Recent Submissions

  • Three-dimensional printing of PLA and PLA/PHA dumbbell-shaped specimens of crisscross and transverse patterns as promising materials in emerging application areas: Prediction study

    Gonzalez Ausejo, Jennifer; Rydz, Joanna; Musioł, Marta; Sikorska, Wanda; Janeczek, Henryk; Sobata, Michał; Włodarczyk, Jakub; Szeluga, Urszula; Hercog, Anna; Kowalczuk, Marek (Elsevier, 2018-08-18)
    This paper presents ex-ante examination of advanced polymer materials to detect defects and define and minimize the potential failure of novel polymer products before they arise. The effect of build directions on the properties of dumbbell-shaped specimens obtained by three-dimensional printing from polylactide and polylactide/polyhydroxyalkanoate commercial filaments was investigated, as well as the hydrolytic degradation of these specimens at 50 ºC and 70 ºC. Taking into account previous studies, we have found further dependences of the properties of 3D printed species before and during abiotic degradation from the orientation of printing. The initial assumption that only the contact time with the 3D printer platform leads to an increase in the crystalline phase during printing turned out to be insufficient. Further investigations of individual parts of the dumbbell-shaped specimens showed that the size of the specimens’ surface in contact with the platform also affected the structural ordering of the material.
  • Atmin mediates kidney morphogenesis by modulating Wnt signaling

    Goggolidou, P.; Hadjirin, N.F.; Bak, A.; Papakrivopoulou, E.; Hilton, H.; Norris, D.P.; Dean, C.H. (Oxford University Press, 2018-10-15)
    The DNA damage protein and transcription factor Atmin (Asciz) is required for both lung tubulogenesis and ciliogenesis. Like the lungs, kidneys contain a tubular network that is critical for their function and in addition, renal ciliary dysfunction has been implicated in the pathogenesis of cystic kidney disease. Using the Atmin mouse mutant Gasping6 (Gpg6), we investigated kidney development and found it severely disrupted with reduced branching morphogenesis, resulting in fewer epithelial structures being formed. Unexpectedly, transcriptional levels of key cilia associated genes were not altered in Atmin(Gpg6/Gpg6) kidneys. Instead, Gpg6 homozygous kidneys exhibited altered cytoskeletal organization and modulation of Wnt signaling pathway molecules, including β-catenin and non-canonical Wnt/planar cell polarity (PCP) pathway factors, such as Daam2 and Vangl2. Wnt signaling is important for kidney development and perturbation of Wnt signaling pathways can result in cystic, and other, renal abnormalities. In common with other PCP pathway mutants, Atmin(Gpg6/Gpg6) mice displayed a shortened rostral-caudal axis and mis-oriented cell division. Moreover, intercrosses between Atmin(Gpg6/+) and Vangl2(Lp/+) mice revealed a genetic interaction between Atmin and Vangl2. Thus we show for the first time that Atmin is critical for normal kidney development and we present evidence that mechanistically, Atmin modifies Wnt signaling pathways, specifically placing it as a novel effector molecule in the non-canonical Wnt/PCP pathway. The identification of a novel modulator of Wnt signaling has important implications for understanding the pathobiology of renal disease.
  • An automatic method for extracting citations from Google Books

    Kousha, Kayvan; Thelwall, Mike (Wiley, 2014-05)
    Recent studies have shown that counting citations from books can help scholarly impact assessment and that Google Books (GB) is a useful source of such citation counts, despite its lack of a public citation index. Searching GB for citations produces approximate matches, however, and so its raw results need time‐consuming human filtering. In response, this article introduces a method to automatically remove false and irrelevant matches from GB citation searches in addition to introducing refinements to a previous GB manual citation extraction method. The method was evaluated by manual checking of sampled GB results and comparing citations to about 14,500 monographs in the Thomson Reuters Book Citation Index (BKCI) against automatically extracted citations from GB across 24 subject areas. GB citations were 103% to 137% as numerous as BKCI citations in the humanities, except for tourism (72%) and linguistics (91%), 46% to 85% in social sciences, but only 8% to 53% in the sciences. In all cases, however, GB had substantially more citing books than did BKCI, with BKCI's results coming predominantly from journal articles. Moderate correlations between the GB and BKCI citation counts in social sciences and humanities, with most BKCI results coming from journal articles rather than books, suggests that they could measure the different aspects of impact, however.
  • Cultural cues and behavioural patterns in stress dynamics: a case of the construction industry

