Search PubMed⌕ Search

Biomedical subjects

A Augustsson

Publications and source records attributed to A Augustsson.

16 recordsLinked to original sources
PubMed2006

Electron correlation and charge transfer in superconducting superlattices.

We use x-ray spectroscopy to examine the electronic structure of high-temperature superconducting superlattices [(Ba0.9Nd0.10)CuO(2 + delta)]2/[CaCuO2]2. The O 2p density of states reveals the insulating character of the individual component layers and the metallic character of the superlattices. We report the first direct observation of Zhang-Rice singlets in artificial high-temperature superconducting heteroepitaxial structures. The experimental findings in the superlattices and its component layers offer evidence of charge transport from the so-called charge reservoir layer to the superconducting infinite layer. This suggests a strong link between superconductivity and both electron correlation and charge transfer within the superlattices.

Journal Article↗
PubMed2005

Electronic structure of phospho-olivines Li(x)FePO4 (x = 0, 1) from soft-x-ray-absorption and -emission spectroscopies.

The electronic structure of the phospho-olivine Li(x)FePO4 was studied using soft-x-ray-absorption (XAS) and emission spectroscopies. Characteristic changes in the valence and conduction bands are observed upon delithation of LiFePO4 into FePO4. In LiFePO4, the Fe-3d states are localized with little overlap with the O-2p states. Delithiation of LiFePO4 gives stronger hybridization between Fe-3d states and O-2p states leading to delocalization of the O-2p states. The Fe L-edge absorption spectra yield "fingerprints" of the different valence states of Fe in LiFePO4 and FePO4. Resonant soft-x-ray-emission spectroscopy at the Fe L edge shows strong contributions from resonant inelastic soft x-ray scattering (RIXS), which is described using an ionic picture of the Fe-3d states. Together the Fe L-edge XAS and RIXS study reveals a bonding character of the Fe 3d-O2p orbitals in FePO4 in contrast to a nonbonding character in LiFePO4.

Journal Article↗
PubMed2005

Conformation dependence of electronic structures of poly(ethylene oxide).

The electronic structure of pure poly(ethylene oxide) (PEO) for four different polymeric chain conformations has been studied by Hartree-Fock (HF) and density functional theory (DFT) through the analysis of their valence band photoelectron spectroscopy (VB-PES), X-ray emission spectroscopy (XES), and resonant inelastic X-ray scattering (RIXS). It is shown that the valence band of PEO presents specific conformation dependence, which can be used as a fingerprint of the polymeric structures. The calculated spectra have been compared with experimental results for PEO powder.

Electrochemistry↗
PubMed2003

Molecular structure of alcohol-water mixtures.

We use x-ray emission spectroscopy to elucidate the molecular structure of liquid methanol, water, and methanol-water solutions. We find that molecules in the pure liquid methanol predominantly persist as hydrogen-bonded chains and rings with six and/or eight molecules of equal abundance. For water-methanol solutions we find evidence of incomplete mixing at the microscopic level. Our results provide a new explanation for a smaller entropy increase in the solution due to water molecules bridging methanol chains to form rings.

Journal Article↗
PubMed2002

X-ray emission spectroscopy of hydrogen bonding and electronic structure of liquid water.

We use x-ray emission spectroscopy to examine the influence of the intermolecular interaction on the local electronic structure of liquid water. By comparing x-ray emission spectra of the water molecule and liquid water, we find a strong involvement of the a(1)-symmetry valence-orbital in the hydrogen bonding. The local electronic structure of water molecules, where one hydrogen bond is broken at the hydrogen site, is separately determined. Our results provide an illustration of the important potential of x-ray emission spectroscopy for elucidating basic features of liquids.

Journal Article↗
PubMed2000

Atopic dermatitis and melanocytic naevi.

A study was performed to test the clinical impression that adults with severe atopic dermatitis (AD) have a low number of common naevi (CN). The number of CN > or = 2 mm was investigated in 51 Caucasian patients aged 20-63 years with severe AD since early childhood. The control group consisted of 379 randomly selected subjects, aged 30-50 years, investigated in an earlier study. Patients with AD had a significantly (P < 0.0001) lower total body count of CN (mean 9, median 5) compared with the control group (mean 67, median 53). It was also found that in the AD group there was a significant (P < 0.001) negative correlation between serum IgE and number of CN [r(s) = -0.50, 95% CI (-0.69; -0.24)]. The explanation for the low number of naevi that we have found in this highly selected subgroup of AD patients is not known. The atopic inflammation in the skin, genetics and treatment used for eczema are possible factors that may influence the formation of melanocytic naevi.

Adult↗
PubMed1992

Regional distribution of melanocytic naevi in relation to sun exposure, and site-specific counts predicting total number of naevi.

