Reversible exchange bias in epitaxial V2O3/Ni hybrid magnetic heterostructures.

In this work we present a temperature and angular dependent study of the structural and magnetic properties in highly crystalline V2O3/Ni/Zr magnetic heterostructure films. Our investigation focuses on the coupling between the ferromagnetic Ni layer and V2O3layer which undergoes an antiferromagnetic/paramagnetic phase transition coupled to the structural phase transition of the material at around 150 K. Structural investigations using x-ray diffraction reveal highly crystalline films of a quality which has previously not been reported in the literature. The Ni layers display an absence of in-plane magnetic anisotropy owing to the highly textured (1 1 1) layering of the Ni films on the underlying V2O3(0 0 0 1) oriented layer. During the transition we observe a strain related enhancement of the coercivity and the onset of a weak exchange bias for cooling under an external magnetic field. Heating the films to above the transition temperature, the exchange bias in the Ni is removed and can be reversed upon subsequent cooling under an inverted external magnetic field. Using temperature dependent polarized neutron reflectometry we investigate the film structure at the interface, capturing the magnetic and nuclear profiles.

Tuneable exchange-spring stiffness in amorphous magnetic trilayer structures.

We investigate the magnetic properties of amorphous Sm10Co90/Co60(Al70Zr30)40/Co85(Al70Zr30)15exchange-spring magnet trilayers. The magnetically soft Co85(Al70Zr30)15layer is coupled to the magnetically hard Sm10Co90layer through the weakly magnetic low-TcCo60(Al70Zr30)40spacer layer. The strength of the coupling can be controlled with temperature and the coupling persists above the intrinsicTcof the spacer layer due to a long-range magnetic proximity effect. Polarized neutron reflectivity is used to examine the magnetic profile of the trilayers during magnetization reversal. A two-step switching occurs, with the switching angle of the soft layer strongly dependent on the strength of the coupling. In the strong coupling regime a magnetic state can be achieved where the soft layer magnetization is perpendicular to the hard layer whereas in the weak coupling regime the soft layer reverses fully.

Temperature responsive lipid liquid crystal layers with embedded nanogels.

Polymer nanogels are embedded within layers consisting of a nonlamellar liquid crystalline lipid phase to act as thermoresponsive controllers of layer compactness and hydration. As the nanogels change from the swollen to the collapsed state via a temperature trigger, they enable on-demand release of water from the mixed polymer-lipid layer while the lipid matrix remains intact. Combining stimuli-responsive polymers with responsive lipid-based mesophase systems opens up new routes in biomedical applications such as functional biomaterials, bioanalysis and drug delivery.

Temperature dependence of the electrical resistivity and electronic structure of amorphous Fe100-xZrx films and multilayers.

The electrical resistivity of amorphous Fe(100-x)Zr(x) metal alloy films and multilayers has been investigated in a wide temperature and composition range. The overall behavior of the resistivity is consistent with bulk measurements, exhibiting prominent semiconductor-like changes at low temperatures. The transition from positive (metallic) to negative temperature coefficient of resistivity behavior is accompanied by minute changes in magnetoresistance and we can therefore rule out magnetic phase changes as being the cause for the observed changes in the resistivity. Using x-ray absorption and emission spectroscopies we are able to probe the unoccupied and occupied electronic densities of states. The corresponding spectra are found to significantly overlap, as expected for a metallic-like electronic structure and the absence of a band gap. Besides a broadening of the x-ray emission lines expected from an amorphous material, remarkably small differences are observed in the electronic structures when changing the amount of Zr. The resistivity data were modeled and agreement with the Mott variable range hopping model was found, indicating localized electronic states due the disordered structure of the Fe(100-x)Zr(x) alloys.

Saturated ablation in metal hydrides and acceleration of protons and deuterons to keV energies with a soft-x-ray laser.

