stresses in a semi infinite elastic medium bounded by a plane, exposed to an arbitrary heat supply. The problem is treated within the classical theory, based on the Fourier equation and Hooke's law. A general analytical solution is obtained in the form of double integrals (by means of Fourier transform method) and it is shown that the stress field is plane and parallel to the boundary. The particular solution corresponding to axisymmetrical surface heat flux is deduced; results are found for different situations and briefly discussed with the aid of some graphs.

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Dreidimensionale thermoelastische Untersuchung eines elastischen Halbraums mit beliebiger Wärmezufuhr

Übersicht Es werden stationäre Temperatur, Verzerrungen und Spannungen in einem elastischen Halbraum ermittelt, der einer beliebigen Wärmezufuhr unterworfen ist. Der Untersuchung liegt die klassische Theorie (Fourier Gleichung, Hookesches Gesetz) zugrunde. Eine allgemeine analytische Lösung wird mit Hilfe der Fourier-Transformation in Form von Doppelintegralen erhalten. Dabei wird gezeigt, daß das Spannungsfeld eben und parallel zum Rand ist. Die Lösung für den Sonderfall eines axialsymmetrischen Wärmestroms an der Oberfläche wird hergeleitet und diskutiert.

     

Temperature in heat generating solids with memory

The present paper is concerned with time dependent heat transport by wave propagation in an homogeneous isotropic elastic solid with memory. The energy generated in the material for electrical heating or chemical or nuclear reactions is propagated with a finite speed.The effect of this thermal wave speed is noticeable in many practical applications involving short time and high heat flux situations. The one dimensional, time dependent temperature distribution in a heat generating solid is analytically determined resorting to the Maxwell-Cattaneo-Vernotte equation, following the theory of complex functions of complex variables. Some results are reported and shortly discussed; a comparison with the classical Fourier theory is made.

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Temperaturverteilung in einem festen Körper mit Wärmeerzeugung und thermischer Nachwirkung

Zusammenfassung Die Arbeit behandelt den zeitabhängigen Wärmetransport durch eine fortschreitende Welle in einem homogenen isotropen elastischen Festkörper mit Gedächtnis. Die im Material durch elektrische Heizung oder durch chemische oder nukleare Reaktionen erzeugte Wärme wird mit endlicher Geschwindigkeit fortgeleitet. Die Wirkung dieser thermischen Wellengeschwindigkeit ist für manche praktische Anwendungen von Bedeutung, soweit kurze Zeiten und hohe Wärmeflüsse eine Rolle spielen. Die eindimensionale zeitabhängige Temperaturverteilung in einem wärmeerzeugenden Körper ist analytisch bestimmt unter Benutzung der Maxwell-Cattaneo-Vernotte-Gleichung nach der Theorie komplexer Funktionen komplexer Variablen. Einige Ergebnisse werden mitgeteilt, kurz diskutiert und mit der klassischen Fourier-Theorie verglichen.

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Nomenclature a heat flux relaxation function - b _n constant defined in (25) - b _n constant defined in (30) - c specific heat at constant pressure - E elasticity modulus - Fo Fourier number defined in (8) - i imaginary unity - K thermal conductivity - L slab half thickness - N integer number defined in (28) - p integration variable for the inverse Laplace transform - q heat flux vector - Q power produced in the unit volume - Q temperature defined in (8) - R _m residue associated to them-th pole - s time - S sound speed - t time - T temperature defined in (8) - T⁺ dimensionless temperature defined in (33) - u function defined in (11) - inverse Laplace transform of the functionu - U unit Heaviside step function - x dimensionless coordinate defined in (8) - thermal diffusivity - vector differential operator - ² Laplace operator - constant defined in (26) - cartesian coordinate - mass density - gq temperature - dimensionless material thermal relaxation time defined in (8) - _R material thermal relaxation time     

Low temperature CEMS of Sn-implanted SiO2

Conversion electron Mössbauer spectroscopy (CEMS) at room and low temperature has been used to study thin SiO₂ films implanted with Sn atoms and annealed at 900°C. This work focuses on the determination of the Debye temperature (θ _D) and Debye–Waller factors (f) of the Sn oxidized phases formed in this system. The Sn²⁺ oxidation state is the predominant one, even if a small percentage of the Sn atoms is in the Sn⁴⁺ oxidation state. The real Sn-oxides fractions are calculated by normalizing the resonant areas to the f values, as calculated from the temperature dependence of the related resonant areas within a Debye model. The Sn⁴⁺ oxidation state, possibly related to Sn atoms close to the SiO₂ surface, represents less than 20% of the Sn atoms. For the Sn²⁺ oxidation state, two different electronics configurations a and b, having different Debye temperature and hyperfine parameters are identified. The component a, with a lower θ _D (137 K), is the predominant one and might be related to small (2–3 nm) amorphous SnO _x clusters in the SiO₂ matrix. The component b could be related to substitutional Sn atoms in the SiO₂ network forming a local Sn environment similar to the SnO amorphous compound.     

An analytical study of space-dependent evolution problems in particle transport theory

Summary Space-dependent evolution problems arising in particle transport theory are analytically studied via a systematic application of the Boltzmann equation. Some explicit solutions, that can improve our knowledge of the spatial effects in such a class of problems, are constructed and briefly commented on a physical ground.

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Riassunto Problemi spaziali di evoluzione che si incontrano nella teoria del trasporto di particelle sono studiati analiticamente per mezzo di una sistematica applicazione dell'equazione di Boltzmann. Alcune soluzioni esplicite, che possono migliorare la nostra conoscenza degli effetti spaziali in tale classe di problemi, sono costruite e commentate brevemente su base fisica.

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Резюме Аналитически, используя уравнение Больцмана, исследуются проблемы пространственной эволюции, зозниакющие в теории переноса частиц. Конструируются некоторые точные решения, которые могут уточнить наше понимание пространственных эффектов в таком классе проблем. Проводится обсуждение этих решений.

     

Radiative transfer in plane media without azimuthal symmetry

A rigorous integral theory is presented in this paper for the solution of radiative heat transfer problems in stratified media, when dependence on the azimuth of the propagating radiation must be taken into account. Anisotropy of scattering and specular and diffuse reflection from the bounding walls are incorporated in the final system of linear integral equations of Fredholm's type. A simple case of physical interest is considered in more detail, and solved explicitly by a constructive technique. Numerical results are reported and briefly discussed.     

Structural and electrical characterization of ALCVD ZrO2 thin films on silicon

We report on the structural and electrical properties of ZrO₂ thin layers grown on Si by atomic layer chemical vapour deposition. Atomic force microscopy, X-ray diffraction, X-ray reflectivity and time-of-flight secondary ion mass spectrometry have been used to characterize as-grown and annealed samples. High frequency capacitance-voltage measurements have been performed to determine the capacitance of the gate dielectric stack. The ZrO₂ film is found to be polycrystalline. Electrical and structural data suggest a coherent picture of film modification upon annealing.