A Binary Gas Transport Model Improves the Prediction of Mass Transfer in Freeze Drying

Monitoring partial vapor pressure in the freeze-drying chamber is a cheap, global, and non-intrusive way to assess the end of the primary drying stage. Most existing dynamic freeze-drying models which predict this partial pressure describe mass transfer between the product and the condenser via a mass transfer resistance or a mass transfer coefficient. Experimental evidence suggests that such models can be significantly in error for some values of the sublimation flux, leading to physically inconsistent predictions and possibly incorrect assessment of primary drying termination, with potential risk of product damage if moving to secondary drying and increasing shelf temperature while some ice is still present. Assuming a binary gas transport model for vapor and inert gas leads to improved and consistent predictions and explains the apparent variation of the mass transfer resistance with total pressure, shelf temperature, and product sublimation area.     

An Interactive Tool for the Optimization of Freeze-Drying Cycles Based on Quality Criteria

Among existing dehydration methods, freeze-drying has unique benefits for the stabilization and preservation of biological activity of pharmaceutical products but remains an expensive and time-consuming process. A user-friendly software tool was developed, allowing for interactive selection of process operating condition profiles in order to maximize process productivity while insuring product quality preservation. The software is based on a dynamic, one-dimensional heat and mass transfer model, which can accurately represent both the primary and secondary drying stages and the gradual transition between them. The model was validated in a wide range of operating conditions: ? 25 to + 25°C shelf temperature and 10 to 34 Pa total pressure. By comparing a reference sucrose solution with a formulated pharmaceutical product containing polyvinylpyrrolidone (PVP), it is shown that controlling product properties such as glass transition temperature and sorption isotherm can reduce the minimum achievable cycle duration by 12 h (33%).     

Studies on the Solvent Extraction of Rare Earth Metals from Fluorescent Lamp Waste Using Cyanex 923

The growing need for materials such as rare earth metals (REMs) has focused attention towards their recovery from various end-of-life products. Fluorescent lamps are considered a viable target, and can be a source of up to six REMs: lanthanum, cerium, europium, gadolinium, terbium, and yttrium. In this study a commercial mix of trialkylphosphine oxides (Cyanex 923) was investigated for the extraction of REMs from fluorescent lamp waste leachates. The kinetics of the extraction is addressed, together with the co-extraction of undesired elements (iron and mercury), the influence of temperature, nitric acid concentration in the aqueous phase and ligand concentration in the organic phase. The extraction of REMs was found to be enthalpically driven, with good separation factors between the light and heavier elements. Selective stripping of REMs was possible in a single step using 4 M hydrochloric acid solution. Further recovery of iron and mercury was carried out using nitric and oxalic acid solutions.     

Collagen immobilization on poly(ethylene terephthalate) and polyurethane films after UV functionalization

An attractive alternative method to add new functionalities such as biocompatibility due to the micro- and nanoscaled modification of surfaces is offered by UV-modified polymers. The aim of this study was to evaluate the effect of the UV light functionalization on two polymers, poly(ethylene terephthalate) (PET) and polyurethane (PU) films, by means of atomic force microscopy (AFM), Fourier transform infrared–attenuated total reflectance (FTIR–ATR), and contact angle measurements. Thus, the UV-irradiation activates the polymers surface by breaking some chemical bonds and generation of new functional groups on the surface. This process can be controlled by the irradiation time. The topography provides the formation of superposed ‘nap’ and ‘wall-type’ structures on both untreated and treated samples. The surface parameters were found to depend on the polymer films before and after irradiation. The immobilization of collagen on PET surface was confirmed by X-ray photoelectron spectroscopy measurements and for PU surface was proved by FTIR–ATR. First technique suggests an increase of the nitrogen content at longer UV exposure time, and the second one reveals the appearance of the protein Amide I band. Supplementary, AFM measurements clearly revealed the presence of collagen attached on the polymer surface. Thus, these new UV-irradiated polymers are promising materials in our further attempts to obtain new biofunctionalized surfaces.     

