bluuebunny/crossref_metadata_2025 huggingface dataset:
Highly low resistance and transparent Ni/ZnO ohmic contacts to p-type GaN
Authors: Song June O , Kim Kyoung-Kook , Park Seong-Ju , Seong Tae-Yeon
Published: July 2003

We report on a promising Ni (5 nm)/Al-doped ZnO (AZO) (450 nm) metallization scheme for low resistance and transparent ohmic contacts to p-GaN (5×1017 cm−3). It is shown that the as-deposited Ni/AZO contact shows a nonohmic characteristic due to the insulating nature of the as-deposited AZO. However, annealing the contacts at 450 and 550 °C for 2 min in air ambient results in linear current–voltage characteristics, giving a specific contact resistance of 1.01×10−5 and 8.46×10−6 Ω cm2, respectively. It is further shown that annealing the contact at 550 °C for 5 min produces a specific contact resistance of 6.23×10−6 Ω cm2. The light transmittance of the contacts annealed at 550 °C for 2 min is measured to be higher than 76% at wavelengths in the range of 400–550 nm. It is shown that the Ni/AZO contact could be a suitable scheme for high-performance optical devices.
Scaling behavior of ferroelectric hysteresis loop in pulsed-laser-deposited SrBi2Ta2O9 thin film
Authors: Park Jong-Ho , Kim Chung-Sik , Choi Byung-Chun , Moon Byung Kee , Jeong Jung Hyun , Kim Ill Won
Published: July 2003

Ferroelectric SrBi2Ta2O9 thin films were grown on a highly oriented Pt/Ti/SiO2/Si substrates using pulsed laser ablation. The hysteresis loop of ferroelectric SrBi2Ta2O9 was studied as a function of applied field amplitude. A scaling analysis of ferroelectric hysteresis loop area showed A∝Eα. The value of scaling exponent, α=0.40, is not similar to the reported theoretical and experimental values. This result shows the possibility that both ferroelectric bulk and thin-film systems may have different universal behaviors. Influence of potential in the surface of SrBi2Ta2O9 thin film was measured in the dc applied field range from 0 to 8 V by using electro force microscopy. Roughness of surface potential of SrBi2Ta2O9 thin film changed rapidly around the coercive voltage, Vc∼1.5 V. It is believed that the switching effect of SrBi2Ta2O9 thin film includes surface polarization at the surface of the thin film as well as pure spontaneous polarization in the bulk.
Location control of crystal grains in excimer laser crystallization of silicon thin films
Authors: Kumomi Hideya
Published: July 2003

Location of crystal grains in polycrystalline Si thin films formed by excimer-laser crystallization is controlled by manipulating the superlateral-growth phenomenon. The superlateral growth of a single grain occurs preferentially at an artificial site where nanometer-sized crystallites are embedded in the precursory amorphous thin films. Only a part of the crystallites embedded in the site could survive the melting and grow to serve as the seed crystal in the subsequent recrystallization. Such grain-location control provides a basis for two-dimensional control of the grain-boundary location in low-temperature polycrystalline Si thin films, which is essential to the device-to-device uniformity of high-performance thin-film transistors.
Nanoshell tubes of ferroelectric lead zirconate titanate and barium titanate
Authors: Luo Yun , Szafraniak Izabela , Zakharov Nikolai D. , Nagarajan Valanoor , Steinhart Martin , Wehrspohn Ralf B. , Wendorff Joachim H. , Ramesh Ramamoorthy , Alexe Marin
Published: July 2003

Wafer-scale fabrication of ferroelectric oxide nanoshell tubes as well as ordered nanotube arrays have been accomplished using a simple and convenient fabrication method that allows full tailoring of tube dimensions as well as array pattern and size. Using different silicon and alumina templates, barium titanate and lead zirconate titanate tubes with diameters ranging from 50 nm up to several micrometers meter and lengths of more 100 μm have been fabricated. Ferroelectric switching of submicrometer tubes has been shown using piezoresponse scanning probe microscopy.
Superconducting properties of polycrystalline Nb nanowires templated by carbon nanotubes
Authors: Rogachev A. , Bezryadin A.
Published: July 2003

Continuous Nb wires, 7–15 nm in diameter, have been fabricated by sputter-coating single fluorinated carbon nanotubes. Transmission electron microscopy revealed that the wires are polycrystalline, having grain sizes of about 5 nm. The critical current of wires thicker than ∼12 nm is very high (107 A/cm2) and comparable to the expected depairing current. The resistance versus temperature curves measured down to 0.3 K are well described by the Langer–Ambegaokar–McCumber–Halperin theory of thermally activated phase slips. Quantum phase slips are suppressed.
Ion characteristics of laser-produced plasma using a pair of collinear femtosecond laser pulses
Authors: Zhang Z. , Van Rompay P. A. , Pronko P. P.
Published: July 2003

