Adsorption of Water onto SrTiO3 from Periodic Møller-Plesset Second-Order Perturbation Theory.

Adsorption of water onto metal oxide surfaces is a long-standing problem motivated by relevance to many promising technological applications. In this work, we compute the adsorption energy of water on SrTiO3 using periodic Møller-Plesset second-order perturbation theory (MP2). We compare our MP2 results to density functional and hybrid density functional theory calculations with and without the widely used D3 dispersion correction. The MP2 ground-state adsorption energy of water on SrTiO3 (001) at one monolayer coverage is 0.9 eV on the TiO2 termination in the molecular configuration and 0.6 eV in the dissociative configuration, the corresponding results on the SrO termination being 0.9 eV for both modes of adsorption. These results are reproduced well by the PBE and PBE0 exchange-correlation functionals. Correcting for dispersion effects through the D3 dispersion correction leads to significantly overestimated adsorption energies for both PBE and PBE0 with respect to MP2. The D3 correction also fails to capture the difference in electron correlation between the molecular and dissociative adsorption states, similarly to the optB86b van der Waals density functional.

The interface of SrTiO3 and H2O from density functional theory molecular dynamics.

We use dispersion-corrected density functional theory molecular dynamics simulations to predict the ionic, electronic and vibrational properties of the SrTiO3/H2O solid-liquid interface. Approximately 50% of surface oxygens on the planar SrO termination are hydroxylated at all studied levels of water coverage, the corresponding number being 15% for the planar TiO2 termination and 5% on the stepped TiO2-terminated surface. The lateral ordering of the hydration structure is largely controlled by covalent-like surface cation to H2O bonding and surface corrugation. We find a featureless electronic density of states in and around the band gap energy region at the solid-liquid interface. The vibrational spectrum indicates redshifting of the O-H stretching band due to surface-to-liquid hydrogen bonding and blueshifting due to high-frequency stretching vibrations of OH fragments within the liquid, as well as strong suppression of the OH stretching band on the stepped surface. We find highly varying rates of proton transfer above different SrTiO3 surfaces, owing to differences in hydrogen bond strength and the degree of dissociation of incident water. Trends in proton dynamics and the mode of H2O adsorption among studied surfaces can be explained by the differential ionicity of the Ti-O and Sr-O bonds in the SrTiO3 crystal.

Spin crossover in ferropericlase from first-principles molecular dynamics.

Ferropericlase, (Mg,Fe)O, is the second-most abundant mineral of Earth's lower mantle. With increasing pressure, the Fe ions in the material begin to collapse from a magnetic to nonmagnetic spin state. We present a finite-temperature first-principles phase diagram of this spin crossover, finding a broad pressure range with coexisting magnetic and nonmagnetic ions due to favorable enthalpy of mixing of the two. Furthermore, we find the electrical conductivity of the mineral to reach semimetallic values inside Earth.

A new parametrization of the Stillinger-Weber potential for an improved description of defects and plasticity of silicon.

A new parametrization of the widely used Stillinger-Weber potential is proposed for silicon, allowing for an improved modelling of defects and plasticity-related properties. The performance of the new potential is compared to the original version, as well as to another parametrization (Vink et al 2001 J. Non-Cryst. Solids, 282 248), in the case of several situations: point defects and dislocation core stability, threshold displacement energies, bulk shear, generalized stacking fault energy surfaces, fracture, melting temperature, amorphous structure, and crystalline phase stability. A significant improvement is obtained in the case of dislocation cores, bulk behaviour under high shear stress, the amorphous structure, and computation of threshold displacement energies, while most of the features of the original version (elastic constants, point defects) are retained. However, despite a slight improvement, a complex process like fracture remains difficult to model.

ADHD symptoms and maturity - a follow-up study in school children.

