Oxidation is a key reaction in organic synthesis and will likely play a significant role in the development of value-added chemicals from biomass. The application of heterogeneous catalysis and ...molecular oxygen to oxidation reactions offers a green alternative to traditional, toxic chemical oxidants. However, making comparisons of catalyst performance (reaction rate, product selectivity) between reports in the literature is difficult because of inconsistencies in the ways results are reported. Herein, we examine the literature on supported metal catalysts for the oxidation of molecules of interest in biomass conversion (primary alcohols, polyols, 5-hydroxymethylfurfural, and various sugars). Reaction rates are calculated and compared in a consistent manner and recommendations for avoiding common pitfalls in kinetic investigations are made.
Selective oxidation reactions will likely play an important role in the development of biorefineries. The use of heterogeneous catalysts with molecular oxygen offers a more environmentally benign route than traditional oxidation processes. This review explores the oxidation mechanism and compares reaction rates over a variety of metal catalysts.
Tumor suppressors with widespread impact on carcinogenesis control broad spectra of oncogenic pathways. Protein degradation is an emerging mechanism by which tumor suppressors regulate a diversity of ...pathways and is exemplified by the SCFFbw7 ubiquitin ligase. Rapidly accumulating data indicate that SCFFbw7 regulates a network of crucial oncoproteins. Importantly, the FBXW7 gene, which encodes Fbw7, is one of the most frequently mutated genes in human cancers. These studies are yielding important new insights into tumorigenesis and may soon enable therapies targeting the Fbw7 pathway. Here, we focus on the mechanisms and consequences of Fbw7 deregulation in cancers and discuss possible therapeutic approaches.
Consumption-based accounting of CO₂ emissions Davis, Steven J; Caldeira, Ken
Proceedings of the National Academy of Sciences - PNAS,
03/2010, Letnik:
107, Številka:
12
Journal Article
Recenzirano
Odprti dostop
CO₂ emissions from the burning of fossil fuels are the primary cause of global warming. Much attention has been focused on the CO₂ directly emitted by each country, but relatively little attention ...has been paid to the amount of emissions associated with the consumption of goods and services in each country. Consumption-based accounting of CO₂ emissions differs from traditional, production-based inventories because of imports and exports of goods and services that, either directly or indirectly, involve CO₂ emissions. Here, using the latest available data, we present a global consumption-based CO₂ emissions inventory and calculations of associated consumption-based energy and carbon intensities. We find that, in 2004, 23% of global CO₂ emissions, or 6.2 gigatonnes CO₂, were traded internationally, primarily as exports from China and other emerging markets to consumers in developed countries. In some wealthy countries, including Switzerland, Sweden, Austria, the United Kingdom, and France, >30% of consumption-based emissions were imported, with net imports to many Europeans of >4 tons CO₂ per person in 2004. Net import of emissions to the United States in the same year was somewhat less: 10.8% of total consumption-based emissions and 2.4 tons CO₂ per person. In contrast, 22.5% of the emissions produced in China in 2004 were exported, on net, to consumers elsewhere. Consumption-based accounting of CO₂ emissions demonstrates the potential for international carbon leakage. Sharing responsibility for emissions among producers and consumers could facilitate international agreement on global climate policy that is now hindered by concerns over the regional and historical inequity of emissions.
The most essential characteristic of any fluid is the velocity field, and this is particularly true for macroscopic quantum fluids1. Although rapid advances2–7 have occurred in quantum fluid velocity ...field imaging8, the velocity field of a charged superfluid—a superconductor—has never been visualized. Here we use superconducting-tip scanning tunnelling microscopy9–11 to image the electron-pair density and velocity fields of the flowing electron-pair fluid in superconducting NbSe2. Imaging of the velocity fields surrounding a quantized vortex12,13 finds electronic fluid flow with speeds reaching 10,000 km h–1. Together with independent imaging of the electron-pair density via Josephson tunnelling, we visualize the supercurrent density, which peaks above 3 × 107 A cm–2. The spatial patterns in electronic fluid flow and magneto-hydrodynamics reveal hexagonal structures coaligned to the crystal lattice and quasiparticle bound states14, as long anticipated15–18. These techniques pave the way for electronic fluid flow visualization studies of other charged quantum fluids.Atomic-scale visualization of the superfluid velocity field, the electron-pair density and the superfluid current density in an electron-pair superfluid surrounding an Abrikosov vortex in a superconducting sample of NbSe2 is demonstrated, using superconducting-tip scanning tunnelling microscopy.
