Diffusion, phase behavior, and gelation in a two-dimensional layer of colloids in osmotic equilibrium with a polymer reservoir.

The addition of enough non-adsorbing polymers to an otherwise stable colloidal suspension gives rise to a variety of phase behaviors and kinetic arrest due to the depletion attraction induced between the colloids by the polymers. We report a study of these phenomena in a two-dimensional layer of colloids. The three-dimensional phenomenology of crystal-fluid coexistence is reproduced, but gelation takes a novel form, in which the strands in the gel structure are locally crystalline. We compare our findings with a previous simulation and theory and find substantial agreement.

Neonatal Anthropometric Measures and Peripherally Inserted Central Catheter Depth.

BACKGROUND: Peripherally inserted central catheters (PICCs) are used routinely in neonatal care. Measures of surface anatomy have been used to estimate appropriate PICC depth in neonates since 1973. However, prior PICC research using anthropometric measures to estimate proper PICC insertion depth has been limited to pediatric and adult literature. PURPOSE: The purpose of this study was to explore the relationships among a neonate's anthropometric measures and the appropriate PICC insertion depth. METHODS: Neonates requiring PICC insertion at Nationwide Children's Hospital were enrolled between January and September 2018. Standard PICC procedures were followed. The research group corroborated appropriate PICC tip position of enrolled infants. Multivariable linear regression with robust standard errors was used to evaluate linear relationships between PICC insertion depth and current weight, current length, and PICC insertion site. RESULTS: Demographics of enrolled infants included gestational ages of 23 to 39 weeks, weights of 510 to 3870 g, and lengths of 31 to 54 cm. Of the 56 infants considered, final statistical analysis included 49 neonates (14 ankle, 16 knee, and 19 antecubital insertions). Current neonatal weight was associated with PICC depth at all sites (all Ps < .0001). Current neonatal length was associated with PICC depth at all sites (all Ps < .0001). Preprocedure surface measurement was also strongly associated with PICC insertion depth (P < .0001). IMPLICATIONS FOR PRACTICE: This investigation demonstrated a relationship for both neonatal weight and length that may be an anthropometric model for neonatal PICC insertion depth. IMPLICATIONS FOR RESEARCH: A more robust sample size could more precisely define the anthropometric model.

Non-Faradaic Electric Currents in the Nernst-Planck Equations and Nonlocal Diffusiophoresis of Suspended Colloids in Crossed Salt Gradients.

In the Nernst-Planck equations in two or more dimensions, a non-Faradaic solenoidal current can arise as a consequence of connecting patches with different liquid junction potentials. Whereas this current vanishes for binary electrolytes or in one-dimensional problems, it is in general nonvanishing, for example, in crossed salt gradients. For a suspended colloidal particle, chemiphoresis in the concentration gradients is generally vectorially misaligned with electrophoresis in the electrostatic potential gradient, and there is a nonlocal contribution to the latter deriving from the Ohmic electric field associated with the current; in a case study this contributes up to 20%-30% of the total effect.

Catheter-directed thrombolysis for submassive pulmonary embolism in children: A case series.

Incidence of venous thromboembolism, including pulmonary embolism (PE), continues to rise in children. Optimum management of submassive PE is unclear. The principal objective of this retrospective study was to investigate the radiological and clinical outcomes in children with submassive PE treated with catheter-directed thrombolysis (CDT). Five patients underwent six episodes of CDT. No patient developed major/clinically relevant non-major bleeding. Most patients had complete radiological thrombus resolution and no patient had evidence of chronic thromboembolic pulmonary hypertension. There is an urgent need for larger prospective cohort studies/randomized controlled trials to investigate the role of CDT in pediatric PE.

Treatment-Related Outcomes in Paget-Schroetter Syndrome-A Cross-Sectional Investigation.

