bluuebunny/crossref_metadata_2025 huggingface dataset:
The relative importance of methanogenesis in the decomposition of organic matter in northern peatlands
Authors: Corbett J. Elizabeth , Tfaily Malak M. , Burdige David J. , Glaser Paul H. , Chanton Jeffrey P.
Published: January 2015

Using an isotope‐mass balance approach and assuming the equimolar production of CO2 and CH4 from methanogenesis (e.g., anaerobic decomposition of cellulose), we calculate that the proportion of total CO2 production from methanogenesis varies from 37 to 83% across a variety of northern peatlands. In a relative sense, methanogenesis was a more important pathway for decomposition in bogs (80 ± 13% of CO2 production) than in fens (64 ± 5.7% of CO2 production), but because fens contain more labile substrates they may support higher CH4 production overall. The concentration of CO2 produced from methanogenesis (CO2‐meth) can be considered equivalent to CH4 concentration before loss due to ebullition, plant‐mediated transport, or diffusion. Bogs produced slightly less CO2‐meth than fens (2.9 ± 1.3 and 3.7 ± 1.4 mmol/L, respectively). Comparing the quantity of CH4 present to CO2‐meth, fens lost slightly more CH4 than bogs (89 ± 2.8% and 82 ± 5.3%, respectively) likely due to the presence of vascular plant roots. In collapsed permafrost wetlands, bog moats produced half the amount of CO2‐meth (0.8 ± 0.2 mmol/L) relative to midbogs (1.6 ± 0.6 mmol/L) and methanogenesis was less important (42 ± 6.6% of total CO2 production relative to 55 ± 8.1%). We hypothesize that the lower methane production potential in collapsed permafrost wetlands occurs because recently thawed organic substrates are being first exposed to the initial phases of anaerobic decomposition following collapse and flooding. Bog moats lost a comparable amount of CH4 as midbogs (63 ± 7.0% and 64 ± 9.3%).
The role of water tracks in altering biotic and abiotic soil properties and processes in a polar desert in Antarctica
Authors: Ball Becky A. , Levy Joseph
Published: January 2015

Groundwater discharge via water tracks is a largely unexplored passageway routing salts and moisture from high elevations to valley floors in the McMurdo Dry Valleys (MDV) of Antarctica. Given the influence that water tracks have on the distribution of liquid water in seasonally thawed Antarctic soils, it is surprising how little is known about their role in structuring biotic and abiotic processes this cold desert ecosystem. Particularly, it is unclear how soil biota will respond to the activation of new water tracks resulting from enhanced active layer thickening or enhanced regional snowmelt. In the MDV, water tracks are both wetter and more saline than the surrounding soils, constituting a change in soil habitat suitability for soil biology and therefore the ecological processes they carry out. To investigate the net impact that water tracks have on Dry Valley soil biology, and therefore the ecosystem processes for which they are responsible, we analyzed microbial biomass and activity in soils inside and outside of three water tracks and relate this to the physical soil characteristics. Overall, our results suggest that water tracks can significantly influence soil properties, which can further impact biological biovolume and both biotic and abiotic fluxes of CO2. However, the nature of its impact differs with water track, further suggesting that not all water tracks can be regarded the same.
Temporal responses of groundwater‐surface water exchange to successive storm events
Authors: Dudley‐Southern Marina , Binley Andrew
Published: January 2015

Groundwater‐surface water exchange within the hyporheic zone is widely recognized as a key mechanism controlling the fate of nutrients within catchments. In gaining river systems, groundwater‐surface water interactions are constrained by upwelling groundwater but there is increasing evidence that a rapid rise in river stage during storm events can result in a temporary reversal of vertical hydraulic gradients, leading to surface water infiltration into the subsurface and supply of surface‐borne reactive solutes to this biogeochemically active interface. At a UK study site, using logged hydraulic heads in the surface water, riverbed, and riverbanks and logged electrical conductivity at multiple depths in the riverbed we show that storm events can lead to a temporary reversal of vertical hydraulic gradient with mixing evident up to 30 cm beneath the riverbed. Cross‐channel variability is evident, with the center of the channel consistently having shorter reversals of hydraulic gradient, compared to the channel margins. The direction of shallow subsurface riverbank flow at the site is also reactive to storm events, temporarily aligning with the surface flow direction and then reverting back to preevent conditions. Such a transition of flow paths during events is also likely to lead to expansion of lateral hyporheic exchange. This study provides evidence that storm events can be a key driver of enhanced hyporheic exchange in gaining river systems, which may support nutrient reactions beyond the duration of event‐driven change. Our observations demonstrate the dynamic nature of the hyporheic zone, which should be considered when evaluating its biogeochemical function.
Cerebral Cortex
Authors: Majewska Ania K
Published: January 2015

The cerebral cortex is a telencephalic structure present in some vertebrate species located at the surface of the cerebral hemispheres. It is the brain area most recently acquired in evolution. The cerebral cortex resembles a six layer sheet of neurons that in many animals, including humans, is folded to fit into the confines of the skull. Each cerebral cortex hemisphere is made of four anatomically distinct lobes: frontal, parietal, occipital and temporal. Within these lobes, different cortical functions are carried out by functionally and anatomically distinct cortical areas. Although structurally similar, the two hemispheres of the cortex are not functionally equivalent. The cerebral cortex is involved in many higher‐level functions such as sensory perception, cognition, language, memory, decision making, motor planning and control.

