The Hypanis Valles delta: The last highstand of a sea on early Mars?

One of the most contentious hypotheses in the geological history of Mars is whether the northern lowlands ever contained an oceanic water body. Arguably, the best evidence for an ocean comes from the presence of sedimentary fans around Mars' dichotomy boundary, which separates the northern lowlands from the southern highlands. Here we describe the palaeogeomorphology of the Hypanis Valles sediment fan, the largest sediment fan complex reported on Mars (area >970 km2). This has an extensive catchment (4.6 x 105 km2) incorporating Hypanis and Nanedi Valles, that we show was active during the late-Noachian/early-Hesperian period (∼3.7 Ga). The fan comprises a series of lobe-shaped sediment bodies, connected by multiple bifurcating flat-topped ridges. We interpret the latter as former fluvial channel belts now preserved in inverted relief. Meter-scale-thick, sub-horizontal layers that are continuous over tens of kilometres are visible in scarps and the inverted channel margins. The inverted channel branches and lobes are observed to occur up to at least 140 km from the outlet of Hypanis Valles and descend ∼500 m in elevation. The progressive basinward advance of the channellobe transition records deposition and avulsion at the margin of a retreating standing body of water, assuming the elevation of the northern plains basin floor is stable. We interpret the Hypanis sediment fan to represent an ancient delta as opposed to a fluvial fan system. At its location at the dichotomy boundary, the Hypanis Valles fan system is topographically open to Chryse Planitia – an extensive plain that opens in turn into the larger northern lowlands basin. We conclude that the observed progradation of fan bodies was due to basinward shoreline retreat of an ancient body of water which extended across at least Chryse Planitia. Given the open topography, it is plausible that the Hypanis fan system records the existence, last highstand, and retreat of a large sea in Chryse Planitia and perhaps even an ocean that filled the northern plains of Mars

Lubricating Bacteria Model for Branching growth of Bacterial Colonies

Various bacterial strains (e.g. strains belonging to the genera Bacillus, Paenibacillus, Serratia and Salmonella) exhibit colonial branching patterns during growth on poor semi-solid substrates. These patterns reflect the bacterial cooperative self-organization. Central part of the cooperation is the collective formation of lubricant on top of the agar which enables the bacteria to swim. Hence it provides the colony means to advance towards the food. One method of modeling the colonial development is via coupled reaction-diffusion equations which describe the time evolution of the bacterial density and the concentrations of the relevant chemical fields. This idea has been pursued by a number of groups. Here we present an additional model which specifically includes an evolution equation for the lubricant excreted by the bacteria. We show that when the diffusion of the fluid is governed by nonlinear diffusion coefficient branching patterns evolves. We study the effect of the rates of emission and decomposition of the lubricant fluid on the observed patterns. The results are compared with experimental observations. We also include fields of chemotactic agents and food chemotaxis and conclude that these features are needed in order to explain the observations.Comment: 1 latex file, 16 jpeg files, submitted to Phys. Rev.

Polarization of Lambda^0 hyperons in nucleus-nucleus collisions at high energies

The measurement of Lambda^0 hyperons polarization in nucleus-nucleus collisions is considered as one of possible tools to study the phase transition. Fixed target and collider experiments are discussed for the case of Lambda^0's production from Au-Au central collisions at \sqrt{s_{NN}} of several GeV.Comment: 15 pages, 6 figure

Hypotheses for the Origin of the Hypanis Fan-Shaped Deposit at the Edge of the Chryse Escarpment, Mars: Is it a Delta?

