23 resultados para BeO


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Some atomic multipoles (charges, dipoles and quadrupoles) from the Quantum Theory of Atoms in Molecules (QTAIM) and CHELPG charges are used to investigate interactions between a proton and a molecule (F2, Cl2, BF, AlF, BeO, MgO, LiH, H2CO, NH3, PH3, BF3, and CO2). Calculations were done at the B3LYP/6-311G(3d,3p) level. The main aspect of this work is the investigation of polarization effects over electrostatic potentials and atomic multipoles along a medium to long range of interaction distances. Large electronic charge fluxes and polarization changes are induced by a proton mainly when this positive particle approaches the least electronegative atom of diatomic heteronuclear molecules. The search for simple equations to describe polarization on electrostatic potentials from QTAIM quantities resulted in linear relations with r-4 (r is the interaction distance) for many cases. Moreover, the contribution from atomic dipoles to these potentials is usually the most affected contribution by polarization what reinforces the need for these dipoles to a minimal description of purely electrostatic interactions. Finally, CHELPG charges provide a description of polarization effects on electrostatic potentials that is in disagreement with physical arguments for certain of these molecules. (c) 2012 Wiley Periodicals, Inc.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Flory-Huggins interaction parameters and thermal diffusion coefficients were measured for aqueous biopolymer solutions. Dextran (a water soluble polysaccharide) and bovine serum albumin (BSA, a water soluble protein) were used for this study. The former polymer is representative for chain macromolecules and the latter is for globular macromolecules. The interaction parameters for the systems water/dextran and water/BSA were determined as a function of composition by means of vapor pressure measurements, using a combination of headspace sampling and gas chromatography (HS-GC). A new theoretical approach, accounting for chain connectivity and conformational variability, describes the observed dependencies quantitatively for the system water/dextran and qualitatively for the system water/BSA. The phase diagrams of the ternary systems water/methanol/dextran and water/dextran/BSA were determined via cloud point measurements and modeled by means of the direct minimization of the Gibbs energy using the information on the binary subsystems as input parameters. The thermal diffusion of dextran was studied for aqueous solutions in the temperature range 15 < T < 55 oC. The effects of the addition of urea were also studied. In the absence of urea, the Soret coefficient ST changes its sign as T is varied; it is positive for T > 45.0 oC, but negative for T < 45.0 oC. The positive sign of ST means that the dextran molecules migrate towards the cold side of the fluid; this behavior is typical for polymer solutions. While a negative sign indicates the macromolecules move toward the hot side; this behavior has so far not been observed with any other binary aqueous polymer solutions. The addition of urea to the aqueous solution of dextran increases ST and reduces the inversion temperature. For 2 M urea, the change in the sign of ST is observed at T = 29.7 oC. At higher temperature ST is always positive in the studied temperature range. To rationalize these observations it is assumed that the addition of urea opens hydrogen bonds, similar to that induced by an increase in temperature. For a future extension of the thermodynamic studies to the effects of poly-dispersity, dextran was fractionated by means of a recently developed technique called Continuous Spin Fractionation (CSF). The solvent/precipitant/polymer system used for the thermodynamic studies served as the basis for the fractionation of dextran The starting polymer had a weight average molar mass Mw = 11.1 kg/mol and a molecular non-uniformity U= Mw / Mn -1= 1.0. Seventy grams of dextran were fractionated using water as the solvent and methanol as the precipitant. Five fractionation steps yielded four samples with Mw values between 4.36 and 18.2 kg/mol and U values ranging from 0.28 to 0.48.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Electron and ion microprobe data on two samples of welshite from the type locality of Langban, Sweden, gave analytical totals of 99.38-99.57 wt.% and BeO contents of 4.82-5.11 wt.%, corresponding to 1.692-1.773 Be/20 O. Mossbauer and optical spectra of one of these samples gave Fe-[iv](3+)/Sigma Fe = 0.91, Fe-[iv](2+)/Sigma Fe = 0.09, and no evidence of Mn3+. The resulting formula for this sample is Ca2Mg3.8Mn0.62+Fe0.12+Sb1.55+O2[Si2.8Be1.7Fe0.653+Al0.7As0.17O18], and that for the second sample, Ca2Mg3.8Mn0.12+Fe0.12+F0.83+Sb1.25+O2[Si2.8Be1.8F0.653+Al0.25As0.25O18], is related by the substitution involving tetrahedral and octahedral sites: 0.59([vi,iv])(Fe,Al)(3+) approximate to 0.42([vi])(Mg,Mn,Fe)(2+) + 0.21(Sb-[vi],As-[iv])(5+), i.e. 3([vi,iv]) M3+ = 2([vi])M(2+) + M-[vi,iv](5+). WelShite is distinctive among aenigmatite-group minerals in the high proportion of Fe 3+ in tetrahedral coordination and is unique in its Be content, substantially exceeding 1Be per formula unit. Given the cation distributions in other minerals related to aenigmatite, we think it is reasonable to assume that at least one tetrahedral site is >50% occupied by Be and that one octahedral site is >50% occupied by Sb, so that welshite should be retained as a distinct species with its own name in the aenigmatite group.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Electron and ion microprobe data on two samples of welshite from the type locality of Langban, Sweden, gave analytical totals of 99.38-99.57 wt.% and BeO contents of 4.82-5.11 wt.%, corresponding to 1.692-1.773 Be/20 O. Mossbauer and optical spectra of on

Relevância:

10.00% 10.00%

Publicador:

Resumo:

No more published?

