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The magnetization states of 20-nm-thick rectangular Co thin-film elements are studied with micromagnetic modeling and x-ray magnetic circular dichroism photoemission electron microscopy. The energies of ten domain configurations obtained in the modeling are compared with the frequency of occurrence of the corresponding virgin domain structures as a function of aspect ratio from 1:1 to 1:3 and of width from 200 to 600 nm. The results show that the abundance of the virgin states is largely determined by the magnetic energy densities of the elements. [ABSTRACT FROM AUTHOR]

Antivortices are fundamental magnetic structures found alongside vortices in soft magnetic extended films and in patterned elements above a few micrometers in size. While the dynamic behavior of vortices has been the object of numerous studies, the magnetization dynamics of antivortices has not been studied as thoroughly. Using micromagnetic simulations, we investigate the dynamics of a single isolated antivortex in response to subnanosecond external field pulses. We find that these pulses can trigger the reversal of the antivortex core. This reversal mechanism is complementary to the one recently found in the vortex core switch. We also investigate the stability of the switching process in the isolated antivortex structure. [ABSTRACT FROM AUTHOR]

Magnetization processes in ideally soft ferromagnetic ellipsoids are studied numerically using the equations of micromagnetism. The ellipsoids have semiaxis in the ratios b/a=c/b=[lowercase_phi_synonym], where [lowercase_phi_synonym] is the golden ratio for which (c-b)/a=1. For a>20 nm, the magnetization processes include the formation and transformation of a vortex core. As vortex core motion takes place with little change in exchange energy, the response of the total magnetization to the applied fields is close to that of an ideally soft magnetic material as long as the vortex is mobile. At critical fields, the vortex core changes between states where it is free to move and those where it is immobilized by symmetry. Complex transformations at critical fields are observed. [ABSTRACT FROM AUTHOR]

Bacillus wild-type strains are genetically difficult to manipulate, and thus, the options for rational strain investigation and design are limited. Here, we present a set of small conjugative shuttle vectors for the use in Bacillus licheniformis and related, genetically difficult accessible wild-type strains. The vector set comprises the modular general-purpose vector pV2 and its derivatives pV3SDlacZ and pV3lacZ. The pV3 vectors are designed for the investigation of transcriptional and translational activities of regulatory regions like promoters and ribosomal binding sites (RBS). The vector set has been tested for investigating gene regulation under aerobic and anaerobic conditions. Significance and Impact of the Study The hereby introduced vectors represent a novel easy to apply toolbox which makes Bacillus strains with low or without natural competences accessible through transconjugation and allows quantitative studies on gene activity and gene regulation. Thus, the tool set enables research on newly isolated wild-type strains with methods normally limited to laboratory strains. [ABSTRACT FROM AUTHOR]

Abstract: We present a mechanism for reversing magnetic vortex cores with ultrashort field pulses. Using fully three-dimensional micromagnetic simulations, we show the details of the core reversal mechanism, which unfolds within a few tens of picoseconds. We investigate the stability of this process with respect to the angle at which the external field is applied, and for the case when strong fields are applied perpendicularly to the sample plane. The understanding of the vortex core dynamics represents a further step towards the controlled ultrafast switching of nanomagnets. [Copyright &y& Elsevier]

We report on the dynamics of magnetic domain structure conversions exhibited by soft magnetic thin-film elements of elementary geometrical shape (square, disc, triangle) when exposed to a strong external magnetic field. Starting from flux closure vortex patterns, the magnetic structures evolve towards an in-plane saturated state under the influence of an external field. This irreversible and nucleation-free magnetization process occurs on the time scale of picoseconds. The details of this conversion are investigated by means of a time-resolved micromagnetic finite element modeling. We find a sensitive dependence of the temporal evolution of the magnetic structure on the value of the damping parameter in Gilbert''s equation of motion. In the case of high damping, domain wall motion dominates the process, while lower damping leads to the formation of a 360° wall which collapses by emitting magnetization waves. It is shown that the mobility of vortices is generally much lower than that of domain walls. The calculations indicate that at a low damping, a magnetic vortex can act almost as a source for concentric waves in ferromagnetic thin-film elements. [Copyright &y& Elsevier]

