Pengujian Mutu Kritex SP Sebagai Penggumpal Lateks

Hampir seluruh lateks kebun untuk produk karet ekspor harus digumpalkan sebelum diproses lanjut. Bahan penggumpal lateks yang selama ini dianjurkan adalah asam format. Dengan alasan harga yang relatif mahal dan ketersediaan yang sulit diperoleh, sebagian besar petani karet jarang menggunakan asam format dan lebih memilih menggunakan penggumpal yang tidak dianjurkan seperti pupuk SP dan TSP, berakibat menurunkan kualitas karet. Penelitian ini bertujuan untuk melakukan pengujian terhadap kualitas Kritex SP (penggumpal alternatif berbahan aktif asam anorganik) dalam menggumpalkan lateks dan membandingkannya dengan asam format sebagai kontrol. Percobaan dilakukan pada skala laboratorium untuk mengetahui mutu krep, dan pada skala pabrik untuk mengetahui pengolahan RSS menggunakan penggumpal Kritex SP. Parameter yang diamati meliputi waktu koagulasi, spesifikasi teknis, dan sifat fisika vulkanisat krep maupun RSS. Hasil percobaan menunjukkan bahwa lama penggumpalan lateks kebun dengan larutan 2,50% Kritex SP (25,00 menit) berbeda nyata dengan lama penggumpalan larutan 7,50% Kritex SP (18,00 menit), tetapi tidak berbeda secara signifikan dibandingkan dengan lama penggumpalan larutan 5% Kritex SP (20,33 menit) dan larutan kontrol (22,33 menit). Koagulum yang dihasilkan dengan penggumpal Kritex SP bersifat lebih lembut dan lunak dibandingkan koagulum dari asam format. Spesifikasi teknis dan sifat fisika vulkanisat krep dari Kritex SP tidak berbeda nyata dengan krep dari asam format. Dosis Kritex SP yang diperlukan dalam pengolahan RSS (2,35 ml/liter lateks) lebih tinggi dibandingkan dosis asam format (1,90 ml/liter lateks). Lembaran sit basah hasil penggumpalan Kritex SP berukuran lebih panjang, lebih tipis dan kurang lebar dibandingkan sit asam format. Spesifikasi teknis dan sifat fisika vulkanisat RSS dari Kritex SP tidak berbeda nyata dengan asam format, kecuali parameter PRI yang lebih rendah (83,50%) dibandingkan kontrol (86,00%). Diterima : 11 Juli 2012; Disetujui : 2 Oktober 2012 How to Cite : Simanjuntak, M., Bachtiar., & Rachmawan, A. (2012). Pengujian mutu kritex sp sebagai penggumpal lateks. Jurnal Penelitian Karet, 30(2), 108-116. Retrieved from http://ejournal.puslitkaret.co.id/index.php/jpk/article/view/12

Non-adiabatic holonomic quantum computation

We develop a non-adiabatic generalization of holonomic quantum computation in which high-speed universal quantum gates can be realized by using non-Abelian geometric phases. We show how a set of non-adiabatic holonomic one- and two-qubit gates can be implemented by utilizing optical transitions in a generic three-level $\Lambda$ configuration. Our scheme opens up for universal holonomic quantum computation on qubits characterized by short coherence times.Comment: Some changes, journal reference adde

Multi Mode Interferometer for Guided Matter Waves

We describe the fundamental features of an interferometer for guided matter waves based on Y-beam splitters and show that, in a quasi two-dimensional regime, such a device exhibits high contrast fringes even in a multi mode regime and fed from a thermal source.Comment: Final version (accepted to PRL

Recent Low x and Diffractive Collider Data

Selected recent data from collider experiments pertaining to the understanding of QCD at low Bjorken-x are reviewed. The status of QCD and Regge factorisation in hard diffractive interactions is discussed in terms of data from HERA and the Tevatron. The possibility of anomalous behaviour in the $\gamma \gamma$ total cross section is confronted with the most recent measurements from LEP. Data from all three colliders that are sensitive to possible BFKL effects are presented and different interpretations are discussed.Comment: 9 pages, introductory talk from the 1999 Durham Phenomenology Workshop on Collider Physic