AIM: To test the hypothesis that there is a subgroup of children with attention deficit hyperactivity disorder (ADHD) who show a decline in ADHD-symptoms that is associated with signs of biological maturation, a phenomenon referred to as a 'maturation catch-up'. METHODS: The parents of 147 children who were given an examination in grades one and two 1999-2000 that included assessment of ADHD-symptoms and estimation of skeletal bone-age by use of hand radiographs (which was repeated in the eighth grade), were contacted 2008-2009 and were asked to answer questions concerning ADHD-symptoms and behavioural maturity in their children. The response frequency was 67%. A complete dataset was achieved in 57 children. A reduction of Conners scores for ADHD-symptoms of eight or more between the evaluations was defined as a marked reduction in symptoms. RESULTS: When the children with a marked symptom reduction (n = 6) were compared with children without such a reduction (n = 51), we found a significant difference in skeletal maturation (p < 0.05). CONCLUSION: This study gives support to the theory that there is a group of children with ADHD-symptoms who have a biological maturational-lag who will show a decrease in their ADHD-symptoms as they show a maturation catch-up with increasing age.

Ab initio method for locating characteristic potential-energy minima of liquids.

It is possible in principle to probe the many-atom potential surface using density functional theory (DFT). This will allow us to apply DFT to the Hamiltonian formulation of atomic motion in monatomic liquids by Wallace [Phys. Rev. E 56, 4179 (1997)]. For a monatomic system, analysis of the potential surface is facilitated by the random and symmetric classification of potential-energy valleys. Since the random valleys are numerically dominant and uniform in their macroscopic potential properties, only a few quenches are necessary to establish these properties. Here we describe an efficient technique for doing this. Quenches are done from easily generated "stochastic" configurations, in which the nuclei are distributed uniformly within a constraint limiting the closeness of approach. For metallic Na with atomic pair potential interactions, it is shown that quenches from stochastic configurations and quenches from equilibrium liquid molecular dynamics configurations produce statistically identical distributions of the structural potential energy. Again for metallic Na, it is shown that DFT quenches from stochastic configurations provide the parameters which calibrate the Hamiltonian. A statistical mechanical analysis shows how the underlying potential properties can be extracted from the distributions found in quenches from stochastic configurations.

Serum bactericidal activity against Neisseria meningitidis in patients with C3 nephritic factors is dependent on IgG allotypes.

The main mechanisms of immune defense against Neisseria meningitidis are serum bactericidal activity (SBA) and opsonophagocytosis. Many complement deficiencies, among them acquired partial C3 deficiency due to stabilizing autoantibodies against the alternative pathway C3 convertase (C3 nephritic factors, C3 NeF); increase the risk of meningococcal infection. SBA against meningococci in patients with C3 NeF was determined along with allelic variants (GM alleles) of the immunoglobulin constant heavy G chain (IGHG) genes. In patients with C3 NeF and in control children, individuals homozygous for G1M*f and G3M*b showed higher SBA against meningococci than heterozygous individuals. Partial complement deficiency in early childhood might explain the influence of GM variants on SBA in control children. These novel findings imply that the IGHG genotype is important in defense against meningococci in individuals with low complement function and possibly in combination with other immunodeficiencies.

High frequency of contact allergy to gold in patients with endovascular coronary stents.

BACKGROUND: Stent implantation is an effective method for treatment of atherosclerotic disease. Factors predisposing to in-stent restenosis are still largely unknown. Contact allergy to metal ions eluted from the stent has been suggested to be a risk factor. OBJECTIVES: To explore whether there is a possible induction of contact allergy to metals used in stents among patients with a stainless steel stent containing nickel (Ni stent) and patients with a gold-plated stent (Au stent). METHODS: Adults (n = 484) treated with coronary stent implantation participated in the study with patch testing. The study design was retrospective and cross-sectional with no assessment of contact allergy before stenting. Age- and sex-matched patch-tested patients with dermatitis (n = 447) served as controls. RESULTS: Of Au-stented patients, 54 of 146 (37%) were allergic to gold compared with 85 of 447 (19%) controls (P < 0.001). Within the stented population there were no statistically significant differences in contact allergy to gold or nickel between Ni-stented and Au-stented patients. In multivariate models where other risk factors for contact allergy to gold were considered, the Au stent showed a trend towards statistical significance (odds ratio 1.43, 95% confidence interval 0.95-2.16; P = 0.09). CONCLUSIONS: As the frequency of contact allergy to gold is higher in stented patients independent of stent type it suggests a previous sensitization. However, several pieces of circumstantial evidence as well as statistical analysis indicate the possibility of sensitization in the coronary vessel by the Au stent. Ni stents and Au stents should not be ruled out as risk factors for induction of contact allergy to these metals.

