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Motivation• Lightweight, portable devices must be physically small.• They can thus have only small, limited capacity batteries making power consumption the key system design parameter.• In addition, it is often desirable to carry out onboard signal processing.• Low power, low computational complexity signal processing methods are thus required.• The Continuous Wavelet Transform (CWT) is one such signal processing technique. It is used by the portable system described in [1] and so a low power implementation requires investigation. Objectives• To illustrate a wavelet approximation procedure termed the Low Power CWT (LPCWT) as it is suitable for low power implementation. The method is similar to that in [2] and related papers, and can be implemented using any desired circuit topology.• To act as a step-by-step wavelet design guide, illustrating the trade-offs that are possible. This could be useful to engineers with similar signal processing requirements.• To give application specific performance metrics for the approximation method. This allows the performance of the LPCWT in a real usage situation to be found which is more meaningful than an arbitrary error norm between the wanted and approximated wavelet shapes. Wavelet design procedure• The CWT of signal x(t) at a scale a, time b and with mother wavelet ψ(t) is defined as• This is equivalent to the convolution of the signal x(t) with an impulse response• All that is needed to implement the CWT at scale a is thus a filter with impulse response h(t), or the corresponding H(s).The design procedure to generate H(s) is summarised as:1. Based on the application determine the mother wavelet required. The Mexican hat wavelet is the example used here.2. Choose the scales at which analysis must be carried out.Reducing the number of scales used will reduce the circuitry required and minimise the power consumption.3. Mathematically approximate the wavelet shape using the procedure outlined here, exploiting the mathematical form if possible.4. Determine a time delay T to ensure that the wavelet approximation is realisable.5. Use the dynamic range and other application specific criteria to select the order of the approximation required.6. Generate the required filter transfer functions and implement these in a suitable circuit.• The Mexican hat mother wavelet is considered here: • But ψ(t) is symmetrical around t = 0 so this is not stable.• To correct for this a time delay T is introduced shifting ψ(t) to the right. Letting jω → s:• This is in rational form, but requires a finite order denominator for implementation.• Thus a Maclaurin series expansion is used to give the final generalised transfer function:• T can be varied to help place the poles in desired positions. The figure below illustrates the case for a 3 rd order approximation. • Note that the bode plots only need to match over the dynamic range of the situation under consideration.• Full numerical transfer functions ready for implementation can now be found.• Substituting a = 0.1 and T = 0.4 into the 7 th order a...

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4-Hydroxyandrostenedione (4-OHA) is a specific inhibitor of aromatase activity used for the treatment of breast cancer in post-menopausal women. Treatment with 4-OHA has been shown to inhibit the peripheral conversion of androstenedione to oestrone and reduce plasma oestrogen concentrations, but the effect of treatment on breast-tissue oestrone concentrations is not known. We have therefore examined the effect of treatment with 4-OHA on oestrone concentrations in normal and malignant breast tissues and also measured plasma and tissue 4-OHA concentrations. Changes in tumour oestrone concentrations were related to DNA polymerase alpha activity, a marker of cellular proliferation. Blood and breast-tissue samples were obtained before and 36 hr after treatment with 4-OHA. The mean plasma concentration of 4-OHA was 27.9 +/- 19.3 ng/ml, compared with levels of 33.7 +/- 25.6 ng/g for breast tumour and 13.5 +/- 11.5 ng/g for normal breast tissue. There was a significant correlation between 4-OHA concentrations in plasma and normal breast tissue (r = 0.91, p less than 0.001). Treatment with 4-OHA resulted in a significant (p less than 0.02) decrease in breast-tissue oestrone concentrations. For 3/4 tumour samples, a marked decrease in the concentration of oestrone (78 +/- 4%) was associated with a similar decrease (64 +/- 16%) in DNA polymerase alpha activity. It is concluded that treatment with 4-OHA effectively reduces breast-tissue exposure to oestrogen.

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