Theoretical and Experimental Insights into Decentralized Combinatorial Auctions

Combinatorial Auctions (CAs) are promising to increase so-cial welfare by enabling bidders to express their valuationon any combination of items. A major issue of many CAsis the requirement to optimally solve the NP-hard Combi-natorial Allocation Problem. To release a centralized auc-tioneer from that computational burden he can shift it tothe bidders. One of the few discussed decentralized auc-tions is PAUSE, in which bidders suggest new allocations tothe auctioneer. In our theoretical analysis we examine thebidders\u27 bid complexity and determine a worst case boundconcerning eciency, if bidders follow a prot maximizingstrategy. Based on these results we conduct computationalexperiments with dierent bidding and computation strate-gies, and analyze their impact on eciency, auctioneer\u27s rev-enue and auction runtime. Surprisingly, even if agents de-viate from the optimal bid price calculation, PAUSE stillachieves high levels of eciency and auctioneer\u27s revenuecompared to the Combinatorial Clock auction

Twisted Thue equations with multiple exponents in fixed number fields

Let $K$ be a number field of degree $d\geq 3$ and fix $s$ multiplicatively independent $\gamma_1, \dots, \gamma_s \in K^*$ that fulfil some technical requirements, which can be vastly simplified to $\mathbb{Q}$-linearly independence, given Schanuel's conjecture. We then consider the twisted Thue equation $$\left|N_{K/\mathbb{Q}}\left(X-\gamma_1^{t_1}\cdots\gamma_s^{t_s}Y\right)\right| = 1,$$ and prove that it has only finitely many solutions $(x,y, (t_1, \dots, t_s) )$ with $xy \neq 0$ and $\mathbb{Q}\left( \gamma_1^{t_1}\cdots \gamma_s^{t_s} \right) = K$, all of which are effectively computable

Diamagnetic pumping near the base of a stellar convection zone

The property of inhomogeneous turbulence in conducting fluids to expel large-scale magnetic fields in the direction of decreasing turbulence intensity is shown as important for the magnetic field dynamics near the base of a stellar convection zone. The downward diamagnetic pumping confines a fossil internal magnetic field in the radiative core so that the field geometry is appropriate for formation of the solar tachocline. For the stars of solar age, the diamagnetic confinement is efficient only if the ratio of turbulent magnetic diffusivity of the convection zone to the (microscopic or turbulent) diffusivity of the radiative interiour is larger than 10^5. Confinement in younger stars require still larger diffusivity ratio. The observation of persistent magnetic structures on young solar-type stars can thus provide evidences for the nonexistence of tachoclines in stellar interiors and on the level of turbulence in radiative cores.Comment: 4 pages, 5 figure

Learning to Predict Image-based Rendering Artifacts with Respect to a Hidden Reference Image

Image metrics predict the perceived per-pixel difference between a reference image and its degraded (e. g., re-rendered) version. In several important applications, the reference image is not available and image metrics cannot be applied. We devise a neural network architecture and training procedure that allows predicting the MSE, SSIM or VGG16 image difference from the distorted image alone while the reference is not observed. This is enabled by two insights: The first is to inject sufficiently many un-distorted natural image patches, which can be found in arbitrary amounts and are known to have no perceivable difference to themselves. This avoids false positives. The second is to balance the learning, where it is carefully made sure that all image errors are equally likely, avoiding false negatives. Surprisingly, we observe, that the resulting no-reference metric, subjectively, can even perform better than the reference-based one, as it had to become robust against mis-alignments. We evaluate the effectiveness of our approach in an image-based rendering context, both quantitatively and qualitatively. Finally, we demonstrate two applications which reduce light field capture time and provide guidance for interactive depth adjustment.Comment: 13 pages, 11 figure

