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Sufficient I intake is important for the synthesis of thyroid hormones, which play an important role in normal growth and development. Our aim was to estimate habitual I intake for the Dutch population and the risk of inadequate or excessive intakes. Further, we aimed to provide an insight into the dietary sources of I and the association with socio-demographic factors. Data from the Dutch National Food Consumption Survey 2007–2010 (n 3819; 7–69 years), and from the Dutch food and supplement composition tables were used to estimate habitual I intake with a calculation model. Contribution of food groups to I intake were computed and multiple linear regression was used to examine associations of intakes with socio-demographic factors. A total of ≤2 % of the population had an intake below the estimated average requirement or above the upper level. The main sources of I were bread containing iodised salt (39 %), dairy products (14 %) and non-alcoholic drinks (6 %). I intake (natural sources only, excluding iodised salt and supplements) was positively associated with (parental) education, which could at least partly be attributed to a higher consumption of dairy products. Among children, the consumption of bread, often containing iodised bakery salt, was positively associated with parental education. The I intake of the Dutch population (7–69 years) seems adequate, although it has decreased since the period before 2008. With the current effort to reduce salt intake and changing dietary patterns (i.e. less bread, more organic foods) it is important to keep a close track on the I status, important sources and potential risk groups.
We investigated the validity and reproducibility of the FFQ used in the Dutch European Investigation of Cancer and Nutrition cohort, in order to rank subjects according to intakes of fatty acid classes and individual fatty acids. In total, 121 men and women (23–72 years) filled out three FFQ at 6-month intervals between 1991 and 1992. As a reference method, they filled out twelve monthly 24-h dietary recalls (24HDR) during the same year. Intra-class correlation coefficients for the FFQ showed moderate to good reproducibility across all fatty acids (classes and individual) in men (0·56–0·81) and women (0·57–0·83). In men, Spearman’s correlation coefficients (rs) for the FFQ compared with the 24HDR indicated moderate to good relative validity (rs=0·45–0·71) for all fatty acids, except for arachidonic acid and marine PUFA (rs<0·40). In women, relative validity was moderate to good for MUFA and trans-fatty acids (TFA) and the majority of SFA (rs=0·40–0·66), was fair for the short-chain SFA and lauric acid (rs=0·30–0·33) and was fair to moderate for PUFA (rs=0·22–0·47). Bland–Altman plots showed good agreement between the FFQ and 24HDR, and proportional bias for fatty acids with very low intakes. In conclusion, the FFQ showed good reproducibility for subject ranking based on intakes of fatty acids (classes and individual). The relative validity measures indicated that the FFQ is an adequate tool to rank subjects according to intakes of high-abundant fatty acids, but less for low-abundant fatty acids.
Measurements of the electrical resistivity and magnetoresistivity are reported for 100 nm buried α-FeSi2 in the temperature range 1.2 to 300 K, and in magnetic fields up to 5 Tesla.The metallic α-FeSi2 phase, formed by ion-beam synthesis and subsequent rapid-thermal annealing, is found to have a high residual resistivity of about 227 μΩ2 cm. Furthermore, a minimum in the electrical resistivity is found at 40 K. Combined with mnagnetore si stance measurements it is concluded that this minimum cannot be attributed to the Kondo effect, but is caused by weak localisation and spin-orbit interaction due to the very strong elastic scattering in the material. From the magnetoresistance measurements, at temperatures below 40 K, the relaxation times due to inelastic and spin-orbit scattering are deduced. The inelastic scattering rate is found to saturate below 4.2 K, and follow a T3 power law between 4.2 K to 40 K.
In this paper the electrical properties of epitaxial CoSi2 on Si obtained by solid-state reaction of a Ti/Co bimetallic layer are investigated. Low temperature resistivity, magnetoresistance and Hall data are presented. The CoSi2ISi Schottky diodes are characterised by current - voltage and capacitance - voltage measurements at temperatures varying between - 100°C and 60°C.