Key Concepts

The cerebral cortex is well‐organised anatomical structure with six neuronal layers and subareas that are anatomically and functionally distinct.

The cerebral cortex is composed of different neuronal subtypes that are organised into networks that connect neurons within and between distinct functional areas.

A large part of the cerebral cortex is devoted to processing sensory stimuli from the environment.

The remainder of the cortex is devoted to motor planning and control, as well as integration of multiple sensory cues and cognitive processing.

The two hemispheres of the brain are similar in organisation but distinct in some functions.

The complex networks of the cerebral cortex are specified in development using intrinsic molecular cues and spontaneous neuronal activity, although sensory‐driven activity can also play a role.
Neurotransmitter Release from Presynaptic Terminals
Authors: Sullivan Jane M , Schweizer Felix E
Published: January 2015

Neurotransmitter release from presynaptic nerve terminals is a central component of synaptic transmission, the main process by which neurons communicate with each other and with target cells. Neurotransmitter is packaged inside small vesicles in the presynaptic nerve terminal. When an action potential invades the nerve terminal, voltage‐gated calcium channels open and calcium flows into the cell. The influx of calcium triggers the fusion of the neurotransmitter‐filled synaptic vesicles with the cell membrane, thereby releasing their contents into the synaptic cleft. In addition to action potential‐evoked release, neurotransmitter can also be released ‘spontaneously’ in the absence of action potential firing. Although evoked and spontaneous release share many features, there is growing evidence that they may serve different functions and might be modulated through different signalling pathways, adding richness to the synaptic repertoire.

Key Concepts

Neurotransmitter release is the main mechanism by which neurons communicate with one another and with muscles—without neurotransmission, we could not sense our environment, think or act.

Neurotransmitter release is tightly regulated, and is very rapidly triggered by the firing of an action potential, which depolarises the presynaptic terminal and causes the influx of calcium ions.

Neurotransmitter release is probabilistic; only a fraction of action potentials succeed in triggering release of neurotransmitter from any particular release site.

Calcium ions are the critical signal that coordinates the molecular interactions responsible for fusion of neurotransmitter‐filled synaptic vesicles with the plasma membrane.

Because synaptic vesicles are roughly the same size and contain about the same amount of neurotransmitter, neurotransmitter release can be characterised as ‘quantal’, that is, occurring in discrete packets.

Neurotransmitter release can occur through three different mechanisms: fast synchronous, slower asynchronous and spontaneous. Synchronous and asynchronous releases are triggered by action potentials, whereas spontaneous release occurs in the absence of action potential firing.

Although synchronous, asynchronous and spontaneous neurotransmitter release share many common features, current evidence suggests that different molecules, signalling pathways and/or vesicle pools might be responsible for mediating and modulating these different forms of neurotransmitter release.
Biotin
Authors: Waldrop Grover L
Published: January 2015

Biotin is a vitamin that is a cofactor for enzymes involved in carbon dioxide metabolism. Biotin‐dependent enzymes catalyse carboxylations, decarboxylations and transcarboxylations. These reactions are involved in a variety of metabolic functions from fatty acid synthesis to gluconeogenesis and are found in all animals, plants and bacteria. The common feature of biotin‐dependent enzymes is they are multifunctional. They contain two separate active sites that catalyse distinct chemical reactions. The biotin moiety, which is covalently attached to the enzyme via the amino acid lysine, alternates between the two distinct active sites. In one active site, biotin is carboxylated, whereas, in the other active site, the carboxyl group is transferred to an acceptor molecule. Avidin and streptavidin are proteins that bind biotin very tightly. The high affinity between biotin and avidin/streptavidin is utilised for a variety of biotechnological techniques such as protein purification and immunoassays such as Western blotting.

Key Concepts

Biotin is a vitamin.

Biotin is a cofactor for enzymes involved in CO2metabolism.

Biotin‐dependent enzymes catalyse carboxylation, decarboxylation and transcarboxylation reactions.

Biotin‐dependent enzymes are multifunctional and contain two distinct active sites.

Biotin, which is covalently attached to a protein, moves between each of the two active sites.

The two active sites and the biotin carrier protein can comprise three separate proteins that form a complex or they can form domains on a single polypeptide.

The biotin‐dependent enzyme acetyl‐CoA carboxylase is an emerging target for antibiotic development.

The proteins avidin and streptavidin bind biotin very tightly and with a high degree of specificity.

The very high affinity and specificity of the biotin avidin/streptavidin interaction is used for many biotechnology techniques.
Amino Acid Degradation
Authors: Sawers R Gary
Published: January 2015

Amino acids are valuable metabolic fuels, providing a supply of both nitrogen and carbon for intermediary metabolism and energy for growth. Controlled degradation of amino acids is important in the maintenance of the carbon–nitrogen balance. It is becoming increasingly apparent that imbalance in amino acid degradation can have important consequences for both development and disease. Generally, the first step in degradation of amino acids results in the amino group either being incorporated into other nitrogenous compounds or being excreted as ammonia or urea, while the carbon skeleton is catabolised to one of a few common metabolic intermediates. Thus, an understanding of amino acid degradation provides knowledge of the interrelationships between metabolic pathways and helps explain some of the clinical features when deficiencies in amino acid metabolism occur.