Abstract: A ferromagnetic block (2a×2b×2c) with three unequal axes supports a vortex structure that intersects each of the two opposite surfaces of largest area. Swirls appear at points (xp, yp, c) and (−xp, yp, −c) in state-A. In state-B the swirls are at points (−xp, −yp, c) and (xp, −yp, −c). With micromagnetic simulations we demonstrate the possibility of a nucleation-free switching between those states, with possible applicability in devices. The oscillations are accompanied by large external fields from the magnetic charge at the core of the intersections of the vortices with the surface. These fields of the order of a quarter of the saturation inductance move over a distance 2xp∼c in fractions of a ns. [Copyright &y& Elsevier]

The authors report on a method to tune the orientation of in-plane magnetic domains and domain walls in thin ferromagnetic strips by manipulating the magnetic anisotropy of the system. Uniaxial in-plane anisotropy is induced in a controlled way by oblique evaporation of magnetic thin strips. A direct correlation between the magnetization direction and the domain wall orientation is found experimentally and confirmed by micromagnetic simulations. The domain walls in the strips are always oriented along the oblique evaporation-induced easy axis, irrespective of the shape anisotropy. The controlled manipulation of domain wall orientations could provide promising possibilities for recently proposed devices based on domain wall propagation. [ABSTRACT FROM AUTHOR]

Presents a study that evaluated the micromagnetic properties of hexagonal arrays of nickel nanowires. Comparison of the magnetic moment of nickel with iron and cobalt; Estimation of the switching field distribution of the nanowires; Influence of the magnetostatic interactions on the coercive field of the nanowires.

We have studied the magnetic states of self-organized Fe islands on W(001) by means of spin-polarized scanning tunneling spectroscopy (Sp-STS). Single-domain and vortex states in the nanoscale islands have been observed. The high-resolution magnetic images enable to experimentally determine the boundary between the single-domain and vortex states. The single-domain state was always found below a thickness of 6 nm and a diameter of 120 nm in Fe islands. The boundary directly observed with Sp-STS is consistent with theoretical predictions. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The article author presents his views on Cholodny-Went theory for plant tropism. Recently, "molecular" evidence for a lateral auxin asymmetry has been added: the redistribution of auxin-induced RNAs during gravitoprism. Often in biology, competing theories are not mutually exclusive but both are "true" and cover different parts of a complex process. The statolith theory and the auxin theory are not mutually exclusive but dealing with early and late steps, respectively, of the same transduction chain. The author wants to merge more old ideas to a theory of gravitropism. The gravireaction of shoots and coleoptiles can he explained by a statolith-stimulated secretion of auxin in each cell and a subsequent increase in IAA at the lower flank with increased growth.

The magnetic domain structure in Co nanowires with dimensions was examined by Lorentz microscopy and micromagnetic simulations. A slab of two collinear Co nanowires separated by Cu were produced from a sputtered and annealed 90nm Co/180nm Cu/90nm Co trilayer by transmission electron microscopy preparation methods. The easy axis of magnetisation in the Co wires with a hexagonal, c-axis-textured grain structure is parallel to the y-direction. The magnetic domains are periodic and have a size of about 80nm. A partially open closure domain pattern with tilted magnetisation was found by numeric simulation. [Copyright &y& Elsevier]

Single-domain, high-remanence particles are the prerequisite for their application in magnetic high-density recording systems. Analytical calculations for the transition between single and multidomain configurations remain unprecise because the calculation of the stray field requires strong simplifications. By means of the three-dimensional finite element method, zero-field magnetization structures of magnetically hard and soft thin film elements and cubic particles have been determined. Numerical results are compared with analytical calculations showing that the latter results depend sensitively on the energy determined for vortex structures. [Copyright &y& Elsevier]