Femtosecond laser-pulse absorption is studied in silicon ablation plasmas by means of a pair of identical 1016 W/cm2 collinear pulses separated on a picosecond time scale. The second laser-pulse modifies ionic characteristics of the preformed plasma, such as ion yield, ion energy, and average charge state. Resonance absorption is demonstrated to be the dominant mechanism by comparing results of s and p polarization. It is shown that maximum effects occur when a well defined critical density surface of the initial plasma forms together with an optimum density gradient scale length of kL=1.5. The optimal enhancement of ion yield, which occurs at 5 ps delay, is a factor of 2 greater than that produced by a single pulse with twice the energy of each individual double pulse. Applications are identified in regard to cluster beam formation and plasma isotope enrichment in ultrafast ablation plumes.
Investigation of electrical conduction in carbon-doped silicon oxide using a voltage ramp method
Authors: Yiang K. Y. , Yoo W. J. , Guo Q. , Krishnamoorthy Ahila
Published: July 2003

Electrical conduction in carbon-doped silicon oxide (SiOC) is investigated over the electric field range of 0 MV/cm to the breakdown field at 300 K. Below 1.4 MV/cm, the dominant conduction mechanisms are electron hopping (<0.2 MV/cm) and Schottky emission (0.2 to 1.4 MV/cm). Poole–Frenkel emission at higher fields (>1.4 MV/cm) confirms the presence and role of electron traps in the conduction of SiOC. Near breakdown field (1.7 to 2.08 MV/cm), Fowler–Nordheim tunneling occurs and this is the major cause of dielectric breakdown in SiOC. The effective dielectric constant of SiOC in an integrated Cu damascene structure is derived from both experimental data and emission modeling.
Passivation and interface state density of SiO2/HfO2-based/polycrystalline-Si gate stacks
Authors: Carter R. J. , Cartier E. , Kerber A. , Pantisano L. , Schram T. , De Gendt S. , Heyns M.
Published: July 2003

We demonstrate that a forming gas annealing temperature of 520 °C significantly improves interface state passivation for SiO2/HfO2-based/polycrystalline-Si gate stacks as compared to annealing at 420 °C normally used for SiO2/polycrystalline-Si gate stacks. We also show that the initial interface state density is dependent upon the interfacial SiO2 preparation, whereby a chemically grown oxide has a higher initial interface state density as compared to a thermally grown oxide.
Investigation of a channel-add/drop-filtering device using acceptor-type point defects in a two-dimensional photonic-crystal slab
Authors: Asano Takashi , Song Bong-Shik , Tanaka Yoshinori , Noda Susumu
Published: July 2003

A channel-drop-filtering device using point and line defects in a two-dimensional photonic-crystal slab is investigated. The efficiency to drop light from a line-defect waveguide to the free space via a point-defect cavity is found to be more than 45%, which is very close to the theoretical maximum of the device. The reverse function of the device (channel-add-filtering) is also demonstrated, where photons incident on a point defect from free space are resonantly trapped and transferred to a line-defect waveguide nearby. The spectrum and polarization characteristic of the add-filtering completely agree with those of the drop-filtering. The results indicate that two-dimensional photonic slabs are very promising for realizing ultrasmall optical functional devices.
Nanoring formation by direct-write inorganic electron-beam lithography
Authors: Jiang N. , Hembree G. G. , Spence J. C. H. , Qiu J. , Garcia de Abajo F. J. , Silcox J.
Published: July 2003

A direct-write inorganic lithography technique is described which is capable of forming nanoscale rings of amorphous metals and semiconductors in glasses. Near-edge electron energy loss spectroscopy and electron diffraction using a subnanometer probe are used to analyze the composition and formation mechanism of these nanorings. The optical absorption cross section of one ring is calculated by multiple scattering methods. Applications in quantum electronics and the design of media with dielectric properties are suggested.
Extraordinary Hall effect and ferromagnetism in Fe-doped reduced rutile
Authors: Wang Zhenjun , Wang Wendong , Tang Jinke , Tung Le Duc , Spinu Leonard , Zhou Weilie
Published: July 2003

Room-temperature ferromagnetism is observed in reduced rutile TiO2−δ by Fe doping. The epitaxial films grown by pulsed-laser deposition are carefully examined by x-ray diffraction, transmission electron microscopy, and magnetic and transport measurements. The films exhibit the extraordinary Hall-effect and thin-film magnetic shape anisotropy. The magnetic moments and anticipated Curie temperatures of the films rule out Fe particles, iron oxides, and Ti–Fe oxides as possible sources for the observed magnetic signals. The carriers of the Fe-doped reduced rutile are p-type, with a carrier density of 1×1022/cm3. This room-temperature dilute magnetic semiconductor should find potential applications in spintronics.
Effects of deep-level defects on ohmic contact and frequency performance of AlGaN/GaN high-electron-mobility transistors
Authors: Jessen G. H. , Fitch R. C. , Gillespie J. K. , Via G. D. , White B. D. , Bradley S. T. , Walker D. E. , Brillson L. J.
Published: July 2003

We have characterized AlGaN/GaN high-electron-mobility-transistors on sapphire and silicon carbide substrates with electrical and microcathodoluminescence spectral measurements. Quarter wafer-scale comparisons of spectral features in the GaN attributed to donor–acceptor pair (DAP) transitions and yellow luminescence (YL) from deep acceptors show that the specific contact resistance is related to the ratio of the DAP to YL defect emission intensities. This suggests that these defects interact to change the contact resistance locally on the GaN side of the AlGaN/GaN interface. We show that changes in the frequency response of these transistors can be attributed to these defects at the interface.
Ideal glass transitions in thin films: An energy landscape perspective
Authors: Truskett Thomas M. , Ganesan Venkat
Published: July 2003

