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At least 19 recordsLinked to original sources
PubMed2006

"Patient-time", "doctor-time", and "institution-time": perceptions and definitions of time among doctors who become patients.

OBJECTIVE: To examine views and experiences of conflicts concerning time in healthcare, from the perspective of physicians who have become patients. METHODS: We conducted two in-depth semi-structured 2-h interviews concerning experiences of being health care workers, and becoming a patient, with each of 50 doctors who had serious illnesses. RESULTS: These doctor-patients often came to realize as they had not before how patients experience time differently, and how "patient-time", "doctor-time", and "institution-time" exist and can conflict. Differences arose in both the long and short term, regarding historical time (prior eras/decades in medicine), prognosis (months/years), scheduling delays (days/weeks), daily medical events and tasks (hours), and periods in waiting rooms (minutes/hours). Definitions of periods of time (e.g., "fast", "slow", "plenty", and "soon") also varied widely, and could clash. Professional socialization had heretofore impeded awareness of these differences. Physicians tried to address these conflicts in several ways (e.g., trying to provide test results more promptly), though full resolution remained difficult. CONCLUSIONS: Doctors who became patients often now realized how physicians and patients differ in subjective experiences of time. Medical education and research have not adequately considered these issues, which can affect patient satisfaction, doctor-patient relationships and communication, and care. PRACTICE IMPLICATIONS: Physicians need to be more sensitive to how their definitions, perceptions, and experiences concerning time can differ from those of patients.

Adult↗
PubMed1975

Diastolic time intervals in ischemic and hypertensive heart disease: A comparison of isovolumic relaxation time and rapid filling time with systolic time intervals.

Isovolumic relaxation time (IVRT) and rapid filling time (RFT) were used to evaluate elasticity and compliance in 11 control subjects (Group 1), in nine patients with angina (Group 2), in 11 with hypertensive heasrt disease (Group 3), and in ten patients with healed myocardial infarction (Group 4). Pre-ejection period (PEP), pre-ejection period index (PEPI), left ventricular ejection time (LVET), left ventricular ejection time index(LVETI) and PEP/LVET ratio were all derived from simultaneous recordings of phonocardiograms, ECGs, apexcardiograms, and external carotid arterial pulses. No patients were in congestive heart failure and none were receiving medication. LVET and LVETI were the same in control patient groups; PEP was slightly increased in patients with healed myocardial infarctions (p smaller than 0.05); and PEPI was prolonged in the patients with angina (p = 0.001). THE PEP/LVET ratio too was different from the control group in patients with angina and hypertension (Groups 2 and 3-p smaller than 0.02 and smaller than 0.05 respectively). The diastolic time intervals were significantly altered in that the IVRT was prolonged in angina patients (113.4 equals or minus 28.3 msec), compared to control patients (85.7) equal or minus 18.4 msec). It was found that in 6 out of 9 patients with angina, this interval exceeded the highest normal value (108 msec), but that in only one out 11 patients with HCVD and in three out of ten with healed infarctions, was the interval prolonged. RFT was increased in HCVD (113.8 equals or minus 18.8 msec) and in healed myocardial infarction (123.8 equals or minus 30.0 msec) patients, compared to the control group (94.5 equals or minus 12.8 msec). Diastolic time intervals reflecting disorders in elasticity and compliance may occur in conjunction with alterations in systolic time intervals.

Adult↗
PubMed1998

[Prothrombin time and thromboplastin time. On-site measurement of the prothrombin time and activated partial thromboplastin time of surgical patients with laser photometry].