Key Concepts

Amino acids are important growth substrates for microorganisms.

Tight control of amino acid degradation and cycling maintains the C–N balance.

Glutamate is a key central amino acid in maintenance of the C–N balance.

The first step in amino acid degradation is removal of the α‐amino group.

Key steps in amino acid degradation include deamination, catalysed by pyridoxal‐phosphate‐dependent transaminases, oxidoreductases or carbon–oxygen lyases, decarboxylase reactions and carbon skeleton rearrangements catalysed by isomerases.

Carbon skeletons arising from amino acid breakdown are channelled into central metabolism.

Production and excretion of urea and uric acid by animals and birds and reptiles, respectively, avoids the accumulation of toxic levels of ammonia in blood and tissues.

Metabolic products derived from
l
‐serine are essential for cell proliferation and a functional nervous system.

Absence of key enzymes, or imbalance in amino acid degradation, leads to severe disease states, such as phenylketonuria and methylmalonic aciduria.
Acquired Bleeding Disorders
Authors: O'Sullivan Jennifer , Hunt Beverley J
Published: January 2015

Acquired bleeding disorders include disseminated intravascular coagulation (
DIC
), vitamin K deficiency, massive transfusion, renal and liver disease and hyperfibrinolysis. A history of a bleeding tendency should be followed by appropriate laboratory investigations.
DIC
is characterised by consumption of platelets and coagulation factors and increased fibrinolytic activity. The treatment of the underlying condition is key to
DIC
management. In major bleeding, serial coagulation tests should be performed to guide use of blood components. Vitamin K deficiency occurs in neonates and malabsorptive states. Abnormalities in liver disease involve coagulation and fibrinolytic defects and platelet dysfunction, whereas in renal disease, abnormal platelet function and adhesion is the primary abnormality. Hyperfibrinolysis involves excessive fibrinolytic activity causing disproportionately elevated
FDPs
(fibrinogen degradation products) (D‐dimer levels) and should be considered in patients with liver disease and disseminated cancers. Acquired coagulation inhibitors result from immune‐mediated inhibition of a coagulation factor in patients with inherited bleeding disorder or previously normal haemostasis.

Key Concepts

Key to management of DIC is treatment of the underlying condition.

Only replace coagulation proteins and platelets in bleeding patient or for planned interventions.

Early use of fresh frozen plasma to prevent coagulopathy development is currently recommended.

Tranexamic acid should be given in all patients at risk of or with significant bleeding.

Vitamin K prophylaxis should be offered to all neonates at birth.

Prothrombin complex concentrate is recommended when rapid reversal of vitamin K antagonist therapy is required.

Vitamin K given either orally or intravenously will reverse the effects of VKAs in 6 h.

In liver disease, asymptomatic patients with abnormal coagulation tests do not routinely require replacement therapy.

Abnormalities of platelet function and adhesion are the major causes of bleeding in renal disease.

Acquired coagulation inhibitors can occur in patients with congenital coagulation factor deficiencies or in patients with previously normal haemostasis.
Competition
Authors: Keddy Paul A
Published: January 2015

Competition is the all‐pervasive interaction between organisms in which each reduces the performance of the other, either by depleting mutually required resources or by directly inflicting damage. Competition is an important factor that controls the distribution and abundance of many if not most plants and animals. More generally, it has been a potent force driving natural selection and is a major factor (along with stress, disturbance, predation and mutualism) in shaping the structure of biological communities. Too often, competition is assumed to be occurring without sufficient evidence. Carefully designed experiments are one of the best sources of evidence for competition. Different kinds of experiments uncover different views of competition. In general, plants are organised into competitive hierarchies in which light is often the key resource. Mathematical models allow us to explore how competition might lead to either coexistence or exclusion.

Key Concepts

The contest between organisms for access to essential resources is called competition.

Competition is an important factor controlling the distribution and abundance of many if not most plants and animals.

Kinds of competition can be described by the mechanism of interaction, the type of organisms involved and the relative impacts of the competitors.

Mathematical models, based on assumptions about organism interactions, are sometimes used to explore the consequences of competition.

Except in relatively trivial cases of aggression, competition between organisms can be detected and measured only through carefully designed experiments.

Competition can be either symmetrical (competitors equally matched) or asymmetrical (a clear winner and loser) depending upon the species and the habitat.

Competition may lead to resource partitioning (particularly among motile animals) or may be counterbalanced by natural disturbances (in plants and among sessile animals).
Bioethics of New Assisted Reproduction
Authors: Purdy Laura
Published: January 2015

Infertility is widespread, and, given socialisation about the value of genetically related children, causes much suffering. Assisted reproduction (AR) can enable the infertile to reproduce. As a mostly private sector enterprise, it is delivered primarily as innovative therapy rather than the product of rigorously vetted research, putting women and children at risk of both some immediate harms and unknown long‐term ones. This state of affairs also means that it is difficult for treatment to proceed with genuinely meaningful informed consent. There is also much ethical controversy about the ever‐widening potential scope of AR, among which can be found IVF, ICSI, PGD, PGS, frozen sperm, embryos and eggs, assisted hatching, surrogacy, genetic screening and testing, mtDNA donation and artificial gametes. Regulation of the procedures ranges from minimal or non‐existent to quite stringent; however, the latter does not necessarily focus on harm prevention.

Key Concepts

Human societies socialise their members to seek genetically related children, even at great cost.

