3,687 research outputs found
A Routing/Assignment Problem in Garden Maintenance Services
We address a routing/assignment problem posed by Neoturf, which is a Portuguese company working in the area of project, building and garden’s main- tenance. The aim is to define a procedure for scheduling and routing efficiently its clients of garden maintenance services. The company has two teams available throughout the year to handle all the maintenance jobs. Each team consists of two or three employees with a fully-equipped vehicle capable of carrying out every kind of maintenance service. At the beginning of each year, the number and frequency of maintenance interventions to conduct during the year, for each client, are agreed. Time windows are established so that visits to the client should occur only within these periods. There are clients that are supposed to be always served by the same team, but other clients can be served indifferently by any of the two teams. Since clients are geographically spread over a wide region, the total distance traveled while visiting clients is a factor that weighs heavily on the company costs. Neoturf is con- cerned with reducing these costs, while satisfying agreements with its clients. We give a mixed integer linear programming formulation for the problem, discuss lim- itations on the size of instances that can be solved to guarantee optimality, present a modification of the Clarke and Wright heuristic for the vehicle routing with time windows, and report preliminary computational results obtained with Neoturf data.info:eu-repo/semantics/publishedVersio
Energy metabolism in human pluripotent stem cells and their differentiated counterparts
Background: Human pluripotent stem cells have the ability to generate all cell types present in the adult organism, therefore harboring great potential for the in vitro study of differentiation and for the development of cell-based therapies. Nonetheless their use may prove challenging as incomplete differentiation of these cells might lead to tumoregenicity. Interestingly, many cancer types have been reported to display metabolic modifications with features that might be similar to stem cells. Understanding the metabolic properties of human pluripotent stem cells when compared to their differentiated counterparts can thus be of crucial importance. Furthermore recent data has stressed distinct features of different human pluripotent cells lines, namely when comparing embryo-derived human embryonic stem cells (hESCs) and induced pluripotent stem cells (IPSCs) reprogrammed from somatic cells. Methodology/Principal Findings: We compared the energy metabolism of hESCs, IPSCs, and their somatic counterparts. Focusing on mitochondria, we tracked organelle localization and morphology. Furthermore we performed gene expression analysis of several pathways related to the glucose metabolism, including glycolysis, the pentose phosphate pathway and the tricarboxylic acid (TCA) cycle. In addition we determined oxygen consumption rates (OCR) using a metabolic extracellular flux analyzer, as well as total intracellular ATP levels by high performance liquid chromatography (HPLC). Finally we explored the expression of key proteins involved in the regulation of glucose metabolism. Conclusions/Findings: Our results demonstrate that, although the metabolic signature of IPSCs is not identical to that of hESCs, nonetheless they cluster with hESCs rather than with their somatic counterparts. ATP levels, lactate production and OCR revealed that human pluripotent cells rely mostly on glycolysis to meet their energy demands. Furthermore, our work points to some of the strategies which human pluripotent stem cells may use to maintain high glycolytic rates, such as high levels of hexokinase II and inactive pyruvate dehydrogenase (PDH). © 2011 Varum et al
Constraining Nonstandard Neutrino-Electron Interactions
We present a detailed analysis on nonstandard neutrino interactions (NSI)
with electrons including all muon and electron (anti)-neutrino data from
existing accelerators and reactors, in conjunction with the ``neutrino
counting'' data (e- e+ -> nu nu gamma) from the four LEP collaborations. First
we perform a one-parameter-at-a-time analysis, showing how most constraints
improve with respect to previous results reported in the literature. We also
present more robust results where the NSI parameters are allowed to vary freely
in the analysis. We show the importance of combining LEP data with the other
experiments in removing degeneracies in the global analysis constraining
flavor-conserving NSI parameters which, at 90 % and 95 % C.L., must lie within
unique allowed regions. Despite such improved constraints, there is still
substantial room for improvement, posing a big challenge for upcoming
experiments.Comment: 19 pages, 4 figures. Final version to appear in Phys. Rev.
Decavanadate interactions with actin: cysteine oxidation and vanadyl formation
Incubation of actin with decavanadate induces cysteine oxidation and oxidovanadium(IV) formation.
The studies were performed combining kinetic with spectroscopic (NMR and EPR) methodologies.
