Synthesis and characterization of nanomagnetite particles and their polymer coated forms

Superparamagnetic nanoparticles were prepared by coprecipitation of ferrous (Fe(2+)) and ferric (Fe(3+)) aqueous solution by a base. Nanomagnetite particles were coated with poly(St/PEG-EEM/DMAPM) and poly(St/PEG-MA/DMAPM) layer by emulsifier-free emulsion polymerization. Chemical structure of nanoparticles was characterized by both FTIR and (1)H NMR. Particle morphologies were determined by Zeta Sizer, DLS, XRD and SAXS. Structural analysis showed that after polymer coating nanomagnetite particles kept their superparamagnetic property. Besides the synthesized magnetites, polymer coated forms of these particles are more biocompatible, well dispersable and uniform. These properties make them a very strong candidate for bioengineering applications, such as bioseparation, gene transfer.     

Hierarchically Structured Magnetic Nanoconstructs with Enhanced Relaxivity and Cooperative Tumor Accumulation

Iron oxide nanoparticles are formidable multifunctional systems capable of contrast enhancement in magnetic resonance imaging, guidance under remote fields, heat generation, and biodegradation. Yet, this potential is underutilized in that each function manifests at different nanoparticle sizes. Here, sub‐micrometer discoidal magnetic nanoconstructs are realized by confining 5 nm ultra‐small super‐paramagnetic iron oxide nanoparticles (USPIOs) within two different mesoporous structures, made out of silicon and polymers. These nanoconstructs exhibit transversal relaxivities up to ≈10 times (r ₂ ≈ 835 mm ^?1 s^?1) higher than conventional USPIOs and, under external magnetic fields, collectively cooperate to amplify tumor accumulation. The boost in r ₂ relaxivity arises from the formation of mesoscopic USPIO clusters within the porous matrix, inducing a local reduction in water molecule mobility as demonstrated via molecular dynamics simulations. The cooperative accumulation under static magnetic field derives from the large amount of iron that can be loaded per nanoconstuct (up to ≈65 fg) and the consequential generation of significant inter‐particle magnetic dipole interactions. In tumor bearing mice, the silicon‐based nanoconstructs provide MRI contrast enhancement at much smaller doses of iron (≈0.5 mg of Fe kg^?1 animal) as compared to current practice.     

Kinetics of coupling of diazotized sulfanilamid with 1-naphthylamine

In this study, the coupling kinetics of sulfanilamid diazonium salt with 1-naphthylamine has been studied by spectrophotometric method. In the experiments conducted at constant temperature, 25°C, pH has been varied between 2.2?3.4, reactant concentration between 1.25 × 10^?5 ? 5 × 10^?5 M, and ionic strength between 0.1?1 M. The reaction has been confirmed to be of second-order and rate constants and the dissociation constant of 1-naphthylamine have been calculated. © 1993 John Wiley & Sons, Inc.     

Characterizing student mathematics teachers’ levels of understanding in spherical geometry

This article presents an exploratory study aimed at the identification of students’ levels of understanding in spherical geometry as van Hiele did for Euclidean geometry. To do this, we developed and implemented a spherical geometry course for student mathematics teachers. Six structured, task-based interviews were held with eight student mathematics teachers at particular times through the course to determine the spherical geometry learning levels. After identifying the properties of spherical geometry levels, we developed Understandings in Spherical Geometry Test to test whether or not the levels form hierarchy, and 58 student mathematics teachers took the test. The outcomes seemed to support our theoretical perspective that there are some understanding levels in spherical geometry that progress through a hierarchical order as van Hiele levels in Euclidean geometry.     

