Timing and number of minor infections as risk factors for childhood arterial ischemic stroke.

ObjectiveIn a population-based case-control study, we examined whether the timing and number of minor infections increased risk of childhood arterial ischemic stroke (AIS).MethodsAmong 102 children with AIS and 306 age-matched controls identified from a cohort of 2.5 million children in a large integrated health care plan (1993-2007), we abstracted data on all medical visits for minor infection within the 2 years prior to AIS or index date for pairwise age-matched controls. We excluded cases of AIS with severe infection (e.g., sepsis, meningitis). Using conditional logistic regression, we examined the effect of timing and total number of minor infections on stroke risk.ResultsAfter adjusting for known pediatric stroke risk factors, the strongest association between infection and AIS was observed for infectious visits ≤3 days prior to stroke (odds ratio [OR] 12.1, 95% confidence interval [CI] 2.5, 57, p = 0.002). Respiratory infections represented 80% of case infections in that time period. Cases had more infectious visits, but not significantly so, for all time periods ≥4 days prior to the stroke. A greater cumulative number of infectious visits over 2 years did not increase risk of AIS.ConclusionsMinor infections appear to have a strong but short-lived effect on pediatric stroke risk, while cumulative burden of infection had no effect. Proposed mechanisms for the link between minor infection and stroke in adults include an inflammatory-mediated prothrombotic state and chronic endothelial injury. The transient effect of infection in children may suggest a greater role for a prothrombotic mechanism

Synthesizing Skyrmion Molecules in Fe-Gd Thin Films

We show that properly engineered amorphous Fe-Gd alloy thin films with perpendicular magnetic anisotropy exhibit room-temperature skyrmion molecules, or a pair of like-polarity, opposite-helicity skyrmions. Magnetic mirror symmetry planes present in the stripe phase, instead of chiral exchange, determine the internal skyrmion structure and the net achirality of the skyrmion phase. Our study shows that stripe domain engineering in amorphous alloy thin films may enable the creation of skyrmion phases with technologically desirable properties.Comment: 15 pages, 6 figures. Accepted for publication in Applied Physics Letter

Role of trauma and infection in childhood hemorrhagic stroke due to vascular lesions.

ObjectiveTrauma and infection have been postulated as "triggers" for hemorrhage from underlying brain vascular lesions (arteriovenous malformations, cavernous malformations, and aneurysms) in pediatric hemorrhagic stroke. We decided to perform an association study examining these environmental risk factors.MethodsIn this case-control study nested within the cohort of 2.3 million children enrolled in a Northern California integrated health plan (1993-2004), we identified childhood hemorrhagic stroke cases through electronic searches of diagnostic and radiology databases, confirmed through chart review. Three age- and facility-matched controls per case were randomly selected from the study population. Exposure variables were measured using medical records documented before stroke diagnosis. Main outcome measure was hemorrhagic stroke.ResultsOf 132 childhood, non-neonatal hemorrhagic stroke cases, 65 had underlying vascular lesions: 34 arteriovenous malformations, 16 cavernous malformations, and 15 aneurysms. A documented exposure to head and neck trauma in the prior 12 weeks was present in 3 cases (4.6%) with underlying vascular lesions, compared with no controls (p < 0.015). However, all 3 vascular lesions were aneurysms, and traumatic pseudoaneurysms were possible. Recent minor infection (prior 4 weeks) was present in 5 cases (7.7%) and 9 controls (4.6%) (p = 0.34).ConclusionsOur observed association between trauma and hemorrhagic stroke with a vascular lesion may be explained by traumatic pseudoaneurysms. Neither recent head or neck trauma nor infection appeared to be a "trigger" for pediatric hemorrhagic stroke due to underlying vascular malformations

Far-UV FUSE spectroscopy of the OVI resonance doublet in Sand2 (WO)

We present Far-Ultraviolet Spectroscopic Explorer (FUSE) spectroscopy of Sand 2, a LMC WO-type Wolf-Rayet star, revealing the OVI resonance P Cygni doublet at 1032-38A. These data are combined with HST/FOS ultraviolet and Mt Stromlo 2.3m optical spectroscopy, and analysed using a spherical, non-LTE, line-blanketed code. Our study reveals exceptional stellar parameters: T*=150,000K, v_inf=4100 km/s, log (L/Lo)=5.3, and Mdot=10^-5 Mo/yr if we adopt a volume filling factor of 10%. Elemental abundances of C/He=0.7+-0.2 and O/He=0.15(-0.05+0.10) by number qualitatively support previous recombination line studies. We confirm that Sand 2 is more chemically enriched in carbon than LMC WC stars, and is expected to undergo a supernova explosion within the next 50,000 yr.Comment: 17 pages, 4 figures, AASTeX preprint format. This paper will appear in a special issue of ApJ Letters devoted to the first scientific results from the FUSE missio

Disorder-induced microscopic magnetic memory

Using coherent x-ray speckle metrology, we have measured the influence of disorder on major loop return point memory (RPM) and complementary point memory (CPM) for a series of perpendicular anisotropy Co/Pt multilayer films. In the low disorder limit, the domain structures show no memory with field cycling--no RPM and no CPM. With increasing disorder, we observe the onset and the saturation of both the RPM and the CPM. These results provide the first direct ensemble-sensitive experimental study of the effects of varying disorder on microscopic magnetic memory and are compared against the predictions of existing theories.Comment: 4 pages, 4 figures. Accepted for publication in Physical Review Letters in Nov. 200

Recent trauma and acute infection as risk factors for childhood arterial ischemic stroke.

ObjectiveTrauma and acute infection have been associated with stroke in adults, and are prevalent exposures in children. We hypothesized that these environmental factors are independently associated with childhood arterial ischemic stroke (AIS).MethodsIn a case-control study nested within a cohort of 2.5 million children (≤19 years old) enrolled in an integrated health care plan (1993-2007), childhood AIS cases (n = 126) were identified from electronic records and confirmed through chart review. Age- and facility-matched controls (n = 378) were randomly selected from the cohort. Exposures were determined from review of medical records prior to the stroke diagnosis, or the same date for the paired controls; time windows were defined a priori.ResultsA medical encounter for head or neck trauma within the prior 12 weeks was an independent risk factor for childhood AIS (odds ratio [OR], 7.5; 95% confidence interval [CI], 2.9-19.3), present in 12% of cases (1.6% of controls). Median time from trauma to stroke was 0.5 days (interquartile range, 0-2 days); post hoc redefinition of trauma exposure (prior 1 week) was more strongly associated with AIS: OR, 39; 95% CI, 5.1-298. A medical encounter for a minor acute infection (prior 4 weeks) was also an independent risk factor (OR, 4.6; 95% CI, 2.6-8.2), present in 33% of cases (13% of controls). No single infection type predominated. Only 2 cases had exposure to trauma and infection.InterpretationTrauma and acute infection are common independent risk factors for childhood AIS, and may be targets for stroke prevention strategies