The role of exposure to ultraviolet light in the formation of melanocytic naevi was analysed by investigating the regional naevus distribution in 310 subjects (30-50 years) from a Swedish census file. The lateral aspect of the arms and the back had the largest concentration of naevi. The mean naevus count per unit surface area was higher in intermittently exposed than in rarely exposed skin (p less than 0.001), while the lowest mean count was found in chronically exposed skin. These results support the idea that intermittent exposure to ultraviolet light has a "naevogenic" effect while chronic exposure might be protective. Dysplastic naevi had a distribution pattern quite different from common naevi. Considering the distribution pattern solely, dysplastic naevi seem to develop independently of exposure to ultraviolet light. The numbers of naevi in different skin areas were tested for their power in predicting the total body naevus count. The strongest correlations were found between total counts and counts on the anterior surface of the thighs and the lateral aspect of the arms. Counts from any of these areas will provide a practical and satisfactory estimate of the total number of naevi.

Adult↗
PubMed1991

Prevalence of common and dysplastic naevi in a Swedish population.

The naevus profile was examined in a Swedish population that was randomly selected from a census file. The participation rate was considered high at 82%. The number of common naevi (CN) and the prevalence of dysplastic naevi (DN) were investigated in 379 subjects (aged 30-50 years). The mean total body count of CN greater than or equal to 2 mm was 67 (range 1-300). As many as 22% of the population had 100 naevi or more and only 18% had less than 25. The counts were not influenced by age or sex. DN were diagnosed clinically in 18% (CI 14-22%) of the subjects and histologically in 8% (CI 5-11%). Subjects with dysplastic naevi had a significantly larger number of common naevi and a more sun-sensitive skin type than subjects without DN, P less than 0.001.

Adult↗
PubMed1991

Melanocytic naevi in sun-exposed and protected skin in melanoma patients and controls.

The possible link between exposure to ultraviolet light and naevus development was studied in 121 melanoma patients and 310 controls by comparing the number of naevi in a sun-exposed area on the back with that in a sun-protected area on the buttocks. Both patients and controls had a four-fold increase in the number of naevi in the exposed compared with the protected area, p less than 0.001. The difference in naevus count between the exposed and the protected area was larger in patients than in controls, p less than 0.001. Subjects with dysplastic naevi, melanoma patients as well as controls, had a larger difference in the number of naevi between the two areas than subjects without dysplastic naevi, p less than 0.001. These results support the idea that sunlight plays an important role in naevus development and may explain why a high naevus count is a risk marker for malignant melanoma.

Adult↗
PubMed1991

Common and dysplastic naevi as risk factors for cutaneous malignant melanoma in a Swedish population.

Common naevi, dysplastic naevi (DN) and other phenotypic features were evaluated as melanoma risk factors in a Swedish case-control study. One-hundred and twenty-one prevalent melanoma cases and 378 randomly selected controls participated. The mean total body naevus count was 115 in the cases and 67 in the controls. Fifty-six per cent of the cases and 18% of the controls had clinical DN. The corresponding figures for histologically diagnosed DN were 40% and 8% respectively. Clinical DN was as good as histologically diagnosed DN in identifying individuals at risk for melanoma. Subjects with sun-sensitive skin, greater than or equal to 150 naevi and presence of DN have 50 times higher melanoma risk than those without these characteristics.

Adult↗
PubMed1991

Melanocytic naevi, melanoma and sun exposure.

The naevus profile was examined in 379 randomly selected Swedes (30-50 years) and in 121 melanoma patients in the same age-range selected from the Regional Cancer Register. The total body count of common naevi (CN) greater than or equal to 2 mm in the population was high (mean 67, range 1-300). Even so, the melanoma patients had almost twice as many CN as the controls (mean 113, range 13-347). The prevalence of clinical dysplastic naevi (DN) was 18% in the population and 56% in the patients. The corresponding figures for histologically diagnosed DN were 8% and 40% respectively. Subjects with dysplastic naevi had a significantly larger number of CN than those without DN. Subjects with a sun-sensitive skin, greater than or equal to 150 naevi and presence of DN had a 50 times higher melanoma risk than those without these characteristics. For identifying subjects at risk of developing cutaneous malignant melanoma (CMM), clinically diagnosed DN was as good a discriminator as histologically diagnosed DN. The numbers of naevi in different skin areas were tested for their power in predicting the total body naevus count. The strongest correlations were found between total counts and counts on the anterior surface of the thighs and the lateral aspect of the arms. Counts from either of these areas will provide a practical and satisfactory estimate of the total number of naevi. To study the possible link between sun exposure, naevus formation and melanoma development, the distribution of CN, DN and CMM over the body surface was studied in the 121 melanoma patients and in 310 consecutive controls. The number of naevi was four times as high in a sun-exposed area on the lower back compared with in an adjacent sun-protected area on the buttocks, indicating that sunlight plays a role in naevus development. Both CN and CMM were found to have a general distribution pattern over the body surface consistent with the idea that sun exposure is important for their formation. The number of CN and CMM per unit body surface area was significantly higher in intermittently sun-exposed than in rarely or chronically exposed skin. The distribution pattern of DN was quite different from that of CN, with few DN on the sun-exposed upper chest and face and many DN in protected areas such as the buttocks and lower abdomen, indicating that DN may develop independently of sun exposure.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