Studies of materials under extreme conditions have relevance to a broad area of research, including planetary physics, fusion research, materials science, and structural biology with x-ray lasers. We study such extreme conditions and experimentally probe the interaction between ultrashort soft x-ray pulses and solid targets (metals and their deuterides) at the FLASH free-electron laser where power densities exceeding 10(17) W/cm(2) were reached. Time-of-flight ion spectrometry and crater analysis were used to characterize the interaction. The results show the onset of saturation in the ablation process at power densities above 10(16) W/cm(2). This effect can be linked to a transiently induced x-ray transparency in the solid by the femtosecond x-ray pulse at high power densities. The measured kinetic energies of protons and deuterons ejected from the surface reach several keV and concur with predictions from plasma-expansion models. Simulations of the interactions were performed with a nonlocal thermodynamic equilibrium code with radiation transfer. These calculations return critical depths similar to the observed crater depths and capture the transient surface transparency at higher power densities.

Iron status at 1 and 6 years versus developmental scores at 6 years in a well-nourished affluent population.

AIM: To examine the association between iron status at 1 and 6 years with development at 6 years. METHODS: In a longitudinal study of children (n = 77), iron status was measured at 1 and 6 years and the Icelandic Developmental Inventory, which evaluates children's motor and verbal development, was filled in by mothers near the children's sixth birthday. RESULTS: Children, iron-deficient at 1 year (n = 10), had lower fine motor development scores at 6 years than non-iron-deficient (n = 56) (46.7 +/- 4.1 vs. 49.3 +/- 2.0; p = 0.011). Fine motor scores were also lower in children with depleted iron stores at 1 year (n = 26) than non-iron-depleted children (n = 40) (48.0 +/- 3.3 vs. 49.5 +/- 1.8; p = 0.045). Multiple regression analyses, with iron status indices at 6 years, showed that mean corpuscular volume along with male gender predicted significantly positively for expression (adj. R(2)= 0.15; p = 0.018; n = 73), while regression analyses, including iron status at 1 and 6 years, showed that haemoglobin at 6 years was positively associated with gross motor (adj. R(2)= 0.05; p = 0.038; n = 63). CONCLUSIONS: In an affluent society, iron deficiency and depleted iron stores at 1 year may contribute to worse fine motor developmental scores at 6 years, while low mean corpuscular volume and haemoglobin at 6 years might affect subsequent expression and gross motor scores negatively.

Associations of iron status with dietary and other factors in 6-year-old children.

OBJECTIVE: To investigate the associations of iron status at 6 years of age with dietary and other factors. DESIGN: In a cross-sectional study, children's dietary intakes (3-day weighed food record) were recorded, body size was measured and blood samples were taken near their sixth birthday. SUBJECTS: A sample of 188 children, from two previous studies (cohorts 1 and 2), was contacted, and 139 (74%) agreed to participate. RESULTS: Multiple regression analyses with dietary and other factors showed that meat and fish consumption, multivitamin/mineral supplement intake (both positively) and cow's milk product consumption (negatively) were associated with log serum ferritin (SF) (adjusted R (2)=0.125; P=0.028; n=129), and juices and residence (rural>urban) with haemoglobin (Hb) (adjusted R (2)=0.085; P=0.034; n=127). Of 21 multivitamin/mineral consumers, none had depleted iron stores compared to 21 iron-depleted of 108 non-consumers (P=0.024). Children living in rural areas (<10,000 inhabitants) (n=33) had higher mean corpuscular volume (MCV) (83.3+/-2.3 fl) than those living in urban areas (>10,000 inhabitants) (82.1+/-3.2 fl; n=103) (P=0.048). Multiple regression analyses with dietary and other factors and growth showed in cohort 1 that residence (rural>urban), weight gain 0-1years (negatively), and meat and fish intake (positively) were associated with Hb (adjusted R (2)=0.323; P=0.030; n=51), meat and fish (positively) with both log SF (adjusted R (2)=0.069; P=0.035; n=52) and MCV (adjusted R (2)=0.064; P=0.035; n=52), and in cohort 2 cow's milk product consumption (negatively) was associated with log SF (adjusted R (2)=0.119; P=0.017; n=41) and residence (rural>urban) with MCV (adjusted R (2)=0.102; P=0.025; n=41). CONCLUSIONS: Consumption of meat and fish and possibly also juices, as well as multivitamin/mineral intake might affect iron status in 6-year-old children positively, whereas cow's milk product consumption might affect iron status negatively. Slower growth in the first year of life and rural residence are positively related to iron status of 6-year-olds.

Iron status in 6-y-old children: associations with growth and earlier iron status.

