A Sense of Belonging: Perceptions of the Medical School Learning Environment among URM and Non-URM Students

Phenomenon: Improving the learning environment (LE), particularly for students underrepresented in medicine (URM), has become an important goal for institutions that provide undergraduate and graduate medical education. Until recently, research and intervention development have been limited by the lack of comprehensive theoretical frameworks. A multi-dimensional conceptual model of the medical school environment, developed by Gruppen and colleagues in 2019, provides a useful framework for guiding research and interventions in this area.Approach: Using Gruppen et al's model, this study investigated experiences of the LE from the perspectives of both URM and non-URM students at a medical school in New York City. In examining experiences of the organizational, social, and physical domains of the LE, we sought to explore the symbolic and experiential links across domains and identify concrete needs for improvement.Findings: Institutional structures and policies, features of the built environment, and social relationships that put learning first and generated a sense of community were highly valued. Although both URM and non-URM students shared many perceptions and experiences, URM students expressed heightened vulnerability to the experiences of devaluation and exclusion.Insights: All participants in the study greatly appreciated aspects of the LE that made them feel like valued members of the community. Medical schools should approach the task of improving the LE for URM students using a comprehensive, multi-dimensional approach.

Development and Evaluation of a Web-Based Dermatology Teaching Tool for Preclinical Medical Students

INTRODUCTION

There is growing interest in, and emphasis on, electronic teaching tools in medicine. Despite relevant testing on the United States Medical Licensing Examination (USMLE), American medical schools offer limited training in skin disorders. Teaching visual topics like dermatology in classroom formats is challenging. We hypothesized that an electronic module would enhance students' dermatology competency.

METHODS

A self-directed, case-based module was created. To test its efficacy, 40 medical students were randomized to have module access (interventional group) or none (conventional group). Learning outcomes were compared using a multiple-choice exam, including questions relevant and irrelevant to the module. Outcomes included proportions of correctly answered module questions (module scores) and nonmodule questions (nonmodule scores). Difference scores were calculated: (module score) - (nonmodule score). Positive values indicated that knowledge of module questions surpassed that of nonmodule questions. If there were a training effect, the interventional group's difference score should exceed that of the conventional group.

RESULTS

The interventional group scored significantly higher than did the conventional group on module questions-75% (interquartile range [IQR], 69-88) versus 50% (IQR, 38-63), p < .001-and nonmodule questions-85% (IQR, 69-92) versus 69% (IQR, 54-77), p = .02. The Hodges-Lehman median difference estimate of the training effect was 13.0 (95% confidence interval, 0.5-25.5).

DISCUSSION

This e-module is effective at enhancing students' competency in dermatology while emphasizing detailed pathophysiology that prepares them for USMLE Step 1. A module-based curriculum may enhance learning in supplement to traditional teaching modalities.

Implementing competency based admissions at the Albert Einstein College of Medicine

The Albert Einstein College of Medicine (Einstein) was founded in 1955 during an era of limited access to medical school for women, racial minorities, and many religious and ethnic groups. Located in the Bronx, NY, Einstein seeks to educate physicians in an environment of state-of-the-art scientific inquiry while simultaneously fulfilling a deep commitment to serve its community by providing the highest quality clinical care. A founding principle of Einstein, the basis upon which Professor Einstein agreed to allow the use of his name, was that admission to the student body would be based entirely on merit. To accomplish this, Einstein has long used a 'holistic' approach to the evaluation of its applicants, actively seeking a diverse student body. More recently, in order to improve its ability to identify students with the potential to be outstanding physicians, who will both advance medical knowledge and serve the pressing health needs of a diverse community, the Committee on Admissions reexamined and restructured the requirements for admission. These have now been categorized as four 'Admissions Competencies' that an applicant must demonstrate. They include: 1) cocurricular activities and relevant experiences; 2) communication skills; 3) personal and professional development; and 4) knowledge. The purpose of this article is to describe the process that resulted in the introduction and implementation of this competency based approach to the admission process.

