Geochemistry of volcanic rocks from the Wawa greenstone belt

The Wawa greenstone belt is located in the District of Algoma and extends east-northeast from Lake Superior to the western part of the Sudbury District in Ontario, Canada. Recent mapping by Attoh has shown that an unconformity at the base of the Dore' Formation and equivalent sedimentary rocks marks a significant stratigraphic break which can be traced throughout the volcanic belt. This break has been used to subdivide the volcanic-sedimentary into pre- and post-Dore' sequences. The pre-Dore' sequence includes at least two cycles of mafic-to-felsic volcanism, each capped by an iron-formation unit. The post-Dore' sequence includes an older mafic-to-felsic unit, which directly overlies sedimentary rocks correlated with the Dore' Formation, and a younger felsic breccia unit interpreted to have formed as debris flows from a felsic volcanic center. In the present study, samples of both the pre-and post-Dore' volcanic sequences were analyzed for major and trace elements, incuding rare earths (REE). This preliminary study is part of an ongoing program to assess the petrogenesis of the volcanic rocks of the Wawa greenstone belt

Rhyolitic components of the Michipicoten greenstone belt, Ontario: Evidence for late Archaen intracontinental rifts or convergent plate margins in the Canadian Shield?

Rhyolitic rocks often are the dominant felsic end member of the biomodal volcanic suites that characterize many late Archean greenstone belts of the Canadian Shield. The rhyolites primarily are pyroclastic flows (ash flow tuffs) emplaced following plinian eruptions, although deposits formed by laval flows and phreatomagmatic eruptions also are presented. Based both on measured tectono-stratigraphic sections and provenance studies of greenstone belt sedimentary sequences, the rhyolites are believed to have been equal in abundance to associated basaltic rocks. In many recent discussions of the tectonic setting of late Archean Canadian greenstone belts, rhyolites have been interpreted as products of intracontinental rifting . A study of the tectono-stratigraphic relationships, rock associations and chemical characteristics of the particularly ell-exposed late Archean rhyolites of the Michipicoten greenstone belt, suggests that convergent plate margin models are more appropriate

Halting Planet Migration in the Evacuated Centers of Protoplanetary Disks

Precise Doppler searches for extrasolar planets find a surfeit of planets with orbital periods of 3-4 days, and no planets with orbital periods less than 3 days. The circumstellar distance, R_0, where small grains in a protoplanetary disk reach sublimation temperature (~1500 K) corresponds to a period of ~6 days. Interior to R_0, turbulent accretion due to magneto-rotational instability may evacuate the disk center. We suggest that planets with orbital periods of 3-4 days are so common because migrating planets halt once this evacuated region contains the sites of their exterior 2:1 Lindblad resonances.Comment: 9 pages, 1 figure, to appear in ApJ letter

Ribosomal DNA representation in the Orbach-Sachs and Vollmer-Yanofsky N. crassa cosmid libraries

We have been employing the Orbach-Sachs (1991 Fungal Genetics Newsl. 38:97) and Vollmer-Yanofsky (Vollmer and Yanofsky 1986 Proc. Natl. Acad. Sci. USA 83:4869-4873) N. crassa cosmid libraries (obtained from the Fungal Genetics Stock Center) in subtractive hybridization experiments designed to identify genes induced under conditions of oxidative stress. Because cosmids containing the 17S and 26S ribosomal RNA genes produce false positives in these experiments, it was necessary for us to identify cosmids in the Orbach-Sachs containing these genes

Area Potentials and Deformation Quantization

Systems built out of N-body interactions, beyond 2-body interactions, are formulated on the plane, and investigated classically and quantum mechanically (in phase space). Their Wigner Functions--the density matrices in phase-space quantization--are given and analyzed.Comment: LaTeX, 7 page

Discovery of Reflection Nebulosity Around Five Vega-like Stars

Coronagraphic optical observations of six Vega-like stars reveal reflection nebulosities, five of which were previously unknown. The nebulosities illuminated by HD 4881, HD 23362, HD 23680, HD 26676, and HD 49662 resemble that of the Pleiades, indicating an interstellar origin for dust grains. The reflection nebulosity around HD 123160 has a double-arm morphology, but no disk-like feature is seen as close as 2.5 arcsec from the star in K-band adaptive optics data. We demonstrate that uniform density dust clouds surrounding HD 23362, HD 23680 and HD 123160 can account for the observed 12-100 micron spectral energy distributions. For HD 4881, HD 26676, and HD 49662 an additional emission source, such as from a circumstellar disk or non-equilibrium grain heating, is required to fit the 12-25 micron data. These results indicate that in some cases, particularly for Vega-like stars located beyond the Local Bubble (>100 pc), the dust responsible for excess thermal emission may originate from the interstellar medium rather than from a planetary debris system.Comment: The Astrophysical Journal, in press for March, 2002 (32 pages, 13 figures