UNLABELLED: Turnaround time for analysis of prothrombin time (PT) and activated partial thromboplastin time (APTT) by standard laboratory methods ranges between 40 min and several hours. The delay in obtaining the test results limits their clinical utility for treatment of perioperative coagulation disorders and adequate anti-coagulation therapy. In this study, we compared on-site coagulation testing (OCT) of whole blood, which takes about 3 min, with standard laboratory plasma coagulation tests by our institutional laboratory (LAB) to assess the accuracy of the OCT in a clinical setting (abdominal and postcardiac surgery). METHODS: PT of 62 patients with abdominal surgery was measured intra- and postoperatively using both LAB (KC 40, Thromborel S, Centeon) and OCT (CoaguChek Plus, Boehringer Mannheim) systems. APTT was determined by LAB-(KC 40, Pathromtin, Centeon) and OCT-methods in 53 patients who underwent cardiac surgery requiring cardiopulmonary bypass. RESULTS: Linear regression demonstrated a strong and significant (p = 0.0001) correlation of OCT- and LAB-determinations both for PT (r = 0.92) and APTT (r = 0.91). For PT testing, bias analyses showed an agreement between OCT- and LAB-International Normalized Ratio (INR) (bias = 0.24; relative error = 14.6%) that was considered clinically acceptable, with 95% of the INR-differences lying between -0,26 and +0,74 (mean +/- 2 SD). Although commercial APTT-reagents usually differ in their sensitivity to heparin, we also found an acceptable agreement between OCT- and LAB-APTT values (bias = 6.7 s +/- 22 s; mean +/- 2 SD; relative error = 12%). CONCLUSION: On-site coagulation monitoring provides a rapid, convenient, and accurate assessment of coagulation that can both guide specific anti-coagulation therapy and optimize therapy control of coagulation disorders after cardiac and abdominal operations. As a consequence, OCT offers a valuable tool to reduce the inappropriate use of fresh frozen plasma and to improve cost-effectiveness.

Humans↗
PubMed2003

Intermanual difference in the Japanese Trail Making Test and its mirror version: intra-subject comparison of the task-completion time, cognitive time, and motor time.

PURPOSE: To investigate intermanual differences in the performance of the Japanese Trail Making Test (JTMT) using an intra-subject comparison, and to investigate how the cognitive and motor times spent in performing the task were related with the total completion time. METHODS: All subjects performed both parts A and B of the following three tasks: JTMT with the right hand (R); JTMT with the left hand (L); and a mirror version of the JTMT with the left hand (M). The order in which these three tasks were performed (RLM, RML, LRM, LMR, MRL, and MLR) was randomly determined. An interval of 4 weeks was scheduled between each examination. In addition to the completion time, we measured 'motor time', a sum of the times for drawing lines to connect the targets, and 'cognitive time', a time obtained by subtracting the motor time from the completion time. RESULTS: The task-completion time was more strongly correlated with the cognitive time than with the motor time. The order of the task performance did not influence the task-completion time. A learning effect was found only between the first and second examinations of part A. The cognitive time for the second and third performances of part A were significantly shorter than that for the first task, whereas the motor time remained unchanged. No intermanual differences in the performance were found in any comparisons. CONCLUSIONS: The non-dominant hand can be used as an alternative hand in the JTMT, and it can be expected to perform comparably to the dominant hand. These findings are consistent with the finding previously obtained by inter-subject comparison. The lack of any significant intermanual difference can be explained by that the total completion time is less influenced by the motor time than by the cognitive time.

Adult↗
PubMed1975

Genetics of susceptibility to plasmacytoma induction. I. BALB/cAnN (C), C57BL/6N (B6), C57BL/Ka (BK), (C times B6)F1, (C times BK)F1, and C times B recombinant-inbred strains.

Plasmacytomas were found in 58% of 373 BALB/cAnN (C) mice given three 0.5-ml doses of mineral oil (Bayol F or light mineral oil) or 2,6,10,14-tetramethylpentadecane (pristane) ip. The incidence of plasmacytomas in C57BL/6N (B6), C57BL/Ka (BK), (C times B6)F1 and (C times BK)F1 was 6.4, 0, 11.5, and 16.5%, respectively. The plasmacytomas occurred in old B6 mice, in contrast to their early appearance in strain C mice. The incidence of plasmacytomas in mineral oil-treated or pristane-treated C times B recombinant-inbred (Rl) strain mice was 28.3% in C times BD, 17.5% IN C times BE, 36.5% IN C times BG, 0% in C times BH, 2.9% in C times Bl, 48% in C times BJ, and 4.3% in C times BK. C times BD, C times BG, and C times BJ strains were considered susceptible to plascytoma induction by mineral oil or pristane; C times BE had a low susceptibility, and C times BH, C times Bl, and C times BK were resistant. The results suggested that there were only a few gene difference between C and B6 or BK that determined susceptibility or resistance to plasmacytoma induction, and that B6 and BK have at least one dominant resistance gene. The distribution pattern of susceptibility and resistance in the C times B Rl strains suggested the presence of a resistance gene on chromosome 9, linkage group II.