Electrical detection methodologies are likely to underpin the progressive drive towards miniaturised, sensitive and portable biomarker detection protocols. In being easily integrated within standard ...electronic microfabrication formats, and developing capability in microfluidics, the facile multiplexed detection of a range of proteins in a small analytical volume becomes entirely feasible with something costing just a few thousand pounds and benchtop or handheld in scale. In this review, we focus on recent important advances in label free assays of protein using a number of electrical methods, including those based on electrochemical impedance spectroscopy (EIS), amperometry/voltammetry, potentiometry, conductometry and field-effect methods. We introduce their mechanistic features and examples of application and sensitivity. The current state of the art, real world applications and challenges are outlined.
The current state of the art and recent advances in the label free electrical detection of protein biomarkers are reviewed.
The endocytic delivery of macromolecules from the mammalian cell surface for degradation by lysosomal acid hydrolases requires traffic through early endosomes to late endosomes followed by transient ...(kissing) or complete fusions between late endosomes and lysosomes. Transient or complete fusion results in the formation of endolysosomes, which are hybrid organelles from which lysosomes are re-formed. We have used synthetic membrane-permeable cathepsin substrates, which liberate fluorescent reporters upon proteolytic cleavage, as well as acid phosphatase cytochemistry to identify which endocytic compartments are acid hydrolase active. We found that endolysosomes are the principal organelles in which acid hydrolase substrates are cleaved. Endolysosomes also accumulated acidotropic probes and could be distinguished from terminal storage lysosomes, which were acid hydrolase inactive and did not accumulate acidotropic probes. Using live-cell microscopy, we have demonstrated that fusion events, which form endolysosomes, precede the onset of acid hydrolase activity. By means of sucrose and invertase uptake experiments, we have also shown that acid-hydrolase-active endolysosomes and acid-hydrolase-inactive, terminal storage lysosomes exist in dynamic equilibrium. We conclude that the terminal endocytic compartment is composed of acid-hydrolase-active, acidic endolysosomes and acid hydrolase-inactive, non-acidic, terminal storage lysosomes, which are linked and function in a lysosome regeneration cycle.
•Late endosome-lysosome fusion creates acidic, cathepsin-active endolysosomes•Terminal storage lysosomes are cathepsin inactive and not acidic•Fusion events creating endolysosomes precede the onset of cathepsin activity•A lysosome regeneration cycle links endolysosomes and terminal storage lysosomes
Bright et al. provide evidence that the terminal endocytic compartment is composed of acid-hydrolase-active, acidic endolysosomes and acid hydrolase-inactive, non-acidic, terminal storage lysosomes, which are linked and function in a lysosome regeneration cycle.
An unidentified quantum fluid designated the pseudogap (PG) phase is produced by electron-density depletion in the CuO
antiferromagnetic insulator. Current theories suggest that the PG phase may be a ...pair density wave (PDW) state characterized by a spatially modulating density of electron pairs. Such a state should exhibit a periodically modulating energy gap Formula: see text in real-space, and a characteristic quasiparticle scattering interference (QPI) signature Formula: see text in wavevector space. By studying strongly underdoped Bi
Sr
CaDyCu
O
at hole-density ~0.08 in the superconductive phase, we detect the 8a
-periodic Formula: see text modulations signifying a PDW coexisting with superconductivity. Then, by visualizing the temperature dependence of this electronic structure from the superconducting into the pseudogap phase, we find the evolution of the scattering interference signature Formula: see text that is predicted specifically for the temperature dependence of an 8a
-periodic PDW. These observations are consistent with theory for the transition from a PDW state coexisting with d-wave superconductivity to a pure PDW state in the Bi
Sr
CaDyCu
O
pseudogap phase.