Infertility is widespread and causes much suffering.

Much infertility could be prevented, but AR focuses on helping infertile individuals reproduce after it has developed.

AR has, for the most part, developed as innovative treatment rather than as the product of rigorous research programmes, putting women and their children at risk of both immediate harm and unknown long‐term risks.

The context within which AR proceeds also makes truly informed decision‐making and informed consent difficult.

There is a much ethical controversy about AR.

AR needs more stringent regulation to protect women and children from harm.
Genetics and Judaism
Authors: Leavitt Frank J
Published: January 2015

Jewish law (Halacha) rarely gives definitive answers and it is not the only source of Jewish thought. A Jewish philosophical–theological attitude may be more useful than Halacha when approaching new questions, such as problems in the ethics of genetics, which were not foreseen by the ancient Rabbis. Jewish mysticism (Kabala) is no less essential. An approach based on these three sources – Halacha, philosophical–theological thought and Kabala – in the context of specific debates, such as those over genetically modified organisms (GMOs), gene therapy, synthetic biology and genetic screening, can be valuable both in themselves and as illustrations of applications of a method. Maimonides' medical writings, although not ‘religious’ in the usual sense, are consistent with his more religious writings. So they are also relevant to a Jewish approach to genetics.

Key Concepts

Judaism includes Jewish law (Halacha), Jewish mysticism (Kabala) and a theologico‐philosophical tradition.

Rabbi Moshe ben Maimon (Maimonides), rabbi, philosopher and physician, is central to Halacha and to the Jewish theologico‐philosophical tradition.

Judaism is open to different and competing interpretations on the part of people who are hopefully learned in the sources.

Judaism is open to technology and may make use of it in Halachic decision making. But limits must be placed on the use of technology to interfere with basic processes of nature.

Even when biotechnology promises a high likelihood of saving human health or life, there may be limits to the extent to which we may violate human dignity.

Kabala presents a basis for serious questions about the mixing of species.

Maimonides' opinion that nature was not created for our benefit should be considered with respect to extreme interference with the basic structure of nature.

Halachic recommendations to go to extremes to avoid harming others preceded the Precautionary Principle and raise questions about experimentation in synthetic biology when safety has not yet been proven and when benefits to human health are still theoretical.
Chicken as a Developmental Model
Authors: Mok Gi F , Alrefaei Abdulmajeed F , McColl James , Grocott Tim , Münsterberg Andrea
Published: January 2015

The development of a complex organism from a single cell, the fertilised egg, has fascinated people for centuries. Embryo development is highly reproducible and exquisitely regulated. How is it that all tissues and organs form in the right places and at the right time? How is the development of different organ systems coordinated, so that they all fit together correctly at the end? It is challenging to study development, because many embryos are small or inaccessible. The chick embryo is a popular model system with many experimental advantages, which include classic ‘cut and paste’ experiments and mechanistic gene function analyses. The combination of micromanipulations with gain‐ or loss‐of‐function is particularly powerful. The recent development of transgenic lines and advanced imaging techniques ensure that the chicken remains an attractive model system, which will continue to make major contributions to our understanding of molecular and cellular mechanisms controlling developmental processes.

Key Concepts

The chick embryo is easy to access and observe and is therefore an attractive model to study developmental processes.

In the early stages, chick embryo morphology is very similar to human, both are amniotes and their development is very similar.

The chicken and human genomes share considerable homology.

Classic embryological manipulations, such as tissue ablations and tissue grafts, provide information about the contribution of particular cell populations to various organs. These experiments have also told us how cells and tissues influence each other in their developmental decisions.

The molecular and cellular basis for many developmental processes and phenomena were first described in the chick, including limb patterning, neural crest migration, dorso‐ventral neural tube patterning, blood vessel formation, somite segmentation and left–right asymmetry.

Experiments in chicken, which examine the function of genes, have helped elucidate the underlying mechanisms of human genetic diseases and provide a basis for testing novel therapies.

Time‐lapse video microscopy can be used to image live chick embryos, eitherin ovoorex ovousing embryo culture.

We can use chick embryos to visualise complex processes, including cell migration, cell–cell communication, cell differentiation and tissue morphogenesis, in an amniote system.
Brachypodium: A Model Temperate Grass
Authors: Mur Luis AJ , Corke Fiona MK , Doonan John H
Published: January 2015

Brachypodium distachyon
 – Purple False Brome – is a model grass species that is being exploited to provide new information on cereals and biofuel crops.
B. distachyon
is a small, erect, annual, self‐fertile grass with undemanding growth requirements and a rapid life cycle.
B. distachyon
has a small genome (∼
350 Mbp
) and the genomes of several accessions have been sequenced. It has no economic value but comparative genomic approaches have used the smaller
B. distachyon
genome to identify key cereal genes, which have been difficult to pin down in larger genomes.
B. distachyon
is readily transformable using
Agrobacterium tumefaciens
; mutated populations have been developed and genome editing has been demonstrated so that it will be possible to assess the function of any gene. As genome sequencing and assembly becomes ever easier, more scientists will work directly on crops rather than models but
B. distachyon
is likely to remain useful for functional genomics approaches because of its small size and rapid life cycle.

Key Concepts

Brachypodium distachyon
is a model for grass and temperate grass species.

