Robust electronic and tunable magnetic states in Sm2 NiMnO6ferromagnetic insulator.

Ferromagnetic insulators (FM-Is) are the materials of interest for the new generation quantum electronic applications. Here, we have investigated the physical observables depicting FM-I ground states in epitaxial Sm2NiMnO6(SNMO) double perovskite thin films fabricated under different conditions to realize the different level of Ni/Mn anti-site disorders (ASDs). The presence of ASDs immensely influence the characteristic magnetic and anisotropy behaviors in SNMO system by introducing short scale antiferromagnetic interactions in predominant long range FM ordered host matrix. Charge disproportion between cation sites, in the form of Ni2++ Mn4+→ Ni3++ Mn3+, causes mixed valency in both Ni and Mn species, which is found insensitive to ASD concentrations. Temperature dependent photo emission, photo absorption measurements duly combined with cluster model configuration interaction simulations, suggest that the eigenstates of Ni and Mn cations can be satisfactorily described as a linear combination of the unscreeneddnand screeneddn+1L̲(L̲: O 2phole) states. The electronic structure across the Fermi level (EF) exhibits closely spaced Ni 3d, Mn 3dand O 2pstates. From occupied and unoccupied bands, estimated values of the Coulomb repulsion energy (U) and ligand to metal charge transfer energy (Δ), indicate charge transfer insulating nature, where remarkable modification in Ni/Mn 3d-O 2phybridization takes place across the FM transition temperature. Existence of ASD broadens the Ni, Mn 3dspectral features, whereas the spectral positions are found to be unaltered. Hereby, present work demonstrates SNMO thin film as a FM-I system, where the FM state can be tuned by manipulating ASD in the crystal structure, while the I state remains intact.

Soft x-ray spectroscopies in liquids and at solid-liquid interface at BACH beamline at Elettra.

The beamline for advanced dichroism of the Istituto Officina dei Materiali-Consiglio Nazionale delle Ricerche, operating at the Elettra synchrotron in Trieste (Italy), works in the extreme ultraviolet-soft x-ray photon energy range with selectable light polarization, high energy resolution, brilliance, and time resolution. The beamline offers a multi-technique approach for the investigation of the electronic, chemical, structural, magnetic, and dynamical properties of materials. Recently, one of the three end stations has been dedicated to experiments based on electron transfer processes at the solid/liquid interfaces and during photocatalytic or electrochemical reactions. Suitable cells to perform soft x-ray spectroscopy in the presence of liquids and reagent gases at ambient pressure were developed. Here, we present two types of static cells working in transmission or in fluorescence yield and an electrochemical flow cell that allows us to carry out cyclic voltammetry in situ and electrodeposition on a working electrode and to study chemical reactions under operando conditions. Examples of x-ray absorption spectroscopy measurements performed under ambient conditions and during electrochemical experiments in liquids are presented.

Functional and radiological outcomes after bridging therapy versus direct thrombectomy in stroke patients with unknown onset: Bridging therapy versus direct thrombectomy in unknown onset stroke patients with 10-point ASPECTS.

BACKGROUND AND PURPOSE: The aim was to assess functional and radiological outcomes after bridging therapy (intravenous thrombolysis plus mechanical thrombectomy) versus direct mechanical thrombectomy (MT) in unknown onset stroke patients. METHODS: A cohort study was conducted on prospectively collected data from unknown onset stroke patients who received endovascular procedures at ≤6 h from symptom recognition or awakening time. RESULTS: Of the 349 patients with a 10-point Alberta Stroke Program Early Computed Tomography Score (ASPECTS), 248 received bridging and 101 received direct MT. Of the 134 patients with 6-9-point ASPECTS, 123 received bridging and 111 received direct MT. Each patient treated with bridging was propensity score matched with a patient treated with direct MT for age, sex, study period, pre-stroke disability, stroke severity, type of stroke onset, symptom recognition to groin time (or awakening to groin time), ASPECTS and procedure time. In the two matched groups with 10-point ASPECTS (n = 73 vs. n = 73), bridging was associated with higher rates of excellent outcome (46.6% vs. 28.8%; odds ratio 2.302, 95% confidence interval 1.010-5.244) and successful recanalization (83.6% vs. 63%; odds ratio 3.028, 95% confidence interval 1.369-6.693) compared with direct MT; no significant association was found between bridging and direct MT with regard to rate of symptomatic intracerebral hemorrhage (0% vs. 1.4%). In the two matched groups with 6-9-point ASPECTS (n = 45 vs. n = 45), no significant associations were found between bridging and direct MT with regard to rates of excellent functional outcome (44.4% vs. 31.1%), successful recanalization (73.3% vs. 76.5%) and symptomatic intracerebral hemorrhage (0% vs. 0%). CONCLUSIONS: Bridging at ≤ 6 h of symptom recognition or awakening time was associated with better functional and radiological outcomes in unknown onset stroke patients with 10-point ASPECTS.

