Scanning Electron Microscopy Investigation of a Sample Depth Profile Through the Martian Meteorite Nakhla

The ongoing scientific debate as to whether or not the Martian meteorite ALH84001 contained evidence of possible biogenic activities showed the need to establish consistent methods to ascertain the origin of such evidence. To distinguish between terrestrial organic material/microbial contaminants and possible indigenous microbiota within meteorites is therefore crucial. With this in mind a depth profile consisting of four samples from a new sample allocation of Martian meteorite Nakhla was investigated using scanning electron microscopy (SEM) and energy dispersive X-ray analysis. SEM imaging of freshly broken fractured chips revealed structures strongly recent terrestrial microorganisms, in some cases showing evidence of active growth. This conclusion was supported by EDX analysis, which showed the presence of carbon associated with these structures, we concluded that these structures represent recent terrestrial contaminants rather than structures indigenous to the meteorite. Pag

The MASSE Project: Applications of Biotechnology for Planetary Exploration

Automated life-detection experiments for solar system exploration have been previously. proposed and used onboard the. Viking, Mars lander,s, although. with ambiguous results. The recent advances in biotechnology such as biosensors, protein microarrays, and microfluidics alongside increased. knowledge in biomarker science have led to vastly improved sophistication and sensitivity for a new approach in life detection. The MASSE project has taken the challenge of integrating all of this knowledge into a new generation of interplanetary flight instrumentation for the main purpose.ot combining several mutually. confirming tests for life, organic/microbial contamination, prebiotic and abiotic chemicals into a small low powered instrument. Although the primary goal is interplanetary exploration, several terrestrial applications have become apparent specifically in point-of-care medical technology, bio-warfare, environmental sensing and microbial monitoring of manned space-flight vehicles

Dehydropolymerization of H3B·NMeH2 Using a [Rh(DPEphos)]+ Catalyst : The Promoting Effect of NMeH2

[Rh(κ2-PP-DPEphos){η2η2-H2B(NMe3)(CH2)2tBu}][BArF4] acts as an effective precatalyst for the dehydropolymerization of H3B·NMeH2 to form N-methylpolyaminoborane (H2BNMeH)n. Control of polymer molecular weight is achieved by variation of precatalyst loading (0.1-1 mol %, an inverse relationship) and use of the chain-modifying agent H2: with Mn ranging between 5 500 and 34 900 g/mol and between 1.5 and 1.8. H2 evolution studies (1,2-F2C6H4 solvent) reveal an induction period that gets longer with higher precatalyst loading and complex kinetics with a noninteger order in [Rh]TOTAL. Speciation studies at 10 mol % indicate the initial formation of the amino-borane bridged dimer, [Rh2(κ2-PP-DPEphos)2(μ-H)(μ-H2BN=HMe)][BArF4], followed by the crystallographically characterized amidodiboryl complex [Rh2(cis-κ2-PP-DPEphos)2(σ,μ-(H2B)2NHMe)][BArF4]. Adding ∼2 equiv of NMeH2 in tetrahydrofuran (THF) solution to the precatalyst removes this induction period, pseudo-first-order kinetics are observed, a half-order relationship to [Rh]TOTAL is revealed with regard to dehydrogenation, and polymer molecular weights are increased (e.g., Mn = 40 000 g/mol). Speciation studies suggest that NMeH2 acts to form the precatalysts [Rh(κ2-DPEphos)(NMeH2)2][BArF4] and [Rh(κ2-DPEphos)(H)2(NMeH2)2][BArF4], which were independently synthesized and shown to follow very similar dehydrogenation kinetics, and produce polymers of molecular weight comparable with [Rh(κ2-PP-DPEphos){ η2-H2B(NMe3)(CH2)2tBu}][BArF4], which has been doped with amine. This promoting effect of added amine in situ is shown to be general in other cationic Rh-based systems, and possible mechanistic scenarios are discussed

Formation of a σ-alkane complex and a molecular rearrangement in the solid-State : [Rh(Cyp2PCH2CH2PCyp2)(η2:η2-C7H12)][BArF 4]

Addition of H2 to the precursor [Rh(Cyp2PCH2CH2PCyp2)(η2:η2- C7H8)][BArF 4] gives the σ-alkane complex [Rh(Cyp2PCH2CH2PCyp2)(η2:η2- C7H12)][BArF 4] by a single-crystal to single-crystal reaction, as characterized by Xray crystallography, SSNMR spectroscopy, and periodic DFT. An unexpected rearrangement of the {Rh(L2)}+ fragment is revealed

