WAFER-SCALE, SOLID FREEFORM FABRICATION OF FULLY-ASSEMBLED METAL MICRO-MECHANISMS FOR MINIMALLY-INVASIVE MEDICAL DEVICES.

The EFAB process was first presented at the SFF Symposium in 1998, at a very early stage of its development. Currently, the technology is able to produce complex 3-D devices-including mechanisms built pre-assembled-in production volumes, using a three-step process of selective electrodeposition of one metal, blanket electrodeposition of another metal, and planarization. Layer thickness is as small as 4 µm, minimum feature size is down to 10 µm, and linear tolerances are ~2 µm. Metals are biocompatible materials with mechanical properties similar to stainless steel. The technology enables new instruments for minimally-invasive surgical and interventional procedures.

Contingent attentional capture or delayed allocation of attention?

Under certain circumstances, external stimuli will elicit an involuntary shift of spatial attention, referred to as attentional capture. According to the contingent involuntary orienting account (Folk, Remington, & Johnston, 1992), capture is conditioned by top-down factors that set attention to respond involuntarily to stimulus properties relevant to one's behavioral goals. Evidence for this comes from spatial cuing studies showing that a spatial cuing effect is observed only when cues have goal-relevant properties. Here, we examine alternative, decision-level explanations of the spatial cuing effect that attribute evidence of capture to postpresentation delays in the voluntary allocation of attention, rather than to on-line involuntary shifts in direct response to the cue. In three spatial cuing experiments, delayed-allocation accounts were tested by examining whether items at the cued location were preferentially processed. The experiments provide evidence that costs and benefits in spatial cuing experiments do reflect the on-line capture of attention. The implications of these results for models of attentional control are discussed.

A dissociation between attention and selection.

It is widely assumed that the allocatian of spatial attention results in the "selection" of attended objects or regions of space. That is, once a stimulus is attended, all its feature dimensions are processed irrespective of their relevance to behavioral goals. This assumption is based in part on experiments showing significant interference for attended stimuli when the response to an irrelevant dimension conflicts with the response to the relevant dimension (e.g., the Stroop effect). Here we show that such interference is not due to attending per se. In two spatial cuing experiments, we found that it was possible to restrict processing of attended stimuli to task-relevant dimensions. This new evidence supports two novel conclusions: (a) Selection involves more than the focusing of attention per se: and (b) task expectations play a key role in detertnining the depth of processing of the elementary feature dimensions of attended stimuli.

Can new objects override attentional control settings?

Previous research suggests that attentional capture by abrupt onsets is contingent on top-down attentional control settings. Four experiments addressed whether similar contingencies hold for capture elicited by the appearance of new perceptual objects. In a modified spatial cuing task, targets defined by abrupt onset or color were paired with distractors consisting of an abrupt brightening of an existing object or the abrupt appearance of a new object. In Experiments 1 and 2, when subjects searched for an onset target, both distractor types produced evidence of capture. When subjects searched for a color target, however, distractors produced no evidence of attentional capture, regardless of whether they consisted of a new perceptual object or not. Experiments 3-5 showed that the lack of distractor effects in the color-target condition cannot be accounted for by rapid recovery from capture. It was concluded that attentional capture by new objects is subject to top-down modulation by attentional control settings.

Selectivity in distraction by irrelevant featural singletons: evidence for two forms of attentional capture.

Four experiments addressed the degree of top-down control over attentional capture in visual search for featural singletons. In a modified spatial cuing paradigm, the spatial relationship and featural similarity of target and distractor singletons were systematically varied. Contrary to previous studies, all 4 experiments showed that when searching for a singleton target, an irrelevant featural singleton captures spatial attention only when defined by the same feature value as the target. Experiments 2, 3 and 4 provided a potential explanation for the discrepancy with previous studies by showing that irrelevant singletons can produce distraction effects that are dissociable from shifts of spatial attention. The results suggest the existence of 2 distinct forms of attentional capture.

The effects of age on guided conjunction search.

The effect of age on top-down guidance in visual search for conjunctions of form and motion was examined with a task developed by Driver et al. (1992). Young (mean age = 19.2 years) and old (mean age = 77.3 years) adults searched for a vertically oscillating X among varying numbers of vertically oscillating Os and horizontally oscillating Xs. The ease with which subjects could use top-down guidance to improve search efficiency was manipulated by varying the motion coherence of display items. Overall, older adults produced steeper response-time-display-size slopes than did young adults, and both age groups showed significant reductions in slopes when distractors oscillated coherently. Older adults, however, produced proportionally smaller reductions in slope than did younger adults, suggesting that age affects the efficiency of top-down guidance in conjunction search for form and motion.

Spatial cuing in a stereoscopic display: Evidence for a "depth-blind" attentional spotlight.