The effect of long-range order on intermolecular interactions in organic semiconductors: zinc octaethyl porphyrin molecular thin film model systems.

In order to optimize the performance of devices based on porphyrin thin films it is of great importance to gain a physical understanding of the various factors which affect their charge transport and light-harvesting properties. In this work, we have employed a multi-technique approach to study vacuum deposited zinc octaethyl porphyrin (ZnOEP) thin films with different degrees of long-range order as model systems. An asymmetrical stretching of the skeletal carbon atoms of the porphyrin conformer has been observed and attributed to ordered molecular stacking and intermolecular interactions. For ordered films, a detailed fitting analysis of the X-ray absorption near edge structure (XANES) using the MXAN code establishes a symmetry reduction in the molecular conformer involving the skeletal carbon atoms of the porphyrin ring; this highlights the consequences of increased π-π stacking of ZnOEP molecules adopting the triclinic structure. The observed asymmetrical stretching of the π conjugation network of the porphyrin structure can have significant implications for charge transport and light harvesting, significantly influencing the performance of porphyrin based devices.

Flow-Diversion Treatment of Unruptured Saccular Anterior Communicating Artery Aneurysms: A Systematic Review and Meta-Analysis.

BACKGROUND: Flow diversion for anterior communicating artery aneurysms required further investigation. PURPOSE: Our aim was to analyze outcomes after treatment of anterior communicating artery aneurysms with flow-diverter stents. DATA SOURCES: A systematic search of 3 data bases was performed for studies published from 2008 to 2018. STUDY SELECTION: According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we included studies reporting anterior communicating artery aneurysms treated with flow diversion. DATA ANALYSIS: Random-effects meta-analysis was used to pool the following: aneurysm occlusion rate, complications, and factors influencing the studied outcomes. DATA SYNTHESIS: We included 14 studies and 148 unruptured saccular anterior communicating artery aneurysms treated with flow diversion. The long-term complete/near-complete (O'Kelly-Marotta C-D) occlusion rate was 87.4% (91/105; 95% CI, 81.3%-93.6%; I2 = 0%) (mean radiologic follow-up of 11 months). The treatment-related complication rate was 8.6% (14/126; 95% CI, 4%-13.1%; I2 = 0%), with morbidity and mortality rates of 3.5% (5/126; 95% CI, 2%-7%; I2 = 0%) and 2.5% (2/148; 95% CI, 0.3%-5%; I2 = 0%), respectively. Most complications were periprocedural (12/126 = 7%; 95% CI, 3%-11%; I2 = 0%). Thromboembolic events were slightly higher compared with hemorrhagic complications (10/126 = 6%; 95% CI, 2%-10%; I2 = 0% and 4/126 = 3%; 95% CI, 1%-6%; I2 = 0%). Branching arteries (A2 or the recurrent artery of Heubner) covered by the stent were occluded in 16% (7/34; 95% CI, 3.5%-28%; I2 = 25%) of cases. Pre- and posttreatment low-dose and high-dose of antiplatelet therapy was not associated with significantly different complication and occlusion rates. LIMITATIONS: We reviewed small and retrospective series. CONCLUSIONS: Flow diversion for unruptured saccular anterior communicating artery aneurysms appears to be an effective alternative treatment for lesions difficult to treat with coiling or microsurgical clipping. The treatment-related complication rate was relatively low. However, larger studies are needed to confirm these results.

