Design and testing of a new aircraft-based cloud water sampling system

December 2002Also issued as Derek J. Straub's dissertation (Ph.D.) -- Colorado State University, 2002.Includes bibliographical references.Experimental studies of cloud processing mechanisms necessitate the collection of representative samples of cloud water for chemical analysis. In order to provide samples from clouds that are inaccessible from ground-based sampling stations, a new aircraft-based cloud water collection system has been developed . The objective of the design process was to produce an automated collector that can acquire well-characterized cloud water samples and is portable between multiple research aircraft. Issues such as cloud drop shatter and re-entrainment, structural integrity, system size and weight, material compatibility with the anticipated chemical analyses, and ease of use during field operation w re all considered during the design process. The new cloud water collection system utilizes an axial-flow cyclone to centrifugally separate cloud drops from the air stream. Up to seven individual samples can be stored over the course of a single research flight. An analysis of the axial-flow cyclone was performed with a finite volume based computational fluid dynamics (CFD) code. Solutions were obtained for air flow patterns and cloud drop trajectories. The predicted continuous phase (air) velocity field indicates that the axial-flow cyclone generates a strong rotational ow field with a tangential velocity of 85 ms-'. Based on simulations of cloud drop trajectories, centrifugal force in the rotational flow field is sufficient to quickly move entrained cloud drops to the wall of the axial-flow cyclone duct where they can be removed for storage. Collection efficiency as a function of drop size was ascertained and the 50% cut diameter was determined to be approximately 8 microns. An experimental laboratory calibration involving monodisperse fluorescein-tagged drops verified the numerical modeling results. The system was deployed during the Dynamics an Chemistry of Marine Stratocumulus, Phase II (DYCOM -II) field project in July 2001. The DYCOMS-II campaign served as a testing and evaluation program for the system as well as an opportunity to study the chemical composition of stratocumulus clouds in the remote marine environment. Over the course of the project, 50 samples were obtained during seven nighttime and two daytime flights. Sample pH was measured on-site after each flight. Peroxide, formaldehyde, S(IV), trace metals and major ions (Cr, NO3-, so/-, Na+, NH/, K+, ca2+, and Mg2+) were preserved on site and analyzed after the field campaign. The analyses were used to characterize the composition of the sampled clouds and to investigate cloud processing mechanisms, including the potential for rapid aqueous phase oxidation of S(IV) to sulfate.Sponsored by the National Science Foundation ATM-0084696, and the National Center for Atmospheric Research Advanced Study Program

Numerical and experimental performance evaluation of two multi-stage cloud collectors

January 1999.Also issued as Derek J. Straub's thesis (M.S.) -- Colorado State University, 1999.Includes bibliographical references.An evaluation of the collection characteristics of two new multi-stage cascade inertial impactors designed for size-resolved cloud drop collection has been performed. The FROSTY supercooled cloud collector is intended for the collection of supercooled cloud drops in a winter environment in three independent size fractions with stage 50% cut diameters of 15 μm, 10 μm, and 4 μm . The CSU 5-Stage cloud collector is designed for sampling warm clouds in five distinct fractions on five stages that have desired 50% cut diameters of 30, 25, 15 , 10, and 4 μm. Two approaches were selected for the evaluation of the FROSTY and CSU 5-Stage cloud collectors. Numerical simulations provided a visualization of the air flow patterns and drop trajectories through the collectors while experimental laboratory calibrations provided a quantitative analysis of true collection performance. For each of these methods, 50% cut diameters, efficiency curves, and wall losses for each stage of the FROSTY and CSU 5-Stage collectors were derived. The experimental calibration work indicated that distinct fractions of cloudwater are collected in each stage of the FROSTY and CSU 5-Stage collectors. At laboratory conditions, the experimentally determined 50% cut diameters for the three stages of the FROSTY supercooled cloud collector were 19, 11.5, and 5 μm. Drop losses to the interstage wall surfaces in the FROSTY collector peaked at approximately 35% for 16 μm drops and were lower for larger and smaller drop sizes. For operation at design conditions of 3000 m elevation and -4° C, the 50% cut diameters are expected to decrease to 17, 10.5, and 4.5 μm. The experimentally determined 50% cut diameters, measured at laboratory conditions, for the CSU 5-Stage cloud collector were 25.5, 29, 17.5, 10.5, and 4.5 μm for stages 1 through 5, respectively. Wall losses tended to be higher than those for the FROSTY cloud collector across the drop size range under consideration. Losses peaked at nearly 45% for drops between 10 and 18 μm in diameter and decreased to about 20% at the largest and smallest drop sizes. 50% cut diameters are expected to remain essentially unchanged for CSU 5-Stage collector operation at sea level design conditions. Numerical modeling of the air flow patterns as well as drop trajectories through the FROSTY and CSU 5-Stage cloud collectors was performed with the commercially available Computational Fluid Dynamics (CFO) software package FLUENT, from Fluent, Inc. FLUENT offered two alternatives for the calculation of drop trajectories. Trajectory simulations based on the average continuous phase (air) velocity field as well as trajectory simulations which included the effects of statistically derived turbulent velocity fluctuations on drop motion were performed. Drop collection patterns based on these types of trajectory calculations were used to generate collection efficiency curves. Comparisons were made between the numerically predicted collection efficiency curves and efficiency curves established through experimental calibration. These comparisons indicated that the inclusion of turbulent fluctuation effects on drop motion provided better agreement with experimental observations than trajectories based only on average flow field velocities. However, the use of velocity fluctuations defined by default parameters also produced unrealistic losses to wall surfaces for small drop sizes. The parameters controlling turb lent velocity fluctuation effects on drop motion were examined in an effort to provide better agreement between the numerical and experimental results. Despite this shortcoming, numerically derived 50% cut diameters and overall collection efficiency curve shapes, for drop trajectories including turbulent velocity fluctuations, agreed reasonably well with experimental observations in most cases.Sponsored by the National Science Foundation ATM-9509596 , and the U.S. Environmental Research and Quality Assurance R82-3979-010

