22,794 research outputs found
Freedom Wears a Cap : The Law, Liberty, and Opportunity for British Convict Servants in Virginia, 1718-1788
Great Britain’s passage of the Transportation Act of 1718 was intended to relieve Great Britain of an unwanted criminal element while at the same time providing much needed labor for her North American colonies. This thesis argues that the legislative body of Virginia initially responded by passing legislation intended to limit the dangers presented by the introduction of convict servants into the colony. However, the significant demand for labor in Virginia resulted in the colony receiving a substantial share of those convicts transported to North America. Contemporaries argued that the importation of convict servants led to an increase in crime. This study employs the court records of eighteen counties in Colonial Virginia. The author contends that the evidence reveals that theft was the most common criminal activity of convict servants in Virginia. However, despite claims to the contrary, convict servants did not commit crimes in excess of their percentage of the tithable population. Moreover, over the course of the eighteenth-century justices county justices increasingly relied on providing lighter sentences than that prescribed by the law. This enabled planters to punish the criminal while maintaining control over their labor. The last chapter moves away from the legal system of Virginia and examines the opportunities the American Revolution provided to convict servants
The Orion constellation as an installation - An innovative three dimensional teaching and learning environment
Visualising the three dimensional distribution of stars within a
constellation is highly challenging for both students and educators, but when
carried out in an interactive collaborative way it can create an ideal
environment to explore common misconceptions about size and scale within
astronomy. We present how the common table top activities based upon the Orion
constellation miss out on this opportunity. Transformed into a walk-through
Orion installation that includes the position of our Solar system, it allows
the students to fully immerse themselves within the model and experience
parallax. It enables participants to explore within the installation many other
aspects of astronomy relating to sky culture, stellar evolution, and stellar
timescales establishing an innovative learning and teaching environment.Comment: 2 pages, submitted to The Physics Teacher - Colum
Efficient Probabilistic Performance Bounds for Inverse Reinforcement Learning
In the field of reinforcement learning there has been recent progress towards
safety and high-confidence bounds on policy performance. However, to our
knowledge, no practical methods exist for determining high-confidence policy
performance bounds in the inverse reinforcement learning setting---where the
true reward function is unknown and only samples of expert behavior are given.
We propose a sampling method based on Bayesian inverse reinforcement learning
that uses demonstrations to determine practical high-confidence upper bounds on
the -worst-case difference in expected return between any evaluation
policy and the optimal policy under the expert's unknown reward function. We
evaluate our proposed bound on both a standard grid navigation task and a
simulated driving task and achieve tighter and more accurate bounds than a
feature count-based baseline. We also give examples of how our proposed bound
can be utilized to perform risk-aware policy selection and risk-aware policy
improvement. Because our proposed bound requires several orders of magnitude
fewer demonstrations than existing high-confidence bounds, it is the first
practical method that allows agents that learn from demonstration to express
confidence in the quality of their learned policy.Comment: In proceedings AAAI-1
Activity of species-specific antibiotics against Crohnʼs disease–associated adherent-invasive Escherichia coli
Background: Crohn's disease (CD) is associated with bacterial dysbiosis that frequently includes colonization by adherent-invasive Escherichia coli (AIEC). AIEC are adept at forming biofilms and are able to invade host cells and stimulate the production of proinflammatory cytokines. The use of traditional antibiotics for the treatment of CD shows limited efficacy. In this study, we investigate the use of species-specific antibiotics termed colicins for treatment of CD-associated AIEC.
Methods: Colicin activity was tested against a range of AIEC isolates growing in the planktonic and biofilm mode of growth. Colicins were also tested against AIEC bacteria associated with T84 intestinal epithelial cells and surviving inside RAW264.7 macrophages using adhesion assays and gentamicin protection assay, respectively. Uptake of colicins into eukaryotic cells was visualized using confocal microscopy. The effect of colicin treatment on the production of proinflammatory cytokine tumor necrosis factor alpha by macrophages was assessed by an enzyme-linked immunosorbent assay.
Results: Colicins show potent activity against AIEC bacteria growing as biofilms when delivered either as a purified protein or through a colicin-producing bacterial strain. In addition, colicins E1 and E9 are able to kill cell-associated and intracellular AIEC, but do not show toxicity toward macrophage cells or stimulate the production of proinflammatory cytokines. Colicin killing of intracellular bacteria occurs after entry of colicin protein into AIEC-infected macrophage compartments by actin-mediated endocytosis.
Conclusions: Our results demonstrate the potential of colicins as highly selective probiotic therapeutics for the eradication of E. coli from the gastrointestinal tract of patients with CD
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