Karakteristik Sifat Fisik Daur Ulang Lapis Perkerasan Aspal (Pemeliharaan Rutin Jalan Paguyaman – Jalan Tabulo Kabupaten Boalemo)

  Berangkat dari Permasalahan Energi dewasa ini telah menuntut kita untuk berupaya memikirkan Alternatif penyelesaian Masalah Energi yang kedepan nanti membutuhkan Penguasaan dan Pemahaman informasi tentang Rekayasa, salah satu cara Alternatif itu  khusunya dibidang Rekayasa Jalan Raya adalah teknologi Daur Ulang (Recycling). Tulisan ini merupakan rangkaian penelitian yang memaparkan tingkat kelayakan Daur Ulang yang dihubungkan dengan acuan spesifikasi yang berlaku, dengan meneliti sejauh mana tingkat Stabiltas Aspal Daur Ulang dengan mengamati Perubahan sifat fisik Aspal Daur Ulang yang dikomposisikan dengan bahan penambah lainnya. Skenario dari penelitian ini adalah dengan mengekstraksi Aspal Bongkaran Lama kemudian menguji dan menganalisa dihubungkan terhadap persyaratan yang berlaku (Spesifikasi Umum Divisi 6 Perkerasan Aspal, 2010), kemudian kita tentukan kadar aspal Optimumnya dengan memvariasikan kadar aspal 4,0% , 4,5% , 5,0% , 5,5% ,  6,0% , 6,5% kemudian kita analisis dengan standar Uji Marshal dilaboratorium beserta nilai Nilai Rongganya dan uji Rendaman Marshall. Dari hasil uji Laboratorium bahwa Kadar Aspal Bongkaran yang memenuhi persyaratan untuk kadar Aspal 6,5% dan semakin menurun stabilitasnya jika kadar aspalnya bertambah walaupun nilai rongganya memenuhi.   Kata Kunci : Aspal Daur Ulang, Marshall Tes

Langevin dynamics with a tilted periodic potential

We study a Langevin equation for a particle moving in a periodic potential in the presence of viscosity $\gamma$ and subject to a further external field $\alpha$. For a suitable choice of the parameters $\alpha$ and $\gamma$ the related deterministic dynamics yields heteroclinic orbits. In such a regime, in absence of stochastic noise both confined and unbounded orbits coexist. We prove that, with the inclusion of an arbitrarly small noise only the confined orbits survive in a sub-exponential time scale.Comment: 38 pages, 6 figure

Residues of Organochlorinated Pesticides in Soil from Tomato Fields, Ngarenanyuki, Tanzania

This work presents the concentrations of five pesticide residues, lindane, chlorpyrifos, endosulfan, p, p'-DDE and p, p'-DDD in soil samples collected from tomato fields in Ngarenanyuki, Tanzania. Endosulfan sulphate was detected in 100 % of the sample analysed with mean concentration of 0.2407 mg/kg dw. Chlorpyrifos was detected in 87 % of the samples with mean concentration of 0.1253 mg/kg dw. p, p'-DDE and p, p'-DDD were detected in 46 and 40 % of the samples analysed with mean concentrations of 0.1482 and 0.154 mg/kg dw, respectively. Lindane was the least detected pesticide. It was detected in 5 (33 %) of soil samples analysed with mean concentration of 0.2126 mg/kg dw. Low concentrations detected indicate the past usage of the pesticides

Bismuth radical catalysis in the activation and coupling of redox-active electrophiles

Radical cross-coupling reactions represent a revolutionary tool to forge C(sp3)–C and C(sp3)–heteroatom bonds, by means of transition metals, photoredox or electrochemical approaches. This study demonstrates how a low-valent bismuth complex is able to undergo one-electron oxidative addition with redox-active alkyl radical precursors in an autonomous manner, mimicking the behavior of first-row transition metals. This reactivity paradigm for bismuth gives rise to unique radical-equilibrium complexes, which could be fully characterized in solution and solid state. The resulting Bi(III)–C(sp3) intermediates display divergent reactivity patterns depending on the α-substituents of the alkyl fragment. Mechanistic investigations on this reactivity led to the development of a bismuth-catalyzed C(sp3)–N cross-coupling reaction that operates under mild conditions and accommodates synthetically relevant N-heterocycles as coupling partners

First-principles study of the ferroelastic phase transition in CaCl_2

First-principles density-functional calculations within the local-density approximation and the pseudopotential approach are used to study and characterize the ferroelastic phase transition in calcium chloride (CaCl_2). In accord with experiment, the energy map of CaCl_2 has the typical features of a pseudoproper ferroelastic with an optical instability as ultimate origin of the phase transition. This unstable optic mode is close to a pure rigid unit mode of the framework of chlorine atoms and has a negative Gruneisen parameter. The ab-initio ground state agrees fairly well with the experimental low temperature structure extrapolated at 0K. The calculated energy map around the ground state is interpreted as an extrapolated Landau free-energy and is successfully used to explain some of the observed thermal properties. Higher-order anharmonic couplings between the strain and the unstable optic mode, proposed in previous literature as important terms to explain the soft-phonon temperature behavior, are shown to be irrelevant for this purpose. The LAPW method is shown to reproduce the plane-wave results in CaCl_2 within the precision of the calculations, and is used to analyze the relative stability of different phases in CaCl_2 and the chemically similar compound SrCl_2.Comment: 9 pages, 6 figures, uses RevTeX

New Symmetries in Crystals and Handed Structures

For over a century, the structure of materials has been described by a combination of rotations, rotation-inversions and translational symmetries. By recognizing the reversal of static structural rotations between clockwise and counterclockwise directions as a distinct symmetry operation, here we show that there are many more structural symmetries than are currently recognized in right- or left-handed handed helices, spirals, and in antidistorted structures composed equally of rotations of both handedness. For example, though a helix or spiral cannot possess conventional mirror or inversion symmetries, they can possess them in combination with the rotation reversal symmetry. Similarly, we show that many antidistorted perovskites possess twice the number of symmetry elements as conventionally identified. These new symmetries predict new forms for "roto" properties that relate to static rotations, such as rotoelectricity, piezorotation, and rotomagnetism. They also enable symmetry-based search for new phenomena, such as multiferroicity involving a coupling of spins, electric polarization and static rotations. This work is relevant to structure-property relationships in all material structures with static rotations such as minerals, polymers, proteins, and engineered structures.Comment: 15 Pages, 4 figures, 3 Tables; Fig. 2b has error