Raman spectroscopic study of the magnesium‐carbonate minerals—artinite and dypingite

Magnesium minerals are important in the understanding of the concept of geosequestration. The two hydrated hydroxy magnesium‐carbonate minerals artinite and dypingite were studied by Raman spectroscopy. Intense bands are observed at 1092 cm⁻¹ for artinite and at 1120 cm⁻¹ for dypingite, attributed ν₁ symmetric stretching mode of CO₃²⁻. The ν₃ antisymmetric stretching vibrations of CO₃²⁻ are extremely weak and are observed at 1412 and 1465 cm⁻¹ for artinite and at 1366, 1447 and 1524 cm⁻¹ for dypingite. Very weak Raman bands at 790 cm⁻¹ for artinite and 800 cm⁻¹ for dypingite are assigned to the CO₃²⁻ν₂ out‐of‐plane bend. The Raman band at 700 cm⁻¹ of artinite and at 725 and 760 cm⁻¹ of dypingite are ascribed to CO₃²⁻ν₂ in‐plane bending mode. The Raman spectrum of artinite in the OH stretching region is characterised by two sets of bands: (1) an intense band at 3593 cm⁻¹ assigned to the MgOH stretching vibrations and (2) the broad profile of overlapping bands at 3030 and 3229 cm⁻¹ attributed to water stretching vibrations. X‐ray diffraction studies show that the minerals are disordered. This is reflected in the difficulty of obtaining Raman spectra of reasonable quality, and explains why the Raman spectra of these minerals have not been previously or sufficiently described. Copyright © 2008 John Wiley & Sons, Ltd.     

Mapping the composition of chondritic meteorite Northwest Africa 3118 with micro-Raman spectroscopy

Meteorites provide precious clues about the formation of planets in the solar system. Here, an analytical method to study chondritic meteorites using low- and high-resolution micro-Raman spectroscopy is presented. An approach in mapping the distribution of mineral compositions of a sample is introduced by measuring ～10⁴ Raman spectra along linear, micron-wide paths that traverse the sample to capture detail on small and large spatial scales (from micrometers to millimeters). To refine these analytical procedures, a well-defined chondrule and surrounding matrix of the carbonaceous chondrite Northwest Africa 3118 are analyzed. The morphology and elemental composition of the sample are also studied using scanning electron microscopy with energy-dispersive X-ray spectroscopy and creating composite maps with the images obtained by these techniques along the same Raman linear path. The Raman line scan maps of this sample show clear spatial segregation of constituents including pyroxene and olivine, both within and outside the chondrule. Graphitic carbon is also present and appears clustered in domains of a few hundred microns both in the matrix and in the central core of the chondrule. The results obtained with the scanning electron microscopy and energy-dispersive X-ray spectroscopy techniques show that iron is most abundant in the matrix surrounding the chondrule, while the chondrule is enhanced in silicon, magnesium, calcium, aluminum, and sodium. These findings provide a detailed identification of the elemental and mineralogical, spatial composition of the analyzed regions of Northwest Africa 3118.     

Preclinical radiotherapy at the Australian Synchrotron's Imaging and Medical Beamline: instrumentation,dosimetry and a small‐animal feasibility study

Therapeutic applications of synchrotron X‐rays such as microbeam (MRT) and minibeam (MBRT) radiation therapy promise significant advantages over conventional clinical techniques for some diseases if successfully transferred to clinical practice. Preclinical studies show clear evidence that a number of normal tissues in animal models display a tolerance to much higher doses from MRT compared with conventional radiotherapy. However, a wide spread in the parameters studied makes it difficult to make any conclusions about the associated tumour control or normal tissue complication probabilities. To facilitate more systematic and reproducible preclinical synchrotron radiotherapy studies, a dedicated preclinical station including small‐animal irradiation stage was designed and installed at the Imaging and Medical Beamline (IMBL) at the Australian Synchrotron. The stage was characterized in terms of the accuracy and reliability of the vertical scanning speed, as this is the key variable in dose delivery. The measured speed was found to be within 1% of the nominal speed for the range of speeds measured by an interferometer. Furthermore, dose measurements confirm the expected relationship between speed and dose and show that the measured dose is independent of the scan direction. Important dosimetric parameters such as peak dose, valley dose, the collimator output factor and peak‐to‐valley dose ratio are presented for 5 mm × 5 mm, 10 mm × 10 mm and 20 mm × 20 mm field sizes. Finally, a feasibility study on three glioma‐bearing rats was performed. MRT and MBRT doses were prescribed to achieve an average dose of 65 Gy in the target, and magnetic resonance imaging follow‐up was performed at various time points after irradiation to follow the tumour volume. Although it is impossible to draw conclusions on the different treatments with such a small number of animals, the feasibility of end‐to‐end preclinical synchrotron radiotherapy studies using the IMBL preclinical stage is demonstrated.     

