Distributed Orientation Agreement in a Group of Robots

In this article, a method for the agreement of a set of robots on a common reference orientation based on a distributed consensus algorithm is described. It only needs that robots detect the relative positions of their neighbors and communicate with them. Two different consensus algorithms based on the exchange of information are proposed, tested and analyzed. Systematic experiments were carried out in simulation and with real robots in order to test the method. Experimental results show that the robots are able to agree on the reference orientation under certain conditions. Scalability with an increasing number of robots was tested successfully in simulation with up to 49 robots. Experiments with real robots succeeded proving that the proposed method works in reality.

Structure Variation And Dynamics of the Nuclear Ribosomal Intergenic Spacer Region in Key Gibberella Fujikuroi Complex Species

The intergenic spacer (IGS) region of the ribosomal DNA was cloned and sequenced in eight species within the Gibberella fujikuroi species complex with anamorphs in the genus Fusarium , a group that includes the most relevant toxigenic species. DNA sequence analyses revealed two categories of repeated elements: long repeats and short repeats of 125 and 8 bp, respectively. Long repeats were present in two copies and were conserved in all the species analyzed, whereas different numbers of short repeat elements were observed, leading to species-specific IGS sequences with different length. In Fusarium subglutinans and Fusarium nygamai , these differences seemed to be the result of duplication and deletion events. Here, we propose a model based on unequal crossing over that can explain these processes. The partial IGS sequence of 22 Fusarium proliferatum isolates was also obtained to study variation at the intraspecific level. The results revealed no differences in terms of number or pattern of repeated elements and detected frequent gene conversion events. These results suggest that the homogenization observed at the intraspecific level might not be achieved primarily by unequal crossing-over events but rather by processes associated with recombination such as gene conversion events.

Secure optical networks based on quantum key distribution and weakly trusted repeaters

Abstract—In this paper we explore how recent technologies can improve the security of optical networks. In particular, we study how to use quantum key distribution(QKD) in common optical network infrastructures and propose a method to overcome its distance limitations. QKD is the first technology offering information theoretic secretkey distribution that relies only on the fundamental principles of quantum physics. Point-to-point QKDdevices have reached a mature industrial state; however, these devices are severely limited in distance, since signals at the quantum level (e.g., single photons) are highly affected by the losses in the communication channel and intermediate devices. To overcome this limitation, intermediate nodes (i.e., repeaters) are used. Both quantum-regime and trusted, classical repeaters have been proposed in the QKD literature, but only the latter can be implemented in practice. As a novelty, we propose here a new QKD network model based on the use of not fully trusted intermediate nodes, referred to as weakly trusted repeaters. This approach forces the attacker to simultaneously break several paths to get access to the exchanged key, thus improving significantly the security of the network. We formalize the model using network codes and provide real scenarios that allow users to exchange secure keys over metropolitan optical networks using only passive components. Moreover, the theoretical framework allows one to extend these scenarios not only to accommodate more complex trust constraints, but also to consider robustness and resiliency constraints on the network.

Worldwide standardization activity for quantum key distribution

We discuss the on-going worldwide activity to develop forward looking standards for quantum key distribution (QKD) in the European Telecommunications Standards Institute (ETSI) QKD industry specification group (ISG). The long term goal is to develop a certification methodology that bridges the gap between theoretical proofs and practical implementations with imperfect devices. Current efforts are focused on the handling of side channels and characterization of the most relevant components.

