Interval identification of FMR parameters for spin reorientation transition in (Ga,Mn)As

In this work we report results of ferromagnetic resonance studies of a 6% 15 nm (Ga,Mn)As layer, deposited on (001)-oriented GaAs. The measurements were performed with in-plane oriented magnetic field, in the temperature range between 5K and 120K. We observe a temperature induced reorientation of the effective in-plane easy axis from [-110] to [110] direction close to the Curie temperature. The behavior of magnetization is described by anisotropy fields, H_{eff} (= 4\piM -H_{2\perp}), H_{2\parallel}, and H_{4\parallel}. In order to precisely investigate this reorientation, numerical values of anisotropy fields have been determined using powerful - but still largely unknown - interval calculations. In simulation mode this approach makes possible to find all the resonance fields for arbitrarily oriented sample, which is generally intractable analytically. In 'fitting' mode we effectively utilize full experimental information, not only those measurements performed in special, distinguished directions, to reliably estimate the values of important physical parameters as well as their uncertainties and correlations.Comment: 3 pages, 3 figures. Presented at The European Conference "Physics of Magnetism 2011" (PM'11), June 27 - July 1, 2011, Poznan, Polan

The chemical composition of egg plugs deposited by Sitophilus granarius L. females on grain

Over 20,000 egg plugs collected from infested wheat grain were subjected to chemical analysis.Elemental analysis showed a relatively high content of nitrogen (about 9%). It suggested that the predominant constituent of egg plugs is a protein. Spectrum obtained in ESI-MS analysis showed a series of peaks characteristic corresponding to protein of molecular weight 30073 Da. The appearance of other peaks in this spectrum suggests that studied protein is not homogenous. A sample of egg plugs incubated with pepsin yielded a complex mixture of peptides. The most abundant peak in the ESI-MS spectrum of zymatic hydrolysis products corresponds to peptide Mw 4560.76 Da. Chemical analysis indicated that the main component of egg plugs is protein. Keywords: egg plugs, chemical composition, Sitophilus granariu

Thickness dependence of magnetic properties of (Ga,Mn)As

We report on a monotonic reduction of Curie temperature in dilute ferromagnetic semiconductor (Ga,Mn)As upon a well controlled chemical-etching/oxidizing thinning from 15 nm down to complete removal of the ferro- magnetic response. The effect already starts at the very beginning of the thinning process and is accompanied by the spin reorientation transition of the in-plane uniaxial anisotropy. We postulate that a negative gradient along the growth direction of self-compensating defects (Mn interstitial) and the presence of surface donor traps gives quantitative account on these effects within the p-d mean field Zener model with adequate mod- ifications to take a nonuniform distribution of holes and Mn cations into account. The described here effects are of practical importance for employing thin and ultrathin layers of (Ga,Mn)As or relative compounds in concept spintronics devices, like resonant tunneling devices in particular.Comment: 4 pages, 4 figures and supplementary information 2 pages, 1 figur

Validation of the Polish version of P-QoL questionnaire

Objective: Pelvic organ prolapse (POP) is a common morbidity that affects many women and significantly decreases quality of life. The severity and the impact of the prolapse on the quality of life are important parameters in the management and follow-up of affected patients. The aim of this validation study was to validate the Polish version of the Prolapse Quality of Life questionnaire (P-QoL). Material and methods: The P-QOL questionnaire was translated into Polish and administered to women recruited from two gynecological outpatient clinics (n = 231). Both symptomatic and asymptomatic women were included in the study and examined in supine position using the Pelvic Organ Prolapse Quantification System (POP-Q). The validity was assessed by comparing symptom scores and quality-of-life scores between symptomatic and asymptomatic women. Results: A total number of 154 symptomatic and 77 asymptomatic women were included. There was a strong correlation between severity of the disease based on physical findings (POP-Q scale) and the P-QoL scores in main prolapse quality-of-life domains. The overall scores for each life domain were significantly different between symptomatic and asymptomatic women (p < 0.001). All the questions regarding symptoms showed significant differences (p < 0.001) between both groups. Conclusions: The Polish version of P-QoL is a valid, reliable, and easily comprehensible instrument to assess quality of life and symptoms in Polish-speaking women suffering from urogenital prolapse

Experimental probing of exchange interactions between localized spins in the dilute magnetic insulator (Ga,Mn)N

The sign, magnitude, and range of the exchange couplings between pairs of Mn ions is determined for (Ga,Mn)N and (Ga,Mn)N:Si with x < 3%. The samples have been grown by metalorganic vapor phase epitaxy and characterized by secondary-ion mass spectroscopy; high-resolution transmission electron microscopy with capabilities allowing for chemical analysis, including the annular dark-field mode and electron energy loss spectroscopy; high-resolution and synchrotron x-ray diffraction; synchrotron extended x-ray absorption fine-structure; synchrotron x-ray absorption near-edge structure; infra-red optics and electron spin resonance. The results of high resolution magnetic measurements and their quantitative interpretation have allowed to verify a series of ab initio predictions on the possibility of ferromagnetism in dilute magnetic insulators and to demonstrate that the interaction changes from ferromagnetic to antiferromagnetic when the charge state of the Mn ions is reduced from 3+ to 2+.Comment: 12 pages, 14 figures; This version contains the detailed characterization of the crystal structure as well as of the Mn distribution and charge stat

Mixotrophic uptake of organic compounds by coccolithophores

Osmotrophy is one of the main modes of mixotrophic acquisition of carbon by phytoplankton, but historically it has been under‐investigated and its physiological and ecological relevance remains poorly understood. Here, we investigate osmotrophy in coccolithophores. Coccolithophores are one of the major contributors to the ocean biomass inhabiting both euphotic and subeuphotic depths in the marine environment. Coccolithophores demonstrate the potential to utilize a wide array of organic compounds in darkness. In experiments with BioLog Ecoplates, we screened a wide array of organic compounds as potential carbon sources, and observed that the major types of organic compounds taken up by coccolithophores were primarily carbohydrates along with a few amino acids and polymers. Furthermore, in subsequent radiotracer experiments, the uptake rates of 14C‐labeled dissolved organic carbon compounds in the dark were low relative to the maximal rates of photosynthetic carbon fixation in the light. The time course of uptake for some compounds suggests constitutive capacity for their transport, while for others the transport appears to be activated. Nonetheless, the collective slow uptake rate of a large array of organic compounds found in seawater, might be the only way that osmotrophy could fuel significant coccolithophore growth in the deep euphotic and subeuphotic zones in the sea