Calculation of dynamic spinal ligament deformation

OBJECTIVE: Previous methods to determine spinal ligament deformation have included either custom-designed transducers or computational methods using rigid body transformation of kinematic data. Goals of the present study were to describe a computational methodology to determine dynamic deformations of an arbitrarily oriented ligament in a spine specimen and its associated errors. METHODS: Calculation of ligament deformation in a spinal segment with vertebral motion tracking flags utilized digital stereophotography, lateral neutral posture radiograph, and detailed quantitative anatomy to develop geometrical relationships between flag markers and ligament attachment points. A custom jig, consisting of two flags each with four markers, was constructed to quantify errors associated with computed ligament deformation, flag marker translation, and flag rotation. RESULTS: Average error in ligament deformation was dependent upon motion direction and ranged between 0.03 mm (SD 0.45 mm) and 0.28 mm (SD 0.18 mm). Average error for flag marker translation ranged between 0.02 mm (SD 0.14 mm) and 0.11 mm (SD 0.39 mm), and for flag rotation ranged between -0.06 degrees (SD 0.17 degrees ) and 0.07 degrees (SD 0.12 degrees ). CONCLUSIONS: Accuracy of the present technique was equivalent to or greater than that of previous methods. The present technique utilized relatively cost-effective digital stereophotography, and may be used to calculate strain in ligaments not readily accessible for transducer application. The methodology has wide-spread applicability for analyses of dynamic or static spinal or other ligament strains, and may be used to determine spinal canal and intervertebral foramen narrowing and area reduction.     

Predicting multiplanar cervical spine injury due to head-turned rear impacts using IV-NIC

OBJECTIVE: Intervertebral Neck Injury Criterion (IV-NIC) hypothesizes that dynamic three-dimensional intervertebral motion beyond physiological limit may cause multiplanar soft-tissue injury. Present goals, using biofidelic whole human cervical spine model with muscle force replication and surrogate head in head-turned rear impacts, were to: (1) correlate IV-NIC with multiplanar injury, (2) determine IV-NIC injury threshold at each intervertebral level, and (3) determine time and mode of dynamic intervertebral motion that caused injury. METHODS: Impacts were simulated at 3.5, 5, 6.5, and 8 g horizontal accelerations of T1 vertebra (n = 6; average age: 80.2 years; four male, two female donors). IV-NIC was defined at each intervertebral level and in each motion plane as dynamic intervertebral rotation divided by physiological limit. Three-plane pre- and post-impact flexibility testing measured soft-tissue injury; that is significant increase in neutral zone (NZ) or range of motion (RoM) at any intervertebral level, above baseline. IV-NIC injury threshold was average IV-NIC peak at injury onset. RESULTS: IV-NIC extension peaks correlated best with multiplanar injuries (P < 0.001): extension RoM (R = 0.55) and NZ (R = 0.42), total axial rotation RoM (R = 0.42) and NZ (R = 0.41), and total lateral bending NZ (R = 0.39). IV-NIC injury thresholds ranged between 1.1 at C0-C1 and C3-C4 to 2.9 at C7-T1. IV-NIC injury threshold times were attained between 83.4 and 150.1 ms following impact. CONCLUSIONS: Correlation between IV-NIC and multiplanar injuries demonstrated that three-plane intervertebral instability was primarily caused by dynamic extension beyond the physiological limit during head-turned rear impacts.     

我国环境监测体制改革探讨

本文分析了目前我国环境监测工作中普遍存在的体制不顺、职责不明、行政干预、重复监测、资源浪费、信息混乱等问题,提出监测机构垂直管理,调整监测职能,打破条块分割,整合社会监测资源,引入第三方检测的具体构想。     

Biosensors for pathogen surveillance

Biologists, chemists, and physicists are collaborating to develop highly sensitive and specific biosensors for pathogen detection in the food, healthcare, and environmental sectors. Those novel biosensors allow quick detection and are thus expected to solve the issues of the emergence of highly virulent or antibiotic-resistant pathogens. This article reviews different types of biosensors used for pathogen detection, classified based on the type of transducer used. Optical biosensors integrate labeled means, e.g., fluorophores, quantum dots, and carbon dots to overcome photobleaching. Surface plasmon resonance is also used for enhanced sensitivity. Mechanical biosensors with piezoelectric crystals and cantilevers are adapted for the detection of food pathogens without sample preparation or labels. Conventional methods using electrodes for the measurement of electrochemical changes with differential pulse voltammetry or impedance spectroscopy are fast and highly sensitive. Immunosensors are developed for pathogen detection at trace levels using sample enrichment, signal amplification, and new visual detection techniques.     

