Significant Two-factor Interaction Research Articles

Sex differences in kinematics and quadriceps activity for fast isokinetic knee extension

BACKGROUND: The quantitative recruitment of motor units depends on specific demands, including movement velocity. DNA microarrays differ according to sex, and these sex-related differences affect the fiber type composition. OBJECTIVE: The aim of this study is to demonstrate inter-sex differences in the isokinetic parameters, isokinetic phases, and muscle activities and to investigate the correlation between muscle activity and isokinetic data. METHODS: A total of 41 healthy adults (20 male, 21 female) performed concentric knee extension at angular velocities of 60∘/s, 180∘/s, and 240∘/s. The outcome measures consisted of the isokinetic peak moment (PM), normalized PM (PM/BW), total work, and power, alongside the acceleration, iso-speed and deceleration, sub-phases. Muscle activity was recorded from the rectus femoris, vastus lateralis, and vastus medialis using surface EMG. RESULTS: There were significant two-factor main effect and interaction between sex and angular velocity on the power of knee extension and isokinetic phase (p< 0.05). As the velocity increased, the increase in power of males was greater than that of females. In contrast, with the increase in velocity, PM, PM/BW, and total work decreased, but no significant interaction was observed between velocity and sex. At high velocity, males showed higher acceleration ability than females. CONCLUSION: The sex-dependent responses to velocity were more affected by differences in total movement time than force production. Fast isokinetic exercise should consider the acceleration ability rather than the ability to produce force.

A preliminary investigation into the impact of shock wave therapy and sonotherapy on postural control of stepping tasks in patients with Achilles tendinopathy.

The outcomes of physical therapy are commonly assessed with subjective scales and questionnaires. Hence, a continuous search to identify diagnostic tests that would facilitate objective assessment of symptom reduction in those patients with Achilles tendinopathy who undergo mechanotherapy. The main aim of this study was to evaluate and compare the effectiveness of shock wave and ultrasound treatments, using objective posturographic assessment during step-up and step-down initiation. The patients with non-insertional Achilles tendinopathy and pain lasting for more than 3 months were randomly assigned to one of the experimental groups, i.e., radial shock wave therapy (RSWT), ultrasound therapy, or placebo ultrasound. All groups also received deep friction massage as the primary therapy. The transitional locomotor task was performed with the affected and unaffected limb in random order, on two force platforms under two conditions (step-up and step-down). The recording of center of foot pressure displacements was divided into three phases: quiet standing before step-up/step-down, transit, and quiet standing until measurement completion. Pre-intervention measurements were performed and then short-term follow-ups at weeks 1 and 6 post-therapy. The three-way repeated measures ANOVA showed few statistically significant two-factor interactions between therapy type, time point of measurement and the type of the locomotor task. Significant increases in postural sway were observed in the entire study population throughout the follow-up period. Three-way ANOVAs revealed a group effect (shock wave vs. ultrasound) on almost all variables of the quiet standing phase prior to step-up/step-down initiation. Overall, postural stability before the step-up and step-down tasks appeared to be more efficient in patients who had undergone RSWT compared to the ultrasound group. Objective posturographic assessment during step-up and step-down initiation did not demonstrate therapeutic superiority of any of the three therapeutic interventions used in patients with non-insertional Achilles tendinopathy.Clinical Trial Registration: The trial was prospectively registered in the Australian and New Zealand Clinical Trials Registry (no. ACTRN12617000860369; registration date: 9.06.2017).

Central composite rotatable design for optimization of trihalomethane extraction and detection through gas chromatography: a case study

Central composite rotatable design (CCRD) was employed to optimize initial temperature (ºC), ramp function (ºC/min) and salt addition for trihalomethane extraction/quantification from the drinking water distribution network in Ratta Amral, Rawalpindi., Pakistan. Drinking water samples were collected from the treatment plant, overhead reservoir and consumer’s taps. The USEPA method for trihalomethane detection 551.1 via gas chromatography was applied using liquid–liquid extraction. The experiments with input variables for sample preparation and operational conditions were performed in a randomized order as per design of experiment by central composite rotatable design and responses were evaluated for model development. A significant (p = 0.005) two-factor interaction model was optimized. Initial temperature was observed to be insignificant (p = 0.64), while ramp function (p = 0.0043) and salt addition (p = 0.04) were significant. Product of salt addition and ramp was significant (p = 0.004), while product of initial temperature and salt addition was insignificant (p = 0.008). With a desirability function of 0.97, an initial temperature of 50 ºC, 6 ºC rise/min to 180 ºC and 0.5 g salt were optimized. It was found that development and optimization of the analytical methods for rapid trihalomethane detection would improve optimization of the current treatment practices in the country.

