First-principles Dzyaloshinskii-Moriya interaction in a non-collinear framework.

We have derived an expression of the Dzyaloshinskii-Moriya interaction (DMI), where all the three components of the DMI vector can be calculated independently, for a general, non-collinear magnetic configuration. The formalism is implemented in a real space-linear muffin-tin orbital-atomic sphere approximation (RS-LMTO-ASA) method. We have chosen the Cr triangular trimer on Au(111) and Mn triangular trimers on Ag(111) and Au(111) surfaces as numerical examples. The results show that the DMI (module and direction) is drastically different between collinear and non-collinear states. Based on the relation between the spin and charge currents flowing in the system and their coupling to the non-collinear magnetic configuration of the triangular trimer, we demonstrate that the DMI interaction can be significant, even in the absence of spin-orbit coupling. This is shown to emanate from the non-collinear magnetic structure, that can induce significant spin and charge currents even with spin-orbit coupling is ignored.

Erratum: The Bethe-Slater curve revisited; new insights from electronic structure theory.

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

The Bethe-Slater curve revisited; new insights from electronic structure theory.

The Bethe-Slater (BS) curve describes the relation between the exchange coupling and interatomic distance. Based on a simple argument of orbital overlaps, it successfully predicts the transition from antiferromagnetism to ferromagnetism, when traversing the 3d series. In a previous article [Phys. Rev. Lett. 116, 217202 (2016)] we reported that the dominant nearestneighbour (NN) interaction for 3d metals in the bcc structure indeed follows the BS curve, but the trends through the series showed a richer underlying physics than was initially assumed. The orbital decomposition of the inter-site exchange couplings revealed that various orbitals contribute to the exchange interactions in a highly non-trivial and sometimes competitive way. In this communication we perform a deeper analysis by comparing 3d metals in the bcc and fcc structures. We find that there is no coupling between the E g orbitals of one atom and T 2g orbitals of its NNs, for both cubic phases. We demonstrate that these couplings are forbidden by symmetry and formulate a general rule allowing to predict when a similar situation is going to happen. In γ-Fe, as in α-Fe, we find a strong competition in the symmetry-resolved orbital contributions and analyse the differences between the high-spin and low-spin solutions.

Microscopic Origin of Heisenberg and Non-Heisenberg Exchange Interactions in Ferromagnetic bcc Fe.

By means of first principles calculations, we investigate the nature of exchange coupling in ferromagnetic bcc Fe on a microscopic level. Analyzing the basic electronic structure reveals a drastic difference between the 3d orbitals of E_{g} and T_{2g} symmetries. The latter ones define the shape of the Fermi surface, while the former ones form weakly interacting impurity levels. We demonstrate that, as a result of this, in Fe the T_{2g} orbitals participate in exchange interactions, which are only weakly dependent on the configuration of the spin moments and thus can be classified as Heisenberg-like. These couplings are shown to be driven by Fermi surface nesting. In contrast, for the E_{g} states, the Heisenberg picture breaks down since the corresponding contribution to the exchange interactions is shown to strongly depend on the reference state they are extracted from. Our analysis of the nearest-neighbor coupling indicates that the interactions among E_{g} states are mainly proportional to the corresponding hopping integral and thus can be attributed to be of double-exchange origin. By making a comparison to other magnetic transition metals, we put the results of bcc Fe into context and argue that iron has a unique behavior when it comes to magnetic exchange interactions.

Selective serotonin reuptake inhibitor use during pregnancy increases the risk of postpartum hemorrhage and anemia: a hospital-based cohort study.

BACKGROUND: Selective serotonin reuptake inhibitors (SSRIs) are known to increase the risk of gastrointestinal bleeding. OBJECTIVE: Study the risk of bleeding-related complications in relation to SSRI in pregnancy. PATIENTS/METHODS: This was a hospital-based cohort study. All women who gave birth at Karolinska University Hospital in Stockholm over a 5-year period (2007 to 2011) were included in the study. Those women who the electronic maternal health record indicated were using SSRI (n = 500) were considered exposed, and all other women formed a control population (n = 39,594). The main outcome measures were blood loss, postpartum hemorrhage (PPH), PP anemia and length of hospitalization. RESULTS: The absolute risk of PPH and PP anemia for the 1.2% exposed to SSRI were 18.0% and 12.8%, respectively. Women with a vaginal non-surgical delivery who reported use of SSRI during pregnancy had approximately a 2-fold increased risk of both PPH (OR, 2.6; 95% CI, 2.0-3.5) and PP anemia (OR, 2.1; 95% CI, 1.5-2.9), as compared with controls. Blood loss and length of hospitalization were significantly higher among women using SSRI than non-users (arithmetic mean 484 mL vs. 398 mL, 3.8 days vs. 2.4 days, respectively). CONCLUSION: The use of SSRI during pregnancy increases blood loss and doubles the risk of PPH and PP anemia in a setting where SSRI had not been considered a risk factor for increased blood loss. Because PPH is a leading cause of maternal mortality and morbidity, the awareness of bleeding-related complications is important, both in relation to pregnancy and to surgery in general.

