Refinements in validity generalization methods: Implications for the situational specificity hypothesis.

Using a large database, this study examined 3 refinements of validity generalization procedures: (1) a more accurate procedure for correcting the residual standard deviation (SD) for range restriction to estimate SDp, (2) use of r? instead of study-observed rs in the formula for sampling error variance, and (3) removal of non-Pearson rs. The 1st procedure does not affect the amount of variance accounted for by artifacts. The addition of the 2nd and 3rd procedures increased the mean percentage of validity variance accounted for by artifacts from 70 to 82%, a 17% increase. The cumulative addition of all 3 procedures decreased the mean SDp estimate from .150 to .106, a 29% decrease. Six additional variance-producing artifacts were identified that could not be corrected for. In light of these it was concluded that the obtained estimates of mean SDp and mean validity variance accounted for were consistent with the hypothesis that the true mean SDp value is close to zero. These findings provide further evidence against the situational specificity hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An image multiresolution representation for lossless and lossycompression

We propose a new image multiresolution transform that is suited for both lossless (reversible) and lossy compression. The new transformation is similar to the subband decomposition, but can be computed with only integer addition and bit-shift operations. During its calculation, the number of bits required to represent the transformed image is kept small through careful scaling and truncations. Numerical results show that the entropy obtained with the new transform is smaller than that obtained with predictive coding of similar complexity. In addition, we propose entropy-coding methods that exploit the multiresolution structure, and can efficiently compress the transformed image for progressive transmission (up to exact recovery). The lossless compression ratios are among the best in the literature, and simultaneously the rate versus distortion performance is comparable to those of the most efficient lossy compression methods.     

Contributions of empirical research to medical ethics

Empirical research pertaining to cardiopulmonary resuscitation (CPR), clinician behaviors related to do-not-resuscitate (DNR) orders and substituted judgment suggests potential contributions to medical ethics. Research quantifying the likelihood of surviving CPR points to the need for further philosophical analysis of the limitations of the patient autonomy in decision making, the nature and definition of medical futility, and the relationship between futility and professional standards. Research on DNR orders has identified barriers to the goal of patient involvement in these life and death discussions. The initial data on surrogate decision making also points to the need for a reexamination of the moral basis for substituted judgment, the moral authority of proxy decision making and the second-order status of the best interests standard. These examples of empirical research suggest that an interplay between empirical research, ethical analysis and policy development may represent a new form of interdisciplinary scholarship to improve clinical medicine.     

Biodistribution of radiolabeled lipid-DNA complexes and DNA in mice

The tissue biodistribution and expression of [33P]DNA-1-[2-[9-(Z)-octadecenoyloxy]ethyl]]-2-[8](Z)-heptadece nyl]-3 -[hydroxyethyl]imidazolinium chloride (DOTIM):cholesterol complexes and 33P-radiolabeled DNA expressing chloramphenicol acetyl transferase (CAT; 4.7 kB) were studied after intravenous (iv) injection in ICR mice. Mice were injected with 200 microL of complex containing DNA at 3 mg/kg or DNA alone. One group received 8 microCi of radioactivity and were sacrificed at 5 and 20 min, and 1, 2, 4 and 24 h post-dose (n = 4/time point). A second group received the equivalent of 3.9 microCi of radioactivity and were sacrificed at 20 min, and 2 and 24 h for subsequent whole body autoradiographic analysis (WBA; n = 2/time point). The tissue distribution of intact DNA was assessed by Southern blot at 24 h post-dose, whereas the integrity of complexes and DNA incubated in heparinized whole blood was studied separately. In further studies, the time course of expression in lung tissue over a 48-h period was examined, and the relative lung-expression of purified open circular (OC) versus supercoiled (SC) DNA at 24 h was evaluated. Approximately 42% of the radioactivity was found in the lungs 5 min after injection and about half this percentage was found in the liver. By 2 h, only 5% remained in the lungs, but 48% was present in the liver. No other tissue accumulated >5% of the dose throughout the duration of the study. WBA radiograms confirmed the tissue distribution results and highlighted significant accumulation of radioactivity in bone over time. Southern Blot analysis demonstrated intact DNA in many tissues 24 h after dosing. In contrast, the majority of DNA incubated in blood was degraded within 2 h, although the complexes afforded some protection relative to DNA alone. The OC DNA expressed equivalently to SC DNA in lung tissue (OC = 1035 +/- 183 pg; SC = 856 +/- 257 pg/mg soluble protein, n = 6, mean +/- SEM) at 24 h, and detectable levels of CAT were present within 2 h of dosing (21.3 +/- 7.2 pg, n >/= 8, mean +/- SD). The results confirm that DNA-DOTIM:cholesterol complexes are initially deposited in the lungs after iv administration.     