Although decavanadate is converted to labile oxovanadates, the rate of deoligomerization can be very slow (half-life time of 5.4 h, at 25 ◦C, with a first order kinetics), which effectively allows decavanadate
to exist for some time under experimental conditions. It was observed that decavanadate inhibits F-actin-stimulated myosin ATPase activity with an IC50 of 0.8 mMV10 species, whereas 50 mMof vanadate or oxidovanadium(IV) only inhibits enzyme activity up to 25%. Moreover, from these three vanadium forms, only decavanadate induces the oxidation of the so called “fast” cysteines (or exposed
cysteine, Cys-374) when the enzyme is in the polymerized and active form, F-actin, with an IC50 of 1 mMV10 species. Decavanadate exposition to F- and G-actin (monomeric form) promotes vanadate reduction since a typical EPR oxidovanadium(IV) spectrum was observed. Upon observation that V10
reduces to oxidovanadium(IV), it is proposed that this cation interacts with G-actin (Kd of 7.48 ±
1.11 mM), and with F-actin (Kd = 43.05 ± 5.34 mM) with 1:1 and 4:1 stoichiometries, respectively, as observed by EPR upon protein titration with oxidovanadium(IV). The interaction of oxidovanadium(IV) with the protein may occur close to the ATP binding site of actin, eventually with
lysine-336 and 3 water molecules
Crystal structure of the zinc-, cobalt-, and iron-containing adenylate kinase from Desulfovibrio gigas: a novel metal-containing adenylate kinase from Gram-negative bacteria
J Biol Inorg Chem (2011) 16:51–61
DOI 10.1007/s00775-010-0700-8Adenylate kinases (AK) from Gram-negative bacteria are generally devoid of metal ions in their LID domain. However, three metal ions, zinc, cobalt, and iron, have been found in AK from Gram-negative bacteria. Crystal structures of substrate-free AK from Desulfovibrio gigas with three different metal ions (Zn2+, Zn-AK; Co2+, Co-AK; and Fe2+, Fe-AK) bound in its LID domain have been determined by X-ray crystallography to resolutions 1.8, 2.0, and 3.0 Å, respectively. The zinc and iron forms of the enzyme were crystallized in space group I222, whereas the cobalt-form crystals were C2. The presence of the metals was confirmed by calculation of anomalous difference maps and by X-ray fluorescence scans. The work presented here is the first report of a structure of a metal-containing AK from a Gram-negative bacterium. The native enzyme was crystallized, and only zinc was detected in the LID domain. Co-AK and Fe-AK were obtained by overexpressing the protein in Escherichia coli. Zn-AK and Fe-AK crystallized as monomers in the asymmetric unit, whereas Co-AK crystallized as a dimer. Nevertheless, all three crystal structures are very similar to each other, with the same LID domain topology, the only change being the presence of the different metal atoms. In the absence of any substrate, the LID domain of all holoforms of AK was present in a fully open conformational state. Normal mode analysis was performed to predict fluctuations of the LID domain along the catalytic pathway
Genetic diversity in a jaborandi ( Pilocarpus microphyllus Stapf.) germplasm bank assessed by RAPD markers.
Diversidade genética em banco de germoplasma de jaborandi ( Pilocarpus microphyllus Stapf .) por meio de marcadores RAPD. O objetivo deste trabalho é avaliar a presença de variabilidade genética no banco de germoplasma de P. microphyllus da Embrapa Amazônia Oriental por meio de marcadores RAPD. Foi extraído o DNA de 93 indivíduos, pertencentes a 12 áreas de coleta presentes no banco de germoplasma. Foram construídos dendrogramas entre indivíduos e entre áreas de coleta, usando os coeficientes de similaridade de Nei & Li por meio do programa NTSYS-pc. Para verificar a distribuição da variabilidade, foi realizada a análise de variância molecular (AMOVA), sendo obtidas as variâncias entre e dentro de áreas de coleta. Foi usado o índice de diversidade de Shannon, para medir a diversidade de cada área. Foi verificada uma boa amplitude de similaridades entre os indivíduos, sendo que o dendrograma não agrupou por completo os indivíduos de acordo com sua origem. A AMOVA obteve 24,16% de variação entre áreas e 75,84% dentro de áreas
Nitric Oxide Detection Using Electrochemical Third-generation Biosensors - Based on Heme Proteins and Porphyrins
Nitric oxide radical (NO) is a signalling molecule involved in virtually all forms of life. Its relevance has been leading to the development of different analytical methodologies to assess the temporal and spatial fluxes of NO under the complex biological milieu. Third‐generation electrochemical biosensors are promising tools for in loco and in vivo NO quantification and, over the past years, heme proteins and porphyrins have been used in their design. Since there are some limitations with the biorecognition element directly adsorbed onto the electrode surface, nanomaterials (carbon nanotubes, gold nanoparticles, etc.) and polymers (cellulose, chitosan, nafion®, polyacrylamide, among others) have been explored to achieve high kinetics and better biosensor performance. In this review, a broad overview of the field of electrochemical third‐generation biosensors for NO electroanalysis is presented, discussing their main characteristics and aiming new outlooks and advances in this field.FG and LBM thank FCT/MCTES for the fellowship
grants SFRH/BD/52502/2014 and SFRH/BPD/111404/
2015, respectively, which are financed by national funds
and co-financed by FSE. CMC acknowledges FCTMCTES funding through project PTDC/BBB-BQB/
0129/2014 (FCT/MCTES). This work was supported by
the PTDC/BB-BQB/0129/2014 project (FCT/MCTES)
and also by the Associate Laboratory Research Unit for
Green Chemistry – Technologies and Processes Clean –
LAQV, financed by national funds from FCT/MEC
(UID/QUI/50006/2013) and co-financed by the ERDF
under the PT2020 Partnership Agreement (POCI-01-
0145-FEDER-007265). Funding through REQUIMTE
project entitled “NOR-based biosensor for nitric oxide
detection in biological and environmental samples” is
also acknowledged.info:eu-repo/semantics/publishedVersio
Minimal Synthesis of String To String Functions From Examples
We study the problem of synthesizing string to string transformations from a
set of input/output examples. The transformations we consider are expressed
using deterministic finite automata (DFA) that read pairs of letters, one
letter from the input and one from the output. The DFA corresponding to these
transformations have additional constraints, ensuring that each input string is
mapped to exactly one output string.
We suggest that, given a set of input/output examples, the smallest DFA
consistent with the examples is a good candidate for the transformation the
user was expecting. We therefore study the problem of, given a set of examples,
finding a minimal DFA consistent with the examples and satisfying the
functionality and totality constraints mentioned above.
We prove that, in general, this problem (the corresponding decision problem)
is NP-complete. This is unlike the standard DFA minimization problem which can
be solved in polynomial time. We provide several NP-hardness proofs that show
the hardness of multiple (independent) variants of the problem.
Finally, we propose an algorithm for finding the minimal DFA consistent with
input/output examples, that uses a reduction to SMT solvers. We implemented the
algorithm, and used it to evaluate the likelihood that the minimal DFA indeed
corresponds to the DFA expected by the user.Comment: SYNT 201
- …