OBJECTIVE: To investigate treatment-related outcomes, namely radiological clot resolution, post-thrombotic syndrome (PTS), and health related quality-of-life (HRQoL) scores, in children with Paget-Schroetter syndrome (PSS) undergoing multidisciplinary management, including anticoagulation and decompressive rib-resection surgery, with or without thrombolytic therapy. STUDY DESIGN: We identified all patients treated for PSS at our institution between the years 2010 and 2017. Baseline clinical and radiologic data were abstracted from medical records. Two validated survey instruments to quantify PTS and HRQoL were mailed to eligible patients. Standard statistical methods were used to summarize these measures. RESULTS: In total, 22 eligible patients were identified; 10 were treated with thrombolysis followed by anticoagulation and rib resection, and 12 were treated with anticoagulation and rib resection alone. Nineteen patients responded to the survey instruments. Median age at deep vein thrombosis diagnosis and survey completion were 16.3 and 20.4 years, respectively. Nineteen of 22 patients had thrombus resolution on radiologic follow-up. Fourteen of 19 survey respondents reported signs/symptoms of PTS of which the majority (12/14) reported mild PTS. Aggregate total, physical, and psychosocial HRQoL scores reported were 90.6, 96.7, and 93.3, respectively. Thrombolytic therapy was not associated with a significant improvement in radiologic, clinical or HRQoL outcomes. CONCLUSIONS: Most patients with PSS had complete thrombus resolution on imaging. Only 11% of survey respondents reported moderate PTS. The entire cohort reported excellent HRQoL scores. The role for thrombolytic therapy in the management of childhood PSS remains incompletely elucidated.

Diffusiophoresis in ionic surfactants: effect of micelle formation.

We explore the consequences of micelle formation for diffusiophoresis of charged colloidal particles in ionic surfactant concentration gradients, using a quasi-chemical association model for surfactant self assembly. The electrophoretic contribution to diffusiophoresis is determined by re-arranging the Nernst-Planck equations, and the chemiphoretic contribution is estimated by making plausible approximations for the density profiles in the electrical double layer surrounding the particle. For sub-micellar solutions we find that a particle will typically be propelled down the concentration gradient, although electrophoresis and chemiphoresis are finely balanced and the effect is sensitive to the detailed parameter choices and simplifying assumptions in the model. Above the critical micelle concentration (CMC), diffusiophoresis becomes much weaker and may even reverse sign, due to the fact that added surfactant goes into building micelles and not augmenting the monomer or counterion concentrations. We present detailed calculations for sodium dodecyl sulfate (SDS), finding that the typical drift speed for a colloidal particle in a ∼100 µm length scale SDS gradient is ∼1 µm s-1 below the CMC, falling to ⪅0.2 µm s-1 above the CMC. These predictions are broadly in agreement with recent experimental work.

Feasibility of Ultrasound in Infant Wrist and Thumb Imaging.

OBJECTIVES: To determine the feasibility of ultrasound (US) in infant lateral carpal and base-of-the-thumb imaging. We hypothesized that US would be a practical modality for visualizing the unossified structures. METHODS: Institutional review board approval was obtained for this single-center pilot study. Healthy infants aged 12 months or younger were enrolled. Ultrasound examinations of the distal radial epiphysis through the first metacarpal were performed with a high-frequency transducer. RESULTS: Ultrasound evaluations of the base of the thumb were performed in 18 healthy infants (mean age ± SD, 13.8 ± 9.1 weeks; 44% female). Assuming an elliptical shape, the mean areas of the scaphoid and first metacarpal epiphysis measured 0.85 ± 0.19 and 0.44 ± 0.087 cm2 , respectively. The mean areas of the trapezium and ossified first metacarpal as approximate rectangular shapes measured 0.23 ± 0.069 and 0.49 ± 0.16 cm2 . A perimeter tracing was also used as an alternative area calculation. The mean trapezium area-to-scaphoid area ratio (0.28 ± 0.10) showed less variability compared to the first metacarpal epiphysis area-to-scaphoid area ratio (0.55 ± 0.20) or first metacarpal area-to-scaphoid area ratio (0.64 ± 0.31). CONCLUSIONS: Our data suggest that US is well suited for the evaluation of the lateral carpus and base of the thumb in young infants. These data serve as a reference to which wrist and thumb abnormalities can be compared.

Size-dependent control of colloid transport via solute gradients in dead-end channels.

Transport of colloids in dead-end channels is involved in widespread applications including drug delivery and underground oil and gas recovery. In such geometries, Brownian motion may be considered as the sole mechanism that enables transport of colloidal particles into or out of the channels, but it is, unfortunately, an extremely inefficient transport mechanism for microscale particles. Here, we explore the possibility of diffusiophoresis as a means to control the colloid transport in dead-end channels by introducing a solute gradient. We demonstrate that the transport of colloidal particles into the dead-end channels can be either enhanced or completely prevented via diffusiophoresis. In addition, we show that size-dependent diffusiophoretic transport of particles can be achieved by considering a finite Debye layer thickness effect, which is commonly ignored. A combination of diffusiophoresis and Brownian motion leads to a strong size-dependent focusing effect such that the larger particles tend to concentrate more and reside deeper in the channel. Our findings have implications for all manners of controlled release processes, especially for site-specific delivery systems where localized targeting of particles with minimal dispersion to the nontarget area is essential.

