VUV and XUV reflectance of optically coated mirrors for selection of high harmonics

We report the reflectance, ~1° from normal incidence, of six different mirrors as a function of photon energy, using monochromatic vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) radiation with energies between 7.5 eV and 24.5 eV. The mirrors examined included both single and multilayer optical coatings, as well as an uncoated substrate. We discuss the performance of each mirror, paying particular attention to the potential application of suppression and selection of high-order harmonics of a Ti:sapphire laser.

Time resolved 3D momentum imaging of ultrafast dynamics by coherent VUV-XUV radiation

We present a new experimental setup for measuring ultrafast nuclear and electron dynamics of molecules after photo-excitation and ionization. We combine a high flux femtosecond vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) source with an internally cold molecular beam and a 3D momentum imaging particle spectrometer to measure electrons and ions in coincidence. We describe a variety of tools developed to perform pump-probe studies in the VUV-XUV spectrum and to modify and characterize the photon beam. First benchmark experiments are presented to demonstrate the capabilities of the system.

Hetero-site-specific X-ray pump-probe spectroscopy for femtosecond intramolecular dynamics

New capabilities at X-ray free-electron laser facilities allow the generation of two-colour femtosecond X-ray pulses, opening the possibility of performing ultrafast studies of X-ray-induced phenomena. Particularly, the experimental realization of hetero-site-specific X-ray-pump/X-ray-probe spectroscopy is of special interest, in which an X-ray pump pulse is absorbed at one site within a molecule and an X-ray probe pulse follows the X-ray-induced dynamics at another site within the same molecule. Here we show experimental evidence of a hetero-site pump-probe signal. By using two-colour 10-fs X-ray pulses, we are able to observe the femtosecond time dependence for the formation of F ions during the fragmentation of XeF2 molecules following X-ray absorption at the Xe site.

Serum lipoprotein ratios as markers of insulin resistance: a study among non-diabetic acute coronary syndrome patients with impaired fasting glucose

BACKGROUND & OBJECTIVES

Recent data suggest that insulin resistance can predict cardiovascular disease independently of the other risk factors, such as hypertension, visceral obesity or dyslipidaemia. However, the majority of available methods to evaluate insulin resistance are complicated to operate, expensive, and time consuming. This study was undertaken to assess whether serum lipoprotein ratios could predict insulin resistance in non-diabetic acute coronary syndrome (ACS) patients.

METHODS

Ninety non-diabetic patients with impaired fasting glucose admitted with a diagnosis of ACS were included in the study. At the time of admission fasting glucose and insulin concentrations were measured. The homeostatic model assessment-insulin resistance (HOMA-IR) was used for insulin resistance. The fasting serum total cholesterol (TC), triglycerides (TG) and high density lipoprotein cholesterol (HDL-C) levels were checked, and then TC/HDL-C and TG/HDL-C ratios were calculated. The areas under the curves (AUC) of the receiver operating characteristic (ROC) curves were used to compare the power of these serum lipoprotein ratios as markers.

RESULTS

Lipoprotein ratios were significantly higher in patients with HOMA-IR index > 2.5 as compared to patients with index <2.5 (P < 0.05). Both TG/HDL-C and TC/HDL-C ratios were significantly correlated with HOMA-IR (P<0.05). The area under the ROC curve of the TG/HDL-C and TC/HDL-C ratio for predicting insulin resistance was 0.80 (95% CI, 0.67 to 0.93), 0.78 (95% CI, 0.65 to 0.91), respectively.

INTERPRETATION & CONCLUSIONS

The findings of this study demonstrate that serum lipoprotein ratios can provide a simple means of identifying insulin resistance and can be used as markers of insulin resistance and cardiovascular diseases risk in adult non-diabetic patients.

Facilitators and barriers to the increased supervisory role of senior charge nurses: a qualitative study

AIMS

To explore the experiences of senior charge nurses provided with 'increased supervisory hours'.

BACKGROUND

Designated supervisory time is essential for senior charge nurses to provide effective clinical leadership. It is important to explore the impact arises of such an increase.

METHODS

An online questionnaire collected exploratory data from senior charge nurses (n = 60). Semi-structured interviews gathered in-depth qualitative data (n = 12). Findings were analysed for common themes associated with implementation of the increased senior charge nurse supervisory role.

