Towards high-speed optical quantum memories

Quantum memories, capable of controllably storing and releasing a photon, are a crucial component for quantum computers and quantum communications. So far, quantum memories have operated with bandwidths that limit data rates to MHz. Here we report the coherent storage and retrieval of sub-nanosecond low intensity light pulses with spectral bandwidths exceeding 1 GHz in cesium vapor. The novel memory interaction takes place via a far off-resonant two-photon transition in which the memory bandwidth is dynamically generated by a strong control field. This allows for an increase in data rates by a factor of almost 1000 compared to existing quantum memories. The memory works with a total efficiency of 15% and its coherence is demonstrated by directly interfering the stored and retrieved pulses. Coherence times in hot atomic vapors are on the order of microsecond - the expected storage time limit for this memory.Comment: 13 pages, 5 figure

Impact of soil and water conservation measuren on catchment hydrological response: a case in north Ethiopia

Impact studies of catchment management in the developing world rarely include detailed hydrological components. Here, changes in the hydrological response of a 200-ha catchment in north Ethiopia are investigated. The management included various soil and water conservation measures such as the construction of dry masonry stone bunds and check dams, the abandonment of post-harvest grazing, and the establishment of woody vegetation. Measurements at the catchment outlet indicated a runoff depth of 5 mm or a runoff coefficient (RC) of 1·6% in the rainy season of 2006. Combined with runoff measurements at plot scale, this allowed calculating the runoff curve number (CN) for various land uses and land management techniques. The pre-implementation runoff depth was then predicted using the CN values and a ponding adjustment factor, representing the abstraction of runoff induced by the 242 check dams in gullies. Using the 2006 rainfall depths, the runoff depth for the 2000 land management situation was predicted to be 26·5mm(RCD 8%), in line with current RCs of nearby catchments. Monitoring of the ground water level indicated a rise after catchment management. The yearly rise in water table after the onset of the rains (ΔT) relative to the water surplus (WS) over the same period increased between 2002-2003 (ΔT/WS D 3·4) and 2006 (ΔT/WS >11·1). Emerging wells and irrigation are other indicators for improved water supply in the managed catchment. Cropped fields in the gullies indicate that farmers are less frightened for the destructive effects of flash floods. Due to increased soil water content, the crop growing period is prolonged. It can be concluded that this catchment management has resulted in a higher infiltration rate and a reduction of direct runoff volume by 81% which has had a positive influence on the catchment water balance. © 2010 John Wiley & Sons, Ltd

Theory of Star Formation

We review current understanding of star formation, outlining an overall theoretical framework and the observations that motivate it. A conception of star formation has emerged in which turbulence plays a dual role, both creating overdensities to initiate gravitational contraction or collapse, and countering the effects of gravity in these overdense regions. The key dynamical processes involved in star formation -- turbulence, magnetic fields, and self-gravity -- are highly nonlinear and multidimensional. Physical arguments are used to identify and explain the features and scalings involved in star formation, and results from numerical simulations are used to quantify these effects. We divide star formation into large-scale and small-scale regimes and review each in turn. Large scales range from galaxies to giant molecular clouds (GMCs) and their substructures. Important problems include how GMCs form and evolve, what determines the star formation rate (SFR), and what determines the initial mass function (IMF). Small scales range from dense cores to the protostellar systems they beget. We discuss formation of both low- and high-mass stars, including ongoing accretion. The development of winds and outflows is increasingly well understood, as are the mechanisms governing angular momentum transport in disks. Although outstanding questions remain, the framework is now in place to build a comprehensive theory of star formation that will be tested by the next generation of telescopes.Comment: 120 pages, to appear in ARAA. No changes from v1 text; permission statement adde

Live lecture versus video podcast in undergraduate medical education: A randomised controlled trial

<p>Abstract</p> <p>Background</p> <p>Information technology is finding an increasing role in the training of medical students. We compared information recall and student experience and preference after live lectures and video podcasts in undergraduate medical education.</p> <p>Methods</p> <p>We performed a crossover randomised controlled trial. 100 students were randomised to live lecture or video podcast for one clinical topic. Live lectures were given by the same instructor as the narrator of the video podcasts. The video podcasts comprised Powerpoint™ slides narrated using the same script as the lecture. They were then switched to the other group for a second clinical topic. Knowledge was assessed using multiple choice questions and qualitative information was collected using a questionnaire.</p> <p>Results</p> <p>No significant difference was found on multiple choice questioning immediately after the session. The subjects enjoyed the convenience of the video podcast and the ability to stop, review and repeat it, but found it less engaging as a teaching method. They expressed a clear preference for the live lecture format.</p> <p>Conclusions</p> <p>We suggest that video podcasts are not ready to replace traditional teaching methods, but may have an important role in reinforcing learning and aiding revision.</p

