The injury phase after myocardial infarcts occurs during reperfusion and is a consequence of calcium release from internal stores combined with calcium entry, leading to cell death by apoptopic and necrotic processes. The mechanism(s) by which calcium enters cells has(ve) not been identified. Here, we identify canonical transient receptor potential channels (TRPC) 3 and 6 as the cation channels through which most of the damaging calcium enters cells to trigger their death, and we describe mechanisms activated during the injury phase. Working in vitro with H9c2 cardiomyoblasts subjected to 9-h hypoxia followed by 6-h reoxygenation (H/R), and analyzing changes occurring in areas-at-risk (AARs) of murine hearts subjected to a 30-min ischemia followed by 24-h reperfusion (I/R) protocol, we found: (i) that blocking TRPC with SKF96365 significantly ameliorated damage induced by H/R, including development of the mitochondrial permeability transition and proapoptotic changes in Bcl2/BAX ratios; and (ii) that AAR tissues had increased TUNEL + cells, augmented Bcl2/BAX ratios, and increased p(S240)NFATc3, p(S473) AKT, p(S9)GSK3β, and TRPC3 and -6 proteins, consistent with activation of a positive-feedback loop in which calcium entering through TRPCs activates calcineurin-mediated NFATc3-directed transcription of TRPC genes, leading to more Ca 2+ entry. All these changes were markedly reduced in mice lacking TRPC3, -6, and -7. The changes caused by I/R in AAR tissues were matched by those seen after H/R in cardiomyoblasts in all aspects except for p-AKT and p-GSK3β, which were decreased after H/R in cardiomyoblasts instead of increased. TRPC should be promising targets for pharmacologic intervention after cardiac infarcts.apoptosis | necrosis | calcium overload | calcineurin | AKT

Weblike aggregates of coalesced Si nanocrystals are produced by a laser vaporization-controlled condensation technique. SEM micrographs show particles with ∼10 nm diameter but the Raman shift suggests the presence of particles as small as ∼4 nm. FTIR of the freshly prepared particles shows weak peaks due to the stretching, bending, and rocking vibrations of the Si-O-Si bonds, indicating the presence of a surface oxidized layer, SiO x (x < 2). Further oxidation of the Si core appears to be very slow and inefficient under ambient temperature, but annealing at higher temperatures facilitates the oxidation. The particles show luminescence properties that are similar to those of porous Si and Si nanoparticles produced by other techniques. The nanoparticles do not luminesce unless, by exposure to air, they acquire the SiO x passivated coating. They show a short-lived blue emission characteristic of the SiO 2 coating and a biexponential longer-lived red emission. The short lifetime component of the red emission, about 12 µs, does not depend on emission wavelength. The longer-lived component has a lifetime that ranges from 80 to over 130 µs (at 300 K), increasing with emission wavelength. The results are consistent with the quantum confinement mechanism as the source of the red photoluminescence. IntroductionIn recent years, there has been an intense interest in the synthesis and characterization of nanoparticles. 1-8 Due to their finite small size, the nanoparticles often exhibit novel properties which are different from the bulk materials' properties. [1][2][3][4][5][6][7][8] Research in this area is motivated by the possibility of designing nanostructured materials that possess novel electronic, optical, magnetic, photochemical, and catalytic properties. Such materials are essential for technological advances in photonics, quantum electronics, nonlinear optics, and information storage and processing.Among the many interesting nanoparticles, silicon nanocrystals show important promise for use in Si-based devices for optical communication. This exciting possibility has been hampered by the indirect band gap of bulk Si which prevents efficient electron-photon energy conversion. However, the discovery that porous and nanocrystalline Si emit visible light with a high quantum yield has raised hopes for new photonic Si-based devices. 9-16 This discovery has also stimulated interest in the synthesis of Si nanocrystals which are believed to be the luminescent centers in porous silicon. 9,[17][18][19][20][21][22][23][24][25] Various methods have been used to make Si nanocrystals. They have been generated by the slow combustion of silane, 26 reduction of SiCl 4 by Na, 27 separation from porous Si, 28 UV or IR laser photolysis of silane-type precursors, 29 thermal evaporation, 30 microwave discharge, 31 RF sputtering, 32 and hightemperature aerosol techniques. 18 In most cases, some control over particle size can be achieved by lowering the concentration of the nucleating particles. Laser vaporization of metals has the advantage ...

