Group divisible designs with block size 4 where the group sizes are congruent to 1 mod 3

In this paper we consider the existence of 4-GDDs on v points with v≤50. We consider the case v≡1(mod3) and construct designs for all feasible group types here. We also enumerate all 4-GDDs with type 74 and compare the actions of their automorphism groups. When v≡0(mod3) and v≤50, there are no feasible group types for which existence has not been determined, but for v≡2(mod3) and v≤50, we obtain 4-GDDs for two more feasible group types

Low temperature shape relaxation of 2-d islands by edge diffusion

We present a precise microscopic description of the limiting step for low temperature shape relaxation of two dimensional islands in which activated diffusion of particles along the boundary is the only mechanism of transport allowed. In particular, we are able to explain why the system is driven irreversibly towards equilibrium. Based on this description, we present a scheme for calculating the duration of the limiting step at each stage of the relaxation process. Finally, we calculate numerically the total relaxation time as predicted by our results and compare it with simulations of the relaxation process.Comment: 11 pages, 5 figures, to appear in Phys. Rev.

Epstein-Barr virus nuclear antigen 3A protein regulates CDKN2B transcription via interaction with MIZ-1

The Epstein-Barr virus (EBV) nuclear antigen 3 family of protein is critical for the EBV-induced primary B-cell growth transformation process. Using a yeast two-hybrid screen we identified 22 novel cellular partners of the EBNA3s. Most importantly, among the newly identified partners, five are known to play direct and important roles in transcriptional regulation. Of these, the Myc-interacting zinc finger protein-1 (MIZ-1) is a transcription factor initially characterized as a binding partner of MYC. MIZ-1 activates the transcription of a number of target genes including the cell cycle inhibitor CDKN2B. Focusing on the EBNA3A/MIZ-1 interaction we demonstrate that binding occurs in EBV-infected cells expressing both proteins at endogenous physiological levels and that in the presence of EBNA3A, a significant fraction of MIZ-1 translocates from the cytoplasm to the nucleus. Moreover, we show that a trimeric complex composed of a MIZ-1 recognition DNA element, MIZ-1 and EBNA3A can be formed, and that interaction of MIZ-1 with nucleophosmin (NPM), one of its coactivator, is prevented by EBNA3A. Finally, we show that, in the presence of EBNA3A, expression of the MIZ-1 target gene, CDKN2B, is downregulated and repressive H3K27 marks are established on its promoter region suggesting that EBNA3A directly counteracts the growth inhibitory action of MIZ-1

The contamination of the surface of Vesta by impacts and the delivery of the dark material

The Dawn spacecraft observed the presence of dark material, which in turn proved to be associated with OH and H-rich material, on the surface of Vesta. The source of this dark material has been identified with the low albedo asteroids, but it is still a matter of debate whether the delivery of the dark material is associated with a few large impact events, to micrometeorites or to the continuous, secular flux of impactors on Vesta. The continuous flux scenario predicts that a significant fraction of the exogenous material accreted by Vesta should be due to non-dark impactors likely analogous to ordinary chondrites, which instead represent only a minor contaminant in the HED meteorites. We explored the continuous flux scenario and its implications for the composition of the vestan regolith, taking advantage of the data from the Dawn mission and the HED meteorites. We used our model to show that the stochastic events scenario and the micrometeoritic flux scenario are natural consequences of the continuous flux scenario. We then used the model to estimate the amounts of dark and hydroxylate materials delivered on Vesta since the LHB and we showed how our results match well with the values estimated by the Dawn mission. We used our model to assess the amount of Fe and siderophile elements that the continuous flux of impactors would mix in the vestan regolith: concerning the siderophile elements, we focused our attention on the role of Ni. The results are in agreement with the data available on the Fe and Ni content of the HED meteorites and can be used as a reference frame in future studies of the data from the Dawn mission and of the HED meteorites. Our model cannot yet provide an answer to the fate of the missing non-carbonaceous contaminants, but we discuss possible reasons for this discrepancy.Comment: 31 pages, 7 figures, 4 tables. Accepted for publication on the journal ICARUS, "Dark and Bright Materials on Vesta" special issu

