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PubMed2002

Dynamic instabilities induced by asymmetric influence: prisoners' dilemma game in small-world networks.

A two-dimensional small-world-type network, subject to spatial prisoners' dilemma dynamics and containing an influential node defined as a special node, with a finite density of directed random links to the other nodes in the network, is numerically investigated. It is shown that the degree of cooperation does not remain at a steady state level but displays a punctuated equilibrium-type behavior manifested by the existence of sudden breakdowns of cooperation. The breakdown of cooperation is linked to an imitation of a successful selfish strategy of the influential node. It is also found that while the breakdown of cooperation occurs suddenly, its recovery requires longer time. This recovery time may, depending on the degree of steady state cooperation, either increase or decrease with an increasing number of long-range connections.

Behavior↗
PubMed2003

Betweenness centrality correlation in social networks.

Scale-free (SF) networks exhibiting a power-law degree distribution can be grouped into the assortative, dissortative, and neutral networks according to the behavior of the degree-degree correlation coefficient. Here we investigate the betweenness centrality (BC) correlation for each type of SF networks. While the BC-BC correlation coefficients behave similarly to the degree-degree correlation coefficients for the dissortative and neutral networks, the BC correlation is nontrivial for the assortative ones found mainly in social networks. The mean BC of neighbors of a vertex with BC g(i) is almost independent of g(i), implying that each person is surrounded by almost the same influential environments of people no matter how influential the person may be.

Journal Article↗
PubMed2004

Population pharmacokinetics of raltitrexed in patients with advanced solid tumours.

AIMS: To investigate the population pharmacokinetics of raltitrexed in patients with advanced solid tumours and to identify patient covariates contributing to the interpatient variability in the pharmacokinetics of raltitrexed. METHODS: Patient covariate and concentration-time data were collected from patients receiving 0.1-4.5 mg m(-2) raltitrexed during the early clinical trials of raltitrexed. Data were fitted using nonlinear mixed effects modelling to generate population mean estimates for clearance (CL) and central volume of distribution (V). The relationship between individual estimates of the pharmacokinetic parameters and patient covariates was examined and the influence of significant covariates on the population parameter estimates and their variance was investigated using stepwise multiple linear regression. The performance of the developed model was tested using an independent validation dataset. All patient data were pooled in the total cohort to refine the population pharmacokinetic model for raltitrexed. RESULTS: three-compartment pharmacokinetic model was used to fit the concentration-time data of raltitrexed. Estimated creatinine clearance (CL(CR)) was found to influence significantly the CL of raltitrexed and explained 35% of variability in this parameter, whilst body weight (WT) and serum albumin concentrations (ALB) accounted for 56% of the variability in V. Satisfactory prediction (mean prediction error 0.17 micro g l(-1) and root mean square prediction error 4.99 micro g l(-1)) of the observed raltitrexed concentrations was obtained in the model validation step. The final population mean estimates were 2.17 l h(-1)[95% confidence interval (CI) 2.06, 2.28] and 6.36 l (95% CI 6.02, 6.70) for CL and V, respectively. Interpatient variability in the pharmacokinetic parameters was reduced (CL 28%, V 25%) when influential covariates were included in the final model. The following covariate relationships with raltitrexed parameters were described by the final population model: CL (l h(-1)) = 0.54 + 0.02 CL(CR) (ml min(-1)) and V (l) = 6.64 + 0.08 WT (kg) - 0.16 ALB (g l(-1)). CONCLUSIONS: A population pharmacokinetic model has been developed for raltitrexed in patients with advanced cancer. Pharmacokinetic parameters of raltitrexed are markedly influenced by the patient's renal function, body weight and serum albumin levels, which may be taken into account in dose individualization. The use of influential covariates to guide anticancer dosage selection may result in less variability in drug exposure and potentially a better clinical outcome.

Adult↗
PubMed2004

Sources of glucose variability in insulin-treated type 2 diabetes: the Diabetes Outcomes in Veterans Study (DOVES).