Service for the pseudonymization of electronic healthcare records based on ISO/EN 13606 for the secondary use of information

The availability of electronic health data favors scientific advance through the creation of repositories for secondary use. Data anonymization is a mandatory step to comply with current legislation. A service for the pseudonymization of electronic healthcare record (EHR) extracts aimed at facilitating the exchange of clinical information for secondary use in compliance with legislation on data protection is presented. According to ISO/TS 25237, pseudonymization is a particular type of anonymization. This tool performs the anonymizations by maintaining three quasi-identifiers (gender, date of birth and place of residence) with a degree of specification selected by the user. The developed system is based on the ISO/EN 13606 norm using its characteristics specifically favorable for anonymization. The service is made up of two independent modules: the demographic server and the pseudonymizing module. The demographic server supports the permanent storage of the demographic entities and the management of the identifiers. The pseudonymizing module anonymizes the ISO/EN 13606 extracts. The pseudonymizing process consists of four phases: the storage of the demographic information included in the extract, the substitution of the identifiers, the elimination of the demographic information of the extract and the elimination of key data in free-text fields. The described pseudonymizing system was used in three Telemedicine research projects with satisfactory results. A problem was detected with the type of data in a demographic data field and a proposal for modification was prepared for the group in charge of the drawing up and revision of the ISO/EN 13606 norm.

Large-scale identification of gibberellin-related transcription factor defines group VII ERFs as functional of DELLA partners

DELLA proteins are the master negative regulators in gibberellin (GA) signaling acting in the nucleus as transcriptional regulators. The current view of DELLA action indicates that their activity relies on the physical interaction with transcription factors (TFs). Therefore, the identification of TFs through which DELLAs regulate GA responses is key to understanding these responses from a mechanistic point of view. Here, we have determined the TF interactome of the Arabidopsis (Arabidopsis thaliana) DELLA protein GIBBERELLIN INSENSITIVE and screened a collection of conditional TF overexpressors in search of those that alter GA sensitivity. As a result, we have found RELATED TO APETALA2.3, an ethylene-induced TF belonging to the group VII ETHYLENE RESPONSE FACTOR of the APETALA2/ethylene responsive element binding protein superfamily, as a DELLA interactor with physiological relevance in the context of apical hook development. The combination of transactivation assays and chromatin immunoprecipitation indicates that the interaction with GIBBERELLIN INSENSITIVE impairs the activity of RELATED TO APETALA2.3 on the target promoters. This mechanism represents a unique node in the cross regulation between the GA and ethylene signaling pathways controlling differential growth during apical hook development.

Vivienda y fondo edificatorio: análisis de las consecuencias del parámetro fondo en el edificio de vivienda colectiva