Y-Stent-Assisted Coiling of Wide-Neck Bifurcation Intracranial Aneurysms: A Meta-Analysis.

BACKGROUND: Y-stent-assisted coiling for wide-neck intracranial aneurysms required further investigation. PURPOSE: Our aim was to analyze outcomes after Y-stent placement in wide-neck aneurysms. DATA SOURCES: We performed a systematic search of 3 data bases for studies published from 2000 to 2018. STUDY SELECTION: According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we included studies reporting Y-stent-assisted coiling of wide-neck aneurysms. DATA ANALYSIS: Random-effects meta-analysis was used to pool the following: aneurysm occlusion rate, complications, and factors influencing the studied outcomes. DATA SYNTHESIS: We included 27 studies and 750 aneurysms treated with Y-stent placement. The immediate complete/near-complete occlusion rate was 82.2% (352/468; 95% CI, 71.4%-93%; I2 = 92%), whereas the long-term complete/near-complete occlusion rate was 95.4% (564/598; 95% CI, 93.7%-97%; I2 = 0%) (mean radiologic follow-up of 14 months). The aneurysm recanalization rate was 3% (20/496; 95% CI, 1.5%-4.5%; I2 = 0%), and half of the recanalized aneurysms required retreatment. The treatment-related complication rate was 8.9% (63/614; 95% CI, 5.8%-12.1%; I2 = 44%). Morbidity and mortality after treatment were 2.4% (18/540; 95% CI, 1.2%-3.7%; I2 = 0%) and 1.1% (5/668; 95% CI, 0.3%-1.9%; I2 = 0%), respectively. Crossing Y-stent placement was associated with a slightly lower complication rate compared with the kissing configuration (56/572 = 8.4%; 95% CI, 5%-11%; I2 = 46% versus 4/30 = 12.7%; 95% CI, 3%-24%; I2 = 0%). Occlusion rates were quite comparable among Enterprise, Neuroform, and LVIS stents, whereas the Enterprise stent was associated with lower rates of complications (8/89 = 6.5%; 95% CI, 1.6%-11%; I2 = 0%) compared with the others (20/131 = 14%; 95% CI, 5%-26%; I2 = 69% and 9/64 = 11%; 95% CI, 3%-20%; I2 = 18%). LIMITATIONS: This was a small, retrospective series. CONCLUSIONS: Y-stent-assisted coiling yields high rates of long-term angiographic occlusion, with a relatively low rate of treatment-related complications. Y-stent placement with a crossing configuration appears to be associated with better outcomes. Although Y-configuration can be obtained using many types of stents with comparable occlusion rates, the Enterprise stent is associated with lower complication rates.

Electronic structure of ZrX2 (X = Se, Te).

The electronic structure of the ZrX2 (X = Se, Te) compounds has been studied using photoelectron, resonant photoelectron and X-ray absorption spectroscopy, theoretical calculations of the X-ray absorption spectra, and density of electronic states. It was found that the absorption spectra and valence band spectra are influenced by the chalcogen type. The results of the multiplet calculation of the Zr4+ atom show that the change in the splitting in the crystal field, which is described by the 10Dq parameter, is due to the change in the ratio of covalent and ionic contributions to the chemical bond. The resonance band near the Fermi level in the valence band spectra is observed for ZrTe2 in the Zr 3p-4d resonant excitation mode. The extent of photon energy indicates the charge localization on the Zr atom. Similar resonance band for ZrSe2 is absent; it indicates the presence of a gap at the Fermi level.

Graphene nanobubbles on TiO2 for in-operando electron spectroscopy of liquid-phase chemistry.

