Probing strongly exchange coupled magnetic behaviors in soft/hard Ni/CoFe2O4 core/shell nanoparticles

Exchange coupling in a model core-shell system is demonstrated as a step on the path to 3d exchange spring magnets. Employing a model system of Ni@CoFe2O4, high quality core-shell nanoparticles were fabricated using a simple two-step method. The microstructural quality was validated using TEM, confirming a well-defined interface between the core and the shell. A strongly temperature dependent two-phase magnetic hysteresis loop was measured, wherein an analysis of step heights indicates coupling of roughly 50% between the core and the shell. Element-specific XMCD hysteresis confirms the presence of exchange coupling, suppressing the superparamagnetism of the Ni core at room temperature, and reaching a coercivity of >6 kOe at 80 K. These results provide a pathway to the development of heterostructured metal-oxide exchange coupled nanoparticles with improved maximum energy product.

Multi-mode analysis of surface losses in a superconducting microwave resonator in high magnetic fields

This paper reports on a surface impedance measurement of a bulk metal niobium-titanium superconducting radio frequency (SRF) cavity in a magnetic field (up to 10 T). A novel method is employed to decompose the surface resistance contributions of the cylindrical cavity end caps and walls using measurements from multiple TM cavity modes. The results confirm that quality factor degradation of a NbTi SRF cavity in a high magnetic field is primarily from surfaces perpendicular to the field (the cavity end caps), while parallel surface resistances (the walls) remain relatively constant. This result is encouraging for applications needing high Q cavities in strong magnetic fields, such as the Axion Dark Matter eXperiment because it opens the possibility of hybrid SRF cavity construction to replace conventional copper cavities.

Spin pumping in magnetic trilayer structures with an MgO barrier

We present a study of the interaction mechanisms in magnetic trilayer structures with an MgO barrier grown by molecular beam epitaxy. The interlayer exchange coupling, Aex, is determined using SQUID magnetometry and ferromagnetic resonance (FMR), displaying an unexpected oscillatory behaviour as the thickness, tMgO, is increased from 1 to 4 nm. Transmission electron microscopy confirms the continuity and quality of the tunnelling barrier, eliminating the prospect of exchange arising from direct contact between the two ferromagnetic layers. The Gilbert damping is found to be almost independent of the MgO thickness, suggesting the suppression of spin pumping. The element-specific technique of x-ray detected FMR reveals a small dynamic exchange interaction, acting in concert with the static interaction to induce coupled precession across the multilayer stack. These results highlight the potential of spin pumping and spin transfer torque for device applications in magnetic tunnel junctions relying on commonly used MgO barriers.

Anisotropic Absorption of Pure Spin Currents

Spin transfer in magnetic multilayers offers the possibility of ultrafast, low-power device operation. We report a study of spin pumping in spin valves, demonstrating that a strong anisotropy of spin pumping from the source layer can be induced by an angular dependence of the total Gilbert damping parameter, α, in the spin sink layer. Using lab- and synchrotron-based ferromagnetic resonance, we show that an in-plane variation of damping in a crystalline Co_{50}Fe_{50} layer leads to an anisotropic α in a polycrystalline Ni_{81}Fe_{19} layer. This anisotropy is suppressed above the spin diffusion length in Cr, which is found to be 8 nm, and is independent of static exchange coupling in the spin valve. These results offer a valuable insight into the transmission and absorption of spin currents, and a mechanism by which enhanced spin torques and angular control may be realized for next-generation spintronic devices.

Study of Dy-doped Bi₂Te₃: thin film growth and magnetic properties

Breaking the time-reversal symmetry (TRS) in topological insulators (TIs) through ferromagnetic doping is an essential prerequisite for unlocking novel physical phenomena and exploring potential device applications. Here, we report the successful growth of high-quality (Dy(x)Bi(1-x))2Te3 thin films with Dy concentrations up to x = 0.355 by molecular beam epitaxy. Bulk-sensitive magnetisation studies using superconducting quantum interference device magnetometry find paramagnetic behaviour down to 2 K for the entire doping series. The effective magnetic moment, μeff, is strongly doping concentration-dependent and reduces from ∼12.6 μ(B) Dy(-1) for x = 0.023 to ∼4.3 μ(B) Dy(-1) for x = 0.355. X-ray absorption spectra and x-ray magnetic circular dichroism (XMCD) at the Dy M4,5 edge are employed to provide a deeper insight into the magnetic nature of the Dy(3+)-doped films. XMCD, measured in surface-sensitive total-electron-yield detection, gives μ(eff )= 4.2 μ(B) Dy(-1). The large measured moments make Dy-doped films interesting TI systems in which the TRS may be broken via the proximity effect due to an adjacent ferromagnetic insulator.

