Influence of building construction work on Aspergillus infection in a hospital setting.

BACKGROUND AND OBJECTIVE: Aspergillus fumigatus is a major pathogen causing nosocomial infections. Hospital outbreaks of invasive aspergillosis have been associated with the renovation and construction of buildings. Building construction work for fire safety upgrading was undertaken during a 16-week period in 2001 at Box Hill Hospital. This study was designed to examine the effect of construction on invasive aspergillosis when using standard and additional protective measures. METHODS: Baseline air sampling was conducted in 18 areas. The validity of the air sampling was assessed by comparing the ability of two air samplers to detect Aspergillus conidia. Surveillance of nosocomial Aspergillus infection was conducted by reviewing the records of patients with a sputum culture positive for Aspergillus and those prescribed amphotericin or itraconazole for the period of construction activity and the same period the previous year. RESULTS: Aspergillus was isolated infrequently and there was no statistically significant difference in the levels of viable pathogenic fungi between areas w here construction work was undertaken and areas where it wasnot undertaken. A moderate agreement was observed between the two air samplers (kappa = 0.4; P < .05). There was no difference in the incidence of invasive aspergillosis between 2000 and 2001 (incidence density ratio, 1.2; 95% confidence interval, 0.3 to 4.1). CONCLUSION: The influence of construction work performed with protective measures needs to be examined in an environment with higher levels of airborne fungi to confirm the findings of this study.

Correlation of human olfactory responses to airborne concentrations of malodorous volatile organic compounds emitted from swine effluent.

Direct multicomponent analysis of malodorous volatile organic compounds (VOCs) present in ambient air samples from 29 swine (Sus scrofa) production facilities was used to develop a 19-component artificial swine odor solution that simulated olfactory properties of swine effluent. Analyses employing either a human panel consisting of 14 subjects or gas chromatography were performed on the air stream from an emission chamber to assess human olfactory responses or odorant concentration, respectively. Analysis of the olfactory responses using Fisher's LSD statistics showed that the subjects were sensitive to changes in air concentration of the VOC standard across dilutions differing by approximately 16%. The effect of chemical synergisms and antagonisms on human olfactory response magnitudes was assessed by altering the individual concentration of nine compounds in artificial swine odor over a twofold concentration range while maintaining the other 18 components at a constant concentration. A synergistic olfactory response was observed when the air concentration of acetic acid was increased relative to the concentration of other VOC odorants in the standard. An antagonistic olfactory response was observed when the air concentration of 4-ethyl phenol was increased relative to the other VOC odorants in the standard. The collective odorant responses for nine major VOCs associated with swine odor were used to develop an olfactory prediction model to estimate human odor response magnitudes to swine manure odorants through measured air concentrations of indicator VOCs. The results of this study show that direct multicomponent analysis of VOCs emitted from swine effluent can be applied toward estimating perceived odor intensity.

Categorical perception of relative orientation in visual object recognition.

The purpose of the present investigation was to determine whether the orientation between an object's parts is coded categorically for object recognition and physical discrimination. In three experiments, line drawings of novel objects in which the relative orientation of object parts varied by steps of 30 degrees were used. Participants performed either an object recognition task, in which they had to determine whether two objects were composed of the same set of parts, or a physical discrimination task, in which they had to determine whether two objects were physically identical. For object recognition, participants found it more difficult to compare the 0 degrees and 30 degrees versions and the 90 degrees and 60 degrees versions of an object than to compare the 30 degrees and 60 degrees versions, but only at an extended interstimulus interval (ISI). Categorical coding was also found in the physical discrimination task. These results suggest that relative orientation is coded categorically for both object recognition and physical discrimination, although metric information appears to be coded as well, especially at brief ISIs.

Differences in the coding of spatial relations in face identification and basic-level object recognition.

