links for 2010-​​08-​​27

links for 2010-​​08-​​24

links for 2010-​​08-​​20

  • “We under­stand the dynam­ics of the world around us as by asso­ci­at­ing pairs of events, where one event has some influ­ence on the other. These pairs of events can be aggre­gated into a web of mem­o­ries rep­re­sent­ing our under­stand­ing of an episode of his­tory. The events and the asso­ci­a­tions between them need not be directly experienced-​​they can also be acquired by com­mu­ni­ca­tion. In this paper we take a net­work approach to study the dynam­ics of mem­o­ries of his­tory. First we inves­ti­gate the net­work struc­ture of a data set con­sist­ing of reported events by sev­eral indi­vid­u­als and how asso­ci­a­tions con­nect them. We focus our mea­sure­ment on degree dis­tri­b­u­tions, degree cor­re­la­tions, cycles (which rep­re­sent incon­sis­ten­cies as they would break the time order­ing) and com­mu­nity structure.…”
  • “he motil­ity of the worm nema­tode \textit{Caenorhabditis ele­gans} is inves­ti­gated in shal­low, wet gran­u­lar media as a func­tion of par­ti­cle size dis­per­sity and area den­sity ($\phi$). Sur­pris­ingly, we find that the nematode’s propul­sion speed is enhanced by the pres­ence of par­ti­cles in a fluid and is nearly inde­pen­dent of area den­sity. The undu­la­tion speed, often used to dif­fer­en­ti­ate loco­mo­tion gaits, is sig­nif­i­cantly affected by par­ti­cle size dis­per­sity for area den­si­ties above $\phi \geq 0.55$, and is char­ac­ter­ized by a change in the nematode’s wave­form from swim­ming to crawl­ing in dense poly­dis­perse media \textit{only}. This change high­lights the organism’s adapt­abil­ity to sub­tle dif­fer­ences in local struc­ture between monodis­perse and poly­dis­perse media.”
  • “A short sur­vey is pro­vided about our recent explo­rations of the young topic of noise-​​based logic. After out­lin­ing the moti­va­tion behind noise-​​based com­pu­ta­tion schemes, we present a short sum­mary of our ongo­ing efforts in the intro­duc­tion, devel­op­ment and design of sev­eral noise-​​based deter­min­is­tic mul­ti­val­ued logic schemes and ele­ments. In par­tic­u­lar, we describe clas­si­cal, instan­ta­neous, con­tin­uum, spike and random-​​telegraph-​​signal based schemes with appli­ca­tions such as cir­cuits that emu­late the brain’s func­tion­ing and string ver­i­fi­ca­tion via a slow com­mu­ni­ca­tion channel.”
  • “We con­sider prob­lems of Bayesian infer­ence for a spa­tial epi­demic on a graph, where the final state of the epi­demic cor­re­sponds to bond per­co­la­tion, and where only the set or num­ber of finally infected sites is observed. We develop appro­pri­ate Markov chain Monte Carlo algo­rithms, demon­strat­ing their effec­tive­ness, and we study prob­lems of opti­mal exper­i­men­tal design. In par­tic­u­lar, we demon­strate that for lattice-​​based processes an exper­i­ment on a spar­si­fied lat­tice can yield more infor­ma­tion on model para­me­ters than one con­ducted on a com­plete lat­tice. We also prove some prob­a­bilis­tic results about the behav­iour of esti­ma­tors asso­ci­ated with large infected clusters.”
  • “At the most fun­da­men­tal level, com­put­ers are an assem­bly of gates that are used to per­form the basic oper­a­tions required to exe­cute a pro­gram. For prob­lems in the prob­a­bil­ity domain, even the val­ues used in these most basic oper­a­tions are not con­strained to be either a 0 or a 1. Instead, the basic gates must deter­mine the prob­a­bil­ity that a bit is a 1, or the prob­a­bil­ity that it is a 0.
    Lyric’s gates are designed to model rela­tion­ships between prob­a­bil­i­ties natively in the device physics. For this rea­son, Lyric can per­form math­e­mat­i­cal oper­a­tions in the prob­a­bil­ity domain with just a hand­ful of tran­sis­tors – cre­at­ing power and area sav­ings of more than 10X over tra­di­tional implementations.”
  • “Zipf’s law seems to be ubiq­ui­tous in human lan­guages and appears to be a uni­ver­sal prop­erty of com­plex com­mu­ni­cat­ing sys­tems. Fol­low­ing an early pro­posal made by Zipf con­cern­ing the pres­ence of a ten­sion between the efforts of speaker and hearer in a com­mu­ni­ca­tion sys­tem, we intro­duce evo­lu­tion by means of a vari­a­tional approach to the prob­lem based on Kullback’s Min­i­mum Dis­crim­i­na­tion of Infor­ma­tion Prin­ci­ple. Using a for­mal­ism fully embed­ded in the frame­work of infor­ma­tion the­ory, we demon­strate that Zipf’s law is the only expected out­come of an evolv­ing, com­mu­nica­tive sys­tem under a rig­or­ous def­i­n­i­tion of the com­mu­nica­tive ten­sion described by Zipf.”
  • “We engi­neer an algo­rithm to solve the approx­i­mate dic­tio­nary match­ing prob­lem. Given a list of words $\mathcal{W}$, max­i­mum dis­tance $d$ fixed at pre­pro­cess­ing time and a query word $q$, we would like to retrieve all words from $\mathcal{W}$ that can be trans­formed into $q$ with $d$ or less edit oper­a­tions. We present data struc­tures that sup­port fault tol­er­ant queries by gen­er­at­ing an index. On top of that, we present a gen­er­al­iza­tion of the method that eases mem­ory con­sump­tion and pre­pro­cess­ing time sig­nif­i­cantly. At the same time, run­ning times of queries are vir­tu­ally unaf­fected. We are able to match in lists of hun­dreds of thou­sands of words and beyond within microsec­onds for rea­son­able distances.”
  • “The effects of sev­eral non­lin­ear reg­u­lar­iza­tion tech­niques are dis­cussed in the frame­work of 3D seis­mic tomog­ra­phy. Tra­di­tional, lin­ear, $\ell_​2$ penal­ties are com­pared to so-​​called spar­sity pro­mot­ing $\ell_​1$ and $\ell_​0$ penal­ties, and a total vari­a­tion penalty. Which of these algo­rithms is judged opti­mal depends on the spe­cific require­ments of the sci­en­tific exper­i­ment. If the cor­rect repro­duc­tion of model ampli­tudes is impor­tant, clas­si­cal damp­ing towards a smooth model using an $\ell_​2$ norm works almost as well as min­i­miz­ing the total vari­a­tion but is much more effi­cient. If gra­di­ents (edges of anom­alies) should be resolved with a min­i­mum of dis­tor­tion, we pre­fer $\ell_​1$ damp­ing of Daubechies-​​4 wavelet coefficients.…”

links for 2010-​​08-​​17