The present study investigated the diversity of culturable rhizobacteria associated with potato (S. tuberosum L.) in Tanzania and assessed their in vitro plant growth-promoting (PGP) activities to deduce their potential as biofertilizers. Potato rhizosphere soil and tuber samples (54 samples in total) were collected from 9 villages in three different agro-ecological regions in Tanzania. A total of 145 rhizobacterial isolates were obtained, 52 of which were selected and identified by partial 16S rRNA gene sequences and screened for various PGP traits in vitro including qualitative and quantitative solubilization of phosphorus (P), zinc (Zn) and potassium (K), nitrogen (N2) fixation and production of ammonia (NH3) in nitrogen-free medium, and indole-3-acetic acid (IAA), gibberellic acids (GA) and siderophores production. The results showed that the isolates were all Gammaproteobacteria, belonging to 4 families (Enterobacteriaceae, Yersiniaceae, Pseudomonadaceae and Morganellaceae) and 9 genera (Enterobacter, Klebsiella, Serratia, Pseudomonas, Morganella, Buttiauxella, Pantoea and Cedecea). Significant differences (P < 0.05) were observed for all assessed PGP abilities of the external and endophytic rhizobacterial isolates except for quantitative siderophore production and qualitative P and K solubilization for the external rhizobacteria and production of IAA and GA for the endophytic rhizobacteria. Among the best PGP isolates which can be exploited for biofertilization of the potato were Klebsiella pneumoniae KIBS1, K. grimontii LUTS10, Serratia liquefaciens KIBT1, Enterobacter ludwigii KIBS10 and Citrobacter freundii MWALS6. Comparative evaluation of PGP abilities of these two groups of isolates revealed significant differences (P < 0.05) only for NH3 and IAA production and qualitative K solubilization. [ABSTRACT FROM AUTHOR]

Here, we present pRH030, a new CRISPR‐Cas9 tool for the genetic engineering of Bacillus phages and beyond. It is based on the Streptococcus pyogenes cas9 with its native constitutive promoter, tracrRNA, and a gRNA precursor. The constitutive expression of Cas9 was conducive to the inactivation of viral attackers and enhanced phage mutagenesis efficiency up to 100%. The gRNA precursor can be built up to an artificial CRISPR array with up to 5 spacers (target sequences) assembled from ordinary oligonucleotides and directly cloned into pRH030. Required time and resources remain comparable to a single gRNA cloning. These properties make pRH030 an attractive new system for the modification of Bacillus phages and qualify it for research beyond genetic construction. [ABSTRACT FROM AUTHOR]

The authors report on the switching of a magnetic vortex core in a submicron Permalloy disk, induced by a short current pulse applied in the film plane. Micromagnetic simulations including the adiabatic and nonadiabatic spin-torque terms are used to investigate the current-driven magnetization dynamics. They predict that a core reversal can be triggered by current bursts a tenth of a nanosecond long. The vortex core reversal process is found to be the same as when an external field pulse is applied. The control of a vortex core’s orientation using current pulses introduces the technologically relevant possibility to address individual nanomagnets within dense arrays. [ABSTRACT FROM AUTHOR]

The magnetization reversal behavior of 20 rim thick cobalt microstructures with a nanoconstriction of variable size has been studied using magnetoresistance measurements and micromagnetic simulations. Depending on the direction of the applied field relative to the current, reversible and irreversible switching events are observed, which can be explained using micromagnetic simulations. Anisotropic magnetoresistance (AMR) is the dominant resistance contribution in the systems measured. The simulations show that instead of one sharp domain wall, which may lead to ballistic magnetoresistance (BMR), two domain walls on each side of the nanocontact precede the complete reversal. [ABSTRACT FROM AUTHOR]

