There is a significant drive to identify alternative materials that exhibit room temperature phosphorescence for technologies including bio-imaging, photodynamic therapy and organic light-emitting ...diodes. Ideally, these materials should be non-toxic and cheap, and it will be possible to control their photoluminescent properties. This was achieved here by embedding carbon nanodots within crystalline particles of alkaline earth carbonates, sulphates and oxalates. The resultant nanocomposites are luminescent and exhibit a bright, sub-second lifetime afterglow. Importantly, the excited state lifetimes, and steady-state and afterglow colours can all be systematically controlled by varying the cations and anions in the host inorganic phase, due to the influence of the cation size and material density on emissive and non-emissive electronic transitions. This simple strategy provides a flexible route for generating materials with specific, phosphorescent properties and is an exciting alternative to approaches relying on the synthesis of custom-made luminescent organic molecules.
Thermoresponsive polymers are a class of “smart” materials that have the ability to respond to a change in temperature; a property that makes them useful materials in a wide range of applications and ...consequently attracts much scientific interest. This review focuses mainly on the studies published over the last 10 years on the synthesis and use of thermoresponsive polymers for biomedical applications including drug delivery, tissue engineering and gene delivery. A summary of the main applications is given following the different studies on thermoresponsive polymers which are categorized based on their 3-dimensional structure; hydrogels, interpenetrating networks, micelles, crosslinked micelles, polymersomes, films and particles.
The similarities between gated quantum dots and the transistors in modern microelectronics--in fabrication methods, physical structure and voltage scales for manipulation--have led to great interest ...in the development of quantum bits (qubits) in semiconductor quantum dots. Although quantum dot spin qubits have demonstrated long coherence times, their manipulation is often slower than desired for important future applications, such as factoring. Furthermore, scalability and manufacturability are enhanced when qubits are as simple as possible. Previous work has increased the speed of spin qubit rotations by making use of integrated micromagnets, dynamic pumping of nuclear spins or the addition of a third quantum dot. Here we demonstrate a qubit that is a hybrid of spin and charge. It is simple, requiring neither nuclear-state preparation nor micromagnets. Unlike previous double-dot qubits, the hybrid qubit enables fast rotations about two axes of the Bloch sphere. We demonstrate full control on the Bloch sphere with π-rotation times of less than 100 picoseconds in two orthogonal directions, which is more than an order of magnitude faster than any other double-dot qubit. The speed arises from the qubit's charge-like characteristics, and its spin-like features result in resistance to decoherence over a wide range of gate voltages. We achieve full process tomography in our electrically controlled semiconductor quantum dot qubit, extracting high fidelities of 85 per cent for X rotations (transitions between qubit states) and 94 per cent for Z rotations (phase accumulation between qubit states).
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Metal oxides, sulphides, selenides and tellurides have routinely been investigated and utilised for a wide range of applications, in particular in the areas of energy (photovoltaic, thermoelectric) ...and catalysis (thermocatalysis, electrocatalysis and photoelectrocatalysis). A recent development in this chemical space is high entropy and entropy-stabilised inorganic materials, which took inspiration from preceding work on high entropy metal alloys (multicomponent alloys). High entropy inorganic materials typically have many (often ≥6) different cations or anions to yield a high configurational entropy, which can give unexpected structures and properties that are conducive to a broad range of applications in energy and catalysis. More recently still, high entropy metal chalcogenides have been developed and have been investigated for thermoelectric energy generation, batteries for energy storage and electrocatalysis. This review sets out to define entropic stabilisation in high entropy materials, along with a discussion of synthetic techniques to produce these compounds, focusing on high entropy metal chalcogenides including extant routes to high entropy sulfides, selenides and tellurides. The resulting advantageous properties of these materials due to their multi-element nature and the currently proposed and investigated applications of these materials are reviewed. We end the perspective with an opinion on future directions.
In this perspective we assess the current status of high entropy metal chalcogenides, the synthetic techniques for them, the currently obtained properties and demonstrated applications and a discussion on the possible future directions.
