Determining whether metals nucleate homogeneously on graphite: A case study with copper

We observe that Cu clusters grow on surface terraces of graphite as a result of physical vapor deposition in ultrahigh vacuum. We show that the observation is incompatible with a variety of models incorporating homogeneous nucleation and calculations of atomic-scale energetics. An alternative explanation, ion-mediated heterogeneous nucleation, is proposed and validated, both with theory and experiment. This serves as a case study in identifying when and whether the simple, common observation of metal clusters on carbon-rich surfaces can be interpreted in terms of homogeneous nucleation. We describe a general approach for making system-specific and laboratory-specific predictions

The (111) Surface of NaAu2: Structure, Composition, and Stability

The (111) surface of single-crystal NaAu2 is a model for catalytically active, powdered NaAu2. We prepare and characterize this surface with a broad suite of techniques. Preparation in ultrahigh vacuum consists of the traditional approach of ion bombardment (to remove impurities) and thermal annealing (to restore surface order). Both of these steps, however, cause loss of sodium (Na), and repeated treatments eventually trigger conversion of the surface and near-surface regions to crystalline gold. The bulk has a limited ability to repopulate the surface Na. Under conditions where Na depletion is minimized, electron diffraction patterns are consistent with the bulkterminated structure, and scanning tunneling microscopy reveals mesa-like features with lateral dimensions of a few tens of nanometers. The tops of the mesas do not possess fine structure characteristic of a periodic lattice, suggesting that the surface layer is disordered under the conditions of these experiments

Bulk single crystal growth and sample surface preparation of catalytic NaAu2

Here in we have grown bulk single crystals of NaAu2 for the first time to enable surface studies on the nature of the (111) bulk surface. This intermetallic compound exhibits surprisingly high catalytic activity for CO oxidation, a benchmark reaction. Theory predicts NaAu2 to be the most thermodynamically stable composition in the Na-Au binary phase diagram and NaAu2 has been seen to preferentially form in experiments containing Na and Au which supports this prediction. The (111) surface was also predicted to be the most stable and is nearly bulk-terminated making single crystal samples prepared with this crystallographic orientation a fitting choice. The crystal quality and surface composition of the metallographically prepared surface was determined by x-ray diffraction methods in addition to optical and electron microscopy

The pattern-recognition molecule H-ficolin in relation to diabetic kidney disease, mortality, and cardiovascular events in type 1 diabetes

H-ficolin recognizes patterns on microorganisms and stressed cells and can activate the lectin pathway of the complement system. We aimed to assess H-ficolin in relation to the progression of diabetic kidney disease (DKD), all-cause mortality, diabetes-related mortality, and cardiovascular events. Event rates per 10-unit H-ficolin-increase were compared in an observational follow-up of 2,410 individuals with type 1 diabetes from the FinnDiane Study. DKD progression occurred in 400 individuals. The unadjusted hazard ratio (HR) for progression was 1.29 (1.18-1.40) and 1.16 (1.05-1.29) after adjustment for diabetes duration, sex, HbA(1c), systolic blood pressure, and smoking status. After adding triglycerides to the model, the HR decreased to 1.07 (0.97-1.18). In all, 486 individuals died, including 268 deaths of cardiovascular causes and 192 deaths of complications to diabetes. HRs for all-cause mortality and cardiovascular mortality were 1.13 (1.04-1.22) and 1.05 (0.93-1.17), respectively, in unadjusted analyses. These estimates lost statistical significance in adjusted models. However, the unadjusted HR for diabetes-related mortality was 1.19 (1.05-1.35) and 1.18 (1.02-1.37) with the most stringent adjustment level. Our results, therefore, indicate that H-ficolin predicts diabetes-related mortality, but neither all-cause mortality nor fatal/non-fatal cardiovascular events. Furthermore, H-ficolin is associated with DKD progression, however, not independently of the fully adjusted model.Peer reviewe

A new model for predicting relative nonwetting phase permeability from soil water retention curves