The decay dynamics and the quenching of the photoluminescence (PL) from Si nanocrystals are investigated. Electron acceptors whose reduction potentials lie below the conduction band (CB) edge of the Si nanocrystals quench the red emission from the Si nanocrystals. The quenching rate constants obtained from Stern-Volmer analyses for 3,5-dinitrobenzonitrile, 4-nitrophthalonitrile, 1,4-dinitrobenzene, 4-nitrobenzonitrile, 2,3-dinitrotoluene, 3,4-dinitrotoluene, 2,4-dinitrotoluene, and 2,6-dinitrotoluene are in the range of 10 6 -10 7 M -1 s -1 . The quenching mechanism occurs via an electron transfer from the CB band of the Si nanocrystals to the vacant orbitals of the quenchers. The PL decay profiles of the Si nanocrystals, in the presence and absence of the quencher, are well described by the stretched exponential decay law. The band gap of the Si nanocrystals estimated from the present study is larger than the PL peak energy. The results are consistent with a quantumconfinement model, where recombination of electrons and holes occurs in a surface state. The ability of nitrotoluenes to quench the PL from Si nanocrystals could be used to develop a sensor based on Si nanostructures for the detection of explosives. IntroductionSilicon nanostructures have stimulated much interest because of their unique properties such as single-electron tunneling, nonlinear optical properties, and visible photoluminescence (PL). 1-7 Studies of Si nanostructures have grown extensively since the discovery of efficient PL from porous Si (p-Si) with the ultimate goals of achieving a complete fundamental understanding of the phenomenon as well as developing potential display devices and chemical-sensor applications. 1-10 Si nanocrystals have optical and PL properties very similar to those of p-Si, and it is generally accepted that they are the emitting chromophores in p-Si. Kinetic quantum confinement appears to be the most reliable model to explain the origin and properties of the PL from Si nanocrystals. The higher energy shift in the PL of Si nanocrystals is attributed to the three-dimensional quantum size effect. The nonradiative recombination process is decreased significantly in the nanocrystal as the electronhole pairs in separate nanocrystals are electrically isolated. However, in both p-Si and Si nanocrystals, the PL properties are related not only to the respective nanocrystalline size but also to the structure and properties of the surrounding medium. The study of these effects is essential for utilizing Si nanostructures in potential device applications.Many organic and inorganic molecules have been shown to efficiently quench the PL from p-Si, and both energy-and electron-transfer mechanisms have been proposed to explain this PL quenching. 11-30 Sailor and co-workers found a number of polar solvent molecules that reversibly quenched the PL from p-Si. 11-15 They also studied the quenching by aromatic molecules and concluded that energy transfer from the p-Si excited state to the triplet levels of the quencher molecules predomi...

The large particle count ͑LPC͒ of fumed silica slurries was evaluated and correlated with scratch counts created on SiO 2 films by table-top, chemical-mechanical planarization ͑CMP͒. Particle sizing results obtained by static light scattering, capillary hydrodynamic fractionation, and dual-sensor single particle optical sensing ͑SPOS͒ pointed to the latter as the superior method for quantitative analyses of the LPC. Dual-sensor SPOS is a new technique that determines the LPC on a silica sphere-equivalent, light-scattering diameter scale for particles as small as 0.469 m. LPC measurements used in combination with dark-field optical microscopy for scratch metrology afforded linear correlations between scratch counts and the LPC. Particles producing scratches had silica sphere-equivalent, light-scattering diameters exceeding 0.68 m. Inclusion of these particles in the LPC produced a two-fold increase in the number of scratch-forming particles in the correlation relative to correlations generated via single-sensor SPOS measurements of LPC. Experimental uncertainty in scratch counts limited the correlation as a scratch predictor. Slurries differing in LPC by a minimum of 1.8 ϫ 10 5 particles/g slurry had statistically different predicted scratch counts at the 95% confidence level. Additional method development is needed to extend LPC-based scratch prediction to other CMP processes producing scratch defects.Among the set of key criteria defining the limits of microelectronic device fabrication, the reduction of surface defects assumes special prominence. It is well established 1 that surface defects on a microelectronic device degrade device performance. A variety of defect types, including delaminated film interfaces, pits, scratches, and chemical and physical changes in film structures, have been identified as the products of surface-damaging events during device fabrication. 1 Given the overwhelming need to reduce the size of microelectronic devices in order to produce faster and more powerful commercial microprocessors, strategies for reducing all types of surface defects have become a critical element of the fabrication processes used by the microelectronic device industry.Reaching the desired state of minimized surface defects on microelectronic devices begins with the recognition that a principal source of surface defects in device fabrication processes is surface polishing and planarization afforded by chemical-mechanical planarization ͑CMP͒. 2,3 The current paradigm of CMP-driven defect generation attributes the creation of defects to the mechanical action of the largest diameter particles in a CMP slurry. 4-6 Although a detailed mechanistic understanding of this process remains elusive, research efforts have sparked the development of many new analytical methods and techniques for the characterization of the abrasive particles and other consumables in CMP slurries. 7 A key analytical metric, widely applied to predict the defect creation potential of CMP slurries, is the large particle count ͑LPC͒ for the slur...

We examine the effect of different anions in solutions containing benzotriazole ͑BTA͒ on the Cu removal rate during chemical mechanical planarization ͑CMP͒. In solutions containing both Cl − and BTA, the Cu removal rate is nearly a factor of twenty lower than in solutions containing either Cl − or BTA alone. As-grown BTA films from solutions containing different anions are characterized using atomic force microscopy, ellipsometry, Raman spectroscopy, mass spectrometry, and open-circuit-potential measurements. Films grown from halide-containing solutions are found to be considerably thicker than those grown from other anions. The difference in Cu removal rate correlates well with the different as-grown film thicknesses.