Topological Analysis of Magnetically Induced Current Densities in Strong Magnetic Fields

Stagnation graphs provide a useful tool to analyse the main topological features of the, often complicated, vector field associated with magnetically induced currents. Previously these graphs have been constructed using response quantities appropriate for modest applied magnetic fields. An implementation capable of producing these graphs in arbitrarily strong magnetic fields is presented, using current-density-functional theory. This enables the study of how the topology of the current vector field changes with the strength and orientation of the applied magnetic field. Applications to CH4, C2H2 and C2H4 are presented. In each case we consider molecular geometries optimized in the presence of the magnetic field. The stagnation graphs reveal subtle changes to this vector field where the symmetry of the molecule remains constant. However, when the electronic state and symmetry of the corresponding equilibrium geometry changes with increasing field strength, the changes to the stagnation graph are extensive. The approach presented here will be helpful in interpreting changes in molecular structure and bonding in the strong-field regime

Topological Analysis of Magnetically Induced Current Densities in Strong Magnetic Fields

Stagnation graphs provide a useful tool to analyse the main topological features of the, often complicated, vector field associated with magnetically induced currents. Previously these graphs have been constructed using response quantities appropriate for modest applied magnetic fields. An implementation capable of producing these graphs in arbitrarily strong magnetic fields is presented, using current-density-functional theory. This enables the study of how the topology of the current vector field changes with the strength and orientation of the applied magnetic field. Applications to CH4, C2H2 and C2H4 are presented. In each case we consider molecular geometries optimized in the presence of the magnetic field. The stagnation graphs reveal subtle changes to this vector field where the symmetry of the molecule remains constant. However, when the electronic state and symmetry of the corresponding equilibrium geometry changes with increasing field strength, the changes to the stagnation graph are extensive. The approach presented here will be helpful in interpreting changes in molecular structure and bonding in the strong-field regime

Incorporating collisions and resistance into the transition from field emission to the space charge regime

Advancements in microelectromechanical systems (MEMS) and microplasmas, particularly with respect to applications in combustion and biotechnology, motivate studies into microscale gas breakdown to enable safe system design and implementation. Breakdown at microscale deviates from that predicted by Paschen’s law due to field emission—the stripping of electrons from the cathode in the presence of strong surface field—and follows the Fowler-Nordheim (FN) law. As injected current increases at this length scale, electrons accumulate in the gap and FN electron emission becomes space charge limited, leading to the Child-Langmuir (CL) law at vacuum and the Mott-Gurney (MG) law at high pressure. While theoretical studies link CL to FN and CL to MG, none links all three to simultaneously assess the importance of pressure and external resistance (perturbation) on electron emission. This study extends existing theory to elucidate the transition between these regimes as a function of applied voltage, gap distance, electron mobility, and external resistance, and in particular, derives asymptotic equations illustrating the transitions between the three. It also demonstrates the presence of a triple point, where one theoretically encounters FN, CL, and MG at once, and characterizes the importance of gap pressure and distance on these regimes, especially when MG dominates at non-vacuum pressures. The sensitivity of the triple point to external resistance, representative of the effects of perturbations in system parameters on electron emission, receives special attention

Interactome comparison of human embryonic stem cell lines with the inner cell mass and trophectoderm

Networks of interacting co-regulated genes distinguish the inner cell mass (ICM) from the differentiated trophectoderm (TE) in the preimplantation blastocyst, in a species specific manner. In mouse the ground state pluripotency of the ICM appears to be maintained in murine embryonic stem cells (ESCs) derived from the ICM. This is not the case for human ESCs. In order to gain insight into this phenomenon, we have used quantitative network analysis to identify how similar human (h)ESCs are to the human ICM. Using the hESC lines MAN1, HUES3 and HUES7 we have shown that all have only a limited overlap with ICM specific gene expression, but that this overlap is enriched for network properties that correspond to key aspects of function including transcription factor activity and the hierarchy of network modules. These analyses provide an important framework which highlights the developmental origins of hESCs

Space-charge-limited current density for nonplanar diodes with monoenergetic emission using Lie-point symmetries

Understanding space-charge limited current density (SCLCD) is fundamentally and practically important for characterizing many high-power and high-current vacuum devices. Despite this, no analytic equations for SCLCD with nonzero monoenergetic initial velocity have been derived for nonplanar diodes from first principles. Obtaining analytic equations for SCLCD for nonplanar geometries is often complicated by the nonlinearity of the problem and over constrained boundary conditions. In this letter, we use the canonical coordinates obtained by identifying Lie-point symmetries to linearize the governing differential equations to derive SCLCD for any orthogonal diode. Using this method, we derive exact analytic equations for SCLCD with a monoenergetic injection velocity for one-dimensional cylindrical, spherical, tip-to-tip (t-t), and tip-to-plate (t-p) diodes. We specifically demonstrate that the correction factor from zero initial velocity to monoenergetic emission depends only on the initial kinetic and electric potential energies and not on the diode geometry and that SCLCD is universal when plotted as a function of the canonical gap size. We also show that SCLCD for a t-p diode is a factor of four larger than a t-t diode independent of injection velocity. The results reduce to previously derived results for zero initial velocity using variational calculus and conformal mapping.Comment: 18 pages, 3 figure