Age Factors↗
PubMed1999

Estimation of post-lead-time survival under dependence between lead-time and post-lead-time survival.

Early detection of cancer by screening advances the date of diagnosis, but may or may not alter time to death. Screening programme need to assess the true benefit of screening, that is, the length of time by which survival has been extended, beyond merely the time by which the diagnosis is advanced (lead-time). One method is to estimate the distribution of the time survived post-lead-time using total survival time data for screen-detected cancer cases, under the assumption of independence of the lead-time and the past-lead-time survival. However, it seems biologically reasonable that the lead-time and the post-lead-time survival are positively correlated. This paper investigates the consequences of departures from independence of lead-time and post-lead-time survival on estimation of post-lead-time survival. We introduce a new model that involves dependence between the lead-time and the post-lead-time survival. We show that the new model can be converted to the model discussed by Xu and Prorok. We consider the non-parametric maximum likelihood estimator of the post-lead-time survival under the new model. We apply the method to data from the HIP (Health Insurance Plan of Greater New York) breast cancer screening trial. We make comparisons with the survival of cancer cases not detected by screening, such as interval cases, cases among individuals who refused screening, and randomized control cases.

Breast Neoplasms↗
PubMed1989

[Nucleation time and growth time in patients with cholesterol gallstone--factors affecting nucleation time and growth time and effect of UDCA and CDCA].

Nucleation time (NT) and growth time (GT) were measured in gallbladder bile of patients with cholesterol gallstones. NT was significantly shortened (NT less than 10 days) in pure cholesterol stones but was moderately shortened (11 less than or equal to NT less than or equal to 21) in mixed and combination stones. GT also was accelerated (GT less than 7 days) in cholesterol stones. NT was shortened in increased biliary total protein, but on the contrary, was shortened in decreased apo A-I. NT of bile by UDCA therapy but not CDCA was extended. This suggests that increased apo A-I during UDCA therapy might imply extension of NT. The strong negative correlation between GT and CSI of bile suggests that CSI plays an important role in crystal growth.

Aged↗
PubMed2006

Part-time and full-time medical specialists, are there differences in allocation of time?

BACKGROUND: An increasing number of medical specialists prefer to work part-time. This development can be found worldwide. Problems to be faced in the realization of part-time work in medicine include the division of night and weekend shifts, as well as communication between physicians and continuity of care. People tend to think that physicians working part-time are less devoted to their work, implying that full-time physicians complete a greater number of tasks. The central question in this article is whether part-time medical specialists allocate their time differently to their tasks than full-time medical specialists. METHODS: A questionnaire was sent by mail to all internists (N = 817), surgeons (N = 693) and radiologists (N = 621) working in general hospitals in the Netherlands. Questions were asked about the actual situation, such as hours worked and night and weekend shifts. The response was 53% (n = 411) for internists, 52% (n = 359) for surgeons, and 36% (n = 213) for radiologists. Due to non-response on specific questions there were 367 internists, 316 surgeons, and 71 radiologists included in the analyses. Multilevel analyses were used to analyze the data. RESULTS: Part-time medical specialists do not spend proportionally more time on direct patient care. With respect to night and weekend shifts, part-time medical specialists account for proportionally more or an equal share of these shifts. The number of hours worked per FTE is higher for part-time than for full-time medical specialists, although this difference is only significant for surgeons. CONCLUSION: In general, part-time medical specialists do their share of the job. However, we focussed on input only. Besides input, output like the numbers of services provided deserves attention as well. The trend in medicine towards more part-time work has an important consequence: more medical specialists are needed to get the work done. Therefore, a greater number of medical specialists have to be trained. Part-time work is not only a female concern; there are also (international) trends for male medical specialists that show a decline in the number of hours worked. This indicates an overall change in attitudes towards the number of hours medical specialists should work.

