Spectrum of a linear fourth‐order differential operator and its applications

In this paper, we apply the disconjugacy theory and Elias's spectrum theory to study the positivity and the spectrum structure of the linear operator coupled with the clamped beam boundary conditions (1.2). We also study the positivity and the spectrum structure of the more general operator coupled with (1.2). As the applications of our results on positivity and spectrum of fourth‐order linear differential operators, we show the existence of nodal solutions for the corresponding nonlinear problems via Rabinowitz's global bifurcation theorem.     

On the class of positive almost weak Dunford–Pettis operators

We introduce and study the class of almost weak Dunford–Pettis operators and we derive the following interesting consequence: other characterizations of the weak Dunford–Pettis property. After that we characterize pairs of Banach lattices for which the adjoint of almost weak Dunford–Pettis operator is almost Dunford–Pettis. Finally, we establish a necessary and sufficient conditions on the pair of Banach lattices E and F which guarantees that if T : E → F is a positive almost weak Dunford–Pettis then T is almost Dunford–Pettis.     

Synthesis of modified peptidoglycan precursor analogues for the inhibition of glycosyltransferase

The peptidoglycan glycosyltransferases (GTs) are essential enzymes that catalyze the polymerization of glycan chains of the bacterial cell wall from lipid II and thus constitute a validated antibacterial target. Their enzymatic cavity is composed of a donor site for the growing glycan chain (where the inhibitor moenomycin binds) and an acceptor site for lipid II substrate. In order to find lead inhibitors able to fill this large active site, we have synthesized a series of substrate analogues of lipid I and lipid II with variations in the lipid, the pyrophosphate, and the peptide moieties and evaluated their biological effect on the GT activity of E. coli PBP1b and their antibacterial potential. We found several compounds able to inhibit the GT activity in vitro and cause growth defect in Bacillus subtilis . The more active was C16-phosphoglycerate-MurNAc-(L-Ala-D-Glu)-GlcNAc, which also showed antibacterial activity. These molecules are promising leads for the design of new antibacterial GT inhibitors.     

Integrated 3D-QSAR,molecular docking,and molecular dynamics simulation studies on 1,2,3-triazole based derivatives for designing new acetylcholinesterase inhibitors

Alzheimer’s disease (AD) is a multifactorial and polygenic disease. It is the most prevalent reason for dementia in the aging population. A dataset of twenty-six 1,2,3-triazole-based derivatives previously synthetized and evaluated for acetylcholinesterase inhibitory activity were subjected to the three-dimensional quantitative structure-activity relationship (3D-QSAR) study. Good predictability was achieved for comparative molecular field analysis (CoMFA) (Q² = 0.604, R² = 0.863, r_ext² = 0.701) and comparative molecular similarity indices analysis (CoMSIA) (Q² = 0.606, R² = 0.854, r_ext² = 0.647). The molecular features characteristics provided by the 3D-QSAR contour plots were quite useful for designing and improving the activity of acetylcholinesterase of this class. Based on these findings, a new series of 1,2,3-triazole based derivatives were designed, among which compound A1 with the highest predictive activity was subjected to detailed molecular docking and compared to the most active compound. The selected compounds were further subjected to 20 ns molecular dynamics (MD) simulations to study the comparative conformation dynamics of the protein after ligand binding, revealing promising results for the designed molecule. Therefore, this study could provide worthy guidance for further experimental analysis of highly effective acetylcholinesterase inhibitors.     

Translation surfaces in the 3-dimensional space satisfying Δ III r i = μ i r i

In this paper we study the translation surfaces in the 3-dimensional Euclidean and Lorentz-Minkowski space under the condition ${\Delta ^{III}r_{i} = \mu _{i}r_{i},\mu _{i} \in \mathbb{R}}$ , where Δ ^III denotes the Laplacian of the surface with respect to the third fundamental form III. We show that in both spaces a translation surface satisfying the preceding relation is a surface of Scherk.     

