Modification of Dzyaloshinskii-Moriya-Interaction-Stabilized Domain Wall Chirality by Driving Currents.

We measure and analyze the chirality of Dzyaloshinskii-Moriya-interaction (DMI) stabilized spin textures in multilayers of Ta|Co_{20}F_{60}B_{20}|MgO. The effective DMI is measured experimentally using domain wall motion measurements, both in the presence (using spin-orbit torques) and absence of driving currents (using magnetic fields). We observe that the current-induced domain wall motion yields a change in effective DMI magnitude and opposite domain wall chirality when compared to field-induced domain wall motion (without current). We explore this effect, which we refer to as current-induced DMI, by providing possible explanations for its emergence, and explore the possibility of its manifestation in the framework of recent theoretical predictions of DMI modifications due to spin currents.

Annealing Stability Study of Co20Fe60B20\MgO\ Co20Fe60B20 Perpendicular Magnetic Tunnel Junctions.

A full Co20Fe60B20\MgO\ Co20Fe60B20 perpendicular magnetic tunnel junction (pMTJ) with (Co\Pt) multilayers as pinning layers and different functional multilayers stacks were made and annealed at different temperatures. The tunneling magnetoresistance ratio (TMR) and MgO barrier resistance-area product (RA) were measured and analyzed as a function of annealing temperature. The TMR of pMTJs dramatically declines with increasing annealing temperatures from 320 °C to 400 °C while the RA increases with temperature from 375 °C to 450 °C. The pMTJs and partial stacks were also measured in a vibrating sample magnetometer (VSM). We found that the (Co\Pt) multilayers are very stable and maintain a magnetization direction perpendicular to the film plane up to 450 °C. However, the magnetization direction of the CoFeB above and below the MgO barrier rotates from perpendicular to in-plane with increasing annealing temperature. Furthermore, the CoFeB layer influences the adjacent (Co\Pt) layers to rotate at the same time. The pMTJs' elemental depth profiles in the as deposited and annealed states were determined by Secondary Ion Mass Spectrometry (SIMS). We found that Boron and Tantalum migrate towards the top of the stack. The other elements (Platinum, Cobalt, Ruthenium, and Magnesium) are very stable and do not interdiffuse during annealing up to 450°C.

Tunneling magnetothermopower in magnetic tunnel junction nanopillars.

We study tunneling magnetothermopower (TMTP) in CoFeB/MgO/CoFeB magnetic tunnel junction nanopillars. Thermal gradients across the junctions are generated by an electric heater line. Thermopower voltages up to a few tens of µV between the top and bottom contact of the nanopillars are measured which scale linearly with the applied heating power and hence the thermal gradient. The thermopower signal varies by up to 10 µV upon reversal of the relative magnetic configuration of the two CoFeB layers from parallel to antiparallel. This signal change corresponds to a large spin-dependent Seebeck coefficient of the order of 100 µV/K and a large TMTP change of the tunnel junction of up to 90%.

Influence of pinholes on MgO-tunnel junction barrier parameters obtained from current-voltage characteristics.

Magnetic tunnel junctions (MTJs) with thin barriers are already used as read sensors in recording media. However, the presence of pinholes across such few A thick barriers cannot be excluded and one needs to investigate their effect on the MTJ-transport properties. By applying large electrical currents we could change the electrical resistance of the studied MgO MTJs (due to pinhole-size variations), and study how pinholes influence the barrier parameters (thickness t and height phi) obtained by fitting current-voltage characteristics to Simmons' model. We found that, with decreasing resistance, the barrier thickness (height) decreases (increases). These results were well reproduced by a model of parallel-resistances, allowing us to estimate pinhole-free barrier parameters.

CD22 is a negative regulator of B-cell receptor signalling.

BACKGROUND: . Antibody responses are triggered by binding of antigen to the B-cell antigen receptor (BCR). The strength of the resulting signal determines the outcome of the response, which may vary from the induction of tolerance to the antigen, to the production of specific high-affinity antibodies. Additional cell-surface proteins assist the BCR in its function, and can facilitate or inhibit an antibody response. CD22 is a BCR-associated transmembrane protein, the cytoplasmic tail of which contains three immunoreceptor tyrosine-based inhibitory motifs. These motifs are phosphorylated upon BCR-crosslinking, and can bind the tyrosine phosphatase SHP-1, a putative negative regulator of signalling from the BCR. In order to assess the role of CD22 in vivo, we have generated CD22(-/-) mice by targeted gene inactivation. RESULTS: . In CD22(-/-) mice, B-cell development is normal. There are normal numbers of peripheral B cells, but these have a more mature phenotype. In addition, recirculating B cells are absent from the bone marrow. However, the distribution of the two B-cell subtypes, B-1 and B-2, is normal. After BCR-crosslinking in vitro, splenic CD22(-/-) B cells show an increased Ca2+ influx and a lower survival due to an increased induction of apoptosis. In contrast, there is an increased proliferative response to the B-cell mitogen lipopolysaccharide (LPS). A shorter average lifespan in the B-cell compartment is also found in vivo. Furthermore, T-cell independent immune responses are impaired, whereas T-cell dependent responses are normal. CONCLUSIONS: . The absence of CD22 expression lowers the signalling threshold for BCR-crosslinking and can thus influence the fate of the B cell. We propose that the low threshold leads to hyperresponsiveness of the B cells and a chronic basal activation. In this model, engagement of the receptor without T-cell help leads to an increased induction of apoptosis, thus explaining the shorter lifespan of CD22(-/-) B cells and the low response to T-cell independent antigens. The alteration in B-cell phenotype and the higher levels of LPS-reactivity are attributable to the chronic basal stimulation.

