The Nonlinear Statistics of High-Contrast Patches in Natural Images

Recently, there has been a great deal of interest in modeling the non-Gaussian structures of natural images. However, despite the many advances in the direction of sparse coding and multi-resolution analysis, the full probability distribution of pixel values in a neighborhood has not yet been described. In this study, we explore the space of data points representing the values of 3 × 3 high-contrast patches from optical and 3D range images. We find that the distribution of data is extremely sparse with the majority of the data points concentrated in clusters and non-linear low-dimensional manifolds. Furthermore, a detailed study of probability densities allows us to systematically distinguish between images of different modalities (optical versus range), which otherwise display similar marginal distributions. Our work indicates the importance of studying the full probability distribution of natural images, not just marginals, and the need to understand the intrinsic dimensionality and nature of the data. We believe that object-like structures in the world and the sensor properties of the probing device generate observations that are concentrated along predictable shapes in state space. Our study of natural image statistics accounts for local geometries (such as edges) in natural scenes, but does not impose such strong assumptions on the data as independent components or sparse coding by linear change of bases.     

New treatments or old remedies: is business process reengineering really socio-technical design?

This paper discusses and compares two tools which are currently recommended to assist organizational redesign. One of these is the socio-technical approach developed by researchers at the Tavistock Institute of Human Relations from the 1950s onwards. The other is business process reengineering which has recently emerged from researchers in the USA. These will be examined critically, compared with each other and their strengths and limitations discussed. The author argues that these approaches are similar in their procedures although, in her view, socio-technical design has a better theoretical basis and a stronger methodology. However, they differ greatly in their values. Socio-technical design argues that when new work systems are being designed equal weight should be given to social and technical factors. It places great emphasis on improving the quality of working life. Business process reengineering, in contrast, places most emphasis on gaining competitive advantage.     

The analysis of rigid polyurethanes by chemical ionization mass spectrometry

Methods for the elucidation of the chemical components of polyurethane foams are described. Foam samples of 50 mg were hydrolyzed in aqueous base and the resulting mixture of polyols and polyamines was analyzed by chemical ionization mass spectrometry (CI-MS) and high-pressure liquid chromatography (HPLC). The aromatic polyamines, which were separated by HPLC, produced few fragment ions under methane chemical ionization and were identified without difficulty. Each propoxylated homolog in the mixture of polyols was detected by CI-MS techniques, and approximate molecular weight profiles are presented for each polyol studied. Chemical ionization spectra are listed for samples of standard polyols and of base-hydrolyzed isocyanates. The hydrolysis products from urethane foam formulations were easily related to the standard compounds via CI-MS. These methods should be applicable to polymeric materials containing urethane, urea, and ester link-ages.     

Occlusion Models for Natural Images: A Statistical Study of a Scale-Invariant Dead Leaves Model

We develop a scale-invariant version of Matheron's dead leaves model for the statistics of natural images. The model takes occlusions into account and resembles the image formation process by randomly adding independent elementary shapes, such as disks, in layers. We compare the empirical statistics of two large databases of natural images with the statistics of the occlusion model, and find an excellent qualitative, and good quantitative agreement. At this point, this is the only image model which comes close to duplicating the simplest, elementary statistics of natural images—such as, the scale invariance property of marginal distributions of filter responses, the full co-occurrence statistics of two pixels, and the joint statistics of pairs of Haar wavelet responses.     

A radiomicroassay for cytotoxic antibody to human spermatozoa. Quantification by tritiated actinomycin d

A radiomicroassay for titration of spermocytotoxic antibody is described. The assay used [3H]AACTINOMYCIN D ([3H]Act D) to label damaged spermatozoa in a fashion analogous to penetration by vital dye. Optimal conditions for and some kinetics of the assay are presented. The assay is sensitive, reliable, simple to perform and uses only small amounts of serum and spermatozoa. Applied to sperm antibody positive human postvasectomy sera, the assay compared favourably in sensitivity eith vital dye microscopic observations and with parallel titration by the Isojima's immobilization tests.     

Effect of Plate Wettability on Dispersed-Phase Holdup in a Pulsed Disc-and-Doughnut Solvent Extraction Column

The effect of plate wettability on the dispersed-phase holdup in a pulsed disc-and-doughnut solvent extraction column is presented. Teflon, nylon, and stainless steel plates have been used to simulate a change in the wetting characteristics of the plate material that can occur in an operating column due to ageing or deposits accumulating on the plate. Experimental holdup data have been measured over a range of operating conditions using a 1.0 m long glass column with an internal diameter of 72.5 mm containing alternating discs and doughnuts. The liquid-liquid system studied was tri-n-octylamine (TOA)-kerosene-water with sulphuric acid as the solute. Results show that there are noticeable changes in the characteristic velocity (determined from measured holdup) and operational regimes for the different plate materials, particularly at low pulsation intensities, when operating under dispersed aqueous conditions. Experimental holdup data from this study have also been compared to correlations from literature for predicting holdup. As none of these correlations for holdup incorporate plate wettability, a new correlation for predicting holdup has been proposed that incorporates the contact angle of the plate material to allow for changes in the wettability of the plate surface. This correlation is able to predict the holdup data from this study to within 10.5% for aqueous dispersed conditions.     

Recent trends in home and work smoking bans

Objectives: Home and work smoking bans at the national and state level in the USA, and their relation to smoking prevalence and to tobacco control policies, are examined.

Data: The Current Population Survey's 1992/93 and 1998/99 tobacco use supplement surveys are the primary data source, supplemented with information on state level tobacco control policies.

Methods: The national and state rate of bans are estimated, and changes over the course of the 1990s and their relation to smoking rates and tobacco control policies are examined.

Results: The prevalence of work and home bans has increased considerably between 1992/93 and 1998/99. By 1999, over 65% of the population age 15 and above work in places with smoking bans, and over 60% live in homes with bans. We found that states with lower than average ban rates in 1993 tended to have had larger increases in ban rates between 1993 and 1999. We also found that home and work bans became more prevalent in states with initially low smoking rates, and that the growth in home bans coincided with a declining prevalence of smoking. States with higher levels of bans by 1999 also tended to have higher cigarette taxes, stricter clean air laws, and media/comprehensive campaigns in place.

Conclusions: The results indicate that lower smoking rates are associated with higher rates of work and home bans, although substantial progress has also been made by those states with initially low rates of bans. While further work is needed to establish the direction of causality, it would appear that reductions in smoking rates, either through stronger tobacco control policies or otherwise, may reduce exposure to tobacco smoke not only by reducing the number of smokers, but also through increasing the number of firms and homes with smoking restrictions.