The purpose of this investigation was to determine if the relations among the primitives used in face identification and in basic-level object recognition are represented using coordinate or categorical relations. In 2 experiments the authors used photographs of famous people's faces as stimuli in which each face had been altered to have either 1 of its eyes moved up from its normal position or both of its eyes moved up. Participants performed either a face identification task or a basic-level object recognition task with these stimuli. In the face identification task, 1-eye-moved faces were easier to recognize than 2-eyes-moved faces, whereas the basic-level object recognition task showed the opposite pattern of results. Results suggest that face identification involves a coordinate shape representation in which the precise locations of visual primitives are specified, whereas basic-level object recognition uses categorically coded relations.

The role of attention in priming for left-right reflections of object images: evidence for a dual representation of object shape.

Three experiments investigated the role of visual attention in priming for object images and their left-right reflections. Objects to which participants attended were visually primed in both the same view and in the left-right reflected view; ignored objects were primed only in the same view. The effects of attention (attended vs. ignored) and view (same vs. reflected) were strictly additive. These results suggest that 2 separate representations mediate human object recognition (J.E. Hummel & B.J. Stankiewicz, 1996): One requires attention but is invariant with left-right reflection, whereas the other can be activated automatically but is sensitive to left-right reflection. Both representations appear to be invariant with translation across the visual field.

High level object recognition without an anterior inferior temporal lobe.

Seven individuals with unilateral anterior inferior temporal (AIT) lobectomies performed two types of shape recognition tasks with line drawing of 3D objects briefly presented in either the left or the right visual field. In one task, subjects named familiar objects in a name priming paradigm. In the other task, subjects judged whether two objects, presented sequentially with an intervening mask, were the same or different in shape, disregarding differences in orientation of up to 60 degrees in depth. They could not use names or basic level concepts to do the matching as the stimuli were either nonsense objects or, if familiar objects, were of same name-different-shaped exemplars on different trials. The disadvantage of presenting an image to the lobectomized hemisphere was negligible in both tasks. Two non-exclusive possibilities are suggested by this result: (a) Object recognition is completed posterior to AIT, likely at the temporal-occipital boundary, with no deleterious retrograde effects on object recognition from the AIT section, or (b) Callosal transfer of object information prior to AIT is completely efficient. These results, along with results of single unit recording and lesion experiments in the monkey, PET and MRI imaging in humans, and a plausibility argument based on the pattern of callosal connections suggest both are correct. Rather than mediating real-time object recognition, AIT may code representations for visual episodes and scenes.

To what extent can matching algorithms based on direct outputs of spatial filters account for human object recognition?

A number of recent successful models of face recognition posit only two layers, an input layer consisting of a lattice of spatial filters and a single subsequent stage by which those descriptor values are mapped directly onto an object representation layer by standard matching methods such as stochastic optimization. Is this approach sufficient for modeling human object recognition? We tested whether a highly efficient version of such a two-layer model would manifest effects similar to those shown by humans when given the task of recognizing images of objects that had been employed in a series of psychophysical experiments. System accuracy was quite high overall, but was qualitatively different from that evidenced by humans in object recognition tasks. The discrepancy between the system's performance and human performance is likely to be revealed by all models that map filter values directly onto object units. These results suggest that human object recognition (as opposed to face recognition) may be difficult to approximate by models that do not posit hidden units for explicit representation of intermediate entities such as edges, viewpoint invariant classifiers, axes, shocks and object parts.

Metric invariance in object recognition: a review and further evidence.

