836 research outputs found
Ekstraksi dan Karakterisasi Selulosa dari Limbah Kulit Kacang Tanah (Arachys hypogaea L.) Sebagai Adsorben Ion Logam Besi
Penelitian ini bertujuan untuk mengetahui karakteristik selulosa dari limbah kulit kacang tanah yang meliputi kadar air, kadar abu, dan kadar selulosa serta mengetahui berapa daya adsorpsi optimum kulit kacang tanah terhadap ion logam besi berdasarkan variasi massa, pH, dan waktu kontak. Metode penelitian yang digunakan adalah metode kualitatif dan kuantitatif. Sampel yang digunakan dalam penelitian ini adalah kulit kacang tanah. Tahap pembuatan selulosa dari kulit kacang tanah terdiri dari tahap dewaxing, delignifikasi dan bleaching. Karakterisasi selulosa menggunakan Instrument Fourier Transform Infrared (FTIR). Aplikasi selulosa digunakan sebagai adsorben logam besi dengan menggunakan Atomic Absorption Spektrofotometri (AAS). Hasil penelitian menunjukkan bahwa selulosa yang diperoleh memiliki kadar abu sebesar 5,01%, kadar air 2,7%, kadar selulosa 59,58%. Hasil optimum untuk variasi massa adalah 1 gram dengan konsentrasi besi yang teradsorpsi adalah 0,7467 mg/L, untuk hasil optimum pada variasi pH adalah pH 5 dengan konsentrasi besi yang teradsorpsi adalah 0,8502 mg/L, dan untuk variasi waktu kontak paling optimum adalah 90 menit dengan konsentrasi besi yang teradsorpsi adalah 0,5386 mg/L
Theoretical study of the thermal behavior of free and alumina-supported Fe-C nanoparticles
The thermal behavior of free and alumina-supported iron-carbon nanoparticles
is investigated via molecular dynamics simulations, in which the effect of the
substrate is treated with a simple Morse potential fitted to ab initio data. We
observe that the presence of the substrate raises the melting temperature of
medium and large nanoparticles ( = 0-0.16, = 80-1000, non-
magic numbers) by 40-60 K; it also plays an important role in defining the
ground state of smaller Fe nanoparticles ( = 50-80). The main focus of our
study is the investigation of Fe-C phase diagrams as a function of the
nanoparticle size. We find that as the cluster size decreases in the
1.1-1.6-nm-diameter range the eutectic point shifts significantly not only
toward lower temperatures, as expected from the Gibbs-Thomson law, but also
toward lower concentrations of C. The strong dependence of the maximum C
solubility on the Fe-C cluster size may have important implications for the
catalytic growth of carbon nanotubes by chemical vapor deposition.Comment: 13 pages, 11 figures, higher quality figures can be seen in article 9
at http://alpha.mems.duke.edu/wahyu
The Haldane-Rezayi Quantum Hall State and Magnetic Flux
We consider the general abelian background configurations for the
Haldane-Rezayi quantum Hall state. We determine the stable configurations to be
the ones with the spontaneous flux of with .
