Gate-defined graphene quantum point contact in the quantum Hall regime

We investigate transport in a gate-defined graphene quantum point contact in the quantum Hall regime. Edge states confined to the interface of p and n regions in the graphene sheet are controllably brought together from opposite sides of the sample and allowed to mix in this split-gate geometry. Among the expected quantum Hall features, an unexpected additional plateau at 0.5h/e2 is observed. We propose that chaotic mixing of edge channels gives rise to the extra plateau.

Gate-controlled guiding of electrons in graphene

Ballistic semiconductor structures have allowed the realization of optics-like phenomena in electronic systems, including the magnetic focusing and electrostatic lensing of electrons. An extension that appears unique to graphene is to use both n and p carrier types to create electronic analogues of optical devices with both positive and negative indices of refraction. Here, we use the gate-controlled density of both p and n carrier types in graphene to demonstrate the electronic analogue of fibre-optic guiding. Two basic effects are investigated: bipolar p-n junction guiding, based on the principle of angle-selective transmission through the interface between the graphene and the p-n junction; and unipolar fibre-optic guiding, using total internal reflection controlled by carrier density. We also demonstrate modulation of the guiding efficiency through gating, and comparison of these data with numerical simulations indicates that guiding performance is limited by the roughness of the interface. The development of p-n and fibre-optic guiding in graphene may lead to electrically reconfigurable wiring in high-mobility devices.

Precision cutting and patterning of graphene with helium ions

We report nanoscale patterning of graphene using a helium ion microscope configured for lithography. Helium ion lithography is a direct-write lithography process, comparable to conventional focused ion beam patterning, with no resist or other material contacting the sample surface. In the present application, graphene samples on Si/SiO2 substrates are cut using helium ions, with computer controlled alignment, patterning, and exposure. Once suitable beam doses are determined, sharp edge profiles and clean etching are obtained, with little evident damage or doping to the sample. This technique provides fast lithography compatible with graphene, with approximately 15 nm feature sizes.

Evidence for an excited-state Efimov trimer in a three-component Fermi gas

We observe enhanced three-body recombination in a three-component ;{6}Li Fermi gas attributable to an excited Efimov trimer state intersecting the three-atom scattering threshold near 895 G. From measurements of the recombination rate we determine the Efimov parameters kappa_{*} and eta_{*} for the universal region above 600 G which includes three overlapping Feshbach resonances. The value of kappa_{*} also predicts the locations of loss features previously observed near 130 and 500 G [T. B. Ottenstein, Phys. Rev. Lett. 101, 203202 (2008)10.1103/PhysRevLett.101.203202; J. H. Huckans, Phys. Rev. Lett. 102, 165302 (2009)10.1103/PhysRevLett.102.165302] suggesting they are associated with a ground-state Efimov trimer near threshold. We also report on the realization of a degenerate three-component Fermi gas with approximate SU(3) symmetry.

Three-body recombination in a three-state Fermi gas with widely tunable interactions

We investigate the stability of a three spin state mixture of ultracold fermionic 6Li atoms over a range of magnetic fields encompassing three Feshbach resonances. For most field values, we attribute decay of the atomic population to three-body processes involving one atom from each spin state and find that the three-body loss coefficient varies by over 4 orders of magnitude. We observe high stability when at least two of the three scattering lengths are small, rapid loss near the Feshbach resonances, and two unexpected resonant loss features. At our highest fields, where all pairwise scattering lengths are approaching a_{t}=-2140a_{0}, we measure a three-body loss coefficient L_{3} approximately 5x10;{-22} cm;{6}/s and a trend toward lower decay rates for higher fields indicating that future studies of color superfluidity and trion formation in a SU(3) symmetric Fermi gas may be feasible.

The management dilemmas of invasive subglottic carcinoma

AIMS

To evaluate a single centre's experience with subglottic laryngeal carcinoma.

MATERIALS AND METHODS

The laryngeal cancer database at the Prince of Wales Hospital was sourced to define a sub-population of patients presenting with primary subglottic carcinoma. Excluded from the analysis were patients having a glottic origin for their carcinoma and secondarily involving the subglottis.

