Novel variants in growth differentiation factor 9 in mothers of dizygotic twins

Context: Genes from the ovarian bone morphogenetic signaling pathway (GDF9 and BMP15) are critical for normal human fertility. We previously identified a deletion mutation in GDF9 in sisters with spontaneous dizygotic (DZ) twins, but the prevalence of rare GDF9 variants in twinning families is unknown. Objective: The objective was to evaluate the frequency of rare variants in GDF9 in families with a history of DZ twinning. Design and Subjects: We recruited 3450 individuals from 915 DZ twinning families (1693 mothers of twins) and 1512 controls of Caucasian origin. One mother of DZ twins was selected from 279 of the 915 families, and a DNA sample was screened for rare variants in GDF9 using denaturant HPLC. Variants were confirmed by DNA sequencing and genotyped in the entire sample by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry. Results: We found two novel insertion/deletions (c.392-393insT, c.1268-1269delAA) and four missense alterations in the GDF9 sequence in mothers of twins. Two of the missense variants (c.307C > T, p.Pro103Ser and c.362C > T, p.Thr121Leu) were located in the proregion of GDF9 and two (c.1121C > T, p.Pro374Leu and c.1360C > T, p.Arg454Cys) in the mature protein region. For each variant, the frequencies were higher in cases compared with controls. The proportion of mothers of DZ twins carrying any variant (4.12%) was significantly higher (P < 0.0001) than the proportion of carriers in controls (2.29%). Conclusion: We describe new variants in the GDF9 gene that are significantly more common in mothers of DZ twins than controls, suggesting that rare GDF9 variants contribute to the likelihood of DZ twinning.

Growth hormone as a cytokine

1. The growth hormone (GH) receptor was the first of the class 1 cytokine receptors to be cloned. It shares a number of structural characteristics with other family members and common signalling mechanisms based on common usage of the Janus kinase 2 (JAK2). 2. Growth hormone receptor activation is initiated by GH-induced homodimerization of receptor molecules. This has enabled the creation of specific hormone antagonists that block receptor dimerization. 3. The details of the transcription factors used by the activated receptor are being revealed as a result of promoter analyses and electrophoretic mobility gelshift analysis. 4. Growth hormone receptors are widespread and their discovery in certain tissues has led to the assignment of new physiological roles for GH, Some of these involve local or paracrine roles for GH, as befits its cytokine status. 5. Four examples of such novel roles are discussed, These are: (i) the brain GH axis; (ii) GH and the vitamin B-12 axis; (iii) GH in early pre-implantation development; and (iv) GH in development of the tooth. 6. We propose that the view that GH acts through the intermediacy of insulin-like growth factor-1 is simplistic; rather, GH acts to induce an array of growth factors and their receptors and the composition of this array varies with tissue type and, probably, stage of development.

Determinants of employment growth at MNEs:evidence from Egypt, India, South Africa and Vietnam

Many foreign investment operations into emerging markets are small, and are likely to have only a limited impact on the local economy. However, host governments often expect transfer of advanced technology from multinational enterprises (MNEs) operating in these markets to local firms by way of inter-firm mobility of skilled labourers. The extent of such transfers would be limited, among other factors, by the size of the pool of skilled labourers that can potentially be mobile between MNEs and local firms. This, in turn, is determined by employment growth at the MNEs. We develop an empirical specification that models this employment growth, by drawing on both the economics and international business literature. This model is then estimated using firm-level data from four emerging markets. We find that wholly owned foreign direct investment operations have higher employment growth, while local industry and institutional characteristics moderate the growth effect. This suggests that policies encouraging foreign investors to set up in form of joint ventures may not actually raise the benefits for the host economy.

High rate growth of nanocrystalline diamond films using high microwave power and pure nitrogen/methane/hydrogen plasma

In this work, we investigate the impact of minute amounts of pure nitrogen addition into conventional methane/hydrogen mixtures on the growth characteristics of nanocrystalline diamond (NCD) films by microwave plasma assisted chemical vapour deposition (MPCVD), under high power conditions. The NCD films were produced from a gas mixture of 4% CH4/H2 with two different concentrations of N2 additive and microwave power ranging from 3.0 kW to 4.0 kW, while keeping all the other operating parameters constant. The morphology, grain size, microstructure and texture of the resulting NCD films were characterized by using scanning electron microscope (SEM), micro-Raman spectroscopy and X-ray diffraction (XRD) techniques. N2 addition was found to be the main parameter responsible for the formation and for the key change in the growth characteristics of NCD films under the employed conditions. Growth rates ranging from 5.4 μm/h up to 9.6 μm/h were achieved for the NCD films, much higher than those usually reported in the literature. The enhancing factor of nitrogen addition on NCD growth rate was obtained by comparing with the growth rate of large-grained microcrystalline diamond films grown without nitrogen and discussed by comparing with that of single crystal diamond through theoretical work in the literature. This achievement on NCD growth rate makes the technology interesting for industrial applications where fast coating of large substrates is highly desirable.