This gives the physical mechanism by which the edge theory of the state becomes
identical to the one for the 331 state. It also provides a new experimental
consequence which can be tested in the enigmatic plateau in a single
layer system.Comment: RevTex, 5 pages, 2 figures. v2:minor corrections. v4: published
version. Discussion on the thermodynamic limit adde
Dependence of the superconducting effective mass on doping in cuprates
Using a doping-determined multiband model spectrum of a "typical'' cuprate
the effective mass of the paired carriers is calculated on the whole doping
scale. Large values quench rapidly with leaving the very underdoped
region. Further slower diminishing of reproduces the trend towards
restoring the Fermi-liquid behaviour in cuprates with progressive doping. The
interband superconducting condensate density () shows similar behaviour to
the transition temperature and superconducting gaps. The ratio
has an expressed maximum close to optimal doping as also the thermodynamic
critical field. All the overlapping band components are intersected by the
chemical potential at this. The pairing strength and the phase coherence
develop simultaneously. In spite of its simplicity, the model describes the
behaviour of various cuprate characteristics on the doping scale.Comment: 9 pages, 5 figure
Evolution of the electronic structure from electron-doped to hole-doped states in the two-dimensional Mott-Hubbard system La1.17-xPbxVS3.17
The filling-controlled metal-insulator transition (MIT) in a two-dimensional
Mott-Hubbard system La1.17-xPbxVS3.17 has been studied by photoemission
spectroscopy. With Pb substitution x, chemical potential mu abruptly jumps by ~
0.07 eV between x=0.15 and 0.17, indicating that a charge gap is opened at x ~=
0.16 in agreement with the Mott insulating state of the d2 configuration. When
holes or electrons are doped into the Mott insulator of x ~= 0.16, the gap is
filled and the photoemission spectral weight at mu, rho(mu), gradually
increases in a similar way to the electronic specific heat coefficient,
although the spectral weight remains depressed around mu compared to that
expected for a normal metal, showing a pseudogap behavior in the metallic
samples. The observed behavior of varrho(mu)->0 for x->0.16 is contrasted with
the usual picture that the electron effective mass of the Fermi-liquid system
is enhanced towards the metal-insulator boundary. With increasing temperature,
the gap or the pseudogap is rapidly filled up, and the spectra at T=300 K
appears to be almost those of a normal metal. Near the metal-insulator
boundary, the spectra around mu are consistent with the formation of a Coulomb
gap, suggesting the influence of long-range Coulomb interaction under the
structural disorder intrinsic to this system.Comment: 8 pages, 12 figure
Pulsed UCN production using a Doppler shifter at J-PARC
We have constructed a Doppler-shifter-type pulsed ultra-cold neutron (UCN)
source at the Materials and Life Science Experiment Facility (MLF) of the Japan
Proton Accelerator Research Complex (J-PARC). Very-cold neutrons (VCNs) with
136- velocity in a neutron beam supplied by a pulsed neutron
source are decelerated by reflection on a m=10 wide-band multilayer mirror,
yielding pulsed UCN. The mirror is fixed to the tip of a 2,000-rpm rotating arm
moving with 68- velocity in the same direction as the VCN. The
repetition frequency of the pulsed UCN is and the time width
of the pulse at production is . In order to increase the UCN
flux, a supermirror guide, wide-band monochromatic mirrors, focus guides, and a
UCN extraction guide have been newly installed or improved. The
-equivalent count rate of the output neutrons with longitudinal
wavelengths longer than is ,
while that of the true UCNs is . The spatial density at
production is . This new UCN source enables us to
research and develop apparatuses necessary for the investigation of the neutron
electric dipole moment (nEDM).Comment: 32 pages, 15 fugures. A grammatical error was fixe
Field theory of spin-singlet quantum Hall states
We formulate a field theory for a class of spin-singlet quantum Hall states
(the Haldane-Rezayi state and its variants) which have been proposed for the
quantized Hall plateaus observed at the second lowest Landau level. A new
essential ingredient is a class of super Chern-Simons field. We show that the
known properties of the states are consistently described by it. We also give a
2+1 dimensional hierarchical construction. Implications of the proposal are
discussed and a new physical picture of composite particles at the second
lowest Landau level emerges.Comment: RevTex, 5 pages, 1 figur
Chemical Potential Shift in NdCeCuO: Contrasting Behaviors of the Electron- and Hole-Doped Cuprates
We have studied the chemical potential shift in the electron-doped
superconductor NdCeCuO by precise measurements of
core-level photoemission spectra. The result shows that the chemical potential
monotonously increases with electron doping, quite differently from
LaSrCuO, where the shift is suppressed in the underdoped
region.
If the suppression of the shift in LaSrCuO is attributed
to strong stripe fluctuations, the monotonous increase of the chemical
potential is consistent with the absence of stripe fluctuations in
NdCeCuO. The chemical potential jump between
NdCuO and LaCuO is found to be much smaller than the
optical band gaps.Comment: 4 pages, 5 figure
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