Pretreatment of silk for digital printing: identifying influential factors using fractional factorial experiments

PurposeThe purpose of this study is to identify the most influential factors affecting the printing properties and print quality of digitally printed silk fabrics in terms of colour strength and fixation percentage.Design/methodology/approachIn this study, five factors (concentration of thickener, concentration of urea, concentration of alkali, pH of pretreatment liquor and steaming duration) were investigated using a blocked 25−1 fractional factorial experiment. The type of thickeners [polyacrylic acid and polyacrylamide (PAM)] were considered as a block.FindingsLinear models were obtained and statistically tested using both analysis of variance and coefficient of determination (R2), and they were found to be accurate at 90 per cent confidence level. It was revealed that concentration of alkali, concentrations of urea and pH of the pretreatment liquor had an increasing effect on colour strength, whereas concentration of thickener and steaming duration showed decreasing effect on colour strength of digitally printed silk fabrics. Furthermore, concentration of alkali, concentrations of urea had increasing effect on dye fixation percentage, whereas steaming duration showed decreasing effect on dye fixation percentage of digitally printed silk fabrics. In addition, PAM thickener based pretreatment recipe exhibited better printing properties for the digitally printing of silk fabrics.Originality/valueThe main influences and significant two-factor interactions were discussed in detail to gain a better understanding of the printing properties of digitally printed silk fabrics. The findings of this study are useful for further optimisation of pre- and post-treatment processes for digital printing of silk fabrics.

Parametric evaluation and performance optimization of fine coal separation in a vibrated gas-fluidized bed using response surface methodology

Fine coal separation in a vibrated gas-fluidized bed (VGFB) is based on the phenomenon of density segregation and provides an easy and efficient way to clean fine coal. In this study, the Response Surface Methodology (RSM) was used to study the influential significance of parameters, parametric interactions, and performance optimization of fine coal separation in a VGFB. The results show that the superficial air velocity, vibration frequency, and vibration amplitude have significant two-factor interactions. The synergy between vibration and airflow contributes to revealing the mechanisms of these interactions. The performance optimization using RSM was conducted and the optimal combination of parameter values with the best performance of density segregation was obtained as followed: U of 36.9 cm/s, f of 29.2 Hz, A of 1.88 mm, and T of 139 s. The verification experiments were carried out and the results were consistent with the results of performance optimization.

Dry sliding wear behaviour of AA6082-T6/SiC/B4C hybrid metal matrix composites using response surface methodology

In the present work, dry sliding wear behaviour of hybrid aluminum metal matrix composites is carried out. A mixture of silicon carbide and boron carbide is used in equal fraction as reinforcement with base material AA6082-T6 to prepare AA6082-T6/SiC/B4C hybrid metal matrix composites using stir casting technique. The weight percentage of silicon carbide and boron carbide mixture taken to prepare hybrid composites is 5, 10, 15 and 20. The wear behaviour of Al-SiC-B4C composites is investigated using a pin-on-disc apparatus at room temperature, and optimization of process parameters is done using response surface methodology. The weight percentage of reinforcement, sliding speed, load and sliding distance are selected as process parameters with five levels of each. Analysis of variance shows that wear increases with increase of load or sliding distance and decreases with an increase in reinforcement or sliding speed. The experimental results revealed that the wear of Al-SiC-B4C hybrid composites has been influenced most by the sliding distance and least by weight percentage of reinforcement. The interaction between load–sliding speed is the only significant two-factor interaction in the present model which increases wear rate in fabricated hybrid composites. Further, the experimental results obtained are verified by conducting confirmation tests, and the errors found are within 3 to 7%.

