Increased patterns of risky behaviours among helmet wearers in skiing and snowboarding

Background

There has been an ongoing debate as to whether wearing helmets in skiing and snowboarding increases the risk tolerance of participants.

Objective

To investigate the roles of demographic and personality variables, and helmet usage in predicting risk taking behaviours in a cross-sectional sample of intermediate and proficient skiers and snowboarders.

Methods

Risk taking in skiing was measured using a validated 10-item self-report measure which was designated as the outcome variable in a three step hierarchical regression. Independent predictors included age, sex, education, sport, ability, helmet usage, and personality traits that have been associated with risk taking: impulsivity and sensation seeking.

Results

In the final regression model, helmet use significantly predicted variance in risk taking (standardized β = .10, p = .024), and the relationship remained after accounting for variance due to demographic variables and general trait measures. The partial relationship between risk taking and sex, ability, impulsivity, and sensation seeking were also significant (p < .05).

Conclusion

High sensation seeking, high impulsivity, male sex, and proficiency were associated with increased patterns of risky behaviours in skiers and snowboarders, and after accounting for these factors, helmet use was a significant predictor of risk taking. The relationship between helmet use and risk taking was modest suggesting that the costs of increased risk taking is not likely to outweigh the protective benefits of a helmet.     

The impact response of motorcycle helmets at different impact severities

Helmets reduce the frequency and severity of head and brain injuries over a range of impact severities broader than those covered by the impact attenuation standards. Our goal was to document the impact attenuation performance of common helmet types over a wide range of impact speeds. Sixty-five drop tests were performed against the side of 10 different helmets onto a flat anvil at impact speeds of 0.9–10.1 m/s (energy = 2–260 J; equivalent drop heights of 0.04–5.2 m). Three non-approved beanie helmets performed poorly, with the worst helmet reaching a peak headform acceleration of 852g at 29 J. Three full-face and one open-face helmet responded similarly from about 100g at 30 J to between 292g and 344g at 256–260 J. Three shorty style helmets responded like the full-face helmets up to 150 J, above which varying degrees of foam densification appeared to occur. Impact restitution values varied from 0.19 to 0.46. A three-parameter model successfully captured the plateau and densification responses exhibited by the various helmets (R² = 0.95–0.99). Helmet responses varied with foam thickness, foam material and possibly shell material, with the largest response differences consistent with either the presence/absence of a foam liner or the densification of the foam liner.     

Alcohol and driving factors in collision risk

In this study we examine the effect of several alcohol-related measures on self-reported collision involvement within the previous 12 months while controlling for demographic and driving exposure factors based on a large representative sample of adults in Ontario. Data are based on the 2002–2006 Centre for Addiction and Mental Health Monitor, an ongoing cross-sectional telephone survey of Ontario adults aged 18 and older (n = 8542). Three logistic regressions of self-reported collision involvement in the past 12 months were implemented, each consisting of 3 steps: (1) demographic factors and driving exposure entered, (2) driving after drinking within the last 12 months entered, and (3) one of three alcohol-related measures (AUDIT subscales of alcohol consumption, dependence and problems) entered. In each step, measures from the preceding step were included in order to control for those variables. In Step 1, age (OR = 0.989), region overall, Central East region (OR = 0.71), West region (OR = 0.67), and North region (OR = 0.67), income overall and those who did not state income (OR = 0.64), marital status overall and those married or living common law (OR = 0.60), and number of kilometers driven in a typical week (OR = 1.00) were found to be significant predictors of collision involvement. The analyses revealed that driving after drinking was a significant predictor of collision involvement in Step 2 (OR = 1.51) and each of the Step 3 models (ORs = 1.52, 1.37, 1.34). The AUDIT Consumption subscale was not a significant factor in collision risk. Both the AUDIT Dependence and AUDIT Problems subscales were significantly related to collision risk (ORs = 1.13 and 1.10, respectively). These findings suggest that alcohol, in addition to its effects on collision risk through its acute impairment of driving skills, may also affect collision risk through processes involved when individuals develop alcohol problems or alcohol dependence.     

