Nuclear magnetic resonance cryoporometry

Nuclear Magnetic Resonance (NMR) cryoporometry is a technique for non-destructively determining pore size distributions in porous media through the observation of the depressed melting point of a confined liquid. It is suitable for measuring pore diameters in the range 2 nm-1 mu m, depending on the absorbate. Whilst NMR cryoporometry is a perturbative measurement, the results are independent of spin interactions at the pore surface and so can offer direct measurements of pore volume as a function of pore diameter. Pore size distributions obtained with NMR cryoporometry have been shown to compare favourably with those from other methods such as gas adsorption, DSC thermoporosimetry, and SANS. The applications of NMR cryoporometry include studies of silica gels, bones, cements, rocks and many other porous materials. It is also possible to adapt the basic experiment to provide structural resolution in spatially-dependent pore size distributions, or behavioural information about the confined liquid

Characterisation of porous solids using small-angle scattering and NMR cryoporometry

The characteristics of several porous systems have been studied by the use of small-angle neutron scattering [SANS] and nuclear magnetic resonance [NMR] techniques. The measurements reveal different characteristics for sol-gel silicas, activated carbons and ordered mesoporous silicas of the MCM and SBA type. Good agreement is obtained between gas adsorption measurements and the NMR and SANS results for pore sizes above 10 nm. Recent measurements of the water/ice phase transformation in SBA silicas by neutron diffraction are also presented and indicate a complex relationship that will require more detailed treatment in terms of the possible effects of microporosity in the silica substrate. The complementarity of the different methods is emphasised and there is brief discussion of issues related to possible future developments

Personality Tests in Employment Selection: Use With Caution

[Excerpt] Many employers utilize personality tests in the employment selection process to identify people who have more than just the knowledge and skills necessary to be successful in their jobs.[1] If anecdotes are to be believed—Dilbert must be getting at something or the cartoon strip would not be so popular—the work place is full of people whose personalities are a mismatch for the positions they hold. Psychology has the ability to measure personality and emotional intelligence (“EQ”), which can provide employers with data to use in the selection process. “Personality refers to an individual’s unique constellation of consistent behavioral traits”[2] and “emotional intelligence consists of the ability to perceive and express emotion, assimilate emotion in thought, understand and reason with emotion, and regulate emotion.”[3] By using a scientific approach in hiring, employers can increase their number of successful employees

H2 molecule in strong magnetic fields

The Pauli-Hamiltonian of a molecule with fixed nuclei in a strong constant magnetic field is asymptotic, in norm-resolvent sense, to an effective Hamiltonian which has the form of a multi-particle Schr\"odinger operator with interactions given by one-dimensional \delta-potentials. We study this effective Hamiltonian in the case of the H2 -molecule and establish existence of the ground state. We also show that the inter-nuclear equilibrium distance tends to 0 as the field-strength tends to infinity

Clathrate formation and dissociation in vapor/water/ice/hydrate systems in SBA-15, sol-gel and CPG porous media, as probed by NMR relaxation, novel protocol NMR cryoporometry, neutron scattering and ab initio quantum-mechanical molecular dynamics simulation

The Gibbs-Thomson effect modifies the pressure and temperature at which clathrates occur, hence altering the depth at which they occur in the seabed. Nuclear magnetic resonance (NMR) measurements as a function of temperature are being conducted for water/ice/ hydrate systems in a range of pore geometries, including templated SBA-15 silicas, controlled pore glasses and sol-gel silicas. Rotator-phase plastic ice is shown to be present in confined geometry, and bulk tetrahydrofuran hydrate is also shown to probably have a rotator phase. A novel NMR cryoporometry protocol, which probes both melting and freezing events while avoiding the usual problem of supercooling for the freezing event, has been developed. This enables a detailed probing of the system for a given pore size and geometry and the exploration of differences between hydrate formation and dissociation processes inside pores. These process differences have an important effect on the environment, as they impact on the ability of a marine hydrate system to re-form once warmed above a critical temperature. Ab initio quantum-mechanical molecular dynamics calculations are also being employed to probe the dynamics of liquids in pores at nanometric dimensions

Identification of polyubiquitin binding proteins involved in NF-kappaB signaling using protein arrays.

Attachment of ubiquitin to proteins represents a central mechanism for the regulation of protein metabolism and function. In the NF-kappaB pathway, binding of NEMO to polyubiquitinated substrates initiates the pathway in response to cellular stimuli. Other polyubiquitin binding proteins can antagonize this pathway by competing with NEMO for polyubiquitin. We have used protein arrays to identify polyubiquitin binding proteins that regulate NF-kappaB activity. Using polyubiquitin as bait, protein arrays were screened and polyubiquitin binders identified. Novel polyubiquitin binders AWP1, CALCOCO2, N4BP1, RIO3, TEX27, TTC3, UBFD1 and ZNF313 were identified using this approach, while known NF-kappaB regulators including NEMO, A20, ABIN-1, ABIN-2, optineurin and p62 were also identified. Overexpressed AWP1 and RIO3 repressed NF-kappaB activity in a manner similar to optineurin, while siRNAs directed against AWP1 and RIO3 also reduced NF-kappaB activity. TNFalpha-dependent degradation of IkappaBalpha was also suppressed by overexpression of AWP1 and RIO3, possibly due to the polyubiquitin binding activity of these proteins. Protein array screening using polyubiquitin enabled rapid identification of many known and novel polyubiquitin binding proteins and the identification of novel NF-kappaB regulators

Expanding the Substantial Interactome of NEMO Using Protein Microarrays

Signal transduction by the NF-kappaB pathway is a key regulator of a host of cellular responses to extracellular and intracellular messages. The NEMO adaptor protein lies at the top of this pathway and serves as a molecular conduit, connecting signals transmitted from upstream sensors to the downstream NF-kappaB transcription factor and subsequent gene activation. The position of NEMO within this pathway makes it an attractive target from which to search for new proteins that link NF-kappaB signaling to additional pathways and upstream effectors. In this work, we have used protein microarrays to identify novel NEMO interactors. A total of 112 protein interactors were identified, with the most statistically significant hit being the canonical NEMO interactor IKKbeta, with IKKalpha also being identified. Of the novel interactors, more than 30% were kinases, while at least 25% were involved in signal transduction. Binding of NEMO to several interactors, including CALB1, CDK2, SAG, SENP2 and SYT1, was confirmed using GST pulldown assays and coimmunoprecipitation, validating the initial screening approach. Overexpression of CALB1, CDK2 and SAG was found to stimulate transcriptional activation by NF-kappaB, while SYT1 overexpression repressed TNFalpha-dependent NF-kappaB transcriptional activation in human embryonic kidney cells. Corresponding with this finding, RNA silencing of CDK2, SAG and SENP2 reduced NF-kappaB transcriptional activation, supporting a positive role for these proteins in the NF-kappaB pathway. The identification of a host of new NEMO interactors opens up new research opportunities to improve understanding of this essential cell signaling pathway