Effects of Spatial Dispersion on Reflection from Mushroom-type Artificial Impedance Surfaces

Several recent works have emphasized the role of spatial dispersion in wire media, and demonstrated that arrays of parallel metallic wires may behave very differently from a uniaxial local material with negative permittivity. Here, we investigate using local and non-local homogenization methods the effect of spatial dispersion on reflection from the mushroom structure introduced by Sievenpiper. The objective of the paper is to clarify the role of spatial dispersion in the mushroom structure and demonstrate that under some conditions it is suppressed. The metamaterial substrate, or metasurface, is modeled as a wire medium covered with an impedance surface. Surprisingly, it is found that in such configuration the effects of spatial dispersion may be nearly suppressed when the slab is electrically thin, and that the wire medium can be modeled very accurately using a local model. This result paves the way for the design of artificial surfaces that exploit the plasmonic-type response of the wire medium slab.Comment: submitted for publication, under revie

Cell-type-specific profiling of protein-DNA interactions without cell isolation using targeted DamID with next-generation sequencing.

This protocol is an extension to: Nat. Protoc. 2, 1467-1478 (2007); doi:10.1038/nprot.2007.148; published online 7 June 2007The ability to profile transcription and chromatin binding in a cell-type-specific manner is a powerful aid to understanding cell-fate specification and cellular function in multicellular organisms. We recently developed targeted DamID (TaDa) to enable genome-wide, cell-type-specific profiling of DNA- and chromatin-binding proteins in vivo without cell isolation. As a protocol extension, this article describes substantial modifications to an existing protocol, and it offers additional applications. TaDa builds upon DamID, a technique for detecting genome-wide DNA-binding profiles of proteins, by coupling it with the GAL4 system in Drosophila to enable both temporal and spatial resolution. TaDa ensures that Dam-fusion proteins are expressed at very low levels, thus avoiding toxicity and potential artifacts from overexpression. The modifications to the core DamID technique presented here also increase the speed of sample processing and throughput, and adapt the method to next-generation sequencing technology. TaDa is robust, reproducible and highly sensitive. Compared with other methods for cell-type-specific profiling, the technique requires no cell-sorting, cross-linking or antisera, and binding profiles can be generated from as few as 10,000 total induced cells. By profiling the genome-wide binding of RNA polymerase II (Pol II), TaDa can also identify transcribed genes in a cell-type-specific manner. Here we describe a detailed protocol for carrying out TaDa experiments and preparing the material for next-generation sequencing. Although we developed TaDa in Drosophila, it should be easily adapted to other organisms with an inducible expression system. Once transgenic animals are obtained, the entire experimental procedure-from collecting tissue samples to generating sequencing libraries-can be accomplished within 5 d.This work was funded by a Wellcome Trust Senior Investigator Award (103792), Wellcome Trust Programme Grant (092545) and BBSRC Project Grant (BB/L00786X/1) to A.H.B. A.H.B acknowledges core funding to the Gurdon Institute from the Wellcome Trust (092096) and CRUK (C6946/A14492).This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nprot.2016.08

Efficient entrapment and separation of anionic pollutants from aqueous solutions by sequential combination of cellulose nanofibrils and halloysite nanotubes

