Late and unusual onset of congenital duodenal obstruction due to combination lesion.

Duodenal obstruction is one of the most common congenital anomalies. Both intrinsic (atresia, web and stenosis) or extrinsic lesions (malrotation, peritoneal bands, intestinal duplication, anterior portal vein and annular pancreas) may be involved. It usually presents within the first week of life with vomiting. We report an unusual congenital duodenal obstruction in a 8-month-old female with atypical symptoms due to a combination of intrinsic and extrinsic lesions.

Mutations in TAZ/WWTR1, a co-activator of NKX2.1 and PAX8 are not a frequent cause of thyroid dysgenesis.

AIM: In 80-85% of cases, congenital hypothyroidism is associated with thyroid dysgenesis (TD), but only in a small percentage of cases mutations in thyroid transcription factors (NKX2.1, PAX8, FOXE1, and NKX2.5) have been associated with the disease. Several studies demonstrated that the activity of the transcription factors can be modulated by the interaction with other proteins, such as coactivators and co-repressors, and TAZ (transcriptional co-activator with PDZ-binding motif or WWTR1) is a co-activator interacting with both NKX2.1 and PAX8. In the present study we investigate the role of TAZ in the pathogenesis of TD. MATERIAL AND METHODS: By Single Stranded Conformational Polymorphism, we screened the entire TAZ coding sequence for mutations in 96 patients with TD and in 96 normal controls. RESULTS: No mutations were found in patients and controls, but we found several polymorphisms in both groups. No significant differences could be demonstrated in the prevalence of the mutations between patients and controls. CONCLUSIONS: Our data indicate that TAZ mutations are not a cause of TD in the series of patients studied.

Incidence of nosocomial rotavirus infections, symptomatic and asymptomatic, in breast-fed and non-breast-fed infants.

Rotavirus is one of the most important aetiological agents of nosocomial infections in childhood. We studied the incidence of nosocomial rotavirus infections in 420 patients (age range 1-18 months) consecutively admitted from 1 December 1999 to 31 May 2000 to the infant ward of the Department of Paediatrics, University of Turin. We also evaluated the protective effect of breast feeding. Faecal specimens were collected from every child (whether developing diarrhoeic symptoms or not) and tested for rotavirus during hospitalization and 72 h after discharge. The incidence of rotavirus nosocomial infections was 27.7%. The incidence of symptomatic nosocomial infections was 16.8%, and the incidence of asymptomatic infections was 10.9%. The attack rate of the infections that occurred during hospitalization was 11.8%, while for those occurring after discharge, it was 15.9%. Rotavirus infection, on average, prolonged hospital stay from 5.2 to 6.4 days. 10.6% of breast-fed infants and 32.4% of non-breast-fed infants contracted rotavirus infection (P<0.005). None of the breast-fed infants who contracted rotavirus infection developed diarrhoeic symptoms.

Speckle velocimetry by means of holographic time-integrative correlation.

We develop the theory of the speckle velocimeter that is based on use of a photorefractive real-time hologram in four-wave mixing as a time-integrative correlator. The theory of the speckle velocimeter has been developed for the time correlation between the far-field spectrum of light scattered from the diffuser and the reference wave that is Doppler shifted. Our theoretical derivation shows that it is possible to extract the velocity with minor processing of the output correlation.

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.

Phase-restricted heterogeneous correlation.

We introduce a new phase-restricted algorithm for producing a heterogeneous correlation filter that permits new in-class members to be added without changing the phase of the filter. This heterogeneous correlation filter uses amplitude modulation both to enhance in-class cross correlations and to suppress selected out-of-class correlations. This new algorithm should substantially improve the performance of existing class-associative correlators and improve their operation.

Synthetic aperture radar image correlation by use of preprocessing for enhancement of scattering centers.

We demonstrate that a significant improvement can be obtained in the recognition of complicated synthetic aperture radar images taken from the Moving and Stationary Target Acquisitions and Recognition database. These images typically have a low number of scattering centers and high noise. We first preprocess the images and the templates formed from them so that their scattering centers are enhanced. Our technique can produce high-quality performance in several correlation criteria. For realistic automatic target recognition systems, our approach should make it easy to implement optical recognition systems with binarized data for many different types of correlation filter and should have a great effect on feeding data-compressed (binarized) information into either digital or optical processors.

Wiener-like correlation filters.

We introduce a new, to our knowledge, design for a Wiener-like correlation filter, which consists of cascading a phase-only filter (POF) with a photorefractive Wiener-like filter. Its performance is compared with that of the POF and the Wiener correlation filter (WCF). Correlation results show that for intermediate and higher levels of noise this correlation filter has a peak-to-noise ratio that is larger than that of either the POF or the WCF while still preserving a correlation peak that is almost as high as that of the POF.

Nonlinear techniques in optical pattern recognition: introduction by the feature editors.

This feature of Applied Optics is dedicated to research in optical pattern-recognition techniques that utilize nonlinear devices and algorithms. Nonlinearities are employed in a variety of ways in optical pattern recognition and play an important role in both hardware implementation and software development for optical pattern-recognition systems.

