| 1. |
- Aziz, Emad F., et al.
(författare)
-
Cation-specific interactions with carboxylate in amino acid and acetate aqueous solutions : X-ray absorption and ab initio calculations
- 2008
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 112:40, s. 12567-12570
-
Tidskriftsartikel (refereegranskat)abstract
- Relative interaction strengths between cations (X = Li+, Na+, K+, NH4+) and anionic carboxylate groups of acetate and glycine in aqueous solution are determined. These model systems mimic ion pairing of biologically relevant cations with negatively charged groups at protein surfaces. With oxygen ls X-ray absorption spectroscopy, we can distinguish between spectral contributions from H2O and carboxylate, which allows us to probe the electronic structure changes of the atomic site of the carboxylate group being closest to the countercation. From the intensity variations of the COOaq- ls X-ray absorption peak, which quantitatively correlate with the change in the local partial density of states from the carboxylic site, interactions are found to decrease in the sequence Na+ > Li+ > K+ > NH4+. This ordering, as well as the observed bidental nature of the -COOaq- and X-aq(+) interaction, is supported by combined ab initio and molecular dynamics calculations.
|
|
| 2. |
- Aziz, Emad F., et al.
(författare)
-
Interaction between liquid water and hydroxide revealed by core-hole de-excitation
- 2008
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 455:7209, s. 89-91
-
Tidskriftsartikel (refereegranskat)abstract
- The hydroxide ion plays an important role in many chemical and biochemical processes in aqueous solution(1). But ourmolecular- level understanding of its unusual and fast transport in water, and of the solvation patterns that allow fast transport, is far from complete. One proposal seeks to explain the properties and behaviour of the hydroxide ion by essentially regarding it as a water molecule that is missing a proton(2), and by inferring transport mechanisms and hydration structures from those of the excess proton. A competing proposal invokes instead unique and interchanging hydroxide hydration complexes, particularly the hypercoordinated OH-(H2O)(4) species and tri- coordinated OH-(H2O)(3) that can form a transient hydrogen bond between the H atom of the OH- and a neighbouring water molecule(3-5). Here we report measurements of core- level photoelectron emission and intermolecular Coulombic decay(6-8) for an aqueous hydroxide solution, which show that the hydrated hydroxide ion is capable of transiently donating a hydrogen bond to surrounding watermolecules. In agreement with recent experimental studies of hydroxide solutions(9-12), our finding thus supports the notion that the hydration structure of the hydroxide ion cannot be inferred from that of the hydrated excess proton.
|
|
| 3. |
- Aziz, Emad F, et al.
(författare)
-
Probing the electronic structure of the hemoglobin active center in physiological solutions.
- 2009
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:6, s. 068103-
-
Tidskriftsartikel (refereegranskat)abstract
- Soft-x-ray absorption spectroscopy at the L_{2,3} edge of the iron center in bovine hemoglobin and hemin under physiological conditions is reported for the first time. Spectra of the same compounds in solid form are presented for comparison. Striking differences in the electronic structure of the metalloporphyrin are observed between the liquid and solid compounds. We unambiguously show that hemoglobin and hemin are in a high-spin ferric state in solution, and that the 2p spin-orbit coupling decreases for hemin compared to the hemoglobin, while this is not the case in solids. The spectra were simulated using ligand field multiplet theory, in good agreement with the experiment, allowing quantification of the amount of charge transfer between the porphyrin and Fe3+ ion in hemoglobin and in hemin.
|
|
| 4. |
- Barendregt, Wolmet, et al.
(författare)
-
Lessons from the Evaluation of Game for Developing Number Sense
- 2013
-
Ingår i: Chi 2013 Workshop.
-
Konferensbidrag (refereegranskat)abstract
- In this paper we describe the methodological lessons that we learned from the evaluation of Fingu, an iPad game to help children between 4 and 7 years old to develop number sense through use of their fingers. We pay attention to the recruitment of the teachers and children, the selection of the measurement instruments, the distribution of the game to the children, handling a group of testers, and controlling of the use of the game during the study.
|
|
| 5. |
- Björneholm, Olle, et al.
(författare)
-
Deeper Insight into Depth-Profiling of Aqueous Solutions Using Photoelectron Spectroscopy
- 2014
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:50, s. 29333-29339
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectroscopy (XPS) is widely used to probe properties such as molecular stoichiometry, microscopic distributions relative to the surface by so-called depth-profiling, and molecular orientation. Such studies usually rely on the core-level photoionization cross sections being independent of molecular composition. The validity of this assumption has recently been questioned, as a number of gas-phase molecules have been shown to exhibit photon-energy-dependent nonstochiometric intensity oscillations arising from EXAFS-like modulations of the photoionization cross section. We have studied this phenomenon in trichloroethanol in both gas phase and dissolved in water. The gas-phase species exhibits pronounced intensity oscillations, similar to the ones observed for other gas-phase molecules. These oscillations are also observed for the dissolved species, implying that the effect has to be taken into account when performing depth-profiling experiments of solutions and other condensed matter systems. The similarity between the intensity oscillations for gas phase and dissolved species allows us to determine the photoelectron kinetic energy of maximum surface sensitivity, approximate to 100 eV, which lies in the range of pronounced intensity oscillations.
|
|
| 6. |
|
|
| 7. |
- Enarsson, Lars-Erik, et al.
