Sign reversal of the Josephson inductance magnetochiral anisotropy and 0-π-like transitions in supercurrent diodes

The recent discovery of the intrinsic supercurrent diode effect, and its prompt observation in a rich variety of systems, has shown that non-reciprocal supercurrents naturally emerge when both space-inversion and time-inversion symmetries are broken. In Josephson junctions, non-reciprocal supercurrent can be conveniently described in terms of spin-split Andreev states. Here we demonstrate a sign reversal of the Josephson inductance magnetochiral anisotropy, a manifestation of the supercurrent diode effect. The asymmetry of the Josephson inductance as a function of the supercurrent allows us to probe the current-phase relation near equilibrium, and to probe jumps in the junction ground state. Using a minimal theoretical model, we can then link the sign reversal of the inductance magnetochiral anisotropy to the so-called 0-π-like transition, a predicted but still elusive feature of multichannel junctions. Our results demonstrate the potential of inductance measurements as sensitive probes of the fundamental properties of unconventional Josephson junctions.

Ultralong 100 ns spin relaxation time in graphite at room temperature

Graphite has been intensively studied, yet its electron spins dynamics remains an unresolved problem even 70 years after the first experiments. The central quantities, the longitudinal (T₁) and transverse (T₂) relaxation times were postulated to be equal, mirroring standard metals, but T₁ has never been measured for graphite. Here, based on a detailed band structure calculation including spin-orbit coupling, we predict an unexpected behavior of the relaxation times. We find, based on saturation ESR measurements, that T₁ is markedly different from T₂. Spins injected with perpendicular polarization with respect to the graphene plane have an extraordinarily long lifetime of 100 ns at room temperature. This is ten times more than in the best graphene samples. The spin diffusion length across graphite planes is thus expected to be ultralong, on the scale of ~ 70 μm, suggesting that thin films of graphite - or multilayer AB graphene stacks - can be excellent platforms for spintronics applications compatible with 2D van der Waals technologies. Finally, we provide a qualitative account of the observed spin relaxation based on the anisotropic spin admixture of the Bloch states in graphite obtained from density functional theory calculations.

Burn-injured patients - the preferably unheard

BACKGROUND

Data on colorectal cancer (CRC) diagnosis to treatment interval (DTI), an index of quality assurance in high-income countries (HICs) is lacking in South Africa. This study aimed to determine DTIs and their impact on CRC survival in a South African cohort.

METHODS

Participants (n = 289) from the Colorectal Cancer in South Africa (CRCSA) cohort were identified for inclusion. The DTI was defined as the duration between the diagnosis and initial definitive treatment and categorised into approximate quartiles (Q1-4). The DTI quartiles were 0-14 days, 15-28 days, 29-70 days, and ≥ 71 days. Overall survival (OS) was illustrated using the Kaplan-Meier method and compared between DTI groups using Cox proportional hazards (PH) regression.

RESULTS

There was no significant impact of the DTI (as quartiles) on overall CRC survival. The median length of time between DTI in this cohort was 29 days. Significant associations were identified between the DTI and self-reported ethnicity (p-value = 0.025), the site of the malignancy (colon vs rectum) (p-value < 0.0001), multidisciplinary team (MDT) review (p-value = 0.015) and the initial treatment modality (p-value < 0.0001).

CONCLUSION

Prolonged DTIs did not significantly impact survival for those with CRC in the CRCSA cohort. Symptom to diagnosis time should be investigated as a determinant of survival.

