Search results for "RATCHET"
showing 10 items of 17 documents
Staged Venture Capital Contracting with Ratchets and Liquidation Rights
2011
Abstract This paper uses real options analysis to study later round financing in the presence of two standard venture capital contracting provisions: anti-dilution (ratchet) and liquidation preference. We argue that such provisions can preclude financing of a positive NPV venture in the case of a large follow-on financing relative to firm value. Liquidation preference contracting at multiples greater than one is not feasible in the later round if the financing is small relative to firm value. We highlight an interaction effect between the two provisions: increasing the liquidation multiple can help to avoid dilution and the need for the prior venture capitalist to waive ratchet provisions.
Electrical Pumping of Potassium Ions Against an External Concentration Gradient in a Biological Ion Channel
2013
We show experimentally and theoretically that significant currents can be obtained with a biological ion channel, the OmpF porin of Escherichia coli, using zero-average potentials as driving forces. The channel rectifying properties can be used to pump potassium ions against an external concentration gradient under asymmetric pH conditions. The results are discussed in terms of the ionic selectivity and rectification ratio of the channel. The physical concepts involved may be applied to separation processes with synthetic nanopores and to bioelectrical phenomena. (C) 2013 AIP Publishing LLC.
EVOLUTIONARY DYNAMICS OF FITNESS RECOVERY FROM THE DEBILITATING EFFECTS OF MULLER'S RATCHET.
1998
The great adaptability shown by RNA viruses is a consequence of their high mutation rates. The evolution of fitness in a severely debilitated, clonal population of the nonsegmented ribovirus vesicular stomatitis virus (VSV) has been compared under five different demographic regimes, ranging from severe serial bottleneck passages (one virion) to large population passages (105 virions or more) under similar environmental conditions (cell culture type and temperature). No matter how small the bottleneck, the fitness of the evolved populations was always higher than the fitness of the starting population; this result is clearly different from that previously reported for viruses with higher fit…
Active Brownian Motion Models and Applications to Ratchets
2008
We give an overview over recent studies on the model of Active Brownian Motion (ABM) coupled to reservoirs providing free energy which may be converted into kinetic energy of motion. First, we present an introduction to a general concept of active Brownian particles which are capable to take up energy from the source and transform part of it in order to perform various activities. In the second part of our presentation we consider applications of ABM to ratchet systems with different forms of differentiable potentials. Both analytical and numerical evaluations are discussed for three cases of sinusoidal, staircase-like and Mateos ratchet potentials, also with the additional loads modeled by…
Evolution of small prokaryotic genomes
2015
As revealed by genome sequencing, the biology of prokaryotes with reduced genomes is strikingly diverse. These include free-living prokaryotes with ∼800 genes as well as endosymbiotic bacteria with as few as ∼140 genes. Comparative genomics is revealing the evolutionary mechanisms that led to these small genomes. In the case of free-living prokaryotes, natural selection directly favored genome reduction, while in the case of endosymbiotic prokaryotes neutral processes played a more prominent role. However, new experimental data suggest that selective processes may be at operation as well for endosymbiotic prokaryotes at least during the first stages of genome reduction. Endosymbiotic prokar…
Diffusion Acceleration in Randomly Switching Sawtooth Potential
2005
We investigate an overdamped Brownian motion in symmetric sawtooth periodic potential switched by Markovian dichotomous noise between two configurations. The two configurations differ each other by a translation of half of period. The calculation of the effective diffusion coefficient is reduced to the mean first‐passage time problem, and we obtain the exact expression valid for arbitrary mean rate of switchings and arbitrary intensity of white Gaussian noise. We find the area at parameters plane where acceleration of diffusion in comparison with the free diffusion case takes place.
Intertextuality as a source of humour in Terry Pratchett's novels
2016
Intertekstuaalisuus on hyvin olennainen osa kirjallisuudentutkimusta, mutta sen merkitystä huumorin keinona kaunokirjallisuudessa ei ole juurikaan tutkittu. Laajimmillaan intertekstuaalisuudella voidaan käsittää kaikkia tekstien välisiä merkityssuhteita, mutta usein se määritellään viittauksella toiseen kirjalliseen teokseen tai kulttuuriseen kohteeseen. Myös huumorin määrittelemiseen ja analysoimiseen on kehitetty monia teorioita. Näistä vallitsevin on inkongruenssiteoria, jonka mukaan huumori syntyy esittämällä kaksi vastakkaista kohdetta samassa kehikossa. Tässä tutkimuksessa tavoitteena on selvittää, kuinka Terry Pratchett on hyödyntänyt intertekstuaalisia viittauksia huumorin keinona. …
Single-layer metal-on-metal islands driven by strong time-dependent forces
2012
Non-linear transport properties of single-layer metal-on-metal islands driven with strong static and time-dependent forces are studied. We apply a semi-empirical lattice model and use master equation and kinetic Monte Carlo simulation methods to compute observables such as the velocity and the diffusion coefficient. Two types of time-dependent driving are considered: a pulsed rotated field and an alternating field with a zero net force (electrophoretic ratchet). Small islands up to 12 atoms were studied in detail with the master equation method and larger ones with simulations. Results are presented mainly for a parametrization of Cu on Cu(001) surface, which has been the main system of int…
The character name translations in the Finnish translation of Terry Pratchett’s Lords and Ladies
2009
Tämän proseminaarityön tarkoituksena oli tutkia minkälaisia käännösratkaisuja on hyödynnetty suomennettaessa henkilönimiä Terry Pratchettin kirjassa Lords and Ladies (suomeksi Herraskaista väkeä). Tarkoitus oli selvittää, onko käännösratkaisut valikoitu jonkin tietyn säännönmukaisuuden perusteella. Aineistona tässä tutkimuksessa oli asianomainen romaani, sekä alkuperäiskielisenä versiona että suomenkielisenä käännöksenä. Aineistosta kerättiin henkilönimet ja alkuperäisiä ja käännöksiä verrattiin keskenään. Lisäksi käännökset luokiteltiin käännösratkaisun mukaan seitsemään ryhmään. Lähestymistavaltaan tutkimus on laadullinen ja analyyttinen. Tutkimuksessa kävi ilmi, että saman teoksen sisäl…
Small genomes and the difficulty to define minimal translation and metabolic machineries
2015
The notion of minimal life has sparked the interest of scientists in different fields, ranging from the origin-of-life research to biotechnology-oriented synthetic biology. Whether the interest is focused on the emergence of protocells out of prebiotic systems or the design of a cell chassis ready to incorporate new devices and functions, proposing minimal combinations of genes for life is not a trivial task. Using comparative genomics and biochemistry of endosymbionts (i.e., intracellular mutualistic symbionts) and intracellular parasites, a decade ago we proposed the core of a minimal gene set for a simple heterotrophic cell adapted to a chemically complex environment. In this work, we di…