Thrill and Adventure Seeking as a modifier of the relationship of perceived risk with risky driving among young drivers

Risky driving contributes to road trauma, a leading cause of mortality among young people. Health-relevant behaviour models suggest a negative relationship between risky driving and perceived risk of its outcomes. However, high sensation seekers may value the “thrill” of the risk, and positive associations between sensation seeking and risky driving have been observed. This is the first study to examine whether aspects of sensation seeking modify the relationship between perceived risk and risky driving. Young drivers in metropolitan Sydney and rural New South Wales [NSW] (n = 797) completed a survey relating to one of the four risky driving behaviours (speeding, drink-driving, driving while fatigued, and failing to wear a seatbelt). Results suggest that the Thrill and Adventure Seeking subscale of Zuckerman's (1994) Sensation Seeking Scale moderate the relationship of perceived risk with risky driving – indicating a negative relationship for low-scores, but not high-scorers, on the TAS subscale. Thus, road safety campaigns that emphasize the riskiness of a particular behaviour may be of limited benefit to thrill and adventure seekers.     

Preparation and characterization of LiFe1/2Ni1/2VO4

A layered ceramic oxide, LiFe_1/2Ni_1/2VO₄ has been prepared using solid-state reaction technique. The preparation conditions have been optimized using thermogravimmetric analysis (TGA) studies. The formation of the material sample under the reported condition has been confirmed by X-ray diffraction (XRD) analysis. XRD analysis indicates the crystal structure to be orthorhombic with lattice parameter: a = 3.5637 Å, b = 17.7486 Å, c = 12.2884 Å. The phase morphology and surface properties studied using scanning electron microscopy (SEM), suggest a polycrystalline texture with reasonable number of the voids. Complex impedance analysis of the sample has indicated: (i) conduction due to bulk contribution at T ≤ 200 °C, (ii) the presence of grain boundary effects at T ≥ 200 °C, (iii) negative temperature coefficient of resistance (NTCR) behaviour and (iv) evidence of temperature dependent electrical relaxation phenomena in the sample. The DC conductivity (σ_DC) shows typical Arrhenius behaviour when observed as a function of the temperature. The activation energy value has been estimated to be 0.42 eV. σ_DC, as evaluated from complex impedance spectrum, shows a jump of nearly ∼4 orders of magnitude in the value at higher temperature when compared to that of the room temperature value. AC conductivity spectrum obeys Jonscher's universal power law. The results of σ_AC as a function of frequency are also discussed.     

Failure analysis of a fluidisation nozzle in biomass boiler and the long-term high temperatures oxidation behaviour of 304 stainless steel

The long-term (> 10 years) oxidation behaviour of stainless steels (SS) at high temperatures was previously unknown. The behaviour was studied through a case study of failure analysis. A fluidisation nozzle made of 304 austenitic SS. After over 100,000 h of service at temperatures of 790–820 °C in a biomass boiler, the nozzle fractured. Failure analysis pinpoints that the nozzle wall temperature fluctuation caused the oxide scale cracking, which intensified the oxidation. The brittle fracture was due to fully oxidization.The long-term oxidation behaviours are distinct from the short-term oxidation behaviours. XRD analysis indicates that the scale was mainly Fe^+ 2Cr₂O₄ and (Fe_0.6 Cr_0.4)₂O₃. ESEM/EDS analysis indicates internal oxidation and sulfidation along the grain boundaries. The different diffusion rates of the Fe, Cr and Ni atoms formed a Ni-rich (48%) layer underneath the scale, and a Cr-rich (35%) core in the remained SS. A schematic is proposed to describe the diffusion mechanism of the internal oxidization and sulfidation behaviour.     

