Reversible redox energy coupling in electron transfer chains

Reversibility is a common theme in respiratory and photosynthetic systems that couple electron transfer with a transmembrane proton gradient driving ATP production. This includes the intensely studied cytochrome bc1, which catalyses electron transfer between quinone and cytochrome c. To understand how efficient reversible energy coupling works, here we have progressively inactivated individual cofactors comprising cytochrome bc1. We have resolved millisecond reversibility in all electron-tunnelling steps and coupled proton exchanges, including charge-separating hydroquinone-quinone catalysis at the Q(o) site, which shows that redox equilibria are relevant on a catalytic timescale. Such rapid reversibility renders popular models based on a semiquinone in Q(o) site catalysis prone to short-circuit failure. Two mechanisms allow reversible function and safely relegate short-circuits to long-distance electron tunnelling on a timescale of seconds: conformational gating of semiquinone for both forward and reverse electron transfer, or concerted two-electron quinone redox chemistry that avoids the semiquinone intermediate altogether.     

Tonks-Girardeau gas of ultracold atoms in an optical lattice

Strongly correlated quantum systems are among the most intriguing and fundamental systems in physics. One such example is the Tonks-Girardeau gas, proposed about 40 years ago, but until now lacking experimental realization; in such a gas, the repulsive interactions between bosonic particles confined to one dimension dominate the physics of the system. In order to minimize their mutual repulsion, the bosons are prevented from occupying the same position in space. This mimics the Pauli exclusion principle for fermions, causing the bosonic particles to exhibit fermionic properties. However, such bosons do not exhibit completely ideal fermionic (or bosonic) quantum behaviour; for example, this is reflected in their characteristic momentum distribution. Here we report the preparation of a Tonks-Girardeau gas of ultracold rubidium atoms held in a two-dimensional optical lattice formed by two orthogonal standing waves. The addition of a third, shallower lattice potential along the long axis of the quantum gases allows us to enter the Tonks-Girardeau regime by increasing the atoms' effective mass and thereby enhancing the role of interactions. We make a theoretical prediction of the momentum distribution based on an approach in which trapped bosons acquire fermionic properties, finding that it agrees closely with the measured distribution.     

A case of biodiversity overestimation in the Balkan Belgrandiella A. J. Wagner, 1927 (Caenogastropoda: Hydrobiidae): molecular divergence not paralleled by high morphological variation

Belgrandiella A. J. Wagner, 1927 is a genus comprising minute snails with conic or turriform shells that are facultative stygobionts, inhabiting subterranean waters and springs. Few specimens or even empty shells of this taxon can be found, so the taxonomy is based mostly on the shell morphology and geographic distribution. Anatomy is known for a few taxa, and its usefulness is restricted. This, coupled with a popular idea that isolation is the first factor shaping divergence and speciation of the spring/cave fauna, resulted in dozens of nominal species of Belgrandiella, known from shells at a given locality. Herein we present shells, anatomy and four molecular markers (nuclear H3, 18S and 28S and mitochondrial cytochrome oxidase subunit I) in Belgrandiella from 16 localities in Slovenia, northern Croatia, and Bosnia and Herzegovina. Five sites are type localities of Boleana umbilicata, Belgrandiella kusceri, Belgrandiella krupensis, Belgrandiella zermanica and Belgrandiella robusta, respectively. Considering the shell and geographic distribution, we have determined B. cf. robusta Belgrandiella cf. croatica, Belgrandiella cf. fontinalis, Belgrandiella cf. kuesteri, Belgrandiella cf. pageti and Belgrandiella cf. koprivnensis The shells of all, as well as penes and female reproductive organs of two putative, species have been illustrated. Molecular analysis indicates four distinct clades, most probably of species rank for B. kusceri, B. cf. kuesteri, B. cf. fontinalis and B. cf. koprivnensis. Four nominal species (B. krupensis, B. robusta, B. umbilicata and B. zermanica) and one genus (Boleana) must be synonymised with Belgrandiella kusceri, and there are no more than four valid, biological species in the studied Belgrandiella. The molecular divergence is completely unmirrored by high morphological variability. Hence the level of endemism is markedly overestimated in these snails.     

