Fall Height Research Articles

Low-Risk Criteria for Pelvic Radiography in Pediatric Blunt Trauma Patients

The American College of Surgeons recommends that any patient with blunt trauma undergoes radiographic evaluation, including a radiograph of the pelvis. Studies have questioned the use of such routine pelvic radiographs (PXR) in pediatrics. Selective elimination of PXR would save time, money and unshielded radiation exposure to the gonads. To determine if a defined set of historical and clinical factors could predict low risk for pelvic fracture and incorporate these factors into a clinical decision guideline. A retrospective chart review of all blunt trauma patients 25 years or younger in whom a PXR was obtained from January 2002 to June 2006 presenting to an urban level 1 trauma center. A total of 579 patients underwent 580 trauma evaluations. Variables including sex, mechanism of injury, Glascow Coma Score, Pediatric Trauma Score, fall height, lower extremity injury, blood on rectal examination, blood at meatus, and clinical need for computed tomography (CT) were compared with outcomes of pelvic fracture and pelvic fracture requiring surgical intervention. There were 22 pelvic fractures identified, resulting in a fracture rate of 4%. The negative predictive value for pelvic fracture was 98.3% (95% confidence interval [95% CI], 96.9%-99.2%) if no lower extremity injury was present, 99% (95% CI, 98.2%-99.6%) if physical examination of the pelvis was normal, and 99.5% (95% CI, 98.6%-99.9%) if there was no need for abdominopelvic CT. The negative predictive value was 100% (95% CI, 98.8%-100%) if any one of these 3 factors is present. Using the clinical findings of (1) lack of lower extremity injury, (2) lack of an abnormal physical examination of the pelvis, and (3) no need for abdominopelvic CT, pelvic fracture can be reliably excluded. Pelvic radiography can be eliminated in the evaluation of these patients, potentially decreasing time expenditure, radiation exposure, and cost.

Patients with pelvic fractures due to falls: A paradigm that contributed to autopsy-based audit of trauma in Greece.

BackgroundEvaluation of the pelvic fractures (PFx) population in auditing effective components of trauma care is the subject of this study.MethodsA retrospective, case-control, autopsy-based study compared a population with PFx to a control-group using a template with trauma outcome variables, which included demographics, ICD-9, intention, mechanisms, toxicology, Abbreviated Injury Scale (AIS-90), Injury Severity Score (ISS), causes of haemorrhage, comorbidity, survival time, pre-hospital response, in hospital data, location of death, and preventable deaths.ResultsOf 970 consecutive patients with fatal falls, 209 (21.5%) had PFx and constituted the PFx-group while 761 (78.5%) formed the control-group.Multivariate analysis showed that gender, age, intention, and height of fall were risk factors for PFx. A 300% higher odds of a psychiatric history was found in the PFx-group compared to the control-group (p < 0.001).The median ISS was 50 (17-75) for the PFx-group and 26 (1-75) for the control-group (p < 0.0001). There were no patients with an ISS less than 16 in the PFx group.Associated injuries were significantly more common in the PFx-group than in the control-group. Potentially preventable deaths (ISS < 75) constituted 78% (n = 163) of the PFx-group. The most common AIS3-5 injuries in the potentially preventable subset of patients were the lower extremities in 133 (81.6%), thorax in 130 (79.7%), abdomen/pelvic contents in 99 (60.7%), head in 95 (58.3%) and the spine in 26 (15.9%) patients.A subset of 126 (60.3%) potentially preventable deaths in the PFx-group had at least one AIS-90 code other than the PFx, denoting major haemorrhage. Deaths directly attributed to PFx were limited to 6 (2.9%).The median survival time was 30 minutes for the PFx-group and 20 hours for the control-group (p < 0.001). For a one-group increment in the ISS-groups, the survival rates over the post-traumatic time intervals were reduced by 57% (p < 0.0001).Pre-hospital mortality was significantly higher in the PFx-group i.e. 70.3% of the PFx-group versus 42.7% of the control-group (p < 0.001).ConclusionsThe PFx-group shared common causative risk factors, high severity and multiplicity of injuries that define the PFx-group as a paradigm of injury for audit. This reduced sample of autopsies substantially contributed to the audit of functional, infrastructural, management and prevention issues requiring transformation to reduce mortality.