Constrained metric variations and emergent equilibrium surfaces

Any surface is completely characterized by a metric and a symmetric tensor satisfying the Gauss–Codazzi–Mainardi equations (GCM), which identifies the latter as its curvature. We demonstrate that physical questions relating to a surface described by any Hamiltonian involving only surface degrees of freedom can be phrased completely in terms of these tensors without explicit reference to the ambient space: the surface is an emergent entity. Lagrange multipliers are introduced to impose GCM as constraints on these variables and equations describing stationary surface states derived. The behavior of these multipliers is explored for minimal surfaces, showing how their singularities correlate with surface instabilities.     

Nepetanudone, a dimer of the α-pyrone 5,9-dehydronepetalactone

The title compound C₂₀H₂₄O₄ crystallizes in the orthorhombic space group P2₁2₁2, with a = 10.245(3), b = 17.103(3), c = 9.879(3) Å, D _c = 1.260 g cm ^–3, and Z = 4. Nepetanudone is postulated to be formed by a [4+4] cycloaddition of two 5,9-dehydronepetalactone moieties to give an asymmetric dimer in which each pair of atoms is magnetically nonequivalent. The compound was recovered from extracts of Nepeta nuda ssp. albiflora.     

Tricetin 4′-<Emphasis Type="Italic">O-α</Emphasis>-L-rhamnopyranoside: A new flavonoid from the aerial parts of <Emphasis Type="Italic">Erica arborea</Emphasis>

Reversed-phase preparative HPLC purification of the methanol (MeOH) extract of the aerial parts of Erica arborea resulted in the isolation of a new flavonoid glycoside, tricetin 4′-O-α-L-rhamnopyranoside, together with the known flavonoid, isorhamnetin 3-O-α-L-rhamnopyranoside. The structures of these compounds were determined by spectroscopic means. The antioxidant properties of these compounds were assessed by the DPPH assay. Published in Khimiya Prirodnykh Soedinenii, No. 2, pp. 138–140, March–April, 2008.     

Physics and applications of photonic crystals

In this article, we investigate how the photonic band gaps and the variety of band dispersions of photonic crystals can be utilized for various applications and how they further give rise to completely novel optical phenomena. The enhancement of spontaneous emission through coupled cavity waveguides in a one-dimensional silicon nitride photonic microcrystal is investigated. We then present the highly directive radiation from sources embedded in two-dimensional photonic crystals. The manifestation of novel and intriguing optical properties of photonic crystals are exemplified experimentally by the negative refraction and the focusing of electromagnetic waves through a photonic crystal slab with subwavelength resolution.     

Impact of non-ideal transport modeling on supercritical flow simulation

The simulation of a supercritical fluid flow requires sophisticated models for real gas thermodynamic and non-ideal phenomena. They both are presently addressed through the simulation of a non-reacting and reacting high pressure H₂/O₂ splitter-plate configuration. In particular, the diffusion velocity of species is evaluated through the gradient of chemical potential (${\mathbf{d}}_l^{\text{NI}}=X_l{\left(?{\mu }_l\right)}_T$) expressed with the Peng–Robinson equation of state, or with the classical low-pressure approach ${\mathbf{d}}_l^{\mathrm{I}}=?X_l,$ which only uses the gradient of the lth species molar fraction, X_l. In addition, the high pressure binary diffusion coefficients are estimated by the correction of Kurochkin et al. or with the Takahashi approach. The results for the non-reaction case are consistent with the literature for mean and rms values using ${\mathbf{d}}_l^{\mathrm{I}}$. The use of ${\mathbf{d}}_l^{\text{NI}}$ has a limited impact but the temperature profiles become steeper. In the reactive case, the two approaches lead to a difference of 50 K on the average temperature just downstream of the injector and about 100 K further downstream. A non-ideal transport is then required for the modeling of supercritical flow simulation.     

Computer aided frequency planning for the radio and TV broadcasts

The frequency planning of the VHF and UHF broadcasts in Turkey is described. This planning is done with the aid of computer databases and digital terrain map. The frequency offset is applied whenever applicable to increase the channel capacity. The offset assignment is done through simulated annealing algorithm. The international rules and regulations concerning Turkey are also considered