Cytocompatibility and mechanical properties of novel porous 316 L stainless steel

Novel 316 L stainless steel (SS) foam with 85% porosity and an open pore diameter of 70–440 μm was developed for hard tissue application. The foam sheet with a 200-μm diameter had superior cell proliferation and penetration as identified through in vitro experiments. Calcification of human osteosarcoma cells in the SS foam was observed. Multi-layered foam preparation is a potential alternative technique that satisfies multi-functional requirements such as cell penetration and binding strength to the solid metal. In tensile tests, Young's modulus and the strength of the SS foam were 4.0 GPa and 11.2 MPa respectively, which is comparable with human cancellous bone.     

Risk assessment in ramps for heavy vehicles—A French study

This paper presents the results of a study dealing with the risk for heavy vehicles in ramps. Two approaches are used. On one hand, statistics are applied on several accidents databases to detect if ramps are more risky for heavy vehicles and to define a critical value for longitudinal slope. χ² test confirmed the risk in ramps and statistical analysis proved that a longitudinal slope superior to 3.2% represents a higher risk for heavy vehicles. On another hand, numerical simulations allow defining the speed profile in ramps for two types of heavy vehicles (tractor semi-trailer and 2-axles rigid body) and different loads. The simulations showed that heavy vehicles must drive more than 1000 m on ramps to reach their minimum speed. Moreover, when the slope is superior to 3.2%, tractor semi-trailer presents a strong decrease of their speed until 50 km/h. This situation represents a high risk of collision with other road users which drive at 80–90 km/h. Thus, both methods led to the determination of a risky configuration for heavy vehicles: ramps with a length superior to 1000 m and a slope superior to 3.2%. An application of this research work concerns design methods and guidelines. Indeed, this study provides threshold values than can be used by engineers to make mandatory specific planning like a lane for slow vehicles.     

Non-isothermal flow of a power law fluid past a rectangular obstacle (of aspect ratio 1 × 2) in a channel: Drag and heat transfer

A two-dimensional numerical study has been carried out to investigate the drag and Nusselt number characteristics under forced convection conditions between a streaming power law liquid and a rectangle (with its longer side aligned with the direction of flow) placed symmetrically between two solid walls. In particular, the values of the individual and total drag coefficients, and of the Nusselt number are obtained as functions of the flow behaviour index (1.4 ⩾ n ⩾ 0.5), of Reynolds number (5 ⩽ Re ⩽ 40) and of the Peclet number (5 ⩽ Pe ⩽ 400) for a fixed value of the blockage ratio (1/8). Within these ranges of kinematic and rheological conditions, the drag and Nusselt number show only fair to moderate deviation from the corresponding Newtonian values at the same values of the Reynolds and Peclet numbers. Qualitatively speaking, the shear-thinning behaviour (n < 1) augments the drag and heat transfer while the shear-thickening behaviour (n > 1) causes both the drag and heat transfer to drop below the corresponding Newtonian values. The power-law fluid behaviour does not seem to alter the streamline, isovorticity and isotherm plots in a significant manner, except for the fact that the shear-thinning behaviour not only delays the formation of a visible wake but the resulting wake is also somewhat shorter than that in a Newtonian fluid. The shear thickening, on the other hand, has exactly the opposite influence on wake formation.     

Bentonite as a natural additive for lime and lime–metakaolin mortars used for restoration of adobe buildings

This work estimates the behaviour of mortars based on lime, seeking their application as renders of adobe walls. Mortars with binder:aggregate 1:3 volumetric ratio were prepared as is traditionally used in old buildings in central parts of Portugal.Due to specificity of the support, two clays, natural clay bentonite (5 wt.%) and artificial clay metakaolin (20 wt.%) were used as additives to lime mortar to prepare 3 types of blended mortars, besides the air lime reference mortar. Mortar prisms 4 × 4 × 16 cm were analysed to assess mechanical properties and salt resistance. Moreover, the mortars were placed in three ways on old adobes taken from demolished houses and their behaviour was verified by artificial accelerated ageing test. Lastly, mortars were applied on a wall made from traditional adobes, where panels were monitored and trials with adhesion strength and Karsten tubes have been conducted. The results obtained by comparison of the characteristics from all the experimental procedures reveal that mortar containing air lime and 5 wt.% of bentonite fulfils in the best way the requirements in its use as render of adobe buildings.     

