Bees and the pollination services they deliver are beneficial to both food crop production, and for reproduction of many wild plant species. Bee decline has stimulated widespread interest in ...assessing hazards and risks to bees from the environment in which they live. While there is increasing knowledge on how the use of broad-spectrum insecticides in agricultural systems may impact bees, little is known about effects of other pesticides (or plant protection products; PPPs) such as herbicides and fungicides, which are used more widely than insecticides at a global scale. We adopted a systematic approach to review existing research on the potential impacts of fungicides and herbicides on bees, with the aim of identifying research approaches and determining knowledge gaps. While acknowledging that herbicide use can affect forage availability for bees, this review focussed on the potential impacts these compounds could have directly on bees themselves. We found that most studies have been carried out in Europe and the USA, and investigated effects on honeybees. Furthermore, certain effects, such as those on mortality, are well represented in the literature in comparison to others, such as sub-lethal effects. More studies have been carried out in the lab than in the field, and the impacts of oral exposure to herbicides and fungicides have been investigated more frequently than contact exposure. We suggest a number of areas for further research to improve the knowledge base on potential effects. This will allow better assessment of risks to bees from herbicides and fungicides, which is important to inform future management decisions around the sustainable use of PPPs.
Great powers use others' territory for spying. Existing work shows that hosts of spying sometimes enjoy high leverage over great powers in exchange for their cooperation. At other times, hosts wield ...less leverage. Why? This paper points to the quality of intelligence that great powers glean from a host's territory and the availability of alternatives to account for this variation. In U.S. spying on the Soviet Union from Iran, changes in these factors during the 1960s caused Iran's leverage over the United States to increase. U.S. concessions enabled the Shah's excesses. But the United States retained access to extraordinary intelligence.
Anisotropic Etching of Atomically Thin MoS2 Yamamoto, Mahito; Einstein, Theodore L; Fuhrer, Michael S ...
Journal of physical chemistry. C,
12/2013, Letnik:
117, Številka:
48
Journal Article
Recenzirano
Exposure to oxygen at 300–340 °C results in triangular etch pits with uniform orientation on the surfaces of atomically thin molybdenum disulfide (MoS2), indicating anisotropic etching terminating on ...lattice planes. The triangular pits grow laterally with oxidation time. The density of pits scarcely depends on oxidation time, temperature, and MoS2 thickness but varies significantly from sample to sample, indicating that etching is initiated at native defect sites on the basal plane surface rather than activated by substrate effects such as charged impurities or surface roughness. Raman spectroscopy confirms that oxygen treatment produces no molybdenum oxide (MoO3) below 340 °C. However, upon oxidation above 200 °C, the Raman A1g mode upshifts and the linewidth decreases, indicating p-type doping of MoS2. Oxidation at 400 °C results in complete conversion to MoO3.
The phase of a quantum state may not return to its original value after the system’s parameters cycle around a closed path; instead, the wave function may acquire a measurable phase difference called ...the Berry phase. Berry phases typically have been accessed through interference experiments. Here, we demonstrate an unusual Berry phase–induced spectroscopic feature: a sudden and large increase in the energy of angular-momentum states in circular graphene p-n junction resonators when a relatively small critical magnetic field is reached. This behavior results from turning on a π Berry phase associated with the topological properties of Dirac fermions in graphene. The Berry phase can be switched on and off with small magnetic field changes on the order of 10 millitesla, potentially enabling a variety of optoelectronic graphene device applications.
The molecular mechanisms that regulate the rapid transcriptional changes that occur during cytotoxic T lymphocyte (CTL) proliferation and differentiation in response to infection are poorly ...understood. We have utilized ChIP-seq to assess histone H3 methylation dynamics within naive, effector, and memory virus-specific T cells isolated directly ex vivo after influenza A virus infection. Our results show that within naive T cells, codeposition of the permissive H3K4me3 and repressive H3K27me3 modifications is a signature of gene loci associated with gene transcription, replication, and cellular differentiation. Upon differentiation into effector and/or memory CTLs, the majority of these gene loci lose repressive H3K27me3 while retaining the permissive H3K4me3 modification. In contrast, immune-related effector gene promoters within naive T cells lacked the permissive H3K4me3 modification, with acquisition of this modification occurring upon differentiation into effector/memory CTLs. Thus, coordinate transcriptional regulation of CTL genes with related functions is achieved via distinct epigenetic mechanisms.
Display omitted
•Specific H3K4me3 and H3K27me3 patterns identify functionally related CTL genes•Many CTL-specific transcription factors are bivalent for H3K4me3 and H3K27me3•Bivalent loci largely resolve to a permissive signature rapidly after activation•H3K4me2 identifies a subset of rapidly transcribed immune-specific gene loci
It is unclear how changes in genome-wide histone methylation status regulate distinct transcriptional signatures observed in naive, effector, and memory virus-specific cytotoxic lymphocytes. Russ et al. identify key epigenetic signatures that delineate distinct transcriptional programs that underpin CD8+ T cell differentiation during infection.