Analysis of the sulfuric acid hydrolysis of wood pulp for cellulose nanocrystal production: A central composite design study

Cellulose nanocrystals (CNCs) are most commonly prepared by sulfuric acid hydrolysis of a purified cellulose starting material but the effects of hydrolysis conditions on CNC yield and properties are incompletely understood. In this study, we use a rotatable central composite experimental design to elucidate parameter interactions between three design factors, acid concentration (x1), hydrolysis temperature (x2), and hydrolysis time (x3), over a broad range of process conditions and determine their effect on yield and sulfate group density. Parameter ranges are 55–65wt.% for x1, 45–65°C for x2, and 30–180min for x3. Regression models of the experimental yield data reveal significant two-factor interactions of x1 with each x2 and x3, whereas x2 has no significant two-factor interaction with x3. The models predict maximum yields of 66–69% at optimum process conditions of 57–58wt.% (x1), 64–67°C (x2), and 134–156min (x3). At these conditions, the sulfate group density is predicted to be between 241 and 265mmol/kg. The sulfate group density is linearly dependent on acid concentration and hydrolysis temperature and not dependent on hydrolysis time. Maximum sulfate group density can only be achieved at the expense of yield. The results presented here provide a foundation for subsequent, sequential optimization using narrower parameter ranges, allowing further optimization of the hydrolysis conditions and potentially enabling higher yield.

Impact of the joint association between sex, age and diabetes on long-term mortality after acute myocardial infarction.

BackgroundThe role of sex, and its joint effect with age and diabetes mellitus, on mortality subsequent to surviving an acute myocardial infarction (AMI) beyond 30 days are unclear. The high prevalence of diabetes mellitus in an ethnically diverse Asian population motivates this study.MethodsThe study population comprised of a nationwide cohort of Asian patients with AMI, hospitalized between 2000 to 2005, who survived the first 30 days post-admission and were followed prospectively until death or 12 years.ResultsAmong the 13,389 survivors, there were fewer women (25.5%) who were older than men (median 70 vs. 58 years) and a larger proportion had diabetes mellitus at admission (51.4% vs. 31.4%). During follow-up 4,707 deaths (women 13.2%; men 22.0%) occurred, with women experiencing higher mortality than men with an averaged hazard ratio (HR): 2.08; 95% confidence interval : 1.96-2.20. However the actual adverse outcome, although always greater, reduced over time with an estimated HR: 2.23 (2.04-2.45) at 30 days to HR: 1.75; (1.47-2.09) 12 years later. The difference in mortality also declined with increasing age: HR 1.80 (1.52-2.13) for those aged 22-59, 1.26 (1.11-1.42) for 60-69, 1.06 (0.96-1.17) and 0.96 (0.85-1.09) for those 70-79 and 80-101 years. Significant two-factor interactions were observed between sex, age and diabetes (P < 0.001). Diabetic women <60 years of age had greater mortality than diabetic men of the same age (adjusted HR: 1.44; 1.14-1.84; P = 0.003), while diabetic women and men ≥60 years of age had a less pronounced mortality difference (adjusted HR: 1.12; 0.99-1.26).ConclusionsOne in two women hospitalized for AMI in this Asian cohort had diabetes and the sex disparity in post-MI mortality was most pronounced among these who were <60 years of age. This underscores the need for better secondary prevention in this high-risk group.

Individual and Joint Impacts of Ethanol Use, BMI, Age and Gender on Serum Gamma-Glutamyltransferase Levels in Healthy Volunteers

Excessive ethanol consumption, obesity and increasing age may all lead to increased serum levels of gamma-glutamyltransferase (GGT) enzyme, which plays a key role in the metabolism of extracellular reduced glutathione. However, as yet, the interactions between the various modulators of GGT activities have remained poorly defined. We analyzed data from 15,617 apparently healthy individuals (7254 men and 8363 women, mean age 46 ± 13 years, range 25–74 years) who participated in a national cross-sectional health survey in Finland between 1997 and 2007. All subjects underwent detailed clinical examinations and interviews, including the amount of ethanol use and smoking habits. GGT levels were measured from all participants, and the individual and joint impacts of the different study variables on GGT levels were assessed. Significant individual effects were noted for ethanol use (p < 0.001), body mass index (BMI) (p < 0.001), age (p < 0.001) and smoking (p < 0.001). In men, significant two-factor interactions occurred between ethanol use and age (p < 0.020). Among those over 40 years of age, ethanol consumption was found to be a stronger determinant of increased GGT levels than in men below 40 years, whereas in the latter age group, BMI was found to predominate. In women, a significant two-factor interaction occurred between ethanol and BMI (p = 0.010), whereas it did not with ethanol use and age. The data underscores the role of ethanol consumption and age as major determinants of increased GGT levels in men, whereas in women, a relatively stronger impact was noted for ethanol intake and BMI. In light of the ability of GGT enzyme to modulate crucial redox-sensitive functions, the present findings also support the use of GGT as a biomarker of oxidative stress.

