Waves and fluid-solid interaction in stented blood vessels.

This paper focuses on the modelling of fluid-structure interaction and wave propagation problems in a stented artery. Reflection of waves in blood vessels is well documented in the literature, but it has always been linked to a strong variation in geometry, such as the branching of vessels. The aim of this work is to detect the possibility of wave reflection in a stented artery due to the repetitive pattern of the stents. The investigation of wave propagation and possible blockages under time-harmonic conditions is complemented with numerical simulations in the transient regime.

Deformation and dynamic response of abdominal aortic aneurysm sealing.

Endovascular sealing is a new technique for the repair of abdominal aortic aneurysms. Commercially available in Europe since 2013, it takes a revolutionary approach to aneurysm repair through minimally invasive techniques. Although aneurysm sealing may be thought as more stable than conventional endovascular stent graft repairs, post-implantation movement of the endoprosthesis has been described, potentially leading to late complications. The paper presents for the first time a model, which explains the nature of forces, in static and dynamic regimes, acting on sealed abdominal aortic aneurysms, with references to real case studies. It is shown that elastic deformation of the aorta and of the endoprosthesis induced by static forces and vibrations during daily activities can potentially promote undesired movements of the endovascular sealing structure.

Spin-orbit-coupled fermions in an optical lattice clock.

Engineered spin-orbit coupling (SOC) in cold-atom systems can enable the study of new synthetic materials and complex condensed matter phenomena. However, spontaneous emission in alkali-atom spin-orbit-coupled systems is hindered by heating, limiting the observation of many-body effects and motivating research into potential alternatives. Here we demonstrate that spin-orbit-coupled fermions can be engineered to occur naturally in a one-dimensional optical lattice clock. In contrast to previous SOC experiments, here the SOC is both generated and probed using a direct ultra-narrow optical clock transition between two electronic orbital states in 87Sr atoms. We use clock spectroscopy to prepare lattice band populations, internal electronic states and quasi-momenta, and to produce spin-orbit-coupled dynamics. The exceptionally long lifetime of the excited clock state (160 seconds) eliminates decoherence and atom loss from spontaneous emission at all relevant experimental timescales, allowing subsequent momentum- and spin-resolved in situ probing of the SOC band structure and eigenstates. We use these capabilities to study Bloch oscillations, spin-momentum locking and Van Hove singularities in the transition density of states. Our results lay the groundwork for using fermionic optical lattice clocks to probe new phases of matter.

Topological phases with long-range interactions.

Topological phases of matter are primarily studied in systems with short-range interactions. In nature, however, nonrelativistic quantum systems often exhibit long-range interactions. Under what conditions topological phases survive such interactions, and how they are modified when they do, is largely unknown. By studying the symmetry-protected topological phase of an antiferromagnetic spin-1 chain with 1/r α interactions, we show that two very different outcomes are possible, depending on whether or not the interactions are frustrated. While unfrustrated long-range interactions can destroy the topological phase for α ≲ 3, the topological phase survives frustrated interactions for all α > 0. Our conclusions are based on strikingly consistent results from large-scale matrix-product-state simulations and effective-field-theory calculations, and we expect them to hold for more general interacting spin systems. The models we study can be naturally realized in trapped-ion quantum simulators, opening the prospect for experimental investigation of the issues confronted here.

Entangling two transportable neutral atoms via local spin exchange.

To advance quantum information science, physical systems are sought that meet the stringent requirements for creating and preserving quantum entanglement. In atomic physics, robust two-qubit entanglement is typically achieved by strong, long-range interactions in the form of either Coulomb interactions between ions or dipolar interactions between Rydberg atoms. Although such interactions allow fast quantum gates, the interacting atoms must overcome the associated coupling to the environment and cross-talk among qubits. Local interactions, such as those requiring substantial wavefunction overlap, can alleviate these detrimental effects; however, such interactions present a new challenge: to distribute entanglement, qubits must be transported, merged for interaction, and then isolated for storage and subsequent operations. Here we show how, using a mobile optical tweezer, it is possible to prepare and locally entangle two ultracold neutral atoms, and then separate them while preserving their entanglement. Ground-state neutral atom experiments have measured dynamics consistent with spin entanglement, and have detected entanglement with macroscopic observables; we are now able to demonstrate position-resolved two-particle coherence via application of a local gradient and parity measurements. This new entanglement-verification protocol could be applied to arbitrary spin-entangled states of spatially separated atoms. The local entangling operation is achieved via spin-exchange interactions, and quantum tunnelling is used to combine and separate atoms. These techniques provide a framework for dynamically entangling remote qubits via local operations within a large-scale quantum register.

Two-particle quantum interference in tunnel-coupled optical tweezers.

The quantum statistics of atoms is typically observed in the behavior of an ensemble via macroscopic observables. However, quantum statistics modifies the behavior of even two particles. Here, we demonstrate near-complete control over all the internal and external degrees of freedom of two laser-cooled (87)Rb atoms trapped in two optical tweezers. This controllability allows us to observe signatures of indistinguishability via two-particle interference. Our work establishes laser-cooled atoms in optical tweezers as a promising route to bottom-up engineering of scalable, low-entropy quantum systems.

Suppressing the loss of ultracold molecules via the continuous quantum Zeno effect.

