Isolable Tetragold(0) Clusters with Polarity-Tunable exo-Au-Au Bond via Intramolecular σ-Aromatization.

Intramolecular π-aromatization is a trait of many organic compounds that enhances the stability of their structures and polarizes related C-C π bonds. In contrast, rare study is focused on this phenomenon in metal clusters. Many existing homometallic clusters exhibit aromaticity, often characterized by nonpolar metal-metal bonds and a high degree of symmetry. However, synthesizing low-symmetric homometallic clusters with high-polar metal-metal bonds is challenging due to their limited thermodynamic stability. Herein, we report a facile strategy for the synthesis of [Au(µ2 -ER2 )]3 -AuPMe3 (E=Ge, Sn; R2 =1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl) clusters and reveal a novel stabilization mode, intramolecular σ-aromatization. Our electronic structure analyses show that these low-symmetric clusters possess a ten-electron σ-aromatic system, which is achieved via intramolecular σ-aromatization. Moreover, the strength of σ-aromaticity gives rise to a polarity-tunable exo-Au-Au bond.

Research of Probability-Based Tunneling Magnetoresistive Sensor Static Hysteresis Model.

Tunneling magnetoresistive (TMR) sensors have broad application prospects because of their high sensitivity and small volume. However, the inherent hysteresis characteristics of TMR affect its applications in high accuracy scenarios. It is essential to build a model to describe the attributes of hysteresis of TMR accurately. Preisach model is one of the popular models to describe the behavior of inherent hysteresis for TMR, whereas it presents low accuracy in high-order hysteresis reversal curves. Furthermore, the traditional Preisach model has strict congruence constraints, and the amount of data seriously affects the accuracy. This paper proposes a hysteresis model from a probability perspective. This model has the same computational complexity as the classic Preisach model while presenting higher accuracy, especially in high-order hysteresis reversal curves. When measuring a small amount of data, the error of this method is significantly reduced compared with the classical Preisach model. Besides, the proposed model's congruence in this paper only needs equal vertical chords.

The attachment process and physiological properties of Escherichia coli O157:H7 on quartz.

BACKGROUND: Manure application and sewage irrigation release many intestinal pathogens into the soil. After being introduced into the soil matrix, pathogens are commonly found to attach to soil minerals. Although the survival of mineral-associated Escherichia coli O157:H7 has been studied, a comprehensive understanding of the attachment process and physiological properties after attachment is still lacking. RESULTS: In this study, planktonic and attached Escherichia coli O157:H7 cells on quartz were investigated using RNA sequencing (RNA-seq) and the isobaric tagging for relative and absolute quantitation (iTRAQ) proteomic method. Based on the transcriptomic and proteomic analyses and gene knockouts, functional two-component system pathways were required for efficient attachment; chemotaxis and the Rcs system were identified to play determinant roles in E. coli O157:H7 attachment on quartz. After attachment, the pyruvate catabolic pathway shifted from the tricarboxylic acid (TCA) cycle toward the fermentative route. The survival rate of attached E. coli O157:H7 increased more than 10-fold under penicillin and vancomycin stress and doubled under alkaline pH and ferric iron stress. CONCLUSIONS: These results contribute to the understanding of the roles of chemotaxis and the Rcs system in the attachment process of pathogens and indicate that the attachment of pathogens to minerals significantly elevates their resistance to antibiotics and environmental stress, which may pose a potential threat to public health.

A Stable Cyclic (R2 SnAu)3 Anion Having In-Plane σ-Möbius Aromaticity.

