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Al–Zn–Mg–Cu alloys have remarkable plasticity and aging-hardening potential, while natural aging during storage and transportation dramatically increases the strength of the alloys and deteriorates the formability by generating massive high-density nano-scaled -clusters. In this study, a combination of pre-aging and regression heat treatment was employed to improve the negative effects of natural aging via regulating the distribution of precipitates and reducing the dissolving ratio. Atomic probe tomography and transmission electron microscope observations were mainly carried out to reveal the mechanism of microstructure evolution caused by heat treatments. The results reveal that the distributions of precipitate density and size vary with different pre-aging time, resulting in the differences in dissolving critical sizes and dissolving ratios of precipitates during regression heat treatments. For the limited pre-aging time, the dramatic dissolution of nano-scale clusters caused the surge of solute concentration in the matrix after regression heat treatments, resulting in considerable secondary precipitation of clusters during the subsequent natural aging process. With the increase of pre-aging time, the size and density of precipitates gradually increased, which reduced the dissolving ratio of precipitates during regression heat treatments. However, as the dissolving ratio declined from around 97.5 % (pre-aging for 0 h) to approx. 69.2 % (pre-aging for 18 h), the solute concentration in the matrix was lower than the secondary precipitation level of clusters, thus suppressing natural aging. Overall, this work provides a novel strategy to control the nature-aging behavior of Al–Zn–Mg–Cu alloys. Meanwhile, the correlation between microstructure evolution and mechanical properties under different heat treatments was systematically discussed.

IMPORTANCE: Guidelines recommend seizure prophylaxis for early posttraumatic seizures (PTS) after severe traumatic brain injury (TBI). Use of antiseizure medications for early seizure prophylaxis after mild or moderate TBI remains controversial. OBJECTIVE: To determine the association between seizure prophylaxis and risk reduction for early PTS in mild and moderate TBI. DATA SOURCES: PubMed, Google Scholar, and Web of Science (January 1, 1991, to April 18, 2023) were systematically searched. STUDY SELECTION: Observational studies of adult patients presenting to trauma centers in high-income countries with mild (Glasgow Coma Scale [GCS], 13-15) and moderate (GCS, 9-12) TBI comparing rates of early PTS among patients with seizure prophylaxis with those without seizure prophylaxis. DATA EXTRACTION AND SYNTHESIS: The Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) reporting guidelines were used. Two authors independently reviewed all titles and abstracts, and 3 authors reviewed final studies for inclusion. A meta-analysis was performed using a random-effects model with absolute risk reduction. MAIN OUTCOME MEASURES: The main outcome was absolute risk reduction of early PTS, defined as seizures within 7 days of initial injury, in patients with mild or moderate TBI receiving seizure prophylaxis in the first week after injury. A secondary analysis was performed in patients with only mild TBI. RESULTS: A total of 64 full articles were reviewed after screening; 8 studies (including 5637 patients) were included for the mild and moderate TBI analysis, and 5 studies (including 3803 patients) were included for the mild TBI analysis. The absolute risk reduction of seizure prophylaxis for early PTS in mild to moderate TBI (GCS, 9-15) was 0.6% (95% CI, 0.1%-1.2%; P = .02). The absolute risk reduction for mild TBI alone was similar 0.6% (95% CI, 0.01%-1.2%; P = .04). The number needed to treat to prevent 1 seizure was 167 patients. CONCLUSION AND RELEVANCE: Seizure prophylaxis after mild and moderate TBI was associated with a small but statistically significant reduced risk of early posttraumatic seizures after mild and moderate TBI. The small absolute risk reduction and low prevalence of early seizures should be weighed against potential acute risks of antiseizure medications as well as the risk of inappropriate continuation beyond 7 days.

Study Design Technical ReportObjective Cerebrospinal fluid (CSF) leak secondary to anterior osteophytes at the cervico-thoracic junction is a rare cause of intracranial hypotension. In this article we describe a technique for anterior repair of spontaneous ventral cerebrospinal fluid leaks in the upper thoracic spine.Methods In this technical report and operative video, we describe a 23-year-old male who presented with positional headaches and bilateral subdural hematoma. Dynamic CT myelography demonstrated a high flow ventral cerebrospinal fluid leak associated with a ventral osteophyte at the level of the T1-T2 disc space. Targeted blood patch provided only temporary improvement in symptoms. An anterior approach was chosen to remove the offending spur and micro-surgically repair the dural defect.Results The patient had complete resolution of his preoperative symptoms after primary repair.Conclusions In select cases, an anterior approach to the upper thoracic spine is effective to repair Type 1 cerebrospinal fluid leaks.