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Enrichment of molecular antenna triplets amplifies upconverting nanoparticle emission
Garfield, David J.,Borys, Nicholas J.,Hamed, Samia M.,Torquato, Nicole A.,Tajon, Cheryl A.,Tian, Bining,Shevitski, Brian,Barnard, Edward S.,Suh, Yung Doug,Aloni, Shaul,Neaton, Jeffrey B.,Chan, Emory M Nature Publishing Group UK 2018 Nature photonics Vol.12 No.7
<P>Efficient photon upconversion at low light intensities promises major advances in technologies spanning solar energy harvesting to deep-tissue biophotonics. Here, we discover the critical mechanisms that enable near-infrared dye antennas to significantly enhance performance in lanthanide-doped upconverting nanoparticle (UCNP) systems, and leverage these findings to design dye-UCNP hybrids with a 33,000-fold increase in brightness and a 100-fold increase in efficiency over bare UCNPs. We show that increasing the lanthanide content in the UCNPs shifts the primary energy donor from the dye singlet to its triplet, and the resultant triplet states then mediate energy transfer into the nanocrystals. Time-gated phosphorescence, density functional theory, singlet lifetimes and triplet-quenching experiments support these findings. This interplay between the excited-state populations in organic antennas and the composition of UCNPs presents new design rules that overcome the limitations of previous upconverting materials, enabling performances now relevant for photovoltaics, biophotonics and infrared detection.</P>
A New Method for Estimating High-Frequency Radar Error Using Data from Central San Francisco Bay
Maxwell Hubbard,Donald Barrick,Newell Garfield,Jim Pettigrew,Carter Ohlmann,Matthew Gough 한국해양과학기술원 2013 Ocean science journal Vol.48 No.1
This study offers a new method for estimating High- Frequency (HF) radar surface current velocity error in data comparisons with other types of instrumentation. A new method is needed in order to remove the zero-mean random spatial and temporal fluctuations present in surface-current measurements from all sensors. Conventional methods for calculating radar error when comparing with another instrument have included their root mean square differences and scatter plots that provide correlation coefficient and slope/intercept of the regression line. It seems that a meaningful estimate of radar error should attempt to remove both sensors' zero mean random fluctuations, inasmuch as possible. We offer and compare a method that does this. The method was tested on data collected in the Central San Francisco Bay, where GPS surface-drifter deployments were conducted within the coverage of four 42 MHz radars over six days in October of 2008. Drifters were continuously deployed in these areas over the sampling days, providing 525 usable drifter measurements. Drifter and radar measurements were averaged into thirty-minute time bins. The three-day long-term averages from the sampling areas were then subtracted from the thirtyminute averages to remove biases associated with comparisons done with short, disjoint time-sample periods. These were then used to develop methods that give radar error or bias after the random fluctuations have been removed. Results for error estimates in this study are commensurate with others where random fluctuations have been filtered, suggesting they are valid. The estimated error for the radars in the SF Bay is low, ranging from -7.57 cm/s to 0.59 cm/s.
Kinetics of penetration influence the apparent potency of vanilloids on TRPV1.
Lazar, Jozsef,Braun, Derek C,Tó,th, Attila,Wang, Yun,Pearce, Larry V,Pavlyukovets, Vladimir A,Blumberg, Peter M,Garfield, Susan H,Wincovitch, Stephen,Choi, Hyun-Kyung,Lee, Jeewoo American Society for Pharmacology and Experimental 2006 Molecular pharmacology Vol.69 No.4
<P>Evidence that the ligand binding site of TRPV1 lies on the inner face of the plasma membrane and that much of the TRPV1 itself is localized to internal membranes suggests that the rate of ligand entry into the cell may be an important determinant of the kinetics of ligand action. In this study, we synthesized a BODIPY TR-labeled fluorescent capsaicin analog (CHK-884) so that we could directly measure ligand entry. We report that CHK-884 penetrated only slowly into Chinese hamster ovary (CHO) cells expressing rat TRPV1, with a t1/2 of 30 +/- 4 min, and localized in the endoplasmic reticulum and Golgi. Although CHK-884 was only weakly potent for TRPV1 binding (Ki = 6400 +/- 230 nM), it was appreciably more potent when assayed by intracellular calcium imaging and was 3.2-fold more potent with a 1-h incubation time (37 nM) than with a 5-min incubation time. Olvanil, a highly lipophilic vanilloid, yielded an EC50 of 4.3 nM upon intracellular calcium imaging with an incubation time of 1 h, compared with an EC50 value of 29.5 nM for calcium imaging assayed at 5 min. Likewise, the antagonist 5-iodo-resiniferatoxin (5-iodo-RTX) displayed a Ki of 4.2 pM if incubated with CHO-TRPV1 cells for 2 h before addition of capsaicin compared with 1.5 nM if added simultaneously. We conclude that some vanilloids may have slow kinetics of uptake; this slow uptake may affect assessment of structure activity relations and may represent a significant factor for vanilloid drug design.</P>