Alcohol and psychoactive drugs increased the pre-hospital mortality in 655 fall-related fatalities in Greece: A call for management protocols

IntroductionThe frequency of alcohol and psychoactive drugs in fall-related fatalities and their effect on type, severity of injury and location of death constitute the subjects of this study. MethodsA retrospective analysis based on autopsy and toxicology compared demographics, location of injury; intention for the injury, height of fall, Abbreviated Injury Scale – 90 (AIS-90), post-mortem Injury Severity Score (ISS), and location of death. ResultsAmongst 655 fall-related fatalities screened for alcohol and psychoactive drugs 123 (18.8%) were classified in the positive toxicology group (PTG) and the remaining in the negative toxicology group (NTG).The median ages were 48 (16–94) years for the PTG and 62 (12–96) years for the NTG.The screened represent 31% of the national toll. The median height of fall was 7m and the median blood alcohol concentration was 53 (1.5–630)mg/dl.Males were more likely to be included in the PTG than females (21.6 versus 13.6%; p=0.014) as were the aged between 11 and 60 years.The odds of severe (AIS≥3) head, thoracic, abdominal, extremity, and spine injuries were not influenced by toxicology status.Fatalities of the PTG were as likely to have severe trauma (ISS≥16) as were fatalities of the NTG (93.5 versus 90.8%; p=0.34).There was no significant difference of ISS between PTG (median ISS 43, range: 6–75) and NTG (median ISS 35, range: 3–75).Nevertheless, 76.4% of the subjects of the PTG died during the pre-hospital stage of care compared to 60.5% of the subjects of the NTG, which was highly significant (or=2.80, p=0.001) after controlling for confounders as age, gender, intention for injury, height of fall, and ISS. ConclusionsIn fall related trauma, alcohol and psychoactive drugs increased the risk of death during the pre-hospital stage by 2.80 times. This is strong evidence that specific protocols for their early management should be instituted.

Characteristics of Falls and Risk of Injury in Children Younger Than 2 Years

Although many studies have shown that short falls by children rarely result in serious injury, no recent study in the United States has assessed the prevalence and the characteristics of such falls. Because the history of a short fall often is given in the instance of suspected child abuse, data addressing the characteristics, the frequency, and the severity of such falls would assist in abuse investigations. Anonymous questionnaires were distributed at primary care offices to parents of children younger than 5 years. Parents answered a series of questions regarding any falls their children had sustained before the age of 2 years. Information gathered included the age of the child at the time of the fall, the details about the fall, the medical attention sought, and any injuries sustained. We received a total of 307 eligible surveys. There were 209 falls reported for 122 children. Only 24% of those children sustained any injury as a result of the fall. Most (85%) of the children who sustained injuries had a bruise or a bump. Of the 20% (40 children) who were brought for medical care, only 13 children received medical treatment. The most severe injuries were in 2 children who sustained concussions; only 4 children had permanent injury (cutaneous scars). Children who fell on a hard surface were 6 times more likely to have an injury compared with children who fell on a soft surface (P = 0.001) In addition, for every 1 unit increase in fall height, risk of injury increased by a factor of 2.3. In short falls, ground surface and fall height were significant predictors of injury risk. The results of this study also support the opinion that short falls rarely cause injury. Therefore, a history of a short fall in a seriously injured child should raise the suspicion of child abuse.

Salmon jumping: behavior, kinematics and optimal conditions, with possible implications for fish passageway design

Behavioral and kinematic properties and capacities of wild migratory salmonid fishes swimming upstream and jumping up waterfalls generally have played only minor roles in the design and construction of passageways intended to help these fishes get past dams and other human-made obstacles blocking their movements. This paper reports the results of an experimental study of relevant behavioral and kinematic properties of adult kokanee salmon (Oncorhynchus nerka) jumping up waterfalls as they migrate upstream. We used a portable, adjustable apparatus to study in the field fish responding to artificial waterfalls under a range of flow conditions. We observed fish under conditions of varying water flow rates, pool depths, fall heights and fall angles. We analyzed digital video recordings of their behaviors. Kokanee salmon spontaneously jump up waterfalls within a relatively narrow range of conditions, including low flow speeds, near vertical angles and pool depth to fall height ratios near 1.0. Preferred values for each parameter are, to some extent, dependent on other parameters. In contrast to previous misconceptions, jumping behavior is initiated by running S-start accelerations from beneath the boils formed in the plunge pools below waterfalls, as opposed to C-start standing jumps from the surface. S-starts are immediately followed by burst swimming to the point of takeoff at the surface. These results can contribute to an improved basis for developing designs of fish passageways that may ultimately make them more effective and efficient.