In vitro wear assessments of fixed and mobile UHMWPE total knee replacement

This work discusses the wear behaviour of two different ultra-high-molecular-weight-polyethylene tibial component designs. Mobile and fixed bearings were tested on a knee wear simulator for 5 million cycles using bovine calf serum as lubricant. We correlated the wear results with the chemical characterisation of the investigated materials: Fourier Transformed Infra Red Spectroscopy analyses, Differential Scanning Calorimetry and cross-link density measurements were used to assess the chemical features of this polyethylene.Mobile and fixed polyethylene inserts showed a different wear behaviour: the mobile designs components showed lower weight losses than the fixed components (109 ± 6 mg and 163 ± 80 mg, respectively). Significant statistical differences were observed in wear rate (P = 0.035, Kolmogorov–Smirnov Test for two samples).From a molecular point of view, typical radiation-induced oxidation profiles were observed in all the tested polyethylene samples, but the overall degradation was more significant in the fixed bearing inserts and this is likely to play a role on the wear performances.     

In-vitro bioactivity,biocorrosion and antibacterial activity of silicon integrated hydroxyapatite/chitosan composite coating on 316 L stainless steel implants

A simple and effective ultrasonication method was applied for the preparation of 0, 0.4, 0.8, 1.0 and 1.6 wt% silicon substituted hydroxyapatite (HAp) (SH). The Ca/P ratio of the synthesised SH nanoparticles were in the range of 1.58–1.70. Morphological changes were noticed in HAp with respect to the amount of Si from 0 to 1.6 wt%. The morphology of the particles changed from spherical shape to rod-like morphology with respect to the amount of Si which was confirmed using transmission electron microscopy. X-ray diffraction studies confirm the formation of phase pure SH nanoparticles without any secondary phase. Chitosan (CTS) blended SH nanocomposites coating on surgical grade 316 L stainless steel (316 L SS) implant was made by spin coating technique. The surface of the coated implant was characterised using scanning electron microscopy which confirms the uniform coating without cracks and pores. The increased corrosion resistance of the 1.6 wt% of SH/CTS-coated SS implant in the simulated body fluid (SBF) indicates the long-term biostability of SH composite-coated ceramics in vitro than the 0 wt% SH/CTS. The testing of SH/CTS nanocomposites with gram-positive and gram-negative bacterial strains confirms that the antibacterial ability improves with the higher substitution of Si. In addition, formation of bone-like apatite layer on the SH/CTS-coated implant in SBF was studied through SEM analysis and it confirms the ability to increase the HAp formation on the surface of 1.0 wt% SH/CTS-coated 316 L SS implant.     

The role of parental alcohol consumption on driving under the influence of alcohol: Results from a longitudinal,nationally representative sample

PurposeMany studies have examined the role of peer and parental alcohol use on drinking behaviors among adolescents. Few studies, however, have examined parental influences on driving under the influence (DUI) of alcohol. The current study uses data from a longitudinal study to examine the role of parental alcohol use during adolescence on the risk for DUI among young adult men and women.MethodsData were derived from 9559 adolescents and young adults who participated in the National Longitudinal Study of Adolescent Health (Add Health) Waves I and III. Survey logistic regression was used to examine the relationship between multilevel risk and protective factors and self-reported DUI. Analyses were stratified by gender and frequency of parental alcohol consumption to understand the role of parental alcohol use on risk for DUI among their youth.ResultsRisk and protective factors for DUI were very similar among men and women. Parental alcohol use significantly predicted DUI among women (OR = 1.39, p < 0.01) and men (OR = 1.33, p < 0.05). When parents did not report alcohol use, peer alcohol use significantly increased risk for DUI for both women (OR = 1.26, p < 0.05) and men (OR = 1.31, p < 0.001). When parents reported alcohol use, however, peer alcohol use was not a significant independent predictor.ConclusionsFindings suggest remarkable similarities in risk and protective factors for DUI across gender groups. For men and women, parental alcohol consumption was a risk factor for DUI. Peers’ alcohol use predicted DUI only when parents did not use alcohol.     