The nature of domain walls in ultrathin ferromagnets revealed by scanning nanomagnetometry.

The capacity to propagate magnetic domain walls with spin-polarized currents underpins several schemes for information storage and processing using spintronic devices. A key question involves the internal structure of the domain walls, which governs their response to certain current-driven torques such as the spin Hall effect. Here we show that magnetic microscopy based on a single nitrogen-vacancy defect in diamond can provide a direct determination of the internal wall structure in ultrathin ferromagnetic films under ambient conditions. We find pure Bloch walls in Ta/CoFeB(1 nm)/MgO, while left-handed Néel walls are observed in Pt/Co(0.6 nm)/AlOx. The latter indicates the presence of a sizable interfacial Dzyaloshinskii-Moriya interaction, which has strong bearing on the feasibility of exploiting novel chiral states such as skyrmions for information technologies.

Fragment kinetic energies and modes of fragment formation

Kinetic energies of light fragments ( A

The research nurse role in a clinic-based oncology research setting.

Public demand and government support for evaluating new cancer drugs and methods in a more timely manner have significantly affected clinical research programs. To meet these demands, it is critical to have research personnel with an appropriate skill mix to ensure that clinical trials are conducted safely and effectively, while scientific integrity is maintained. This article describes the development and integration of the research nurse role within an oncology research program in a large outpatient oncology clinic. Methods for evaluating the research nurse role included literature review, analysis of job descriptions, and dialogue with research staff, oncology staff, and a clinical nurse specialist. A Review of the Nurse Practice Act of Wisconsin and the Oncology Nursing Society standards provided license and practice standards. Similarities and differences between the roles of the research nurse and the chemotherapy nurse are analyzed. Complementary roles and functions are identified, and areas of role overlap are defined. This report expands the limited current literature regarding this subject. The findings provide the reader with a framework for evaluating the roles of registered nurse personnel in a clinical setting. Although each institution has unique characteristics or research needs, the method used to address the reported program is transferable.

Determination of the spin torque non-adiabaticity in perpendicularly magnetized nanowires.

Novel nanofabrication methods and the discovery of an efficient manipulation of local magnetization based on spin polarized currents has generated a tremendous interest in the field of spintronics. The search for materials allowing for fast domain wall dynamics requires fundamental research into the effects involved (Oersted fields, adiabatic and non-adiabatic spin torque, Joule heating) and possibilities for a quantitative comparison. Theoretical descriptions reveal a material and geometry dependence of the non-adiabaticity factor ß, which governs the domain wall velocity. Here, we present two independent approaches for determining ß: (i) measuring the dependence of the dwell times for which a domain wall stays in a metastable pinning state on the injected current and (ii) the current-field equivalence approach. The comparison of the deduced ß values highlights the problems of using one-dimensional models to describe two-dimensional dynamics and allows us to ascertain the reliability, robustness and limits of the approaches used.

Biased quasiballistic spin torque magnetization reversal.

We explore the ultrafast limit of spin torque magnetization reversal time. Spin torque precession during a spin torque current pulse and free magnetization ringing after the pulse is detected by time-resolved magnetotransport. Adapting the duration of the pulse to the precession period allows coherent control of the final orientation of the magnetization. In the presence of a hard axis bias field, we find optimum quasiballistic spin torque magnetization reversal by a single precessional turn directly from the initial to the reversed equilibrium state.

Development- and light-dependent regulation of the expression of two different chalcone synthase transcripts in mustard cotyledons.

Two different chalcone synthase (CHS) transcripts show similar expression characteristics under different light regimes in cotyledons of mustard (Sinapis alba L.). Etiolated seedlings show an increase in dark-expression 36-42 h after sowing. Under continuous red or far-red irradiation both CHS transcripts start to accumulate to levels above those of the dark control at 24-27 h after sowing. This time point can therefore be considered as the starting (or competence) point for phytochrome control of CHS. Continuous far-red irradiation stimulates transcript accumulation more than red light, indicating the involvement of a high-irradiance response (HIR). Irradiation of etiolated seedlings with 5 min long-wavelength far-red light (RG9) at 6-21 h after sowing decreases CHS-mRNA levels below those of the dark control. It is concluded that CHS dark-expression in etiolated seedlings is controlled by a pool of stabletype phytochrome which is derived from seed tissue. By contrast, an RG9-light pulse given to etiolated seedlings 30 h after sowing causes accumulation of CHS-mRNA above the dark-control level. This response and the HIR are attributed to the action of labile phytochrome for which the seedling becomes competent at the starting point 24-27 h after sowing. The different starting points for CHS-mRNA expression in darkness and in light (36 h and 24 h, respectively, after sowing) also indicate that the tested CHS genes in mustard are under the photocontrol of two distinct phytochrome pools. Northern analysis shows that both CHS-mRNAs are expressed in primary leaves, epicotyls and young flower buds. In-situ hybridization with gene-specific CHS probes reveals similar expression patterns for both transcripts in cotyledons of seedlings grown under 42 h continuous far-red light.