Needs and opportunities for improving the health, safety, and productivity of medical research facilities

Medical research facilities, indeed all the nation's constructed facilities, must be designed, operated, and maintained in a manner that supports the health, safety, and productivity of the occupants. The National Construction Goals, established by the National Science and Technology Council, envision substantial improvements in occupant health and worker productivity. The existing research and best practices case studies support this conclusion, but too frequently building industry professionals lack the knowledge to design, construct, operate, and maintain facilities at these optimum levels. There is a need for more research and more collaborative efforts between medical and facilities engineering researchers and practitioners in order to attain the National Construction Goals. Such collaborative efforts will simultaneously support attainment of the National Health Goals. This article is the summary report of the Healthy Buildings Committee for the Leadership Conference: Biomedical Facilities and the Environment sponsored by the National Institutes of Health, the National Association of Physicians for the Environment, and the Association of Higher Education Facilities Officers on 1--2 November 1999 in Bethesda, Maryland, USA.

The ruv proteins of Thermotoga maritima: branch migration and resolution of Holliday junctions

In homologous recombination in bacteria, the RuvAB Holliday junction-specific helicase catalyzes Holliday junction branch migration, and the RuvC Holliday junction resolvase catalyzes formation of spliced or patched structures. RuvAB and RuvC from the hyperthermophile Thermotoga maritima were expressed in Escherichia coli and purified to homogeneity. An inverted repeat sequence with unique termini was produced by PCR, restriction endonuclease cleavage, and head-to-tail ligation. A second inverted repeat sequence was derived by amplification of a second template containing a three-nucleotide insertion. Reassociation products from a mixture of these two sequences were homoduplex linear molecules and heteroduplex heat-stable Holliday junctions, which acted as substrates for both T. maritima RuvAB and RuvC. The T. maritima RuvAB helicase catalyzed energy-dependent Holliday junction branch migration at 70 degrees C, leading to heteroduplex linear duplex molecules with two three-nucleotide loops. Either ATP or ATP gamma S hydrolysis served as the energy source. T. maritima RuvC resolved Holliday junctions at 70 degrees C. Remarkably, the cleavage site was identical to the preferred cleavage site for E. coli RuvC [(A/T)TT(downward arrow)(G/C)]. The conservation of function and the ease of purification of wild-type and mutant thermophilic proteins argues for the use of T. maritima proteins for additional biochemical and structural studies.

The journalist's role in bioethics

In the late 1950s and early 1960s, emerging advances in the biomedical sciences raised insufficiently noticed ethical issues, prompting science reporters to serve as a sort of Early Warning System. As awareness of bioethical issues increased rapidly everywhere, and bioethics itself arrived as a recognized discipline, the need for this early-warning press role has clearly diminished. A secondary but important role for the science journalist is that of investigative reporter/whistleblower, as in the Tuskegee syphilis trials and the government's secret plutonium experiments. Because the general public gets most of its information from the popular media, ways are suggested for journalists and bioethicists to work together.

Optimally isotropic Laplacian operator

Laplacian operators used in the literature for digital image processing are not rotationally invariant. We examine the anisotropy of 3 x 3 Laplacian operators for images quantized in square pixels, and find the operator which has the minimum overall anisotropy.

Dose response of various radiation detectors to synchrotron radiation

Accurate dosimetry is particularly difficult for low- to medium-energy x-rays as various interaction processes with different dependences on material properties determine the dose distribution in tissue and radiation detectors. Monoenergetic x-rays from synchrotron radiation offer the unique opportunity to study the dose response variation with photon energy of radiation detectors without the compounding effect of the spectral distribution of x-rays from conventional sources. The variation of dose response with photon energies between 10 and 99.6 keV was studied for two TLD materials (LiF:Mg,Ti and LiF:Mg,Cu,P), MOSFET semiconductors, radiographic and radiochromic film. The dose response at synchrotron radiation energies was compared with the one for several superficial/orthovoltage radiation qualities (HVL 1.4 mm Al to 4 mm Cu) and megavoltage photons from a medical linear accelerator. A calibrated parallel plate ionization chamber was taken as the reference dosimeter. The variation of response with x-ray energy was modelled using a two-component model that allows determination of the energy for maximum response as well as its magnitude. MOSFET detectors and the radiographic film were found to overrespond to low-energy x-rays by up to a factor of 7 and 12 respectively, while the radiochromic film underestimated the dose by approximately a factor of 2 at 24 keV. The TLDs showed a slight overresponse with LiF:Mg, Cu, P demonstrating better tissue equivalence than LiF:Mg, Ti (maximum deviation from water less than 25%). The results of the present study demonstrate the usefulness of monoenergetic photons for the study of the energy response of radiation detectors. The variations in energy response observed for the MOSFET detectors and GAF chromic film emphasize the need for a correction for individual dosimeters if accurate dosimetry of low- to medium-energy x-rays is attempted.