Towards Scalable OLTP Over Fast Networks

Online Transaction Processing (OLTP) underpins real-time data processing in many mission-critical applications, from banking to e-commerce. These applications typically issue short-duration, latency-sensitive transactions that demand immediate processing. High-volume applications, such as Alibaba's e-commerce platform, achieve peak transaction rates as high as 70 million transactions per second, exceeding the capacity of a single machine. Instead, distributed OLTP database management systems (DBMS) are deployed across multiple powerful machines. Historically, such distributed OLTP DBMSs have been primarily designed to avoid network communication, a paradigm largely unchanged since the 1980s. However, fast networks challenge the conventional belief that network communication is the main bottleneck. In particular, emerging network technologies, like Remote Direct Memory Access (RDMA), radically alter how data can be accessed over a network. RDMA's primitives allow direct access to the memory of a remote machine within an order of magnitude of local memory access. This development invalidates the notion that network communication is the primary bottleneck. Given that traditional distributed database systems have been designed with the premise that the network is slow, they cannot efficiently exploit these fast network primitives, which requires us to reconsider how we design distributed OLTP systems. This thesis focuses on the challenges RDMA presents and its implications on the design of distributed OLTP systems. First, we examine distributed architectures to understand data access patterns and scalability in modern OLTP systems. Drawing on these insights, we advocate a distributed storage engine optimized for high-speed networks. The storage engine serves as the foundation of a database, ensuring efficient data access through three central components: indexes, synchronization primitives, and buffer management (caching). With the introduction of RDMA, the landscape of data access has undergone a significant transformation. This requires a comprehensive redesign of the storage engine components to exploit the potential of RDMA and similar high-speed network technologies. Thus, as the second contribution, we design RDMA-optimized tree-based indexes — especially applicable for disaggregated databases to access remote data efficiently. We then turn our attention to the unique challenges of RDMA. One-sided RDMA, one of the network primitives introduced by RDMA, presents a performance advantage in enabling remote memory access while bypassing the remote CPU and the operating system. This allows the remote CPU to process transactions uninterrupted, with no requirement to be on hand for network communication. However, that way, specialized one-sided RDMA synchronization primitives are required since traditional CPU-driven primitives are bypassed. We found that existing RDMA one-sided synchronization schemes are unscalable or, even worse, fail to synchronize correctly, leading to hard-to-detect data corruption. As our third contribution, we address this issue by offering guidelines to build scalable and correct one-sided RDMA synchronization primitives. Finally, recognizing that maintaining all data in memory becomes economically unattractive, we propose a distributed buffer manager design that efficiently utilizes cost-effective NVMe flash storage. By leveraging low-latency RDMA messages, our buffer manager provides a transparent memory abstraction, accessing the aggregated DRAM and NVMe storage across nodes. Central to our approach is a distributed caching protocol that dynamically caches data. With this approach, our system can outperform RDMA-enabled in-memory distributed databases while managing larger-than-memory datasets efficiently

Online Mentoring for Talented Girls in STEM: The Role of Relationship Quality and Changes in Learning Environments in Explaining Mentoring Success

Although participation rates of women in science, technology, engineering, and mathematics (STEM) are continually improving, low rates are still an issue in many countries. While previous studies found positive effects of online mentoring for increasing girls’ interests in STEM, research concerning explanatory mechanisms is lacking. We found evidence that in a 1‐year online mentoring program for girls (age: M = 13.82 years, N = 998) in STEM, suitably implemented mentoring (operationalized via relationship quality in a program that systematically incorporates structural and organizational aspects of successful mentoring) was associated with positive changes in the learning environments of the mentees (as indicated by their increasing educational capital). These positive changes were associated with increases in the program‐related mentoring outcomes STEM activities and elective intentions in STEM. Finally, we found that suitably implemented online mentoring was indirectly related to an increase in these two mentoring outcomes via an increase in educational capital. These results indicate the importance of paying close attention to learning environments when planning interventions

Local Anesthetics and Recurrence after Cancer Surgery-What’s New? A Narrative Review

The perioperative use of regional anesthesia and local anesthetics is part of almost every anesthesiologist’s daily clinical practice. Retrospective analyses and results from experimental studies pointed towards a potential beneficial effect of the local anesthetics regarding outcome—i.e., overall and/or recurrence-free survival—in patients undergoing cancer surgery. The perioperative period, where the anesthesiologist is responsible for the patients, might be crucial for the further course of the disease, as circulating tumor cells (shed from the primary tumor into the patient’s bloodstream) might form new micro-metastases independent of complete tumor removal. Due to their strong anti-inflammatory properties, local anesthetics might have a certain impact on these circulating tumor cells, either via direct or indirect measures, for example via blunting the inflammatory stress response as induced by the surgical stimulus. This narrative review highlights the foundation of these principles, features recent experimental and clinical data and provides an outlook regarding current and potential future research activities

Distinguishing simple and residual consistencies in functionally equivalent and non-equivalent situations: Evidence from experimental and observational longitudinal data

The current work examines consistencies of personality state scores across functionally equivalent and non-equivalent situations. We argue that simple consistency, defined as the correlation between state scores without taking people’s straits into account, needs to be distinguished from residual consistency that does account for traits. The existence of residual consistency reflects systematic interindividual differences in how people respond to situations, above and beyond what is expected from their traits. We examine the level and individual differences in all of these forms of consistency. In four micro-longitudinal studies (total N = 671), participants first provided trait self-ratings and then state ratings, either in response to two situation vignettes presented at separate testing occasions (Studies 1 and 2) or during experience sampling in daily life (Studies 3 and 4). In all studies, simple consistency was substantial, and the level of residual consistency varied with the level of functional equivalence of the situations. Further, individual differences in both simple and residual consistencies were only weakly correlated, suggesting no underlying general factor but only trait-specific consistencies. We conclude that there are consistent individual differences in how people respond to equivalent situations, even when their personality trait scores have been taken into account.Peer Reviewe