K^- ^3He and K^+K^- interactions in the pd -> ^3He K^+K^- reaction

We investigate the K^- ^3He and K^+ K^- interactions in the reaction pd -> ^3He K^+ K^- near threshold and compare our model calculations with data from the MOMO experiment at COSY-Juelich. A large attractive effective K^- p amplitude would give a significant K^- ^3He final-state interaction effect which is not supported by the experimental data. We also estimate upper limits for the a_0(980) and f_0(980) contributions to the produced K^+ K^- pairs.Comment: 5 pages, 2 figures, accepted for publication in PR

Technical Report Scintigraphic Evaluation of Bone Formation in Göttingen Minipigs

In experiments and processes requiring the application of nuclear tracers in large animals, statutory provisions  and safety standards as well as a variety of techniques have to be regarded and employed. In order to sufficiently analyze questions pertaining to osseointegration as well as the possibility of ectopic  bone formation in Göttingen minipigs, we decided to use scintigraphic examinations using 99mTc-HDP  (Technetium - hydroxymethane diphosphonate). In this study, metallic implants coated in different forms  with rhBMP-2 (recombinant human bone morphogenetic protein-2) were surgically introduced into the  pigs’ femora. A total of 26 adult female minipigs (Ellegard, Dalmose, Denmark) averaging 40 months in  age were post-surgically evaluated through the application of a radionuclide and its subsequent distribution  using a scintillation camera. Each animal received approximately 10 MBq/kg BW (mega Becquerel per  kilogram bodyweight). This paper describes the procedures of anaesthesia, the quite challenging transvaginal- urethral catheterization,  the application of a catheter in the jugular vein, the radionuclide injection and the disposal of the  sacrificed animals under statutory provisions and safety standards. The technical report reveals that the scintigraphic evaluation in large animal experiments is a practicable  – yet sophisticated – method of examination and also strives to encourage further research groups to implement  this elegant procedure.

Seasonal Dispersal of Fjord Meltwaters as an Important Source of Iron and Manganese to Coastal Antarctic Phytoplankton

Glacial meltwater from the western Antarctic Ice Sheet is hypothesized to be an important source of cryospheric iron, fertilizing the Southern Ocean, yet its trace-metal composition and factors that control its dispersal remain poorly constrained. Here we characterize meltwater iron sources in a heavily glaciated western Antarctic Peninsula (WAP) fjord. Using dissolved and particulate ratios of manganese to iron in meltwaters, porewaters, and seawater, we show that surface glacial melt and subglacial plumes contribute to the seasonal cycle of iron and manganese within a fjord still relatively unaffected by climate-change-induced glacial retreat. Organic ligands derived from the phytoplankton bloom and the glaciers bind dissolved iron and facilitate the solubilization of particulate iron downstream. Using a numerical model, we show that buoyant plumes generated by outflow from the subglacial hydrologic system, enriched in labile particulate trace metals derived from a chemically modified crustal source, can supply iron to the fjord euphotic zone through vertical mixing. We also show that prolonged katabatic wind events enhance export of meltwater out of the fjord. Thus, we identify an important atmosphere–ice–ocean coupling intimately tied to coastal iron biogeochemistry and primary productivity along the WAP

Tuning spontaneous emission through waveguide cavity effects in semiconductor nanowires

The ability to tailor waveguide cavities and couple them with quantum emitters has developed a realm of nanophotonics encompassing, for example, highly efficient single photon generation or the control of giant photon nonlinearities. Opening new grounds by pushing the interaction of the waveguide cavity and integrated emitters further into the deep subwavelength regime, however, has been complicated by nonradiative losses due to the increasing importance of surface defects when decreasing cavity dimensions. Here, we show efficient suppression of nonradiative recombination for thin waveguide cavities using core-shell semiconductor nanowires. We experimentally reveal the advantages of such nanowires, which host mobile emitters, that is, free excitons, in a one-dimensional (1D) waveguide, highlighting the resulting potential for tunable, active, nanophotonic devices. In our experiment, controlling the nanowire waveguide diameter tunes the luminescence lifetime of excitons in the nanowires across 2 orders of magnitude up to 80 ns. At the smallest wire diameters, we show that this luminescence lifetime can be manipulated by engineering the dielectric environment of the nanowires. Exploiting this unique handle on the spontaneous emission of mobile emitters, we demonstrate an all-dielectric spatial control of the mobile emitters along the axis of the 1D nanowire waveguide

Formative Assessment of ARM-U: A Modular Intervention for Decreasing Risk Behaviors Among HIV-Positive and HIV-Negative Methamphetamine-Using MSM

BACKGROUND: Methamphetamine is a major contributor to HIV transmission among men who have sex with men (MSM). Recent studies show that up to one-third of methamphetamine-using MSM (MUMSM) inject the drug. We developed a behavioral intervention for MUMSM to decrease unprotected anal intercourse and increase awareness of parenteral HIV transmission risk. This 6-session (3 in-person, 3 by telephone) modular intervention was designed to be tailored to participants' HIV (+/-) and injection drug user ([IDU] yes/no) status. We present results of formative research used to evaluate the content and to assess feasibility and acceptability of this individual-level HIV risk-reduction intervention. SETTING: HIV research clinic in a high MSM and methamphetamine prevalence neighborhood. PROJECT: Avoiding Risks from Methamphetamine-Use (ARM-U) is a brief toolbox intervention that allows counselors to select modules that suit a client's individual risk profile and intervention needs employing motivational interviewing and cognitive behavioral theory. We evaluated the format and content of the intervention through focus groups and pre-testing of the entire intervention using volunteers from the target population stratified into four groups (HIV+/IDU, HIV-/IDU, HIV+/non-IDU, HIV-/non-IDU). Four individuals in each stratum were recruited to undergo the intervention and complete a satisfaction survey at the end of each in-person session. RESULTS: In total, 25 MUMSM attended one of five focus groups. Participants thought all proposed intervention topics were important and could aid in reducing sexual risk behaviors among MUMSM. However, the neurocognitive effects of methamphetamine were reported to be a barrier to practicing safer sex, condom use negotiation or HIV status disclosure. Fifteen (94%) of 16 participants completed all 6 sessions and the satisfaction survey. On average, participants felt the intervention was useful for MUMSM, made them contemplate and move toward behavior change, and would recommend the program to their peers. LESSONS LEARNED: Based on our formative research, we revised the ARM-U intervention to emphasize pre-planning to avoid combining methamphetamine use and sex or develop strategies to avoid sex risk following methamphetamine use. We also increased emphasis on referrals for care and other requested services. Future efficacy trials are needed to evaluate the intervention's ability to reduce HIV-associated risk behaviors

Building Blocks for Wavelength Converters: A Study of Monolithic Devices in Piezoelectric Materials

