5,700 research outputs found
Copper(I)-Phosphinite Complexes in Click Cycloadditions: Three-Component Reactions and Preparation of 5-Iodotriazoles
© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.The remarkable activity displayed by copper(I)–phosphinite complexes of general formula [CuBr(L)] in two challenging cycloadditions is reported: a) the one-pot azidonation/cycloaddition of boronic acids, NaN3, and terminal alkynes; b) the cycloaddition of azides and iodoalkynes. These air-stable catalysts led to very good results in both cases and the expected triazoles could be isolated in pure form under ‘Click-suitable’ conditions
Single-molecule electrical contacts on silicon electrodes under ambient conditions
The ultimate goal in molecular electronics is to use individual molecules as the active electronic component of a real-world sturdy device. For this concept to become reality, it will require the field of single-molecule electronics to shift towards the semiconducting platform of the current microelectronics industry. Here, we report silicon-based single-molecule contacts that are mechanically and electrically stable under ambient conditions. The single-molecule contacts are prepared on silicon electrodes using the scanning tunnelling microscopy break-junction approach using a top metallic probe. The molecular wires show remarkable current–voltage reproducibility, as compared to an open silicon/nano-gap/metal junction, with current rectification ratios exceeding 4,000 when a low-doped silicon is used. The extension of the single-molecule junction approach to a silicon substrate contributes to the next level of miniaturization of electronic components and it is anticipated it will pave the way to a new class of robust single-molecule circuits
Electron Tunneling in Ferritin and Associated Biosystems
Ferritin is a 12 nanometer (nm) diameter iron storage protein complex that is found in most plants and animals. A substantial body of evidence has established that electrons can tunnel through and between ferritin protein nanoparticles and that it exhibits Coulomb blockade behavior, which is also seen in quantum dots and nanoparticles. This evidence can be used to understand the behavior of these particles for use in nanoelectronic devices, for biomedical applications and for investigation of quantum biological phenomena. Ferritin also has magnetic properties that make it useful for applications such as memristors and as a contrast agent for magnetic resonance imaging. This article provides a short overview of this evidence, as well as evidence of ferritin structures in vivo and of tunneling in those structures, with an emphasis on ferritin structures in substantia nigra pars compacta (SNc) neurons. Potential biomedical applications that could utilize these ferritin protein nanoparticles are also discussed.</p
The origin of the Acheulean: the 1.7 million-year-old site of FLK West, Olduvai Gorge (Tanzania)
The appearance of the Acheulean is one of the hallmarks of human evolution. It represents the
emergence of a complex behavior, expressed in the recurrent manufacture of large-sized tools, with
standardized forms, implying more advance forethought and planning by hominins than those required
by the precedent Oldowan technology. The earliest known evidence of this technology dates back to
c. 1.7 Ma. and is limited to two sites (Kokiselei [Kenya] and Konso [Ethiopia]), both of which lack fauna.
The functionality of these earliest Acheulean assemblages remains unknown. Here we present the
discovery of another early Acheulean site also dating to c. 1.7 Ma from Olduvai Gorge. This site provides
evidence of the earliest steps in developing the Acheulean technology and is the oldest Acheulean site in
which stone tools occur spatially and functionally associated with the exploitation of fauna. Simple and
elaborate large-cutting tools (LCT) and handaxes co-exist at FLK West, showing that complex cognition
was present from the earliest stages of the Acheulean. Here we provide a detailed technological study
and evidence of the use of these tools on the butchery and consumption of fauna, probably by early
Homo erectus sensu lato
Experiencing the possibility of near death on a daily basis: A phenomenological study of patients with chronic heart failure
Background: Chronic heart failure (CHF) is a syndrome that greatly impacts people’s lives. Due to the poor
prognosis of CHF, together with the frequent exacerbations of symptoms, death is a topic that is very present
in the lives of patients with CHF.
Objective: To explore thoughts about death experienced by patients with chronic heart failure in their daily lives.
Methods: A hermeneutic phenomenological study was carried out. Conversational interviews were conducted with 20 outpatients with chronic heart failure. Analysis of the responses was based on the method
proposed by van Manen.
Results: From the analysis, four main themes emerged: (1) Feeling afraid of the possibility of dying; (2) Acceptance of the possibility of death; (3) Desiring death for relief from suffering; and (4) Striving to continue living to enjoy family.