Why Clothes Don't Fall Apart: Tension Transmission in Staple Yarns.

The problem of how staple yarns transmit tension is addressed within abstract models in which the Amontons-Coulomb friction laws yield a linear programing (LP) problem for the tensions in the fiber elements. We find there is a percolation transition such that above the percolation threshold the transmitted tension is in principle unbounded. We determine that the mean slack in the LP constraints is a suitable order parameter to characterize this supercritical state. We argue the mechanism is generic, and in practical terms, it corresponds to a switch from a ductile to a brittle failure mode accompanied by a significant increase in mechanical strength.

Inferior vena cava atresia predisposing to acute lower extremity deep vein thrombosis in children: A descriptive dual-center study.

PURPOSE: Thrombosis in the healthy pediatric population is a rare occurrence. Little is known about the optimal treatment or outcomes of children with unprovoked acute lower extremity (LE) deep vein thrombosis (DVT) associated with atresia of the inferior vena cava (IVC). METHODS: We retrospectively analyzed the records of patients with acute LE DVT subsequently found to have IVC atresia who presented to two tertiary pediatric institutions between 2008 and 2016. Data were reviewed for thrombophilia risk factors, treatment, and outcomes. RESULTS: Eighteen patients, aged 13-18 years (median: 16 years), presenting with acute LE DVT were found to have IVC atresia. Three patients also presented with pulmonary embolism. Fourteen patients underwent site-directed thrombolysis in addition to anticoagulation. Five patients (28%) had confirmed or suspected recurrent thrombosis. Thirteen patients (72%) had no identified provocation for DVT. Ten patients (56%) had post-thrombotic syndrome, and 17 of 18 patients remain on indefinite anticoagulation. CONCLUSION: This study suggests that IVC atresia is a risk factor for LE DVT and pulmonary embolism in otherwise healthy children and highlights the importance of dedicated imaging of the IVC in young patients with unprovoked LE DVT. Indefinite anticoagulation may be considered in pediatric patients presenting with unprovoked thrombosis secondary to an atretic IVC.

Image-guided percutaneous removal of ballistic foreign bodies secondary to air gun injuries.

BACKGROUND: Ballistic injuries with retained foreign bodies from air guns is a relatively common problem, particularly in children and adolescents. If not removed in a timely fashion, the foreign bodies can result in complications, including pain and infection. Diagnostic methods to identify the presence of the foreign body run the entire gamut of radiology, particularly radiography, ultrasound (US) and computed tomography (CT). Removal of the foreign bodies can be performed by primary care, emergency, surgical, and radiologic clinicians, with or without imaging guidance. OBJECTIVE: To evaluate the modalities of radiologic detection and the experience of image-guided ballistic foreign body removal related to air gun injuries within the interventional radiology department of a large pediatric hospital. MATERIALS AND METHODS: A database of more than 1,000 foreign bodies that were removed with imaging guidance by the interventional radiologists at our institution was searched for ballistic foreign bodies from air guns. The location, dimensions, diagnostic modality, duration, complications and imaging modality used for removal were recorded. In addition, the use of sedation and anesthesia required for the procedures was also recorded. RESULTS: Sixty-one patients with ballistic foreign bodies were identified. All foreign bodies were metallic BBs or pellets. The age of the patients ranged from 5 to 20 years. The initial diagnostic modality to detect the foreign bodies was primarily radiography. The primary modality to assist in removal was US, closely followed by fluoroscopy. For the procedure, 32.7% of the patients required some level of sedation. Only two patients had an active infection at the time of the removal. The foreign bodies were primarily in the soft tissues; however, successful removal was also performed from intraosseous, intraglandular and intratendinous locations. All cases resulted in successful removal without complications. CONCLUSION: Image-guided removal of ballistic foreign bodies secondary to air guns is a very effective procedure that can obviate the need for open surgical procedures in children.

Diffusiophoresis in one-dimensional solute gradients.

