Prevalence of, and predictors of, bile acid malabsorption in outpatients with chronic diarrhea

BACKGROUND

Many physicians do not consider the diagnosis of bile acid malabsorption in patients with chronic diarrhea, or do not have access to testing. We examined yield of 23-seleno-25-homo-tauro-cholic acid (SeHCAT) scanning in chronic diarrhea patients, and attempted to identify predictors of a positive test.

METHODS

Consecutive patients with chronic diarrhea undergoing SeHCAT scan over a 7-year period were identified retrospectively. Bile acid malabsorption was defined as present at a retention of <15%. Medical records were reviewed to obtain information regarding proposed risk factors. Gastrointestinal symptoms were recorded, and patients were classified as having diarrhea-predominant irritable bowel syndrome (IBS-D) if they reported abdominal pain or discomfort. Independent risk factors were assessed using multivariate logistic regression, and odds ratios (ORs) with 99% confidence intervals (CIs) were calculated.

KEY RESULTS

Of 373 patients, 190 (50.9%) had bile acid malabsorption. Previous cholecystectomy (OR 2.51; 99% CI 1.10-5.77), terminal ileal resection or right hemicolectomy for Crohn's disease (OR 12.4; 99% CI 2.42-63.8), and terminal ileal resection or right hemicolectomy for other reasons (OR 7.94; 99% CI 1.02-61.6) were associated with its presence. Seventy-seven patients had IBS-D, and 21 (27.3%) tested positive. There were 168 patients with no risk factors for a positive SeHCAT scan, other than chronic diarrhea, and 63 (37.5%) had bile acid malabsorption.

CONCLUSIONS & INFERENCES

Bile acid malabsorption was present in 50% of patients undergoing SeHCAT scanning. Almost 40% of those without risk factors had evidence of bile acid malabsorption, and in those meeting criteria for IBS-D prevalence was almost 30%.

Juvenile-onset OCD: clinical features in children, adolescents and adults

OBJECTIVE

To examine clinical correlates of juvenile-onset OCD across the lifespan.

METHOD

Data collected at the intake interview from 257 consecutive participants with juvenile-onset OCD (20 children, 44 adolescents and 193 adults) in a naturalistic study of the clinical course of OCD were examined. Participants and parents of juvenile participants completed a structured diagnostic interview, rater-administered severity measures and self-report questionnaires.

RESULTS

Children and adolescents (i.e. juveniles) shared similar features with the exception of age at onset and OCD symptom expression. Clinically meaningful differences between juvenile and adult participants were also found. Compared with adults, juveniles were more likely to be male, recall an earlier age at OCD onset and have different lifetime comorbidity patterns.

CONCLUSION

Juvenile-onset OCD symptom expression is remarkably similar across the lifespan. However, findings also suggest clinically meaningful differences between juveniles and adults. Future work using a prospective design will improve our understanding of course patterns of juvenile-onset OCD.

A smart pixel-based feedforward neural network

A novel smart pixel-based neural network was realized experimentally. The matrix multiplication is split into positive and negative components and computed optically. The necessary subtraction, binarization, and transmission of the resulting matrices is accomplished via a prototype smart pixel spatial light modulator. The result is a neural network that performs truly parallel computation without requiring the use of an external processor.

Homodyne and heterodyne imaging through a scattering medium

We introduce a novel two-dimensional (2D) homodyne and heterodyne technique for imaging objects through or embedded in a scattering medium. Our imaging approach is based on heterodyning of light with different Doppler broadenings that is scattered from objects of two different textures or from an opaque object and a textured scattering medium. We report on the initial demonstration of pulling signals out of noise for an object hidden behind a scattering medium. Enhancements of signal-to-noise ratio of the order of 50 have been achieved by use of a 2D holographic phase-sensitive detector. We also discuss the experimental feasibility of this approach for objects embedded in a scattering medium.

Realizing optical logic with a smart-pixel spatial light modulator

A method of implementing optical logic has been realized experimentally with a novel liquid crystal on silicon spatial light modulator with an integrated lens arrays. The device allows for three optical inputs and one optical output per pixel. The different logic functions realized, OR, and, nor, nand, and xor, are discussed.

Optoelectronic winner-take-all VLSI shunting neural network

In this paper we present an analog winner-take-all MOS VLSI (metal-oxide semiconductor/very large scale integration) optoelectronic network. By varying either the input current or circuit parameters, the circuit can evidence several different behaviors such as contrast enhancement, strict winner-take-all, or winner-take-all with hysteresis. Simulation and experimental results from the prototype circuit are also discussed.

All-optical nonlinear joint Fourier transform correlator

We present the first all-optical nonlinear joint transform correlator based on a square-law receiver in the Fourier plane. Our device uses a photorefractive limiting quadratic processor. The compressional nonlinearity associated with the transfer function of the limiting quadratic processor enables the correlator to detect signals embedded in Gaussian and non-Gaussian noise. In the limiting region this device correlates the phase-only information of the input. This is the first time to our knowledge that photorefractives or real-time holography has been used in the correlation of the phase-only information. We demonstrate the operation of this device experimentally, and we evaluate its performance throughcomputer simulation for various forms of noise.

Real-time holographic baseband frequency demodulator

The multiplicative and low-bandpass filtering characteristics of real-time holograms in photorefractive media are used as a basis for a baseband frequency demodulator by means of holographic homodyne detection. We experimentally demonstrate the demodulation of spatial bandpass signals in the kilohertz regime and homodyne detection in the gigahertz regime.

Dual-sided lithography: a method for evaluating alignment accuracy

We describe a method for measuring the accuracy of aligners used to align lithographic patterns on opposite sides of a substrate (back-to-front aligners). The method, with minor modifications, can also be used as an aid in performing back-to-front alignments. The method is based on interferometric principles, is insensitive to manufacturing errors, and is simple to implement. The version described in this paper is fabricated by using binary optics technology and can measure the accuracy of aligners to +/-0.2 microm.

Binary phase-only filter associative memory

An associative memory is implemented by using a binary phase-only filter as the memory element in a two-focal-length (2-f) correlator architecture. A sharp autocorrelation peak, combined with the 2-f architecture, allows the noise to be separated adequately from the signal such that a simple plane mirror can be used in the correlation plane instead of a nonlinearity.

Self-pumped optical phase conjugation with a sodium Raman laser

We report self-pumped optical phase conjugation in which the pumps are self-induced as standing waves in a linear Raman laser. Self-pumped reflectivities approaching 5% are obtained for input intensities of 20 W/cm(2). This low optical input intensity combined with predicted submicrosecond response times suggests that the resonant Raman interaction may provide the basis for a promising new class of nonlinear-optical material.