Depinning and dynamics of AC driven vortex lattices in random media

We study the different dynamical regimes of a vortex lattice driven by AC forces in the presence of random pinning via numerical simulations. The behaviour of the different observables is charaterized as a function of the applied force amplitude for different frequencies. We discuss the inconveniences of using the mean velocity to identify the depinnig transition and we show that instead, the mean quadratic displacement of the lattice is the relevant magnitude to characterize different AC regimes. We discuss how the results depend on the initial configuration and we identify new hysteretic effects which are absent in the DC driven systems.Comment: 6 pages, 4 figure

Dynamic reorganization of vortex matter into partially disordered lattices

We report structural evidence of dynamic reorganization in vortex matter in clean NbSe$_2$ by joint small angle neutron scattering and ac-susceptibility measurements. The application of oscillatory forces in a transitional region near the order-disorder transition results in robust bulk vortex lattice configurations with an intermediate degree of disorder. These dynamically-originated configurations correlate with intermediate pinning responses previously observed, resolving a long standing debate regarding the origin of such responses.Comment: 9 pages, 7 figures. To be published in Physical Review Letter

Oscillatory dynamics of a superconductor vortex lattice in high amplitude ac magnetic fields

In this work we study by ac susceptibility measurements the evolution of the solid vortex lattice mobility under oscillating forces. Previous work had already shown that in YBCO single crystals, below the melting transition, a temporarily symmetric magnetic ac field (e.g. sinusoidal, square, triangular) can heal the vortex lattice (VL) and increase its mobility, but a temporarily asymmetric one (e.g. sawtooth) of the same amplitude can tear the lattice into a more pinned disordered state. In this work we present evidence that the mobility of the VL is reduced for large vortex displacements, in agreement with predictions of recent simulations. We show that with large symmetric oscillating fields both an initially ordered or an initially disordered VL configuration evolve towards a less mobile lattice, supporting the scenario of plastic flow.Comment: 5 pages, 4 figures. To appear in Phys. Rev.

History effects and pinning regimes in solid vortex matter

We propose a phenomenological model that accounts for the history effects observed in ac susceptibility measurements in YBa2Cu3O7 single crystals [Phys. Rev. Lett. 84, 4200 (2000) and Phys. Rev. Lett. 86, 504 (2001)]. Central to the model is the assumption that the penetrating ac magnetic field modifies the vortex lattice mobility, trapping different robust dynamical states in different regions of the sample. We discuss in detail on the response of the superconductor to an ac magnetic field when the vortex lattice mobility is not uniform inside the sample. We begin with an analytical description for a simple geometry (slab) and then we perform numerical calculations for a strip in a transverse magnetic field which include relaxation effects. In calculations, the vortex system is assumed to coexist in different pinning regimes. The vortex behavior in the regions where the induced current density j has been always below a given threshold (j_c^>) is described by an elastic Campbell-like regime (or a critical state regime with local high critical current density, j_c^>). When the VS is shaken by symmetrical (e.g. sinusoidal) ac fields, the critical current density is modified to j_c^) at regions where vortices have been forced to oscillate by a current density larger than j_c^>. Experimentally, an initial state with high critical current density (j_c^>) can be obtained by zero field cooling, field cooling (with no applied ac field) or by shaking the vortex lattice with an asymmetrical (e.g. sawtooth) field. We compare our calculations with experimental ac susceptibility results in YBa2Cu3O7 single crystals.Comment: 11 pages, 7 figures. To be published in PR

Assessing the Accuracy and Precision of LA-ICP-MS Compared to SEM Analyses for Feldspar Characterization

As part of a larger study to better understand the tectonic history of western Idaho, we have studied the reliability of laser ablation inductively coupled mass spectrometry (LA-ICP-MS) to characterize the major cation composition of feldspar. Feldspar is a common rock forming mineral composed of three phases with differing major cation proportions, internal textures, and isotopic composition, all reflective of its formation conditions. The major cation proportions need to be quantified in order to contextualize more advanced classifications. Feldspar samples were collected from various intrusive igneous rocks within the Salmon River Canyon. These samples were then analyzed by Scanning Electron Microscopy (SEM), and those same sample spots were reanalyzed by LA-ICP-MS, then compared. We hypothesized that major cations determined by LA-ICP-MS would be \u3c 5% different than those derived by SEM. However, we found that on average there are significant discrepancies between the results obtained by SEM and LA-ICP-MS. We discuss how these discrepancies are likely attributed to issues such as fractured mineral grains, spot size inconsistency over fine-scale compositional zonations, and technical limitations leading to human error. To overcome these limitations, we further assess precision and accuracy between the two techniques using mineral standards with known and more homogeneous compositions

