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Biomedical subjects

T L White

Publications and source records attributed to T L White.

At least 19 recordsLinked to original sources
PubMed2002

Age-age and trait-trait correlations for Eucalyptus grandis Hill ex Maiden and their implications for optimal selection age and design of clonal trials.

Previous results from seven locations of Eucalyptus grandis clonal trials in Colombia supported the a priori contention of sub-dividing them into three different environmental zones for testing and deployment. Within these zones, the determination of age-age genetic correlations for both height and mean annual increment (MAI) showed that strong age-age correlations are present for a rotation age of 6 years starting at 3 years age and, thereafter, suggesting this age as appropriate for selection. This biological selection age coincides with an "economical" age for selection based on discounted selection efficiency in perpetuity, considering a range of interest rates between 10% and 20%. High genetic correlations between wood density at 3 years and 6 years as well as the lack of genetic correlation between this trait and growth traits, also favors selection at age 3 and facilitates breeding strategies that consider the utilization of both traits for improvement. A simulation of optimal clonal test designs indicated that by using six locations and six blocks per location in a single-tree plot design, between 80% and 90% of the maximum selection efficiency could be obtained. This type of design allows testing of a large number of genotypes across a reasonable number of locations in a cost-effective manner.

Chromosome Mapping↗
PubMed2001

Odorant confusion matrix: the influence of patient history on patterns of odorant identification and misidentification in hyposmia.

The odorant confusion matrix (OCM) is an odorant identification test in which the number of correct odorant identifications quantifies the level of olfactory function. As with other confusion matrices, the OCM reflects distortions of sensory perception as errors in identification. Previous work with the OCM suggests that, within an individual, hyposmia is associated with a stable shift in odorant perception. The current study examined whether consistent shifts in odorant perception are also characteristic of the various pathologies that lead to an olfactory loss. In a retrospective study, OCM response patterns for 135 hyposmic patients were fit into a five-dimensional space in which the distances between subjects reflected the dissimilarities between their OCM response patterns. Multivariate regression was performed relating position in the five-dimensional space to each of 11 factors representing 33 demographic and medical history variables. One factor, named congestion (gathering the variables of past polyposis, current polyposis, and current nasal obstruction due to swelling), was significantly indicative of patterns of responses on the OCM, independent of the level of hyposmia. These data suggest that conductive olfactory loss may be associated with alterations in odorant perception, which are reflected in consistent odorant confusions. Such alterations in perception may eventually serve as a basis for a clinical test to provide differential diagnoses as to the sources of olfactory losses.

Adolescent↗
PubMed2000

The labeled dissimilarity scale: a metric of perceptual dissimilarity.

Fundamental to the concept of psychological distance is the idea that confusability allows discovery of the perceptual relationships between objects, which provides understanding of the underlying principles that govern the functioning of a system. Thus, judgments of dissimilarity (conceptually proportional to the inverse of confusability) may provide insight into the elusive underlying quality-coding mechanisms in that sensory system. In the present experiments, a labeled dissimilarity scale (LDS) that reflects the magnitude of odorant dissimilarity was developed in a fashion similar to that reported by Green (Green, Shaffer, & Gilmore, 1993). This scale was produced by rating the perceptual intensity implied by adverbs describing different levels of dissimilarity, and then attaching those descriptors to appropriate locations on a numerical scale. The usefulness of the scale was demonstrated by its ability to produce visual color space with ratings of dissimilarity of Munsell color chips. The stability and reliability of the LDS was evaluated by comparing it with the traditional scaling technique of magnitude estimation (ME). It was found that the scales produced similar ratings of odorant dissimilarity and showed a similar susceptibility to the effects of contrast convergence. However, the coefficients of variation of dissimilarities rated with ME were much higher than those produced with the LDS. The subjects also dealt with the LDS without the anxiety that usually accompanies first-time users of ME. The LDS provided stable ratings of odorant dissimilarity and preserved the inferred ratio scale properties of ME.

