Effect of Conformation of Sugar Beet Pectin on the Interfacial and Emulsifying Properties

The influence of the conformation of sugar beet pectin (SBP) on the interfacial and emulsifying properties was investigated. The colloidal properties of SBP, such as zeta potential and hydrodynamic diameter, were characterized at different pH levels. Furthermore, pendant drop tensiometry and quartz crystal microgravimetry were used to study adsorption behavior (adsorbed mass and adsorption rate) and stabilizing mechanism (layer thickness and interfacial tension). A more compact conformation resulted in a faster reduction of interfacial tension, higher adsorbed mass, and a thicker adsorption layer. In addition, emulsions were prepared at varying conditions (pH 3–5) and formulations (1–30 wt% MCT oil, 0.1–2 wt% SBP), and their droplet size distributions were measured. The smallest oil droplets could be stabilized at pH 3. However, significantly more pectin was required at pH 3 compared to pH 4 or 5 to sufficiently stabilize the oil droplets. Both phenomena were attributed to the more compact conformation of SBP at pH < pKa: On the one hand, pectins adsorbed faster and in greater quantity, forming a thicker interfacial layer. On the other hand, they covered less interfacial area per SBP molecule. Therefore, the SBP concentration must be chosen appropriately depending on the conformation.

Design and Modelling of a Cooling Unit by Adsorption Geothermal Heat Pump in a Tropical Climate Zones

This work is a contribution of a modelling of air conditioner by adsorption for a habitat in a tropical climate. The system mainly consists of a captor adsorber powered by a geothermal pump, a condenser and an evaporator. We use the zeolite/methanol couple and the different thresholds temperatures to define the thermodynamic system cycle. Moreover, we use a methodology based on nodal approach to establish heat and mass transfer equations. Dubinin-Astakhov thermodynamic model is employed to express the mass adsorbed, the coefficient of performance (COP) and the cold production. We make use of the climatic data in Comoros for 2009-2019 period to obtain the ambient temperature. The model validation is done by comparing the shape of the cycle we obtain with the state of the art. First, the results show a relationship between temperature, pressure and adsorbed mass. The increase in temperature is accompanied by an increase of pressure and an increase of adsorbed mass, and in the same way a decrease in the temperature causes a decrease of the pressure as well as a decrease of adsorbed mass. The mixture zeolite/methanol reaches 356K at the regeneration temperature with an input water temperature of 363K. We observed the influence of main important parameters on the mixture temperature such as fluid input temperature, fluid velocity or zeolite thermal conductivity. Finally, we show the thresholds temperatures influence on the COP and the cold production at evaporator.

Optical-Thermally Excited Graphene Resonant Mass Detection: A Molecular Dynamics Analysis

In consideration of the presented optical-thermally excited resonant mass detection scheme, molecular dynamics calculations are performed to investigate the thermal actuation and resonant mass sensing mechanism. The simulation results indicate that an extremely high temperature exists in a 6% central area of the graphene sheet exposed to the exciting laser. Therefore, constraining the laser driving power and enlarging the laser spot radius are essential to weaken the overheating in the middle of the graphene sheet, thus avoiding being burned through. Moreover, molecular dynamics calculations demonstrate a mass sensitivity of 214 kHz/zg for the graphene resonator with a pre-stress of 1 GPa. However, the adsorbed mass would degrade the resonant quality factor from 236 to 193. In comparison, the sensitivity and quality factor could rise by 1.3 and 4 times, respectively, for the graphene sheet with a pre-stress of 5 GPa, thus revealing the availability of enlarging pre-stress for better mass sensing performance.