We introduce a mean-field model for the potential energy landscape of a thin fluid film confined between parallel substrates. The model predicts how the number of accessible basins on the energy landscape and, consequently, the film’s ideal glass transition temperature depend on bulk pressure, film thickness, and the strength of the fluid–fluid and fluid–substrate interactions. The predictions are in qualitative agreement with the experimental trends for the kinetic glass transition temperature of thin films, suggesting the utility of landscape-based approaches for studying the behavior of confined fluids.
GaN/AlN-based quantum-well infrared photodetector for 1.55 μm
Authors: Hofstetter Daniel , Schad Sven-Silvius , Wu Hong , Schaff William J. , Eastman Lester F.
Published: July 2003

We report optical absorption and photocurrent measurements on a GaN/AlN-based superlattice. The optical absorption has a full width at half maximum of 120 meV and takes place at an energy of 660 meV (5270 cm−1); this corresponds to a wavelength of 1.9 μm. While the optical absorption remained unchanged up to room temperature, the photocurrent signal could be observed up to 170 K. With respect to the optical absorption, the photocurrent peak was slightly blueshifted (710 meV/5670 cm−1) and had a narrower width of 115 meV. Using this quantum-well infrared photodetector, we were able to measure the spectrum of a 1.55 μm superluminescent light-emitting diode.
Tunneling transport in polyoxometalate based composite materials
Authors: Glezos N. , Argitis P. , Velessiotis D. , Diakoumakos C. D.
Published: July 2003

Molecular materials containing tungsten polyoxometalates as the active elements embedded into polymer matrices are investigated as candidates for electronic device applications. The transport properties of these materials are investigated varying the interelectrode spacing and the polyoxometalate concentration. The I–V characteristics of planar devices reveal a conductivity peak at room temperature conditions for intermolecular distances less than 3 nm and electrode distances less than 100 nm. The transport characteristics are discussed in terms of tunneling mechanisms.
Photoreflectance evidence of the N-induced increase of the exciton binding energy in an InxGa1−xAs1−yNy alloy
Authors: Geddo M. , Guizzetti G. , Capizzi M. , Polimeni A. , Gollub D. , Forchel A.
Published: July 2003

The binding energy of the heavy-hole ground-state exciton in In0.25Ga0.75As1−yNy/GaAs single quantum wells (y=0, 0.011) was experimentally derived by photoreflectance measurements. We measured a binding energy of 6.6 and 8.5 meV for the N-free and the N-containing sample, respectively. The observed increase of the exciton binding energy can be accounted for by an increase of the exciton reduced mass of about 30% upon N introduction into the InxGa1−xAs lattice, consistently with recent experimental results and in agreement with earlier theoretical predictions.
Confocal two-photon spectroscopy of red mercuric iodide
Authors: Wen X. M. , Xu Paul , Lukins Philip B. , Ohno N.
Published: July 2003

One- and two-photon fluorescence of red mercuric iodide single crystal was studied using confocal laser scanning microscopy and spectroscopy at room temperature. There is a clear difference in the fluorescence spectra for one- and two-photon excitation. With two-photon excitation, a fluorescent band is found at the band gap and its central wavelength shifts toward lower energy with increasing depth below the surface, whereas the fluorescent band for one-photon excitation remains invariant with depth. There is an approximately 70 μm thick defect transition layer near the surface and the defect concentration decreases approximately linearly from the surface to the bulk. The band-gap energy at room temperature is determined as 2.12 eV, which is consistent with previous studies.
Switching a spin valve back and forth by current-induced domain wall motion
Authors: Grollier J. , Boulenc P. , Cros V. , Hamzić A. , Vaurès A. , Fert A. , Faini G.
Published: July 2003

We have studied the current-induced displacement of a domain wall (DW) in the permalloy (Py) layer of a Co/Cu/Py spin valve structure at zero and very small applied field. The displacement is in opposite direction for opposite dc currents, and the current density required to move DW is only of the order of 106 A/cm2. For H=3 Oe, a back and forth DW motion between two stable positions is observed. We also discuss the effect of an applied field on the DW motion.
Direct and inverse photoemission spectroscopy studies of potassium intercalated films of two organic semiconductors
Authors: Schwieger T. , Knupfer M. , Gao W. , Kahn A.
Published: July 2003

A combined direct and inverse photoemission spectroscopy study of the occupied and unoccupied states of the organic semiconductors ZnPc and α-[N,N′-diphenyl-N,N′-bis(1-naphthyl)-1, 1′-biphenyl-4,4″ diamine] in the pristine and reduced state is presented. The splitting of the lowest unoccupied molecular orbital observed upon potassium intercalation leads to an evaluation of the size of correlation effects in both molecular systems. As expected, the Fermi level is found to shift towards the vacuum level upon intercalation. However, the results clearly demonstrate that the Fermi level in potassium intercalated organic semiconductors cannot a priori be assumed to be pinned at the onset of the lowest unoccupied molecular orbital in all cases.
An improved density functional description of hard sphere polymer fluids at low density
Authors: Forsman Jan , Woodward Clifford E.
Published: July 2003