OBJECTIVE: To investigate the iron status of 6-y-old children and its association with growth and earlier iron status. DESIGN: In a cross-sectional study, children's body size measurements were recorded and blood samples taken near their sixth birthday. SUBJECTS: A sample of 188 children, randomly selected in two previous studies, was contacted, and 139(74%) agreed to participate. RESULTS: No children had iron deficiency anaemia, one was iron-deficient (serum ferritin (SF) <15 microg/l and mean corpuscular volume (MCV) <76 fl but 16% had depleted iron stores (SF<15 microg/l). Iron status indices were generally higher than at 1 and 2 y, but correlation was seen between iron status indices at 6 y and earlier values. Haemoglobin concentration at 6 y was negatively associated with length gain from birth to 1 y (B+/-s.e.=-1.269+/-0.452; P=0.007; adj. R2=0.119) (n=52), and proportional weight gain from birth to 1 y was higher among children with SF<15 microg/l at 6 y (295+/-33%; n=10) than those with SF> or =15 microg/l (258+/-31%; n=49) (P=0.001). MCV at 2 y predicted weight gain from 2 to 6 y (B+/-s.e.=1.721+/-0.581; P=0.005; adj. R2=0.153) (n=44); also, children with SF<15 microg/l at 6 y (n=9) gained 7.8+/-1.2 kg from 2 to 6 y, while children with SF> or =15 microg/l (n=35) gained 9.6+/-2.8 kg (P=0.007), furthermore a difference was seen in proportional weight gain from 2 to 6 y between children with depleted iron stores at 2 y and not, or 156+/-13 vs 169+/-18% (P=0.038). CONCLUSION: The results suggest that low iron status at 1 and 2 y might lead to slower growth up to 6 y of age. Low iron status at 1 and 2 y and/or slower growth from 1 and 2 y up to 6 y might contribute to worse iron status at 6 y, while faster growth in early childhood is related to lower iron status.

Iron status in 2-year-old Icelandic children and associations with dietary intake and growth.

OBJECTIVE: To investigate the effects of food and nutrient intake at 2 y and growth from birth on iron status at 2 y in a population with high birth weight. DESIGN: In a cross-sectional study, children's food consumption and body size measurements were recorded and blood samples taken. Weighed 3-day food records were used to analyse food and nutrient intake. SETTING: Children were recruited from across Iceland from the Icelandic National Registry by the University of Iceland, Computing Services. The children in the sample were born over a 1-y period. SUBJECTS: Parents of randomly selected 2-year-old children (n=130) were contacted, and 72% (n=94) participated. Blood samples were analysed in 76% (n=71) of participating children. RESULTS: In total, 9% of the children were iron-deficient (serum ferritin (SF)<12 microg/l and mean corpuscular volume (MCV) <74 fl) and 1.4% were also anaemic (Hb<105 g/l), while 27% of children were iron-depleted (SF<12 microg/l). Iron status indices were negatively associated with cow's milk consumption. Half of children consuming>500 g cow's milk/day (n=10) were iron-deficient, while one child in 58 consuming<500 g cow's milk/day had iron deficiency (P<0.001). In multiple regression analyses, also biscuits and crackers consumption was positively associated with MCV. Weight gain from birth to 2 y was negatively associated with SF (adjusted R(2)=0.15; P=0.002; n=58). Iron-depleted children were heavier than children not iron-depleted (14.7+/-1.3 vs 13.8+/-1.7 kg; P=0.043), had higher BMI (17.7+/-1.5 vs 16.7+/-1.4 kg/m(2); P=0.028) and gained more weight from birth (11.2+/-1.3 vs. 10.0+/-1.6 kg; P=0.011). CONCLUSIONS: The results suggest that cow's milk consumption above 500 g/day should be avoided at the age of 2 y for better iron status. Iron depletion at 2 y is associated with faster growth from birth.

Birth weight, growth and feeding in infancy: relation to serum lipid concentration in 12-month-old infants.