Course transfer - a tripod capacity building approach

This paper presents Capacity Building (CB), Technical Assistance (TA) and Partnership Building (PB) as key elements to successful knowledge transfer, in this case course transfer. Water Supply and Sanitation for Low Income Communities course was transferred from WEDC in UK to UMI in Uganda. On the basis of the case, a Tripod Model is advanced as key to successful implementation of course transfer. The paper recommends CB at the local level instrumental to sustainability of course transferred especially when external support ceases

Exact properties of Frobenius numbers and fraction of the symmetric semigroups in the weak limit for n=3

We generalize and prove a hypothesis by V. Arnold on the parity of Frobenius number. For the case of symmetric semigroups with three generators of Frobenius numbers we found an exact formula, which in a sense is the sum of two Sylvester's formulaes. We prove that the fraction of the symmetric semigroups is vanishing in the weak limit

Pandangan atau Tanggapan Akhir Peserta Mata Kuliah Pendidikan Pancasila terhadap Pendidikan Pancasila di UNPAR

Pancasila adalah philosophische grondslag, weltanschauung bangsa Indonesia. Nilai-nilai Pancasila sudah hidup jauh sebelum dirumuskan para pendiri. Maka tak berlebihan bila dikatakan bahwa Pancasila merupakan inti jiwa bangsa Indonesia. Pancasila bisa juga dikatakan sebagai kerangka pandang orang Indonesia melihat dirinya. Perjalanan sejarah bangsa seharusnya menjadikan Pancasila semakin terbuka untuk dibicarakan. Pancasila yang sudah dirumuskan itu harus terus ditafsirkan dalam konteks Indonesia yang berubah. Dengan demikian, ia menjadi semakin hidup dan kaya makna karena menjadi milik seluruh komponen bangsa.Kesan yang muncul di awal perkuliahan berhadapan dengan perkuliahan Pendidikan Pancasila adalah negatif. Mayoritas mahasiswa menganggap dan memandang mata kuliah Pendidikan Pancasila sekadar menjadi ideologi yang melayani kehendak penguasa. Model pendidikan yang indoktrinatif merupakan salah satu cara yang kerap digunakan untuk menanamkan nilai-nilai Pancasila sehingga cenderung represif. Karena itu, kecurigaan bahwa Pendidikan Pancasila merupakan sebuah upaya manipulasi dalam kerangka tafsir kelompok yang berkuasa. Sehingga menurut mayoritas mahasiswa Pancasila sebagai falsafah hidup bangsa ini tidak lagi memiliki daya atau kekuatan mempengaruhi sehingga mempelajarinya pun sekedar sebuah tuntutan teknis-akademis. Universitas Katolik Parahyangan (UNPAR) sebagai salah satu lembaga pendidikan yang masih setia pada sejarah Pendidikan Pancasila di Perguruan Tinggi merasa selalu terpanggil untuk mencoba merumuskan ulang Pancasila. UNPAR sebagai sebuah universitas yang mendasari diri pada spirit multi-kultur dan muliti-religi menjadikan Pancasila sebagai falsafah. Hal ini pula yang membuat Mata Kuliah Pendidikan Nilai Pancasila tetap dipertahankan di kampus ini. Penelitian ini mencoba menggali dan menganalisis sejauh mana mahasiswa UNPAR menyadari spirit ini.Salah satu komponen penting dinamika pembelajaran mata kuliah ini adalah mahasiswa. Maka penelitian ini mencoba menggali pendapat akhir peserta mata kuliah. Pandangan atau pendapat ini berhubungan dengan pengalaman mereka mengikuti perkuliahan Pendidikan Pancasila selama satu semester. Dalam penelitian ini ada tiga pendapat yang coba digali diantara mahasiswa peserta mata kuliah. Ketiga pendapat itu berkaitan dengan pertama, pendapat akhir tentang materi; kedua, pendapat akhir terhadap metode yang digunakan; ketiga, pendapat akhir terhadap dosen atau pengajar mata kuliah Pendidikan Pancasila.Pendapat akhir mahasiswa ini yang kemudian ditangkap dan dianalisis sehingga akhirnya pendapat akhir dari peserta didik ini memperkaya pengembangan mata kuliah ini. Sehingga sebagai falsafah bangsa Pancasila tetap hidup dalam hati, pikiran dan tindakan manusia Indonesia pada umumnya dan civitas academica UNPAR pada khususnya