Routine ultrasound examination at 41 weeks of gestation and risk of post-term severe adverse fetal outcome: a retrospective evaluation of two units, within the same hospital, with different guidelines.

OBJECTIVE: To study whether a routine with a routine ultrasound examination (routine scan) at 41 gestational weeks as compared with ultrasound on clinical indication (indicated scan), lowered the risk of severe adverse fetal outcome in post-term period. DESIGN: A retrospective cohort study. SETTING: Karolinska University Hospital, Stockholm, Sweden. POPULATION: Eight years of deliveries, 2002-2009. METHOD: One of the two delivery units at Karolinska University Hospital used a routine scan at 41 week of gestation and the other unit used an indicated scan. Severe adverse fetal outcome were defined: severe asphyxia, death or cerebral damage. The study was analysed using logistic regression with adjustment for potential confounders. MAIN OUTCOME MEASURES: Differences in post-term severe adverse fetal outcome. RESULTS: No increased risk of post-term severe adverse fetal outcome was seen at the unit using a routine scan; conversely, a 48% significantly increased risk was seen at the unit using an indicated scan (OR 0.89, 95% confidence interval, CI, 0.5-1.5 and OR 1.48, 95% CI 1.06-2.1, respectively). Comparing post-term periods, there was no significantly increased risk at the unit using indicated scans (OR 1.6, 95% CI 0.9-3.0). There was a 60% increased prevalence of small-for-gestational age (SGA) newborns in the post-term period at the unit using indicated scans (OR 1.6, 95% CI 1.1-2.4), but no differences in operative delivery. CONCLUSION: A policy to use routine scans at 41 weeks of gestation seems to normalise an increased post-term risk of severe adverse fetal outcome, possible due to increased awareness of SGA and/or oligohydramniosis.

Interatomic exchange interactions for finite-temperature magnetism and nonequilibrium spin dynamics.

We derive ab inito exchange parameters for general noncollinear magnetic configurations, in terms of a multiple scattering formalism. We show that the general exchange formula has an anisotropiclike term even in the absence of spin-orbit coupling, and that this term is large, for instance, for collinear configuration in bcc Fe, whereas for fcc Ni it is quite small. We demonstrate that keeping this term leads to what one should consider a biquadratic effective spin Hamiltonian even in the case of collinear arrangement. In noncollinear systems this term results in new tensor elements that are important for exchange interactions at finite temperatures, but they have less importance at low temperature. To illustrate our results in practice, we calculate for bcc Fe magnon spectra obtained from configuration-dependent exchange parameters, where the configurations are determined by finite-temperature effects. Our theory results in the same quantitative results as the finite-temperature neutron scattering experiments.

Lactate production as a response to intrapartum hypoxia in the growth-restricted fetus.