CRISPR/Cas9-Mediated Gene Knock-Down in Post-Mitotic Neurons

The prokaryotic adaptive immune system CRISPR/Cas9 has recently been adapted for genome editing in eukaryotic cells. This technique allows for sequence-specific induction of double-strand breaks in genomic DNA of individual cells, effectively resulting in knock-out of targeted genes. It thus promises to be an ideal candidate for application in neuroscience where constitutive genetic modifications are frequently either lethal or ineffective due to adaptive changes of the brain. Here we use CRISPR/Cas9 to knock-out Grin1, the gene encoding the obligatory NMDA receptor subunit protein GluN1, in a sparse population of mouse pyramidal neurons. Within this genetically mosaic tissue, manipulated cells lack synaptic current mediated by NMDA-type glutamate receptors consistent with complete knock-out of the targeted gene. Our results show the first proof-of-principle demonstration of CRISPR/Cas9-mediated knock-down in neurons in vivo, where it can be a useful tool to study the function of specific proteins in neuronal circuits

Bayesian inference with Subset Simulation: Strategies and improvements

Bayesian Updating with Structural reliability methods (BUS) reinterprets the Bayesian updating problem as a structural reliability problem; i.e. a rare event estimation. The BUS approach can be considered an extension of rejection sampling, where a standard uniform random variable is added to the space of random variables. Each generated sample from this extended random variable space is accepted if the realization of the uniform random variable is smaller than the likelihood function scaled by a constant c. The constant c has to be selected such that 1∕c is not smaller than the maximum of the likelihood function, which, however, is typically unknown a-priori. A c chosen too small will have negative impact on the efficiency of the BUS approach when combined with sampling-based reliability methods. For the combination of BUS with Subset Simulation, we propose an approach, termed aBUS, for adaptive BUS, that does not require c as input. The proposed algorithm requires only minimal modifications of standard BUS with Subset Simulation. We discuss why aBUS produces samples that follow the posterior distribution –even if 1∕c is selected smaller than the maximum of the likelihood function. The performance of aBUS in terms of the computed evidence required for Bayesian model class selection and in terms of the produced posterior samples is assessed numerically for different example problems. The combination of BUS with Subset Simulation (and aBUS in particular) is well suited for problems with many uncertain parameters and for Bayesian updating of models where it is computationally demanding to evaluate the likelihood function

Editorial: Insect pollinators in the Anthropocene: how multiple environmental stressors are shaping pollinator health

Editorial of the special issue "Insect pollinators in the Anthropocene: how multiple environmental stressors are shaping pollinator health

Embryonic sympathoblasts transiently express TrkB in vivo and proliferate in response to brain-derived neurotrophic factor in vitro