    Hampton, Paul; Chinyio, Ezekiel; Riva, Silvia (Marketing Aumentado, 2018)
    Critical factors underpinning stress development in the Construction Industry were investigated in an ethnographic study. Data were collected from three construction organizations in the UK and analysed by content analysis. The results show the pivotal importance of interpersonal relationships to coping with the uncertainty of working conditions, coordination of activities involving teamwork and managing responsibilities and power interactions. The study underlines the importance of dedicated services for stress management and specific trainingrelated abilities devoted to reinforcing positive dynamics between persons and organizations. In particular, these related to managing the impacts of stress on physical status, interpersonal relationships, work performance, and emotional well-being. Communication systems, tools and software and their application were also claimed to have been carefully implemented as effective stress deterrents in the management of daily routine activities.
  • Best practices: in the 21st century, taxonomic decisions in herpetology are acceptable only when supported by a body of evidence and published via peer-review

    Kaiser, Hinrich; Crother, Brian I.; Kelly, Christopher M.R; Luiselli, Luca; O'Shea, Mark; Ota, Hidetoshi; Passos, Paulo; Schleip, Wulf D.; Wüster, Wolfgang (2013)
  • Security and Privacy of Things: Regulatory Challenges and Gaps for the Secure Integration of Cyber-Physical Systems

    Lee, Geraldine; Epiphaniou, Gregory; Al-Khateeb, Haider; Maple, Carsten (Springer, 2018-02-27)
    The rise of interconnected “intelligent” objects that move their capabilities from sensing and data processing to decision-making will be a disruptive phenomenon that further widens the gaps between legal, regulatory and technological approaches. This research sets out to establish a guided roadmap through the maze of regulation by incorporating the fragmented governance efforts into a single focus where security and privacy gaps unique to Machine-to-Machine communication (M2M) are identified against key performance metrics. We use privacy, ethics, trust, legality, data sharing, operational integration and device and communication protocols as our key performance metrics to highlight areas of significant overlap and gaps in a comprehensive list of standards to assist policymakers and researchers in the field. Results also indicate that policy concerns and diffused responses from existing standards raise unacceptable risks for the cyber and physical spheres in the IoT preventing their integration with existing hierarchical security architectures and reducing the opportunities for mass-market economies of scale.
  • The implementation of stakeholder management and building information modelling (BIM) in UK construction projects

    Singh, Sukhtaj; Chinyio, Ezekiel; Suresh, Subashini (Association of Researchers in Construction Management, 2018-09-03)
    The implementation and usage of Building Information Modelling (BIM) on construction projects affects procurement and the supply chain activities. BIM process is changing the traditional modus operandi of the construction industry where many projects have failed to achieve its objectives due to ineffective stakeholder management. An on-going PhD study explores how to mitigate delays and conflicts between stakeholders on BIM implemented projects in the UK. This paper is based on critical literature review and primary data collection through semi-structured interviews. Findings from the literature review show that BIM publication such as PAS 1192-2:2013, Employers Information Requirements (EIR) and BIM Execution Plan (BEP) sets out clear requirements for the coordination and collaboration process for the BIM model production. This provides a huge potential to enhance and facilitate communication among stakeholders. This helps in mitigating conflicts among stakeholders. The findings from the interviewees shows that BIM can help project teams to proactively satisfy stakeholders by engaging them early on in the construction process and seek solutions to avoid or minimise delays and conflicts. The paper concludes that it has culture, trust, people, technology, communication and structures are at its core for managing stakeholders within BIM projects.
  • Predominance of the A allele but no association of the KCNJ11 rs5219 E23K polymorphism with type 2 diabetes in a Nigerian population