Revealing the impact of strain in the optical properties of bubbles in monolayer MoSe2

Strain plays an important role for the optical properties of monolayer transition metal dichalcogenides (TMDCs). Here, we investigate strain effects in a monolayer MoSe₂ sample with a large bubble region using μ-Raman, second harmonic generation (SHG), μ-photoluminescence and magneto μ-photoluminescence at low temperature. Remarkably, our results reveal the presence of a non-uniform strain field and the observation of emission peaks at lower energies which are the signatures of exciton and trion quasiparticles red-shifted by strain effects in the bubble region, in agreement with our theoretical predictions. Furthermore, we have observed that the emission in the strained region decreases the trion binding energy and enhances the valley g-factors as compared to non-strained regions. Considering uniform biaxial strain effects within the unit cell of the TMDC monolayer (ML), our first principles calculations predict the observed enhancement of the exciton valley Zeeman effect. In addition, our results suggest that the exciton-trion fine structure plays an important role for the optical properties of strained TMDC ML. In summary, our study provides fundamental insights on the behaviour of excitons and trions in strained monolayer MoSe₂ which are particularly relevant to properly characterize and understand the fine structure of excitonic complexes in strained TMDC systems/devices.

Patient perceptions of surgical training in the private sector in South Africa - a single centre survey

BACKGROUND

As the worldwide demand for specialist surgeons increases, and to complement surgical training provided through governmental institutions, private hospitals are increasingly hosting trainees. Wits Donald Gordon Medical Centre (WDGMC) is a private academic hospital in Johannesburg with a Colorectal Unit (CRU) that hosts several trainees. While published studies demonstrate that the involvement of trainees in surgery does not adversely impact outcomes, private patients' perceptions of the role of trainees in their care have not been as widely researched.

METHODS

This was a prospective, cross-sectional study using a self-administered questionnaire hosted on a REDCap database. Statistical analysis was performed using SPSS version 26.

RESULTS

One hundred and seventy-four patients participated in the study, and 74.1% of respondents felt that training of doctors should occur in private hospitals in South Africa. Of the sample, 83.3% would allow a supervised trainee to perform a part of their operation, provided they had been made aware of trainee participation in advance (78%). Sixty per cent of patients felt that interaction with a trainee enhanced their care, and 52.3% of patients suggested that seeing more than one doctor a day improved their experience.

CONCLUSION

Our results suggest that privately funded patients support the surgical training of medical doctors in private academic training hospitals, and they are willing to be participants in the training process. Moreover, training programmes in this setting appear to enhance the patient experience. We are optimistic that these findings could be used to advocate for expanded training opportunities across the private sector in South Africa.

Effect of Rashba and Dresselhaus spin-orbit coupling on supercurrent rectification and magnetochiral anisotropy of ballistic Josephson junctions

Simultaneous breaking of inversion- and time-reversal symmetry in Josephson junction (JJ) leads to a possible violation of theI(φ) = -I(-φ) equality for the current-phase relation. This is known as anomalous Josephson effect and it produces a phase shiftφ₀in sinusoidal current-phase relations. In ballistic JJs with non-sinusoidal current phase relation the observed phenomenology is much richer, including the supercurrent diode effect and the magnetochiral anisotropy (MCA) of Josephson inductance. In this work, we present measurements of both effects on arrays of JJs defined on epitaxial Al/InAs heterostructures. We show that the orientation of the current with respect to the lattice affects the MCA, possibly as the result of a finite Dresselhaus component. In addition, we show that the two-fold symmetry of the Josephson inductance reflects in the activation energy for phase slips.

Adult liver transplant for hepatocellular carcinoma at Wits Donald Gordon Medical Centre in Johannesburg, South Africa

BACKGROUND

For those with unresectable hepatocellular carcinoma, liver transplantation is considered the treatment of choice. Since 2006, the transplant programme at Wits Donald Gordon Medical Centre (WDGMC) has offered liver transplantation for selected patients with hepatocellular carcinoma. While the number of patients transplanted was small, we are unaware of any published data from Southern Africa describing outcomes in this group of liver transplant recipients. The aim of this study was to describe our experience as a case series.

METHODS

The records of all patients with HCC who underwent deceased donor liver transplantation between April 2006 and March 2018 were reviewed retrospectively. Data were extracted from transplant clinic patient files, histopathology and pathology laboratory reports and an existing database of all liver transplant recipients at WDGMC. Patient survival was calculated from the time of transplant and survival estimates were determined by the Kaplan-Meier method.

