Improving hydrogen yields, and hydrogen: Steam ratio in the chemical looping production of hydrogen using Ca<inf>2</inf>Fe<inf>2</inf>O<inf>5</inf>

A thermodynamic property of Ca2Fe2O5 was exploited to improve the efficiency of the steam-iron process to produce hydrogen. The ability of reduced Ca2Fe2O5 to convert a higher fraction of steam to hydrogen than chemically unmodified Fe was demonstrated in a packed bed. At 1123 K, the use of Ca2Fe2O5 achieved an equilibrium conversion of steam to hydrogen of 75%, in agreement with predicted thermodynamics and substantially higher than that theoretically achievable by iron oxide, viz. 62%. Furthermore, in Ca2Fe2O5, the full oxidation from Fe(0) to Fe(III) can be utilised for hydrogen production – an improvement from the Fe to Fe3O4 transition for unmodified iron. Thermodynamic considerations demonstrated in this study allow for the rational design of oxygen carriers in the future. Modifications of reactors to capitalise on this new material are discussed.Dr Matthew T. Dunstan is acknowledged for help with the XRD analysis. M.S.C.C acknowledges financial support from an EPSRC Doctoral Training Grant. W.L and Y.Y acknowledge funding from the National Research Foundation (NRF), Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.cej.2016.03.13

Organic Single-Crystalline p-n Heterojunctions for High-Performance Ambipolar Field-Effect Transistors and Broadband Photodetectors

Organic semiconducting single crystals are ideal building blocks for organic field-effect transistors (OFETs) and organic photodetectors (OPDs) because they can potentially exhibit the best charge transport and photoelectric properties in organic materials. Nevertheless, it is usual for single-crystal OFETs to be built from one kind of organic material in which the dominant transport is either electron or hole; such OFETs show unipolar charge transport. Furthermore, single-crystal OPDs present high performance only in restricted regions because of the limited absorption of one-component single crystals. In an ideal situation, devices which comprise both electron- and hole-transporting single crystals with complementary absorptions, such as single-crystalline p–n heterojunctions (SCHJs), can permit broadband photoresponse and ambipolar charge transport. In this paper, a solution-processing crystallization strategy to prepare an SCHJ composed of C60 and 6,13-bis­(triisopropylsilylethynyl)­pentacene (TIPS-PEN) was shown. These SCHJs demonstrated ambipolar charge-transport characteristics in OFETs with a balanced performance of 2.9 cm2 V–1 s–1 for electron mobility and 2.7 cm2 V–1 s–1 for hole mobility. This demonstration is the first of single-crystal OFETs in which both electron and hole mobilities were over 2.5 cm2 V–1 s–1. OPDs fabricated upon as-prepared SCHJs exhibited highly sensitive photoconductive properties ranging from ultraviolet to visible and further to near-infrared regions as a result of complementary absorption between C60 and TIPS-PEN, thereby attaining photoresponsivities that are among the highest reported values within the OPDs. This work would provide valuable references for developing novel SCHJ systems to achieve significant progress in high-performance ambipolar OFETs and broadband OPDs

Synthesis and evaluation of analogues of the glycinocin family of calcium-dependent antibiotics

The glycinocins are a class of calcium-dependent, acidic cyclolipopeptide antibiotics that are structurally related to the clinically approved antibiotic daptomycin. In this article, we describe the synthesis of a small library of glycinocin analogues that differ by variation in the exocyclic fatty acyl substituent. The glycinocin analogues were screened against a panel of Gram-positive bacteria (as well as Gram-negative P. aeruginosa). These analogues exhibited similar calcium-dependent activity to the parent natural products against Gram-positive bacteria but showed no activity against P. aeruginosa. The length of the fatty acid was shown to be important for optimal biological activity, while the hybridisation at the α,β position and branching within the fatty acyl chain had only subtle effects on activity

Evolution of precipitate morphology during heat treatment and its implications for the superconductivity in KxFe1.6+ySe2 single crystals