Viscosity measurements have a wide range of applications from industrial chemical production to medical diagnosis. In this work, we have developed a simple droplet-based, water-in-oil continuous ...viscometer capable of measuring viscosity changes in 10 s or less and consuming a total sample volume of less than 1 μL/h. The viscometer employs a flow-focusing geometry and generates droplets under constant pressure. The length of the droplets (L d) is highly correlated to the aqueous-phase viscosity (μaq) at high ratios of aqueous-inlet to oil-inlet pressure (AIP/OIP), yielding a linear relationship between μaq and 1/(L d – L c) where L c is the minimal obtainable droplet length and approximately equals to the width of the droplet-generating channel. Theoretical analysis verifies this linear relationship, and the resulting equations can be used to optimize the design of the device such as the channel width, depth, and length. The viscometer can be used for Newtonian fluids and, by accurately calculating the shear rate, for non-Newtonian fluids such as Boger fluids and shear thinning fluids. In these latter cases, the shear rates depend on the velocity of the aqueous phase and can be adjusted by varying the input pressures. The applicable range of viscosity measurements depends on the oil-phase viscosity (μoil), and viscosities within the range of 0.01–10 μoil can be measured reliably with less than 5% error.
The synthesis of 1-methylphenoxazine via CO2-directed lithiation chemistry is reported. This electron donor was coupled with 2,8-dibromodibenzothiophene-S,S-dioxide with Buchwald–Hartwig chemistry to ...give a new donor–acceptor–donor charge-transfer fluorescent molecule 1b. X-ray crystal structures and calculations show that the phenoxazinyl groups are coplanar and equatorial (eq) to the acceptor plane in nonmethylated 1a but are pyramidal and axial (ax) in 1b. The bond rotation energy barriers between donor and acceptor groups for 1a and 1b are only 0.13 and 0.19 eV, respectively, from hybrid-DFT computations at the CAM-B3LYP/6-31G(d) level. Many possible conformers are present in solutions and in zeonex. In zeonex, the methyl groups in 1b shift the emission band 0.13 eV higher in energy compared to 1a. Excited state eq–eq and ax–ax geometries were identified with DFT calculations with charge transfer (CT) emission assigned as 1CT(eq) and 1CT(ax) dominating. The lower energy 1CT(eq) contributes to thermally activated delayed fluorescence, whereas the higher energy 1CT(ax) does not. Phenothiazine analogues 2a and 2b also have major fluorescence emissions assigned as 1CT(eq) and 1CT(ax), respectively. 2a and 2b have substantial room temperature phosphorescence (RTP), whereas 1a and 1b do not, highlighting the importance of the sulfur atom in 2a and 2b to obtain RTP emission.
Plant mycorrhizal associations influence the accumulation and persistence of soil organic matter and could therefore shape ecosystem biogeochemical responses to global changes that are altering ...forest composition. For instance, arbuscular mycorrhizal (AM) tree dominance is increasing in temperate forests, and ericoid mycorrhizal (ErM) shrubs can respond positively to canopy disturbances. Yet how shifts in the co-occurrence of trees and shrubs with different mycorrhizal associations will affect soil organic matter pools remains largely unknown. We examine the effects of ErM shrubs on soil carbon and nitrogen stocks and indicators of microbial activity at different depths across gradients of AM versus ectomycorrhizal (EcM) tree dominance in three temperate forest sites. We find that ErM shrubs strongly modulate tree mycorrhizal dominance effects. In surface soils, ErM shrubs increase particulate organic matter accumulation and weaken the positive relationship between soil organic matter stocks and indicators of microbial activity. These effects are strongest under AM trees that lack fungal symbionts that can degrade organic matter. In subsurface soil organic matter pools, by contrast, tree mycorrhizal dominance effects are stronger than those of ErM shrubs. Ectomycorrhizal tree dominance has a negative influence on particulate and mineral-associated soil organic matter pools, and these effects are stronger for nitrogen than for carbon stocks. Our findings suggest that increasing co-occurrence of ErM shrubs and AM trees will enhance particulate organic matter accumulation in surface soils by suppressing microbial activity while having little influence on mineral-associated organic matter in subsurface soils. Our study highlights the importance of considering interactions between co-occurring plant mycorrhizal types, as well as their depth-dependent effects, for projecting changes in soil carbon and nitrogen stocks in response to compositional shifts in temperate forests driven by disturbances and global change.
