Time-limited Conditions Research Articles

Virtual Patients for assessment of medical student ability to integrate clinical and laboratory data to develop differential diagnoses: Comparison of results of exams with/without time constraints

Introduction: We have evaluated medical student ability in a problem-based learning course using a Virtual Patient (VP)-based exam with variable parameters for assessment purposes.Methods: A class of 155 second year medical students was assessed using a VP exam with unlimited access during a 1-week period; 2 years later, the identical exam was administered to 175 students with a 3-h time limit.Results: Students taking the exam without time constraints utilized approximately twice as much time than students with the time limit. Without the pressure of a time-limit, students utilized half as many inquiries of the patient history, physical, and lab/imaging tests than were used by students having a time constraint, indicating that the time limited students used a “shotgun approach” to try to collect as many “required” inquiries as possible. Most students (91%) taking the untimed exam were able to correctly diagnose the exam case but only 31% of the time limited students correctly diagnosed the VP exam case, despite their higher number of inquiries.Conclusions: Our results demonstrate that an identical VP exam, administered with variables to compare untimed versus time-limited conditions, resulted in an unraveling of student's ability to integrate the data discovered during the process of progressive disclosure.

Is depression a chronic mental illness?

Over the past few decades, theory and research on depression have increasingly focused on the recurrent and chronic nature of the disorder. These recurrent and chronic forms of depression are extremely important to study, as they may account for the bulk of the burden associated with the disorder. Paradoxically, however, research focusing on depression as a recurrent condition has generally failed to reveal any useful early indicators of risk for recurrence. We suggest that this present impasse is due to the lack of recognition that depression can also be an acute, time-limited condition. We argue that individuals with acute, single lifetime episodes of depression have been systematically eclipsed from the research agenda, thereby effectively preventing the discovery of factors that may predict who, after experiencing a first lifetime episode of depression, goes on to have a recurrent or chronic clinical course. Greater awareness of the high prevalence of people with a single lifetime episode of depression, and the development of research designs that identify these individuals and allow comparisons with those who have recurrent forms of the disorder, could yield substantial gains in understanding the lifetime pathology of this devastating mental illness.

Recurrence in major depression: A conceptual analysis.

Theory and research on major depression have increasingly assumed a recurrent and chronic disease model. Yet not all people who become depressed suffer recurrences, suggesting that depression is also an acute, time-limited condition. However, few if any risk indicators are available to forecast which of the initially depressed will or will not recur. This prognostic impasse may be a result of problems in conceptualizing the nature of recurrence in depression. In the current paper we first provide a conceptual analysis of the assumptions and theoretical systems that presently structure thinking on recurrence. This analysis reveals key concerns that have distorted views about the long-term course of depression. Second, as a consequence of these theoretical problems we suggest that investigative attention has been biased toward recurrent forms of depression and away from acute, time-limited conditions. Third, an analysis of how these theoretical problems have influenced research practices reveals that an essential comparison group has been omitted from research on recurrence: people with a single lifetime episode of depression. We suggest that this startling omission may explain why so few predictors of recurrence have as yet been found. Finally, we examine the reasons for this oversight, document the validity of depression as an acute, time-limited disorder, and provide suggestions for future research with the goal of discovering early risk indicators for recurrent depression.

Age differences in forgiveness: The role of future time perspective.

This study investigated whether the age trend in forgiveness is partly attributable to age differences in time perspective. Eighty-nine younger and 91 older adults were randomized into 3 experimental conditions: time-expanded, time-limited, and neutral. They responded to hypothetical offensive scenarios and rated the degree to which they would forgive the perpetrator. Results showed that older adults were more forgiving than younger adults, but regardless of age, those in the time-limited condition were more forgiving than those in the time-expanded or the neutral condition. An Age x Time perspective interaction showed that only in older adults did a time-expanded manipulation lead to lower forgiveness than the neutral condition.