Cervical spine loads and intervertebral motions during whiplash

OBJECTIVE: To quantify the dynamic loads and intervertebral motions throughout the cervical spine during simulated rear impacts. METHODS: Using a biofidelic whole cervical spine model with muscle force replication and surrogate head and bench-top mini-sled, impacts were simulated at 3.5, 5, 6.5, and 8 g horizontal accelerations of the T1 vertebra. Inverse dynamics was used to calculate the dynamic cervical spine loads at the centers of mass of the head and vertebrae (C1-T1). The average peak loads and intervertebral motions were statistically compared (P < 0.05) throughout the cervical spine. RESULTS: Load and motion peaks generally increased with increasing impact acceleration. The average extension moment peaks at the lower cervical spine, reaching 40.7 Nm at C7-T1, significantly exceeded the moment peaks at the upper and middle cervical spine. The highest average axial tension peak of 276.9 N was observed at the head, significantly greater than at C4 through T1. The average axial compression peaks, reaching 223.2 N at C5, were significantly greater at C4 through T1, as compared to head-C1. The highest average posterior shear force peak of 269.5 N was observed at T1. CONCLUSION: During whiplash, the cervical spine is subjected to not only bending moments, but also axial and shear forces. These combined loads caused both intervertebral rotations and translations.     

Occurrence of pesticides and polychlorinated biphenyls in water of the Nile river at the estuaries of Rosetta and Damiatta branches,north of delta,Egypt

Abstract

A study was conducted from summer 1995 to summer 1997 to assess the seasonal occurrence of pesticide residues and other organic contaminants, polychlorinated biphenyls (PCBs), in water at the estuaries of Rosetta and Damiatta branches of the Nile river. The results indicated that organochlorine compounds (OCs) including HCB, lindane, p,p‘‐DDE, p,p‘DDD, p,p‘‐DDT, aroclor 1254 and aroclor 1260 were present in all the water samples at concentration levels ranging between 0.195–0.240, 0.286–0.352, 0.035–0.067, 0.019–0.033, 0.024–0.031, 0.390–0.70 and 0.166–0.330 μg/l, respectively. The levels of these compounds were higher in water of Damiatta branch than those found in water of Rosetta branch. Aldrin, dieldrin and endrin were not detected in all water samples. Only 4 compounds from 36 organophosphorus insecticides, fungicides and s‐triazine herbicides tested were detected in water samples collected during summer and autumn seasons from Rosetta branch. The concentration levels of these detected compounds, dimethoate, malathion, captan, and ametryne, ranged from 0.011 to 0.340 μg/l, respectively. Similar compounds during the same seasons as found in water of Rosetta branch were also detected in water of Damiatta branch except ametryne. The levels of the detected compounds (dimethoate, malathion and captan) ranged between 0.030 and 0.330 μg/l. The levels of detected organophosphorus insecticides, fungicides and s‐triazine herbicides were in the order: dimethoate > malathion > captan > ametryne.     

Intervertebral neck injury criterion for prediction of multiplanar cervical spine injury due to side impacts

OBJECTIVE: Intervertebral Neck Injury Criterion (IV-NIC) is based on the hypothesis that dynamic three-dimensional intervertebral motion beyond physiological limits may cause multiplanar injury of cervical spine soft tissues. Goals of this study, using a biofidelic whole human cervical spine model with muscle force replication and surrogate head in simulated side impacts, were to correlate IV-NIC with multiplanar injury and determine IV-NIC injury threshold for each intervertebral level. METHODS: Using a bench-top apparatus, side impacts were simulated at 3.5, 5, 6.5, and 8 g horizontal accelerations of the T1 vertebra. Pre- and post-impact flexibility testing in three-motion planes measured the soft tissue injury, i.e., significant increase (p < 0.05) in neutral zone (NZ) or range of motion (RoM) at any intervertebral level, above corresponding physiological limit. RESULTS: IV-NIC in left lateral bending correlated well with total lateral bending RoM (R = 0.61, P < 0.001) and NZ (R = 0.55, P < 0.001). Additionally, the same IV-NIC correlated well with left axial rotation RoM (R = 0.50, P < 0.001). IV-NIC injury thresholds (95% confidence limits) varied among intervertebral levels and ranged between 1.5 (0.6-2.4) at C3-C4 and 4.0 (2.4-5.7) at C7-T1. IV-NIC injury threshold times were attained beginning at 84.5 ms following impact. CONCLUSIONS: Present results suggest that IV-NIC is an effective tool for determining multiplanar soft tissue neck injuries by identifying the intervertebral level, mode, time, and severity of injury.