3,084 research outputs found
Outpost: Life on the Frontlines of American Diplomacy,by Christopher Hill
An American diplomat for over three decades, Christopher Hill’s service took him all over the globe and into some of the most challenging cir- cumstances faced by a member of the Foreign Service. This account of his unique postings during that dy- namic time frame is a vivid reminder of how much the world has changed
Transverse instability and its long-term development for solitary waves of the (2+1)-Boussinesq equation
The stability properties of line solitary wave solutions of the
(2+1)-dimensional Boussinesq equation with respect to transverse perturbations
and their consequences are considered. A geometric condition arising from a
multi-symplectic formulation of this equation gives an explicit relation
between the parameters for transverse instability when the transverse
wavenumber is small. The Evans function is then computed explicitly, giving the
eigenvalues for transverse instability for all transverse wavenumbers. To
determine the nonlinear and long time implications of transverse instability,
numerical simulations are performed using pseudospectral discretization. The
numerics confirm the analytic results, and in all cases studied, transverse
instability leads to collapse.Comment: 16 pages, 8 figures; submitted to Phys. Rev.
Relationship between X-ray and ultraviolet emission in 3C 273
In 3C 273, ultraviolet flux and X-ray flux measured by BATSE are not well
correlated, contrarily to predictions of several models, unless the X-ray flux
lags the UV emission by 1.75 yr. The absence of observed correlation at small
lag cannot be due to spectral variability. A Comptonizing corona model is
however compatible with all UV and X-ray observations covering the BATSE
period.Comment: LaTeX, 4 pages, 6 figures. espcrc2.sty style file included. Poster
contribution to the symposium "The Active X-ray Sky: Results from BepppoSAX
and Rossi-XTE", Rome, October 199
How to deal with reality when we're not built to
Philip K. Dick’s writing can be infuriatingly confusing. It feeds readers many ambiguoussignals that convey no real sense of closure—and The Man in the High Castle is no exception. Perhaps bewildering the audience is the intent, not a side-effect. We crave closure for many of the questions we find in Dick’s books, and he consistently denies us any real sense of arriving at definite answers. Lingering confusion and the gnawing feeling that the true nature of reality is just out of our grasp have been the dominant themes of both Dick’s narratives and philosophical and psychological studies for decades. Together, they all attest to how important understanding and embracing confusion can be in the business of dealing with reality
Postharvest Handling of Fresh Vegetables: Proceedings of a workshop held in Beijing, People’s Republic of China, 9–11 May 2001
This proceedings covers papers presented at end of project workshop in Beijing in 2001. The workshop introduced new research challenges that have been proposed in the fields of postharvest handling of melons and in improvements to microbial safety of fresh vegetables. (ISSN 1447-0837
Cremmer-Gervais r-matrices and the Cherednik Algebras of type GL2
We give an intepretation of the Cremmer-Gervais r-matrices for sl(n) in terms
of actions of elements in the rational and trigonometric Cherednik algebras of
type GL2 on certain subspaces of their polynomial representations. This is used
to compute the nilpotency index of the Jordanian r-matrices, thus answering a
question of Gerstenhaber and Giaquinto. We also give an interpretation of the
Cremmer-Gervais quantization in terms of the corresponding double affine Hecke
algebra.Comment: 6 page
The quantitative soil pit method for measuring belowground carbon and nitrogen stocks
Many important questions in ecosystem science require estimates of stocks of soil C and nutrients. Quantitative soil pits provide direct measurements of total soil mass and elemental content in depth-based samples representative of large volumes, bypassing potential errors associated with independently measuring soil bulk density, rock volume, and elemental concentrations. The method also allows relatively unbiased sampling of other belowground C and nutrient stocks, including roots, coarse organic fragments, and rocks. We present a comprehensive methodology for sampling these pools with quantitative pits and assess their accuracy, precision, effort, and sampling intensity as compared to other methods. At 14 forested sites in New Hampshire, nonsoil belowground pools (which other methods may omit, double-count, or undercount) accounted for upward of 25% of total belowground C and N stocks: coarse material accounted for 4 and 1% of C and N in the O horizon; roots were 11 and 4% of C and N in the O horizon and 10 and 3% of C and N in the B horizon; and soil adhering to rocks represented 5% of total B-horizon C and N. The top 50 cm of the C horizon contained the equivalent of 17% of B-horizon carbon and N. Sampling procedures should be carefully designed to avoid treating these important pools inconsistently. Quantitative soil pits have fewer sources of systematic error than coring methods; the main disadvantage is that because they are time-consuming and create a larger zone of disturbance, fewer observations can be made than with cores
Impact of seeding rate on weed-free field peas
Non-Peer ReviewedThe impact of seed placement and seeding rate on crop yield is not clearly understood for field pea (Pisum sativum L.). A field experiment was conducted at seven sites across Saskatchewan in 2001 to examine the influence of a wide range of seeding rates (20, 30, 40, 50, 60, 70, 80, 90, 100, and 120 target plants m-2). Yield component compensation occurred where increased plant density from higher seeding rates reduced seed weight. Seed yield benefits were small at seeding rates greater than 50 target plants m-2. There was a tendency for lower yields with seeding rates less than 50, especially at sites with higher yield potential. Yields of field peas grown under relatively weed-free conditions should be optimized with a seeding rate of 50 to 75 seeds m-2
Earthworms and furrow irrigation infiltration
Infiltration rates into furrows in southcentral Idaho,
after decreasing toward a base rate, sometimes
increase. The increase is sometimes sufficient to cause
tailwater runoff to cease and the furrow stream to recede
up the furrow, resulting in poor water distribution. The
infiltration increase is caused by earthworms piercing the
furrow wetted perimeter during the irrigation allowing
water to enter and infiltrate from their extensive burrow
system. Low concentrations of aqua ammonia in the
irrigation water prevent the infiltration increase,
apparently by repelling the worms from the furrows
Multiwavelength analysis of four millisecond pulsars
Radio timing observations of millisecond pulsars (MSPs) in support of Fermi
LAT observations of the gamma-ray sky enhance the sensitivity of high-energy
pulsation searches. With contemporaneous ephemerides we have detected gamma-ray
pulsations from PSR B1937+21, the first MSP ever discovered, and B1957+20, the
first known black-widow system. The two MSPs share a number of properties: they
are energetic and distant compared to other gamma-ray MSPs, and both of them
exhibit aligned radio and gamma-ray emission peaks, indicating co-located
emission regions in the outer magnetosphere of the pulsars. However, radio
observations are also crucial for revealing MSPs in Fermi unassociated sources.
In a search for radio pulsations at the position of such unassociated sources,
the Nan\c{c}ay Radio Telescope discovered two MSPs, PSRs J2017+0603 and
J2302+4442, increasing the sample of known Galactic disk MSPs. Subsequent radio
timing observations led to the detection of gamma-ray pulsations from these two
MSPs as well. We describe multiwavelength timing and spectral analysis of these
four pulsars, and the modeling of their gamma-ray light curves in the context
of theoretical models.Comment: 4 pages, 3 figures, to appear in the proceedings of the Pulsar 2010
Conference, Italy, 10 - 15 October 201
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