Este estudio ofrece una herramienta de aproximación al espacio morfológico-métrico en el que se formula la ciudad de alta densidad desde la vivienda colectiva. La vivienda colectiva es la célula básica de la ciudad. El estudio configurativo y dimensional del tejido urbano muestra la importancia del fondo edificatorio como parámetro clave a mitad de camino entre la vivienda y la ciudad. El fondo edificatorio traza el margen de la arquitectura en la ciudad y desde él se equipa y cuantifica el territorio urbano. Sus dinámicas van caracterizando los distintos entornos, mientras en su interior se formula el tipo en un ajuste de continua verificación y adaptación. La forma de la ciudad y sus distintas posibilidades configurativas —en cuanto masa construida y espacio público, pero sin perder de vista la relación entre ambos— depende en gran medida del fondo edificatorio. Se trata, por tanto, de un parámetro importante de relación entre las distintas configuraciones del espacio exterior e interior. Al proyectar, una vez establecido un fondo, algunas propiedades se adaptan con facilidad mientras que otras requieren un cierto grado de interpretación o deben ser descartadas. Dada una superficie, la especificación del fondo fuerza la dimensión del frente en las configuraciones posibles. Ambas dimensiones son vitales en el valor del factor de forma del continuo edificado y en su relación se produce el complejo rango de posibilidades. Partiendo de la ciudad, un gran fondo encierra y mezcla en su interior todo tipo de usos sin distinción, repercute un menor coste por unidad de superficie edificada y comparte su frente reduciendo los intercambios térmicos y lumínicos. Sin embargo la ciudad de fondo reducido ajusta la forma al uso y se desarrolla linealmente con repetitividad a lo largo de sus frentes exteriores. En ella, el fuerte intercambio energético se opone a las grandes posibilidades del espacio libre. En cambio desde la casa las distintas medidas del fondo se producen bajo determinados condicionantes: clima, compacidad, ocupación, hibridación, tamaño de casa, etc., mientras que el tipo se desarrolla en base a una métrica afín. Este trabajo parte de esta dialéctica. Estudia la relación de dependencia entre las condiciones del edificio de viviendas y su métrica. Jerarquiza edificios en base al parámetro “fondo” para constituir una herramienta que como un ábaco sea capaz de visibilizar las dinámicas relacionales entre configuración y métrica bajo la condición de alta densidad. Para ello en una primera fase se gestiona una extensa muestra de edificios representativos de vivienda colectiva principalmente europea, extraída de tres prestigiosos libros en forma de repertorio. Se ordenan y categorizan extrayendo datos conmensurables y temas principales que ligan la profundidad de la huella a la morfología y posteriormente, esta información se estudia en diagramas que ponen de manifiesto convergencias y divergencias, acumulaciones y vacíos, límites, intervalos característicos, márgenes y ejes, parámetros y atributos... cuya relación trata de factorizar el lugar morfológico y métrico de la casa como metavivienda y ciudad. La herramienta se establece así como un complejo marco relacional en el que posicionar casos concretos y trazar nexos transversales, tanto de tipo morfológico como cultural, climático o técnico, normativo o tecnológico. Cada nuevo caso o traza añadida produce consonancias y disonancias en el marco que requieren interpretación y verificación. De este modo este instrumento de análisis comparativo se tempera, se especializa, se completa y se perfecciona con su uso. La forma de la residencia en la ciudad densa se muestra así sobre un subsistema morfológico unitario y su entendimiento se hace más fácilmente alcanzable y acumulable tanto para investigaciones posteriores como para el aprendizaje o el ejercicio profesional. ABSTRACT This research study offers a tool to approach the morphometric space in which (multi-family) housing defines high-density cities. Multi-family housing is the basic cell of the city. The configuration and dimension studies of the urban fabric render the importance of building depth as a key parameter half way between the dwelling and the city. The building depth traces de limit of architecture in the city. It qualifies and quantifies the urban territory. Its dynamics characterize the different environments while in its essence, an adjustment process of continuous verification and adaption defines type. The shape of the city and its different configuration possibilities —in terms of built fabric and public space, always keeping an eye on the relationship between them— depend majorly on the building depth. Therefore, it is a relevant parameter that relates the diverse configurations between interior and exterior space. When designing, once the depth is established, some properties are easily adpated. However, others require a certain degree of interpretation or have to be left out of the study. Given a ceratin surface, the establishment of the depth forces the dimensions of the facade in the different configurations. Both depth and facade dimensions are crucial for the form factor of the built mass. Its relationship produces a complex range of possibilities. From an urban point of view, great depth means multiple uses (making no distinction whatsoever,) it presents a lower cost per unit of built area and shares its facade optimizing temperature and light exchange. On the contrary, the city of reduced depth adjusts its shape to the use, and develops linearly and repetitively along its facades. The strong energy exchange opposes to the great possibilities of free space. From the perspective of the dwelling, the different dimensions of depth are produced under certain determinants: climate, compactness, occupancy, hybridization, dwelling size, etc. Meanwhile, the type is developed based on a related meter (as in poetry). This work starts from the previous premise. It studies the dependency relation bewteen the conditions of the dwellings and their meter (dimensions). It organizes buildings hierarchically based on the parameter “depth” to create a tool that, as an abacus, is able to visibilise the relational dynamics between configuration and dimension in high density conditions. For this, in the first stage a large group of representative multi-family housing buildings is managed, mostly from Europe, picked from three prestigious books as a repertoir. They are categorized and ordered drawing commensurable data and key issues that link the depth of the fooprint to its morphology. Later, this information is studied deeply with diagrams that bring out connections and discrepancies, voids and accumulations, limits, charasteristic intervals, margins and axii, parameters, attributes, etc. These relationships try to create factors from a morphological and metrical point of view of the house as a metadwelling. This tool is established as a complex relation frame in which case studies are postitioned and cross-cutting nexii are traced. These can deal with morphology, climate, technique, law or technology. Each new case or nexus produces affinities and discrepancies that require interpretation and verification. Thus, this instrument of comparative analysis is fine-tuned, especialized and completed as its use is improved. The way housing is understood in high density cities is shown as a unitary metric subsystem and its understanding is easy to reach and accumulate for future researchers, students or practicing architects.

