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إيران والعراق
تشتمل هذه الدراسة على ثلاثة أقسام ؛ حيث يمثل القسم الأول والذي بعنوان : \"نهاية الاحتواء المزدوج : العراق وإيران والعقوبات الذكية\"، نصا محررا لوقائع الندوة التي عقدت في مكتبة الكونجرس الأمريكي بتاريخ 20 حزيران / يونيو 2001، برعاية قسم الشرق الأوسط وأفريقيا بالمكتبة المذكورة، ومجلس الأطلسي في الولايات المتحدة الأمريكية، ومجلس سياسات الشرق الأوسط، ومؤسسة ستانلي. وتحتوي مناقشات الندوة على آراء هامة لدبلوماسيين ومتخصصين تتعلق بسياسات الولايات المتحدة تجاه منطقة الشرق الأوسط بصفة عامة، وتجاه إيران والعراق (قبل الحرب الأخيرة) بصفة خاصة، إضافة إلى طرح بعض الأفكار حول موضوعات أخرى متصلة أهمها الوجود العسكري الأمريكي في منطقة الخليج العربي. ويضم القسم الثاني بحثا بعنوان \"سياسة الهيمنة : الولايات المتحدة الأمريكية وإيران\"، من إعداد الدكتور جيمس بيل، الذي سعى في تحليله إلى استخدام تقرير مجلس الأطلسي-الذي أعدته على مدى ثلاثة أعوام مجموعة العمل حول إيران في المجلس، بهدف تطوير \"استراتيجية مختلفة\" ونهج أمريكي جديد نحو إيران- بوصفه نقطة انطلاق نحو فهم جديد للعلاقات الأمريكية الإيرانية. أما القسم الثالث فهو عبارة عن وثيقة بعنوان : \"فشل السياسة الأمريكية تجاه العراق والبدائل المقترحة\"، من إعداد ثلاثة خبراء في شأن السياسة الأمريكية إزاء العراق هم : فيليس بينيس وستيفن زيونس ومارثا هوني. وتعد هذه الوثيقة حصيلة اجتماعين عقدا في واشنطن عام 2001 بمبادرة من مركز السياسة الخارجية تحت المجهر (FPIF) ؛ لبحث أسباب فشل سياسة الولايات المتحدة الأمريكية التي كانت معتمدة ضد العراق، وصياغة بيان يحدد عناصر لما كان يفترض (قبل الحرب الأخيرة) أن تكون سياسة جديدة وأكثر إنسانية وفاعلية تجاهه.
Do We Really Need a New ‘Constructivist Institutionalism’ to Explain Institutional Change?
Rational choice, historical institutionalism and sociological institutionalism are under criticism from a new ‘constructivist institutionalism’ – with critics claiming that established positions cannot explain institutional change effectively, because agents are highly constrained by their institutional environments. These alleged problems in explaining institutional change are exaggerated and can be dealt with by using a suitably tailored historical institutionalism. This places active, interpretive agents at the centre of analysis, in institutional settings modelled as more flexible than those found in ‘sticky’ versions of historical institutionalism. This alternative approach also absorbs core elements of constructivism in explaining institutional change. The article concludes with empirical illustrations, mainly from Australian politics, of the key claims about how agents operate within institutions with ‘bounded discretion’, and how institutional environments can shape and even empower agency in change processes.
Journal Article
The best American mystery stories 2016
The Best American Mystery Stories 2016 is a feast of both literary crime and hard-boiled detection, featuring a seemingly innocent murderer, a drug dealer in love, a drunken prank gone terribly wrong, and plenty of other surprising twists and turns.
Book
Chromosome Duplication in Saccharomyces cerevisiae
The accurate and complete replication of genomic DNA is essential for all life. In eukaryotic cells, the assembly of the multi-enzyme replisomes that perform replication is divided into stages that occur at distinct phases of the cell cycle. Replicative DNA helicases are loaded around origins of DNA replication exclusively during G1 phase. The loaded helicases are then activated during S phase and associate with the replicative DNA polymerases and other accessory proteins. The function of the resulting replisomes is monitored by checkpoint proteins that protect arrested replisomes and inhibit new initiation when replication is inhibited. The replisome also coordinates nucleosome disassembly, assembly, and the establishment of sister chromatid cohesion. Finally, when two replisomes converge they are disassembled. Studies in Saccharomyces cerevisiae have led the way in our understanding of these processes. Here, we review our increasingly molecular understanding of these events and their regulation.