    Engwa, Godwill Azeh; Nwalo, Friday Nweke; Obi, Chosen E.; Onyia, Christie; Ojo, Opeolu Oyejide; Mbacham, Wilfred Fon; Ubi, Benjamin Ewa (GMR, 2018-03-01)
    Though the rs5219 E23K variant of the KCNJ11 gene is commonly known to be associated with Type 2 diabetes (T2D) in Caucasian and Asian populations, little or none of such findings have been revealed in Nigeria. Hence, this study was aimed to assess the relationship between E23K polymorphic variant of the KCNJ11 gene and T2D in a Nigerian population. A case-control study involving 73 T2D patients and 75 non-diabetic (ND) patients aged above 30 years was conducted. Demographic, clinical, and anthropometric data was collected and the fasting blood glucose (FBG), total cholesterol (TC), triglyceride (TG), LDL-c and HDL-c were assayed. The KCNJ11 E23K polymorphism was genotyped by RFLP–PCR using BanII restriction enzyme. There was predominance of the mutant A allele as well as the homozygote AA genotype (92.5%) in both T2D and ND patients than the wild G allele and homozygote GG genotype (7.5%). The heterozygote AG genotype was completely absent in the T2D and ND patients. The AA genotype showed no significant risk of T2D when compared to the GG genotype (OR: 1.183, 95% CI: 0.345-4.059, p= 0.790) in. Genotype frequencies did not violate the Hardy-Weinberg equilibrium in the study population (χ2 = 0.071; p = 0.790). HDL-c was significantly higher (p = 0.002) in patients with the GG genotype compared to the patients with the AA genotype. In conclusion, the KCNJ11 E23K polymorphism was not associated with T2D though there was predominance of the mutant A allele in the study population.
  • α-Catenin Structure and Nanoscale Dynamics in Solution and in Complex with F-Actin

    Nicholl, Iain; Matsui, Tsutomu; Weiss, Thomas M; Stanley, Christopher B; Heller, William T; Martel, Anne; Farago, Bela; Callaway, David JE; Bu, Zimei (Elsevier, 2018-08-21)
    As a core component of the adherens junction, α-catenin stabilizes the cadherin/catenin complexes to the actin cytoskeleton for the mechanical coupling of cell-cell adhesion. α-catenin also modulates actin dynamics, cell polarity, and cell-migration functions that are independent of the adherens junction. We have determined the solution structures of the α-catenin monomer and dimer using in-line size-exclusion chromatography small-angle X-ray scattering, as well as the structure of α-catenin dimer in complex to F-actin filament using selective deuteration and contrast-matching small angle neutron scattering. We further present the first observation, to our knowledge, of the nanoscale dynamics of α-catenin by neutron spin-echo spectroscopy, which explicitly reveals the mobile regions of α-catenin that are crucial for binding to F-actin. In solution, the α-catenin monomer is more expanded than either protomer shown in the crystal structure dimer, with the vinculin-binding M fragment and the actin-binding domain being able to adopt different configurations. The α-catenin dimer in solution is also significantly more expanded than the dimer crystal structure, with fewer interdomain and intersubunit contacts than the crystal structure. When in complex to F-actin, the α-catenin dimer has an even more open and extended conformation than in solution, with the actin-binding domain further separated from the main body of the dimer. The α-catenin-assembled F-actin bundle develops into an ordered filament packing arrangement at increasing α-catenin/F-actin molar ratios. Together, the structural and dynamic studies reveal that α-catenin possesses dynamic molecular conformations that prime this protein to function as a mechanosensor protein.
  • Knowledge management practices in Oman construction