RESULTS

Of 969 patients with newly diagnosed laryngeal cancer, 10 (1%) had subglottic origin. T stage was six T2 and four T3, all were N0. A total laryngectomy was carried out in five patients, four of whom had postoperative radiotherapy, a hemilaryngectomy in one patient and definitive radiotherapy in four patients. There was only one local failure, who could not be salvaged, and one patient died locally controlled with metastatic disease. Thus, local control was achieved in nine of 10 patients.

CONCLUSION

Although an infrequent sub-population, subglottic carcinoma has a high likelihood of being locally controlled.

Relationship between disc injury and manual lifting: a poroelastic finite element model study

Understanding how failure originates in a lumbar motion segment subjected to loading conditions that are representative of manual lifting is important because it will pave the way for a better formulation of the exposure-injury relationship. The aim of the current investigation was to use a poroelastic finite element model of a human lumbar disc to determine its biomechanical characteristics under loading conditions that corresponded to three different, commonly occurring lifting activities and to identify the most hazardous type of loading with regard to damage to the disc. The current study showed that asymmetric lifting may increase the risk of back injury and pain. Lifting that involved lateral bending (asymmetric lifting) of the trunk was found to produce stresses at a localized area in the annulus, annuluar fibres, end plates, and facet joints that were higher than their respective tissue failure strength. Thus asymmetric lifting, if performed over a large number of cycles, might help to propagate this localized failure of the disc tissue to a larger area, owing to fatigue. The analyses also showed that largest fluid exchange between the nucleus and the end plates occurred during asymmetric lifting. If the fluid exchange is restricted owing to end plate calcification or sclerosis of the subchondral bone, high intradiscal pressure might develop, leading to higher disc bulge causing back pain.

Shot noise in graphene

We report measurements of current noise in single-layer and multilayer graphene devices. In four single-layer devices, including a p-n junction, the Fano factor remains constant to within +/-10% upon varying carrier type and density, and averages between 0.35 and 0.38. The Fano factor in a multilayer device is found to decrease from a maximal value of 0.33 at the charge-neutrality point to 0.25 at high carrier density. These results are compared to theories for shot noise in ballistic and disordered graphene.

Medulloblastomas-primitive neuroectodermal tumours in the adult population

Medulloblastomas - primitive neuroectodermal tumours are rare in adults. This review will evaluate a single centre's experience with this malignancy. The medulloblastoma - primitive neuroectodermal tumour database was evaluated for all patients aged more than 18 years who were referred for management. Relevant information from the database was abstracted to provide a descriptive record of this malignancy. Between 1977-2004 there were 11 patients referred, 1 with persistent disease and 10 were eligible, presenting with initial diagnosis. There was increased intracranial pressure in 50% of patients. Most patients had symptoms >3 months, with three having symptoms 1-3 months before diagnosis and one patient having thoracic dural metastases at presentation. Complete resection was recorded in four patients and six had 50-90% resection. All patients completed craniospinal radiotherapy (35-36 Gy at 1.8-2.0 Gy fractions) barring one patient, who died of surgical complications during his radiotherapy. Chemotherapy was given in five of the nine patients postradiotherapy. There were two posterior fossa recurrences, with associated supratentorial and extra central nervous system disease. Of the 10 primary patients 7 are alive with no evidence of disease, 2 died because of disease, with 1 intercurrent death. One patient developed a second malignancy. The outcome for adults matches that of the more common paediatric patients. Radiotherapy could control local disease even where complete resection was not achieved.

Quantum Hall Effect in a Gate-Controlled p-n Junction of Graphene

The unique band structure of graphene allows reconfigurable electric-field control of carrier type and density, making graphene an ideal candidate for bipolar nanoelectronics. We report the realization of a single-layer graphene p-n junction in which carrier type and density in two adjacent regions are locally controlled by electrostatic gating. Transport measurements in the quantum Hall regime reveal new plateaus of two-terminal conductance across the junction at 1 and 32 times the quantum of conductance, e(2)/h, consistent with recent theory. Beyond enabling investigations in condensed-matter physics, the demonstrated local-gating technique sets the foundation for a future graphene-based bipolar technology.