Synthesis and structure determination of new open-framework chromium carboxylate MIL-105 or CrIII(OH)·{O2C–C6(CH3)4–CO2}·nH2O

Two new three-dimensional chromium(III) dicarboxylate, MIL-105 or Cr^III(OH)·{O₂C-C₆(CH₃)₄-CO₂}·nH₂O, have been obtained under hydrothermal conditions, and their structures solved using X-ray powder diffraction data. Both solids are structural analogs of the known Cr benzenedicarboxylate compound (MIL-53). Both contain trans corner-sharing CrO₄(OH)₂ octahedral chains connected by tetramethylterephthalate di-anions. Each chain is linked by the ligands to four other chains to form a three-dimensional framework with an array of 1D pores channels. The pores of the high temperature form of the solid, MIL-105ht, are empty. However, MIL-105ht re-hydrates at room temperature to finally give MIL-105lt with pores channels filled with free water molecules (lt: low temperature form; ht: high temperature form). The thermal behaviour of the two solids has been investigated using TGA. Crystal data for MIL-105ht: monoclinic space group C2/c with a = 19.653(1) Å, b = 9.984(1) Å, c = 6.970(1) Å, β = 110.67(1)° and Z = 4. Crystal data for MIL-105lt: orthorhombic space group Pnam with a = 17.892(1) Å, b = 11.165(1) Å, c = 6.916(1) Å and Z = 4.     

Synthesis,characterization, EPR and thermoluminescence properties of CaTiO3 nanophosphor

Calcium titanate (CaTiO₃) nanophosphors were synthesized by three different routes namely solution combustion (SC), modified solid-state reaction (MSS) and solid-state (SS) methods. Rietveld refinement studies revealed the presence of an orthorhombic structure with traces of CaCO₃. The crystallite sizes were found to be in the 43–45 nm range. TEM studies also confirm the nano size with well crystalline nature. EPR spectrum for SS method exhibits a broad resonance signal at g = 2.027 is attributed to [TiO₆]⁹⁻ center, whereas in MSS sample the resonance signals are attributed to surface electron and hole trapping sites. The TL behavior has been investigated for the first time using γ-irradiation. TL glow peak at 169 °C were recorded in CaTiO₃ prepared by SC, MSS and SS methods. The trapping parameters such as activation energy (E) and order of kinetics (b) were estimated using peak shape method and results are discussed in detail.     

Crystal structure and electrical properties of CaxWO3 (0.01 ≤ x ≤ 0.15) prepared by hybrid microwave synthesis

Calcium tungsten bronzes Ca_xWO₃ (0.01 ≤ x ≤ 0.15) were synthesized by hybrid microwave method from mixtures of CaO, WO₃ and tungsten powder. Single-phased samples can be obtained by microwave heating within 40 min. With the increase of calcium content, the crystal structure of Ca_xWO₃ transforms from orthorhombic (0.01 ≤ x ≤ 0.02) to tetragonal (0.03 ≤ x ≤ 0.11) and then to cubic (0.12 ≤ x ≤ 0.15). The average size of crystallites is in the range 1–5 μm. All samples show semiconductor behaviour in their temperature dependence of resistivity. The electrical conduction mechanism changes from variable-range hopping to the thermally activated mechanism when x > 0.12.     