AbstractThe synergistic combination of different nanomaterials for improved performance in environmental applications such as the removal of aqueous micropollutants has attracted increasing interest in recent years. This study demonstrates a novel sequential adsorption–aggregation concept that harnesses tubular halloysite nanotubes (HNTs) and flexible cellulose nanofibrils (CNFs) for the removal of a small, anionic dye molecule, chrome azurol S, from water. Hollow HNTs were first allowed to interact with the aqueous dye solution, after which the dye-loaded colloidal nanotubes were aggregated and separated from the water phase with cationized CNFs. The combination of 25 mg CNFs with 1 g HNTs at pH 7 resulted in efficient removal of dye (80%) and turbidity (~100%) and the removal of dye was further promoted in more acidic conditions (within the pH range of 6–8.5) because of the attractive electrostatic interactions. Cationic CNFs not only enabled the separation of dye-loaded clay particles from the water phase through a rapid aggregation but also participated in dye removal through adsorption (~20%). In comparison with nano-sized HNTs, the dye removal performance of micro-sized and chemically similar kaolin was poor (43%). Given the good availability of both HNTs and CNFs and the low consumption of the more expensive component (i.e., CNFs) in the process, the concept is straightforward, readily applicable, environmentally benign, and potentially cost-effective.Abstract The synergistic combination of different nanomaterials for improved performance in environmental applications such as the removal of aqueous micropollutants has attracted increasing interest in recent years. This study demonstrates a novel sequential adsorption–aggregation concept that harnesses tubular halloysite nanotubes (HNTs) and flexible cellulose nanofibrils (CNFs) for the removal of a small, anionic dye molecule, chrome azurol S, from water. Hollow HNTs were first allowed to interact with the aqueous dye solution, after which the dye-loaded colloidal nanotubes were aggregated and separated from the water phase with cationized CNFs. The combination of 25 mg CNFs with 1 g HNTs at pH 7 resulted in efficient removal of dye (80%) and turbidity (~100%) and the removal of dye was further promoted in more acidic conditions (within the pH range of 6–8.5) because of the attractive electrostatic interactions. Cationic CNFs not only enabled the separation of dye-loaded clay particles from the water phase through a rapid aggregation but also participated in dye removal through adsorption (~20%). In comparison with nano-sized HNTs, the dye removal performance of micro-sized and chemically similar kaolin was poor (43%). Given the good availability of both HNTs and CNFs and the low consumption of the more expensive component (i.e., CNFs) in the process, the concept is straightforward, readily applicable, environmentally benign, and potentially cost-effective

Pre-Exposure to 50 Hz Magnetic Fields Modifies Menadione-Induced Genotoxic Effects in Human SH-SY5Y Neuroblastoma Cells

BACKGROUND: Extremely low frequency (ELF) magnetic fields (MF) are generated by power lines and various electric appliances. They have been classified as possibly carcinogenic by the International Agency for Research on Cancer, but a mechanistic explanation for carcinogenic effects is lacking. A previous study in our laboratory showed that pre-exposure to ELF MF altered cancer-relevant cellular responses (cell cycle arrest, apoptosis) to menadione-induced DNA damage, but it did not include endpoints measuring actual genetic damage. In the present study, we examined whether pre-exposure to ELF MF affects chemically induced DNA damage level, DNA repair rate, or micronucleus frequency in human SH-SY5Y neuroblastoma cells. METHODOLOGY/PRINCIPAL FINDINGS: Exposure to 50 Hz MF was conducted at 100 µT for 24 hours, followed by chemical exposure for 3 hours. The chemicals used for inducing DNA damage and subsequent micronucleus formation were menadione and methyl methanesulphonate (MMS). Pre-treatment with MF enhanced menadione-induced DNA damage, DNA repair rate, and micronucleus formation in human SH-SY5Y neuroblastoma cells. Although the results with MMS indicated similar effects, the differences were not statistically significant. No effects were observed after MF exposure alone. CONCLUSIONS: The results confirm our previous findings showing that pre-exposure to MFs as low as 100 µT alters cellular responses to menadione, and show that increased genotoxicity results from such interaction. The present findings also indicate that complementary data at several chronological points may be critical for understanding the MF effects on DNA damage, repair, and post-repair integrity of the genome

Saturated fat is more metabolically harmful for the human liver than unsaturated fat or simple sugars