Adult↗
PubMed2000

Odorant quality perception: a metric individual differences approach.

Perceptual spaces, in which similar stimuli are located close to each other and dissimilar stimuli are located far apart, have aided in the understanding of the physiological and psychological bases for sensory quality coding. Differences in perception between individuals should be reflected by differences in the spatial relationships between stimuli. If the dimensionality of the perceptual space is small (e.g., color space), individual differences that reflect specific pathologies are readily apparent from visual inspection. On the other hand, if the dimensionality of the perceptual space is large (as is proposed for odor space), visual inspection alone may not reveal individual differences in quality perception. The present work presents an information-theory-based method for quantifying individual differences in quality perception from perceptual confusion matrices. The ability of this method to quantify individual differences in quality perception is shown in a hypothetical example of specific anosmia. Finally, the method is applied to the examination of intrasubject consistency of odorant quality perception.

Adult↗
PubMed1999

Differential association of traits of fear and anxiety with norepinephrine- and dark-induced pupil reactivity.

The relation between fear and anxiety remains unclear, though psychometric data strongly suggest they are independent emotional systems. Because central norepinephrine (NE) projection systems are at the core of models of both fear and anxiety, the present experiment explored whether this independence extends to NE functioning. Two different aspects of NE functioning were assessed in a healthy young adult sample (N = 18): pupillary reactivity to (a) a specific NE alpha-1 agonist challenge to assess receptor reactivity and (b) a darkness challenge to assess contributions of central NE. Pupillary reactivity to the former was strongly and specifically related to A. Tellegen's (1982) Multidimensional Personality Questionnaire (MPQ) Harm Avoidance scale (i.e., trait fear), whereas the latter was strongly and specifically related to MPQ Negative Emotionality (i.e., trait anxiety). Implications for conceptualizing fear and anxiety as emotional systems are discussed.

Adrenergic alpha-Agonists↗
PubMed1999

What a tangled web we weave: discriminating between malingering and anosmia.

Two groups of normosmic subjects were instructed to feign a total olfactory loss when tested with the Olfactory Confusion Matrix (OCM). One of the groups was given specific instructions as to the number of odorants and trials in the test, as well as the number of items that might be expected to be correctly identified by chance. The responses of both groups of malingerers were compared with responses gathered from a group of anosmic patients. The groups did not differ in terms of performance level (percent correct). In spite of the similarity in terms of accuracy level, an analysis of the pattern of OCM responses to an irritant allowed the anosmic patients to be distinguished from subjects attempting to feign a loss. Subjects were given explicit details about the test performed at the same level as those simply told to feign a loss. These results suggest that the OCM is an effective tool in separating malingering from anosmia.

Adult↗
PubMed1998

Phonological and perceptual components of short-term memory for odors.

Just as a written word can be encoded and retained in memory either verbally or in a visual form, so it might seem that an odor might be retained as either a verbal description/name or as a perceptual (olfactory) code. However, one view has it that olfactory memory in the short term does not exist as a separate perceptual code. This was examined in an experimental paradigm in which errors in memory could be recognized as deriving from the substitution of similar verbal codes or of similar olfactory codes. The set of odorants presented for recall was divided into three groups: (i) base odorants (odorants that might be replaced in memory either by similar verbal or similar olfactory representations); (ii) verbal foils (stimuli dissimilar to the base stimuli in odor but which is similar in name); and (iii) odor foils (the reverse). The substitution errors made when attempting to recall test odorants were classified as verbal errors or olfactory errors. A substantial proportion of the errors were olfactory, but verbal errors also occurred. These results support the presence of short-term perceptual olfactory memory, rather than simply verbal encoding of olfactory perceptions.

Humans↗
PubMed1998

Metrics of odorant dissimilarity. Labeled magnitude scale vs magnitude estimation.