Particle-image velocimetry measurements of flow over interacting barchan dunes

Barchan dunes are crescentic planform-shaped dunes that are present in many natural environments, and may occur either in isolation or in groups. This study uses high-resolution particle-image velocimetry (PIV) experiments using fixed-bed models to examine the effects of barchan dune interaction upon the flow field structure. The barchan dune models were created from an idealized contour map, the shape and dimensions of which were based upon previous empirical studies of dune morphology. The experimental setup comprised two, co-axially aligned, barchan dune models that were spaced at different distances apart. In this paper, two volumetric ratios (V _r, upstream dune: downstream dune) of 1.0 and 0.175 were examined. Models were placed in a boundary-layer wind tunnel and flow quantification was achieved via PIV measurements of the mean and turbulent flow field in the streamwise–wall-normal plane, along the centerline of the barchan(s), at an average flow Reynolds number of 59,000. The presence of an upstream barchan dune induces a “sheltering effect” on the flow. Flow on the stoss side of the downstream dune is controlled by the developing internal boundary layer from the upstream dune, as well as by the turbulent flow structures shed from the free shear layer of the upstream dune leeside. At both volumetric ratios, enhanced turbulence is present over the downstream barchan dune leeside, which is proposed to be caused by the interaction of shear layers from the upstream and downstream dunes. Both the size and magnitude of the shear layer formed in the leeside of the upstream dune control this interaction, together with the proximity of this shear layer to the stoss side of the downstream dune. Proper orthogonal decomposition (POD) analysis shows that the distribution of turbulent kinetic energy is shifted to higher modes (i.e., smaller spatial scales) over interacting barchan dunes, which also reflects the role of the leeside free shear layer in dominating the flow field by generation, or redistribution, of TKE to smaller scales.     

Multi‐Sensitive Microgels Filled with Conducting Poly(3,4‐ethylenedioxythiophene) Nanorods

In this work we describe the synthesis of multi‐sensitive aqueous microgel particles with incorporated conducting poly(3,4‐ethylenedioxythiophene) (PEDOT) nanorods. We demonstrate that the loaded amount of PEDOT nanorods as well as their morphology can be varied by controlling the reaction conditions such as monomer concentration and alcohol concentration in aqueous phase. Obtained microgels can be stimulated by changes in the environment temperature as well as by the repulsion/attraction forces within polymeric network due to the reversible oxidation/reduction of the conjugated polymer. Microgels with unique properties can be operated in colloidal systems or used as building blocks for the preparation of nanostructured films.

     

Synthesis of Indomorphan Pseudo‐Natural Product Inhibitors of Glucose Transporters GLUT‐1 and ‐3

Bioactive compound design based on natural product (NP) structure may be limited because of partial coverage of NP‐like chemical space and biological target space. These limitations can be overcome by combining NP‐centered strategies with fragment‐based compound design through combination of NP‐derived fragments to afford structurally unprecedented “pseudo‐natural products” (pseudo‐NPs). The design, synthesis, and biological evaluation of a collection of indomorphan pseudo‐NPs that combine biosynthetically unrelated indole‐ and morphan‐alkaloid fragments are described. Indomorphane derivative Glupin was identified as a potent inhibitor of glucose uptake by selectively targeting and upregulating glucose transporters GLUT‐1 and GLUT‐3. Glupin suppresses glycolysis, reduces the levels of glucose‐derived metabolites, and attenuates the growth of various cancer cell lines. Our findings underscore the importance of dual GLUT‐1 and GLUT‐3 inhibition to efficiently suppress tumor cell growth and the cellular rescue mechanism, which counteracts glucose scarcity.     

