On predicting scan profiles: the nature of the 'aberration function'

In an earlier treatment [Destro & Marsh (1987). Acta Cryst. A43, 711-718], an attempt was made to predict the shapes of high-angle θ-2θ scan profiles by convoluting a low-angle profile with the presumedly known spectral distribution function for the incident (crystal-monochromated Mo Kα) radiation but it was found necessary to introduce a third component, an 'aberration function', that varied with the Bragg angle θ. It is shown here that the primary purpose of the aberration function is to correct for defects in the spectral-distribution function. In particular, the effective intensity ratio between the K_(α2) and K_(α1) spectral lines can apparently deviate greatly (by more than 10%) from the theoretical value of 0.499, depending upon the alignment of the monochromator crystal, and an appreciable amount of white radiation may also be present. By a suitable modification of the spectral-distribution function, high-angle scan profiles can be predicted from accurate measurements of a low-angle profile; as a result, scan-truncation losses can, for the most part, be removed. However, modeling the spectral distribution function appropriate to a particular experiment remains a difficult empirical procedure

Experimental Charge Density of α-Glycine at 23 K

The electrostatic properties of crystals of α-glycine have been obtained from extensive X-ray diffraction data collected at approximately 23 K and carefully processed, including corrections for scan truncation losses, anisotropic extinction, and multiple reflection. From a multipole parameterization of the X-ray intensities we have obtained an unusually precise - and we are confident, accurate - model of the total electron distribution in the crystal including the topological features, atom and group charges, the dipole moment for the glycine zwitterion, electrostatic potentials, electric field gradients at the nucleii of the three hydrogen atoms of the ammonium group, and intermolecular electrostatic energies within the crystal. We have also calculated the total interaction energies involving the six distinct types of intermolecular pairings and examined these energies in terms of the molecular arrangement

Lamination And Microstructuring Technology for a Bio-Cell Multiwell array

Microtechnology becomes a versatile tool for biological and biomedical applications. Microwells have been established long but remained non-intelligent up to now. Merging new fabrication techniques and handling concepts with microelectronics enables to realize intelligent microwells suitable for future improved cancer treatment. The described technology depicts the basis for the fabrication of a elecronically enhanced microwell. Thin aluminium sheets are structured by laser micro machining and laminated successively to obtain registration tolerances of the respective layers of 5..10\^A$\mu$m. The microwells lasermachined into the laminate are with 50..80\^A$\mu$m diameter, allowing to hold individual cells within the well. The individual process steps are described and results on the microstructuring are given.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

Evaluation of predictive models for post-fire debris flow occurrence in the western United States

Abstract. Rainfall-induced debris flows in recently burned mountainous areas cause significant economic losses and human casualties. Currently, prediction of post-fire debris flows is widely based on the use of power-law thresholds and logistic regression models. While these procedures have served with certain success in existing operational warning systems, in this study we investigate the potential to improve the efficiency of current predictive models with machine-learning approaches. Specifically, the performance of a predictive model based on the random forest algorithm is compared with current techniques for the prediction of post-fire debris flow occurrence in the western United States. The analysis is based on a database of post-fire debris flows recently published by the United States Geological Survey. Results show that predictive models based on random forest exhibit systematic and considerably improved performance with respect to the other models examined. In addition, the random-forest-based models demonstrated improvement in performance with increasing training sample size, indicating a clear advantage regarding their ability to successfully assimilate new information. Complexity, in terms of variables required for developing the predictive models, is deemed important but the choice of model used is shown to have a greater impact on the overall performance

When data sharing gets close to 100%. What human paleogenetics can teach the open science movement

This study analyzes data sharing regarding mitochondrial, Y chromosomal and autosomal polymorphisms in a total of 162 papers on ancient human DNA published between 1988 and 2013. The estimated sharing rate was not far from totality (97.6% ± 2.1%) and substantially higher than observed in other fields of genetic research (evolutionary, medical and forensic genetics). Both a questionnaire-based survey and the examination of Journals’ editorial policies suggest that this high sharing rate cannot be simply explained by the need to comply with stakeholders requests. Most data were made available through body text, but the use of primary databases increased in coincidence with the introduction of complete mitochondrial and next-generation sequencing methods. Our study highlights three important aspects. First, our results imply that researchers’ awareness of the importance of openness and transparency for scientific progress may complement stakeholders’ policies in achieving very high sharing rates. Second, widespread data sharing does not necessarily coincide with a prevalent use of practices which maximize data findability, accessibility, useability and preservation. A detailed look at the different ways in which data are released can be very useful to detect failures to adopt the best sharing modalities and understand how to correct them. Third and finally, the case of human paleogenetics tells us that a widespread awareness of the importance of Open Science may be important to build reliable scientific practices even in the presence of complex experimental challenges