    Almarshoudi, Abdulaziz; Suresh, Subashini; Renukappa, Suresh (IJKE, 2018-06)
    Implementing the strategies of Knowledge Management (KM) in the construction industry in Oman can produce significant benefits, such as continuous improvement and the improved performance of construction projects. In addition, the need to understand the determinants of successful Knowledge Management cannot be underestimated in organisations in the Middle East; specifically, those which are members of the Gulf Cooperation Council (GCC). The accelerated development in recent years regarding the GCC countries, highlights the need for these nations and their organisations to empower themselves through Knowledge Management. Nevertheless, very little empirical research has been conducted to understand this phenomenon. This paper investigates the role of Knowledge Management in relation to reducing the Cost of Poor Quality in the construction industry in Oman. Data was collected via questionnaires and interviews with Omani construction engineers from public and private sector. The findings reveal that knowledge capture and knowledge sharing are paramount to the contributory factors to the Cost of Poor Quality in practice, which includes the cost of errors and omissions, cost of design changes and the cost of poor skills.
  • Tangled skeins: a first report of non-captive mating behavior in the Southeast Asian Paradise Flying Snake (Reptilia: Squamata: Colubridae: Chrysopelea paradisi)

    Kaiser, Hinrich; Kim, Johnny; Worth, Heike; O'Shea, Mark (Threatened Taxa, 2016-02)
    We describe the courtship behavior of the Paradise Flying Snake, Chrysopelea paradisi, from a series of images taken near Sandakan, eastern Sabah, Borneo, Malaysia. During the episode observed, four males moved together with a female in various states of entanglement, traveling at ground level and into a series of bushes. The observations took place over the course of a 30-min period until the snakes were lost to view. Our report is the first direct observation of mating behavior in C. paradisi in the wild and provides another rare glimpse of the multi-male courtship in Southeast Asian colubrids.
  • Satellite-5G integration: a network perspective

    Giambene, Giovanni; Kota, Sastri; Pillai, Prashant (IEEE, 2018-09)
    Future 5G mobile communication systems are expected to integrate different radio access technologies, including the satellite component. Within the 5G framework, the terrestrial services can be augmented with the development of HTS systems and new mega-constellations meeting 5G requirements, such as high bandwidth, low latency, and increased coverage including rural areas, air, and seas. This article provides an overview of the current 5G initiatives and projects followed by a proposed architecture for 5G satellite networks where the SDN/NFV approach facilitates the integration with the 5G terrestrial system. In addition, a novel technique based on network coding is analyzed for the joint exploitation of multiple paths in such an integrated satellite-terrestrial system. For TCP-based applications, an analytical model is presented to achieve an optimal traffic split between terrestrial and satellite paths and optimal redundancy levels.
  • Photon-number-resolved measurement of an exciton-polariton condensate

    Klaas, M.; Schlottmann, E.; Flayac, H.; Laussy, F. P.; Gericke, F.; Schmidt, M.; Helversen, M. v.; Beyer, J.; Brodbeck, S.; Suchomel, H.; Höfling, S.; Reitzenstein, S.; Schneider, C. (Physical Review Letters, 2018)
    We measure the full photon-number distribution emitted from a Bose condensate of microcavity exciton polaritons confined in a micropillar cavity. The statistics are acquired by means of a photon-number-resolving transition edge sensor. We directly observe that the photon-number distribution evolves with the nonresonant optical excitation power from geometric to quasi-Poissonian statistics, which is canonical for a transition from a thermal to a coherent state. Moreover, the photon-number distribution allows one to evaluate the higher-order photon correlations, shedding further light on the coherence formation and phase transition of the polariton condensate. The experimental data are analyzed in terms of thermal-coherent states, which gives direct access to the thermal and coherent fraction from the measured distributions. These results pave the way for a full understanding of the contribution of interactions in light-matter condensates in the coherence buildup at threshold.
  • Negative-mass effects in spin-orbit coupled Bose-Einstein condensates

    Colas, David; Laussy, Fabrice P.; Davis, Matthew J. (APS, 2018)
    Negative effective masses can be realized by engineering the dispersion relation of a variety of quantum systems. A recent experiment with spin-orbit coupled Bose-Einstein condensates has shown that a negative effective mass can halt the free expansion of the condensate and lead to fringes in the density [M. A. Khamehchi et al., Phys. Rev. Lett. 118, 155301 (2017)]. Here, we show that the underlying cause of these observations is the self-interference of the wave packet that arises when only one of the two effective mass parameters that characterize the dispersion of the system is negative. We show that spin-orbit coupled Bose-Einstein condensates may access regimes where both mass parameters controlling the propagation and diffusion of the condensate are negative, which leads to the novel phenomenon of counterpropagating self-interfering packets.
  • Topological order and equilibrium in a condensate of exciton-polaritons