An ultra-compact, high-throughput molecular beam epitaxy growth system

We present a miniaturized molecular beam epitaxy (miniMBE) system with an outer diameter of 206 mm, optimized for flexible and high-throughput operation. The three-chamber system, used here for oxide growth, consists of a sample loading chamber, a storage chamber, and a growth chamber. The growth chamber is equipped with eight identical effusion cell ports with linear shutters, one larger port for either a multi-pocket electron beam evaporator or an oxygen plasma source, an integrated cryoshroud, retractable beam-flux monitor or quartz-crystal microbalance, reflection high energy electron diffraction, substrate manipulator, main shutter, and quadrupole mass spectrometer. The system can be combined with ultrahigh vacuum (UHV) end stations on synchrotron and neutron beamlines, or equivalently with other complex surface analysis systems, including low-temperature scanning probe microscopy systems. Substrate handling is compatible with most UHV surface characterization systems, as the miniMBE can accommodate standard surface science sample holders. We introduce the design of the system, and its specific capabilities and operational parameters, and we demonstrate the epitaxial thin film growth of magnetoelectric Cr2O3 on c-plane sapphire and ferrimagnetic Fe3O4 on MgO (001).

The effect of a Bacillus-based direct-fed microbial supplemented to sows on the gastrointestinal microbiota of their neonatal piglets

Direct-fed microbials (DFM) supplemented in sow diets may confer health benefits to the host and their piglets by reducing pathogens in the sow and environment. In this study we evaluated the effect of a Bacillus-based DFM on the gastrointestinal microbiota of neonatal piglets. A total of 208 sows were divided into 2 treatments: a control diet and the control diet supplemented with a Bacillus subtilis-based DFM (3.75 × 10(5) cfu/g feed). Twenty-one piglets sampled from each sow treatment group were euthanized on d 3 of lactation followed by an additional 15 piglets per treatment on d 10 of lactation. Litters from DFM-supplemented sows had greater (P = 0.02) weaning weights and a tendency (P = 0.09) for improvement in litter ADG. Sows supplemented with the DFM weaned more pigs (P = 0.06) than control sows which was reflected in numerically lower but not statistically different (P = 0.12) decrease in piglet mortality in DFM litters. Terminal RFLP was used to characterize gastrointestinal (GI) microbial populations in the ileum and colon of the piglets. Terminal restriction fragments (T-RF) were compared between control and DFM treatments. There was a greater incidence and quantity of T-RF B423 and H330 (binary P = 0.01, 0.08; quantitative P = 0.01, 0.05, respectively), putatively identified as Lactobacillus gasseri/johnsonii, in the ileum of pigs nursing sows supplemented with DFM at d 3. Terminal restriction fragment peaks B423 and H330 were also greater (binary P = 0.01, 0.08; quantitative P = 0.01, 0.01, respectively) in the colon of pigs nursing sows supplemented with DFM at d 3. Peaks M495 and B394, putatively identified as E. coli, were greater (binary P = 0.01, 0.04; quantitative P = 0.01, 0.01, respectively) in the colon of the control pigs at d 3. At d 10, both the presence and quantity of Lactobacillus species were greater (P < 0.05) in the colon of pigs with the DFM treatment. Additionally, there was a tendency for T-RF B227 and H257 (binary P = 0.07, 0.07, respectively), putatively identified as Clostridium perfringens, to be present in the ileum of the control pigs at d 10 compared with treated pigs. Results of this study reveal that the developing gastrointestinal microbiota of a neonatal piglet can be affected by DFM supplementation to the sow.

Effects of Visual and Auditory Short-Term Memory Tasks on the Spatiotemporal Dynamics and Variability of Postural Sway

The authors measured postural sway while participants (N = 20 in each experiment) stood on a rigid or a compliant surface, with their eyes open or closed, and while they did or did not perform a short-term memory (STM) task. In Experiment 1, the STM stimuli were presented visually; in Experiment 2, the stimuli were presented auditorily. In both experiments, fine-scaled, mediolateral postural-sway variability decreased as the cognitive load imposed by the STM task increased. That effect was independent of support surface and vision manipulations. The spatiotemporal profile of postural sway was affected by both visual and auditory STM tasks, but to a greater degree by the auditory task. The authors discuss implications of the results for theories and models of postural control.

