Microfluidic Platform for Adherent Single Cell High-Throughput Screening

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Traditionally, in vitro investigations on biology and physiology of cells rely on averaging the responses eliciting from heterogeneous cell populations, thus being unsuitable for assessing individual cell behaviors in response to external stimulations. In the last years, great interest has thus been focused on single cell analysis and screening, which represents a promising tool aiming at pursuing the direct and deterministic control over cause-effect relationships guiding cell behavior. In this regard, a high-throughput microfluidic platform for trapping and culturing adherent single cells was presented. A single cell trapping mechanism was implemented based on dynamic variation of fluidic resistances. A round-shaped culture chamber (Φ=250μm, h=25μm) was conceived presenting two connections with a main fluidic path: (i) an upper wide opening, and (ii) a bottom trapping junction which modulates the hydraulic resistance. Several layouts of the chamber were designed and computationally validated for the optimization of the single cell trapping efficacy. The optimized chamber layouts were integrated in a polydimethylsiloxane (PDMS) microfluidic platform presenting two main functionalities: (i) 288 chambers for trapping single cells, and (ii) a chaoticmixer based serial dilution generator for delivering both soluble factors and non-diffusive molecules under spatio-temporally controlled chemical patterns. The devices were experimentally validated and allowed for trapping individual U87-MG (human glioblastoma-astrocytoma epithelial-like) cells and culturing them up to 3 days

High-throughput microfluidic platform for adherent single cells non-viral gene delivery

The widespread use of gene therapy as a therapeutic tool relies on the development of DNA-carrying vehicles devoid of any safety concerns. In contrast to viral vectors, non-viral gene carriers show promise in this perspective, although their low transfection efficiency leads to the necessity to carry out further optimizations. In order to overcome the limitations of traditional macroscale approaches, which mainly consist of time-consuming and simplified models, a microfluidic strategy has been developed to carry out transfection studies on single cells in a high-throughput and deterministic fashion. A single cell trapping mechanism has been implemented, based on the dynamic variation of fluidic resistances. For this purpose, we designed a round-shaped culture chamber integrated with a bottom trapping junction, which modulates the hydraulic resistance. Several layouts of the chamber were designed and computationally validated for optimization of the single cell trapping efficacy. The optimized chamber layout was integrated in a polydimethylsiloxane (PDMS) microfluidic platform presenting two main functionalities: (i) 288 chambers for trapping single cells, and (ii) a serial dilution generator with chaotic mixing properties, able to deliver to the chambers both soluble factors and non-diffusive particles (i.e., polymer/DNA complexes, polyplexes) under spatio-temporally controlled chemical patterns. The devices were experimentally validated and allowed the trapping of individual human glioblastoma–astrocytoma epithelial-like cells (U87-MG) with a trapping efficacy of about 40%. The cells were cultured within the device and underwent preliminary transfection experiments using 25 kDa linear polyethylenimine (lPEI)-based polyplexes, confirming the potentiality of the proposed platform for the future high-throughput screening of gene delivery vectors and for the optimization of transfection protocols

Implicit neural representations for unsupervised super-resolution and denoising of 4D flow MRI

4D flow MRI is a non-invasive imaging method that can measure blood flow velocities over time. However, the velocity fields detected by this technique have limitations due to low resolution and measurement noise. Coordinate-based neural networks have been researched to improve accuracy, with SIRENs being suitable for super-resolution tasks. Our study investigates SIRENs for time-varying 3-directional velocity fields measured in the aorta by 4D flow MRI, achieving denoising and super-resolution. We trained our method on voxel coordinates and benchmarked our approach using synthetic measurements and a real 4D flow MRI scan. Our optimized SIREN architecture outperformed state-of-the-art techniques, producing denoised and super-resolved velocity fields from clinical data. Our approach is quick to execute and straightforward to implement for novel cases, achieving 4D super-resolution

Results of the studies on energy deposition in IR6 superconducting magnets from continuous beam loss on the TCDQ system

A single sided mobile graphite diluter block TCDQ, in combination with a two-sided secondary collimator TCS and an iron shield TCDQM, will be installed in front of the superconducting quadrupole Q4 magnets in IR6, in order to protect it and other downstream LHC machine elements from destruction in the event of a beam dump that is not synchronised with the abort gap. The TCDQ will be positioned close to the beam, and will intercept the particles from the secondary halo during low beam lifetime. Previous studies (1-4) have shown that the energy deposited in the Q4 magnet coils can be close to or above the quench limit. In this note the results of the latest FLUKA energy deposition simulations for Beam 2 are described, including an upgrade possibility for the TCDQ system with an additional shielding device. The results are discussed in the context of the expected performance levels for the different phases of LHC operation

An instrument for low-level measurements of the leakage current from high-voltage biased detectors

Resistive Plates Chambers (RPC) are detectors biased at High-Voltage (HV) in excess of 4 kV. When fired by a particle, they develop a large signal current that can be read across a small resistance, 100 Omega or so. A characterization has been made of their ageing as a function of the behaviour of their leakage current with time. An array of 10 detectors has been developed for this purpose. We present the instrument designed and built to perform a continuous and automatic monitoring of the leakage current from each detector of the array, while the system is taking data. For the particular biasing set-up adopted, the current has been measured in series to the terminal connected to the HV of every channel. Since the small value of the currents, order of tens of nA, a special circuit solution and special precautions have been adopte

