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Rational Design of Pore Size and Functionality in a Series of Isoreticular Zwitterionic Metal-Organic Frameworks
The isoreticular expansion and functionalization of charged-polarized porosity has been systematically explored by the rational design of 11 isostructural zwitterionic metal-organic frameworks (ZW-MOFs). This extended series of general structural composition {[M3F(L1)3(L2)1.5]·guests}n was prepared by employing the solvothermal reaction of Co and Ni tetrafluoroborates with a binary ligand system composed of zwitterionic pyridinium derivatives and traditional functionalized ditopic carboxylate auxiliary ligands (HL1·Cl = 1-(4-carboxyphenyl)-4,4′-bipyridinium chloride, Hcpb·Cl; or 1-(4-carboxyphenyl-3-hydroxyphenyl)-4,4′-bipyridinium chloride, Hchpb·Cl; and H2L2 = benzene-1,4-dicarboxylic acid, H2bdc; 2-aminobenzene-1,4-dicarboxylic acid, H2abdc; 2,5-dihydroxy-1,4-benzenedicarboxylic acid, H2dhbdc; biphenyl-4,4′-dicarboxylic acid, H2bpdc; or stilbene-4,4′-dicarboxylic acid, H2sdc). Single-crystal structure analyses revealed cubic crystal symmetry (I-43m, a = 31-36 Å) with a 3D pore system of significant void space (73-81%). The pore system features three types of pores being systematically tunable in size ranging from 17.4 to 18.8 Å (pore I), 8.2 to 12.8 Å (pore II), and 4.8 to 10.4 Å (pore III) by the choice of auxiliary ligands. All members of this series have noninterpenetrating structures and exhibit robust architectures, as evidenced by their permanent porosity and high thermal stability (up to 300 °C). The structural integrity and specific surface areas could be systematically optimized using supercritical CO2 exchange methods for framework activation resulting in BET surface areas ranging from 1250 to 2250 m2/g. Most interestingly, as a structural landmark, we found the pore surfaces lined with charge gradients employed by the pyridinium ligands. This key feature results in significant adsorption of carbon dioxide and methane which is attributed to polarization effects. With this contribution we pioneer the reticulation of pyridinium building blocks into extended zwitterionic networks in which specific properties can be targeted
Influence of plant residues on denitrification rates in conventional and zero tilled soils, The
Includes bibliographical references (page 794).A field study was conducted with treatments consisting of a factorial combination of N (0 or 100 kg N ha−1 as (NH4)2SO4, straw (0 or 3000 kg ha−1), and two tillage treatments. Ground straw was mixed with the plow layer of soil in the conventional till (CT) plots and chopped straw was spread over the surface of the zero till (ZT) plots. Wheat (Triticum aestivum L.) was grown as the test crop. Gaseous losses of N were measured using the acetylene inhibition-soil core technique and compared with loss estimates obtained from the imbalance in the N budget of 15N-treated microplots located within the larger yield plots. When adequate inorganic N was present, the incorporation of straw in CT soil or the application of straw on the surface of ZT soil approximately doubled the accumulative gaseous N losses. The straw apparently increased the supply of energy material available to denitrifying organisms, and also increased surface soil moisture content (particularly during the month of June). This further stimulated denitrification in ZT soil. Unaccounted 15N on the fertilizer N balance studies agreed closely with cumulative N losses using the acetylene inhibition technique
Minimal SUSY SO(10) model and predictions for neutrino mixings and leptonic CP violation
We discuss a minimal Supersymmetric SO(10) model where B-L symmetry is broken
by a {\bf 126} dimensional Higgs multiplet which also contributes to fermion
masses in conjunction with a {\bf 10} dimensional superfield. This minimal
Higgs choice provides a partial unification of neutrino flavor structure with
that of quarks and has been shown to predict all three neutrino mixing angles
and the solar mass splitting in agreement with observations, provided one uses
the type II seesaw formula for neutrino masses. In this paper we generalize
this analysis to include arbitrary CP phases in couplings and vevs. We find
that (i) the predictions for neutrino mixings are similar with as before and other parameters in a somewhat bigger range and (ii) that
to first order in the quark mixing parameter (the Cabibbo angle), the
leptonic mixing matrix is CP conserving. We also find that in the absence of
any higher dimensional contributions to fermion masses, the CKM phase is
different from that of the standard model implying that there must be new
contributions to quark CP violation from the supersymmetry breaking sector.
