Anomalous tumbling of colloidal ellipsoids in Poiseuille flows.

Shear flows cause aspherical colloidal particles to tumble so that their orientations trace out complex trajectories known as Jeffery orbits. The Jeffery orbit of a prolate ellipsoid is predicted to align the particle's principal axis preferentially in the plane transverse to the axis of shear. Holographic microscopy measurements reveal instead that colloidal ellipsoids' trajectories in Poiseuille flows strongly favor an orientation inclined by roughly π/8 relative to this plane. This anomalous observation is consistent with at least two previous reports of colloidal rods and dimers of colloidal spheres in Poiseuille flow and therefore appears to be a generic, yet unexplained feature of colloidal transport at low Reynolds numbers.

An Interlaboratory Comparison on the Characterization of a Sub-micrometer Polydisperse Particle Dispersion.

The measurement of polydisperse protein aggregates and particles in biotherapeutics remains a challenge, especially for particles with diameters of ≈ 1 µm and below (sub-micrometer). This paper describes an interlaboratory comparison with the goal of assessing the measurement variability for the characterization of a sub-micrometer polydisperse particle dispersion composed of five sub-populations of poly(methyl methacrylate) (PMMA) and silica beads. The study included 20 participating laboratories from industry, academia, and government, and a variety of state-of-the-art particle-counting instruments. The received datasets were organized by instrument class to enable comparison of intralaboratory and interlaboratory performance. The main findings included high variability between datasets from different laboratories, with coefficients of variation from 13 % to 189 %. Intralaboratory variability was, on average, 37 % of the interlaboratory variability for an instrument class and particle sub-population. Drop-offs at either end of the size range and poor agreement on maximum counts of particle sub-populations were noted. The mean distributions from an instrument class, however, showed the size-coverage range for that class. The study shows that a polydisperse sample can be used to assess performance capabilities of an instrument set-up (including hardware, software, and user settings) and provides guidance for the development of polydisperse reference materials.

Large-scale synthesis of colloidal bowl-shaped particles.

We describe a general procedure for the large-scale fabrication of bowl-shaped colloidal particles using an emulsion templating technique. Following this method, single polymeric seed particles become located on individual oil droplet surfaces. The polymer phase is subsequently plasticized using an appropriate solvent. In this critical step, the compliant seed is deformed by surface tension, with the droplet serving as a templating surface. Solvent evaporation freezes the desired particle shape and the oil is subsequently removed by alcohol dissolution. The resulting uniformly-shaped colloidal particles were studied using scanning electron and optical microscopy. By adjusting the droplet size and the seed particle diameter, we demonstrate that the final particle shape can be controlled precisely, from shallow lenses to deep bowls. We also show that the colloid's uniformity and abundant quantity allowed the depletion-mediated assembly of flexible colloidal chains and clusters.

The fate of patients with large abdominal aortic aneurysms referred for consideration for elective repair.