Bond strength of self-adhesive resin cements to dentin after antibacterial and chelating solution treatment

Objective.The aim of this study was to evaluate the effect of tetracycline HCl, 1-hydroxyethylidene−1, 1-bisphosphonate (HEBP) and chlorhexidine digluconate (CHX) on micro push-out (µ-PO) bond strengths of two self-adhesive resin cements on dentin. Materials and methods.Sixty discs of 1.25 mm thickness (middle dentin) were prepared from human molars perpendicular to the tooth axis. Two standardized occlusal cavities of 2.20 mm occlusal diameter and 1.25 mm cervical diameter were prepared in each disc. The cavities were divided into three groups in accordance with the surface treatment (50 mg/ml tetracycline HCl, 18% HEBP and 2% CHX solutions). Following the treatment of the discs for 5 min, cavities were filled with two different self-adhesive resin cements (Clearfil™ SA Cement and RelyX™ Unicem). After light polymerization of cements, µ-PO bond strength tests were performed. Failure modes were examined and dentin morphologic assessments were done. Statistical significance was determined by a multivariate analysis of variance (MANOVA) followed by Tukey's post-hoc test (p < 0.05). Additionally, a paired-samples T-test was used to compare the µ-PO bond strengths of self-adhesive resin cements (p < 0.05). Results.Paired-samples T-test revealed that there was no significant difference between tested self-adhesive resin cements (p = 0.612). No significant two-factor interaction was observed between Clearfil™ SA Cement and chemical agents (p = 0.457). Similarly, tetracycline HCl and CHX did not have a significant effect on the bond strength of RelyX™ Unicem (p > 0.05). However, HEBP significantly decreased the bond strength of RelyX™ Unicem when compared to the control (p < 0.05). Conclusion.The tetracycline HCl and CHX solutions do not have beneficial effects on µ-PO bond strengths of self-adhesive resin cements. Additionally, the results of this study do not justify the use of self-adhesive resin cements, following HEBP treatment of dentin. Clinical significance: The application of topical HEBP solution treatment to dentin could have adverse effects on the µ-PO bond strengths of RelyX™ Unicem.

On Correlated Sources of Uncertainty in Four Dimensional Computed Tomography Data Sets

The purpose of this work is to estimate the degree of uncertainty inherent to a given four dimensional computed tomography (4D-CT) imaging modality and to test for interaction of the investigated factors (i.e., object displacement, velocity, and the period of motion) when determining the object motion coordinates, motion envelope, and the confomality in which it can be defined within a time based data series. A motion phantom consisting of four glass spheres imbedded in low density foam on a one dimensional moving platform was used to investigate the interaction of uncertainty factors in motion trajectory that could be used in comparison of trajectory definition, motion envelope definition and conformality in an optimal 4D-CT imaging environment. The motion platform allowed for a highly defined motion trajectory that could be as the ground truth in the comparison with observed motion in 4D-CT data sets. 4D-CT data sets were acquired for 9 different motion patterns. Multifactor analysis of variance (ANOVA) was performed where the factors considered were the phantom maximum velocity, object volume, and the image intensity used to delineate the high density objects. No statistical significance was found for three factor interaction for definition of the motion trajectory, motion envelope, or Dice Similarity Coefficient (DSC) conformality. Two factor interactions were found to be statistically significant for the DSC for the interactions of 1) object volume and the HU threshold used for delineation and 2) the object velocity and object volume. Moreover, a statistically significant single factor direct proportionality was observed between the maximum velocity and the mean tracking error. In this work multiple factors impacting on the uncertainty in 4D data sets have been considered and some statistically significant two-factor interactions have been identified. Therefore, the detailed evaluation of errors and uncertainties in 4D imaging modalities is recommended in order to assess the clinical implications of interaction among the various uncertainty factors.

Gender-dependent impacts of body mass index and moderate alcohol consumption on serum uric acid—an index of oxidant stress status?