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Acknowledgements We thank Brian Roberts and Mike Harris for responding to our questions regarding their paper; Zoltan Dienes for advice on Bayes factors; Denise Fischer, Melanie Römer, Ioana Stanciu, Aleksandra Romanczuk, Stefano Uccelli, Nuria Martos Sánchez, and Rosa María Beño Ruiz de la Sierra for help collecting data; Eva Viviani for managing data collection in Parma. We thank Maurizio Gentilucci for letting us use his lab, and the Centro Intradipartimentale Mente e Cervello (CIMeC), University of Trento, and especially Francesco Pavani for lending us his motion tracking equipment. We thank Rachel Foster for proofreading. KKK was supported by a Ph.D. scholarship as part of a grant to VHF within the International Graduate Research Training Group on Cross-Modal Interaction in Natural and Artificial Cognitive Systems (CINACS; DFG IKG-1247) and TS by a grant (DFG – SCHE 735/3-1); both from the German Research Council.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Ceann de phrionsabail bhunaidh An Ghúim téacsleabhair agus leabhair ghinearálta a sholáthar do dhaltaí scoile is do lucht léitheoireachta na Gaeilge. Ábhair a bhaineann le curaclam na scoile, cuir i gcás, eolaíocht is tíos, oideachas, saoránaíocht, spórt, na teangacha Clasaiceacha, tíreolaíocht, taisteal agus an nádúr, creideamh is stair, a roghnaítear don taighde seo. Tugtar Aguisín (921 lch) le bheith ina threoir do phríomh-bhunachar sonraí na dochtúireachta seo (an chiall ghinearálta mar bhailiúchán eolais atá i gceist le “bunachar” sa tráchtas seo in ionad brí theicniúil ar leith). Trí phríomhchuid atá sa staidéar: “buneolas”, “anailís” is “toradh”. Sa “Bhuneolas”, tugtar cuntas beathaisnéiseach ar na bunúdair, soláthraítear achoimre ar na foilseacháin faoi staidéar, mar aon le faisnéis bhibleagrafaíochta i dtaobh na n- aistritheoirí, agus eolas faoi na comhlachtaí foilsitheoireachta a bhí páirteach sna tograí. Pléann “Anailís” brainsí de chuid an státchórais mar an Roinn Oideachais agus an Roinn Airgeadais i gcúrsaí maoinithe, nó gníomhairí lasmuigh de, cosúil le lucht deartha is clóchuradóireachta; moladh is coimisiúnú na saothar; sonraí cóipchirt na bhfoilseachán; roghnú, monatóireacht is díolaíocht na n-aistritheoirí, mar aon le breithniú inmheánach is seachtrach. Sa chuid dheireanach, féachtar le “Toradh” na hiarrachta a mheas, ag tagairt den líon cóipeanna de na leabhair a díoladh. Faightear eolas ar fhiosrú léitheoirí; praghas na leabhar; a ndíolachán is a n- athchló. Tugtar léirmheasanna a scríobhadh ar na haistriúcháin Ghaeilge agus na cúiseanna nár tháinig tograí ar leith chun críche. Is é aidhm na hoibre thar aon ní eile gné lárnach chasta d’eisint An Ghúim atá ligthe i ndíchuimhne a thabhairt ar ais chugainn go beo beathaíoch faoi mar a bhí lena ré saoil féin.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Introduction: Alterations in the musculoskeletal system, especially in the lower limbs, limit physical activity and affect balance and walking. Postural impairments in haemophilic preteens could increase the risk of bleeding events and deteriorate the physical condition, promoting the progression of haemophilic arthropathy. Aim: This study aims to evaluate static postural balance in haemophilic children, assessed by means of the Wii Balance Board® (WBB). Methods: Nineteen children with haemophilia and 19 without haemophilia aged 9-10 years, have participated in this study. Postural balance was assessed by performing four tests, each one lasting 15 s: bipodal eyes open (BEO), bipodal eyes closed (BEC), monopodal dominant leg (MD) and monopodal non-dominant leg (MND). Two balance indices, standard deviation of amplitude (SDA) and standard deviation of velocity (SDV) were calculated in the anterior-posterior (AP) and medial-lateral (ML) directions. Results: Index values were higher in haemophilic group and the differences were statistically significant (P < 0.05) in only six (SDAAP in BEO, BEC and MD conditions, SDAML in BEO, SDVAP in BEO and SDVML in MND condition) of 16 parameters analysed. Conclusion: Tests performed indicate a poorer static postural balance in the haemophilic cohort compared to the control group. Accordingly, physiotherapy programmes, physical activity and sports should be designed to improve the postural balance with the aim of preventing joint deterioration and improving quality of life. © 2016 John Wiley & Sons Ltd.