Effect of mean stress on hydrogen assisted fatique crack propagation in duplex stainless steel

Hydrogen assisted subcritical cleavage of the ferrite matrix occurs during fatigue of a duplex stainless steel in gaseous hydrogen. The ferrite fails by a cyclic cleavage mechanism and fatigue crack growth rates are independent of frequency between 0.1 and 5 Hz. Macroscopic crack growth rates are controlled by the fraction of ferrite grains cleaving along the crack front, which can be related to the maximum stress intensity, Kmax. A superposition model is developed to predict simultaneously the effects of stress intensity range (ΔK) and K ratio (Kmin/Kmax). The effect of Kmax is rationalised by a local cleavage criterion which requires a critical tensile stress, normal to the {001} cleavage plane, acting over a critical distance within an embrittled zone at the crack tip. © 1991.

Temperature effects on the mechanism of time independent hydrogen assisted fatigue crack propagation in steels

The effects of temperature on hydrogen assisted fatigue crack propagation are investigated in three steels in the low-to-medium strength range; a low alloy structural steel, a super duplex stainless steel, and a super ferritic stainless steel. Significant enhancement of crack growth rates is observed in hydrogen gas at atmospheric pressure in all three materials. Failure occurs via a mechanism of time independent, transgranular, cyclic cleavage over a frequency range of 0.1-5 Hz. Increasing the temperature in hydrogen up to 80°C markedly reduces the degree of embrittlement in the structural and super ferritic steels. No such effect is observed in the duplex stainless steel until the temperature exceeds 120°C. The temperature response may be understood by considering the interaction between absorbed hydrogen and micro-structural traps, which are generated in the zone of intense plastic deformation ahead of the fatigue crack tip. © 1992.

In-situ XPS study on the reducibility of Pd-promoted Cu/CeO2 catalysts for the oxygen-assisted water-gas-shift reaction

Cu/CeO2, Pd/CeO2, and CuPd/CeO2 catalysts were prepared and their reduction followed by in-situ XPS in order to explore promoter and support interactions in a bimetallic CuPd/CeO2 catalyst effective for the oxygen-assisted water-gas-shift (OWGS) reaction. Mutual interactions between Cu, Pd, and CeO2 components all affect the reduction process. Addition of only 1 wt% Pd to 30 wt% Cu/CeO2 greatly enhances the reducibility of both dispersed CuO and ceria support. In-vacuo reduction (inside XPS chamber) up to 400 °C results in a continuous growth of metallic copper and Ce3+ surface species, although higher temperatures results in support reoxidation. Supported copper in turn destabilizes metallic palladium metal with respect to PdO, this mutual perturbation indicating a strong intimate interaction between the Cu–Pd components. Despite its lower intrinsic reactivity towards OWGS, palladium addition at only 1 wt% loading significantly improved CO conversion in OWGS reaction over a monometallic 30 wt% Cu/CeO2 catalysts, possibly by helping to maintain Cu in a reduced state during reaction.

Characterisation of cascaded Raman-assisted fibre optical parametric amplifiers using WDM QPSK signals

We report the first WDM numerical characterisation of crosstalk growth in cascaded Raman-Assisted Fibre Optical Parametric Amplifiers (RA-FOPAs). A cascade of ten RA-FOPAs results in ∼13dB lower crosstalk than the equivalent cascade of conventional FOPAs.