Studies on physico-chemical and antibacterial properties of grafted pullulans solutions

The physico-chemical properties of three grafted pullulans (P) having linked poly(3-acrylamidopropyl)trimethylammonium chloride (pAPTAC) as side chains (P-g-pAPTAC1, P-g-pAPTAC2 and P-g-pAPTAC3 with 22.53, 29.05, and 34.51 (wt.%) of pAPTAC content in polymer, respectively) and possessing polyelectrolyte character were determined by light scattering analysis. All grafted pullulan aqueous solutions were tested in the presence of 0.5 M NaCl, KCl, NaNO₃ or KNO₃. The biggest associations were recorded in 0.5 M NaCl aqueous solutions for P-g-pAPTAC1, P-g-pAPTAC2 and P-g-pAPTAC3 according to the maximum values for R_g extracted from MALLS (multiangle laser light scattering) measurements. Also, the dominant conformation in salted solution of these polyelectrolytes was random coil as Debye plot analysis revealed. Antibacterial activity was tested by Kirby–Bauer diffusion method and all grafted pullulans dissolved in aqueous solutions of 0.5 M NaCl have developed inhibition zone against Staphylococcus aureus (ATCC 25923).     

Synthesis and Theoretical Study of New Guanylated Cyclophosphazenes and Their Use in the CO2 Fixation into Styrene Carbonate

Three new guanylated cyclophosphazenes G1–G3 have been synthesized through the catalytic guanylation of three different bi, tetra and hexa (p-aminophenoxy)-cyclophosphazenes by using N,N’-diisopropylcarbodiimide as guanylating agent, ZnEt₂ as catalyst and dry tetrahydrofuran as solvent. The resulting products have been characterized by ¹H, ¹³C{¹H} and ³¹P{¹H} NMR spectroscopy. The hexaguanylated cyclophosphazenes exhibit a deep purple colour, unusual for this type of compounds. The electronic structure of these compounds was investigated by carrying out density functional calculations at PBE-D3(BJ)/TZP level of theory. The molecular structural analysis reveals that aromatic rings are stacked and time dependent density functional calculations show that a charge transfer electronic transition occurs between the aromatic rings which absorb light around 500–700 nm. Finally, the catalytic usefulness of guanylated cyclophosphazene compounds G1–G3 has been proven by the preparation of styrene carbonate from the reaction between styrene oxide and carbon dioxide.

     

Senescent CD4+CD28− T Lymphocytes as a Potential Driver of Th17/Treg Imbalance and Alveolar Bone Resorption during Periodontitis

Senescent cells express a senescence-associated secretory phenotype (SASP) with a pro-inflammatory bias, which contributes to the chronicity of inflammation. During chronic inflammatory diseases, infiltrating CD4⁺ T lymphocytes can undergo cellular senescence and arrest the surface expression of CD28, have a response biased towards T-helper type-17 (Th17) of immunity, and show a remarkable ability to induce osteoclastogenesis. As a cellular counterpart, T regulatory lymphocytes (Tregs) can also undergo cellular senescence, and CD28⁻ Tregs are able to express an SASP secretome, thus severely altering their immunosuppressive capacities. During periodontitis, the persistent microbial challenge and chronic inflammation favor the induction of cellular senescence. Therefore, senescence of Th17 and Treg lymphocytes could contribute to Th17/Treg imbalance and favor the tooth-supporting alveolar bone loss characteristic of the disease. In the present review, we describe the concept of cellular senescence; particularly, the one produced during chronic inflammation and persistent microbial antigen challenge. In addition, we detail the different markers used to identify senescent cells, proposing those specific to senescent T lymphocytes that can be used for periodontal research purposes. Finally, we discuss the existing literature that allows us to suggest the potential pathogenic role of senescent CD4⁺CD28⁻ T lymphocytes in periodontitis.     

Simulating Microstructural Evolution and Electrical Transport in Ceramic Gas Sensors

An integrated computational approach to microstructural evolution and electrical transport in ceramic gas sensors has been proposed. First, the particle-flow model and the continuum-phase-field method are used to describe the microstructural development during the sintering of a prototype two-dimensional film. Then, the conductivity of the sintering samples is calculated concurrently as the microstructure evolves, using both resistor lattice models and effective medium theory for electrical transport in porous aggregates of lightly sintered particles. This approach, when combined with the modeling of resistivity at the grain–grain contacts as a function of neck geometry, ambient gas concentration and temperature, could facilitate the development and optimization of novel microstructures for advanced ceramic gas sensors.