Sparse coding for improved signal-to-noise ratio in MRI

Magnetic Resonance images (MRI) do not only exhibit sparsity but their sparsity take a certain predictable shape which is common for all kinds of images. That region based localised sparsity can be used to de-noise MR images from random thermal noise. This paper present a simple framework to exploit sparsity of MR images for image de-noising. As, noise in MR images tends to change its shape based on contrast level and signal itself, the proposed method is independent of noise shape and type and it can be used in combination with other methods.

Application of power functions to chromatographic data for the enhancement of signal to noise ratios and separation resolution

Chromatographic detection responses are recorded digitally. A peak is represented ideally by a Guassian distribution. Raising a Guassian distribution to the power ‘n’ increases the height of the peak to that power, but decreases the standard deviation by √n. Hence there is an increasing disparity in detection responses as the signal moves from low level noise, with a corresponding decrease in peak width. This increases the S/N ratio and increases peak to peak resolution. The ramifications of these factors are that poor resolution in complex chromatographic data can be improved, and low signal responses embedded at near noise levels can be enhanced. The application of this data treatment process is potentially very useful in 2D-HPLC where sample dilution occurs between dimension, reducing signal response, and in the application of post-reaction detection methods, where band broadening is increased by virtue of reaction coils. In this work power functions applied to chromatographic data are discussed in the context of (a) complex separation problems, (b) 2D-HPLC separations, and (c) post-column reaction detectors.

Performance of juvenile Murray cod, Maccullochella peelii peelii (Mitchell), fed with diets of different protein to energy ratio

The results of a 56-day experiment on juvenile Murray cod, Maccullochella peelii peelii, an Australian native fish with a high aquaculture potential, of mean weight 14.9 ± 0.04 g, fed with five experimental diets, one a series of 40% protein content and lipid levels of 10, 17 and 24% (P40L10, P40L17 and P40L24), and another of 50% protein and 17 and 24% (P50L17 and P50L24) lipid are presented. The specific growth rate (SGR) (% day−1) of fish maintained on different diets ranged from 1.18 to 1.41, and was not significantly different between dietary treatments, except P40L10 and the rest. However, there was a general tendency for SGR to increase with increasing dietary lipid content at both protein levels. The food conversion ratio (FCR) for the 40% protein series diets were poorer compared with those of the 50% protein diets, and the best FCR of 1.14 was observed with the P50L17 diet. The protein efficiency ratio (PER), however, was better in fish reared on low protein diets. The net protein utilization (NPU) also did not differ significantly (P > 0.05) in relation to dietary treatment. As in the case of PER the highest NPU was observed in Murray cod reared on diet P40L24 and the lowest in fish fed with diet P50L24. The carcass lipid content reflected that of the diets, when significant increases in the lipid content was observed in relation to dietary lipid content at both protein levels. However, body muscle lipid content did not increase with increasing dietary lipid content, and was significantly lower than in the whole body. The fatty acids found in highest concentration amongst the saturates, monoenes and polyunsaturates (PUFAs) were 16 : 0, 18 : 1n-9 and 22 : 6n-3, respectively, and each of these accounted for more than 60% of each of the group's total. The muscle fatty acid content was affected by the dietary lipid content; for example the total amount (in μg mg−1 lipid) of monoenes ranged from 72 ± 5.1 (P40L10) to 112 ± 10 (P40L24) and 112 ± 2.8 (P50L17) to 132 ± 11.8 (P50L24) and the n-6 series fatty acids increased with increasing dietary lipid content, although not always significant. Most notably, 18 : 2n-6 increased with the dietary lipid level in both series of diets.

Waist-to-Hip Ratio and Unhealthy Body Change in Women

The role of waist-to-hip ratio (WHR) in unhealthy body change was examined in a sample of 143 women university students. They completed the Eating Disorder Examination-Questionnaire (EDE-Q), reported their level of concern with weight and with WHR, and used unmarked measuring tapes to record their subjective (self-perceived), ideal, and objective (measured) waist and hip circumference. Although body shape was reported as important, and concern with WHR correlated significantly with symptoms of disordered eating, the relationships involving WHR were not independent of those involving body weight. Thus, there appears to be little behavioural and/or clinical significance in the aesthetic evaluations made by women of their WHR. Reasons for this are considered in light of evidence that women regard WHR as more difficult to control and less amenable to change than their overall body weight.