UVB irradiation induces melanocyte increase in both exposed and shielded human skin.

This study demonstrates for the first time in humans that UV light induces an increase of the melanocyte population in exposed skin as well as in shielded areas. Because an increased mitotic activity could promote tumor development, UV exposure might play a role in melanoma development not only in exposed but also in covered skin. In addition, it was found that subjects who initially had a small melanocyte population showed a larger increase in both exposed and covered skin compared to those with a high initial density. Individuals with a low density might therefore constitute a risk group for the development of malignant melanoma. These findings support the view that infrequent periods of intensive UV irradiation might be more harmful than regular exposure.

Adult↗
PubMed1988

Urinary excretion of 5-S-cysteinyldopa in relation to skin type, UVB-induced erythema, and melanocyte proliferation in human skin.

5-S-Cysteinyldopa (5-S-CD) is found in all pigment-producing cells and is the major precursor of phaeomelanin. However, the melanocyte specificity of the compound has been questioned. In order to elucidate the origin of 5-S-CD, we have now systematically studied the relationship between the 5-S-CD excretion in urine and the size of the melanocyte organ, UV-induced melanocyte proliferation, skin type, and the erythemal reaction. The skin type had no influence on the basal excretion of 5-S-CD. There was no significant correlation between the basal 5-S-CD excretion and the size of the melanocyte organ; that is, the number of skin melanocytes and nevi. During the irradiation, subjects with skin type II developed a more pronounced erythema (p less than 0.01) and had a significantly higher 5-S-CD excretion than those with skin type III-IV (p less than 0.01). No correlation was found between 5-S-CD excretion and UV-induced melanocyte proliferation. The lack of correlation between the basal 5-S-CD excretion and skin type or number of melanocytes suggests that the basal 5-S-CD in urine is mainly of extra-melanocytic origin. Our findings favor the view that the increase in 5-S-CD excretion during UV irradiation is due to UV damage.

Adult↗
PubMed1988

UVB-induced melanocyte proliferation and 5-S-cysteinyldopa excretion in dysplastic nevus syndrome.

This is the first in vivo study of the effects of UV on the epidermal melanocytes in dysplastic nevus syndrome (DNS). Eleven DNS patients and 22 healthy subjects were given total body UVB irradiation 8 times during 17 days and the melanocyte population was estimated in biopsies from shielded and irradiated skin. There was a doubling of the melanocyte counts in irradiated skin and a less pronounced but significant increase in the shielded skin area. The urinary excretion of 5-S-cysteinyldopa (5-S-CD) was measured before, during and after the irradiation period. The 5-S-CD excretion reached a maximum after 2 weeks of irradiation and returned towards the basal value after the irradiation period. We were not able to document any abnormal melanocytic UV response in DNS patients before, during or after the irradiation.

Adult↗
PubMedDate not supplied

Regional distribution of common and dysplastic naevi in relation to melanoma site and sun exposure. A case-control study.

The frequency of melanoma (CMM), and of common and dysplastic naevi (CN and DN) in areas of skin chronically, intermittently and rarely exposed to UV light was investigated in 121 melanoma patients (30-50 years) and 310 controls. Both cases and controls had significantly more CN in intermittently exposed areas than in areas chronically or rarely exposed. The ratio of observed to expected number of CMM was also highest in intermittently exposed skin (1.3 compared to 0.8 in chronically exposed and 0.5 in rarely exposed areas). Thus, intermittent UV exposure seems to have the most potent 'naevogenic' as well as carcinogenic effect on melanocytes. Nineteen per cent of controls and 56% of cases had naevi fulfilling the clinical criteria for DN. The distribution pattern of DN was clearly different from that of CN and does not accord with the idea that UV light is a major aetiological factor for DN. The probability of CMM significantly increased with the degree of relative clustering of CN (p less than 0.05) and of DN (p less than 0.01). This co-variation of naevi and CMM over the body surface might be the result of the local insults to the melanocyte system caused by UV light and/or to the fact that naevi are precursor lesions of CMM.

Adult↗