Scaling of domain cascades in stripe and skyrmion phases.

The origin of deterministic macroscopic properties often lies in microscopic stochastic motion. Magnetic fluctuations that manifest as domain avalanches and chaotic magnetization jumps exemplify such stochastic motion and have been studied in great detail. Here we report Fourier space studies of avalanches in a system exhibiting competing magnetic stripe and skyrmion phase using a soft X-ray speckle metrology technique. We demonstrate the existence of phase boundaries and underlying critical points in the stripe and skyrmion phases. We found that distinct scaling and universality classes are associated with these domain topologies. The magnitude and frequency of abrupt magnetic domain jumps observed in the stripe phase are dramatically reduced in the skyrmion phase. Our results provide an incisive way to probe and understand phase stability in systems exhibiting complex spin topologies.

Publisher Correction: Scaling of domain cascades in stripe and skyrmion phases.

The original version of this Article contained an error in Fig. 4d, in which the label of the region to the left of the white dashed lines incorrectly read 'Order stripes'. The correct version states 'Disorder stripes'. This has been corrected in both the PDF and HTML versions of the Article.

Continuous Uptake or Saturation-Investigation of Concentration and Surface-Packing-Specific Hemin Interaction with Lipid Membranes.

Drug design and targeted delivery in cells serve as a flourishing area not only for scientific inquiry, owing to numerous clinical applications, but also for understanding cell interaction with exogenous materials. The membrane localization of heme and its analog hemin, one of the most biologically relevant planar organic molecule, is very important to understand the molecular mechanism of intercalation and adsorption of this cytotoxic molecule after its dissociation from proteins such as hemoglobin. Herein, we investigate the differential behavior of hemin on the soft membrane surfaces of phospholipids by synchrotron-based X-ray scattering techniques, Langmuir monolayer measurements, and molecular dynamics simulation. A continuous hemin uptake from the subphase and intercalation into and/or adsorption on to the membrane surface have been witnessed in a strong membrane surface packing-specific manner. Competitive interactions between hemin-membrane and hemin-hemin are proposed to be responsible for the critical hemin concentration. Up to the limit, a continuous hemin uptake is possible and beyond that the hemin-hemin interaction dominates, effectively reducing the hemin intercalation into the membrane. This structural model of the hemin-uptake process can be generalized to understand the localization and transport across membranes and also for the development and design of new drugs.

Reversible monolayer-to-crystalline phase transition in amphiphilic silsesquioxane at the air-water interface.

We report on the counter intuitive reversible crystallisation of two-dimensional monolayer of Trisilanolisobutyl Polyhedral Oligomeric SilSesquioxane (TBPOSS) on water surface using synchrotron x-ray scattering measurements. Amphiphilic TBPOSS form rugged monolayers and Grazing Incidence X-ray Scattering (GIXS) measurements reveal that the in-plane inter-particle correlation peaks, characteristic of two-dimensional system, observed before transition is replaced by intense localized spots after transition. The measured x-ray scattering data of the non-equilibrium crystalline phase on the air-water interface could be explained with a model that assumes periodic stacking of the TBPOSS dimers. These crystalline stacking relaxes upon decompression and the TBPOSS layer retains its initial monolayer state. The existence of these crystals in compressed phase is confirmed by atomic force microscopy measurements by lifting the materials on a solid substrate.

Structural reordering in monolayers of gold nanoparticles during transfer from water surface to solid substrate.

Structural reordering in monolayers of gold nanoparticles during transfer from water surface to solid substrate has been studied by synchrotron x-ray scattering techniques. Grazing incidence diffraction (GID) and grazing incidence x-ray off-specular scattering (GIXOS) measurements were performed as a function of time to track the in-plane and out-of-plane structural reordering in the transferred monolayers. GID measurements show shift in the in-plane particle-particle correlation peak toward the lower in-plane momentum transfer value, signifying possible expansion of triangular lattice formed on the water surface. However, GIXOS data and supportive microscopy measurements clearly show compactification in the in-plane structure and associated out-of-plane movements. A model that assumes the possibility of a two-dimensional short-range structural reordering from triangular to square-like lattice as a function of time could explain all the data. The observed change in the electron densities of the nanoparticles before and after the structural reordering matches well with the expected change in the calculated electron densities of the nanoparticles arranged in triangular (pretransition) and square-like (post-transition) symmetry.

Influence of stabilizers on quality of sandesh from buffalo milk.

