Jong-Chul Park

Preparation of Mesoporous Catalyst Supported on Silica with Finely Dispersed Ni Particles

A novel nickel catalyst supported on SBA-15 type mesoporous silica was synthesized by the grafting of N-(trimethoxysilylpropyl)ethylene diamine triacetic acid salt (EDTA) onto the surface of SBA-15 and followed by adsorption of nickel ions and calcinations (Ni-E-SBA). The catalysts prepared were characterized using XRD, TEM, TED, SAXS and N2 adsorption/desorption measurements. While nickel particles loaded on catalysts prepared by the wet impregnation method were found to be aggregated on the outer wall of the supports, nickel particles were finely dispersed on the surface of the mesopores in the Ni-E-SBA catalyst. The catalytic performances of the prepared catalysts were evaluated using the hydrodechlorination (HDC) of 1,1,2-trichloroethane (TCEa) as a model reaction. Results showed that the Ni-E-SBA catalyst had the highest activities of the catalysts examined under the given conditions.

Preparation of polyelectrolyte-functionalized mesoporous silicas for the selective adsorption of anionic dye in an aqueous solution

Polyelectrolytes (PDDA, poly (diallydimethylammonium chloride)) functionalized mesoporous silica adsorbent (PDDA/MS) was prepared and characterized by N(2) adsorption, transmission electron microscopy (TEM) and zeta potential. The PDDA/MS showed ordered pore structure and the surface charge was successfully converted from negative to positive by PDDA functionalization. The adsorption capability of the prepared adsorbents was evaluated using nine different dye solutions with positive, neutral and negative charges. For the comparison purpose, commercial silica (CS, Davisil) and granular activated carbon (GAC), which are conventionally used as adsorbents, were also treated by PDDA impregnation. The batch adsorption experiments showed that the PDDA/MS exhibited the highest selective adsorption capacity of negative acid dye dissolved in an aqueous solution. Taken together, the results of this work indicate that polyelectrolyte functionalization of the inorganic surface could be a simple and suitable method for the surface modified adsorbent and the PDDA/MS suggested in this study could be used for the effective removal of acid dye from aqueous solutions.

Galactic 511 keV line from MeV millicharged dark matter

We present a possible explanation of the recently observed 511 keV {gamma}-ray anomaly with a new millicharged fermion. The new fermion is light [O(MeV)] but has never been observed by any collider experiments mainly because of its tiny electromagnetic charge {epsilon}e. We show that constraints from its relic density in the Universe and collider experiments allow a parameter range such that the 511 keV cosmic {gamma}-ray emission from the galactic bulge may be due to positron production from this millicharged fermion.

Dynamical U(1)R breaking in the metastable vacua

In the Intriligator-Seiberg-Shih model, we parametrize spontaneous breaking of U(1)R symmetry with two gauge singlets with R-charges 1 and –1. These singlets can play the role of the messengers. The messenger scale is dynamically generated, and hence there is no hierarchy problem between the supersymmetry breaking scale and the messenger scale. In the gauge mediation scenario, supersymmetry breaking scale turns out to be around (106) GeV.

A comparison of implant stability quotients measured using magnetic resonance frequency analysis from two directions: a prospective clinical study during the initial healing period.

OBJECTIVESnGiven that the orientation of the transducer (mesiodistal or buccolingual) affects the data obtained from a piezoelectric resonance frequency analysis (RFA), this study evaluated whether it is necessary to use measurements taken in two different directions (mesiodistal and buccolingual) when using magnetic RFA to assess changes in the stiffness of dental implants.nnnMATERIALS AND METHODSnA prospective clinical trial was completed, in a total of 53 patients, on 71 non-submerged dental implants that were inserted to replace the unilateral loss of mandibular molars. All of the implants were of the same diameter (4.1 mm), length (10 mm), and collar height (2.8 mm). The implant stability quotient (ISQ) was measured during the surgical procedure, and at 4 and 10 weeks after surgery. Measurements were taken twice in each direction: in the buccolingual direction from the buccal side and in the mesiodistal direction from the mesial side. The average of two measurements in each direction was regarded as the representative ISQ of that direction. The higher and lower values of the two ISQs (buccolingual and mesiodistal) were also classified separately. In addition, the variation in ISQ was quantified by subtracting the lower value from the higher value, and the implants were classified into two groups according to this variation: one with ISQ variation of 3 or more and the other with a variation of <3.nnnRESULTSnThere were no differences between the two ISQs when measured from different directions, but there were significant differences between the higher and lower values of the ISQs at each measurement point. A significant difference was also observed between the two ISQ variation groups in the pattern of change of the lower value for the period from immediately after surgery to 10 weeks after surgery.nnnCONCLUSIONnAcquisition of two directional measurements and classification of the higher and lower values of the two directional ISQs may allow clinicians to detect patterns of change in ISQ that would not be identified if only one directional measurement were made.