Journal Article
Biomimetic mineralization of metal-organic frameworks as protective coatings for biomacromolecules
Enhancing the robustness of functional biomacromolecules is a critical challenge in biotechnology, which if addressed would enhance their use in pharmaceuticals, chemical processing and biostorage. Here we report a novel method, inspired by natural biomineralization processes, which provides unprecedented protection of biomacromolecules by encapsulating them within a class of porous materials termed metal-organic frameworks. We show that proteins, enzymes and DNA rapidly induce the formation of protective metal-organic framework coatings under physiological conditions by concentrating the framework building blocks and facilitating crystallization around the biomacromolecules. The resulting biocomposite is stable under conditions that would normally decompose many biological macromolecules. For example, urease and horseradish peroxidase protected within a metal-organic framework shell are found to retain bioactivity after being treated at 80 °C and boiled in dimethylformamide (153 °C), respectively. This rapid, low-cost biomimetic mineralization process gives rise to new possibilities for the exploitation of biomacromolecules.
Robust biomacromolecules could be used for a wide range of biotechnological applications. Here the authors report a biomimetic mineralization process, in which biomolecules are encapsulated within metal-organic frameworks, and their stability is subsequently increased without significant bioactivity loss.
Journal Article
Tree species identity drives the vertical distribution of soil carbon and nutrient concentrations in the Loess Plateau, China
Aims
Afforestation is considered an effective strategy to improve soil carbon (C) and fertility in degraded drylands. However, how specific species identities (e.g., conifers or broadleaves) impact C and nutrient concentrations across deep soil layers remains uncertain.
Methods
Three most important plantation forests, including plantations of native mono-species
Pinus tabuliformis
(coniferous species), exotic mono-species
Robinia pseudoacacia
(broadleaf and nitrogen-fixing species), and their mixed, were selected to explore their effects on soil organic C (SOC) and nutrient concentrations throughout soil profile (0–200 cm) in the Loess Plateau.
Results
The results showed that soil C and nutrient concentrations were strongly affected by species identity. Specifically,
R. pseudoacacia
contained significantly higher SOC, total nitrogen (N), and ammonia N concentrations than other plantations at the top layer (0–60 cm), but
R. pseudoacacia
contained lower total phosphorus (P) concentrations than other plantations. In the deep layer (60–200 cm),
R. pseudoacacia
contained lower total N, nitrate N, and total P concentrations than other plantations. There was no significant difference in SOC concentration among plantation types in the deep layer. We found antagonistic effects of tree mixtures on soil P in the top and deep layers. Furthermore, microbial biomass C and N was the primary driver of SOC and N concentration in the top layer, respectively. Conversely, fine root biomass was the primary factor influencing N and P concentrations in the deep layer. This suggests that planting exotic
R. pseudoacacia
with higher root biomass has the potential to exacerbate soil N and P depletion in the deep layer.
Conclusion
Our work emphasizes the key role of species identities in regulating soil nutrient concentrations, especially in the deep layer, and the importance of tree species selection in dryland afforestation.
Journal Article
Structural insights into S-lignin O-demethylation via a rare class of heme peroxygenase enzymes
The
O
-demethylation of lignin aromatics is a rate-limiting step in their bioconversion to higher-value compounds. A recently discovered cytochrome P450, SyoA, demethylates the S-lignin aromatic syringol. In this work, we solve high-resolution X-ray crystal structures of substrate-free and substrate-bound SyoA and evaluate demethylation of
para
-substituted S-lignin aromatics via monooxygenase and peroxide shunt pathways. We find that SyoA demethylates S-lignin aromatics exclusively using the peroxide shunt pathway. The atomic-resolution structures reveal the position of non-canonical residues in the I-helix (Gln252, Glu253). Mutagenesis of this amide-acid pair in SyoA shows they are critical for catalytic activity. This work expands the enzymatic toolkit for improving the capacity to funnel lignin derived aromatics towards higher value compounds and defines the chemistry within the active site of the enzyme that enables peroxygenase activity. These insights provide a framework for engineering peroxygenase activity in other heme enzymes to generate easier to use biocatalysts.
