A CNDO study of the electronic structure of oxyanions XO4n− with X = Si, P, S, Cl, Ge, As, Se and Br

Höjer, Germund; Meza-Höjer, Sara; Pedrero, Gisela Hernández de

doi:10.1016/0009-2614(76)80220-5

Cited by 30 publications

(9 citation statements)

References 25 publications

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“…For K-PO 4 samples, the P-O distances in the PO 4 tetrahedron are 1.55 and 1.53-1.54 Å, for aqueous and solid samples, respectively. The P-O distance for aqueous samples is close to the free ion bond distance of 1.56 Å for PO 4 , 37 while that of solid samples is consistent with average P-O distances based on crystal structure data as reported in the literature. 23,[26][27][28] This alludes to some relaxation of the structure in solution.…”

Section: Exafs the Experimental Ksupporting

confidence: 88%

X-ray Absorption Fine Structure Study of the Effect of Protonation on Disorder and Multiple Scattering in Phosphate Solutions and Solids

et al. 2009

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Phosphorus K-edge X-ray absorption fine structure (XAFS) was explored as a means to distinguish between aqueous and solid phosphates and to detect changes in phosphate protonation state. Data were collected for H 3 PO 4 , KH 2 PO 4 , K 2 HPO 4 and K 3 PO 4 solids and solutions and for the more complex phosphates, hydroxylapatite (HAP) and struvite (MAP). The X-ray absorption near-edge structure (XANES) spectra for solid samples are distinguishable from those of solutions by a shoulder at ∼4.5 eV above the edge, caused by scattering from cation sites. For phosphate species, the intensity of the white line peak increased for solid and decreased for aqueous samples, respectively, with phosphate deprotonation. This was assigned to increasing charge delocalization in solid samples, and the effect of solvating water molecules on charge for aqueous samples. In the extended X-ray absorption fine structure (EXAFS), backscattering from first-shell O atoms dominated the (k) spectra. Multiple scattering (MS) via a four-legged P-O 1 -P-O 1 -P collinear path was localized in the lower k region at ∼3.5 Å -1 and contributed significantly to the beat pattern of the first oscillation. For EXAFS analysis, increasing Debye-Waller factors suggest more disorder in the P-O shell with addition of protons to the crystal structure due to the lengthening effects of P-OH bonds. This disorder produces splitting in the hybridized P 3p-O 2p band in the density of states. For aqueous samples, however, increased protonation reduced the structural disorder within this shell. This was linked to a change from kosmotropic to chaotropic behavior of the phosphate species, with reduced effects of H bonding on structural distortion. The intensity of MS is correlated to the degree of disorder in the P-O shell, with more ordered structures exhibiting enhanced MS. The observed trends in the XAFS data can be used to distinguish between phosphate species in both solid and aqueous samples. This is applicable to many chemical, geochemical and biological systems, and may be an important tool for determining the behavior of phosphate during the hydrothermal gasification of biomass.

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Section: Exafs the Experimental Ksupporting

confidence: 88%

X-ray Absorption Fine Structure Study of the Effect of Protonation on Disorder and Multiple Scattering in Phosphate Solutions and Solids

et al. 2009

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“…31 Considering the dipole selection rule, peak A is due to the excitation from P 1s into P 3p-derived orbitals ͑t 2 * ͒ and the higher-energy peak B is originating from shape resonance into the orbitals with d character. 32 The x-ray absorption spectrum for InP͑100͒ is the same as the reported one. 33 The spectrum was interpreted by full multiple scattering calculations.…”

Section: Resultsmentioning

confidence: 94%

Localization of electrons in the sugar/phosphate backbone in DNA investigated via resonant Auger decay spectra

et al. 2006

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In order to elucidate the localized nature of electrons in sugar/phosphate backbone in DNA molecules, resonant Auger decay spectra excited by soft x-rays around the inner-shell ionization thresholds have been measured for single-strand DNA. The systems investigated are thin films of DNA as well as related phosphorus compounds such as nucleotide ͑adenosine triphosphate, ATP͒, sodium phosphate, and indium phosphide. For ATP and DNA, it was observed that the resonant excitations from P 1s to valence unoccupied * orbitals are followed by spectator-type Auger decays where the excited electrons remain in valence orbitals during the core-hole decays. It was also found that the energy of the P KL 2,3 L 2,3 ͑2p −1 · * ͒ spectator Auger peak shifts linearly with the photon energy due to the resonant Auger Raman scattering. Most of the decay channel at the core-to-valence resonant excitation is spectator-type Auger decay in DNA, which is quite different from the Auger decay processes in metallic and semiconducting materials. We conclude that the excited electrons in valence unoccupied states around the phosphates in DNA molecules are strongly localized, resulting in the insulating properties in a one-dimensional direction along sugar/phosphate backbone.

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“…After Rajkumari Amrit Kaur had resigned as minister of health in 1957, Höjer wrote: "the Indian association of family planning could continue its work along more secure lines". 118 This was just about the time when contraceptive sterilizations began to be performed in some parts of India. Does this mean that Wahlund personally endorsed or promoted sterilizations?…”

Section: Ideals Of Self-disciplinementioning

confidence: 99%

“…85 In her book Travancore -välsignat land (Travancore -blessed country), published in 1955 and addressed to a Swedish audience, Signe Höjer underlined that her project could not have been implemented without financial support from Swedish women's groups. 86 Rather than overemphasizing her own role in the process, she noted at her departure that "education in birth control has miraculously transformed into a matter of course". At that time, the first municipal agency had been opened, and the local government had asked the family planning association to draw up a plan for the whole state.…”

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confidence: 98%

“…At that time, the first municipal agency had been opened, and the local government had asked the family planning association to draw up a plan for the whole state. 87 Under the socialist government of 1954-1955, ten staterun birth-control clinics were opened in Travancore-Cochin. 88 Soon, a network of child healthcare centers that had received initial help from Axel Höjer was also integrated into the operations, with assistance from some of the educators who had been trained in Signe Höjer's courses.…”

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A Suitable Country: The Relationship between Sweden's Interwar Population Policy and Family Planning in Postindependence India

Berg¹

2010

Ber Wissenschaftsgesch

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This article delineates a strong continuity, particularly in terms of personnel, between interwar domestic population policies and Sweden's postwar participation in international and transnational population-control programs. It argues that Swedish engagement in population control and family planning in the emerging Third World, and particularly in South Asia, was motivated by the conviction that poverty and underdevelopment must be attacked on several fronts simultaneously, with population control being one of the most important. In its first bilateral aid programs Sweden would prioritize the promotion of birth control primarily because it was still too controversial to be promoted multilaterally, not least for religious reasons; and because Swedish experts were regarded as especially liberal, rational, and secularized. Sterilization expertise played no decisive part in this continuity. When first establishing themselves in South Asia, Swedish experts would recommend the rhythm method and other contraceptive methods that depended on self-control.

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A CNDO study of the electronic structure of oxyanions XO4n− with X = Si, P, S, Cl, Ge, As, Se and Br

Cited by 30 publications

References 25 publications

X-ray Absorption Fine Structure Study of the Effect of Protonation on Disorder and Multiple Scattering in Phosphate Solutions and Solids

X-ray Absorption Fine Structure Study of the Effect of Protonation on Disorder and Multiple Scattering in Phosphate Solutions and Solids

Localization of electrons in the sugar/phosphate backbone in DNA investigated via resonant Auger decay spectra

A Suitable Country: The Relationship between Sweden's Interwar Population Policy and Family Planning in Postindependence India

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