A cyclic (R2 SnAu)3 anion (3- , R2 Sn=2,2,5,5-tetrakis(trimethylsilyl)-1-stannacyclopentane-1,1-diyl) has been synthesized as a stable blue salt with K+ (THF)6 through the reaction of stable dialkylstannylene 1 with R'3 PAuCl (R'=Et, Ph) followed by the reduction with KC8 . Crystallographic and NMR analysis shows that the six-membered (SnAu)3 ring of 3- is planar and highly symmetric with an equal distance of six Au-Sn bonds. A UV/Vis spectrum of 3- in hexane reveals an intense absorption maximum at 598 nm. While cyclic Au3 - with four valence electrons is known as unstable anti-aromatic anion, 3- with three divalent tin ligands is stable σ aromatic anion with an unprecedented Möbius orbital array as predicted by the perturbation MO and CCSD analysis of 3- .

Borane-Catalyzed Cross-Metathesis Strategy for Facile Transformation of Cyclic (Alkyl)(Amino)Germylenes.

A borane B(C6 F5 )3 -catalyzed metathesis reaction between the Si-C bond in the cyclic (alkyl)(amino)germylene (CAAGe) 1 and the Si-H bond in a silane (R3 SiH; 2) is reported. Mechanistic studies propose that the initial step of the reaction involves Si-H bond activation to furnish an ionic species [1-SiR3 ]+ [HB(C6 F5 )3 ]- , from which [Me3 Si]+ [HB(C6 F5 )3 ]- and an azagermole intermediate are generated. The former yields Me3 SiH concomitant with the regeneration of B(C6 F5 )3 whereas the latter undergoes isomerization to afford CAAGes bearing various silyl groups on the carbon atom next to the germylene center. This strategy allows the straightforward synthesis of eight new CAAGes starting from 1.

Isolation of a Cyclic (Alkyl)(amino)germylene.

A 1,4-addition of a dichlorogermylene dioxane complex with α,ß-unsaturated imine 1 gave a dichlorogermane derivative 2 bearing a GeC3N five-membered ring skeleton. By reducing 2 with KC8, cyclic (alkyl)(amino)germylene 3 was synthesized and fully characterized. Germylene 3 readily reacted with TEMPO, N2O and S8, producing the 1:2 adduct 4, the oxo-bridged dimer 5 and the sulfido-bridged dimer 6, respectively.

Reactivity of Cyclic (Alkyl)(amino)germylene towards Copper(I) and Gold(I) Complexes.

The reactions of cyclic (alkyl)(amino)germylenes (CAAGe) with copper(I) and gold(I) complexes were investigated. CAAGe (1) reacts with CuBr(SMe2 ) leading to a tetrameric germylene complex [CAAGeCuBr]4 (2), whereas CAAGe (3) undergoes Au-Cl bond insertion with LAuCl (L=phosphine or N-heterocyclic carbene) to afford germanium gold(I) complexes (5 and 6). Chlorine abstraction of 6 gives the cationic germylene gold(I) complex 7.

Trinuclear anionic gold clusters bridged by dialkylsilylene and dialkylgermylene.

While the chemistry of gold clusters has been developed rapidly, the knowledge of trinuclear gold clusters with low-valent gold remains scarce. Herein, we report the synthesis, structural characterization, and density functional theory (DFT) calculations of trinuclear anionic gold clusters 3a and 3b ligated by dialkylsilylene (1a) and dialkylgermylene (1b), respectively.

Development of a Formability Prediction Model for Aluminium Sandwich Panels with Polymer Core.

In the present work, the compatibility relationship on the failure criteria between aluminium and polymer was established, and a mechanics-based model for a three-layered sandwich panel was developed based on the M-K model to predict its Forming Limit Diagram (FLD). A case study for a sandwich panel consisting of face layers from AA5754 aluminium alloy and a core layer from polyvinylidene difluoride (PVDF) was subsequently conducted, suggesting that the loading path of aluminium was linear and independent of the punch radius, while the risk for failure of PVDF increased with a decreasing radius and an increasing strain ratio. Therefore, the developed formability model would be conducive to the safety evaluation on the plastic forming and critical failure of composite sandwich panels.

Structure and reactivity of germylene-bridged digold complexes.