Magnitude estimation (ME) has long been the standard rating tool for stimulus intensity because of the simplicity and generalizability of the resultant power function relationships. However, the choice of a scaling procedure for rating complex stimuli (odorant) dissimilarity must be based on a different set of criteria due to an inability to evaluate relationships against a physical continuum. Recently, chemosensory labeled magnitude scales (LMS) have been developed, which produce ratings with many of the same properties as ME. The current study sought compare LMS to ME as metrics for describing the magnitude of perceived odorant dissimilarity. Forty subjects rated pair-wise odorant dissimilarity with either a LMS or ME. Each subject evaluated two sets of odorants with differing ranges of dissimilarity (high contrast and low contrast) in order to compare the sensitivity of the two measures to possible contrast convergence. The ME ratings were normalized such that the two metrics produced equal means. The scales produced similar ratings of odorant dissimilarity (r = 0.92) and showed small but similar effects of contrast convergence. However, the coefficient of variation of dissimilarities rated with ME was 2.8 times that of dissimilarities rated with the LMS. Subjects accepted the LMS without the usual anxiety that accompanies first time users of ME. LMS provide stable ratings of odorant dissimilarity while preserving the inferred ratio scale properties of ME.

Adolescent↗
PubMed1998

Olfactory memory: the long and short of it.

It has been proposed that memory for odors does not have a short-term (or working) memory system. The distinction between short- and long-term memory in other sensory modalities has been generally supported by three main lines of evidence: capacity differences between the proposed systems, evidence of differential coding, and differential memory losses in neuropsychological patients. The present paper examines these issues in an effort to establish a similar distinction for the memory of olfactory stimuli. Each of these lines of evidence is examined in relation to the literature on olfactory memory. Based on this examination, it seems that there is at least preliminary support from each of these lines of evidence to advocate a distinction between a long- and short-term memory for olfactory stimuli. Emphasis is placed upon the qualitative similarity of olfactory memory to other memory systems. This similarity is further highlighted through an examination of the literature pertinent to serial position effects in memory for olfactory stimuli.

Humans↗
PubMed1998

Phonological and perceptual components of short-term memory for odors.

Just as a written word can be encoded and retained in memory verbally or visually, an odor might be retained as a verbal description or perceptual (olfactory) code. However, one view holds that olfactory memory in the short term does not exist as a separate perceptual code. This was examined in an experiment in which memory errors could be seen as deriving from the substitution of similar verbal or olfactory codes. The odorants presented for recall were divided into three groups: base odorants (which might be replaced in memory by similar verbal or olfactory representations), verbal foils (stimuli dissimilar to the base stimuli in odor but similar in name), and odor foils (the reverse). The substitution errors made in attempting to recall test odorants were classified as verbal or olfactory. A substantial proportion of the errors were olfactory, but verbal errors also occurred. These results support the presence of short-term perceptual olfactory memory rather than simply verbal encoding of olfactory perceptions.

Adolescent↗
PubMed1997

A comparison of the encoding of content and order in olfactory memory and in memory for visually presented verbal materials.

The claim that there is no olfactory short-term memory store, as olfactory serial position (SP) effects are absent (Engen, 1987, 1989; Lawless & Engen, 1977), raises the issue whether memory for sensory qualities is differently organized from memories for more cognitive materials in vision and hearing. Early memory processing in olfaction is re-examined by comparing the results of similarly designed experiments which examine short-term memory for words and consonants, and for odours. Memory for content and memory for order were separately examined in each case. Serial position functions were obtained both for visually presented verbal materials and for odours. The serial position effects for content and order memory in both modalities are sufficiently similar in pattern to support the conclusion that short-term memory processing of olfactory and verbal stimuli is conducted by analogous memory mechanisms.

Adolescent↗
PubMed1992

Growth and phenology of seedlings of four contrasting slash pine families in ten nitrogen regimes.

