296 research outputs found
Оптичні властивості CdTe, легованого Ca
The optical absorption, reflection and luminescence of CdTe:Ca were studied. It was established that the obtained Ca doped surface layers are characterized by intense photoluminescence from η = 8-10% in the edge region. Radiation is formed due to interband recombination of free charge carriers and the annihilation of excitons bound on isovalent impurities of Ca. The indicated components are observed in the differential optical reflection spectra Ŕω in the surface layer obtained by doping CdTe substrates with an isovalent Ca impurity. It is established that doping causes the formation of p-type conductivity.Досліджено оптичне поглинання, відбивання і люмінесценцію CdTe:Ca. Встановлено, що отримані леговані Ca поверхневі шари характеризуються інтенсивною фотолюмінесценцією з η = 8-10% у крайовій області. Випромінювання формується внаслідок міжзонної рекомбінації вільних носіїв заряду і анігіляцією зв’язаних на ізовалентних домішках Ca екситонів. Зазначені складові спостерігаються у диференційних спектрах оптичного відбивання Ŕω у приповерхневому шарі отриманому при легування ізовалентною домішкою Ca підкладинок CdTe. Встановлено, що легування обумовлює утворення p-типу провідності
Діркова провідність тонких шарів кадмій телуриду з домішками Li та Ca
By low-temperature annealing of n-CdTe substrates in aqueous suspensions of LiNO3 and Ca(NO3)2 salts pconductivity layers are created. The estimated concentration of free holes in diffusion layers at 300K is (5-50)∙1015 см-3Низькотемпературним відпалом підкладок n-CdTe у водяних суспензіях солей LiNO3 та Ca(NO3)2 створені шари p-типу провідності. Оціночна концентрація вільних дірок в дифузійних шарах при 300 К становить (5-50)∙1015 см-3
Light sources based on CdTe/CdS/ZnS heterostructures
The optimal modes of isovalent substitution and the CdTe/CdS/ZnS heterostructure obtained for the first time were established, the main parameters of the band structure of the constituent heterolayers and the characteristics of the obtained radiation sources were determined. The high quantum efficiency η ≈ 12-14 % of surface ZnS is caused by isovalent impurities. The band structure parameters of the obtained isovalently substituted CdS layers of atypical cubic modification and their luminescence efficiency of η ≈ 7-8 % were established. The emission of the resulting layers is localized in the edge region of the material and is formed by interband emitting transitions and the dominant annihilation of bound excitons
Limiting nutrients for bean production on contrasting soil types of Lake Victoria Crescent of Uganda
Common bean (Phaseolus vulgaris L.) is one of the most important grain
legumes in East Africa, but its yield has remained below the genetic
potential. Declining soil fertility is among the primary constraints to
bean production in most East African bean producing regions. Often
existing recommendations are generic and inept to guide farm level
decision making on nutrient replenishment. A greenhouse nutrient
omission study was conducted to determine the limiting nutrients in
three soils of Masaka District, commonly cropped to beans:
\u201cLiddugavu\u201d a Phaeozem, \u201cLimyufumyufu\u201d a
Cambisol and \u201cLuyinjayinga\u201d an Umbrisol soil. Nine
treatments; (i) complete nutrient treatment, (ii) N omitted, (iii) P
omitted, (iv) K omitted, (v) Mg omitted, (vi) S omitted, (vii) Ca
omitted, (viii) Micronutrients omitted and (ix) control without
nutrients. Each treatment was randomly assigned to the three soils and
replicated three times using a completely randomised design. Nitrogen,
phosphorus and potassium were limiting nutrients for bean production in
Umbrisol (Luyinjayinja) while in Cambisol (\u2018Limyufumyufu), common
bean production was most limited by soil acidity. The performance
varied with soil types, with beans grown on the Phaeozem registering
greater leaf number and growth, confirming both scientist\u2019s and
local farmer\u2019s knowledge that this soil has greater potential
than the other two soils.Le haricot commun (Phaseolus vulgaris L.) est un des l\ue9gumes
\ue0 grains les plus importants en Afrique de l\u2019Est, mais son
rendement reste toujours en dessous de son potentiel
g\ue9n\ue9tique. La baisse de la fertilit\ue9 du sol est parmi
les contraintes primaires \ue0 la production du haricot dans la
plupart des r\ue9gions productrices de l\u2019Afrique de
l\u2019Est. Le plus souvent, les recommandations sont
g\ue9n\ue9riques et inad\ue9quates pour guider la prise de
d\ue9cision au niveau champ sur le r\ue9approvisionnement en
nutriment. Une \ue9tude sous serre sur l\u2019omission de nutriment
a \ue9t\ue9 conduite pour d\ue9terminer les nutriments limitants
dans les trois sols du district de Masaka, commun\ue9ment
utilis\ue9s pour produire du haricot\ua0: \u201cLiddugavu\u201d
un sol du Phaeozem, \u201cLimyufumyufu\u201d un sol du Cambisol et
\u201cLuyinjayinga\u201d un sol du Umbrisol. Neuf traitements, (i)
