2,455 research outputs found
Climatological distributions of δ¹³C of dissolved inorganic carbon in the global oceans
No full textThis data set provides climatological distributions of d13C of dissolved inorganic carbon for the global oceans. This includes present and reconstructed preindustrial d13C, and the decline over the industrialized period; the full oceanic 13C Suess effect. These distributions were constructed as described in:
Eide, Marie; Olsen, Are; Ninnemann, Ulysses S; Eldevik, Tor (in press): A global estimate of the full oceanic 13C Suess Effect since the Preindustrial. Global Biogeochemical Cycles, 31(3), 492-514, doi:10.1002/2016GB005472
and
Eide, Marie; Olsen, Are; Ninnemann, Ulysses S; Johannessen, Truls (in press): A global ocean climatology of preindustrial and modern ocean d13C. Global Biogeochemical Cycles, 31(3), 515-534, doi:10.1002/2016GB005473
These articles should be cited whenever the data are used.
The data are provided as two files; one for the global oceans for 200 m and deeper levels, this includes present and preindustrial d13C and the 13C Suess effect; and one that cover the entire water column but only includes the 13C Suess effect estimates as d13C distributions have not been constructed for the upper 200 m. See Eide et al. (2017a) and Eide et al. (2017b) for details. The Suess effect estimates from 200 m and downwards are the same in the two data files.
The climatology is based on data that were mostly collected during the 1990s, and the present d13C and 13C Suess effect distributions should be considered to represent that time period. The preindustrial distribution is based on the modern observations, corrected for the full 13C Suess effect since the industrial revolution.
The data are provided on a 1 degree x 1 degree grid at the following depth levels:
For the present and preindustrial d13C and the 13C Suess effect: 10 to 33 (200 m to 5500 m)
For the 13C Suess effect including the upper 200 m: 1 to 33 (0 to 5500 m
Tor over QUIC
No full textTor is the most popular tool for anonymous online communication. However, the performance of Tor's volunteer-run network is suboptimal when network congestion occurs. Within Tor, many connections are multiplexed over a single TCP connection between relays, which causes a head-of-line blocking problem, degrading relay performance. In this thesis, Tor's TCP transport layer protocol is replaced by QUIC, a UDP-based protocol that natively supports multiplexing streams asynchronously, effectively solving head-of-line blocking. Its performance is evaluated within various network environments through Containernet, a flexible Docker-based network test bed that allows for simple reproduction of results. Along with testing multiple congestion control algorithms, the impact of using Hystart++ within Tor over QUIC is evaluated. It is found that QUIC over Tor can perform up to 50% better in time to last byte performance than vanilla Tor in a realistic network environment, while featuring more consistent time to first byte performance. Additionally, the evaluations shows that throughput consistency and fairness amongst downloaders are improved as well, Besides offering improved performance, Tor over QUIC is designed with deployability and security in mind. This makes QUIC an attractive replacement as Tor's transport layer protol.Computer Scienc
TOR Is required for the retrograde regulation of synaptic homeostasis at the drosophila neuromuscular junction
No full textHomeostatic mechanisms operate to stabilize synaptic function; however, we know little about how they are regulated. Exploiting Drosophila genetics, we have uncovered a critical role for the target of rapamycin (TOR) in the regulation of synaptic homeostasis at the Drosophila larval neuromuscular junction. Loss of postsynaptic TOR disrupts a retrograde compensatory enhancement in neurotransmitter release that is normally triggered by a reduction in postsynaptic glutamate receptor activity. Moreover, postsynaptic overexpression of TOR or a phosphomimetic form of S6 ribosomal protein kinase, a common target of TOR, can trigger a strong retrograde increase in neurotransmitter release. Interestingly, heterozygosity for eIF4E, a critical component of the cap-binding protein complex, blocks the retrograde signal in all these cases. Our findings suggest that cap-dependent translation under the control of TOR plays a critical role in establishing the activity dependent homeostatic response at the NMJ
Adding QUIC support to the Tor network
No full textPrivacy in the Internet is under attack by governments and companies indiscriminately spying on everyone. The anonymity network Tor is a solution to restore some privacy, however, Tor is slow in both bandwidth and latency. It uses a TCP-based connection to multiplex different circuits between nodes and this causes different independent circuits to interfere with each other. To solve this, we propose a transport layer implementation using the UDP-based protocol QUIC, as it allows independent streams over a single connection. We built a Tor prototype that uses this protocol and evaluated its performance using a custom network simulator, as existing simulators were shown to be incompatible. We show that the QUIC-based implementation increased performance in several of the use case scenarios, mainly outperforming on the ‘time to first byte’ metric.Electrical Engineering | Embedded System