(författare)
-
Tailoring the chemistry of polyelectrolytes to control their adsorption on cellulosic surfaces
- 2009
-
Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 340:1-3, s. 135-142
-
Tidskriftsartikel (refereegranskat)abstract
- The adsorption of two types of cationic polyacrylamides in the presence of a background electrolyte was studied on substrates including silicon oxide, kraft pulp fibres and thin films of regenerated cellulose. One of the polyelectrolytes was a conventional cationic polyacrylamide (MeCPAM) and the other was a benzyl-containing derivative of cationic polyacrylamide (BzCPAM). It was found that the aromatic substituents of BzCPAM strongly enhanced the adsorption on substrates of hydrophobically modified silicon oxide when a background electrolyte was present. A similar effect was also seen in the case of BzCPAM adsorption on unbleached pulp fibres, but in this case MeCPAM also exhibited a strong adsorption at high background electrolyte concentrations. On bleached pulp fibres, BzCPAM maintained a high adsorption up to a concentration of 100 mM NaCl whereas MeCPAM adsorption showed a significant decrease at this salt concentration. On model cellulose films, the adsorption of BzCPAM was similar to that of MeCPAM and the non-ionic interactions with cellulose appeared weak, since there was no adsorption of either polyelectrolyte in 300 mM NaCl.
|
|
| 8. |
- Eriksson, Susanna K., et al.
(författare)
-
Solvent Dependence of the Electronic Structure of I- and I-3(-)
- 2014
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 118:11, s. 3164-3174
-
Tidskriftsartikel (refereegranskat)abstract
- We present synchrotron-based I4d photoelectron spectroscopy experiments of solutions from LiI and LiI3 in water, ethanol, and acetonitrile. The experimentally determined solvent-induced binding energy shifts (SIBES) for the monatomic I- anion are compared to predictions from simple Born theory, PCM calculations, as well as multiconfigurational quantum chemical spectral calculations from geometries obtained through molecular dynamics of solvated clusters. We show that the SIBES for I- explicitly depend on the details of the hydrogen bonding configurations of the solvent to the I- and that static continuum models such as the Born model cannot capture the trends in the SIBES observed both in experiments and in higher-level calculations. To extend the discussion to more complex polyatomic anions, we also performed experiments on I-3(-) and I-/I-3(-) mixtures in different solvents and the results are analyzed in the perspective of SIBES. The experimental SIBES values indicate that the solvation effects even for such similar anions as I- and I-3(-) can be rather different in nature.
|
|
| 9. |
- Granberg, Mark, et al.
(författare)
-
Do ethnicity and sex of employers affect applicants job interest? : An experimental exploration
- 2020
-
Ingår i: JOURNAL FOR LABOUR MARKET RESEARCH. - : Springer Berlin/Heidelberg. - 2510-5019 .- 2510-5027. ; 54:1
-
Tidskriftsartikel (refereegranskat)abstract
- Starting a business is one way out of unemployment for many people. Having a small pool of job applicants may, however, affect the quality of manpower available to employers. This paper reports the results of an experimental study that examined whether job-seekers discriminate against prospective employers based on those employers ethnicity and sex. We conducted an experiment with 889 university students, where we presented 10 hypothetical job vacancies in the restaurant sector to the participants. We then asked participants to state their willingness to apply to each job. The ethnicity and sex of the employers were conveyed through employers names by using typical male and female Arabic- and Swedish-sounding names. Overall, our results provided no evidence of ethnic or sex discrimination by job-seekers against employers.
|
|
| 10. |
- Josefsson, Ida, et al.
(författare)
-
Collective hydrogen-bond dynamics dictates the electronic structure of aqueous I-3(-)
- 2013
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 15:46, s. 20189-20196
-
Tidskriftsartikel (refereegranskat)abstract
- The molecular and electronic structures of aqueous I-3 and I ions have been investigated through ab initio molecular dynamics (MD) simulations and photoelectron (PE) spectroscopy of the iodine 4d core levels. Against the background of the theoretical simulations, data from our I4d PE measurements are shown to contain evidence of coupled solute-solvent dynamics. The MD simulations reveal large amplitude fluctuations in the I-I distances, which couple to the collective rearrangement of the hydrogen bonding network around the I-3(-) ion. Due to the high polarizability of the I-3(-) ion, the asymmetric I-I vibration reaches partially dissociated configurations, for which the electronic structure resembles that of I-2 + I-. The charge localization in the I-3(-) ion is found to be moderated by hydrogen-bonding. As seen in the PE spectrum, these soft molecular vibrations are important for the electronic properties of the I-3(-) ion in solution and may play an important role in its electrochemical function.
|
|