Imaging submandibular pathology in the paediatric patient

A wide range of pathologies may arise from the submandibular space (SMS) or submandibular gland (SMG) in children. We review herein the normal anatomy of the SMS and describe the role of imaging in the evaluation of SMS lesions. A schematic approach for the categorisation of SMS pathology based on imaging characteristics is provided.

Thalamic shape and connectivity abnormalities in children with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is characterized by widespread structural and functional abnormalities in the cortico-striato-thalmo-cortical (CSTC) loops that subserve attention and executive functions. In this study, we analyzed thalamic shape and its white matter connections using structural magnetic resonance imaging and diffusion (DTI) data acquired from children with ADHD (n=19) and controls (n=19). Shape morphology of the thalamus was assessed using shape-based analysis, while connectivity between the thalamus and other brain regions was determined using probabilistic diffusion tractography. Shape-based analysis indicated significant regional atrophy in the left thalamus in children with ADHD compared to controls. Group analyses of white matter connectivity measures showed significantly decreased mean fractional anisotropy (FA) and volume of the tracts between thalamus and striatum, hippocampus, and prefrontal lobe in children with ADHD compared to controls. The structural abnormalities within the thalamus and the reduced integrity of the white matter tracks between the thalamus and other brain regions, as shown from the results of this study, may be the anatomical bases of the impaired cognitive performances in the attention and executive function domains in ADHD.

Echinoderms: their culture and bioactive compounds

Of the five extant classes of echinoderms, it is the sea urchins (Echinoidea) and the sea cucumbers (Holothuroidea) that are both commercially fished and heavily overexploited. In sea urchins, it is the gonad of both males and females, normally referred to as'roe', that is a sought-after food. In the sea cucumber, the principal product is the boiled and dried body-wall or 'bêche-de-mer' for which there is an increasing demand. Many sea urchin and sea cucumber fisheries still have no management system or restrictions in place, and for those that do, the prognosis for catches to continue even at a reduced level is poor. Cultivation of these species increasingly becomes a necessity, both for stock enhancement programs and as a means to meet market demand. Sea urchin culture has been practised on a large scale in Japan for many decades, and effective methods for the culture and reseeding of species in these waters have been long established. Juvenile urchins are produced in their millions in state-sponsored hatcheries, for release to managed areas of seafloor. Outside of Japan, sea urchin cultivation is still a fairly recent practice, less than 10 years old, and largely still at a research level, although a range of species are now being produced in a variety of different culture systems. It is essential that the culture systems are adapted to be species-specific and meet with local environmental constraints. Sea cucumber cultivation originated in Japan in the 1930s and is now well established there and in China. Methods for mass cultivation of the tropical Holothuria scabra are now well established and practised in India, Australia, Indonesia, the Maldives and the Solomon Islands, with the focus of the research effort for both temperate and tropical species being centred on the production of juveniles in hatcheries for the restoration and enhancement of wild stocks. Like many other marine organisms, echinoderms have been, and continue to be, examined as a source of biologically active compounds with biomedical applications. Sea cucumber has been valued in Chinese medicine for hundreds of years as a cure for a wide variety of ailments. Some more recently isolated compounds, mainly from sea cucumbers and starfish, and including those with antitumour, antiviral, anticoagulant and antimicrobial activity are summarised below. When wild stocks decline, the demand created in the market place raises to the price of the product and, consequently, culturing is more likely to become viable economically. As this review shows, there have been dramatic advances in the culture methods of sea urchins and sea cucumbers in the last 10-15 years, to the extent that one can conclude that currently the major obstacles to successful cultivation are indeed economic rather than biological. Hence the future of the echinoculture industry is closely linked to that of the fisheries, whose fate will ultimately determine the market forces that will shape this growing industry.

