Ballistic (precessional) contribution to the conventional magnetic switching

We consider a magnetic moment with an easy axis anisotropy energy, switched by an external field applied along this axis. Additional small, time-independent bias field is applied perpendicular to the axis. It is found that the magnet's switching time is a non-monotonic function of the rate at which the field is swept from "up" to "down". Switching time exhibits a minimum at a particular optimal sweep time. This unusual behavior is explained by the admixture of a ballistic (precessional) rotation of the moment caused by the perpendicular bias field in the presence of a variable switching field. We derive analytic expressions for the optimal switching time, and for the entire dependence of the switching time on the field sweep time. The existence of the optimal field sweep time has important implications for the optimization of magnetic memory devices

Comment on "Ferromagnetic film on a superconducting substrate"

A superconducting substrate is not able to shrink drastically domains in a ferromagnetic film, contrary to the prediction of Bulaevskii and Chudnovsky [Phys. Rev. B, 63, issue1 (2001)]. This is shown on the basis of the exact solution for the stripe domain structure.Comment: 8 pages, 1 figure, the version published in Phys. Rev.

Serravallian Shales in the Monte dei Corvi Pelagic Sequence (Ancona, Italy): An Organic Geochemical Perspective

In addition to the predominant marly lithologies, the Serravallian-Tortonian sequence at Monte dei Corvi (MDC), south of Ancona, Italy, contains at least 85 thin, dark calcareous shales. Such shales, averaging 14 cm in thickness, comprise 9% of the total Serravallian sequence. Sixteen of them were sampled for a preliminary organic geochemical evaluation. All the MDC shales appear to have been deposited during periodic anoxic events, as demonstrated by the presence of significant quantities of organic matter and authigenic pyrite. The degree of anoxicity (and thus the amount of organic matter preserved) appears to have differed from one event to the next. The quantity of organic matter preserved is highly variable, with Rock Eval S2 ranging from 0.4 to 27.6 mg/g. However, the type is remarkably consistent from sample to sample, as evidenced both by analytical pyrolysis-gas chromatography/mass spectrometry (GC/MS) of the solid organic matter and by the GC/MS analysis of the extractable material. This implies a regeneration of similar microfloral/microbial assemblages and depositional conditions during each anoxic event. The dominant organic matter types are marine, including several types of fossil algae and amorphous material (largely the product of bacterial reworking of organic matter). There is evidence of minor terrestrial input. The presence of isoprenoid hydrocarbons (prist-1-ene) in the pyrolyzates and 17β(H),21β(H) hopanes in the extractable organic matter attest to the low level of thermal alteration of the MDC shales. The MDC organic matter appears to be partially oxidized, probably from weathering at the outcrop, which partly obscures its original nature. To avoid this problem in any future organic geochemical study of the MDC sequence, the authors recommend that fresh, unweathered samples be obtained, preferably by coring

Geochemical Characterization of Maceral Concentrates from Herrin No. 6 Coal (Illinois Basin) and Lower Toarcian Shale Kerogen (Paris Basin)

Density gradient centrifugation (DGC) is a physical method for the separation of sedimentary organic matter into its constituents. Using DGC, it is possible to prepare maceral concentrates from a single sample, which are amenable to microanalysis. DGC fractions from a coal sample from the Illinois Basin (Herrin No. 6, Upper Carboniferous) and from the kerogen of a marine shale sample from the Paris Basin (Lower Toarcian) were analyzed by flash pyrolysis-gas chromatography-mass spectrometry, after extraction by CH2Cl2. Chemical differences between the coal DGC fractions are the easiest to recognize, indicating very distinctive biological precursors. For example, the liptinite fraction ( = 1.12 g ml-1) is dominated by long-chain aliphatic compounds (n-alkanes and n-alkenes) along with alkylbenzenes and alkylphenols. Vitrinite (1.29 g ml-1) shows a predominance of alkylbenzenes and phenolic compounds. Polyaromatic hydrocarbons (especially naphthalene, phenanthrene, anthracene and their pseudohomologues) are major compounds in the pyrolyzate of fusinite (1.45 g ml-1). In contrast, there is less variety of organic compounds in the Toarcian sample. Petrographically, this kerogen is primarily amorphous. However, a main DGC peak ( = 1.18 g ml-1) with two shoulders (1.15 and 1.23 g ml-1) is resolved using multi-step centrifugation. The chemical differences between these fractions are subtle but significant. Concentrations of alkylbenzenes, alkylthiophenes, alkylpyrroles and phenolic compounds increase with density, relative to the aliphatics. This indicates that this kerogen, probably of algal and bacterial origin, is partially separable by DGC