Phenomenologically, human shape recognition appears to be invariant with changes of orientation in depth (up to parts occlusion), position in the visual field, and size. Recent versions of template theories (e.g., Ullman, 1989; Lowe, 1987) assume that these invariances are achieved through the application of transformations such as rotation, translation, and scaling of the image so that it can be matched metrically to a stored template. Presumably, such transformations would require time for their execution. We describe recent priming experiments in which the effects of a prior brief presentation of an image on its subsequent recognition are assessed. The results of these experiments indicate that the invariance is complete: The magnitude of visual priming (as distinct from name or basic level concept priming) is not affected by a change in position, size, orientation in depth, or the particular lines and vertices present in the image, as long as representations of the same components can be activated. An implemented seven layer neural network model (Hummel & Biederman, 1992) that captures these fundamental properties of human object recognition is described. Given a line drawing of an object, the model activates a viewpoint-invariant structural description of the object, specifying its parts and their interrelations. Visual priming is interpreted as a change in the connection weights for the activation of: a) cells, termed geon feature assemblies (GFAs), that conjoin the output of units that represent invariant, independent properties of a single geon and its relations (such as its type, aspect ratio, relations to other geons), or b) a change in the connection weights by which several GFAs activate a cell representing an object.

Unexceptional spatial memory in an exceptional memorist.

Rajan Mahadevan evidences an exceptional memory for arrays of digits. We tested whether Rajan's spatial memory was likewise exceptional. Eight control Ss and Rajan were instructed to remember the position and orientation of 48 images of common objects shown either to the left or the right of fixation and facing either left or right. Rajan's accuracy for judging whether the position and orientation of these pictures had changed when they were shown in a different sequence was lower than that of control Ss for both judgments. Rajan's exceptional memory capacity apparently does not extend to spatial relations.

Priming contour-deleted images: evidence for intermediate representations in visual object recognition.

The speed and accuracy of perceptual recognition of a briefly presented picture of an object is facilitated by its prior presentation. Picture priming tasks were used to assess whether the facilitation is a function of the repetition of: (a) the object's image features (viz., vertices and edges), (b) the object model (e.g., that it is a grand piano), or (c) a representation intermediate between (a) and (b) consisting of convex or singly concave components of the object, roughly corresponding to the object's parts. Subjects viewed pictures with half their contour removed by deleting either (a) every other image feature from each part, or (b) half the components. On a second (primed) block of trials, subjects saw: (a) the identical image that they viewed on the first block, (b) the complement which had the missing contours, or (c) a same name-different exemplar of the object class (e.g., a grand piano when an upright piano had been shown on the first block). With deletion of features, speed and accuracy of naming identical and complementary images were equivalent, indicating that none of the priming could be attributed to the features actually present in the image. Performance with both types of image enjoyed an advantage over that with the different exemplars, establishing that the priming was visual rather than verbal or conceptual. With deletion of the components, performance with identical images was much better than that with their complements. The latter were equivalent to the different exemplars, indicating that all the visual priming of an image of an object is through the activation of a representation of its components in specified relations. In terms of a recent neural net implementation of object recognition (Hummel & Biederman, in press), the results suggest that the locus of object priming may be at changes in the weight matrix for a geon assembly layer, where units have self-organized to represent combinations of convex or singly concave components (or geons) and their attributes (e.g., aspect ratio, orientation, and relations with other geons such as TOP-OF). The results of these experiments provide evidence for the psychological reality of intermediate representations in real-time visual object recognition.

Control of attention around the fovea.

Three experiments tested young adults' abilities to use size and location cues to find and identify a target letter in a visual field containing 8 to 12 letters. Location cues (relatively near to or far from the fovea) and size cues (relatively large or small) were given before the display. Compared with response times on neutral, no-cue trials, location and size cues produced independent cost and benefit effects. The best fitting quantitative models allow attentional resources to be distributed in ringlike areas varying in distance from the fixation point, within which further selection of items by their relative size is possible.

Object recognition and laterality: null effects.

In two experiments, normal subjects named briefly presented pictures of objects that were shown either to the left or to the right of fixation. The net effects attributable to hemifield were negligible: naming RTs were 12 msec lower for pictures shown in the left visual field but error rates were slightly lower, by 0.8%, for pictures shown in the right visual field. In both experiments, a second block of trials was run to assess whether hemifield effects would be revealed in object priming. Naming RTs to same name--different shaped exemplar pictures were significantly longer than RTs for identical pictures, thus establishing that a component of the priming was visual, rather than only verbal or conceptual, but hemifield effects on priming were absent. Allowing for the (unlikely) possibility that variables with large differential left-right hemifield effects may be balancing and cancelling each other out, we conclude that there are no differential hemifield effects in either object recognition or object priming.