This experiment explored whether attentional selection observed in a spatial cuing task is based on a representation that includes depth information or not. Targets were presented inside placeholders appearing at the samex,y location on a stereoscopic display, but on different depth planes, or at differentx,y locations on the same depth plane. A peripheral precue produced significant cuing effects in the latter but not in the former condition. In a control experiment, significant cuing effects were found for targets appearing at differentx,y coordinates within the fovea, confirming that the lack of cuing effects in the depth condition was not due to foveal presentation. Together, the results suggest that spatial selection in spatial cuing tasks operates on a representation that does not include depth information.

Shifting visual attention in stereographic displays: a time course analysis.

According to a growing number of studies, the stereographic presentation of three-dimensional information improves overall performance relative to displays with only monocular depth cues. Based on studies using real-world, three-dimensional stimuli, however, the efficiency (i.e., speed) of shifting attention between objects located at different depths is impaired relative to that of attention shifts between objects located at the same depth. In the present study we tested whether similar impairments occur when attention is shifted in stereographic space. We compared the time course of attention shifts across and within depth planes using a spatial cuing task. Contrary to the results from studies of real-world stimuli, we found no difference between the time course of within-plane and across-plane attention shifts.

Do locally defined feature discontinuities capture attention?

Results from previous visual search studies have suggested that abrupt onsets produce involuntary shifts of attention (i.e., attentional capture), but discontinuities in simple features such as color and brightness do not (Jonides & Yantis, 1988). In the present study we tested whether feature discontinuities (i.e., "singletons") can produce attentional capture in a visual search task if defined "locally" or over a small spatial range. On each trial, a variable number of letters appeared, one of which differed from the others in color or intensity. The location of this singleton was uncorrelated with target location. Local discontinuities were created by embedding the letters in a dot texture. In Experiment 1, display size effects for singleton targets were not reduced with the addition of a background dot texture. Similar results were obtained in Experiment 2, regardless of variations in texture density. Experiment 3 confirmed that when targets are defined by a color or intensity singleton, they are detected preattentively, and that increasing texture density yields faster detection. We conclude that the spatial range over which feature discontinuities are defined may influence the guidance of spatial attention, but it has no influence on their ability to capture attention.

The structure of attentional control: contingent attentional capture by apparent motion, abrupt onset, and color.

Five spatial cuing experiments tested 2 hypotheses regarding attentional capture: (a) Attentional capture is contingent on endogenous attentional control settings, and (b) attentional control settings are limited to the distinction between dynamic and static discontinuities (C. L. Folk, R. W. Remington, & J. C. Johnston, 1992). In Experiments 1 and 2, apparent-motion precues produced significant costs in performance for targets signaled by motion but not for targets signaled by color or abrupt onset. Experiment 3 established that this pattern is not due to differences in the difficulty of target discrimination. Experiments 4 and 5 revealed asymmetric capture effects between abrupt onset and apparent motion related to stimulus salience. The results support the hypotheses of Folk et al. (1992) and suggest that stimulus salience may also play a role in attentional capture.

Beta-carotene in HIV infection.

beta-Carotene has been reported to have an immunostimulatory effect. Recent studies suggest that beta-carotene supplementation can increase CD4 counts in HIV-infected patients. Our double-blind, placebo-controlled clinical trial was designed to test the efficacy of beta-carotene in raising CD4 counts in HIV-infected patients. Twenty-one HIV-seropositive patients were randomized to receive either beta-carotene, 180 mg/day or placebo for 4 weeks, and then crossed over to receive the alternative treatment for the following 4 weeks. beta-Carotene resulted in a statistically significant increase in total WBC count (p = 0.01), % change in CD4 count (p = 0.02), and % change in CD4/CD8 ratios (p = 0.02) compared to placebo. The absolute CD4 count, absolute CD4/CD8 ratio, and total and B-lymphocytes all increased on carotene and fell during placebo, but these differences did not reach statistical significance. No toxicity was observed on either treatment. beta-Carotene appears to have an immunostimulatory effect in HIV-infected patients. Further studies are needed to demonstrate whether beta-carotene has a role as adjunct therapy in treatment of HIV-infected patients.

Incidence of Toxoplasma gondii in populations of wild birds in the Czech Republic.

The protozoan parasite Toxoplasma gondii was isolated from 193 individuals of 25 wild avian species, in a survey between 1981 and 90 in which 5880 individuals, comprising 76 species, were examined. The incidence of T. gondii was 18% in rooks (Corvus frugilegus), 12% in mallards (Anas platyrhynchos), 8% in common buzzards (Buteo buteo), 2% in pheasants (Phasianus colchicus) and 0.5% in house sparrows (Passer domesticus) and differed significantly in these species (X(2) test, P<0.001). In rooks, the cysts of T. gondii were found in the heart, brain, sex organs, skeletal muscle and liver.

The role of spatial attention in visual word processing.

Subjects made lexical decisions on a target letter string presented above or below fixation. In Experiments 1 and 2, target location was cued 100 ms in advance of target onset. Responses were faster on validly than on invalidly cued trials. In Experiment 3, the target was sometimes accompanied by irrelevant stimuli on the other side of fixation; in such cases, responses were slowed (a spatial filtering effect). Both cuing and filtering effects on response time were additive with effects of word frequency and lexical status (words vs. nonwords). These findings are difficult to reconcile with claims that spatial attention is less involved in processing familiar words than in unfamiliar words and nonwords. The results can be reconciled with a late-selection locus of spatial attention only with difficulty, but are easily explained by early-selection models.