The bonding between gold and main-group metallic elements (M) featuring Auδ--Mδ+ polarity, has been studied recently. The gold in the bonds is expected to have the oxidation number of -1, and hence, nucleophilic. However, the knowledge of the reactivity of the gold-metal bonds remains limited. Here, we report digold-substituted germanes of the form of R'2Ge(AuPR3)(AuGeR'2) (3a; R = Me, 3b; R = Et), featuring two Au-Ge(IV) and one Au-Ge(II) bonds. DFT calculations of 3a revealed the existence of high-lying σ(Ge-Au) type HOMO and low-lying LUMO with germylene pπ nature. A pendular motion of AuPR3 group between Ge(IV) and Ge(II) of 3 occurs in the NMR time scale, suggesting that the Ge(II) center has an enhanced electrophilicity to be attacked by the nucleophilic gold (-I) atom. 3a reacts with nucleophilic Cl- and electrophilic MeOTf reagents at Ge(II) and Ge(IV) centers, respectively.

Digitally-enhanced lubricant evaluation scheme for hot stamping applications.

Digitally-enhanced technologies are set to transform every aspect of manufacturing. Networks of sensors that compute at the edge (streamlining information flow from devices and providing real-time local data analysis), and emerging Cloud Finite Element Analysis technologies yield data at unprecedented scales, both in terms of volume and precision, providing information on complex processes and systems that had previously been impractical. Cloud Finite Element Analysis technologies enable proactive data collection in a supply chain of, for example the metal forming industry, throughout the life cycle of a product or process, which presents revolutionary opportunities for the development and evaluation of digitally-enhanced lubricants, which requires a coherent research agenda involving the merging of tribological knowledge, manufacturing and data science. In the present study, data obtained from a vast number of experimentally verified finite element simulation results is used for a metal forming process to develop a digitally-enhanced lubricant evaluation approach, by precisely representing the tribological boundary conditions at the workpiece/tooling interface, i.e., complex loading conditions of contact pressures, sliding speeds and temperatures. The presented approach combines the implementation of digital characteristics of the target forming process, data-guided lubricant testing and mechanism-based accurate theoretical modelling, enabling the development of data-centric lubricant limit diagrams and intuitive and quantitative evaluation of the lubricant performance.

Identification of COUP-TFII orphan nuclear receptor as a retinoic acid-activated receptor.

The chicken ovalbumin upstream promoter-transcription factors (COUP-TFI and II) make up the most conserved subfamily of nuclear receptors that play key roles in angiogenesis, neuronal development, organogenesis, cell fate determination, and metabolic homeostasis. Although the biological functions of COUP-TFs have been studied extensively, little is known of their structural features or aspects of ligand regulation. Here we report the ligand-free 1.48 A crystal structure of the human COUP-TFII ligand-binding domain. The structure reveals an autorepressed conformation of the receptor, where helix alpha10 is bent into the ligand-binding pocket and the activation function-2 helix is folded into the cofactor binding site, thus preventing the recruitment of coactivators. In contrast, in multiple cell lines, COUP-TFII exhibits constitutive transcriptional activity, which can be further potentiated by nuclear receptor coactivators. Mutations designed to disrupt cofactor binding, dimerization, and ligand binding, substantially reduce the COUP-TFII transcriptional activity. Importantly, retinoid acids are able to promote COUP-TFII to recruit coactivators and activate a COUP-TF reporter construct. Although the concentration needed is higher than the physiological levels of retinoic acids, these findings demonstrate that COUP-TFII is a ligand-regulated nuclear receptor, in which ligands activate the receptor by releasing it from the autorepressed conformation.

Analysing the Interaction between Microscopic Deformation, Microstructure and Void Evolution of Near-α Titanium Alloys during Non-Superplastic Hot Deformation by an Integrated Crystal Plasticity Finite Element Model.

