On the linear shift invariance of photon diffusion imaging in highly scattering media

Abstract

We present an analytical perturbation analysis for studying the imaging characteristics of photon diffusion imaging in highly scattering media such as human tissues. Factors affecting the image formation in practical imaging system are taken into account, including the photon source, the optical properties of the sample, and the measurement system. A concise relationship between the internal structure and the detected signal is derived. Based on this, it is proved that photon diffusion imaging possess the property of linear shift invariance. The image formation mechanism in measurements such as functional imaging or tumour early diagnosis is illustrated from the viewpoint of the linear shift invariant system.     

Use of nicotine replacement therapy in socioeconomically deprived young smokers: a community-based pilot randomised controlled trial

Background

Smoking is common in young people, particularly in disadvantaged groups, and continued smoking has a major impact on quality and quantity of life. Although many young smokers want to stop smoking, little is known about the design and effectiveness of cessation services for them.

Objective

To determine whether nicotine replacement therapy (NRT) when combined with counselling is effective in young smokers in a deprived area of Nottingham, UK

Methods and subjects

We surveyed smoking prevalence and attitudes to smoking and quitting in young people accessing an open access youth project in a deprived area of Nottingham, and used the information gained to design a community based smoking cessation service incorporating a randomised controlled trial of nicotine patches against placebo given in association with individual behavioural support. We resurveyed smoking prevalence among project attendees after completing the pilot study.

Results

Of 264 young people surveyed (median age 14 years, range 11–21), 49% were regular smokers. A total of 98 young people were recruited and randomised to receive either active nicotine patches on a six week reducing dose regimen (49 participants), or placebo (49 participants). Adherence to therapy was low, the median duration being one week, and 63 participants did not attend any follow up. At four weeks, five subjects receiving active NRT and two receiving placebo were abstinent, and at 13 weeks none were. Adverse effects were more common in the active group but none were serious. Smoking prevalence among 246 youth project attendees surveyed after the trial was 44%.

Conclusions

This study suggests that NRT in this context is unlikely to be effective in young smokers, not least because of low adherence to therapy. It also suggests that young smokers want help with smoking cessation, but that establishing the efficacy of smoking cessation services for young people who need them most will be very difficult.     

Rational Design and Synthesis of Selective PRMT4 Inhibitors: A New Chemotype for Development of Cancer Therapeutics**

Protein arginine N-methyl transferase 4 (PRMT4) asymmetrically dimethylates the arginine residues of histone H3 and nonhistone proteins. The overexpression of PRMT4 in several cancers has stimulated interest in the discovery of inhibitors as biological tools and, potentially, therapeutics. Although several PRMT4 inhibitors have been reported, most display poor selectivity against other members of the PRMT family of methyl transferases. Herein, we report the structure-based design of a new class of alanine-containing 3-arylindoles as potent and selective PRMT4 inhibitors, and describe key structure–activity relationships for this class of compounds.     

Glucosinolates and Differential Herbivory in Wild Populations of Brassica oleracea

Glucosinolates are known to elicit responses from Brassica herbivores in laboratory studies. To study their importance in interactions with herbivores in the field, glucosinolate profiles and levels of herbivory were ascertained for wild cabbage plants growing in four neighboring populations in the UK. Glucosinolate profiles differed between plant populations, but not between different habitats within populations. Within habitats, there was no link between individual plant glucosinolate profiles and herbivory by Pieris spp., slugs and snails, flea beetles or aphids. Plants attacked by the micromoth, Selania leplastriana, contained higher levels of 2–hydroxy-3–butenylglucosinolate and 3–indolylmethylglucosinolate than plants within the same population that were not attacked. It is concluded that the differences in glucosinolate profiles between the plant populations are unlikely to be due to differential selection pressures from herbivores feeding on the mature plants over the two years studies.     

An integrated CMOS time interval measurement system withsubnanosecond resolution for the WA-98 calorimeter

The time interval measurement system of the WA-98 calorimeter is presented. This system consists of a constant fraction discriminator (CFD), a variable delay circuit, a time-to-amplitude converter (TAC), and a Wilkinson analog-to-digital converter (ADC) all realized in a 1.2-μm N-well CMOS process. These circuits measured the time interval between a reference logic signal and a photomultiplier tube (PMT) signal that had amplitude variations of 100:1 and 10-ns rise and fall times. The system operated over the interval range from 2 ns to 200 ns with a resolution of ~±300 ps including all walk and jitter components. The variable delay circuit allowed the CFD output to be delayed by up to 1 μs with a jitter component of ~0.04% of the delay setting. These circuits operated with a 5-V power supply. Although this application was in nuclear physics instrumentation, these circuits could also be useful in other scientific measurements, medical imaging, automatic test equipment, ranging systems, and industrial electronics