Attempted hydrogen–deuterium exchange of the protio-trimethyloxonium dication (CH3)3OH2+, study of methylating ability of (CH3)3O+ in superacids and theoretical investigations

Attempted hydrogen–deuterium exchange of trimethyloxonium ion, (CH3)3O+ with excess of 1:1 2HF/SbF5 superacid at −30°C over a period of 30 days showed no exchange. Theoretical calculations at the MP2/6–31G** level are in accord with the lack of hydrogen–deuterium exchange in the methyl group of the (CH3)3O+ cation as protonation (protosolvation) prefers the oxygen lone pair of electrons, instead of a C—H bond. Methylation of aromatics with the (CH3)3O+CF3SO3− in CF3SO3H and 2CF3SO3H:B(O3SCF3)3 was also studied. Whereas in triflic acid no alkylation was observed, in triflatoboric acid, a powerful superacid, alkylation takes place, indicating protolytic activation of the trimethyloxonium ion.

Adjustment of conformational flexibility is a key event in the thermal adaptation of proteins

3-Isopropylmalate dehydrogenase (IPMDH, E.C. 1.1.1.85) from the thermophilic bacterium Thermus thermophilus HB8 is homologous to IPMDH from the mesophilic Escherichia coli, but has an approximately 17°C higher melting temperature. Its temperature optimum is 22–25°C higher than that of the E. coli enzyme; however, it is hardly active at room temperature. The increased conformational rigidity required to stabilize the thermophilic enzyme against heat denaturation might explain its different temperature-activity profile. Hydrogen/deuterium exchange studies were performed on this thermophilic-mesophilic enzyme pair to compare their conformational flexibilities. It was found that Th. thermophilus IPMDH is significantly more rigid at room temperature than E. coli IPMDH, whereas the enzymes have nearly identical flexibilities under their respective optimal working conditions, suggesting that evolutionary adaptation tends to maintain a “corresponding state” regarding conformational flexibility. These observations confirm that conformational fluctuations necessary for catalytic function are restricted at room temperature in the thermophilic enzyme, suggesting a close relationship between conformational flexibility and enzyme function.

Molecular keys to speciation: DNA polymorphism and the control of genetic exchange in enterobacteria

Speciation involves the establishment of genetic barriers between closely related organisms. The extent of genetic recombination is a key determinant and a measure of genetic isolation. The results reported here reveal that genetic barriers can be established, eliminated, or modified by manipulating two systems which control genetic recombination, SOS and mismatch repair. The extent of genetic isolation between enterobacteria is a simple mathematical function of DNA sequence divergence. The function does not depend on hybrid DNA stability, but rather on the number of blocks of sequences identical in the two mating partners and sufficiently large to allow the initiation of recombination. Further, there is no obvious discontinuity in the function that could be used to define a level of divergence for distinguishing species.

Efficient exchange of the primary quinone acceptor QA in isolated reaction centers of Rhodopseudomonas viridis