OBJECTIVE: To analyse whether the increase in lactate in response to intrapartum hypoxia differs between small- (SGA), appropriate- (AGA) and large-for-gestational-age (LGA) fetuses. DESIGN: Observational cohort study. SETTING: Ten obstetric units in Sweden. POPULATION: A cohort of 1496 women. METHODS: A secondary analysis of a randomised controlled trial, in which 1496 women with fetal heart rate abnormalities, indicating fetal scalp blood sampling, were randomised to lactate analyses. After delivery, the neonates were divided according to birthweight for gestational age into SGA, AGA and LGA groups. MAIN OUTCOME MEASURE: Lactate concentration in fetal scalp blood. SECONDARY OUTCOME MEASURES: Acid-base balance in cord artery blood and Apgar score <7 at 5 minutes. RESULTS: Median lactate concentrations in the SGA, AGA and LGA groups were 3.8, 3.0 and 2.2 mmol/l, respectively (SGA versus AGA, P = 0.017; LGA versus AGA, P = 0.009). In the subgroups with scalp lactate >4.8 mmol/l (lactacidaemia), the corresponding median (range) values were 6.2 (4.9-14.6), 5.9 (4.9-15.9) and 5.7 mmol/l (5.0-7.9 mmol/l), respectively (no significant differences between the groups). The proportions of neonates with cord artery pH < 7.00, metabolic acidaemia or Apgar score <7 at 5 minutes were similar in all weight groups. CONCLUSION: SGA fetuses with fetal heart rate abnormalities have the same ability to produce lactate as a response to intrapartum hypoxia as AGA and LGA fetuses. The risk of a poor outcome associated with high lactate concentration is the same in SGA, AGA and LGA fetuses. Scalp blood lactate analysis is therefore a reliable method for intrapartum fetal surveillance of suspected growth-restricted fetuses scheduled for vaginal delivery at ≥ 34 weeks of gestation.

Epitaxial Fe films on ZnSe(001): effect of the substrate surface reconstruction on the magnetic anisotropy.

It is well known that Fe films deposited on a c(2 × 2)-reconstructed ZnSe(001) surface show a strong in-plane uniaxial magnetic anisotropy. Here, the effect of the substrate reconstruction on the magnetic anisotropy of Fe has been studied by in situ Brillouin light scattering. We found that the in-plane uniaxial anisotropy is strongly reduced for Fe films grown on a (1 × 1)-unreconstructed ZnSe substrate while the in-plane biaxial one is nearly unaffected by the substrate reconstruction. Calculations of magnetic anisotropy energies within the framework of ab initio density functional theory reveal that the strong suppression of anisotropy at the (1 × 1) interface occurs due to complex atomic relaxations as well as the competing effects originating from magnetocrystalline anisotropy and dipole-dipole interactions. For both sharp and intermixed c(2 × 2) interfaces, the magnetic anisotropy is enhanced compared to the (1 × 1) case due to the further lowering of symmetry. The theoretical results are in agreement with the experimental findings.

Prediction of time to spontaneous onset of labour with lactate concentration in vaginal fluid in women with suspected preterm prelabour rupture of the membranes.

OBJECTIVE: To assess whether lactate determination in vaginal fluid is associated with and can predict onset of labour for women with suspected preterm prelabour rupture of membranes (PPROMs). DESIGN: Prospective observational study. SETTING: Labour ward at South General Hospital, Stockholm, Sweden. POPULATION/PARTICIPANTS: Women with suspected PPROMs at 20-36 completed weeks of gestation (n = 81). METHODS: All women underwent a speculum examination and a test for determining lactate concentration in vaginal fluid. We used logistic regression to estimate the association between lactate concentration in vaginal fluid and time to onset of labour. MAIN OUTCOME MEASURE: Time from examination to spontaneous onset of labour (cervix > or =4 cm). RESULTS: The median time between examination and onset of labour was 13.6 hours for those with a high (> or =4.5 mmol/l) lactate concentration and 1152 hours (i.e. 48 days) for those with a low (<4.5 mmol/l) lactate concentration. For a lactate threshold of 4.5 mmol/l, the likelihood ratio for positive test (LR+) was 12.6, and LR- was 0.14 for the outcome of spontaneous onset of labour within 48 hours. CONCLUSIONS: A high lactate concentration in vaginal fluid is strongly associated with whether a woman with suspected PPROM will commence onset of labour within 48 hours. If confirmed, use of lactate ('LAC test') as a predictive test for onset of preterm labour may be an attractive tool in bedside obstetrics.

Determination of pH or lactate in fetal scalp blood in management of intrapartum fetal distress: randomised controlled multicentre trial.