A refined formulation of an existing polymer density functional theory is presented, wherein an intrachain stiffness is introduced via a bending potential. Comparisons with Metropolis Monte Carlo simulations in a slit geometry shows that this leads to a considerable improvement of the predicted density profile for a hard sphere polymer melt, at low density. We also show how the corresponding surface interactions are affected by the inclusion of this intramolecular correlation. We expect that the improvement obtained will be even more important in the description of, for example, polyelectrolytes, although such comparisons are not made in this preliminary study.
American canine hepatozoonosis
Authors: Panciera R. J. , Ewing S. A.
Published: July 2003

American canine hepatozoonosis is an emerging, tick-transmitted infection of domestic dogs caused by a recently recognized species of apicomplexan parasite,Hepatozoon americanum. The known definitive host of the protozoan is the Gulf Coast tick,Amblyomma maculatum. Presently recognized intermediate hosts include the domestic dog and the coyote,Canis latrans. Laboratory-reared larval or nymphalA. maculatumcan be infected readily by feeding to repletion on a parasitemic intermediate host; sporogony requires 35–40 days. Transmission of infection to the dog has been produced experimentally by oral administration of mature oocysts or oocyst-containing ticks. Canine disease follows experimental exposure in 4–6 weeks and is characterized by systemic illness, extreme neutrophilic leukocytosis, muscle and bone pain, and proliferation of periosteal bone. Histopathological findings include multifocal skeletal and cardiac myositis associated with escape of mature merozoites from within the host-cell environment. There is also rapid onset of periosteal activation and osteogenesis and, less frequently, glomerulopathy and amyloidosis. Sequential stages of development ofH. americanumin both the dog and the tick have been elucidated. Gamonts potentially infectious to ticks have been observed in peripheral blood leukocytes of the dog in as few as 28 days after exposure to oocysts. Young coyotes experimentally exposed to a canine strain ofH. americanumacquired disease indistinguishable from that of similarly exposed young dogs.
Non-infectious and iatrogenic diseases of salmon in commercial aquaculture
Authors: Speare David J.
Published: July 2003

Based on current commercial aquaculture production practices, the production cycle for Atlantic salmon (Salmo salar) extends over a 36-month period during which time the fish are first exposed to intensive freshwater rearing conditions followed by transportation to marine netpen sites for ongrowing. It is predictable that, because of the duration of the production cycle and the variety of water conditions, deleterious environmental conditions have many opportunities to affect salmon health directly and indirectly. Furthermore, diseases which are iatrogenic arise from current methods used to prevent or treat infectious diseases. Specific, more frequently encountered examples are explored, with reference to the possible roles which these diseases may have in favouring the onset of infectious diseases.
Global perspectives on nematode parasite control in ruminant livestock: the need to adopt alternatives to chemotherapy, with emphasis on biological control
Authors: Waller Peter J.
Published: July 2003

Effective, sustainable control of nematode parasites of grazing livestock is becoming evermore challenging and difficult. This is largely due to two contrasting issues. One is the rapid escalation of resistance to anthelmintic drugs, which is arguably the greatest problem now facing the small ruminant industries worldwide. Secondly, there is the increasing trend towards organic farming, in which there is prohibition of the prophylactic use of all chemical compounds. Livestock producers urgently need non-chemotherapeutic alternatives in parasite control. Researchers have responded to this challenge and a variety of quite different approaches have been the subject of intense investigation in many countries for several decades now. These vary in relation to their stage of development for on-farm use, their utility, and their applicability across the spectrum of grazing livestock enterprises throughout the world. One relatively recent innovation is the biological control approach to nematode parasites. This has now reached the stage of commercialization. This review focuses on these issues and provides an overview of the possible ways in which the biological control of nematode parasites could be employed in grazing ruminant livestock systems worldwide.
A key mechanism of pathogenesis in sheep infected with the nematodeTeladorsagia circumcincta
Authors: Stear M. J. , Bishop S. C. , Henderson N. G. , Scott I.
Published: July 2003

Infection of sheep with the abomasal nematodeTeladorsagia circumcinctacan cause a relative protein deficiency and reduce growth rate in growing lambs. A key event appears to be the destruction of junctions between epithelial cells. If the infection is heavy or prolonged, this leads to increased mucus production, hyperplasia, decreased acid production, gastrinemia, inappetance and pepsinogenemia. The severity of the infection depends upon the extent of concurrent infection, the nutritional status of the host and genetically controlled variation in the ability to mount protective immune responses.
Cryptosporidiumand host resistance: historical perspective and some novel approaches
Authors: Harp James A.
Published: July 2003

Cryptosporidium parvumis recognized as a major cause of diarrheal disease in neonatal bovine calves. In addition, this protozoan parasite has emerged as an important cause of disease in both immunocompromised and immunocompetent humans. Despite years of research, no consistently effective means of prevention or treatment are readily available for cryptosporidiosis in any species. Infection through ingestion of contaminated water has been widely documented;C. parvumwas reported to be responsible for the largest waterborne outbreak of infectious disease in US history. In addition to its role as a primary disease agent,C. parvumhas potential to initiate or exacerbate other gastrointestinal disorders, such as inflammatory bowel disease. Thus, control ofC. parvuminfection in both animals and humans remains an important objective. Research in our laboratory has focused on understanding mechanisms of resistance toC. parvum. We have demonstrated that acquisition of intestinal flora increases resistance toC. parvum.Substances present in the intestinal mucosa of adult animals can transfer resistance when fed to susceptible infants. Both expression of intestinal enzymes and rate of proliferation of epithelial cells may be altered followingC. parvuminfection. These and other changes may have profound effects on host resistance toC. parvum.
Canine distemper, a re-emerging morbillivirus with complex neuropathogenic mechanisms
Authors: Griot Christian , Vandevelde Marc , Schobesberger Martina , Zurbriggen Andreas
Published: July 2003