Test of APEX for nine forested watersheds in East Texas

Hydrologic/water quality models are increasingly used to explore management and policy alternatives for managing water quality and quantity from intensive silvicultural practices with best management practices (BMPs) in forested watersheds due to the limited number of and cost of conducting watershed monitoring. The Agricultural Policy/Environmental eXtender (APEX) model was field-tested using 6 yr of data for flow, sediment, nutrient, and herbicide losses collected from nine small (2.58 to 2.74 ha) forested watersheds located in southwest Cherokee County in East Texas. Simulated annual average stream flow for each of the nine watersheds was within +/- 7% of the corresponding observed values; simulated annual average sediment losses were within +/- 8% of measured values for eight out of nine watersheds. Nash-Sutcliffe efficiency (EF) values ranged from 0.68 to 0.94 based on annual stream flow comparison and from 0.60 to 0.99 based on annual sediment comparison. Similar to what was observed, simulated flow, sediment, organic N, and P were significantly increased on clear-cut watersheds compared with the control watersheds. APEX reasonably simulated herbicide losses, with an EF of 0.73 and R(2) of 0.74 for imazapyr, and EF of 0.65 and R(2) of 0.68 for hexazinone based on annual values. Overall, the results show that APEX was able to predict the effects of silvicultural practices with BMPs on water quantity and quality and that the model is a useful tool for simulating a variety of responses to forest conditions.

Mercury pollution from irrigation with treated sewage water (TSW)

The lack of potable water in arid countries leads to the use of treated sewage water (TSW) for crop growth. Mercury accumulation (up to 500 ng/g) in agricultural soil originating from daily irrigation with TSW was found at two sites fed separately from a hospital sewage plant and an industrial plant. A control site irrigated with potable water ([Hg] <0.01 ng/ml) had much reduced levels in soil (<12 ng/g). Cold-vapour analysis of TSW revealed that Hg concentrations fluctuated widely, and were between 10-100 times higher than those of potable water. The TSW data originated from a total of 46 samples (1 L each), from both plants, collected over a 6-month period. The Hg levels varied from 0.1 to 1.0 ng/ml, which suggested that the possible source of the accumulation could be found in continuous irrigation with comparatively higher Hg levels. Remedial measures could be approached from the perspective of curbing this inconsistency to produce more consistent Hg concentrations below 0.5 ng/ml. It was found that the electrical conductivity of TSW is a useful indicator to rapidly monitor fluctuations in treatment. A novel development in the study was the potential capacity of the plastic TSW discharge-pipes to behave as crude 'chromatographic' columns for possible Hg adsorption. If this property of the pipes is developed further it could have a considerable mitigating effect on the Hg levels. Possible recommendations for remediation to limit the Hg levels and promote sustainable development are discussed.

Bonding at the SiC-SiO2 interface and the effects of nitrogen and hydrogen

Unlike the Si-SiO2 interface, the SiC-SiO2 interface has large defect densities. Though nitridation has been shown to reduce the defect density, the effect of H remains an open issue. Here we combine experimental data and the results of first-principles calculations to demonstrate that a Si-C-O bonded interlayer with correlated threefold-coordinated C atoms accounts for the observed defect states, for passivation by N and atomic H, and for the nature of residual defects.

What is the achievable effectiveness of the India AIDS Initiative intervention among female sex workers under target coverage? Model projections from southern India

BACKGROUND

The India AIDS Initiative (Avahan) prevention programme funded by the Bill and Melinda Gates Foundation aims to reduce HIV prevalence in high risk groups such as female and male sex workers and their clients, to limit HIV transmission in the general population.

OBJECTIVES

To assess the potential effectiveness of the Avahan intervention at the level of coverage targeted, in different epidemiological settings in India.

METHODS

A deterministic compartmental model of the transmission dynamics of HIV and two sexually transmitted infections, and sensitivity analysis techniques, were used, in combination with available behavioural and epidemiological data from Mysore and Bagalkot districts in the Indian state of Karnataka, to evaluate the syndromic sexually transmitted infection (STI) management (STI treatment), periodic presumptive treatment of STI (PPT), and condom components of the Avahan intervention targeted to female sex workers (FSW).