Measuring accessibility of popular websites while using Tor
No full textTor is an anonymity network used by a vast number of users in order to protect their privacy on the internet. It should not come as a surprise that this service is also used for abuse such as Denial of service attacks and other malicious activities because of the anonymity it provides. For protecting themselves from this abuse, websites block Tor in various ways. We investigate the extent and frequency of this kind of blocking by requesting the Alexa top 1000 websites with and without Tor with the objective of highlighting the differential treatment observed by privacy-minded users. We build upon existing studies by using diverse metrics to measure discrimination and by extending our search to three sub pages of websites for detecting sophisticated blocking. We find at least 25.8% of the Alexa top 1000 websites discriminating on the home page against Tor users as opposed to 20.03% observed in previous studies. This number rises to 31.7% after including the three sub pages. We also discover new types of blocks such as Tor users being served old or different versions of websites. We categorize the blocked websites and find that Online Shopping and Finance/ Banking categories discriminate most against Tor while Social Networking sites and Search Engines discriminate the least.CSE3000 Research ProjectComputer Science and Engineerin
Products on Tor
No full textIn 1974 work establishing the collapse of certain Eilenberg-Moore spectral
sequences, Munkholm constructs, in passing, a bilinear multiplication operation
on Tor of a triple of -algebras. In 2020, the present author,
pursuing a multiplicative collapse result extending Munkholm's, studied a
variant of this product, without actually showing it agrees with Munkholm's. In
2019, Franz had defined a weak product on the two-sided bar construction of a
triple of -algebras under similar hypotheses, with which this author
proved a related collapse result, but without investigating the properties of
the induced product on Tor.
The present work demonstrates that the two products on Tor agree and are
induced by the product of Franz.Comment: 19 pages, comments welcom
Android Tor Tribler Tunneling (AT3): TI3800 Bachelorproject
No full textTribler is a decentralized peer-to-peer file sharing system. Recently the Tribler development team has introduced anonymous internet communication using a Tor-like protocol in their trial version. The goal of our bachelor project is to port this technology to Android devices. This is a challenging task because cross-compiling the necessary libraries to the ARM CPU architecture is uncharted territory. We have successfully ported all dependencies of Tribler to Android. An application called Android Tor Tribler Tunneling (AT3) has been developed that tests whether these libraries work. This application downloads a test torrent and measures information such as CPU usage and download speed. Based on this information we have concluded that it is currently not viable to run the anonymous tunnels on an Android smartphone. Creating circuits with several hops that use encryption is very computationally expensive and modern smartphones can hardly keep up. By using optimized cryptographic libraries such as gmp or with the recently announced ARMv8 architecture which supports hardware-accelerated AES encryption, creating such circuits might become possible.Tribler developmentParallel and Distributed Systems groupElectrical Engineering, Mathematics and Computer Scienc
Impact of replacing TCP by QUIC in Tor on website fingerprinting resistance
No full textPrivacy is a human right, yet, people’s behavior on the web is constantly tracked. Tor, an anonymity network, is an effective defence against tracking. However, Tor’s multiplexing of logically independent data streams into a single TCP connection causes issues. Tor with QUIC has been implemented as an alternative with better performance but it has not been studied whether and by how much QUIC increases the vulnerability to timing-based attacks.The most threatening attacks are website fingerprinting attacks, which can track a Tor user by only controlling the guard node, first of the relays that forward traffic in Tor. In this work, Tor with QUIC is evaluated against website fingerprinting attacks with various levels of defences active. Without defences, Tor is vulnerable to website fingerprinting for both TCP and QUIC but the attacks are more effective on QUIC. On the positive side, defences against website fingerprinting remain effective for QUIC in that they decrease the effectiveness of the attack by asimilar fraction as for TCP.Computer Science | Cyber Securit
Avoiding recording user activities: TOR, Linux Tails