OBJECTIVE: Glucose variability can be a significant barrier to glycaemic control for diabetic patients on insulin. The study identified clinical and behavioural factors associated with glucose variability in type 2 diabetes. DESIGN: Observational study. SUBJECTS: Randomly selected veterans with stable, insulin-treated type 2 diabetes. MEASUREMENTS: Baseline data included demographics, clinical characteristics, diet, activity and haemoglobin A1c. Subjects self-monitored blood glucose before all meals and at bedtime for 8 weeks. Monitoring data were used to derive an overall glucose mean and glucose coefficient of variation (100*SD/mean) for each subject. Univariate and multivariate analyses were used to evaluate the relationship between glucose coefficient of variation and clinical factors. RESULTS: Two-hundred and four subjects completed the protocol. The 8-week mean (+/- SD) glucose was 9.9 +/- 2.2 mmol/l, and the average overall coefficient of variation was 35.6 +/- 7.7%. Univariate analysis showed a higher variation in older subjects and in those with longer duration of insulin treatment, greater consumption of sugars and greater confidence in their self-care abilities. Variation was lower in subjects who were obese, more compliant with medications and receiving larger insulin doses. Multivariate analysis showed that treatment duration, sugar consumption, medication compliance and insulin dose were independently associated with glucose variation. Medication compliance was more influential for fasting variation, while body mass index was more influential for before lunch variation. CONCLUSIONS: Numerous behavioural, clinical and treatment factors were independently associated with glucose variability. Reducing sugar consumption and improving medication compliance might offset the greater glucose fluctuation observed in lean patients with longstanding diabetes.

Age Factors↗
PubMed2004

Experiences of infant-feeding decision-making among urban economically disadvantaged pregnant adolescents.

AIM: The aim of this paper is to report a pilot study of influencing factors in disadvantaged urban pregnant adolescents' decision-making about infant-feeding choices. BACKGROUND: Research related to decision-making among adolescents indicates that attitudinal, social, perceived control, and commitment factors are influential in choosing and initiating breast- or bottle-feeding. However, there is a need for further description of decision-making processes in disadvantaged teenagers before intervention research is done. METHODS: Focus group interviews with the Theory of Planned Behavior guiding the questioning were used with 14 pregnant adolescents between 18 and 39 weeks of gestation and between the ages of 14 and 18 in two obstetric clinics in Midwestern USA urban teaching hospitals. The majority of adolescents were African-American and primiparae. FINDINGS: The experiences of infant-feeding decision-making among pregnant adolescents were captured by two major themes: benefits vs. barriers of breastfeeding and bottle-feeding, and independent choice vs. social influences. A common thread in these themes was ambivalence and uncertainty. The adolescents had both positive and negative attitudes toward methods, with many expressing their desire to combine breast- and bottle-feeding. Many reported the health benefits of breastfeeding, yet identified barriers of pain, public exposure, and the complexity of breastfeeding. They viewed bottle-feeding as automatic and simple, allowing freedom to leave the infant with others. Although adolescents were adamant that choice of feeding method was their independent decision, social and family influences were evident. CONCLUSIONS: Consistent with the Theory of Planned Behaviour and other research, attitudes, perceived social influences, and perceived control factors were influential to adolescents when choosing infant feeding methods. The findings suggest that adolescents need education on decision-making, and are being used to fine-tune the interventions of a randomized clinical trial to investigate promoting and supporting breastfeeding among adolescent mothers.

Adolescent↗
PubMed2007

Enhancement of acid amylase production by an isolated Aspergillus awamori.

