How to identify which patients with asymptomatic carotid stenosis could benefit from endarterectomy or stenting

Offering routine carotid endarterectomy (CEA) or carotid artery stenting (CAS) to patients with asymptomatic carotid artery stenosis (ACS) is no longer considered as the optimal management of these patients. Equally suboptimal, however, is the policy of offering only best medical treatment (BMT) to all patients with ACS and not considering any of them for prophylactic CEA. In the last few years, there have been many studies aiming to identify reliable predictors of future cerebrovascular events that would allow the identification of patients with high-risk ACS and offer a prophylactic carotid intervention only to these patients to prevent them from becoming symptomatic. All patients with ACS should receive BMT. The present article will summarise the evidence suggesting ways to identify these high-risk asymptomatic individuals, namely: (1) microemboli detection on transcranial Doppler, (2) plaque echolucency on Duplex ultrasound, (3) progression in the severity of ACS, (4) silent embolic infarcts on brain CT/MRI, (5) reduced cerebrovascular reserve, (6) increased size of juxtaluminal hypoechoic area, (7) identification of intraplaque haemorrhage using MRI and (8) carotid ulceration. The evidence suggests that approximately 10%-15% of patents with asymptomatic stenosis might benefit from intervention; this will become more clear after publication of ongoing studies comparing stenting or endarterectomy with best medical therapy. In the meantime, no patient should be offered intervention unless there is evidence of high risk of ipsilateral stroke, from modalities such as those discussed here

Mjerenje vremena poluraspada 8Li

The β-decay half-life of 8Li has been measured along with in a β-NMR experiment, using thermal 8Li atoms adsorbed in ultra high vacuum on a silicon single crystal surface. A special hardware-based scaler electronics was used to circumvent part of the dead time corrections. The half-life is found to be (839.60 ± 1.06) ms, in accordance with previous experiments.Mjerili smo vrijeme poluraspada u β-raspadu 8Li (uz eksperiment β-NMR) rabeći termičke 8Li atome koji su bili adsorbirani na površini monokristala Si u ultravisokom vakuumu. Primijenili smo poseban elektronički brojački sustav radi izbjegavanja dijela popravki za mrtvo vrijeme. Ishod za vrijeme poluraspada je (839.60 ± 1.06) ms, i on je u skladu s ranijim mjerenjima

Effective passivation of crystalline silicon surfaces by ultrathin atomic-layer-deposited TiOx layers

We characterize the surface passivation properties of ultrathin titanium oxide (TiOx) films deposited by atomic layer deposition (ALD) on crystalline silicon by means of carrier lifetime measurements. We compare different silicon surface treatments prior to TiOx deposition, such as native silicon oxide (SiOy), chemically grown SiOy and thermally grown SiOy. The best passivation quality is achieved with a native SiOy grown over 4 months and a TiOx layer thickness of 5 nm, resulting in an effective lifetime of 1.2 ms on 1.3 Ωcm p-type float-zone silicon. The measured maximum lifetime corresponds to an implied open-circuit voltage (iVoc) of 710 mV. For thinner TiOx layers the passivation quality is reduced, however, samples passivated with only 2 nm of TiOx still show a lifetime of 612 μs and an iVoc of 694 mV. The contact resistivity of the TiOx including the SiOy interlayer between the silicon wafer and the TiOx is below 0.8 Ωcm2. The combination of excellent surface passivation and low contact resistivity has the potential for silicon solar cells with efficiencies exceeding 26%

Mechanisms to explain the poor results of carotid artery stenting (CAS) in symptomatic patients to date and options to improve CAS outcomes

BackgroundCarotid artery stenting (CAS) is considered by many as an alternative to carotid endarterectomy (CEA) for the management of carotid artery stenosis. However, recent trials demonstrated inferior results for CAS in symptomatic patients compared with CEA. We reviewed the literature to evaluate the appropriateness of CAS for symptomatic carotid artery stenosis and to determine the pathogenetic mechanism(s) associated with stroke following the treatment of such lesions. Based on this, we propose steps to improve the results of CAS for the treatment of symptomatic carotid stenosis.MethodsPubMed/Medline was searched up to March 25, 2010 for studies investigating the efficacy of CAS for the management of symptomatic carotid stenosis. Search terms used were “carotid artery stenting,” “symptomatic carotid artery stenosis,” “carotid endarterectomy,” “stroke,” “recurrent carotid stenosis,” and “long-term results” in various combinations.ResultsCurrent data suggest that CAS is not equivalent to CEA for the treatment of symptomatic carotid stenosis. Differences in carotid plaque morphology and a higher incidence of microemboli and cerebrovascular events during and after CAS compared with CEA may account for these inferior results.ConclusionsCurrently, most symptomatic patients are inappropriate candidates for CAS. Improved CAS technology referable to stent design and embolic protection strategies may alter this conclusion in the future