Kondo physics in non-local metallic spin transport devices.

The non-local spin-valve is pivotal in spintronics, enabling separation of charge and spin currents, disruptive potential applications and the study of pressing problems in the physics of spin injection and relaxation. Primary among these problems is the perplexing non-monotonicity in the temperature-dependent spin accumulation in non-local ferromagnetic/non-magnetic metal structures, where the spin signal decreases at low temperatures. Here we show that this effect is strongly correlated with the ability of the ferromagnetic to form dilute local magnetic moments in the NM. This we achieve by studying a significantly expanded range of ferromagnetic/non-magnetic combinations. We argue that local moments, formed by ferromagnetic/non-magnetic interdiffusion, suppress the injected spin polarization and diffusion length via a manifestation of the Kondo effect, thus explaining all observations. We further show that this suppression can be completely quenched, even at interfaces that are highly susceptible to the effect, by insertion of a thin non-moment-supporting interlayer.

Surface roughness dominated pinning mechanism of magnetic vortices in soft ferromagnetic films.

Although pinning of domain walls in ferromagnets is ubiquitous, the absence of an appropriate characterization tool has limited the ability to correlate the physical and magnetic microstructures of ferromagnetic films with specific pinning mechanisms. Here, we show that the pinning of a magnetic vortex, the simplest possible domain structure in soft ferromagnets, is strongly correlated with surface roughness, and we make a quantitative comparison of the pinning energy and spatial range in films of various thickness. The results demonstrate that thickness fluctuations on the lateral length scale of the vortex core diameter, i.e., an effective roughness at a specific length scale, provides the dominant pinning mechanism. We argue that this mechanism will be important in virtually any soft ferromagnetic film.

Non-lift-off block copolymer lithography of 25 nm magnetic nanodot arrays.

Although nanolithographic techniques based on self-assembled block copolymer templates offer tremendous potential for fabrication of large-area nanostructure arrays, significant difficulties arise with both the lift-off and etch processes typically used for pattern transfer. These become progressively more important in the limit of extreme feature sizes. The few techniques that have been developed to avoid these issues are quite complex. Here, we demonstrate successful execution of a nanolithographic process based on solvent annealed, cylinder-forming, easily degradable, polystyrene-b-polylactide block copolymer films that completely avoids lift-off in addition to the most challenging aspects of etching. We report a "Damascene-type" process that overfills the polystyrene template with magnetic metal, employs ion beam milling to planarize the metal surface down to the underlying polystyrene template, then exploits the large etch rate contrast between polystyrene and typical metals to generate pattern reversal of the original template into the magnetic metal. The process is demonstrated via formation of a large-area array of 25 nm diameter ferromagnetic Ni(80)Fe(20) nanodots with hexagonally close-packed order. Extensive microscopy, magnetometry, and electrical measurements provide detailed characterization of the pattern formation. We argue that the approach is generalizable to a wide variety of materials, is scalable to smaller feature sizes, and critically, minimizes etch damage, thus preserving the essential functionality of the patterned material.

Barriers to domestic violence screening in the pediatric setting.

OBJECTIVE: By surveying practitioners in our community, we hoped to determine what pediatricians and family physicians (FPs) perceive as barriers to the American Academy of Pediatrics (AAP) Recommendation on Domestic Violence Screening. BACKGROUND: When screened in the pediatric setting, as many as 40% of mothers will disclose domestic violence (DV) by their partner. Recognizing the profound effects of DV on children, the AAP recently recommended that all practitioners incorporate DV screening as a part of routine anticipatory guidance. Yet, there is little information about whether pediatricians have the training, the time to screen, or understand the magnitude of this problem. DESIGN/METHODS: A 22-question survey about attitudes, training, and current DV screening practice was sent to all general pediatricians and FPs with admitting privileges to Children's Hospital Medical Center in Cincinnati, Ohio. A copy of the AAP recommendation on screening was included. The vast majority of practitioners with an appreciable pediatric practice in the surrounding tri-state area of 1.8 million people have privileges at the institution. RESULTS: After 2 mailings, 310 (57%) of 547 of questionnaires were returned. The majority of practitioners (64%) were unaware of the AAP recommendation, but 51% of practitioners screened at least high-risk families for DV and 49% had identified a case of DV in their practice. Still, only 8.5% routinely screened for DV and 74% had received no specific DV training. Fifty-eight percent of practitioners estimated the incidence of DV to be <5% in their practice. The most commonly perceived barriers to screening were lack of education (61%), office protocol (60%), time (59%), and support staff (55%). FPs were significantly more likely to have DV training (64% vs 21%), more likely to screen at least high-risk women (79% vs 56%), and more likely to have identified a case of DV (92% vs 40%) than pediatricians. FPs were less likely to cite lack of education (46% vs 65%) and lack of time (50% vs 61%) than pediatricians. Physicians licensed in Ohio were less likely to have specific domestic violence training (23% vs 60%) as compared with Kentucky physicians, where domestic violence education is required for licensing. Kentucky physicians were less likely to cite lack of education as barrier to DV screening (20% vs 62%). When comparing the characteristics of those who screen to those who do not, those with DV training were 10.9 times (odds adjusted ratio) more likely to screen. CONCLUSIONS: Practitioners grossly underestimate the incidence of DV in their practices. Lack of education including knowledge of screening recommendations is a barrier to DV screening by pediatricians. Greater efforts are needed to educate pediatricians on DV for the AAP recommendations to be accepted.domestic violence, child abuse, screening, physician attitude.