Uric acid seems to be causally involved in a variety of medical disorders involving oxidative stress. Although alcohol abuse and obesity are known to increase serum uric acid, the interactions between moderate drinking, adiposity, and uric acid metabolism have remained poorly understood. We examined serum uric acid concentrations from 2062 apparently healthy volunteers (970 men, 1092 women) reporting either no alcohol (abstainers) or <40 g of ethanol consumption per day (moderate drinkers). The study population was further classified according to BMI as follows: <19 (underweight), 19–25 (normal weight), 25–30 (overweight), and >30 (obese). Serum uric acid concentrations in male moderate drinkers were significantly higher, and in females they were lower, than in the corresponding groups of abstainers. In the BMI-based subgroups, the highest concentrations were found in those who were overweight or obese. Significant two-factor interactions occurred between gender and drinking status (p<0.001) and between gender and BMI (p<0.02). Serum uric acid also correlated with indices of hepatocellular health (GGT, ALT, AST). The data indicate distinct gender-dependent impacts of alcohol consumption and BMI on serum uric acid. These findings should be applicable to the assessment of oxidative stress status and associated morbidity in alcohol consumers and individuals with excess body weight.

Crosslinking of drug–alginate granules: Part 2. Effect of granule preparation and composition on granule properties

Paracetamol–alginate (Keltone HVCR) (1:1) granules were prepared by a wet granulation process followed by crosslinking of dried granules in calcium chloride solution. The effect of shear (planetary (low), Brabender (high)), binder quantity (1:2, 1:1 water:powder) and drug particle size (PS 98, 275 μm) were studied using a factorial design. Supporting studies were carried out varying binder quantity and alginate grade (viscosity). In the pre-treated granules, drug entrapment was mainly influenced by drug PS, where the smaller particles showed better embedding. After crosslinking, drug particle size continued to be the most important factor influencing drug recovery. All factors influenced early stage release where high shear, high binder, small drug PS granules showed least release and the low shear, low binder and large drug PS granules showed greatest release. Some significant two-factor interactions were found. Granule consolidation (shown by SEM) and particle embedding increased with binder quantity and reduced as the alginate viscosity was increased. Crosslinking, as shown by Na and Ca contents was >90%. The impact of granule consolidation on drug entrapment and recovery was relatively small (<10%) when compared to its effect on early stage drug release (>60%) which may be important if these granule systems are to be used for taste improvement.

Effects of Rosiglitazone (a Peroxysome Proliferator-Activated Receptor .GAMMA. Agonist) on the Blood Pressure and Aortic Structure in Metabolically Programmed (Perinatal Low Protein) Rats

This study investigated the effects of rosiglitazone on nutritionally programmed chronic disease, with a focus on blood pressure (BP) and aortic wall structural remodeling. Wistar pregnant rats were fed one of two diets: a normal protein diet (19% protein; NP rats) or low-protein diet (5% protein; LP rats). Male offspring at 3 months of age were randomly divided into four groups: NP offspring treated with rosiglitazone (NPR); untreated NP offspring (NP); LP offspring treated with rosiglitazone (LPR); untreated LP offspring (LP). Rosiglitazone was administered at a dose of 5 mg/kg/d until 6 months of age. BP was elevated in LP offspring. Rosiglitazone reduced BP beginning in the first week of treatment in the LPR offspring. The insulin sensitivity was increased in LP offspring, and was not altered by rosiglitazone. LP offspring exhibited a 40% reduction in the amount of elastic fibers in the aorta wall compared with NP offspring (p < 0.01), and the quantity of elastic fibers was not altered by rosiglitazone. The smooth muscle cells, elastic lamellae, circumferential wall tension (CWT) and tensile stress (TS) were increased in LP offspring, indicating increased blood flow in the aorta. Rosiglitazone reduced both CWT and TS by 30% compared to the levels in untreated LP offspring (p < 0.01 for both). Rosiglitazone restored the expressions of angiotensin II type 1 receptor and endothelial nitric oxide synthase nearly to the levels in the NP offspring. ANOVA disclosed a significant two-factor interaction between protein content in the diet and rosiglitazone treatment (p < 0.001 for CWT and p < 0.00001 for TS, two-way ANOVA). We conclude that rosiglitazone has beneficial effects in reducing the BP and the aortic tunica media hypertrophy with consequent balance of the wall stress in metabolically programmed offspring.