AuxAg1-x alloy seeds: A way to control growth, morphology and defect formation in Ge nanowires

Germanium (Ge) nanowires are of current research interest for high speed nanoelectronic devices due to the lower band gap and high carrier mobility compatible with high K-dielectrics and larger excitonic Bohr radius ensuing a more pronounced quantum confinement effect [1-6]. A general way for the growth of Ge nanowires is to use liquid or a solid growth promoters in a bottom-up approach which allow control of the aspect ratio, diameter, and structure of 1D crystals via external parameters, such as precursor feedstock, temperature, operating pressure, precursor flow rate etc [3, 7-11]. The Solid-phase seeding is preferred for more control processing of the nanomaterials and potential suppression of the unintentional incorporation of high dopant concentrations in semiconductor nanowires and unrequired compositional tailing of the seed-nanowire interface [2, 5, 9, 12]. There are therefore distinct features of the solid phase seeding mechanism that potentially offer opportunities for the controlled processing of nanomaterials with new physical properties. A superior control over the growth kinetics of nanowires could be achieved by controlling the inherent growth constraints instead of external parameters which always account for instrumental inaccuracy. The high dopant concentrations in semiconductor nanowires can result from unintentional incorporation of atoms from the metal seed material, as described for the Al catalyzed VLS growth of Si nanowires [13] which can in turn be depressed by solid-phase seeding. In addition, the creation of very sharp interfaces between group IV semiconductor segments has been achieved by solid seeds [14], whereas the traditionally used liquid Au particles often leads to compositional tailing of the interface [15] . Korgel et al. also described the superior size retention of metal seeds in a SFSS nanowire growth process, when compared to a SFLS process using Au colloids [12]. Here in this work we have used silver and alloy seed particle with different compositions to manipulate the growth of nanowires in sub-eutectic regime. The solid seeding approach also gives an opportunity to influence the crystallinity of the nanowires independent of the substrate. Taking advantage of the readily formation of stacking faults in metal nanoparticles, lamellar twins in nanowires could be formed.

MOVPE growth and characterization of Al(Ga)N and InAlN/AlGaN quantum wells for UV LED applications

The study of III-nitride materials (InN, GaN and AlN) gained huge research momentum after breakthroughs in the production light emitting diodes (LEDs) and laser diodes (LDs) over the past two decades. Last year, the Nobel Prize in Physics was awarded jointly to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for inventing a new energy efficient and environmental friendly light source: blue light-emitting diode (LED) from III-nitride semiconductors in the early 1990s. Nowadays, III-nitride materials not only play an increasingly important role in the lighting technology, but also become prospective candidates in other areas, for example, the high frequency (RF) high electron mobility transistor (HEMT) and photovoltaics. These devices require the growth of high quality III-nitride films, which can be prepared using metal organic vapour phase epitaxy (MOVPE). The main aim of my thesis is to study and develop the growth of III-nitride films, including AlN, u-AlGaN, Si-doped AlGaN, and InAlN, serving as sample wafers for fabrication of ultraviolet (UV) LEDs, in order to replace the conventional bulky, expensive and environmentally harmful mercury lamp as new UV light sources. For application to UV LEDs, reducing the threading dislocation density (TDD) in AlN epilayers on sapphire substrates is a key parameter for achieving high-efficiency AlGaNbased UV emitters. In Chapter 4, after careful and systematic optimisation， a working set of conditions, the screw and edge type dislocation density in the AlN were reduced to around 2.2×108 cm-2 and 1.3×109 cm-2 , respectively, using an optimized three-step process, as estimated by TEM. An atomically smooth surface with an RMS roughness of around 0.3 nm achieved over 5×5 µm 2 AFM scale. Furthermore, the motion of the steps in a one dimension model has been proposed to describe surface morphology evolution, especially the step bunching feature found under non-optimal conditions. In Chapter 5, control of alloy composition and the maintenance of compositional uniformity across a growing epilayer surface were demonstrated for the development of u-AlGaN epilayers. Optimized conditions (i.e. a high growth temperature of 1245 °C) produced uniform and smooth film with a low RMS roughness of around 2 nm achieved in 20×20 µm 2 AFM scan. The dopant that is most commonly used to obtain n-type conductivity in AlxGa1-xN is Si. However, the incorporation of Si has been found to increase the strain relaxation and promote unintentional incorporation of other impurities (O and C) during Si-doped AlGaN growth. In Chapter 6, reducing edge-type TDs is observed to be an effective appoach to improve the electric and optical properties of Si-doped AlGaN epilayers. In addition, the maximum electron concentration of 1.3×1019 cm-3 and 6.4×1018 cm-3 were achieved in Si-doped Al0.48Ga0.52N and Al0.6Ga0.4N epilayers as measured using Hall effect. Finally, in Chapter 7, studies on the growth of InAlN/AlGaN multiple quantum well (MQW) structures were performed, and exposing InAlN QW to a higher temperature during the ramp to the growth temperature of AlGaN barrier (around 1100 °C) will suffer a significant indium (In) desorption. To overcome this issue, quasi-two-tempeature (Q2T) technique was applied to protect InAlN QW. After optimization, an intense UV emission from MQWs has been observed in the UV spectral range from 320 to 350 nm measured by room temperature photoluminescence.

