Estimating drizzle drop size and precipitation rate using two-colour lidar measurements

A method to estimate the size and liquid water content of drizzle drops using lidar measurements at two wavelengths is described. The method exploits the differential absorption of infrared light by liquid water at 905 nm and 1.5 μm, which leads to a different backscatter cross section for water drops larger than ≈50 μm. The ratio of backscatter measured from drizzle samples below cloud base at these two wavelengths (the colour ratio) provides a measure of the median volume drop diameter D0. This is a strong effect: for D0=200 μm, a colour ratio of ≈6 dB is predicted. Once D0 is known, the measured backscatter at 905 nm can be used to calculate the liquid water content (LWC) and other moments of the drizzle drop distribution. The method is applied to observations of drizzle falling from stratocumulus and stratus clouds. High resolution (32 s, 36 m) profiles of D0, LWC and precipitation rate R are derived. The main sources of error in the technique are the need to assume a value for the dispersion parameter μ in the drop size spectrum (leading to at most a 35% error in R) and the influence of aerosol returns on the retrieval (≈10% error in R for the cases considered here). Radar reflectivities are also computed from the lidar data, and compared to independent measurements from a colocated cloud radar, offering independent validation of the derived drop size distributions

Theory and observations of ice particle evolution in cirrus using Doppler radar: evidence for aggregation

Vertically pointing Doppler radar has been used to study the evolution of ice particles as they sediment through a cirrus cloud. The measured Doppler fall speeds, together with radar-derived estimates for the altitude of cloud top, are used to estimate a characteristic fall time tc for the `average' ice particle. The change in radar reflectivity Z is studied as a function of tc, and is found to increase exponentially with fall time. We use the idea of dynamically scaling particle size distributions to show that this behaviour implies exponential growth of the average particle size, and argue that this exponential growth is a signature of ice crystal aggregation.Comment: accepted to Geophysical Research Letter

Effective Hamiltonian study of excitations in a boson- fermion mixture with attraction between components

An effective Hamiltonian for the Bose subsystem in the mixture of ultracold atomic clouds of bosons and fermions with mutual attractive interaction is used for investigating collective excitation spectrum. The ground state and mode frequencies of the $^{87}$Rb and $^{40}$K mixture are analyzed quantitatively at zero temperature. We find analytically solutions of the hydrodynamics equations in the Thomas- Fermi approximation. We discuss the relation between the onset of collapse and collective modes softening and the dependence of collective oscillations on scattering length and number of boson atoms.Comment: 9 pages, 5 figure

Middle manager responses to hospital co-workers’ unprofessional behaviours within the context of a professional accountability culture change program:a qualitative analysis

Background: The critical role that middle managers play in enacting organisational culture change designed to address unprofessional co-worker behaviours has gone largely unexplored. We aimed to explore middle managers’ perspectives on i) whether they speak up when they or their team members experience unprofessional behaviours (UBs); ii) how concerns are handled; iii) the outcomes; and iv) the role of a professional accountability culture change program (known as Ethos) in driving change. Methods: Qualitative, constructivist approach. Five metropolitan hospitals in Australia which had implemented Ethos. Purposive sampling was used to invite middle-level managers from medicine, nursing, and non-clinical support services. Semi-structured interviews conducted remotely. Inductive, reflexive thematic and descriptive thematic analyses undertaken using NVivo. Results: Thirty interviews (approximately 60 min; August 2020 to May 2021): Nursing (n = 12), Support Services (n = 10), and Medical (n = 8) staff, working in public (n = 18) and private (n = 12) hospitals. One-third (n = 10) had a formal role in Ethos. All middle managers (hearers) had experienced the raising of UBs by their team (speakers). Themes representing reasons for ongoing UBs were: staying silent but active; history and hierarchy; and double-edged swords. The Ethos program was valued as a confidential, informal, non-punitive system but required improvements in profile and effectiveness. Participants described four response stages: i) determining if reports were genuine; ii) taking action depending on the speaker’s preference, behaviour factors (type, frequency, impact), if the person was known/unknown; iii) exploring for additional information; and iv) addressing either indirectly (e.g., change rosters) or directly (e.g., become a speaker). Conclusions: Addressing UBs requires an organisational-level approach beyond supporting staff to speak up, to include those hearing and addressing UBs. We propose a new hearer’s model that details middle managers’ processes after a concern is raised, identifying where action can be taken to minimise avoidant behaviours to improve hospital culture, staff and patient safety

