A dominant form of human congenital nightblindness is caused by a gly903asp (G90D) mutation in rhodopsin. G90D has been shown to activate the phototransduction cascade in the absence of light in vitro. Such constitutive activity of G90D rhodopsin in vivo would desensitize rod photoreceptors and lead to nightblindness. In contrast, other rhodopsin mutations typically give rise to nightblindness by causing rod cell death. Thus, the proposed desensitization without rod degeneration would be a novel mechanism for this disorder. To explore this possibility, we induced mice to express G90D opsin in their rods and then examined rod function and morphology, after first crossing the transgenic animals with rhodopsin knock-out mice to obtain appropriate levels of opsin expression. The G90D mouse opsin bound the chromophore and formed a bleachable visual pigment with max of 492 nm that supported rod photoresponses. (Gϩ/Ϫ, Rϩ/Ϫ) retinas, heterozygous for both G90D and wildtype (WT) rhodopsin, possessed normal numbers of photoreceptors and had a normal rhodopsin complement but exhibited considerable loss of rod sensitivity as measured electroretinographically. The rod photoresponses were desensitized, and the response time to peak was faster than in (Rϩ/Ϫ) animals. An equivalent desensitization resulted by exposing WT retinas to a background light producing 82 photoisomerizations rod Ϫ1 sec Ϫ1 , suggesting that G90D rods in darkness act as if they are partially "light-adapted." Adding a second G90D allele gave (Gϩ/ϩ, Rϩ/Ϫ) animals that exhibited a further increase of equivalent background light level but had no rod cell loss by 24 weeks of age. (Gϩ/ϩ, RϪ/Ϫ) retinas that express only the mutant rhodopsin develop normal rod outer segments and show minimal rod cell loss even at 1 year of age. We conclude that G90D is constitutively active in mouse rods in vivo but that it does not cause significant rod degeneration. Instead, G90D desensitizes rods by a process equivalent to light adaptation.

A novel series of pyrene dendronized porphyrins bearing two and four pyrenyl groups (Py(2)-TMEG1 and Py(4)-TMEG2) were successfully synthesized. First and second generation Fréchet type dendrons (Py(2)-G1OH and Py(4)-G2OH) were prepared from 1-pyrenylbutanol and 3,5-dihydroxybenzyl alcohol. These compounds were further linked to a trimesitylphenylporphyrin containing a butyric acid spacer via an esterification reaction to obtain the desired products. Dendrons and dendronized porphyrins were fully characterized by FTIR and (1)H NMR spectroscopy and their molecular weights were determined by matrix-assisted laser desorption ionization time of flight mass spectrometry. Their optical and photophysical properties were studied by absorption and fluorescence spectroscopies. The formation of dynamic excimers was detected in the pyrene-labeled dendrons, with more excimer being produced in the higher generation dendron. The fluorescence spectra of the pyrene dendronized porphyrins exhibited a significant decrease in the amount of pyrene monomer and excimer emission, jointly with the appearance of a new emission band at 661 nm characteristic of porphyrin emission, an indication that fluorescence resonance energy transfer (FRET) occurred from one of the excited pyrene species to the porphyrin. The FRET efficiency was found to be almost quantitative ranging between 97% and 99% depending on the construct. Model Free analysis of the fluorescence decays acquired with the pyrene monomer, excimer, and porphyrin core established that only residual pyrene excimer formation in the dendrons could occur before FRET from the excited pyrene monomer to the ground-state porphyrin core.

This paper has presented a comparative study of the temperature and velocity distributions within the mini-channel cold plates placed on a prismatic lithium-ion battery cell using experimental and numerical techniques. The study was conducted for water cooling methods at 1C and 2C discharge rates and different operating temperatures of 5°C, 15°C, and 25°C. A total of nineteen thermocouples were used for this experimental work, and were purposefully placed at different locations. Ten T-type thermocouples were placed along the principal surface of the battery, and four K-type thermocouples were used to measure water inlet and outlet temperature. Computationally, the k-ε model in ANSYS Fluent was used to simulate the flow in a mini-channel cold plate, and the data was validated with the experimental data for temperature profiles. The present results show that increased discharge rates and increased operating temperature results in increased temperature of the cold plates. Furthermore, the sensors nearest the electrodes (anode and cathode) measured the higher temperatures than the sensors located at the center of the battery surface.

A simple mesoscopic model is presented which accounts for the inhomogeneity of physical properties and bi-stable nature of phase-change insertion materials used in battery electrodes. The model does not include any geometric detail of the active material and discretizes the total active material domain into meso-scale units featuring basic thermodynamic (non-monotonic equilibrium potential as a function of Li content) and kinetic (insertion-de-insertion resistance) properties. With only these two factors incorporated, the model is able to simultaneously capture unique phenomena including the memory effect observed in lithium iron phosphate electrodes. The analysis offers a new physical insight into modeling of phase-change active materials which are of special interest for use in high power Li-ion batteries.