RESULTS

The majority of senior charge nurses were unable to use their full allocation of supervisory time. They struggled to accomplish leadership goals because of managing staffing levels, increased workload, time constraints and limited support. Factors that facilitated the role included preparation and support, adequate staff capacity, effective leadership skills and availability of supervisory time. The senior charge nurses took pride in providing clinical leadership, promoting staff development and delivering patient care. Support, in terms of preparation, capacity building and ongoing mentoring, was a key factor for achieving senior charge nurse goals.

CONCLUSION

Senior charge nurses should be supported to maximise supervisory time through the provision of an induction programme, formal coaching and ongoing training and development.

IMPLICATIONS FOR NURSING MANAGEMENT

Preparation and support is essential for senior charge nurses to deliver enhanced clinical leadership through increased supervisory time.

The effect of ethnicity on in-hospital mortality following emergency abdominal surgery: a national cohort study using Hospital Episode Statistics

OBJECTIVES

Ethnicity has complex effects on health and the delivery of health care in part related to language and cultural barriers. This may be important in patients requiring emergency abdominal surgery where delays have profound impact on outcomes. The aim here was to test if variations in outcomes (e.g. in-hospital mortality) exist by ethnic group following emergency abdominal surgery.

STUDY DESIGN

Retrospective cohort study using population-level routinely collected administrative data from England (Hospital Episode Statistics).

METHODS

Adult patients undergoing emergency abdominal operations between April 2008 and March 2012 were identified. Operations were divided into: 'major', 'hepatobiliary' or 'appendectomy/minor'. The primary outcome was all cause in-hospital mortality. Univariable and multivariable analysis odds ratios (OR with 95% confidence intervals, CI) adjusting for selected factors were performed.

RESULTS

359,917 patients were identified and 80.7% of patients were White British, 4.7% White (Other), 2.4% Afro-Caribbean, 1.6% Indian, 2.6% Chinese, 3.1% Asian (Other) and 4.9% not known, with crude in-hospital mortality rates of 4.4%, 3.1%, 2.0%, 2.6%, 1.6%, 1.7% and 5.17%, respectively. The majority of patients underwent appendectomy/minor (61.9%) compared to major (20.9%) or hepatobiliary (17.2%) operations (P < 0.001) with an in-hospital mortality of 1.7%, 11.5% and 3.9% respectively. Adjusted mortality was largely similar across ethnic groups except where ethnicity was not recorded (compared to White British patients following major surgery OR 2.05, 95% 1.82-2.31, P < 0.01, hepatobiliary surgery OR 2.78, 95% CI 2.31-3.36, P = 0.01 and appendectomy/minor surgery OR 1.78, 95% 1.52-2.08, P < 0.01).

CONCLUSIONS

Ethnicity is not associated with poorer outcomes following emergency abdominal surgery. However, ethnicity is not recorded in 5% of this cohort and this represents an important, yet un-definable, group with significantly poorer outcomes.

Influence of day of surgery on mortality following elective colorectal resections

BACKGROUND

The aim of this study was to investigate whether the increased mortality previously identified for surgery performed on Fridays was apparent following major elective colorectal resections and how this might be affected by case mix.

METHODS

Patients undergoing elective colorectal resections in England from 2001 to 2011 were identified using Hospital Episode Statistics. Propensity scores were used to match patients having operations on a Friday in a 1 : 1 ratio with those undergoing surgery on other weekdays. Multivariable analyses were used to investigate overall deaths within 1 year of operation.

RESULTS

A total of 204,669 records were extracted for patients undergoing major elective colorectal resections. Patients who had surgery on Fridays were more deprived (4780 (17.1 per cent) of 27,920 versus 28,317 (16.0 per cent) of 176,749; P < 0.001), a greater proportion had had an emergency admission in the 3 previous months (7870 (28.2 per cent) of 27,920 versus 48,623 (27.5 per cent) of 176,749; P = 0.019), underwent minimal access surgery (4565 (16.4 per cent) of 27,920 versus 23,783 (13.5 per cent) of 176,749; P < 0.001) and had surgery for benign diagnoses (6502 (23.3 per cent) of 27,920 versus 38,725 (21.9 per cent) of 176,749; P < 0.001) than those who had surgery on Mondays to Thursdays. In a matched analysis the odds ratio for 30-day mortality after colorectal resections performed on Fridays compared with other weekdays was 1.25 (95 per cent c.i. 1.13 to 1.37); odds ratios for 90-day and 1-year mortality were 1.16 (1.07 to 1.25) and 1.10 (1.04 to 1.16) respectively.