Abstract
Spin-triplet topological superconductors should exhibit many unprecedented electronic properties, including fractionalized electronic states relevant to quantum information processing. ...Although UTe
2
may embody such bulk topological superconductivity
1–11
, its superconductive order parameter Δ(
k
) remains unknown
12
. Many diverse forms for Δ(
k
) are physically possible
12
in such heavy fermion materials
13
. Moreover, intertwined
14,15
density waves of spin (SDW), charge (CDW) and pair (PDW) may interpose, with the latter exhibiting spatially modulating
14,15
superconductive order parameter Δ(
r
), electron-pair density
16–19
and pairing energy gap
17,20–23
. Hence, the newly discovered CDW state
24
in UTe
2
motivates the prospect that a PDW state may exist in this material
24,25
. To search for it, we visualize the pairing energy gap with μeV-scale energy resolution using superconductive scanning tunnelling microscopy (STM) tips
26–31
. We detect three PDWs, each with peak-to-peak gap modulations of around 10 μeV and at incommensurate wavevectors
P
i
=1,2,3
that are indistinguishable from the wavevectors
Q
i
=1,2,3
of the prevenient
24
CDW. Concurrent visualization of the UTe
2
superconductive PDWs and the non-superconductive CDWs shows that every
P
i
:
Q
i
pair exhibits a relative spatial phase
δϕ
≈ π. From these observations, and given UTe
2
as a spin-triplet superconductor
12
, this PDW state should be a spin-triplet PDW
24,25
. Although such states do exist
32
in superfluid
3
He, for superconductors, they are unprecedented.
The elementary CuO
2
plane sustaining cuprate high-temperature superconductivity occurs typically at the base of a periodic array of edge-sharing CuO
5
pyramids. Virtual transitions of electrons ...between adjacent planar Cu and O atoms, occurring at a rate t/ℏ and across the charge-transfer energy gap
E
, generate “superexchange” spin–spin interactions of energy
J
≈
4
t
4
/
E
3
in an antiferromagnetic correlated-insulator state. However, hole doping this CuO
2
plane converts this into a very-high-temperature superconducting state whose electron pairing is exceptional. A leading proposal for the mechanism of this intense electron pairing is that, while hole doping destroys magnetic order, it preserves pair-forming superexchange interactions governed by the charge-transfer energy scale
E
. To explore this hypothesis directly at atomic scale, we combine single-electron and electron-pair (Josephson) scanning tunneling microscopy to visualize the interplay of
E
and the electron-pair density
n
P
in Bi
2
Sr
2
CaCu
2
O
8+x
. The responses of both
E
and
n
P
to alterations in the distance
δ
between planar Cu and apical O atoms are then determined. These data reveal the empirical crux of strongly correlated superconductivity in CuO
2
, the response of the electron-pair condensate to varying the charge-transfer energy. Concurrence of predictions from strong-correlation theory for hole-doped charge-transfer insulators with these observations indicates that charge-transfer superexchange is the electron-pairing mechanism of superconductive Bi
2
Sr
2
CaCu
2
O
8+x
.
There has been growing speculation that a pair density wave state is a key component of the phenomenology of the pseudogap phase in the cuprates. Recently, direct evidence for such a state has ...emerged from an analysis of scanning tunneling microscopy data in halos around the vortex cores. By extrapolation, these vortex halos would then overlap at a magnetic-field scale where quantum oscillations have been observed. Here, we show that a biaxial pair density wave state gives a unique description of the quantum oscillation data, bolstering the case that the pseudogap phase in the cuprates may be a pair density wave state.
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