Plutonium content of human placental tissues after occupational exposure

The placenta and umbilical cord were obtained following a normal live delivery from a volunteer donor who had received an accidental inhalation intake of plutonium 12 years prior to her pregnancy (Case 0777). Her employer estimated the intake to be about 73 Bq Class W plutonium. Based on bioassay results and clearance models in use at that time, they calculated her body content at the beginning of pregnancy to be about 5.6 Bq with an average concentration of approximately 60 mBq kg(-1). The placenta and cord from this pregnancy, along with the placenta and cord from a donor with no known exposure to plutonium (Case 0835), were divided and assayed for plutonium by ultrasensitive fission track analysis at two collaborating laboratories. Placental 239Pu concentration values obtained by the two laboratories for Case 0777 agreed within a factor of 2 and were several-fold greater than for the control, Case 0835, as well as values that had been reported by others for unexposed populations. There was no elevated concentration of plutonium in the umbilical cord from the exposed person. The data yielded values of 0.16 and 0.27 for placental to maternal concentrations (CPl: CM) that were of the same order of magnitude as the value of 0.1 the ICRP calculated for intakes before pregnancy.     

妊娠期胎盘超声图像分形特征的数量化分析

应用分数布朗运动模型 (FBM) ,对孕妇不同妊娠期的胎盘B型超声图像进行分形处理 ,提取出用以胎盘分级的分形特征参数 ,并结合临床医学专家的判断 ,利用数量化理论 ,建立起胎盘功能的自动分级模型。通过 10 6例胎盘图像的分析 ,结果表明 :胎盘B型超声图像的分形特征可以有效地表征胎盘的功能状况 ,而数量化理论可以使胎盘功能的无损自动分级成为可能 ,因此有较好的临床应用前景。     

Effect of ultrafiltration on placental‐fetal blood flow in pregnancy of woman undergoing chronic hemodialysis

Introduction: Patient who was undergoing hemodialysis (HD) thrice weekly usually gain 1 to 4 kg of weight in interdialytic period, mainly due to fluid accumulation by ingestion of water. Ultrafiltration (UF) during HD will be need to remove fluid excess to avoid severe medical complications secondary to fluid overload. However, in pregnant woman UF can increase the episodes of intradialytic hypotension which may lead to placental ischemic injury and predispose to fetal distress. There is little information about safe fluid amount withdrawn by UF during pregnancy. Methods: We prospectively study by obstetric Doppler ultrasonography the fluxometric parameters: pulsatility index (PI) and resistance index (RI) of fetal middle cerebral, uterine, and umbilical artery obtained at the beginning and the end of HD session, the acute and chronic effect of UF on placenta and fetus blood flow, as well as the fetal outcome in 1 pregnant woman on chronic HD. Findings: We did not observe any acute harmful effect on fetal middle cerebral, placental and umbilical artery blood flow when UF rate of 2.1 ± 0.04 L (6 < 8 mL/h/kg) during HD session, no significant statistical difference was observed when compared PI and RI before and after UF and also when we compared these data with reference value on normal pregnancy to the same gestational age. Discussion: UF rate of 6 < 8 mL/h/kg during HD did not bring any acute harmful effect on fetal middle cerebral, placental, and umbilical blood flow and the UF rate of 1.4 6 0.4 L (< 6 mL/h/kg) / HD session that was done in all others HD during pregnancy was safe, without any chronic fetal deleterious effect. Obstetric Doppler ultrasonography is a simple and noninvasive method to fetal follow‐up and can aid to determine safe UF rate in pregnant women during gestation.     

A mesh-updating scheme for hemodynamic simulations in vessels undergoing large deformations

Several arteries, notably the coronary arteries,experience large motions and deformations believed to affect their hemodynamic environment. These arterial motions are 3D and complex, and in vivo data sets usually do not completely describe the resulting arterial wall motions. Here we present a mesh-updating scheme for such situations, thus allowing numerical simulation of arterial hemodynamics in arteries whose motion is described by (necessarily) incomplete in vivo data sets. The scheme works by first coupling information about arterial cross-sectional shape to motion of the artery axis. Motion of a subset of surface nodes (“control nodes”) is then specified, and this motion is used to drive all nodes in the mesh through an extension of a semi-torsional spring-analogy model. Numerical experiments were carried out on unstructured tetrahedral meshes generated in model geometries and in a right coronary artery model undergoing physiologically accurate motion. Results show that the quality of the dynamic mesh, as evaluated through elemental aspect ratios and Jacobian values, is extremely well preserved by this scheme, even during large deformations. Testing indicates the number of control nodes necessary to attain a high level of geometric fidelity of the mesh. We conclude that the algorithm is valuable for computing hemodynamic patterns in moving arteries using fully unstructured meshes.     