OBJECTIVE: To assess the effects of birth size, growth and feeding in infancy on serum lipids in 12-month-old infants. DESIGN: A longitudinal observation study on infants' consumption and growth. Food and growth records were made every month. At 6, 9 and 12 months, food records were weighed to calculate intake. Serum total cholesterol (TC), high-density lipoprotein-cholesterol (HDL), low-density lipoprotein (LDL) -cholesterol and triglyceride concentrations were analysed at 12 months. SETTINGS: Birth and growth information was gathered from maternity wards and healthcare centres in Iceland and food consumption data at home. SUBJECTS: Randomly selected newborns (n=180) according to the mother's domicile and 77% (n=138) participated, of them 75% (n=103), came in for blood sampling. RESULTS: Among boys, a 1 kg higher birth weight resulted in a 0.79 mmol/l higher TC (P=0.005), but nonsignificant after adjustment for growth. Duration of breastfeeding was related to LDL-cholesterol (B=0.06 +/-0.02, P=0.020, adj. R(2)=0.039), adjusting for gender. Independent of size at birth and breastfeeding, increase in length from 6 to 12 months and in weight from birth to 12 months were negatively related to TC (B=-0.455+/-0.156, P=0.008 and B=-1.086+/-0.474, P=0.032, respecitvely) in boys. PUFA was the strongest nutrient variable predicting TC (B=0.332, adj. R(2)=0.24, P>0.001). Cod liver oil consumption increased both TC and LDL-cholesterol in girls (B=0.141+/-0.051, P=0.008 and B=0.112+/-0.047, P=0.021, respectively). CONCLUSION: Slower growth of high birth weight infants and breastfeeding contributes to higher TC concentration at the age of 12 months. Nutrient intake in infancy also affects lipid profile. The effect of birth weight, growth and nutrient intake in infancy on lipid profile is different for boys and girls.

Iron status at 12 months of age -- effects of body size, growth and diet in a population with high birth weight.

OBJECTIVE: To investigate effects of growth and food intake in infancy on iron status at the age of 12 months in a population with high birth weight and high frequency of breast-feeding. DESIGN: In a longitudinal observational study infants' consumption and growth were recorded. Weighed 2 day food records at the ages of 6, 9 and 12 months were used to analyse food and nutrient intake. SETTING: Healthy-born participants were recruited from four maternity wards. Blood samples and growth data were collected from healthcare centres and food consumption data at home. SUBJECTS: Newborn infants (n=180) were selected randomly according to the mother's domicile and 77% (n=138) participated, of them, 83% (n=114), or 63% of original sample, came in for blood sampling. RESULTS: Every fifth child was iron-deficient (serum ferritin <12 microg/l and mean corpuscular volume<74 fl) and 2.7% were also anaemic (Hb<105 g/l). Higher weight gain from 0 to 12 months was seen in infants who were iron-deficient at 12 months (6.7+/-0.9 kg) than in non-iron-deficient infants (6.2+/-0.9 kg) (P=0.050). Serum transferrin receptors at 12 months were positively associated with length gain from 0 to 12 months (adjusted r(2)=0.14; P=0.045) and mean corpuscular volume negatively to ponderal index at birth (adjusted r(2)=0.14; P=0.019) and 12 months (adjusted r(2)=0.17; P=0.006). Iron-deficient infants had shorter breast-feeding duration (5.3+/-2.2 months) than non-iron-deficient (7.9+/-3.2 months; P=0.001). Iron status indices were negatively associated with cow's milk consumption at 9-12 months, significant above 460 g/day, but were positively associated with iron-fortified breakfast cereals, fish and meat consumption. CONCLUSIONS: : In a population of high birth weight, iron deficiency at 12 months is associated with faster growth and shorter breast-feeding duration from 0 to 12 months of age. The results suggest that a diet of 9-12-month-olds should avoid cow's milk above 500 g/day and include fish, meat and iron-fortified breakfast cereals to improve iron status.

Association of birth weight and breast-feeding with coronary heart disease risk factors at the age of 6 years.

