Constraints on the mass of a habitable planet with water of nebular origin

From an astrobiological point of view, special attention has been paid to the probability of habitable planets in extrasolar systems. The purpose of this study is to constrain a possible range of the mass of a terrestrial planet that can get water. We focus on the process of water production through oxidation of the atmospheric hydrogen--the nebular gas having been attracted gravitationally--by oxide available at the planetary surface. For the water production to work well on a planet, a sufficient amount of hydrogen and enough high temperature to melt the planetary surface are needed. We have simulated the structure of the atmosphere that connects with the protoplanetary nebula for wide ranges of heat flux, opacity, and density of the nebular gas. We have found both requirements are fulfilled for an Earth-mass planet for wide ranges of the parameters. We have also found the surface temperature of planets of <= 0.3 Earth masses is lower than the melting temperature of silicate (~ 1500K). On the other hand, a planet of more than several Earth masses becomes a gas giant planet through runaway accretion of the nebular gas.Comment: 25 pages, 8 figures, to appear in the 01 September 2006 issue of Ap

Magnetic field induced enhancement of spin-order peak intensity in La(1.875)Ba(0.125)CuO(4)

We report on neutron-scattering results on the impact of a magnetic field on stripe order in the cuprate La$_{1.875}$Ba$_{0.125}$CuO$_4$. It is found that a 7 T magnetic field applied along the {\it c} axis causes a small but finite enhancement of the spin-order peak intensity and has no observable effect on the peak width. Inelastic neutron-scattering measurements indicate that the low-energy magnetic excitations are not affected by the field, within experimental error. In particular, the small energy gap that was recently reported is still present at low temperature in the applied field. In addition, we find that the spin-correlation length along the antiferromagnetic stripes is greater than that perpendicular to them.Comment: 4 pages, 5 figure

Studi Arus Dan Sebaran Sedimen Dasar Di Perairan Teluk Ujungbatu Kabupaten Jepara

Perairan Teluk Ujungbatu Kabupaten Jepara merupakan pantai yang rentan terhadap proses erosi dan sedimentasi yang disebabkan karena faktor fisik ataupun sifat dari material sedimen. Untuk mengetahui kecepatan dan arah arus yang selalu berlawanan arah setiap tahun sehingga dapat mempengaruhi sebaran sedimen dasar di sekitar pantai, diperlukan beberapa analisa mengenai kondisi arus dan pola sebaran sedimen dasar di perairan Teluk Unjung Batu. Tujuan dari penelitian ini adalah untuk mengetahui kecepatan dan arah arus serta sebaran sedimen dasar di perairan Teluk Ujungbatu Kabupaten Jepara. Penelitian ini dilakukan 2 tahap, pengumpulan data lapangan dan pengolahan data. Pengumpulan data lapangan yang meliputi pengukuran dan pengambilan data arus, pasang surut, dan sedimen dasar pada tanggal 17 Februari – 5 Maret 2014, serta proses pengolahan data yang dilaksanakan di LaboratoriumOseanografi Tropis Jurusan Ilmu Kelautan tanggal 8 – 11 Maret 2014. Teknik pengambilan sampel sedimen menggunakan metode sampling purposive method (Grab sampler), untuk pengambilan data arus dan pasang surut menggunakan metode Euler ADCP (Accoustic Doppler Profiler) dan Palem pasut. Berdasarkan analisis data, diperoleh bahwa kecepatan arus rata-rata berkisar antara 1,77cm/s - 4,55 cm/s dengan arah dominan menuju Barat dan Barat Laut. Kecepatan rata-rata pada kolom air permukaan adalah 5,8 cm/s, kolom air tengah 4,26 cm/s, dan kolom air dasar 3.51 cm/s. Pola pergerakan arus dominan dipengaruhi oleh arus pasang surut. Sebaran sedimen dasar di perairan Teluk Ujungbatu dipengaruhi oleh masukan sedimen dari Sungai Wiso dan Sungai Mati, sehingga ukuran partikel sedimen dasar di perairan Teluk tersebut didominasi oleh pasir

Looking up and down: Strong collaboration is only the first step in tackling parachute science

Abstract Critiques of parachute science argue for closer collaborations among local and international scientists. Here, building on such a collaboration, we highlight further challenges when outsiders, typically working through international nongovernmental organizations, fail to respect both the governance framework within which they are working and the realities on the ground. Specifically, we emphasize the importance of observing governance structures, maintaining transparency, and responding flexibly to national and regional priorities (?looking up?), as well as stressing the need to keep a close focus on local cultural context when designing interventions such as educational programs (?looking down?). Addressing the shortcomings for conservation practice contingent on parachute science interventions requires nimble, creative, and respectful actions, which at least in the context of Tanzania, we all still struggle to put into action

Assessment of 1991 NEHRP Provisions for Nonstructural Components and Recommended Revisions

As one part of the 1994 update effort of the 1991 NEHRP provisions, the seismic design force formulas for nonstructural components as they exist in the 1991 provisions are critically assessed and some of their shortcomings are identified. Various levels of improvements to these formulas are then presented which, on the one hand, preserve the equivalent lateral force format for design applicability and, on the other, correct some of the deficiencies on the basis of analyses, experimental results and observation data from past earthquakes. Based on different interpretations of the component seismic coefficients as well as different degrees of simplicity required in practical design, three recommendations are proposed. The first recommended revision is the most comprehensive in that both effects of nonstructural component anchorage detailing and its supporting structural characteristics are taken into account. The second recommendation is a structure-driven type of modification of the current provisions and is motivated by the possibility that nonstructural component information during a design process is not available. The third revision, however, mainly concentrates on the effect of nonstructural component characteristics on the design force although it partially implies structural effects in the process of determining the response modification coefficient. The maximum and minimum design forces in the three recommendations are compared with those produced by the 1991 NEHRP provisions, the 1991 UBC, and the 1985 Tri-Service codes. Case studies of a parapet, a storage rack and a general equipment attached to a reinforced concrete shear wall structure are provided to show the relative conservatism involved in different codes and the importance of the factors ignored in the current provisions. Simple displacement equations are also developed in this report to provide deformation information needed in some cases of practical design