Methanococcus jannaschii flap endonuclease: expression, purification, and substrate requirements

The flap endonuclease (FEN) of the hyperthermophilic archaeon Methanococcus jannaschii was expressed in Escherichia coli and purified to homogeneity. FEN retained activity after preincubation at 95 degrees C+ for 15 min. A pseudo-Y-shaped substrate was formed by hybridization of two partially complementary oligonucleotides. FEN cleaved the strand with the free 5' end adjacent to the single-strand-duplex junction. Deletion of the free 3' end prevented cleavage. Hybridization of a complementary oligonucleotide to the free 3' end moved the cleavage site by 1 to 2 nucleotides. Hybridization of excess complementary oligonucleotide to the free 5' end failed to block cleavage, although this substrate was refractory to cleavage by the 5'-3' exonuclease activity of Taq DNA polymerase. For verification, the free 5' end was replaced by an internally labeled hairpin structure. This structure was a substrate for FEN but became a substrate for Taq DNA polymerase only after exonucleolytic cleavage had destabilized the hairpin. A circular duplex substrate with a 5' single-stranded branch was formed by primer extension of a partially complementary oligonucleotide on virion phiX174. This denaturation-resistant substrate was used to examine the effects of temperature and solution properties, such as pH, salt, and divalent ion concentration on the turnover number of the enzyme.

Psychiatry and children in the child welfare system

The child welfare system is, for better or worse, an unavoidable associate of the child and adolescent psychiatrist. Although the child psychiatrist rarely plays an integral role in decision making about the children who are involved with the system, the authors point out that a large percentage of children maintained in and involved with the system have psychiatric and developmental disorders. When these children's difficulties are either minimized or unrecognized by child welfare workers, the interventions and treatment that the children receive may be inappropriate. Worse still, when the children's difficulties are improperly addressed, the vicissitudes of the system may further harm them. The authors propose several ways in which the child and adolescent psychiatrist can have an important reparative role and voice in child welfare systems.

Identification of electrophoretically separated proteases from midgut and hemolymph of adult Anopheles stephensi mosquitoes

Digestion of blood within the mosquito midgut is mediated primarily by a series of proteases, and several previous studies have described protease activity within homogenates of the midgut of the malaria vector Anopheles stephensi. We have expanded on these previous data by resolving protease isoforms from the midgut as well as the hemolymph of adult An. stephensi mosquitoes via gel electrophoresis and zymography. Using this procedure, we have been able to identify multiple isozymes of trypsin, chymotrypsin, and aminopeptidase. We were able to detect an increase in the intensity of some of these protease bands plus the appearance of new bands 24 hr after mosquitoes had taken a blood meal. Furthermore, we detected 2 endogenous trypsin isozymes within the hemolymph. There was no upregulation of these hemolymph isozymes after a blood meal, thus suggesting that they may not be involved in digestion of the blood meal by the mosquito.

Refining the scale-up of chromatographic separations

The use of heavily loaded columns and complex processing conditions makes scale-up of chromatographic separations a non-trivial process. The wide ranges of process conditions that must be investigated demands that a large number of preliminary experiments must usually be made in small columns and laboratory-scale work stations. These preliminary data can be biased by improper column packing, poor distributors and dispersion in auxiliary apparatus, and it is important to understand these disturbing factors in detail. Moreover, it is precisely at this macroscopic level that our understanding of the chromatographic process is weakest, for large columns as well as small. This paper addresses three of these factors: Efficient elimination of peripheral effects and characterization of both header flow distribution and packing non-uniformity. This will be done using a variety of experimental and analytical approaches including nuclear magnetic resonance imaging, computational fluid dynamics and mass transfer, and careful experimentation.

Curve detection in a noisy image

In this paper we propose a new theory of the Gestalt law of good continuation. In this theory perceptual processes are modeled by an exponential pyramid algorithm. To test the new theory we performed three experiments. The subject's task was to detect a target (a set of dots arranged along a straight or curved line) among background dots. Detectability was high when: (a) the target was long; (b) the density of target dots relative to the density of background dots was large; (c) the local change of angle was small along the entire line; (d) local properties of the target were known to the subject. These results are consistent with our new model and they contradict prior models.