X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Absorption Spectroscopy (XAS) provide unique knowledge on the electronic structure and chemical properties of materials. Unfortunately this information is scarce when investigating solid/liquid interfaces and chemical or photochemical reactions under ambient conditions because of the short electron inelastic mean free path (IMFP) that requires a vacuum environment, which poses serious limitation on the application of XPS and XAS to samples present in the atmosphere or in the presence of a solvent. One promising approach is the use of graphene (Gr) windows transparent to both photons and electrons. This paper proposes an innovative system based on sealed Gr nanobubbles (GNBs) on a titanium dioxide TiO2 (100) rutile single crystal filled with the solution of interest during the fabrication stage. The GNBs were successfully employed to follow in-operando the thermal-induced reduction of FeCl3 to FeCl2 in aqueous solution. The electronic states of chlorine, iron and oxygen were obtained through a combination of electron spectroscopy methods (XPS and XAS) in different phases of the process. The interaction of various components in solution with solid surfaces constituting the cell was obtained, also highlighting the formation of a covalent C-Cl bond in the Gr structure. For the easiness of GNB fabrication and straightforward extension to a large variety of solutions, we envisage a broad application of the proposed approach to investigate in detail electronic mechanisms that regulate liquid/solid electron transfer in catalytic and energy conversion related applications.

The nature of the Fe-graphene interface at the nanometer level.

The emerging fields of graphene-based magnetic and spintronic devices require a deep understanding of the interface between graphene and ferromagnetic metals. This paper reports a detailed investigation at the nanometer level of the Fe-graphene interface carried out by angle-resolved photoemission, high-resolution photoemission from core levels, near edge X-ray absorption fine structure, scanning tunnelling microscopy and spin polarized density functional theory calculations. Quasi-free-standing graphene was grown on Pt(111), and the iron film was either deposited atop or intercalated beneath graphene. Calculations and experimental results show that iron strongly modifies the graphene band structure and lifts its π band spin degeneracy.

Silver nanoparticles linked by a Pt-containing organometallic dithiol bridge: study of local structure and interface by XAFS and SR-XPS.

Silver nanoparticles (AgNPs) functionalized with an organometallic bifunctional thiol containing Pt(ii) centers, generated in situ from trans-trans-[thioacetyl-bistributylphosphine-diethynylbiphenyl-diplatinum(ii)], were synthesized with different sulphur/metal molar ratios (i.e. AgNPs-1 and AgNPs-2) with the aim to obtain nanosystems of different mean size and self-organization behaviour. AgNPs spontaneously self-assemble, giving rise to 2D networks, as previously assessed. In this work a deeper insight into the chemico-physical properties of these AgNPs is proposed by means of synchrotron radiation induced X-ray photoelectron spectroscopy (SR-XPS) and X-ray absorption fine structure spectroscopy (XAFS) techniques. The results are discussed in order to probe the interaction at the interface between a noble metal and a thiol ligand at the atomic level and the aim of this study is to shed light on the chemical structure and self-organization details of nanosystems. The nature of the chemical interaction between the dithiol ligand and the Ag atoms on the nanoparticle surface was investigated by combining SR-XPS (S2p, Ag3d core levels) and XAS (S and Ag K-edges) analysis. UV-visible absorption and emission measurements were also carried out on all samples and compared with TD-DFT calculations so as to get a better understanding of their optical behavior and establish the nature of the excitation and emission processes.

Rapidly progressive cognitive impairment in a patient with high flow dural arteriovenous fistulas, cerebral sinus thrombosis and protein S deficiency.

Dural arteriovenous fistula (DAVF) may present with a variety of neurological symptoms, ranging from tinnitus to fatal hemorrhage. We report a case of rapidly progressive cognitive impairment due to cerebral venous engorgement that reversed after endovascular treatment in a patient with DAVF, cerebral sinus thrombosis and protein S deficiency. DAVF may be a cause of vascular cognitive impairment and should be considered particularly in cases with a rapidly progressive course because they are potentially treatable.

Magnetic nanoparticle clusters as actuators of ssDNA release.

One of the major areas of research in nanomedicine is the design of drug delivery systems with remotely controllable release of the drug. Despite the enormous progress in the field, this aspect still poses a challenge, especially in terms of selectivity and possible harmful interactions with biological components other than the target. We report an innovative approach for the controlled release of DNA, based on clusters of core-shell magnetic nanoparticles. The primary nanoparticles are functionalized with a single-stranded oligonucleotide, whose pairing with a half-complementary strand in solution induces clusterization. The application of a low frequency (6 KHz) alternating magnetic field induces DNA melting with the release of the single strand that induces clusterization. The possibility of steering and localizing the magnetic nanoparticles, and magnetically actuating the DNA release discloses new perspectives in the field of nucleic-acid based therapy.