Objective Weight gain predisposes to increased intrahepatic triglycerides (IHTG) and insulin resistance (IR), but these do not occur in all obese subjects. Adipose tissue lipolysis and hepatic de novo lipogenesis (DNL) are the main pathways contributing to IHTG, while ceramides, which synthesis is induced by saturated fatty acids and endotoxin, are key mediators of IR. We hypothesized that dietary macronutrient composition influences the mechanisms and magnitude of weight gain-induced changes in IHTG and IR. Research Design and Methods We overfed 38 overweight subjects (age 48±2, BMI 31±1 kg/m2, liver fat 4.7±0.9%) 1000 extra kilocalories/day of either saturated or unsaturated fat or simple sugars for 3 weeks. We measured IHTG (1H-MRS), pathways contributing to IHTG (lipolysis ([2H5]glycerol) and DNL (2H2O) basally and during euglycemic hyperinsulinemia), IR, plasma ceramides (UPLC-MS) and endotoxemia at 0 and 3 weeks. Results Overfeeding saturated fat increased IHTG more (+55%) than unsaturated fat (+15%) or simple sugars (+33%) despite similar increases in body weight. Simple sugars increased DNL (+98%) whilst saturated fat increased lipolysis (+11%). Saturated fat but not other diets induced IR (+23%), endotoxemia (+9%) and increased multiple plasma ceramides (+32 to +63%). Conclusions These data demonstrate that the macronutrient composition of the diet overconsumed matters. Saturated fat exerts greater metabolic harm on the liver than unsaturated fat or simple sugars

Team size matters : collaboration and scientific impact since 1900

This paper provides the first historical analysis of the relationship between collaboration and scientific impact, using three indicators of collaboration (number of authors, number of addresses, and number of countries) and including articles published between 1900 and 2011. The results demonstrate that an increase in the number of authors leads to an increase in impact–-from the beginning of the last century onwards—and that this is not simply due to self-citations. A similar trend is also observed for the number of addresses and number of countries represented in the byline of an article. However, the constant inflation of collaboration since 1900 has resulted in diminishing citation returns: larger and more diverse (in terms of institutional and country affiliation) teams are necessary to realize higher impact. The paper concludes with a discussion of the potential causes of the impact gain in citations of collaborative papers

Tracking and coordinating an international curation effort for the CCDS Project

The Consensus Coding Sequence (CCDS) collaboration involves curators at multiple centers with a goal of producing a conservative set of high quality, protein-coding region annotations for the human and mouse reference genome assemblies. The CCDS data set reflects a ‘gold standard’ definition of best supported protein annotations, and corresponding genes, which pass a standard series of quality assurance checks and are supported by manual curation. This data set supports use of genome annotation information by human and mouse researchers for effective experimental design, analysis and interpretation. The CCDS project consists of analysis of automated whole-genome annotation builds to identify identical CDS annotations, quality assurance testing and manual curation support. Identical CDS annotations are tracked with a CCDS identifier (ID) and any future change to the annotated CDS structure must be agreed upon by the collaborating members. CCDS curation guidelines were developed to address some aspects of curation in order to improve initial annotation consistency and to reduce time spent in discussing proposed annotation updates. Here, we present the current status of the CCDS database and details on our procedures to track and coordinate our efforts. We also present the relevant background and reasoning behind the curation standards that we have developed for CCDS database treatment of transcripts that are nonsense-mediated decay (NMD) candidates, for transcripts containing upstream open reading frames, for identifying the most likely translation start codons and for the annotation of readthrough transcripts. Examples are provided to illustrate the application of these guidelines

Overweight, obesity, and risk of cardiometabolic multimorbidity: pooled analysis of individual-level data for 120 813 adults from 16 cohort studies from the USA and Europe

Summary Background Although overweight and obesity have been studied in relation to individual cardiometabolic diseases, their association with risk of cardiometabolic multimorbidity is poorly understood. Here we aimed to establish the risk of incident cardiometabolic multimorbidity (ie, at least two from: type 2 diabetes, coronary heart disease, and stroke) in adults who are overweight and obese compared with those who are a healthy weight. Methods We pooled individual-participant data for BMI and incident cardiometabolic multimorbidity from 16 prospective cohort studies from the USA and Europe. Participants included in the analyses were 35 years or older and had data available for BMI at baseline and for type 2 diabetes, coronary heart disease, and stroke at baseline and follow-up. We excluded participants with a diagnosis of diabetes, coronary heart disease, or stroke at or before study baseline. According to WHO recommendations, we classified BMI into categories of healthy (20·0–24·9 kg/m2), overweight (25·0–29·9 kg/m2), class I (mild) obesity (30·0–34·9 kg/m2), and class II and III (severe) obesity (≥35·0 kg/m2). We used an inclusive definition of underweight (Peer reviewe