An exponential pyramid model of the time-course of size processing

Two prior approaches to size processing are discussed in this paper. The first approach is based on measurements of mental size transformations, the second on measurements of thresholds for size and separation. We first analyze these prior approaches and point out differences among prior models and similarities among prior results. This analysis led to new psychophysical experiments that tested the effect of size, relative precision, and eccentricity on the speed of perceptual processing. Speed was not affected by size, but was affected by relative precision and eccentricity. These new results, along with prior results, are then used to formulate a new model based on an exponential pyramid algorithm. This new model, which uses elements of both traditional approaches, can better account for prior, as well as our new results, on the time-course of size processing.

[Anticardiolipin antibodies in patients with cerebral ischemia]

Six patients with high level of anticardiolipin antibodies were hospitalized for ischaemic strokes or transient ischaemic attacks. The clinical findings in these cases varied greatly. In three ischaemic episodes were recurrent. In two stroke developed at old age without prodromal symptoms. In two females the vascular involvement was generalized. Although the role of anticardiolipin antibodies in the pathogenesis of vascular changes of the central nervous system is not yet clear it is thought that they may be a risk factor for stroke.

The interaction of luminance, velocity, and shape information in the perception of motion transparency, coherence, and non-rigid motion

The perception of luminance transparency for superimposed patterns depends on how luminance, figural, and topological conditions are simultaneously satisfied. Motion transparency or coherence for two superimposed patterns, which correspond to the perception of both patterns moving across one another or to the perception of compound motion of the regions of pattern intersection, depends on the relation between the local velocity, luminance, and shape information. This study analyzes how luminance, shape, and local velocity interact in the perception of motion transparency and coherence. Psychophysical experiments done with sinusoidally modulated bar patterns are presented which show that the perception of motion transparency or coherence can be described as the result of the interaction of two integration modules: the velocity-luminance and the velocity-shape processes. The velocity-luminance process describes the integration of the local velocity with luminance information. When the luminance transparency rules are satisfied this process always generates the perception of motion transparency independently of the shape or contour information. On the other hand, when the luminance transparency rules are violated one can either perceive motion coherence or non-rigid motion; one perceives motion coherence when the patterns have small or zero amplitude, and non-rigid motion when the patterns have large amplitude. The velocity-shape process describes the integration of local velocity with shape information, and this depends on the relation between the error in the extraction of the local velocity and the magnitude of the contour amplitude. As a result of these experiments it is conjectured that the velocity-luminance and the velocity-shape processes do interact constructively or destructively. The constructive interaction occurs when the luminance transparency rules are satisfied. The destructive interaction occurs when the luminance transparency rules are violated, and such that, although the patterns contain sufficient shape information to solve the aperture problem and therefore generate the perception of motion transparency, one perceives non-rigid motion. This shows that global information describing the stratification of superimposed patterns can affect the integration of local velocity information with, for example, shape information, and this is not described by current motion theories.

Computer vision

The field of computer vision is devoted to discovering algorithms, data representations, and computer architectures that embody the principles underlying visual capabilities. This article describes how the field of computer (and robot) vision has evolved, particularly over the past 20 years, and introduces its central methodological paradigms.

Improving primary care in nursing homes

We conducted a quasi-experiment to evaluate the impact of a Medicare waiver which allowed the use of nurse practitioners (NPs) and physicians assistants (PAs) to deliver primary care to Massachusetts nursing home patients and removed the limits on the reimbursable numbers of visits per month. A carefully matched set of 1,327 Medicaid patients from 95 non-participating homes in the same areas of Massachusetts was compared to 1,324 Medicaid demonstration patients from 75 homes. Information came from specially designed record reviews and the Medicaid and Medicare information systems. Separate analyses were done for newly admitted cases and rollovers. Comparisons of quality of care suggested that the medical groups using NPs and PAs provided as good or better care than did the physicians in the control group. There were no differences in functional status changes or in the use of medications. The demonstration patients received more attention, as reflected in more orders written and an average of one additional visit a month. Demonstration patients showed higher scores on three of seven specially designed quality tracers, congestive heart failure and hypertension for both new administrations and rollovers, and new urinary incontinence for new admissions. Rollovers had significantly fewer emergency and total hospital days. A cost analysis suggests that the use of NPs and PAs saves at least as much as it costs and may save additional money with more sustained use.

Line segregation

Six experiments investigated the preattentive segregation of line-like patterns composed of discrete elements in a background of distractors. The results indicate that other factors in addition to spatial density influence line segregation. Edge alignment, edge length and principal axis orientation also affect line segregation. Differences in the outputs of Gabor filters fail to account for the perceived segregation of the lines. Possible models of line segregation based on element grouping, feature density and search are briefly discussed.

Computer vision: a source of models for biological visual processes?

This paper reviews some basic computer vision techniques and speculates about their possible relevance to the modeling of human visual processes. Special emphasis is given to image segmentation techniques and how they relate to processes of perceptual organization, such as those embodied in the Gestalt "laws."