Genetic variation of durum wheat landraces using morphological and protein markers

Genetic variations of cultivars are very interesting in reducing genetic vulnerability and lead to stable control of production. The aim of this research was to study genetic diversity among six durum wheat cultivars. For the first assay we evaluated seven morphological traits which are: spikelet per spike, spike length, spike width, beard length, plant height, width of truncation and barb length. The tested genotypes were classified in three groups according to the linkage distance analysis. The genetic variability was also evaluated for seed storage-proteins by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE). Electrophoregram allowed the estimation of the durum wheat genetic similarity (GS). This GS analysis based on Unweighted Pair Group Method with Arithmetic averages (UPGMA), permits to obtain the same genotypic clustering. No significant correlation was observed among the two methods tested. It is concluded that seed storage protein profiles could be useful markers in the studies of genetic diversity and genotypes classification, which can be used to improve the efficiency of wheat breeding programs.Key words: Wheat genotypes, SDS-PAGE, genetic diversity, cluster analysis

In situ Control of Si/Ge Growth on Stripe-Patterned Substrates Using Reflection High-Energy Electron Diffraction and Scanning Tunneling Microscopy

Si and Ge growth on the stripe-patterned Si (001) substrates is studied using in situ reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). During Si buffer growth, the evolution of RHEED patterns reveals a rapid change of the stripe morphology from a multifaceted “U” to a single-faceted “V” geometry with {119} sidewall facets. This allows to control the pattern morphology and to stop Si buffer growth once a well-defined stripe geometry is formed. Subsequent Ge growth on “V”-shaped stripes was performed at two different temperatures of 520 and 600°C. At low temperature of 520°C, pronounced sidewall ripples are formed at a critical coverage of 4.1 monolayers as revealed by the appearance of splitted diffraction streaks in RHEED. At 600°C, the ripple onset is shifted toward higher coverages, and at 5.2 monolayers dome islands are formed at the bottom of the stripes. These observations are in excellent agreement with STM images recorded at different Ge coverages. Therefore, RHEED is an efficient tool for in situ control of the growth process on stripe-patterned substrate templates. The comparison of the results obtained at different temperature reveals the importance of kinetics on the island formation process on patterned substrates

Energy-band engineering for improved charge retention in fully self-aligned double floating-gate single-electron memories

We present a new fully self-aligned single-electron memory with a single pair of nano floating gates, made of different materials (Si and Ge). The energy barrier that prevents stored charge leakage is induced not only by quantum effects but also by the conduction-band offset that arises between Ge and Si. The dimension and position of each floating gate are well defined and controlled. The devices exhibit a long retention time and single-electron injection at room temperature

The dynamic cilium in human diseases

Cilia are specialized organelles protruding from the cell surface of almost all mammalian cells. They consist of a basal body, composed of two centrioles, and a protruding body, named the axoneme. Although the basic structure of all cilia is the same, numerous differences emerge in different cell types, suggesting diverse functions. In recent years many studies have elucidated the function of 9+0 primary cilia. The primary cilium acts as an antenna for the cell, and several important pathways such as Hedgehog, Wnt and planar cell polarity (PCP) are transduced through it. Many studies on animal models have revealed that during embryogenesis the primary cilium has an essential role in defining the correct patterning of the body. Cilia are composed of hundreds of proteins and the impairment or dysfunction of one protein alone can cause complete loss of cilia or the formation of abnormal cilia. Mutations in ciliary proteins cause ciliopathies which can affect many organs at different levels of severity and are characterized by a wide spectrum of phenotypes. Ciliary proteins can be mutated in more than one ciliopathy, suggesting an interaction between proteins. To date, little is known about the role of primary cilia in adult life and it is tempting to speculate about their role in the maintenance of adult organs. The state of the art in primary cilia studies reveals a very intricate role. Analysis of cilia-related pathways and of the different clinical phenotypes of ciliopathies helps to shed light on the function of these sophisticated organelles. The aim of this review is to evaluate the recent advances in cilia function and the molecular mechanisms at the basis of their activity

Charge carrier traffic at self-assembled Ge quantum dots on Si

Due to their interesting size-dependent properties, semiconductor Quantum Dots (QDs) have many potential applications in nanoelectronics and optoelectronics. Ge QDs are particularly attractive because of the compatibility of Ge with Si technology and the ability to grow dislocation-free Ge QDs through the Stranski-Krastanov growth mode. Recently given examples include mm-wave circuit operation [1] with Ge QD Schottky diodes of 1.1 THz transit frequency or room temperature single electron memory [2] function of double (Si,Ge) dots. In this paper the voltage dependent occupation of states and their filling dynamics is investigated in two terminal device structures (Schottky barrier diode, p/n junction) by capacitance voltage (C-V) and deep level transient spectroscopy (DLTS) methods. Frequency scanned DLTS (FS-DLTS) was used, where the DLTS signal at a constant temperature is measured as a function of the repetition frequency of electrical pulses, f, with the emission voltage of the pulses, VR, as a parameter. Presenting DLTS spectra as a contour plot on a (f, VR)-plane, where contour lines with negative (positive) slope reflect signals related to thermal (tunnelling) transitions makes it possible to distinguish between these emission paths