CONCLUSION

Patients selected for colorectal resections on Fridays had a higher mortality rate than patients operated on from Monday to Thursday and had different characteristics, suggesting that increased mortality may reflect patient factors rather than hospital variables alone.

Collective transport properties of driven Skyrmions with random disorder

We use particle-based simulations to examine the static and driven collective phases of Skyrmions interacting with random quenched disorder. We show that nondissipative effects due to the Magnus term reduce the depinning threshold and strongly affect the Skyrmion motion and the nature of the dynamic phases. The quenched disorder causes the Hall angle to become drive dependent in the moving Skyrmion phase, while different flow regimes produce distinct signatures in the transport curves. For weak disorder, the Skyrmions form a pinned crystal and depin elastically, while for strong disorder the system forms a pinned amorphous state that depins plastically. At high drives the Skyrmions can dynamically reorder into a moving crystal, with the onset of reordering determined by the strength of the Magnus term.

Influence of hydrotropic coions on the shape transitions of sodium dioctylsulfosuccinate aggregates in an aqueous medium

The slope change of the CH plot is a manifestation of the shape change of the ionic micelles. However, binding of the salicylate coion to ionic micelles is an exception to this inference.

Structure and interaction in the polymer-dependent reentrant phase behavior of a charged nanoparticle solution

Small-angle neutron scattering (SANS) studies have been carried out to examine the evolution of interaction and structure in a nanoparticle (silica)-polymer (polyethylene glycol) system. The nanoparticle-polymer solution interestingly shows a reentrant phase behavior where the one-phase charged stabilized nanoparticles go through a two-phase system (nanoparticle aggregation) and back to one-phase as a function of polymer concentration. Such phase behavior arises because of the nonadsorption of polymer on nanoparticles and is governed by the interplay of polymer-induced attractive depletion with repulsive nanoparticle-nanoparticle electrostatic and polymer-polymer interactions in different polymer concentration regimes. At low polymer concentrations, the electrostatic repulsion dominates over the depletion attraction. However, the increase in polymer concentration enhances the depletion attraction to give rise to the nanoparticle aggregation in the two-phase system. Further, the polymer-polymer repulsion at high polymer concentrations is believed to be responsible for the reentrance to one-phase behavior. The SANS data in polymer contrast-matched conditions have been modeled by a two-Yukawa potential accounting for both repulsive and attractive parts of total interaction potential between nanoparticles. Both of these interactions (repulsive and attractive) are found to be long range. The magnitude and the range of the depletion interaction increase with the polymer concentration leading to nanoparticle clustering. At higher polymer concentrations, the increased polymer-polymer repulsion reduces the depletion interaction leading to reentrant phase behavior. The nanoparticle clusters in the two-phase system are characterized by the surface fractal with simple cubic packing of nanoparticles within the clusters. The effect of varying ionic strength and polymer size in tuning the interaction has also been examined.

Casimir effect in active matter systems

We numerically examine run-and-tumble active matter particles in Casimir geometries composed of two finite parallel walls. We find that there is an attractive force between the two walls of a magnitude that increases with increasing run length. The attraction exhibits an unusual exponential dependence on the wall separation, and it arises due to a depletion of swimmers in the region between the walls by a combination of the motion of the particles along the walls and a geometric shadowing effect. This attraction is robust as long as the wall length is comparable to or smaller than the swimmer run length, and is only slightly reduced by the inclusion of steric interactions between swimmers. We also examine other geometries and find regimes in which there is a crossover from attraction to repulsion between the walls as a function of wall separation and wall length.