Distinct Solute Removal Patterns by Similar Surface High-Flux Membranes in Haemodiafiltration: The Adsorption Point of View

<b><i>Introduction:</i></b> Haemodialysis (HD) allow depuration of uraemic toxins by diffusion, convection, and adsorption. Online haemodiafiltration (HDF) treatments add high convection to enhance removal. There are no prior studies on the relationship between convection and adsorption in HD membranes. The possible benefits conferred by intrinsic adsorption on protein-bound uraemic toxins (PBUTs) removal are unknown. <b><i>Methods:</i></b> Twenty-two patients underwent their second 3-days per week HD sessions with randomly selected haemodialysers (polysulfone, polymethylmethacrylate, cellulose triacetate, and polyamide copolymer) in high-flux HD and HDF. Blood samples were taken at the beginning and at the end of the treatment to assess the reduction ratio (RR) in a wide range of molecular weight uraemic toxins. A mid-range removal score (GRS) was also calculated. An elution protocol was implemented to quantify the amount of adsorbed mass (<i>M</i>_ads) for each molecule in every dialyser. <b><i>Results:</i></b> All synthetic membranes achieved higher RR for all toxins when used in HDF, specially the polysulfone haemodialyser, resulting in a GRS = 0.66 ± 0.06 (<i>p</i> &#x3c; 0.001 vs. cellulose triacetate and polyamide membranes). Adsorption was slightly enhanced by convection for all membranes. The polymethylmethacrylate membrane showed expected substantial adsorption of β₂-microglobulin (<i>M</i>_ads^HDF = 3.5 ± 2.1 mg vs. <i>M</i>_ads^HD = 2.1 ± 0.9 mg, <i>p</i> = 0.511), whereas total protein adsorption was pronounced in the cellulose triacetate membrane (<i>M</i>_ads^HDF = 427.2 ± 207.9 mg vs. <i>M</i>_ads^HD = 274.7 ± 138.3 mg, <i>p</i> = 0.586) without enhanced PBUT removal. <b><i>Discussion/Conclusion:</i></b> Convection improves removal and slightly increases adsorption. Adsorbed proteins do not lead to enhanced PBUTs depuration and limit membrane efficiency due to fouling. Selection of the correct membrane for convective therapies is mandatory to optimize removal efficiency.

Anticoagulant Activity of Cellulose Nanocrystals from Isora Plant Fibers Assembled on Cellulose and SiO2 Substrates via a Layer-by-Layer Approach

In this study, we report the isolation of cellulose nanocrystals (CNCs) from Isora plant fibers by sulfuric acid hydrolysis and their assembly on hydrophilic cellulose and silicon-di-oxide (SiO2) surfaces via a layer-by-layer (LBL) deposition method. The isolated CNCs were monodispersed and exhibited a length of 200–300 nm and a diameter of 10–20 nm, a negative zetapotential (–34–39 mV) over a wide pH range, and high stability in water at various concentrations. The multi-layered structure, adsorbed mass, conformational changes, and anticoagulant activity of sequentially deposited anionic (sulfated) CNCs and cationic polyethyleneimine (PEI) on the surfaces of cellulose and SiO2 by LBL deposition were investigated using a quartz crystal microbalance technique. The organization and surface features (i.e., morphology, thickness, wettability) of CNCs adsorbed on the surfaces of PEI deposited at different ionic strengths (50–300 mM) of sodium chloride were analysed in detail by profilometry layer-thickness, atomic force microscopy and contact angle measurements. Compared to cellulose (control sample), the total coagulation time and plasma deposition were increased and decreased, respectively, for multilayers of PEI/CNCs. This study should provide new possibilities to fabricate and tailor the physicochemical properties of multilayer films from polysaccharide-based nanocrystals for various biomedical applications.

Laser-Induced Graphene on a Quartz Crystal Microbalance for Humidity Sensing

In this study, a simple method for synthesizing graphene layer directly on a quartz crystal microbalance (QCM) using a laser was developed. This laser-induced graphene (LIG) was used for sensing surface to simultaneously measure changes in the adsorbed mass, film stiffness, and electrical resistance during water adsorption. The developed LIG-QCM is convenient because its fabrication process is free of any tedious masking and vacuuming steps. A thin layer of polyimide (PI) film was spin-coated on one side of a quartz crystal microresonator, and interdigitated electrodes (IDE) were patterned on the PI surface using a laser engraver. The adsorption of water molecules on the sensing surface induced changes in mass, stiffness, and electrical conductivity, which were measured from the changes in resonance frequency, Q factor of the quartz crystal, and electrical resistance, respectively. The results indicated that the developed sensor could be a humidity sensing platform using LIG.