Effects of hyper-early (<12 hours) endovascular treatment of ruptured intracranial aneurysms on clinical outcome.

Despite the encouraging results obtained with the endovascular treatment of ruptured intracranial aneurysms, few data are available on the effects of the timing of this approach on clinical outcome. The aim of our study was to evaluate the effects of the hyper-early timing of treatment and of pre-treatment and treatment-related variables on the clinical outcome of patients with ruptured intracranial aneurysms. Five hundred and ten patients (167 M, 343 F; mean age 56.45 years) with 557 ruptured intracranial aneurysms were treated at our institution from 2000 to 2011 immediately after their admission. The total population was divided into three groups: patients treated within 12 hours (hyper-early, group A), between 12-48 hours (early, group B) and after 48 hours (delayed, group C). A statistical analysis was carried out for global population and subgroups. Two hundred and thirty-four patients (46%) were included in group A, 172 (34%) in group B and 104 (20%) in group C. Pre-treatment variables (Hunt&Hess, Fisher grades, older age) and procedure-related variable (ischaemic/haemorrhagic complications) showed a significant correlation with worse clinical outcomes. The hyper-early treatment showed no correlation with good clinical outcomes. The incidence of intra-procedural complications was not significantly different between the three groups; 1.2% of pre-treatment rebleedings were observed. The hyper-early endovascular treatment of ruptured intracranial aneurysm does not seem to be statistically correlated with good clinical outcomes although it may reduce the incidence of pre-treatment spontaneous rebleedings without being associated with a higher risk of intra-procedural complications. However, since no significant differences in terms of clinical outcome and pre-treatment rebleeding rate were observed, a hyper-early treatment is not be supported by our data.

Endovascular treatment of deep hemorrhagic brain arteriovenous malformations with transvenous onyx embolization.

SUMMARY: Brain AVMs are a rare cause of cerebral hemorrhage and SAH, and their treatment is still debated. The aim of this study was to describe a novel endovascular approach with transvenous embolization of deep hemorrhagic brain AVMs. Five patients (3 females, 2 males; mean age, 33.2 years) underwent a transvenous embolization of a deep hemorrhagic brain AVM at our institution between February and April 2012. Clinical and angiographic data at the end of the procedure and after 6 months are reported. All the AVMs were completely obliterated, and no intra- or postprocedural complications occurred. The clinical outcome was unchanged or improved in all patients. Transvenous endovascular treatment may be considered in small, hemorrhagic, and deep AVMs with single deep drainage in those cases in which neurosurgical and radiosurgical treatment might not be indicated.

Five to ten years follow-up after coiling of 241 patients with acutely ruptured aneurysms. A single centre experience.

Endovascular treatment has assumed a role of first choice in the management of ruptured intracranial aneurysms. We describe the clinical and morphological data after the treatment of 258 ruptured intracranial aneurysms in 241 patients, in order to evaluate the safety and the efficacy of the endovascular treatment. Two hundred and forty-one patients with saccular ruptured aneurysms were treated at our institution between 2000 and 2005. After the endovascular treatment a clinical and angiographic follow-up was conducted. The clinical follow-up was carried out with a medical examination and telephonic interviews and mRS was used for evaluation. Two hundred and forty-nine acutely ruptured aneurysms were successfully treated and immediately after the endovascular procedure 81.9% of the aneurysms resulted completely occluded, 12.1% had a residual neck and 6% revealed a residual sac. The evolution of each grade was evaluated at six months and two years. During the follow-up we observed five early and one late re-bleedings. Twenty-four patients underwent a second procedure. After the discharge and up to ten years 73.1% of patients had a good clinical outcome (mRS0-1), 8.9% died and the remainder showed moderate-severe disability (mRS2-3). The long-term stability of the anatomical result is a critic-al issue of this approach because eventual re-bleedings may occur even after several months or years. A careful clinical and radiological follow-up for up to two years after the embolization may prevent recurrences but may not be sufficient.

