Peer-review in a world with rational scientists: Toward selection of the average

One of the virtues of peer review is that it provides a self-regulating selection mechanism for scientific work, papers and projects. Peer review as a selection mechanism is hard to evaluate in terms of its efficiency. Serious efforts to understand its strengths and weaknesses have not yet lead to clear answers. In theory peer review works if the involved parties (editors and referees) conform to a set of requirements, such as love for high quality science, objectiveness, and absence of biases, nepotism, friend and clique networks, selfishness, etc. If these requirements are violated, what is the effect on the selection of high quality work? We study this question with a simple agent based model. In particular we are interested in the effects of rational referees, who might not have any incentive to see high quality work other than their own published or promoted. We find that a small fraction of incorrect (selfish or rational) referees can drastically reduce the quality of the published (accepted) scientific standard. We quantify the fraction for which peer review will no longer select better than pure chance. Decline of quality of accepted scientific work is shown as a function of the fraction of rational and unqualified referees. We show how a simple quality-increasing policy of e.g. a journal can lead to a loss in overall scientific quality, and how mutual support-networks of authors and referees deteriorate the system.Comment: 5 pages 4 figure

Adult participation in children’s word searches: on the use of prompting, hinting, and supplying a model

Although word searching in children is very common, very little is known about how adults support children in the turns following the child’s search behaviours, an important topic because of the social, educational and clinical implications. This study characterises, in detail, teachers’ use of prompting, hinting and supplying a model. From a classroom dataset of 53 instances, several distinctive patterns emerged. A prompted completion sequence is initiated by a ‘word retrieval elicitor’ (‘fishing’) and is interpreted as a request to complete the phrase. Non-verbal prompting is accomplished through a combination of gaze and gesture and, also, as a series of prompts. Hinting supplies a verbal clue, typically via a wh-question, or by specifying the nature of the repairable. In contrast, the strategies that supply a linguistic model include both embedded and exposed corrections and offers of candidates. A sequential relationship was found between prompting, hinting and supplying a model which has implications for how clinicians and teachers can foster self-repair

Early Surgery for Traumatic Spinal Cord Injury: Where Are We Now?

Study Design: Narrative review. Objective: There is a strong biological rationale to perform early decompression after traumatic spinal cord injury (SCI). With an enlarging clinical evidence base, most spine surgeons internationally now favor early decompression for the majority of SCI patients; however, a number of pertinent questions remain surrounding this therapy. Methods: A narrative review evaluating the status of early surgery for SCI. In particular, we addressed the following questions: (1) Which patients stand to benefit most from early surgery? 2) What is the most appropriate time threshold defining early surgery? Results: Although heterogeneity exists, the evidence generally seems to support early surgery. While the best evidence exists for cervical SCI, there is insufficient data to support a differential effect for early surgery depending on neurological level or injury severity. When comparing thresholds to define early versus late surgery-including a later threshold (48-72 hours), an earlier threshold (24 hours), and an ultra-early threshold (8-12 hours)-the 2 earlier time points seem to be associated with the greatest potential for improved outcomes. However, existing prehospital and hospital logistics pose barriers to early surgery in a significant proportion of patients. An overview of recommendations from the recent AOSpine guidelines is provided. Conclusion: In spite of increasing acceptance of early surgery post SCI, further research is needed to (1) identify subgroups of patients who stand to derive particular benefit-in particular to develop more evidence-based approaches for central cord syndrome and (2) investigate the efficacy and feasibility of ultra-early surgery targeting more aggressive timelines

Entanglement between static and flying qubits in quantum wires

A weakly bound electron in a semiconductor quantum wire is shown to become entangled with an itinerant electron via the coulomb interaction. The degree of entanglement and its variation with energy of the injected electron, may be tuned by choice of spin and initial momentum. Full entanglement is achieved close to energies where there are spin-dependent resonances. Possible realisations of related device structures are discussed

Crossover from Anderson- to Kondo-like behavior: Universality induced by spin-charge separation

The thermodynamics of a lattice regularized asymmetric Anderson impurity in a correlated host is obtained by an exact solution. The crossover from the Anderson- to the Kondo-regime is studied, thus making contact with predictions by scaling theory. On the basis of the exact solution, the transition to universal Kondo behavior is shown to be realized by a graduate separation of the energy scales of spin and charge excitations.Comment: 18 pages, 5 figure

Effective charge-spin models for quantum dots

It is shown that at low densities, quantum dots with few electrons may be mapped onto effective charge-spin models for the low-energy eigenstates. This is justified by defining a lattice model based on a many-electron pocket-state basis in which electrons are localised near their classical ground-state positions. The equivalence to a single-band Hubbard model is then established leading to a charge-spin ($t-J-V$) model which for most geometries reduces to a spin (Heisenberg) model. The method is refined to include processes which involve cyclic rotations of a ``ring'' of neighboring electrons. This is achieved by introducing intermediate lattice points and the importance of ring processes relative to pair-exchange processes is investigated using high-order degenerate perturbation theory and the WKB approximation. The energy spectra are computed from the effective models for specific cases and compared with exact results and other approximation methods.Comment: RevTex, 24 pages, 7 figures submitted as compressed and PostScript file

Transition from electron accumulation to depletion at InGaN surfaces

The composition dependence of the Fermi-level pinning at the oxidized (0001) surfaces of n-type InxGa1−xN films (0<=x<=1) is investigated using x-ray photoemission spectroscopy. The surface Fermi-level position varies from high above the conduction band minimum (CBM) at InN surfaces to significantly below the CBM at GaN surfaces, with the transition from electron accumulation to depletion occurring at approximately x=0.3. The results are consistent with the composition dependence of the band edges with respect to the charge neutrality level

Band gap reduction in GaNSb alloys due to the anion mismatch

The structural and optoelectronic properties in GaNxSb1–x alloys (0<=x<0.02) grown by molecular-beam epitaxy on both GaSb substrates and AlSb buffer layers on GaAs substrates are investigated. High-resolution x-ray diffraction (XRD) and reciprocal space mapping indicate that the GaNxSb1–x epilayers are of high crystalline quality and the alloy composition is found to be independent of substrate, for identical growth conditions. The band gap of the GaNSb alloys is found to decrease with increasing nitrogen content from absorption spectroscopy. Strain-induced band-gap shifts, Moss-Burstein effects, and band renormalization were ruled out by XRD and Hall measurements. The band-gap reduction is solely due to the substitution of dilute amounts of highly electronegative nitrogen for antimony, and is greater than observed in GaNAs with the same N content