Magnetic Control of the Light Reflection Anisotropy in a Biogenic Guanine Microcrystal Platelet

Bioinspired but static optical devices such as lenses, retarders, and reflectors have had a significant impact on the designs of many man-made optical technologies. However, while numerous adaptive and flexible optical mechanisms are found throughout the animal kingdom, highly desirable biomimetic copies of these remarkable smart systems remain, in many cases, a distant dream. Many aquatic animals have evolved highly efficient reflectors based on multilayer stacks of the crystallized nucleic acid base guanine. With exceptional levels of spectral and intensity control, these reflectors represent an interesting design pathway towards controllable micromirror structures. Here we show that individual guanine crystals, with dimensions of 5 μm × 20 μm × 70 nm, can be magnetically controlled to act as individual micromirrors. By applying magnetic fields of 500 mT, the reflectivity of these crystals can be switched off and on for the change in reflectivity. Overall, the use of guanine represents a novel design scheme for a highly efficient and controllable synthetic organic micromirror array

Improvement of Thermoelectric Properties through Reduction of Thermal Conductivity by Nanoparticle Addition and Stoichiometric Change to Mg2Si

Thermoelectric materials have been of interest for several decades due to their ability to recapture waste heat of various systems and convert it to useful electricity. One method used to improve the thermoelectric figure of merit, given by ZT = (σS2T)/(ke+kp), is to reduce the lattice thermal conductivity (kp) while not affecting the other properties. In order to reduce kp of the material, this paper introduces nanoparticles of Si in Mg2Si to manipulate phonon scattering and mean free path. LAMMPS molecular dynamics software is employed using the nonequilibrium molecular dynamics (NEMD) method to perform a series of simulations with the metal silicide thermoelectric material MgxSix. The objective of this work is two-fold: 1) to determine the optimal nanoparticle concentration and 2) to determine the optimal MgxSix stoichiometry for minimizing the thermal conductivity of the system. It should be noted, however, that the assumed reduction in thermal conductivity is only a result of reduced phonon transport and minimal impact is made on the transport of electrons. Interestingly, the uniform off-stoichiometry (41.37 percent Si) sample of MgxSix resulted in a reduction of kp of 72.39 percent, while the Si nanoparticle sample, with matching percent Si, resulted in a reduction of kp of 65.59 percent

Light Assisted Collisional Loss in a 85/87^{85/87}Rb Ultracold Optical Trap

We have studied hetero- and homonuclear excited state/ground state collisions by loading both $^{85}$Rb and $^{87}$Rb into a far off resonant trap (FORT). Because of the relatively weak confinement of the FORT, we expect the hyperfine structure of the different isotopes to play a crucial role in the collision rates. This dependence on hyperfine structure allows us to measure collisions associated with long range interatomic potentials of different structure: such as long and short ranged; or such as purely attractive, purely repulsive, or mixed attractive and repulsive. We observe significantly different loss rates for different excited state potentials. Additionally, we observe that some collisional channels' loss rates are saturated at our operating intensities (~15 mW/cm$^{2}$). These losses are important limitations in loading dual isotope optical traps.Comment: about 8 pages, 5 figure

Emergency department hyperoxia is associated with increased mortality in mechanically ventilated patients: A cohort study

Definitions of comorbid conditions. (DOCX 13 kb

Endoscopic Assessment and Prediction of Prostate Urethral Disintegration After Histotripsy Treatment in a Canine Model*

Abstract Background and Purpose: Histotripsy is a nonthermal focused ultrasound technology that uses acoustic cavitation to homogenize tissue. Previous research has demonstrated that the prostatic urethra is more resistant to histotripsy effects than prostate parenchyma, a finding that may complicate the creation of transurethral resection of the prostate-like treatment cavities. The purpose of this study was to characterize the endoscopic appearance of the prostatic urethra during and after histotripsy treatment and to identify features that are predictive of urethral disintegration. Materials and Methods: Thirty-five histotripsy treatments were delivered in a transverse plane traversing the prostatic urethra in 17 canine subjects (1?3/prostate ≥1?cm apart). Real-time endoscopy was performed in the first four subjects to characterize development of acute urethral treatment effect (UTE). Serial postprocedure endoscopy was performed in all subjects to assess subsequent evolution of UTE. Results: Endoscopy during histotripsy was feasible with observation of intraurethral cavitation, allowing characterization of the real-time progression of UTE from normal to frank urethral disintegration. While acute urethral fragmentation occurred in 3/35 (8.6%) treatments, frank urethral disintegration developed in 24/35 (68.5%) within 14 days of treatment. Treating until the appearance of hemostatic pale gray shaggy urothelium was the best predictor of achieving urethral fragmentation within 14 days of treatment with positive and negative predictive values of 0.91 and 0.89, respectively. Conclusion: Endoscopic assessment of the urethra may be a useful adjunct to prostatic histotripsy to help guide therapy to ensure urethral disintegration, allowing drainage of the homogenized adenoma and effective tissue debulking.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98446/1/end%2E2011%2E0349.pd