Atomic Structure of Graphene on SiO2 Ishigami, Masa; Chen, J. H.; Cullen, W. G. ...
Nano letters,
06/2007, Letnik:
7, Številka:
6
Journal Article
Recenzirano
Odprti dostop
We employ scanning probe microscopy to reveal atomic structures and nanoscale morphology of graphene-based electronic devices (i.e., a graphene sheet supported by an insulating silicon dioxide ...substrate) for the first time. Atomic resolution scanning tunneling microscopy images reveal the presence of a strong spatially dependent perturbation, which breaks the hexagonal lattice symmetry of the graphitic lattice. Structural corrugations of the graphene sheet partially conform to the underlying silicon oxide substrate. These effects are obscured or modified on graphene devices processed with normal lithographic methods, as they are covered with a layer of photoresist residue. We enable our experiments by a novel cleaning process to produce atomically clean graphene sheets.
Postpolymerization modification offers a versatile strategy for synthesizing complex macromolecules, yet modifying acrylamide polymers like poly(N,N-dimethylacrylamide) (PDMA) is notoriously ...challenging due to the inherent stability and low reactivity of amide bonds. In this study, we unveil a novel approach for the direct transamidation of PDMA, leveraging recent advances in the transamidation of unactivated tertiary amide substrates. By exploiting photoiniferter polymerization, we extended this direct transamidation approach to ultrahigh-molecular-weight (UHMW) PDMA, showcasing the unprecedented postpolymerization modification of synthetic polymers exceeding 106 g/mol. We also designed acrylamide copolymers comprising both the moderately reactive N-methyl-N-phenyl tertiary amides, along with the less reactive, fully alkyl-substituted N,N-dimethyl amides inherent to PDMA. This disparate reactivity enabled a sequential, chemoselective transamidation by initially targeting the more reactive pendant aryl amides with less nucleophilic aromatic amines, and second, transamidating the untouched N,N-dimethyl amide moieties with more nucleophilic aliphatic amines, yielding a uniquely diversified acrylamide copolymer. This work not only broadens the scope of postpolymerization modification strategies by pioneering direct transamidation of unactivated amides but also provides a robust platform for the design of intricate macromolecules, particularly in the realm of UHMW polymers.
States frequently acquire proof of other states' norm violations, from
nuclear proliferation to harboring terrorists to interfering in elections.
Existing theories do not fully explain how states ...that catch others red-handed
wield a form of coercive power over the wrongdoers. Discoverers may conceal
proof of wrongdoing, share such proof with other actors privately, or reveal
their proof to the world. States with more leverage over wrongdoers have two
incentives to conceal proof of wrongdoing. They can blackmail wrongdoers by
threatening to go public with proof of their guilt, and they can simultaneously
allow wrongdoers to save face. States that possess proof of wrongdoing but have
less leverage are more likely to share that proof with others. If a discoverer
distrusts the intentions of states with more leverage, it will reveal evidence
publicly, catalyzing others to act. Publicizing proof weaponizes the prospect
that other states will pay reputation and hypocrisy costs if they do not follow
through on punishing norm violations. Four case studies of nuclear proliferation
(Taiwan, Libya, South Africa, and North Korea) probe this novel theory.
Introduction
Appendicectomy may reduce relapses and need for medication in patients with ulcerative colitis, but long‐term prospective data are lacking. This study aimed to analyse the effect of ...appendicectomy in patients with refractory ulcerative colitis.
Methods
In this prospective multicentre cohort series, all consecutive patients with refractory ulcerative colitis referred for proctocolectomy between November 2012 and June 2015 were counselled to undergo laparoscopic appendicectomy instead. The primary endpoint was clinical response (reduction of at least 3 points in the partial Mayo score) at 12 months and long‐term follow‐up. Secondary endpoints included endoscopic remission (endoscopic Mayo score of 1 or less), failure (colectomy or start of experimental medication), and changes in Inflammatory Bowel Disease Questionnaire (IBDQ) (range 32–224), EQ‐5D™ and EORTC‐QLQ‐C30‐QL scores.