Paramyxoviruses are responsible for a wide variety of diseases both in humans and in animals. Common to many paramyxoviruses is the fact that they can cause neurological symptoms in their final host. Newly discovered paramyxoviruses, such as the Hendra and Nipah viruses, show the same pattern of pathogenesis as that of the paramyxoviruses already known. Canine distemper virus (CDV) is a well-studied member of the genusMorbillivirus. Study of the neuropathogenesis of CDV might give insight into disease mechanisms and suggest approaches for the prevention of other recently discovered paramyxovirus infections.
‘Malnutrition’ in the aged: the dietary assessment
Authors: Wahlqvist Mark L
Published: July 2003

Changing demography towards older populations requires nutritionists to review food–health relationships in regard to older age groups, to the ageing process, to precursors of disability and survival, and to the changeability of health status through diet in later life. Nutritional status in later life may be complex with combined features of under-, over- and disordered nutrition – dysnutrition. Further, beyond food components (essential nutrients and more), foods themselves, integrals of food intake and the socio-cultural aspects of food intake play a significant role in the health and well-being of the aged and require measurement. Ageing socio-biology provides opportunities and imposes limitations on the usual food intake instruments. However, rapid assessment procedures can be particularly valuable as highlighted in the Food Habits in Later Life project of the International Union of Nutritional Sciences. There are critical issues to which dietary methodology can be applied to the aged: a disappearing knowledge base, relevant health-enhancing strategies and the creation of new food–health opportunities. Many communities now wish to use such information to develop food-based dietary guidelines for their aged members.
Understanding the nutrition transition: measuring rapid dietary changes in transitional countries
Authors: Popkin Barry M , Lu Bing , Zhai Fengying
Published: July 2003

Objective:

To understand methodological concerns related to dietary intake collection in transitional societies.

Design:

Three days of household weighing and measurement of all food used and repeated 24-hour recalls.

Setting:

Eight Chinese provinces.

Subjects:

Five thousand nine hundred and fifty-two and 5152 adults aged 20–45 years in 1989 and 1997, respectively.

Results:

Great variance exists in the types and quantity of animal products used in common recipes. For example, the proportion of pork from lean cuts in ‘stir-fried fresh pepper and pork’ varies between 14 and 24% in urban and rural areas and the total pork content for 100 g (dish) varies by 15 to 19 g between rural and urban areas in each of eight provinces. Another challenge relates to the variation in the edible vegetable oil content added during food preparation. Reliance on standard recipes for each fried dish would miss the variations in oil use over time, space and socio-economic status.

Conclusions:

Dietary change is rapid in transitional countries. Reliance on recipes standardised for animal food and edible oil contents will lead to very large systematic errors in the measurement of energy, fat and protein intakes.
Development of a questionnaire and a database for assessing dietary D-limonene intake
Authors: Hakim Iman A , Hartz Vern , Graver Ellen , Whitacre Robin , Alberts David
Published: July 2003

Objective:

Increasing recognition of the potential importance of phytochemicals in the aetiology of cancer and heart diseases has highlighted the need for methods to measure individual phytochemical consumption that are sufficiently simple to be used in large epidemiological studies and whose reproducibility and accuracy have been quantified. D-Limonene is a natural component of a variety of foods and beverages and is found mainly in citrus fruits. However, D-limonene is not assessed by any nationally available analysis database.

Design:

We designed our study to assess the D-limonene content of different citrus juices and beverages and to develop a dietary assessment instrument to measure consumption of citrus foods (fruit, juice and peel) and D-limonene intake and test it for reliability.

Subjects and methods:

A total of 120 citrus juice samples were analysed and used to develop the preliminary D-limonene database. A self-administered citrus food-frequency questionnaire was developed and administered twice to participants, separated by a 2-month interval. The questionnaire was tested for reproducibility of estimates of citrus food consumption and D-limonene intake among 120 participants.

Results:

Correlation coefficients between the two administrations of the questionnaire ranged from 0.50 for citrus peel use to 0.82 for orange juice. Mean intakes (range) of D-limonene from citrus juices among consumers were 13.0 (0.24–141.9) mg day−1and 13.2 (0.07–83.9) mg day−1(r= 0.60,P< 0.001).

Conclusion:

The citrus frequency questionnaire developed in this study provided highly reproducible estimates of citrus foods, citrus peel and D-limonene intakes. This instrument may be a useful tool in studies of the associations between citrus peel use, D-limonene intake and risk for chronic disease.
Comparison of dietary intakes of micro- and macronutrients in rural, suburban and urban populations in Costa Rica
Authors: Kabagambe Edmond K , Baylin Ana , Siles Xinia , Campos Hannia
Published: July 2003

Objective:

To compare, along with behavioural habits, the potential atherogenicity of diets in rural and urban areas in Costa Rica.