Internal structure of the starch granule revealed by AFM

Atomic force microscopy images of sectioned native corn starch granules show evidence of the well-known radial organisation of the starch macromolecules, with the less-ordered hilum region near to the centre. Native granules show blocks 400-500 nm in size that span the growth rings. Lintnerised starch granules, where a mild acid hydrolysis has been used to remove the amorphous and less crystalline parts of the granule, clearly show smaller 'blocklets' within the rings approximately 10-30 nm in size. This level of organisation within the growth rings corresponds to the blocklet or superhelix structures that have been proposed in the literature for the association or clustering of amylopectin helices. Mechanical property imaging techniques have provided enhanced contrast to view this morphology, and shown the deformability of the starch structure under contact mode imaging conditions.

New insight into cellulose structure by atomic force microscopy shows the i(alpha) crystal phase at near-atomic resolution

The organization of the surface of cellulose is important in cell structure, as well as in industrial processing and modification. Using atomic force microscopy, we show that the I(alpha) phase of native cellulose first proposed in 1984 and subsequently characterized by a triclinic unit cell exists over large areas of the surface of microcrystals from Valonia, one of the most highly crystalline celluloses. There is startling agreement between the observed structure and crystal models, and it is possible to identify the specific crystal face being imaged. The near-atomic resolution images also offer an insight into structural reconstructions at the surface compared to the interior. We are able to assign features in the images to particular side groups attached to the glucose ring and find indications of subtle modifications of the position of surface hydroxyls due to changes in hydrogen bonding.

High-Resolution Atomic Force Microscopy of Native Valonia Cellulose I Microcrystals

We have studied the surface of native Valonia cellulose I microcrystals under propanol and waterby atomic force microscopy (AFM). Ultra-high-resolution images of the surface are presented, as well as lower resolution morphological observations of whole crystals. The pitch of 0.52 nm along the molecule due to the asymmetrical glucose unit and the intermolecular spacing of approximately 0.6 nm are clearly resolved in both imaging environments. The relationship between the crystalline bulk and the surface are discussed, with particular attention being paid to previous crystallographic studies. We also show that the glucose units along the cellulose chains are not topographically equivalent due to the twofold screw symmetry and accordingly present strong evidence of triclinic character by direct surface imaging, rather than by taking average measurements in reciprocal space. The crystallographic distinction between monoclinic and triclinic structure is a displacement of the cellulose chains by a quarter of the c axis period, resulting in either a stagger or a diagonal shifting, respectively, of the cellobiose unit along the chain axis by 0.26 nm. This structural identification (in real space) represents, as far as we are aware, the highest resolution AFM imaging of a biological specimen to date. This study opens up the future possibility of identifying the localized triclinic or monoclinic nature of the Valonia cellulose surface with AFM.

Effect of reduced daylight length on oestrus occurrence and superovulatory response in ewes treated with follicle stimulating hormone during the non-breeding season

Twenty-three non-pregnant merino ewes were divided randomly into two groups (A and B) during the non-breeding season (December and January). Group A (treated) was subjected to 16 hours of darkness and eight hours of daylight, while group B (control) was subjected to 14.5 hours of daylight per day. Seven ewes out of 12 from the treated group and five out of 11 from the control group showed oestrus within four weeks; the difference was not significant. Ewes from both groups were then superovulated with follicle stimulating hormone-P after 14 days of intravaginal sponge treatment. Following sponge withdrawal, group A manifested oestrus earlier (P less than 0.05), had more ovulations and subsequently more embryos were recovered (P less than 0.01) than group B. However, the subsequent oestrous cycle length and the functional lifespan of the resultant corpora lutea, as indicated by the plasma progesterone levels was the same in the two groups.

