@inproceedings{11852,
  abstract     = {We present a general framework of designing efficient dynamic approximate algorithms for optimization problems on undirected graphs. In particular, we develop a technique that, given any problem that admits a certain notion of vertex sparsifiers, gives data structures that maintain approximate solutions in sub-linear update and query time. We illustrate the applicability of our paradigm to the following problems. (1)A fully-dynamic algorithm that approximates all-pair maximum-flows/minimum-cuts up to a nearly logarithmic factor in O~(n2/3) 11The O~(⋅) notation is used in this paper to hide poly-logarithmic factors. amortized time against an oblivious adversary, and O~(m3/4) time against an adaptive adversary. (2)An incremental data structure that maintains O(1) - approximate shortest path in no(1) time per operation, as well as fully dynamic approximate all-pair shortest path and transshipment in O~(n2/3+o(1)) amortized time per operation. (3)A fully-dynamic algorithm that approximates all-pair effective resistance up to an (1+ϵ) factor in O~(n2/3+o(1)ϵ−O(1)) amortized update time per operation. The key tool behind result (1) is the dynamic maintenance of an algorithmic construction due to Madry [FOCS' 10], which partitions a graph into a collection of simpler graph structures (known as j-trees) and approximately captures the cut-flow and metric structure of the graph. The O(1)-approximation guarantee of (2) is by adapting the distance oracles by [Thorup-Zwick JACM '05]. Result (3) is obtained by invoking the random-walk based spectral vertex sparsifier by [Durfee et al. STOC '19] in a hierarchical manner, while carefully keeping track of the recourse among levels in the hierarchy. See https://arxiv.org/pdf/2005.02368.pdf for the full version of this paper.},
  author       = {Chen, Li and Goranci, Gramoz and Henzinger, Monika H and Peng, Richard and Saranurak, Thatchaphol},
  booktitle    = {61st Annual Symposium on Foundations of Computer Science},
  isbn         = {978-1-7281-9622-0},
  issn         = {2575-8454},
  location     = {Durham, NC, United States},
  pages        = {1135--1146},
  publisher    = {Institute of Electrical and Electronics Engineers},
  title        = {{Fast dynamic cuts, distances and effective resistances via vertex sparsifiers}},
  doi          = {10.1109/focs46700.2020.00109},
  year         = {2020},
}

@inproceedings{11880,
  abstract     = {Given a directed graph and a source vertex, the fully dynamic single-source reachability problem is to maintain the set of vertices that are reachable from the given vertex, subject to edge deletions and insertions. It is one of the most fundamental problems on graphs and appears directly or indirectly in many and varied applications. While there has been theoretical work on this problem, showing both linear conditional lower bounds for the fully dynamic problem and insertions-only and deletions-only upper bounds beating these conditional lower bounds, there has been no experimental study that compares the performance of fully dynamic reachability algorithms in practice. Previous experimental studies in this area concentrated only on the more general all-pairs reachability or transitive closure problem and did not use real-world dynamic graphs.

In this paper, we bridge this gap by empirically studying an extensive set of algorithms for the single-source reachability problem in the fully dynamic setting. In particular, we design several fully dynamic variants of well-known approaches to obtain and maintain reachability information with respect to a distinguished source. Moreover, we extend the existing insertions-only or deletions-only upper bounds into fully dynamic algorithms. Even though the worst-case time per operation of all the fully dynamic algorithms we evaluate is at least linear in the number of edges in the graph (as is to be expected given the conditional lower bounds) we show in our extensive experimental evaluation that their performance differs greatly, both on generated as well as on real-world instances.},
  author       = {Hanauer, Kathrin and Henzinger, Monika H and Schulz, Christian},
  booktitle    = {2020 Symposium on Algorithm Engineering and Experiments},
  location     = {Salt Lake City, UT, United States},
  pages        = {106--119},
  publisher    = {Society for Industrial and Applied Mathematics},
  title        = {{Fully dynamic single-source reachability in practice: An experimental study}},
  doi          = {10.1137/1.9781611976007.9},
  year         = {2020},
}

@inproceedings{11881,
  abstract     = {We introduce the fastest known exact algorithm for the multiterminal cut problem with k terminals. In particular, we engineer existing as well as new data reduction rules. We use the rules within a branch-and-reduce framework and to boost the performance of an ILP formulation. Our algorithms achieve improvements in running time of up to multiple orders of magnitudes over the ILP formulation without data reductions, which has been the de facto standard used by practitioners. This allows us to solve instances to optimality that are significantly larger than was previously possible.},
  author       = {Henzinger, Monika H and Noe, Alexander and Schulz, Christian},
  booktitle    = {2020 Symposium on Algorithm Engineering and Experiments},
  location     = {Salt Lake City, UT, United States},
  pages        = {42--55},
  publisher    = {Society for Industrial and Applied Mathematics},
  title        = {{Shared-memory branch-and-reduce for multiterminal cuts}},
  doi          = {10.1137/1.9781611976007.4},
  year         = {2020},
}

