A pseudo-matched filter for chaos

A matched filter maximizes the signal-to-noise ratio of a signal. In the recent work of Corron et al. [Chaos 20, 023123 (2010)], a matched filter is derived for the chaotic waveforms produced by a piecewise-linear system. Motivated by these results, we describe a pseudo-matched filter, which removes noise from the same chaotic signal. It consists of a notch filter followed by a first-order, low-pass filter. We compare quantitatively the matched filter's performance to that of our pseudo-matched filter using correlation functions in a simulated radar application. On average, the pseudo-matched filter performs with a correlation signal-to-noise ratio that is 2.0 dB below that of the matched filter. Our pseudo-matched filter, though somewhat inferior in comparison to the matched filter, is easily realizable at high speed (> 1 GHz) for potential radar applications

Subwavelength position sensing using nonlinear feedback and wave chaos

We demonstrate a position-sensing technique that relies on the inherent sensitivity of chaos, where we illuminate a subwavelength object with a complex structured radio-frequency field generated using wave chaos and a nonlinear feedback loop. We operate the system in a quasi-periodic state and analyze changes in the frequency content of the scalar voltage signal in the feedback loop. This allows us to extract the object's position with a one-dimensional resolution of ~\lambda/10,000 and a two-dimensional resolution of ~\lambda/300, where \lambda\ is the shortest wavelength of the illuminating source.Comment: 4 pages, 4 figure

Ultra-high-frequency piecewise-linear chaos using delayed feedback loops

We report on an ultra-high-frequency (> 1 GHz), piecewise-linear chaotic system designed from low-cost, commercially available electronic components. The system is composed of two electronic time-delayed feedback loops: A primary analog loop with a variable gain that produces multi-mode oscillations centered around 2 GHz and a secondary loop that switches the variable gain between two different values by means of a digital-like signal. We demonstrate experimentally and numerically that such an approach allows for the simultaneous generation of analog and digital chaos, where the digital chaos can be used to partition the system's attractor, forming the foundation for a symbolic dynamics with potential applications in noise-resilient communications and radar

Investigating the effects of temperature on secondary metabolism in Vitis vinifera L. cv. merlot berries

Grapes (e.g. Vitis vinifera L.) are one of the more important fruit crops from an economic standpoint with world market values over 550 million US dollars in 2007 and 2008, second to apples (United States Department of Agriculture). While a satisfactory level of ripeness is of primary concern, the quality of wine grapes is determined the contribution of secondary metabolites. econdary metabolites provide the color, aroma, flavor, and tactile sensations associated with wine and are believed to be of biological value to humans. Anthocyanins provide the color to red grapes and wine while flavonols are thought to provide color stability to wine through copigmentation with anthocyanins. Proanthocyanidins (PAs) provide astringency or a tactile response in the mouth, which is a primary element of wine quality. For the plant, secondary metabolites are involved in signaling, seed dissemination, and protection against biotic and abiotic stresses. In this work, the temperature of field-grown grapes, Vitis vinifera L. cv. Merlot, was manipulated by cooling and heating berries relative to ambient temperatures during three growing seasons. A range of thermal time was investigated by delivering cold air during the day (Cool) or warm air at night (Heat). Additionally, the effect of reducing the diurnal temperature range (DTR) was investigated by daytime cooling and nighttime heating without a significant change in the accumulated thermal time compared to ambient berries. The impact on PAs was studied by imposing treatments from fruit set to véraison during active PA biosynthesis. Treatments imposed from véraison to harvest maturity (≥ 22.0°Brix) were intended to assess the impact on flavonol and anthocyanin accumulation and changes in PAs during ripening. In 2008, experiments focused on PA accumulation by examining metabolites and the expression of genes involved in PA biosynthesis at ten-day intervals up to véraison. Treatment effects described here demonstrate a complex response of grape berries to shifts in temperatures. The data suggest periods of sensitivity with respect to secondary metabolism that may dictate the response to changes in temperatures. To the authors’ knowledge, the data presented here is the first of it’s kind; examining the effect of temperature on active PA biosynthesis in both the skin and seed of grape as well as the effect of altering the DTR of berries grown under field conditions. This research has implications in understanding fundamental plant responses to their environment and the impact of climate shifts and seasonal temperature variations on grape berry composition