Specificity of human cathepsin S determined by processing of peptide substrates and MHC class II-associated invariant chain

Cathepsin S (CatS) is a lysosomal cysteine protease of the papain family, the members of which possess relatively broad substrate specificities. It has distinct roles in major histocompatibility complex (MHC) class II-associated peptide loading and in antigen processing in both the MHC class I and class II pathways. It may therefore represent a target for interference with antigen presentation, which could be of value in the therapy of (auto)immune diseases. To obtain more detailed information on the specificity of CatS, we mapped its cleavage site preferences at subsites S3-S1' by in vitro processing of a peptide library. Only five amino acid residues at the substrate's P2 position allowed for cleavage by CatS under time-limited conditions. Preferences for groups of amino acid residues were also observed at positions P3, P1 and P1'. Based on these results, we developed highly CatS-sensitive peptides. After processing of MHC class II-associated invariant chain (Ii), a natural protein substrate of CatS, we identified CatS cleavage sites in Ii of which a majority matched the amino acid residue preference data obtained with peptides. These observed cleavage sites in Ii might be of relevance for its in vivo processing by CatS.

Types of morbidity and categories of patients in a Swedish countyApplying the Johns Hopkins adjusted clinical groups system to encounter data in primary health care

Objective – To elucidate types of morbidity and categories of patients in a large population. Design – A one-year retrospective study of encounter data from electronic patient record databases in primary health care, with application of the Johns Hopkins Adjusted Clinical Groups System. Setting – Blekinge County Council, southeastern Sweden, with 149 552 inhabitants. Subjects – All patients with a diagnosis-registered encounter with a GP in 2002 at 13 publicly managed PHC centres. Main outcome measures – Anonymous identification number, age, gender, type of morbidity (Aggregated Diagnostic Groups), and category of patient (Adjusted Clinical Groups). Results – About 45% of the county's inhabitants had at least one diagnosis-registered encounter with a GP during the year. The most common types of morbidity were “time limited” (24.0% of all types), “likely to recur” (19.6%), and “signs/symptoms” (19.0%). About 33.3% of all patients had one and only one time-limited condition, about 16.8% had one and only one recurring condition, and about 12.1% of the patients had only a chronic condition. Conclusion – Types of morbidity in primary health care are dominated by nearly equal proportions of “time limited”, “likely to recur”, “chronic”, and “signs/symptoms”. The predominant categories of patients are those with only one type of morbidity, while about one-third of the patients had a constellation of two or more types of morbidity during a one-year period.

Procrastination as self‐regulation failure of performance: effects of cognitive load, self‐awareness, and time limits on ‘working best under pressure’

Effects of cognitive load, objective self‐awareness and time limits on the self‐regulation of performance speed and accuracy were investigated between procrastinators and non‐procrastinators. In experiment 1 chronic procrastinators completed fewer items (slow speed) and made more errors (less accuracy) than non‐procrastinators under high but not low cognitive load conditions when the time span was limited and brief. In experiment 2 chronic procrastinators performed slower than non‐procrastinators under a 2 second, but not under no limit, 1 second, or 4 second time limit conditions. Chronic procrastinators compared to non‐procrastinators also performed more slowly and made more performance errors under objective self‐awareness conditions regardless of the length of time. These experiments indicate that chronic procrastinators regulate ineffectively their performance speed and accuracy when they ‘work under pressure’ (defined by high cognitive load, objective self‐awareness, and imposed time limitations). Copyright © 2001 John Wiley & Sons, Ltd.

Procrastination as self-regulation failure of performance: effects of cognitive load, self-awareness, and time limits on ‘working best under pressure’

Effects of cognitive load, objective self‐awareness and time limits on the self‐regulation of performance speed and accuracy were investigated between procrastinators and non‐procrastinators. In experiment 1 chronic procrastinators completed fewer items (slow speed) and made more errors (less accuracy) than non‐procrastinators under high but not low cognitive load conditions when the time span was limited and brief. In experiment 2 chronic procrastinators performed slower than non‐procrastinators under a 2 second, but not under no limit, 1 second, or 4 second time limit conditions. Chronic procrastinators compared to non‐procrastinators also performed more slowly and made more performance errors under objective self‐awareness conditions regardless of the length of time. These experiments indicate that chronic procrastinators regulate ineffectively their performance speed and accuracy when they ‘work under pressure’ (defined by high cognitive load, objective self‐awareness, and imposed time limitations). Copyright © 2001 John Wiley & Sons, Ltd.

