Awake craniotomy for excision of arteriovenous malformations? A qualitative comparison study with stereotactic radiosurgery.

Treatment of arteriovenous malformations (AVM) located at the eloquent area has been a challenge. Awake brain mapping allows identification of a non-eloquent gyrus for intervention and can potentially facilitate resection with preservation of functions. An alternative treatment option is stereotactic radiosurgery (SRS). The objective of this study was to perform a qualitative comparison of the treatment outcome of awake AVM excision versus SRS. We conducted a 13-year retrospective review of AVM excision under awake craniotomy performed at Prince of Wales Hospital, Hong Kong, from 2003 to 2016. Patients' presentation, Spetzler-Martin (SM) grading, rate of obliteration and complication were reviewed and analyzed with the modified radiosurgery-based AVM score (RS score). Six patients had excision of AVM under awake mapping during this period of time. Two were SM Grade II and four were SM Grade III. Five located at the peri-rolandic region while one at the temporal language area. None had failed mapping. Five out of six achieved complete obliteration (83.3%). Qualitative comparative analysis had revealed better treatment outcome with awake AVM excision as compared to SRS with the obliteration rate of 100% versus 96% for RS score ≤1.00, 100% versus 78% for RS score 1.01-1.50, and 66% versus 50% for RS score >2.00 respectively. In conclusion, awake mapping and excision of AVMs at the eloquent area is feasible. Qualitative comparative analysis had revealed higher obliteration rate with awake AVM excision as compared to SRS.

Supersaturated calcium carbonate solutions are classical.

Mechanisms of CaCO3 nucleation from solutions that depend on multistage pathways and the existence of species far more complex than simple ions or ion pairs have recently been proposed. Herein, we provide a tightly coupled theoretical and experimental study on the pathways that precede the initial stages of CaCO3 nucleation. Starting from molecular simulations, we succeed in correctly predicting bulk thermodynamic quantities and experimental data, including equilibrium constants, titration curves, and detailed x-ray absorption spectra taken from the supersaturated CaCO3 solutions. The picture that emerges is in complete agreement with classical views of cluster populations in which ions and ion pairs dominate, with the concomitant free energy landscapes following classical nucleation theory.

5-Aminolevulinic acid fluorescence guided resection of malignant glioma: Hong Kong experience.

BACKGROUND: 5-Aminolevulinic Acid (5-ALA) induced fluorescence is useful in guiding glioma resection. The extent of 5-ALA accumulation is beyond gadolinium contrast enhancement.1,2 Supratotal resection may be achieved, potentially granting patients with better survival. We present our experience on 5-ALA guided glioma resection in Chinese ethnics. METHOD: Sixteen Patients ingested 5-ALA (Gliolan, Medas Germany) 20 mg/kg·m2 4 h before surgery. The tumor resection was guided by fluorescence with neurosurgical microscope. Patient was monitored for general condition, especially for new neurological deficits. Postoperative MRI served as the assessment for extent of resection (EOR). RESULT: High grade glioma was confirmed in 12 cases, low grade glioma in three and one inflammation. 5-ALA was used in ten patients with known malignant glioma, and in six patients with presumed diagnosis of malignant glioma. Fifteen cases had positive fluorescence. The intensity was strong in eight and moderate in seven cases. MRI suggested total resection was achieved in 9 patients, near total resection in two and five had subtotal resection. EOR was associated with duration between ingestion of 5-ALA and timing when microscope was brought in for visualization of fluorescence (p = 0.038). Two patients suffered from temporary visual field defects. One patient developed hemiparesis after surgery. CONCLUSION: 5-ALA is a useful intra-operative guidance for resection. It increases the percentage of total removal of the tumor. It should be used within the window period of the action (4-12 h).

Electronic and Chemical State of Aluminum from the Single- (K) and Double-Electron Excitation (KLII&III, KLI) X-ray Absorption Near-Edge Spectra of α-Alumina, Sodium Aluminate, Aqueous Al(3+)·(H2O)6, and Aqueous Al(OH)4(-).