Rotationally inelastic scattering of ND 3

Differential cross sections (DCSs) are reported for rotationally inelastic scattering of ND3 with H2, measured using a crossed molecular beam apparatus with velocity map imaging (VMI). ND3 molecules were quantum-state selected in the ground electronic and vibrational levels and, optionally, in the j±k = 14- rotation-inversion level prior to collisions. Inelastic scattering of state-selected ND3 with H2 was measured at the mean collision energy of 580 cm-1 by resonance-enhanced multiphoton ionisation spectroscopy and VMI of ND3 in selected single final j'±k' levels. Comparison of experimental DCSs with close-coupling quantum-mechanical scattering calculations serves as a test of a recently reported ab initio potential energy surface. Calculated integral cross sections reveal the propensities for scattering into various final j'±k' levels of ND3 and differences between scattering by ortho and para H2. Integral and differential cross sections are also computed at a mean collision energy of 430 cm-1 and compared to our recent results for inelastic scattering of state-selected ND3 with He.</p

Piezoelectric-assisted removal of a benign fibrous histiocytoma of the mandible: An innovative technique for prevention of dentoalveolar nerve injury

In this article, we present our experience with a piezoelectric-assisted surgical device by resection of a benign fibrous histiocytoma of the mandible

Immunogenicity Is Not Improved by Increased Antigen Dose or Booster Dosing of Seasonal Influenza Vaccine in a Randomized Trial of HIV Infected Adults

The risk of poor vaccine immunogenicity and more severe influenza disease in HIV necessitate strategies to improve vaccine efficacy.A randomized, multi-centered, controlled, vaccine trial with three parallel groups was conducted at 12 CIHR Canadian HIV Trials Network sites. Three dosing strategies were used in HIV infected adults (18 to 60 years): two standard doses over 28 days, two double doses over 28 days and a single standard dose of influenza vaccine, administered prior to the 2008 influenza season. A trivalent killed split non-adjuvanted influenza vaccine (Fluviral™) was used. Serum hemagglutinin inhibition (HAI) activity for the three influenza strains in the vaccine was measured to assess immunogenicity.297 of 298 participants received at least one injection. Baseline CD4 (median 470 cells/µL) and HIV RNA (76% of patients with viral load <50 copies/mL) were similar between groups. 89% were on HAART. The overall immunogenicity of influenza vaccine across time points and the three influenza strains assessed was poor (Range HAI ≥ 40 =  31-58%). Double dose plus double dose booster slightly increased the proportion achieving HAI titre doubling from baseline for A/Brisbane and B/Florida at weeks 4, 8 and 20 compared to standard vaccine dose. Increased immunogenicity with increased antigen dose and booster dosing was most apparent in participants with unsuppressed HIV RNA at baseline. None of 8 serious adverse events were thought to be immunization-related.Even with increased antigen dose and booster dosing, non-adjuvanted influenza vaccine immunogenicity is poor in HIV infected individuals. Alternative influenza vaccines are required in this hyporesponsive population.ClinicalTrials.gov NCT00764998

Biased decision making in realistic extra-procedural nuclear control room scenarios

In normal operations and emergency situations, operators of nuclear control rooms rely on procedures to guide their decision making. However, in emergency situations, where several interacting problems can cause unpredictable adverse effects, these procedures may be insufficient in guiding operators to safe shutdown of the power plant. Little is known about the decision making strategies that operators employ in these extra-procedural situations. To address this, a realistic simulation study was conducted with five crews of active, licensed nuclear operators to see the behavioural patterns that occur when procedures are not sufficient. This paper, a re-analysis of a dataset collected for a different study, investigates how the design and existence of procedures influence, and possibly bias, decision making strategies. We found evidence that operators were affected by confirmation bias, and that, in some cases, the mismatch between their home power plant and the simulated power plant made them commit errors due to misapplied expertise. We further found that this effect was amplified by the existence and design of the procedures used. Based on these findings, we suggest that designers may improve safety by creating procedures that bear the risks of these biases in mind, or by specifically aiming to debias the users. Avenues for debiasing through design are discussed