Worldwide outdoor round robin study of organic photovoltaic devices and modules

Accurate characterization and reporting of organic photovoltaic (OPV) device performance remains one of the important challenges in the field. The large spread among the efficiencies of devices with the same structure reported by different groups is significantly caused by different procedures and equipment used during testing. The presented article addresses this issue by offering a new method of device testing using “suitcase sample” approach combined with outdoor testing that limits the diversity of the equipment, and a strict measurement protocol. A round robin outdoor characterization of roll-to-roll coated OPV cells and modules conducted among 46 laboratories worldwide is presented, where the samples and the testing equipment were integrated in a compact suitcase that served both as a sample transportation tool and as a holder and test equipment during testing. In addition, an internet based coordination was used via plasticphotovoltaics.org that allowed fast and efficient communication among participants and provided a controlled reporting format for the results that eased the analysis of the data. The reported deviations among the laboratories were limited to 5% when compared to the Si reference device integrated in the suitcase and were up to 8% when calculated using the local irradiance data. Therefore, this method offers a fast, cheap and efficient tool for sample sharing and testing that allows conducting outdoor measurements of OPV devices in a reproducible manner.

The pedagogic prosthetic: Augmented learning as content-in-motion in hybrid educational spheres

This article draws on the design and implementation of three mobile learning projects introduced by Flanagan in 2011, 2012 and 2014 engaging a total of 206 participants. The latest of these projects is highlighted in this article. Two other projects provide additional examples of innovative strategies to engage mobile and cloud systems describing how electronic and mobile technology can help facilitate teaching and learning, assessment for learning and assessment as learning, and support communities of practice. The second section explains the theoretical premise supporting the implementation of technology and promulgates a hermeneutic phenomenological approach. The third section discusses mobility, both in terms of the exploration of wearable technology in the prototypes developed as a result of the projects, and the affordances of mobility within pedagogy. Finally the quantitative and qualitative methods in place to evaluate m-learning are explained.

Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN.

Nonclassical rotational inertia in a two-dimensional bosonic solid containing grain boundaries

We study the occurrence of nonclassical rotational inertia (NCRI) arising from superfluidity along grain boundaries in a two-dimensionalbosonic system. We make use of a standard mapping between the zero-temperature properties of this system and the statistical mechanics of interacting vortex lines in the mixed phase of a type-II superconductor. In the mapping, the liquid phase of the vortex system corresponds to the superfluid bosonic phase. We consider numerically obtained polycrystalline configurations of the vortex lines in which the microcrystals are separated by liquidlike grain-boundary regions which widen as the vortex system temperature increases. The NCRI of the corresponding zero-temperature bosonic systems can then be numerically evaluated by solving the equations of superfluid hydrodynamics in the channels near the grain boundaries. We find that the NCRI increases very abruptly as the liquid regions in the vortex system (equivalently, superfluid regions in the bosonic system) form a connected, system-spanning structure with one or more closed loops. The implications of these results for experimentally observed supersolid phenomena are discussed.

Phase diagram of a hard-sphere system in a quenched random potential: A numerical study

We report numerical results for the phase diagram in the density-disorder plane of a hard-sphere system in the presence of quenched, random, pinning disorder. Local minima of a discretized version of the Ramakrishnan-Yussouff free energy functional are located numerically and their relative stability is studied as a function of the density and the strength of disorder. Regions in the phase diagram corresponding to liquid, glassy, and nearly crystalline states are mapped out, and the nature of the transitions is determined. The liquid to glass transition changes from first to second order as the strength of the disorder is increased. For weak disorder, the system undergoes a first-order crystallization transition as the density is increased. Beyond a critical value of the disorder strength, this transition is replaced by a continuous glass transition. Our numerical results are compared with those of analytical work on the same system. Implications of our results for the field-temperature phase diagram of type-II superconductors are discussed.

Murtuma mieheydessä. Aikuisiän selkäydinvamma ja maskuliinisuuden rakentuminen.