RESULTS

Thirty-one liver transplants were reviewed. The most common causes of underlying liver disease were infectious, mostly hepatitis B virus, and diseases of lifestyle including alcoholic/non-alcoholic steatohepatitis. Median age at transplant, 57 years (IQR 44-65 years), was younger than observed internationally, but consistent with reports from Africa. Male recipients predominated, in keeping with published trends. Overall, outcomes were worse than expected but for recipients who were within the University of California at San Francisco (UCSF) criteria for transplantation; survival was comparable to previously published data.

CONCLUSION

Despite limitations, this is the first documented series of patients undergoing liver transplantation for HCC in South Africa and demonstrates that good results can be achieved in appropriately selected patients.

Living donor liver transplantation in South Africa: the donor experience

BACKGROUND

Living donor liver transplantation (LDLT) plays a crucial role in liver transplant programmes, particularly in regions with a scarcity of deceased donor organs and especially for paediatric recipients. LDLT is a complex and demanding procedure which places a healthy living donor in harm's way. Donor safety is therefore the overriding concern. This study aimed to report our standardised approach to the evaluation, technical aspects and outcomes of LDLT donor hepatectomy at Wits Donald Gordon Medical Centre.

METHOD

The study population consisted of all patients undergoing LDLT donor hepatectomy since the inception of the programme in March 2013 until 2018. Sixty five living donor hepatectomies were performed. Primary outcome measures included donor demographics, operative time, peak bilirubin, aspartate and alanine transaminase levels postoperatively, length of hospital stay and postoperative complications using the Clavien-Dindo classification.

RESULTS

The majority of the donors were female, most were parents with mothers being the donor almost 85% of the time. The median operative time was 374 minutes with a downward trend over time as experience was gained. The median length of hospital stay was 7 days. There was no mortality and the complication rate was 30% with the majority being minor (Grade 1).

CONCLUSION

Living donor liver transplant from adult-to-child has been successfully initiated in South Africa. Living donor hepatectomy can be safely performed with acceptable outcomes for the donor. Wait-list mortality however remains unacceptably high. Expansion of LDLT as well as real change in deceased donor policy is required to address this issue.

Outcomes of paediatric liver transplant for biliary atresia

BACKGROUND

Despite the widespread use of Kasai Portoenterostomy (KPE) for biliary atresia, more than two thirds of these patients require liver transplant. Liver transplantation is not widely available in South Africa, and Wits Donald Gordon Medical Centre is one of two centres performing paediatric liver transplantation in the country, and the only centre performing living related donor transplants.

METHOD

A retrospective review was performed at the centre. Demographic data were collected, and tabulated. Survival analysis was performed using the Kaplan Meier method. Complication rates were categorised into biliary, vascular and enteric, and classified as early and late.

RESULTS

Sixty-seven first time liver transplants were performed for biliary atresia at WDGMC from 2005 to 2017. Sixty-nine percent were female patients and thirty-one percent were male patients. Forty-eight percent of patients under the age of 5 years had a z-score of -2 or worse for mid upper arm circumference (MUAC). One year overall survival of the cohort is 84.5%, and overall graft survival is 82.9%. Overall mortality was 22%, with infection being the most common cause of death.

CONCLUSION

Early referral of all patients with biliary atresia to a paediatric liver transplant centre is essential for early assessment of indications, and medical and nutritional optimisation of patients. Primary liver transplant should be considered for a select group of patients with unique clinical indications.