BACKGROUND: The premise of the Vascular Services Quality Improvement Programme (VSQIP) in management of patients with asymptomatic large abdominal aortic aneurysms (AAA) is reducing mortality from ruptured AAA in a sustainable way without introducing excessive procedure related mortality. Inevitably a proportion of patients are deemed unfit for elective repair. The aim of this study was to report outcomes of patients who were referred with large asymptomatic AAAs including those turned down for elective repair and identify independent risk factors for being turned down for elective open or endovascular repair of AAA. METHODS: Consecutive patients referred to a regional vascular center with a large AAA (greater than 55 mm) between 1st January 2008 and 31st March 2018 were included. All patients underwent the nationally agreed VSQIP pathway which included preoperative cardio-pulmonary exercise testing and contrast enhanced CT scan of aorta. The decision to repair and the modality of repair were made through a Multi-Disciplinary Team MDT process on each patient. Patients were classified into two groups; those managed non-operatively and those offered elective repair. Survival was assessed using Kaplan-Meier analysis. Factors associated with non-operative management were examined using multivariate analysis. RESULTS: A total of 876 patients of whom 768 were men and 108 were women with a mean age of 74 years (SD: 7.2) and a diagnosis of a large asymptomatic AAA were assessed. One hundred and seventy-four patients (19.9%) were turned down for elective repair and 702 (80.1%) underwent repair [Open: 244(34.8%), EVAR: 458 (65.2%] with perioperative and 30 day mortality of 1.13% (8 patients). Median duration of follow-up was 1530 days (51 months), (inter quartile range: 1714 days). Patients who underwent repair had significantly higher survival rates compared with those who were turned down (P<0.0001). Risk factors for being turned down for elective AAA included anaerobic threshold <8 mL kg-1 min-1 [OR: (95% CI): 2.27 (1.31-3.92)], (P=0.0005), Age>80 yrs. [OR (95% CI): 1.32 (1.012-1.52], (P=0.0203), complex aneurysm morphology [OR (95% CI): 3.70 (2.82-4.87], (P<0.0001), Female gender: [OR: (95% CI): 2.41 (1.32-3.92)], (P<0.0001) and being classed high or very high risk for open AAA repair OR: (95% CI): 6.48 (4.01-10.49)], (P<0.0001). CONCLUSIONS: A significant cohort of patients with large asymptomatic AAA is turned down for elective AAA repair. These patients appear to have significantly lower survival rates than those who are treated. Information on patients turned down for elective AAA repair should be routinely reported.

Holographic immunoassays: direct detection of antibodies binding to colloidal spheres.

The size of a probe bead reported by holographic particle characterization depends on the proportion of the surface area covered by bound target molecules and so can be used as an assay for molecular binding. We validate this technique by measuring the kinetics of irreversible binding for the antibodies immunoglobulin G (IgG) and immunoglobulin M (IgM) as they attach to micrometer-diameter colloidal beads coated with protein A. These measurements yield the antibodies' binding rates and can be inverted to obtain the concentration of antibodies in solution. Holographic molecular binding assays therefore can be used to perform fast quantitative immunoassays that are complementary to conventional serological tests.

Is gender still a risk factor for mortality in patients who undergo elective repair of abdominal aortic aneurysms? Experience of a single center.

BACKGROUND: Vascular Services Quality Improvement Program (VSQIP) was introduced to reduce mortality from elective repair of AAA in the UK. This study examines the differences in perioperative mortality and postoperative survival between men and women following elective repair of AAAs in the 10 years after implementation of the (VSQIP). METHODS: Consecutive patients who underwent elective repair of AAA between 1st January 2008 and 31st March 2018 were included. All patients were assessed using the nationally agreed VSQIP pathway which involved cardiopulmonary exercise testing as well as contrast enhanced CT scan of aorta and multidisciplinary assessment to plan each treatment. CT scans were examined to assess the morphology of AAA. Patients were stratified by age, gender, AAA morphology and preoperative anaerobic threshold. Postoperative survival was assessed using Kaplan-Meier analysis. Cox regression analysis was used to determine predictors of postoperative mortality. RESULTS: A total of 702 patients underwent elective repair of AAA of whom 632 were men and 70 were women. The mean age of study cohort was 73.5±7.3 years and mean AAA diameter was 62±9.9 mm. Two hundred and forty-four patients underwent open repair, 402 underwent infrarenal endovascular aneurysm repair (EVAR) and 56 underwent complex EVAR with perioperative and 30-day mortality of 1.13%. No significant difference was observed in perioperative/30-day mortality between men and women (χ2=0.06, P=0.81). Anaerobic threshold <8 (HR=0.68 [95% CI: 0.51-0.92]), complex aneurysm morphology (HR=1.7 [95% CI: 1.39-2.19]) risk category (HR=1.89 [95% CI: 1.48-2.42]) and patients age (HR=1.41 [95% CI: 1.13-1.89]) were independent risk factor for mortality following repair of AAA, whilst female gender (HR=0.89 [95% CI: 0.54-1.48]) and AAA size (HR=1.01 [95% CI: 0.84-1.22]) were not. There was no difference in postoperative survival between men and women who underwent elective repair of AAA (Log rank: 1.82, P=0.61). CONCLUSIONS: Following the implementation of VSQIP female gender is no longer a significant risk factor for perioperative mortality or reduced survival following elective repair of large asymptomatic AAA.