Buffalo milk standardized to solids-not-fat (SNF) to fat ratio of 1.4 was added separately with 0.1% (w/w) each of carrageenan, sodium alginate and carboxymethyl cellulose and then heated, cooled and coagulated to obtain chhana which was converted into sandesh by adding 1.5% (w/w) wheat flour and 25% (w/w) cane sugar followed by heating (40 min/kg chhana). The treated samples of sandesh were compared with control prepared similarly manner but without stabilizer. Addition of stabilizer decreased hardness, fracturability, adhesiveness, cohesiveness, gumminess and chewiness of sandesh and improved sensory body and texture, colour and appearance as well as overall acceptability of the product when compared with control. Textural and sensory properties of different samples of sandesh indicated that the product made by adding carrageenan proved best. Carrageenan at 0.1% produced better results in terms of textural and sensory profile of sandesh as compared to 0, 0.075 and 0.125% (w/w) of carrageenan.

Nanopattern formation in self-assembled monolayers of thiol-capped Au nanocrystals.

The structure and the stability of the transferred monolayers of gold-thiol nanoparticles, formed at air-water interface at different surface pressure, on to silicon surface have been studied using two complementary techniques, x-ray reflectivity and atomic force microscopy (AFM). Networklike nanopatterns, observed through AFM, of the in-plane aggregated nanoparticles can be attributed to the late stage drying of the liquid trapped in the islands formed by nanoparticles. During drying process the trapped liquid leaves pinholes in the islands which by the process of nucleation and growth carry the mobile nanoparticles on their advancing fronts such that the nanoparticles are trapped at the boundaries of similar adjacent holes. This process continues bringing about in-plane as well as out-of-plane restructuring in the monolayer until the liquid evaporates completely rendering a patterned structure to the islands and instability in the monolayer is then stabilized.

Growth of bimolecular films of three-tailed amphiphiles.

The three-tailed amphiphile ferric stearate molecule, which forms a bimolecular layer on water surface with molecules in the lower and upper layers in different conformations, has been studied to understand transfer and growth of bimolecular films on the surface of hydrophilic silicon substrates. This bimolecular film forms a two-dimensional lattice on water with a slightly distorted hexagonal lattice where both the in-plane and out-of-plane domain sizes are small. The film also showed larger microscopic rigidity compared to its macroscopic mechanical response. This asymmetric bimolecular layer was found to be preserved when the film is transferred on the substrates at different values of surface pressures ranging from 1 mN/m to near-collapse (55 mN/m). Both the upper and lower layers become denser and interfaces between these layers become sharper with increase in deposition pressure but the growths have different natures. The lower layer of transferred film is dense from 1 mN/m and, except for a steplike increase between 20 and 30 mN/m, changes slowly in density. The density of the upper molecular layer grows continuously with surface pressure.

Dramatic enhancement of capillary wave fluctuations of a decorated water surface.

We have demonstrated by x-ray diffuse scattering that a bimolecular layer of a preformed three-tailed amphiphile, ferric stearate, drastically enhances capillary wave fluctuations on water surface due to a reduction in surface tension to 1 mN/m . The bimolecular layer is composed of molecules in symmetric configuration, on top of molecules in asymmetric configuration with ferric ions in contact with water. Unlike the usual Langmuir monolayers, this layer of molecules does not rupture under compression, but becomes thicker. This behavior mimics folding of a membrane on a liquid surface and is closely related to the cohesive interaction brought by the ferric ions. The low effective tension of this artificial membrane depends on the available area and reduces as the microscopic excess area increases.

Glass transition in ultrathin polymer films: a thermal expansion study.

The glass transition process gets affected in ultrathin films having thickness comparable to the size of the molecules. We observe systematic broadening of the glass transition temperature (T(g)) as the thickness of an ultrathin polymer film reduces below the radius of gyration but the change in the average T(g) was found to be very small. The existence of reversible negative and positive thermal expansion below and above T(g) increased the sensitivity of our thickness measurements performed using energy-dispersive x-ray reflectivity. A simple model of the T(g) variation as a function of depth expected from sliding motion could explain the results.

Reversible negative thermal expansion of polymer films.

A basic understanding of the properties of thin polymer films is of fundamental importance for developing applications in nanotechnology. Results of energy and angle dispersive x-ray reflectivity measurements on polymer thin films as a function of temperature exhibit reversible negative thermal expansion below the glass transition temperature T(g). Above T(g), the thickness expansion becomes almost equal to the expected bulk volume expansion. These results could be explained on the basis of evolution of disorder with temperature at the interfaces, chain entanglement and associated entropy changes.