Estimating expected excess returns using historical and option-implied volatility

We test the relation between expected and realized excess returns for the S&P 500 index from January 1994 through December 2003 using the proportional reward-to-risk measure to estimate expected returns. When risk is measured by historical volatility, we find no relation between expected and realized excess returns. In contrast, when risk is measured by option-implied volatility, we find a positive and significant relation between expected and realized excess returns in the 1994–1998 subperiod. In the 1999–2003 subperiod, the option-implied volatility risk measure yields a positive, but statistically insignificant, risk-return relation. We attribute this performance difference to the fact that, in the 1994–1998 subperiod, return volatility was lower and the average return was much higher than in the 1999–2003 subperiod, thereby increasing the signal-to-noise ratio in the latter subperiod.

Fourier transform infrared microspectroscopy as a tool to identify macroalgal propagules

Understanding of macroalgal dispersal has been hindered by the difficulty in identifying propagules. Different carrageenans typically occur in gametophytes and tetrasporophytes of the red algal family Gigartinaceae, and we may expect that carpospores and tetraspores also differ in composition of carrageenans. Using Fourier transform infrared (FT-IR) microspectroscopy, we tested the model that differences in carrageenans and other cellular constituents between nuclear phases should allow us to discriminate carpospores and tetraspores of Chondrus verrucosus Mikami. Spectral data suggest that carposporophytes isolated from the pericarp and female gametophytes contained κ-carrageenan, whereas tetrasporophytes contained λ-carrageenan. However, both carpospores and tetraspores exhibited absorbances in wave bands characteristic of κ-,ι-, and λ-carrageenans. Carpospores contained more proteins and may be more photosynthetically active than tetraspores, which contained more lipid reserves. We draw analogies to planktotrophic and lecithotrophic larvae. These differences in cellular chemistry allowed reliable discrimination of spores, but pretreatment of spectral data affected the accuracy of classification. The best classification of spores was achieved with extended multiplicative signal correction (EMSC) pretreatment using partial least squares discrimination analysis, with correct classification of 86% of carpospores and 83% of tetraspores. Classification may be further improved by using synchrotron FT-IR microspectroscopy because of its inherently higher signal-to-noise ratio compared with microspectroscopy using conventional sources of IR. This study demonstrates that FT-IR microspectroscopy and bioinformatics are useful tools to advance our understanding of algal dispersal ecology through discrimination of morphologically similar propagules both within and potentially between species.

First year pre-service teachers' mathematical content knowledge : methods of solution to a ratio question

In this article, pre-service teachers' mathematics content knowledge is explored through the analysis of two items about ratio from a Mathematical Competency, Skills and Knowledge Test. Pre-service teachers' thinking strategies, common errors and misconceptions in their responses are presented and discussed. Of particular interest was the range and nature of common incorrect responses for one whole-whole ratio question. Results suggested pre-service teachers had difficulty interpreting a worded multi-step, ratio (scale) question, with errors relating to ratio and/or conversion of measurement knowledge. These difficulties reveal underdeveloped knowledge of mathematical structure and mathematical connections as well as an inability to deconstruct key components of a mathematical problem. Most pre-service teachers also lacked knowledge of standard procedures and methods of solutions.

A spectral slit approach to doubletalk detection

A new class of doubletalk detector based on exploiting a spectral slit is proposed. This is achieved by spectrally deleting a frequency band in the far-end signal such that when the near-end signal is present, only the near-end spectral information is present. The proposed method relies solely on the detection of speech activity period in the slit area, and significantly, it requires no estimation of the echo path. Evaluation in typical acoustic echo setups shows that the proposed method outperforms other conventional doubletalk detectors in terms of probability of miss detection even under poor echo-to-noise ratio (ENR), low echo-to-far-end ratio (EFR) conditions, and echo path change.

Neuron’s spikes noise level classification using hidden markov models

Considering that the uncertainty noise produced the decline in the quality of collected neural signal, this paper proposes a signal quality assessment method for neural signal. The method makes an automated measure to detect the noise levels in neural signal. Hidden Markov Models were used to build a classification model that classifies the neural spikes based on the noise level associated with the signal. This neural quality assessment measure will help doctors and researchers to focus on the patterns in the signal that have high signal to noise ratio and carry more information.

Lower protein-to-carbohydrate ratio in maternal diet is associated with higher childhood systolic blood pressure up to age four years