Knee kinematics and kinetics during gait, step and hop in males with a 16 years old ACL injury compared with matched controls.

The objective of this study was to compare subjects who sustained an ACL injury during soccer 16 years ago with a control group with regard to knee kinematics and kinetics of gait, step activity and cross over hop. Secondly, in the injured subjects, the purpose was to study the impact on kinematics and kinetics of characteristics such as operative status, meniscal resection, being symptomatic, having knee extensor weakness and of having radiographic knee OA. Data from a 3-dimensional gait analysis system (VICON) were used to calculate kinetics and kinematics during gait, step activity and cross over hop of 12 male subjects who had an anterior cruciate ligament injury 16 years earlier. Twelve uninjured subjects matched for age, sex, BMI and activity level served as controls. No significant differences in knee kinematics and kinetics between the ACL group and the control group were found. The variability of some parameters of step and all parameters of hop activity was generally larger in the ACL injured subjects compared with the controls. The ACL injured subjects had a significantly worse clinical status compared with the controls. Reduced knee extension strength was associated with joint moment reductions especially during step activity and cross over hop. Despite a significantly worse clinical status, as determined by self-report and isokinetic strength testing, no significant differences were seen in knee joint kinetics and kinematics in an ACL injured group 16 years after injury compared with a matched control group. The variation was larger among the ACL injured subjects indicating the need for larger study groups in gait and movement analysis in long-term follow-up of ACL injury.

Competing exchange interactions in magnetic multilayers.

We have studied alloying of the nonmagnetic spacer layer with a magnetic material as a method of tuning the interlayer coupling in magnetic multilayers. We have specifically studied the Fe/V(100) system by alloying the spacer V with various amounts of Fe. For some Fe concentrations in the spacer, it is possible to create a competition between antiferromagnetic Ruderman-Kittel-Kasuya-Yoshida exchange and direct ferromagnetic exchange coupling. The exchange coupling and transport properties for a large span of systems with different spacer concentrations and thicknesses were calculated and measured experimentally and good agreement between observations and theory was observed. A reduction in magnetoresistance of about 50% was observed close to the switchover from antiferromagnetic to ferromagnetic coupling.

Sample preserving deep interface characterization technique.

We propose a nondestructive technique based on atomic core-level shifts to characterize the interface quality of thin film nanomaterials. Our method uses the inherent sensitivity of the atomic core-level binding energies to their local surroundings in order to probe the layer-resolved binary alloy composition profiles at deeply embedded interfaces. From an analysis based upon high energy x-ray photoemission spectroscopy and density functional theory of a Ni/Cu fcc (100) model system, we demonstrate that this technique is a sensitive tool to characterize the sharpness of a buried interface. We performed controlled interface tuning by gradually approaching the diffusion temperature of the multilayer, which lead to intermixing. We show that core-level spectroscopy directly reflects the changes in the electronic structure of the buried interfaces, which ultimately determines the functionality of the nanosized material.

On the sharpness of the interfaces in metallic multilayers.

We show that the three most relevant magnetic properties (magnetic moment, critical temperature, and interlayer exchange coupling) of metallic multilayers can be reproduced with good accuracy by first principles theory, provided that the picture of atomically sharp interfaces is abandoned and one allows instead for both interface alloying and interface roughness. The interface of a metallic multilayer (exemplified by the Fe/V system) is demonstrated to, at best, have interdiffusion essentially over two to three atomic layers on each side of the interface. Our conclusions are the result of combining experimental work with theoretical modeling, and we argue that this approach is the best avenue to obtain accurate information about the interface quality of metallic multilayers.

Vaccination responses to capsular polysaccharides of Neisseria meningitidis and Haemophilus influenzae type b in two C2-deficient sisters: alternative pathway-mediated bacterial killing and evidence for a novel type of blocking IgG.