AIMS: Evaluation of the influence of fermentation components on extracellular acid amylase production by an isolated fungal strain Aspergillus awamori. METHODS AND RESULTS: Eight fungal metabolic influential factors, viz. soluble starch, corn steep liquor (CSL), casein, potassium dihydrogen phosphate (KH(2)PO(4)) and magnesium sulfate (MgSO(4) x 7H(2)O), pH, temperature and inoculum level were selected to optimize amylase production by A. awamori using fractional factorial design of Taguchi methodology. Significant improvement in acid amylase enzyme production (48%) was achieved. The optimized medium composition consisted of soluble starch--3%; CSL--0.5%; KH(2)PO(4)--0.125%; MgSO(4) x 7H(2)O--0.125%; casein--1.5% at pH 4.0 and temperature at 31 degrees C. CONCLUSION: Optimization of the components of the fermentation medium was carried out using fractional factorial design of Taguchi's L-18 orthogonal array. Based on the influence of interaction components of fermentation, these could be classified as the least significant and the most significant at individual and interaction levels. Least significant factors of individual level have higher interaction severity index and vice versa at enzyme production in this fungal strain. The pH of the medium and substrate (soluble starch) showed maximum production impact (60%) at optimized environment. Temperature and CSL were the least influential factors for acid amylase production. SIGNIFICANCE AND IMPACT OF THE STUDY: Acid amylase production by isolated A. awamori is influenced by the interaction of fermentation factors with fungal metabolism at individual and interaction levels. The pH of the fermentation medium and substrate concentration regulates maximum enzyme production process in this fungal strain.

Amylases↗
PubMed2005

Physician counselling practices and decision-making for extremely preterm infants in the Pacific Rim.

OBJECTIVES: This study was undertaken to evaluate physician counselling practices and resuscitation decisions for extremely preterm infants in countries of the Pacific Rim. We sought to determine the degree to which physician beliefs, parents' opinion and medical resources influence decision-making for infants at the margin of viability. METHODS: A survey was administered to neonatologists and paediatricians who attend deliveries of preterm infants in Australia, Hong Kong, Japan, Malaysia, Taiwan and Singapore. Questions were asked regarding physician counselling practices, decision-making for extremely preterm infants and demographic information. RESULTS: Physicians counsel parents antenatally with increasing frequency as gestational age increases. Most physicians discuss infant mortality and morbidity with parents prior to delivery. Physicians less frequently discuss the option of no resuscitation of an extremely preterm infant, withdrawal of support at a later time, or financial costs to parents. Severe congenital malformations, perception of a poor future quality of life, parental wishes and a high probability of death for the infant are influential in limiting resuscitation in very preterm infants for a majority of physicians. Less influential factors are parent socioeconomic status, language barriers, financial costs for the family, allocation of national resources, moral or religious considerations, or fear of litigation. Physician thresholds for resuscitation of infants ranged between 22 and 25 weeks gestation and between 400 and 700 g birthweight. CONCLUSIONS: We report physician beliefs and practices regarding resuscitation and the counselling of parents of extremely preterm infants in Pacific Rim countries. While we find variation among countries, physician practices appear to be determined by ethical decision-making and medical factors rather than social or economic factors in each country.

Adult↗
PubMed1998

Childhood incidence of acute lymphoblastic leukaemia and exposure to broadcast radiation in Sydney--a second look.

INTRODUCTION: Recent findings of an apparent association between incidence of childhood leukaemia and radio frequency radiation (RFR) from television transmission antennas in Sydney, NSW, are examined. METHODS: Incidence of childhood (0-14 years) acute lymphoblastic leukaemia (ALL) at the local government area (LGA) level is related to estimated exposure levels of RFR from television transmission antennas, using Poisson regression techniques. RESULTS: Most of the association between ALL incidence and television transmission RFR is shown to be the result of an influential observation: one of the highly exposed LGAs contributes all the excess, while in a similarly exposed LGA childhood ALL incidence was found to be no higher than the rate expected for NSW. With the influential observation excluded from the analysis, no positive correlation between exposure to RFR and leukaemia is evident. Conversely, under the assumption of an association with RFR, the low probability of the observed incident cases in LGAs under conditions of relatively high exposure to RFR conflicts with the assumption of an effect. CONCLUSION: The apparent association between childhood ALL incidence and RFR radiation from television towers is weaker when an LGA-level analysis is conducted.

Adolescent↗
PubMed2005

Influence of distributional shape of substance parameters on exposure model output.