High-efficiency and low-cost hot forming technologies for titanium alloys have been developed for producing complex-shaped, thin-walled tubular components under non-superplastic forming conditions. Under these forming conditions, there exist complex and highly integrated material evolution processes including microscopic heterogeneous deformation, microstructure evolution and damage behaviour. This paper presents an integrated crystal plasticity finite element model of near-α titanium alloys during non-superplastic hot deformation conditions considering grain boundary sliding (GBS), dynamic recrystallisation (DRX), as well as void evolution. The polycrystalline model of a near-α TA15 titanium alloy was established, containing α phase, ß phase and grain boundary (GB) regions, in which the GB region was a visualised representation of GBS. The quantitative strength ratio between the GB regions and α phase was calculated according to the Zener-Holloman parameter Z and grain size, which determined the microscopic deformation behaviour. There were found to be two high microscopic strain regions in the α phase: intragranular deformation bands through the most favourable slipping and near the GBs through multiple slipping, which promoted continuous and discontinuous DRX, respectively. With the decrease in parameter Z or grain size, the activated dislocations accommodating GBS were found to no longer pile up inside the grain, but instead travel across the grain interior. Finally, methods to improve the macroscopic plastic formability were proposed for the difficult-to-form titanium alloys experiencing non-superplastic hot deformation.

Diverse reactions of a fluorostannylenoid towards ethynes.

Fluoro(dialkyl)stannylenoid 2 exhibits unique reactivity towards ethynes with acetylenic hydrogen and those with trimethylsilyl groups, though the corresponding free dialkylstannylene 1 is inactive against those ethynes. Stannylenoid 2 reacts smoothly with gaseous ethyne and phenylethyne at room temperature, giving the corresponding diethynylstannanes, di(phenylethynyl)stannane 3 and diethynylstannane 6, respectively, in good yields with the concomitant evolution of H2. Trimethylsilyl-substituted ethynes such as 1-trimethylsilyl-(2-phenyl)ethyne and 1,2-bis(trimethylsilyl)ethyne react similarly to give 3 and bis(trimethylsilylethynyl)stannane 8, respectively. Rather unexpectedly, the reaction of 2 with (trimethylsilyl)ethyne affords 1,2-bis(ethenylstannyl)ethyne 7 in a good yield. The reactions of 2 with methyl and ethyl propynoates give the same products 4 and 5 as those obtained during the reaction of dialkylstannylene 1 without CsF. Pathways involving the nucleophilic attack of cesium acetylide to an ethyne-complexed stannylene were proposed, while the detailed mechanisms remain unknown. The structure of 7 was studied by single crystal X-ray diffraction analysis.

Knowledge Based Cloud FE Simulation of Sheet Metal Forming Processes.

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques. This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions.

A novel rabies vaccine based-on toll-like receptor 3 (TLR3) agonist PIKA adjuvant exhibiting excellent safety and efficacy in animal studies.

Vaccination alone is not sufficiently effective to protect human from post-exposure rabies virus infection due to delayed generation of rabies virus neutralizing antibodies and weak cellular immunity. Therefore, it is vital to develop safer and more efficacious vaccine against rabies. PIKA, a stabilized chemical analog of double-stranded RNA that interacts with TLR3, was employed as adjuvant of rabies vaccine. The efficacy and safety of PIKA rabies vaccine were evaluated. The results showed that PIKA rabies vaccine enhanced both humoral and cellular immunity. After viral challenge, PIKA rabies vaccine protected 70-80% of animals, while the survival rate of non-adjuvant vaccine group (control) was 20-30%. According to the results of toxicity tests, PIKA and PIKA rabies vaccine are shown to be well tolerated in mice. Thus, this study indicates that PIKA rabies vaccine is an effective and safe vaccine which has the potential to develop next-generation rabies vaccine and encourage the start of clinical studies.

Anti-Markovnikov hydroimination of terminal alkynes in gold-catalyzed pyridine construction from ammonia.

