ABSTRACT
Objective To establish a valid human head-neck model and ballistic helmet model, and analyze biomechanical responses of the cervical spine under bullet impacts on ballistic helmet with different weights. Methods A uniformly distributed weight of 2 kg was applied on the helmet (1.24 kg), and bullet impacts from frontal, lateral and crown directions at the speed of 450 m/s were considered to obtain the mechanical response of human vertebrae. Results The stress of the cervical spine was significantly higher than that of the skull under bullet impacts, and the stress of C3 segment was the largest, indicating that the cervical spine was more vulnerable than the head during bullet impacts under the protection of ballistic helmet. When the weight of helmet attachment was not considered, the maximum stress of the cervical spine under lateral impact was 2.58% higher than that under frontal and crown impacts. The frontal impact led to the greatest damage to the head, with an increase of 59.4% in head stress. When the weight of helmet attachment was considered, a lager helmet weight would cause a more serious spine injure. When the helmet weight was increased from 1.24 kg to 3.24 kg, the crown impact led to the greatest damage to the cervical spine, with an increase of 12.98% in cervical stress compared with impacts from other directions. Conclusions Lightweight should be considered in the design of ballistic helmet, and the research findings provide scientific references for the design of ballistic helmet.
ABSTRACT
Objective To establish a valid human head-neck model and ballistic helmet model, and analyze biomechanical responses of the cervical spine under bullet impacts on ballistic helmet with different weights. Methods A uniformly distributed weight of 2 kg was applied on the helmet (1.24 kg), and bullet impacts from frontal, lateral and crown directions at the speed of 450 m/s were considered to obtain the mechanical response of human vertebrae. Results The stress of the cervical spine was significantly higher than that of the skull under bullet impacts, and the stress of C3 segment was the largest, indicating that the cervical spine was more vulnerable than the head during bullet impacts under the protection of ballistic helmet. When the weight of helmet attachment was not considered, the maximum stress of the cervical spine under lateral impact was 2.58% higher than that under frontal and crown impacts. The frontal impact led to the greatest damage to the head, with an increase of 59.4% in head stress. When the weight of helmet attachment was considered, a lager helmet weight would cause a more serious spine injure. When the helmet weight was increased from 1.24 kg to 3.24 kg, the crown impact led to the greatest damage to the cervical spine, with an increase of 12.98% in cervical stress compared with impacts from other directions. Conclusions Lightweight should be considered in the design of ballistic helmet, and the research findings provide scientific references for the design of ballistic helmet.
ABSTRACT
<p><b>OBJECTIVE</b>To study the possible relationship between the mitochondrial DNA (mtDNA) mutation and spinocerebellar ataxia type 3 (SCA3).</p><p><b>METHODS</b>Genetic diagnosis of SCA3 was made by detecting the CAG-repeat expansion of MJD1 gene using PCR and DNA sequencing techniques. Then polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) was performed to analyze the mitochondrial DNA extracted from peripheral white blood cells from 43 patients and presymptomatic individuals diagnosed according to CAG expansion, and 30 healthy individuals. Mitochondrial DNAs of subjects with abnormal SSCP were sequenced.</p><p><b>RESULTS</b>A new mitochondrial DNA deletion of 9 bp at mtDNA 8282-8290 was identified in 1 patient and 3 presymptomatic individuals.</p><p><b>CONCLUSION</b>A new deletion mutation of mitochondrial DNA in 1 SCA3 patient and 3 presymptomatic individuals is reported.</p>
Subject(s)
Adolescent , Adult , Aged , Child , Child, Preschool , Female , Humans , Male , Middle Aged , Base Sequence , Case-Control Studies , DNA Mutational Analysis , DNA, Mitochondrial , Genetics , Machado-Joseph Disease , Genetics , Molecular Sequence Data , Mutation , Polymerase Chain Reaction , Polymorphism, Single-Stranded Conformational , Sequence DeletionABSTRACT
Objective To study the gene mutation of the spinocerebellar ataxia(SCA) types 1～3 in the patients with primary dystonia.Methods The CAG triplet repeat expansion of SCA1～3 were detected with the polymerase chain reaction(PCR) in two patients with primary dystonia(father and son) and their 21 health family members.Results The two patients with primary dystonia were found to have the gene mutation of SCA3,the CAG repeat were 80 and 75 respectively.The gene mutations of SCA1,2 were not found in the two patients.The gene mutation of SCA1～3 were not found in the 21 family members.Conclusions The patients with primary dystonia have the gene mutation of SCA3.The gene mutations of SCA3 may be relatived to the incidence of primary dystonia.