An investigation of the influence of an intermediate titanium thin film on the silicidation reaction between an overlying iron film and the (100)-oriented silicon substrate is presented. The Fe-Ti bilayers were obtained by consecutive sputtering of a Ti layer and an Fe layer on Si substrates. In addition, single iron layers were made by sputtering for comparison with the bilayers. By subsequent rapid-thermnal processing (RTP), depending on the annealing conditions, both the semiconducting β- and the metallic α-FeSi2 thin films could be formed. The phase formation has been investigated as a function of the thickness of the titanium layer, the annealing time and temperature. In this paper the first results on iron disilicide formation through Fe-Ti-Si diffusion couples are shown. Characterisation of the FeSi2 layers using Rutherford backscattering spectrometry (RBS), channelling RBS, X-ray diffraction (XRD), sheet resistivity measurements will be presented.
Epidemiological studies suggest health-protective effects of flavan-3-ols and their derived compounds on chronic diseases. The present study aimed to estimate dietary flavan-3-ol, proanthocyanidin (PA) and theaflavin intakes, their food sources and potential determinants in the European Prospective Investigation into Cancer and Nutrition (EPIC) calibration cohort. Dietary data were collected using a standardised 24 h dietary recall software administered to 36 037 subjects aged 35–74 years. Dietary data were linked with a flavanoid food composition database compiled from the latest US Department of Agriculture and Phenol-Explorer databases and expanded to include recipes, estimations and retention factors. Total flavan-3-ol intake was the highest in UK Health-conscious men (453·6 mg/d) and women of UK General population (377·6 mg/d), while the intake was the lowest in Greece (men: 160·5 mg/d; women: 124·8 mg/d). Monomer intake was the highest in UK General population (men: 213·5 mg/d; women: 178·6 mg/d) and the lowest in Greece (men: 26·6 mg/d in men; women: 20·7 mg/d). Theaflavin intake was the highest in UK General population (men: 29·3 mg/d; women: 25·3 mg/d) and close to zero in Greece and Spain. PA intake was the highest in Asturias (men: 455·2 mg/d) and San Sebastian (women: 253 mg/d), while being the lowest in Greece (men: 134·6 mg/d; women: 101·0 mg/d). Except for the UK, non-citrus fruits (apples/pears) were the highest contributors to the total flavan-3-ol intake. Tea was the main contributor of total flavan-3-ols in the UK. Flavan-3-ol, PA and theaflavin intakes were significantly different among all assessed groups. This study showed heterogeneity in flavan-3-ol, PA and theaflavin intake throughout the EPIC countries.
Flavonols, flavanones and flavones (FLAV) are sub-classes of flavonoids that exert cardioprotective and anti-carcinogenic properties in vitro and in vivo. We aimed to estimate the FLAV dietary intake, their food sources and associated lifestyle factors in ten European countries participating in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. FLAV intake and their food sources for 36 037 subjects, aged between 35 and 74 years, in twenty-seven study centres were obtained using standardised 24 h dietary recall software (EPIC-SOFT). An ad hoc food composition database on FLAV was compiled using data from US Department of Agriculture and Phenol-Explorer databases and was expanded using recipes, estimations and flavonoid retention factors in order to increase its correspondence with the 24 h dietary recall. Our results showed that the highest FLAV-consuming centre was the UK health-conscious group, with 130·9 and 97·0 mg/d for men and women, respectively. The lowest FLAV intakes were 36·8 mg/d in men from Umeå and 37·2 mg/d in women from Malmö (Sweden). The flavanone sub-class was the main contributor to the total FLAV intake ranging from 46·6 to 52·9 % depending on the region. Flavonols ranged from 38·5 to 47·3 % and flavones from 5·8 to 8·6 %. FLAV intake was higher in women, non-smokers, increased with level of education and physical activity. The major food sources were citrus fruits and citrus-based juices (especially for flavanones), tea, wine, other fruits and some vegetables. We concluded that the present study shows heterogeneity in intake of these three sub-classes of flavonoids across European regions and highlights differences by sex and other sociodemographic and lifestyle factors.
The paper presents a systematic study of grown-in and process-induced defects on LEC GaAs substrates. Defects have been revealed by photoetching the wafers with diluted Sirti-like solutions after various processing steps. MESFET arrays have been processed on the wafers and a systematic mapping of the I-V characteristics has been performed. A correlation between various defect configurations and the FET threshold voltage shifts has been established.