Memory, emotion, and REM sleep.

Explored the manner in which REM sleep deprivation might affect various aspects of memory processing. A series of tests, including S. Sternberg's (see record 1966-10810-001) test of scanning of immediate memory, past personal and nonpersonal memory, and past emotional memories, was administered to 8 college students after baseline, control-awakening, and REM-deprivation nights. Results show that only past, emotionally important memories may have been affected by REM deprivation; access to the emotion connected with the memories was decreased. This finding is discussed in relation to a possible function of REM sleep and to the effects of REM deprivation on depression. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Canonical forms for bilinear input/output maps

In an earlier paper [1], necessary and sufficient conditions were obtained for a state-space realization of a bilinear inout/output map to be quasi-reachable and observable, and procedures were introduced for reducing any realization not of this type to one which is. In rids paper, it is shown that any two such quasi-reachable and observable (or canonical) realizations are isomorphic, and using this result, it is possible to generate canonical forms for these realizations by means of complete sets of independent invariants.     

Progress in validity generalization: Comments on Callender and Osburn and further developments.

Examined the simulation study of J. C. Callender and H. G. Osburn (see record 1981-27033-001) aimed at determining the relative accuracy of equations used in validity generalization (transportability) research to estimate the variance of true validities. Certain incorrect statements about equations derived and used by the present authors and their associates (1980, 1981) shown to be predicated on the mistaken impression that their derivational assumptions were the same as those of Callender and Osburn. The following conclusions are made: There is only 1 model for validity generalization, although there are different equations for estimating its parameters. There are now 3 accurate equations available for estimating the variance of true validities: All 3 equations are correctly derived and are of necessity approximations rather than perfect reflections of reality, although for different reasons. Validity generalization is such a robust phenomenon that it is possible based on only corrections for simple sampling error. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimal Quantization of the Rayleigh Probability Distribution

We have derived an efficient and general algorithm for optimal quantization and applied it to the important, but neglected Rayleigh random variable. The optimal quantization range and output levels for the distortion criterion of minimum mean squared error have been calculated and tabulated for numbers of output levels from 1 to 64. We also compute and report the corresponding distortions and output entropies. For the sake of comparison, we also calculate and tabulate level spacings, minimum errors, and entropies for the optimal uniform (equal step size) quantization of the Rayleigh density. Distortion-rate curves are presented for uncoded and entropy coded quantizer outputs and compared with the distortion-rate function. We judge that these results will be useful to workers in the fields of optical holography, image processing, and communications.     

Region-based wavelet coding methods for digital mammography

Spatial resolution and contrast sensitivity requirements for some types of medical image techniques, including mammography, delay the implementation of new digital technologies, namely, computer-aided diagnosis, picture archiving and communications systems, or teleradiology. In order to reduce transmission time and storage cost, an efficient data-compression scheme to reduce digital data without significant degradation of medical image quality is needed. In this study, we have applied two region-based compression methods to digital mammograms. In both methods, after segmenting the breast region, a region-based discrete wavelet transform is applied, followed by an object-based extension of the set partitioning in hierarchical trees (OB-SPIHT) coding algorithm in one method, and an object-based extension of the set partitioned embedded block (OB-SPECK) coding algorithm in the other. We have compared these specific implementations against the original SPIHT and the new standard JPEG 2000, both using reversible and irreversible filters, on five digital mammograms compressed at rates ranging from 0.1 to 1.0 bit per pixel (bbp). Distortion was evaluated for all images and compression rates by the peak signal-to-noise ratio. For all images, OB-SPIHT and OB-SPECK performed substantially better than the traditional SPIHT and JPEG 2000, and a slight difference in performance was found between them. A comparison applying SPIHT and the standard JPEG 2000 to the same set of images with the background pixels fixed to zero was also carried out, obtaining similar implementation as region-based methods. For digital mammography, region-based compression methods represent an improvement in compression efficiency from full-image methods, also providing the possibility of encoding multiple regions of interest independently.