@article{11889,
  abstract     = {We study the problem of computing a minimum cut in a simple, undirected graph and give a deterministic 𝑂(𝑚log2𝑛loglog2𝑛) time algorithm. This improves on both the best previously known deterministic running time of 𝑂(𝑚log12𝑛) (Kawarabayashi and Thorup [J. ACM, 66 (2018), 4]) and the best previously known randomized running time of 𝑂(𝑚log3𝑛) (Karger [J. ACM, 47 (2000), pp. 46--76]) for this problem, though Karger's algorithm can be further applied to weighted graphs. Moreover, our result extends to balanced directed graphs, where the balance of a directed graph captures how close the graph is to being Eulerian. Our approach is using the Kawarabayashi and Thorup graph compression technique, which repeatedly finds low conductance cuts. To find these cuts they use a diffusion-based local algorithm. We use instead a flow-based local algorithm and suitably adjust their framework to work with our flow-based subroutine. Both flow- and diffusion-based methods have a long history of being applied to finding low conductance cuts. Diffusion algorithms have several variants that are naturally local, while it is more complicated to make flow methods local. Some prior work has proven nice properties for local flow-based algorithms with respect to improving or cleaning up low conductance cuts. Our flow subroutine, however, is the first that both is local and produces low conductance cuts. Thus, it may be of independent interest.},
  author       = {Henzinger, Monika H and Rao, Satish and Wang, Di},
  issn         = {1095-7111},
  journal      = {SIAM Journal on Computing},
  number       = {1},
  pages        = {1--36},
  publisher    = {Society for Industrial & Applied Mathematics},
  title        = {{Local flow partitioning for faster edge connectivity}},
  doi          = {10.1137/18m1180335},
  volume       = {49},
  year         = {2020},
}

@article{11894,
  abstract     = {Graph sparsification aims at compressing large graphs into smaller ones while preserving important characteristics of the input graph. In this work we study vertex sparsifiers, i.e., sparsifiers whose goal is to reduce the number of vertices. We focus on the following notions: (1) Given a digraph 𝐺=(𝑉,𝐸) and terminal vertices 𝐾⊂𝑉 with |𝐾|=𝑘, a (vertex) reachability sparsifier of 𝐺 is a digraph 𝐻=(𝑉𝐻,𝐸𝐻), 𝐾⊂𝑉𝐻 that preserves all reachability information among terminal pairs. Let |𝑉𝐻| denote the size of 𝐻. In this work we introduce the notion of reachability-preserving minors (RPMs), i.e., we require 𝐻 to be a minor of 𝐺. We show any directed graph 𝐺 admits an RPM 𝐻 of size 𝑂(𝑘3), and if 𝐺 is planar, then the size of 𝐻 improves to 𝑂(𝑘2log𝑘). We complement our upper bound by showing that there exists an infinite family of grids such that any RPM must have Ω(𝑘2) vertices. (2) Given a weighted undirected graph 𝐺=(𝑉,𝐸) and terminal vertices 𝐾 with |𝐾|=𝑘, an exact (vertex) cut sparsifier of 𝐺 is a graph 𝐻 with 𝐾⊂𝑉𝐻 that preserves the value of minimum cuts separating any bipartition of 𝐾. We show that planar graphs with all the 𝑘 terminals lying on the same face admit exact cut sparsifiers of size 𝑂(𝑘2) that are also planar. Our result extends to flow and distance sparsifiers. It improves the previous best-known bound of 𝑂(𝑘222𝑘) for cut and flow sparsifiers by an exponential factor and matches an Ω(𝑘2) lower-bound for this class of graphs.},
  author       = {Goranci, Gramoz and Henzinger, Monika H and Peng, Pan},
  issn         = {1095-7146},
  journal      = {SIAM Journal on Discrete Mathematics},
  number       = {1},
  pages        = {130--162},
  publisher    = {Society for Industrial & Applied Mathematics},
  title        = {{Improved guarantees for vertex sparsification in planar graphs}},
  doi          = {10.1137/17m1163153},
  volume       = {34},
  year         = {2020},
}