RESULTS

If all components of the intervention reach target coverage (that is, PPT, STI treatment and condom use), the intervention is expected to prevent 22-35% of all new HIV infections in FSW and in the total population over 5 years in a low transmission setting like Mysore, and to be half as effective in high transmission settings such as Bagalkot. The results were sensitive to small variations in intervention coverage. The condom component alone is expected to prevent around 20% of all new HIV infections over 5 years in Mysore and around 6% for the STI component alone; compared with 7%-14% for the PPT component alone. Multivariate sensitivity analyses suggested that interventions may be more effective in settings with low FSW HIV prevalence and small FSW populations, whereas HIV prevalence was most influenced by sexual behaviour and condom use parameters for FSW.

CONCLUSION

The Avahan intervention is expected to be effective. However, to be able to demonstrate effectiveness empirically in the different settings, it is important to achieve target coverage or higher, which in the case of PPT could take a number of years to achieve. These preliminary model predictions need to be validated with more detailed mathematical models, as better data on sexual behaviour, condom use, STI and HIV trends over time, and intervention coverage data accumulate over the course of the programme.

Simulating long-term and residual effects of nitrogen fertilization on corn yields, soil carbon sequestration, and soil nitrogen dynamics

Soil carbon sequestration (SCS) has the potential to attenuate increasing atmospheric CO2 and mitigate greenhouse warming. Understanding of this potential can be assisted by the use of simulation models. We evaluated the ability of the EPIC model to simulate corn (Zea mays L.) yields and soil organic carbon (SOC) at Arlington, WI, during 1958-1991. Corn was grown continuously on a Typic Argiudoll with three N levels: LTN1 (control), LTN2 (medium), and LTN3 (high). The LTN2 N rate started at 56 kg ha(-1) (1958), increased to 92 kg ha(-1) (1963), and reached 140 kg ha(-1) (1973). The LTN3 N rate was maintained at twice the LTN2 level. In 1984, each plot was divided into four subplots receiving N at 0, 84, 168, and 252 kg ha(-1). Five treatments were used for model evaluation. Percent errors of mean yield predictions during 1958-1983 decreased as N rate increased (LTN1 = -5.0%, LTN2 = 3.5%, and LTN3 = 1.0%). Percent errors of mean yield predictions during 1985-1991 were larger than during the first period. Simulated and observed mean yields during 1958-1991 were highly correlated (R2 = 0.961, p < 0.01). Simulated SOC agreed well with observed values with percent errors from -5.8 to 0.5% in 1984 and from -5.1 to 0.7% in 1990. EPIC captured the dynamics of SOC, SCS, and microbial biomass. Simulated net N mineralization rates were lower than those from laboratory incubations. Improvements in EPIC's ability to predict annual variability of crop yields may lead to improved estimates of SCS.

Optimization of a High-Performance Liquid Chromatography Method to Quantify Bilirubin and Separate It From Its Photoproducts: Effect of Column Length, pH, Mobile Phase Composition, and Flow Rate

A rapid reversed-phase (RP) high-performance liquid chromatography method for the isolation of bilirubin from its photoproducts (e.g., biliverdin) is reported. The method is based on isocratic elution using methanol:water as the mobile phase. A 24 full-factorial experimental design approach was adopted. For the optimization, the best separation was obtained using a flow rate of 1.50 mL/min, a mobile phase of 99:1 methanol:water (v/v) at pH 3.60, and a 150 x 4.6 mm id RP (C18) column containing 5-microm particles. These conditions produced the fastest total retention time of 3.38 +/- 0.055 min, and other chromatographic parameters were acceptable. Under the optimum conditions, a linear calibration curve for bilirubin was obtained over the 1.0-40.0 microg/L concentration range studied. The limit of quantification was 0.79 g/L and the limit of detection was 0.24 microg/L. Bilirubin in solution was monitored by ultraviolet detection at 450 nm.

