When resources collide: Towards a theory of coincidence in information spaces

This paper is an attempt to lay out foundations for a general theory of coincidence in information spaces such as the World Wide Web, expanding on existing work on bursty structures in document streams and information cascades. We elaborate on the hypothesis that every resource that is published in an information space, enters a temporary interaction with another resource once a unique explicit or implicit reference between the two is found. This thought is motivated by Erwin Shroedingers notion of entanglement between quantum systems. We present a generic information cascade model that exploits only the temporal order of information sharing activities, combined with inherent properties of the shared information resources. The approach was applied to data from the world's largest online citizen science platform Zooniverse and we report about findings of this case study

Biochemical and molecular diagnosis of erythropoietic protoporphyria in an Ashkenazi Jewish family

Summary: Erythropoietic protoporphyria (EPP) is a rare hereditary disorder due to a partial deficiency of ferrochelatase (FECH). The genotype of EPP patients features a mutation on one allele of the FECH gene and a common hypomorphic FECH IVS3-48c on the other allele (M/c). The resulting enzyme activity in patients is ∼35% of that in normal individuals. Ferrochelatase deficiency results in the accumulation of protoporphyrin in the skin, which is responsible for the clinical symptom of cutaneous photosensitivity in patients. In this study, we report the identification of a novel FECH mutation delT23 in an 11-member EPP family of Jewish origin. Two EPP siblings shared an identical genotype of delT23/IVS3-48c (M/c). They were both photosensitive and showed highly increased erythrocyte protoporphyrin. The genotype of the patients' mother, who did not present with any EPP clinical symptoms, was delT23/IVS3-48t (M/t). The patients' father, an offspring of consanguineous parents, was homozygous IVS3-48 c/c. He exhibited a mild photosensitivity, and an increase of 4-fold in erythrocyte protoporphyrin. His FECH mRNA amount was 71% of that of genotype t/t. It is the first reported case of an individual with c/c genotype who exhibits both biochemical and clinical indications of EPP. These results suggest that IVS3-48c is a functional variant of ferrochelatase. The clinical symptoms and biochemical abnormalities in the patients' father could be the result of an interaction between genetic and environmental factors. In addition, the frequency of IVS3-48c in the Ashkenazi Jewish population was estimated at 8%, which is similar to that in the European population

Crystal structure of the human ATP-dependent splicing and export factor UAP56

Pre-mRNA splicing requires the function of a number of RNA-dependent ATPases/helicases, yet no three-dimensional structure of any spliceosomal ATPases/helicases is known. The highly conserved DECD-box protein UAP56/Sub2 is an essential splicing factor that is also important for mRNA export. The expected ATPase/helicase activity appears to be essential for the UAP56/Sub2 functions. Here, we show that purified human UAP56 is an active RNA-dependent ATPase, and we also report the crystal structures of UAP56 alone and in complex with ADP, as well as a DECD to DEAD mutant. The structures reveal a unique spatial arrangement of the two conserved helicase domains, and ADP-binding induces significant conformational changes of key residues in the ATP-binding pocket. Our structural analyses suggest a specific protein-RNA displacement model of UAP56/Sub2. The detailed structural information provides important mechanistic insights into the splicing function of UAP56/Sub2. The structures also will be useful for the analysis of other spliceosomal DExD-box ATPases/helicases

A KNOWLEDGE BASED APPROACH FOR RESOURCE MANAGEMENT

This paper discusses the applicability of a knowledge based system to resource management in the context of information centers. The Information Center Expert (ICE) system has been developed in the MIS Department of the University of Arizona to support the consultation process of information center personnel. The system determines the (software) resource requirements of the end-users and makes appropriate recommendations. ICE further aids the management of the IC software resources by keeping track of user consultations and the recommendations made. Issues of knowledge requirements, acquisition, representation and implementation of ICE are discussed. ICE is currently being tested at IBM/Endicott (New York), IBM/Tucson (Arizona) and the Center for the Management of Information at the University of Arizona. Preliminary feedback from users has confirmed the applicability of the knowledge based approach to resource management. The implications of this approach for future research are discussed

Synthesizing a σ^z\hat{\sigma}_z spin-dependent force for optical, metastable, and ground state trapped-ion qubits

A single bichromatic field near-resonant to a qubit transition is typically used for $\hat{\sigma}_x$ or $\hat{\sigma}_y$ M{\o}lmer-S{\o}rensen type interactions in trapped ion systems. Using this field configuration, we present a novel scheme to synthesize a $\hat{\sigma}_z$ spin-dependent force instead; this basis change merely requires adjusting the beat-note frequency of the bichromatic field. We implement this scheme with a laser near-resonant to a quadrupole transition in $^{88}$Sr$^+$. We characterise its robustness to optical phase and qubit frequency offsets and demonstrate its versatility by entangling optical, metastable, and ground state qubits.Comment: O. B\u{a}z\u{a}van and S. Saner contributed equally to this wor

