Search

Aim Little is known about the prevalence of discrete white matter abnormalities (WMA) beyond the first years in children born extremely preterm (EPT) and the relation to neurodevelopmental outcomes. Our aim was to investigate the prevalence of discrete WMA in children born EPT and the relationship to neonatal WMI, white matter volume, white matter diffusivity and neurodevelopment. Methods The study was a part of a longitudinal follow-up study of EPT neonates. All children were scanned at Karolinska University hospital 2004-2007 (neonates) and 2014-2015 (children at 8-11 years). WMA was qualitatively assessed by visual inspection. Developmental assessment was conducted at 12 years. Results In total 112 children (median age 10.3 years, 56 girls) underwent MRI of the brain (68 EPT, 45 controls). In the EPT group, a subset had MRI around term equivalent age (n=61). In the EPT group, the prevalence of discrete WMA at 8-11 years was 52%. There was a positive association between white matter injuries (WMI) at TEA and 8-11 years. There was no association between WMI and WM volumes or diffusivity at 8-11 years. Discrete WMA was not related to neurodevelopmental outcomes. Conclusion Discrete WMA was prevalent in children born EPT at 8-11 years but were not related to neurodevelopmental outcomes.

Purpose The purpose of this study is to propose a novel simulation framework and show that it captures the main effects of the deposition process, such as droplet shape, volume and speed. Design/methodology/approach In the framework, the time-dependent flow and the fluid-structure interaction between the suspension, the moving piston and the deflection of the jetting head is simulated. The system is modelled as a two-phase system with the surrounding air being one phase and the dense suspension the other. The non-Newtonian suspension is modelled as a mixed single phase with properties determined from material testing. The simulations were performed with two coupled in-house solvers developed at Fraunhofer-Chalmers Centre; IBOFlow, a multiphase flow solver; and LaStFEM, a large strain FEM solver. Experimental deposition was performed with a commercial jet printer and quantitative measurements were made with optical profilometry. Findings Jetting behaviour was shown to be affected by not only piston motion, fluid rheology and head deformation but also the viscous energy loss in the jetting head nozzle. The simulation results were compared to experimental data obtained from an industrial jetting head and found to match characteristic lengths, speed and volume within ca 10%. Research limitations/implications The simulations are based on a rheological description using the Carreau model that does not include a time-dependent relaxation of the fluid. This modelling approach limits the descriptive nature of the deposit after impact on the substrate. The simulation also adopts a continuum approach to the suspension, which will not accurately model the break-off of the droplet filament under the characteristic diameter of the particles in the suspension. Practical implications The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and minimised product development duration. Social implications The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and therefore an improvement from a sustainability perspective. The ability to plan deposition strategies virtually will also enable a decrease in consumables at manufacturers which will in turn decrease their carbon foot print. Originality/value While basic fluid dynamic simulations have been performed to simulate flow through nozzles, the ability to include both fluid-structure interaction and multiphase capability together with a more accurate rheological description of the suspension and with a substrate for surface mount applications has not been published to the knowledge of the authors.

When concentrated particle suspensions flow into a constricting channel, the suspended particles may either smoothly flow through the constriction or jam and clog the channel. These clogging events are typically detrimental to technological processes, such as in the printing of dense pastes or in filtration, but can also be exploited in micro-separation applications. Many studies have to date focused on important parameters influencing the occurrence of clogs, such as flow velocity, particle concentration, and channel geometry. However, the investigation of the role played by the particle surface properties has surprisingly received little attention so far. Here, we study the effect of surface roughness on the clogging of suspensions of silica particles under pressure-driven flows along a microchannel presenting a constriction. We synthesize micron-sized particles with uniform surface chemistry and tunable roughness and determine the occurrence of clogging events as a function of velocity and volume fraction for a given surface topography. Our results show that there is a clear correlation between surface roughness and flow rate, indicating that rougher particles are more likely to jam at the constriction for slower flows. These findings identify surface roughness as an essential parameter to consider in the formulation of particulate suspensions for applications where clogging plays an important role., Soft Matter, 17 (31), ISSN:1744-683X, ISSN:1744-6848