DESIGN AND CONTROL SENSITIVITY ANALYSIS OF MULTIPLE HYPERELASTIC BODY SYSTEMS

A statement of Hamilton's principle for a multiple-body system in the finite theory of elasticity is presented. Surface interaction, among the bodies and with the ground, is materialized by kinematic boundary condition, holonomic constraints, a potential and a dissipation function. As additional data, there are body forces and tractions, and three kinds of time limit conditions. The design and control of the system is defined by a parametric representation of data. Material properties, time interval of analysis and control discontinuities are considered. An incremental form of Hamilton's principle is presented, in connection with a perturbation of the data. The virtual work of stress, global and incremental, is represented by differential operators and transformation laws for these operators, under rigid-body motions, are derived. Sensitivity analysis results by the adjoint method for a mechanical system with small strains overlying large rigid-body motions are presented.

The Diagnostic Meaning of 'Nervous Breakdown' Among Lay Populations

Two studies investigated the nature of nervous breakdown (NB): a mental illness commonly referred to by individuals not professionally related to the field of mental health. The clinical profile of NB was first surveyed among 121 undergraduates using a symptom checklist. Descriptive statistics and analysis of variance indicated NB is a time-limited condition that presents with primarily anxious and depressed features, associated with a series of external precipitating stressors (e.g., interpersonal, employment, and financial losses). Dimensions significantly uncharacteristic of NB included psychoticism, somatization, phobic anxiety, and mania. These results were replicated in a community sample of 189 adults from urban and suburban areas of a large metropolitan city. Respondents held a relatively unitary view of NB: Combined-sample cluster analysis (N = 310) revealed 2 groups with similar symptom profiles that differed primarily with regard to level of distress associated with disorder. Thus, among this population, NB is not an amorphous term for generalized psychiatric disturbance.

INTERDEPENDENT EXITING: THE EFFECTS OF GROUP SIZE, TIME LIMIT, AND GENDER ON THE COORDINATION OF EXITING

Two experiments were performed on interdependent exiting using a new paradigm, choices made to exit or wait on discrete rounds. The smaller the group size, the larger the proportion of group members exiting, regardless of whether the exit space was held constant and the number of rounds was proportional to group size or the number of rounds was held constant and the exit space was proportional to group size. A larger proportion exited in the long time limit conditions rather than the short. There was no main effect due to gender, but a complex triple interaction involving gender, group size, and time limit was obtained. In general, the results were consistent with the theoretical model of Kelley et al. (1965). The relevance of this research to the areas of tacit coordination and queue models of traffic flow was discussed.

Interaction of endothelin-1 with cloned bovine ETA receptors: biochemical parameters and functional consequences.

This paper defines the properties of interaction of endothelin-1 (Et-1) with cloned bovine ETA receptors. The Kd value of Et-1/ETA receptor complexes was estimated in membrane preparations to 20 pM using kinetic experiments and saturation experiments performed under quasi equilibrium conditions. Competition experiments yield a wide range of apparent Kd(Et-1) values from 20 pM to 1 nM which were in fact measures of the receptor concentrations rather than of Kd values. This resulted from the fact that complex second-order rate kinetics rather than pseudo-first-order kinetics control the association of Et-1 to its receptor when the receptor concentration is larger than Kd(Et-1). Et-1 induced a production of inositol phosphates with an apparent affinity of 2.3 nM, 100 times higher than the Kd(Et-1) value determined previously. Numerical simulation suggested that under time-limited conditions, sub-nanomolar rather than picomolar concentrations of Et-1 are necessary to occupy an important fraction of picomolar sites. It is concluded that bovine ETA receptors have a single affinity state for Et-1 (Kd = 20 pM) and that this affinity state can account for nanomolar actions of Et-1 in intact cells. It is suggested that the sensitivity of a preparation to Et-1 is a cell property rather than a receptor property. It is also suggested that the main advantage of high-affinity Et-1 binding is to promote autocrine actions rather than a high potency of the peptide.

