Neck Forces Research Articles

Determination of head/neck loads during manoeuvring acceleration

: Neck injury risk can increase when aircrew wear head mounted equipment while exposed to +Gz-loads. The effects of added weight and change in centre-of-gravity were determined during a centrifuge study using an instrumented manikin at Brooks AFB, Texas. Data included centrifuge Gz, head acceleration (three axes), and head and C7-TI pitch moment, compressive and shear forces. Helicopter (0.5G/s at +1.75 and +4Gz) and tactical aircraft (2Gk and 6GIs from +4 to 12Gz) accelerations were simulated (5s plateau at each level). Effect of added weights (up to overall 2.7kg) were measured in the forward pitch and lateral planes and tested using ANOVA. Seven real helmet systems were also tested. Head Gx and Gy increased with increasing +Gz-load, head weight, as CG shifted in the forward pitch plane, and onset rate. Head Gz was greatest when weight was distributed laterally. The resultant head and neck force and moment increased with increasing weight, pitch angle, and +Gz load. Neck forces and moments were significantly larger than those measured in the head.

Surface friction in near-vertex head and neck impact increases risk of injury

A computational head–neck model was developed to test the hypothesis that increases in friction between the head and impact surface will increase head and neck injury risk during near-axial impact. The model consisted of rigid vertebrae interconnected by assemblies of nonlinear springs and dashpots, and a finite element shell model of the skull. For frictionless impact surfaces, the model reproduced the kinematics and kinetics observed in near-axial impacts to cadaveric head–neck specimens. Increases in the coefficient of friction between the head and impact surface over a range from 0.0 to 1.0 resulted in increases of up to 40, 113, 9.8, and 43% in peak post-buckled resultant neck forces, peak moment at the occiput-C1 joint, peak resultant head accelerations, and HIC values, respectively. The most dramatic increases in injury-predicting quantities occurred for COF increases from 0.0 to 0.2, while further COF increases above 0.5 generally produced only nominal changes. These data suggest that safety equipment and impact environments which minimize the friction between the head and impact surface may reduce the risk of head and neck injury in near-vertex head impact.

The mechanism of defluidization of iron particles in a fluidized bed

To develop a qualitative model for the fluidization characteristics of cohesive iron particles, a systematic investigation was performed focusing attention on the mechanism of defluidization and the particle-to-particle neck growth. The neck growth rate determined by a scanning electron microscope (SEM) agreed fairly well with the prediction by the surface diffusion model. Below 1200 K, cohesion force was successfully explained by the neck growth model with the surface diffusion mechanism. The tensile strength of a neck measured by the diametral compression test was 20 MPa. This value agreed with the one obtained from the bed breaking velocity measurement. Defluidization criterion was discussed based on the balance between bubble buoyancy force and neck force. The prediction was validated experimentally.

Elective Irradiation of the Neck in Patients With Primary Carcinoma of the Head and Neck

The lack of a randomized prospective study of the efficacy of elective irradiation of the cervical lymph nodes in patients with primary carcinoma of the head and neck forces us to carefully study retrospective studies for the contemporary evaluation of this therapeutic concept. In spite of this shortcoming, it has become increasingly obvious that the contention that irradiation is unable to control cervical lymph node metastases is no longer tenable. Furthermore, increasing evidence from several centers indicates that lethal irradiation of occult, ie, microscopic, foci of carcinoma of epithelial origin which is deposited in cervical adenopathy is highly effective. In order to develop the argument for elective neck irradiation, it is pertinent to briefly review some of the evidence in favor of the ability of radiation therapy alone to control more obvious cervical metastatic disease. A previous communication²⁰analyzed the results of radiation therapy alone in 69 patients with