Edward Bailey

Rapid Acquisition of Gigapascal-High-Pressure Resistance by Escherichia coli

ABSTRACT Pressure and temperature are important environmental variables that influence living systems. However, while they vary over a considerable range on Earth and other planets, it has hardly been addressed how straightforwardly and to what extent cellular life can acquire resistance to extremes of these parameters within a defined genomic context and a limited number of generations. Nevertheless, this is a very pertinent question with respect to the penetration of life in allegedly inhospitable environments. In this study, directed evolution was used to reveal the potential of the nonsporulating and mesophilic model bacterium Escherichia coli to develop the ability to survive exposure to high temperature or pressure. While heat resistance could only marginally be increased, our data show that piezoresistance could readily and reproducibly be extended into the GPa range, thereby greatly exceeding the currently recognized maximum for growth or survival. IMPORTANCE While extremophilic microorganisms generally serve as the reference for microbial survival capacities in inhospitable environments, we set out to examine how readily a mesophilic model bacterium such as Escherichia coli could build up resistance to extremes of temperature or pressure within a very short evolutionary time scale. Both heat and high pressure constitute ecologically important physical stresses that are able to irrevocably penetrate the entire cell. Our results for the first time establish that cellular life can acquire resistance to pressures extending into the GPa range. While extremophilic microorganisms generally serve as the reference for microbial survival capacities in inhospitable environments, we set out to examine how readily a mesophilic model bacterium such as Escherichia coli could build up resistance to extremes of temperature or pressure within a very short evolutionary time scale. Both heat and high pressure constitute ecologically important physical stresses that are able to irrevocably penetrate the entire cell. Our results for the first time establish that cellular life can acquire resistance to pressures extending into the GPa range.

High-Pressure and -Temperature Ion Exchange of Aluminosilicate and Gallosilicate Natrolite

The simultaneous application of high pressure and high temperature has been used to achieve direct ion exchange of large cesium cations for the small sodium cations found in the zeolite natrolite by putting it into a superhydrated state with increased pore size. The larger cations remain trapped upon pressure release, and thus, this method is a means of producing new cationic forms of zeolites.

Mechanical Properties of Titanium Nitride Nanocomposites Produced by Chemical Precursor Synthesis Followed by High-P,T Treatment

We investigated the high-P,T annealing and mechanical properties of nanocomposite materials with a highly nitrided bulk composition close to Ti3N4. Amorphous solids were precipitated from solution by ammonolysis of metal dialkylamide precursors followed by heating at 400–700 °C in flowing NH3 to produce reddish-brown amorphous/nanocrystalline materials. The precursors were then densified at 2 GPa and 200–700 °C to form monolithic ceramics. There was no evidence for N2 loss during the high-P,T treatment. Micro- and nanoindentation experiments indicate hardness values between 4–20 GPa for loads ranging between 0.005–3 N. Youngs modulus values were measured to lie in the range 200–650 GPa. Palmqvist cracks determined from microindentation experiments indicate fracture toughness values between 2–4 MPa·m1/2 similar to Si3N4, SiC and Al2O3. Significant variations in the hardness may be associated with the distribution of amorphous/crystalline regions and the very fine grained nature (~3 nm grain sizes) of the crystalline component in these materials.

Deformation T-Cup: A new multi-anvil apparatus for controlled strain-rate deformation experiments at pressures above 18 GPa.

A new multi-anvil deformation apparatus, based on the widely used 6-8 split-cylinder, geometry, has been developed which is capable of deformation experiments at pressures in excess of 18 GPa at room temperature. In 6-8 (Kawai-type) devices eight cubic anvils are used to compress the sample assembly. In our new apparatus two of the eight cubes which sit along the split-cylinder axis have been replaced by hexagonal cross section anvils. Combining these anvils hexagonal-anvils with secondary differential actuators incorporated into the load frame, for the first time, enables the 6-8 multi-anvil apparatus to be used for controlled strain-rate deformation experiments to high strains. Testing of the design, both with and without synchrotron-X-rays, has demonstrated the Deformation T-Cup (DT-Cup) is capable of deforming 1-2 mm long samples to over 55% strain at high temperatures and pressures. To date the apparatus has been calibrated to, and deformed at, 18.8 GPa and deformation experiments performed in conjunction with synchrotron X-rays at confining pressures up to 10 GPa at 800 °C .

Metastable phase transitions and structural transformations in solid-state materials at high pressure

We use a combination of diamond anvil cell techniques and large volume (multi-anvil press, piston cylinder) devices to study the synthesis, structure and properties of new materials under high pressure conditions. The work often involves the study of structural and phase transformations occurring in the metastable regime, as we explore the phase space determined as a function of the pressure, temperature and chemical composition. The experimental studies are combined with first principles calculations and molecular dynamics simulations, as we determine the structures and properties of new phases and the nature of the transformations between them. Problems currently under investigation include structural studies of transition metal and main group nitrides, oxides and oxynitrides at high pressure, exploration of new solid-state compounds that are formed within the C-N-O system, polyamorphic low- to high-density transitions among amorphous semiconductors such as a-Si, and transformations into metastable forms of the element that occur when its “expanded” clathrate polymorph is compressed.

High pressure synthesis of superconducting nitrides in the MoN–NbN system

We have synthesized a range of Mo–Nb nitrides at 2.5 GPa and T = 1600 °C or 2200 °C using high pressure–high temperature techniques. Following syntheses at 1600 °C Mo-rich compositions are hexagonal and Nb-rich phases are cubic, with a narrow two-phase region indicating the presence of a solvus. The maximum Mo content in the cubic phase derived from δ-NbN is 40–44 mol%, and the maximum Nb content in the hexagonal δ-MoN phase is 46–47 mol%. There was little variation in the superconducting transition temperature Tc for hexagonal δ-(Mo,Nb)N samples produced in the study. Previous studies showed maximum Tc values of 12–15 K for pure δ-MoN as a function of N-site ordering in high-P,T experiments. Here we recorded Tc = 14 K for the limiting Mo-rich composition prepared in the study. We observed Tc = 11.5–16 K for cubic δ-NbN depending on high-P,T synthesis and annealing conditions. This value falls to 5 K for the cubic Mo0.37Nb0.63N0.98 solid solution phase. Some high-P,T synthesis or annealing experiments were carried out at T = 2200 °C. At this temperature δ-MoN decomposes to produce γ-MoN0.54. A minor phase in this sample achieves Tc = 9.5 K. A new superconducting hexagonal oxynitride MoN0.74O0.38 with Tc = 16 K was also produced during this study.

High-temperature equation of state of vanadium

ABSTRACT The unit cell dimensions of vanadium, NaCl and Au have been collected to 11. 5 GPa and 1000 K by powder X-ray diffraction and are used to constrain a practical high-temperature EoS for bcc vanadium. The resulting third-order Birch–Murnaghan EoS is described with parameters KT0,300 = 150.4 ± 6.2 GPa,  = 5.5 ± 1.0, α0 = 4.8(6)·10−5, α1 = −2.4(9)·10−8 and δKTδT = −0.0446(7) GPa/K. The parameter α.K0,300 is 616·10−5 K−1 GPa and reduces to zero at an estimated 60 GPa at RT. This EoS description is entirely consistent with the majority of X-ray, ultrasonic, shock wave and calculated data-sets in this p, T range. These measurements facilitate the estimation of in situ temperatures under high pressures when vanadium is used inside sample assemblies and are useful, when used with h-BN, to estimate p, T over the full range of h-BN stability.