Conductive Fused Porphyrin Tapes on Sensitive Substrates by a Chemical Vapor Deposition Approach

Oxidative polymerization of nickel(II) 5,15‐diphenyl porphyrin and nickel(II) 5,15‐bis(di‐3,5‐tert‐butylphenyl) porphyrin by oxidative chemical vapor deposition (oCVD) yields multiply fused porphyrin oligomers in thin film form. The oCVD technique enables one‐step formation, deposition, and p‐doping of conjugated poly(porphyrins) coatings without solvents or post‐treatments. The decisive reactions and side reactions during the oCVD process are shown by high‐resolution mass spectrometry. Owing to the highly conjugated structure of the fused tapes, the thin films exhibit an electrical conductivity of 3.6×10^?2 S cm^?1 and strong absorption in the visible to near‐infrared spectral region. The formation of smooth conjugated poly(porphyrins) coatings, even on sensitive substrates, is demonstrated by deposition and patterning on glass, silicon, and paper. Formation of conductive poly(porphyrins) thin films could enable the design of new optoelectronic devices using the oCVD approach.     

Exploiting the Hydrogen Bond Donor/Acceptor Properties of PN‐Heterocycles: Selective Anion Receptors for Hydrogen Sulfate

We describe two novel hybrid receptors combining a phosphorus‐/nitrogen‐containing (PN) phosphonamidate heterocycle with urea recognition units in an arylethynyl backbone. Structural, spectroscopic and computational studies reveal that the origin of superior binding for hydrogen sulfate (HSO₄^?) anion is correlated with the formation of strong hetero‐complementary hydrogen bonds with the phosphonamidate motif. We further demonstrate that the hybrid host system is capable of capturing/transporting the HSO₄^? anion from an aqueous, biphasic system.     

Synthesis and Microtubule‐Destabilizing Activity of N‐Cyclopropyl‐4‐((3,4‐dihydroquinolin‐1(2H)‐yl)sulfonyl)benzamide and its Analogs

While clinically useful, microtubule‐targeting agents are limited by factors that include their susceptibility to multidrug resistance. A series of aryl sulfonamides, terminally substituted with an amide or carboxylic acid, was synthesized and assayed for biological activity in two human cancer cell lines. The resulting antiproliferative activity data demonstrated that an amide was superior to a carboxylic acid in the para position. The most potent compound ( 3 ) had an IC₅₀ for growth inhibition in the low micromolar range, caused cells to accumulate in G₂M of the cell cycle, and led to depolymerization of microtubules. It was also not susceptible to the P‐glycoprotein drug efflux pump that underpins the resistance of cells to long‐term drug treatment schedules.     

Alkene–Azide 1,3‐Dipolar Cycloaddition as a Trigger for Ultrashort Peptide Hydrogel Dissolution

An alkene–azide 1,3‐dipolar cycloaddition between trans‐cyclooctene (TCO) and an azide‐capped hydrogel that promotes rapid gel dissolution is reported. Using an ultrashort aryl azide‐capped peptide hydrogel (PhePhe), we have demonstrated proof‐of‐concept where upon reaction with TCO, the hydrogel undergoes a gel–sol transition via 1,2,3‐triazoline degradation and 1,6‐self‐immolation of the generated aniline. The potential application of this as a general trigger in sustained drug delivery is demonstrated through release of encapsulated cargo (doxorubicin). Administration of TCO resulted in 87 % of the cargo being released in 10 h, compared to 13–14 % in the control gels. This is the first example of a potential bioorthogonal‐triggered hydrogel dissolution using a traditional click‐type reaction. This type of stimulus could be extended to other aryl azide‐capped hydrogels.