X-ray reflectivity study of semiconductor interfaces.

The results of an X-ray reflectivity study of thick AlAs-AlGaAs and thin Ge-Si-Ge multilayers grown using metal-organic vapour-phase epitaxy and ion-beam sputtering deposition techniques, respectively, are presented. Asymmetry in interfaces is observed in both of these semiconductor multilayers. It is also observed that although the Si-on-Ge interface is sharp, an Si(0.4)Ge(0.6) alloy is formed at the Ge-on-Si interface. In the case of the III-V semiconductor, the AlAs-on-AlGaAs interface shows much greater roughness than that observed in the AlGaAs-on-AlAs interface. For thin multilayers it is demonstrated that the compositional profile as a function of depth can be obtained directly from the X-ray reflectivity data.

Augmentation of DNA synthesis in placental and fetal tissues in utero by maternal growth hormone treatment.

The influence of maternal exogenous growth hormone treatment on in utero conceptus development was evaluated in the rat. The periods of response and stimulation of DNA synthesis on embryo/fetal and placental tissues were assessed by subcutaneous injections of ovine growth hormone (oGH) preparations during pregnancy days 11-15, autopsied on day 16; and during pregnancy days 11-20 and 16-20, autopsied on day 21. To determine DNA biosynthesis potential, thymidine (methyl-3H) was administered through the jugular vein 14-16 h prior to sacrifice. DNA content and uptake of radiolabeled thymidine into DNA were analyzed for whole embryos on day 16, and for fetal liver, brain and remaining body tissues on day 21 of pregnancy. Placental tissues from oGH-treated mother and controls were also quantified for DNA content and radiolabeled thymidine uptake. oGH treatment produced a significant increase (p < 0.05) in radiolabeled thymidine uptake into DNAs of different fetal organs compared to saline-treated controls matched for weight and litter number during the latter part of gestation (fetal histogenesis period; pregnancy days 16-20). The stimulatory influence of maternal growth hormone treatment on DNA contents and radiolabled thymidine uptake on placental tissues at this period of gestation was also significantly different from that of the controls. Rat conceptus tissues (embryos and placentas) during the organogenesis period of early gestation (days 11-15) appeared to be unresponsive to such treatment. Thus, these results suggest that maternal growth hormone influences conceptus growth during the latter part of gestation and activation of placental functions may be an important aspect of stimulation of cell proliferation in the rat fetus.

Pre-labour rupture of membrane: the histological study of membrane and bacteriological profile.

One hundred two (102) cases of pre-labour rupture of membrane (PROM) were studied and special attention was given to the histological study of the amniotic membrane as well as to the bacteriological study of high vaginal flora, cervical flora and flora of amniotic fluid, in search of probable causes or factors leading to PROM. The incidence was found to be 3.16% in the age group of 20-25 years without any relation to parity; and the duration of gestation was 38 to 40 weeks in most of the cases. The histological study revealed: (a) Focally denuded amniotic epithelium, focally separated amniotic epithelium from chorion layer, lesser density of focal squamoid change of the epithelium and thicker chorion layer probably indicating focal immaturity of the chorio-amnion, (b) lesser thickness of collagen layer, focal hydropic degeneration and mild cellular infiltrate, (c) presence of focal hyaline degeneration and focal calcification of chorio-amnion. Microbial culture revealed: (a) Higher rate of positive culture in high vaginal swab, cervical swab and amniotic fluid showing presence predominantly of Esch coli, Strept haemolyticus, klebseilla species, Staph aureus, Strept non-haemolyticus, proteus species and pseudomonas species against that of positive cultures in the control cases, (b) no anaerobic bacteria from high vaginal swab, cervical swab or from amniotic fluid. It was presumed that focal immaturity of chorio-amnion or focal irregularity in the chorio-amnion at the microscopical level, focal degeneration of collagen superadded with bacterial infection, however mild, could be the factors leading to weakness in the tensile strength of chorio-amnion, again leading to PROM, in the face of stress factors of foetal origin.

Metabolism of polynuclear aromatic hydrocarbon in human term placenta influenced by cigarette smoke exposure.