Gold-catalyzed hydroimination of terminal alkynes, giving rise to anti-Markovnikov adducts concomitant with unstable Markovnikov adducts is described. The elementary step can be applied for the construction of pyridine derivatives from ammonia and alkynes.

Expression of human papillomavirus type 6 L1 and L2 isolated in China and self assembly of virus-like particles by the products.

To study variations of genome late region of human papillomavirus type 6 (HPV-6) isolated in China and assembling capabilities of the encoded capsid proteins, HPV-6 L1 and L2 sequences were cloned and used for expression in Bac-to-Bac baculovirus expression systems (Gibco BRL). Based upon L1 and L2 overlapping sequence two sequences (GenBank accession number AY015006, AY015008) of HPV-6 late region (2869 bp long) were assembled and classified into HPV-6b by phylogenetic analysis. Compared with prototype sequence, nine point mutations were found, including four missense mutations. L1, instead of L2, could self-assemble into virus-like particles (VLPs) in Sf9 nucleus. VLPs self-assembled by L1 alone (L1-VLPs) and by L1 plus L2 (L1+L2-VLPs) were purified and further characterized. Both types of VLPs were spherical particles with a diameter of approximately 50 nm. L1+L2 VLPs comprising L1 and L2 in the molar ratio of about 4:1 possessed the HPV-6 L1 VLP surface and conformational epitopes. In co-expression assay with a series of MOI combination of L1 and L2 recombinant baculoviruses (total MOI=10), existence of L2 of certain level enhanced L1 production by 0.8 fold and VLP production by 3 - 4 folds under experimental conditions. In conclusion, variation rate of HPV-6 genome late region is less than 0.28% and the substitutions A to G at position 7081 and G to A at 7099 may represent region characteristics. The cloned HPV-6 L1 and L2 sequences can be expressed efficiently in Sf9 cells, and the expressed products (L1 or L1+L2) can self-assemble into VLPs that resemble naturally occurring virions.

Diverse reactivity of an isolable dialkylsilylene toward imines.

The reactions of isolable dialkylsilylene 10 with various aldimines proceed smoothly at low temperatures to give diverse products depending on the substituents on the imine. The reactions of 10 with 4-XC(6)H(4)CH=NPh [X = H (11a), MeO (11b), and Cl (11c)] give the corresponding silaaziridines 12a-12c in high yields, which are thermally very stable and remain intact in the air and moisture for a long time. In contrast, the reactions of 10 with 4-F(3)CC(6)H(4)CH=NPh (11d) and 3,5-(F(3)C)(2)C(6)H(3)CH=NPh (11e) having strong electron-withdrawing aryl substituents on imine carbon are accompanied by 1,2-trimethylsilyl migration rather unexpectedly to give silaazetidines 13d-13e incorporated into a bicyclo[3.2.0]heptane ring. The reaction of 10 with N-benzylbenzaldimine 11f affords the corresponding (dibenzylamino)silane 14f in a moderate yield. Molecular structures of 12a-12c, 13d-13e and 14f were determined by X-ray crystallography. All these reactions are proposed to occur via the initial formation of the corresponding imine silaylides, while the subsequent reactions leading to the final products are controlled by the electronic structure of the ylide depending on the substituents. N-phenylbenzophenimine 11g does not react with 10.

Reactions of an isolable dialkylsilylene with aromatic nitriles providing a new type of heterosilole.

The 1 : 2 reactions of isolable dialkylsilylene with nitriles having electron-donating aromatic substituents gave 1,4-diaza-2-siloles with a hitherto-unknown type of ring system, in contrast to the previous studies showing exclusive formation of the corresponding 1,3-diaza-2-siloles; the reactions of with aromatic nitriles bearing electron-withdrawing substituents afforded the latter ring system. The remarkable diversity of the reactions is explained by invoking the corresponding nitrile silaylides as key intermediates whose polarity switches depending on the substituents of nitriles.