Global Aspects of Age-Structured Cigarette Smoking Model

Smoking impacts health and as a result creates several problems related to age which means smoking has a strong correlation with age. Keeping this problem in view, we consider the global asymptotic properties of age-structured smoking model. First, we formulate the model and present the existence and uniqueness of solution. Then we discuss the equilibrium points and construct the Lyapunov function to examine global stability of the free smoking and positive smoking equilibrium points. Finally, we fixed the age factor and use the non-standard finite difference (NSFD) scheme for numerical solutions and compare our results obtained with RK4 and ODE45 graphically with the help of MATLAB.     

On an analogue of Selberg's eigenvalue conjecture for

Let be the homogeneous space associated to the group
. Let where and consider the first nontrivial eigenvalue of the Laplacian on . Using geometric considerations, we prove the inequality . Since the continuous spectrum is represented by the band , our bound on can be viewed as an analogue of Selberg's eigenvalue conjecture for quotients of the hyperbolic half space.

     

Flow injection colorimetric method for the assay of vitamin C in drug formulations using tris,1-10-phenanthroline-iron(III) complex as an oxidant in sulfuric acid media

A simple, fast and accurate colorimetric flow injection (FI) method suitable for the assay of vitamin C in drug formulations was proposed. In the method, vitamin C was injected into a flowing stream of iron(III) and then mixed with 1,10-phenanthroline in 0.05M sulphuric acid media. The mixture was allowed to react in a 45-cm long coil and the resulting solution of tris, 1-10-phenanthroline-iron(II) complex was monitored at 510 nm. The method was adopted by fully investigating the kinetics of the reaction and proposing a suitable mechanism. A throughput of 100 samples per hour was achieved with a relative standard deviation of 0.88% for vitamin C concentration range of 100-400 ppm.     

On Line Determination of Perphenazine Using Flow Injection Analysis

An accurate specific flow injection spectrophotometric method for the determination of perphenazine in the range 50-250 ppm is introduced. In the method, 110 μl of the drug is injected through a stream of 0.2% (w/v) potassium dichromate in 0.25 M sulfuric acid flowing on line as a carrier stream. The drug is oxidized on the flow to the red monocation radical, the peak absorbance of which is monitored at 525 nm. A throughput of up to 300 samples per hour is attained. The mechanism of the reaction is suggested and the method is compared with the United States Pharmacopeia method.     

Preparation and properties of poly(urethane-imide)s derived from amine-blocked-polyurethane prepolymer and pyromellitic dianhydride

Poly(urethane-imide)s were prepared using amine-blocked-polyurethane (PU) prepolymer and pyromellitic dianhydride. The PU prepolymers were prepared by the reaction of different diols (polypropyleneoxy glycol, polytetramethyleneoxy glycol, polycaprolactonediol and hydroxyl terminated polybutadiene) and different diisocyanates (2,4-tolylene diisocyanate, 1,4-phenelene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate and 4,4^′-methylenebis(cyclohexyl)isocyanate) and end capped with N-methylaniline. The polymerization was faster with aromatic isocyanates than with aliphatic isocyanates. The effect of imide content on the thermal and mechanical properties was studied. The poly(urethane-imide)s were characterized by FTIR, GPC, TGA and for dynamic and static mechanical properties. Weight average molecular weight (M_w) of the polymers did not vary significantly with change in -NCO/-OH ratio where as number average molecular weight (M_n) increased with increasing -NCO/-OH ratio, correspondingly, the dispersity (PD) decreased. Polymers with higher hard segment content exhibited higher glass transition temperature. The thermal stability of the PU was found to increase significantly by the introduction of imide component.     

Synthesis and properties of aromatic secondary amine-blocked isocyanates

N-Methylaniline-, diphenylamine-, and N-phenylnaphthylamine-blocked toluene diisocyanates (TDI) were prepared and characterized by IR, NMR spectroscopy, and nitrogen content analyses. The structure–property relationship of these adducts was established by reacting with hydroxyl-terminated polybutadiene (HTPB). The cure rate of the adduct increases from the N-phenylnaphthylamine- to diphenylamine- and to N-methylaniline-blocked TDI adduct. Simultaneous TGA/DTA results also confirm this trend, and the thermal stability of the adduct decreases in the following order: N-phenylnaphthylamine–TDI > diphenylamine–TDI > N-methylaniline–TDI. The gas chromatogram of the amine-blocked isocyanate confirms that the thermolysis products are the blocking agent and isocyanate. The solubilities of the adducts were carried out in polyether, polyester, and hydrocarbon polyols, and it was found that the N-methylaniline–TDI adduct shows higher solubility than the rest and also found that the polyester polyol shows higher solvating power against the adducts than the polyether and hydrocarbon polyols. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1815–1821, 1999     

Simultaneous Determination of Caffeine and Paracetamol in Commercial Formulations Using Greener Normal-Phase and Reversed-Phase HPTLC Methods: A Contrast of Validation Parameters

There has been no assessment of the greenness of the described analytical techniques for the simultaneous determination (SMD) of caffeine and paracetamol. As a result, in comparison to the greener normal-phase high-performance thin-layer chromatography (HPTLC) technique, this research was conducted to develop a rapid, sensitive, and greener reversed-phase HPTLC approach for the SMD of caffeine and paracetamol in commercial formulations. The greenness of both techniques was calculated using the AGREE method. For the SMD of caffeine and paracetamol, the greener normal-phase and reversed-phase HPTLC methods were linear in the 50–500 ng/band and 25–800 ng/band ranges, respectively. For the SMD of caffeine and paracetamol, the greener reversed-phase HPTLC approach was more sensitive, accurate, precise, and robust than the greener normal-phase HPTLC technique. For the SMD of caffeine paracetamol in commercial PANEXT and SAFEXT tablets, the greener reversed-phase HPTLC technique was superior to the greener normal-phase HPTLC approach. The AGREE scores for the greener normal-phase and reversed-phase HPTLC approaches were estimated as 0.81 and 0.83, respectively, indicated excellent greenness profiles for both analytical approaches. The greener reversed-phase HPTLC approach is judged superior to the greener normal-phase HPTLC approach based on numerous validation parameters and pharmaceutical assays.     

Smart Nanocarriers as an Emerging Platform for Cancer Therapy: A Review

Cancer is a group of disorders characterized by uncontrolled cell growth that affects around 11 million people each year globally. Nanocarrier-based systems are extensively used in cancer imaging, diagnostics as well as therapeutics; owing to their promising features and potential to augment therapeutic efficacy. The focal point of research remains to develop new-fangled smart nanocarriers that can selectively respond to cancer-specific conditions and deliver medications to target cells efficiently. Nanocarriers deliver loaded therapeutic cargos to the tumour site either in a passive or active mode, with the least drug elimination from the drug delivery systems. This review chiefly focuses on current advances allied to smart nanocarriers such as dendrimers, liposomes, mesoporous silica nanoparticles, quantum dots, micelles, superparamagnetic iron-oxide nanoparticles, gold nanoparticles and carbon nanotubes, to list a few. Exhaustive discussion on crucial topics like drug targeting, surface decorated smart-nanocarriers and stimuli-responsive cancer nanotherapeutics responding to temperature, enzyme, pH and redox stimuli have been covered.