Klein-Gordon lower bound to the semirelativistic ground-state energy

For the class of attractive potentials V(r) <= 0 which vanish at infinity, we prove that the ground-state energy E of the semirelativistic Hamiltonian H = \sqrt{m^2 + p^2} + V(r) is bounded below by the ground-state energy e of the corresponding Klein--Gordon problem (p^2 + m^2)\phi = (V(r) -e)^2\phi. Detailed results are presented for the exponential and Woods--Saxon potentials.Comment: 7 pages, 4 figure

The Mass Dependence of Stellar Rotation in the Orion Nebula Cluster

We have determined new rotation periods for 404 stars in the Orion Nebula Cluster using the Wide Field Imager attached to the MPG/ESO 2.2 m telescope on La Silla, Chile. Mass estimates are available for 335 of these and most have M < 0.3 M_sun. We confirm the existence of a bimodal period distribution for the higher mass stars in our sample and show that the median rotation rate decreases with increasing mass for stars in the range 0.1 < M <0.4 M_sun. While the spread in angular momentum (J) at any given mass is more than a factor of 10, the majority of lower mass stars in the ONC rotate at rates approaching 30% of their critical break-up velocity, as opposed to 5-10% for solar-like stars. This is a consequence of both a small increase in observed specific angular momentum (j=J/M) and a larger decrease in the critical value of j with decreasing mass. Perhaps the most striking fact, however, is that j varies by so little - less than a factor of two - over the interval 0.1-1.0 M_sun. The distribution of rotation rates with mass in the ONC (age ~ 1 My) is similar in nature to what is found in the Pleiades (age ~ 100 My). These observations provide a significant new guide and test for models of stellar angular momentum evolution during the proto-stellar and pre-main sequence phases.Comment: 11 pages, 3 figure

The existence of a stable noncollinear phase in a Heisenberg model with a complex structure

We have analyzed the properties of a noncollinear magnetic phase obtained in the mean-field analysis of the model of two coupled Heisenberg subsystems. The domain of its existence and stability is narrow and depends on the ratio between the averaged over nearest neighbours microscopic exchange parameters.Comment: 7 pages, miktex, 3 figure

Considerations in the Dairy Relocation Decision

Historically, U.S. dairymen have been thought to move to a new location to seek better economic opportunities or to leave an area that has become disadvantaged due to regulation or economics. Recently, there again have been major shifts in dairy production across the United States.Livestock Production/Industries,

Evidence for Differential Rotation on a T Tauri Star

Five years of photometric monitoring of the T Tauri star HBC 338 in NGC 1333 has revealed that it is a periodic variable, but the period has changed significantly with time. From 2000-2003, a period near 5.6 days was observed, while in the last two seasons, the dominant period is near 4.6 days. No other T Tauri star has been seen to change its period by such a large percentage. We propose a model in which a differentially rotating star is seen nearly equator-on and a high latitude spot has gradually been replaced by a low latitude spot. We show that this model provides an excellent fit to the observed shapes of the light curves at each epoch. The amplitude and sense of the inferred differential rotation is similar to what is seen on the Sun. This may be surprising given the likely high degree of magnetic surface activity on the star relative to the Sun but we note that HBC 338 is clearly an exceptional T Tauri star.Comment: Acepted for publication in PAS

Natural Coronagraphic Observations of the Eclipsing T Tauri System KH 15D: Evidence for Accretion and Bipolar Outflow in a WTTS

We present high resolution (R $\sim$ 44,000) UVES spectra of the eclipsing pre-main sequence star KH 15D covering the wavelength range 4780 to 6810 {\AA} obtained at three phases: out of eclipse, near minimum light and during egress. The system evidently acts like a natural coronagraph, enhancing the contrast relative to the continuum of hydrogen and forbidden emission lines during eclipse. At maximum light the H$\alpha$ equivalent width was $\sim$2 {\AA} and the profile showed broad wings and a deep central absorption. During egress the equivalent width was much higher ($\sim$70 {\AA}) and the broad wings, which extend to $\pm$ 300 km/s, were prominent. During eclipse totality the equivalent width was less than during egress ($\sim$40 {\AA}) and the high velocity wings were much weaker. H$\beta$ showed a somewhat different behavior, revealing only the blue-shifted portion of the high velocity component during eclipse and egress. [OI] $\lambda\lambda$6300, 6363 lines are easily seen both out of eclipse and when the photosphere is obscured and exhibit little or no flux variation with eclipse phase. Our interpretation is that KH 15D, although clearly a weak-line T Tauri star by the usual criteria, is still accreting matter from a circumstellar disk, and has a well-collimated bipolar jet. As the knife-edge of the occulting matter passes across the close stellar environment it is evidently revealing structure in the magnetosphere of this pre-main sequence star with unprecedented spatial resolution. We also show that there is only a small, perhaps marginally significant, change in the velocity of the K7 star between the maximum light and egress phases probed here

Regional and Structural Impacts of Alternative Dairy Policy Options

Milk and dairy product prices have fallen to their lowest levels in 3 years following the record highs of 2004 and 2005. The large government stockpiles of non-fat dry milk are gone, but threaten to build again as non-fat dry milk and cheese prices decline nearer the support price level. A new farm bill is scheduled to be written in 2007. The Milk Income Loss Contract (MILC) program included in the last farm bill was only authorized through September 2005. Subsequent legislation reinstated the MILC program through August 2007. WTO negotiations are on-going and could influence U.S. farm programs 1/. Dairy’s role in the U.S. amber box limit of $19.1 billion may necessitate some possible trade-offs with other commodities. Dairy counts about$4.2 billion toward the annual amber box limit, but actual spending only averages about $1 billion (Outlaw, et al). The pressure of low prices, WTO negotiations, MILC continuation, and a new farm bill has created the potential for a number of options and alternatives for dairy policy. This paper examines the regional and structural impacts of 3 dairy policy options: MILC continuation, a target price/deficiency payment program, and an increase in the support price. All three options are designed to spend$400 million in amber box payments per year. The analysis uses representative dairy farms in major milk producing regions of the country developed by the AFPC for policy analysis.Agribusiness, Agricultural and Food Policy, Livestock Production/Industries,

The Effectiveness of Dairy Risk Management at Managing Income, Revenue, and Margin Risk

With the 2009 milk prices still fresh on everyone’s mind, there has been increased interest in ways to limit milk price volatility. Using SERF, this paper determined some dairies are willing to pay for limited milk price volatility and found a value they are willing to pay using risk premiums.Dairy, Stochastic Simulation, price volatility, Agricultural and Food Policy, Farm Management,

The Effects of Sex-Sorted Semen on Southern Dairy Farms

This paper examines the impact of sex-sorted semen adoption on dairy farm level economics. Representative dairies are used to simulate the financial impacts of moving to this new technology. Key economic, financial and herd dynamics will be compared among dairies to show how the uses of sex-sorted semen will affect dairy farms. All seven of the representative dairies that were analyzed sold surplus replacement heifers using sex-sorted semen. The increase use of sex-sorted semen can have very positive impacts on dairies throughout the Southern United States.Dairy production, sex sorted semen, production economics, scenario analysis, Agribusiness, Farm Management, Livestock Production/Industries, Production Economics,