Not Just Efficiency: Insolvency Law in the EU and Its Political Dimension

Certain insolvency law rules, like creditors’ priorities and set-off rights, have a distributive impact on creditors. Distributional rules reflect the hierarchies of values and interests in each jurisdiction and, as a result, have high political relevance and pose an obstacle to reforming the EU Insolvency Regulation. This paper will show the difficulty of reform by addressing two alternative options to regulate cross-border insolvencies in the European Union. The first one is the ‘choice model’, under which companies can select the insolvency law they prefer. Although such a model would allow distressed firms to select the most efficient insolvency law, it would also displace Member States’ power to protect local constituencies. The choice model therefore produces negative externalities and raises legitimacy concerns. The opposite solution is full harmonisation of insolvency law at EU level, including distributional rules. Full harmonisation would have the advantage of internalising all externalities produced by cross-border insolvencies. However, the EU legislative process, which is still based on negotiations between states, is not apt to decide on distributive insolvency rules; additionally, if harmonisation includes such rules, it will indirectly modify national social security strategies and equilibria. This debate shows that the choice regarding power allocation over bankruptcies in the EU depends on the progress of European integration and is mainly a matter of political legitimacy, not only of efficiency

Using atomic interference to probe atom-surface interaction

We show that atomic interference in the reflection from two suitably polarized evanescent waves is sensitive to retardation effects in the atom-surface interaction for specific experimental parameters. We study the limit of short and long atomic de Broglie wavelength. The former case is analyzed in the semiclassical approximation (Landau-Zener model). The latter represents a quantum regime and is analyzed by solving numerically the associated coupled Schroedinger equations. We consider a specific experimental scheme and show the results for rubidium (short wavelength) and the much lighter meta-stable helium atom (long wavelength). The merits of each case are then discussed.Comment: 11 pages, including 6 figures, submitted to Phys. Rev. A, RevTeX sourc

Development and validation of a mathematical equation to estimate glomerular filtration rate in cirrhosis: The rfh cirrhosis Gfr

Current expressions based on serum creatinine concentration overestimate kidney function in cirrhosis leading to significant differences between "true" and calculated glomerular filtration rate (GFR). We compared the performance of MDRD-4, MDRD-6 and CKD-EPI with "true" GFR and the impact of this difference on MELD calculation. We subsequently developed and validated a GFR equation specifically for cirrhosis and compared the performance of the new derived formula with existing GFR formulas. We included 469 consecutive patients who had a transplant assessment between 2011 and 2014. "True" GFR (mGFR) was measured using plasma isotope clearance according to a technique validated in patients with ascites. A corrected creatinine was derived from the mGFR after application of the MDRD formula. Subsequently, a corrected MELD was calculated and was compared with the conventionally calculated MELD. Stepwise multiple linear regression was used to derive a GFR equation. This was compared with the measured GFR in independent external and internal validation sets of 82 and 174 patients with cirrhosis respectively. A difference>20 ml/min/1.73m(2) between existing formulae and mGFR was observed in 226 (48.2%) patients. The corrected MELD score was ≥3 points higher in 177 (37.7%) patients. The predicted equation derived (R(2) =74·6%) was: GFR=45·9x(creatinine(-0) ·(836) )x(urea(-0) ·(229) )x(INR(-0) ·(113) )x(age(0) ·(129) )x(sodium(0) ·(972) )x1·236(if male)x0·92(if moderate/severe ascites). The model was a good fit and showed the greatest accuracy compared to that of existing formulae. CONCLUSION: We developed and validated a new accurate model for GFR assessment in cirrhosis, the RFH cirrhosis GFR, using readily available variables. This remains to be tested and incorporated in prognostic scores in patients with cirrhosis

Diffuse reflection of a Bose-Einstein condensate from a rough evanescent wave mirror

We present experimental results showing the diffuse reflection of a Bose-Einstein condensate from a rough mirror, consisting of a dielectric substrate supporting a blue-detuned evanescent wave. The scattering is anisotropic, more pronounced in the direction of the surface propagation of the evanescent wave. These results agree very well with theoretical predictions.Comment: submitted to J Phys B, 10 pages, 6 figure

Trapped-ion probing of light-induced charging effects on dielectrics

We use a string of confined $^{40}$Ca$^+$ ions to measure perturbations to a trapping potential which are caused by light-induced charging of an anti-reflection coated window and of insulating patches on the ion-trap electrodes. The electric fields induced at the ions' position are characterised as a function of distance to the dielectric, and as a function of the incident optical power and wavelength. The measurement of the ion-string position is sensitive to as few as $40$ elementary charges per $\sqrt{\mathrm{Hz}}$ on the dielectric at distances of order millimetres, and perturbations are observed for illumination with light of wavelengths as long as 729\,nm. This has important implications for the future of miniaturised ion-trap experiments, notably with regards to the choice of electrode material, and the optics that must be integrated in the vicinity of the ion. The method presented can be readily applied to the investigation of charging effects beyond the context of ion trap experiments.Comment: 11 pages, 5 figure