Meningitis caused by Neisseria meningitidis serogroup W-135 was diagnosed in a 14-year-old girl with a history of neonatal septicemia and meningitis caused by group B streptococci type III. C2 deficiency type I was found in the patient and her healthy sister. Both sisters were vaccinated with tetravalent meningococcal vaccine and a conjugate Haemophilus influenzae type b vaccine. Three main points emerged from the analysis. First, vaccination resulted in serum bactericidal responses demonstrating anticapsular antibody-mediated recruitment of the alternative pathway. Second, addition of C2 to prevaccination sera produced bactericidal activity in the absence of anticapsular antibodies, which suggested that the bactericidal action of antibodies to subcapsular antigens detected in the sera might strictly depend on the classical pathway. A third point concerned a previously unrecognized type of blocking activity. Thus, postvaccination sera of the healthy sister contained IgG that inhibited killing of serogroup W-135 in C2-deficient serum, and the deposition of C3 on enzyme-linked immunosorbent assay plates coated with purified W-135 polysaccharide. Our findings suggested blocking to be serogroup-specific and dependent on early classical pathway components. Retained opsonic activity probably supported post-vaccination immunity despite blocking of the bactericidal activity. The demonstration of functional vaccination responses with recruitment of alternative pathway-mediated defense should encourage further trial of capsular vaccines in classical pathway deficiency states.

Low concentrations of immunoglobulin G antibodies to Salmonella serogroup C in C2 deficiency: suggestion of a mannan-binding lectin pathway-dependent mechanism.

The influence of complement on immune responses to polysaccharides is debatable. We examined the serum concentrations of IgM and IgG antibody against Salmonella O-antigen specific oligosaccharides representing the serogroups B, C and D, and against capsular polysaccharides of Streptococcus pneumoniae serotypes 6 and 23 in C2-deficient adults and in healthy controls. A sharp contrast of findings was found for antibodies against the CO antigen, an activator of the mannan-binding lectin (MBL) pathway of complement activation. The C2-deficient group showed normal IgM and markedly low IgG antibody levels. Similar findings were made in adults with low concentrations of MBL. This suggests that the recruitment of classical pathway C3 convertase through the MBL pathway is critically involved in isotype switching of antibodies against MBL pathway activating antigens during immune system maturation. The findings imply a new role of the MBL pathway, and an additional link between innate and acquired immunity. Specific IgM against BO was moderately low in C2 deficiency. Other differences for the Salmonella antigens were not found. Markedly raised IgM antibody levels against pneumococcal polysaccharides in C2 deficiency probably Salmonella reflected past infections. The absence of a concomitant increase of specific IgG might possibly be explained by impaired IgM to IgG switching.

Binding of properdin to solid-phase immune complexes: critical role of the classical activation pathway of complement.

The capacity of serum to support deposition of C3, properdin and factor B was studied by enzyme-linked immunosorbent assay using solid-phase immune complexes (IC) for activation of complement. Deposition of C3 and properdin occurred in fairly dilute normal human serum (NHS), but factor B uptake was hardly detectable. Alternative pathway-mediated deposition of C3 with slow kinetics was demonstrated in C2-deficient serum and in NHS depleted of C1q, factor D and properdin (C1qDP-depleted serum) after reconstitution with factor D and properdin. Efficient uptake of properdin required a functional classical pathway, in the presence of which C3 and properdin were rapidly deposited onto the IC. Judging from findings in C3-deficient serum, factor I-deficient serum, and C1qDPB-depleted serum, the uptake of properdin was strictly C3-dependent, and did not require the presence of factors B and D. Thus, C3b fixed to IC was the principal ligand for properdin in the assay. The findings could have biological implications relating to complement-mediated modification of immune complexes in disease.

Progression of atherosclerosis in middle-aged men: effects of multifactorial intervention.