    Caputo, Davide; Ballarini, Dario; Dagvadorj, Galbadrakh; Sanchez Munoz, Carlos; De Giorgi, Milena; Dominici, Lorenzo; West, Kenneth; Pfeiffer, Loren N.; Gigli, Giuseppe; Laussy, Fabrice P.; Szymanska, Marzena H.; Sanvitto, Daniele (Nature publishing group, 2018)
    We report the observation of the Berezinskii-Kosterlitz-Thouless transition for a 2D gas of exciton-polaritons, and through the joint measurement of the first-order coherence both in space and time we bring compelling evidence of a thermodynamic equilibrium phase transition in an otherwise open driven/dissipative system. This is made possible thanks to long polariton lifetimes in high-quality samples with small disorder and in a reservoir-free region far away from the excitation spot, that allow topological ordering to prevail. The observed quasi-ordered phase, characteristic for an equilibrium 2D bosonic gas, with a decay of coherence in both spatial and temporal domains with the same algebraic exponent, is reproduced with numerical solutions of stochastic dynamics, proving that the mechanism of pairing of the topological defects (vortices) is responsible for the transition to the algebraic order. Finally, measurements in the weak-coupling regime confirm that polariton condensates are fundamentally different from photon lasers and constitute genuine quantum degenerate macroscopic states.
  • Filtering Multiphoton Emission from State-of-the-Art Cavity QED

    Sanchez Munoz, Carlos; Laussy, Fabrice P.; Valle, Elena del; Tejedor, Carlos; Gonzalez-Tudela, Alejandro (OSA, 2018)
    Engineering multiphoton states is an outstanding challenge with applications in multiple fields such as quantum metrology, quantum lithography, or even biological sensing. State-of-the-art methods to obtain them rely on post-selection, multi-level systems, or Rydberg atomic ensembles. Recently, it was shown that a strongly driven two-level system interacting with a detuned cavity mode can be engineered to continuously emit 𝑛-photon states. In the present work, we show that spectral filtering of its emission relaxes considerably the requirements on the system parameters even to the more accessible bad-cavity situation, opening up the possibility of implementing this protocol in a much wider landscape of different platforms. This improvement is based on a key observation: in the imperfect case where only a certain fraction of emission is composed of 𝑛-photon states, these have a well-defined energy separated from the rest of the signal, which allows one to reveal and purify multiphoton emission just by frequency filtering. We demonstrate these results by obtaining analytical expressions for the relevant figures of merit of multiphoton emission, such as the 𝑛-photon coupling rate between cavity and emitter, the fraction of light emitted as 𝑛-photon states, and 𝑛-photon emission rates. This allows us to make a systematic study of such figures of merit as a function of the system parameters and demonstrate the viability of the protocol in several relevant types of cavity quantum electrodynamics setups, where we take into account the impact of their respective experimental limitations.
  • First observation of the quantized exciton-polariton field and effect of interactions on a single polariton.

    Cuevas, Álvaro; López Carreño, Juan Camilo; Silva, Blanca; De Giorgi, Milena; Suárez-Forero, Daniel G; Sánchez Muñoz, Carlos; Fieramosca, Antonio; Cardano, Filippo; Marrucci, Lorenzo; Tasco, Vittorianna; Biasiol, Giorgio; Del Valle, Elena; Dominici, Lorenzo; Ballarini, Dario; Gigli, Giuseppe; Mataloni, Paolo; Laussy, Fabrice P; Sciarrino, Fabio; Sanvitto, Daniele (AAAS, 2018-04-01)
    Polaritons are quasi-particles that originate from the coupling of light with matter and that demonstrate quantum phenomena at the many-particle mesoscopic level, such as Bose-Einstein condensation and superfluidity. A highly sought and long-time missing feature of polaritons is a genuine quantum manifestation of their dynamics at the single-particle level. Although they are conceptually perceived as entangled states and theoretical proposals abound for an explicit manifestation of their single-particle properties, so far their behavior has remained fully accounted for by classical and mean-field theories. We report the first experimental demonstration of a genuinely quantum state of the microcavity polariton field, by swapping a photon for a polariton in a two-photon entangled state generated by parametric downconversion. When bringing this single-polariton quantum state in contact with a polariton condensate, we observe a disentangling with the external photon. This manifestation of a polariton quantum state involving a single quantum unlocks new possibilities for quantum information processing with interacting bosons.
  • Frequency-resolved Monte Carlo.