Improved sample preparation has the potential to address unmet needs for fast turnaroundsepsis tests. In this work, we report elasto-inertial based rapid bacteria separation from diluted blood at high separation efficiency. In viscoelastic flows, we demonstrate novel findings where blood cells prepositioned at the outer wall entering a spiral device remain fullyfocused throughout the channel length while smaller bacteria migrate to the opposite wall.Initially, using microparticles, we show that particles above a certain size cut-off remainfully focused at the outer wall while smaller particles differentially migrate toward the inner wall. We demonstrate particle separation at 1 μm resolution at a total throughput of1 mL/min. For blood-based experiments, a minimum of 1:2 dilution was necessary to fullyfocus blood cells at the outer wall. Finally, Escherichia coli spiked in diluted blood were continuously separated at a total flow rate of 1 mL/min, with efficiencies between 82 and 90%depending on the blood dilution. Using a single spiral, it takes 40 min to process 1 mLof blood at a separation efficiency of 82%. The label-free, passive, and rapid bacteria isolation method has a great potential for speeding up downstream phenotypic and genotypicanalysis. QC 20220426

Holes through silicon substrates are used in silicon microsystems, for example in vertical electrical interconnects. In comparison to deep reactive ion etching, laser drilling is a versatile method for forming these holes, but laser drilling suffers from poor hole quality. In this article, water is used in the silicon drilling process to remove debris and the shape deformations of the holes. Water is introduced into the drilling process through the backside of the substrate to minimize negative effects to the drilling process. Drilling of inclined holes is also demonstrated. The inclined holes could find applications in radio frequency devices.

Novel sequences (NSs), not present in the human reference genome, are abundant and remain largely unexplored. Here, we utilize de novo assembly to study NS in 1,000 Swedish individuals first sequenced as part of the SweGen project revealing a total of 46 Mb in 61,044 distinct contigs of sequences not present in GRCh38. The contigs were aligned to recently published catalogs of Icelandic and Pan-African NSs, as well as the chimpanzee genome, revealing a great diversity of shared sequences. Analyzing the positioning of NS across the chimpanzee genome, we find that 2,807 NS align confidently within 143 chimpanzee orthologs of human genes. Aligning the whole genome sequencing data to the chimpanzee genome, we discover ancestral NS common throughout the Swedish population. The NSs were searched for repeats and repeat elements: revealing a majority of repetitive sequence (56%), and enrichment of simple repeats (28%) and satellites (15%). Lastly, we align the unmappable reads of a subset of the thousand genomes data to our collection of NS, as well as the previously published Pan-African NS: revealing that both the Swedish and Pan-African NS are widespread, and that the Swedish NSs are largely a subset of the Pan-African NS. Overall, these results highlight the importance of creating a more diverse reference genome and illustrate that significant amounts of the NS may be of ancestral origin.

Purpose The purpose of the paper is to develop a methodology to characterize the rheological behaviour of macroscopic non-Brownian suspensions, like solder paste, based on microstructural evolution. Design/methodology/approach A structure-based kinetics model, whose parameters are derived analytically based on assumptions valid for any macroscopic suspension, is developed to describe the rheological behaviour of a given fluid. The values of the parameters are then determined based on experiments conducted at a constant shear rate. The parameter values, obtained from the model, are then adjusted using an optimization algorithm using the mean deviation from experiments as the cost function to replicate the measured rheology. A commercially available solder paste is used as the test fluid for the proposed method. Findings The initial parameter values obtained through the analytical model indicates a structural breakdown that is much slower than observations. But optimizing the parameter values, especially the ones associated with the structural breakdown, replicates the thixotropic behaviour of the solder paste reasonably well, but it fails to capture the structure build-up during the three interval thixotropy test. Research limitations/implications The structural kinetics model tends to under-predict the structure build-up rate. Practical implications This study details a more realistic prediction of the rheological behaviour of macroscopic suspensions like solder paste, thermal interface materials and other functional materials. The proposed model can be used to characterize different solder pastes and other functional fluids based on the structure build-up and breakdown rates. The model can also be used as the viscosity definitions in numerical simulations instead of simpler models like Carreau–Yasuda and cross-viscosity models. Originality/value The rheological description of the solder paste is critical in determining its validity for a given application. The methodology described in the paper provides a better description of thixotropy without relying on the existing rheological measurements or the behaviour predicted by a standard power-law model. The proposed model can also provide transient viscosity predictions when shear rates vary in time.