Nearly optimal correlations for shift-invariant associative memories.

The optical implementation of the Hopfield algorithm in shift-invariant holographic associative memories is based on the use of correlators with matched filters. However, it is well known that such correlators have poor discrimination. We propose nearly optimal correlation designs for associative memories based on correlation filters that have maximum discrimination ability. These new designs avoid large cross-correlation-peak terms caused by a mismatch between partial input and the fully stored information in the filter. These solutions rely on whitened spectra of the stored and the recalled information.Computer simulations are made of eight different combinations.

Analysis of spatial light modulator contrast ratios and optical correlation.

We have performed a general analysis of optical correlators with spatal light modulators (SLM's) whose primary defect is a finite contrast ratio (CR). Our mathematical analysis identifies three noise terms that appear in addition to the correlation term. The filter SLM contains either a phase-only filter (POF) or a binary-phase-only filter (BPOF). Insertion of a dc block at the center of the filter SLM decreases the noise background in the correlator plane; this dc block is larger than that required for the same level of performance in a correlator whose SLM's have transmissive (or reflective) dead zones. With a noise-free input and the dc block, our computer simulations that show the peak intensity falling off as the CR decreases are in quantitative agreement with the correlation term of the mathematical model. For a cluttered, disjoint noise input this agreement is only qualitative, and at low CR's the dc block is definitely required for the BPOF correlator if the secondary peaks in the output are to be brought below the correlation peak.

General treatment of spatial light modulator dead-zone effects on optical correlation. I. Computer simulations.

In Part I we present an approximate mathematical analysis and exact computer simulations for optical correlation in correlators having pixellated spatial light modulators with transmissive (or reflective) dead zones in both the input and filter planes. We show that the correlation amplitude consists of four terms: a true correlation plus three different types of noise terms originating from the transmissive dead zones in both spatial light modulators; we describe the role that each of these terms plays in the correlation process. We calculate peak intensity, signal-to-noise ratio, and energy throughput efficiency as a function of dead-zone area in both spatial light modulators using either phase-only or matched filters. We utilize a dc block in the filter plane for noise reduction. We also use a filter reference image smaller than the input spatial light modulator size to reduce false correlation peaks. We discuss the effects of fabricating a filter from a filter reference image whose center has been offset rom optic axis. In Part II [Appl. Opt. 32,6536 (1993)] we present a general analytical treatment of our model that can justify the simulation results of Part I. This analysis is applicable even to mixed cases of opaque and transmissive dead zones.

General treatment of spatial light modulator dead-zone effects on optical correlation. II. Mathematical analysis.

We present a general analytical treatment of optical correlation in correlators that use pixellated spatial light modulators with transmissive (or reflective) dead zones in both the input and filter planes. The active areas of the pixels modulate the light intensity while the dead zones transmit (or reflect) all of the light. Our model can predict the changes in the correlation peak and the signal-to-noise ratio with changes in dead zones, calculated in Part I [Appl. Opt. 32, 6527(1993)] from computer simulations. This model is also a general one: It applies to correlators in which one spatial light modulator contaions only opaque dead zones while the other contains only transmissive dead zones; it also applies to the case in which any one spatial light modulator contains both opaque and transmissive dead zones.

[Growth velocity in thalassemic children receiving different protocols of chelating therapy]. / Velocità di crescita dei bambini talassemici sottoposti a diversi protocolli di terapia chelante.

The aim of this study was to compare growth velocity in thalassemic children using two different treatment protocols. Thalassemic children were initially treated with high daily doses of desferrioxamine, obtaining a good rate of initial growth which then unexpectedly slowed down later. The introduction of a new treatment protocol reducing both the dose and frequency with which the drug was administered provoked a significant increase in the rate of growth greater than that observed in the group treated using the previous protocol.

Effects of quadratic phase distortion on correlator performance.

The deformable mirror spatial light modulator (SLM) has an inherent distortion characteristic that can be approximated as a square-law transfer function. We examine the result of this distortion when this SLM is used in an optical correlator.

Effects of spatial light modulator opaque dead zones on optical correlation.

Each pixel of a spatial light modulator (SLM) consists of a phase- or amplitude-modulating area (the active zone) within an inactive area (the dead zone). Here we study optical correlators that contain input and filter SLM's whose dead zones are opaque. Computer simulations and analytical calculations are carried out for these correlators when a phase-only, a binary phase-only, or a classical matched filter is written on the filter SLM. The correlation signal-to-noise ratio for a particular filter is independent of a dead zone since its energy throughput is proportional to its peak correlation intensity.

Signal-dependent phase distortion in optical correlators.

We examine the effect of phase distortion inherent in a spatial light modulator on the performance of an optical correlator. We examine such areas as input plane distortion, input and Fourier plane distortion, effect of phase mismatch between these planes, and the effect of additive white noise. When large distortions are present and the proper compensation is incorporated into the filter, we find a significant enhancement in performance in that the correlation response converges to a function and the SNR increases significantly. A theory is presented to explain this behavior.