Epitaxial growth of molecular crystals on van der Waals substrates for high-performance organic electronics

Epitaxial van der Waals (vdW) heterostructures of organic and layered materials are demonstrated to create high-performance organic electronic devices. High-quality rubrene films with large single-crystalline domains are grown on h-BN dielectric layers via vdW epitaxy. In addition, high carrier mobility comparable to free-standing single-crystal counterparts is achieved by forming interfacial electrical contacts with graphene electrodes.

Residential planning, driver mobility and CO2 emission

The literature on residences and citizens’ transports has focused on either reforming traffic managing in response to residential relocation or post-evaluation of urban planning policies or the evolution of the urban spatial form. In a city there are hotspots that attract the citizens and most of the transportation in the city arises as the citizens’ movement between their residence and the hotspots. Little scholarly attention has been devoted to the possibility to minimize citizens’ transportation in the city by the urban planning of residential areas. In this paper we propose a method to evaluate the environmental impact (in terms of CO2-emissions) of urban plans of residential areas. The method is illustrated in a Swedish case of a midsize city which is presently preoccupied with urban planning of new residential areas in response to substantial population growth due to immigration. The residential plans aims to increase the compactness and residential density in the current center and sub centers leads to less CO2 emissions compare to urban expansion to the edge of the city. The plans of concentrated apartment buildings are more effective in meeting residential needs and mitigating CO2 emissions than dispersed single-family houses.

How to motivate faster growth in Colombia : the leading sector strategy revisited

This paper reproduces two public lectures given at an Incolda conference in Bogota, October 1, 2002 on «La Realidad de la Economía Colombiana ». It reviews the great structuralchanges in output and employment over recent decades and how macroeconomic policies can strengthen or weaken the natural forces underlying these changes. It distinguishes between potentially inflationary policies designed to increase demand ina monetary sense, and those that focus on institutional changes that enhance competition and mobility. It explains how inflation distorts the allocation of resources, and why it especially harms long-term housing finance and exports. It explains the logic of Lauchlin Currie¿s leading sector theory of growth and shows whyand how housing and exports can be given special protection to accelerate development.

Vacuum-assisted closure treatment of leg skin necrosis after angiographic embolization of a giant plexiform neurofibroma

Type 1 neurofibromatosis is a relatively common inherited disease of the nervous system, with a frequency of almost 1 in 3000. It is associated with neurofibromas of various sites. Our case report is about the surgical management of a giant neurofibroma of the right gluteal fold in a 46-year-old male with NF1. The patient presented with increasing edema and accelerated growth of the mass; he underwent percutaneous embolization of lesion vessels that induced necrosis of the neurofibroma. The patient was taken to the operating room, where surgical resection of the bulk of the lesion was undertaken. The postoperative course was complicated by delayed wound closure managed with antibiotics and vacuum-assisted wound closure. Giant neurofibromas similar to this tumor require complex preoperative, intraoperative and postoperative management strategies. Surgical debulk is best managed with preoperative percutaneous embolization that help to avoid surgical bleeding. Postoperative delayed wound closure was managed with the application of negative pressure in a closed environment that triggers granulation and tissue formation.

Growth and characterization of III-V compound semiconductor nanostructures by metalorganic chemical vapor deposition

Planar <110> GaAs nanowires and quantum dots grown by atmospheric MOCVD have been introduced to non-standard growth conditions such as incorporating Zn and growing them on free-standing suspended films and on 10° off-cut substrates. Zn doped nanowires exhibited periodic notching along the axis of the wire that is dependent on Zn/Ga gas phase molar ratios. Planar nanowires grown on suspended thin films give insight into the mobility of the seed particle and change in growth direction. Nanowires that were grown on the off-cut sample exhibit anti-parallel growth direction changes. Quantum dots are grown on suspended thin films and show preferential growth at certain temperatures. Envisioned nanowire applications include twin-plane superlattices, axial pn-junctions, nanowire lasers, and the modulation of nanowire growth direction against an impeding barrier and varying substrate conditions.