Complex Master Slave Interferometry

A general theoretical model is developed to improve the novel Spectral Domain Interferometry method denoted as Master/Slave (MS) Interferometry. In this model, two functions, g and h are introduced to describe the modulation chirp of the channeled spectrum signal due to nonlinearities in the decoding process from wavenumber to time and due to dispersion in the interferometer. The utilization of these two functions brings two major improvements to previous implementations of the MS method. A first improvement consists in reducing the number of channeled spectra necessary to be collected at Master stage. In previous MSI implementation, the number of channeled spectra at the Master stage equated the number of depths where information was selected from at the Slave stage. The paper demonstrates that two experimental channeled spectra only acquired at Master stage suffice to produce A-scans from any number of resolved depths at the Slave stage. A second improvement is the utilization of complex signal processing. Previous MSI implementations discarded the phase. Complex processing of the electrical signal determined by the channeled spectrum allows phase processing that opens several novel avenues. A first consequence of such signal processing is reduction in the random component of the phase without affecting the axial resolution. In previous MSI implementations, phase instabilities were reduced by an average over the wavenumber that led to reduction in the axial resolution

From master slave interferometry to complex master slave interferometry: theoretical work

A general theoretical framework is described to obtain the advantages and the drawbacks of two novel Fourier Domain Optical Coherence Tomography (OCT) methods denoted as Master/Slave Interferometry (MSI) and its extension denoted as Complex Master/Slave Interferometry (CMSI). Instead of linearizing the digital data representing the channeled spectrum before a Fourier transform can be applied to it (as in OCT standard methods), channeled spectrum is decomposed on the basis of local oscillations. This replaces the need for linearization, generally time consuming, before any calculation of the depth profile in the range of interest. In this model two functions, g and h, are introduced. The function g describes the modulation chirp of the channeled spectrum signal due to nonlinearities in the decoding process from wavenumber to time. The function h describes the dispersion in the interferometer. The utilization of these two functions brings two major improvements to previous implementations of the MSI method. The paper details the steps to obtain the functions g and h, and represents the CMSI in a matrix formulation that enables to implement easily this method in LabVIEW by using parallel programming with multi-cores

Witnessing Intimate Partner Violence as a Child Does Not Increase the Likelihood of Becoming an Adult Itimate Partner Violence Victim

Objectives: To determine whether adults who witnessed intimate partner violence (IPV) as children would have an increased rate of being victims of ongoing IPV, as measured by the Ongoing Violence Assessment Tool (OVAT), compared with adult controls who did not witness IPV as children. The authors also sought to determine whether there were differences in demographics in these two groups. Methods: This was a cross sectional cohort study of patients presenting to a high-volume academic emergency department. Emergency department patients presenting from November 16, 2005, to January 5, 2006, during 46 randomized four-hour shifts were included. A confidential computer touch-screen data entry program was used for collecting demographic data, including witnessing IPV as a child and the OVAT. Main outcome measures were witnessing IPV as a child, ongoing IPV, and associated demographics. Assuming a prevalence of IPV of 20% and a clinically significant difference of 20% between adults who witnessed IPV as children and adult controls who did not witness IPV as children, the study was powered at 80%, with 215 subjects included. Results: A total of 280 subjects were entered; 256 had complete data sets. Forty-nine percent of subjects were male, 45% were Hispanic, 72 (28%) were adults who witnessed IPV as children, and 184 (72%) were adult controls who did not witness IPV as children. Sixty-three (23.5%) were positive for ongoing IPV. There was no correlation of adults who witnessed IPV as children with the presence of ongoing IPV, as determined by univariate and bivariate analysis. Twenty-three of 72 (32%) of the adults who witnessed IPV as children, and 39 of 184 (21%) of the adult controls who did not witness IPV as children, were positive for IPV (difference, 11%; 95% confidence interval [CI] = 2% to 23%). Significant correlations with having witnessed IPV as a child included age younger than 40 years (odds ratio [OR], 4.2; 95% CI = 1.7 to 9.1), income less than $20,000/year (OR, 5.1; 95% CI = 1.6 to 12.5), and abuse as a child (OR, 9.1; 95% CI = 4.2 to 19.6). Other demographics were not significantly correlated with having witnessed IPV as a child. Conclusions: Adults who witnessed IPV as children were more likely to have a lower income, be younger, and have been abused as a child, but not more likely to be positive for ongoing IPV, when compared with patients who had not witnessed IPV

Q-switch-pumped supercontinuum for ultra-high resolution optical coherence tomography

In this Letter, we investigate the possibility of using a commercially availabl

Supercontinuum applications in high resolution non invasive optical imaging

Progress will be presented in adapting supercontinuum sources to a variety of applications with emphasis on signal processing procedures. These are customised to alleviate noise and take full advantage of the large bandwidth and large power spectral density of modern supercontinuum sources

Mechanical Properties of Composites Used in High-Voltage Applications

Materials used in high voltage applications have to meet a lot of regulations for their safety and functional usage during their lifetime. For high voltage applications the electrical properties are the most relevant designing criteria. However, the mechanical properties of such materials have rarely been considered for application dimensioning over the last decades. This article gives an overview of composite materials used in high voltage applications and some basic mechanical and thermo-mechanical characterization methods of such materials, including a discussion of influences on practically used epoxy based thermosets

Bioinspired fracture toughness enhancement of a fully bio-based epoxy resin

In this work, the concept of fracture toughness improvement via spatial variation of mechanical properties is applied to a composite with 100% bio-based carbon content based on epoxidized linseed oil. By proper selection of the hardener, either citric acid or sebacic acid, the mechanical properties were adjusted in a way that a bio-composite exhibits a stiff-soft-stiff layer architecture. Samples with two different thicknesses of soft interlayer (approx. 0.1 mm and 1.3 mm) were subsequently analyzed regarding their final performance. Specimen characteristics, owing to the curing and manufacturing process, were analyzed by means of local Fourier-transform infrared spectroscopy and differential scanning calorimetry. Fracture mechanics tests were performed to verify if the soft interlayer acts as a crack arrester. The results propose a high chemical compatibility between the used epoxy resins. Embedding a soft thin interlayer into a stiff resin matrix led to an increase in fracture toughness of 13 times, compared to the pure stiff resin. An increase in interlayer thickness led to a further increase in fracture toughness of 24 times. However, the stiffness decreased by 44% and 67%, respectively