Spatial quantum noise interferometry in expanding ultracold atom clouds

In a pioneering experiment, Hanbury Brown and Twiss (HBT) demonstrated that noise correlations could be used to probe the properties of a (bosonic) particle source through quantum statistics; the effect relies on quantum interference between possible detection paths for two indistinguishable particles. HBT correlations--together with their fermionic counterparts--find numerous applications, ranging from quantum optics to nuclear and elementary particle physics. Spatial HBT interferometry has been suggested as a means to probe hidden order in strongly correlated phases of ultracold atoms. Here we report such a measurement on the Mott insulator phase of a rubidium Bose gas as it is released from an optical lattice trap. We show that strong periodic quantum correlations exist between density fluctuations in the expanding atom cloud. These spatial correlations reflect the underlying ordering in the lattice, and find a natural interpretation in terms of a multiple-wave HBT interference effect. The method should provide a useful tool for identifying complex quantum phases of ultracold bosonic and fermionic atoms.     

Integration of geoscience and engineering in the oil industry - just a dream?

The past two decades of the twentieth century have been very 'rocky' for the oil industry, as shown by the overall negative perception of the oil companies by the general public. Fluctuating oil prices, many rounds of staff redundancies, environmental disasters and budget cuts supported the overall image of the oil industry as being 'the technology impaired and environmentally insensible giant'. But advances and positive changes have been quietly happening in most of the oil companies. In the twenty-first century, we will witness the metamorphosis of the oil and gas companies into energy businesses - the era of cleaner and safer oil and gas production, and alternative energy resources such as wind, solar and hydrogen is already underway.     

Controlled collisions for multi-particle entanglement of optically trapped atoms

Entanglement lies at the heart of quantum mechanics, and in recent years has been identified as an essential resource for quantum information processing and computation. The experimentally challenging production of highly entangled multi-particle states is therefore important for investigating both fundamental physics and practical applications. Here we report the creation of highly entangled states of neutral atoms trapped in the periodic potential of an optical lattice. Controlled collisions between individual neighbouring atoms are used to realize an array of quantum gates, with massively parallel operation. We observe a coherent entangling-disentangling evolution in the many-body system, depending on the phase shift acquired during the collision between neighbouring atoms. Such dynamics are indicative of highly entangled many-body states; moreover, these are formed in a single operational step, independent of the size of the system.     

沤竹产物的性能表征

采用核磁共振碳谱、傅里叶变换衰减全反射红外光谱(ATR-FTIR)分析的方法,结合纺织标准GB/T 5889—1986,定性和定量地分析沤竹产物(简称竹束)的化学成分.通过光学显微镜和X射线衍射研究竹束的形态及结晶构型.通过热重(TG)分析研究竹束的热性能,并与竹子原料及纤维成品进行对比.此外,还研究了竹束对环境湿度的敏感性,包括吸水能力和吸湿放湿特性.研究结果表明,沤制工艺可以有效分解和去除竹子中的黏结物质,分离出竹束.所得竹束主要成分为纤维素、半纤维素和木质素,各组分质量分数分别为42.25%,35.61%,19.39%,与竹原料各组分质量分数有所不同.该竹束可作为竹纤维生物脱胶工艺中的半成品,为后道机械细化处理或酶处理提供原料基础.     

Lifespan and mitochondrial control of neurodegeneration

We examine the allometric (comparative scaling) relationships between rates of neurodegeneration resulting from equivalent mutations in a diverse group of genes from five mammalian species with different maximum lifespan potentials. In both retina and brain, rates of neurodegeneration vary by as much as two orders of magnitude and are strongly correlated with maximum lifespan potential and rates of formation of mitochondrial reactive oxygen and nitrogen species (RONS). Cell death in these disorders is directly or indirectly regulated by the intrinsic mitochondrial cell death pathway. Mitochondria are the main source of RONS production and integrate cellular stress signals to coordinate the intrinsic pathway. We propose that these two functions are intimately related and that steady-state RONS-mediated signaling or damage to the mitochondrial stress-integration machinery is the principal factor setting the probability of cell death in response to a diverse range of cellular stressors. This provides a new and unifying framework for investigating neurodegenerative disorders.