Results
A total of 28 patients (13 women; median age 40·5 years) underwent appendicectomy. The mean baseline IBDQ score was 127·0, the EQ‐5D™ score was 0·65, and the EORTC‐QLQ‐C30‐QL score was 41·1. At 12 months, 13 patients had a clinical response, five were in endoscopic remission, and nine required a colectomy (6 patients) or started new experimental medical therapy (3). IBDQ, EQ‐5D™ and EORTC‐QLQ‐C30‐QL scores improved to 167·1 (P < 0·001), 0·80 (P = 0·003) and 61·0 (P < 0·001) respectively. After a median of 3·7 (range 2·3–5·2) years, a further four patients required a colectomy (2) or new experimental medical therapy (2). Thirteen patients had a clinical response and seven were in endoscopic remission. The improvement in IBDQ, EQ‐5D™ and the EORTC‐QLQ‐C30‐QL scores remained stable over time.
Conclusion
Appendicectomy resulted in a clinical response in nearly half of patients with refractory ulcerative colitis and a substantial proportion were in endoscopic remission. Elective appendicectomy should be considered before proctocolectomy in patients with therapy‐refractory ulcerative colitis.
Antecedentes
La apendicectomía puede reducir las recaídas y la necesidad de medicación en pacientes con colitis ulcerosa (ulcerative colitis, UC), sin embargo, faltan datos a largo plazo obtenidos de forma prospectiva. El objetivo de este estudio fue analizar el efecto de la apendicectomía en pacientes con UC refractarios al tratamiento.
Métodos
En esta serie prospectiva de cohortes multicéntrica, a todos los pacientes consecutivos con UC refractaria remitidos para proctocolectomía entre noviembre de 2012 y junio de 2015 se les recomendó en su lugar someterse a una apendicectomía laparoscópica. El criterio de valoración principal fue la respuesta clínica (disminución de ≥ 3 puntos del sistema de puntuación parcial de Mayo que varía de 0 a 9) a los 12 meses y en el seguimiento a largo plazo. Los criterios de valoración secundarios incluyeron la remisión endoscópica (puntuación endoscópica de Mayo ≤ 1), fracaso (colectomía o inicio de medicación experimental) y cambios en el IBDQ (rango 32‐224), EQ‐5D y EORTC‐QLQ‐C30‐QL.
Resultados
En total, 28 pacientes (13 mujeres, mediana de edad 40,5) se sometieron a una apendicectomía. El IBDQ de referencia promedio fue de 127,0; el EQ‐5D 0,65 y el EORTC‐QLQ‐C30‐QL 41,1. A los 12 meses, 13 pacientes presentaban una respuesta clínica, cinco estaban en remisión endoscópica y nueve precisaron colectomía (n = 6) o un nuevo tratamiento médico experimental (n = 3). El IBDQ, EQ‐5D y EORTC‐QLQ‐C30‐QL mejoraron a 167,1 (P < 0,001); 0,80 (P = 0,003) y 61,0 (P < 0,001) respectivamente. Después de una mediana de 3,7 años (rango 2,3‐5,2), otros cuatro pacientes requirieron una colectomía (n = 2) o un nuevo tratamiento médico experimental (n = 2). Trece pacientes presentaron respuesta clínica y siete se encontraban en remisión endoscópica. La mejora del IBDQ, el EQ‐5D y el EORTC‐QLQ‐C30‐QL se mantuvo estable a lo largo del tiempo.
Conclusión
La apendicectomía consiguió una respuesta clínica en casi la mitad de los pacientes con UC refractaria. La apendicectomía electiva debería ser considerada antes que la proctocolectomía en pacientes con UC refractaria al tratamiento.
Appendicectomy may reduce relapses and need for medication in patients with ulcerative colitis, but long‐term prospective data are lacking. In this study, appendicectomy resulted in a clinical response in 13 of 28 patients with therapy‐refractory ulcerative colitis and a substantial proportion were in endoscopic remission. Elective appendicectomy should therefore be considered before proctocolectomy in these patients.
Has promise
When intelligence agencies assess whether a state is pursuing nuclear weapons, how much evidence is enough? I argue that intelligence agencies adopt different standards for rendering definitive ...judgments in such situations. This, in turn, pushes them toward different kinds of mistakes. Urgent judges reach definitive conclusions about the existence of secret nuclear weapons programs more quickly and with less evidence than their peers. They risk seeing ambitious nuclear schemes where none exist. Skeptical judges wait longer and accumulate more proof before reaching definitive conclusions. They risk erring in the direction of underestimation. Where existing work focuses on intelligence accuracy, I show that variation in judgment is a distinct and important dimension of performance. What, then, drives judgment? I test an explanation based on the dynamic influence of previous intelligence failure. I observe that the judgment of intelligence agencies in two states, the United States and Israel, was differentially affected by failure as they tracked potential nuclear proliferation by Libya and Syria. These controlled comparisons constitute a novel approach to the study of nuclear intelligence performance. I find significant support for my explanation. Fearing repeat failure, intelligence agencies alter their efforts and standards of proof in an area critical to statecraft.
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