Holographic molecular binding assays.

We demonstrate that holographic particle characterization can directly detect binding of proteins to functionalized colloidal probe particles by monitoring the associated change in the particles' size. This label-free molecular binding assay uses in-line holographic video microscopy to measure the diameter and refractive index of individual probe spheres as they flow down a microfluidic channel. Pooling measurements on 104 particles yields the population-average diameter with an uncertainty smaller than 0.5 nm, which is sufficient to detect sub-monolayer coverage by bound proteins. We demonstrate this method by monitoring binding of NeutrAvidin to biotinylated spheres and binding of immunoglobulin G to spheres functionalized with protein A.

Anaerobic threshold as an independent predictor of mid-term survival following elective endovascular repair of abdominal aortic aneurysm.

BACKGROUND: The aim of this study was to examine the value preoperative AT as predictor of postoperative survival in patients who underwent elective EVAR for repair of asymptomatic AAA. METHODS: Consecutive patients who underwent elective EVAR between 2008 and 2018 were analyzed. Cardiopulmonary exercise testing was performed. Perioperative 30-day mortality was compared between patients who had AT ≥8 mL/kg/min and those with AT<8 mL/kg/min. Risk factors for postoperative survival following EVAR were examined using Cox's regression analysis. RESULTS: Between 1st January 2008 and 31st December 2017, 430 patients underwent elective EVAR (standard device: N.=374, fenestrated/branched: N.=56); their median age was 76 years (range: 53-91 years), median AT was 9.3 (range: 5.4-16.1), and 30-day mortality was 0.9%. These patients were followed up for a median of 1630 days. There was no significant difference in perioperative 30-day mortality between patients who had AT≥8 and those who had AT<8 (χ2=1.56, P=0.22). Age (HR=1.51 [CI: 1.07-1.99], P<0.05) and AT (HR=0.59 [CI: 0.45-0.76], P=0.0003) were predictors of reduced postoperative survival following elective EVAR whereas gender (HR=0.75 [CI: 0.4-1.4], P=0.37), AAA diameter (HR=0.95 [CI: 0.77-1.16], P=0.6), and AAA morphology (HR=1.23 [CI: 0.68-1.76], P=0.95) were not. CONCLUSIONS: Anaerobic threshold is an independent predictor of prolonged survival following elective EVAR and can be used to identify patients who receive most benefit from elective EVAR.

A feasibility randomised controlled trial to evaluate the role of computed tomography in adults with atypical right iliac fossa pain.

BACKGROUND: In patients with right iliac fossa pain, the need for surgery is largely determined by the likelihood of appendicitis. Patients often undergo ultrasound scanning despite a low diagnostic accuracy for appendicitis. This study aimed to determine the feasibility of a larger trial of computed tomography in the evaluation of patients with atypical right iliac fossa pain. MATERIALS AND METHODS: A single-centre, unblinded, parallel randomised controlled trial of computed tomography in the assessment of patients with atypical right iliac fossa pain. After a retrospective evaluation, standard care was defined as serial examination with or without ultrasound. Atypical right iliac fossa pain was defined as no firm diagnosis after initial senior review. Simple descriptions of the risks and benefits of computed tomography were devised for patients to consider. Primary objectives were to assess feasibility and acceptability of the study procedures. RESULTS: A total of 71 patients were invited to participate and 68 were randomised. Final analysis included 31 participants in the standard care arm and 33 in the computed tomography arm, with comparable demographics. Computed tomography was associated with superior diagnostic accuracy, with 100% positive and negative predictive value. The proportion of scans that positively influenced management was 73% for computed tomography and 0% for ultrasound. In the computed tomography arm, there was a trend towards a shorter length of stay (2.3 vs 3.1 days) and a lower negative laparoscopy rate (2 of 11 vs 4 of 9). CONCLUSION: A large randomised trial to evaluate the use of unenhanced computed tomography in atypical right iliac fossa pain appears feasible and justified.