Vascular endothelial growth factor receptors in osteoclast differentiation and function

Osteoclasts are derived from haematopoietic stem cell precursors of the monocyte/macrophage cell lineage, through interaction with factors that are believed to include M-CSF and RANKL. VEGF is a proangiogenic cytokine that has been shown to promote osteoclast differentiation and survival. In this study, we assessed the role of VEGF and its receptors in osteoclastogenesis, in vitro, by culturing osteoclast precursors in the presence of VEGF, VEGF receptor-specific ligands, and blocking antibodies to VEGF receptors. Activation of VEGFR1 in the presence of RANKL induces osteoclast differentiation. Stimulating the receptors individually induced increased resorption by osteoclasts compared to controls but not to the level observed when stimulating both receptors simultaneously. We have shown that VEGF induces osteoclast differentiation through its action on VEGFR1. The way in which VEGF mediates its effect on mature osteoclast activity, however, may be through its interaction with both receptor subtypes.

Impaired forearm rotation after tension-band-wiring fixation of olecranon fractures: evaluation of the transcortical K-wire technique

The tension-band-wiring technique is a well-accepted method of internal fixation of olecranon fractures. In addition, it is suggested that transcortical placement of the k-wires results in lower rates wire migration. We encountered two clinical cases in which transcortical placement of the k-wires led to impairment of forearm rotation. An anatomic study was conducted to study the effect of transcortical wire placement to avoid similar future complications. Using specimens from 10 embalmed cadavers, we found that transcortical wires inserted in <30 degrees of ulnar angulation in the coronal plane to the medial ridge of the olecranon, impinged on the radial neck, supinator muscle, or biceps tendon. This was avoided in all 10 specimens when the wires were inserted, with the forearm in supination, at 30 degrees of ulnar angulation. We recommend this technique to be adopted to avoid forearm rotation impairment.

A comparison of functional, patient-based scores in subacromial impingement

The goal of this study was to compare the Oxford Shoulder Score (OSS), the Shoulder Pain and Disability Index (SPADI), and the Short Form 36 (SF-36) for their correlation, agreement, sensitivity to change, and test-retest reliability in patients with a clinical diagnosis of subacromial impingement. All patients attending a specialist subacromial impingement clinic over a 6-month period completed the OSS, SPADI, and SF-36 at each visit. A total of 323 sets of observations were recorded in 110 patients. The first 38 of these patients were also sent the questionnaires to complete before their visit. There was good correlation between the OSS and SPADI scores (correlation coefficient = 0.85) and good agreement between the scores on each scale (weighted kappa = 0.79). The correlation with total SF-36 was poor (0.37 for OSS and 0.26 for SPADI). The OSS and SPADI showed good effect sizes compared with the total SF-36 score and good test-retest reliability. These data support the use of the OSS or SPADI in patients with subacromial impingement.

Incorporating ethics in priority setting: a case study of a regional health board in Canada

The authors were involved in developing an ethical framework to assist the Queens Region Board (Prince Edward Island, Canada) set priorities in health and health care. Two and one half years after the adoption of this framework, the authors undertook an evaluation of the framework. This paper will discuss: (a) the historical background of regionalization in Canada, and in particular the circumstances leading up to the institution of regional boards in Prince Edward Island; (b) the sorts of ethical issues facing the Queens Regional Board; (c) issues arising in connection with the use and development of ethics frameworks for managing ethical issues in priority setting; (d) the framework adopted by the Queens Board and the process that led to its development; (e) issues arising as concerns implementation of the framework; (f) questions and issues pertinent to other boards and bodies considering similar initiatives.

Vascular endothelial growth factor acts as an osteolytic factor in breast cancer metastases to bone

Vascular endothelial growth factor (VEGF) is a proangiogenic cytokine that is expressed highly in many solid tumours often correlating with a poor prognosis. In this study, we investigated the expression of VEGF and its receptors in bone metastases from primary human breast tumours and further characterised its effects on osteoclasts in vitro. Breast cancer metastases to bone were immunohistochemically stained for VEGF, its receptors VEGFR1 and 2 (vascular endothelial growth factor receptor 1 and 2), demonstrating that breast cancer metastases express VEGF strongly and that surrounding osteoclasts express both VEGFR1 and VEGFR2. RAW 264.7 cells (mouse monocyte cell line) and human peripheral blood mononuclear cells (PBMCs) were cultured with VEGF, RANKL and M-CSF. VEGF and RANKL together induced differentiation of multinucleated, tartrate-resistant acid phophatase (TRAP)-positive cells in similar numbers to M-CSF and RANKL. The PBMCs were also able to significantly stimulate resorption of mineralised matrix after treatment with M-CSF with RANKL and VEGF with RANKL. We have shown that VEGF in the presence of RANKL supports PBMC differentiation into osteoclast-like cells, able to resorb substrate. Vascular endothelial growth factor may therefore play a role in physiological bone resorption and in pathological situations. Consequently, VEGF signalling may be a therapeutic target for osteoclast inhibition in conditions such as tumour osteolysis.