Raman spectroscopy is used to study crystal damage and electrical damage in n+-GaAs produced by reactive ion etching (REE). H2 RIE is compared with CH4/H2 RIE and the effect of temperature annealing is studied. The results are compared with C-V analysis. It is found that structural damage introduced by RIE in the surface layers of the sample is larger for the H2 plasma than for the CH4/H2 plasma. Annealing results in a decrease of this structural damage. H2 RIE as well as CH4/H2 RIE cause an increase of the inactive surface region. This increase is found to be larger for the H2 RDE. C-V experiments show that annealing results in a reactivation and associated decrease of the width of the inactive region.
The amorphous phaseformation in Ti-Si bilayers upon ion mixing at elevated temperatures and in Ti-Si multilayers upon thermal treatment was studied. In the case of ion mixing with 5×1015 cm−2 Xe atoms at temperatures around 240°C a 100nm thick amorphous Ti-Si alloy is formed with a very homogeneous Ti:Si=3 :4 composition. Thermal treatment of the Ti-Si multilayer structure at similar temperatures also yields amorphous silicide layers. The results are interpreted according to the evolution in a planar binary diffusion couple, where the Si and Ti concentrations in the reacted layer are dictated by thermodynamic and kinetic arguments.
Te atoms were implanted in GaAs with doses ranging from 1013 to 1016 atoms/cm2, and annealed with the rapid thermal annealing technique. The samples were studied by Mössbauer Spectroscopy, Rutherford Backscattering Spectroscopy – Channeling, and the Van der Pauw-method. While at the lowest implantation dose an unperturbed substitutional site is observed at all annealing temperatures, at the highest implantation dose a strong deviation from a central position in an unperturbed configuration is observed at all temperatures. At the intermediate doses a high degree of substitutionality is observed between annealing temperatures of 200°C and 500°C only.
The damage introduced by CH4/H2 reactive ion etching (RIE) and its recovery after thermal annealing has been investigated by Hall measurements and low temperature photoluminescence (PL) on pseudomorphic AlGaAs/InGaAs modulation doped structures. After plasma exposure, the PL intensity has significantly decreased and shifted in energy. In order to study the recovery of the damage introduced by the plasma, thermal annealing was done at temperatures between 350 and 500°C. We observed that the luminescence emission is totally recovered after annealing at 450°C. Hall measurements at room temperature (RT) and at 77K showed that the electrical characteristics of these structures can be restored only after thermal annealing at 500°C.
The optimised etching conditions have been applied in a fabrication process for submicron dry gate recessed pseudomorphic delta-doped AlGaAs/InGaAs modulation doped field effect transistors (MODFETs). For a 0.25 mm gatelength device the maximum DC transconductance value was as high as 680 mS/mm. The same value was extracted from measurements at 15 GHz.
The formation of pulsed laser processed AuTe/n—GaAs ohmic contacts was investigated using I—V measurements, Rutherford Backscattering, and Mössbauer spectroscopy. Ohmic contact resistances comparable to those of furnace processed AuTe and AuGe/GaAs contacts were measured; however, a much thinner intermixed layer was obtained by the laser processing. No evidence for the formation of a n++—GaAs layer could be derived from the experimental data. The results are more consistent with the model explaining the ohmic conduction mechanism by the formation of a graded heterojunction structure.
We have compared the formation of amorphous alloys from Ni-Hf multilayer films by ion mixing and solid state diffusion. We find that ion mixing and solid state reaction produce significant differences in the composition range of the amorphous phase inside the mixed samples. Moreover, the thermochemical parameters which are of primary importance for the solid state reaction also influence the behavior of the Ni-Hf system under ion mixing.
A study on ion beam synthesis of buried α- and β-FeSi2 in >100< Si is presented. Phase formation has been investigated as a function of implant and anneal temperature. Layer characterization was performed by RBS, XRD, resistivity, spreading resistance and Hall effect measurements. Orientation effects in the layers have been observed depending on the implant temperature. Transport measurements show that die holes are the majority carriers in the semiconducting layers.
We report for the first time the realization of submicron pseudomorphic Al.15, Ga.85As-In.20Ga.80As HEMT’s with non-alloyed Pd/Ge ohmic coi tacts. Best results of contact resistance were obtained at a sintering temperature of 340°C with values as low as 0.057 Ωmm. Enhanced contrast, needed for accurate alignment of the gate by electron-beam lithography, was obtained by using Pd/Ge/Ti/Pd and Pd/Ge/Ti/Pt metal sequences. These contacts exhibited even lower contact resistances than the standard Pd/Ge contacts. Although Pd/Ge/Ti/Pd exhibits good morphology, reaction is witnessed at the edges, reducing the accuracy of alignment.
