High speed video capture for mobile phone cameras

We consider an electromechanical model for the operation of a voice coil motor in a mobile phone camera, with the aim of optimizing how a lens can be moved to a desired focusing motion. Although a methodology is developed for optimizing lens shift, there is some concern about the experimentally-determined model parameters that are at our disposal. Central to the model is the value of the estimated magnetic force constant, Kf: its value determines how far it is actually possible to move lens, but it appears that, from the value given, it would not be possible to shift the lens through the displacements desired. Furthermore, earlier experiments have also estimated the value of the back EMF constant, Kg , to be roughly five times greater than Kf, even though we present two theoretical arguments that show that Kf = Kg: a conclusion supported by readily-available manufacturers’ data

Dementia after Stroke Increases the Risk of Long-Term Stroke Recurrence

Background: Although risk factors for first stroke have been identified, the predictors of long-term stroke recurrence are less well understood. We performed the present study to determine whether dementia diagnosed three months after stroke onset is an independent risk factor for long-term stroke recurrence. Methods: We examined 242 patients (age = 72.0 ± 8.7 years) hospitalized with acute ischemic stroke who had survived the first three months without recurrence and followed them to identify predictors of long-term stroke recurrence. We diagnosed dementia three months after stroke using modified DSM-III-R criteria based on neuropsychological and functional assessments. The effects of conventional stroke risk factors and dementia status on survival free of recurrence were estimated using Kaplan-Meier analyses, and the relative risks (RR) of recurrence were calculated using Cox proportional hazards models. Results: Dementia (RR = 2.71, 95% CI = 1.36 to 5.42); cardiac disease (RR = 2.18, CI = 1.15 to 4.12); and sex, with women at higher risk (RR = 2.03, CI = 1.01 to 4.10), were significant independent predictors of recurrence, while education (RR = 1.90, CI = 0.77 to 4.68), admission systolic blood pressure >160 mm Hg (RR = 1.80, CI = 0.94 to 3.44) and alcohol intake exceeding 160 grams per week (RR = 1.86, CI = 0.79 to 4.38) were weakly related. Conclusions: Our results suggest that dementia significantly increases the risk of long-term stroke recurrence, with additional independent contributions by cardiac disease and sex. Cognitive impairment may be a surrogate marker for multiple vascular risk factors and larger infarct volume that may serve to increase the risk of recurrence. Alternatively, less aggressive medical management of stroke patients with cognitive impairment or noncompliance of such patients with medical therapy may be bases for an increased rate of stroke recurrence

A novel α-type carbonic anhydrase associated with the thylakoid membrane in Chlamydomonas reinhardtii is required for growth at ambient CO\u3csub\u3e2\u3c/sub\u3e

A 29.5 kDa intracellular α-type carbonic anhydrase, designated Cah3, from the unicellular green alga Chlamydomonas reinhardtii is the first of this type discovered inside a photosynthetic eukaryote cell. We describe the cloning of a cDNA which encodes the protein. Immunoblot studies with specific antibodies raised against Cah3 demonstrate that the polypeptide is associated exclusively with the thylakoid membrane. The putative transit peptide suggests that Cah3 is directed to the thylakoid lumen, which is confirmed further by the presence of mature sized Cah3 after thermolysin treatment of intact thylakoids. Complementation of the high inorganic carbon concentration-requiring mutant, cia3, with a subcloned cosmid containing the cah3 gene yielded transformants that grew on atmospheric levels of CO2 (0.035%) and contained an active 29.5 kDa α-type carbonic anhydrase. Although, cia3 has reduced internal carbonic anhydrase activity, unexpectedly the level of Cah3 was similar to that of the wild-type, suggesting that the mutant accumulates an inactive Cah3 polypeptide. Genomic sequence analysis of the mutant revealed two amino acid changes in the transit peptide. Results from photosynthesis and chlorophyll a fluorescence parameter measurements show that the cia3 mutant is photosynthetically impaired. Our results indicate that the carbonic anhydrase, extrinsically located within the chloroplast thylakoid lumen, is essential for growth of C.reinhardtii at ambient levels of CO2, and that at these CO2 concentrations the enzyme is required for optimal photosystem II photochemistry

Second-Order Coherence Across the Brillouin Lasing Threshold

Brillouin-Mandelstam scattering is one of the most accessible nonlinear optical phenomena and has been widely studied since its theoretical discovery one hundred years ago. The scattering mechanism is a three-wave mixing process between two optical fields and one acoustic field and has found a broad range of applications spanning microscopy to ultra-narrow-linewidth lasers. Building on the success of utilizing this nonlinearity at a classical level, a rich avenue is now being opened to explore Brillouin scattering within the paradigm of quantum optics. Here, we take a key step in this direction by employing quantum optical techniques yet to be utilized for Brillouin scattering to characterize the second-order coherence of Stokes scattering across the Brillouin lasing threshold. We use a silica microsphere resonator and single-photon counters to observe the expected transition from bunched statistics of thermal light below the lasing threshold to Poissonian statistics of coherent light above the threshold. Notably, at powers approaching the lasing threshold, we also observe super-thermal statistics, which arise due to instability and a ``flickering'' in and out of lasing as the pump field is transiently depleted. The statistics observed across the transition, including the ``flickering'', are a result of the full nonlinear three-wave mixing process and cannot be captured by a linearized model. These measurements are in good agreement with numerical solutions of the three-wave Langevin equations and are well demarcated by analytical expressions for the instability and the lasing thresholds. These results demonstrate that applying second-order-coherence and photon-counting measurements to Brillouin scattering provides new methods to advance our understanding of Brillouin scattering itself and progress toward quantum-state preparation and characterization of acoustic modes.Comment: Main (8 pages, 2 figures) + Supplementary (6 pages, 1 figures), Submitte

The Workshop Tutorial project book launch during the 2003 UniServe Science Conference

The Workshop Tutorial project has grown in answer to the perceived need to provide students with an opportunity to use and discuss principles of physics and their applications in a learning environment that encourages interaction with peers and supervising staff. In this manner the Workshops compliment the large traditional lectures that students are expected to attend. The style of the questions and activities are chosen to provide a mixture of quantitative and qualitative conceptbased questions and concrete hands-on activities. Reference to research in physics education on student misconceptions has been made in formulating questions (Sharma, Millar and Seth 1999)

Planning for Sustainability in Small Municipalities: The Influence of Interest Groups, Growth Patterns, and Institutional Characteristics

How and why small municipalities promote sustainability through planning efforts is poorly understood. We analyzed ordinances in 451 Maine municipalities and tested theories of policy adoption using regression analysis.We found that smaller communities do adopt programs that contribute to sustainability relevant to their scale and context. In line with the political market theory, we found that municipalities with strong environmental interests, higher growth, and more formal governments were more likely to adopt these policies. Consideration of context and capacity in planning for sustainability will help planners better identify and benefit from collaboration, training, and outreach opportunities