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Testing the efficacy of atmospheric boundary layer height detection algorithms using uncrewed aircraft system data from MOSAiC
During the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, meteorological conditions over the lowest 1âkm of the atmosphere were sampled with the DataHawk2 (DH2) fixed-wing uncrewed aircraft system (UAS). These in situ observations of the central Arctic atmosphere are some of the most extensive to date and provide unique insight into the atmospheric boundary layer (ABL) structure. The ABL is an important component of the Arctic climate, as it can be closely coupled to cloud properties, surface fluxes, and the atmospheric radiation budget. The high temporal resolution of the UAS observations allows us to manually identify the ABL height (ZABL) for 65 out of the total 89 flights conducted over the central Arctic Ocean between 23 March and 26 July 2020 by visually analyzing profiles of virtual potential temperature, humidity, and bulk Richardson number. Comparing this subjective ZABL with ZABL identified by various previously published automated objective methods allows us to determine which objective methods are most successful at accurately identifying ZABL in the central Arctic environment and how the success of the methods differs based on stability regime. The objective methods we use are the LiuâLiang, Heffter, virtual potential temperature gradient maximum, and bulk Richardson number methods. In the process of testing these objective methods on the DH2 data, numerical thresholds were adapted to work best for the UAS-based sampling. To determine if conclusions are robust across different measurement platforms, the subjective and objective ZABL determination processes were repeated using the radiosonde profile closest in time to each DH2 flight. For both the DH2 and radiosonde data, it is determined that the bulk Richardson number method is the most successful at identifying ZABL, while the LiuâLiang method is least successful. The results of this study are expected to be beneficial for upcoming observational and modeling efforts regarding the central Arctic ABL
Very Constrained Minimal Supersymmetric Standard Models
We consider very constrained versions of the minimal supersymmetric extension
of the Standard Model (VCMSSMs) which, in addition to constraining the scalar
masses m_0 and gaugino masses m_{1/2} to be universal at some input scale,
impose relations between the trilinear and bilinear soft supersymmetry breaking
parameters A_0 and B_0. These relations may be linear, as in simple minimal
supergravity models, or nonlinear, as in the Giudice-Masiero mechanism for
generating the Higgs-mixing mu term. We discuss the application of the
electroweak vacuum conditions in VCMSSMs, which may be used to make a
prediction for tan beta as a function of m_0 and m_{1/2} that is usually
unique. We baseline the discussion of the parameter spaces allowed in VCMSSMs
by updating the parameter space allowed in the CMSSM for fixed values of tan
beta with no relation between A_0 and B_0 assumed {\it a priori}, displaying
contours of B_0 for a fixed input value of A_0, incorporating the latest CDF/D0
measurement of m_t and the latest BNL measurement of g_mu - 2. We emphasize
that phenomenological studies of the CMSSM are frequently not applicable to
specific VCMSSMs, notably those based on minimal supergravity, which require
m_0 = m_{3/2} as well as A_0 = B_0 + m_0. We then display (m_{1/2}, m_0) planes
for selected VCMSSMs, treating in a unified way the parameter regions where
either a neutralino or the gravitino is the LSP. In particular, we examine in
detail the allowed parameter space for the Giudice-Masiero model.Comment: 26 pages, 32 eps figure
Probing F-theory With Multiple Branes
We study multiple 3-branes on an F theory orientifold. The world-volume
theory of the 3-branes is d=4, N=2 Sp(2k) gauge theory with an antisymmetric
tensor and four flavors of matter in the fundamental. The solution of this
gauge theory is found for vanishing bare mass of the antisymmetric tensor
matter, and massive fundamental matter. The integrable system underlying this
theory is constructed.Comment: 9 pages, harvma
Type IIA Superstrings, Chiral Symmetry, and N=1 4D Gauge Theory Dualities
We study N=1 four dimensional gauge theories as the world volume theory of
D4-branes between NS 5-branes. We find constructions for a number of known
field theory dualities involving groups, coupled by
matter fields F in the representation, in terms of branes of
type IIA string theory. The dual gauge group follows from simply reversing the
ordering of the NS 5-branes and the D6-branes while conserving magnetic charge
on the world volume of the branes. We interpret many field theory phenomena
such as deformation of the superpotential W = \Tr (F\tilde F)^{k+1} in terms
of the position of branes. By looking to D-branes for guidance, we find new N=1
dualities involving arbitrary numbers of gauge groups. We propose a mechanism
for enhanced chiral symmetry in the brane construction which, we conjecture, is
associated with tensionless threebranes in six dimensions.Comment: 32 pages, 9 figures, uses harvmac, tables, and eps
Modeling Networks of Coupled Enzymatic Reactions Using the Total Quasi-Steady State Approximation