Assessing the impact of temperature on grape phenolic metabolism

Many climatic factors influence grape berry composition including nutrient status, water availability, biotic stress, sun exposure and temperature. Previous research examined the effects of many factors listed above and much progress has been made. It is often difficult, however, to separate effects that typically confound each other, such as sun exposure and temperature. Increasing exposure of a berry to the sun will lead to some degree of heating unless the temperature is otherwise maintained. In this study berry temperatures where manipulated independent of sun exposure, necessarily separating the two effects. The objective of this study was to assess the impact of fruit temperature on the phenolic metabolism of grape berries (Vitis vinifera L. cv. Merlot) grown under field conditions with controlled exposure to sunlight. While similar studies have focused on production and accumulation of anthocyanins our primary focus was on proanthocyanidins or ‘tannins’. Here we report the effects of modulating daytime and nighttime temperatures as well as damping the diurnal temperature range. Furthermore, research was broken into two phases: berry set to véraison (phase I) and véraison to commercial harvest (phase II). This was to assess the effects of treatments during two discrete phases of berry development characterized by accumulation of distinct phenolic metabolites. Samples collected at véraison indicated that damping the diurnal temperature fluctuation advanced the onset of ripening. Those berries were larger (doubledamped: 0.753±0.015 vs control: 0.512±0.034 g/berry) and more colored than all others. Phenolic material from grape seed and skin was quantified and characterized using three chromatography methods. Proanthocyanidin accumulation at véraison was linearly related to heat summation over the developmental period with nighttime heating yielding the highest concentration and daytime cooling yielding the lowest (night-heat: 1.46±0.13 vs day-cool: 0.97±0.09 mg/berry). Damping the diurnal temperature fluctuation reduced proanthocyanidin mDP (double-damped: 21.8±1.0 vs control: 28.0±1.7). Day-Cooling resulted in an increase in the concentration of flavonols at the end of phase I yet a decrease at the end of phase II. The goal of this work is to provide researchers with additional information regarding climatic factors influencing phenolic biosynthesis and to provide grape growers with tools to better manage their crop

Postsynthetic modification of coordination networks

Belgium Herbarium image of Meise Botanic Garden

The Risk of Fracture in Patients Undergoing Androgen Deprivation May Be Overstated: Analysis of an Unselected Cohort of Patients

Objective: In this study we examined the prevalence of fracture among men undergoing ADT for prostate cancer to determine if the fracture risk was increased among this population.Background: Androgen deprivation therapy (ADT) is a therapeutic approach for men with various prostate cancer disease states. Treatment-related side effects of ADT include rapid bone loss. Previous studies have found that the bone loss related to ADT leads to the development of fractures. Methods: This is a retrospective cohort study of patients treated with ADT in a radiation oncology and medical oncology practice at an urban academic medical center from 2005 to 2010. Patients with evidence of bone metastases responsive to ADT were included. Those with androgen-independent prostate cancer were excluded. Results: One hundred thirty patients met the inclusion criteria and among them only three fractures occurred during 373 person-years of follow-up. The fracture-free survival (FFS) rate at three years for all was 97.7%. Excluding fractures occurring within six months of ADT initiation, the FFS rate was 100% at three years. No significant difference was demonstrated in those screened with a pretreatment dual-emission X-ray absorptiometry (DEXA) scan; there was no relationship between the number of ADT cycles, recovery of testosterone to normal, or total time on ADT. Older patients, surprisingly, had a lower risk (p = 0.054). Patients with normal bone mineral density (BMD) had an FFS rate of 93.8% at three years, osteopenic patients had 94.7%, and patients with osteoporosis and hormone-responsive metastases had 100%. Conclusion: The prevalence of fracture among this group is significantly less than what has previously been reported for men receiving ADT, potentially suggesting an overstatement of risk in the literature to date. Further prospective study with a larger sample size is needed