Lightwave valleytronics in a monolayer of tungsten diselenide

As conventional electronics is approaching its ultimate limits1, nanoscience has urgently sought for novel fast control concepts of electrons at the fundamental quantum level2. Lightwave electronics3 – the foundation of attosecond science4 – utilizes the oscillating carrier wave of intense light pulses to control the translational motion of the electron’s charge faster than a single cycle of light5–15. Despite being particularly promising information carriers, the internal quantum attributes of spin16 and valley pseudospin17–19 have not been switchable on the subcycle scale20–21. Here we demonstrate lightwave-driven changes of the valley pseudospin and introduce distinct signatures in the optical read out. Photogenerated electron–hole pairs in a monolayer of tungsten diselenide are accelerated and collided by a strong lightwave. The emergence of high odd-order sidebands and anomalous changes in their polarization direction directly attest to the ultrafast pseudospin dynamics. Quantitative computations combining density-functional theory with a non-perturbative quantum many-body approach assign the polarization of the sidebands to a lightwave-induced change of the valley pseudospin and confirm that the process is coherent and adiabatic. Our work opens the door to systematic valleytronic logic at optical clock rates.

Robust spin-orbit torque and spin-galvanic effect at the Fe/GaAs (001) interface at room temperature

Interfacial spin-orbit torques (SOTs) enable the manipulation of the magnetization through in-plane charge currents, which has drawn increasing attention for spintronic applications. The search for material systems providing efficient SOTs, has been focused on polycrystalline ferromagnetic metal/non-magnetic metal bilayers. In these systems, currents flowing in the non-magnetic layer generate—due to strong spin–orbit interaction—spin currents via the spin Hall effect and induce a torque at the interface to the ferromagnet. Here we report the observation of robust SOT occuring at a single crystalline Fe/GaAs (001) interface at room temperature. We find that the magnitude of the interfacial SOT, caused by the reduced symmetry at the interface, is comparably strong as in ferromagnetic metal/non-magnetic metal systems. The large spin-orbit fields at the interface also enable spin-to-charge current conversion at the interface, known as spin-galvanic effect. The results suggest that single crystalline Fe/GaAs interfaces may enable efficient electrical magnetization manipulation.

Interfacial spin-orbit torque allows electrical manipulation of magnetization, but this has been shown mostly in polycrystalline metal bilayers. Here the authors show robust spin-orbit torque in single crystalline Fe/GaAs interface at room temperature, observing conversion between spin and charge current.

Early Versus Delayed Autologous Stem Cell Transplantation and Interferon Maintenance in Multiple Myeloma: Single-Center Experience of 18 Years

BACKGROUND

Autologous stem cell transplantation (ASCT) has become the mainstay of 1st-line treatment in younger patients with multiple myeloma (MM), but statistical confirmation of its superiority over other therapies, especially in the era of novel agents, is still lacking.

METHODS

We reviewed the results of all 548 myeloma ASCTs performed in our institute over the past 18 years.

RESULTS

More than one-half of the patients had access to novel agents before their transplantations. Although the age of the transplanted patients increased significantly over the years, treatment-related mortality (TRM) was remarkably low, especially in 1st-line transplanted patients (100-day TRM, 0.3%). The median overall survival (OS) of the entire cohort was 98.4 months. Patients transplanted within 12 months from the start of their therapy had significantly better responses than those having delayed ASCT (complete response rate, 58.1% vs 46.8%; P = .016) and significant post-ASCT progression-free survival (PFS) benefit (30.2 [26.1-34.3] mo vs 23.3 [16.8-29.8] mo; P = .036), but we found no significant overall survival difference. The results were similar in patients treated with or without novel agents before ASCT. During a period of time, interferon maintenance was our standard approach to post-ASCT maintenance. Our analysis showed not only a significant PFS advantage with interferon, but also a highly significant overall survival benefit (150.4 [105.1-195.8] mo vs 86.1 [72.5-99.7] mo; P = .003).

CONCLUSIONS

Our findings demonstrate that delayed ASCT can be feasible in selected patients.