We study the relationship between precipitate morphology and superconductivity in KxFe1.6+ySe2 single crystals grown by self-flux method. Scanning electron microscopy (SEM) measurements revealed that superconducting phase forms a network in the samples quenched above iron vacancy order-disorder transition temperature Ts. For the samples obtained by natural cooling down to room temperature in the furnace, referred to as furnace cooling, superconducting phase aggregates into micrometer-sized rectangular bars and aligns as disconnected chains. Accompanying this change in morphology the superconducting shielding fraction is strongly reduced in the furnace-cooling samples. By post-annealing above Ts followed by quenching in room temperature water, the network recovers with superconducting shielding fraction approaching 80%. A reversible change from network to bar chains was realized by a secondary heat treatment in annealed samples showing large shielding fraction, i.e., heating above Ts followed by slow cooling across Ts. The large shielding fraction observed in KxFe1.6+ySe2 single crystals actually results from a uniform and contiguous distribution of superconducting phase. Through the measurements of temperature dependent x-ray diffraction, it is found that the reflection corresponding to superconducting phase merges into that from iron vacancy ordered phase upon warming. It is a solid solution above Ts, where iron atoms randomly occupy the both Fe1 and Fe2 sites in iron vacancy disordering status. By cooling across Ts, superconducting phase precipitates while iron vacancy ordered phase forms together, suggesting that phase separation in KxFe1.6+ySe2 single crystals is driven by the iron vacancy order-disorder transition.Comment: to be published in PR

An Efficient One-move Nominative Signature Scheme

A signer in a Nominative Signature (NS) scheme can arbitrarily choose a nominee, then jointly generate a signature in such a way that the signature can only be verified with the nominee\u27s consent. NS is particularly useful in user certification systems. Currently, the only secure NS scheme available requires multi-round communications between the nominator and the nominee during signature generation. This implies that an NS-based user certification system requires a certification issuer to interact with a user using a complicated multi-round protocol for certificate issuance. It remains an open problem to construct an efficient and non-interactive NS scheme. In this paper, we solve this problem by proposing the first efficient one-move (i.e. non-interactive) NS scheme. In addition, we propose an enhanced security requirement called Strong Invisibility, and prove that our scheme satisfies this strong security requirement

Coronavirus disease 2019 among pregnant Chinese women : case series data on the safety of vaginal birth and breastfeeding

Funding Information: National Key Research and Development Program of China. Grant Numbers: 2016YFC1000203, 2018YFC1002804Peer reviewedPublisher PD

Targeting tRNA-Synthetase Interactions Towards Novel Therapeutic Discovery Against Eukaryotic Pathogens

The development of chemotherapies against eukaryotic pathogens is especially challenging because of both the evolutionary conservation of drug targets between host and parasite, and the evolution of strain-dependent drug resistance. There is a strong need for new nontoxic drugs with broad-spectrum activity against trypanosome parasites such as Leishmania and Trypanosoma. A relatively untested approach is to target macromolecular interactions in parasites rather than small molecular interactions, under the hypothesis that the features specifying macromolecular interactions diverge more rapidly through coevolution. We computed tRNA Class-Informative Features in humans and independently in eight distinct clades of trypanosomes, identifying parasite-specific informative features, including base pairs and base mis-pairs, that are broadly conserved over approximately 250 million years of trypanosome evolution. Validating these observations, we demonstrated biochemically that tRNA:aminoacyl-tRNA synthetase (aaRS) interactions are a promising target for anti-trypanosomal drug discovery. From a marine natural products extract library, we identified several fractions with inhibitory activity toward Leishmania major alanyl-tRNA synthetase (AlaRS) but no activity against the human homolog. These marine natural products extracts showed cross-reactivity towards Trypanosoma cruzi AlaRS indicating the broad-spectrum potential of our network predictions. We also identified Leishmania major threonyl-tRNA synthetase (ThrRS) inhibitors from the same library. We discuss why chemotherapies targeting multiple aaRSs should be less prone to the evolution of resistance than monotherapeutic or synergistic combination chemotherapies targeting only one aaRS

Janus monolayers of transition metal dichalcogenides.

Structural symmetry-breaking plays a crucial role in determining the electronic band structures of two-dimensional materials. Tremendous efforts have been devoted to breaking the in-plane symmetry of graphene with electric fields on AB-stacked bilayers or stacked van der Waals heterostructures. In contrast, transition metal dichalcogenide monolayers are semiconductors with intrinsic in-plane asymmetry, leading to direct electronic bandgaps, distinctive optical properties and great potential in optoelectronics. Apart from their in-plane inversion asymmetry, an additional degree of freedom allowing spin manipulation can be induced by breaking the out-of-plane mirror symmetry with external electric fields or, as theoretically proposed, with an asymmetric out-of-plane structural configuration. Here, we report a synthetic strategy to grow Janus monolayers of transition metal dichalcogenides breaking the out-of-plane structural symmetry. In particular, based on a MoS2 monolayer, we fully replace the top-layer S with Se atoms. We confirm the Janus structure of MoSSe directly by means of scanning transmission electron microscopy and energy-dependent X-ray photoelectron spectroscopy, and prove the existence of vertical dipoles by second harmonic generation and piezoresponse force microscopy measurements