Influence of defects on fatigue strength and failure mechanisms in the VHCF-region for quenched and tempered steel and nodular cast iron

Investigations are presented in this paper on quenched and tempered steel 42CrMoS4 from two batches, with two different tensile strengths (R_m = 1100 MPa, 1350 MPa) but with similar microstructure, and a nodular cast iron EN-GJS-900-2 (R_m = 930 MPa). Fatigue tests with smooth (K_t = 1) and notched (K_t = 1.75) specimens were performed at R = −1 and R = 0 up to the number of cycles N = 2·10⁹ in order to determine the fatigue strength behaviour and failure mechanisms, especially in the VHCF-region. Failure in smooth specimens often initiated at material defects such as oxides in the quenched and tempered steel and shrinkage holes in the nodular cast iron. Firstly, a fatigue strength analysis was performed that did not consider these defects. A possibility of analysis of experimental data including VHCF-results has been discussed. Next, a linear elastic fracture mechanics analysis was performed in order to describe the defect behaviour, assuming that the defects act like cracks. The results showed that there are lower limit or threshold values of the stress intensity factor range ΔK for crack propagation in both materials. Analysis of defects and defect distribution in run-out specimens confirmed this conclusion. From the comparison of the results with an S–N curve from the design code FKM-Guideline Analytical strength assessment of components, recommendations for design and assessment of components have been derived.     

The impact response of traditional and BMX-style bicycle helmets at different impact severities

Bicycle helmets reduce the frequency and severity of severe to fatal head and brain injuries in bicycle crashes. Our goal here was to measure the impact attenuation performance of common bicycle helmets over a range of impact speeds. We performed 127 drop tests using 13 different bicycle helmet models (6 traditional style helmets and 7 BMX-style helmets) at impact speeds ranging from 1 to 10 m/s onto a flat anvil. Helmets were struck on their left front and/or right front areas, a common impact location that was at or just below the test line of most bicycle helmet standards. All but one of the 10 certified helmet models remained below the 300 g level at an impact speed of 6 m/s, whereas none of the 3 uncertified helmets met this criterion. We found that the helmets with expanded polystyrene liners performed similarly and universally well. The single certified helmet with a polyurethane liner performed below the level expected by the Consumer Product Safety Commission (CPSC) standard at our impact location and the helmet structure failed during one of two supplemental tests of this helmet above the test line. Overall, we found that increased liner thickness generally reduced peak headform acceleration, particularly at higher impact speeds.     

The effects of visibility conditions,traffic density,and navigational challenge on speed compensation and driving performance in older adults

Research on how older drivers react to natural challenges in the driving environment is relevant for both the research on mental workload and that on age-related compensation. Older adults (M age = 70.8 years) were tested in a driving simulator to assess the impact of three driving challenges: a visibility challenge (clear day, fog), a traffic density challenge (low density, high density) and a navigational challenge (participants followed the road to arrive at their destination, participants had to use signs and landmarks). The three challenge manipulations induced different compensatory speed adjustments. This complicated interpretation of the other measures of driving performance. As a result, speed adjustment indices were calculated for each condition and participant and composite measures of performance were created to correct for speed compensation. (These speed adjustment indices correlated with vision test scores and subscales of the Useful Field of View^®.) When the composite measures of driving performance were analyzed, visibility × density × navigational challenge interactions emerged for hazard RT and SD of lane position. Effects were synergistic: the impact of the interaction of challenge variables was greater than the sum of independent effects. The directions of the effects varied depending on the performance measure in question though. For hazard RT, the combined effects of high-density traffic and navigational challenge were more deleterious in good visibility conditions than in fog. For or SD of lane position, the opposite pattern emerged: combined effects of high-density traffic and navigational challenge were more deleterious in fog than in clear weather. This suggests different aspects of driving performance tap different resources.     

High-temperature electrical resistivity and heat capacity studies on nano-crystalline geikielite

We report here for the first time the temperature dependence of the electrical resistivity and heat capacity of nano-crystalline MgTiO₃ geikielite of up to 1000 K. The temperature dependence of heat capacity of nano-crystalline geikielite expressed as C_p = 46.44(5) + 0.0502(2)T − 4.56 × 10⁶T² + 1.423 × 10³T^− 0.5 − 8.672 × 10^− 6T^− 2, where C_p = is specific heat expressed in J/mol. K and T is the temperature in K. Both the electrical resistivity and heat capacity behaviour show that the geikielite (both the natural and synthetic nano-crystalline samples) are stable and remains electrically insulating up to 1000 K.