A unified theory is presented for data-aided equalization of digital data signals passed through noisy linear dispersive channels. The theory assumes that some past and/or future transmitted data ...symbols are perfectly detected. We use this hypothesis to derive the minimum mean-square error receiver. The optimum structure consists of a matched filter in cascade with a transversal filter combined with a linear intersymbol interference canceler which uses the ideally detected data symbols. The main result is an expression for the optimized mean-square error as a function of the number and location of the canceler coefficients, the s/n, and the channel transfer function. When the number of canceler coefficients is zero, we get the well-known result for linear equalization. When the causal or postcursor canceler approaches infinite length, we obtain the well-known decision feedback result. When both the precursor and postcursor cancelers become infinite, we obtain the very best result possible, namely, the matched-filter bound dictated from fundamental theoretical considerations. Neither the decision feedback nor the matched-filter results can be achieved in practice since their implementation requires infinite memory and storage. Our theory can be used to calculate the rate of approach to these ideals with finite cancelers.
We studied the chromosomes of a mentally retarded boy with minor anomalies and of his parents using a G-band stained high-resolution chromosome method. This documented dup (8q24.1 = to 8qter) and ...dup(22pter = to 22q11.2) in the boy due to a maternal balanced reciprocal translocation of chromosomes 8 and 22 and 3:1 disjunction during meiosis I. The karyotype of the boy is 47,XY, +der(22) (22pter = to 22q11.2::8q24.1 = to 8qter). The der(22) was involved in satellite associations and stained positively with AgNO3 in mother and child. The case is compared to similar cases in the literature and the function of the small acrocentric marker chromosome during meiosis is discussed.
Preoperative and postoperative corneascope photographs of 368 myopic patients undergoing radial keratotomy in the Prospective Evaluation of Radial Keratotomy (PERK) study were optically scanned and ...digitized. A high-resolution scanning system was developed in order to quantify the preoperative and postoperative corneal shape accurately. Careful analysis of the 72 data points in the nine representative rings demonstrated that corneal topography is best represented by radius of curvature from the center to the periphery. The normal myopic cornea flattens approximately +0.28 mm from the center to the periphery, demonstrating the cornea's aspheric nature. More highly myopic patients in the PERK population (-4.50 to -8.00 diopters D) demonstrated corneas that are 0.08 to 0.10 mm steeper than the less myopic population (-2.00 to -3.12 D). Optical zone, patient age, and gender are all correlated to changes in corneal topography after radial keratotomy. In more myopic populations, men have corneas which are flatter than those of women by 0.09 to 0.11 mm in all rings represented on corneoscopy. Highly myopic males also experience more corneal flattening after 3.0-mm optical zone radial keratotomy. Regardless of the optical zone used in radial keratotomy, the resulting corneal topography flattens in all rings. However, the ratio of millimeters of radius of curvature change to diopters of correction is consistent for each ring. The dioptric change observed after radial keratotomy corresponds closely with the millimeters of flattening at the respective rings being examined. The central rings flatten 0.166-mm radius of curvature per diopter of refractive alteration obtained. The largest degree of corneal flattening occurs centrally, 0.72 mm, in the more highly myopic patients who underwent 3-mm optical zone radial keratotomy. The use of smaller optical zones in radial keratotomy produces larger changes in the radius of curvature and, consequently, in the amount of refraction than when larger optical zones are used. When compared with younger patients, older patients with 3.0, 3.5, and 4.0 optical zone radial keratotomies experience more central and peripheral corneal flattening. This study of the corneal topography of the myopic population demonstrates that the refractive change resulting from radial keratotomy is related to alterations in corneal topography. The use of similar modifications of the corneal surface may be effective for newer refractive surgical procedures.
The Patient Tahzib, Nayyirih G.; Nuijts, Rudy M. M. A.; Salz, James J. ...
Management of Complications in Refractive Surgery,
2008
Book Chapter
The relationship between patient expectations, the medical outcome, and patient satisfaction is complex.It is important to determine patient’s motivations and expectations before surgery.Patients ...should be educated on the potential side effects of refractive surgery.In case of complications, patients should be informed as soon as possible, whereby the doctor should try to maintain their trust.
In this study, we investigated nine independent echovirus 9 isolates obtained from sick children in 1995. It is discovered that these isolates differ in respect to their pathogenicity for newborn ...mice indicating that the degree of human pathogenicity of an echovirus 9 variant does not necessarily correlate with mouse pathogenicity. Nevertheless, all virus variants are found to code for an RGD-motif within their VP1 protein. Hence, the RGD-motif and its highly conserved flanking regions are the
conditio sine qua non, but, as expected, not sufficient for the mouse-pathogenic character.
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