Design:

Subjects (n= 503) were randomly selected from the general population in Costa Rica. A validated food-frequency questionnaire that inquired about dietary intake in the previous year was administered once to each subject. Each subject provided plasma and an adipose tissue biopsy, which were used as biomarkers for carotenoid, tocopherol and/or fatty acid intakes. Each subject also answered another questionnaire on personal profile and household characteristics.

Setting:

A dietitian visited all subjects and conducted the interviews at their homes.

Subjects:

Adult male and female free-living rural, suburban and urban Costa Ricans without a history of physical or mental disability.

Results:

Subjects in rural areas were significantly (P< 0.05) more active physically, earned less income and had a higher intake of dietary fibre than urban dwellers. Urban residents reported a significantly (P< 0.05) higher consumption of total fat, specifically unsaturated fat mostly from soyabean oil, and had higher plasma and adipose tissue tocopherol and lycopene concentrations. Interestingly, no differences in body mass index were observed.

Conclusions:

These data show differences in cardiovascular disease (CVD) risk factors of rural and urban populations in Costa Rica. In rural areas, low socio-economic status and low intake of unsaturated fatty acids appear to be the prevalent CVD risk factors, while in urban areas they were low physical activity, hightrans-fatty acids in the diet and adipose tissue, and low dietary fibre intake.
Measuring flavonoid intake: need for advanced tools
Authors: Dwyer Johanna T , Peterson Julia J
Published: July 2003

Objective:

Flavonoids are phytochemicals with potentially beneficial biological effects that are poorly characterised in existing tables of food composition.

Design:

To describe new techniques for analysis, absorption, informatics and dietary assessment that are important in measuring the flavonoid content in foods and in developing a flavonoid food composition database.

Setting:

Data on chemical analyses of the major flavonoid compounds that exist in the food science literature are being located, collated and compiled into a preliminary flavonoid food composition database.

Results:

The analytical process begins with preparation of the food for flavonoid analysis using techniques to disrupt the food matrix, alcoholic extraction, and enzymatic or acidic hydrolysis to remove sugars. Separation is usually accomplished using high-performance liquid chromatography. Flavonoids are identified by diode array spectrometry, mass spectrometry or nuclear magnetic resonance spectroscopy. Quantification usually employs comparison of the sample with standards, if available, using the area under the curve of the chromatogram to estimate quantity. Absorption studies are useful since flavonoids vary in their absorption. Finally, information management technologies (informatics) are used to translate flavonoid data information into food composition databases. This process involves identification of foods containing the compounds of interest, collection and organisation of sources of existing analytical data, assignment of quality scores or aggregation of acceptable data for each component and food, calculation of appropriate statistics, assignment of food codes and verification, and finalisation. The resulting food flavonoid database can be used with state-of-the-art dietary assessment methods to develop estimates of flavonoid intakes in foods and to correlate these with estimates of disease risk.

Conclusions:

A provisional flavonoid database, including at least two components from each of six classes of flavonoids, should be completed in 2002.
The use of food-frequency questionnaires for various purposes in China
Authors: Zhao Wenhua , Hasegawa Kyoko , Chen Junshi
Published: July 2003

Objective:

To compare various food-frequency questionnaires (FFQs) used in nutritional studies in China for various purposes.

Design:

In Study 1, a simplified FFQ with 17 questions on food was used in a large rural study. In Study 2, a questionnaire consisting of 84 questions on food consumption of 16 food categories was used in a study comparing dietary consumption data and various health indicators of elderly people in four geographical areas in China. In Study 3, a questionnaire with 149 items in 17 food categories is being validated by comparison with data obtained by repeated 24-hour recalls.

Setting:

Study 1 was carried out in one southern site and a northern site in 1996 to 1997. Study 2 was conducted in four different geographical sites in 1998. The on-going study, Study 3, has been carried out in Jiangsu and Beijing since 1999.

Subjects:

Study 1 included 12 234 rural Chinese adults aged 40 years. There were 546 elderly people in Study 2. Study 3 is collecting data from 300 healthy adults.

Results:

The results of food consumption and nutrient intakes from Study 1 were comparable with those obtained from a previous household dietary survey, in which sensible correlations between diet and diseases were also found. In Study 2, the dietary data from the four geographical areas showed significant differences in food and nutrient intakes among the different areas. The validation of the new FFQ in Study 3 is still going on.

Conclusion:

The FFQ is a useful method for the collection of individual food consumption information. The above FFQ forms could be used in studies with different purposes, especially in studying the relationship between diet, nutrition and chronic diseases.
Using national dietary data to measure dietary changes
Authors: Champagne Catherine M , Bogle Margaret L , Karge William H
Published: July 2003

Objective:

To demonstrate that dietary datasets from the Continuing Survey of Food Intakes by Individuals, a US population survey, allow comparisons with national data and provide food composition datasets that can be used to generate similar dietary data.

Design:

Two studies are described: the Lower Mississippi Delta Nutrition Intervention Research Initiative (Delta NIRI), which used a 24-hour recall, and a Department of Defense Military Nutrition Research Task, which used 3-day dietary records. Both studies used the same food composition tables.