Nano-Theranostic Modality for Visualization of the Placenta and Photo-Hyperthermia for Potential Management of Ectopic Pregnancy

Ectopic pregnancy (EP) is the leading cause of maternity-related death in the first trimester of pregnancy. Approximately 98% of ectopic implantations occur in the fallopian tube, and expedient management is crucial for preventing hemorrhage and maternal death in the event of tubal rupture. Current ultrasound strategies misdiagnose EP in up to 40% of cases, and the failure rate of methotrexate treatment for confirmed EP exceeds 10%. Here the first theranostic strategy for potential management of EP is reported using a near-infrared naphthalocyanine dye encapsulated within polymeric nanoparticles. These nanoparticles preferentially accumulate in the developing murine placenta within 24 h following systemic administration, and enable visualization of implantation sites at various gestational stages via fluorescence and photoacoustic imaging. These nanoparticles do not traverse the placental barrier to the fetus or impact fetal development. However, excitation of nanoparticles localized in specific placentas with focused NIR light generates heat (>43 °C) sufficient for disruption of placental function, resulting in the demise of targeted fetuses with no effect on adjacent fetuses. This novel approach would enable diagnostic confirmation of EP when current imaging strategies are unsuccessful, and elimination of EP could subsequently be achieved using the same nano-agent to generate localized hyperthermia resulting in targeted placental impairment.     

A massively multi-scale approach to characterizing tissue architecture by synchrotron micro-CT applied to the human placenta

Multi-scale structural assessment of biological soft tissue is challenging but essential to gain insight into structure–function relationships of tissue/organ. Using the human placenta as an example, this study brings together sophisticated sample preparation protocols, advanced imaging and robust, validated machine-learning segmentation techniques to provide the first massively multi-scale and multi-domain information that enables detailed morphological and functional analyses of both maternal and fetal placental domains. Finally, we quantify the scale-dependent error in morphological metrics of heterogeneous placental tissue, estimating the minimal tissue scale needed in extracting meaningful biological data. The developed protocol is beneficial for high-throughput investigation of structure–function relationships in both normal and diseased placentas, allowing us to optimize therapeutic approaches for pathological pregnancies. In addition, the methodology presented is applicable in the characterization of tissue architecture and physiological behaviours of other complex organs with similarity to the placenta, where an exchange barrier possesses circulating vascular and avascular fluid spaces.     

Transfer studies of polystyrene nanoparticles in the ex vivo human placenta perfusion model: key sources of artifacts

Nanotechnology is a rapidly expanding and highly promising new technology with many different fields of application. Consequently, the investigation of engineered nanoparticles in biological systems is steadily increasing. Questions about the safety of such engineered nanoparticles are very important and the most critical subject with regard to the penetration of biological barriers allowing particle distribution throughout the human body. Such translocation studies are technically challenging and many issues have to be considered to obtain meaningful and comparable results. Here we report on the transfer of polystyrene nanoparticles across the human placenta using an ex vivo human placenta perfusion model. We provide an overview of several challenges that can potentially occur in any translocation study in relation to particle size distribution, functionalization and stability of labels. In conclusion, a careful assessment of nanoparticle properties in a physiologically relevant milieu is as challenging and important as the actual study of nanoparticle–cell interactions itself.     

Determination of stress intensity factors for three-dimensional subsurface cracks in hypoid gears

Aim of this paper is to propose a numerical tool able to compute the stress intensity factor for the Mode I, II and III along the front of any subsurface cracks found in spiral and hypoid gear teeth, allowing to assess the criticality of the crack itself. The described approach is based on two steps: firstly the contact pressures in the un-cracked teeth are efficiently computed by an advanced contact solver; in this way the complex tooth geometry and the intricate meshing condition can be accurately considered; then, the displacements field due to those pressures is applied as boundary conditions to a finite element model of the cracked zone and the SIFs are efficiently computed. This information, together with the knowledge of the ΔK threshold value of the material, makes possible to decide whether the defect is acceptable and to evaluate the conditions of propagation.     