Chargelocationeffectonthehydrationpropertiesofsyntheticsaponiteandhectorite saturated byNa+, Ca2+cations:XRDinvestigation

International audienceThispaperaimsatcomparingtheeffectofchargelocationonthehydrationpropertiesof twotrioctahedral syntheticminerals:saponiteandhectorite. Thesampleswerecharacterisedbyalayerchargeof 0.4charge perhalfunitcellandweresaturatedwithNa+orCa2+. Thehydrationbehaviourwasstudiedbydetermining thestructural characteristicswhichwereobtainedbymodellingXRDpatterns. XRDpatternswererecordedundercontrolledrelativehumidity(RH). Thehydratedstatesof Ca-hectorite weremorehomogeneousthanthoseofsaponitewhereasthetransitionfrom1Wto2WoccurredatlowerRH rates for saponitethanfor hectorite. For heterogeneous samples, the1Wand2Wlayers werestacked randomlyfashionforhectorite. Na-saponite-0.4andCa-saponite-0.4weremadeupof typesof layer; one waterlayer(1W)andtwo-waterlayers(2W). Thestackingof theselayersshowedsomesegregation

Charge carrier traffic at self-assembled Ge quantum dots on Si

Germanium quantum dots (QDs) have been characterized by deep level transient spectroscopy (DLTS) and capacitance versus voltage (C-V) technique. Two types of dots, grown by molecular beam epitaxy (MBE) at different temperatures, were investigated and assessed with respect to morphological properties. Samples with dots grown at 350 degrees C, were designed as n(++)-p-p(++) silicon junctions with the QDs positioned in the depleted p-region, while a second type of samples were Shottky diodes based on medium doped silicon with the QDs prepared at 550 degrees C and positioned in the Schottky depletion region. From the combined results of temperature scanned and frequency scanned DLTS, and by varying hole filling levels of the QD potentials, the energy distribution of states in the QD potentials were investigated. A wider distribution was found for the low-temperature QDs, probably related with a larger variation of size. By using a technique for separating tunneling and thermal hole emission, the average thermal activation energy for emitting holes to the valence band was found close to 0.40 eV for both types of QDs

Effect of interlayer cation and relative humidity on the hydration properties of a dioctahedral smectite

International audienceThis paper aims at characterizing the structural evolution of a dioctahedral smectite (i.e. Wyoming montmorillonite) saturated by Na+, Cu2+or Pb2+. Hydration properties of the <2μm size fraction of Wyoming montmorillonite smectite (SWy) source clay (low charge i.e. 0.35) were studied by modelling of X-ray diffraction (XRD) patterns recorded under controlled relative humidity (RH) conditions on Na, Cu or Pb saturated specimens. The Cation Exchange Capacity (CEC) of the starting sample was first Na+ saturated to guarantee better dispersion, followed by exchanges with the cations Cu2+ or Pb2+. The resulting complexes were respectively labelled Wy-Na, Wy-Cu and Wy-Pb. The qualitative analysis of XRD patterns obtained under room pressure and temperature conditions showed that all complexes have one water layer hydration state. In order to highlight the specific hydration properties of each complex, we studied the XRD patterns under controlled relative humidity (%RH). The quantitative analysis of XRD patterns is achieved using an indirect method based on the comparison of experimental XRD patterns with calculated ones. This quantitative study showed that for Wy-Na, Wy-Cu and Wy-Pb at low RH (≈15%) the d001 spacing corresponds to a low hydration state characterized by one water layer, whereas for higher studied rates of relative humidity (75%), differences of hydration state can be distinguished for Wy-Na, Wy-Cu and Wy-Pb samples

Study of the structural evolution and selectivity of Wyoming montmorillonite in relation with the concentration of Cu2+ and Ni2+

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Growth of ultrahigh-density quantum-confined germanium dots on SiO 2 thin films

The spontaneous formation of nanometric and highly dense (similar to 3x10(12) cm(-2)) Ge droplets on thin SiO2 film on Si(001) is investigated by scanning tunneling microscopy and spectroscopy. Ge dots have been grown by depositing Ge on the clean SiO2 surface at room temperature and then annealing the sample at 500 degrees C. Ge dots appear to be free of germanium oxides and characterized by a flat surface with the onset of {113} faceting. I-V curves show that they have an energy gap of approximately 1.8 eV, well above that of bulk Ge. Fabrication of nanometer-sized, highly dense pure Ge droplets is very promising for nanoelectronics applications. (c) 2006 American Institute of Physics