Organic Geochemistry and Petrology of Oil Source Rocks, Carpathian Overthrust Region, Southeastern Poland — Implications for Petroleum Generation

The organic matter rich Oligocene Menilite black shales and mudstones are widely distributed in the Carpathian Overthrust region of southeastern Poland and have excellent hydrocarbon generation potential, according to TOC, Rock-Eval, and petrographic data. Extractable organic matter was characterized by an equable distribution of steranes by carbon number, by varying amounts of 28,30-dinor-hopane, 18α(H)-oleanane and by a distinctive group of C24 ring-A degraded triterpanes. The Menilite samples ranged in maturity from pre-generative to mid-oil window levels, with the most mature in the southeastern portion of the study area. Carpathian petroleum samples from Campanian-Oligocene sandstone reservoirs were similar in biomarker composition to the Menilite rock extracts. Similarities in aliphatic and aromatic hydrocarbon distributions between petroleum asphaltene and source rock pyrolyzates provided further evidence genetically linking Menilite kerogens with Carpathian oils

Theoretical Simulations of 0.25 Monolayer Iodine Adsorption on Cu(100)

Simulations of adsorption 0.25 monolayer of iodine on Cu(100) were performed using a local-orbital minimal basis technique based on density functional theory and compared with plane-wave basis results. It was found that iodine adsorption changes the spacings between surface layers of copper substrate and can cause the reconstruction of this surface to rhombus-like arrangement with a stable threefold hollow adsorption site. The calculated structure of I/Cu(100) is presented together with the simulated scanning tunneling microscopy images of this surface. The obtained results are discussed in comparison with experimental results

The sonographic morphology of musculus palmaris longus in humans

Background: The aim of this work was to describe morphology and morphometry of musculus palmaris longus and compare the outcome of Shaeffer’s test with ultrasound imaging.Materials and methods: Forty forearms of 20 healthy volunteers (11 females, 9 males) were tested by Shaeffer’s test and ultrasound imaging. Anthropological measurements of the forearm and ultrasound guided measurements of musculus palmaris longus were taken. The outcome was tested for statistical significanceby Fisher’s test.Results: The examination revealed agenesis of palmaris longus in 6 cases, as well as 6 muscles showing quality variations. The Shaeffer’s test gave 4 false-negative results. 28 muscles were described as spindle-shaped and 8 as pennated or bipennated. However, all the spindle-shaped muscles demonstrated a tendon going inside of the muscle’s belly ranging from 2 cm to 11.5 cm. The relation between the circumference of the forearm right below the elbow (mean: 15.38 cm, SD: 1.83 cm) and the approximated volume of the palmaris longus muscle’s belly(mean: 4.72 cm3, SD: 1.57 cm3) proved to be statistically significant (Fisher’s test p-value < 0.05).Conclusions: Uncommon morphological variations have been shown. Spindle-shaped muscles have proved to have their tendons continued inside them. Palmaris longus muscle’s belly has proved to take significant amount of volume within the proximal forearm. Shaeffer’s test has shown to have 10% false-negative ratio

Ossa Sesamoidea — prevalence of sesamoid bones in human hands

Background: This study describes the morphology of sesamoid bones in the human hand. Ultrasound imaging was used to record the presence and measurements of sesamoids in 120 hands of 60 healthy, young adults of Caucasian ethnicity. Materials and methods: The mean number of sesamoid bones was 4.16 in the left hand and 4.03 in the right hand. 21.6% of cases showed asymmetry between the right hand and the left. There was a significant difference in the prevalence of sesamoid bones between right and left hand in males in this study. Females show a higher incidence of sesamoid bones overall, but do not demonstrate a significant difference between the sides. Results: Prevalence findings: Two in the 1st metacarpophalangeal joint (MCPJ) in 99.2% of cases, with 1 case of a single bone. One in the 2nd MCPJ in 43.3% of cases. One in the 5th MCPJ in 84.2% of cases. One in the 1st interphalangeal joint (IPJ) in 83.4% of cases. Aside from that there was 1 case of sesamoid in the 3rd MCPJ and separate case of sesamoid in the 3rd proximal IPJ. Conclusions: Moreover, this study discusses discrepancies of opinion regarding sesamoid bones in morphological research