Characterization of microscope objective lenses from 1,400 to 1,650 nm to evaluate performance for long-wavelength nonlinear microscopy applications

We have demonstrated a simple method for characterization of objective lens performance at longer wavelengths for 3PLSM and THG imaging. We investigated a range of air and oil-immersion objective lenses across a wavelength range of 1,400-1,650 nm using a synchronously pumped optical parametric oscillator laser source. In the first instance, we investigated the percentage light transmission across this spectral range. Second, we used a simple second harmonic autocorrelation pulse measurement technique to study the dispersion properties of these lenses at the range of input wavelengths. For the objective lenses investigated, we observed pulse broadening on the order of around 4%-7% for air immersion lenses and 9%-12% for oil immersion lenses. Even for the greater dispersion incurred by the application of the oil immersion lenses, these objectives are suitable for longer wavelength application in conjunction with a suitable light source. The same techniques could easily be applied for a larger range of objective lenses and adapted for alternative spectral windows and pulse durations.     

A promising new wavelength region for three-photon fluorescence microscopy of live cells

We report three-photon laser scanning microscopy (3PLSM) using a bi-directional pumped optical parametric oscillator (OPO) with signal wavelength output at λ= 1500 nm. This novel laser was used to overcome the high optical loss in the infrared spectral region observed in laser scanning microscopes and objective lenses that renders them otherwise difficult to use for imaging. To test our system, we performed 3PLSM auto-fluorescence imaging of live plant cells at λ= 1500 nm, specifically Spirogyra, and compared performance with two-photon excitation (2PLSM) imaging using a femtosecond pulsed Ti:Sapphire laser at λ= 780 nm. Analysis of cell viability based on cytoplasmic organelle streaming and structural changes of cells revealed that at similar peak powers, 2PLSM caused gross cell damage after 5 min but 3PLSM showed little or no interference with cell function after 15 min. The λ= 1500 nm OPO is thus shown to be a practical laser source for live cell imaging.     

Collaboration promotes proportional reasoning about resource distribution in young children.

The authors investigated how children and adults evaluate the “niceness” of individuals who engage in resource distribution, with a focus on their sensitivity to the proportion of resources given. Across 3 experiments, subjects evaluated the niceness of a child who gave a quantity of pennies to another child. In Study 1 (N = 30), adults showed sensitivity to the proportion given, whereas 5- and 7-year-old children did not. In Study 2 (N = 74), both younger (3- to 5-year-old) and older (6- to 8-year-old) children were sensitive to proportion only when resources were earned by a giver in collaboration with the recipient rather than by the giver alone. Adults, however, were sensitive to proportion in both cases. In Study 3 (N = 44), the authors tested 5- and 6-year-olds and their parents to be sure that socioeconomic and ethnic differences between samples did not drive results and replicated key findings from Studies 1 and 2. Together, these findings indicate that children favor proportional resource distribution in situations that invoke intuitions about equity. The authors suggest that these intuitions may form the basis for adult notions of fairness and generosity. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effects of RH on Glass Microfiber Filtration Efficiency for Airborne Bacteria and Bacteriophage Over Time

This study investigated the removal efficiency of viable signals of aerosolized bacteria and viruses, stabilized with respect to relative humidity, by simple glass microfiber filters. When examined over an extended time period, relative humidity affected both the size distribution of the stabilized aerosols and the removal efficiency of aerosolized microorganisms by simple glass microfiber filters. The size distribution of the generated humidity stabilized aerosol particles differed, with 50% relative humidity having a greater number of small diameter particles ( < .02 microns) than aerosols generated at 23% relative humidity, and 23% relative humidity having more particles in the range between .02 and .3 microns than 50%. The removal efficiency of aerosols containing viable bacteria (E. coli) and bacterial viruses (MS2) initially showed greater than 5 logs of removal (99.999%) at both 23% and 50% RHs for both aerosolized microorganisms. Increased RH was related to improved removal of viable aerosolized bacteria and viruses at all timepoints measured over a 60-minute test period. RH had more impact upon removal efficiencies for MS2 bacteriophages than E. coli bacteria, with removal efficiencies for MS2 at 50% RH declining after 30 minutes to levels seen at 23% RH. Some interesting findings of this study were that the two microorganisms that were mixed into a single cocktail at similar concentrations to generate the aerosol apparently did not associate, to a large extent, in the same aerosol particles, as inferred by significant differences in their removal behavior at higher RH of 50%. This study shows that the relative humidity of an aerosol-containing stream should be considered as an important experimental control variable, and that the removal of aerosolized viruses cannot be predicted from bacteria.     