Local optical spectroscopy of semiconductor nanostructures in the linear regime

We present a theoretical approach to calculate the local absorption spectrum of excitons confined in a semiconductor nanostructure. Using the density-matrix formalism, we derive a microscopic expression for the nonlocal susceptibility, both in the linear and nonlinear regimes, which includes a three-dimensional description of electronic quantum states and their Coulomb interaction. The knowledge of the nonlocal susceptibility allows us to calculate a properly defined local absorbed power, which depends on the electromagnetic field distribution. We report on explicit calculations of the local linear response of excitons confined in single and coupled T-shaped quantum wires with realistic geometry and composition. We show that significant interference effects in the interacting electron-hole wave function induce new features in the space-resolved optical spectra, particularly in coupled nanostructures. When the spatial extension of the electromagnetic field is comparable to the exciton Bohr radius, Coulomb effects on the local spectra must be taken into account for a correct assignment of the observed features

Local Optical Spectroscopy in Quantum Confined Systems: A Theoretical Description

A theoretical description of local absorption is proposed in order to investigate spectral variations on a length scale comparable with the extension of the relevant quantum states. A general formulation is derived within the density-matrix formalism including Coulomb correlation, and applied to the prototypical case of coupled quantum wires. The results show that excitonic effects may have a crucial impact on the local absorption with implications for the spatial resolution and the interpretation of near-field optical spectra.Comment: To appear in Phys. Rev. Lett. - 11 pages, 3 PostScript figures (1 figure in colors) embedded. Uses RevTex, and psfig style

Electron and Hole Spin Splitting and Photogalvanic Effect in Quantum Wells

A theory of the circular photogalvanic effect caused by spin splitting in quantum wells is developed. Direct interband transitions between the hole and electron size-quantized subbands are considered. It is shown that the photocurrent value and direction depend strongly on the form of the spin-orbit interaction. The currents induced by structure-, bulk-, and interface-inversion asymmetry are investigated. The photocurrent excitation spectra caused by spin splittings in both conduction and valence bands are calculated.Comment: 7 pages, 3 figure

Direct Search for Charged Higgs Bosons in Decays of Top Quarks

We present a search for charged Higgs bosons in decays of pair-produced top quarks in pbar p collisions at sqrt(s) = 1.8 TeV using 62.2 pb^-1 of data recorded by the D0 detector at the Fermilab Tevatron collider. No evidence is found for signal, and we exclude at 95% confidence most regions of the (M higgs, tan beta) parameter space where the decay t->H b has a branching fraction greater than 0.36 and B(H -> tau nu) is large.Comment: 11 pages, 4 figures, submitted to Phys. Rev. Let

Limits on Anomalous WWgamma and WWZ Couplings

Limits on the anomalous WWgamma and WWZ couplings are presented from a simultaneous fit to the data samples of three gauge boson pair final states in pbar-p collisions at sqrt(s)=1.8 TeV: Wgamma production with the W boson decaying to enu or munu, W boson pair production with both of the W bosons decaying to enu or munu, and WW or WZ production with one W boson decaying to enu and the other W boson or the Z boson decaying to two jets. Assuming identical WWgamma and WWZ couplings, 95 % C.L. limits on the anomalous couplings of -0.30<Delta kappa<0.43 (lambda = 0) and -0.20<lambda<0.20 (Delta kappa = 0) are obtained using a form factor scale Lambda = 2.0 TeV. Limits found under other assumptions on the relationship between the WWgamma and WWZ couplings are also presented.Comment: 13 pages, 3 figures, submitted to Physical Review

Morphology of supported polymer electrolyte ultra-thin films: a numerical study

Morphology of polymer electrolytes membranes (PEM), e.g., Nafion, inside PEM fuel cell catalyst layers has significant impact on the electrochemical activity and transport phenomena that determine cell performance. In those regions, Nafion can be found as an ultra-thin film, coating the catalyst and the catalyst support surfaces. The impact of the hydrophilic/hydrophobic character of these surfaces on the structural formation of the films has not been sufficiently explored yet. Here, we report about Molecular Dynamics simulation investigation of the substrate effects on the ionomer ultra-thin film morphology at different hydration levels. We use a mean-field-like model we introduced in previous publications for the interaction of the hydrated Nafion ionomer with a substrate, characterized by a tunable degree of hydrophilicity. We show that the affinity of the substrate with water plays a crucial role in the molecular rearrangement of the ionomer film, resulting in completely different morphologies. Detailed structural description in different regions of the film shows evidences of strongly heterogeneous behavior. A qualitative discussion of the implications of our observations on the PEMFC catalyst layer performance is finally proposed