Ovarian response, ova recovery and fertility in merino ewes superovulated either during the luteal phase of their oestrous cycle or after intravaginal progestagen treatment

Five groups of merino ewes were treated with 1000 i.u. of pregnant mare serum gonadotropin (PMSG) as a single injection per ewe. Three of these groups received treatment on days 7,9 and 11 of their oestrous cycle. Oestrus was synchronized with 125 mg of prostaglandin F2(alpha) (PG) given two days after PMSG. Oestrus in the other two groups was synchronized by intravaginal progesterone sponges inserted for 14 days. In one group, the sponges were inserted nine days after oestrus onset. In the other group the stage of the oestrous cycle was unknown. In both these groups, PMSG was given a day prior to sponge removal. No significant differences were recorded for either the mean numbers of corpora lutea, unovulated follicles or ova recovery between the five groups. However, progestagen synchronized ewes yielded significantly more fertilized ova (p < 0.05) than PG synchronized ewes.

Unsuccessful attempts to collect ova by surgical fixation of uterine catheters in superovulated cows

Attempts were made to collect ova from superovulated cows by surgically fixing indwelling silastic balloon catheters in the uterine lumen. No ova were collected from the four catheterised cows and it was shown that ovarian activity was depressed. In this group, only 16 ovulations occurred compared with six control cows in which a total of 121 ovulations were recorded and 84 ova were collected. Also the ovaries of the catheterised cows had six large cysts, whereas no cysts were recorded in the control cows. The catheters flushed perfectly and bacteriological cultures of the flushing and uteri showed that no infections had occurred. The cows tolerated the catheters extremely well. There was no depression in appetite nor was any abnormal behaviour recorded. However, the severe depression of ovulation and the formation of ovarian cystic follicles prevents the technique from having any practical application as a means of collecting ova.

Transcervical transfer of bovine embryos

Six-to nine-day-old embryos collected either surgically or nonsurgically from superovulated donor cows were transferred transcervically to recipient cows. Polyethylene tubes and plastic insemination pipettes were used to transfer the embryos. When embryos were transferred under controlled conditions (laboratory transfer) to 12 recipients, 10 (83.3 per cent) and eight (66.7 per cent) were tested pregnant at 45 and 90 days after transfer respectively. When transfers were made to 12 recipients under field conditions (paddock transfer), nine (75 per cent) and five (41.7 per cent) were tested pregnant at 45 and 90 days after transfer respectively. The difference in pregnancy rates between laboratory and paddock transfers was not statistically significant.

Techniques of surgical and non-surgical ova collection of superovulated cows

A comparison is made of the results of ova collection from 65 superovulated cows of varying ages using the conventional surgical technique and a non-surgical (transcervical) technique. Two types of apparatus, rigid and flexible, were developed for non-surgical collections. The problems associated with these techniques are discussed and some remedial measures suggested. A mean of 9.8 ova per donor cow were recovered by the surgical method compared to 2.9 and 3.0 ova recovered by the transcervical method using flexible and rigid apparatus respectively. Eight young cows, which had not been previosly subjected to superovulation and embryo collection, yielded an average of 5.6 ova per donor by the non-surgical technique.

Preparation of teaser bulls by dorsal scrotal penile deflection

A simple, quick and reliable technique of preparing teaser bulls has been developed. Four Bos indicus aged between 1 year 6 months and 2 years were subjected to this method by deflecting their penes backwards about 2 to 3 cm posterior and dorsal to the attachment of the scrotum. No serious postoperative complications were recorded. The sexual behaviour and libido of the bulls did not change after subjecting them to this technique.

Serological studies in the elderly

Sera from 108 elderly patients in psychiatric and general hospitals were tested for antibodies to seven viruses. Measles virus antibody levels were significantly higher in patients from the psychiatric hospital, regardless of diagnosis, than in those from other hospitals. Demented patients, regardless of their hospital, had significantly higher levels of antibody to adenovirus than control patients.

Successful transfer of a bovine embryo through a cannulated fallopian tube

The fallopian tubes of a recipient cow were surgically cannulated and the cannulae brought out through the flank. Two fertilised eggs, recovered surgically from a donor cow, were transferred to the uterus of the recipient cow through the cannulae. The recipient became pregnant and gave birth to a live normal female calf 289 days after the transfer. After the birth of the calf one cannula was found to be patent.

Another style of psychogeriatric service

This paper describes a psychogeriatric service in Gloucestershire. Agreement on policies was reached with general practitioners, Social Services, other psychiatrists and hospital nursing staff. The day hospital is regarded as the preferred area of treatment for a wide variety of patients, including the severely demented. In this service less than five per cent of admissions appear to become long-stay. With emphasis on day hospital and community support the number of beds for this type of patient recommended by DHSS may be excessive.