OBJECTIVE: To examine the effectiveness of pH analysis of fetal scalp blood compared with lactate analysis in identifying hypoxia in labour to prevent acidaemia at birth. DESIGN: Randomised controlled multicentre trial. SETTING: Labour wards. PARTICIPANTS: Women with a singleton pregnancy, cephalic presentation, gestational age >or=34 weeks, and clinical indication for fetal scalp blood sampling. INTERVENTIONS: Standard pH analysis (n=1496) or lactate analysis (n=1496) with an electrochemical microvolume (5 mul) test strip device. The cut-off levels for intervention were pH <7.21 and lactate >4.8 mmol/l, respectively. MAIN OUTCOME MEASURE: Metabolic acidaemia (pH <7.05 and base deficit >12 mmol/l) or pH <7.00 in cord artery blood. RESULTS: Metabolic acidaemia occurred in 3.2% in the lactate group and in 3.6% in the pH group (relative risk 0.91, 95% confidence interval 0.61 to 1.36). pH <7.00 occurred in 1.5% in the lactate group and in 1.8% in the pH group (0.84, 0.47 to 1.50). There was no significant difference in Apgar scores <7 at 5 minutes (1.15, 0.76 to 1.75) or operative deliveries for fetal distress (1.02, 0.93 to 1.11). CONCLUSION: There were no significant differences in rate of acidaemia at birth after use of lactate analysis or pH analysis of fetal scalp blood samples to determine hypoxia during labour. TRIAL REGISTRATION: ISRCT No 1606064.

Vagal activation by sham feeding improves gastric motility in functional dyspepsia.

Antral hypomotility and impaired gastric accommodation in patients with functional dyspepsia have been ascribed to vagal dysfunction. We investigated whether vagal stimulation by sham feeding would improve meal-induced gastric motor function in these patients. Fourteen healthy volunteers and 14 functional dyspepsia patients underwent a drink test twice, once with and once without simultaneous sham feeding. After ingesting 500 mL clear meat soup (20 kcal, 37 degrees C) in 4 min, sham feeding was performed for 10 min by chewing a sugar-containing chewing gum while spitting out saliva. Using two- and three-dimensional ultrasound, antral motility index (contraction amplitude x frequency) and intragastric volumes were estimated. Without sham feeding, functional dyspepsia patients had lower motility index than healthy volunteers (area under curve 8.0 +/- 1.2 vs 4.4 +/- 1.0 min(-1), P = 0.04). In functional dyspepsia patients, but not in healthy volunteers, motility index increased and intragastric volume tended to increase by sham feeding (P = 0.04 and P = 0.06 respectively). The change in motility index was negatively correlated to the change in pain score (r = -0.59, P = 0.007). In functional dyspepsia patients, vagal stimulation by sham feeding improves antral motility in response to a soup meal. The result supports the view that impaired vagal stimulation is implicated in the pathogenesis of gastric motility disturbances in functional dyspepsia.

Influence of ligand states on the relationship between orbital moment and magnetocrystalline anisotropy.

The spin and orbital moments of Au/Co/Au trilayers grown on a W(110) single crystal substrate have been investigated by means of x-ray magnetic circular dichroism. Our findings suggest that the orbital moment of Co does not obtain a maximum value along the easy axis, in contrast with previous experience. This is attributed to the large spin-orbit interaction within the Au caps. Both second order perturbation theory and first principles calculations show how the magnetocrystalline anisotropy (MCA) is dramatically influenced by this effect, and how this leads to the fact that the orbital moment anisotropy is not proportional to the MCA.

First-principles approach to noncollinear magnetism: towards spin dynamics.

A description of noncollinear magnetism in the framework of spin-density functional theory is presented for the exact exchange energy functional which depends explicitly on two-component spinor orbitals. The equations for the effective Kohn-Sham scalar potential and magnetic field are derived within the optimized effective potential (OEP) framework. With the example of a magnetically frustrated Cr monolayer it is shown that the resulting magnetization density exhibits much more noncollinear structure than standard calculations. Furthermore, a time-dependent generalization of the noncollinear OEP method is well suited for an ab initio description of spin dynamics. We also show that the magnetic moments of solids Fe, Co, and Ni are well reproduced.

Association between lactate in vaginal fluid and time to spontaneous onset of labour for women with suspected prelabour rupture of the membranes.