Uncertainty of environmental concentrations is calculated with the regional multimedia exposure model of EUSES 1.0 by considering probability input distributions for aqueous solubility, vapor pressure, and octanol-water partition coefficient, K(ow). Only reliable experimentally determined data are selected from available literature for eight reference chemicals representing a wide substance property spectrum. Monte Carlo simulations are performed with uniform, triangular, and log-normal input distributions to assess the influence of the choice of input distribution type on the predicted concentration distributions. The impact of input distribution shapes on output variance exceeds the effect on the output mean by one order of magnitude. Both are affected by influence and uncertainty (i.e., variance) of the input variable as well. Distributional shape has no influence when the sensitivity function of the respective parameter is perfectly linear. For nonlinear relationships, overlap of probability mass of input distribution with influential ranges of the parameter space is important. Differences in computed output distribution are greatest when input distributions differ in the most influential parameter range.

Environmental Exposure↗
PubMed2005

Tryptophan tryptophylquinone cofactor biogenesis in the aromatic amine dehydrogenase of Alcaligenes faecalis. Cofactor assembly and catalytic properties of recombinant enzyme expressed in Paracoccus denitrificans.

The heterologous expression of tryptophan trytophylquinone (TTQ)-dependent aromatic amine dehydrogenase (AADH) has been achieved in Paracoccus denitrificans. The aauBEDA genes and orf-2 from the aromatic amine utilization (aau) gene cluster of Alcaligenes faecalis were placed under the regulatory control of the mauF promoter from P. denitrificans and introduced into P. denitrificans using a broad-host-range vector. The physical, spectroscopic and kinetic properties of the recombinant AADH were indistinguishable from those of the native enzyme isolated from A. faecalis. TTQ biogenesis in recombinant AADH is functional despite the lack of analogues in the cloned aau gene cluster for mauF, mauG, mauL, mauM and mauN that are found in the methylamine utilization (mau) gene cluster of a number of methylotrophic organisms. Steady-state reaction profiles for recombinant AADH as a function of substrate concentration differed between 'fast' (tryptamine) and 'slow' (benzylamine) substrates, owing to a lack of inhibition by benzylamine at high substrate concentrations. A deflated and temperature-dependent kinetic isotope effect indicated that C-H/C-D bond breakage is only partially rate-limiting in steady-state reactions with benzylamine. Stopped-flow studies of the reductive half-reaction of recombinant AADH with benzylamine demonstrated that the KIE is elevated over the value observed in steady-state turnover and is independent of temperature, consistent with (a) previously reported studies with native AADH and (b) breakage of the substrate C-H bond by quantum mechanical tunnelling. The limiting rate constant (k(lim)) for TTQ reduction is controlled by a single ionization with pK(a) value of 6.0, with maximum activity realized in the alkaline region. Two kinetically influential ionizations were identified in plots of k(lim)/K(d) of pK(a) values 7.1 and 9.3, again with the maximum value realized in the alkaline region. The potential origin of these kinetically influential ionizations is discussed.

Alcaligenes faecalis↗
PubMed1999

Community decision-making about critical access hospitals: lessons learned from Montana's Medical Assistance Facility Program.

Limited-service hospitals have been used as a means of maintaining health care services in rural communities with full-service hospitals at risk of closure. The Medical Assistance Facility (MAF) limited-service hospital model has been implemented in 12 communities in Montana and has been evaluated by the Health Care Financing Administration as a viable alternative to a full-service hospital in frontier communities. The 1997 federal Critical Access Hospital (CAH) legislation is the most recent nationwide alternative for maintaining health care in rural communities, and it incorporates many of the features of the MAF model. The purpose of this study was to examine rural community decision making regarding MAF conversion from the perspectives of key informants who were involved in the decision-making process. A descriptive multiple case study design was used. Data were obtained through interviews with community members during site visits. The research focused on identification of local issues that were influential in the decision to convert to or reopen as an MAF, features of the MAF model that made it a locally acceptable alternative, and elements that characterized the decision-making process. The issues found to be influential in the conversion decision and the features that made the MAF locally acceptable were those that made the provision of basic services more stable and sustainable. The study suggests that programs to maintain health care services in isolated communities should allow for and encourage an expanded role for nonphysician providers. The lessons learned from the communities included in this study are instructive to rural communities nationwide that are considering a CAH as well as to policy-makers, researchers, and regional and national health care decision makers.