Gene expression signatures predict response to therapy with growth hormone

Xarxes reguladores de gens; Marcadors predictiusRedes reguladoras de genes; Marcadores predictivosGene regulatory networks; Predictive markersRecombinant human growth hormone (r-hGH) is used as a therapeutic agent for disorders of growth including growth hormone deficiency (GHD) and Turner syndrome (TS). Treatment is costly and current methods to model response are inexact. GHD (n = 71) and TS patients (n = 43) were recruited to study response to r-hGH over 5 years. Analysis was performed using 1219 genetic markers and baseline (pre-treatment) blood transcriptome. Random forest was used to determine predictive value of transcriptomic data associated with growth response. No genetic marker passed the stringency criteria for prediction. However, we identified an identical set of genes in both GHD and TS whose expression could be used to classify therapeutic response to r-hGH with a high accuracy (AUC > 0.9). Combining transcriptomic markers with clinical phenotype was shown to significantly reduce predictive error. This work could be translated into a single genomic test linked to a prediction algorithm to improve clinical management. Trial registration numbers: NCT00256126 and NCT00699855.This work was supported by Merck KGaA, Darmstadt, Germany

Topological Analysis of Magnetically Induced Current Densities in Strong Magnetic Fields Using Stagnation Graphs

Stagnation graphs provide a useful tool to analyze the main topological features of the often complicated vector field associated with magnetically induced currents. Previously, these graphs have been constructed using response quantities appropriate for modest applied magnetic fields. We present an implementation capable of producing these graphs in arbitrarily strong magnetic fields, using current-density-functional theory. This enables us to study how the topology of the current vector field changes with the strength and orientation of the applied magnetic field. Applications to CH4, C2H2 and C2H4 are presented. In each case, we consider molecular geometries optimized in the presence of the magnetic field. The stagnation graphs reveal subtle changes to this vector field where the symmetry of the molecule remains constant. However, when the electronic state and symmetry of the corresponding equilibrium geometry changes with increasing field strength, the changes to the stagnation graph are extensive. We expect that the approach presented here will be helpful in interpreting changes in molecular structure and bonding in the strong-field regime

Community and service provider views to inform the 2013 WHO consolidated antiretroviral guidelines:key findings and lessons learnt

Objective:The objective was to evaluate community and healthcare worker (HCW) values and preferences on key topics to inform the development of the 2013 WHO consolidated guidelines for antiretroviral therapy in low and middle income countries. Design:Cross-sectional e-survey and e-forum discussion; focus group discussions (FGDs) Methods:Data were collected on community perspectives regarding a range of potential clinical and operational recommendations in the 2013 guidelines between November 2012 and January 2013 through an e-survey (n = 1088) and e-forum (n = 955). Additional FGDs were held with people living with HIV (PLHIV) in Malawi and Uganda (n = 88) on antiretroviral therapy (ART) use among pregnant women. Two surveys were also undertaken on similar topics covered in the e-survey for health care workers caring for adults (n = 98) and children (n = 348). Results:There were 1088 e-survey respondents from 117 countries: of whom 37.7% (298/791) were females, 49.9% (431/864) PLHIV, and 20.9% (174/831) from low-income countries. The proportion of e-survey respondents who supported raising the CD4 T-cell threshold for ART initiation in adults from 350 to 500 cells/μl was 51.0% (355/696), and regardless of CD4 T-cell count for all pregnant females 89.8% (607/676), HIV serodiscordant partners 71.9% (486/676), and all children on diagnosis of infection 47.4% (212/447). E-survey respondents strongly supported discontinuing use of stavudine (72.7%, 416/572), task-shifting/sharing from doctors to nurses (75.2%, 275/365) and from nurses to community health workers (71.1%, 261/367) as strategies to expand access to HIV testing, care, and treatment. Focus group discussion respondents identified service capacity, and social and legal concerns as key considerations influencing the decisions of women living with HIV to continue ART after the risk of vertical transmission has passed. Key lessons learnt in these consultations included the need for piloting and validation of questions; sufficient time to adequately disseminate the survey; and consideration of using FGDs and mobile phone technology to improve participation of people with limited internet access. Conclusion:Community participation in guideline development processes is important to ensure that their perspectives are considered in the resulting recommendations. Communities should be actively involved in the adaptation, implementation, and accountability processes related to the guidelines

Fine needle aspiration of human lymph nodes reveals cell populations and soluble interactors pivotal to immunological priming

Lymph node (LN) fine needle aspiration (LN FNA) represents a powerful technique for minimally invasive sampling of human LNs in vivo and has been used effectively to directly study aspects of the human germinal center response. However, systematic deep phenotyping of the cellular populations and cell-free proteins recovered by LN FNA has not been performed. Thus, we studied human cervical LN FNAs as a proof-of-concept and used single-cell RNA-sequencing and proteomic analysis to benchmark this compartment, define the purity of LN FNA material, and facilitate future studies in this immunologically pivotal environment. Our data provide evidence that LN FNAs contain bone-fide LN-resident innate immune populations, with minimal contamination of blood material. Examination of these populations reveals unique biology not predictable from equivalent blood-derived populations. LN FNA supernatants represent a specific source of lymph- and lymph node-derived proteins, and can, aided by transcriptomics, identify likely receptor–ligand interactions. This represents the first description of the types and abundance of immune cell populations and cell-free proteins that can be efficiently studied by LN FNA. These findings are of broad utility for understanding LN physiology in health and disease, including infectious or autoimmune perturbations, and in the case of cervical nodes, neuroscience