Maximum-likelihood parameter estimation in terahertz time-domain spectroscopy.

We present a maximum-likelihood method for parameter estimation in terahertz time-domain spectroscopy. We derive the likelihood function for a parameterized frequency response function, given a pair of time-domain waveforms with known time-dependent noise amplitudes. The method provides parameter estimates that are superior to other commonly used methods and provides a reliable measure of the goodness of fit. We also develop a simple noise model that is parameterized by three dominant sources and derive the likelihood function for their amplitudes in terms of a set of repeated waveform measurements. We demonstrate the method with applications to material characterization.

Pharmaceutical companies' policies on access to trial data, results, and methods: audit study.

Objectives To identify the policies of major pharmaceutical companies on transparency of trials, to extract structured data detailing each companies' commitments, and to assess concordance with ethical and professional guidance.Design Structured audit.Setting Pharmaceutical companies, worldwide.Participants 42 pharmaceutical companies.Main outcome measures Companies' commitments on sharing summary results, clinical study reports (CSRs), individual patient data (IPD), and trial registration, for prospective and retrospective trials.Results Policies were highly variable. Of 23 companies eligible from the top 25 companies by revenue, 21 (91%) committed to register all trials and 22 (96%) committed to share summary results; however, policies commonly lacked timelines for disclosure, and trials on unlicensed medicines and off-label uses were only included in six (26%). 17 companies (74%) committed to share the summary results of past trials. The median start date for this commitment was 2005. 22 companies (96%) had a policy on sharing CSRs, mostly on request: two committed to share only synopses and only two policies included unlicensed treatments. 22 companies (96%) had a policy to share IPD; 14 included phase IV trials (one included trials on unlicensed medicines and off-label uses). Policies in the exploratory group of smaller companies made fewer transparency commitments. Two companies fell short of industry body commitments on registration, three on summary results. Examples of contradictory and ambiguous language were documented and summarised by theme. 23/42 companies (55%) responded to feedback; 7/1806 scored policy elements were revised in light of feedback from companies (0.4%). Several companies committed to changing policy; some made changes immediately.Conclusions The commitments made by companies to transparency of trials were highly variable. Other than journal submission for all trials within 12 months, all elements of best practice were met by at least one company, showing that these commitments are realistic targets.