B. distachyon
has one of the smallest genomes in the Gramineae and it has been sequenced and annotated.

The genome sequence has been used in comparative genomic approaches to help map key trait in larger genome cereal crops.

Several
genetic
resources have been developed to aid elucidating gene function including mutagenised populations.

B. distachyon
has been used to give insights into cell wall construction, seed development and responses to environmental stress.
Chronic Traumatic Encephalopathy
Authors: Zetterberg Henrik
Published: January 2015

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease in individuals with a history of multiple concussions or other forms of repetitive brain injury. A definite diagnosis can only be made post‐mortem and it is unclear why some individuals appear more susceptible to progressive neurological symptoms following repetitive brain injury than others. CTE has become a major concern in individuals exposed to increased risk of concussion, for example, sports athletes and some military personnel, but its prevalence in such risk groups is unknown. The condition shares some molecular pathologies with other neurodegenerative disorders and it appears that repetitive concussion can initiate a degenerative process involving protein misfolding that may propagate over the brain many years after the trauma. Clinical manifestations of CTE include a wide range of neurological and psychiatric symptoms. These should be treated but presently there is no disease‐modifying therapy against CTE. In contrast to most other neurodegenerative diseases, the condition is preventable.

Key Concepts

Chronic traumatic encephalopathy (CTE) may develop secondary to repetitive mild traumatic brain injuries.

A definite diagnosis of CTE can only be made post‐mortem.

CTE can be prevented but not cured – prevention and symptomatic treatment are important.

Brain changes in CTE should be possible to detect and monitor using biomarkers.

It is important to study risk factors for CTE – why do some individuals appear to be more susceptible to chronic and sometimes progressive symptoms following traumatic brain injury than others?
Transparent Conductive Metal Thin‐Film Electrodes Structured by Direct Laser Interference Patterning
Authors: Müller‐Meskamp Lars , Schubert Sylvio , Roch Teja , Eckhardt Sebastian , Lasagni Andrés‐Fabián , Leo Karl
Published: January 2015

Thin, transparent silver films sandwiched between dielectric layers are a versatile and high performance transparent electrode technology. Using direct laser interference patterning (DLIP), we are able to structure thin metal films by direct ablation in a fast, single step process. To achieve beneficial pattern and ablation properties, different sublayers of MoOx, Au, Al, Cr, or organics below the silver film and different laser power densities and pulse numbers are investigated. The resulting hexagonally periodic array of apertures shows improved transmittance and sheet resistance. For the best parameter set, the silver network contains little superfluous material at the joints and benefits from partial recrystallization, improving the conductivity. The nanostructured thin‐films have great potential to be combined with dielectric antireflection layers as transparent electrode for any thin‐film optoelectronic devices.
PEGylated Polypyrrole Nanoparticles Conjugating Gadolinium Chelates for Dual‐Modal MRI/Photoacoustic Imaging Guided Photothermal Therapy of Cancer
Authors: Liang Xiaolong , Li Yanyan , Li Xiaoda , Jing Lijia , Deng Zijian , Yue Xiuli , Li Changhui , Dai Zhifei
Published: January 2015

Polypyrrole nanoparticles conjugating gadolinium chelates were successfully fabricated for dual‐modal magnetic resonance imaging (MRI) and photoacoustic imaging guided photothermal therapy of cancer, from a mixture of pyrrole and pyrrole‐1‐propanoic acid through a facile one‐step aqueous dispersion polymerization, followed by covalent attachment of gadolinium chelate, using polyethylene glycol as a linker. The obtained PEGylated poly­pyrrole nanoparticles conjugating gadolinium chelates (Gd‐PEG‐PPy NPs), sized around around 70 nm, exhibited a high T1 relaxivity coefficient of 10.61 L mm−1 s−1, more than twice as high as that of the relating free Gd3+ complex (4.2 L mm–1 s−1). After 24 h intravenous injection of Gd‐PEG‐PPy NPs, the tumor sites exhibited obvious enhancement in both T1‐weighted MRI intensity and photoacoustic signal compared with that before injection, indicating the efficient accumulation of Gd‐PEG‐PPy NPs due to the introduction of the PEG layer onto the particle surface. In addition, tumor growth could be effectively inhibited after treatment with Gd‐PEG‐PPy NPs in combination with near‐infrared laser irradiation. The passive targeting and high MRI/photo­acoustic contrast capability of Gd‐PEG‐PPy NPs are quite favorable for precise cancer diagnosing and locating the tumor site to guide the external laser irradiation for photothermal ablation of tumors without damaging the surrounding healthy tissues. Therefore, Gd‐PEG‐PPy NPs may assist in better monitoring the therapeutic process, and contribute to developing more effective “personalized medicine,” showing great potential for cancer diagnosis and therapy.
Recent Advances in Solution‐Processable Dendrimers for Highly Efficient Phosphorescent Organic Light‐Emitting Diodes (PHOLEDs)
Authors: Xu Xianbin , Yang Xiaolong , Zhao Jiang , Zhou Guijiang , Wong Wai‐Yeung
Published: January 2015

