On arc index and maximal Thurston-Bennequin number

We discuss the relation between arc index, maximal Thurston--Bennequin number, and Khovanov homology for knots. As a consequence, we calculate the arc index and maximal Thurston--Bennequin number for all knots with at most 11 crossings. For some of these knots, the calculation requires a consideration of cables which also allows us to compute the maximal self-linking number for all knots with at most 11 crossings.Comment: 10 pages, v4: corrected typo

Techno-Utopians, Scammers, and Bullshitters: The Promise and Peril of Web3 and Blockchain Technologies According to Operators and Venture Capital Investors

Proponents and developers of Web3 and blockchain argue that these technologies can revolutionize how people live and work by empowering individuals and distributing decision-making power. While technologists often have expansive hopes for what their technologies will accomplish over the long term, the practical challenges of developing, scaling, and maintaining systems amidst present-day constraints can compromise progress toward this vision. How technologists think about the technological future they hope to enable and how they navigate day-to-day issues impacts the form technologies take, their potential benefits, and their potential harms. In our current work, we aimed to explore the visions of Web3 and blockchain technologists and identify the immediate challenges that could threaten their visions. We conducted semi-structured interviews with 29 operators and professional investors in the Web3 and blockchain field. Our findings revealed that participants supported several ideological goals for their projects, with decentralization being a pivotal mechanism to enable user autonomy, distribute governance power, and promote financial inclusion. However, participants acknowledged the practical difficulties in fulfilling these promises, including the need for rapid technology development, conflicts of interest among stakeholders due to platform financing dynamics, and the challenge of expanding to mainstream users who may not share the "Web3 ethos." If negotiated ineffectively, these challenges could lead to negative outcomes, such as corrupt governance, increased inequality, and increased prevalence of scams and dubious investment schemes. While participants thought education, regulation, and a renewed commitment to the original blockchain ideals could alleviate some problems, they expressed skepticism about the potential of these solutions

New Approach to Silver Halide Photography Using Radical Cation Chemistry

A new mechanism for spectral sensitization of silver halide is described, which can potentially double the sensitivity of photographic emulsions. The photooxidized sensitizing dye is trapped using an organic donor molecule, which fragments to form a cation and a reducing radical, which injects an electron into the conduction band of the silver halide. In this way, two conduction-band electrons can be produced for each absorbed photon

Visible-to-telecom quantum frequency conversion of light from a single quantum emitter

Quantum frequency conversion (QFC), a nonlinear optical process in which the frequency of a quantum light field is altered while conserving its non-classical correlations, was first demonstrated 20 years ago. Meanwhile, it is considered an essential tool for the implementation of quantum repeaters since it allows for interfacing quantum memories with telecom-wavelength photons as quantum information carriers. Here we demonstrate efficient (>30%) QFC of visible single photons (711 nm) emitted by a quantum dot (QD) to a telecom wavelength (1,313 nm). Analysis of the first and second-order coherence before and after wavelength conversion clearly proves that important properties, such as the coherence time and photon antibunching, are fully conserved during the frequency translation process. Our findings underline the great potential of single photon sources on demand in combination with QFC as a promising technique for quantum repeater schemes.Comment: 11 pages, 4 figure

Quantum correlations between single telecom photons and a multimode on-demand solid-state quantum memory

Quantum correlations between long-lived quantum memories and telecom photons that can propagate with low loss in optical fibers are an essential resource for the realization of large-scale quantum information networks. Significant progress has been realized in this direction with atomic and solid-state systems. Here, we demonstrate quantum correlations between a telecom photon and a multimode ondemand solid state quantum memory. This is achieved by mapping a correlated single photon onto a spin collective excitation in a Pr 3+ :Y 2 SiO 5 crystal for a controllable time. The stored single photons are generated by cavity-enhanced spontaneous parametric down-conversion and heralded by their partner photons at telecom wavelength. These results represent the first demonstration of a multimode on-demand solid state quantum memory for external quantum states of light. They provide an important resource for quantum repeaters and pave the way for the implementation of quantum information networks with distant solid state quantum nodes.We acknowledge financial support by the ERC Starting Grant QuLIMA, by the Spanish Ministry of Economy and Competitiveness (MINECO) and Fondo Europeo de Desarrollo Regional (FEDER) (FIS2015-69535-R), by MINECO Severo Ochoa through Grant No. SEV-2015-0522 and through the Ph.D. Fellowship Program (for A. S.), by AGAUR via 2014 SGR 1554, by Fundació Cellex, and by CERCA Programme/Generalitat de Catalunya