Naujas moterų šlapimo nelaikymo gydymo metodas

Tonaras BekerisVšĮ Šiaulių ligoninės Urologijos skyrius,Kudirkos g. 99, LT-76304 ŠiauliaiEl paštas: [email protected] Įvadas / tikslas Straipsnyje analizuojami pirmieji moterų šlapimo nelaikymo krūvio metu gydymo rezultatai polipropileno juostele, vedant transobturaciniu metodu. Ligoniai ir metodai Gydyta 14 moterų. Pacienčių amžius – 62–78 metai. Juostelė vedama nuo vienos užtvarinės angos į kitą, vidurinę dalį – po šlaplės vidurine dalimi. Juostelė, pakeldama šlaplę, atitaiso užpakalinį uretrovezikalinį kampą, grąžina šlapimo pūslės kaklelį į normalią padėtį. Šio metodo naujumas tas, kad juostelė guli horizontaliai ir švelniau prilaiko šlaplę. Rezultatai Operacijos trukmė – 25–40 min. Pooperaciniu laikotarpiu vienai ligonei buvo gaktinio nervo neuralgija. Šis skausmas išnyko po 5 dienų. Dviem ligonėm maksimali šlapimo srovė buvo mažesnė kaip 15 ml/s. Tai galėjo lemti mažesnis nei 200 ml šlapimo kiekis pūslėje. Išvados Šlapimo nelaikymo gydymas transobturaciniu metodu, naudojant polipropileno juostelę – naujas ir gana paprastas metodas. Šis metodas fiziologiškesnis už anksčiau siūlytuosius. Galimybė operuojant sužaloti šlapimo pūslę, žarnas, kraujagysles yra maža. Reikšminiai žodžiai: šlapimo nelaikymas, spaustukas, polipropileno juostelė A new method of stress female urinary incontinence treatment Tonaras BekerisDepartment of Urology, Šiauliai City Hospital,Kudirkos str. 99, LT-76304 Šiauliai, LithuaniaE-mail: [email protected] Background / Objective UraTape transobturator tape is the practical realization of a new concept in minimally invasive procedures to treat stress urinary incontinence. The novel aspects of its design are a horizontal orientation, a mechanism of support rather than suspension, and a path through the perineum rather than the pelvis. The aim of the study was to summarize the first experience in the treatment of female stress urinary incontinence by using a transobturator sling (uratape). Patients and methods Fourteen fresh women aged between 62 and 78 years were operated on. Five of these women had had gynecological operations before. The transobturator sling was used during the operation. The patients were followed for one and three months. Results Duration of the operation was 25–40 min. One patient suffered postoperatively from n. pudendus inflamatory reaction pain, but after five days the symptom disapeared. Conclusion This method is effective in treating female stress urinary incontinence. Keywords: urinary incontinence, polypropylene sling, cli

Field-Scale Evaluation of Enhanced Agricultural Management Practices Using a Novel Unsaturated Zone Nitrate Mass Load Approach

The monitoring of nitrate mass load through the unsaturated zone below agricultural land was proposed as a novel technique to assess the effect of agricultural best management practices (BMPs). The objectives of the study were to: develop field techniques and apply computational models for the quantification of unsaturated zone nitrate mass flux; scale the point mass flux results to a nitrate mass load across an agricultural parcel; and assess the resulting nitrate mass load measurements as indicators to evaluate the effect of a BMP. At several locations across the study site, groundwater quality and profiles of soil water content and temperature were regularly monitored, and several rounds of geologic cores were collected for analysis of bulk soil nitrate and an applied bromide tracer. The field data were applied in several analytical techniques for estimating recharge, and in two unsaturated zone numerical models used to refine the recharge estimates. The recharge rate at each measurement location was then combined with unsaturated zone nitrate data to quantify nitrate mass flux. Upscaling of the flux values to field-scale mass load was based mainly on topography, geology and field observations. The calculation of stored nitrate mass in the shallow subsurface showed some correlation to changes in surface nitrogen application, with the greatest decreases in stored mass observed at locations underlain by sand where there was a switch to a grass crop. In contrast, the calculation of nitrate mass load suggested that the post-BMP value (4.1 t NO3-N/yr) was greater than the pre-BMP value (2.2 t NO3-N/yr). However, the calculation of nitrate mass load was limited by several factors, including a lack of nitrate concentration data from the deep unsaturated zone and an above-average annual precipitation rate; as a result, the findings suggesting an increase in nitrate mass load in response to decreasing nutrient inputs should be interpreted with caution. Continued monitoring of nitrate mass load and stored nitrate mass in the unsaturated zone is recommended to determine whether further benefits from the BMPs are observed as the measurement period lengthens and the unsaturated zone is progressively flushed