@article{11954,
  abstract     = {The combination of nickel and photocatalysis has unlocked a variety of cross-couplings. These protocols rely on a few photocatalysts that can only convert a small portion of visible light (<500 nm) into chemical energy. The high-energy photons that excite the photocatalyst can result in unwanted side reactions. Dyes that absorb a much broader spectrum of light are not applicable because of their short-lived singlet excited states. Here, we describe a self-assembling catalyst system that overcomes this limitation. Immobilization of a nickel catalyst on dye-sensitized titanium dioxide results in a material that catalyzes carbon–heteroatom and carbon–carbon bond formations. The modular approach of dye-sensitized metallaphotocatalysts accesses the entire visible light spectrum and allows tackling selectivity issues resulting from low wavelengths strategically. The concept overcomes current limitations of metallaphotocatalysis by unlocking the potential of dyes that were previously unsuitable.},
  author       = {Reischauer, Susanne and Strauss, Volker and Pieber, Bartholomäus},
  issn         = {2155-5435},
  journal      = {ACS Catalysis},
  number       = {22},
  pages        = {13269–13274},
  publisher    = {American Chemical Society},
  title        = {{Modular, self-assembling metallaphotocatalyst for cross-couplings using the full visible-light spectrum}},
  doi          = {10.1021/acscatal.0c03950},
  volume       = {10},
  year         = {2020},
}

@article{11966,
  abstract     = {The front cover artwork is provided by the group of Dr. Bartholomäus Pieber at the Max Planck Institute of Colloids and Interfaces (Germany). The image symbolizes the activation of a heterogeneous photocatalyst by visible light and its application for organic synthesis. Read the full text of the Review at 10.1002/cptc.202000014.},
  author       = {Gisbertz, Sebastian and Pieber, Bartholomäus},
  issn         = {2367-0932},
  journal      = {ChemPhotoChem},
  number       = {7},
  pages        = {454--454},
  publisher    = {Wiley},
  title        = {{Heterogeneous photocatalysis in organic synthesis}},
  doi          = {10.1002/cptc.202000137},
  volume       = {4},
  year         = {2020},
}

@article{11969,
  abstract     = {Photochemistry enables new synthetic means to form carbon–heteroatom bonds. Photocatalysts can catalyze carbon–heteroatom cross-couplings by electron or energy transfer either alone or in combination with a second catalyst. Photocatalyst-free methods are possible using photolabile substrates or by generating photoactive electron donor-acceptor complexes. This review summarizes and discusses the strategies used in light-mediated carbon–heteroatom bond formations based on the proposed mechanisms.},
  author       = {Cavedon, Cristian and Seeberger, Peter H. and Pieber, Bartholomäus},
  issn         = {1099-0690},
  journal      = {European Journal of Organic Chemistry},
  number       = {10},
  pages        = {1379--1392},
  publisher    = {Wiley},
  title        = {{Photochemical strategies for carbon–heteroatom bond formation}},
  doi          = {10.1002/ejoc.201901173},
  volume       = {2020},
  year         = {2020},
}

@article{11978,
  abstract     = {Dual photocatalysis and nickel catalysis can effect cross-coupling under mild conditions, but little is known about the in situ kinetics of this class of reactions. We report a comprehensive kinetic examination of a model carboxylate O-arylation, comparing a state-of-the-art homogeneous photocatalyst (Ir(ppy)3) with a competitive heterogeneous photocatalyst (graphitic carbon nitride). Experimental conditions were adjusted such that the nickel catalytic cycle is saturated with excited photocatalyst. This approach was designed to remove the role of the photocatalyst, by which only the intrinsic behaviors of the nickel catalytic cycles are observed. The two reactions did not display identical kinetics. Ir(ppy)3 deactivates the nickel catalytic cycle and creates more dehalogenated side product. Kinetic data for the reaction using Ir(ppy)3 supports a turnover-limiting reductive elimination. Graphitic carbon nitride gave higher selectivity, even at high photocatalyst-to-nickel ratios. The heterogeneous reaction also showed a rate dependence on aryl halide, indicating that oxidative addition plays a role in rate determination. The results argue against the current mechanistic hypothesis, which states that the photocatalyst is only involved to trigger reductive elimination.},
  author       = {Malik, Jamal A. and Madani, Amiera and Pieber, Bartholomäus and Seeberger, Peter H.},
  issn         = {1520-5126},
  journal      = {Journal of the American Chemical Society},
  number       = {25},
  pages        = {11042--11049},
  publisher    = {American Chemical Society},
  title        = {{Evidence for photocatalyst involvement in oxidative additions of nickel-catalyzed carboxylate O-arylations}},
  doi          = {10.1021/jacs.0c02848},
  volume       = {142},
  year         = {2020},
}