OBJECTIVE: To determine the effect of multifactorial intervention against cardiovascular risk factors on ultrasound-determined progression of atherosclerosis in healthy middle-aged men. DESIGN: One hundred and forty-nine healthy middle-aged men were assigned to an intervention group (IG) or a control group (CG). SUBJECTS: The participants had moderately increased risk-factor scores for cardiovascular disease. They were recruited from a health screening programme at the Preventive Medicine Section, Department of Medicine, Lund University, University Hospital, Malmö. During the study period, 32 of the subjects were lost to follow-up, leaving 59 in the IG and 58 in the CG. INTERVENTION: The IG subjects underwent multifactorial intervention for 2 years, the goal being to help them stop smoking and to reduce their blood lipids and blood pressure. MAIN OUTCOME MEASURES: Intima-media thickness and plaque score in the right carotid artery were ultrasonographically determined initially and after 2 years. Blood lipids and blood pressure were measured at the same time, and in the IG also after 3, 6, 12 and 18 months after entry into the study. RESULTS: At the entry into the study, there were no significant differences in major risk factors or ultrasound variables between IG and CG. Blood lipids and smoking decreased significantly during the 2 years of intervention in the IG, whilst these factors remained unchanged in the CG. Intima-media thickness and plaque scores increased significantly in both groups. CONCLUSIONS: No effects on ultrasound variables could be detected after 2 years of multifactorial intervention. A more aggressive intervention programme, possibly more dependent on pharmacological treatment, may be required to obtain reduced progression or regression of atherosclerosis.

Musculoskeletal disorders in construction workers.

Physical factors that contribute to musculoskeletal disorders in construction workers are described, and the clinical findings associated with muscular, tendon, articular, spinal, and peripheral nerve entrapment disorders are reviewed. Psychosocial factors and individual factors such as the worker's age, smoking habits, and endurance are considered.

Serum bactericidal activity and induction of chemiluminescence of polymorphonuclear leukocytes: complement activation pathway requirements in defense against Neisseria meningitidis.

Serum bactericidal activity and chemiluminescence (CL) responses of polymorphonuclear leukocytes (PMNL) to pathogenic Neisseria meningitidis serogroups B and W-135 and to nonpathogenic serogroup 29E were examined with pooled normal human serum depleted of the complement proteins C1q, factor D, properdin and C5. Purified C1q, factor D, properdin and C5 were added alone or in combination. For investigation of serogroup W-135 meningococci, a C1q, factor D and properdin-depleted postvaccination serum with high concentrations of anticapsular antibodies was also used. Serogroup B and W-135 cultured to log phase were resistant to the bactericidal activity of pooled normal human serum but were efficiently killed through the classical pathway alone when the bacteria were cultured to stationary phase. Nonpathogenic serogroup 29E meningococci in log or stationary growth phases were efficiently killed in serum, predominantly through the classical pathway. Serogroup W-135 meningococci grown to log phase were resistant to classical pathway-mediated bactericidal activity in postvaccination serum but were killed on addition of alternative pathway proteins. Stationary phase serogroup W-135 meningococci were killed through both pathways in the postvaccination serum. In the pooled normal human serum CL responses of PMNL were consistently more pronounced with fully reconstituted C1q, factor D, properdin, C5-depleted serum than with serum reconstituted with C1q, factor D and properdin suggesting contribution of actions related to terminal components. In the absence of C1q, serogroup W-135 meningococci in postvaccination serum induced a significant but delayed alternative pathway-mediated CL response. CL responses induced by serum-opsonized meningococci, in contrast to serum bactericidal activity, were not influenced by culture conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of lumbar belts on trunk muscle strength and endurance: a follow-up study of construction workers.

The effects on maximal isometric trunk muscle strength and endurance after wearing a soft heat-retaining lumbar belt or a weightlifter's belt were studied. The soft belt (SB) study group comprised 12 construction workers with healthy backs, and the weightlifter's belt (WB) group comprised 24 construction workers with current or previous low back pain. The strength and endurance measurements were performed before the start of belt use, and after 1 and 2 months. The SB group increased the trunk flexor strength by 13% (p less than or equal to 0.01) after 2 months. The WB group increased the trunk flexor strength and endurance by 12% and 29%, respectively (p less than or equal to 0.001). No significant decrease of trunk muscle strength and endurance was found at the end of the follow-up period.