Phosphorescent dendrimers together with dendritic host materials have inherent advantages in achieving highly efficient phosphorescent organic light‐emitting diodes (PHOLEDs) with low‐cost, solution‐processed device fabrication. Recently, much research effort has been devoted to developing these dendritic materials in the field of electroluminescence (EL). In this Focus Review, the major advances in this line of research are summarized and discussed. The crucial roles played by these dendritic organic electronic materials in coping with the key issues in the field of PHOLEDs have been specially emphasized. These include alleviating the triplet‐triplet annihilation effect through the site‐isolation effect associated with the dendritic structures, promoting charge‐carrier injection/transporting ability and ambipolar properties through functionalized dendrons, fulfilling simple PHOLEDs with high EL efficiencies, obtaining self‐hosting phosphorescent emitters, and avoiding undesired energy transfer process from phosphorescent cores to the dendrons. In addition, the future perspectives and ongoing challenges of this research frontier are also highlighted.
Reversible Reconfiguration of DNA Origami Nanochambers Monitored by Single‐Molecule FRET
Authors: Saccà Barbara , Ishitsuka Yuji , Meyer Rebecca , Sprengel Andreas , Schöneweiß Elisa‐Charlott , Nienhaus G. Ulrich , Niemeyer Christof M.
Published: January 2015

Today, DNA nanotechnology is one of the methods of choice to achieve spatiotemporal control of matter at the nanoscale. By combining the peculiar spatial addressability of DNA origami structures with the switchable mechanical movement of small DNA motifs, we constructed reconfigurable DNA nanochambers as dynamic compartmentalization systems. The reversible extension and contraction of the inner cavity of the structures was used to control the distance‐dependent energy transfer between two preloaded fluorophores. Interestingly, single‐molecule FRET studies revealed that the kinetics of the process are strongly affected by the choice of the switchable motifs and/or actuator sequences, thus offering a valid method for fine‐tuning the dynamic properties of large DNA nanostructures. We envisage that the proposed DNA nanochambers may function as model structures for artificial biomimetic compartments and transport systems.
Structure and Mechanism of an Aspartimide‐Dependent Peptide Ligase in Human Legumain
Authors: Dall Elfriede , Fegg Julia C. , Briza Peter , Brandstetter Hans
Published: January 2015

Peptide ligases expand the repertoire of genetically encoded protein architectures by synthesizing new peptide bonds, energetically driven by ATP or NTPs. Here, we report the discovery of a genuine ligase activity in human legumain (AEP) which has important roles in immunity and tumor progression that were believed to be due to its established cysteine protease activity. Defying dogma, the ligase reaction is independent of the catalytic cysteine but exploits an endogenous energy reservoir that results from the conversion of a conserved aspartate to a metastable aspartimide. Legumain’s dual protease–ligase activities are pH‐ and thus localization controlled, dominating at acidic and neutral pH, respectively. Their relevance includes reversible on–off switching of cystatin inhibitors and enzyme (in)activation, and may affect the generation of three‐dimensional MHC epitopes. The aspartate–aspartimide (succinimide) pair represents a new paradigm of coupling endergonic reactions in ATP‐scarce environments.
[Ag21{S2P(OiPr)2}12]+: An Eight‐Electron Superatom
Authors: Dhayal Rajendra S. , Liao Jian‐Hong , Liu Yu‐Chiao , Chiang Ming‐His , Kahlal Samia , Saillard Jean‐Yves , Liu C. W.
Published: January 2015

A novel discrete [Ag21{S2P(OiPr)2}12](PF6) nanocluster has been synthesized and characterized by single‐crystal X‐ray diffraction and also NMR spectroscopy (1H, 31P), ESI mass spectrometry, and other analytic techniques (XPS, EDS, UV/Vis spectroscopy). The Ag21 skeleton has an unprecedented silver‐centered icosahedron that is capped by eight additional metal atoms. The whole framework is protected by twelve dithiophosphate ligands. According to the spherical Jellium model, the stability of monocationic nanocluster can be described by an 8‐electron superatom with 1S2 1P6 configuration, as confirmed by DFT calculations.
Highly Fluorescent and Water‐Soluble Diketopyrrolopyrrole Dyes for Bioconjugation
Authors: Heyer Elodie , Lory Pauline , Leprince Jérôme , Moreau Mathieu , Romieu Anthony , Guardigli Massimo , Roda Aldo , Ziessel Raymond
Published: January 2015

The preparation of highly water‐soluble and strongly fluorescent diketopyrrolopyrrole (DPP) dyes using an unusual taurine‐like sulfonated linker has been achieved. Exchanging a phenyl for a thienyl substituent shifts the emission wavelength to near λ=600 nm. The free carboxylic acid group present in these new derivatives was readily activated and the dyes were subsequently covalently linked to a model protein (bovine serum albumin; BSA). The bioconjugates were characterized by electronic absorption, fluorescence spectroscopy and MALDI‐TOF mass spectrometry, thus enabling precise determination of the labeling density (ratio DPP/BSA about 3 to 8). Outstanding values of fluorescence quantum yield (30 % to 59 %) for these bioconjugates are obtained. The photostability of these DPP dyes is considerably greater than that of fluorescein under the same irradiation conditions. Remarkably low detection limits between 80 and 300 molecules/μm2 were found for the BSA bioconjugates by fluorescence imaging with a epifluorescence microscope.
Preparation of Nanocrystalline Silicon from SiCl4 at 200 °C in Molten Salt for High‐Performance Anodes for Lithium Ion Batteries
Authors: Lin Ning , Han Ying , Wang Liangbiao , Zhou Jianbin , Zhou Jie , Zhu Yongchun , Qian Yitai
Published: January 2015