The relative contributions of biologic and environmental factors on embryo-fetal development were elucidated in a population of pregnant women who were exposed to varying amounts of active cigarette smoke and women who were not exposed to cigarette smoke. The neonatal weight at birth, placental weight at delivery, duration of pregnancy, and placental xenobiotic (polynuclear aromatic hydrocarbon, PAH) metabolism potential were assessed in this population. The overall metabolic capability in exposed and unexposed placental tissue was measured by in vitro assays using microsomes and a PAH substrate, benzo[a]pyrene (B[a]P). Toxicity potential was determined by B[a]P-metabolite-DNA adduct generation under the same incubation condition. Cigarette smoke exposure increased the overall PAH metabolism potential in placental tissues by approximately 200% (nonsmoker 176.2 +/- 33.6, n = 25; smoker 524.5 +/- 75.5, n = 32 pmol/mg protein) whereas PAH-DNA adduct formation potential did not increase significantly over the basal level (nonsmoker 5002 +/- 830, n = 15; smoker 6172 +/- 1443, n = 22 fmol B[a]P equivalent/mumol DNA/mg protein). Exposure to cigarette smoke during pregnancy is deleterious to fetal development as reflected by reduced neonatal weight at birth. In contrast, placental weight reduction is indistinct, but placentae expressed markedly augmented overall xenobiotic (PAH) metabolism capability in response to cigarette smoke exposure during pregnancy, indicating placental metabolism may be an important mediator of adverse effects induced by such xenobiotic exposure.

Augmentation of polynuclear aromatic hydrocarbon metabolism of human placental tissues of first-trimester pregnancy by cigarette smoke exposure.

OBJECTIVE: Polynuclear aromatic hydrocarbons are important components of cigarette smoke. The toxicity of polynuclear hydrocarbons depends on their metabolic biotransformation by tissues. This study was performed to assess the effects of cigarette smoke exposure on polynuclear aromatic hydrocarbon metabolism in the human placental tissues of first-trimester pregnancy. STUDY DESIGN: The expression of essential enzymes that metabolize polynuclear aromatic hydrocarbons and regulate toxic metabolism, aryl hydrocarbon hydroxylase, epoxide hydrolase, and glutathione S-transferase, were determined by immunocytochemical staining of the specific enzymes in first-trimester placental samples from both smoker and nonsmoker donors. The overall polynuclear aromatic hydrocarbon metabolism by such tissues was quantitated by a radiometric assay with benzo[a]pyrene substrate in placental villi tissues and also in isolated trophoblast cells or in cultured trophoblast cells in the presence of polynuclear aromatic hydrocarbon agent. RESULTS: Immunocytochemical staining revealed that aryl hydrocarbon hydroxylase was localized on trophoblast cells of first-trimester placentas from smoker donors. Epoxide hydrolase was present in stromal and trophoblast cells, and glutathione S-transferase (pi) was present in trophoblast cells of both nonsmoker and smoker subjects. In addition, the overall metabolism of polynuclear aromatic hydrocarbon xenobiotics in such tissues (8 to 11 weeks) of donors who smoked cigarettes was observed to be increased compared with that of nonsmokers by radiometric assay of metabolic products. The increased polynuclear aromatic hydrocarbon metabolism from such exposure was also shown in isolated and purified trophoblast cells of first-trimester placental villi and in culture of such trophoblast cells of nonsmoker donors with polynuclear aromatic hydrocarbon by the same assay procedure. CONCLUSIONS: Therefore, contrary to previous assumptions, these data demonstrate that cigarette smoke exposure increases the polynuclear aromatic hydrocarbon metabolism of placentas even during the early stages of pregnancy. Augmented polynuclear aromatic hydrocarbon metabolism may produce genotoxic metabolites deleterious to conceptus development.

Humoral immunity status in patients with complicated pregnancies.

Serum immunoglobulin levels of 136 females inclusive of 20 non-pregnant volunteers, 21 normal pregnant mothers and 95 cases with complicated pregnancies were studied by radial immunodiffusion technique. Compared to normal western values immunoglobulin M levels were higher in 132 out of total 136 cases, immunoglobulin G levels were higher in 65 out of 95 cases with complicated pregnancies the majority of which included cases of eclampsia (16 cases), pre-eclamptic toxaemia (21 cases) and pre-eclamptic toxaemia with antepartum haemorrhage (11 cases) and immunoglobulin A levels were normal in all except 11 cases comprising normal pregnancy (1 case), eclampsia (3 cases), pre-eclamptic toxaemia (5 cases) and pregnancy with hypertension (2 cases).