Genes that control the fidelity of endoplasmic reticulum to Golgi transport identified as suppressors of vesicle budding mutations.

Although convergent evidence suggests that proteins destined for export from the endoplasmic reticulum (ER) are separated from resident ER proteins and are concentrated into transport vesicles, the proteins that regulate this process have remained largely unknown. In a screen for suppressors of mutations in the essential COPII gene SEC13, we identified three genes (BST1, BST2/EMP24, and BST3) that negatively regulate COPII vesicle formation, preventing the production of vesicles with defective or missing subunits. Mutations in these genes slow the secretion of some secretory proteins and cause the resident ER proteins Kar2p and Pdi1p to leak more rapidly from the ER, indicating that these genes are also required for proper discrimination between resident ER proteins and Golgi-bound cargo molecules. The BST1 and BST2/EMP24 genes code for integral membrane proteins that reside predominantly in the ER. Our data suggest that the BST gene products represent a novel class of ER proteins that link the regulation of vesicle coat assembly to cargo sorting.

The origin of greater-than-unit-length plasmids generated during bacterial conjugation.

In Gram-negative bacteria, the general mechanism of conjugal plasmid transfer, which is probably similar for many different groups of plasmids, involves the transfer of a single plasmid DNA strand with 5' to 3' polarity. Transfer is initiated by nicking of the duplex DNA at a particular site, i.e. the origin of transfer (oriT). We constructed plasmids containing two directly repeated copies of oriT, derived from the broad-host-range plasmid R1162 and flanking the lac operator. The number of lacO copies in the plasmid after transfer could be determined from the colour of transconjugant colonies on medium containing X-Gal. When the oriTs were mutated to prevent initiation and termination of transfer at the same oriT, almost all of the transconjugant cells contained greater-than-unit-length plasmids with two copies of lacO and three copies of oriT. We show that these molecules were generated by an intramolecular, conjugation-dependent mechanism unlikely to depend solely on a pre-existing population of circular or linear multimers in donor cells. We propose that the greater-than-unit-length molecules were instead generated by a rolling-circle mechanism of DNA replication.

Recombination between directly repeated origins of conjugative transfer cloned in M13 bacteriophage DNA models ligation of the transferred plasmid strand.

When two, directly-repeated copies of the origin of transfer (oriT) of the conjugatively mobilizable, broad host-range plasmid R1162 are cloned into bacteriophage M13mp9 DNA, they undergo recombination in the presence of one of the R1162-encoded proteins required for mobilization [Meyer, R. (1989) J. Bacteriol., 171, 799-806]. Mutations in the outer arm of the inverted repeat within oriT inhibit this recombination. These mutations also affect a late step in transfer. We propose that recombination on the phage DNA models the processing of single-stranded DNA after entry into a recipient cell. The two, directly-repeated oriTs are not equivalent during the recombination reaction, because they are differently affected by the outer-arm mutations. A mutation was also isolated that reduces the specificity of the cleavage site in one of the two oriTs. Together, the results with the mutations suggest that phage recombinants can form only when the first cleavage occurs at one of the two oriTs. This is followed by the resulting free 3' end joining to the 5' end at the cleavage site of the other oriT.