Adult↗
PubMed2006

Time-measurement-regulating peptide PIN may alter a timer conformation of Time Interval Measuring Enzyme (TIME).

The TIME (Time Interval Measuring Enzyme) ATPase measures time intervals in accordance with diapause development, which indispensably requires cold for resumption of embryonic development in the silkworm (Bombyx mori). The PIN (Peptidyl Inhibitory Needle) peptide regulates the time measurement function of TIME. In the present study we investigated the interaction between TIME and PIN in order to address the mechanism of diapause development. When TIME was isolated from eggs later than 12 days after oviposition, transient bursts of ATPase activity occurred 18h after isolation of TIME, and the younger the eggs and pupal ovaries from which TIME was isolated, the earlier the bursts of ATPase activity appeared. However, no interval-timer activation of ATPase occurred in ovaries earlier than 6 days after pupation. Similar patterns of ATPase activity occurred in test tubes after mixing TIME with PIN. The shorter the time PIN was mixed with TIME, the earlier the ATPase activity appeared. The timer may be built into the protein conformation of TIME, and PIN (which is present in ovaries beginning 6 days after pupation) appears able to alter this timer conformation through pupal stages to laid eggs. We discuss the possible mechanism of diapause development in relation to the timer mechanism of TIME.

Adenosine Triphosphatases↗
PubMed1999

Relying solely on historical surgical times to estimate accurately future surgical times is unlikely to reduce the average length of time cases finish late.

STUDY OBJECTIVE: To determine whether using only previous cases' surgical times for predicting accurately surgical times of future cases is likely to reduce the average length of time cases finish late (after their scheduled finish times). DESIGN: Computer simulation. MEASUREMENTS AND MAIN RESULTS: Data from an operating room (OR) information system for two surgical suites were analyzed. For each case performed in fiscal year 1996, we searched backward for 1 year and counted the number of previous cases that were the same type of procedure performed by the same surgeon. Then, for each suite, surgical times were fitted to a statistical model estimating the effect of the type of procedure and who the surgeon was on surgical time. The estimated "variance components" were used in Monte-Carlo computer simulations to evaluate whether a hypothetical increase in the number of previous cases available to estimate the next case's surgical time would improve scheduling accuracy. Predictions of how long newly scheduled cases should take were impaired because 36.5% +/- 0.4% (mean +/- SE) of cases at a tertiary surgical suite and 28.6% +/- 0.7% of cases at an ambulatory surgery center did not have any cases in the previous year with the same procedure type and surgeon. Computer simulation was used to generate additional hypothetical cases. Using this data, even having many previous cases on which to base predictions of future surgical times would only decrease the average length of time that cases finish late by a few minutes. CONCLUSION: An OR manager considering using only historical surgical times to estimate future surgical times should first investigate, using data from their own surgical suite, what percentage of cases do not have historical data. Even if there are sufficient historical data to estimate future surgical times accurately, relying solely on historical times is probably an ineffective strategy to have future cases finish on time.

Ambulatory Surgical Procedures↗
PubMed2006

Theory of time-dependent reactive scattering: cumulative time-evolving differential cross sections and nearside-farside analyses of time-dependent scattering amplitudes for the H + D2 --> HD + D reaction.