Biosynthesis of eicosapentaenoic acid in the sea urchin Psammechinus miliaris

The sea urchin Psammechinus miliaris (Gmelin) (Echinodermata: Echinoidea) was shown by using a deuterated tracer (D5-18:3n-3) and quantitation by negative chemical ionization gas chromatography-mass spectrometry to convert 18:3n-3 to 20:5n-3. The rate of conversion was very slow, corresponding to 0.09 microg/g tissue/mg 18:3n-3 eaten over 14 d. Deuterated arachidonic acid (D8-20:4n-6) was also included in the diet to give a measure of the relative amounts of diet eaten by the different animals. The recovery of this fatty acid in tissue lipids was 33.7% compared with only 0.95% recovery of D5-18:3n-3 and its anabolites, indicating that the majority of the D5-tracer was catabolized. Considerable elongation of D5-18:3n-3 into 20:3n-3 and a trace of 22:3n-3 was found, and these were accompanied by minor amounts of the intermediates 18:4n-3 and 20:4n-3. No deuterated 22:6n-3 was found.

Fatty acid compositions of gonadal material and diets of the sea urchin, Psammechinus miliaris: trophic and nutritional implications

The fatty acid compositions of gonadal material was examined for the sea urchin Psammechinus miliaris (Gmelin) held in aquaria and fed either salmon feed pellets or the macroalga, Laminaria saccharina for 18 months. Gonadal material was also examined from P. miliaris collected from four field sites, including commercial scallop lines encrusted with the mussel, Mytilus edulis, sea cages stocked with Atlantic salmon Salmo salar and two intertidal sea-loch sites, characterised by either a fine mud or a macroalgal substratum. The fatty acid compositions of known and potential dietary material was examined. The proportions of certain fatty acids in the gonads of P. miliaris were significantly affected by diet type and location. Docosahexaenoic acid (DHA) 22:6 n-3 was significantly higher in the gonads of the sea urchins fed salmon feed in aquaria and collected from the salmon cages and scallop lines than in the gonads of the sea urchins fed L. saccharina in aquaria and collected from the intertidal sea loch sites. The salmon feed and the mussel tissue also contained a high proportion of this fatty acid. Stearidonic acid 18:4 n-3 and arachidonic acid 20:4 n-6, however, were found in significantly higher proportions than DHA in the gonads of the sea urchins fed L. saccharina and collected from the two intertidal sea-loch sites. L. saccharina was also found to contain high proportions of stearidonic and arachidonic acid. The gonads of the sea urchins collected from the intertidal site, characterised by a mud substratum, and from the scallop lines were found to contain a lower 18:1 n-9/18:1 n-7 ratio and a higher proportion of branched and odd-chained fatty acids, signifying a high dietary bacterial input, than the sea urchins held in the aquaria and collected from the salmon cage. 20:2 and 22:2 non-methylene-interrupted dienoic fatty acids (NMIDs) were found in P. miliaris fed diets lacking these fatty acids suggesting de novo biosynthesis. These results, therefore, suggest that the proportions/ratios of certain fatty acids in the gonads of P. miliaris could be used to give an indication of the predominant diet type of this species in the wild.

Intraoral radiographic storage phosphor image mean pixel values and signal-to-noise ratio: effects of calibration

OBJECTIVE

The DIGORA intraoral radiographic storage phosphor system needs to be calibrated before images are made. Calibration involves inputting of the maximum exposure to be used. This investigation studied the effects of different maximum exposure calibration settings on the mean pixel value for selected regions of interest and the signal-to-noise ratio for images of a test phantom.

STUDY DESIGN

A dental phantom containing a step wedge made of different thicknesses of homogeneously radiopaque bone-equivalent material was imaged at 70 kVp with exposures ranging from 12.8 to 105.2 microC.kg-1. Images were displayed through use of imaging software, and a region of interest was set for each bone-step. The mean pixel values and their standard deviations were measured.

RESULTS

Except for very low exposures (< 10% of the calibrated maximum), there was a linear relationship between exposure and the pixel values within the regions of interest irrespective of the calibrated maximum exposure. Low exposures resulted in underexposed low-contrast images. Low calibrated maximum exposures (< 54.5 microC.kg-1) resulted in low-density images with poor signal-to-noise ratios.