Crystalline Si nanoparticles are prepared by reduction of SiCl4 with metallic magnesium in the molten salt of AlCl3 at 200 °C in an autoclave. AlCl3 not only acts as molten salt, but also participates in the reaction. The related experiments confirm that metallic Mg reduces AlCl3 to create nascent Al which could immediately reduce SiCl4 to Si, and the by‐product MgCl2 would combine with AlCl3 forming complex of MgAl2Cl8. As anode for rechargeable lithium ion batteries, the as‐prepared Si delivers the reversible capacity of 3083 mAh g−1 at 1.2 A g−1 after 50 cycles, and 1180 mAh g−1 at 3 A g−1 over 500 cycles.
A Facile Synthetic Route to a New SHG Material with Two Types of Parallel π‐Conjugated Planar Triangular Units
Authors: Song Jun‐Ling , Hu Chun‐Li , Xu Xiang , Kong Fang , Mao Jiang‐Gao
Published: January 2015

A new SHG material, namely, Pb2(BO3)(NO3), which contains parallel π‐conjugated nitrate and borate anions, was obtained through a facile hydrothermal reaction by using Pb(NO3)2 and Mg(BO2)2⋅H2O as starting materials. Its structure contains honeycomb [Pb2(BO3)]∞ layers with noncoordination [NO3]− anions located at the interlayer space. Pb2(BO3)(NO3) shows a remarkable strong SHG response of approximately 9.0 times that of potassium dihydrogen phosphate (KDP) and the material is also phase‐matchable. The large SHG coefficient of Pb2(BO3)(NO3) arises from the synergistic effect of the stereoactive lone pairs on Pb2+ cations and parallel alignment of π‐conjugated BO3 and NO3 units. Based on its unique properties, Pb2(BO3)(NO3) may have great potential as a high performance NLO material in photonic applications.
Nano‐SiO2/PMMA‐PU composite particles with core‐shell structure via emulsion polymerization and their application in epoxy resin
Authors: Huang Zeng Fang , Qu Xiao Yue , Chen Zheng
Published: January 2015

A novel method of nano‐SiO2/poly(methyl methacrylate)(PMMA)‐polyurethane(PU) composite particles modifying epoxy resin is reported. The composite particles with the obvious core‐shell structure were prepared by emulsion polymerization of PMMA and PU prepolymer on the surface of nano‐SiO2. The diameter of the composite particles was 50–100 nm with dark core SiO2 (30–60 nm) and light shell polymer of PMMA and PU (20–30 nm); moreover, PU was well distributed in PMMA with about 10 nm diameter. After nano‐SiO2 was encapsulated by PMMA and PU, the Si content on the surface decreased rapidly to 2.08% and the N content introduced by PU was about 1.27%. The ratio of polymer to original nano‐SiO2 (fp), the grafting ratio of polymer to original nano‐SiO2 (fr) and the efficiency grafting ratio of polymer (fe) were, respectively, about 116.7%, 104.4%, and 89.5%. The as‐prepared composite particles were an effective toughness agent to modify epoxy resin, and the impact strength of the modified epoxy resin increased to 46.64 kJ m−2 from 19.12 kJ m−2 of the neat epoxy resin. This research may enrich the field of inorganic nanoparticles with important advances toward the modification for polymer composite materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41919.
Transformation of self‐assembled structures from spherical aggregates in solution to a network structure on a two‐dimensional surface
Authors: Wu Xu , Lin Jing , Yu Danfeng , Wang Jinben , Yang Hui , Su Yuzhi , Ma Aiqing , Sun Keji , Chen Yibo
Published: January 2015

Self‐assembled films of brush‐like amphiphilic copolymers with varying hydrophobic contents (fc12, 10–90 mol %) were prepared on glass slides. In addition, the surface tension and contact angles of solutions of these copolymers were also investigated. By combining the data obtained investigating the morphologies of the films, with the micropolarities, dimensions, and morphologies of the copolymer aggregates in solution phase, it was attempted to illustrate how the self‐assembled structures would adapt to a change in their surrounding environment from a three‐dimensional space in the solution phase into a two‐dimensional solid surface. The copolymer chains underwent inter‐ and intramolecular hydrophobic association simultaneously in the solution phase. When fc12 was increased, the stronger hydrophobicity led the side‐chains that were attached to the same backbone to become packed together, and this intramolecular association caused the copolymers to form smaller and more compact spherical aggregates. The solutions of these smaller and more compact spherical aggregates exhibited a lower surface tension and better wetting behavior on glass surfaces. In addition, these solutions ultimately formed thinner and more orderly network‐based porous films on glass surfaces. The observations described in this report revealed that the copolymer assemblies exhibited a morphological transformation from spherical aggregates in solution to a network structure when the copolymer became confined to a solid surface. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41945.
Years of life lived with disease and years of potential life lost in children who die of cancer in the United States, 2009
Authors: de Blank Peter M. , Ostrom Quinn T. , Rouse Chaturia , Wolinsky Yingli , Kruchko Carol , Salcido Joanne , Barnholtz‐Sloan Jill S.
Published: January 2015