Conclusions: This study presents, as a novel finding, that people with CHF experience the possibility of near
death on a daily basis. This experience, which they must encounter on their own, makes them afraid. In addition, some of them, in view of the discomfort they are living, wish to die, with some even considering committing suicide
Comparison of pepper accessions acting as rootstocks: A case with low P inputs
Fertilization is essential for maintaining production in agriculture. Yet, in too high quantity it causes high impact in environment and in farmers economy. This is especially true in the case of phosphorus (P) fertilization. Finding genotypes adapted to low P conditions may help to reduce the problem. P efficiency depends to some extend on the ability of the roots to acquire this mineral, therefore using efficient rootstocks would provide a higher acquisition of P, maintaining the good characteristics of the scion varieties. In this study, twenty diverse pepper accessions (Capsicum annuum L.) have been evaluated as possible rootstocks to increase P acquisition and yield in pepper under no P fertilization. Plant production, biomass, P content and physiological phosphorous use efficiency were evaluated for ‘Lobo’ variety grafted onto different rootstocks. In addition, root traits, measured manually (shovelomics) and semi-automatically (Winrhizo) were studied. The results showed a great diversity in the root traits for the studied accessions. These root traits changed significantly when the accessions act as rootstock, indicating great rootstock/scion interactions. In general, all the rootstocks adapted their root size and shape to that displayed by ‘Lobo’ root system. Some accessions seemed to have some incompatibility whereas some others enhanced the scion performance. It was possible to identify some genotypes suitable to act as rootstocks for pepper with good performance under low P conditions. Root length, root weight, branching, and root angle were identified as key root traits for plant growth and P acquisition under low P conditions
Evangelical Visitor- October 2, 1911. Vol. XXV. No. 20.
Evangelical Visitor published in Harrisburg, Pa., for the exposition of true, practical piety and devoted to the spread of evangelical truths and the unity of the church. Published in the interest of the church of the Brethren in Christ on October 2, 1911. Vol. XXV. No. 20
Mutual optical injection in coupled DBR laser pairs
We report an experimental study of nonlinear effects, characteristic of mutual optical coupling, in an ultra-short coupling regime observed in a distributed Bragg reflector laser pair fabricated on the same chip. Optical feedback is amplified via a double pass through a common onchip optical amplifier, which introduces further nonlinear phenomena. Optical coupling has been introduced via back reflection from a cleaveended fibre. The coupling may be varied in strength by varying the distance of the fibre from the output of the chip, without significantly affecting the coupling time. © 2008 Optical. Society of America
CentrosomeDB: a human centrosomal proteins database
Active research on the biology of the centrosome during the past decades has allowed the identification and characterization of many centrosomal proteins. Unfortunately, the accumulated data is still dispersed among heterogeneous sources of information. Here we present centrosome:db, which intends to compile and integrate relevant information related to the human centrosome. We have compiled a set of 383 likely human centrosomal genes and recorded the associated supporting evidences. Centrosome:db offers several perspectives to study the human centrosome including evolution, function and structure. The database contains information on the orthology relationships with other species, including fungi, nematodes, arthropods, urochordates and vertebrates. Predictions of the domain organization of centrosome:db proteins are graphically represented at different sections of the database, including sets of alternative protein isoforms, interacting proteins, groups of orthologs and the homologs identified with blast. Centrosome:db also contains information related to function, gene–disease associations, SNPs and the 3D structure of proteins. Apart from important differences in the coverage of the set of centrosomal genes, our database differentiates from other similar initiatives in the way information is treated and analyzed. Centrosome:db is publicly available at http://centrosome.dacya.ucm.es
Management of Glucocorticoid-Induced Osteoporosis
This review summarizes the available evidence-based data that form the basis for therapeutic intervention and covers the current status of glucocorticoid-induced osteoporosis (GIOP) management, regulatory requirements, and risk-assessment options. Glucocorticoids are known to cause bone loss and fractures, yet many patients receiving or initiating glucocorticoid therapy are not appropriately evaluated and treated. An European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis workshop was convened to discuss GIOP management and to provide a report by a panel of experts. An expert panel reviewed the available studies that discussed approved therapeutic agents, focusing on randomized and controlled clinical trials reporting on bone mineral density and/or fracture risk of at least 48weeks' duration. There is no evidence that GIOP and postmenopausal osteoporosis respond differently to treatments. The FRAX algorithm can be adjusted according to glucocorticoid dose. Available antiosteoporotic therapies such as bisphosphonates and teriparatide are efficacious in GIOP management. Several other agents approved for the treatment of postmenopausal osteoporosis may become available for GIOP. It is advised to stop antiosteoporotic treatment after glucocorticoid cessation, unless the patient remains at increased risk of fracture. Calcium and vitamin D supplementation as an osteoporosis-prevention measure is less effective than specific antiosteoporotic treatment. Fracture end-point studies and additional studies investigating specific subpopulations (pediatric, premenopausal, or elderly patients) would strengthen the evidence base and facilitate the development of intervention thresholds and treatment guideline
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