Development of primary reference facilities and measurement comparison of standard artifacts for the bidirectional transmittance distribution function.

To determine the bidirectional transmittance distribution function (BTDF) of diffusely transmitting materials, two new primary facilities have been developed at the Physikalisch-Technische Bundesanstalt (PTB) and Aalto University (Aalto). A detailed description of both facilities and the different approaches used are presented in this paper. The performance of both facilities is compared by determining the BTDF of two different diffuser types in both in-plane and out-of-plane bidirectional geometries at four different wavelengths in the visible spectral range. Due to delayed completion of PTB's primary facility, the measured BTDF values are compared between Aalto's primary facility and another PTB setup, whose measurement scales are successfully transferred to PTB's primary facility by an internal comparison. A thorough analysis of the measurement uncertainty is presented, leading to a combined k = 1 standard uncertainty of 0.8%-1.2% for PTB's primary facility and 1.3%-1.7% for Aalto's primary facility. The BTDF results obtained agree well within their expanded k = 2 uncertainty. This indirect bilateral comparison shows that Aalto's and PTB's new facilities are suited as primary reference setups for the determination of the BTDF. These studies also reveal action points to improved measurement capabilities and for a reduction of the measurement uncertainty, depending on the type of diffuser under test.

A new method for determining the insertion depth of tracheal tubes in children: a pilot study.

BACKGROUND: Choosing the correct insertion depth of tracheal tubes is crucial for successful airway management in paediatrics. Currently used formulas are based on patient characteristics such as age, body weight and height. The aim of the study is to devise and evaluate more suitable body surface area based diagrams for predicting the correct tracheal insertion depth. METHODS: Calculated insertion depth according to currently used formulas, primary insertion depth and insertion depth corrected by chest radiography ('gold standard') were collected from 237 children. Age, body weight, height and body surface area were noted. Body surface area based diagrams were devised and prospectively evaluated in another set of 123 paediatric patients. RESULTS: Tracheal tube position according to currently used formulas had to be corrected in 37% of all intubations. New body surface area based diagrams were created. In 20.3%, depth of the tracheal tube had to be corrected according to the new body surface area based diagrams. CONCLUSIONS: The body surface area based diagrams may be a reliable tool for predicting the correct tracheal insertion depth in children.

Background-free imaging of plasmonic structures with cross-polarized apertureless scanning near-field optical microscopy.

We present advances in experimental techniques of apertureless scanning near-field optical microscopy (aSNOM). The rational alignment procedure we outline is based upon a phase singularity that occurs while scanning polarizers around the nominal cross-polarized configuration of s-polarized excitation and p-polarized detection. We discuss the theoretical origin of this topological feature of the setup, which is robust against small deviations, such as minor tip misalignment or shape variations. Setting the polarizers to this singular configuration point eliminates all background signal, allowing for reproducible plasmonic eigenmode mapping with optimal signal-to-noise ratio.

A double-blind study of domperidone in the symptomatic treatment of chronic post-prandial upper gastrointestinal distress.

Oral domperidone (30 mg/day) or placebo tablets were given to 41 patients presenting with symptoms of chronic post-prandial dyspepsia, in a double blind study. The tablets were taken three times a day before meals. The first part of the study lasted four weeks and was followed by a second four week period in which domperidone was given on an open basis to all subjects. At the end of the double-blind phase all indices but one (bitter regurgitation) as well as the gastro-oesophageal reflux cluster had significantly improved on domperidone treatment while none had done so on placebo. During the subsequent open four weeks of domperidone all items improved in both study groups. No side effects were seen in any of the participants in the study.