Development and analysis of a malaria transmission mathematical model with seasonal mosquito life-history traits

In this paper, we develop and analyze a malaria model with seasonality of mosquito life-history traits: periodic-mosquitoes per capita birth rate, -mosquitoes death rate, -probability of mosquito to human disease transmission, -probability of human to mosquito disease transmission, and -mosquitoes biting rate. All these parameters are assumed to be time dependent leading to a nonautonomous differential equation system. We provide a global analysis of the model depending on two threshold parameters and (with ). When , then the disease-free stationary state is locally asymptotically stable. In the presence of the human disease-induced mortality, the global stability of the disease-free stationary state is guarantied when . On the contrary, if , the disease persists in the host population in the long term and the model admits at least one positive periodic solution. Moreover, by a numerical simulation, we show that a sub-critical (backward) bifurcation is possible at . Finally, the simulation results are in accordance with the seasonal variation of the reported cases of a malaria-epidemic region in Mpumalanga province in South Africa.     

Influence of the SiO thickness on the photoluminescence properties of Er-doped SiO/SiO2 multilayers

Er-doped SiO single layer and Er-doped SiO/SiO₂ multilayers with different SiO thicknesses were prepared by evaporation. In the as-deposited samples, the erbium ions exhibit a very weak photoluminescence emission at 1.54 μm. This luminescence is strongly enhanced after annealing treatments between 500 and 1050 °C, with an optimal annealing temperature which is dependent from the SiO thickness. For the SiO single layer, this optimal temperature is around 700 °C while it is shifted at highest temperature for the multilayers. The origin of the higher luminescence intensity in the SiO layer is also discussed.     

Using synchrotron radiation inline phase‐contrast imaging computed tomography to visualize three‐dimensional printed hybrid constructs for cartilage tissue engineering

Synchrotron radiation inline phase‐contrast imaging combined with computed tomography (SR‐inline‐PCI‐CT) offers great potential for non‐invasive characterization and three‐dimensional visualization of fine features in weakly absorbing materials and tissues. For cartilage tissue engineering, the biomaterials and any associated cartilage extracellular matrix (ECM) that is secreted over time are difficult to image using conventional absorption‐based imaging techniques. For example, three‐dimensional printed polycaprolactone (PCL)/alginate/cell hybrid constructs have low, but different, refractive indices and thicknesses. This paper presents a study on the optimization and utilization of inline‐PCI‐CT for visualizing the components of three‐dimensional printed PCL/alginate/cell hybrid constructs for cartilage tissue engineering. First, histological analysis using Alcian blue staining and immunofluorescent staining assessed the secretion of sulfated glycosaminoglycan (GAGs) and collagen type II (Col2) in the cell‐laden hybrid constructs over time. Second, optimization of inline PCI‐CT was performed by investigating three sample‐to‐detector distances (SDD): 0.25, 1 and 3 m. Then, the optimal SDD was utilized to visualize structural changes in the constructs over a 42‐day culture period. The results showed that there was progressive secretion of cartilage‐specific ECM by ATDC5 cells in the hybrid constructs over time. An SDD of 3 m provided edge‐enhancement fringes that enabled simultaneous visualization of all components of hybrid constructs in aqueous solution. Structural changes that might reflect formation of ECM also were evident in SR‐inline‐PCI‐CT images. Summarily, SR‐inline‐PCI‐CT images captured at the optimized SDD enables visualization of the different components in hybrid cartilage constructs over a 42‐day culture period.     

Why pinning by surface irregularities can explain the peak effect in transport properties and neutron diffraction results in NbSe2 and Bi- 2212 crystals?

The existence of a peak effect in transport properties (a maximum of the critical current as function of magnetic field) is a well-known but still intriguing feature of Type II superconductors such as NbSe₂ and Bi-2212. Using a model of pinning by surface irregularities in anisotropic superconductors, we have developed a calculation of the critical current which allows estimating quantitatively the critical current in both the high critical current phase and the low critical current phase. The only adjustable parameter of this model is the angle of the vortices at the surface. The agreement between the measurements and the model is really very impressive. In this framework, the anomalous dynamical properties close to the peak effect is due to coexistence of two different vortex states with different critical currents. Recent neutron diffraction data in NbSe₂ crystals in the presence of transport current support this point of view.     