Effect of light curing type on cytotoxicity of dentine‐bonding agents

To compare the cytotoxic effects of dentine-bonding agents (DBAs) polymerized with two different curing units at 24 h and 72 h on L-929 cells. Disc-shaped test samples of light-activated DBAs were prepared according to manufacturers' instructions and cured with either conventional quartz tungsten halogen or light-emitting diode light curing units (LCUs). After curing, the samples were transferred into a culture medium for 24 h. Eluates were obtained and pipetted onto L-929 mouse fibroblast cultures (3 x 10(4) cells per well), incubated for evaluation after 24 and 72 h. After both incubation periods, measurements were performed by an dimethylthiazol diphenyltetrazolium assay. The degree of cytotoxicity for each sample was determined according to the reference value represented by the cells with a control (culture without sample). Statistical significance was determined by a three-way analysis of variance followed by the Mann-Whitney U-test. No significant three-factor interaction occurred amongst LCUs, DBAs and time factors (P = 0.955). LCUs and DBAs had a significant two-factor interaction (P < 0.001). In general, the test materials cured with the light-emitting diode LCU demonstrated higher cell survival rates when compared with the those cured with the quartz tungsten halogen. Differential toxic effects of the DBAs cured with the quartz tungsten halogen or the light-emitting diode on the fibroblast cells may prove to be very important when suitable DBAs or LCUs are used for operative restorations.

Statistical analysis of optimal culture conditions for Gluconacetobacter hansenii cellulose production

The purpose of this study was to analyse the effects of different culture parameters on Gluconacetobacter hansenii (ATCC 10821) to determine which conditions provided optimum cellulose growth. Five culture factors were investigated: carbon source, addition of ethanol, inoculation ratio, pH and temperature. jmp Software (SAS, Cary, NC, USA) was used to design this experiment using a fractional factorial design. After 22 days of static culture, the cellulose produced by the bacteria was harvested, purified and dried to compare the cellulose yields. The results were analysed by fitting the data to a first-order model with two-factor interactions. The study confirmed that carbon source, addition of ethanol, and temperature were significant factors in the production of cellulose of this G. hansenii strain. While pH alone does not significantly affect average cellulose production, cellulose yields are affected by pH interaction with the carbon source. Culturing the bacteria on glucose at pH 6.5 produces more cellulose than at pH 5.5, while using mannitol at pH 5.5 produces more cellulose than at pH 6.5. The bacteria produced the most cellulose when cultured on mannitol, at pH 5.5, without ethanol, at 20 degrees C. Inoculation ratio was not found to be a significant factor or involved in any significant two-factor interaction. These findings give insight into the conditions necessary to maximize cellulose production from this G. hansenii strain. In addition, this work demonstrates how the fractional factorial design can be used to test a large number of factors using an abbreviated set of experiments. Fitting a statistical model determined the significant factors as well as the significant two-factor interactions.

Non‐fatal injuries among Pacific infants in Auckland: Data from the Pacific Islands Families First Two Years of Life study

Child injury is the leading cause of mortality and morbidity in developed countries. While Pacific infant death rates are relatively high in New Zealand, little is known about non-fatal injury rates. We seek to describe maternally reported injury in Pacific infants aged between 0-24 months. A cohort of Pacific infants born during 2000 in Auckland, New Zealand, was followed. Maternal home interviews were conducted at 6 weeks, 12 months and 24 months postpartum and injury events were recalled. Marginal models using generalized estimating equations (GEEs) were used to analysis the longitudinal data. The inception cohort included 1398 infants at 6 weeks, 1241 infants at 12 months and 1161 infants at 24 months. The age-specific injury incidence per 1000 person-years exposure was estimated at 48 (95% CI: 23, 88) injuries for infants aged 0-6 weeks, 106 (95% CI: 88, 127) injuries for infants aged 7 weeks-12 months and 174 (95% CI: 151, 199) injuries for infants aged 13-24 months. In the multivariable GEE model, older infants (P < 0.001), infants who were male (P = 0.01), born to Pacific Island fathers and non-Pacific Island mothers (P < 0.001), and in higher or unknown income groups (P = 0.01) were significantly more likely to suffer injury events. No significant two-factor interaction with infant age was identified. Among Pacific infants, non-fatal injury is common and injury incidence rates are considerably higher than national levels. Male infants and those born into ethnically mixed families, where the father was of Pacific Island ethnicity and the mother was non-Pacific, were at increased relative risk of injury and might benefit from specific injury prevention targeting. However, given the high injury incidence levels found, we advocate that investigation and targeting of culturally appropriate prevention strategies for all Pacific families with young children is required to reduce injury rates for Pacific infants in New Zealand.