Measurements of heavy ion beam losses from collimation

The collimation efficiency for Pb ion beams in the LHC is predicted to be lower than requirements. Nuclear fragmentation and electromagnetic dissociation in the primary collimators create fragments with a wide range of Z/A ratios, which are not intercepted by the secondary collimators but lost where the dispersion has grown sufficiently large. In this article we present measurements and simulations of loss patterns generated by a prototype LHC collimator in the CERN SPS. Measurements were performed at two different energies and angles of the collimator. We also compare with proton loss maps and find a qualitative difference between Pb ions and protons, with the maximum loss rate observed at different places in the ring. This behavior was predicted by simulations and provides a valuable benchmark of our understanding of ion beam losses caused by collimation.Comment: 12 pages, 20 figure

Effect of the quantum well thickness on the performance of InGaN photovoltaic cells

International audienceWe report on the influence of the quantum well thickness on the effective band gap and conversion efficiency of In0.12Ga0.88N/GaN multiple quantum well solar cells. The band-to-band transition can be redshifted from 395 to 474 nm by increasing the well thickness from 1.3 to 5.4 nm, as demonstrated by cathodoluminescence measurements. However, the redshift of the absorption edge is much less pronounced in absorption: in thicker wells, transitions to higher energy levels dominate. Besides, partial strain relaxation in thicker wells leads to the formation of defects, hence degrading the overall solar cell performance. InGaN alloys are considered as promising candidates for high-efficiency photovoltaic devices [1-4] since their band gap spans almost the whole solar spectrum from 0.7 eV (InN) to 3.4 eV (GaN). This makes theoretically possible the development of all-InGaN multijunction solar cells with a freely customizable number of junctions to enhance the overall efficiency. However, the large lattice mismatch between GaN and InN has led several groups to study the possibility of hybrid integration, combining an InGaN cell in a tandem device with silicon [5,6] or other non-III-nitride [7] photovoltaic cells. The difficulty of growing high-quality InGaN layers increases with the In content. Reports of InGaN-based junctions with an In mole fraction exceeding 0.3 are rare [1]; the best external quantum efficiencies (EQEs) exceeding 0.7 are obtained at around 400 nm and quickly drop for longer wavelengths [8-10]. The main challenges are the large dislocation density and In-clustering, caused by the strong tendency to phase separation during growth. Absorbing layers in the form of a multiple quantum well (MQW) structure are often used to delay strain relaxation. Furthermore, the quantum confined Stark effect (QCSE) associated to the strong piezoelectric fields in the InGaN/GaN system [11] offers the possibility to tune the effective band gap of the structure by adjusting the quantum well (QW) and barrier thickness (tQW and tB, respectively). The effect of tuning tB in InGaN/GaN MQW photovoltaic devices has been studied by Wierer et al. [12] and Watanabe et al. [13]. According to their results, the absorption cutoff of the solar cells redshifts with decreasing tB. However, this does not always translate in enhanced overall cell efficiency, since the short circuit current density (Jsc) and open circuit voltage (Voc) also depend on tB. In this paper, we focus on the influence of the QW thickness on the effective band gap of the junction and its impact on the overall cell efficiency. We experimentally demonstrate that the band-to-band transition in InGaN QWs can be significantly redshifted in larger QWs. However, this redshift appears linked to a dramatic enlargement of the Stokes shift, so that increasing the tQW above a few nm is n

The Green Bank Ammonia Survey: Unveiling the Dynamics of the Barnard 59 star-forming Clump

Understanding the early stages of star formation is a research field of ongoing development, both theoretically and observationally. In this context, molecular data have been continuously providing observational constraints on the gas dynamics at different excitation conditions and depths in the sources. We have investigated the Barnard 59 core, the only active site of star formation in the Pipe Nebula, to achieve a comprehensive view of the kinematic properties of the source. These information were derived by simultaneously fitting ammonia inversion transition lines (1,1) and (2,2). Our analysis unveils the imprint of protostellar feedback, such as increasing line widths, temperature and turbulent motions in our molecular data. Combined with complementary observations of dust thermal emission, we estimate that the core is gravitationally bound following a virial analysis. If the core is not contracting, another source of internal pressure, most likely the magnetic field, is supporting it against gravitational collapse and limits its star formation efficiency.Comment: 18 pages, 18 figure

Influence of biological maturation on postural control in young soccer players

Biological maturation does not follow a linear development path; the process presents inter- individual differences concerning the timing of psychophysical development. The nonlinear nature of the biological maturation process often results in sudden and rapid modifications that can influence the sensorimotor functions, in particular when the peak height velocity (PHV) is approaching. Static standing balance and postural control are fundamental skills, both for daily living and sport performance, that can be strongly affected by PHV. We examined the influence of biological maturation on the performance of static standing balance, an index for sensorimotor control. Two-hundred and 38 young healthy soccer players (U9 to U17), playing in a sub-\ue9lite club (at least two training sessions and an official match per week), were evaluated. After anthropometric measurement, standing balance was assessed using a baropodometric platform (BTS P-Walk, Italy). Subjects stood barefooted on the platform and were recorded at 20 Hz during two 30-s tests, the first with eyes open and the second keeping eyes closed. Participants were split into six groups based on the Maturity Offset (MO), representing the estimated time to/from the PHV and calculated according to Mirwald et al1. The body center of pressure (CoP) sway area and velocity were calculated. Differences between MO groups were tested using a 2-factor (MO and condition) ANOVA with repeated measures on the condition factor (eyes open/closed). The sway area showed a decreasing trend as the MO increased, in particular in MO<-1.5 was higher than in MO>0.5 (p<0.001). Likewise, CoP velocity presented a similar pattern (p<0.001), with a marked decline in groups with MO>0.5. The results suggest that biological maturation is associated with changes in standing balance control. The reduction of CoP sway area and velocity as the MO increase represents the improved efficiency of the postural control system