High throughput discovery of heteroaromatic-modifying enzymes allows enhancement of novobiocin selectivity

Glycosylated analogues of novobiocin, discovered using a broad library of enzymes, have 100-fold improved activity against breast, brain, pancreatic, lung and ovarian cancers and ablated associated off-target activity leading to an up to 2.7 × 10(4) fold increase in selectivity.     

Synthesis of anisotropic PbS nanoparticles using heterocyclic dithiocarbamate complexes

We report the synthesis of lead piperidine and lead tetrahydroquinoline dithiocarbamate (DTC) complexes and their use as single source precursors for the preparation of anisotropic PbS nanoparticles. The complexes were thermolysed in coordinating solvents such hexadecylamime (HDA), tri-n-octylphosphine oxide (TOPO), oleylamine (OA) and decylamine (DA) at various reaction temperatures. The variation of the reaction conditions and precursors produced PbS particles with shapes ranging from spheres to cubes and rods. The size of the particles is generally larger than those synthesized by conventional precursor routes. The electron microscopy and X-ray diffraction data confirm the particles to be very crystalline with the dominant cubic rock salt phase present in all samples.     

Functional Characterization of Mung Bean Meal Protein-Derived Antioxidant Peptides

The aim of this work was to characterize the antioxidant properties of some of the peptides present in bromelain mung bean meal protein hydrolysate (MMPH). The MMPH was subjected to two rounds of bioassay-guided reversed-phase HPLC separation followed by peptide identification in the most potent fractions using tandem mass spectrometry. Twelve antioxidant peptides, namely, HC, CGN, LAN, CTN, LAF, CSGD, MMGW, QFAAD, ERF, EYW, FLQL, and QFAW were identified and assayed for antioxidant properties. CTN, HC, CGN, and CSGD were the most potent (p < 0.05) DPPH radical scavengers with EC₅₀ values of 0.30, 0.29, 0.28, and 0.30 mg/mL, respectively, which are lower than the 0.03 mg/mL obtained for reduced glutathione (GSH). CTN, HC, CGN, and CSGD exhibited the most potent (p < 0.05) scavenging activities against hydroxyl and superoxide radicals with EC₅₀ values that are similar to those of GSH. The cysteine-containing peptides also had stronger ferric reducing antioxidant power and metal chelation activity than peptides devoid of cysteine. In contrast, MMGW, ERF, and EYW had poor radical scavenging and metal chelation activities. We conclude that the availability of the sulfhydryl group may have enhanced antioxidant potency while the presence of bulky groups such phenylalanine and tryptophan had an opposite effect.     

Development and validation of a liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) method for the quantification of tigecycline in rat brain tissues

Tigecycline (TIG), a derivative of minocycline, is the first in the novel class of glycylcyclines and is currently indicated for the treatment of complicated skin structure and intra‐abdominal infections. A selective, accurate and reversed‐phase high‐performance liquid chromatography‐tandem mass spectrometry (HPLC‐MS/MS) method was developed for the determination of TIG in rat brain tissues. Sample preparation was based on protein precipitation and solid phase extraction using Supel‐Select HLB (30 mg/1 mL) cartridges. The samples were separated on a YMC Triart C₁₈ column (150 mm x 3.0 mm. 3.0 µm) using gradient elution. Positive electrospray ionization (ESI+) was used for the detection mechanism with the multiple reaction monitoring (MRM) mode. The method was validated over the concentration range of 150–1200 ng/mL for rat brain tissue. The precision and accuracy for all brain analyses were within the acceptable limit. The mean extraction recovery in rat brain was 83.6%. This validated method was successfully applied to a pharmacokinetic study in female Sprague Dawley rats, which were given a dose of 25 mg/kg TIG intraperitoneally at various time‐points. Copyright © 2015 John Wiley & Sons, Ltd.