Finely-dispersed Ni/Cu catalysts supported on mesoporous silica for the hydrodechlorination of chlorinated hydrocarbons

Abstract Ni/Cu and Ni catalysts supported on the mesoporous silica were prepared via grafting, metal adsorption and calcination steps. The prepared catalyst was characterized using XRD, TEM, N 2 sorption, and SAXS. Pore structure of the support was maintained throughout the preparation procedures. In addition, no specific metal particle image was appeared in XRD, because the metal particles are highly dispersed in the support as a very small size. Hydrodechlorination of TCEa (Trichloroethane) was selected as a model system to test the catalytic activity and selectivity to VCM. The activity of Ni/Cu-E-SBA is higher than that of Ni-E-SBA. The decrease in activity of Ni/Cu-E-SBA was much slow, because copper was added in the Ni catalyst. Cu may plays an important role to retard the deactivation by, such as coking. Further research is on progress. 97% selectivity to VCM was achieved after about 600min on Ni/Cu-E-SBA catalyst.

Functionalized mesoporous adsorbents for Pt(II) and Pd(II) adsorption from dilute aqueous solution

Abstract The surface of the SBA-15 was functionalized with imidazole or thiol functional group via grafting method. Binding behaviors of the adsorbents toward Pt(II) and Pd(II) were examined. The properties of the adsorbents such as pore structure and pore uniformity were also investigated. The pore structure of as-synthesized adsorbents was conserved throughout the preparing steps. The results showed that imidazole- or thiol-functionalized adsorbents showed a high affinity for Pt(II) and Pd(II) metals in aqueous solution.

A Singlet-Extension of the MSSM for 125 GeV Higgs with the Least Tuning

In order to raise the Higgs mass up to 125 GeV and relieve the fine-tuning associated with the heavy s-top mass in the minimal supersymmetric standard model (MSSM), we propose a new singlet extension of the MSSM. In this scenario, the additional Higgs mass is radiatively generated also in a hidden sector, and the effect is tansmitted to the Higgs through a messenger field. The Higgs mass can be efficiently increased by the parameters of the superpotential as in the extra matter scenario, but free from the constraints on extra colored matter fields by the LHC experiments. As a result, the tuning problem can be remarkably mitigated by taking low enough messenger mass (sim 300 GeV) and mass parameter scales (sim 500 GeV).

Zinc Ion Removal from Aqueous Solutions Using Modified Silica Impregnated with 2-Ethylhexyl 2-Ethylhexyl Phosphonic Acid

2-Ethylhexyl 2-ethylhexyl phosphonic acid was immobilized on a silica surface after treatment with dichlorodimethylsilane. Batch and fixed-bed tests were conducted in order to evaluate the metal ion removal capabilities using the prepared adsorbent (SDSP). Equilibrium isotherm data showed that the amount of adsorption is dependent on solution pH. The adsorption of zinc and the elution rate of the SDSP were examined, thus permitting a breakthrough curve to be obtained for the zinc solution. The adsorbed zinc ions were eluted with 0.1 M HCl. The elution ratio using a fixed bed was 91%. The selective recovery of zinc ion from Cu2+, Cd2+, and Co2+ was also investigated. The results showed that the SDSP adsorbed zinc ions selectively in the presence of Cu2+, Cd2+, and Co2+ in the 2–4 pH range. The effects of Mg2+, Ca2+, Na+, Cl−, NO3 −, and SO4 2− on the removal of zinc were relatively small.

Quantum numbers of heavy neutrinos, tri-bi-maximal mixing through double seesaw with permutation symmetry, and comment on θsol + θc ≃ π/4

Using the family symmetry, in the neutrino mass matrix we remove the Yukawa coupling (arising in the Dirac type mass between the heavy neutrinos and light lepton doublets) dependence in the double seesaw mechanism so that it is directly proportional to the mass matrix m(nn) of heavy Majorana neutrinos. The family symmetry is supposed to be broken spontaneously at high energy scale so that the neutrino mass matrix is given by the family symmetry at high energy scale. With the permutation symmetry S3, we note a variety of possible mass hierarchies arising distinctly in neutrinos, charged leptons, Qem = ?1/3 quarks, and Qem = 2/3 quarks. Distinguishing these hierarchies, we obtain a relation between the CKM angles and the MNS angles. Finally, we comment on the approximate relation ?sol + ?c ?/4.