No full textSieć TOR (The Onion Router) jest wirtualną siecią komputerową zapewniającą anonimizację oraz dostęp do często nielegalnych danych lub dla unikających cenzury. Linux Tails (The Amnesic Incognito Live System) stanowi natomiast system operacyjny bootowany wyłącznie z nośnika przenośnego (np.: pendrive, karty pamięci czy też płyty DVD) lub uruchamiany w sposób zwirtualizowany. Tails jako jedno z narzędzi oferuje dostęp do sieci TOR, zapewniając ponadto dalece wyszukane mechanizmy służące do unikania pozostawienia śladów cyfrowych na maszynie, z której korzysta użytkownik. Mimo innych intencji twórców obu omawianych powyżej narzędzi stały się one ulubionym pakietem olbrzymiej grupy przestępców na całym świecie. Autor w niniejszej publikacji skupia się na omówieniu zarówno obszarów powstawania śladów cyfrowych użytkowania TOR oraz Tails, jak i na możliwościach badawczych oraz możliwościach wnioskowania na ich podstawie. W pierwszej części artykułu opisany został mechanizm działania anonimizującej sieci TOR. Następnie autor zapoznaje czytelnika ze środowiskiem Linux Tails oraz odnosi się do faktycznych przypadków użycia.The Tor (The Onion Router) network is a virtual computer network that provides anonymisation and access to often illegal data or for those avoiding censorship. Linux Tails (The Amnesic Incognito Live System), on the other hand, is an operating system bootable only from a removable media (e.g.: flash drive, memory card or DVD) or run in a virtualized manner. Tails, as one of the tools, offers access to the Tor network providing, in addition, far sophisticated mechanisms to avoid leaving digital traces on the user’s machine. Despite the different intentions of the developers of the two tools discussed above, they have also become the favorite package of a huge group of criminals around the world. In this publication, the author focuses on discussing both the areas of formation of digital traces of Tor and Tails usage, as well as the research possibilities and inference possibilities based on them. The first part of the article describes the mechanism of the Tor anonymizing network. The author then introduces the reader to the Linux Tails environment and refers to actual use cases
Quantitative phosphoproteomics reveal that mTOR regulates cell growth and proliferation by phosphorylating a functionally diverse set of substrates
No full textThe atypical Ser/Thr kinase target of rapamycin (TOR) is a central controller of cell growth and proliferation. TOR forms two distinct multiprotein complexes, TORC1 and TORC2, which are structurally and functionally conserved from yeast to humans. Four major inputs control mammalian TOR (mTOR): growth factors, such as insulin; cellular energy levels, such as the AMP:ATP ratio; stress, such as hypoxia; and nutrients, such as amino acids. mTOR controls cell growth by the positive and negative regulation of several anabolic and catabolic processes, respectively, that collectively regulate cell size and proliferation. These cellular processes include autophagy, cytoskeleton rearrangement, glycolysis, lipogenesis, nutrient transport, ribosome biogenesis, and translation. Dysregulation of the mTOR signaling network has been associated with aging, and a multitude of diseases including cancer, cardiovascular disease, diabetes, inflammation, immune dysfunctions, and neurodegeneration. However, relatively few direct substrates of either one of the two mTOR complexes, mTORC1 and mTORC2, are known.
To determine downstream effectors of mammalian TOR (mTOR), we applied a functional, quantitative phosphoproteomics workflow to identify novel mTORC1 or mTORC2 regulated phosphorylations. Raptor and Rictor are essential components of mTORC1 and mTORC2, respectively. To distinguish phosphorylations regulated by mTORC1 or mTORC2, we specifically deleted Raptor or Rictor using an inducible gene knockout system in mouse embryonic fiberblasts (MEFs). We detected 4584 phosphorylation sites on 1398 proteins, and identified 335 novel mTOR effectors. Many of the novel effectors are implicated in cancer and metabolic diseases, but have no known links to mTOR. To distinguish direct mTOR substrates from indirect effectors, we combined peptide array in vitro kinase assays with phosphorylation motif analysis. This revealed that mTORC1 phosphorylates CAD in vivo and in vitro. CAD (carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase) is the initial and rate limiting enzyme in de novo pyrimidine synthesis. The macrolide rapamycin, which forms a complex with FKBP12, binds and acutely inhibits mTORC1 but not mTORC2. Rapamycin treatment inhibited growth factor stimulated CAD phosphorylation and oligomerization, decreased de novo pyrimidine synthesis, and delayed progression of S-phase where CAD activity is essential. Thus mTORC1 phosphorylates CAD and thereby stimulates de novo pyrimidine synthesis to promote cell proliferation.
Separately, we characterize the autophosphorylation of mTOR on Ser2481. Insulin stimulates the phosphorylation of mTOR at Ser2481 specifically in mTORC2. Knockout of Rictor, but not Raptor, abolished mTOR autophosphorylation at Ser2481. Prolonged treatment with rapamycin, which indirectly inhibits mTORC2 complex formation, inhibited Ser2481 phosphorylation. Surprisingly, mTORC2 autophosphorylation at Ser2481 temporally occurs after the insulin-induced phosphorylation of Akt/PKB and the SGK1 substrate NDGR1. Mutation of Ser2481 to aspartic acid rendered mTOR unable to phosphorylate Akt/PKB in vitro. However the function of mTOR-Ser2481 phosphorylation in vivo remains elusive, as mutation of mTOR-Ser2481 did not alter Akt/PKB phosphorylation in vivo.
In summary, mTORC1 and mTORC2 regulate the phosphorylation of a functionally diverse set of substrates to control several anabolic and catabolic processes that determine cell size and proliferation. As a central controller of cell growth and proliferation, mTOR plays a key role in regulating development, whereas dysregulation of mTOR signaling has been linked to aging and diseases such as cancer and metabolic disorders
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