CONCLUSIONS

Because of the very wide image latitude of the DIGORA system, loss of image quality was not observed as a result of adjustments in the calibration setting over the range of exposure commonly used in dental practice. The highest accepted exposure was limited by prior calibration; hence, if diligence is applied, patient exposure can be minimized without detriment to image quality.

Charge-coupled device panoramic radiography: effect of beam energy on radiation exposure

OBJECTIVE

To determine the consequences for entrance exposure of varying the beam energy and operating current for panoramic radiography using a charge-coupled device receptor.

MATERIAL AND METHODS

Images were made of a RANDO average man phantom (Alderson Research Laboratories, Stamford, CT) at kVcp settings of 60, 66, 70 and 80 and an mA of 2.0, 3.2, 6.4 and 10.0. The exposure cycle was set as recommended by the manufacturer at 17.6 s. Diagnostic image quality was rated by a panel of two oral and maxillofacial radiologists and one oral and maxillofacial pathologist. Entrance exposures were assessed using a 3 cc ionization chamber placed at the beam entry points while imaging the molar, premolar, and anterior teeth both using the DigiPan (Trophy Radiologie, Vincennes, France) CCD receptor and conventional T-Mat G film/Lanex Regular screens (Eastman Kodak, Rochester, NY, USA).

RESULTS

Acceptable image quality was attained with combinations of 60 kVcp and 3.2, 6.4 or 10 mA, 70 kVcp and 2.0, 3.2 or 6.4 mA; at 80 kVcp irrespective of the mA it was unacceptable. The maximum reduction in entrance dose was 77%, averaged over the three sites, at 70 kVcp and 2 mA.

CONCLUSION

The DigiPan receptor produces satisfactory images with saving in entry exposure saving of approximately 70% when compared with a conventional film/rare earth screen combination.

Tissue radiation dosages using the RVG-S with and without niobium filtration

Tissue doses for a modified Rando head- and-neck phantom were measured for imaging with speed group E film with standardized aluminium filtration and the RVG-S both with and without added niobium filtration. Cylindrical holes drilled into the phantom's tissue-equivalent material permitted the placement of a small ionization chamber into anatomically correct sites representing the thyroid, parotid, submandibular and sublingual glands. To establish the necessary cone positions, angulations and time settings for each exposure, diagnostically acceptable images of six teeth, representative of different intraoral regions, were made for a DXXTR mannequin. Entrance and exit points were marked and transferred to the phantom to allow reproducible repeat exposures. The RVG-S provided reductions in average skin entrance dose of 31 per cent to 39 per cent with standard aluminium filtration and 51 per cent to 60 per cent with the addition of niobium filtration to attenuate the beam. While dose reductions relative to E-speed film usage were found for deep tissue sites, these were site and projection specific. The cumulative reduction from use of the RVG-S without niobium filtration was 32 per cent. It was 42 per cent with additional niobium filtration. It should be noted, however, that adding niobium filtration resulted in increased dosages to the deeper soft tissues such as the thyroid gland.

Adults with severe reading and learning difficulties: a challenge for the family physician

BACKGROUND

An estimated 40 to 44 million adults living in the United States have severe difficulty reading, writing, spelling, and doing arithmetic. These deficiencies interfere with their receiving adequate health care. Many of these adults have reading or other learning disabilities that further compromise their ability to understand their medical conditions and to participate fully in their own care.

METHODS

The literature on the cognitive and effective characteristics of adults with reading and learning disabilities was searched using the MEDLINE, PsychLIT, and ERIC databases. This literature is reviewed with an emphasis placed on how these characteristics might challenge a family physician's ability to provide optimal patient care, and what can be done to meet these challenges. Illustrative case vignettes of adults with these disabilities are described.