In metabolic networks, metabolites are usually present in great excess over the enzymes that catalyze their interconversion, and describing the rates of these reactions by using the MichaelisâMenten rate law is perfectly valid. This rate law assumes that the concentration of enzymeâsubstrate complex (C) is much less than the free substrate concentration (S (0)). However, in protein interaction networks, the enzymes and substrates are all proteins in comparable concentrations, and neglecting C with respect to S (0) is not valid. Borghans, DeBoer, and Segel developed an alternative description of enzyme kinetics that is valid when C is comparable to S (0). We extend this description, which Borghans et al. call the total quasi-steady state approximation, to networks of coupled enzymatic reactions. First, we analyze an isolated GoldbeterâKoshland switch when enzymes and substrates are present in comparable concentrations. Then, on the basis of a real example of the molecular network governing cell cycle progression, we couple two and three GoldbeterâKoshland switches together to study the effects of feedback in networks of protein kinases and phosphatases. Our analysis shows that the total quasi-steady state approximation provides an excellent kinetic formalism for protein interaction networks, because (1) it unveils the modular structure of the enzymatic reactions, (2) it suggests a simple algorithm to formulate correct kinetic equations, and (3) contrary to classical MichaelisâMenten kinetics, it succeeds in faithfully reproducing the dynamics of the network both qualitatively and quantitatively
Sodium content as a predictor of the advanced evolution of globular cluster stars
The asymptotic giant branch (AGB) phase is the final stage of nuclear burning
for low-mass stars. Although Milky Way globular clusters are now known to
harbour (at least) two generations of stars they still provide relatively
homogeneous samples of stars that are used to constrain stellar evolution
theory. It is predicted by stellar models that the majority of cluster stars
with masses around the current turn-off mass (that is, the mass of the stars
that are currently leaving the main sequence phase) will evolve through the AGB
phase. Here we report that all of the second-generation stars in the globular
cluster NGC 6752 -- 70 per cent of the cluster population -- fail to reach the
AGB phase. Through spectroscopic abundance measurements, we found that every
AGB star in our sample has a low sodium abundance, indicating that they are
exclusively first-generation stars. This implies that many clusters cannot
reliably be used for star counts to test stellar evolution timescales if the
AGB population is included. We have no clear explanation for this observation.Comment: Published in Nature (online 29 May 2013, hard copy 13 June), 12
pages, 3 figures + supplementary information sectio
Probing The Multiphase Interstellar Medium Of The Dwarf Starburst Galaxy NGC 625 With FUSE Spectroscopy
We present new FUSE spectroscopy of the dwarf starburst galaxy NGC 625. These
observations probe multiple phases of the interstellar medium, including the
coronal, ionized, neutral and molecular gas. This nearby (D = 3.9 +/- 0.2 Mpc)
system shows a clear detection of outflowing coronal gas as traced by OVI 1032
Angstrom absorption. The centroid of the OVI profile is blueshifted with
respect to the galaxy systemic velocity by ~ 30 km/sec, suggesting a
low-velocity outflow. The implied OVI velocity extent is found to be 100 +/- 20
km/sec, which is fully consistent with the detected HI outflow velocity found
in radio synthesis observations. We detect multiple lines of diffuse H2
absorption from the ISM of NGC 625; this is one of only a few extragalactic
systems with FUSE detections of H2 lines in the Lyman and Werner bands. We find
a potential abundance offset between the neutral and nebular gas that exceeds
the errors on the derived column densities. Since such an offset has been found
in multiple dwarf galaxies, we discuss the implications of a lower-metallicity
halo surrounding the central star forming regions of dwarf galaxies. The
apparent offset may be due to saturation of the observed OI line, and higher
S/N observations are required to resolve this issue.Comment: ApJ, in press; full-resolution version may be obtained at
http://www.astro.umn.edu/~cannon/n625.fuse.p
Optimal use of tandem biotin and V5 tags in ChIP assays
Background: Chromatin immunoprecipitation (ChIP) assays coupled to genome arrays (Chip-on-chip) or massive parallel sequencing (ChIP-seq) lead to the genome wide identification of binding sites of chromatin associated proteins. However, the highly variable quality of antibodies and the availability of epitopes in crosslinked chromatin can compromise genomic ChIP outcomes. Epitope tags have often been used as more reliable alternatives. In addition, we have employed protein in vivo biotinylation tagging as a very high affinity alternative to antibodies. In this paper we describe the optimization of biotinylation tagging for ChIP and its coupling to a known epitope tag in providing a reliable and efficient alternative to antibodies. Results: Using the biotin tagged erythroid transcription factor GATA-1 as example, we describe several optimization steps for the application of the high affinity biotin streptavidin system in ChIP. We find that the omission of SDS during sonication, the use of fish skin gelatin as blocking agent and choice of streptavidin beads can lead to significantly improved ChIP enrichments and lower background compared to antibodies. We also show that the V5 epitope tag performs equally well under the conditions worked out for streptavidin ChIP and that it may suffer less from the effects of formaldehyde crosslinking. Conclusion: The combined use of the very high affinity biotin tag with the less sensitive to crosslinking V5 tag provides for a flexible ChIP platform with potential implications in ChIP sequencing outcomes
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