The prenatal environment can influence development of offspring blood pressure (BP), which tracks into adulthood. This prospective longitudinal study investigated whether maternal pregnancy dietary intake is associated with the development of child BP up to age four years. Data are from 129 mother-child dyads enrolled in the Women and Their Children's Health study. Maternal diet was assessed using a validated 74-item food frequency questionnaire at 18 to 24 weeks and 36 to 40 weeks, with a reference period of the previous three months. Child systolic and diastolic BP were measured at 3, 6, 9, 12, 24, 36 and 48 months, using an automated BP monitor. Using mixed-model regression analyses adjusted for childhood growth indices, pregnancy intakes of percentage of energy (E%) polyunsaturated fat (β coefficient 0.73; 95% CI 0.003, 1.45; p = 0.045), E% omega-6 fatty acids (β coefficient 0.89; 95% CI 0.09, 1.69; p = 0.03) and protein-to-carbohydrate (P:C) ratio (β coefficient -14.14; 95% CI -27.68, -0.60; p = 0.04) were associated with child systolic BP trajectory up to 4 years. Child systolic BP was greatest at low proportions of dietary protein (<16% of energy) and high carbohydrate (>40% of energy) intakes. There may be an ideal maternal macronutrient ratio associated with optimal infant BP. Maternal diet, which is potentially modifiable, may play an important role in influencing offspring risk of future hypertension.

Book-to-market ratio, default risk and return implications: from a negative perspective

A paradox is created by the common practice in stock evaluation models of excluding stocks with a negative book equity (BE). If we interpret the book-to-market ratio as a proxy for distress risk, it makes no sense to exclude these negative BE stocks since they are, prima facie, most prone to distress risk. This paper reassesses the relationship between default risk, return and the book-to-market ratio by incorporating negative BE stocks into the study. We find that negative BE stocks carry higher default risks than their positive BE counterparts and that these risks are not totally offset by higher returns. This suggests that a default risk filter can be used in the investment universe selection process through which the portfolio return can be enhanced.

Noise level classification for EEG using Hidden Markov Models

EEG signal is one of the most important signals for diagnosing some diseases. EEG is always recorded with an amount of noise, the more noise is recorded the less quality is the EEG signal. The included noise can represent the quality of the recorded EEG signal, this paper proposes a signal quality assessment method for EEG signal. The method generates an automated measure to detect the noise level of the recorded EEG signal. Mel-Frequency Cepstrum Coefficient is used to represent the signals. Hidden Markov Models were used to build a classification model that classifies the EEG signals based on the noise level associated with the signal. This EEG quality assessment measure will help doctors and researchers to focus on the patterns in the signal that have high signal to noise ratio and carry more information. Moreover, our model was applied on an uncontrolled environment and on controlled environment and a result comparison was applied.

The catheter to vein ratio and rates of symptomatic venous thromboembolism in patients with a peripherally inserted central catheter (PICC): a prospective cohort study.

BACKGROUND: Peripherally inserted central catheters (PICCs) are a common vascular access device used in clinical practice. Their use may be complicated by adverse events such as venous thromboembolism (VTE). The size of the vein used for PICC insertion and thus the catheter to vein ratio is thought to be a controllable factor in the reduction of VTE rates in patients who have a PICC. However, an optimal catheter to vein ratio for PICC insertion has not previously been investigated to inform clinical practice. OBJECTIVES: To determine the effect of the catheter to vein ratio (proportion of the vein measured at the insertion point taken up by the catheter) on rates of symptomatic VTE in patients with a PICC and identify the optimal ratio cut-off point to reduce rates of this adverse event. METHOD: Adult patients waiting for PICC insertion at a large metropolitan teaching hospital were recruited between May and December 2013. Vein diameter at the PICC insertion site was measured using ultrasound with in-built callipers. Participants were followed up at eight weeks to determine if they developed symptomatic VTE. RESULTS: Data were available for 136 patients (50% cancer; 44% infection; 6% other indication for PICC). Mean age was 57 years with 54% males. There were four cases of confirmed symptomatic VTE (two involving the deep veins, one peripheral vein and one pulmonary embolism). Receiver operator characteristic (ROC) analysis determined that a 45% catheter to vein ratio was the ideal cut off point to maximise sensitivity and specificity (AUC 0.761; 95% CI 0.681-0.830). When a ratio of 46% or above was compared to one that was less than or equal to 45% using a log binomial generalised linear model it was found that participants with a catheter to vein ratio >45% were 13 times more likely to suffer VTE (relative risk 13, p=0.022; CI 1.445-122.788). CONCLUSION: It was found that a 45% catheter to vein ratio was the optimal cut off with high sensitivity and specificity to reduce the risk of VTE. However, further research is needed to confirm these results as although adequately powered; the number of cases of VTE was comparatively small, resulting in wide confidence intervals.

MMSE precoder for unitary space–time codes in correlated time-varying channels

This letter addresses the problem of the design of a precoder for multiple transmit antenna communication systems with spatially and temporally correlated fading channels. By using the asymptotic (high signal-to-noise ratio) mean-square error of the channel estimates, the letter derives a precoder for unitary space-time codes that can exploit the spatiotemporal correlation in the time-varying fading channels. Simulation results illustrate that significant performance gains can be achieved by using the new precoder.