Three-Dimensional Micromechanical Modeling of Cord-Rubber Composites

A three-dimensional micromechanical model was developed to investigate the load-deformation characteristics of cord-rubber composites. A finite-element model that integrates a solid rubber element and a twisted cord element which takes into account coupling effects of various deformations is developed to investigate the influence of cord shape on the load-deformation characteristics. The finite-element model developed was validated by comparing the results with those from a solid three-dimensional finite-element analysis. Numerical results of deformations and stress distributions are presented to illustrate the influence of cord shape, cord-rubber anisotropy, and rubber thickness. The results presented illustrate that cord shape and rubber thickness surrounding the cord have a strong effect on the values of deformations and interface stress distributions.     

Transformation and thickening of chip during high throughput drilling

One of the major difference in drilling process when related to other conventional metal removal processes like turning and milling is that the drill tool has to work beneath harsh environment as the metal cutting region is situated deep inside the work material. Also, the chip flow is restricted only through the flutes, and hence there occurs transformation of chip shape, chip thickening, and changes in force and torque. In the present investigation, high throughput drilling has been performed under a dry and wet environment in an intermetallic titanium aluminide which is an exceptional class of material with superior properties. It is found that the chip shape transformed from spiral to folded ribbon as the depth of hole increased. Also, a substantial increase in chip thickness, thrust, and torque was observed, and toward the end of drilling, chip clogging occurred. An analytical model was established by applying the mechanics of oblique cutting to find the torque and thrust by measuring the thickness of chip, and this model was validated experimentally.     

A three-dimensional model describing stress-temperature induced solid phase transformations: thermomechanical coupling and hybrid composite applications

Between composite materials, shape memory alloy (SMA) composites are having a more and more relevant role. Typically, SMA wires are embedded in a metallic or a polymeric matrix to obtain materials with native multi-functionality and adaptive properties. This work approaches the computational study of the mechanical response of a composite in which SMA wires, previously deformed, are activated by electrical current heating, and accordingly try to recover the original shape inducing a shape change or a prestress in the structure. In particular, since the SMA behaviour is strongly affected by the thermo-mechanical coupling, in the first part of this work we present a 3D phenomenological model able to take into account this aspect. The model time-discrete counterpart is used to develop a 3D solid finite element able to describe the thermo-electro-mechanical coupled problem due to shape memory alloy response and to Joule effect. Finally, in the second part of the paper, we employ the developed computational tool to simulate different feasible SMA composite applications. Copyright © 2004 John Wiley & Sons, Ltd.     

From Farming to Engineering: The Microbiota and Allergic Diseases

The steady increase of IgE-dependent allergic diseases after the Second World War is a unique phenomenon in the history of humankind. Numerous cross-sectional studies, comprehensive longitudinal cohort studies of children living in various types of environment, and mechanistic experimental studies have pointed to the disappearance of “protective factors” related to major changes in lifestyle and environment. A common unifying concept is that of the immunoregulatory role of the gut microbiota. This review focuses on the protection against allergic disorders that is provided by the farming environment and by exposure to microbial diversity. It also questions whether and how microbial bioengineering will be able in the future to restore an interplay that was beneficial to the proper immunological development of children in the past and that was irreversibly disrupted by changes in lifestyle. The protective “farming environment” includes independent and additional influences: contact with animals, stay in barns/stables, and consumption of unprocessed milk and milk products, by mothers during pregnancy and by children in early life. More than the overall quantity of microbes, the biodiversity of the farm microbial environment appears to be crucial for this protection, as does the biodiversity of the gut microbiota that it may provide. Use of conventional probiotics, especially various species or strains of Lactobacillus and Bifidobacterium, has not fulfilled the expectations of allergists and pediatricians to prevent allergy. Among the specific organisms present in cowsheds that could be used for prevention, Acinetobacter (A.) lwoffii F78, Lactococcus (L.) lactis G121, and Staphylococcus (S.) sciuri W620 seem to be the most promising, based on experimental studies in mouse models of allergic respiratory diseases. However, the development of a new generation of probiotics based on very productive research on the farming environment faces several obstacles that cannot be overcome without a close collaboration between microbiologists, immunologists, and bioengineers, as well as pediatricians, allergists, specialists of clinical trials, and ethical committees.     