Experimental Studies of Nanofluid Droplets in Spray Cooling

Spray cooling is used in cooling of electronic devices to remove large heat fluxes. Heat transfer to droplets impinging on a heated surface and boiling off has been studied. Most work is on a well-controlled system of a single drop falling onto a horizontal heated plate from a fixed height. These have revealed the droplet impingement mechanics to be a function largely of Weber number and excess temperature, and a range of regimes is observed similar to those in pool boiling, with a clearly identifiable critical heat flux. Nanofluids exhibit enhanced boiling heat transfer in pool boiling. The effect of nanoparticles on droplet boil-off was studied in this work. Nanofluid drops were let fall onto a surface at temperature greater than the saturation temperature, and behavior and heat flux were recorded and contrasted to that of a pure fluid. The working fluids used were pure water, ethanol, and dimethyl sulfoxide (DMSO) and ethanol– or DMSO–nanoparticle solutions (the nanoparticles were aluminum, with concentrations of up to 0.1% by weight in DMSO and 3.2% by weight in ethanol). High-speed photographic images of droplet evolution in time were obtained and indicate that there are differences in the behavior of nanofluid droplets as they boil off the surface, compared to pure fluids. Increasing nanoparticle concentration decreases the receding droplet breakup on rebound after impingement and appears to reduce the maximum spreading of a droplet as well. Maximum recoil height is reduced with increasing nanoparticle concentration. Experimental measurements of the heat fluxes associated with the pure and nanofluid droplets did not show significant enhancement, though there was noticeable improvement in the DMSO nanofluids.     

Embryonic-Derived Myb− Macrophages Enhance Bacterial Clearance and Improve Survival in Rat Sepsis

Peritoneal resident macrophages play a key role in combating sepsis in the peritoneal cavity. We sought to determine if peritoneal transplantation of embryonic Myb⁻ “peritoneal-like” macrophages attenuate abdominal fecal sepsis. Directed differentiation of rodent pluripotent stem cells (PSCs) was used in factor-defined media to produce embryonic-derived large “peritoneal-like” macrophages (Ed-LPM) that expressed peritoneal macrophage markers and demonstrated phagocytic capacity. Preclinical in vivo studies determined Ed-LPM efficacy in rodent abdominal fecal sepsis with or without Meropenem. Ex vivo studies explored the mechanism and effects of Ed-LPM on host immune cell number and function, including phagocytosis, reactive oxygen species (ROS) production, efferocytosis and apoptosis. Ed-LPM reduced sepsis severity by decreasing bacterial load in the liver, spleen and lungs. Ed-LPM therapy significantly improved animal survival by ~30% and reduced systemic bacterial burden to levels comparable to Meropenem therapy. Ed-LPM therapy decreased peritoneal TNFα while increasing IL-10 concentrations. Ed-LPMs enhanced peritoneal macrophage phagocytosis of bacteria, increased macrophage production of ROS and restored homeostasis via apoptosis and efferocytosis-induced clearance of neutrophils. In conclusion, Ed-LPM reduced systemic sepsis severity, improved survival and reduced bacterial load by enhancing peritoneal macrophage bacterial phagocytosis and killing and clearance of intra-peritoneal neutrophils. Macrophage therapy may be a potential strategy to address sepsis.