Dissolved Microcystin Release Coincident with Lysis of a Bloom Dominated by Microcystis spp. in Western Lake Erie Attributed to a Novel Cyanophage

Western Lake Erie (Laurentian Great Lakes) is prone to annual cyano- bacterial harmful algal blooms (cHABs) dominated by Microcystis spp. that often yield microcystin toxin concentrations exceeding the federal EPA recreational con-tact advisory of 8 μg liter-1. In August 2014, microcystin levels were detected in fin-ished drinking water above the World Health Organization 1.0 μg liter-1 threshold for consumption, leading to a 2-day disruption in the supply of drinking water for \u3e400,000 residents of Toledo, Ohio (USA). Subsequent metatranscriptomic analysis of the 2014 bloom event provided evidence that release of toxin into the water sup-ply was likely caused by cyanophage lysis that transformed a portion of the intracel-lular microcystin pool into the dissolved fraction, rendering it more difficult to elimi-nate during treatment. In August 2019, a similar increase in dissolved microcystins at the Toledo water intake was coincident with a viral lytic event caused by a phage consortium different in composition from what was detected following the 2014 To-ledo water crisis. The most abundant viral sequence in metagenomic data sets was a scaffold from a putative member of the Siphoviridae, distinct from the Ma-LMM01-like Myoviridae that are typically documented to occur in western Lake Erie. This study provides further evidence that viral activity in western Lake Erie plays a signifi-cant role in transformation of microcystins from the particulate to the dissolved frac-tion and therefore requires monitoring efforts from local water treatment plants. Ad-ditionally, identification of multiple lytic cyanophages will enable the development of a quantitative PCR toolbox to assess viral activity during cHABs. IMPORTANCE Viral attack on cHABs may contribute to changes in community com-position during blooms, as well as bloom decline, yet loss of bloom biomass does not eliminate the threat of cHAB toxicity. Rather, it may increase risks to the public by delivering a pool of dissolved toxin directly into water treatment utilities when the dominating Microcystis spp. are capable of producing microcystins. Detecting, characterizing, and quantifying the major cyanophages involved in lytic events will assist water treatment plant operators in making rapid decisions regarding the pool of microcystins entering the plant and the corresponding best practices to neutralize the toxin

Solid-state molecular organometallic chemistry. Single-crystal to single-crystal reactivity and catalysis with light hydrocarbon substrates

Single-crystal to single-crystal solid/gas reactivity and catalysis starting from the precursor sigma-alkane complex [Rh(Cy2PCH2CH2PCy2)(η2η2-NBA)][BArF4] (NBA = norbornane; ArF = 3,5-(CF3)2C6H3) is reported. By adding ethene, propene and 1-butene to this precursor in solid/gas reactions the resulting alkene complexes [Rh(Cy2PCH2CH2PCy2)(alkene)x][BArF4] are formed. The ethene (x = 2) complex, [Rh(Cy2PCH2CH2PCy2)(ethene)2][BArF4]-Oct, has been characterized in the solid-state (single-crystal X-ray diffraction) and by solution and solid-state NMR spectroscopy. Rapid, low temperature recrystallization using solution methods results in a different crystalline modification, [Rh(Cy2PCH2CH2PCy2)(ethene)2][BArF4]-Hex, that has a hexagonal microporous structure (P6322). The propene complex (x = 1) [Rh(Cy2PCH2CH2PCy2)(propene)][BArF4] is characterized as having a π-bound alkene with a supporting γ-agostic Rh⋯H3C interaction at low temperature by single-crystal X-ray diffraction, variable temperature solution and solid-state NMR spectroscopy, as well as periodic density functional theory (DFT) calculations. A fluxional process occurs in both the solid-state and solution that is proposed to proceed via a tautomeric allyl-hydride. Gas/solid catalytic isomerization of d3-propene, H2CCHCD3, using [Rh(Cy2PCH2CH2PCy2)(η2η2-NBA)][BArF4] scrambles the D-label into all possible positions of the propene, as shown by isotopic perturbation of equilibrium measurements for the agostic interaction. Periodic DFT calculations show a low barrier to H/D exchange (10.9 kcal mol-1, PBE-D3 level), and GIPAW chemical shift calculations guide the assignment of the experimental data. When synthesized using solution routes a bis-propene complex, [Rh(Cy2PCH2CH2PCy2)(propene)2][BArF4], is formed. [Rh(Cy2PCH2CH2PCy2)(butene)][BArF4] (x = 1) is characterized as having 2-butene bound as the cis-isomer and a single Rh⋯H3C agostic interaction. In the solid-state two low-energy fluxional processes are proposed. The first is a simple libration of the 2-butene that exchanges the agostic interaction, and the second is a butene isomerization process that proceeds via an allyl-hydride intermediate with a low computed barrier of 14.5 kcal mol-1. [Rh(Cy2PCH2CH2PCy2)(η2η2-NBA)][BArF4] and the polymorphs of [Rh(Cy2PCH2CH2PCy2)(ethene)2][BArF4] are shown to be effective in solid-state molecular organometallic catalysis (SMOM-Cat) for the isomerization of 1-butene to a mixture of cis- and trans-2-butene at 298 K and 1 atm, and studies suggest that catalysis is likely dominated by surface-active species. [Rh(Cy2PCH2CH2PCy2)(η2η2-NBA)][BArF4] is also shown to catalyze the transfer dehydrogenation of butane to 2-butene at 298 K using ethene as the sacrificial acceptor