Involuntary covert orienting is contingent on attentional control settings.

Four experiments tested a new hypothesis that involuntary attention shifts are contingent on the relationship between the properties of the eliciting event and the properties required for task performance. In a variant of the spatial cuing paradigm, the relation between cue property and the property useful in locating the target was systematically manipulated. In Experiment 1, invalid abrupt-onset precues produced costs for targets characterized by an abrupt onset but not for targets characterized by a discontinuity in color. In Experiment 2, invalid color precues produced greater costs for color targets than for abrupt-onset targets. Experiment 3 provided converging evidence for this pattern. Experiment 4 investigated the boundary conditions and time course for attention shifts elicited by color discontinuities. The results of these experiments suggest that attention capture is contingent on attentional control settings induced by task demands.

Aging and shifts of visual spatial attention.

Three experiments examined adult age differences in the efficiency of endogenous (voluntary) and exogenous (involuntary) attention shifts. Younger and older subjects performed a spatial cuing task in which abruptly onset peripheral cues (Experiment 1) or central, symbolic cues (Experiments 2 and 3) were presented before a target stimulus at intervals ranging from 50 to 250 ms. With peripheral cues, the magnitude of cuing effects was at least as great for older as for younger adults and followed a similar time course. Similar results were obtained with symbolic cues, although cuing effects for older adults varied with cue difficulty. The results suggest that cue encoding may decline with advancing age but that the efficiency of the shift process is preserved.

Does the identification of simple features require serial processing?

Several recent studies have shown performance decrements with increasing display size when background texture elements are present in a same-different feature discrimination task--a result that challenges the traditional notion that the identities of simple visual features are processed in parallel, preattentively. Four experiments are reported that explore the implications of these results. Experiment 1 replicates the recent studies but limits the generalizability of the results to small target numbers. Experiments 2 and 3 show that the observed performance decrements are not due to a serial or even limited-capacity, parallel process. Experiment 4 suggests that decision factors idiosyncratic to the use of texture elements in a same-different task are responsible for the effect. It is concluded that the identification of simple visual features proceeds in parallel, with unlimited capacity (i.e., preattentively).

Dietary management of Type I glycogen storage disease.

The most commonly recognized type of glycogen storage disease (von Gierke's disease) results from deficient glucose-6-phosphatase activity. This enzyme is the last step in the release of free glucose from the liver into the circulation. Thus, the most prominent and life-threatening complication in the illness is severe and often prolonged hypoglycemia, which occurs after the dietary glucose is normally removed from the circulation. With an optimal dietary intake spaced at 2 1/2- to 3 1/2-hour intervals, the blood glucose can be maintained in the normal range during the daytime, but hypoglycemia may occur during overnight fasting. Recent advances in the understanding of the pathophysiology of the illness have led to the use of frequent high-starch feedings during the day and nocturnal intragastric infusions of liquid formulas containing glucose polymers. The liquid formula is infused through either a nasogastric or a gastrostomy tube continuously at night while the patient sleeps. The success of this treatment not only has improved the survival rate but also has corrected the abnormal blood chemistries and generated a more normal rate of growth and development. Because patients with this disease are reaching adulthood in greater numbers, it is necessary for dietitians caring for adults as well as for children to become familiar with the prescribed methods of treatment.

Rapidly declining serum albumin values in newly hospitalized patients: prevalence, severity, and contributory factors.

We had noted that a number of hospitalized patients showed abnormally low serum albumin levels within a few days of admission, although the albumin had been normal at admission. Since this rapid decline in albumin could not be accounted for on the basis of starvation, we hypothesized that the changes were due to the increase in intravascular fluid volume which normally occurs with assumption of the recumbent position. Since albumin is often a nutritional screening parameter in hospitalized patients, it is important to ascertain the incidence of such profound changes in albumin as well as to identify possible causes for this change. A survey of 34 concurrent hospital admissions showed that 28 out of 34 (82%) patients had a decline in serum albumin within 5 days of hospitalization. These 28 patients had a decrease of 0.5 +/- 0.09 g/dl. Twenty-five additional patients were studied in order to elucidate causative factors. Twenty out of the 25 showed a decrease in serum albumin within 5 days of admission (mean decrease 0.5 +/- 0.05 g/dl). Hemoglobins in these patients decreased by a mean of 1.1 +/- 0.34 g/dl (p less than 0.01), but BUN and uric acid levels did not change significantly. The one factor common to all patients with declining albumin values was change in posture. All patients were ambulatory at the time of the initial albumin determination but were on bedrest for at least 6 1/2 hours before the second determination. The findings indicate that most hospitalized patients have significant changes in serum albumin levels which occur with change in posture. If the albumin level is to be used as a nutritional indicator, the patient's position at the time of phlebotomy is essential for accurate interpretation of results.