Breaking the entangling gate speed limit for trapped-ion qubits using a phase-stable standing wave

All laser-driven entangling operations for trapped-ion qubits have hitherto been performed without control of the optical phase of the light field, which precludes independent tuning of the carrier and motional coupling. By placing $^{88}$Sr$^+$ ions in a $\lambda=674$ nm standing wave, whose relative position is controlled to $\approx\lambda/100$, we suppress the carrier coupling by a factor of $18$, while coherently enhancing the spin-motion coupling. We experimentally demonstrate that the off-resonant carrier coupling imposes a speed limit for conventional traveling-wave M{\o}lmer-S{\o}rensen gates; we use the standing wave to surpass this limit and achieve a gate duration of $15\ \mu$s, restricted by the available laser power.Comment: S. Saner and O. B\u{a}z\u{a}van contributed equally to this wor

Phase noise characterisation of a 2-km hollow-core nested antiresonant nodeless fibre for twin-field quantum key distribution

The performance of quantum key distribution (QKD) is heavily dependent on the physical properties of the channel over which it is executed. Propagation losses and perturbations in the encoded photons' degrees of freedom, such as polarisation or phase, limit both the QKD range and key rate. The maintenance of phase coherence over optical fibres has lately received considerable attention as it enables QKD over long distances, e.g., through phase-based protocols like Twin-Field (TF) QKD. While optical single mode fibres (SMFs) are the current standard type of fibre, recent hollow core fibres (HCFs) could become a superior alternative in the future. Whereas the co-existence of quantum and classical signals in HCF has already been demonstrated, the phase noise resilience required for phase-based QKD protocols is yet to be established. This work explores the behaviour of HCF with respect to phase noise for the purpose of TF-QKD-like protocols. To achieve this, two experiments are performed. The first, is a set of concurrent measurements on 2 km of HCF and SMF in a double asymmetric Mach-Zehnder interferometer configuration. The second, uses a TF-QKD interferometer consisting of HCF and SMF channels. These initial results indicate that HCF is suitable for use in TF-QKD and other phase-based QKD protocols

The variability of refractivity in the atmospheric boundary layer of a tropical island volcano measured by ground-based interferometric radar

For 24 h we measured continuously the variability of atmospheric refractivity over a volcano on the tropical island of Montserrat using a ground-based radar interferometer. We observed variations in phase that we interpret as due to changing water vapour on the propagation path between the radar and the volcano and we present them here in the context of the behaviour of the atmospheric boundary layer over the island. The water vapour behaviour was forced by diurnal processes, the passage of a synoptic-scale system and the presence of a plume of volcanic gas. The interferometer collected images of amplitude and phase every minute. From pairs of phase images, interferograms were calculated and analyzed every minute and averaged hourly, together with contemporaneous measurements of zenith delays estimated from a network of 14 GPS receivers. The standard deviation of phase at two sites on the volcano surface spanned a range of about 1–5 radians, the lowest values occurring at night on the lower slopes and the highest values during the day on the upper slopes. This was also reflected in spatial patterns of variability. Two-dimensional profiles of radar-measured delays were modelled using an atmosphere with water vapour content decreasing upwards and water vapour variability increasing upwards. Estimates of the effect of changing water vapour flux from the volcanic plume indicate that it should contribute only a few percent to this atmospheric variability. A diurnal cycle within the lower boundary layer producing a turbulence-dominated mixed layer during the day and stable layers at night is consistent with the observed refractivity

An overview of the cutaneous porphyrias

This is an overview of the cutaneous porphyrias. It is a narrative review based on the published literature and my personal experience; it is not based on a formal systematic search of the literature. The cutaneous porphyrias are a diverse group of conditions due to inherited or acquired enzyme defects in the porphyrin–haem biosynthetic pathway. All the cutaneous porphyrias can have (either as a consequence of the porphyria or as part of the cause of the porphyria) involvement of other organs as well as the skin. The single commonest cutaneous porphyria in most parts of the world is acquired porphyria cutanea tarda, which is usually due to chronic liver disease and liver iron overload. The next most common cutaneous porphyria, erythropoietic protoporphyria, is an inherited disorder in which the accumulation of bile-excreted protoporphyrin can cause gallstones and, rarely, liver disease. Some of the porphyrias that cause blistering (usually bullae) and fragility (clinically and histologically identical to porphyria cutanea tarda) can also be associated with acute neurovisceral porphyria attacks, particularly variegate porphyria and hereditary coproporphyria. Management of porphyria cutanea tarda mainly consists of visible-light photoprotection measures while awaiting the effects of treating the underlying liver disease (if possible) and treatments to reduce serum iron and porphyrin levels. In erythropoietic protoporphyria, the underlying cause can be resolved only with a bone marrow transplant (which is rarely justifiable in this condition), so management consists particularly of visible-light photoprotection and, in some countries, narrowband ultraviolet B phototherapy. Afamelanotide is a promising and newly available treatment for erythropoietic protoporphyria and has been approved in Europe since 2014