Anisotropic Polar Magneto-Optic Kerr Effect of Ultrathin Fe/GaAs(001) Layers due to Interfacial Spin-Orbit Interaction

We report the observation of the anisotropic polar magneto-optical Kerr effect in thin layers of epitaxial Fe/GaAs(001) at room temperature. A clear twofold symmetry of the Kerr rotation angle depending on the orientation of the linear polarization of the probing laser beam with respect to the crystallographic directions of the sample is detected for ultrathin magnetic films saturated out of the film plane. The amplitude of the anisotropy decreases with increasing Fe film thickness, suggesting that the interfacial region is the origin of the anisotropy. The twofold symmetry is fully reproduced by model calculations based on an interference of interfacial Bychkov-Rashba and Dresselhaus spin-orbit coupling.

Applying animal-based welfare assessments on New Zealand dairy farms: feasibility and a comparison with United Kingdom data

AIMS

To assess the feasibility of applying animal-based welfare assessments developed for use in Europe on New Zealand dairy farms; in particular, to identify measures which could be evaluated during a single visit at milking time alongside whole herd locomotion scoring.

METHODS

A protocol for animal welfare assessment, developed in the United Kingdom (UK), was evaluated. Measures that were suitable for use on pasture-based dairy farms in New Zealand were then assessed for practicability on 59 farms across New Zealand, during and immediately after milking, alongside whole herd locomotion scoring. Where data were collected the results were compared to those from a UK study of 53 dairy farms.

RESULTS

Thirteen observations of the physical condition of cows were considered suitable for measurement, excluding observations related to hock lesions as they are rarely observed on pasture-based farms. Five of these measures were not assessed as there was not time to do so during milking alongside whole herd locomotion scoring. Thus, the prevalence of dirty flanks, hind limbs and udders, dull coat, thick hairy coat, significant hair loss, very fat cows (body condition score (BCS) ≥7 on 1-10 scale) and very thin cows (BCS≤3), were recorded. Three measures of behaviour were considered suitable for measurement on-farm, but only locomotion score was practicable and was measured. Farmer-estimates for the incidence of mastitis, lameness, sudden death, milk fever and other diseases were also obtained.Overall, dirty flanks, dirty udders and estimated milk fever incidence were more prevalent in this study than in the UK. The prevalence of thin and fat cows, lame cows and estimated mastitis incidence were much lower in the present study than on UK farms.

CONCLUSIONS AND CLINICAL RELEVANCE

Animal-based assessments can be used on dairy farms in New Zealand, but need to be modified from those developed for housed cows.Welfare on these farms was generally good compared to those in the UK, but these results need to be confirmed on more farms using a wider range of assessments than proved practicable in this study.

Electric Field Control of Spin Lifetimes in Nb-SrTiO_{3} by Spin-Orbit Fields

We show electric field control of the spin accumulation at the interface of the oxide semiconductor Nb-SrTiO_{3} with Co/AlO_{x} spin injection contacts at room temperature. The in-plane spin lifetime τ_{∥}, as well as the ratio of the out-of-plane to in-plane spin lifetime τ_{⊥}/τ_{∥}, is manipulated by the built-in electric field at the semiconductor surface, without any additional gate contact. The origin of this manipulation is attributed to Rashba spin orbit fields (SOFs) at the Nb-SrTiO_{3} surface and shown to be consistent with theoretical model calculations based on SOF spin flip scattering. Additionally, the junction can be set in a high or low resistance state, leading to a nonvolatile control of τ_{⊥}/τ_{∥}, consistent with the manipulation of the Rashba SOF strength. Such room temperature electric field control over the spin state is essential for developing energy-efficient spintronic devices and shows promise for complex oxide based (spin) electronics.

Tunneling Anomalous and Spin Hall Effects

We predict, theoretically, the existence of the anomalous Hall effect when a tunneling current flows through a tunnel junction in which only one of the electrodes is magnetic. The interfacial spin-orbit coupling present in the barrier region induces a spin-dependent momentum filtering in the directions perpendicular to the tunneling current, resulting in a skew tunneling even in the absence of impurities. This produces an anomalous Hall conductance and spin Hall currents in the nonmagnetic electrode when a bias voltage is applied across the tunneling heterojunction. If the barrier is composed of a noncentrosymmetric material, the anomalous Hall conductance and spin Hall currents become anisotropic with respect to both the magnetization and crystallographic directions, allowing us to separate this interfacial phenomenon from the bulk anomalous and spin Hall contributions. The proposed effect should be useful for proving and quantifying the interfacial spin-orbit fields in metallic and metal-semiconductor systems.