RESULTS AND CONCLUSIONS

The cognitive and affective characteristics of this patient population make it difficult for the family physician to provide optimal medical services. Suggestions are given to make medical care more accessible and appropriate for these patients.

The OP 100 Digipan: evaluation of the image layer, magnification factors, and dosimetry

OBJECTIVES

The purpose of this study was to describe the Orthopantomograph OP 100 Digipan modification and to determine the image-layer and dosimetric characteristics of this system.

RESEARCH DESIGN

Image-layer contours for the Digipan were determined at resolution limits of 4.0, 3.0, and 1.5 line pairs (Ip) mm(-1) using a resolution grid positioned at intervals along the beam projection paths. A hexagonal test device was placed above the grid to determine the magnification factors at the selected resolution limits. For dosimetry, a 30 mm2 ionization chamber was placed at the beam entry points while imaging the molar, premolar, and anterior teeth using both the Digipan and conventional film receptors.

RESULTS

The maximum resolution exceeded 4.0 Ip mm(-1)in the center of the image layer. Using a 1.5 Ip mm(-1) resolution limit, the focal trough width was 14 mm at 0-degree horizontal angulation, 20 mm at 37 degrees, and 36 mm at 83 degrees. At 1.5 Ip mm(-1), the horizontal magnification was -21% facial and +42% lingual to the center of the image layer in the incisor region; -25% facial and +19% lingual to the center of the image layer at a horizontal angulation of 83 degrees. At 4.0 Ip mm(-1), horizontal magnifications in the incisor region were -2.0% facially and +0.5% lingually; at 83 degrees they were -3.9% facially and +1.1% lingually. The neck entrance dose for imaging the anterior and premolar regions averaged 89.5 (+/-5.6) microGy. The cheek entrance doses for imaging the molar region averaged 220.6 (+/-8.0)microGy with the Digipan. With film the average entrance doses were 297.9 (+/-8.6) microGy (anterior and premolar regions) and 682.1 (+/-16.9) microGy (molar region).

CONCLUSIONS

The Digipan image layer is similar, but slightly narrower than that previously reported for the Orthopantomograph OP 100 using standard film-screen combinations. The resolution at the center of the image layer exceeded 4.0 Ip mm(-1). The Digipan produced images with an entry dose savings of approximately 70% when compared with photo-timed exposures using conventional film with the Orthopantomograph OP 100.

Inner-city adults with severe reading difficulties: a closer look

Relatively little is known about the characteristics of inner-city adults who seek assistance from literacy programs. Increased knowledge about this population will enhance the development of more effective programs, as well as policy options. This study describes the characteristics of 280 adults, ages 16 to 63, who came to an adult literacy program that focused on severe reading difficulties. The program, located within a hospital complex in a large, urban area, attracted these individuals through an extensive multimedia outreach effort. Results suggested that the adults who sought help were generally characterized by a vast array of cognitive, academic, and social difficulties. In addition, the extent of these difficulties increased dramatically as literacy level declined. These findings suggest that comprehensive educational, social, and vocational services may be needed to help adults with severe reading difficulties cope with the diverse and severe problems they face.

Perceptibility of defects in an aluminum test object: a comparison of the RVG-S and first generation VIXA systems with and without added niobium filtration

OBJECTIVE

To compare the first generation VIXA (Gendex, Milan, Italy) and the RVG-S (Trophy Radiologie, Vincennes, France) for detection of defects in an aluminium test object at various exposures both with and without added niobium filtration.

METHODS

Images of a 7 mm aluminium test object with defects ranging from 0.1 to 1.5 mm with standardized projection geometry. Seven dentists acted as observers. Perceptibility curves were developed for both sensors under the various filtration conditions and exposures.

RESULTS

At optimum exposures both the VIXA and the RVG-S permitted the same number of defects to be observed. The optimum exposures were similar for the two systems, but the dynamic range was greater for the RVG-S. Addition of niobium filtration did not appreciably alter the radiation dose required to perceive a given number of defects using either system.

