Continuous-action Reinforcement Learning for Playing Racing Games: Comparing SPG to PPO

In this paper, a novel racing environment for OpenAI Gym is introduced. This environment operates with continuous action- and state-spaces and requires agents to learn to control the acceleration and steering of a car while navigating a randomly generated racetrack. Different versions of two actor-critic learning algorithms are tested on this environment: Sampled Policy Gradient (SPG) and Proximal Policy Optimization (PPO). An extension of SPG is introduced that aims to improve learning performance by weighting action samples during the policy update step. The effect of using experience replay (ER) is also investigated. To this end, a modification to PPO is introduced that allows for training using old action samples by optimizing the actor in log space. Finally, a new technique for performing ER is tested that aims to improve learning speed without sacrificing performance by splitting the training into two parts, whereby networks are first trained using state transitions from the replay buffer, and then using only recent experiences. The results indicate that experience replay is not beneficial to PPO in continuous action spaces. The training of SPG seems to be more stable when actions are weighted. All versions of SPG outperform PPO when ER is used. The ER trick is effective at improving training speed on a computationally less intensive version of SPG.Comment: 12 pages, 9 figures. Code is available at https://github.com/mario-holubar/RacingR

Bullous Pemphigoid, Herpes Gestationis and Linear Dermatitis Herpetiformis: Circulating Anti-Basement Membrane Zone Antibodies; in Vitro Studies

It is well established that suprabasal acantholysis can be produced in tissue culture of normal human skin in the presence of pemphigus IgG autoantibody. In this study, bullous pemphigoid, herpes gestationis and linear dermatitis herpetiformis anti-basement membrane zone antibodies failed to produce dermoepidermal separation in a tissue culture model in spite of the presence of complement. The binding of the antibodies was demonstrated by immunofluorescence and immunoelectron microscopy; ultrastructurally, identical binding sites of anti-basement membrane zone antibodies could be demonstrated in vitro, as has been observed in vivo previously. Tissue culture is a suitable model for studying the binding sites of circulating anti-basement membrane zone antibodies but the functional activity (blister formation) of these antibodies cannot be assessed thereby

Salomon Stricker (1834.-1898.): Pionir mikrobiologije

The paper presents basic biographical data on the Austrian pioneer of experimental medicine Salomon Stricker (1834-1898), and emphasizes the link of his experimental work to important research projects of this time period. His influence on Carl Heitzmann and Carl Koller was pointed out. The work of both was connected directly with Sticker’s experimental designs, far less known in published literature. Demonstrating ad oculos the world of capillaries, diapedesis of blood cells, cell division in vivo by Stricker, paved the way for investigations in immunology and allergology.U radu se iznose osnovni biografski podaci o austrijskom pioniru eksperimentalne medicine Salomonu Strickeru (1834.-1898.) te se podvlači poveznica njegova eksperimentalnog rada s važnim istraživačkim projektima tog vremena. Osvjetljen je utjecaj Strickera na Carla Heitzmanna (1836.-1896.) te na Carla Kollera (1857.-1944.) koji je uveo kokain u oftalmologiju. Strickerovom eksperimentalnom utjecaju pripisuje se Kollerov istražvački interes, što je do sada bilo nepoznato u objavljenoj literaturi. Stricker je istražujući ulogu kapilara staničnu diapedezu i diobu utro put kasnim istraživanjima na području fiziologije, imunologije i alergologije

Does infliximab increase complications after surgery for inflammatory bowel disease?

Conflicting data exist regarding the association between pre-operative monoclonal anti-tumor necrosis factor-alpha antibody therapy with infliximab for Crohn disease and chronic ulcerative colitis, and the occurrence of post-operative complications. This report reviews the current literature that supports and refutes this association