Porous Polysaccharide‐Based Scaffolds for Human Endothelial Progenitor Cells

Human ECFCs contribute to vascular repair. For this reason, they are considered as valuable cell therapy products in ischemic diseases. Porous scaffolds are prepared that are composed of natural polysaccharides, pullulan and dextran, by chemical crosslinking without use of organic solvents. These porous scaffolds, which have pores with an average size of 42 µm and a porosity of 21%, preserve the viability and the proliferation of cord‐blood ECFCs. After 7 d of culture in porous scaffolds, ECFCs express endothelial markers (CD31 and vWf) and maintain endothelial functions. The cultured cells can be easily retrieved by enzymatic degradation of the porous scaffolds. In vitro results suggest that the porous scaffold could allow cell delivery of ECFCs for treatment of vascular diseases.

     

A Novel Method for Inhalation Control of Workplace Anthropogenic Pollutant Particles

This in vitro study investigated electrically charging effect on the deposition of inhaled workplace anthropogenic pollutant particles (APP) in a hollow throat cast model. Many occupational lung diseases are associated with exposure to workplace dust particles and other pollutants. Since the human throat is an effective filter, this study devised a novel idea of charging particles, and studying their deposition in the throat. Simulated workplace aerosol particles were generated from a commercially available nebulizer, and charged by a corona charger. Charged and uncharged particles were allowed to pass through a polyester resin cast of cadaver based throat, a replicate of a human oropharyngeal region. The aerosol particles' size and charge distribution were characterized by an Electronic Single Particle Aerodynamic Relaxation Time (ESPART) analyzer before and after passing the throat cast. The ESPART operates on the principle of Laser Doppler Velocimetry to measure simultaneously aerodynamic diameter and electrostatic charge on a single particle basis and in real time. The study results revealed that electrically charging increased agglomeration of smaller particles and increased deposition. Deposition of charged particles increased with increasing particle size which can be explained as the effect of inertial impaction.     

A new megastigmane glycoside, phoenixoside A, from Phoenix dactylifera

A new megastigmane glycoside, phoenixoside A (1), has been isolated from the n-butanol--soluble fraction of seeds of Phoenix dactylifera. The structure was characterized as (6S,7Z,9R)-hydroxy-3-oxo-ionol-9-O-beta-D-glucopyranosyl-(1" --> 6')-beta-D-glucopyranoside on the basis of 1D and 2D NMR spectroscopy, high-resolution mass spectrometry, and CD spectroscopy.     

A flux-limiter method for dam-break flows over erodible sediment beds

Finite volume methods for dam-break flows over erodible sediment beds require a monotone numerical flux. In the present study we present a new flux-limiter scheme based on the Lax–Wendroff method coupled with a non-homogeneous Riemann solver and a flux limiter function. The non-homogeneous Riemann solver consists of a predictor stage for the discretization of gradient terms and a corrector stage for the treatment of source terms. The proposed method satisfy the conservation property such that the discretization of the flux gradients and the source terms are well-balanced in the numerical solution of suspended sediment models. The flux-limiter method provides accurate results avoiding numerical oscillations and numerical dissipation in the approximated solutions. Several standard test examples are considered to verify the performance and the accuracy of the proposed method.     

A tutorial on the deterministic Impulse Control Maximum Principle: Necessary and sufficient optimality conditions

This paper considers a class of optimal control problems that allows jumps in the state variable. We present the necessary optimality conditions of the Impulse Control Maximum Principle based on the current value formulation. By reviewing the existing impulse control models in the literature, we point out that meaningful problems do not satisfy the sufficiency conditions. In particular, such problems either have a concave cost function, contain a fixed cost, or have a control-state interaction, which have in common that they each violate the concavity hypotheses used in the sufficiency theorem. The implication is that the corresponding problem in principle has multiple solutions that satisfy the necessary optimality conditions. Moreover, we argue that problems with fixed cost do not satisfy the conditions under which the necessary optimality conditions can be applied. However, we design a transformation, which ensures that the application of the Impulse Control Maximum Principle still provides the optimal solution. Finally, we show for the first time that for some existing models in the literature no optimal solution exists.