Trampoline-related injuries in children: a preliminary biomechanical model of multiple users

BackgroundThe recent popularity of domestic trampolines has seen a corresponding increase in injured children. Most injuries happen on the trampoline mat when there are multiple users present. This study sought...

Biomechanics of the toddler head during low-height falls: an anthropomorphic dummy analysis

Falls are the most common environmental setting for closed head injuries in children between 2 and 4 years of age. The authors previously found that toddlers had fewer skull fractures and scalp/facial soft-tissue injuries, and more frequent altered mental status than infants for the same low-height falls (<or=3 ft). To identify potential age-dependent mechanical load factors that may be responsible for these clinical findings, the authors created an instrumented dummy representing an 18-month-old child using published toddler anthropometry and mechanical properties of the skull and neck, and they measured peak angular acceleration during low-height falls (1, 2, and 3 ft) onto carpet pad and concrete. They compared these results from occiput-first impacts to previously obtained values measured in a 6-week-old infant dummy. Peak angular acceleration of the toddler dummy head was largest in the sagittal and horizontal directions and increased significantly (around 2-fold) with fall height between 1 and 2 ft. Impacts onto concrete produced larger peak angular accelerations and smaller impact durations than those onto carpet pad. When compared with previously measured infant drops, toddler head accelerations were more than double those of the infant from the same height onto the same surface, likely contributing to the higher incidence of loss of consciousness reported in toddlers. Furthermore, the toddler impact forces were larger than those in the infant, but because of the thicker toddler skull, the risk of skull fracture from low-height falls is likely lower in toddlers compared with infants. If similar fracture limits and brain tissue injury thresholds between infants and toddlers are assumed, it is expected that for impact events, the toddler is likely less vulnerable to skull fracture but more vulnerable to neurological impairment compared with the infant.

Analysis of factors influencing deflection in sandwich panels subjected to low-velocity impact

Fiber reinforced sandwich structures typically respond very poorly to transverse impact events. This paper is an attempt to investigate the impact response of sandwich panels subjected to low-velocity impact. Experimental investigations were carried out on the influence of three design factors: height of fall, core thickness, and impactor mass, which are the most relevant parameters to be considered for deflection. The study of behavior of the mentioned response was done by using Design of Experiments tool. Response surface methodology (RSM), a sequential experimentation strategy for model building, is used to model the response in order to determine the most significant factor among the influential factors. In this case, full factorial face-centered central composite design was chosen due to the number of factors and their levels in the study. The specimen consisted of face sheets made up of bi-woven glass fiber cloth with polyurethane foam as core material. The parametric analysis reveals that deflection increases steadily with an increase in the height of fall when compared with the impactor mass and the core thickness. The reason for this study is imperative for the next generation aircraft, marine, road, and rail vehicles with improved lightweight stiff materials that can absorb higher impact energy with higher resistance to deflection.

Fall arrest characteristics of a scissor lift

Problem Census of Fatal Occupational Injuries (CFOI) data indicate 306 aerial lift fatalities between 1992-2003. Seventy-eight of these fatalities specifically involved scissor lifts. Members of standards committees have requested that NIOSH conduct research to determine the effects of safety-control practices related to using fall-protection systems for scissor lifts. Method This research examined the structural and dynamic stability of a scissor lift subjected to fall arrest forces. This was accomplished by conducting drop tests from a scissor lift. Anchorage locations evaluated included manufacturer-supplied anchorage points on the scissor lift platform as well as mid-rail and top-rail locations. Results Preliminary drop tests determined that a 2400 lb maximum arrest force (MAF) could be generated by dropping 169 lb through a fall height of 36” using Nystron® rope as a lanyard. The scissor lift maintained structural and dynamic stability for all drop tests when fully extended and on an incline. Discussion Anchoring a fall arrest system to either the mid-rail or top-rail is not a recommended practice by the scissor lift manufacturer. Anchor points are provided on the platform floor of the scissor lift for this purpose. However, our results demonstrate that the mid-rail and top-rail absorb substantial energy from an arrested fall and may have potential as appropriate anchorage points. Impact to Industry Employers and workers should consider implementing fall arrest systems when using scissor lifts as part of their overall risk mitigation plan for fall injury prevention.