Measurement of electric-field noise from interchangeable samples with a trapped-ion sensor

We demonstrate the use of a single trapped ion as a sensor to probe electric-field noise from interchangeable test surfaces. As proof of principle, we measure the magnitude and distance dependence of electric-field noise from two ion-trap-like samples with patterned Au electrodes. This trapped-ion sensor could be combined with other surface characterization tools to help elucidate the mechanisms that give rise to electric-field noise from ion-trap surfaces. Such noise presents a significant hurdle for performing large-scale trapped-ion quantum computations.Comment: 11 pages, 4 figure

Tolerant to air σ-alkane complexes by surface modification of single crystalline solid-state molecular organometallics using vapour-phase cationic polymerisation : SMOM@polymer

Vapour-phase surface-initiated cationic polymerisation of ethylvinylether occurs at single-crystals of the σ-alkane complex [Rh(Cy2PCH2CH2PCy2)(NBA)][BArF4]. This new surface interface makes these normally very air sensitive materials tolerant to air, while also allowing for onward single-crystal to single-crystal reactivity at metal sites within the lattice

Mobile phones support adherence and retention of indigenous participants in a randomised controlled trial: strategies and lessons learnt

BackgroundEnsuring adherence to treatment and retention is important in clinical trials, particularly in remote areas and minority groups. We describe a novel approach to improve adherence, retention and clinical review rates of Indigenous children.MethodsThis descriptive study was nested within a placebo-controlled, randomised trial (RCT) on weekly azithromycin (or placebo) for 3-weeks. Indigenous children aged ≤24-months hospitalised with acute bronchiolitis were recruited from two tertiary hospitals in northern Australia (Darwin and Townsville). Using mobile phones embedded within a culturally-sensitive approach and framework, we report our strategies used and results obtained. Our main outcome measure was rates of adherence to medications, retention in the RCT and self-presentation (with child) to clinic for a clinical review on day-21.ResultsOf 301 eligible children, 76 (21%) families declined participation and 39 (13%) did not have access to a mobile phone. 186 Indigenous children were randomised and received dose one under supervision in hospital. Subsequently, 182 (99%) children received dose two (day-7), 169 (93%) dose three (day-14) and 180 (97%) attended their clinical review (day-21). A median of 2 calls (IQR 1–3) were needed to verify adherence. Importantly, over 97% of children remained in the RCT until their clinical endpoint at day-21.ConclusionsIn our setting, the use of mobile phones within an Indigenous-appropriate framework has been an effective strategy to support a clinical trial involving Australian Indigenous children in urban and remote Australia. Further research is required to explore other applications of this approach, including the impact on clinical outcomes

Exploiting Carbonyl Groups to Control Intermolecular Rhodium-Catalyzed Alkene and Alkyne Hydroacylation

Readily available β-carbonyl-substituted aldehydes are shown to be exceptional substrates for Rh-catalyzed intermolecular alkene and alkyne hydroacylation reactions. By using cationic rhodium catalysts incorporating bisphosphine ligands, efficient and selective reactions are achieved for β-amido, β-ester, and β-keto aldehyde substrates, providing a range of synthetically useful 1,3-dicarbonyl products in excellent yields. A correspondingly broad selection of alkenes and alkynes can be employed. For alkyne substrates, the use of a catalyst incorporating the Ampaphos ligand triggers a regioselectivity switch, allowing both linear and branched isomers to be prepared with high selectivity in an efficient manner. Structural data, confirming aldehyde chelation, and a proposed mechanism are provided