Disruption of the normal patterns of structural brain asymmetry, and in language-related areas, has been reported in individuals with autism spectrum disorder (ASD). We tested the hypothesis that 16 children born extremely preterm (EPT), and diagnosed with ASD at 6.5 years of age (EPT-ASD), would have different patterns of brain structural asymmetry, particularly in language-related areas, to 21 EPT children without ASD and 15 term-born children. They all underwent neonatal magnetic resonance imaging scans at 40 weeks of gestation. ASD diagnoses and the Weschler Intelligence Scale for Children-Fourth Edition, were performed in the EPT children, but not in the term group. Asymmetry indices (AIs) were assessed at three levels: global (hemispheres), lobar (brain lobes), and modular (primary sensorimotor, unimodal, and higher-order association areas). AIs were also assessed in language-related regions and correlational analyses were performed between these AIs and verbal scores. The EPT-ASD group showed reduced structural asymmetry at the modular level, mainly involving the higher-order association cortices and the language-related areas. Predominant positive correlations between language functioning and leftward AIs in the inferior frontal gyrus (opercular) and supplementary cortices, and rightward asymmetry in the angular and supramarginal gyri, were identified in the EPT-ASD group. The overall results suggest that reduced brain structural asymmetry identified during the neonatal period would be a risk factor for the development of ASD in EPT infants. This finding could identify EPT children at risk at an early stage, so that tailored interventions could be used to optimize their functions and quality of life. Autism Res 2019, 12: 1334-1343. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Babies born before the expected date (preterm) are more likely to develop autism, due to abnormal brain development. Compared with children without autism, preterm children with autism did not display the important physical differences between the two sides of their brain that are needed for normal functioning. As this alteration was found just after birth, this information could be used to identify children who are likely to develop autism, so that they can get medical support at an earlier age.

Main objectives: executive functions are frequently a weakness in children born preterm. We examined associations of executive functions and general cognitive abilities with brain structure in preterm born adolescents who were born with appropriate weight for gestational age and who have no radiological signs of preterm brain injury on neuroimaging. Methods: The Stockholm Neonatal Project (SNP) is a longitudinal, population-based study of children born preterm (Results: significant differences in grey and white matter regional volumes and widespread differences in FA were seen between the two groups. No significant correlations were found between cognitive measures and brain volumes in any group after correction for multiple comparisons. However, there were significant correlations between FA in projection fibres and long association fibres, linking frontal, temporal, parietal, and occipital lobes, and measures of executive function and general cognitive abilities in the preterm born adolescents, but not in the term born adolescents. Overall significance of the study: in persons born preterm, in the absence of perinatal brain injury on visual inspection of MRI, widespread alterations in regional brain tissue volumes and microstructure are present in adolescence/young adulthood. Importantly, these alterations in WM tracts are correlated with measures of executive function and general cognitive abilities. Our findings suggest that disturbance of neural pathways, rather than changes in regional brain volumes, are involved in the impaired cognitive functions.

