Modelling and engineering artificial burnt-bridge ratchet molecular motors

Nature has evolved many mechanisms for achieving directed motion on the subcellular level. The burnt-bridge ratchet (BBR) is one mechanism used to accomplish superdiffusive motion over long distances via the successive cleavage of surface-bound energy-rich substrate sites. The BBR mechanism is utilized throughout Nature: it can be found in bacteria, plants, mammals, arthropods (for example Crustaceans and Cheliceratans), as well as non-life forms such as influenza. Motivated to understand how fundamental engineering principles alter BBR kinetics, we have built both computer models and synthetic experimental systems to understand BBR kinetics. By exploring the dynamics of BBRs through simulation we find that their motor-like properties are highly dependent on the number of catalytic legs, the distance that the legs can reach from the central hub, and the hub topology. We further explore how design features in the underlying landscape affect BBR dynamics. We find that reducing the landscape from two- to one-dimensional increases superdiffusivity but leads to a loss in processivity. We also find that landscape elasticity affects all motor-like dynamical properties of BBRs: there are different optimal stiffnesses for distinct dynamical characteristics. For a spherical-hub BBR, speed, processivity, and persistence length are optimized at high, intermediate and soft stiffnesses, respectively, while rolling is also optimized at a high surface stiffness. Towards our development of a novel micron-sized protein-based BBR in the lab, we develop a new surface chemistry passivation technique and apply it to the surface of nanowires, turning an array of waveguiding nanowires into a high-throughput biosensing assay. In a separate assay, our protein-based BBR, which we call the lawnmower, is implemented in two dimensions on glass cover slips prepared with our surface chemistry (which serves as the lawn). We find the lawnmower dynamics reproduce key observations found in other similar systems, such as saltatory motion and broadly varying anomalously diffusive behaviour. The successful implementation of the lawnmower marks the first demonstration of an artificial protein-based molecular motor

The Changing Nature of Homicide and Its Impact on Homicide Clearance Rates: A Quantitative Analysis of Two Trends From 1984-2009

The following analyses uses the Federal Bureau of Investigation’s (FBI) Supplementary Homicide Report (SHR) data from 1984 to 2009 to examine factors that predict whether a homicide will be cleared or not (N=439,542). Two theories inform the current study: 1) Black’s theory of law (discretionary variables) proposes that characteristics of the victim, such as age or race, influence how diligently police work to solve a homicide; and 2) non-discretionary theories propose that characteristics of the homicide act, such as geographic location and weapon use, are more important to the solvability of a homicide. Preliminary analyses of clearance rates indicate decreasing rates from 1984-2004, and increasing rates from 2004-2009; therefore, separate analyses are performed for each trend. Results indicate that firearm use, unknown weapons, males, minority victims, population size, and western regions predict lower clearance rates. However, predicted probabilities analysis provide a more complete picture of the relative importance of each variable. Most variables support non-discretionary theories of crime, where aspects of the homicide itself determine its solvability. Theoretical implications are discussed alongside directions for future research oriented toward more practical analyses of homicide clearance rates and police practices

Legal Ethics and the Poverty Program

This paper has attempted to reconcile the neighborhood legal services plan with the existing Canons of Professional Ethics.The prime argument is that the plan provides benefits to society, and that the Canons were designed to prevent evils far different from the questions presented by the project. This is the fundamental issue: whether the canons are merely bent, or, in reality, broken. In either event, the canons should not prevent justice for those too poor to pay for a lawyer. The redeeming social interest spoken of by the Court in obscenity cases and the overriding social importance talked about in social legislation are phrases which are very apt in this context. If bent, the Canons should stand with that permanent crook so as to aid the indigent. If broken, the canons should be revised to fit current needs and modern situations, not to shut out the poor in their quest for the justice which is promised to every individual under the system of law in our nation

A case study of change facilitators for technology-enhanced learning in relation to one university’s strategic intent

Research into implementing change related to technology-enhanced learning in higher education includes researching the contributions and strategic action of individuals within an institution. Institutions may produce a structured strategic plan or a framework of strategic intent to accommodate changes in the higher education sector and opportunities for transforming learning and teaching through technology-enhanced learning tools and resources. Change facilitators are individuals in formal as well as informal positions within an institution who assume different levels of strategic action depending on their role and their self-identification as a facilitator of change. In this case study of a single university in England, the perceptions, concerns, and practices of academic and support staff who were functioning both formally and informally as facilitators of technology-related change are explored. A sequential, mixed-methods research approach was adopted. An online questionnaire measuring change facilitators’ levels of concern, including 35 pre-defined questions, categorical questions and open text questions, was disseminated to a purposive sample followed by semi-structured interviews with individuals who all identified themselves as facilitators of technology-related change. The discussion highlights strategic dissonance and sensemaking practices emerging from this study as well as the lack of patterns of concerns across change facilitator roles. Strategic dissonance was identified between the explicit strategic plan and the implicit, de facto, strategic intent as expressed through institutional structure in the Case Study University. Sensemaking practices served as a heuristic for addressing wicked problems of technology-enhanced learning transience. The recommendations of this research supports higher education institutions in establishing more effective links between innovative facilitators of technology-enhanced learning and structured support within a framework of strategic intent