CONCLUSIONS

The two systems performed equally at optimum exposure when the dose is approximately the same irrespective of the presence or absence of niobium filtration. Beyond the optimal level, the RVG-S outperformed the VIXA system.

The Incidence and Morphology of Subcuticular Bacteria in the Echinoderm Fauna of New Zealand

New Zealand echinoderms (33 species drawn from all five extant classes) were examined for the presence of symbiotic bacteria by fluorescence and electron microscopy. Gram-negative, subcuticular bacteria (SCB) were found in 17 species from four classes. The SCB could be classified into two major morphological types. Some species had both types of SCB. The distribution of SCB was not obviously linked to host ecology but did appear to be related to host phylogeny. Related species usually all have SCB or all lack them. The number of SCB in five species was estimated to be between 8.41 x 108 and 4.96 x 109 g-1 ash-free dry weight of host tissue. Significant differences in bacterial load and relative proportions of the different types of bacteria were found among three congeneric echinoids (Pseudechinus huttoni, P. albocinctus and P. novaezealandia). Ophiocoma bollonsi was peculiar in having groups of bacteria enclosed in host cells (bacteriocytes) within the connective tissue of the tube feet.

Comparing the sensitometric properties of dental X-ray films

This article describes a study that compared the sensitometric properties and information yields of four dental X-ray films: Eastman Kodak Ultra-Speed DF-57 and Ektaspeed EP-21, Flow DV-58 and Agfa Gevaert Dentus M2 Comfort. Dentus M2 Comfort gave the greatest contrast, a speed between the conventional D- and E-speed film groups and an exposure latitude wider than Ultra-Speed but less than DV-58. A significant difference in detail was found with low exposures, Dentus M2 Comfort and Ektaspeed outperforming the other two film types.

Direct digital radiography for the detection of defects in a standard aluminium test object through composite resin restorative materials

While the RVG 32000 (Trophy Radiologie, Vincennes, France) is in wide use for direct digital intraoral radiography in dentistry, there is a dearth of information in the literature concerning the system's sensitivity to small changes in radiographic density consistent with initial and recurrent dental caries. A standardized 7 mm aluminium test block was used as a phantom for perceptibility testing of density changes, both with and without the superimposition of composite resin sheets of various thicknesses. Defects in the block were randomly positioned and varied from 0.1 to 1.5 mm. Thermal prints were used for evaluation. Standard linear images, with no enhancement, were compared with three enhanced modes, standard mode with gradient enhancement (enhanced standard), standard X-function and zoom high resolution (ZHR). Sensitivity improved in the following sequence: standard 0.58 < enhanced standard 0.75 < X-function 0.94 < ZHR 0.95. Accuracy improved in the following sequence: standard 0.45 < enhanced standard 0.58 < X-function 0.73 < ZHR 0.74. Specificity was 1.0 both for X-function and for ZHR. These two modes both proved significantly better (P < 0.05) for the detection of 0.1 mm defects than the other two modes tested. No significant difference was found between X-function and ZHR. As ZHR requires four times the radiation exposure as standard exposures with the X-function, the latter is preferred for the task described in this study.

Flash Dent: an alternative charge-coupled device/scintillator-based direct digital intraoral radiographic system

The Flash Dent digital intraoral radiographic system is yet to be described in the scientific literature. A Windows operating environment, a lens based optical scintillator charge-coupled device (CCD) and 'IMG' image format are the major features which distinguish this from other available systems. In this paper we describe the component of the Flash Dent system, investigate the validity of the X-ray generator specifications, determine comparative image doses and assess the performance of the intraoral sensor. Although we found Flash Dent software facilitates image processing, X-ray generator operation, sensor performance and dimensional measurements, inconsistencies between sensors and the use of a non-standard image format require further consideration for improvements on the part of the manufacturer.