We investigated the origin of the fan-shaped deposit at the end of Hypanis Valles that has previously been proposed as an ExoMars, Mars 2020, and human mission candidate landing site, and found evidence that the landform is an ancient delta. Previous work suggests that the deposit originated from a time of fluvial activity both distinct from and prior to catastrophic outflow, and crater counting placed the deposit’s age at  ≥ 3.6 Ga. We found over 30 thin sedimentary strata in the proposed delta wall, and from our slope analysis conclude that the fluvial sequence is consistent with a lowering/retreating shoreline. We measured nearly horizontal bedding dip angles ranging from 0° to 2° over long stretches of cliff and bench exposures seen in HiRISE images and HiRISE stereo DTMs. From THEMIS night IR images we determined that the fan-shaped deposit has a low thermal inertia (150-240 Jm-2 K-1 s-1/2) and the surrounding darker-toned units correspond to thermal inertia values as high as 270-390 Jm-2 K-1 s-1/2. We interpret these findings to indicate that the fan-shaped deposit consists mostly of silt-sized and possibly finer grains, and that the extremely low grade and large lateral extent of these beds implies that the depositional environment was calm and relatively long-lived. We interpret the geomorphology and composition as incompatible with an alluvial fan or mudflow hypothesis. From our stratigraphic mapping we interpret the order of events which shaped the region. After the Chryse impact, sediment filled the basin, a confined lake or sea formed allowing a large delta to be deposited near its shoreline, the water level receded to the north, darker sedimentary/volcanic units covered the region and capped the light-toned deposit as hydro-volcanic eruptions shaped the interior of Lederberg crater, freeze/thaw cycles and desiccation induced local fracturing, and finally wrinkle ridges associated with rounded cones warped the landscape following trends in degraded crater rims and existing tectonic features. The ancient deltaic deposit we observe today was largely untouched by subsequent catastrophic outflows, and its surface has been only moderately reshaped by over 3 billion years of aeolian erosion

Smart Swarms of Bacteria-Inspired Agents with Performance Adaptable Interactions

Collective navigation and swarming have been studied in animal groups, such as fish schools, bird flocks, bacteria, and slime molds. Computer modeling has shown that collective behavior of simple agents can result from simple interactions between the agents, which include short range repulsion, intermediate range alignment, and long range attraction. Here we study collective navigation of bacteria-inspired smart agents in complex terrains, with adaptive interactions that depend on performance. More specifically, each agent adjusts its interactions with the other agents according to its local environment – by decreasing the peers' influence while navigating in a beneficial direction, and increasing it otherwise. We show that inclusion of such performance dependent adaptable interactions significantly improves the collective swarming performance, leading to highly efficient navigation, especially in complex terrains. Notably, to afford such adaptable interactions, each modeled agent requires only simple computational capabilities with short-term memory, which can easily be implemented in simple swarming robots

The role of knowledge management strategies and task knowledge in stimulating service innovation

Are service firms that enact strategies to manage their new service development (NSD) knowledge able to generate a sustainable competitive advantage (SCA)? Based on analysis of data from a large survey of service companies, the answer is yes. We find that companies employing the knowledge management strategies of codification and personalization reflect higher levels of NSD knowledge. However, the two strategies vary in their individual performance outcomes, with codification promoting NSD proficiency (an ability to execute NSD activities) and personalization promoting greater NSD innovativeness (market perception of the company as novel and as an innovator). When used together, the two strategies magnify NSD knowledge, which when combined with NSD proficiency and NSD innovativeness, promote a SCA. Therefore, companies planning to invest in a knowledge management system should heed the outcomes desired from their NSD process. A system based on documentation exemplifies a codification strategy and will drive NSD proficiency; a system emphasizing interpersonal communication exemplifies a personalization strategy and will drive NSD innovativeness. A system that blends the two strategies appears the most advantageous for service companies’ NSD efforts aiming to build a long-term sustainable competitive advantage

Recent results in relativistic heavy ion collisions: from ``a new state of matter'' to "the perfect fluid"

Experimental Physics with Relativistic Heavy Ions dates from 1992 when a beam of 197Au of energy greater than 10A GeV/c first became available at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL) soon followed in 1994 by a 208Pb beam of 158A GeV/c at the Super Proton Synchrotron (SPS) at CERN (European Center for Nuclear Research). Previous pioneering measurements at the Berkeley Bevalac in the late 1970's and early 1980's were at much lower bombarding energies (~ 1 A GeV/c) where nuclear breakup rather than particle production is the dominant inelastic process in A+A collisions. More recently, starting in 2000, the Relativistic Heavy Ion Collider (RHIC) at BNL has produced head-on collisions of two 100A GeV beams of fully stripped Au ions, corresponding to nucleon-nucleon center-of-mass energy, sqrt(sNN)=200 GeV, total c.m. energy 200A GeV. The objective of this research program is to produce nuclear matter with extreme density and temperature, possibly resulting in a state of matter where the quarks and gluons normally confined inside individual nucleons (r < 1 fm) are free to act over distances an order of magnitude larger. Progress from the period 1992 to the present will be reviewed, with reference to previous results from light ion and proton-proton collisions where appropriate. Emphasis will be placed on the measurements which formed the basis for the announcements by the two major laboratories: "A new state of matter", by CERN on Feb 10, 2000 and "The perfect fluid", by BNL on April 19, 2005.Comment: 62 pages, 39 figures. Review article published in Reports on Progress in Physics on June 23, 2006. In this published version, mistakes, typographical errors, and citations have been corrected and a subsection has been adde