Epidemiology of balcony fall–related injuries, United States, 1990-2006

Background Falls from heights are common in urban areas in the United States. This study describes the epidemiology of balcony fall–related injuries requiring emergency department (ED) treatment among children and adults in the United States from 1990 through 2006. Methods In 2009, a retrospective analysis of data from the National Electronic Injury Surveillance System of the US Consumer Product Safety Commission was conducted to describe the epidemiology of balcony fall–related injuries. Results An estimated 86 500 (95% confidence interval [CI], 68 400-104 600) balcony fall–related injuries were treated in US hospital EDs from 1990 through 2006; 70% of cases were male; 63% were adults (≥18 years old); 94% of injury events occurred at home; 24% of patients were hospitalized; and 8 patients died. The rate of balcony fall–related injuries among children decreased significantly during 1990 to 2006 and was similar to that of adults by the end of the study period. Fall heights ranged from 5 to 87.5 ft. Structural failure of the balcony was involved in an estimated 5600 cases. Patients younger than 18 years were more likely to sustain a concussion/closed head injury (relative risk, 2.42; 95% CI, 1.84-3.18) or skull fracture (relative risk, 5.86; 95% CI, 2.58-13.30) than adults. Conclusions This is the first study of balcony fall–related injuries requiring emergency treatment using a nationally representative sample. Balcony falls are an important cause of injury in the United States. Age, male sex, and warm months of the year were associated with balcony fall–related injuries in our study population.

The predicted risk of head injury from fall-related impacts on to third-generation artificial turf and grass soccer surfaces: A comparative biomechanical analysis

The risk of soccer players sustaining mild traumatic brain injury (MTBI) following head impact with a playing surface is unclear. This study investigates MTBI by performing headform impact tests from varying heights onto a range of third-generation artificial turf surfaces. Each turf was prepared as per manufacturers specifications within a laboratory, before being tested immediately following installation and then again after a bedding-in period. Each turf was tested dry and when wetted to saturation. Data from the laboratory tests were compared to an in situ third-generation surface and a professional grass surface. The surface performance threshold was set at a head impact criterion (HIC) = 400, which equates to a 10% risk of the head impact causing MTBI. All six third-generation surfaces had a >10% risk of MTBI from a fall >0.77 m; the inferior surfaces required a fall from just 0.46 m to have a 10% MTBI risk. Wetting the artificial turf did not produce a statistically significant improvement (P > 0.01). The in situ third-generation playing surface produced HIC values within the range of bedded-in experimental values. However, the natural turf pitch was the superior performer – necessitating fall heights exceeding those achievable during games to achieve HIC = 400.

Retrospective analysis of fatal falls

Fatal falls are frequent and inhomogeneous events and affect every age. The criminalistic classification can often only be done on the basis of extensive investigations and the autopsy results. We retrospectively surveyed 291 cases of fatal falls on which a post-mortem examination had been carried out in the institutes of Forensic Medicine in Bonn and Greifswald. In large part, these cases are falls from height ( n = 123) and ground-level falls ( n = 122). These are compared to fatal falls down a stairs ( n = 46); the analysis is confined to injuries to the cranium. In ground-level falls the injury pattern in falls under the influence of alcohol differs from that of falls with no alcohol in the case history: all injuries are seen in higher relative frequency in casualties after the consumption of alcohol. In falls from height, the previous consumption of alcohol did not influence the injury pattern; the intracranial traumas are seen in decreasing frequency with increasing heights. The aim of this retrospective analysis is to present injury patterns and influencing factors like fall heights and alcohol for the different kinds of falls on the basis of our collective and to demonstrate similarities and differences between the subgroups.

