ESI-FTICR mass spectrometry employing Data-dependent external ion selection and accumulation

Data-dependent external m/z selection and accumulation of ions is demonstrated in use with ESI-FTICR instrumentation, with two different methods for ion selection being explored. One method uses RF/DC quadrupole filtering and is described in use with an 11.5 tesla (T) FTICR instrument, while the second method employs RF-only resonance dipolar excitation selection and is described in use with a 3.5 T FTICR instrument. In both methods ions are data-dependently selected on the fly in a linear quadrupole ion guide, then accumulated in a second linear RF-only quadrupole trap that immediately follows. A major benefit of ion preselection prior to external accumulation is the enhancement of ion populations for low-level species. This development is expected to expand the dynamic range and sensitivity of FTICR for applications including analysis of complex polypeptide mixtures (e.g., proteomics).     

Effects of the physical properties of atomic layer deposition grown seeding layers on the preparation of ZnO nanowires

Zinc oxide (ZnO) nanowires are growing in interest as the number of devices for which they are well suited increases. Success in these applications requires defined and controlled geometric incorporation of the wires into the various platforms. Therefore, establishing the ability to tailor the growth ZnO nanowires to produce specified sizes, surface densities, and orientation will be important. In the reported work, the effects of the seeding layer on these factors were accessed. Atomic layer deposition (ALD) was used to produce thin films of ZnO under varying growth and post-processing conditions. These films were fully characterized, including their thickness, surface roughness, and crystalline orientation. Using these well-defined films as the seeding layer, ZnO nanowires were grown and subsequently characterized in terms of morphology and crystalline properties. It was shown that the resulting nanowire properties are dependent upon the nature of the seeding layer, and careful production of the seeding layer allows for some control over these properties.     

Residual entropy of ice nanotubes and ice layers

A relatively simple algorithm is presented for the complete enumeration of all H-bond networks in finite fragments of ice nanotubes and ice layers with periodic boundary conditions. This algorithm is based on the well-known transfer matrix method and it includes a convenient procedure for calculation of the elements of transfer matrices themselves. To facilitate this, it is necessary to specify only very small local matrices of sizes 2×2 or 4×4. We present exhaustive statistics of H-bonds arrangements for finite-size zigzag- and armchair-like ice nanotubes, for the fragments of hexagonal monolayer and bilayer and also for ice nanotubes consisting of stacked n$n$-membered rings. Using the new algorithm, we have also calculated the specific residual entropy for the infinite two-dimensional lattices. The agreement with the well-known solution for a square ice model demonstrates the reliability of the obtained results.     

Stress-induced phase transitions in diamond

A phase transformation in diamond into an intermediate carbon phase (ICP) was revealed in regions of maximal shear stress of diamond anvils. The transition was stimulated by additional stresses supplied to the compressed anvils with torque by a rotation of the anvil around the anvil's axis; maximal shear stress approached 55 GPa during the rotation. Creation of an ICP is considered as a mechanism of the stress-induced stability loss of the diamond structure. The characteristic Raman bands of ICP near 250, 500, 650–850 and 1050–1390 cm^?1 were observed in the failure regions.     

Correlation of Electronic and Magnetic Properties of Thin Polymer Layers with Cobalt Nanoparticles

Nanoparticles (NPs) of cobalt are synthesized in shallow layers of polyimide using 40 keV implantation of Co⁺ ions with a few different fluences at various ion current densities. Nucleation of individual NPs at low fluencies and their percolation at high fluencies are crucial processes governing the electrical and magnetic properties of the metal/polymer nanocomposites that can be controlled by the implantation regimes. In particular, one can tune the magnetoresistance between negative and positive through appropriate choice of ion fluence and current density. The found non‐monotonous dependence of the magnetoresistance on the applied magnetic field allows suggestion of spin‐dependent domain wall scattering affecting the electron transport. The samples implanted with low fluencies demonstrate superparamagnetic behavior down to very low blocking temperatures. For high fluence (1.25 × 10¹⁷ cm⁻²) the transition to ferromagnetic ordering is observed that is related to the increased magnetic interaction of NPs.     

On the codimension growth of almost nilpotent Lie algebras

We study codimension growth of infinite dimensional Lie algebras over a field of characteristic zero. We prove that if a Lie algebra L is an extension of a nilpotent algebra by a finite dimensional semisimple algebra then the PI-exponent of L exists and is a positive integer.     

On 2-Systoles of Hyperbolic 3-Manifolds

We investigate the geometry of π ₁-injective surfaces in closed hyperbolic 3-manifolds. First we prove that for any ${\epsilon > 0}$ , if the manifold M has sufficiently large systole sys₁(M), the genus of any such surface in M is bounded below by ${{\rm exp}((\frac{1}{2} - \epsilon){\rm sys}_1(M))}$ . Using this result we show, in particular, that for congruence covers M _i → M of a compact arithmetic hyperbolic 3-manifold we have: (a) the minimal genus of π ₁-injective surfaces satisfies ${{\rm log} \, {\rm sysg}(M_i) \gtrsim \frac{1}{3} {\rm log} \, {\rm vol}(M_i) ; (b)}$ there exist such sequences with the ratio Heegard ${{\rm genus}(M_i)/{\rm sysg}(M_i) \gtrsim {\rm vol}(M_i)^{1/2}}$ ; and (c) under some additional assumptions π ₁(M _i ) is k-free with ${{\rm log} \, k \gtrsim \frac{1}{3}{\rm sys}_1(M_i)}$ . The latter resolves a special case of a conjecture of Gromov.     

Conformationally locked chromophores as models of excited-state proton transfer in fluorescent proteins

Members of the green fluorescent protein (GFP) family form chromophores by modifications of three internal amino acid residues. Previously, many key characteristics of chromophores were studied using model compounds. However, no studies of intermolecular excited-state proton transfer (ESPT) with GFP-like synthetic chromophores have been performed because they either are nonfluorescent or lack an ionizable OH group. In this paper we report the synthesis and photochemical study of two highly fluorescent GFP chromophore analogues: p-HOBDI-BF2 and p-HOPyDI:Zn. Among known fluorescent compounds, p-HOBDI-BF(2) is the closest analogue of the native GFP chromophore. These irrreversibly (p-HOBDI-BF(2)) and reversibly (p-HOPyDI:Zn) locked compounds are the first examples of fully planar GFP chromophores, in which photoisomerization-induced deactivation is suppressed and protolytic photodissociation is observed. The photophysical behavior of p-HOBDI-BF2 and p-HOPyDI:Zn (excited state pK(a)'s, solvatochromism, kinetics, and thermodynamics of proton transfer) reveals their high photoacidity, which makes them good models of intermolecular ESPT in fluorescent proteins. Moreover, p-HOPyDI:Zn is a first example of "super" photoacidity in metal-organic complexes.