We probe, at high energy resolution, the double electron excitation (KLII&II) X-ray absorption region that lies approximately 115 eV above the main Al K-edge (1566 eV) of α-alumina and sodium aluminate. The two solid standards, α-alumina (octahedral) and sodium aluminate (tetrahedral), are compared to aqueous species that have the same Al coordination symmetries, Al(3+)·6H2O (octahedral) and Al(OH)4(-) (tetrahedral). For the octahedral species, the edge height of the KLII&III-edge is approximately 10% of the main K-edge; however, the edge height is much weaker (3% of K-edge height) for Al species with tetrahedral symmetry. For the α-alumina and aqueous Al(3+)·6H2O the KLII&III spectra contain white line features and extended absorption fine structure (EXAFS) that mimics the K-edge spectra. The KLII&III-edge feature interferes with an important region in the EXAFS spectra of the crystalline and aqueous standards. The K-edge spectra and K-edge energy positions are predicted using time-dependent density functional theory (TDDFT). The TDDFT calculations for the K-edge X-ray absorption near-edge spectra (XANES) reproduce the observed transitions in the experimental spectra of the four Al species. The KLII&II and KLI onsets and their corresponding chemical shifts for the four standards are estimated using the delta self-consistent field (ΔSCF) method.

Quantitatively probing the Al distribution in zeolites.

The degree of substitution of Si(4+) by Al(3+) in the oxygen-terminated tetrahedra (Al T-sites) of zeolites determines the concentration of ion-exchange and Brønsted acid sites. Because the location of the tetrahedra and the associated subtle variations in bond angles influence the acid strength, quantitative information about Al T-sites in the framework is critical to rationalize catalytic properties and to design new catalysts. A quantitative analysis is reported that uses a combination of extended X-ray absorption fine structure (EXAFS) analysis and (27)Al MAS NMR spectroscopy supported by DFT-based molecular dynamics simulations. To discriminate individual Al atoms, sets of ab initio EXAFS spectra for various T-sites are generated from DFT-based molecular dynamics simulations, allowing quantitative treatment of the EXAFS single- and multiple-photoelectron scattering processes out to 3-4 atom shells surrounding the Al absorption center. It is observed that identical zeolite types show dramatically different Al distributions. A preference of Al for T-sites that are part of one or more 4-member rings in the framework over those T-sites that are part of only 5- and 6-member rings in an HBEA150 zeolite has been determined using this analysis.

Studying the surface reaction between NiO and Al2O3 via total reflection EXAFS (ReflEXAFS).

The reaction between NiO and (0001)- and (1102)-oriented Al2O3 single crystals has been investigated on model experimental systems by using the ReflEXAFS technique. Depth-sensitive information is obtained by collecting data above and below the critical angle for total reflection. A systematic protocol for data analysis, based on the recently developed CARD code, was implemented, and a detailed description of the reactive systems was obtained. In particular, for (1102)-oriented Al2O3, the reaction with NiO is almost complete after heating for 6 h at 1273 K, and an almost uniform layer of spinel is found below a mixed (NiO + spinel) layer at the very upmost part of the sample. In the case of the (0001)-oriented Al2O3, for the same temperature and heating time, the reaction shows a lower advancement degree and a residual fraction of at least 30% NiO is detected in the ReflEXAFS spectra.

EXAFS-XANES evidence of in situ cesium reduction in Cs-Ru/C catalysts for ammonia synthesis.

We present here a X-ray absorption spectroscopy (XAS) investigation on the local chemical order and electronic structure of Cs and Ba, promoters of the Ru/C catalysts for ammonia synthesis that attracted interest because of highly increased productivity. The role of the promoters is still largely unclear, although indirect evidence for Cs partial reduction has been obtained by this and other groups. Our XAS analysis with in situ H(2) reduction directly supports the partial Cs reduction in the promoted Ru/C catalysts, depending on the presence of Ru and on the graphitization degree of the support. Higher coordination of Ba was observed with respect to Cs in the reduced samples, without evidence of heavy atoms (Ru, Cs, and Ba) in the surroundings. Because of the strong electropositive nature of Cs, direct experimental evidence of its partial reduction is of outstanding significance also for other applications.

Micro-XANES mapping of buried interfaces: pushing microbeam techniques to the nanoscale.

A specific preparation procedure makes possible to obtain in one shot structural and compositional characterization of a buried interface at the nanometre scale using a micrometre scale probe. A specific example based on dispersive mu-XAS, micro X-ray absorption spectroscopy, shows that nearly-atomic scale changes in local structure, composition, as well as local disorder are faithfully detected. The approach could in principle be applied to any probe with a micrometric resolution.