Fatal accidental fall from height in infants and children: a study from South Delhi

One hundred and seventy-four deaths of infants and children due to accidental fall from height received from South Delhi for autopsy were studied during the 10-year period from January 1998 to December 2007 at the All India Institute of Medical Sciences, New Delhi. Data were analysed with regard to age, sex, location of fall, height of fall, pattern of injury, cause of death and seasonal variation. These cases represented approximately 22.56% of all deaths due to a fall from height and 1.31% of all medicolegal autopsies conducted during the period. There were 106 male (60.9%) and 68 female (39.1%) victims. Age-specific rate of fall showed that the highest rate was in toddlers (39.65%), followed by 26.43% each in preschool children and school-going children and the least in infants (7.47%). The head and face was the most frequently injured body region (93.67%) and the skull was the commonest bone fractured (59.19%). The most common cause of death was head injury (84.48%). Major fall sites in decreasing order of frequency were rooftop (38.50%), balcony (24.13%), household furniture (21.26%), staircase (6.89%), window (4.59%), wall (1.72%), rickshaw/bicycle (1.15%) and tree (0.57%). Most fatalities due to a fall from height were reported in the rainy season.

Intracranial Pressure and Experimental Model of Diffuse Brain Injury in Rats

In this study, we present a simple closed head injury model as a two-stage experiment. The height of the weight drop enables gradation of head trauma severity. The head injury device consists of three parts and there are three adjustable parameters-weight (100-600 g), height of fall (5-100 cm) and elasticity of the springs. Thirty male Wistar rats underwent monitoring of intracranial pressure with and without induction of the head injury. The weight drop from 45 to 100 cm led to immediate seizure activity and early death of the experimental animals. Severe head injury was induced from 40 cm weight drop. There was 50% mortality and all surviving rats had behavioral deterioration. Intracranial pressure was 9.3 +/- 3.76 mmHg. Moderate head injury was induced from 35 cm, mortality decreased to 20-40%, only half of the animals showed behavioral pathology and intracranial pressure was 7.6 +/- 3.54 mmHg. Weight drop from 30 cm caused mild head injury without mortality and neurological deterioration. Intracranial pressure was slightly higher compared to sham group- 5.5 +/- 0.74 mmHg and 2.9 +/- 0.81 mmHg respectively. This model is an eligible tool to create graded brain injury with stepwise intracranial pressure elevation.

Polyacrylamide Influence on Runoff and Sediment Detachment from a Silt Loam Soil

Alternative erosion control practices using polyacrylamide (PAM) have received increased attention. This study examines the effect of PAM applied to soil when rainfall intensity, rainfall kinetic energy (KE), and PAM applied all interact, influencing time to runoff (ROt), cumulative runoff (ROc), and cumulative soil detachment (Dc). This study evaluated the response of a silt loam soil to aqueous PAM rates of 0 (untreated control), 20, and 40 kg ha-1 when applied to an initially air-dried soil. A total of 0.5 L of reverse osmosis water was sprayed on all soil beds. Simulated rainfall using a gravity-fed rainfall simulator was applied from 13.8 and 0.8 m fall heights at application rates of 64, 96, and 128 mm h-1. Results show significant benefit, as evidenced by increased ROt and reduced ROc and Dc for 20 and 40 kg ha-1 PAM application levels. This was true for all rain rates and durations up to 75 min whether rainfall was at or less than terminal velocity. Polyacrylamide was less effective at increasing ROt as rain rate increased. There was no difference in ROt with 40 kg ha-1 PAM compared to 20 kg ha-1 PAM; thus, the greater PAM application rate would not be recommended for this purpose. The benefits of reduced ROc and Dc with PAM were always greater for lower KE-rain (29% lower KE) than for higher KE-rain at a given rainfall intensity. Although both PAM application levels reduced ROc, for high KE-rain, only application of 40 kg ha-1 was significantly less than the untreated soil. For low KE-rain, ROc was significantly less with either PAM application level. Results show that PAM alone has a limited effect for maintaining infiltration rate; therefore, it is likely that regions with fewer intense convective storms would receive greater benefit from an increased PAM application rate. The greatest benefit of PAM was in reduced Dc where justification can be made for using increased PAM rates for high KE-rain, as documented by significantly less Dc for 40 kg ha-1 PAM compared to 20 kg ha-1 PAM at rain rates of 96 and 128 mm h-1. Under these conditions, both PAM rates significantly reduced Dc compared to untreated soil. With low KE-rain, Dc was significantly less for 20 kg ha-1 PAM compared to the untreated control, but 40 kg ha-1 PAM did not significantly reduce Dc since soil loss was so small.