BACKGROUND: Nerve growth factor and neurotrophin-3 are involved in the development of sympathetic neurons; however, whether brain derived neurotrophic factor also plays a role is not known. The purpose of this study was to determine whether BDNF and its receptor, TrkB, are expressed during the development of paravertebral sympathetic ganglia in vivo and to determine the effect of BDNF in vitro. RESULTS: As neural crest cells coalesce to form sympathetic ganglia, TrkB-positive cells are seen in both chicken and mouse embryos. In chicken embryos, TrkB-expressing cells first appear at Hamburger-Hamilton Stage (St) 27 and they co-express HNK-1, confirming that they are migrating neural crest cells. The TrkB-positive cells lack neural markers at this stage; however, they migrate with other neurally differentiating cells that are TrkA and TrkC-positive. By St. 29/30, TrkB-positive cells begin to express the neural specific markers Hu C/D and Islet-1; eventually, all TrkB positive cells commence neural differentiation. By St. 34, TrkB and TrkC staining are lost. BDNF transcript expression parallels that of TrkB. In the mouse, TrkB-positive cells surround newly formed sympathetic ganglia and a small number of TrkB positive cells that co-express tyrosine hydroxylase are seen within ganglia between E13.5-15. In cell culture, many cells from St. 29–30 chicken lumbar sympathetic ganglia express neural markers and are dividing, indicating that they are sympathoblasts. Sympathoblasts and neurons require both nerve growth factor and neurotrophin-3 for survival. BDNF increases the number of cells expressing neural markers in culture by increasing number of cells that incorporate bromodeoxyuridine. In contrast, most TrkB-positive sympathetic cells in vivo are not actively proliferating between E6–E8. CONCLUSION: Developing paravertebral sympathetic ganglia in avian and murine embryos contain a subpopulation of sympathoblasts that transiently express TrkB and ultimately commence neuronal differentiation. These TrkB expressing sympathoblasts are not actively dividing in vivo; yet, when placed in vitro, will divide in response to BDNF. This suggests that the availability of BDNF in vivo fails to reach a threshold necessary to induce proliferation. We suggest that excess TrkB stimulation of sympathoblasts in vivo may lead to the genesis of neuroblastoma

How Does Individual Recognition Evolve? Comparing Responses to Identity Information in P olistes Species with and Without Individual Recognition

A wide range of complex social behaviors are facilitated by the recognition of individual conspecifics. Individual recognition requires sufficient phenotypic variation to provide identity information as well as receivers that process and respond to identity information. Understanding how a complex trait such as individual recognition evolves requires that we consider how each component has evolved. Previous comparative studies have examined phenotypic variability in senders and receiver learning abilities, although little work has compared receiver responses to identity information among related species with and without individual recognition. Here, we compare responses to identity information in two Polistes paper wasps: P. fuscatus, which visually recognizes individuals, and P. metricus , which does not normally show evidence of individual recognition. Although the species differ in individual recognition, the results of this study show that receiver responses to experimentally manipulated identity information are surprisingly similar in both species. Receivers direct less aggression toward identifiable individuals than unidentifiable individuals. Therefore, the responses necessary for individual recognition may pre‐date its evolution in the P. fuscatus lineage. Additionally, our data demonstrate the apparent binary differences in a complex behavior between the two species, such as individual recognition, likely involve incremental differences along a number of axes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102093/1/eth12191.pd

Revertant fibres and dystrophin traces in Duchenne muscular dystrophy: Implication for clinical trials

Duchenne muscular dystrophy (DMD) is characterised by the absence of dystrophin in muscle biopsies, although residual dystrophin can be present, either as dystrophin-positive (revertant) fibres or traces. As restoration of dystrophin expression is the end point of clinical trials, such residual dystrophin is a key factor in recruitment of patients and may also confound the analysis of dystrophin restoration in treated patients, if, as previously observed in the mdx mouse, revertant fibres increase with age. In 62% of the diagnostic biopsies reports of 65 DMD patients studied, traces or revertants were recorded with no correlation between traces or revertants, the patients' performance, or corticosteroids response. In nine of these patients, there was no increase in traces or revertants in biopsies taken a mean of 8.23 years (5.8-10.4 years) after the original diagnostic biopsy. This information should help in the design and execution of clinical trials focused on dystrophin restoration strategies. (C) 2010 Elsevier B.V. All rights reserved