OBJECTIVES: To assess whether lactate determination in vaginal fluid is associated with, and can predict, onset of labour for women with suspected prelabour rupture of the membranes (PROM). DESIGN: Prospective observational study. SETTING: Labour ward at Soder Hospital, Stockholm, Sweden. POPULATION: Women with suspected PROM after 34 weeks of gestation, who later had spontaneous onset of labour (n = 179). METHODS: All women underwent a speculum examination and a test for determining lactate concentration in vaginal fluid. We used logistic regression to estimate the association between lactate concentration in vaginal fluid and time to onset of labour. MAIN OUTCOME MEASURES: Time from examination to onset of labour (cervix > or =4 cm), within 24 hours and 48 hours. RESULTS: The median time interval between examination and spontaneous onset of labour was 8.4 hours for women with 'high' lactate (> or =4.5 mmol/l) and 54 hours for those with 'low' lactate concentrations (<4.5 mmol/l). Among 86 women with high lactate concentrations, 76 (88%) had started labour within 24 hours compared with 20 of 93 (22%) women with low lactate concentrations (OR 27.7, 95% CI 12.2-63.3). After checking for the effect of visible amniotic fluid, the corresponding odds were still substantially increased (OR 13.5, 95% CI 5.3-34.3). CONCLUSIONS: High lactate concentration (> or =4.5 mmol/l) in vaginal fluid can be used to predict whether a woman with suspected PROM will commence spontaneous onset of labour within 24 or 48 hours.

Indications associated with increased cesarean section rates in a Swedish hospital.

OBJECTIVE: To analyze the indications and Robson classes associated with the rapid increase in cesarean section (CS) rates at Söder Hospital, Stockholm, Sweden, in the late 1990s. METHOD: Records of women who underwent CSs in 1994 and 1999 at Söder Hospital were retrospectively reviewed. Diagnostic frequency and Robson class, which takes into account characteristics such as parity, previous deliveries, prematurity, and fetal presentation, were compared for the 2 years. RESULTS: Suspected fetal distress (+1.6%; P = .0001), maternal request (+1.5%; P < .0001), and labor dystocia (+0.8%; P = .03) were associated with the increase in CS rates. The rate of CSs with cephalic presentation and spontaneous onset of labor at term, as well as the rate of CSs following induced labor or elective CSs, increases significantly in both nulliparas and multiparas (Robson classes 1-4) (P < .02). CONCLUSION: The increasing CS rate was due to maternal preference and lower thresholds of decision for physicians.

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.

Origin of magnetic anisotropy of Gd metal.

Using first-principles theory, we have calculated the energy of Gd as a function of spin direction, theta, between the c and a axes and found good agreement with experiment for both the total magnetic anisotropy energy and its angular dependence. The calculated low temperature direction of the magnetic moment lies at an angle of 20 degrees to the c axis. The calculated magnetic anisotropy energy of Gd metal is due to a unique mechanism involving a contribution of 7.5 microeV from the classical dipole-dipole interaction between spins plus a contribution of 16 microeV due to the spin-orbit interaction of the conduction electrons. The 4f spin polarizes the conduction electrons via exchange interaction, which transfers the magnetic anisotropy of the conduction electrons to the 4f spin.

Efficacy of epoetin beta on hemoglobin, quality of life, and transfusion needs in patients with anemia due to hormone-refractory prostate cancer--a randomized study.

OBJECTIVE: Erythropoietin is shown to be an effective treatment for anemia in various types of cancers, however only limited studies have evaluated its benefits in advanced hormone-refractory prostate cancer (HRPC). This multi-center study investigated the influence of 2 different doses of epoetin beta on quality of life, hemoglobin level, need for blood transfusion, and safety, in the treatment of anemia in patients with metastatic HRPC. MATERIALS AND METHODS: This study randomized 180 patients to receive either epoetin beta 1000 IU or 5000 IU subcutaneously 3 times per week for 12 weeks. Hemoglobin was evaluated at study start and 6 time-points during the study. Quality of life (QoL) was assessed by the European Organization for Research and Treatment of Cancer questionnaire, QLC-C30, before treatment start and after 6 and 12 weeks of treatment. Best supportive care and blood transfusions were given, if clinically indicated. Additional laboratory values and adverse events were followed for safety. RESULTS: Hemoglobin increased significantly (>20 g/l) in 43% in the high dose (HD) group and 25% in the low dose (LD) group in response to treatment. Levels were significantly higher in the HD group than the LD group (p < 0.001) after 8 and 12 weeks. QoL improved significantly if the increase in hemoglobin was >20 g/l. Significantly more patients in the LD group received blood transfusions than the HD group (p < 0.005). There were no differences between the groups regarding overall quality of life and fatigue. The treatment was well tolerated in both groups. CONCLUSIONS: Epoetin beta is shown to be safe and effective for the treatment of anemia in many patients with HRPC. It is found to improve QoL and physical functioning, and relieve fatigue symptoms, in many of these critically ill patients.