Setting:

Rural Lower Mississippi Delta and an Army post.

Subjects:

Four hundred and nine residents (adults and children) from the rural Delta region of Arkansas, Louisiana and Mississippi, and 74 career soldiers from the Sergeants Major Academy, Fort Bliss, Texas.

Results:

The Delta NIRI study found that fruit and vegetable consumption for these rural residents was lower than that found nationally. Additionally, the quality of vegetable servings is of concern since a large percentage came from french fries and potato chips. In the Sergeants Major Academy study, the national survey food composition tables allowed for easy analysis of intake data and comparisons with dietary recommendations.

Conclusions:

Strategies similar to those used for the Delta NIRI and Military Nutrition Research Task can be used widely, allowing comparisons of ‘defined populations’ with nationally distributed data. Additionally, measurement of dietary change is more efficient when the same protocol is used subsequently to collect more data, a method similar to that used by the US Department of Agriculture to describe food consumption patterns from one survey to another.
The SENECA study: potentials and problems in relating diet to survival over 10 years
Authors: Van Staveren Wija A , de Groot Lisette CPMG , Haveman-Nies Annemien
Published: July 2003

Objective:

To give an overview of the evaluation of the modified diet history applied in the SENECA study (Survey in Europe on Nutrition and the Elderly; a Concerted Action).

Design:

Nineteen centres in 12 countries participated at baseline. Nine of these SENECA centres conducted a repeat measurement scheme in elderly people born between 1913 and 1918. These longitudinal centres included 100 subjects per sex per site.

Methods:

The relative validity of the method was tested by comparing results of the modified diet history with results obtained from a weighed record in 82 subjects. In the follow-up we compared changes in energy intake with changes in body weight and calculated the physical activity ratio in all longitudinal centres. In SENECA's finale we examined the predictive value of dietary patterns observed at baseline for survival 10 years later, making use of the original and an adapted Mediterranean Diet Score.

Results:

The modified diet history overestimated intake, compared with the weighed record. However, the physical activity ratio and an in-depth study in a metabolic room indicated that the diet history rather underestimated energy intake. We did not find a relationship between changes in energy intake and changes in body weight, but this could be explained by the fact that most likely we did not measure intake in the dynamic phase of body weight change. Based on the adapted Mediterranean Diet Score, the study results showed a positive relation between a healthy diet and survival.

Conclusion:

We conclude that the modified diet history has given sufficiently reliable results for the purposes of the study
Measuring household food security in poor Venezuelan households
Authors: Lorenzana Paulina A , Mercado Carmen
Published: July 2003

Objective:

To validate abbreviated methods that estimate food security level among poor communities in Caracas, Venezuela.

Design:

Two independent cross-sectional studies were undertaken to internally and externally validate simple quantitative/qualitative methods. The quantitative measure was constructed from data on household food availability, gathered using the list-recall method. It is a count of the foods that explain 85% or more of household energy availability. The qualitative measure is a score of female-perceived food insecurity level estimated with a modified ‘hunger index’, reflecting food resource constraints and hunger experiences within the home. Socio-economic and food behaviour data that may predict household food security (HFS) levels were gathered. The second study was repeated a year later to measure the impact of an increase in the minimum wage on HFS levels.

Setting:

Two poor urban communities in Caracas, Venezuela.

Subjects:

All households in both communities that complied with selection criteria (poor and very poor families that share food resources) and were willing to participate. The sample comprised 238 and 155 female household food managers in the two communities.

Results:

In 1995, data from females in 238 urban poor households provided evidence for the overall validity of the method. Its application in 1997 to 155 households in the other community gave support to the external validity of the method. Measures were repeated in 1998 on 133 subjects of the above sample, when the minimum wage was increased by 23%. Evidence is presented showing the sensitivity of the method to changes in the determinants of HFS. Data analysed during these three periods suggest that the method can be simplified further by using the food diversity score instead of the quantitative measure since these variables correlate highly with one another (r ≥ 0:854).

Conclusions:

This simple method is a valid and precise measure of food security among poor urban households in Caracas. The qualitative/quantitative measures complement each other as they capture different dimensions of HFS.
Validation of habitual energy intake
Authors: Schoeller Dale A
Published: July 2003

Objective:

To provide a framework for use of the doubly labelled water method to measure energy expenditure in order to validate dietary instruments for the assessment of energy.

Design:

Review and description of the use of doubly labelled water method for use as a biomarker for habitual energy intake.

Results:

The doubly labelled water method has a relative accuracy of 1% and within-subject precision of 5 to 8%. Comparison of self-reported energy intake with energy expenditure demonstrated that over one-third of individuals may underreport energy intake by more than 25%.

Conclusions:

The doubly labelled water method, although expensive and dependent on non-routine laboratory instrumentation, is an excellent biomarker of energy intake.
Measuring the intakes of foods and nutrients of marginal populations in north-west Mexico
Authors: Ortega MI , Valencia ME
Published: July 2003

Objective:

To describe methodological issues regarding the measurement of food intake of marginal populations in the north-west of Mexico.

