“Microbiology Topics” discusses various topics in microbiology of practical use in validation and compliance. We intend this column to be a useful resource for daily work applications. Reader comments, questions, and suggestions are needed to help us fulfill our objective for this column. Please send your comments and suggestions to column coordinator Scott Sutton at scott. [email protected]...

A fundamental aspect of predictive microbiology is the shape of the microbial growth curve and many models are used to fit microbial count data, the modified Gompertz and Baranyi equation being two of the most widely used. Rapid, automated methods such as turbidimetry have been widely used to obtain growth parameters, but do not directly give the microbial growth curve. Optical density (OD) dat...

ZnO nanorods with various aspect ratios (by changing the time of growth between 0-240 min) were synthesized using hydrothermal method and were investigated using XRD, SEM, UV–Vis and PL. It was found that growth time is directly coupled with the length, orientation and aspect ratio of the nanorod arrays. The optical transmittance of the NR arrays indicated a regular decrement of average transmi...

A design approach is described to achieve spectral blocking filters of any spectral width and optical density for narrow blocking bands. The ratio of the thickness of the high-index material to the low-index material in the layer pairs is adjusted to obtain the desired bandwidth in the first-harmonic reflection band. The number of layer pairs is adjusted to provide the required optical density....

Nanostructures of noble metal materials have been used in organic solar cells for enhancement of performance and light trapping. In this study, we have introduced branched silver cauliflower-like nanopatterns as sub-wavelength structured metal grating in organic solar cells. Self-assembled fabrication process of branched nanopatterns was carried out on a bio-template of cicada wing nanonipple a...

We have developed an objective procedure, using a modified retinal camera, to determine macular pigment (MP) optical density distributions in the human retina. Using two multi-band filters, reflectance maps of the retinas of young subjects (<25 years old) were obtained at 460, 528, 610 and 670 nm, without pupil dilation. The log-transformed maps were combined linearly to yield optical density m...

PURPOSE To measure the optical density of the crystalline lens and macular pigments in a group of patients with diabetes mellitus and compare the results with those in a group of control subjects. METHODS Color matches were performed using a Wright tristimulus colorimeter. The reference wavelength used was 490 nm, desaturated with 650 nm. Lens optical density was measured by mixing spectral p...

We present experimental evidence that the intensity correlations of light scattered from a cold-atom cloud are sensitive to the presence of small amounts of radiation trapping in an atomic sample of density 6 x 10(8)/cm3, with an optical depth (for a resonant light beam) of 0.4. This density and optical depth are approximately an order of magnitude less than the density and on-resonance optical...