We investigate theoretically the suppression of two-body losses when the on-site loss rate is larger than all other energy scales in a lattice. This work quantitatively explains the recently observed suppression of chemical reactions between two rotational states of fermionic KRb molecules confined in one-dimensional tubes with a weak lattice along the tubes [Yan et al., Nature (London) 501, 521 (2013)]. New loss rate measurements performed for different lattice parameters but under controlled initial conditions allow us to show that the loss suppression is a consequence of the combined effects of lattice confinement and the continuous quantum Zeno effect. A key finding, relevant for generic strongly reactive systems, is that while a single-band theory can qualitatively describe the data, a quantitative analysis must include multiband effects. Accounting for these effects reduces the inferred molecule filling fraction by a factor of 5. A rate equation can describe much of the data, but to properly reproduce the loss dynamics with a fixed fillingfraction for all lattice parameters we develop a mean-field model and benchmark it with numerically exacttime-dependent density matrix renormalization group calculations.

Microscopic model for feshbach interacting fermions in an optical lattice with arbitrary scattering length and resonance width.

We numerically study the problem of two fermions in a three-dimensional optical lattice interacting via a zero-range Feshbach resonance and display the dispersions of the bound states as a two-particle band structure with unique features compared to typical single-particle band structures. We show that the exact two-particle solutions of a projected Hamiltonian may be used to define an effective two-channel, few-band model for the low-energy, low-density physics of many fermions at arbitrary s-wave scattering length. Our method applies to resonances of any width and can be adapted to multichannel situations or higher-ℓ pairing. In strong contrast to usual Hubbard physics, we find that pair hopping is significantly altered by strong interactions and the presence of the lattice, and the lattice induces multiple molecular bound states.

Use of durometry in assessment of venous disease.

OBJECTIVES: Ulceration of the lower limbs is a common debilitating complication of chronic venous hypertension. Detection of preulcerative skin changes would allow for identification of high-risk patients; early active treatment may prevent ulcer formation. METHODS: Patients with isolated venous disease and volunteers attending outpatient clinics underwent assessment of their clinical, aetiological, anatomical and pathological (CEAP) classification. We employed an industrial durometer, an instrument that measures the hardness of metals and plastic, to assess skin induration. The durometer probe was rested perpendicular on their skin 15 cm above the medial malleolus in non-ulcerated tissue, with the patient and limb in recumbency. The average of four measurements was derived. RESULTS: In 107 people, 203 lower limbs (mean age 55.6 years) were assessed. A significant difference in durometry readings was demonstrated between patients with CEAP classes 0, 1 and 2, and those with classes 4, 5 and 6 (P < 0.0005). There was statistically significant evidence that age and CEAP classification correlated with durometry (P < 0.0001). CONCLUSION: Durometry is of potential value in the assessment and monitoring of preulcerative venous disease, and could help to identify high-risk patients. This would assist in the institution of timely and appropriate treatment.

Local versus general anaesthesia for varicose veins surgery: a prospective non-randomized controlled trial.

OBJECTIVE: To compare the acceptability and outcome of primary varicose vein (VV) surgery (saphenofemoral or saphenopopliteal ligation/excision) under local anaesthesia (LA) with that of general anaesthesia (GA). METHODS: A non-randomized controlled trial of consecutive patients treated between April 2004 and March 2006 was performed. After complete informed consent individual patients were asked to select their preferred form of anaesthesia (LA or GA). Preoperative disease status and co-morbidities were recorded. Outcomes were assessed perioperatively and at six weeks and six months postoperatively using patient scoring systems including the Aberdeen varicose veins severity score (AVVSS). RESULTS: Seventy-two (LA 46[62%] and GA 26[38%]) patients participated; median (range) age was 48 (21-74) years versus 36 (21-59) years (P = 0.0164), respectively. All procedures were performed as day cases. Median postoperative pain scores for LA and GA did not differ at 12 hours (4 versus 4; P = 0.48) and four days (5 versus 6; P = 0.44). Median improvement in the AVVSS at six weeks and six months for LA and GA cohorts were 5.7 versus 6.1 (P = 0.875) and 6.5 versus 8.3 (P = 0.131), respectively. Overall patient satisfaction did not show any intergroup difference at six weeks. CONCLUSIONS: Surgical treatment of VV under LA can be performed safely with comparable results to GA in self-selected patients.

Laparoscopic hernia repair--the best option?

For 100 years the Bassini-type repair for inguinal hernia was the standard method. The Lichtenstein "tension free" mesh repair replaced it on the grounds of much lower recurrence rates, < 5% vs approximately 15%. However, open procedures all have significant long-term discomfort rates of up to 53%. Laparoscopic repair has become a genuine option in the last 15 years and offers low recurrence (< 1%) and minimal long-term discomfort. However, it has not been widely taken up. There is a common misconception that it takes longer to perform, has more complications and is much more expensive. None of these caveats stand up under objective scrutiny. It is time that laparoscopic repair became the method of choice for most elective inguinal hernia repairs.

1990 surgical technologist job analysis.

The job analysis provides information about job tasks currently performed by surgical technologists that will be used to update the certifying examination outline. Looking beyond this essential need, it also provides a wealth of information about the people in the job. It ensures that surgical technologists have a clear picture of their important role in the larger field of health care. This knowledge will enable them to chart a course for the future.