School Playground Surfacing and Arm Fractures in Children: A Cluster Randomized Trial Comparing Sand to Wood Chip Surfaces

The risk of playground injuries, especially fractures, is prevalent in children, and can result in emergency room treatment and hospital admissions. Fall height and surface area are major determinants of playground fall injury risk. The primary objective was to determine if there was a difference in playground upper extremity fracture rates in school playgrounds with wood fibre surfacing versus granite sand surfacing. Secondary objectives were to determine if there were differences in overall playground injury rates or in head injury rates in school playgrounds with wood fibre surfacing compared to school playgrounds with granite sand surfacing. The cluster randomized trial comprised 37 elementary schools in the Toronto District School Board in Toronto, Canada with a total of 15,074 students. Each school received qualified funding for installation of new playground equipment and surfacing. The risk of arm fracture from playground falls onto granitic sand versus onto engineered wood fibre surfaces was compared, with an outcome measure of estimated arm fracture rate per 100,000 student-months. Schools were randomly assigned by computer generated list to receive either a granitic sand or an engineered wood fibre playground surface (Fibar), and were not blinded. Schools were visited to ascertain details of the playground and surface actually installed and to observe the exposure to play and to periodically monitor the depth of the surfacing material. Injury data, including details of circumstance and diagnosis, were collected at each school by a prospective surveillance system with confirmation of injury details through a validated telephone interview with parents and also through collection (with consent) of medical reports regarding treated injuries. All schools were recruited together at the beginning of the trial, which is now closed after 2.5 years of injury data collection. Compliant schools included 12 schools randomized to Fibar that installed Fibar and seven schools randomized to sand that installed sand. Noncompliant schools were added to the analysis to complete a cohort type analysis by treatment received (two schools that were randomized to Fibar but installed sand and seven schools that were randomized to sand but installed Fibar). Among compliant schools, an arm fracture rate of 1.9 (95% confidence interval [CI] 0.04-6.9) per 100,000 student-months was observed for falls into sand, compared with an arm fracture rate of 9.4 (95% CI 3.7-21.4) for falls onto Fibar surfaces (p< or =0.04905). Among all schools, the arm fracture rate was 4.5 (95% CI 0.26-15.9) per 100,000 student-months for falls into sand compared with 12.9 (95% CI 5.1-30.1) for falls onto Fibar surfaces. No serious head injuries and no fatalities were observed in either group. Granitic sand playground surfaces reduce the risk of arm fractures from playground falls when compared with engineered wood fibre surfaces. Upgrading playground surfacing standards to reflect this information will prevent arm fractures. Current Controlled Trials ISRCTN02647424.

Model for Coiling and Meandering Instability of Viscous Threads

A numerical model is presented to describe both the transient and steady-state dynamics of viscous threads falling onto a plane. The steady-state coiling frequency w is calculated as a function of fall height H. In the case of weak gravity, w ~ H^{-1} and w ~ H are obtained for lower and higher fall heights respectively. When the effect of gravity is significant, the relation w ~ H^2 is observed. These results agree with the scaling laws previously predicted. The critical Reynolds number for coil-uncoil transition is discussed. When the gravity is weak, the transition occurs with hysteresis effects. If the plane moves horizontally at a constant speed, a variety of meandering oscillation modes can be observed experimentally. The present model also can describe this phenomenon. The numerically obtained state diagram for the meandering modes qualitatively agrees with the experiment.