This article demonstrates that native P450 peroxygenases with the in-built machinery for hydrogen peroxide utilisation exist; defines the molecular template for native P450 peroxygenase activity; and suggests that these could be useful biocatalysts in future synthetic biology applications.
Journal Article
A helicase-tethered ORC flip enables bidirectional helicase loading
Replication origins are licensed by loading two Mcm2-7 helicases around DNA in a head-to-head conformation poised to initiate bidirectional replication. This process requires origin–recognition complex (ORC), Cdc6, and Cdt1. Although different Cdc6 and Cdt1 molecules load each helicase, whether two ORC proteins are required is unclear. Using colocalization single-molecule spectroscopy combined with single-molecule Förster resonance energy transfer (FRET), we investigated interactions between ORC and Mcm2-7 during helicase loading. In the large majority of events, we observed a single ORC molecule recruiting both Mcm2-7/Cdt1 complexes via similar interactions that end upon Cdt1 release. Between first- and second-helicase recruitment, a rapid change in interactions between ORC and the first Mcm2-7 occurs. Within seconds, ORC breaks the interactions mediating first Mcm2-7 recruitment, releases from its initial DNA-binding site, and forms a new interaction with the opposite face of the first Mcm2-7. This rearrangement requires release of the first Cdt1 and tethers ORC as it flips over the first Mcm2-7 to form an inverted Mcm2-7–ORC–DNA complex required for second-helicase recruitment. To ensure correct licensing, this complex is maintained until head-to-head interactions between the two helicases are formed. Our findings reconcile previous observations and reveal a highly coordinated series of events through which a single ORC molecule can load two oppositely oriented helicases.
Journal Article
An archaeal nucleoid-associated protein binds an essential motif in DNA replication origins
DNA replication typically has defined start sites, or replication origins, which are designated by their recognition by specific initiator proteins. In addition to initiators, general chromatin or nucleoid-associated proteins have been shown to play roles in modulating origin efficiency in eukaryotes and bacteria. The role of chromatin proteins in origin function in the archaeal domain of life is poorly understood. Here, we describe a dissection of sequences elements required for in vivo function of an archaeal DNA replication origin. Our data reveal a hitherto uncharacterized sequence element, the
ucm
, is required for origin activity. We identify a protein, UBP, that interacts with the
ucm
and additionally with hundreds of other sites on the genome. We solve the crystal structure of UBP alone and in complex with
ucm
DNA, and further show that UBP interacts with the MCM replicative helicase. Taken together, our data provide evidence that UBP functions as a general nucleoid-associated protein that plays a key role in facilitating the egress of the MCM replicative helicase from DNA replication origins.
The mechanisms that regulate the initiation of DNA replication in archaea are poorly understood. Here, Dhanaraju et al. identify a sequence element and its interacting protein required for DNA replication initiation in the model archaeon
Sulfolobus islandicus
.
Journal Article
Automatic data-driven design and 3D printing of custom ocular prostheses
Millions of people require custom ocular prostheses due to eye loss or congenital defects. The current fully manual manufacturing processes used by highly skilled ocularists are time-consuming with varying quality. Additive manufacturing technology has the potential to simplify the manufacture of ocular prosthetics, but existing approaches just replace to various degrees craftsmanship by manual digital design and still require substantial expertise and time. Here we present an automatic digital end-to-end process for producing custom ocular prostheses that uses image data from an anterior segment optical coherence tomography device and considers both shape and appearance. Our approach uses a statistical shape model to predict, based on incomplete surface information of the eye socket, a best fitting prosthesis shape. We use a colour characterized image of the healthy fellow eye to determine and procedurally generate the prosthesis’s appearance that matches the fellow eye. The prosthesis is manufactured using a multi-material full-colour 3D printer and postprocessed to satisfy regulatory compliance. We demonstrate the effectiveness of our approach by presenting results for 10 clinic patients who received a 3D printed prosthesis. Compared to a current manual process, our approach requires five times less labour of the ocularist and produces reproducible output.
Manual processes to produce ocular prostheses are time-consuming and yield varying quality. Here, authors present an automatic digital end-to-end process for custom ocular prostheses. It creates shape and appearance from image data of an OCT device and produces them using a full-colour 3D printer.
Journal Article