Systematic human/zebrafish comparative identification of cis-regulatory activity around vertebrate developmental transcription factor genes

AbstractPan-vertebrate developmental cis-regulatory elements are discernible as highly conserved noncoding elements (HCNEs) and are often dispersed over large areas around the pleiotropic genes whose expression they control. On the loci of two developmental transcription factor genes, SOX3 and PAX6, we demonstrate that HCNEs conserved between human and zebrafish can be systematically and reliably tested for their regulatory function in multiple stable transgenes in zebrafish, and their genomic reach estimated with confidence using synteny conservation and HCNE density along these loci. HCNEs of both human and zebrafish function as specific developmental enhancers in zebrafish. We show that human HCNEs result in expression patterns in zebrafish equivalent to those in mouse, establishing zebrafish as a suitable model for large-scale testing of human developmental enhancers. Orthologous human and zebrafish enhancers underwent functional evolution within their sequence and often directed related but non-identical expression patterns. Despite an evolutionary distance of 450 million years, one pax6 HCNE drove expression in identical areas when comparing zebrafish vs. human HCNEs. HCNEs from the same area often drive overlapping patterns, suggesting that multiple regulatory inputs are required to achieve robust and precise complex expression patterns exhibited by developmental genes

An assessment of ADAMs in bone cells: absence of TACE activity prevents osteoclast recruitment and the formation of the marrow cavity in developing long bones

AbstractADAMs (A Disintegrin And Metalloprotease domain) are metalloprotease–disintegrin proteins that have been implicated in cell adhesion, protein ectodomain shedding, matrix protein degradation and cell fusion. Since such events are critical for bone resorption and osteoclast recruitment, we investigated whether they require ADAMs. We report here which ADAMs we have identified in bone cells, as well as our analysis of the generation, migration and resorptive activity of osteoclasts in developing metatarsals of mouse embryos lacking catalytically active ADAM 17 [TNFα converting enzyme (TACE)]. The absence of TACE activity still allowed the generation of cells showing an osteoclastic phenotype, but prevented their migration into the core of the diaphysis and the subsequent formation of marrow cavity. This suggests a role of TACE in the recruitment of osteoclasts to future resorption sites

Regeneration in starved planarians depends on TRiC/CCT subunits modulating the unfolded protein response

Planarians are able to stand long periods of starvation by maintaining adult stem cell pools and regenerative capacity. The molecular pathways that are needed for the maintenance of regeneration during starvation are not known. Here, we show that down‐regulation of chaperonin TRiC/CCT subunits abrogates the regeneration capacity of planarians during starvation, but TRiC/CCT subunits are dispensable for regeneration in fed planarians. Under starvation, they are required to maintain mitotic fidelity and for blastema formation. We show that TRiC subunits modulate the unfolded protein response (UPR) and are required to maintain ATP levels in starved planarians. Regenerative defects in starved CCT‐depleted planarians can be rescued by either chemical induction of mild endoplasmic reticulum stress, which leads to induction of the UPR, or by the supplementation of fatty acids. Together, these results indicate that CCT‐dependent UPR induction promotes regeneration of planarians under food restriction

JASPAR 2016: a major expansion and update of the open-access database of transcription factor binding profiles.

JASPAR (http://jaspar.genereg.net) is an open-access database storing curated, non-redundant transcription factor (TF) binding profiles representing transcription factor binding preferences as position frequency matrices for multiple species in six taxonomic groups. For this 2016 release, we expanded the JASPAR CORE collection with 494 new TF binding profiles (315 in vertebrates, 11 in nematodes, 3 in insects, 1 in fungi and 164 in plants) and updated 59 profiles (58 in vertebrates and 1 in fungi). The introduced profiles represent an 83% expansion and 10% update when compared to the previous release. We updated the structural annotation of the TF DNA binding domains (DBDs) following a published hierarchical structural classification. In addition, we introduced 130 transcription factor flexible models trained on ChIP-seq data for vertebrates, which capture dinucleotide dependencies within TF binding sites. This new JASPAR release is accompanied by a new web tool to infer JASPAR TF binding profiles recognized by a given TF protein sequence. Moreover, we provide the users with a Ruby module complementing the JASPAR API to ease programmatic access and use of the JASPAR collection of profiles. Finally, we provide the JASPAR2016 R/Bioconductor data package with the data of this release