Effects of Explicit Time-Limits on the Initial Therapeutic Alliance

This study investigated the hypothesis that the setting of explicit time-limits in individual counseling enhances the formation of the therapeutic alliance. Students at a university-based counseling center were randomly assigned to a 5-session, time-limited therapy condition (n = 16) or a time-unlimited therapy condition (n = 15). Contrary to the hypothesis, statistical analyses showed no differences between audiotaped segments from the second and third therapy sessions rated on the Vanderbilt Therapeutic Alliance Scale.

Some general theorems and generalized and piecewise generalized variational principles for linear elastodynamics

From the concept of four-dimensional space and under the four kinds of time limit conditions, some general theorems for elastodynamics are developed, such as the principle of possible work action, the virtual displacement principle, the virtual stress-momentum principle, the reciprocal theorems and the related theorems of time terminal conditions derived from it. The variational principles of potential energy action and complementary energy action, the H-W principles, the H-R principles and the constitutive variational principles for elastodynamics are obtained. Hamilton's principle, Toupin's work and the formulations of Ref. [5],[17]–[24] may be regarded as some special cases of the general principles given in the paper. By considering three cases: piecewise space-time domain, piecewise space domain, piecewise time domain, the piecewise variational principles including the potential, the complementary and the mixed energy action fashions are given. Finally, the general formulation of piecewise variational principles is derived. If the time dimension is not considered, the formulations obtained in the paper will become the corresponding ones for elastostatics.

Anxiety and the inclusiveness of information processing

This study examined the extent to which anxious and nonanxious persons differed in their inclusiveness of information processing, and identified cognitive mediational processes responsible for these differences. One hundred thirteen anxious and nonanxious subjects solved geometric analogies under time-limited conditions. Subjects committed inclusion errors (i.e., included extraneous information in the problem solution) or exclusion errors (i.e., omitted relevant information from the problem solution). Anxious persons made more inclusion errors than did nonanxious persons ( p < .002), more exclusion errors than did nonanxious persons with few-transformation analogies ( p < .02), and more inclusion than exclusion errors with many-transformation analogies ( p < .05). These results are not attributable to a decrease in the range of cue utilization, but are rather attributed to anxious persons' slow rate of information processing caused by a decreased allocation of attentional resources and/or a reduction of working memory capacity, which promotes the adoption of a partial information search strategy.

Age-related effects of temporal contingencies on response speed and memory: an operant analysis.

Single-subject methods were used to study influences of extended training and temporal contingencies. Five younger (18 to 21 years) and five older (65 to 74 years) healthy men responded to a series of matching-to-sample discriminations with sample-choice intervals of 0, 5, 10, and 15 s. During baseline sessions, there was no time limit placed on the response to the choice stimuli. Subsequently, correct responses were reinforced only if they occurred within a specified limit. Men of both ages responded faster to the choice stimuli as increasingly stringent limits were imposed, and speeds exceeded those under the baseline condition when the men had been instructed to be accurate and prompt. When the limits subsequently were removed, response speeds decreased somewhat but still were above earlier baseline performances. Under both baseline and time limit conditions, responding was slower when the choice stimuli were delayed, indicating that the procedure tapped short-term memory processes as well as psychomotor speed. Responding also was slower when the stimulus pool involved eight rather than two stimuli. Although performances of the older men improved substantially during the course of training, the younger men improved to the same extent so that age differences were not appreciably reduced.