Overview of mathematical approaches used to model bacterial chemotaxis II: bacterial populations

We review the application of mathematical modeling to understanding the behavior of populations of chemotactic bacteria. The application of continuum mathematical models, in particular generalized Keller–Segel models, is discussed along with attempts to incorporate the microscale (individual) behavior on the macroscale, modeling the interaction between different species of bacteria, the interaction of bacteria with their environment, and methods used to obtain experimentally verified parameter values. We allude briefly to the role of modeling pattern formation in understanding collective behavior within bacterial populations. Various aspects of each model are discussed and areas for possible future research are postulated

Entangled Stories: The Red Jews in Premodern Yiddish and German Apocalyptic Lore

“Far, far away from our areas, somewhere beyond the Mountains of Darkness, on the other side of the Sambatyon River…there lives a nation known as the Red Jews.” The Red Jews are best known from classic Yiddish writing, most notably from Mendele's Kitser masoes Binyomin hashlishi (The Brief Travels of Benjamin the Third). This novel, first published in 1878, represents the initial appearance of the Red Jews in modern Yiddish literature. This comical travelogue describes the adventures of Benjamin, who sets off in search of the legendary Red Jews. But who are these Red Jews or, in Yiddish, di royte yidelekh? The term denotes the Ten Lost Tribes of Israel, the ten tribes that in biblical times had composed the Northern Kingdom of Israel until they were exiled by the Assyrians in the eighth century BCE. Over time, the myth of their return emerged, and they were said to live in an uncharted location beyond the mysterious Sambatyon River, where they would remain until the Messiah's arrival at the end of time, when they would rejoin the rest of the Jewish people. This article is part of a broader study of the Red Jews in Jewish popular culture from the Middle Ages through modernity. It is partially based on a chapter from my book, Umstrittene Erlöser: Politik, Ideologie und jüdisch-christlicher Messianismus in Deutschland, 1500–1600 (Göttingen: Vandenhoeck & Ruprecht, 2011). Several postdoctoral fellowships have generously supported my research on the Red Jews: a Dr. Meyer-Struckmann-Fellowship of the German Academic Foundation, a Harry Starr Fellowship in Judaica/Alan M. Stroock Fellowship for Advanced Research in Judaica at Harvard University, a research fellowship from the Heinrich Hertz-Foundation, and a YIVO Dina Abramowicz Emerging Scholar Fellowship. I thank the organizers of and participants in the colloquia and conferences where I have presented this material in various forms as well as the editors and anonymous reviewers of AJS Review for their valuable comments and suggestions. I am especially grateful to Jeremy Dauber and Elisheva Carlebach of the Institute for Israel and Jewish Studies at Columbia University, where I was a Visiting Scholar in the fall of 2009, for their generous encouragement to write this article. Sue Oren considerably improved my English. The style employed for Romanization of Yiddish follows YIVO's transliteration standards. Unless otherwise noted, translations from the Yiddish, Hebrew, German, and Latin are my own. Quotations from the Bible follow the JPS translation, and those from the Babylonian Talmud are according to the Hebrew-English edition of the Soncino Talmud by Isidore Epstein

Active Brownian Particles. From Individual to Collective Stochastic Dynamics

We review theoretical models of individual motility as well as collective dynamics and pattern formation of active particles. We focus on simple models of active dynamics with a particular emphasis on nonlinear and stochastic dynamics of such self-propelled entities in the framework of statistical mechanics. Examples of such active units in complex physico-chemical and biological systems are chemically powered nano-rods, localized patterns in reaction-diffusion system, motile cells or macroscopic animals. Based on the description of individual motion of point-like active particles by stochastic differential equations, we discuss different velocity-dependent friction functions, the impact of various types of fluctuations and calculate characteristic observables such as stationary velocity distributions or diffusion coefficients. Finally, we consider not only the free and confined individual active dynamics but also different types of interaction between active particles. The resulting collective dynamical behavior of large assemblies and aggregates of active units is discussed and an overview over some recent results on spatiotemporal pattern formation in such systems is given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte