Cold Collision Frequency Shift of the 1S-2S Transition in Hydrogen

We have observed the cold collision frequency shift of the 1S-2S transition in trapped spin-polarized atomic hydrogen. We find $\Delta \nu_{1S-2S} = -3.8(8)\times 10^{-10} n Hz cm^3$, where $n$ is the sample density. From this we derive the 1S-2S s-wave triplet scattering length, $a_{1S-2S}=-1.4(3)$ nm, which is in fair agreement with a recent calculation. The shift provides a valuable probe of the distribution of densities in a trapped sample.Comment: Accepted for publication in PRL, 9 pages, 4 PostScript figures, ReVTeX. Updated connection of our measurement to theoretical wor

Marine fish may be biochemically constrained from inhabiting the deepest ocean depths

No fish have been found in the deepest 25% of the ocean (8,400-11,000 m). This apparent absence has been attributed to hydrostatic pressure, although direct evidence is wanting because of the lack of deepest-living species to study. The common osmolyte trimethylamine N-oxide (TMAO) stabilizes proteins against pressure and increases with depth, going from 40 to 261 mmol/kg in teleost fishes from 0 to 4,850 m. TMAO accumulation with depth results in increasing internal osmolality (typically 350 mOsmol/kg in shallow species compared with seawater\u27s 1,100 mOsmol/kg). Preliminary extrapolation of osmolalities of predicted isosmotic state at 8,000-8,500 m may indicate a possible physiological limit, as greater depths would require reversal of osmotic gradients and, thus, osmoregulatory systems. We tested this prediction by capturing five of the second-deepest known fish, the hadal snailfish (Notoliparis kermadecensis; Liparidae), from 7,000 m in the Kermadec Trench. We found theirmuscles to have a TMAOcontent of 386 ± 18 mmol/kg and osmolality of 991 ± 22 mOsmol/kg. These data fit previous extrapolations and, combined with new osmolalities from bathyal and abyssal fishes, predict isosmotic state at 8,200 m. This is previously unidentified evidence that biochemistry could constrain the depth of a large, complex taxonomic group

The variable phase method used to calculate and correct scattering lengths

It is shown that the scattering length can be obtained by solving a Riccati equation derived from variable phase theory. Two methods of solving it are presented. The equation is used to predict how long-range interactions influence the scattering length, and upper and lower bounds on the scattering length are determined. The predictions are compared with others and it is shown how they may be obtained from secular perturbation theory.Comment: 7 pages including 3 figure

Preparation of anti-vicinal amino alcohols: asymmetric synthesis of D-erythro-Sphinganine, (+)-spisulosine and D-ribo-phytosphingosine

Two variations of the Overman rearrangement have been developed for the highly selective synthesis of anti-vicinal amino alcohol natural products. A MOM-ether directed palladium(II)-catalyzed rearrangement of an allylic trichloroacetimidate was used as the key step for the preparation of the protein kinase C inhibitor D-erythro-sphinganine and the antitumor agent (+)-spisulosine, while the Overman rearrangement of chiral allylic trichloroacetimidates generated by asymmetric reduction of an alpha,beta-unsaturated methyl ketone allowed rapid access to both D-ribo-phytosphingosine and L-arabino-phytosphingosine

Hydrodynamic object recognition using pressure sensing

Hydrodynamic sensing is instrumental to fish and some amphibians. It also represents, for underwater vehicles, an alternative way of sensing the fluid environment when visual and acoustic sensing are limited. To assess the effectiveness of hydrodynamic sensing and gain insight into its capabilities and limitations, we investigated the forward and inverse problem of detection and identification, using the hydrodynamic pressure in the neighbourhood, of a stationary obstacle described using a general shape representation. Based on conformal mapping and a general normalization procedure, our obstacle representation accounts for all specific features of progressive perceptual hydrodynamic imaging reported experimentally. Size, location and shape are encoded separately. The shape representation rests upon an asymptotic series which embodies the progressive character of hydrodynamic imaging through pressure sensing. A dynamic filtering method is used to invert noisy nonlinear pressure signals for the shape parameters. The results highlight the dependence of the sensitivity of hydrodynamic sensing not only on the relative distance to the disturbance but also its bearing

Architecture for high-sensitivity single-shot readout and control of the electron spin of individual donors in silicon

We describe a method to control and detect in single-shot the electron spin state of an individual donor in silicon with greatly enhanced sensitivity. A silicon-based Single-Electron Transistor (SET) allows for spin-dependent tunneling of the donor electron directly into the SET island during the read-out phase. Simulations show that the charge transfer signals are typically \Delta q > 0.2 e - over an order of magnitude larger than achievable with metallic SETs on the SiO2 surface. A complete spin-based qubit structure is obtained by adding a local Electron Spin Resonance line for coherent spin control. This architecture is ideally suited to demonstrate and study the coherent properties of donor electron spins, but can be expanded and integrated with classical control electronics in the context of scale-up.Comment: 5 pages, 4 figure

An Analysis of the Reflection Component in the EPICS Model of Service Learning

Service learning is a pedagogy providing a structured environment for students to link service with course learning objectives. Key to the service learning experience is critical reflection. This gives students the opportunity to examine their coursework in the context of the service they provide to their community and, in a broader sense, the impact they can have on the world. Research has shown that students participating in service learning have a higher comprehension of the course material and also develop an awareness of their local community and the issues it faces. In engineering, there are many examples of service-learning programs ranging from freshman introductory courses to senior capstone courses. Despite their successes, an area that the engineering education community has yet to fully develop is the reflection component of service learning. This paper addresses the development of reflection activities and materials in the Engineering Projects in Community Service (EPICS) program at Purdue University. EPICS engages students in long-term design projects that provide technical solutions to problems faced by local community service organizations. It is a multidisciplinary (composed of students from 20 majors), vertically integrated (freshman-senior), engineering-based design course. Students design, build, test, and deploy projects meeting the specific needs of their community partners. Reflection has been integrated in the EPICS program through curricular activities and key milestones of the course. These activities guide students through the reflection process on a variety of topics. Critical reflection on the design process and teaming complement those on more traditional areas of ethics and social context to enhance a student\u27s service learning experience. This paper presents an overview of the reflection activities that have been developed, interpretations of student reflections from these activities, and plans to evolve the reflection component in EPICS

Thrombocytosis and abnormal liver enzymes:A trigger for investigation of underlying malignancy

BackgroundThrombocytosis is often an incidental finding in primary care with a range of causes. Despite evidence of a strong association between thrombocytosis and malignancy, guidelines for investigating thrombocytosis in the absence of red flag symptoms remain unclear. A novel automated system of laboratory analysis, intelligent Liver Function Testing (iLFT), launched in Tayside in 2018 and has identified a patient group with thrombocytosis and abnormal liver test (LFT) results. This study analysed the outcome of these patients and investigated the use of thrombocytosis combined with LFTs in predicting risk of cancer.Methods and findingsBetween August 2018 and August 2020, 6792 patients underwent iLFT, with 246 found to have both thrombocytosis and at least one abnormal LFT. A random case-matched control group of 492 iLFT patients with normal platelet count and at least one abnormal LFT was created. 7.7% (95% CI 4.7-11.8%) of patients with thrombocytosis had cancer compared to 2.0% (1.0-3.7%) of controls. Patients ConclusionsThese findings suggest a substantial increased risk of cancer in patients with thrombocytosis and raised ALP. This could be developed as an adjunct to current investigation algorithms, highlighting high-risk patients and prompting further investigation (such as computed tomography scans) where indicated