179 research outputs found
Depression and Substance Abuse: A Rationalization of a Vicious Circle
While a mind-altering-substance consumption alleviates current level of depression, it facilitates future depression. Our analysis incorporates this trade off and shows that the stationary state of a consistently overly ambitious sophisticated substance user is improved by impatience, and that this improvement is amplified by the ratio of the instantaneous depression-relief effect to the state-degradation effect of the substance. The analysis also shows that the existence of a supportive personal community leads to permanent cyclical substance consumption when the user is relatively patient.Substance abuse, ambition, consistency, sophistication, impatience, state-maturation, state-degradation, depression, relief, community support, cycles
Loop exponent in DNA bubble dynamics
Dynamics of DNA bubbles are of interest for both statistical physics and
biology. We present exact solutions to the Fokker-Planck equation governing
bubble dynamics in the presence of a long-range entropic interaction. The
complete meeting time and meeting position probability distributions are
derived from the solutions. Probability distribution functions reflect the
value of the loop exponent of the entropic interaction. Our results extend
previous results which concentrated mainly on the tails of the probability
distribution functions and open a way to determining the strength of the
entropic interaction experimentally which has been a matter of recent
discussions. Using numerical integration, we also discuss the influence of the
finite size of a DNA chain on the bubble dynamics. Analogous results are
obtained also for the case of subdiffusive dynamics of a DNA bubble in a
heteropolymer, revealing highly universal asymptotics of meeting time and
position probability functions.Comment: 24 pages, 11 figures, text identical to the published version; v3 -
updated Ref. [47] and corrected Eqs. (3.6) and (3.10
Itinerary planner: A mashup case study
The wide adoption of Web Services and the availability of web APIs are transforming the web into a programmatic environment for developing innovative web applications that combine information from various sources to provide a rich user experience. These mashup applications are characterized by rapid development using existing data sources and the use of new technologies such as AJAX, JSON, etc. Developers often focus on delivering rich functionality via the browser environment and pay little attention to the design and maintainability of the applications. In this paper we describe our experience in developing an Itinerary Planner travel application, and discuss the challenges associated with developing mashups. In the conclusion, we briefly discuss the lessons learned in addressing these challenges and how these lessons can be applied to future mashup projects. © 2009 Springer Berlin Heidelberg
End User and Expert Perceptions of Threats and Potential Countermeasures
Experts often design security and privacy technology with specific use cases and threat models in mind.
In practice however, end users are not aware of these
threats and potential countermeasures. Furthermore, misconceptions about the benefits and limitations of security
and privacy technology inhibit large-scale adoption by end
users. In this paper, we address this challenge and contribute
a qualitative study on end users’ and security experts’ perceptions of threat models and potential countermeasures. We
follow an inductive research approach to explore perceptions
and mental models of both security experts and end users.
We conducted semi-structured interviews with 8 security experts and 13 end users. Our results suggest that in contrast to
security experts, end users neglect acquaintances and friends
as attackers in their threat models. Our findings highlight
that experts value technical countermeasures whereas end
users try to implement trust-based defensive methods
The Devil's Calculus: Mathematical Models of Civil War
In spite of the movement to turn political science into a real science, various mathematical methods that are now the staples of physics, biology, and even economics are thoroughly uncommon in political science, especially the study of civil war. This study seeks to apply such methods - specifically, ordinary differential equations (ODEs) - to model civil war based on what one might dub the capabilities school of thought, which roughly states that civil wars end only when one side’s ability to make war falls far enough to make peace truly attractive. I construct several different ODE-based models and then test them all to see which best predicts the instantaneous capabilities of both sides of the Sri Lankan civil war in the period from 1990 to 1994 given parameters and initial conditions. The model that the tests declare most accurate gives very accurate predictions of state military capabilities and reasonable short term predictions of cumulative deaths. Analysis of the model reveals the scale of the importance of rebel finances to the sustainability of insurgency, most notably that the number of troops required to put down the Tamil Tigers is reduced by nearly a full order of magnitude when Tiger foreign funding is stopped. The study thus demonstrates that accurate foresight may come of relatively simple dynamical models, and implies the great potential of advanced and currently unconventional non-statistical mathematical methods in political science.civil war; mathematical model; differential equations; dynamic model
Firm Size Distribution and EPL in Italy
We study the role of employment protection legislation (EPL) in explaining the relative small average size of Italian firms. We construct a simple model that shows that the smooth relation between size and growth probability is disturbed in proximity of the thresholds at which EPL applies di.erentially. We use a comprehensive dataset of all Italian firms between 1986 and 1998 to estimate the e.ects of EPL in terms of discouraging small firms from growing. We then construct a stochastic transition matrix for firm size that, together with the estimates, allows for a quantitative evaluation of the e.ects of EPL in the long run. Our results show that EPL does influence firm size distribution, but that its e.ects are quantitatively modest: average firm size would increase by less than 1% when removing the threshold e.ect. In terms of policy, these findings suggest that changes in EPL are not likely to have a large impact on the propensity of small firms to growhttp://deepblue.lib.umich.edu/bitstream/2027.42/39999/3/wp613.pd
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Fiscal Policy in an Unemployment Crisis
This article shows that equilibrium unemployment dynamics can significantly increase the efficacy of fiscal policy. In response to a shock that brings the economy into a liquidity trap, an expansion in government spending increases output and causes a fall in the unemployment rate. Since movements in unemployment are persistent, the effects of current spending prevail into the future, leading to an enduring rise in income. As an enduring rise in income boosts private demand, an increase in government spending sets in motion a virtuous employment-spending spiral with large effects on macroeconomic aggregates
The Devil's Calculus: Mathematical Models of Civil War
In spite of the movement to turn political science into a real science, various mathematical methods that are now the staples of physics, biology, and even economics are thoroughly uncommon in political science, especially the study of civil war. This study seeks to apply such methods - specifically, ordinary differential equations (ODEs) - to model civil war based on what one might dub the capabilities school of thought, which roughly states that civil wars end only when one side’s ability to make war falls far enough to make peace truly attractive. I construct several different ODE-based models and then test them all to see which best predicts the instantaneous capabilities of both
sides of the Sri Lankan civil war in the period from 1990 to 1994 given parameters and initial conditions.
The model that the tests declare most accurate gives very accurate predictions of state military capabilities and reasonable short term predictions of cumulative deaths. Analysis of the model reveals the scale of the importance of rebel finances to the sustainability of insurgency, most notably that the number of troops required to put down the Tamil Tigers is reduced by nearly a full order of magnitude when Tiger foreign funding is stopped. The study thus demonstrates that accurate foresight may come of relatively simple dynamical models, and implies the great potential of advanced and currently unconventional non-statistical mathematical methods in political science
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