Iodoacetoxylation of glycals using cerium(IV) ammonium nitrate, sodium iodide, and acetic acid: stereoselective synthesis of 2-deoxy-2-iodo-alpha-mannopyranosyl acetates

[formula: see text] The reactions of glycals with ceric(IV) ammonium nitrate and sodium iodide in the presence of acetic acid provides 2-deoxy-2-iodo-alpha-mannopyranosyl acetates with good stereoselectivity. In the majority of the cases examined, the selectivity was considerably better than that from reactions using N-iodosuccinimide and HOAc.     

A note on the use of the new variable n for elastic scattering and inclusive reactions

The usefulness of the kinematical variable n² which has been proposed in connection with elastic scattering and inclusive reactions is examined in the context of a certain historical background which already exists, and a modification to the proposed formulae is presented.     

Acceleration of the universe with a simple trigonometric potential

In this paper, we investigate the quintessence model with a minimally coupled scalar field in the context of recent supernovae observations. By choosing a particular form of the deceleration parameter q, which gives an early deceleration and late time acceleration for the dust dominated model, we show that this sign flip in q can be obtained by a simple trigonometric potential. The early matter dominated model expands with q = 1/2 as desired and enters a negative q phase quite late during the evolution.     

Polycaprolactone biopolymer thin films obtained by matrix assisted pulsed laser evaporation

We report the successful deposition of polycaprolactone polymer by MAPLE using a KrF* excimer laser (λ = 248 nm, τ = 7 ns). According to FTIR spectra the deposited films have similar chemical structure to the dropcast material. The fluence plays a key role in optimizing the performances of MAPLE-synthesized polycaprolactone structures. We demonstrated that MAPLE allows for controlling the morphology of films to the level required in targeted drug delivery of pharmacologic agents.     

Matrix assisted pulsed laser evaporation of poly(d,l-lactide) thin films for controlled-release drug systems

We report the successful deposition of the porous polymer poly(d,l-lactide) by matrix assisted pulsed laser evaporation (MAPLE) using a KrF* excimer laser (248 nm, τ = 7 ns) operated at 2 Hz repetition rate. The chemical structure of the starting materials was preserved in the resulting thin films. Fluence played a key role in optimizing our depositions of the polymer. We demonstrated MAPLE was able to improve current approaches to grow high quality thin films of poly(d,l-lactide), including a porosity control highly required in targeted drug delivery.     

Adaptive optics interferometer using superspeckles for high resolution deformation measurement

Digital speckle pattern interferometry (DSPI) is a well-known technique for measuring deformations, but it is limited in range by speckle decorrelation. We developed an adaptive interferometer with increased measurement range by combining the DSPI set-up with a pupil filter that generates optical superresolution. As a result, a decrease in the transverse speckle size is observed accompanied with a substantial increase in the longitudinal speckle size. The increase in the speckle correlation length along the optical axis allows for obtaining an out-of-plane deformation measurement over a significantly extended depth. An experimental verification of this concept of superspeckles is presented with an intensity-only LCD spatial light modulator (SLM) acting as a pupil filter. Comparison of speckle correlation fringes with and without the superresolution filter confirms the proposed concept. The present work demonstrates a doubling of the measurement range when using the superresolution interferometer. A standard set-up in which the speckle length is comparably elongated by stopping down the lens has a similar loss of intensity, but its lateral resolution is only half as good.     

Room temperature ferromagnetism and magnetotransport properties of the layered manganite system La1.2Ba1.8Mn2−xRuxO7 (0≤x≤1.0)

The dc magnetization and ac susceptibility measurements on two dimensional layered manganite La_1.2Ba_1.8Mn₂O₇ samples reveal the occurrence of ferromagnetism above room temperature with ferromagnetic (FM) to paramagnetic (PM) transitions at 338 K. The bifurcation temperatures shown by the zero-field cooled (ZFC) and field cooled (FC) dc magnetization curves at high temperatures shift towards lower temperatures as the applied field is increased from 100 to 2500 Oe. The data are suggestive of a large magnetic anisotropy due to the strong competing ferromagnetic and antiferromagnetic interactions resulting in a spin-glass-like state. Ru doping is found to enhance the ferromagnetism and metallicity of the system in a remarkable way. The magnetoresistance (MR) values obtained are very high and about 40% even at 260 K for the undoped sample.     

Multinuclear complexes containing [Pt2(μ-S)2(Ptolyl3)4] as a metallo-ligand

Treatment of [PtCl₂(Ptolyl₃)₂] (tolyl = 4-MeC₆H₄) with Na₂S in benzene gave [Pt₂(μ₂-S)₂(Ptolyl₃)₄] (1), which is soluble in common organic solvents. Reactions of (1) with various metal complexes have been studied and several polynuclear metal aggregates isolated. These new complexes were characterized by elemental analysis and n.m.r. spectroscopy. This revised version was published online in June 2006 with corrections to the Cover Date.     

"Click" synthesis and properties of carborane-appended large dendrimers

Large dendrimers, noted G(n)-3(n+2)cage, containing 3(n+2) o-carborane cluster cages MeC(2)B(10)H(10) at their peripheries (n = number of generation noted G(n)) have been synthesized by Huisgen-type azide alkyne Cu(I)-catalyzed dipolar "click" cycloaddition reactions (CuAAC) between an o-carborane monomeric cluster containing an ethynyl group and arene-centered azido-terminated dendrimers G(n)-3(n+2)N(3) of generations 0, 1, and 2. Attempts to synthesize higher-generation dendrimers of this family yielded insoluble materials. The carborane dendrimers G(0)-9cage, G(1)-27cage, and G(2)-81cage have been characterized by (1)H, (13)C, (11)B NMR, elemental analysis, matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectroscopy, and size exclusion chromatography (SEC) showing low polydispersities, dynamic light scattering (DLS) showing hydrodynamic diameters of 5.7 nm for the G(1)-27cage and the 12.9 nm for the G(2)-81cage. These dendrimers are extremely robust thermally, with 10% mass loss temperatures of 411 °C for the G(0)-9cage, 371 °C for the G(1)-27cage, and 392 °C for the G(2)-81cage. They all showed a strong absorption in the UV region peaking at 258 nm, whereas emission spectra of low intensities were observed between 280 and 480 nm.