Community-Institutional Relations↗
PubMed2001

Sensitivity of forelimb swing phase inverse dynamics to inertial parameter errors.

Estimations of segmental inertial parameters are required for true inverse dynamics calculations during the swing phase of locomotion. This study attempts to quantify the effect of inertial parameter errors on inverse dynamic solutions. Swing phase forelimb net joint moments and powers at the trot (mean +/- s.d 3.03 +/- 0.16 m/s) were calculated with sagittal plane kinematic data from 5 Dutch Warmbloods using inertial parameters based on published regression equations for the breed. Significant peaks in the net moment and power curves for each forelimb joint were identified and measured. Net joint moments and powers were then recalculated after varying the segment mass, location of the segment centre of mass and the mass moment of inertia separately for each of the limb segments. Peak values for the net joint moments and joint powers were determined after each variation, and the percent change in peak value per percent change in inertial parameter was calculated. Segment mass was the most influential parameter, followed by location of the centre of mass. Changes in the mass moment of inertia showed little effect on peak values. The most influential single inertial parameter was the mass of the hoof segment with a mean +/- s.d effect 0.74 +/- 0.22 and 0.69 +/- 0.18 percent peak change per percent parameter change on net joint moments and powers, respectively, across all joints. The results demonstrate the need for an accurate approximation of segment masses during the swing phase, especially the hoof, and the need to account for any additional masses in the model, such as shoes.

Animals↗
PubMed2001

Design and analysis of robust total joint replacements: finite element model experiments with environmental variables.

Computer simulation of orthopaedic devices can be prohibitively time consuming, particularly when assessing multiple design and environmental factors. Chang et al. (1999) address these computational challenges using an efficient statistical predictor to optimize a flexible hip implant, defined by a midstem reduction, subjected to multiple environmental conditions. Here, we extend this methodology by: (1) explicitly considering constraint equations in the optimization formulation, (2) showing that the optimal design for one environmental distribution is robust to alternate distributions, and (3) illustrating a sensitivity analysis technique to determine influential design and environmental factors. A thin midstem diameter with a short stabilizing distal tip minimized the bone remodeling signal while maintaining satisfactory stability. Hip joint force orientation was more influential than the effect of the controllable design variables on bone remodeling and the cancellous bone elastic modulus had the most influence on relative motion, both results indicating the importance of including uncontrollable environmental factors. The optimal search indicated that only 16 to 22 computer simulations were necessary to predict the optimal design, a significant savings over traditional search techniques.

Arthroplasty, Replacement, Hip↗
PubMed2006

Contralateral white noise selectively changes left human auditory cortex activity in a lexical decision task.

In a previous study, we hypothesized that the approach of presenting information-bearing stimuli to one ear and noise to the other ear may be a general strategy to determine hemispheric specialization in auditory cortex (AC). In that study, we confirmed the dominant role of the right AC in directional categorization of frequency modulations by showing that fMRI activation of right but not left AC was sharply emphasized when masking noise was presented to the contralateral ear. Here, we tested this hypothesis using a lexical decision task supposed to be mainly processed in the left hemisphere. Subjects had to distinguish between pseudowords and natural words presented monaurally to the left or right ear either with or without white noise to the other ear. According to our hypothesis, we expected a strong effect of contralateral noise on fMRI activity in left AC. For the control conditions without noise, we found that activation in both auditory cortices was stronger on contralateral than on ipsilateral word stimulation consistent with a more influential contralateral than ipsilateral auditory pathway. Additional presentation of contralateral noise did not significantly change activation in right AC, whereas it led to a significant increase of activation in left AC compared with the condition without noise. This is consistent with a left hemispheric specialization for lexical decisions. Thus our results support the hypothesis that activation by ipsilateral information-bearing stimuli is upregulated mainly in the hemisphere specialized for a given task when noise is presented to the more influential contralateral ear.

Acoustic Stimulation↗
PubMed2006

Regression tree approach to studying factors influencing acoustic voice analysis.

