Corneal minimal visible lesion thresholds for 2.0 microm laser radiation

To support refinement of the ANSI Maximum Permissible Exposure safety limits, a series of experiments were conducted in vivo on Dutch Belted rabbit corneas to determine corneal minimum visible lesion thresholds for 2.0 microm continuous-wave laser irradiation. Single pulse radiant exposures were made at specified pulse durations of 0.1, 0.25, 0.5, 1.0, 2.0, and 4.0 s for spot 1/e(2) diameters of 1.17 mm and 4.02 mm. Threshold lesions were defined as the presence of a superficial surface whitening one hour after irradiation. Temperature measurements indicated that threshold peak temperatures were dependent on spot size and exposure duration. The exposure duration dependence of threshold average radiant exposure was described by an empirical power law equation: threshold radiant exposure[J/cm(2)]=a x exposure duration[s](b).     

High-performance elastomeric nanocomposites via solvent-exchange processing

The incorporation of nanoparticles into engineering thermoplastics affords engineers an opportunity to synthesize polymer nanocomposites that potentially rival the most advanced materials in nature. Development of these materials is difficult because thermodynamic and kinetic barriers inhibit the dispersal of inorganic, often hydrophilic nanoparticles in hydrophobic polymer matrices. Using a new solvent-exchange approach, we preferentially reinforce the hard microdomains of thermoplastic elastomers with smectic clay of similar characteristic dimensions. The strong adhesion between the clay and the hard microdomains coupled with the formation of a percolative network not only stiffens and toughens, but increases the heat distortion temperature of the material and induces reversible thermotropic liquid-crystalline transitions. The discotic clay platelets induce morphological ordering over a range of length scales, which results in significant thermomechanical enhancement and expands high-temperature applications. Merging block-copolymer processing techniques with this method for preferential ordering of nanoparticle facilitates the development of new, hierarchically ordered materials.     

Changes of arginyl and leucyl aminopeptidase activities in biceps femoris along Jinhua ham processing

Sixty experimental Jinhua hams were processed by a traditional method. The potential arginyl (RAP) and leucyl (LAP) aminopeptidase activities in biceps femoris were determined. The effects of temperature, salt content, sodium nitrate content and pH value on muscle RAP and LAP activities were evaluated using response surface methodology. Porcine muscle was found to possess very strong potential RAP and LAP activities that decreased gradually during processing from 165,980.97Ug(-1) and 89,201.52Ug(-1) before salting to 3164.70Ug(-1) and 5373.66Ug(-1) after aging, respectively. Temperature, pH value and salt content had significant effects on RAP and LAP activities (P<0.0001). They interacted with each other in their effects on RAP activity (P<0.0001) and influenced LAP activity in exponential way (P<0.05). However, 0-50mgL(-1) sodium nitrate had no detectable effect on either RAP or LAP activity (P>0.05). The regression models showed that muscle RAP and LAP maintained their activities all through Jinhua ham processing. LAP could display very strong actual activity during aging and post-aging, indicating that muscle LAP may play the most important role in generating free amino acids during the processing of Jinhua ham.     

Wide-angle catadioptric lens with a rectilinear projection scheme

A catadioptric wide-angle lens having a rectilinear projection scheme has been developed with a view to possible applications in the security-surveillance area. The lens has been designed for a miniature camera with a video graphics array-grade 1/3 in. color CCD sensor. The field of view of the lens is over 151 degrees , and still distortion is under 1%. Furthermore, the modulation transfer function is better than 0.3 at 70 line pairs/mm over the whole active area of the image sensor.     

Conversion of a Bi nanowire array to an array of Bi-Bi2O3 core-shell nanowires and Bi2O3 nanotubes

A template-based heat-treatment method has been developed to convert metal nanowire arrays into arrays of metal-metal oxide core-shell nanowires and single-crystalline metal oxide nanotubes. This process is demonstrated by kinetically controlling the conversion of single-crystalline Bi nanowires to Bi-Bi(2)O(3) core-shell nanowires via a multistep, slow oxidation method, and then controlling their further conversion to a single-crystalline Bi(2)O(3) nanotube array via fast oxidation. This process can conveniently be extended to fabricate a free-standing, easily oxidized metal-metal oxide nanowire and metal oxide nanotube array, which may have future applications in nanoscale optics, electronics, and magnetics.     

