Analysis of a system of fractional differential equations

We prove existence and uniqueness theorems for the initial value problem for the system of fractional differential equations , where D^α denotes standard Riemann-Liouville fractional derivative, 0<α<1, and A is a square matrix. The unique solution to this initial value problem turns out to be , where E_α denotes the Mittag-Leffler function generalized for matrix arguments. Further we analyze the system , , 0<α<1, and investigate dependence of the solutions on the initial conditions.     

Exosomes as New Generation Vehicles for Drug Delivery: Biomedical Applications and Future Perspectives

Currently, particular interest among the scientific community is focused on exploring the use of exosomes for several pharmaceutical and biomedical applications. This is due to the identification of the role of exosomes as an excellent intercellular communicator by delivering the requisite cargo comprising of functional proteins, metabolites and nucleic acids. Exosomes are the smallest extracellular vesicles (EV) with sizes ranging from 30–100 nm and are derived from endosomes. Exosomes have similar surface morphology to cells and act as a signal transduction channel between cells. They encompass different biomolecules, such as proteins, nucleic acids and lipids, thus rendering them naturally as an attractive drug delivery vehicle. Like the other advanced drug delivery systems, such as polymeric nanoparticles and liposomes to encapsulate drug substances, exosomes also gained much attention in enhancing therapeutic activity. Exosomes present many advantages, such as compatibility with living tissues, low toxicity, extended blood circulation, capability to pass contents from one cell to another, non-immunogenic and special targeting of various cells, making them an excellent therapeutic carrier. Exosome-based molecules for drug delivery are still in the early stages of research and clinical trials. The problems and clinical transition issues related to exosome-based drugs need to be overcome using advanced tools for better understanding and systemic evaluation of exosomes. In this current review, we summarize the most up-to-date knowledge about the complex biological journey of exosomes from biogenesis and secretion, isolation techniques, characterization, loading methods, pharmaceutical and therapeutic applications, challenges and future perspectives of exosomes.     

A highly efficient TEMPO mediated oxidation of sugar primary alcohols into uronic acids using 1-chloro-1,2-benziodoxol-3(1H)-one at room temperature

Oxidation of various sugar primary alcohols into corresponding uronic acids was demonstrated using 1-chloro-1,2-benziodoxol-3(1H)-one and TEMPO. The reaction proceeds at room temperature in good to excellent yields. Primary alcohols get oxidized selectively over the secondary alcohols under mild reaction conditions.     

Investigation of liquid–solids fluidized bed of different particle size through radioactive particle tracking techniques

Radioactive particle tracking technique (RPT) has proven to be a powerful and versatile technique both in terms of the richness of information it provides as well as the variety of multiphase flow situations it has been successfully employed. This work reports the execution of RPT technique for investigation of liquid–solids fluidized bed of different particle sizes (1.2 and 0.6 mm). Experiments are performed in a 10 cm ID cylindrical column for different liquid velocities. Further, RPT experiments are performed for both the solids and effect of liquid velocity and particle size on flow behaviour of liquid–solid fluidized bed is quantified.     

Uptake of 3H-cAMP by retinal pigment epithelium isolated from bluegill sunfish (Lepomis macrochirus)

Background  

In bluegill sunfish, the melanin-containing pigment granules of the retinal pigment epithelium undergo cyclic movements in response both to ambient lighting and circadian cues. Pigment granules aggregate into the cell body at night (in the dark), and disperse into apical processes during the day (in the light). Regulation of pigment granule aggregation in a number of fishes depends on modulating the intracellular levels of cyclic adenosine monophosphate.     

Synthesis,characterization, and insecticidal activity of new tin (IV) complexes

A three-component reaction of dimethyltin dibromide with imidazo[1,2-a]pyridine, pyridine derivatives, or isoquinoline and allyl bromide in refluxing ethanol affords the ionic complex, bis(1-allylcycloiminium) dimethyltetrabromostannate (II). The reaction involves N-allylation of cycloimine accompanied by the coordination of two bromide ions with the tin atom of dimethyltin dibromide. The complexes have been characterized by infrared and ¹H NMR, ¹³C NMR, and ¹¹⁹Sn NMR studies. The X-ray crystal structure analysis of a complex reveals the tin atom to be hexacoordinated and the dimethyltetrabromostannate (II) anion having octahedral geometry. Some of the complexes tested for their insecticidal activity are found to exhibit strong activity against Tribolium castaneum insect with LC₅₀ ranging from 0.4 to 0.8 ppm.     

Doping and Surface Modification of Carbon Quantum Dots for Enhanced Functionalities and Related Applications

Carbon quantum dots (CQDs) are a unique class of 0D nanomaterials, featured by a graphitic core and shell layers saturated with hydrogen atoms and functional groups. CQDs are prepared through top-down and bottom-up strategies from natural and synthetic precursors. CQDs can be modified through chemical (e.g., surface functionalization/passivation, doping, etc.) and physical (e.g., core–shell architecture, composite material blending, etc.) strategies to control their properties. This review highlights the effect of such modifications on the photophysical properties of CQDs, such as photoluminescence (PL), absorbance, and relaxivity. The dependence of PL upon the size, orientation at the edges, surface and edge functionalization, doping, excitation wavelength, concentration, pH, aggregate formation, etc., are summarized along with the supporting theoretical evidence available in the literature. Also, this review outlines the recent advancements, and future prospective of optical (e.g., sensing, bioimaging, and fluorescent ink) and catalytic applications (e.g., photocatalysis and electrocatalysis) of CQDs enhanced through physical and chemical modifications of their structure and composition.     

Conformational Analysis of Longifolene

We describe the stable conformation of the tricyclic sesquiterpenoid, longifolene, by experimental NMR data and molecular mechanics calculations of the coupling constants. The flexible seven-membered ring of longifolene adopts a twist-chair conformation. Analysis of the coupling constants, particularly of the methylene protons in the cycloheptane ring moiety, agrees with this low-energy conformation. Low-temperature NMR experiments and nuclear Overhauser effect measurements indicate that there is a single exchange-averaged NMR spectrum that has the highest population of the most stable conformer.     

Pyrimidin‐/thiazol‐/thiazolin‐ylidenamidothiophosphoric dichlorides

Nine new amidodichlorothiophosphorus(V) derivatives incorporating pyrimidine, thiazole, and thiazoline rings were obtained by sulfurization of the corresponding aminodichlorophosphines generated in situ from the reaction of the respective N‐alkyl‐2‐aminocycloiminium halide with PCl₃ in the presence of triethylamine. These pyrimidin‐/thiazol‐/thiazolin‐ylidenamidothiophosphoric dichlorides were isolated as stable crystalline solids and are well characterized by elemental analysis, NMR, and mass spectroscopy. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:498–502, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10170     

XPS study of the exchange-splitting in the s-levels of Mn and R in RMn2Si2 (R = La to Nd,Sm and Gd)

Exchange (or multiplet) splitting, ΔE_s of the 3s core-level of Mn in RMn₂Si₂ (R = La to Nd, Sm and Gd) has been observed using XPS technique. The measured value of ΔE_s is used to determine the magnetic moment on Mn ion in RMn₂Si₂. ΔE_s has also been measured for the 4s and 5s levels of R in RMn₂Si₂ and it is found that the value of ΔE_s increases with increase in the number of unpaired spins (La to Gd).