On the problem of Dirac cones in fullerenes on gold.

Artificial graphene based on molecular networks enables the creation of novel 2D materials with unique electronic and topological properties. Landau quantization has been demonstrated by CO molecules arranged on the two-dimensional electron gas on Cu(111) and the observation of electron quantization may succeed based on the created gauge fields. Recently, it was reported that instead of individual manipulation of CO molecules, simple deposition of nonpolar C60 molecules on Cu(111) and Au(111) produces artificial graphene as evidenced by Dirac cones in photoemission spectroscopy. Here, we show that C60-induced Dirac cones on Au(111) have a different origin. We argue that those are related to umklapp diffraction of surface electronic bands of Au on the molecular grid of C60 in the final state of photoemission. We test this alternative explanation by precisely probing the dimensionality of the observed conical features in the photoemission spectra, by varying both the incident photon energy and the degree of charge doping via alkali adatoms. Using density functional theory calculations and spin-resolved photoemission we reveal the origin of the replicating Au(111) bands and resolve them as deep leaky surface resonances derived from the bulk Au sp-band residing at the boundary of its surface projection. We also discuss the manifold nature of these resonances which gives rise to an onion-like Fermi surface of Au(111).

Improved outcomes in paediatric intestinal failure with aggressive prevention of liver disease.

BACKGROUND/PURPOSE: A protocol-driven care algorithm for the care of intestinal failure (IF) centred on therapies to prevent Parenteral Nutrition Associated Cholestasis (PNAC) was instituted in 2006. We report our results from 2006-2009, and compare them to the outcomes of our previous cohort of patients (1998-2006). METHODS: With regional ethics board approval, we have been prospectively gathering data on patient with IF cared for by our regional surgical unit. IF was defined as a residual bowel length of <40 cm or a requirement for PN for greater than 60 days. With the development of a multidisciplinary care team, a protocol-driven strategy to prevent PNAC was instituted in 2006, with aggressive introduction of enteral feeds, use of prophylactic antibiotics to prevent bacterial overgrowth, lipid reduction and use of a fish oil-derived lipid preparation for cholestasis and Serial Transverse Enteroplasty (STEP) if bowel dilation occurred. RESULTS: In the era from 1998-2006, 33 patients were identified, with a 72% survival; the direct bilirubin averaged 112+/-34 microM/L after 3 months of PN. 8/33 (27%) of patients received prophylactic antibiotics, and none received fish oil-based lipids. The most common causes of IF were gastroschisis (30%) and atresia (21%); 31 of 33 patients were infants. Average time to intestinal rehabilitation/death was 4.5+/-3 months. All deaths were related to sepsis or PN/liver failure. In the era from 2006-2009, 22 patients have been followed, with 100% survival*. Average bilirubin after 3 months of PN was 8+/-2.2 microM/L*, 20/22 (90%)* received prophylactic antibiotics, and 6/22(27%)* received fish oil-based lipid PN. The common causes of IF were gastroschisis 15/22 (68%) and atresia (27%). 18/22 are weaned from PN, and the average time to intestinal rehabilitation was 2.7+/-1.3 months, 4 patients underwent STEP procedures. (*p<0.05 by Fischer's exact or Student's t-test, data mean+/-SD). CONCLUSIONS: The institution of an aggressive protocol of advancing enteric feeds, oral antibiotic prophylaxis for bacterial overgrowth, fish oil-based lipid use, and the STEP procedure for dilated bowel has resulted in an apparent increase in survival and a remarkable improvement in liver function in a paediatric IF population. Further studies to define the relative importance of these therapies are recommended.

Choroid plexus tumours.

Choroid plexus tumours are rare epithelial brain tumours and limited information is available regarding their biology and the best treatment. A meta-analysis was done to determine prognostic factors and the influence of various treatment modalities. A thorough review of the medical literature (1966-1998) revealed 566 well-documented choroid plexus tumours. These were entered into a database, which was analysed to determine prognostic factors and treatment modalities. Most patients with a supratentorial tumour were children, while the most common sites in adults were the fourth ventricle and the cerebellar pontine angle. Cerebellar pontine angle tumours were more frequently benign. Histology was the most important prognostic factor, as one, five, and 10-year projected survival rates were 90, 81, and 77% in choroid plexus-papilloma (n=353) compared to only 71, 41, and 35% in choroid plexus-carcinoma respectively (P<0.0005). Surgery was prognostically relevant for both choroid plexus-papilloma (P=0.0005) and choroid plexus-carcinoma (P=0.0001). Radiotherapy was associated with significantly better survival in choroid plexus-carcinomas. Eight of 22 documented choroid plexus-carcinomas responded to chemotherapy. Relapse after primary treatment was a poor prognostic factor in choroid plexus-carcinoma patients but not in choroid plexus-papilloma patients. Treatment of choroid plexus tumours should start with radical surgical resection. This should be followed by adjuvant treatment in case of choroid plexus-carcinoma, and a "wait and see" approach in choroid plexus-papilloma.