Cockayne syndrome (CS) is an accelerated aging disorder characterized by progressive neurodegeneration caused by mutations in genes encoding the DNA repair proteins CS group A or B (CSA or CSB). ...Since dietary interventions can alter neurodegenerative processes, Csbm/m mice were given a high-fat, caloric-restricted, or resveratrol-supplemented diet. High-fat feeding rescued the metabolic, transcriptomic, and behavioral phenotypes of Csbm/m mice. Furthermore, premature aging in CS mice, nematodes, and human cells results from aberrant PARP activation due to deficient DNA repair leading to decreased SIRT1 activity and mitochondrial dysfunction. Notably, β-hydroxybutyrate levels are increased by the high-fat diet, and β-hydroxybutyrate, PARP inhibition, or NAD+ supplementation can activate SIRT1 and rescue CS-associated phenotypes. Mechanistically, CSB can displace activated PARP1 from damaged DNA to limit its activity. This study connects two emerging longevity metabolites, β-hydroxybutyrate and NAD+, through the deacetylase SIRT1 and suggests possible interventions for CS.
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•Hyperactivation of PARP1 drives SIRT1 depression in Cockayne syndrome (CS)•A high-fat diet, β-hydroxybutyrate, or NAD+ replenishment rescue phenotypes in CS•PARP inhibition and β-hydroxybutyrate increase SIRT1 activity in CS-cells•CSB displaces PARylated PARP1 from damaged DNA and suppresses its activity
Cockayne syndrome group B (CSB) is associated with hyperactivation of the DNA damage response enzyme PARP1 leading to NAD+ depletion, SIRT1 attenuation, and decreased acetyl-CoA formation. Increasing NAD+ or enhancing acetyl-CoA via ketogenesis rescues the accelerated aging. CSB protein interacts with PARP1 to prevent increasing signaling.
Recently discovered bacteria and archaea adaptive immune system consisting of clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) endonuclease has been ...explored in targeted genome editing in different species.Streptococcus pyogenesCas9-guide RNA (gRNA) was successfully applied to generate targeted mutagenesis, gene integration, and gene editing in soybean (Glycine max). Two genomic sites,DD20andDD43on chromosome 4, were mutagenized with frequencies of 59% and 76%, respectively. Sequencing randomly selected transgenic events confirmed that the genome modifications were specific to the Cas9-gRNA cleavage sites and consisted of small deletions or insertions. Targeted gene integrations through homology-directed recombination were detected by border-specific polymerase chain reaction analysis for both sites at callus stage, and oneDD43homology-directed recombination event was transmitted to T1 generation. T1 progenies of the integration event segregated according to Mendelian laws and clean homozygous T1 plants with the donor gene precisely inserted at theDD43target site were obtained. The Cas9-gRNA system was also successfully applied to make a directed P178S mutation of acetolactate synthase1 gene through in planta gene editing.
Mutations in the enzyme cytosolic isocitrate dehydrogenase 1 (IDH1) are a common feature of a major subset of primary human brain cancers. These mutations occur at a single amino acid residue of the ...IDH1 active site, resulting in loss of the enzyme's ability to catalyse conversion of isocitrate to alpha-ketoglutarate. However, only a single copy of the gene is mutated in tumours, raising the possibility that the mutations do not result in a simple loss of function. Here we show that cancer-associated IDH1 mutations result in a new ability of the enzyme to catalyse the NADPH-dependent reduction of alpha-ketoglutarate to R(-)-2-hydroxyglutarate (2HG). Structural studies demonstrate that when arginine 132 is mutated to histidine, residues in the active site are shifted to produce structural changes consistent with reduced oxidative decarboxylation of isocitrate and acquisition of the ability to convert alpha-ketoglutarate to 2HG. Excess accumulation of 2HG has been shown to lead to an elevated risk of malignant brain tumours in patients with inborn errors of 2HG metabolism. Similarly, in human malignant gliomas harbouring IDH1 mutations, we find markedly elevated levels of 2HG. These data demonstrate that the IDH1 mutations result in production of the onco-metabolite 2HG, and indicate that the excess 2HG which accumulates in vivo contributes to the formation and malignant progression of gliomas.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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