Nearside-farside (NF) theory, originally developed in the energy domain for the time-independent description of molecular collisions and chemical reactions, is applied to the plane wave packet (PWP) formulation of time-dependent scattering. The NF theory decomposes the partial wave series representation for the time-dependent PWP scattering amplitude into two time-dependent subamplitudes: one N, the other F. In addition, NF local angular momentum (LAM) theory is applied to the PWP scattering amplitude. The novel concept of a cumulative time-evolving differential cross section is introduced, in which the upper infinite time limit of a half-Fourier transform is replaced by a finite time. In a similar way, a cumulative energy-evolving angular distribution is defined. Application is made to the state-to-state reaction, H + D2(v(i) = 0, j(i) = 0) --> HD(v(f) = 3, j(f) = 0) + D, where v(i), j(i) and v(f), j(f) are vibrational and rotational quantum numbers for the initial and final states, respectively. This reaction exhibits time-direct and time-delayed (by about 25 fs) collision mechanisms. It is shown that the direct-time mechanism is N dominant scattering, whereas the time-delayed mechanism exhibits characteristics of NF interference. The NF and LAM theories provide valuable insights into the time-dependent properties of a reaction, as do snapshots from a movie of the cumulative time-evolving differential cross section.

Journal Article↗
PubMed1986

"Haemostasis time", a modified bleeding time test and its comparison with the Duke and Ivy/template bleeding times. I. Normal values, application in thrombocytopenic patients and evaluation of heparin and aspirin effects.

The occlusion time ("haemostasis time" - HT) of a thin, short cannula inserted into the cubital vein, was compared with the skin bleeding times of the Duke and Ivy/template techniques. 25 male and 25 female volunteers without a history of bleeding were divided into 5 equally large age groups ranging from 10 to over 50 years of age. They exhibited a range of 46 s-6 min 38 s (95% tolerance interval), while the Duke and Ivy/template bleeding times, which were simultaneously determined, corresponded to values given by other authors. HT is different from the skin bleeding times in that endothelium is replaced by a standard foreign surface which allows better standardization of the method. Similar results were obtained with HT compared to the skin bleeding times. These and a similar, non-significant heparin response with all three techniques suggest that HT is not more influenced by clotting factors than the Duke and Ivy/template bleeding times and, indeed, may be regarded as a bleeding time modification. HT, like both of the skin bleeding times, reflected lowered platelet counts and is even more sensitive in this respect. As tested in a group of 20 male and 20 female volunteers, HT showed a significant prolongation two hours after ingestion of 1 g aspirin. While male individuals exhibited longer bleeding times than females with the Ivy/template technique (sex-related difference p = 0.01), no male to female differences were found both with HT and the Duke bleeding time. HT is easy to perform, inexpensive, leaves no scars and is safe even for the patient with severe bleeding. Moreover, compared to the skin bleeding times, it permits a differential evaluation of vessel wall and tissue effects.

Adolescent↗
PubMed2006

Sudden Infant Death Syndrome and the time of death: factors associated with night-time and day-time deaths.

OBJECTIVE: To investigate the diurnal occurrence of Sudden Infant Death Syndrome (SIDS) and interaction with established risk factors in the infant sleeping environment. METHODS: A 3 year population-based case-control study, in five English Health Regions. Parentally defined day-time or night-time deaths of 325 SIDS infants and reference sleep of 1300 age-matched controls. RESULTS: The majority of SIDS deaths (83%) occurred during night-time sleep, although this was often after midnight and at least four SIDS deaths occurred during every hour of the day. The length of time from last observed alive until the discovery of death ranged from <l to 14 h but was not significantly different from the corresponding sleep period amongst the controls. Amongst the day-time deaths, 38% of the infants were observed alive 30 min prior to discovery and 9% within 10 min. The risk of placing infants asleep on their side was more marked for day-time deaths (interaction: P = 0.0001) nearly half of whom were found prone, while the risk associated with paternal smoking [OR = 3.25 (95%CI: 1.88-5.62)] was more marked for night-time deaths (interaction: P = 0.02). The adverse effect of unsupervised sleep recognized for night-time practice [OR = 5.38 (95%CI: 2.67-10.85)] was also significant for day-time sleep [OR = 10.57 (95%CI: 1.47-75.96)]. Significantly more (P = 0.002) unobserved SIDS infants (24.8%) were found with bedclothes over the head compared with those SIDS infants where a parent was present in the room (11.3%). CONCLUSIONS: SIDS can happen at any time of the day and relatively quickly. Parents need to be made aware that placing infants supine and keeping them under supervision is equally important for day-time sleeps.