    López Carreño, Juan Camilo; Del Valle, Elena; Laussy, Fabrice P (Nature publishing group, 2018-05-03)
    We adapt the Quantum Monte Carlo method to the cascaded formalism of quantum optics, allowing us to simulate the emission of photons of known energy. Statistical processing of the photon clicks thus collected agrees with the theory of frequency-resolved photon correlations, extending the range of applications based on correlations of photons of prescribed energy, in particular those of a photon-counting character. We apply the technique to autocorrelations of photon streams from a two-level system under coherent and incoherent pumping, including the Mollow triplet regime where we demonstrate the direct manifestation of leapfrog processes in producing an increased rate of two-photon emission events.
  • Joint subnatural-linewidth and single-photon emission from resonance fluorescence

    Lopez Carreno, J.C.; Zubizarreta Casalengua, E.; Laussy, F.P.; Valle, E. del (IOP, 2018-07-10)
    Resonance fluorescence—the light emitted when exciting resonantly a two-level system—is a popular quantum source as it seems to inherit its spectral properties from the driving laser and its statistical properties from the two-level system, thus providing a subnatural-linewidth single-photon source (SPS). However, these two qualities do not actually coexist in resonance fluorescence, since an optical target detecting these antibunched photons will either be spectrally broad itself and not benefit from the spectrally narrow source, or match spectrally with the source but in this case the antibunching will be spoiled. We first explain this failure through a decomposition of the field-emission and how this gets affected by frequency resolution. We then show how to restore the sought joint subnatural linewidth and antibunched properties, by interfering the resonance fluorescence output with a coherent beam. We finally discuss how the signal that is eventually generated in this way features a new type of quantum correlations, with a plateau of antibunching which suppresses much more strongly close photon pairs. This introduces a new concept of perfect SPS.
  • Molecular Level Structure of Biodegradable Poly(Delta-Valerolactone) Obtained in the Presence of Boric Acid.

    Duale, Khadar; Zięba, Magdalena; Chaber, Paweł; Di Fouque, Dany Jeanne; Memboeuf, Antony; Peptu, Cristian; Radecka, Iza; Kowalczuk, Marek; Adamus, Grażyna (MDPI, 2018-08-14)
    In this study, low molecular weight poly(δ-valerolactone) (PVL) was synthesized through bulk-ring openings polymerization of δ-valerolactone with boric acid (B(OH)₃) as a catalyst and benzyl alcohol (BnOH) as an initiator. The resulting homopolymer was characterized with the aid of nuclear magnetic resonance (NMR) and mass spectrometry (MS) techniques to gain further understanding of its molecular structure. The electrospray ionization mass spectrometry (ESI-MS) spectra of poly(δ-valerolactone) showed the presence of two types of homopolyester chains-one terminated by benzyl ester and hydroxyl end groups and one with carboxyl and hydroxyl end groups. Additionally, a small amount of cyclic PVL oligomers was identified. To confirm the structure of PVL oligomers obtained, fragmentation of sodium adducts of individual polyester molecules terminated by various end groups was explored in ESI-MSn by using collision induced dissociation (CID) techniques. The ESI-MSn analyses were conducted both in positive- and negative ion mode. The comparison of the fragmentation spectra obtained with proposed respective theoretical fragmentation pathways allowed the structure of the obtained oligomers to be established at the molecular level. Additionally, using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), it was proven that regardless of the degree of oligomerization, the resulting PVL samples were a mixture of two types of linear PVL oligomers differing in end groups and containing just a small amount of cyclic oligomers that tended to be not visible at higher molar masses.

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