949 research outputs found
Some Factors Influencing Distribution Coefficients of Trace Amounts of M2+ Ions During the Crystallization of Mn(CH3COO)2·4H2O
Distribution coefficients,D2/1 (Henderson – Kracek, Khlopin) of trace amounts of Ni2+,Mg2+, Cu2+, Co2+, Zn2+, Cd2+, Ca2+, and Sr2+ have been determined during the crystallization of Mn(CH3COO)2·4H2O. Their dependencies on several properties of co-crystallizing acetate hydrates M(CH3COO)2·nH2O as well as co-crystallizing M2+ ions have been analyzed. The D2/1 values fall in the range from 0.011 (DCu) to 0.28 (DCo) and indicate the possibility of effective removal of trace amounts of most investigated ions during the crystallization of Mn(CH3COO)2·4H2O at 25 °C. They generally do not depend directly on most investigated factors, but those of Mg2+, Ni2+ and Co2+ ions, which form acetate tetrahydrates like Mn(CH3COO)2·4H2O, closely depend on electronegativity of the elements as well as solubility and η parameter and may be estimated on the basis of the mentioned properties using simple formulae.Keywords: Crystallization, manganese(II) acetate tetrahydrate, Henderson-Kracek, Khlopin distribution coefficients,
Exploring A Five Factor Mentoring Model Within Elementary Science
The purpose of the study was to explore and describe the perceptions of several elementary science mentors and their mentees within one school district based on a fivefactor mentoring model. Utilizing a qualitative methodology in the form of a case study, five mentors and three mentees were interviewed using a structured protocol. From verbatim interview data and field notes, three themes pertaining to the role of the mentor within elementary science emerged as emotional support, technical support, and educative support. Within the five-factor mentoring model, personal attributes suggested notions of support and expert status as critical elements for effective mentoring. The factors of system requirements, pedagogical knowledge, modeling, and feedback were found to be interrelated amongst themselves and with the factor of personal attributes. Effective mentors demonstrated a commitment to the role as well as a flexibility pertaining to role adjustment depending on the context of the mentoring relationship
Nueva estrategia para el diseño y fabricación de cabezales de fresadora de altas prestaciones
Los cabezales de transmisión mecánica de altas prestaciones son una de las partes más complejas, costosas y problemáticas
de una maquina fresadora. Esto es debido a la gran cantidad de canalizaciones para la transmisión de fluidos que
deben de contener y a las altas prestaciones mecánicas que se les exigen. En este trabajo se presenta una estrategia
para optimizar el diseño y la fabricación de los cuerpos de estos cabezales basada en la incorporación de aleaciones
de aluminio y la inclusión de insertos tubulares de acero en la propia fundición que conforma el cabezal. Los insertos
tubulares sustituyen a los canales de refrigeración realizados actualmente por taladros de mecanizado y quedan
integrados en la masa de aluminio. La nueva metodología ha permitido realizar un diseño que mantiene las prestaciones
mecánicas, aumenta la fiabilidad y reduce la masa de estos elementos móviles de fresadoras como ha demostrado la
validación experimental de un primer prototipo.High-performance mechanical-transmission heads are one of the most complex, costly and problematic
parts of a
milling machine, owing to the large amount of piping required for transporting fluids and to the
high level of mechanical performance that is required from them. This study proposes a strategy for
optimising the design and manufacture of head bodies by using aluminium alloys and by integrating
tubular stainless steel inserts in the casting of the head. These tubular inserts that are
integrated into the aluminium mass are an alternative to cooling conduits currently made by machine
drilling. As demonstrated in the experimental validation of the first prototype, the new method has
created a design that retains the same mechanical performance, increases its reliability and
reduces the weight
of the milling machine’s moving parts.Spanish Ministry of Science and Innovation in the
PROFIT Project FIT-020500-2006-50 and by the
Agencia de Desarrollo Economico of the Junta de
Castilla-Leon (04/06/BU/0008)
First atom lifetime and scattering length measurements
The results of a search for hydrogen-like atoms consisting of
mesons are presented. Evidence for atom production
by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen
in terms of characteristic pairs from their breakup in the same target
() and from Coulomb final state interaction (). Using
these results the analysis yields a first value for the atom lifetime
of fs and a first model-independent measurement of
the S-wave isospin-odd scattering length
( for isospin ).Comment: 14 pages, 8 figure
Results on correlations and fluctuations from NA49
The large acceptance and high momentum resolution as well as the significant
particle identification capabilities of the NA49 experiment at the CERN SPS
allow for a broad study of fluctuations and correlations in hadronic
interactions. In the first part recent results on event-by-event charge and p_t
fluctuations are presented. Charge fluctuations in central Pb+Pb reactions are
investigated at three different beam energies (40, 80, and 158 AGeV), while for
the p_t fluctuations the focus is put on the system size dependence at 158
AGeV. In the second part recent results on Bose Einstein correlations of h-h-
pairs in minimum bias Pb+Pb reactions at 40 and 158 AGeV, as well as of K+K+
and K-K- pairs in central Pb+Pb collisions at 158 AGeV are shown. Additionally,
other types of two particle correlations, namely pi p, Lambda p, and Lambda
Lambda correlations, have been measured by the NA49 experiment. Finally,
results on the energy and system size dependence of deuteron coalescence are
discussed.Comment: 10 pages, 12 figures, Presented at Quark Matter 2002, Nantes, France,
Corrected error in Eq.
Determination of scattering lengths from measurement of atom lifetime
The DIRAC experiment at CERN has achieved a sizeable production of
atoms and has significantly improved the precision on its lifetime
determination. From a sample of 21227 atomic pairs, a 4% measurement of the
S-wave scattering length difference
has been attained, providing an important test of Chiral Perturbation Theory.Comment: 6 pages, 6 figure
Shower development of particles with momenta from 15 GeV to 150 GeV in the CALICE scintillator-tungsten hadronic calorimeter
We present a study of showers initiated by electrons, pions, kaons, and
protons with momenta from 15 GeV to 150 GeV in the highly granular CALICE
scintillator-tungsten analogue hadronic calorimeter. The data were recorded at
the CERN Super Proton Synchrotron in 2011. The analysis includes measurements
of the calorimeter response to each particle type as well as measurements of
the energy resolution and studies of the longitudinal and radial shower
development for selected particles. The results are compared to Geant4
simulations (version 9.6.p02). In the study of the energy resolution we include
previously published data with beam momenta from 1 GeV to 10 GeV recorded at
the CERN Proton Synchrotron in 2010.Comment: 35 pages, 21 figures, 8 table
Infrastructure for Detector Research and Development towards the International Linear Collider
The EUDET-project was launched to create an infrastructure for developing and
testing new and advanced detector technologies to be used at a future linear
collider. The aim was to make possible experimentation and analysis of data for
institutes, which otherwise could not be realized due to lack of resources. The
infrastructure comprised an analysis and software network, and instrumentation
infrastructures for tracking detectors as well as for calorimetry.Comment: 54 pages, 48 picture
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