Studies on acrylamide levels in roasting, storage and brewing of coffee

The content of acrylamide in coffee reaches a peak early in the roasting process, reflecting occurrence of both formation and destruction of acrylamide during roasting. Levels of acrylamide in the fully roasted product are a small fraction of the peak reached earlier. Glucose and moisture in green coffee do not show a significant correlation with acrylamide in roasted coffee. Pre-roasting levels of asparagine show a correlation only in Arabica coffee. The main factors affecting the level of acrylamide in roasted coffee appear to be the Arabica/Robusta ratio, with Robusta giving higher levels; time and degree of roast, with both shorter and lighter roasting at the edges of the normal roasting range giving higher levels; storage condition and time, with clear reduction at ambient storage. This storage reduction of acrylamide followed second order reaction kinetics with an activation energy of 73 KJ/mole. The acrylamide in roasted coffee is largely extracted into the brew and stable within usual time of consumption. As these four main factors also substantially affect the sensorial characteristics of the brew, and as modifications of the process have to comply with the consumer-accepted boundaries of taste profiles, only small effects on the acrylamide level are expected to be achievable.     

Inductively heated shape memory polymer for the magnetic actuation of medical devices

Presently, there is interest in making medical devices such as expandable stents and intravascular microactuators from shape memory polymer (SMP). One of the key challenges in realizing SMP medical devices is the implementation of a safe and effective method of thermally actuating various device geometries in vivo. A novel scheme of actuation by Curie-thermoregulated inductive heating is presented. Prototype medical devices made from SMP loaded with nickel zinc ferrite ferromagnetic particles were actuated in air by applying an alternating magnetic field to induce heating. Dynamic mechanical thermal analysis was performed on both the particle-loaded and neat SMP materials to assess the impact of the ferrite particles on the mechanical properties of the samples. Calorimetry was used to quantify the rate of heat generation as a function of particle size and volumetric loading of ferrite particles in the SMP. These tests demonstrated the feasibility of SMP actuation by inductive heating. Rapid and uniform heating was achieved in complex device geometries and particle loading up to 10% volume content did not interfere with the shape recovery of the SMP.     

Hologram reconstruction corrected for measurements through layers with different refractive indices in digital in-line holographic microscopy

Digital in-line holographic microscopy (DIHM) using point sources has been shown to be a versatile technique, especially for three-dimensional tracking of particles or microorganisms. However, the spherical source wave is altered when measurements are performed through layers with different refractive indices, such as water cuvettes. The situations where a layer of medium with a refractive index different than that of the predominant surrounding propagation medium (usually air) is situated behind or in front of the plane to be reconstructed are analyzed in detail, and a general approach for reconstruction under such circumstances is developed. The proposed refractive index correction is tested experimentally and compared to conventional reconstruction algorithms. Using 3D traces of swimming algal spores, the influence on the velocity calculation is also shown.     

Excretion of volatile ¹³¹I from rats following administration of Na¹³¹I or MIBG-¹³¹I

Current practice for radiation protection associated with (131)I therapy mainly focuses on external and internal exposure caused by physical contamination of the hospital staff, other patients and family members. However, if volatile (131)I is excreted by the treated patients, these individuals could also be exposed through inhalation of (131)I. This study quantifies the amount of volatile (131)I excreted by rats after intravenous administration of metaiodobenzylguanidine (MIBG)-(131)I or Na(131)I, the two most common forms of (131)I therapy. The results indicate that in 4 d following administration, the total excretion of volatile (131)I was 0.036 and 0.17 % of the administered activities of MIBG-(131)I and Na(131)I, respectively. As administered activities for (131)I therapy are typically of the order of 1-10 GBq, the overall excretion of volatile (131)I from a patient can be as high as 20 MBq. As a result, a family member can receive up to 0.07 mSv committed effective dose from inhaling the volatile (131)I excreted by the patient.     

Memristive tri-stable resistive switching at ruptured conducting filaments of a Pt/TiO₂/Pt cell

A tri-stable memristive switching was demonstrated on a Pt/TiO?/Pt device and its underlying mechanism was suggested through a series of electrical measurements. Tri-stable switching could be initiated from a device in unipolar reset status. The unipolar reset status was obtained by performing an electroforming step on a pristine cell which was then followed by unipolar reset switching. It was postulated that tri-stable switching occurred at the location where the conductive filament (initially formed by the electroforming step) was ruptured by a subsequent unipolar reset process. The mechanism of the tri-stable memristive switching presented in this article was attributed to the migration of oxygen ions through the ruptured filament region and the resulting modulation of the Schottky-like interfaces. The assertion was further supported by a comparison study performed on a Pt/TiO?/TiO(2-x)/Pt cell.