Processed enhancement mode devices exhibit maximum transconductances in excess of 520 mS/mm and currents of 300 mA/mm for 0.3 micron gatelength. This study shows that the contact resistance is no longer a restriction for obtaining very high transconductances in high performance devices.
Alloyed Au/Te/n–GaAs ohmic contacts, with contact resistivities comparable to those of the AuGe device standard, have been developed and studied by Mässbauer spectroscopy, Raman scattering and X-Ray Diffraction. The formation of Au-doped Ga2Te3 crystallites, grown epitaxially on a defectively GaAs surface was observed. No evidence for the formation of an n++–GaAs surface layer could be derived. The interpretation of all experimental results leads to a description of the ohmic conduction mechanism based on a resonant tunneling process assisted by defect/impurity related deep levels through low barrier metal/Te/(Au)Ga2Te3/GaAs interfaces
The results of our recent research on the ohmic contact formation mechanism in furnace alloyed Au/Te/Au/GaAs contacts are summarized, and preliminary Raman measurements on annealed Ge/Pd/GaAs structures are presented. The data and those reported in literature on the AuGe- and Ge/Pd- GaAs systems are argued to be more in agreement with the graded crystalline heterojunction concept (the formation of n+-Ge/GaAs, n+Ga2Te3/GaAs junctions) than with the doping model (the formation of n+-GaAs).
The effect of CH4/H2 reactive ion etching (RIE) on Si-doped AlxGa1−xAs (x=0.25) is studied by deep level transient spectroscopy (DLTS) and Hall measurements. After RIE exposure, the samples were annealed between 250 and 500°C in order to study the recovery kinetics of deep and shallow levels. Non-etched reference samples showed broad DLTS spectra which were deconvoluted in two different emission peaks. We assigned them to DX1 and DX2 centers. The different deep levels are characierized by different aluminium configurations, one or two aluminium atoms, surrounding the silicon donor which are responsible for the DX centers. After RIE exposure and subsequent thermal annealing, a third emission peak is observed. This emission is attributed to the DX3 center, which is characterized by three aluminium atoms neighbouring the silicon donor. The recovery activation energy is calculated based on first-order kinetics. The activation energies are found to be around 1.9 eV in all cases.
Complementary Hall measurements as a function of temperature (4-300 K) were used to characterize the electron capture of deep levels in Si-doped AlGaAs exposed to CH4/H2 RIE. We observed that the samples exposed to RIE and annealed at temperatures higher than 400°C exhibit electron capture in the 120-150 K temperature range. On the other hand, samples annealed at lower temperatures, showed additional capture features between 200 and 230 K.
The damage introduced by CH4/H2 reactive ion etching (RIE) on Si-doped AlGaAs layers is studied by X-Ray Photoelectron Spectroscopy (XPS), Auger electron spectrocopy (AES) and electrical measurements on Schottky contacts. The XPS analysis of the surface stoichiometry after RIE exposure shows arsenic depletion and adsorbed carbon as the main characteristics. The carbon spectrum consists of a component due to atmospheric contamination and an additional photoelectron peak at 283 eV, which we correlate with the formation of Ga-C radicals at the AlGaAs surface during RIE. The reaction process at the Au/TiW/Ti/AlGaAs interface after RIE exposure and subsequent thermal annealing is monitored by AES. Also by this technique, carbon was detected at the Ti/AlGaAs interface and no interdiffusion was observed. The electrical behaviour of the contacts is characterized by capacitance-voltage (CV) and current-voltage (IV) measurements. Schottky barrier height, ideality factor and reverse breakdown were determined. The barrier height extracted from CV measurements of the samples exposed to RIE shows increased values (1.1 to 1.4 eV) compared to the reference samples (1.0 to 1.1 eV), depending on the aluminium concentration. The same behaviour was observed in the ideality factor. The results are explained by the formation of a p-n junction below the metal/AlGaAs barrier. Good agreement between experimental and theoretical values is found when the compensation of Si donors was taken into account.