Modeling of Hysteretic Behavior of Soil–Water Retention Curves Using an Original Pore Network Model

Soil–water retention curve (SRWC), also called soil moisture characteristic, is used for simulation models of soil water storage or soil aggregate stability. The present study addresses the modeling of SRWC with particular attention paid to hysteresis effects of water filling and draining the pores attributed to ink-bottle effects. For that purpose, an idealized pore size distribution previously developed for predicting water sorption isotherms on cementitious materials, and which can consider the double porosity structure of soils, is used. The input data of the model are assessed only from mercury intrusion porosimetry tests (MIP) and from grain size distribution (GSD). The hysteretic behavior of SRWC is reproduced in a satisfactory way. The model can also predict the specific surface area.

     

Extremum principles for optimal control in normed linear spaces

Extremum principles intended for use in optimal control are derived in the form of necessary conditions and sufficient conditions, formulated in general normed linear spaces. The method of application is illustrated by several examples involving optimal control problems, mathematical programming problems, lumped-parameter systems, and distributed-parameter systems. The basic theorems provide a unified approach which is applicable to a wide variety of problems in open-loop optimal control.     

Hydrogels Incorporating GdDOTA: Towards Highly Efficient Dual T(1) /T(2) MRI Contrast Agents

Do not tumble dry: Gadolinium-DOTA encapsulated into polysaccharide nanoparticles (GdDOTA?NPs) exhibited high relaxivity (r(1) =101.7?s(-1) mM(-1) per Gd(3+) ion at 37?°C and 20?MHz). This high relaxation rate is due to efficient Gd loading, reduced tumbling of the Gd complex, and the hydrogel nature of the nanoparticles. The efficacy of the nanoparticles as a T(1) /T(2) dual-mode contrast agent was studied in C6 cells.     

Magnetohydrodynamic thermochemotherapy and MRI of mouse tumors

A dextran-ferrite magnetic fluid was successfully tested as magnetic resonance imaging (MRI) contrast agent. The same magnetic fluid was then combined with Melphalan, a chemotherapeutic drug, and used for magnetohydrodynamic thermochemotherapy of different tumors. The placement of the tumors in an AC magnetic field led to hyperthermia at 46 °C for 30 min. In combination with tumor slime aspiration, a 30% regression of ∼130 mm³ non-metastatic P388 tumors in BDF₁ mice was reached, together with a life span increase of 290%. The same procedure associated with cyclophosphamide treatment of ∼500 mm³ metastases tumor increased the animal's life span by 180%.     

Synthesis of 2,5‐Disubstituted Derivatives of Pyrano[2,3‐d][1,3]thiazines via the Interaction of 2‐Substituted 4‐Hydroxy‐6H‐1,3‐thiazine‐6‐ones with Aldehydes

A new and efficient route for the synthesis of derivatives of the poorly investigated pyrano[2,3‐d][1,3]thiazine heterocyclic system is disclosed. These compounds were prepared via annulation of 2‐aryl‐4‐hydroxy‐6H‐1,3‐thiazine‐6‐ones with aliphatic and aromatic aldehydes in the presence of pyridine. The method is general and versatile, and the interaction is independent on the nature of the aldehyde, the only exceptions being formaldehyde and salicylaldehydes.     

Biocompatible nanoparticles and gadolinium complexes for MRI applications

Performances of double-emulsion techniques (W/O/W and W/O/O) and ionotropic gelation process were compared to achieve encapsulation of gadolinium MRI contrast agents (GdCAs) into biocompatible polymeric nanoparticles (NPs) with high Gd-loadings. The better approach proved to be ionotropic gelation with H[Gd(DOTA)] as GdCA. Relaxometry evaluation of H[Gd(DOTA)]?NPs efficiency demonstrated that incorporation of H[Gd(DOTA)] inside an hydrogel matrix highly improved H[Gd(DOTA)] relaxivity. Particle efficacy as MR contrast agents was further demonstrated on a 3 T clinical imager: a significant improvement of T₁- and T₂- MR signals was obtained at doses much lower than the currently used.