Characterisation of the shrinkage of calcium alginate gel membrane with immobilised Lactobacillus rhamnosus.

To quantify the shrinkage of calcium alginate gel membrane as a support matrix for immobilising cells during the fermentation of Lactobacillus rhamnosus, factors including time, pH, membrane thickness, and the concentrations of immobilised cells, lactic acid, glucose, and calcium chloride were examined by statistical experimental design. A Plackett-Burman design was used for the first screening experiment to identify the important factors which caused the divergent effects. Uniform Design, a powerful modelling design technique, was thus chosen to design the modelling experiments. Through a non-linear step-wise regression analysis, the predictive mathematical model of the shrinkage in membrane thickness was established and the significant main effects and two-factor interactions were identified. However, no significant model equations could be obtained for the shrinkage in area and volume of gel membranes. The methodology developed can be extrapolated to the quantitative characterisation of shrinkage in other immobilised gel matrices, which will be very useful in mathematical modelling, design, operation and scale-up of gel immobilised cell systems.

Truncal site and detoxifying enzyme polymorphisms significantly reduce time to presentation of further primary cutaneous basal cell carcinoma.

Basal cell carcinoma (BCC) is the commonest cancer in Caucasians. Its incidence is rising and many patients develop multiple primary tumours at separate sites. Factors determining time between first primary tumour presentation and the next new primary lesion are unclear. We used Cox's proportional hazards model to study, in 856 Caucasians, the influence of tumour site, individual characteristics and polymorphism in glutathione S-transferase (GSTM1, GSTT1) and cytochrome P450 (CYP2D6, CYP1A1) loci on time to next primary tumour presentation. More than one tumour at first presentation (P <0.0001, hazard ratio 2.72) and GSTT1 null (P = 0.028, hazard ratio 1.74) were associated with decreased time to next primary tumour presentation. Significant two-factor interactions, corrected for number of tumours at presentation, were identified between a truncal tumour at first presentation and each of male gender, GSTM1 null and CYP2D6 EM (P <0.003, hazard ratios 3.09-3.82). In each of these cases, all patients with the risk combination demonstrated further separate tumours within 5 years of first presentation. Thus, patients with a truncal tumour at first presentation, especially males and those presenting with more than one lesion have a significantly decreased time to presentation of further tumours and should receive more meticulous follow-up. Polymorphism in GSTM1 and CYP2D6 also influences the rate of new primary tumour accrual giving insights into the link between ultraviolet exposure and multiple tumour development.

Fractional factorial design study of a pressure swing adsorption-solvent vapor recovery process

A two-level fractional factorial study was performed by computer simulation on the periodic state process performance of a pressure swing adsorption-solvent vapor recovery process (PSA-SVR). The goal was to investigate factor (parameter) interaction effects on the process performance, i.e., interaction effects that cannot be ascertained from the conventional “one-at-a-time” approach. Effects of seven factors, i.e., the purge to feed ratio, pressure level, pressure ratio, heat transfer coefficient, feed concentration, feed volumetric flow rate and bed length to diameter ratio, on the process performance were investigated. The results were judged in terms of the light product purity, heavy product enrichment (and relative enrichment) and recovery, and bed capacity factor. Only the purge to feed ratio, pressure ratio, and feed concentration had significant effects on the benzene vapor enrichment (and relative enrichment); and no two-factor and higher interactions were observed. The light product purity was affected by all seven factors; and the relative importance of the effect of each factor depended on the levels of the other factors, i.e., significant two-factor interaction effects existed. Two-factor interaction effects also existed on the benzene vapor recovery, although the effects of all seven factors and their interactions were relatively small. The bed capacity factor was affected mainly by the purge to feed ratio, the heat transfer coefficient and the feed concentration; two factor and higher order interaction effects were insignificant. Overall, this study demonstrated the utility of fractional factorial design for revealing factor interactions and their effects on the performance of a PSA-SVR process.