traitement complet de nutriments, (ii) N omis, (iii) P omis, (iv) K
omis, (v) Mg omis, (iv) S omis, (vii) Ca omis, (viii) micronutriments
omis et (ix) control sans nutriments. Chacun des traitements a
\ue9t\ue9 al\ue9atoirement distribu\ue9 aux trois types de sols
et r\ue9pliqu\ue9 trois fois dans un dispositif compl\ue8tement
al\ue9atoire. Azote, phosphore, et potassium ont \ue9t\ue9 les
nutriments limitants pour la production du haricot dans Umbrisol
(Luyinjayinja) tandis que dans Cambisol (\u2018Limyufumyufu), la
production du haricoct commun a \ue9t\ue9 limit\ue9e par
l\u2019acidit\ue9 du sol. Les performances varient en fonction des
types de sols, avec le haricot produit sur le Phaeozem comptant plus de
feuilles et de croissance, confirmant \ue0 la fois les connaissances
des scientifiques et des populations locales qui stipulent que le sol a
un potentiel plus \ue9lev\ue9 que les deux autres sols
Classtalk: A Classroom Communication System for Active Learning
This pdf file is an article describing the advantages of using Classtalk technology in the classroom to enhance classroom communication. Classtalk technology cab facilitate the presentation of questions for small group work, collec the student answers and then display histograms showing how the class answered. This new communication technology can help instructors create a more interactive, student centered classroom, especially when teaching large courses. The article describes Classtalk as a very useful tool not only for engaging students in active learning, but also for enhancing the overall communication within the classroom. This article is a selection from the electronic Journal for Computing in Higher Education. Educational levels: Graduate or professional
From thermal rectifiers to thermoelectric devices
We discuss thermal rectification and thermoelectric energy conversion from
the perspective of nonequilibrium statistical mechanics and dynamical systems
theory. After preliminary considerations on the dynamical foundations of the
phenomenological Fourier law in classical and quantum mechanics, we illustrate
ways to control the phononic heat flow and design thermal diodes. Finally, we
consider the coupled transport of heat and charge and discuss several general
mechanisms for optimizing the figure of merit of thermoelectric efficiency.Comment: 42 pages, 22 figures, review paper, to appear in the Springer Lecture
Notes in Physics volume "Thermal transport in low dimensions: from
statistical physics to nanoscale heat transfer" (S. Lepri ed.
Evidence for a mixed mass composition at the `ankle' in the cosmic-ray spectrum
We report a first measurement for ultra-high energy cosmic rays of the
correlation between the depth of shower maximum and the signal in the water
Cherenkov stations of air-showers registered simultaneously by the fluorescence
and the surface detectors of the Pierre Auger Observatory. Such a correlation
measurement is a unique feature of a hybrid air-shower observatory with
sensitivity to both the electromagnetic and muonic components. It allows an
accurate determination of the spread of primary masses in the cosmic-ray flux.
Up till now, constraints on the spread of primary masses have been dominated by
systematic uncertainties. The present correlation measurement is not affected
by systematics in the measurement of the depth of shower maximum or the signal
in the water Cherenkov stations. The analysis relies on general characteristics
of air showers and is thus robust also with respect to uncertainties in
hadronic event generators. The observed correlation in the energy range around
the `ankle' at differs significantly from
expectations for pure primary cosmic-ray compositions. A light composition made
up of proton and helium only is equally inconsistent with observations. The
data are explained well by a mixed composition including nuclei with mass . Scenarios such as the proton dip model, with almost pure compositions, are
thus disfavoured as the sole explanation of the ultrahigh-energy cosmic-ray
flux at Earth.Comment: Published version. Added journal reference and DOI. Added Report
Numbe
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a
significant distance from their production point into a final state containing
charged hadrons in association with a high-momentum muon. The search is
conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV
and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS
detector operating at the Large Hadron Collider. Production of such particles
is expected in various scenarios of physics beyond the standard model. We
observe no signal and place limits on the production cross-section of
supersymmetric particles in an R-parity-violating scenario as a function of the
neutralino lifetime. Limits are presented for different squark and neutralino
masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final
version to appear in Physics Letters
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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