Late-onset sporadic ataxia, pontine lesion, and retroperitoneal fibrosis: a case of Erdheim-Chester disease.

A 60-year-old man with progressive gait ataxia and mild pyramidal signs showed at MRI a pontine lesion with post-contrast enhancement in the left middle cerebellar peduncle. Diagnosis of Erdheim-Chester disease (ECD), a rare non-Langerhans cell histiocytosis, was suggested, further supported by a previously diagnosed retroperitoneal fibrosis. X-ray films demonstrated characteristic bilateral and symmetric osteosclerosis of the long bones of the lower limbs, which at radionuclide studies exhibited a marked increase in technetium-99 uptake. A cerebral 18FDG-PET showed a relevant pontine uptake of the tracer. Re-evaluation of a past retroperitoneal biopsy showed an intense CD68+, CD1a-, and S100- infiltrate of histiocytes with foamy cytoplasm, thus confirming the diagnosis. ECD should be regarded as a rare cause of adult-onset sporadic ataxia, especially when pontine lesions and extraneurological manifestations are present.

Iatrogenic intracranial pseudoaneurysms: neuroradiological and therapeutical considerations, including endovascular options.

Intracranial pseudoaneurysms represent a potentially fatal complication of intracranial surgery. Our purpose is to describe their neuroradiological characteristics, prognostic features and possible treatment. Eight cases of postsurgical intracranial pseudoaneurysms have been observed at our institution since 1988. Four were observed following transsphenoidal (TS) surgery and four after pterional craniotomies. Two types of iatrogenic pseudoaneurysms were observed: "fusiform", probably due to weakening of the adventitia during surgical peeling of the tumour from the artery (three cases) and "saccular", occurring after a more focal or complete laceration of the vessel (five cases), more often after TS surgery. A thorough preoperative neuroradiological examination may identify anatomical conditions at risk for development of this severe complication. Postoperative neuroradiological follow-up is mandatory in cases in which unusual bleeding has occurred during the perioperative period, but absence of bleeding does not exclude the possible development of a pseudoaneurysm. Endovascular treatment of pseudoaneurysms represents a safe and durable procedure, specifically in those cases in which damage to the carotid siphon occurred during TS surgery.

Spontaneous low cerebrospinal pressure: a mini review.

Spontaneous intracranial hypotension (SIH) is a syndrome of low cerebrospinal fluid (CSF) pressure characterised by postural headaches in patients without any history of dural puncture or penetrating trauma. Described by Schaltenbrand in 1938, SIH is thought to result from an occult CSF leak resulting in decreased CSF volume and, consequently, in low CSF pressure. Magnetic resonance imaging of the head and spine has improved the diagnosis of the syndrome showing peculiar radiographic abnormalities including diffuse pachymeningeal enhancement, subdural fluid collections and downward displacement of the cerebral structures. Treatment of SIH headache should start with conservative, non-invasive therapies while epidural blood patch has emerged as the treatment of choice for those symptomatic patients who have failed medical noninvasive approaches.

Headache and intracranial hypotension: neuroradiological findings.

The cardinal and classic features of postural headache and low cerebrospinal fluid (CSF) pressure in intracranial hypotension may not dominate the clinical picture of the syndrome and may be associated with additional various neurological symptoms and signs. Reports of unusual clinical presentations continue to appear in the literature. Despite the considerable variability of the clinical spectrum, neuroradiological studies reveal more constant and characteristic features. Brain MRI findings include intracranial pachymeningeal thickening and post-contrast enhancement, subdural fluid collections and downward displacement or "sagging" of the brain. Spinal MRI findings include collapse of the dural sac with a festooned appearance, intense epidural enhancement owing to dilatation of the epidural venous plexus, and possible epidural fluid collections. In fact, spinal studies may demonstrate CSF leakage from spinal dural defects, which are considered the most common cause of the syndrome. Myelo-MR may suggest the possible point of CSF leakage, by demonstrating an irregular root sleeve; myelo-CT and radioisotope myelocisternography (RMC) are often needed to confirm the point of CSF leakage. Neuroimaging studies are, therefore, essential for suggesting and confirming the diagnosis.