Measles elimination in Italy: projected impact of the National Elimination Plan

A mathematical model was used to evaluate the impact of the Italian Measles National Elimination Plan (NEP), and possible sources of failure in achieving its targets. The model considered two different estimates of force of infection, and the possible effect on measles transmission of the current Italian demographic situation, characterized by a below-replacement fertility. Results suggest that reaching all NEP targets will allow measles elimination to be achieved. In addition, the model suggests that achieving elimination by reaching a 95 % first-dose coverage appears unlikely; and that conducting catch-up activities, reaching high vaccination coverage, could interrupt virus circulation, but could not prevent the infection re-emerging before 2020. Also, the introduction of the second dose of measles vaccine seems necessary for achieving and maintaining elimination. Furthermore, current Italian demography appears to be favourable for reaching elimination.

In vivo mammary tumourigenesis in the Sprague-Dawley rat and microdosimetric correlates

Standard methods for risk assessments resulting from human exposures to mixed radiation fields in Space consisting of different particle types and energies rely upon quality factors. These are generally defined as a function of linear energy transfer (LET) and are assumed to be proportional to the risk. In this approach, it is further assumed that the risks for single exposures from each of the radiation types add linearly. Although risks of cancer from acute exposures to photon radiations have been measured in humans, quality factors for protons and ions of heavier atomic mass are generally inferred from animal and/or cellular data. Because only a small amount of data exists for such particles, this group has been examining tumourigenesis initiated by energetic protons and iron ions. In this study, 741 female Sprague-Dawley rats were irradiated or sham irradiated at approximately 60 days of age with 250 MeV protons, 1 GeV/nucleon iron ions or both protons and iron ions. The results suggest that the risk of mammary tumours in the rats sequentially irradiated with 1 GeV/nucleon 56Fe ions and 250 MeV protons is less than additive. These data in conjunction with earlier results further suggest that risk assessments in terms of only mean LETs of the primary cosmic rays may be insufficient to accurately evaluate the relative risks of each type of particle in a radiation field of mixed radiation qualities.

Psychiatric comorbidities in patients with Parkinson disease and psychosis

OBJECTIVE

To determine the prevalence and impact of comorbid psychiatric disturbances in Parkinson disease (PD) patients with psychosis.

METHODS

Subject data were derived from a research database of 116 PD patients participating in standardized motor, cognitive, psychiatric, and caregiver assessments.

RESULTS

There were 25 patients (22%) with psychosis manifest as hallucinations (n = 9), delusions (n = 1), or hallucinations and delusions (n = 15) and 25 patients (22%) who had no current or past psychiatric comorbidities (PDN). In the psychotic group, 44% had psychosis only (PSY), and 56% had psychosis plus at least one other comorbid psychiatric disturbance (PSY+), including depressive disorders (71%), anxiety disorders (21%), apathetic syndromes (14%), and delirium (14%). There were no differences in age, sex, education, or age onset or duration of PD among the PSY, PSY+, and PDN groups. Both psychotic groups had greater motor, functional, and frontal cognitive deficits and increased caregiver burden scores relative to PDN. PSY+ showed greater global and selective cognitive deficits compared to PDN. Psychosis was a primary predictor of caregiver burden, whereas depressive symptoms indirectly enhanced motor impairments.

CONCLUSIONS

Nonpsychotic psychiatric disturbances, especially affective disturbances, are common comorbidities in PD patients with psychosis and warrant clinical attention to reduce morbidity and caregiver distress.