A key step in the conversion of solar energy into chemical energy by photosynthetic reaction centers (RCs) occurs at the level of the two quinones, QA and QB, where electron transfer couples to proton transfer. A great deal of our understanding of the mechanisms of these coupled reactions relies on the seminal work of Okamura et al. [Okamura, M. Y., Isaacson, R. A., & Feher, G. (1975) Proc. Natl. Acad. Sci. USA 88, 3491–3495], who were able to extract with detergents the firmly bound ubiquinone QA from the RC of Rhodobacter sphaeroides and reconstitute the site with extraneous quinones. Up to now a comparable protocol was lacking for the RC of Rhodopseudomonas viridis despite the fact that its QA site, which contains 2-methyl-3-nonaprenyl-1,4-naphthoquinone (menaquinone-9), has provided the best x-ray structure available. Fourier transform infrared difference spectroscopy, together with the use of isotopically labeled quinones, can probe the interaction of QA with the RC protein. We establish that a simple incubation procedure of isolated RCs of Rp. viridis with an excess of extraneous quinone allows the menaquinone-9 in the QA site to be almost quantitatively replaced either by vitamin K1, a close analogue of menaquinone-9, or by ubiquinone. To our knowledge, this is the first report of quinone exchange in bacterial photosynthesis. The Fourier transform infrared data on the quinone and semiquinone vibrations show a close similarity in the bonding interactions of vitamin K1 with the protein at the QA site of Rp. viridis and Rb. sphaeroides, whereas for ubiquinone these interactions are significantly different. The results are interpreted in terms of slightly inequivalent quinone–protein interactions by comparison with the crystallographic data available for the QA site of the two RCs.

A Rap guanine nucleotide exchange factor enriched highly in the basal ganglia

Ras proteins, key regulators of growth, differentiation, and malignant transformation, recently have been implicated in synaptic function and region-specific learning and memory functions in the brain. Rap proteins, members of the Ras small G protein superfamily, can inhibit Ras signaling through the Ras/Raf-1/mitogen-activated protein (MAP) kinase pathway or, through B-Raf, can activate MAP kinase. Rap and Ras proteins both can be activated through guanine nucleotide exchange factors (GEFs). Many Ras GEFs, but to date only one Rap GEF, have been identified. We now report the cloning of a brain-enriched gene, CalDAG-GEFI, which has substrate specificity for Rap1A, dual binding domains for calcium (Ca2+) and diacylglycerol (DAG), and enriched expression in brain basal ganglia pathways and their axon-terminal regions. Expression of CalDAG-GEFI activates Rap1A and inhibits Ras-dependent activation of the Erk/MAP kinase cascade in 293T cells. Ca2+ ionophore and phorbol ester strongly and additively enhance this Rap1A activation. By contrast, CalDAG-GEFII, a second CalDAG-GEF family member that we cloned and found identical to RasGRP [Ebinu, J. O., Bottorff, D. A., Chan, E. Y. W., Stang, S. L., Dunn, R. J. & Stone, J. C. (1998) Science 280, 1082–1088], exhibits a different brain expression pattern and fails to activate Rap1A, but activates H-Ras, R-Ras, and the Erk/MAP kinase cascade under Ca2+ and DAG modulation. We propose that CalDAG-GEF proteins have a critical neuronal function in determining the relative activation of Ras and Rap1 signaling induced by Ca2+ and DAG mobilization. The expression of CalDAG-GEFI and CalDAG-GEFII in hematopoietic organs suggests that such control may have broad significance in Ras/Rap regulation of normal and malignant states.

Explosive invasion of plant mitochondria by a group I intron

Group I introns are mobile, self-splicing genetic elements found principally in organellar genomes and nuclear rRNA genes. The only group I intron known from mitochondrial genomes of vascular plants is located in the cox1 gene of Peperomia, where it is thought to have been recently acquired by lateral transfer from a fungal donor. Southern-blot surveys of 335 diverse genera of land plants now show that this intron is in fact widespread among angiosperm cox1 genes, but with an exceptionally patchy phylogenetic distribution. Four lines of evidence—the intron’s highly disjunct distribution, many incongruencies between intron and organismal phylogenies, and two sources of evidence from exonic coconversion tracts—lead us to conclude that the 48 angiosperm genera found to contain this cox1 intron acquired it by 32 separate horizontal transfer events. Extrapolating to the over 13,500 genera of angiosperms, we estimate that this intron has invaded cox1 genes by cross-species horizontal transfer over 1,000 times during angiosperm evolution. This massive wave of lateral transfers is of entirely recent occurrence, perhaps triggered by some key shift in the intron’s invasiveness within angiosperms.