BACKGROUND AND AIM: It has been shown that early growth and nutrition affect health in childhood and later life. The aim of this study was to assess the association of birth weight and breast-feeding in infancy with body mass index (BMI) and serum lipids at the age of six years. The contributions of current macronutrient intake, maternal age and BMI were assessed. METHODS AND RESULTS: This was a longitudinal observational study of 120 randomly chosen children whose birth weight and duration of breast-feeding had been recorded. At the age of six years, their weight and height, and serum cholesterol (total, LDL and HDL) and triglyceride levels were measured at healthcare centres in Iceland. Dietary intake at six years was estimated using 3-day weighed food records. The duration of breast-feeding negatively correlated with BMI in 6-year-old boys (B = -0.19 +/- 0.07, p = 0.011) but not in girls; after adjusting for maternal BMI, the relationship in boys was of borderline significance (p = 0.087). The 6-year-old boys who had been breast-fed for < 6 months had a significantly higher BMI (18.0 +/- 2.5 kg/m2) than those breast-fed for 8-9 months (15.8 +/- 1.2 kg/m2, p = 0.006) or > or = 10 months (15.7 +/- 1.2 kg/m2, p = 0.005). A longer duration of breast-feeding was related to higher HDL-cholesterol levels in 6-year-old girls (B = 0.03 +/- 0.01, p = 0.032), but not boys. Birth weight was not related to BMI or serum lipid levels at the age of 6 years. CONCLUSION: In this high birth weight population, a longer duration of breast-feeding may be effective in preventing childhood overweight, at least among boys. Breast-feeding also seems to be related to an improved lipid profile in girls.

The Icelandic genome debate.

Three of the central issues in contemporary debates about the commodification of the human body are those of property, ownership, and access. This article uses the case of the central medical database on Icelanders to discuss contesting claims about the ownership of the human genome, with respect to the rapid development of biotechnology, human genome projects and DNA collections. We emphasize the contrast between commercial and communitarian perspectives and to illustrate our argument we explore debates about the Icelandic database. These debates have been intense, focusing on a range of issues, including ethics, academic freedom, public health and, last but not least, the control and ownership of medical records, genetic information and genealogical data. This article should be seen primarily as an anthropological commentary on ongoing developments.

[Height and weight of Icelandic children 6-20 years of age.].

INTRODUCTION: Monitoring growth rate in children reflects the state of health and nutrition of the individual as well as the state of health of a nation. Until now little information has been available about the growth pattern of Icelandic children. We report here the results of a nationwide cross-sectional study of growth in Icelandic children aged 6-20 years. MATERIAL AND METHODS: Height, standing and sitting and weight were measured in a total of 6500 schoolchildren, 3173 girls and 3327 boys. The measurements were performed 1983-1987. Children were randomly selected from The National Registry according to date of birth from both urban and rural areas of the whole country of Iceland. Stature was measured by a Harpenden stadiometer and the children were weighed in underwear only using a standardized scale. RESULTS: The mean values and standard deviations for height, standing and sitting and weight are presented in tables. Growth charts for height weigt and sitting height are presented. No difference in height and weight was found between children from rural and urban areas. The results show that the growth of Icelandic children is in all age groups almost identical to the growth of Norwegian children. Compaired to other Nordic and WHO growth standards, Icelandic children are tall, especially during early pubertal development. CONCLUSIONS: Icelandic children are tall and the growth of Icelandic and Norwegian children follows the same pattern wich supports the theory that the two nations are closely related.

[Puberty in Icelandic girls.].

In a crosssectional study, 2775 healthy Icelandic girls, aged 6-16 years, were examined for physical signs of puberty. The study was performed in 1983-1987 and was a part of a larger crosssectional study of growth and development of 5526 Icelandic children all of whom were examined by the authors. Breast development stage 2 according to Tanner (B 2) was considered the first sign of puberty in girls. The mean age of Icelandic girls reaching B 2 was 10.84 years (SD 1.43). The mean time interval between B 2 and menarche was 2.42 years. The first signs of pubic hair growth, Tanner stage 2 (PH 2) were found at 11.46 years (SD 1.25). The mean time interval between PH 2 and PH 5 was 3.40 years. Comparison with studies from other countries is difficult because of different methods and different study designs, but the timing and tempo of puberty in Icelandic girls seems to be similar to what has been reported from other Nordic countries and countries in Western-Europe.

[Puberty in Icelandic boys.].

In a crosssectional study, 2751 healthy Icelandic boys aged 6-16 years, were examined for physical signs of puberty. The study was performed in 1983-1987 and was a part of a larger crosssectional growth study of 5526 Icelandic children all of whom were examined by the authors. Testicular volume of 4 ml (T 4) was considered the first sign of puberty in boys. The mean age of Icelandic boys reaching T 4 was 11.89 years (SD 1.08). The mean time interval between T 4 and T 12 was 2.21 years. The first signs of pubic hair growth, Tanner stage 2 (PH 2), were found at 12.74 years (SD 1.37). The mean time interval between PH 2 and PH 5 was 2.43 years. Even though comparison with studies from other countries is difficult because of different methods and different study design, we find that the timing and tempo of puberty in Icelandic boys is similar to what has been reported from other Nordic countries and countries in Western-Europe.