Age Factors↗
PubMed1992

On the relation between time perception and the timing of motor action: evidence for a temporal oscillator controlling the timing of movement.

Studies of time estimation have provided evidence that human time perception is determined by an internal clock containing a temporal oscillator and have also provided estimates of the frequency of this oscillator (Treisman, Faulkner, Naish, & Brogan, 1990; Treisman & Brogan, 1992). These estimates were based on the observation that when the intervals to be estimated are accompanied by auditory clicks that recur at certain critical rates, perturbations in time estimation occur. To test the hypothesis that the mechanisms that underlie the perception of time and those that control the timing of motor performance are similar, analogous experiments were performed on motor timing, with the object of seeing whether evidence for a clock would be obtained and if so whether its properties resemble those of the time perception clock. The prediction was made that perturbations in motor timing would be seen at the same or similar critical auditory click rates. The experiments examined choice reaction time and typing. The results support the hypothesis that a temporal oscillator paces motor performance and that this oscillator is similar to the oscillator underlying time perception. They also provide an estimate of the characteristic frequency of the oscillator.

Adult↗
PubMedDate not supplied

The "opening time" and "pelvic floor electromyographic lag time": two novel tools in the assessment of the anorectal evacuation time.

Rectal evacuation necessitates rectal contraction and pelvic floor muscles relaxation; it is not known which action precedes the other. We investigated the hypothesis that pelvic floor muscles relaxation precedes rectal contraction so that rectal contents find the anal canal already opened. Electromyographic activity of the external anal sphincter as well as anal and rectal pressures were recorded during rectal balloon distension and evacuation. Pelvic floor muscles electromyographic lag time (time from start of pelvic floor muscles relaxation to start of evacuation) and opening time (time from start of rectal contraction to start of evacuation) were measured. Rectal balloon distension in increments of 20 mL up to 100 mL effected progressive increase of both external anal sphincter electromyography and anal pressure. At 120 mL balloon distension up to 180 mL, external anal sphincter electromyography and anal pressure exhibited gradual decrease whereas rectal pressure showed no changes. At 200 to 220 mL rectal balloon distension, rectal pressure increased and anal pressure decreased, while external anal sphincter showed no electromyographic activity; rectal balloon was expelled. The opening time recorded a mean of 1.8 +/- 0.7 s and pelvic floor muscles electromyographic lag time of 2.2 +/- 0.9; the two recordings showed no significant difference (p > .05). These, two diagnostic tools in anorectal investigations are presented: the opening time and pelvic floor muscles electromyographic lag time. Pelvic floor muscles relaxation preceded rectal contraction. As there is no significant difference between opening time and pelvic floor muscles electromyographic lag time, it appears easier to apply the latter as it is simple, objective, and noninvasive.

Adult↗
PubMed2006

Optical absorption coefficient, time of thermal relaxation, time of surface threshold, and time of heat incubation for PMMA samples at the CO2 laser-beam wavelength of 10.6 microm.