@article{11979,
  abstract     = {Dual photoredox/nickel-catalysed C–N cross-couplings suffer from low yields for electron-rich aryl halides. The formation of catalytically inactive nickel-black is responsible for this limitation and causes severe reproducibility issues. Here, we demonstrate that catalyst deactivation can be avoided by using a carbon nitride photocatalyst. The broad absorption of the heterogeneous photocatalyst enables wavelength-dependent control of the rate of reductive elimination to prevent nickel-black formation during the coupling of cyclic, secondary amines and aryl halides. A second approach, which is applicable to a broader set of electron-rich aryl halides, is to run the reactions at high concentrations to increase the rate of oxidative addition. Less nucleophilic, primary amines can be coupled with electron-rich aryl halides by stabilizing low-valent nickel intermediates with a suitable additive. The developed protocols enable reproducible, selective C–N cross-couplings of electron-rich aryl bromides and can also be applied for electron-poor aryl chlorides.},
  author       = {Gisbertz, Sebastian and Reischauer, Susanne and Pieber, Bartholomäus},
  issn         = {2520-1158},
  journal      = {Nature Catalysis},
  number       = {8},
  pages        = {611--620},
  publisher    = {Springer Nature},
  title        = {{Overcoming limitations in dual photoredox/nickel-catalysed C–N cross-couplings due to catalyst deactivation}},
  doi          = {10.1038/s41929-020-0473-6},
  volume       = {3},
  year         = {2020},
}

@article{11980,
  abstract     = {Small organic radicals are ubiquitous intermediates in photocatalysis and are used in organic synthesis to install functional groups and to tune electronic properties and pharmacokinetic parameters of the final molecule. Development of new methods to generate small organic radicals with added functionality can further extend the utility of photocatalysis for synthetic needs. Herein, we present a method to generate dichloromethyl radicals from chloroform using a heterogeneous potassium poly(heptazine imide) (K-PHI) photocatalyst under visible light irradiation for C1-extension of the enone backbone. The method is applied on 15 enones, with γ,γ-dichloroketones yields of 18–89%. Due to negative zeta-potential (−40 mV) and small particle size (100 nm) K-PHI suspension is used in quasi-homogeneous flow-photoreactor increasing the productivity by 19 times compared to the batch approach. The resulting γ,γ-dichloroketones, are used as bifunctional building blocks to access value-added organic compounds such as substituted furans and pyrroles.},
  author       = {Mazzanti, Stefano and Kurpil, Bogdan and Pieber, Bartholomäus and Antonietti, Markus and Savateev, Aleksandr},
  issn         = {2041-1723},
  journal      = {Nature Communications},
  publisher    = {Springer Nature},
  title        = {{Dichloromethylation of enones by carbon nitride photocatalysis}},
  doi          = {10.1038/s41467-020-15131-0},
  volume       = {11},
  year         = {2020},
}

@article{11986,
  abstract     = {Carbon nitride materials have emerged as an efficient and sustainable class of heterogeneous photocatalysts, particularly when paired with nickel in dual catalytic cross-coupling reactions. Performing these transformations on larger scales using a continuous process is difficult due to the problems associated with handling solids in flow. By combining an oscillatory pump with a microstructured plug flow photoreactor, a stable suspension of the photocatalyst can be maintained, circumventing clogging of the reactor channels. Through careful tuning of the oscillator properties, the residence time distribution (RTD) was optimized, whilst maintaining a stable catalyst suspension. Short residence times (20 min) were achieved using optimized conditions and the recyclability of the photocatalyst was demonstrated over 10 cycles with no loss of activity. During a stable 4.5 hour scale-out demonstration, the model substrate could be isolated on 12 g scale (90% yield, 2.67 g h−1). Moreover, the method was applied for the gram scale synthesis of an intermediate of the active pharmaceutical ingredient tetracaine.},
  author       = {Rosso, Cristian and Gisbertz, Sebastian and Williams, Jason D. and Gemoets, Hannes P. L. and Debrouwer, Wouter and Pieber, Bartholomäus and Kappe, C. Oliver},
  issn         = {2058-9883},
  journal      = {Reaction Chemistry and Engineering},
  number       = {3},
  pages        = {597--604},
  publisher    = {Royal Society of Chemistry},
  title        = {{An oscillatory plug flow photoreactor facilitates semi-heterogeneous dual nickel/carbon nitride photocatalytic C–N couplings}},
  doi          = {10.1039/d0re00036a},
  volume       = {5},
  year         = {2020},
}