Interposers with through-silicon vias (TSVs) play a key role in the three-dimensional integration and packaging of integrated circuits and microelectromechanical systems. In the current practice of fabricating interposers, solder balls are placed next to the vias; however, this approach requires a large foot print for the input/output (I/O) connections. Therefore, in this study, we investigate the possibility of placing the solder balls directly on top of the vias, thereby enabling a smaller pitch between the solder balls and an increased density of the I/O connections. To reach this goal, inkjet printing (that is, piezo and super inkjet) was used to successfully fill and planarize hollow metal TSVs with a dielectric polymer. The under bump metallization (UBM) pads were also successfully printed with inkjet technology on top of the polymer-filled vias, using either Ag or Au inks. The reliability of the TSV interposers was investigated by a temperature cycling stress test (−40 °C to +125 °C). The stress test showed no impact on DC resistance of the TSVs; however, shrinkage and delamination of the polymer was observed, along with some micro-cracks in the UBM pads. For proof of concept, SnAgCu-based solder balls were jetted on the UBM pads.

Handling highly concentrated solid-liquid two-phase fluids in microfluidics is challenging. In this paper, we present the first studies of flowing solder paste with a high solid content in a transparent high-pressure tolerant glass chip, thereby increasing the understanding of how multiphase liquids with high density difference between the phases behave in small channels (840 mu m in diameter). The system, including a custom made high-pressure, low resistance, interface, was continuously operated at pressures up to of 6 MPa and devices where shown to have pressure tolerance up to 17 MPa. During flow through the chip, the packing density of the solder balls displayed inhomogeneity over the channel where chains of solder balls in contact with each other were formed together with voids. These in-homogeneities persisted along the channel during flow. The flow rate of the paste through the chip oscillated between 63 to 350 mu m/s when pumping at constant volume rate of 30 mu l/min. When a pressure of 2 MPa was applied, the volume of the solder paste particle segment decreased 1.6%, and 0.1% was elastically recovered when the pressure was released. It is concluded that this transparent microfluidic high-pressure glass chip with the special developed interface is suitable for flow studies of solder paste with a high solid content.

The aim of this study was to investigate whether prematurity per se or perinatal risk factors explain altered brain structure after preterm birth, in extremely preterm (EPT) infants without focal brain lesions.A population-based cohort of 58 EPT infants [gestational age (GA)27 + 0 weeks] was examined with diffusion magnetic resonance imaging at term-equivalent age and compared with 14 term-born controls. Associations of diffusion measures with prematurity and neonatal risk factors were explored. Data were analysed with tract-based spatial statistics (TBSS) for whole-brain analysis and region-of-interest (ROI) analysis.Whole-brain analyses showed lower fractional anisotropy (FA) and higher mean diffusivity (MD) in several white matter (WM) tracts in the preterms, which was essentially confirmed by ROI analyses. Within the preterm GA range (23 + 0 to 26 + 6 weeks), GA at birth was not significantly associated with diffusion measures. Bronchopulmonary dysplasia predicted lower FA in the corpus callosum and right inferior longitudinal fasciculus; mechanical ventilation2 days was predictive of higher MD in the right external capsule.White matter microstructure is influenced by preterm birth and by neonatal respiratory factors, whereas the degree of prematurity within the EPT range appears to be of less importance.

Preterm infants face an increased risk of autism spectrum disorder (ASD). The relationship between autism during childhood and early brain development remains unexplored. We studied 84 preterm children born at

PurposeA precise and rapid temperature cycling of a small volume of fluid is vital for an effective DNA replication process using the polymerase chain reaction (PCR). The purpose of this paper is to study the velocity and temperature fields inside a rotating PCR‐tube during cooling of the enclosed liquid.Design/methodology/approachThe velocity and temperature fields inside a rotating PCR‐tube during cooling of the enclosed liquid are studied. By using computational fluid dynamics, the time development of the flow can be investigated in detail. Owing to the rotation, the flow exhibits features which could never arise in a non‐rotating system.FindingsAn intricate azimuthal boundary layer flow is presented and explained. The inherent problem of stratification of the temperature is discussed, and different methods towards a remedy are presented. By analyzing the governing equations, some properties of the flow observed in the simulations are explained. It is shown that increasing the rate of rotation does not improve temperature homogenization.Research limitations/implicationsThe simulations were performed for a limited number of temperature boundary conditions, as well as a specific simulation geometry.Practical implicationsThe analytical and simulation results offer fundamental insight into the physics behind increased DNA duplication. Further simulations offer possible design improvements.Originality/valueWhile many studies have probed the effects of buoyancy in rotating cylinders and the development of boundary layers in stratified flows in conical containers rotating around their axis of symmetry, little work has been specifically focused on the case where the axis of rotation is normal to the direction of the stratification, which is the case in the present study.