Evidence for complete translational and reflectional invariance in visual object priming.

The magnitude of priming on naming reaction times and on the error rates, resulting from the perception of a briefly presented picture of an object approximately 7 min before the primed object, was found to be independent of whether the primed object was originally viewed in the same hemifield, left-right or upper-lower, or in the same left-right orientation. Performance for same-name, different-examplar images was worse than for identical images, indicating that not only was there priming from block one to block two, but that some of the priming was visual, rather than purely verbal or conceptual. These results provide evidence for complete translational and reflectional invariance in the representation of objects for purposes of visual recognition. Explicit recognition memory for position and orientation was above chance, suggesting that the representation of objects for recognition is independent of the representations of the location and left-right orientation of objects in space.

The control of visual attention using multiple target features.

An experiment was conducted to determine how visual attention is allocated in response to pairwise combinations of location, color, and size cues. Subjects viewed displays of eight letters arranged into an 'X' pattern emanating from a central fixation point. The letters varied on the dimensions of location (foveal or parafoveal positions), size (large or small), and color (red or blue). Seven of the letters were 'X's and the remaining, critical letter was either an 'R' or an 'L'. Subjects were given advance cues about characteristics of the critical letter on two of the three dimensions (location size, and color). The cues varied in their validity such that on any trial either both dimensions were validly cued, one dimension was validly cued while the other was invalidly cued, or both cues were invalid. Subjects were instructed to try to use the cues to find the critical letter, and response times to identify it as an 'R' or an 'L' served as the main dependent measure. Two models were evaluated against the data; in one, location cues are viewed as having distinct effects on an early stage of attention whereas color and size cues operate only in a later, selection stage. In the other model, all cues are used in a similar way to select display items for serial, focal attention. In general, the serial processing model provides a more complete account of the data.

Cholesterol-lowering effect of colestipol hydrochloride given twice daily in hypercholesterolemic patients.

In a randomized design study in 66 hypercholesterolemic patients, dosages of 10 g of colestipol HCl twice daily lowered serum cholesterol an average of 19% more than placebo therapy. These results are comparable to those in other studies in which the same total daily dose was given in three or four doses. The most common side effect was constipation, reported by 6 patients on colestipol HCl and 3 patients on placebo. No untoward systemic reactions or abnormal laboratory data were seen except for a slight rise in serum alkaline phosphatase during colestipol HCl therapy. The drug was well accepted by most patients.

Colestipol hydrochloride, a new hypolipidemic drug: a two-year study.

Colestipol hydrochloride is an insoluble, nonabsorbable copolymer with bile-acid-binding capacity. It prevents reabsorption of cholates from the intestinal tract into the enterohepatic circulation causing a net loss of bile acids, and therefore of cholesterol. Sixty subjects with cholesterol levels over 250 mg/100 ml were studied for 104 weeks. Patients with normal phenotypes, types 2,3, and 4, were given 5 gm three times daily and experienced an average drop of 40 mg/100 ml (14%). While patients with types 2,3, and 4 hyperlipidemia responded effectively, cholesterol levels in type 2 patients dropped earliest and most consistently with an average decrease of 58 mg/100 ml (19%). A comparable group of patients with hyperlipidemia taking placebo showed on average no change in serum cholesterol. Serum triglyceride values were not altered significantly. The resin is not absorbed from the gastrointestinal tract and produces a slight increase in fecal volume. Results of chemistries, enzyme assays, prothrombin times, hematology, and urinalysis and body weights wer unaltered. There was no evidence of lithogenic bile production. Colestipol is a tasteless and ordorless copolymer with high acceptability. Side effects were limited to occasional bloating, gas, and constipation. The drug is a safe, effective, palatable hypolipedmic agent.