Emergence of spin-orbit fields in magnetotransport of quasi-two-dimensional iron on gallium arsenide

The desire for higher information capacities drives the components of electronic devices to ever smaller dimensions so that device properties are determined increasingly more by interfaces than by the bulk structure of the constituent materials. Spintronic devices, especially, benefit from the presence of interfaces—the reduced structural symmetry creates emergent spin–orbit fields that offer novel possibilities to control device functionalities. But where does the bulk end, and the interface begin? Here we trace the interface-to-bulk transition, and follow the emergence of the interfacial spin–orbit fields, in the conducting states of a few monolayers of iron on top of gallium arsenide. We observe the transition from the interface- to bulk-induced lateral crystalline magnetoanisotropy, each having a characteristic symmetry pattern, as the epitaxially grown iron channel increases from four to eight monolayers. Setting the upper limit on the width of the interface-imprinted conducting channel is an important step towards an active control of interfacial spin–orbit fields.

Broken symmetry at material interfaces allows for novel spintronic functionality via emergent spin–orbit effects. Here, Hupfauer et al. follow the interface-to-bulk transition of ultra-thin epitaxial iron films on gallium arsenide via anisotropic magnetoresistance measurements and first-principle calculations.

Quality-of-life for individuals with a vestibular impairment following an acquired brain injury (ABI); the clients' perspective

PRIMARY OBJECTIVE

To investigate how a vestibular deficit following an acquired brain injury (ABI) affects an individuals' quality-of-life.

RESEARCH DESIGN

A qualitative exploratory design.

PARTICIPANTS

Nine community dwelling individuals who experienced significant symptoms and limitations as a result of their vestibular deficits.

METHODS

The individuals participated in face-to-face interviews with open ended questions. Data was analysed initially using a case study research approach, exploring the experience for each individual and then cross-case analysis to determine common themes for the group with the assistance of nVivo 10 qualitative analysis software.

RESULTS

Thematic analysis determined four main themes arising from the interviews; (1) validation, (2) definitive diagnosis is more difficult amongst an array of ABI symptoms, (3) vestibular adaptation is more difficult in the presence of an ABI and (4) emotional and social.

CONCLUSION

Individuals who suffer a brain injury and experience vestibular symptoms as part of their overall presentation are not diagnosed in a timely manner, with individuals, their families, associates and even health professionals feeling uncertain of the legitimacy of their reported symptoms. It is important that all patients who experience an acquired brain injury are screened for vestibular impairment and, if necessary, receive vestibular rehabilitation including explanation and education.

Synthese und Eigenschaften von 3-Äthoxy-1.2-dithiolium-Salzen

Die farblosen, feuchtigkeitsempfindlichen 3-Äthoxy-1.2-dithioliumfluoborate (1, X = BF4) können durch Umsetzung von 1.2-Dithiolonen- (3) (2) mit Triäthyloxoniumfluoborat in Dichlormethan erhalten werden. Das Fluoborat-Anion ist austauschbar, ein nucleophiler Angriff ist an verschiedenen Stellen des reaktionsfähigen Moleküls möglich. Dialkylsulfate, Alkyltosylate und Alkylhalogenide sind zur Alkylierung der 2 ungeeignet, die Umsetzung von 3-Chlor-1.2-dithiolium-Salzen (4) mit Alkoholen führt ebenfalls nicht zu 3-Alkoxy-1.2-dithiolium-Verbindungen.

