SAPG: Split and Aggregate Policy Gradients

Despite extreme sample inefficiency, on-policy reinforcement learning, aka policy gradients, has become a fundamental tool in decision-making problems. With the recent advances in GPU-driven simulation, the ability to collect large amounts of data for RL training has scaled exponentially. However, we show that current RL methods, e.g. PPO, fail to ingest the benefit of parallelized environments beyond a certain point and their performance saturates. To address this, we propose a new on-policy RL algorithm that can effectively leverage large-scale environments by splitting them into chunks and fusing them back together via importance sampling. Our algorithm, termed SAPG, shows significantly higher performance across a variety of challenging environments where vanilla PPO and other strong baselines fail to achieve high performance. Website at https://sapg-rl.github.io/Comment: In ICML 2024 (Oral). Website at https://sapg-rl.github.io

Effect of Phosphorus Levels on Early Seedlings of Rice (Oryza sativa) under Varying Moisture Stress Conditions

This study investigated the impact of moisture levels and phosphorus applications on different rice varieties. It aimed to: 1. Identify optimal rice varieties for specific moisture and phosphorus combinations. 2. Understand how moisture stress affects seed germination speed and root and shoot development. 3. Analyze the influence of increased phosphorus on root growth, especially under moisture stress. 4. Evaluate if additional NPK application enhances the positive effects of phosphorus. The meticulously controlled experiment, conducted within the International Rice Research Institute (IRRI)'s RGA facility from October to November 2023, utilized five rice varieties, three moisture levels (flooded, ideal, and Drought-like), and varying phosphorus levels. The findings revealed a positive correlation between phosphorus levels and root length across all rice varieties. This emphasizes the crucial role of phosphorus in promoting root development under challenging conditions. Notably, while increased phosphorus significantly enhanced root adhesion under flooding and aided seedling recovery, drought remained a significant barrier to root growth, regardless of phosphorus application. Interestingly, despite general genetic uniformity in germination and root-shoot parameters among the varieties, a clear positive correlation between phosphorus levels and root length was still observed. In conclusion, this study highlights the importance of phosphorus in strengthening root grip during floods, thereby aiding seedling recovery. However, it also emphasizes that drought remains a dominant factor hindering plant growth. The consistency observed across different rice varieties strengthens the findings, and the significant increase in root length with increased phosphorus application underscores its vital role in root development under challenging conditions. This study provides valuable insights for optimizing rice growth strategies by considering specific rice varieties, moisture levels, and phosphorus applications

Endovascular Management of a Post-traumatic Popliteal Fossa Arteriovenous Fistula

Background: Arteriovenous fistulas (AVFs) are abnormal communications between an artery and a vein. Posttraumatic AVFs, including those in the popliteal fossa, are rare but require prompt management to prevent complications. Case Report: A 35-year-old male presented with a painful, pulsatile swelling over the left knee, 15 days postarthroscopic anterior cruciate ligament and posterior cruciate ligament reconstruction. Clinical examination showed a 5 × 5 cm2 tender swelling with a palpable thrill. Computed tomography angiography revealed a communication between the popliteal artery and vein. An endovascular intervention was performed using two Bentley covered balloon expandable stents. Post-procedure, the patient showed uneventful recovery, with follow-up Doppler scans indicating normal vascular flow and no residual abnormalities. Conclusions: Post-traumatic AVFs, often resulting from penetrating injuries or iatrogenic causes, can present with painful, pulsatile swellings and may lead to severe complications if untreated. Advances in endovascular techniques, such as stenting, have improved outcomes such as reduced post-operative morbidity, eliminating complications associated with open surgery

Indicator-Impregnated Agarose Films for Colorimetric Measurement of pH

In this article, we report on the development of indicator-impregnated agarose sensor films for colorimetric estimation of the pH of different standard buffer solutions and urine samples. In contrast to the conventional paper-based dipstick method, the presented method employs dried agarose that was infused with a chemical indicator, which when exposed to the test sample results in an appropriate chromogenic outcome. The color change was then quantified by the smart camera system. The divulged instrument has been calibrated with standard buffers and also tested with clinical urine samples. The systematic study was conducted to characterize the performance of the presented technique, such as interplate variations, time variations, volume variations, and shelf life study of agarose sensor films for the commercial viability of such a technique. The employed method is competent enough to bring a change in the paradigm of dipstick method from being qualitative estimation to quantitative, manual detection to automated, and a subjective approach of diagnosis to an objective one. The technique presented here has potential application in the field of point-of-care diagnostics with high fidelity, multiplexing, and robust quantitative estimation