Silica and titanium dioxide nanoparticles cause pregnancy complications in mice

The increasing use of nanomaterials has raised concerns about their potential risks to human health. Recent studies have shown that nanoparticles can cross the placenta barrier in pregnant mice and cause neurotoxicity in their offspring, but a more detailed understanding of the effects of nanoparticles on pregnant animals remains elusive. Here, we show that silica and titanium dioxide nanoparticles with diameters of 70 nm and 35 nm, respectively, can cause pregnancy complications when injected intravenously into pregnant mice. The silica and titanium dioxide nanoparticles were found in the placenta, fetal liver and fetal brain. Mice treated with these nanoparticles had smaller uteri and smaller fetuses than untreated controls. Fullerene molecules and larger (300 and 1,000 nm) silica particles did not induce these complications. These detrimental effects are linked to structural and functional abnormalities in the placenta on the maternal side, and are abolished when the surfaces of the silica nanoparticles are modified with carboxyl and amine groups.     

分子束外延PbTe/Cd 0.98 Zn 0.02 Te异系材料的微结构特性研究

采用分子束外延方法在Ⅱ-Ⅵ族Cd0.98Zn0.02Te(111)衬底上实现了异系Ⅳ-Ⅵ族半导体(PbTe)的外延生长.原子力显微镜(AFM)的表面形貌表征表明,PbTe表面形貌主要由三角形台阶线和螺旋形台阶面构成;理论计算表明,螺旋形台阶面的分布受到滑移位错弹性应变能的影响.通过高分辨透射电镜(HRTEM)观察,发现在PbTe和Cd0.98Zn0.02Te界面处存在Frank位错.分析表明,这些Frank位错在运动过程中会形成不同的位错组态,位错组态的相互作用是表面上形成三角形台阶线和螺旋形台阶面的主要原因.     

A design aid for crystal growth engineering

With the highly competitive development of chemical and pharmaceutical industries, mastering crystal growth is becoming increasingly necessary. Modern industrial manufacturers place high importance on the ability to grow crystals with a specific habit using tailored operating conditions. A detailed understanding of crystal growth is, therefore, vital for researchers in crystallography and crystallization to respond and realize this objective. Various models to predict crystal shape in the literature are reviewed here. The most commonly adopted are usually non-mechanistic and limited in their predictive power and utility, especially for products of industrial interest. Mechanistic models offer far more potential for rational crystal design, but require significant expertise to use and each new system studied typically requires additional investment. In this context, an automated implementation of mechanistic models (simulating and visualizing crystal growth under different environmental parameters) could eliminate this barrier to entry and promote widespread adoption to propel design of crystalline-based products into the next generation. With this need in mind, we have developed prototype software named ADDICT (Advanced Design and Development of Industrial Crystallization Technology), that enables an established spiral growth model to be applied to general systems of industrial interest. This proof-of-concept software provides an advanced theoretical framework to account for the solid state physics and surface chemistry, to guide experiments in a more efficient search of the design space for conditions that confer optimum functionality to the product. ADDICT calculates relative growth rates of crystal faces under the spiral regime, grown from vapor or solution, using information on the solid-state interactions that are organized into periodic bond chains. Solvent effects are principally accounted for by an interfacial modification of surface energies and the evolution of crystal habit under cycles of growth or dissolution can be predicted also. ADDICT has been tested for a variety of organic molecules, both centrosymmetric and non-centrosymmetric, resulting in successful predictions (examples for naphthalene, anthracene, paracetamol, lovastatin, D-mannitol, and α-glycine are presented).     

How selection forces dictate the variant surface antigens used by malaria parasites

Red blood cells infected by the malaria parasite Plasmodium falciparum express variant surface antigens (VSAs) that evade host immunity and allow the parasites to persist in the human population. There exist many different VSAs and the differential expression of these VSAs is associated with the virulence (damage to the host) of the parasites. The aim of this study is to unravel the differences in the effect key selection forces have on parasites expressing different VSAs such that we can better understand how VSAs enable the parasites to adapt to changes in their environment (like control measures) and how this may impact the virulence of the circulating parasites. To this end, we have built an individual-based model that captures the main selective forces on malaria parasites, namely parasite competition, host immunity, host death and mosquito abundance at both the within- and between-host levels. VSAs are defined by the net growth rates they infer to the parasites and the model keeps track of the expression of, and antibody build-up against, each VSA in all hosts. Our results show an ordered acquisition of VSA-specific antibodies with host age, which causes a dichotomy between the more virulent VSAs that reach high parasitaemias but are restricted to young relatively non-immune hosts, and less virulent VSAs that do not reach such high parasitaemias but can infect a wider range of hosts. The outcome of a change in the parasite''s environment in terms of parasite virulence depends on the exact balance between the selection forces, which sets the limiting factor for parasite survival. Parasites will evolve towards expressing more virulent VSAs when the limiting factor for parasite survival is the within-host parasite growth and the parasites are able to minimize this limitation by expressing more virulent VSAs.     