Optimizing the Synthesis of Monodisperse Colloidal Spheres Using Holographic Particle Characterization.

Holographic particle characterization measures the sizes and compositions of individual colloidal particles dispersed in fluid media and rapidly amasses statistics on the distributions of these properties, even for complex heterogeneous dispersions. This information is useful for analyzing and optimizing protocols for synthesizing colloidal particles. We illustrate how holographic characterization can guide process design through a case study on a particularly versatile model system composed of an aqueous dispersion of micrometer-scale spheres synthesized from the organosilane monomer 3-(trimethoxysilyl)propyl methacrylate.

Endovascular Management of Acute Lower Limb Deep Vein Thrombosis: A Systematic Review and Meta-analysis.

BACKGROUND: Deep vein thrombosis (DVT) is associated with significant complications, including the development of post-thrombotic syndrome (PTS). Traditional management is with oral anticoagulation, but the endovascular techniques of catheter-directed thrombolysis (CDT), pharmacomechanical thrombolysis, and venous stenting are now increasingly used. This study aims to review the evidence for these endovascular techniques in the management of acute lower limb DVT, and their role in the reduction of complications such as PTS. METHODS: A systematic review and meta-analysis was carried out, with studies that compared CDT, pharmacomechanical thrombolysis, and/or venous stenting with oral anticoagulation included. Primary outcome measure was the incidence of PTS; secondary outcome measures were the incidence of recurrent venous thromboembolism (VTE) and bleeding complications. Treatment effects were calculated as risk ratios (RR) with their 95% confidence interval (CI). RESULTS: Five studies met the final inclusion criteria. CDT reduced the incidence of PTS (RR 0.56, 95% CI 0.43-0.73), whereas pharmacomechanical thrombolysis had only a minor effect on the incidence of PTS that did not achieve statistical significance (RR 0.87, 95% CI 0.75-1.01). Recurrent VTE following CDT was reduced compared to oral anticoagulation (RR 0.62, 95% CI 0.34-1.13), while bleeding complications were more likely following CDT (RR 5.11, 95% CI 2.16-12.08). CONCLUSIONS: CDT decreases the incidence of PTS when treating iliofemoral DVT, but pharmacomechanical thrombolysis does not. CDT also reduces the incidence of recurrent VTE, but leads to more bleeding complications when compared to oral anticoagulation. Further randomized controlled trials are needed to determine the role of endovascular management of DVT occurring below the iliofemoral level, and the role of venous stenting.

Aneurysm Morphology Is a More Significant Predictor of Survival than Hardman's Index in Patients with Ruptured or Acutely Symptomatic Abdominal Aortic Aneurysms.