Diffusion of gold nanoclusters on graphite

We present a detailed molecular-dynamics study of the diffusion and coalescence of large (249-atom) gold clusters on graphite surfaces. The diffusivity of monoclusters is found to be comparable to that for single adatoms. Likewise, and even more important, cluster dimers are also found to diffuse at a rate which is comparable to that for adatoms and monoclusters. As a consequence, large islands formed by cluster aggregation are also expected to be mobile. Using kinetic Monte Carlo simulations, and assuming a proper scaling law for the dependence on size of the diffusivity of large clusters, we find that islands consisting of as many as 100 monoclusters should exhibit significant mobility. This result has profound implications for the morphology of cluster-assembled materials

The combined effect of elevation and meteorology on potato crop dynamics : a 10-year study in the Gamo Highlands, Ethiopia

Potato (Solanum tuberosum L.) is an important crop in the Gamo Highlands in Ethiopia. The region is characterised by a complex topography with large inter-annual weather variations, where potatoes grow in a range of altitudes between 1,600 and 3,200 m above sea level (a.s.l.). Traditional large-scale crop modelling studies only crudely represent the effect of complex topography, misrepresenting spatial variability in meteorology and potato growth in the region. Here, we investigate how weather influenced by topography affects crop growth. We used the Weather Research and Forecasting (WRF) model to simulate weather in relation to topography in coarse (54 km × 54 km) and fine (2 km × 2 km) resolution domains. The first has a resolution similar to those used by large-scale crop modelling studies that only crudely resolve the horizontal and vertical spatial effects of topography. The second realistically represents the most important topographical variations. The weather variables modelled in both the coarse and fine resolution domains are given as input to the GECROS model (Genotype-by-Environment interaction on CROp growth Simulator) to simulate the potato growth. We modelled potato growth from 2001 to 2010 and studied its inter-annual variability. This enabled us to determine for the first time in Ethiopia how variations in weather are linked to crop dynamics as a function of elevation at a fine resolution. We found that due to its finer representation of topography, weather and crop growth spatio-temporal variations were better represented in the fine than in the coarse resolution domain. The magnitude of crop growth variables such as Leaf Area Index (LAI) and Length of the Growing Season (LGS) obtained with weather from the coarse resolution domain were unrealistically low, hence unacceptable. Nevertheless, the resulting potato yields in the coarse resolution domain were comparable with the yields from the fine resolution domain. We explain this paradoxical finding in terms of a compensating effect, as the opposite effects of temperature and precipitation on yield compensated for each other along the major potato growing transect in the Gamo Highlands. These offsetting effects were also dependent on the correct estimations of the LGS, LAI. We conclude that a well-resolved representation of complex topography is crucial to realistically model meteorology and crop physiology in tropical mountainous areas

Variations in the amount of water ice on Ceres' surface suggest a seasonal water cycle.

The dwarf planet Ceres is known to host a considerable amount of water in its interior, and areas of water ice were detected by the Dawn spacecraft on its surface. Moreover, sporadic water and hydroxyl emissions have been observed from space telescopes. We report the detection of water ice in a mid-latitude crater and its unexpected variation with time. The Dawn spectrometer data show a change of water ice signatures over a period of 6 months, which is well modeled as ~2-km2 increase of water ice. The observed increase, coupled with Ceres' orbital parameters, points to an ongoing process that seems correlated with solar flux. The reported variation on Ceres' surface indicates that this body is chemically and physically active at the present time

First mineralogical maps of 4 Vesta

Before Dawn arrived at 4 Vesta only very low spatial resolution (~50 km) albedo and color maps were available from HST data. Also ground-based color and spectroscopic data were utilized as a first attempt to map Vesta’s mineralogical diversity [1-4]. The VIR spectrometer [5] onboard Dawn has ac-quired hyperspectral data while the FC camera [6] ob-tained multi-color data of the Vestan surface at very high spatial resolutions, allowing us to map complex geologic, morphologic units and features. We here re-port about the results obtained from a preliminary global mineralogical map of Vesta, based on data from the Survey orbit. This map is part of an iterative map-ping effort; the map is refined with each improvement in resolution

The Lantern Vol. 27, No. 1, December 1958

• Thoughts • The Fifth Year • Grouse Shooting • Light • On Selfishness • A Christmas Prayer • Modern Magnificat • Pauses • Termination • Cynthilia • My Petticoat Princess • ?? • Stormhttps://digitalcommons.ursinus.edu/lantern/1076/thumbnail.jp