Fractionation factors and activation energies for exchange of the low barrier hydrogen bonding proton in peptidyl trifluoromethyl ketone complexes of chymotrypsin

NMR investigations have been carried out of complexes between bovine chymotrypsin Aα and a series of four peptidyl trifluoromethyl ketones, listed here in order of increasing affinity for chymotrypsin: N-Acetyl-l-Phe-CF3, N-Acetyl-Gly-l-Phe-CF3, N-Acetyl-l-Val-l-Phe-CF3, and N-Acetyl-l-Leu-l-Phe-CF3. The D/H fractionation factors (φ) for the hydrogen in the H-bond between His 57 and Asp 102 (His 57-Hδ1) in these four complexes at 5°C were in the range φ = 0.32–0.43, expected for a low-barrier hydrogen bond. For this series of complexes, measurements also were made of the chemical shifts of His 57-Hɛ1 (δ2,2-dimethylsilapentane-5-sulfonic acid 8.97–9.18), the exchange rate of the His 57-Hδ1 proton with bulk water protons (284–12.4 s−1), and the activation enthalpies for this hydrogen exchange (14.7–19.4 kcal⋅mol−1). It was found that the previously noted correlations between the inhibition constants (Ki 170–1.2 μM) and the chemical shifts of His 57-Hδ1 (δ2,2-dimethylsilapentane-5-sulfonic acid 18.61–18.95) for this series of peptidyl trifluoromethyl ketones with chymotrypsin [Lin, J., Cassidy, C. S. & Frey, P. A. (1998) Biochemistry 37, 11940–11948] could be extended to include the fractionation factors, hydrogen exchange rates, and hydrogen exchange activation enthalpies. The results support the proposal of low barrier hydrogen bond-facilitated general base catalysis in the addition of Ser 195 to the peptidyl carbonyl group of substrates in the mechanism of chymotrypsin-catalyzed peptide hydrolysis. Trends in the enthalpies for hydrogen exchange and the fractionation factors are consistent with a strong, double-minimum or single-well potential hydrogen bond in the strongest complexes. The lifetimes of His 57-Hδ1, which is solvent shielded in these complexes, track the strength of the hydrogen bond. Because these lifetimes are orders of magnitude shorter than those of the complexes themselves, the enzyme must have a pathway for hydrogen exchange at this site that is independent of dissociation of the complexes.

Energetics of the interaction between water and the helical peptide group and its role in determining helix propensities

The alanine helix provides a model system for studying the energetics of interaction between water and the helical peptide group, a possible major factor in the energetics of protein folding. Helix formation is enthalpy-driven (−1.0 kcal/mol per residue). Experimental transfer data (vapor phase to aqueous) for amides give the enthalpy of interaction with water of the amide group as ≈−11.5 kcal/mol. The enthalpy of the helical peptide hydrogen bond, computed for the gas phase by quantum mechanics, is −4.9 kcal/mol. These numbers give an enthalpy deficit for helix formation of −7.6 kcal/mol. To study this problem, we calculate the electrostatic solvation free energy (ESF) of the peptide groups in the helical and β-strand conformations, by using the delphi program and parse parameter set. Experimental data show that the ESF values of amides are almost entirely enthalpic. Two key results are: in the β-strand conformation, the ESF value of an interior alanine peptide group is −7.9 kcal/mol, substantially less than that of N-methylacetamide (−12.2 kcal/mol), and the helical peptide group is solvated with an ESF of −2.5 kcal/mol. These results reduce the enthalpy deficit to −1.5 kcal/mol, and desolvation of peptide groups through partial burial in the random coil may account for the remainder. Mutant peptides in the helical conformation show ESF differences among nonpolar amino acids that are comparable to observed helix propensity differences, but the ESF differences in the random coil conformation still must be subtracted.