Multiple factors influence voice quality measurements (VQM) obtained during an acoustic voice assessment including: gender, intrasubject variability, microphone, environmental noise (type and level), data acquisition (DA) system, and analysis software. This study used regression trees to investigate the order and relative importance of these factors on VQM including interaction effects of the factors and how the outcome differs when the acoustic environment is controlled for noise. Twenty normophonic participants provided 20 voice samples each, which were recorded synchronously on five DA systems combined with six different microphones. The samples were mixed with five noise types at eight signal-to-noise ratio (SNR) levels. The resulting 80,000 audio samples were analyzed for fundamental frequency (F(0)), jitter and shimmer using three software analysis systems: MDVP, PRAAT, and TF32 (CSpeech). Fifteen regression trees and their Variable Importance Measures were utilized to analyze the data. The analyses confirmed that all of the factors listed above were influential. The results suggest that gender, intrasubject variability, and microphone were significant influences on F(0). Software systems and gender were highly influential on measurements of jitter and shimmer. Environmental noise was shown to be the prominent factor that affects VQM when SNR levels are below 30 dB.

Acoustic Stimulation↗
PubMedDate not supplied

Kinetic mechanisms determining variability in low density lipoprotein levels and rise with age.

Levels of plasma low density lipoproteins (LDL) vary among individuals at any given age and frequently rise with increasing age. Both production rates and fractional clearance rates (FCRs) of LDL theoretically could affect the plasma levels of LDL. To evaluate the relative importance of these two factors, turnover rates of LDL apoprotein (apoLDL) were determined in two groups: 19 young adult men aged 23 to 29 years and 15 middle-aged men aged 40 to 60 years. Results were compared to a group of six healthy young adults (aged 22 to 28 years) who we previously studied and who were on a cholesterol-lowering diet. In both groups in the current study, a diet resembling the average American diet was consumed, and LDL levels ranged from low-to-high normal. On average, the 19 young adult men had lower levels of total cholesterol and LDL cholesterol than did the middle-aged men. The younger men also had significantly higher FCRs and lower production rates of apoLDL. When data from all subjects were pooled, apoLDL levels were negatively and significantly correlated with FCRs and positively and significantly correlated with production rates. Similar relations were found with LDL cholesterol levels. These results show that both FCRs and production rates of apoLDL are important regulators of plasma LDL levels; the correlation suggests that the FCR is more influential at lower LDL concentrations, and that production rates are more influential at higher LDL concentrations.

Adult↗
PubMed1983

Continuing education in pulmonary disease for primary-care physicians.

A continuing medical education program was implemented and evaluated in 16 community hospitals. It was targeted at primary-care physicians and used physicians identified by their peers as being educationally influential for the dissemination of information. Self-study materials were used, followed by an intensive 2-wk preceptorship that resulted in a significant increase in physician knowledge. Inpatient chart audits identified a series of changes in the management of chronic obstructive pulmonary disease in the intervention hospitals that were not noted in the control hospitals. These included the increased use of intravenously administered fluids, loading doses of intravenously administered bronchodilators, aerosolized and single agent bronchodilators, and respiratory therapy services. Continuing medical education, delivered through community-based educationally influential physicians, is an effective way of changing physician behavior in small communities with no prior ongoing educational programs. This approach should improve patient care and may reduce the need for participation of academic faculty in traditional continuing education programs.

Education, Medical, Continuing↗
PubMed1983

DSM-III and the diagnosis of borderline.

In order to achieve more understanding of the diagnosis of borderline personality, particularly as it relates to DSM-III, a historical review of influential diagnostic approaches is undertaken. DSM-III defines the borderline personality disorder in a simple way, enhancing reliability and research value. In comparison to other influential approaches, however, there is an overemphasis on affective disturbance, plus an obvious omission amongst the diagnostic criteria of the vulnerability to brief psychotic regressions under stress. The checklist approach of DSM-III greatly takes away from dynamic understanding and makes potentially valuable items such as defensive organization difficult to include. The DSM-III concept of the borderline personality as one of many distinct personality disorders seems unfounded. The concept of the borderline as a superordinate diagnosis under which more specific personality disorders would fall, appears more reasonable.

Borderline Personality Disorder↗