Scoring systems such as Hardman's index are used to predict outcomes and stratify patients with ruptured abdominal aortic aneurysm (RAAA) or acutely symptomatic abdominal aortic aneurysm (SAAA) to active treatment or palliation. Aneurysm morphology is not included in these scoring systems. The aim of this study was to assess whether aneurysm morphology was an independent predictor of survival. Consecutive patients admitted from January 2006 to March 2017 with emergency presentation and primary diagnosis of abdominal aortic aneurysm were identified. Patients were stratified by age, gender, mode of presentation (RAAA versus SAAA), Hardman's Index, aneurysm morphology (suitability for endovascular aneurysm repair [EVAR]), and the procedure performed (endovascular versus open). Multivariable logistic regression analysis was used to determine predictors of survival. A total of 346 patients were included (RAAA: 250, SAAA: 96). Median age of patients was 75 years (range: 44-96); 284 (79%) were men and 75 (21%) were women. Three hundred twenty-five patients underwent preoperative computed tomography (CT) scan of these 156 (48%) fulfilled conservative instructions for use (IFU) for EVAR and another 64 (20%) were within the liberal IFU for EVAR. Median Hardman Index was 1 (range 0-5). Age (odds ratio [OR]: 1.72 [95% confidence interval {CI}: 1.15-2.23] [P < 0.001]), mode of presentation [(OR: 2.05 (95% CI: 1.45-3.31) (P < 0.001)], and aneurysm morphology being within conservative IFU for EVAR [(OR: 1.61 (95% CI: 1.08-2.03) (P = 0.02)], modality of repair (open versus EVAR), (OR: 0.81 [95% CI: 0.67-0.92], [P < 0.001]) were independent predictors of survival. Hardman's index (OR: 0.86 [95% CI: 0.69-1.11], [P = 0.16]) and gender (OR: 1.15 [95% CI: 0.83-1.32], [P = 0.24]) were not. Aneurysm morphology is a significant predictor of survival after RAAA. This information should be included in any scoring system.

Freezing on a sphere.

The best understood crystal ordering transition is that of two-dimensional freezing, which proceeds by the rapid eradication of lattice defects as the temperature is lowered below a critical threshold. But crystals that assemble on closed surfaces are required by topology to have a minimum number of lattice defects, called disclinations, that act as conserved topological charges-consider the 12 pentagons on a football or the 12 pentamers on a viral capsid. Moreover, crystals assembled on curved surfaces can spontaneously develop additional lattice defects to alleviate the stress imposed by the curvature. It is therefore unclear how crystallization can proceed on a sphere, the simplest curved surface on which it is impossible to eliminate such defects. Here we show that freezing on the surface of a sphere proceeds by the formation of a single, encompassing crystalline 'continent', which forces defects into 12 isolated 'seas' with the same icosahedral symmetry as footballs and viruses. We use this broken symmetry-aligning the vertices of an icosahedron with the defect seas and unfolding the faces onto a plane-to construct a new order parameter that reveals the underlying long-range orientational order of the lattice. The effects of geometry on crystallization could be taken into account in the design of nanometre- and micrometre-scale structures in which mobile defects are sequestered into self-ordered arrays. Our results may also be relevant in understanding the properties and occurrence of natural icosahedral structures such as viruses.

Preparation of Colloidal Organosilica Spheres through Spontaneous Emulsification.

Colloidal particles of controlled size are promising building blocks for the self-assembly of functional materials. Here, we systematically study a method to synthesize monodisperse, micrometer-sized spheres from 3-(trimethoxysilyl)propyl methacrylate (TPM) in a benchtop experiment. Their ease of preparation, smoothness, and physical properties provide distinct advantages over other widely employed materials such as silica, polystyrene, and poly(methyl methacrylate). We describe that the spontaneous emulsification of TPM droplets in water is caused by base-catalyzed hydrolysis, self-condensation, and the deprotonation of TPM. By studying the time-dependent size evolution, we find that the droplet size increases without any detectable secondary nucleation. Resulting TPM droplets are polymerized to form solid particles. The particle diameter can be controlled in the range of 0.4 to 2.8 µm by adjusting the volume fraction of added monomer and the pH of the solution. Droplets can be grown to diameters of up to 4 µm by adding TPM monomer after the initial emulsification. Additionally, we characterize various physical parameters of the TPM particles, and we describe methods to incorporate several fluorescent dyes.

Phase behavior of charged colloids at a fluid interface.