Seedlings of two fast- and two slow-growing families of slash pine, Pinus elliottii Englm. var. elliottii, were grown in a greenhouse for one growing season in one of 10 nitrogen (N) regimes. Increasing the N concentration in the nutrient solution resulted in both increased growth rates during the exponential growth phase and extended duration of the growing season. The two components of total height, free growth (epicotyl length to the first bud) and summer growth (height growth after the first bud), both increased significantly with increasing N concentrations up to 40-60 mg l(-1) but decreased at N concentrations above 180 mg l(-1). Compared to seedlings grown in the presence of an optimum N concentration, seedlings grown in the presence of trace amounts of N were smaller and had less summer growth as a percentage of total growth, earlier cessation of height growth, fewer flushes, lower shoot/root ratio, higher root fibrosity, and lower N concentrations in all seedling tissues. Compared to slow-growing families, fast-growing families had more summer height growth, more flushes and later growth cessation, higher shoot/root ratios and higher root fibrosity at all N concentrations. In the presence of an optimum or higher concentration of N, the fast-growing families also had higher needle and total N concentrations than the slow-growing families. Strong family by N-treatment interactions occurred for height, phenology and biomass traits because of the extra responsiveness of one family to increasing N concentration. Several seedling traits were identified that appear promising for predicting field performance in slash pine. The results indicated that the nutrient environment greatly influences genetic expression (e.g., family patterns of summer growth were most closely related to field rankings for seedlings in the trace-N treatment).

Journal Article↗
PubMed1991

Slash pine bud dormancy as affected by lifting date and root wrenching in the nursery.

Bud dormancy of root wrenched and unwrenched slash pine (Pinus elliottii Engelm.) seedlings growing in a forest nursery was measured on five lifting dates. Determination of bud dormancy was based on days to budbreak (DBB) under optimal growing conditions, mitotic activity in the apical meristem, chilling hours accumulated, and bud morphology. Based on DBB, seedlings were most dormant at Lift 2 on November 24 after exposure to 189 hours below 10 degrees C and 93 hours below 6.7 degrees C. Mitotic activity in the apical meristem was at its lowest 23 days later at Lift 3, possibly indicating the period when seedlings are most resistant to transplanting stresses. Multiple wrenching resulted in a slight shift in the dormancy cycle as wrenched seedlings set bud sooner in the nursery and broke bud sooner at the planting site in the spring than control seedlings. This implies that wrenched seedlings can be successfully lifted from the nursery earlier and will initiate spring shoot growth earlier than control seedlings.

Journal Article↗
PubMed1989

Use of sequential B-mode ultrasonography to manage abdominal aortic aneurysms.

The utility and safety of sequential B-mode ultrasonography to treat male patients with small (less than 6.0 cm in diameter) abdominal aortic aneurysms (AAAs) were studied retrospectively in 149 consecutive patients. Sixty-three of these patients have had operative repair of the AAA. Eight-six remain unoperated on. Mean growth rate was 0.79 cm/y (1.06 cm/y in the operated-on group and 0.36 cm/y in the unoperated-on group). Seven patients sustained rupture of the AAA during follow-up and 4 patients died as a consequence of elective repair, for a combined mortality rate of 7.4% (11/149). Only one AAA that was less than 5.0 cm ruptured. This has proved to be an effective way to manage AAAs in this population.

Aged↗
PubMed1987

Paradoxical effects of thought suppression.

In a first experiment, subjects verbalizing the stream of consciousness for a 5-min period were asked to try not to think of a white bear, but to ring a bell in case they did. As indicated both by mentions and by bell rings, they were unable to suppress the thought as instructed. On being asked after this suppression task to think about the white bear for a 5-min period, these subjects showed significantly more tokens of thought about the bear than did subjects who were asked to think about a white bear from the outset. These observations suggest that attempted thought suppression has paradoxical effects as a self-control strategy, perhaps even producing the very obsession or preoccupation that it is directed against. A second experiment replicated these findings and showed that subjects given a specific thought to use as a distracter during suppression were less likely to exhibit later preoccupation with the thought to be suppressed.

Adult↗