Die charakteristischen Absorptionen der 3-Äthoxy-1.2-dithioliumionen (1) im Ultravioletten werden angegeben und durch SCF-LCI-PPP-Berechnungen theoretisch abgeleitet. Ein Vergleich dieser Absorptionen mit den Spektren der 1.2-Dithiolone-(3) (2) in konzentrierter Schwefelsäure zeigt, daß die Carbonyl-Verbindungen unter diesen Bedingungen am Sauerstoff protoniert werden.

Bandstruktur der linearen Polyacene

For infinite polyacenes the energy gap (ΔE∞) is given by ΔE = , where Δcorr is a factor determined by the electronic correlation and Δgeom is a molecular geometry dependent factor. We find in the selected case Δcorr>Δgeom .The energy gap values calculated with this formula are in good agreement with the values calculated from the spectroscopic data of polyacenes (0.8-0.9 eV).

Synthese und UV-Spektrum von Thiopyrano[4.3-b]indol

Thiopyrano[4.3-b]indol (1) wird durch Dehydrierung von Tetra-hydro-1 mit Chloranil erhalten und durch das UVS-Spektrum charakterisiert. SCF-LCI-PPP-Berechnungen werden auf Aza-schwefelheterocyclen ausgedehnt und zur Berechnung des Spektrums von 1 verwendet.

The prevalence of lameness on New Zealand dairy farms: a comparison of farmer estimate and locomotion scoring

Lameness is a significant welfare and economic issue in all dairy systems. However, there is only a limited amount of published data on the incidence and prevalence of lameness in the pasture-based systems used in New Zealand. One key area where knowledge is lacking is how well farmer perception of lameness matches that identified by more objective locomotion scoring. Previous studies of this topic have focussed on housed cows. Fifty-nine herds, 26 based in the South Island and 33 in the North Island, were surveyed. All farms were visited on one occasion at the expected peak time for lameness, and data were collected via a questionnaire which included details on farm size, and productivity as well as lameness. The latter included a farmer estimate of the number of lame cows which were currently on-farm and the number of lame cows there had been in the previous 12 months. Whole herd locomotion scoring, using the DairyCo 0-3 scale, was then used to estimate the prevalence of lameness in the herd. Farmers estimated that between 0 and 20% of their herd was lame (mean 2.2%), while locomotion scoring identified that between 1.2% and 36% of a herd was lame (mobility score ≥ 2; mean 8.1%). This finding indicated that, on a herd basis, only 27.3% (range 0-95%) of the cows with reduced mobility had been identified as such. There was no significant effect of herd size or geographical location on this percentage. The prevalence of lameness in this study was much lower than that reported in housed cattle, but the percentage of cows with reduced mobility recognised as lame was very similar. There is significant room for improvement in the detection of lameness on New Zealand farms, where routine mobility scoring, particularly at critical periods, could prove a valuable tool.

Magnetic quantum ratchet effect in graphene

A periodically driven system with spatial asymmetry can exhibit a directed motion facilitated by thermal or quantum fluctuations. This so-called ratchet effect has fascinating ramifications in engineering and natural sciences. Graphene is nominally a symmetric system. Driven by a periodic electric field, no directed electric current should flow. However, if the graphene has lost its spatial symmetry due to its substrate or adatoms, an electronic ratchet motion can arise. We report an experimental demonstration of such an electronic ratchet in graphene layers, proving the underlying spatial asymmetry. The orbital asymmetry of the Dirac fermions is induced by an in-plane magnetic field, whereas the periodic driving comes from terahertz radiation. The resulting magnetic quantum ratchet transforms the a.c. power into a d.c. current, extracting work from the out-of-equilibrium electrons driven by undirected periodic forces. The observation of ratchet transport in this purest possible two-dimensional system indicates that the orbital effects may appear and be substantial in other two-dimensional crystals such as boron nitride, molybdenum dichalcogenides and related heterostructures. The measurable orbital effects in the presence of an in-plane magnetic field provide strong evidence for the existence of structure inversion asymmetry in graphene.