In cavity optomechanics, optical fields are coupled to the displacement of mechanical resonators. While it is interesting to study fundamental aspects of this interaction, it is the ability to link this mechanical displacement to various other degrees of freedom that inspires many applications in the field. In these applications, the mechanical resonator can be used as a handle to an external influence for the purpose of sensing, but also as a transducer between two otherwise detached degrees of freedom. The latter approach is the focus of this work. A particularly interesting regime for such a transduction process is between a few-gigahertz microwave tone and optical photons at telecom wavelengths around 1550 nm, connecting the operating regimes of long-range telecommunication with that of superconducting quantum nodes. Bridging the gap between these domains is an essential step towards any size of quantum network based on superconducting nodes, as the losses encountered in microwave transmission lines prohibits the connection of such nodes over length scales extending beyond a few meters. As such, a transducer between the few-gigahertz and optical telecom domains would enable the use of low-loss optical channels to connect remote superconducting nodes, given that the quantum information is preserved throughout the conversion process. One approach of realizing such a converter makes use of a gigahertz-frequency mechanical mode as the transducing element, which is coupled to the optical telecom domain using the optomechanical interaction and to the microwave domain using the electromechanical interaction. In this work, we aim to unify both of these interactions in a single device by designing and fabricating optomechanical devices from the III/V semiconductors, which, alongside their good optical properties, are also piezoelectric. In Chapter 2, we motivate our material choice and introduce the relevant properties of the materials, as well as their impact on the fabrication process. Following the material discussion, we then set out in Chapter 3 to realize a microwave-to-optics converter made of an optomechanical crystal in gallium arsenide, which we resonantly couple to a interdigital transducer using surface-acoustic-waves. With this device, we demonstrate the first microwave-to-optics conversion using a mechanical mode with an average number of thermal excitations below one. As well as verifying the coherence of the conversion process, our experiments also highlight the limitations arising from the material choice due to absorption-induced incoherent heating of the mechanical mode. The material choice itself then becomes the central topic of Chapter 4, where we opt for a gallium phosphide, a relative of gallium arsenide, which prominently features a larger bandgap. With this material we show non-classical correlations between photons an phonons. We enter a a regime that was previously inaccessible to devices made from piezoelectric materials, a promising step towards realizing the noise-requirements for microwave-to-optics converters. In Chapter 5, we use the insights from the two previous chapters to design a new type of electro-opto-mechanical resonator, specifically aimed at microwave-to-optics conversion. We miniaturize the electromechanical interface and use strongly coupled mechanical resonators for the transfer of excitations between the microwave and mechanical mode. We fabricate and characterise initial devices as well as demonstrate the validity of the functioning principle. Finally in Chapter 6, we reflect on the results of the previous chapters and highlight some potential advantages of other approaches

Effects of Coarse Woody Debris on Soil Temperature and Water Content in Two Reconstructed Soils in Reclaimed Boreal Forest

Coarse woody debris (CWD) and cover soils are used to expedite ecological processes in reclaimed boreal forests after oil sands mining. Soil water content and soil temperature are considered key factors for revegetation during mine reclamation as they impact soil surface and atmosphere interactions and plant growth. However, the effects of CWD and cover soils on soil water content and temperature are not well studied. This study assessed the impact of CWD size (large, small) and type (spruce: Picea mariana, aspen: Populus tremuloides) on soil water content and temperature in two soils constructed with forest floor-mineral mix (FMM) and peat-mineral mix (PMM)) at oil sands reclamation sites. Annual and summer precipitation showed year-to-year variability; mean air temperature did not. Soil cover type had a greater impact on moderating soil water content than CWD, with PMM having a stronger influence on water content and temperature than FMM. Adding CWD increased soil water content more in FMM than PMM, and the effect on soil temperature was mostly observed during the summer months. In PMM, spruce small CWD was associated with greater water content, whereas there was no distinct differentiation between CWD size and type in FFM. This study suggests application of CWD in FMM would be more beneficial than in PMM for reclamation

Effects of Coarse Woody Debris on Soil Temperature and Water Content in Two Reconstructed Soils in Reclaimed Boreal Forest

Coarse woody debris (CWD) and cover soils are used to expedite ecological processes in reclaimed boreal forests after oil sands mining. Soil water content and soil temperature are considered key factors for revegetation during mine reclamation as they impact soil surface and atmosphere interactions and plant growth. However, the effects of CWD and cover soils on soil water content and temperature are not well studied. This study assessed the impact of CWD size (large, small) and type (spruce: Picea mariana, aspen: Populus tremuloides) on soil water content and temperature in two soils constructed with forest floor-mineral mix (FMM) and peat-mineral mix (PMM)) at oil sands reclamation sites. Annual and summer precipitation showed year-to-year variability; mean air temperature did not. Soil cover type had a greater impact on moderating soil water content than CWD, with PMM having a stronger influence on water content and temperature than FMM. Adding CWD increased soil water content more in FMM than PMM, and the effect on soil temperature was mostly observed during the summer months. In PMM, spruce small CWD was associated with greater water content, whereas there was no distinct differentiation between CWD size and type in FFM. This study suggests application of CWD in FMM would be more beneficial than in PMM for reclamation