Inclusion of higher dimensional terms however allows the standard model CKM
phase to be maintained.Comment: 22 pages, 6 figure
High scale perturbative gauge coupling in R-parity conserving SUSY SO(10) with longer proton lifetime
It is well known that in single step breaking of R-parity conserving SUSY
SO(10) that needs the Higgs representations the GUT-gauge
coupling violates the perturbative constraint at mass scales few times larger
than the GUT scale. Therefore, if the SO(10) gauge coupling is to remain
perturbative up the Planck scale(=2x10^{18} GeV), the scale of GUT
symmetry breaking is to be bounded from below. The bound depends upon specific
Higgs representations used for SO(10) symmetry breaking but, as we find, can
not be lower than GeV. In order to obtain such high unification
scale we propose a two-step SO(10) breaking through
intermediate gauge
symmetry. We estimate potential threshold and gravitational corrections to the
running of gauge couplings and show that they can make the picture of
perturbative GUT- gauge coupling running consistent at least up to the Planck
scale. We also show that when by ,
gravitational corrections alone with negligible threshold effects may guarantee
such perturbative gauge coupling. The lifetime of the proton is found to
increase by nearly 6 orders over the current experimental limit for . For the proton decay mediated by dim.5 operator a wide range of
lifetimes is possible extending from the current experimental limit up to
values 2-3 orders longer.Comment: 11 pages epjc LaTex as per specifications of European Physical
Journal
Supersymmetric Unification in the Light of Neutrino Mass
We argue that with the discovery of neutrino mass effects at Super-Kamiokande
there is a clear logical chain leading from the Standard Model through the MSSM
and the recently developed Minimal Left Right Supersymmetric models with a
renormalizable see-saw mechanism for neutrino mass to Left Right symmetric SUSY
GUTS : in particular, SO(10) and . The
progress in constructing such GUTS explicitly is reviewed and their
testability/falsifiability by proton decay measurements emphasized.Comment: 16 pages, REVTEX. Invited talk presented at XIII DAE Symposium on
High Energy Physics, Chandigarh, December 199
Signals of neutralinos and charginos from gauge boson fusion at the CERN Large Hadron Collider
We point out that interesting signals of the non-strongly interacting sector
of the supersymmetric standard model arise from the production of charginos and
neutralinos via vector boson fusion (VBF) at the Large Hadron Collider (LHC).
In particular, if R-parity is violated, the hadronically quiet signals of
charginos and neutralinos through direct production get considerably
suppressed. We show that in such cases, the VBF channel can be useful in
identifying this sector through clean and background-free final states.Comment: 10 pages Latex, 8 figures, minor changes in text and few references
added, to be published in Phys. Rev.
Like Sign Dilepton Signature for R-Parity Violating SUSY Search at the Tevatron Collider
The like sign dileptons provide the most promising signature for
superparticle search in a large category of -parity violating SUSY models.
We estimate the like sign dilepton signals at the Tevatron collider, predicted
by these models, over a wide region of the MSSM parameter space. One expects an
unambiguous signal upto a gluino mass of GeV ( GeV) with
the present (proposed) accumulated luminosity of .Comment: 12 page LaTeX file; 5 figures available upon request from the autho
Testing radiative neutrino mass generation via R-parity violation at the Tevatron
An R-parity violating SUSY model with lepton-number violating couplings
, i=2,3 can generate a neutrino mass spectrum that explains the
recent results from neutrino oscillation experiments. These R-parity violating
couplings lead to a clean signal with at least one isolated lepton and at least
three tagged jets that is accessible in chargino and neutralino production
at the Tevatron collider. This signature can be probed at up to
GeV (320 GeV) with an integrated luminosity of ().Comment: Version to appear in PL
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