Spin edge helices in a perpendicular magnetic field

We present an exact solution to the problem of the spin edge states in the presence of equal Bychkov-Rashba and Dresselhaus spin-orbit fields in a two-dimensional electron system, restricted by a hard-wall confining potential and exposed to a perpendicular magnetic field. We find that the spectrum of the spin edge states depends critically on the orientation of the sample edges with respect to the crystallographic axes. Such a strikingly different spectral behavior generates new modes of the persistent spin helix-spin edge helices with novel properties, which can be tuned by the applied electric and magnetic fields.

Theory of the spin relaxation of conduction electrons in silicon

A realistic pseudopotential model is introduced to investigate the phonon-induced spin relaxation of conduction electrons in bulk silicon. We find a surprisingly subtle interference of the Elliott and Yafet processes affecting the spin relaxation over a wide temperature range, suppressing the significance of the intravalley spin-flip scattering, previously considered dominant, above roughly 120 K. The calculated spin relaxation times T1 agree with the spin resonance and spin injection data, following a T(-3) temperature dependence. The valley anisotropy of T1 and the spin relaxation rates for hot electrons are predicted.

Tunneling anisotropic magnetoresistance and spin-orbit coupling in Fe/GaAs/Au tunnel junctions

We report the observation of tunneling anisotropic magnetoresistance effect in the epitaxial metal-semiconductor system Fe/GaAs/Au. The observed twofold anisotropy of the resistance can be switched by reversing the bias voltage, suggesting that the effect originates from the interference of the spin-orbit coupling at the interfaces. Corresponding model calculations reproduce the experimental findings very well.

Chronic kidney disease in human immunodeficiency virus infection

The number of people living with human immunodeficiency virus (HIV) worldwide was estimated to be 39.5 million in 2006, 2.6 million more than in 2004. The manifestations of HIV infection in the kidney are multiple and varied, highlighting the complexity of the disease process. There is a wide spectrum of renal disease that occurs in the course of HIV infection. Biopsy studies reveal varying frequencies of histological patterns. HIV-associated nephropathy (HIVAN) is most common. A biopsy study at Chris Baragwanath Hospital in Soweto, South Africa showed that HIVAN was present in 27% and immune complex disease in 21%. Han et al. studied HIV-positive patients in Durban, South Africa and screened for proteinuria, including microalbuminuria. They found persistent proteinuria in 6%; HIVAN in 21/30 (72.4%) and the prevalence of HIVAN in patients with persistent microalbuminuria was 85.7%. Studies in black patients have shown a higher prevalence of both severe glomerular lesions (focal glomerulosclerosis) and nephrotic range proteinuria with renal dysfunction in the presence of normo-hypotension. There have been no prospective randomised controlled studies with any form of therapy for HIVAN to date. Therapy of HIVAN has included corticosteroids, cyclosporine and antiretroviral therapy (ART). ART appears to be a logical choice in the management of HIV-associated renal disease. Regimens containing protease inhibitors have been shown to be associated with significant slowing of the decline in creatinine clearance. Both peritoneal dialysis and haemodialysis are appropriate treatment modalities for HIV-infected patients with end stage renal disease. The choice of dialysis modality between haemodialysis and peritoneal dialysis is not a factor in predicting survival, if patients are stable on ART. Preliminary short-term data in case reports and small cohorts of liver, kidney, and heart transplant recipients suggest that patient survival rates may be similar to those in HIV-uninfected transplant recipients. However, high rates of acute and chronic rejection have been observed among HIV-infected kidney transplant recipients. The Infectious Diseases Society of America (IDSA) published guidelines in 2005, recommending that all individuals be assessed for kidney disease at the time of diagnosis of HIV infection with a screening urinalysis for proteinuria and a calculated estimate of renal function. Therefore any patient with persistent proteinuria, persistent haematuria or glomerular filtration rate < 60 mL/min per 1.73 m(2) should be referred to an institution where a specialist can evaluate this patient for further investigations. An integrated plan to reduce the progression to kidney failure together with lifestyle measures, focusing also on high risk groups with effective management at all levels of chronic kidney disease remains essential.