Methods:

Dietary data from three sources were analysed. The Sonora State Food Basket Study (505 individuals from all ages, both sexes, high, medium and low income, and from urban and rural settings), 144 individuals from rural Indian communities, and 152 low-income urban women. Methods of dietary data collection were single 24-hour recalls for the first two studies, and four non-consecutive 24-hour recalls as well as a food-frequency questionnaire (FFQ) for low-income urban women.

Results:

The food patterns in the three studies showed similar core foods; however, food diversity resulted in 19, 13 and 57 different foods reported by 90% of the population in the state, Indian communities and urban women, respectively. Mean intakes of selected food components in the sample of urban women vs. a representative sample of the population of the state were similar, although smaller variation in consumption was observed in urban women with repeated 24-hour recalls. Inter-individual variation in intake of food components was similar in the state and urban women samples, but the Indian communities showed lower coefficients of variation (CVs). Use of four 24-hour recalls decreased the inter-individual variation in food component intakes of low-income urban women, especially for vitamin intakes. The FFQ did not show an additional decrease in inter-individual variation for macronutrients, but reduced even more the CVs for vitamins. Intra-individual variation was higher than inter-individual variation for urban women's intakes when estimated by repeated 24-hour recalls. This effect was reversed when estimated by duplicate food frequencies. Ratios of intra-individual to inter-individual variation in food intake were lower for Mexican when compared with US women. These results should be considered, especially for association analysis of low-income women's diets and health outcomes.
Uses and limitations of statistical accounting for random error correlations, in the validation of dietary questionnaire assessments
Authors: Kaaks Rudolf , Ferrari Pietro , Ciampi Antonio , Plummer Martyn , Riboli Elio
Published: July 2003

Objective:

To examine statistical models that account for correlation between random errors of different dietary assessment methods, in dietary validation studies.

Setting:

In nutritional epidemiology, sub-studies on the accuracy of the dietary questionnaire measurements are used to correct for biases in relative risk estimates induced by dietary assessment errors. Generally, such validation studies are based on the comparison of questionnaire measurements (Q) with food consumption records or 24-hour diet recalls (R). In recent years, the statistical analysis of such studies has been formalised more in terms of statistical models. This made the need of crucial model assumptions more explicit. One key assumption is that random errors must be uncorrelated between measurements Q and R, as well as between replicate measurements R1 and R2 within the same individual. These assumptions may not hold in practice, however. Therefore, more complex statistical models have been proposed to validate measurements Q by simultaneous comparisons with measurements R plus a biomarker M, accounting for correlations between the random errors of Q and R.

Conclusions:

The more complex models accounting for random error correlations may work only for validation studies that include markers of diet based on physiological knowledge about the quantitative recovery, e.g. in urine, of specific elements such as nitrogen or potassium, or stable isotopes administered to the study subjects (e.g. the doubly labelled water method for assessment of energy expenditure). This type of marker, however, eliminates the problem of correlation of random errors between Q and R by simply taking the place of R, thus rendering complex statistical models unnecessary.
Erythrocyte cell membrane phospholipid levels compared against reported dietary intakes of polyunsaturated fatty acids in pregnant Mexican women
Authors: Parra Maria-Socorro , Schnaas Lourdes , Meydani Mohsen , Perroni Estela , Martíanez Sandra , Romieu Isabelle
Published: July 2003

Objective:

To evaluate the validity of a food-frequency questionnaire (FFQ) for assessment of the dietary intakes of polyunsaturated fatty acids (PUFAs) against a biochemical marker of fat intake, erythrocyte cell membrane phospholipid levels, during pregnancy.

Design:

Cross-sectional analysis.

Setting:

Developmental Neurobiology Department, National Institute of Perinatology, Mexico City.

Subjects:

One hundred forty-six healthy pregnant women during the last trimester of pregnancy. Among women enrolled, the first 35 pregnant women (24%) had their erythrocytes analysed for fatty acid status.

Methods:

We administered an FFQ and compared intakes of PUFAs against their erythrocyte cell membrane concentrations, processed by gas chromatography.

Results:

Pearson correlation coefficients among α-linolenic acid (ALN), docosahexaenoic acid (DHA) and eicosapentaenoic acid in erythrocyte cell membranes against their crude dietary counterparts were 0.32, 0.35 and 0.36 (each P < 0.05). In a simple linear regression, erythrocyte DHA and arachidonic acid (AA) were significantly related to their respective dietary intakes (β = 0.30, 95% confidence interval (CI): 0.007–0.60, P = 0.045 for DHA; β = 0.49, 95% CI: 0.010–0.98, P = 0.044 for AA). Erythrocyte cell membrane ALN concentration (%/total) was only marginally related to ALN dietary intake (mg day−1) (β = 0.52, 95% CI: −0.020–1.10, P = 0.061). However, after adjustment for long-chain n–3 PUFA/AA, this association reached significance (β = 0.44, 95% CI: 0.026–0.825, P = 0.038). Main dietary sources for n–3 PUFAs were canned tuna fish and fresh catfish; for n–6 these were eggs and cow's milk. The use of this FFQ in these pregnant Mexican women provided estimates of average long-term intakes of PUFAs and correlated reasonably well with their erythrocyte cell membrane phospholipid status. However, we need to consider that, during pregnancy, there is a faster turnover of PUFAs from fat storage that may modify the profile of erythrocyte PUFAs and lower the correlation between dietary intake and erythrocyte PUFAs.