Tutkimukseni tavoitteena oli ensinnäkin selvittää, miten aikuisiällä tapahtunut vammautuminen uhkaa maskuliinista identiteettiä. Olin kiinnostunut niistä vammaisuuteen liittyvistä sosiaalisista prosesseista, joiden takia maskuliinisuus joutuu vammautumisen myötä koetukselle. Toiseksi halusin selvittää, miten haastattelemani selkäydinvammaiset miehet rakentavat maskuliinista identiteettiään. Tutkimukseni teoreettisena taustana toimi yhtäältä vammaistutkimuksen piirissä tehty, vammaisten elettyä kokemusta tarkasteleva tutkimus, toisaalta kriittinen miestutkimus, josta erityisesti R.W. Connellin teoria hegemonisesta maskuliinisuudesta. Tämän laadullisen tutkimuksen kohdejoukkona oli kahdeksan 23–68-vuotiasta miestä, joiden selkäydin oli vaurioitunut aikuisiällä tapahtuneen tapaturman seurauksena. Teemahaastattelut toteutettiin vuoden 2010 kevään ja syksyn aikana ja ne käsittelivät vammautumisen kokemusta ja sen seurauksia muun muassa miesten toimintakykyyn, sosiaalisiin suhteisiin, seksuaalisuuteen ja maskuliinisuuteen. Analyysivaiheessa tukeuduin grounded theoryn aineistolähtöiseen teemoitteluun. Haastatteluiden lisäksi tein lyhyen ekskursion pääkaupunkiseudulla sijaitsevaan kauppakeskukseen, jossa kiertelin pyörätuolissa istuen. Hyödynsin tekemiäni havaintoja esteettömyydestä ja sosiaalisesta vuorovaikutuksesta analyysissäni. Tutkimuksessa kävi selväksi, että vammautuminen oli uhannut haastateltujen maskuliinisuutta eri tavoin. Miehet olivat pelänneet menettäneensä itsenäisyytensä, toimintakykynsä, ihmissuhteensa ja näiden myötä myös mieheytensä. Kotiuduttuaan heille olikin ollut tärkeää todistaa sekä itselleen että läheisilleen olevansa edelleen itsenäisesti pärjääviä miehiä. Useimmille miehille vammautuminen oli myös johtanut ajoittaiseen yksityisyyden menettämiseen. Miehet kertoivat, että pyörätuoli herättää huomiota ja johtaa tungetteleviin katseisiin, kysymyksiin ja kosketuksiin. Totesin, että tällainen avulias tungettelu kuluttaa maskuliinista identiteettiä, koska se rikkoo kulttuurista käsitystä, jonka mukaan miehen kuuluu pärjätä ilman toisten apua. Toisaalta osa miehistä myös koki, että näkyvän vammansa takia heitä ajoittain myös vältellään. Arkisissa kohtaamisissa haastatellut pyrkivät rikkomaan vammaisuutta koskevia stereotypioita korostamalla maskuliinisia piirteitään. Haastateltavat liittivät kulttuurisesti arvostettuun maskuliinisuuteen käsityksiä itsenäisestä pärjäämisestä, urheilullisuudesta, teknisestä taitavuudesta, emotionaalisesta järkkymättömyydestä ja seksuaalisesta suorituskyvystä. Miehet kokivat, että vammaisuuden takia heidän maskuliinisuutensa voidaan nähdä viallisena tai puutteellisena. Tämän takia he pyrkivät maskuliinisuuden performatiiveissaan minimoimaan oman heikkouden ja riippuvaisuuden julkitulemista ja sen sijaan korostivat hegemonisen maskuliinisuuden mukaisia piirteitä. Tarkastelin tätä maskuliinisuuden tekemistä erityisesti parisuhteen, työn ja esteellisen tilan konteksteissa. Haastateltavat kertoivat, että vammautumisesta seurannut fyysinen ja henkinen rasitus oli asettanut heidän parisuhteensa koetukselle. Kotitöiden tekemisen kautta miehet neuvottelivat vastuullisuudestaan ja pärjäämisestään. Kaikkien miesten maskuliininen identiteetti näytti nojaavan työn tekemiseen ja sen tuomaan statukseen. Miesten suhdetta esteelliseen tilaan väritti jatkuva rajankäynti avun tarpeen ja miehisen kunnian välillä.

Nonlinear hydrodynamics of a hard-sphere fluid near the glass transition

We conduct a numerical study of the dynamic behavior of a dense hard-sphere fluid by deriving and integrating a set of Langevin equations. The statics of the system is described by a free-energy functional of the Ramakrishnan-Yussouff form. We find that the system exhibits glassy behavior as evidenced through a stretched exponential decay and a two-stage relaxation of the density correlation function. The characteristic times grow with increasing density according to the Vogel-Fulcher law. The wave-number dependence of the kinetics is extensively explored. The connection of our results with experiment, mode-coupling theory, and molecular-dynamics results is discussed.

Time scales for transitions between free-energy minima of a dense hard-sphere system

Time scales associated with activated transitions between glassy metastable states of a free-energy functional appropriate for a dense hard-sphere system are calculated by using a new Monte Carlo method for the local density variables. In particular, we calculate the time the system, initially placed in a shallow glassy minimum of the free-energy, spends in the neighborhood of this minimum before making a transition to the basin of attraction of another free-energy minimum. This time scale is found to increase as the average density is increased. We find a crossover density near which this time scale increases very sharply and becomes longer than the longest times accessible in our simulation. This time scale does not show any evidence of increasing with sample size

Out of equilibrium plasticity dynamics and the annealing of supersolidity in solid He-4

We present a numerical study of a continuum plasticity field coupled to a Ginzburg-Landau model for superfluidity. The results suggest that a supersolid fraction may appear as a long-lived transient during the time evolution of the plasticity field at higher temperatures where both dislocation climb and glide are allowed. Supersolidity, however, vanishes with annealing. As the temperature is decreased, dislocation climb is arrested and any residual supersolidity due to incomplete annealing remains frozen. Our results may provide a resolution of many perplexing issues concerning a variety of experiments on bulk solid He-4.