Relative permeability of the nonwetting phase in a multiphase flow in porous media is a function of phase saturation. Specific expressions of this function are commonly determined by combining soil water retention curves with relative nonwetting phase permeability models. Experimental evidence suggests that the relative permeability of the nonwetting phase can be significantly overestimated by the existing relative permeability models. A new model for the prediction of relative nonwetting phase permeability from soil water retention curves is proposed in this paper. A closed form expression can be obtained in combination with soil water retention curves. The model is mathematically simple and can easily and efficiently be implemented in numerical models of multiphase flow processes in porous media. The predicting capability of the proposed model is contrasted with well-supported models by comparing the measured and predicted relative air permeability data for 11 soils, representing a wide range of soil textures, from sand to silty clay loam. In most of the cases the proposed model improves the agreement between the predicted relative air permeability and the measured data. Copyright 2011 by the American Geophysical Union.published_or_final_versio

Whole-exome re-sequencing in a family quartet identifies POP1 mutations as the cause of a novel skeletal dysplasia

Recent advances in DNA sequencing have enabled mapping of genes for monogenic traits in families with small pedigrees and even in unrelated cases. We report the identification of disease-causing mutations in a rare, severe, skeletal dysplasia, studying a family of two healthy unrelated parents and two affected children using whole-exome sequencing. The two affected daughters have clinical and radiographic features suggestive of anauxetic dysplasia (OMIM 607095), a rare form of dwarfism caused by mutations of RMRP. However, mutations of RMRP were excluded in this family by direct sequencing. Our studies identified two novel compound heterozygous loss-of-function mutations in POP1, which encodes a core component of the RNase mitochondrial RNA processing (RNase MRP) complex that directly interacts with the RMRP RNA domains that are affected in anauxetic dysplasia. We demonstrate that these mutations impair the integrity and activity of this complex and that they impair cell proliferation, providing likely molecular and cellular mechanisms by which POP1 mutations cause this severe skeletal dysplasia

Human and mouse mutations in WDR35 cause short-rib polydactyly syndromes due to abnormal ciliogenesis

Defects in cilia formation and function result in a range of human skeletal and visceral abnormalities. Mutations in several genes have been identified to cause a proportion of these disorders, some of which display genetic (locus) heterogeneity. Mouse models are valuable for dissecting the function of these genes, as well as for more detailed analysis of the underlying developmental defects. The short-rib polydactyly (SRP) group of disorders are among the most severe human phenotypes caused by cilia dysfunction. We mapped the disease locus from two siblings affected by a severe form of SRP to 2p24, where we identified an in-frame homozygous deletion of exon 5 in WDR35. We subsequently found compound heterozygous missense and nonsense mutations in WDR35 in an independent second case with a similar, severe SRP phenotype. In a mouse mutation screen for developmental phenotypes, we identified a mutation in Wdr35 as the cause of midgestation lethality, with abnormalities characteristic of defects in the Hedgehog signaling pathway. We show that endogenous WDR35 localizes to cilia and centrosomes throughout the developing embryo and that human and mouse fibroblasts lacking the protein fail to produce cilia. Through structural modeling, we show that WDR35 has strong homology to the COPI coatamers involved in vesicular trafficking and that human SRP mutations affect key structural elements in WDR35. Our report expands, and sheds new light on, the pathogenesis of the SRP spectrum of ciliopathies

Complement component C4 structural variation and quantitative traits contribute to sex-biased vulnerability in systemic sclerosis

Altres ajuts: Fondo Europeo de Desarrollo Regional (FEDER), "A way of making Europe".Copy number (CN) polymorphisms of complement C4 play distinct roles in many conditions, including immune-mediated diseases. We investigated the association of C4 CN with systemic sclerosis (SSc) risk. Imputed total C4, C4A, C4B, and HERV-K CN were analyzed in 26,633 individuals and validated in an independent cohort. Our results showed that higher C4 CN confers protection to SSc, and deviations from CN parity of C4A and C4B augmented risk. The protection contributed per copy of C4A and C4B differed by sex. Stronger protection was afforded by C4A in men and by C4B in women. C4 CN correlated well with its gene expression and serum protein levels, and less C4 was detected for both in SSc patients. Conditioned analysis suggests that C4 genetics strongly contributes to the SSc association within the major histocompatibility complex locus and highlights classical alleles and amino acid variants of HLA-DRB1 and HLA-DPB1 as C4-independent signals