Surface Interactions between Bacterial Nanocellulose and B-Complex Vitamins

The interactions between films of bacterial nanocellulose (BNC) and B complex vitamins were studied using a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D). Thin films of BNC were generated in situ by QCM-D, followed by real-time measurements of the vitamin adsorption. The desorption of vitamins was induced by rinsing the system using phosphate buffers at a pH of 2 and 6.5, emulating gastric conditions. Changes in frequency (which are proportional to changes in adsorbed mass, ∆m) detected by QCM-D were used to determine the amounts of vitamin adsorbed and released from the BNC film. Additionally, changes in dissipation (∆D) were proven to be useful in identifying the effects of the pH in both pristine cellulose films and films with vitamin pre-adsorbed, following its changes during release. The effects of pH on the morphology of the vitamin-BNC surfaces were also monitored by changes in rugosity from images obtained by atomic force microscopy (AFM). Based on this data, we propose a model for the binding phenomena, with the contraction on the relaxation of the cellulose film depending on pH, resulting in an efficient vitamin delivery process.

Label-Free Monitoring of Histone Acetylation Using Aptamer-Functionalized Field-Effect Transistor and Quartz Crystal Microbalance Sensors

Chemical and enzymatic modifications of amino acid residues in protein after translation contain rich information about physiological conditions and diseases. Histone acetylation/deacetylation is the essential post-translational modification by regulating gene transcription. Such qualitative changes of biomacromolecules need to be detected in point-of-care systems for an early and accurate diagnosis. However, there is no technique to aid this issue. Previously, we have applied an aptamer-functionalized field-effect transistor (FET) to the specific protein biosensing. Quantitative changes of target protein in a physiological solution have been determined by detecting innate charges of captured protein at the gate-solution interface. Moreover, we have succeeded in developing an integrated system of FET and quartz crystal microbalance (QCM) sensors for determining the adsorbed mass and charge, simultaneously or in parallel. Prompted by this, in this study, we developed a new label-free method for detecting histone acetylation using FET and QCM sensors. The loss of positive charge of lysine residue by chemically induced acetylation of histone subunits (H3 and H4) was successfully detected by potentiometric signals using anti-histone aptamer-functionalized FET. The adsorbed mass was determined by the same anti-histone aptamer-functionalized QCM. From these results, the degree of acetylation was correlated to the charge-to-mass ratio of histone subunits. The histone required for the detection was below 100 nM, owing to the high sensitivity of aptamer-functionalized FET and QCM sensors. These findings will guide us to a new way of measuring post-translational modification of protein in a decentralized manner for an early and accurate diagnosis.

Prototype’s seizing and design of a solar refrigerator based on solid adsorption

Solar refrigerator machines based on solid adsorption present a highly interesting solution to the Industry of Cooling Production. In one hand, they are significantly attractive economy ways because of the abundance of the solar energy resources. In the other hand, they are environment friendly. As a result, these machines could present one of the most competitive solutions to the improvement of this very industry. The aim of this paperwork is to provide an accurate study on how to design, seize and build a prototype of an adsorption solar refrigerator using activated-carbon/ammonia pair: Firstly, we used a static model, which is based on the use of state equations (vapor/liquid) at thermodynamic equilibrium. This model computes the cycled mass and the cycle coefficient of performance (COPc) for each four characteristic temperatures of the cycle. Secondly, we develop a dynamic simulation program based on conservation equations of energy and mass in the reactor, this program allow the calculation of the temperature, the pressure inside the reactor, the adsorbed mass and the solar coefficient of performance (COPs). Finally, in the light of our results, we design this prototype, it would consist of the reactor: a solar panel, size 1 m2contain tubes with a diameter of 10cm, an air condenser, and a cold chamber containing an air evaporator.