Introduction: Aim of this study was to evaluate outcomes of operative as compared to conserveative treatment for two-part humerus fractures at the surgical neck. Methods: Data from a prospective multi-centre cohort study on four treatment options (conservative treatment and three implants, i.e. LPHP, PHILOS and PHN) for proximal humerus fractures were evaluated in this post hoc analysis. All patients with two-part fractures of the surgical neck (AO types A2, n = 54 and A3, n = 110) were identified and included for the analysis. All operatively treated patients were gathered and compared to those receiving conservative treatment. Primary outcome parameters were pain, range of motion and absolute and relative Constant scores at 3, 6 and 12 months following injury and coronal plane alignment at 12 months. Results : Operative ( n = 133) and non-operative ( n = 31) groups were comparable with regard to all parameters assessed including mean age (62.9 vs. 65.6, P = 0.479), gender (27 vs. 29 % male, P = 0.826) and fracture distribution (65 vs. 77 % A3 type, P = 0.207). 26 of the 31 conservatively treated and 103 of the 133 operatively treated patients (84 and 77 %, respectively) were available for final follow-up. There was a continuous improvement for all outcome parameters in both treatment groups ( P < 0.001). Operative treatment resulted in a more effective reduction of pain at 3 months (51 vs. 76 % reporting pain at fracture site, P = 0.03) and a reduction of coronal plane malalignment. Both range of motion and Constant scores were, however, comparable in both groups at all follow-up visits. Relative and absolute Constant scores were generally excellent at final follow-up (74 vs. 74, P = 0.528 and 89 vs. 91, P = 0.494, respectively). Conclusions: Both non-operative treatment and operative treatment using modern implants (LPHP, PHILOS and PHN) can be considered safe and effective treatment options for two-part fractures of the proximal humerus. Operative treatment may result in better range of motion and reduced pain in the early postoperative course of treatment. [ABSTRACT FROM AUTHOR]

We present a combined analytical and numerical study on double-vortex spin-torque nano-oscillators and describe a mechanism that suppresses the windmill modes. The magnetization dynamics is dominated by the gyrotropic precession of the vortex in one of the ferromagnetic layers. In the other layer, the vortex gyration is strongly damped. The dominating layer for the magnetization dynamics is determined by the sign of the product between sample current and the chiralities. Measurements on Fe/Ag/Fe nanopillars support these findings. The results open up a new perspective for building high quality-factor spin-torque oscillators operating at selectable, well-separated frequency bands. [ABSTRACT FROM AUTHOR]

We analyze the origin of the electrical resistance arising in domain walls of perpendicularly magnetized materials by considering a superposition of anisotropic magnetoresistance and the resistance implied by the magnetization chirality. The domain wall profiles of Ll0-FePd and Ll0-FePt are determined by micromagnetic simulations based on which we perform first-principles calculations to quantify electron transport through the core and closure region of the walls. The wall resistance, being twice as high in Ll0-FePd than in Ll0-FePd, is found to be clearly dominated in both cases by a high gradient of magnetization rotation, which agrees well with experimental observations. [ABSTRACT FROM AUTHOR]

We present measurements and simulations of spin-transfer torque (STT) induced magnetization dynamics in nanopillars containing a thin, circular, single-crystalline Fe nanomagnet with four-fold in-plane magnetocrystalline anisotropy as a free layer. The magnetocrystalline anisotropy inherent to bcc-Fe allows for a consecutive switching of the magnetization by 900 between parallel and antiparallel alignment to the fixed layer magnetization. Additionally, the anisotropy gives rise to steady-state precession of the magnetization at low or even zero applied magnetic field as well as at large fields exceeding the coercive field. While the low-field mode is governed by the interplay between the STT and the anisotropy, the high-field dynamics result from the STT acting against the externally applied magnetic field. [ABSTRACT FROM AUTHOR]

The vortex state, characterized by a curling magnetization, is one of the equilibrium configurations of soft magnetic materials and occurs in thin ferromagnetic square and disk-shaped elements of micrometre size and below. The interplay between the magnetostatic and the exchange energy favours an in-plane, closed flux domain structure. This curling magnetization turns out of the plane at the centre of the vortex structure, in an area with a radius of about 10 nanometres—the vortex core. The vortex state has a specific excitation mode: the in-plane gyration of the vortex structure about its equilibrium position. The sense of gyration is determined by the vortex core polarization. Here we report on the controlled manipulation of the vortex core polarization by excitation with small bursts of an alternating magnetic field. The vortex motion was imaged by time-resolved scanning transmission X-ray microscopy. We demonstrate that the sense of gyration of the vortex structure can be reversed by applying short bursts of the sinusoidal excitation field with amplitude of about 1.5 mT. This reversal unambiguously indicates a switching of the out-of-plane core polarization. The observed switching mechanism, which can be understood in the framework of micromagnetic theory, gives insights into basic magnetization dynamics and their possible application in data storage. [ABSTRACT FROM AUTHOR]