Impurity Band Conduction in a High Temperature Ferromagnetic Semiconductor

The band structure of a prototypical dilute ferromagnetic semiconductor, Ga$_{1-x}$Mn$_{x}$As, is studied across the phase diagram via optical spectroscopy. We prove that the Fermi energy ($E_{F}$) resides in a Mn induced impurity band (IB). This conclusion is based upon careful analysis of the frequency and temperature dependence of the optical conductivity ($\sigma_{1}(\omega,T)$). From our analysis of $\sigma_{1}(\omega,T)$ we infer a large effective mass ($m^*$) of the carriers, supporting the view that conduction occurs in an IB. Our results also provide useful insights into the transport properties of Mn-doped GaAs.Comment: 4 pages, 4 figure

Weekend hospitalization and additional risk of death: An analysis of inpatient data

Objective To assess whether weekend admissions to hospital and/or already being an inpatient on weekend days were associated with any additional mortality risk.Design Retrospective observational survivorship study. We analysed all admissions to the English National Health Service (NHS) during the financial year 2009/10, following up all patients for 30 days after admission and accounting for risk of death associated with diagnosis, co-morbidities, admission history, age, sex, ethnicity, deprivation, seasonality, day of admission and hospital trust, including day of death as a time dependent covariate. The principal analysis was based on time to in-hospital death.Participants National Health Service Hospitals in England.Main Outcome Measures 30 day mortality (in or out of hospital).Results There were 14,217,640 admissions included in the principal analysis, with 187,337 in-hospital deaths reported within 30 days of admission. Admission on weekend days was associated with a considerable increase in risk of subsequent death compared with admission on weekdays, hazard ratio for Sunday versus Wednesday 1.16 (95% CI 1.14 to 1.18; P < .0001), and for Saturday versus Wednesday 1.11 (95% CI 1.09 to 1.13; P < .0001). Hospital stays on weekend days were associated with a lower risk of death than midweek days, hazard ratio for being in hospital on Sunday versus Wednesday 0.92 (95% CI 0.91 to 0.94; P < .0001), and for Saturday versus Wednesday 0.95 (95% CI 0.93 to 0.96; P < .0001). Similar findings were observed on a smaller US data set.Conclusions Admission at the weekend is associated with increased risk of subsequent death within 30 days of admission. The likelihood of death actually occurring is less on a weekend day than on a mid-week day

Fatal toxoplasmosis in Little Penguins (Eudyptula minor) from Penguin Island, Western Australia

Routine post mortems of deceased penguins from Penguin Island, Western Australia, found that a temporal cluster of cases presented with characteristic gross and microscopic changes, namely birds in good body condition with hepatomegaly and splenomegaly, multifocal hepatic and splenic necrosis and numerous, 1–2 μm diameter protozoan parasites within the necrotic foci. Electron microscopy identified the protozoa as belonging to the phylum Apicomplexa. Molecular investigations by PCR gave inconsistent results. PCR performed by an external laboratory identified a novel Haemoproteus spp. organism in samples from 4 of 10 cases from this group, while PCR at Murdoch University identified Toxoplasma gondii in 12 of 13 cases (including 9 of the 10 assayed at the external laboratory). Immunohistochemistry of formalin fixed tissues also identified Toxoplasma in the hepatic and splenic lesions. The distinctive mortalities which were observed in this group of penguins are attributed to a fulminant toxoplasmosis, with a concurrent Haemoproteus infection in some cases. Though the clinical signs of infection are unknown, the gross and microscopic appearance at post mortem is sufficiently characteristic to allow a diagnosis to be made on these features. Definitive confirmation of Toxoplasma infection can be made by immunohistochemistry or PCR

Signal of Quark Deconfinement in the Timing Structure of Pulsar Spin-Down

The conversion of nuclear matter to quark matter in the core of a rotating neutron star alters its moment of inertia. Hence the epoch over which conversion takes place will be signaled in the spin-down "signal_prl.tex" 581 lines, 22203 characters characteristics of pulsars. We find that an observable called the braking index should be easily measurable during the transition epoch and can have a value far removed (by orders of magnitude) from the canonical value of three expected for magnetic dipole radiation, and may have either sign. The duration of the transition epoch is governed by the slow loss of angular momentum to radiation and is further prolonged by the reduction in the moment of inertia caused by the phase change which can even introduce an era of spin-up. We estimate that about one in a hundred pulsars may be passing through this phase. The phenomenon is analogous to ``bachbending'' observed in the moment of inertia of rotating nuclei observed in the 1970's, which also signaled a change in internal structure with changing spin.Comment: 5 pages, 4 figures, Revtex. (May 12, 1997, submitted to PRL