Incidence and survival rates are commonly reported statistics, but these may fail to capture the full impact of childhood cancers. We describe the years of potential life lost (YPLL) and years of life lived with disease (YLLD) in children and adolescents who died of cancer in the United States to estimate the impact of childhood cancer in the United States in 2009. We examined mortality data in 2009 among children and adolescents <20 years old in both the National Vital Statistics System (NVSS) and the Surveillance, Epidemiology, and End Results (SEER) datasets. YPLL and YLLD were calculated for all deaths due to cancer. Histology‐specific YPLL and YLLD of central nervous system (CNS) tumors, leukemia, and lymphoma were estimated using SEER. There were 2233 deaths and 153,390.4 YPLL due to neoplasm in 2009. CNS tumors were the largest cause of YPLL (31%) among deaths due to cancer and were the cause of 1.4% of YPLL due to all causes. For specific histologies, the greatest mean YPLL per death was due to atypical teratoid/rhabdoid tumor (78.0 years lost). The histology with the highest mean YLLD per death in children and adolescents who died of cancer was primitive neuroectodermal tumor (4.6 years lived). CNS tumors are the most common solid malignancy in individuals <20 years old and have the highest YPLL cost of all cancers. This offers the first histology‐specific description of YPLL in children and adolescents and proposes a new measure of cancer impact, YLLD, in individuals who die of their disease. YPLL and YLLD complement traditional indicators of mortality and help place CNS tumors in the context of other childhood malignancies.
Cu‐Decorated Ru Catalysts Supported on Layered Double Hydroxides for Selective Benzene Hydrogenation to Cyclohexene
Authors: Liu Jie , Xu Simin , Bing Weihan , Wang Fei , Li Changming , Wei Min , Evans David G. , Duan Xue
Published: January 2015

The selective hydrogenation of benzene to cyclohexene is of high value for the chemical industry owing to its inexpensive feedstock, atom economy, and operational simplicity. A tunable catalytic behavior towards the selective hydrogenation of benzene was obtained over Cu‐decorated Ru catalysts supported on a layered double hydroxide (denoted as RuxCuy/MgAl‐LDH), reaching a maximum cyclohexene yield of 44.0 % over Ru1.0Cu0.5/MgAl‐LDH at 150 °C and 5.0 MPa without employment of any additives. CO‐TPD (TPD=temperature‐programmed desorption) and in situ CO‐FTIR techniques demonstrated that Cu atoms preferentially deposit on the surface of low‐coordinated Ru atoms in RuxCuy/MgAl‐LDH catalysts, resulting in a low adsorption energy of cyclohexene on the modified sites as revealed by DFT calculations. This work not only gives an understanding of the correlation between the surface exposure of Ru active sites and the resulting selectivity, but also provides a green and additive‐free catalytic process for the selective hydrogenation of benzene.
Binder Effects in SiO2‐ and Al2O3‐Bound Zeolite ZSM‐5‐Based Extrudates as Studied by Microspectroscopy
Authors: Whiting Gareth T. , Meirer Florian , Mertens Machteld M. , Bons Anton‐Jan , Weiss Brian M. , Stevens Paul A. , de Smit Emiel , Weckhuysen Bert M.
Published: January 2015

Microspectroscopic methods were explored to investigate binder effects occurring in ZSM‐5‐containing SiO2‐ and Al2O3‐bound millimetre‐sized extrudates. Using thiophene as a selective probe for Brønsted acidity, coupled with time‐resolved in situ UV/Vis and confocal fluorescence microspectroscopy, variations in reactivity and selectivity between the two distinct binder types were established. It was found that aluminium migration occurs in ZSM‐5‐containing Al2O3‐bound extrudates, forming additional Brønsted acid sites. These sites strongly influence the oligomer selectivity, favouring the formation of thiol‐like species (i.e., ring‐opened species) in contrast to higher oligomers, predominantly formed on SiO2‐bound ZSM‐5‐containing extrudates. Not only were the location and distribution of these oligomers visualised by 3 D analysis, it was also observed that more conjugated species appeared to grow off the surface of the zeolite ZSM‐5 crystals (containing less conjugated species) into the surrounding binder material. Furthermore, a higher binder content resulted in an increasing overall reactivity owing to the greater number of stored thiophene monomers available per Brønsted acid site.
Efficient Organocatalyst Supported on a Simple Ionic Liquid as a Recoverable System for the Asymmetric Diels–Alder Reaction in the Presence of Water
Authors: De Nino Antonio , Maiuolo Loredana , Merino Pedro , Nardi Monica , Procopio Antonio , Roca‐López David , Russo Beatrice , Algieri Vincenzo
Published: January 2015

The synthesis, characterization, and evaluation of a new highly efficient organocatalyst, namely, (5S)‐2,2,3‐trimethyl‐5‐thiobenzylmethyl‐4‐imidazolidinone hydrochloride, has been achieved. The catalyst possesses important structural features that should increase the catalytic efficiency and solubility in polar media. The application of the ionic‐liquid‐supported imidazolidinone catalyst in enantioselective Diels–Alder reactions was investigated. The Diels–Alder reactions of several dienes and dienophiles proceeded efficiently in the presence of the catalyst to provide the desired products in moderate to good yields and from good to excellent enantioselectivities. The conformation study confirms that in the transition state the Re face is shielded completely by the phenyl ring and an approach on the less hindered Si face is preferred. Particularly remarkable is the fact that the entire ionic liquid/HCl 0.01 M/catalyst system can be recovered and reused in up to six runs without an appreciable loss of catalytic activity.