A Theoretical Modeling of the Static and Dynamic Polarizability of O2- in Large and Complex Oxides

A time-dependent approach is employed in conjunction with a crystal potential model to study the environment-specific optical linear response of the O2- ions in a number of cubic oxides with varying number of constituents, unit-cell dimension and degree of complexity. It is shown that the static polarizability of the anion may vary significantly depending on the position of the anion within the unit-cell. Due to neglect of overlap compression, our method has limited success in predicting the refractive indices of large crystals of complex structures. For small binary oxides the frequency-dependent polarizability of the O2- ion is found to exhibit the first poles close to the ultraviolet absorption edges ascribed to the lowest excitonic transitions in these crystals.

Kinetics of heterogeneous reactions of ozone with representative PAHs and an alkene at the air-ice interface at 258 and 188 K

The kinetics of the reaction of an alkene (E-stilbene) and three polycyclic aromatic hydrocarbons (perylene, anthracene and fluoranthene), as examples of environmental pollutants, with ozone on the surface of ice grains (also called "artificial snow"), produced by shock-freezing of aqueous solutions, was studied at submonolayer pollutant coverages (c = 1.5 × 10(-8) to 3 × 10(-10) mol kg(-1)) and two different temperatures (258 and 188 K). This work supports and extends our previous discovery of a remarkable increase in the apparent ozonation rates with decreasing temperature. The ozonation kinetic results were evaluated using the Langmuir-Hinshelwood model and, in one case, the Eley-Rideal kinetic model. It is shown that the apparent rate enhancement is related to the specific nature of the ice surface at different temperatures, which influences the availability of contaminants to gaseous ozone, and to inherent reactivities of the contaminants. The maximum pseudofirst-order rate constants and the lifetimes of the studied compounds are provided. At a typical atmospheric ozone concentration in polar areas (50 ppbv), the lifetimes were estimated to be on the order of hours (258 K) or tens of minutes (188 K) for alkenes, and hundreds (258 K) or tens (188 K) of days for PAHs, thus approximately of the same magnitude or longer than those found for the gas-phase reactions. We imply that this rate enhancement at lower temperatures is a general phenomenon, and we provide data to implement heterogeneous reactions in snow in models that predict the extent of chemical reactions occurring in cold environments.

Transition between mechanisms of laser-induced field-free molecular orientation

The transition between two distinct mechanisms for the laser-induced field-free orientation of CO molecules is observed via measurements of orientation revival times and subsequent comparison to theoretical calculations. In the first mechanism, which we find responsible for the orientation of CO up to peak intensities of 8 × 10(13) W/cm(2), the molecules are impulsively oriented through the hyperpolarizability interaction. At higher intensities, asymmetric depletion through orientation-selective ionization is the dominant orienting mechanism. In addition to the clear identification of the two regimes of orientation, we propose that careful measurements of the onset of the orientation depletion mechanism as a function of the laser intensity will provide a relatively simple route to calibrating absolute rates of nonperturbative strong-field molecular ionization.

Acute kidney injury following unselected emergency admission: role of the inflammatory response, medication and co-morbidity

BACKGROUND/AIMS

Acute kidney injury (AKI) following admission to hospital is associated with increased mortality, morbidity and length of stay. Factors that predispose patients to AKI frequently co-exist. The precise description of their representation in unselected admissions could help define mechanistic inter-relationships and optimise risk stratification strategies. Our aim was therefore to define precisely, using electronically available data, the variables that are associated with AKI.

METHODS

A cohort study of 112,987 emergency admissions to an urban academic medical centre between 2006 and 2010 was performed. Post-admission AKI was defined using KDIGO aligned, proportionate changes in serum creatinine, denominated by the first measured. AKI correlated with co-morbidities, medications received and the C-reactive protein concentration (CRP).

RESULTS

The relationship between post-admission AKI and putative risk factors was defined in univariate and multivariate analyses. Inclusion of CRP in multivariate analyses significantly reduced the strength of association between some co-variables such as radiological contrast and gentamicin administration but not others.

CONCLUSION

The effect of CRP in these analyses supports the role of systemic inflammation in susceptibility to post-admission AKI. It accounts for the greater part of univariate associations between AKI and some nephrotoxic agents, placing the risk attributable to their use in context. Quantification of the systemic inflammatory response may have utility in AKI risk stratification, integrating various determinants of susceptibility.