Quaternary stratigraphy of the Lake Sakakawea area, Mclean County, North Dakota

The Quaternary stratigraphy of central North Dakota is best exposed along the nearly continuous, 20-meter-high, vertical bluffs of Lake Sakakawea in the Missouri River trench. The following lithostratigraphic units (in ascending order) are exposed just north of Riverdale, North Dakota, and can be correlated for tens of kilometers along the bluffs: (1) Sentinel Butte Formation (lignite-bearing sediment of Paleocene age), (2) lower Medicine Hill Formation (fluvial sand and gravel), (3) upper Medicine Hill Formation (massive pebble loam with silt and gravel inclusions\u3e glacial sediment), (4) lower Horseshoe Valley Formation (fluvial sand and gravel), (5) upper Horseshoe Valley Formation (jointed pebble-loam, glacial sediment), (6) lower Snow School Formation (fluvial sand and gravel), (7) mid dle Snow School Formation (reddish sandy pebble-loam, glacial sediment), (8) upper Snow School Formation (jointed pebble-loam, glacial sediment, (9) Oahe Formation with four numbers recognize able throughout the area (silt, eolian sediment). The sand bodies are the main aquifers in the Lake Sakakawea groundwater discharge area

Observation of Spin Flips with a Single Trapped Proton

Radio-frequency induced spin transitions of one individual proton are observed for the first time. The spin quantum jumps are detected via the continuous Stern-Gerlach effect, which is used in an experiment with a single proton stored in a cryogenic Penning trap. This is an important milestone towards a direct high-precision measurement of the magnetic moment of the proton and a new test of the matter-antimatter symmetry in the baryon sector

Caryophyllaeid Cestodes from Two Species of Redhorse (Moxostoma)

Two caryophyllaeid tapeworms, lsoglaridacris longus sp. n., and I. folius sp. n., are described from two species of redhorse, namely, Moxostoma macolepidotum and M. erythrurum, respectively. Members of the genus lsoglaridacris appear to be host specific, since the two species mentioned in this study occur in different fish hosts collected from the same rivers. Both I. longus and I. folius appear to exhibit seasonal periodicity, the smallest populations occurring in late summer. Their presence or absence in fish during the winter months, however, is unknown. Infected fish usually harbor a small number of cestodes, generally only a single worm. The annual per cent of infection is 38% for the northern redhorse and 37% for the golden redhorse. Eggs are operculate and oncospheres show well-defined hooks after 17 days. A key to the three known species of the genus lsoglaridacris is presented

The Stream-Stream Collision after the Tidal Disruption of a Star Around a Massive Black Hole

A star can be tidally disrupted around a massive black hole. It has been known that the debris forms a precessing stream, which may collide with itself. The stream collision is a key process determining the subsequent evolution of the stellar debris: if the orbital energy is efficiently dissipated, the debris will eventually form a circular disk (or torus). In this paper, we have numerically studied such stream collision resulting from the encounter between a 10^6 Msun black hole and a 1 Msun normal star with a pericenter radius of 100 Rsun. A simple treatment for radiative cooling has been adopted for both optically thick and thin regions. We have found that approximately 10 to 15% of the initial kinetic energy of the streams is converted into thermal energy during the collision. The angular momentum of the incoming stream is increased by a factor of 2 to 3, and such increase, together with the decrease in kinetic energy, significantly helps the circularization process. Initial luminosity burst due to the collision may reach as high as 10^41 erg/sec in 10^4 sec, after which the luminosity increases again (but slowly this time) to a steady value of a few 10^40 erg/sec in a few times of 10^5 sec. The radiation from the system is expected to be close to Planckian with effective temperature of \~10^5K.Comment: 19 pages including 12 figures; Accepted for publication in Ap

Direct high-precision measurement of the magnetic moment of the proton

The spin-magnetic moment of the proton $\mu_p$ is a fundamental property of this particle. So far $\mu_p$ has only been measured indirectly, analysing the spectrum of an atomic hydrogen maser in a magnetic field. Here, we report the direct high-precision measurement of the magnetic moment of a single proton using the double Penning-trap technique. We drive proton-spin quantum jumps by a magnetic radio-frequency field in a Penning trap with a homogeneous magnetic field. The induced spin-transitions are detected in a second trap with a strong superimposed magnetic inhomogeneity. This enables the measurement of the spin-flip probability as a function of the drive frequency. In each measurement the proton's cyclotron frequency is used to determine the magnetic field of the trap. From the normalized resonance curve, we extract the particle's magnetic moment in units of the nuclear magneton $\mu_p=2.792847350(9)\mu_N$. This measurement outperforms previous Penning trap measurements in terms of precision by a factor of about 760. It improves the precision of the forty year old indirect measurement, in which significant theoretical bound state corrections were required to obtain $\mu_p$, by a factor of 3. By application of this method to the antiproton magnetic moment $\mu_{\bar{p}}$ the fractional precision of the recently reported value can be improved by a factor of at least 1000. Combined with the present result, this will provide a stringent test of matter/antimatter symmetry with baryons.Comment: published in Natur

Theoretical methods for the calculation of Bragg curves and 3D distributions of proton beams

The well-known Bragg-Kleeman rule RCSDA = A dot E0p has become a pioneer work in radiation physics of charged particles and is still a useful tool to estimate the range RCSDA of approximately monoenergetic protons with initial energy E0 in a homogeneous medium. The rule is based on the continuous-slowing-down-approximation (CSDA). It results from a generalized (nonrelativistic) Langevin equation and a modification of the phenomenological friction term. The complete integration of this equation provides information about the residual energy E(z) and dE(z)/dz at each position z (0 <= z <= RCSDA). A relativistic extension of the generalized Langevin equation yields the formula RCSDA = A dot (E0 +E02/2M dot c2)p. The initial energy of therapeutic protons satisfies E0 << 2M dot c2 (M dot c2 = 938.276 MeV), which enables us to consider the relativistic contributions as correction terms. Besides this phenomenological starting-point, a complete integration of the Bethe-Bloch equation (BBE) is developed, which also provides the determination of RCSDA, E(z) and dE(z)/dz and uses only those parameters given by the BBE itself (i.e., without further empirical parameters like modification of friction). The results obtained in the context of the aforementioned methods are compared with Monte-Carlo calculations (GEANT4); this Monte-Carlo code is also used with regard to further topics such as lateral scatter, nuclear interactions, and buildup effects. In the framework of the CSDA, the energy transfer from protons to environmental atomic electrons does not account for local fluctuations.Comment: 97 pages review pape

Resolution of Single Spin-Flips of a Single Proton

The spin magnetic moment of a single proton in a cryogenic Penning trap was coupled to the particle's axial motion with a superimposed magnetic bottle. Jumps in the oscillation frequency indicate spin-flips and were identified using a Bayesian analysis.Comment: accepted for publication by Phys. Rev. Lett., submitted 6.June.201