OBJECTIVE: This paper discusses in detail the mathematical identification of the optical absorption alpha (cm(1)) of Beer's law, a crucial parameter to study the development of laser beam craters into dry poly(methyl methacrylate) (PMMA) samples exposed to steady CO(2) laser beams emitting radiation at lambda = 10.6 microm in continuous- wave (CW) mode. Three additional time-dependent coefficients have been determined as well. In clinical applications, these results are important in order to precisely quantify and forecast the ablation capabilities of the CO(2) laser beam, to optimize its usage in the operating room, and to address the safety issues related to surgical interventions on human tissue. BACKGROUND DATA: Currently, the data available in the literature do not allow the identification of the numerical value of alpha (cm(1)) for PMMA at lambda = 10.6 microm with enough, and therefore satisfactory, accuracy. Additionally, the correct identification of the optical absorption of PMMA would allow the isolation, with better accuracy, of other key time-dependent coefficients, such as relaxation time, surface threshold time, and heat incubation time, which are all described in the literature in a qualitative rather than quantitative fashion. Correct bone cement preparation depends on the value of alpha (cm(1)) of the PMMA in order to avoid unwanted complications in patients during cement removal via laser techniques. METHODS: The laser in use was configured in different combinations with the following parameters: transverse electromagnetic modes (TEMnm), output power (I0), exposure times (te), and focal lengths (fk). Several PMMA blocks (1 cm x 4 cm x 4 cm) were exposed to CW radiation of three commercially available CO(2) medical laser devices showing a TEM11 mode. Each block was exposed to the beam on a horizontal and well-polished surface of each sample. Four focal lengths (2.5", 5", 7.5", and 15.75" [400 mm]) were used to focus the beam on the well-polished and dry surface of the PMMA samples. The resulting dimensions of the craters were measured after each exposure, which has been kept at a 10-Watt CW beam. Exposure time ranged from 0.5 to 2 sec. RESULTS: The value of alpha = 502 (cm(1)) for PMMAat 10.6 microm was identified, matching other results reported in the literature for similar compact media in the absence of water content, such as PMMA. The time of thermal relaxation was 9.358 x 10(4) sec, the time of surface threshold was 9.365 x 10(4) sec, and the time of heat incubation was 3.6 x 10(7) sec (all three for PMMAat 10.6 microm for any exposure). Using the calculated value of alpha, one of the practical clinical recommendations would be, for instance, to reduce or to abolish the utilization of colorant dopants in the preparation of the bone cement mixture and therefore reduce the danger of bone damage possible during the removal of bone cement via laser techniques. Other examples refer to other clinical bone and dental treatments.

Bone Cements↗
PubMed2005

Population structure attributable to reproductive time: isolation by time and adaptation by time.

Many populations are composed of a mixture of individuals that reproduce at different times, and these times are often heritable. Under these conditions, gene flow should be limited between early and late reproducers, even within populations having a unimodal temporal distribution of reproductive activity. This temporal restriction on gene flow might be called "isolation by time" (IBT) to acknowledge its analogy with isolation by distance (IBD). IBD and IBT are not exactly equivalent, however, owing to differences between dispersal in space and dispersal in time. We review empirical studies of natural populations that provide evidence for IBT based on heritabilities of reproductive time and on molecular genetic differences associated with reproductive time. When IBT is present, variation in selection through the reproductive season may lead to adaptive temporal variation in phenotypic traits [adaptation by time (ABT)]. We introduce a novel theoretical model that shows how ABT increases as (i) selection on the trait increases; (ii) environmental influences on reproductive time decrease; (iii) the heritability of reproductive time increases; and (iv) the temporal distribution of reproductive activity becomes increasingly uniform. We then review empirical studies of natural populations that provide evidence for ABT by documenting adaptive temporal clines in phenotypic traits. The best evidence for IBT and ABT currently comes from salmonid fishes and flowering plants, but we expect that future work will show these processes are more widespread.

Adaptation, Physiological↗
PubMed2006

Parental education, time in paid work and time with children: an Australian time-diary analysis.

How does parental education affect time in the paid workforce and time with children? Potentially, the effects are contradictory. An economic perspective suggests higher education means a pull to the market. Human capital theory predicts that, because higher education improves earning capacity, educated women face higher opportunity costs if they forego wages, so will allocate more time to market work and less to unpaid domestic labour. But education may also exercise a pull to the home. Attitudes to child rearing are subject to strong social norms, and parents with higher levels of education may be particularly receptive to the current social ideal of attentive, sustained and intensive nurturing. Using data from the Australian Bureau of Statistics Time-use Survey 1997, this study offers a snapshot of how these contradictory pulls play out in daily life. It finds that in Australia, households with university-educated parents spend more daily time with children than other households in physical care and in developmental activities. Sex inequality in care time persists, but fathers with university education do contribute more time to care of children, including time alone with them, than other fathers. Mothers with university education allocate more daily time than other mothers to both childcare and to paid work.

Adult↗