An aerial parallel manipulator with shared compliance

Accessing and interacting with difficult to reach surfaces at various orientations is of interest within a variety of industrial contexts. Thus far, the predominant robotic solution to such a problem has been to leverage the maneuverability of a fully actuated, omnidirectional aerial manipulator. Such an approach, however, requires a specialised system with a high relative degree of complexity, thus reducing platform endurance and real-world applicability. The work here presents a new aerial system composed of a parallel manipulator and conventional, underactuated multirotor flying base to demonstrate interaction with vertical and non-vertical surfaces. Our solution enables compliance to external disturbance on both subsystems, the manipulator and flying base, independently with a goal of improved overall system performance when interacting with surfaces. To achieve this behaviour, an admittance control strategy is implemented on various layers of the flying base's dynamics together with torque limits imposed on the manipulator actuators. Experimental evaluations show that the proposed system is compliant to external perturbations while allowing for differing interaction behaviours as compliance parameters of each subsystem are altered. Such capabilities enable an adjustable form of dexterity in completing sensor installation, inspection and aerial physical interaction tasks. A video of our system interacting with various surfaces can be found here: https://youtu.be/38neGb8-lXg

Tonic inhibition of accumbal spiny neurons by extrasynaptic 4 GABAA receptors modulates the actions of psychostimulants

Within the nucleus accumbens (NAc), synaptic GABAA receptors (GABAARs) mediate phasic inhibition of medium spiny neurons (MSNs) and influence behavioral responses to cocaine. We demonstrate that both dopamine D1- and D2-receptor-expressing MSNs (D-MSNs) additionally harbor extrasynaptic GABAARs incorporating α4, β, and δ subunits that mediate tonic inhibition, thereby influencing neuronal excitability. Both the selective δ-GABAAR agonist THIP and DS2, a selective positive allosteric modulator, greatly increased the tonic current of all MSNs from wild-type (WT), but not from δ−/− or α4−/− mice. Coupling dopamine and tonic inhibition, the acute activation of D1 receptors (by a selective agonist or indirectly by amphetamine) greatly enhanced tonic inhibition in D1-MSNs but not D2-MSNs. In contrast, prolonged D2 receptor activation modestly reduced the tonic conductance of D2-MSNs. Behaviorally, WT and constitutive α4−/− mice did not differ in their expression of cocaine-conditioned place preference (CPP). Importantly, however, mice with the α4 deletion specific to D1-expressing neurons (α4D1−/−) showed increased CPP. Furthermore, THIP administered systemically or directly into the NAc of WT, but not α4−/− or α4D1−/− mice, blocked cocaine enhancement of CPP. In comparison, α4D2−/− mice exhibited normal CPP, but no cocaine enhancement. In conclusion, dopamine modulation of GABAergic tonic inhibition of D1- and D2-MSNs provides an intrinsic mechanism to differentially affect their excitability in response to psychostimulants and thereby influence their ability to potentiate conditioned reward. Therefore, α4βδ GABAARs may represent a viable target for the development of novel therapeutics to better understand and influence addictive behaviors

Implications of Pseudospin Symmetry on Relativistic Magnetic Properties and Gamow - Teller Transitions in Nuclei

Recently it has been shown that pseudospin symmetry has its origins in a relativistic symmetry of the Dirac Hamiltonian. Using this symmetry we relate single - nucleon relativistic magnetic moments of states in a pseudospin doublet to the relativistic magnetic dipole transitions between the states in the doublet, and we relate single - nucleon relativistic Gamow - Teller transitions within states in the doublet. We apply these relationships to the Gamow - Teller transitions from $^{39}Ca$ to its mirror nucleus $^{39}K$.Comment: 17 pages, 2 figures, to be published in PRC. Slightly revised text with one reference adde

Undergraduate views of critical thinking

Clemson University\u27s Quality Enhanement Plan (QEP) is designed to assist undergraduates in the development of their critical thinking skills. Paul et al. (1997) found that professors indicate that they value critical thinking as important, explicit, and achieved in their students, but faculty also are vague and confusing in their open-ended descriptions of the conceptual and practical components of critical thinking instruction in the classroom. The purpose of the current study was to assess student views of the a typical professor\u27s views and student\u27s own personal views using modified versions of the survey items that Paul et al. (1997) employed. Students (n = 139) completed two eleven-item surveys; one framed a typical professor\u27s view and the other framed the student\u27s personal views of critical thinking. Students do not rate a typical professor as valuing critical thinking as important explicit and achieved in their students

Electroencephalogram findings in patients with posterior cortical atrophy

Aim of the study: The aim of this study is to evaluate standard scalp EEG findings in patients with posterior cortical atrophy (PCA), an atypical variant of Alzheimer's disease (AD). Clinical rationale: PCA is a topographically selective variant of AD. Patients with typical AD have an increased likelihood of seizures, which may negatively impact overall functional performance and cognition. It is currently unknown what the typical EEG findings are for patients with PCA. Materials and methods: A retrospective chart review was performed on patients identified either with autopsy confirmed (n = 13) or clinically (n = 126) as PCA. Results: 139 patients were included though only 23 (16.5%) had undergone EEG recording. The EEG was normal in 6 (26%), while an abnormal EEG was present in 17 (74%). Interictal epileptic discharges (IEDs) were found in 2 of the 23 patients (9%). Conclusions: This study of limited sample size suggests that there may be an increased predilection to find IEDs within PCA when compared to typical AD. Larger cohorts are required to determine frequency of abnormal EEGs in PCA, roles of AEDs in therapy, and in the selection of preferred AED. Clinical implications: Patients with PCA would potentially benefit from an EEG for assessment of IEDs which may provide the clinician with a therapeutic opportunity