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Evolution of surface roughness during CVD growth
Monte Carlo simulations of physical and chemical vapor deposition are used to study roughening kinetics of films that grow by nucleation and coalescence of clusters. The effects of interlayer transport, preferential dissociation of molecular precursors and energetic differences between the clusters and the substrate are examined
Contact Interactions and Resonance-Like Physics at Present and Future Colliders from Unparticles
High scale conformal physics can lead to unusual unparticle stuff at our low
energies. In this paper we discuss how the exchange of unparticles between
Standard Model fields can lead to new contact interaction physics as well as a
pseudoresonance-like structure, an unresonance, that might be observable at the
Tevatron or LHC in, e.g., the Drell-Yan channel. The specific signatures of
this scenario are quite unique and can be used to easily identify this new
physics given sufficient integrated luminosity.Comment: 20 pages, 10 figs; minor text changes, ref added; typos correcte
Cyclin-dependent kinase activity enhances phosphatidylcholine biosynthesis in Arabidopsis by repressing phosphatidic acid phosphohydrolase activity
Coordination of endomembrane biogenesis with cell cycle progression is considered to be important in maintaining cell function during growth and development. We previously showed that disruption of PHOSPHATIDIC ACID PHOSPHOHYDROLASE (PAH) activity in Arabidopsis thaliana stimulates biosynthesis of the major phospholipid phosphatidylcholine (PC) and causes expansion of the endoplasmic reticulum. Here we show that PC biosynthesis is repressed by disruption of the core cell cycle regulator CYCLIN-DEPENDENT KINASE A;1 (CDKA;1) and that this repression is reliant on PAH. Furthermore, we show that CDKs phosphorylate PAH1 at serine 162, which reduces both its activity and membrane association. Expression of a CDK-insensitive version of PAH1 with a serine 162 to alanine substitution represses PC biosynthesis and also reduces the rate of cell division in early leaf development. Together our findings reveal a physiologically important mechanism that couples the rate of phospholipid biosynthesis and endomembrane biogenesis to cell cycle progression in Arabidopsis
Scintillation and charge extraction from the tracks of energetic electrons in superfluid helium-4
An energetic electron passing through liquid helium causes ionization along
its track. The ionized electrons quickly recombine with the resulting positive
ions, which leads to the production of prompt scintillation light. By applying
appropriate electric fields, some of the ionized electrons can be separated
from their parent ions. The fraction of the ionized electrons extracted in a
given applied field depends on the separation distance between the electrons
and the ions. We report the determination of the mean electron-ion separation
distance for charge pairs produced along the tracks of beta particles in
superfluid helium at 1.5 K by studying the quenching of the scintillation light
under applied electric fields. Knowledge of this mean separation parameter will
aid in the design of particle detectors that use superfluid helium as a target
material.Comment: 10 pages, 8 figure
An adaptive array excitation scheme for the unidirectional enhancement of guided waves
Control over the direction of wave propagation allows an engineer to spatially locate defects. When imaging with longitudinal waves, time delays can be applied to each element of a phased array transducer to steer a beam. Because of the highly dispersive nature of guided waves (GWs), this beamsteering approach is suboptimal. More appropriate time delays can be chosen to direct a GW if the dispersion relation of the material is known. Existing techniques, however, need a priori knowledge of material thickness and acoustic velocity, which change as a function of temperature and strain. The scheme presented here does not require prior knowledge of the dispersion relation or properties of the specimen to direct a GW. Initially, a GW is generated using a single element of an array transducer. The acquired waveforms from the remaining elements are then processed and retransmitted, constructively interfering with the wave as it travels across the spatial influence of the transducer. The scheme intrinsically compensates for the dispersion of the waves, and thus can adapt to changes in material thickness and acoustic velocity. The proposed technique is demonstrated in simulation and experimentally. Dispersion curves from either side of the array are acquired to demonstrate the scheme's ability to direct a GW in an aluminum plate. The results show that unidirectional enhancement is possible without a priori knowledge of the specimen using an arbitrary pitch array transducer. The experimental results show a 34-dB enhancement in one direction compared with the other
Application of novel analytical ultracentrifuge analysis to solutions of fungal mannans
Polysaccharides, the most abundant biopolymers, are required for a host of activities in lower organisms, animals, and plants. Their solution characterization is challenging due to their complex shape, heterogeneity, and size. Here, recently developed data analysis approaches were applied for traditional sedimentation equilibrium and velocity methods in order to investigate the molar mass distribution(s) of a subtype of polysaccharide, namely, mannans from four Candida spp. The molecular weight distributions of these mannans were studied using two recently developed equilibrium approaches: SEDFIT-MSTAR and MULTISIG, resulting in corroboratory distribution profiles. Additionally, sedimentation velocity data for all four mannans, analyzed using ls-g*(s) and Extended Fujita approaches, suggest that two of the fungal mannans (FM-1 and FM-3) have a unimodal distribution of molecular species whereas two others (FM-2 and FM-4) displayed bi-modal and broad distributions, respectively: this demonstrates considerable molecular heterogeneity in these polysaccharides, consistent with previous observations of mannans and polysaccharides in general. These methods not only have applications for the characterization of mannans but for other biopolymers such as polysaccharides, DNA, and proteins (including intrinsically disordered proteins)
The universal Glivenko-Cantelli property
Let F be a separable uniformly bounded family of measurable functions on a
standard measurable space, and let N_{[]}(F,\epsilon,\mu) be the smallest
number of \epsilon-brackets in L^1(\mu) needed to cover F. The following are
equivalent:
1. F is a universal Glivenko-Cantelli class.
2. N_{[]}(F,\epsilon,\mu)0 and every probability
measure \mu.
3. F is totally bounded in L^1(\mu) for every probability measure \mu.
4. F does not contain a Boolean \sigma-independent sequence.
It follows that universal Glivenko-Cantelli classes are uniformity classes
for general sequences of almost surely convergent random measures.Comment: 26 page
Nuclear Modification Factor for Charged Pions and Protons at Forward Rapidity in Central Au+Au Collisions at 200 GeV
We present spectra of charged pions and protons in 0-10% central Au+Au
collisions at GeV at mid-rapidity () and forward
pseudorapidity () measured with the BRAHMS experiment at RHIC. The
spectra are compared to spectra from p+p collisions at the same energy scaled
by the number of binary collisions. The resulting nuclear modification factors
for central Au+Au collisions at both and exhibit suppression
for charged pions but not for (anti-)protons at intermediate . The
ratios have been measured up to GeV/ at the two
rapidities and the results indicate that a significant fraction of the charged
hadrons produced at intermediate range are (anti-)protons at both
mid-rapidity and
Forward and midrapidity like-particle ratios from p+p collisions at sqrt(s)=200 GeV
We present a measurement of pi-\pi+, K-/K+ and pbar/p from p+p collisions at
sqrt(s) = 20 0GeV over the rapidity range 0<y<3.4. For pT < 2.0 GeV/c we see no
significant transverse momentum dependence of the ratios. All three ratios are
independent of rapidity for y ~< 1.5 and then steadily decline from y ~ 1.5 to
y ~ 3. The pi-\pi+ ratio is below unity for y > 2.0. The pbar/p ratio is very
similar for p+p and 20% central Au+Au collisions at all rapidities. In the
fragmentation region the three ratios seem to be independent of beam energy
when viewed from the rest frame of one of the protons. Theoretical models based
on quark-diquark breaking mechanisms overestimate the pbar/p ratio up to y ~<
3. Including additional mechanisms for baryon number transport such as baryon
junctions leads to a better description of the data.Comment: 15 pages, 4 figures, uses elsart.sty. Changes to references and
discussion based on referee comments, resubmitted to Phys. Lett.
Characterisation of insulin analogues therapeutically available to patients
The structure and function of clinical dosage insulin and its analogues were assessed. This included ‘native insulins’ (human recombinant, bovine, porcine), ‘fast-acting analogues’ (aspart, glulisine, lispro) and ‘slow-acting analogues’ (glargine, detemir, degludec). Analytical ultracentrifugation, both sedimentation velocity and equilibrium experiments, were employed to yield distributions of both molar mass and sedimentation coefficient of all nine insulins. Size exclusion chromatography, coupled to multi-angle light scattering, was also used to explore the function of these analogues. On ultracentrifugation analysis, the insulins under investigation were found to be in numerous conformational states, however the majority of insulins were present in a primarily hexameric conformation. This was true for all native insulins and two fast-acting analogues. However, glargine was present as a dimer, detemir was a multi-hexameric system, degludec was a dodecamer (di-hexamer) and glulisine was present as a dimer-hexamer-dihexamer system. However, size-exclusion chromatography showed that the two hexameric fast-acting analogues (aspart and lispro) dissociated into monomers and dimers due to the lack of zinc in the mobile phase. This comprehensive study is the first time all nine insulins have been characterised in this way, the first time that insulin detemir have been studied using analytical ultracentrifugation and the first time that insulins aspart and glulisine have been studied using sedimentation equilibrium. The structure and function of these clinically administered insulins is of critical importance and this research adds novel data to an otherwise complex functional physiological protein
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