Genetic and epigenetic changes in primary metastatic and nonmetastatic colorectal cancer

Colorectal cancer (CRC) develops as multistep process, which involves genetic and epigenetic alterations. K-Ras, p53 and B-Raf mutations and RASSF1A, E-Cadherin and p16INK4A promoter methylation were investigated in 202 CRCs with and without lymph node and/or liver metastasis, to assess whether gene abnormalities are related to a metastogenic phenotype. K-Ras, B-Raf and p53 mutations were detected in 27, 3 and 32% of the cases, with K-Ras mutations significantly associated with metastatic tumour (P=0.019). RASSF1A, E-Cadherin and p16INK4A methylation was documented in 20, 44 and 33% of the cases with p16INK4A significantly associated with metastatic tumours (P=0.001). Overall, out of 202 tumours, 34 (17%) did not show any molecular change, 125 (62%) had one or two and 43 (21%) three or more. Primary but yet metastatic CRCs were prevalent in the latter group (P=0.023) where the most frequent combination was one genetic (K-Ras in particular) and two epigenetic alterations. In conclusion, this analysis provided to detect some molecular differences between primary metastatic and nonmetastatic CRCs, with K-Ras and p16INK4A statistically altered in metastatic tumours; particular gene combinations, such as coincidental K-Ras mutation with two methylated genes are associated to a metastogenic phenotype

The effect of gain saturation in a gain compensated perfect lens

The transmission of evanescent waves in a gain-compensated perfect lens is discussed. In particular, the impact of gain saturation is included in the analysis, and a method for calculating the fields of such nonlinear systems is developed. Gain compensation clearly improves the resolution; however, a number of nonideal effects arise as a result of gain saturation. The resolution associated with the lens is strongly dependent on the saturation constant of the active medium.Comment: to appear in J. Opt. Soc. Am.

Experimental Charge Density of α-Glycine at 23 K

The electrostatic properties of crystals of α-glycine have been obtained from extensive X-ray diffraction data collected at approximately 23 K and carefully processed, including corrections for scan truncation losses, anisotropic extinction, and multiple reflection. From a multipole parameterization of the X-ray intensities we have obtained an unusually precise - and we are confident, accurate - model of the total electron distribution in the crystal including the topological features, atom and group charges, the dipole moment for the glycine zwitterion, electrostatic potentials, electric field gradients at the nucleii of the three hydrogen atoms of the ammonium group, and intermolecular electrostatic energies within the crystal. We have also calculated the total interaction energies involving the six distinct types of intermolecular pairings and examined these energies in terms of the molecular arrangement

Ethnic fragmentation and degree of urbanization strongly affect the discrimination power of Y-STR haplotypes in central Sahel

Y chromosome short tandem repeats (Y-STRs) are commonly used to identify male lineages for investigative and judicial purposes and could represent the only source of male-specific genetic information from unbalanced female-male mixtures. The Yfiler Plus multiplex, which includes twenty conventional and seven rapidly-mutating Y-STRs, represents the most discriminating patrilineal system commercially available to date. Over the past five years, this multiplex has been used to analyze several Eurasian populations, with a reported discrimination capacity (DC) approaching or corresponding to the highest possible value. However, despite the inclusion of rapidly mutating Y-STRs, extensive haplotype sharing was still reported for some African populations due to a number of different factors affecting the effective population size. In the present study, we analyzed 27 Y-STRs included in the Yfiler Plus multiplex and 82 Y-SNPs in central Sahel (northern Cameroon and western Chad), an African region characterized by a strong ethnic fragmentation and linguistic diversity. We evaluated the effects of population sub-structuring on genetic diversity by stratifying a sample composed of 431 males according to their ethnicity (44 different ethnic groups) and urbanization degree (four villages and four towns). Overall, we observed a low discrimination capacity (DC = 0.90), with 71 subjects (16.5 %) sharing 27 Y-STR haplotypes. Haplotype sharing was essentially limited to subjects with the same binary haplogroup, coming from the same location and belonging to the same ethnic group. Haplotype sharing was much higher in rural areas (average DC = 0.83) than urban settlements (average DC = 0.96) with a significant correlation between DC and census size (r = 0.89; p = 0.003). Notably, we found that genetic differentiation between villages from the same country (ΦST = 0.14) largely exceeded that found among countries (ΦST = 0.02). These findings have important implications for the choice of the appropriate reference population database to evaluate the statistical relevance of forensic Y-haplotype matches