Hydrodynamics of compressible superfluids in confined geometries

We present a study of the hydrodynamics of compressible superfluids in confined geometries. We use a perturbative procedure in terms of the dimensionless expansion parameter (v/v(s))(2) where v is the typical speed of the flow and vs is the speed of sound. A zero value of this parameter corresponds to the incompressible limit. We apply the procedure to two specific problems: the case of a trapped superfluid with a Gaussian profile of the local density, and that of a superfluid confined in a rotating obstructed cylinder. We find that the corrections due to finite compressibility which are, as expected, negligible for liquid He, are important but amenable to the perturbative treatment for typical ultracold atomic systems.

Ising model on a random network with annealed or quenched disorder

We study the equilibrium properties of an Ising model on a disordered random network where the disorder can be quenched or annealed. The network consists of fourfold coordinated sites connected via variable length one-dimensional chains. Our emphasis is on nonuniversal properties and we consider the transition temperature and other equilibrium thermodynamic properties, including those associated with one-dimensional fluctuations arising from the chains. We use analytic methods in the annealed case, and a Monte Carlo simulation for the quenched disorder. Our objective is to study the difference between quenched and annealed results with a broad random distribution of interaction parameters. The former represents a situation where the time scale associated with the randomness is very long and the corresponding degrees of freedom can be viewed as frozen, while the annealed case models the situation where this is not so. We find that the transition temperature and the entropy associated with one-dimensional fluctuations are always higher for quenched disorder than in the annealed case. These differences increase with the strength of the disorder up to a saturating value. We discuss our results in connection to physical systems where a broad distribution of interaction strengths is present.

An estimate of the number of tropical tree species

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher's alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between similar to 40,000 and similar to 53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of similar to 19,000-25,000 tree species. Continental Africa is relatively depauperate with a minimum of similar to 4,500-6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.

Na2.44Mn1.79(SO4)(3): a new member of the alluaudite family of insertion compounds for sodium ion batteries

Sodium-ion batteries have been extensively pursued as economic alternatives to lithium-ion batteries. Investigating the polyanion chemistry, alluaudite structured Na2Fe2II(SO4)(3) has been recently discovered as a 3.8 V positive electrode material (Barpanda et al., Nature Commun., 5: 4358, 2014). Registering the highest ever Fe-III/Fe-II redox potential (vs. Na/Na+) and formidable energy density, it has opened up a new polyanion family for sodium batteries. Exploring the alluaudite family, here we report isotypical Na2+2xMn2-xII(SO4)(3) (x = 0.22) as a novel high-voltage cathode material for the first time. Following low-temperature (ca. 350 degrees C) solid-state synthesis, the structure of this new alluaudite compound has been solved adopting a monoclinic framework (s.g. C2/c) showing antiferromagnetic ordering at 3.4 K. Synergising experimental and ab initio DFT investigation, Na2+2xMn2-xII(SO4)(3) has been found to be a potential high-voltage (ca. 4.4 V) cathode material for sodium batteries.

Ionothermal Synthesis of High-Voltage Alluaudite Na2+2xFe2-x(SO4)(3) Sodium Insertion Compound: Structural, Electronic, and Magnetic Insights

Exploring future cathode materials for sodium-ion batteries, alluaudite class of Na2Fe2II(SO4)(3) has been recently unveiled as a 3.8 V positive insertion candidate (Barpanda et al. Nat. Commun. 2014, 5, 4358). It forms an Fe-based polyanionic compound delivering the highest Fe-redox potential along with excellent rate kinetics and reversibility. However, like all known SO4-based insertion materials, its synthesis is cumbersome that warrants careful processing avoiding any aqueous exposure. Here, an alternate low temperature ionothermal synthesis has been described to produce the alluaudite Na2+2xFe2-xII(SO4)(3). It marks the first demonstration of solvothermal synthesis of alluaudite Na2+2xM2-xII(SO4)(3) (M = 3d metals) family of cathodes. Unlike classical solid-state route, this solvothermal route favors sustainable synthesis of homogeneous nanostructured alluaudite products at only 300 degrees C, the lowest temperature value until date. The current work reports the synthetic aspects of pristine and modified ionothermal synthesis of Na2+2xFe2-xII(SO4)(3) having tunable size (300 nm similar to 5 mu m) and morphology. It shows antiferromagnetic ordering below 12 K. A reversible capacity in excess of 80 mAh/g was obtained with good rate kinetics and cycling stability over 50 cycles. Using a synergistic approach combining experimental and ab initio DFT analysis, the structural, magnetic, electronic, and electrochemical properties and the structural limitation to extract full capacity have been described.