Multi-Photon Sensitized Excitation of Near Infrared Emitting Lanthanides

Near infrared (NIR) multi-photon excitation of the NIR-emitting lanthanides neodymium (Nd³⁺) and ytterbium (Yb³⁺) sensitized by a fluorescein-linked chelator was demonstrated. Because tissues display minimal absorbance near the excitation wavelength of 800 nm, and because the lanthanides display long decay times, these results suggest the use of Nd³⁺ and Yb³⁺ as luminescent probes in tissues with multi-photon excitation.     

A New Method for the Oxybromination of Aromatic Compounds with Copper(II)bromide and Potassium Dichromate

Abstract

A new and mild method for oxybromination of aromatic compounds with CuBr ₂ and K ₂ Cr ₂ O ₇ in HOAC is reported.     

The layered iron phosphate KMgFe(PO4)2: Crystal structure,Mössbauer spectroscopy and ionic conductivity

A new iron phosphate, KMgFe(PO₄)₂ has been synthesized and investigated by X-ray diffraction, Mössbauer spectroscopy and ionic conductivity. This compound crystallizes in the monoclinic space group C2/c with the parameters a = 18.529(7) Å, b = 5.402(3) Å, c = 9.374(9) Å, β = 120.64(5)° and Z = 4. Its original structure can be described as the stacking along the [101] direction of [MgFe(PO₄)^?₂]_∞ layers of corner-sharing MO₄ (M = 0.5 Fe + 0.5 Mg) and PO₄ tetrahedra. The K⁺ ions are occupying the inter-layer space. The Mössbauer spectroscopy confirms the occurrence of only tetrahedral Fe³⁺ ions and gives a definitive proof of the disordered character of their distribution. Ionic conductivity results obtained by the impedance spectroscopy technique show that this material is a two-dimensional ionic conductor, with low activation energy, 0.51 eV, that is interpreted on the basis of two-dimensional pathways.     

A Nitronaphthalimide Probe for Fluorescence Imaging of Hypoxia in Cancer Cells

The bioreductive enzymes typically upregulated in hypoxic tumor cells can be targeted for developing diagnostic and drug delivery applications. In this study, a new fluorescent probe 4?(6?nitro?1,3?dioxo?1H?benzo[de]isoquinolin?2(3H)?yl)benzaldehyde (NIB) based on a nitronaphthalimide skeleton that could respond to nitroreductase (NTR) overexpressed in hypoxic tumors is designed and its application in imaging tumor hypoxia is demonstrated. The docking studies revealed favourable interactions of NIB with the binding pocket of NTR-Escherichia coli. NIB, which is synthesized through a simple and single step imidation of 4?nitro?1,8?naphthalic anhydride displayed excellent reducible capacity under hypoxic conditions as evidenced from cyclic voltammetry investigations. The fluorescence measurements confirmed the formation of identical products (NIB-red) during chemical as well as NTR?aided enzymatic reduction in the presence of NADH. The potential fluorescence imaging of hypoxia based on NTR-mediated reduction of NIB is confirmed using in-vitro cell culture experiments using human breast cancer (MCF?7) cells, which displayed a significant change in the fluorescence colour and intensity at low NIB concentration within a short incubation period in hypoxic conditions.

Graphical abstract

     

A Sausage Heuristic for Steiner Minimal Trees in Three-Dimensional Euclidean Space

Given a set V of size N≥4 vertices in a metric space, how can one interconnect them with the possible use of a set S of size M vertices not in the set V, but in the same metric space, so that the cumulative cost of the inter-connections between all the vertices is a minimum? When one uses the Euclidean metric to compute these inter-connections, this is referred to as the Euclidean Steiner Minimal Tree Problem. This is an NP-hard problem. The Steiner Ratio ρ of a vertex set is the length of this Steiner Minimal Tree (SMT), divided by the length of the Minimum Spanning Tree (MST), and is a popular and tractable measure of solution quality.The ?-Sausage heuristic described in this paper employs a decomposition technique to explore the point set. The fixed vertices of the set are connected to a set of centroid vertices of Delaunay tetrahedrons. The path topology is preserved as far as possible, together with a cycle prevention rule, where junctions, and deviations from the ?-Sausage structure occur. Furthermore, repeated sweeps, with different root vertices are accommodated.The computational complexity of the heuristic is shown to be O(N²). Experimental results with thousands of vertices are presented. Comparisons with an exponential running time Branch and Bound algorithm are also shown.     

Selecting optimum maintenance strategy by fuzzy interactive linear assignment method

In the current competitive environment managers of manufacturing and service organizations try to make their organizations competitive by providing timely delivery of high quality products. Maintenance, as a system, plays a key role in reducing cost, minimizing equipment downtime, improving quality, increasing productivity and providing reliable equipment and as a result achieving organizational goals and objectives. This paper presents a new approach for selecting optimum maintenance strategy using qualitative and quantitative data through interaction with the maintenance experts. This approach has been based on linear assignment method (LAM) with some modifications to develop interactive fuzzy linear assignment method (IFLAM).     

Dynamical horizons: energy,angular momentum,fluxes, and balance laws

Dynamical horizons are considered in full, nonlinear general relativity. Expressions of fluxes of energy and angular momentum carried by gravitational waves across these horizons are obtained. Fluxes are local, the energy flux is positive, and change in the horizon area is related to these fluxes. The flux formulas also give rise to balance laws analogous to the ones obtained by Bondi and Sachs at null infinity and provide generalizations of the first and second laws of black-hole mechanics.     

Reactivity of transition metal-substituted phosphoranes: Crystal and molecular structure of 2-pentacarbonylmanganese-1,3,2-benzodioxaphosphole-2-oxide

The crystal and molecular structure of 2-pentacarbonylmanganese-1,3,2-benzodi-oxaphosphole-2-oxide,$\text{OC}{}_6\text{H}{}_4\text{OP}$(O)Mn(CO)₅, has been determined by single crystal X-ray diffraction. The crystal belongs to the triclinic system with a space group of P$\text{1}$. The unit cell parameters are: a 6.753(2), b 8.818(3), c 12.004(4) Å, α 106.79(2), β 105.37(2), γ 98.82(2)°, and Z = 2. Graphite monochromatic Mo-K_α radiation was used in the intensity measurements. The final disagreement index was 0.073 for 2293 reflections. The Mn and P atoms have distorted octahedral and tetrahedral configurations, respectively. The phenyl ring is essentially planar; however, the dioxaphosphole 5-membered ring is slightly puckered. The PO has an almost eclipsed conformation with one of the equatorial carbonyls, leading to pseudo mirror symmetry.     

A Novel,One-Pot Synthesis of 2,5-Disubstituted-1,3,4-Oxadiazoles Using 1,4-Bis(Triphenylphosphonium)-2-Butene Peroxodisulfate

An efficient and convenient synthesis of 1,3,4-oxadiazoles from aromatic aldehydes, acyl hydrazide, and 1,4- bis(triphenylphosphonium)-2-butene peroxodisulfate is reported.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.