The diffusiophoretic motion of suspended colloidal particles under one-dimensional solute gradients is solved using numerical and analytical techniques. Similarity solutions are developed for the injection and withdrawal dynamics of particles into semi-infinite pores. Furthermore, a method of characteristics formulation of the diffusion-free particle transport model is presented and integrated to realize particle trajectories. Analytical solutions are presented for the limit of small particle diffusiophoretic mobility Γp relative to the solute diffusivity Ds for particle motions in both semi-infinite and finite domains. Results confirm the build up of local maxima and minima in the propagating particle front dynamics. The method of characteristics is shown to successfully predict particle motions and the position of the particle front, although it fails to accurately predict suspended particle concentrations in the vicinity of sharp gradients, such as at the particle front peak seen in some injection cases, where particle diffusion inevitably plays an important role. Results inform the design of applications in which the use of applied solute gradients can greatly enhance particle injection into and withdrawal from pores.

Perspective: Dissipative particle dynamics.

Dissipative particle dynamics (DPD) belongs to a class of models and computational algorithms developed to address mesoscale problems in complex fluids and soft matter in general. It is based on the notion of particles that represent coarse-grained portions of the system under study and allow, therefore, reaching time and length scales that would be otherwise unreachable from microscopic simulations. The method has been conceptually refined since its introduction almost twenty five years ago. This perspective surveys the major conceptual improvements in the original DPD model, along with its microscopic foundation, and discusses outstanding challenges in the field. We summarize some recent advances and suggest avenues for future developments.

Dissipative particle dynamics: Systematic parametrization using water-octanol partition coefficients.

We present a systematic, top-down, thermodynamic parametrization scheme for dissipative particle dynamics (DPD) using water-octanol partition coefficients, supplemented by water-octanol phase equilibria and pure liquid phase density data. We demonstrate the feasibility of computing the required partition coefficients in DPD using brute-force simulation, within an adaptive semi-automatic staged optimization scheme. We test the methodology by fitting to experimental partition coefficient data for twenty one small molecules in five classes comprising alcohols and poly-alcohols, amines, ethers and simple aromatics, and alkanes (i.e., hexane). Finally, we illustrate the transferability of a subset of the determined parameters by calculating the critical micelle concentrations and mean aggregation numbers of selected alkyl ethoxylate surfactants, in good agreement with reported experimental values.

Improvement of hepatic steatosis in cystic fibrosis with ivacaftor therapy.

Treatment of liver disease, including hepatic steatosis, in patients with cystic fibrosis (CF) is limited. With the development of ivacaftor, which corrects the gating defect of the CF transmembrane regulator channel, there is a potential new therapy available for this subgroup of the CF patient population. We present an adolescent with CF who had significant improvement in hepatic steatosis with ivacaftor treatment while hypothesizing on a mechanism of why it occurred.

Screening properties of four mesoscale smoothed charge models, with application to dissipative particle dynamics.

We extend our previous study [J. Chem. Phys. 138, 204907 (2013)] to quantify the screening properties of four mesoscale smoothed charge models used in dissipative particle dynamics. Using a combination of the hypernetted chain integral equation closure and the random phase approximation, we identify regions where the models exhibit a real-valued screening length, and the extent to which this agrees with the Debye length in the physical system. We find that the second moment of the smoothed charge distribution is a good predictor of this behaviour. We are thus able to recommend a consistent set of parameters for the models.

Efficient digest of high-throughput sequencing data in a reproducible report.

BACKGROUND: High-throughput sequencing (HTS) technologies are spearheading the accelerated development of biomedical research. Processing and summarizing the large amount of data generated by HTS presents a non-trivial challenge to bioinformatics. A commonly adopted standard is to store sequencing reads aligned to a reference genome in SAM (Sequence Alignment/Map) or BAM (Binary Alignment/Map) files. Quality control of SAM/BAM files is a critical checkpoint before downstream analysis. The goal of the current project is to facilitate and standardize this process. RESULTS: We developed bamchop, a robust program to efficiently summarize key statistical metrics of HTS data stored in BAM files, and to visually present the results in a formatted report. The report documents information about various aspects of HTS data, such as sequencing quality, mapping to a reference genome, sequencing coverage, and base frequency. Bamchop uses the R language and Bioconductor packages to calculate statistical matrices and the Sweave utility and associated LaTeX markup for documentation. Bamchop's efficiency and robustness were tested on BAM files generated by local sequencing facilities and the 1000 Genomes Project. Source code, instruction and example reports of bamchop are freely available from https://github.com/CBMi-BiG/bamchop. CONCLUSIONS: Bamchop enables biomedical researchers to quickly and rigorously evaluate HTS data by providing a convenient synopsis and user-friendly reports.