Diagnostic image quality and dose reduction using niobium filtration for cephalometric radiography

The usefulness of added filtration is contingent upon the maintenance of high image quality while effectively reducing the radiation dose. High-quality cephalometric radiographs, defined objectively by a panel of orthodontists, were obtained of a tissue-equivalent phantom both without and with 30 microns and 50 microns supplemental niobium filtration. Skin entrance doses in the temporomandibular joint region were compared at diagnostically acceptable exposures where there was no significant difference in radiographic image quality. Dose reductions ranged from 17% to 31% with 30 microns niobium filtration, and 17% to 39% with 50 microns. However, as kVp and HVL were increased to maintain the same level of perceived image quality, image contrast decreased. Contrast loss with 30 microns and 50 microns niobium filtration averaged 8% and 22% respectively compared with standard aluminium filtration. It would appear that additional niobium filtration can be used to reduce radiation dose without significant loss of image quality.

The effect of cocaine on sperm motility characteristics and bovine cervical mucus penetration

OBJECTIVES

To determine the in vitro effects of cocaine on sperm motility and bovine mucus penetration because cocaine abuse is associated with decreased sperm motility, and related compounds, such as procaine, are known to decrease sperm motility.

DESIGN

Human semen samples were exposed to a range of cocaine concentrations and the effects quantified using computer-assisted sperm analysis and the bovine mucus penetration test.

SETTING

University research laboratory.

PATIENTS, PARTICIPANTS

Samples were obtained from 18 healthy volunteers.

INTERVENTIONS

Normal semen samples were exposed to concentrations of cocaine ranging from 10(-11) to 10(-4) M. Motility characteristics were evaluated after 2 hours, and bovine mucus penetration was evaluated after 30 minutes, 1 hour, and 2 hours. Mucus penetration by washed sperm was also evaluated.

MAIN OUTCOME MEASURES

Motility characteristics were evaluated using computer-assisted sperm analysis, and functional sperm motility was evaluated using the bovine mucus penetration test.

RESULTS

Cocaine exposure decreased the percentage of motile sperm in a concentration-dependent manner with a maximum decrease of 23% at 10(-4) M but had no effect on other motility characteristics. Cocaine decreased bovine mucus penetration by 12% at high cocaine concentrations (10(-4) M), but increased penetration by 69% at low concentrations (10(-9) M). Washing sperm before cocaine exposure attenuated the increased sperm penetration.

CONCLUSION

The ability of cocaine to decrease the percentage of motile sperm at high concentrations may explain the decreased sperm motility associated with cocaine use. Cocaine's ability to augment sperm penetration at low concentrations suggests an interaction of cocaine with the sperm adrenergic system.

Cognitive processing deficits in reading disabilities: a prefrontal cortical hypothesis

Much research investigating the neuropsychological underpinnings of reading disabilities has emphasized posterior brain regions. However, recent evidence indicates that prefrontal cortex may also play a role. This study investigated cognitive processes that are associated with prefrontal and posterior brain functions. Subjects were 12-year-old reading disabled and nondisabled boys. Discriminant analysis procedures indicated that measures of prefrontal functions distinguished between the two groups better than measures of posterior functions. The results suggest that reading disabled boys have difficulty with cognitive processes involving selective and sustained attention, inhibition of routinized responses, set maintenance, flexibility in generating and testing alternative hypotheses, and phonemically based language production.

Evaluation of aluminum-yttrium filtration for intraoral radiography

In comparison with the use of traditional aluminum filtration, a radiation dose reduction of 40% at 90 kVp and 25% at 70 kVp was found with the use of aluminum-yttrium (Al-Y) filtration for intraoral bitewing and periapical radiographs. An increased exposure time, and consequent greater tube loading, was necessary to maintain film density. Extended gray-scales (i.e., reduced radiographic contrast) occurred at both energy levels tested with the use of Al-Y filtration. Subjective evaluation of image quality in terms of clarity, resolution, and contrast was carried out independently by nine periodontologists. Despite some interoperator variance, there was a preponderant preference for traditional aluminum filtration.