A novel polymerase chain reaction (PCR) method is presented that utilizes Coriolis and centrifugal effects, produced by rotation of the sample disc, in order to increase internal circulatory rates, and with them temperature homogenization and mixing speeds. A proof of concept has been presented by testing a rapid 45-cycle PCR DNA amplification protocol. During the repeated heating and cooling that constitutes a PCR process, the 100 microL samples were rotated at a speed equivalent to an effective acceleration of gravity of 7,000 g. A cycle time of 20.5 s gave a total process time of 15 min to complete the 45 cycles. A theoretical and numerical analysis of the resulting flow, which describes the increased mixing and temperature homogenization, is presented. The device gives excellent reaction speed efficiency, which is beneficial for rapid PCR.

Rapidly rotating duct flow is studied experimentally with Rotation numbers in the interval [0, 1]. To achieve this, in combination with relatively high Reynolds numbers (5,000–30,000 based on the hydraulic radius), water was used as the working medium. Square and rectangular duct cross-sections were used and the angle between the rotation vector and the main axis of the duct was varied. The influence of the rotation on the pressure drop in the duct was investigated and suitable scalings of this quantity were studied.

The forced transverse vibration of a single-walled carbon nanotube (SWNT) embedded with atomic-size particles was investigated using molecular dynamic simulations. The particles inside the cylindrical cantilever can be trapped near the antinodes or at the vicinity of the SWNT tip. The trapping phenomenon is highly sensitive to the external driving frequencies such that even very small changes in driving frequency can have a strong influence on the probability of the location of the particle inside the SWNT. The trapping effect could potentially be employed to realize the atomic scale control of particle position inside an SWNT via the finite adjustment of the external driving frequency. It may also be suggested that the trapping phenomenon could be utilized to develop high-sensitive mass detectors based on a SWNT resonator.

Passive particle focusing based on inertial microfluidics was recently introduced as a high-throughput alternative to active focusing methods that require an external force field to manipulate particles. In inertial microfluidics, dominant inertial forces cause particles to move across streamlines and occupy equilibrium positions along the faces of walls in flows through straight micro channels. In this study, we systematically analyzed the addition of secondary Dean forces by introducing curvature and show how randomly distributed particles entering a simple u-shaped curved channel are focused to a fixed lateral position exiting the curvature. We found the lateral particle focusing position to be fixed and largely independent of radius of curvature and whether particles entering the curvature are pre-focused (at equilibrium) or randomly distributed. Unlike focusing in straight channels, where focusing typically is limited to channel cross-sections in the range of particle size to create single focusing point, we report here particle focusing in a large cross-section area (channel aspect ratio 1:10). Furthermore, we describe a simple u-shaped curved channel, with single inlet and four outlets, for filtration applications. We demonstrate continuous focusing and filtration of 10 μm particles (with >90% filtration efficiency) from a suspension mixture at throughputs several orders of magnitude higher than flow through straight channels (volume flow rate of 4.25 ml/min). Finally, as an example of high throughput cell processing application, white blood cells were continuously processed with a filtration efficiency of 78% with maintained high viability. We expect the study will aid in the fundamental understanding of flow through curved channels and open the door for the development of a whole set of bio-analytical applications.

Here we show the detection of single gas molecules inside a carbon nanotube based on the change in resonance frequency and amplitude associated with the inertia trapping phenomenon. As its direct implication, a method for controlling the sequence of small molecule is then proposed to realize the concept of manoeuvring of matter atom by atom in one dimension. The detection as well as the implication is demonstrated numerically with the molecular dynamics method. It is theoretically assessed that it is possible for a physical model to be fabricated in the very near future.