Private Dispute Resolution in the Card Context: Structure, Reputation, and Incentives

Explosive growth in credit, debit, and other card payment systems in recent years has produced a parallel growth in private dispute resolution systems based on the web of contracts entered into by merchants, merchant acquirers, consumers, card issuers, card associations, and transaction processors. These contracts have produced legal systems based on contract and the enforcement of which rests primarily on reputational constraints. To cost-effectively resolve disputes, these private legal systems have evolved innovative procedures using resources at the lowest-possible level, including incentive-payments for producing information and rigid deadlines for parties\u27 actions. This paper describes and analyzes these legal systems and their procedures as a potential model for resolving other categories of disputes

Involute spiral face couplings and gears: design approach and manufacturing technique

This paper presents spiral face gears with an involute tooth line and an identical tooth profile in the normal section at any radius. There are two main applications for such face gears. One of them is an alternative solution with certain advantages in performance and fabrication technology to the straight tooth, Hirth, or Curvic flange couplings. Another application is when a face gear is engaged with an involute helical pinion or worm at intersecting or crossed axes. Potential advantages of spiral face couplings and gears include high power transmission density and highly productive machining of face spiral gears. The paper describes gear geometry analysis, and design technique of spiral face involute gears with symmetric and asymmetric tooth profiles. It also explains a hobbing method of these gears and tool design specifics, and then illustrates gear and tool design with numerical examples.У даній роботі представлена спіралеподібні шестерні з эвольвентным зубом лінії і однаковим профілем зуба в нормальному перерізі на будь-якому радіусі. Існують дві основні області застосування таких форм шестерень. Один з них являє собою альтернативне рішення з певними перевагами в продуктивності і технології виготовлення з прямим зубом. Інший додаток, коли форма шестерні з евольвентної косозубой шестірнею або черв'яком на пересічних осях. Потенційні переваги спіральних муфт і шестерень забезпечує високу потужність передачі крутного моменту поряд з високопродуктивною обробкою. У статті описується геометричний аналіз проектування шестерен та методика проектування спіральних форм евольвентних зубчастих коліс із симетричним і несиметричним профілями зубів. Запропонований технологічний спосіб зубофрезеровання шестерень, розглянуто особливості конструкції та розрахунок інструменту

Private Dispute Resolution in the Card Context: Structure, Reputation, and Incentives

Explosive growth in credit, debit, and other card payment systems in recent years has produced a parallel growth in private dispute resolution systems based on the web of contracts entered into by merchants, merchant acquirers, consumers, card issuers, card associations, and transaction processors. These contracts have produced legal systems based on contract and the enforcement of which rests primarily on reputational constraints. To cost-effectively resolve disputes, these private legal systems have evolved innovative procedures using resources at the lowest-possible level, including incentive-payments for producing information and rigid deadlines for parties\u27 actions. This paper describes and analyzes these legal systems and their procedures as a potential model for resolving other categories of disputes

A Review of State Procurement and Contracting

Are states effectively managing contracting and procurement activities? Are they striking the right balance between central administrative control and empowerment through delegation? How effective is training and monitoring? How do these practices compare to the principles of best practice? What role will information technology play in the future for procurement and contracting? As part of the Government Performance Project, budget, procurement, and contracting managers in 48 states were surveyed, providing descriptions of their procurement and contracting practices. There are numerous developments that speak to the practical details of contemporary public management. Five key findings are (1) information technology needs are challenging states, with some responding well, but others struggling, (2) in most states staff training needs to be improved, (3) restrictions prohibiting best value purchasing need to be removed, (4) states can learn from and improve practices by partnering with other governments and private organizations, and (5) most states use a hybrid of both centralized and decentralized management structures when it comes to contracting and procurement

Are City Managers Greedy Bureaucrats?

William A. Niskanen\u27s (1971, 1975) theory of bureaucracy has been a source of much debate and research.^ The theory assumes that utility-maximizing bureaucrats will seek to maximize their agency\u27s discretionary budget. A central implication of this theory is that bureaus will supply output inefficiently or in quantities greater than that desired by citizens. The authors test Niskanen\u27s hypothesis by examining the decision of cities to contract out for services. Their premise is that city managers fit the characteristics of the greedy bureaucrat Niskanen describes. If his theory is valid, then city managers should be expected to avoid contracting out because it would expose their discretionary budget and make it more difficult to use for their own purposes