[Puberty in Icelandic boys.].

In a crosssectional study, 2751 healthy Icelandic boys aged 6-16 years, were examined for physical signs of puberty. The study was performed in 1983-1987 and was a part of a larger crosssectional growth study of 5526 Icelandic children all of whom were examined by the authors. Testicular volume of 4 ml (T 4) was considered the first sign of puberty in boys. The mean age of Icelandic boys reaching T 4 was 11.89 years (SD 1.08). The mean time interval between T 4 and T 12 was 2.21 years. The first signs of pubic hair growth, Tanner stage 2 (PH 2), were found at 12.74 years (SD 1.37). The mean time interval between PH 2 and PH 5 was 2.43 years. Even though comparison with studies from other countries is difficult because of different methods and different study design, we find that the timing and tempo of puberty in Icelandic boys is similar to what has been reported from other Nordic countries and countries in Western-Europe. Key words: puberty, growth, Icelandic boys. Correspondence: Arni V. Thorsson. E-mail: arniv@shr.is.

[Height and weight of Icelandic children 6-20 years of age.].

INTRODUCTION: Monitoring growth rate in children reflects the state of health and nutrition of the individual as well as the state of health of a nation. Until now little information has been available about the growth pattern of Icelandic children. We report here the results of a nationwide cross-sectional study of growth in Icelandic children aged 6-20 years. MATERIAL AND METHODS: Height, standing and sitting and weight were measured in a total of 6500 schoolchildren, 3173 girls and 3327 boys. The measurements were performed 1983-1987. Children were randomly selected from The National Registry according to date of birth from both urban and rural areas of the whole country of Iceland. Stature was measured by a Harpenden stadiometer and the children were weighed in underwear only using a standardized scale. RESULTS: The mean values and standard deviations for height, standing and sitting and weight are presented in tables. Growth charts for height weigt and sitting height are presented. No difference in height and weight was found between children from rural and urban areas. The results show that the growth of Icelandic children is in all age groups almost identical to the growth of Norwegian children. Compaired to other Nordic and WHO growth standards, Icelandic children are tall, especially during early pubertal development. CONCLUSIONS: Icelandic children are tall and the growth of Icelandic and Norwegian children follows the same pattern wich supports the theory that the two nations are closely related. KEYWORDS: Icelandic children, growth, height, weight. Correspondance: Atli Dagbjartsson. E-mail: atlid@rsp.is Arni V. Thorsson. E-mail: arniv@shr.is.

[Perinatal death classification in Iceland 1994-1998.].

OBJECTIVE: To analyse perinatal deaths in Iceland (>22 weeks or 500 g) over a five year period by a new Nordic classification. MATERIAL AND METHODS: Medical records for all cases of perinatal death in Iceland from 1994-1998 were analysed. A classification focussing on potential avoidability from a health service perspective was used to identify major groups and areas for improvement. The classification is based on the following variables: time of death in relation to admission and delivery, fetal malformation, gestational age, growth-retardation and Apgar score at five minutes. RESULTS: One hundred and fifty-eight perinatal deaths occurrecl. Of these 103 (65%) were stillborn babies and 55 were early neonatal deaths. The cumulative perinatal mortality rate (PNMR) was 7.3/1000 births for the period and all perinatal deaths, but using a cut-off point >28 weeks or 1000 g this was lower, 5.1/1000. Potentially avoidable groups accounted for 12% of the perinatal deaths, i.e. growthretarded singletons after >28 weeks and intrapartum deaths after >28 weeks. Almost half of the perinatal deaths (41.1%) could probably not be prevented with present methods in perinatal care. These included intrauterine deaths of non-growth retarded singletons after 28 weeks (27.8%) and intrauterine deaths be-fore 28 weeks, still considered miscarriages in some countries (13.3%). Two-thirds of the early neonatal. CONCLUSIONS: The Nordic classification used gave a good picture of the causes of avoidable and unavoidable perinatal deaths and may facilitate comparison between populations and periods.