Rockfall travel distance analysis by using empirical models (Solà d'Andorra la Vella, Central Pyrenees)

Abstract. The prediction of rockfall travel distance below a rock cliff is an indispensable activity in rockfall susceptibility, hazard and risk assessment. Although the size of the detached rock mass may differ considerably at each specific rock cliff, small rockfall (&lt;100 m3) is the most frequent process. Empirical models may provide us with suitable information for predicting the travel distance of small rockfalls over an extensive area at a medium scale (1:100 000–1:25 000). "Solà d'Andorra la Vella" is a rocky slope located close to the town of Andorra la Vella, where the government has been documenting rockfalls since 1999. This documentation consists in mapping the release point and the individual fallen blocks immediately after the event. The documentation of historical rockfalls by morphological analysis, eye-witness accounts and historical images serve to increase available information. In total, data from twenty small rockfalls have been gathered which reveal an amount of a hundred individual fallen rock blocks. The data acquired has been used to check the reliability of the main empirical models widely adopted (reach and shadow angle models) and to analyse the influence of parameters which affecting the travel distance (rockfall size, height of fall along the rock cliff and volume of the individual fallen rock block). For predicting travel distances in maps with medium scales, a method has been proposed based on the "reach probability" concept. The accuracy of results has been tested from the line entailing the farthest fallen boulders which represents the maximum travel distance of past rockfalls. The paper concludes with a discussion of the application of both empirical models to other study areas.

Experimental investigation of weir instability in main vessel cooling system of 1/4 FBR model

The 500 MWe Prototype Fast Breeder Reactor (PFBR) is under construction at Kalpakkam, India. The main vessel of this pool type reactor acts as the primary containment in the reactor assembly. In order to keep the main vessel temperature below creep range and to reduce high temperature embrittlement and also to ensure its healthiness for 40 years of reactor life, a small fraction of core flow (0.5 m 3/s) is sent through an annular space formed between the main vessel and a cylindrical baffle (primary thermal baffle) to cool the vessel. The sodium after cooling the main vessel overflows the primary baffle (weir shell) and falls into another concentric pool of sodium separated from the cold pool by the secondary thermal baffle and then returned to cold pool. The weir shell, where the overflow of liquid sodium takes place, is a thin shell prone to flow induced vibrations due to instability caused by sloshing and fluid–structure interaction. A similar vibration phenomenon was first observed during the commissioning of Super-Phenix reactor. In order to understand the phenomenon and provide necessary experimental back up to validate the analytical models, weir instability experiments were conducted in a 1:4 scale stainless steel (SS) model installed in a water loop. The experiments were conducted with flow rate and fall height as the varying parameters. The experimental results showed that the instability of the weir shell was caused due to fluid structure interaction. This paper discusses the details of the model, the modeling laws, similitude criteria adopted, analytical prediction, the experimental results and conclusion.

Epidemiology of Cheerleading Fall-Related Injuries in the United States

Over the past several decades, cheerleaders have been performing fewer basic maneuvers and more gymnastic tumbling runs and stunts. As the difficulty of these maneuvers has increased, cheerleading injuries have also increased. To describe the epidemiology of cheerleading fall-related injuries by type of cheerleading team and event. Prospective injury surveillance study. Participant exposure and injury data were collected from US cheerleading teams via the Cheerleading RIO (Reporting Information Online) surveillance tool. Athletes from 412 enrolled cheerleading teams who participated in official, organized cheerleading practices, pep rallies, athletic events, or cheerleading competitions. The numbers and rates of cheerleading fall-related injuries during a 1-year period (2006-2007) are reported. A total of 79 fall-related injuries were reported during the 1-year period. Most occurred during practice (85%, 67/79) and were sustained by high school cheerleaders (51%, 40/79). A stunt or pyramid was being attempted in 89% (70/79) of cases. Fall heights ranged from 1 to 11 ft (0.30-3.35 m) (mean = 4.7 + or - 2.0 ft [1.43 + or - 0.61 m]). Strains and sprains were the most common injuries (54%, 43/79), and 6% (5/79) of the injuries were concussions or closed head injuries. Of the 15 most serious injuries (concussions or closed head injuries, dislocations, fractures, and anterior cruciate ligament tears), 87% (13/15) were sustained while the cheerleader was performing on artificial turf, grass, a traditional foam floor, or a wood floor. The fall height ranged from 4 to 11 ft (1.22-1.52 m) for 87% of these cases (13/15). Cheerleading-related falls may result in severe injuries and even death, although we report no deaths in the present study. The risk for serious injury increases as fall height increases or as the impact-absorbing capacity of the surfacing material decreases (or both).