We study the phase behavior of a system of charged colloidal particles that are electrostatically bound to an almost flat interface between two fluids. We show that, despite the fact that our experimental system consists of only 10^{3}-10^{4} particles, the phase behavior is consistent with the theory of melting due to Kosterlitz, Thouless, Halperin, Nelson, and Young. Using spatial and temporal correlations of the bond-orientational order parameter, we classify our samples into solid, isotropic fluid, and hexatic phases. We demonstrate that the topological defect structure we observe in each phase corresponds to the predictions of Kosterlitz-Thouless-Halperin-Nelson-Young theory. By measuring the dynamic Lindemann parameter γ_{L}(τ) and the non-Gaussian parameter α_{2}(τ) of the displacements of the particles relative to their neighbors, we show that each of the phases displays distinctive dynamical behavior.

The Operative Burden of General Surgical Disease and Non-Battle Injury in a Deployed Military Treatment Facility in Afghanistan.

OBJECTIVES: Contemporary medical operations support a mobile, nonconventional force involved in nation building, counterinsurgency, and humanitarian operations. Prior reports have described surgical care for disease and nonbattle injuries (DNBI). The purpose of this report is to describe the prevalence and scope of DNBI managed by general surgeons in a contemporary, deployed medical facility. METHODS: A 2-year retrospective review of the operative logbook from the U.K. Role 3 Multinational Hospital, Camp Bastion, Afghanistan, was performed to determine the prevalence and makeup of procedures performed for DNBI by general surgeons. RESULTS: Nontrauma general surgical procedures accounted for 7.7% (n = 279 of 3,607 cases) of cases; appendectomy (n = 146) was the most common, followed by drainage of soft tissue (n = 55) and oral abscesses (n = 5), scrotal exploration (n = 12), and hernia repair (n = 7). A total of 7.2% (n = 20 of 279) of cases fell outside the standard scope of practice of an urban, civilian general surgeon. CONCLUSION: Although the prevalence of operative procedures for DNBI was low, the spectrum of cases included those not typically managed in the civilian setting of the United Kingdom. With an evolving decline in case volume performed in multiple anatomic locations due to subspecialization during surgical training, this gap in expertise is likely to increase.

Charge renormalization in nominally apolar colloidal dispersions.

We present high-resolution measurements of the pair interactions between dielectric spheres dispersed in a fluid medium with a low dielectric constant. Despite the absence of charge control agents or added organic salts, these measurements reveal strong and long-ranged repulsions consistent with substantial charges on the particles whose interactions are screened by trace concentrations of mobile ions in solution. The dependence of the estimated charge on the particles' radii is consistent with charge renormalization theory and, thus, offers insights into the charging mechanism in this interesting class of model systems. The measurement technique, based on optical-tweezer manipulation and artifact-free particle tracking, makes use of optimal statistical methods to reduce measurement errors to the femtonewton frontier while covering an extremely wide range of interaction energies.

Patchy particle packing under electric fields.

Colloidal particles equipped with two, three, or four negatively charged patches, which endow the particles with 2-fold, 3-fold, or tetrahedral symmetries, form 1D chains, 2D layers, and 3D packings when polarized by an AC electric field. Two-patch particles, with two patches on opposite sides of the particle (2-fold symmetry) pack into the cmm plane group and 3D packings with I4mm space group symmetry, in contrast to uncharged spherical or ellipsoidal colloids that typically crystallize into a face-centered ABC layer packing. Three-patch particles (3-fold symmetry) form chains having a 21 screw axis symmetry, but these chains pair in a manner such that each individual chain has one-fold symmetry but the pair has 21 screw axis symmetry, in an arrangement that aligns the patches that would favor Coulombic interactions along the chain. Surprisingly, some chain pairs form unanticipated double-helix regions that result from mutual twisting of the chains about each other, illustrating a kind of polymorphism that may be associated with nucleation from short chain pairs. Larger 2D domains of the three-patch particles crystallize in the p6m plane group with alignment (with respect to the field) and packing densities that suggest random disorder in the domains, whereas four-patch particles form 2D domains in which close-packed rows are aligned with the field.