Calculation of elastic properties of natural fibers

This article deals with the calculation of the elastic properties of cellulose based natural fibers by using two different types of idealization and assumptions. One model (model A) bases on antisymmertrical laminated structure, while the second one (model B) bases on a thick laminated composite tube model. Model B is able to take into account the elliptic geometry, the hollow based structure of the cross section of the fiber cell. The calculated relationships between spiral angle and modulus in fiber axis by model A fits successful experimental data for holocellulose fibers which were published elsewhere. In general, modulus in fiber axis decreases with increasing spiral angle as well as the degree of anisotropy, while shear modulus reaches a maximum for a spiral angle of 45°. Fiber cell modulus increases linear with increasing cellulose content for both, the calculated (model A) and measured values. The correlation between experimental data and calculation ones was not as high as in the case of modulus versus spiral angle. The discrepancy between model A and a more real cross section is calculated (model B) with roughly 30%.     

Spiral hyperlens with enhancements of image resolution and magnification

Abstract

A subwavelength spiral hyperlens that is able to image beyond the diffraction limit is studied. The spiral hyperlens is made from an anisotropic metamaterial with a hyperbolic dispersion relation in which the evanescent wave is converted into a propagating wave. Therefore, the propagating wave can be processed by conventional optical systems outside of the spiral hyperlens. The possibility of using a cylindrical hyperlens for overcoming the diffraction limit has been proven analytically and experimentally. In this study, we designed two types of spiral hyperlenses composed of a spiral periodic stack of silver and alumina multilayers. A spiral hyperlens utilizes the spiral geometry to magnify the objects. In comparison with a cylindrical hyperlens, a spiral hyperlens has improved performance in terms of higher image resolution and better image magnifications. Numerical simulations illustrate that the far-field imaging resolution of cylindrical spiral hyperlens is no greater than 110 nm at 365 nm working wavelength.     

Quantifying the correlation between spatially defined oxygen gradients and cell fate in an engineered three-dimensional culture model

A challenge in three-dimensional tissue culture remains the lack of quantitative information linking nutrient delivery and cellular distribution. Both in vivo and in vitro, oxygen is delivered by diffusion from its source (blood vessel or the construct margins). The oxygen level at a defined distance from its source depends critically on the balance of diffusion and cellular metabolism. Cells may respond to this oxygen environment through proliferation, death and chemotaxis, resulting in spatially resolved gradients in cellular density. This study extracts novel spatially resolved and simultaneous data on tissue oxygenation, cellular proliferation, viability and chemotaxis in three-dimensional spiralled, cellular collagen constructs. Oxygen concentration gradients drove preferential cellular proliferation rates and viability in the higher oxygen zones and induced chemotaxis along the spiral of the collagen construct; an oxygen gradient of 1.03 mmHg mm⁻¹ in the spiral direction induced a mean migratory speed of 1015 μm day⁻¹. Although this movement was modest, it was effective in balancing the system to a stable cell density distribution, and provided insights into the natural cell mechanism for adapting cell number and activity to a prevailing oxygen regime.     

新型二维TiSe2纳米片的可控合成及其生长机理

溶液法是一种反应温和、易控制且常用的合成方法。目前已报道的溶液法制备TiSe₂时通常采用三辛基膦(TOP)为溶剂, 但这种试剂有毒, 对人体和环境都有潜在的危害。本研究通过简单的、无TOP的溶液法成功地制备了单分散的六边形TiSe₂纳米片, 并通过调整反应时间研究TiSe₂纳米片的形貌演变规律。利用XRD、SEM、EDS和紫外-可见漫反射对其物相、形貌、元素以及光学性能进行了系统的表征; 根据SEM结果对其生长过程及形貌演变规律进行了研究, 并提出一种螺旋状逐层生长的机理; 分析考察了TiSe₂纳米片对罗丹明B(RhB)的光催化活性, 发现其具有高于P25的降解能力, 这表明TiSe₂纳米片作为光催化材料具有广阔的应用前景。