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• Obesity at 33y resulted in more than twice the odds of poor physical functioning at 50y. • Causal mediation models assessed the role of c-reactive protein on this relationship. • 23% of the obesity effect on PF operated via a downstream effect on CRP. Obesity in adulthood is associated with reduced physical functioning (PF) at older ages. However, mechanisms underpinning this association are not well understood. We investigated whether and the extent to which C-reactive protein (CRP) mediates the association between early-adult obesity and mid-life PF. We used data from 8495 participants in the 1958 British birth cohort study. Body mass index (BMI), CRP and PF were measured at 33, 45 and 50y, respectively. Poor PF was defined as the lowest (sex-specific) 10% on the Short-form 36 Physical Functioning subscale. We accounted for prospectively measured confounders in early-life (e.g., social class at birth) and in mid-adulthood (e.g., 42y comorbidities). We decomposed the total effect of early-adult obesity on mid-life PF into direct and indirect (via CRP) effects, by employing a mediation analysis based on parametric g-computation. The estimated total effect of obesity at 33y on poor PF at 50y, expressed as an odds ratio (OR), was 2.41 (95% CI: 1.89, 3.08). The direct effect of obesity on poor PF (i.e., not operating via CRP), was 1.97 (95% CI: 1.51, 2.56), with an indirect effect of 1.23 (95% CI: 1.10, 1.37). As such, the proportion of the total effect which was mediated by the effect of obesity on CRP at 45y, was 23.27% (95% CI: 8.64%, 37.90%). Obesity in early-adulthood was associated with over twice the odds of poor PF in mid-life, with approximately 23% of the obesity effect operating via a downstream effect on CRP. As current younger generations are likely to spend greater proportions of their life course in older age and with obesity, both of which are associated with poor PF, there is an urgent need to identify mechanisms, and thus potential modifiable intermediaries, linking obesity to poor PF. [ABSTRACT FROM AUTHOR]

Background: Most studies on secular trends in body mass index (BMI) are cross-sectional and the few longitudinal studies have typically only investigated changes over time in mean BMI trajectories. We aimed to describe how the evolution of the obesity epidemic in Great Britain reflects shifts in the proportion of the population demonstrating different latent patterns of childhood-to-adulthood BMI development.Methods: We used pooled serial BMI data from 25,655 participants in three British cohorts: the 1946 National Survey of Health and Development (NSHD), 1958 National Child Development Study (NCDS), and 1970 British Cohort Study (BCS). Sex-specific growth mixture models captured latent patterns of BMI development between 11 and 42 years. The classes were characterised in terms of their birth cohort composition.Results: The best models had four classes, broadly similar for both sexes. The 'lowest' class (57% of males; 47% of females) represents the normal weight sub-population, the 'middle' class (16%; 15%) represents the sub-population who likely develop overweight in early/mid-adulthood, and the 'highest' class (6%; 9%) represents those who likely develop obesity in early/mid-adulthood. The remaining class (21%; 29%) reflects a sub-population with rapidly 'increasing' BMI between 11 and 42 years. Both sexes in the 1958 NCDS had greater odds of being in the 'highest' class compared to their peers in the 1946 NSHD but did not have greater odds of being in the 'increasing' class. Conversely, males and females in the 1970 BCS had 2.78 (2.15, 3.60) and 1.87 (1.53, 2.28), respectively, times higher odds of being in the 'increasing' class.Conclusions: Our results suggest that the obesity epidemic in Great Britain reflects not only an upward shift in BMI trajectories but also a more recent increase in the number of individuals demonstrating more rapid weight gain, from normal weight to overweight, across the second, third, and fourth decades of life. [ABSTRACT FROM AUTHOR]

Using femtosecond differential transmission spectroscopy, we observed a “nondegenerate” biexciton, consisting of an electron-hole pair in the dot ground state and an electron-hole pair in the excited state, in InGaAs self-organized quantum dots. We resonantly pumped the ground state transition in the quantum dots and observed an induced resonance in the probe differential transmission spectrum near the first excited-state transition, which we attribute to the formation of a nondegenerate biexciton state. The binding energy of 15 meV does not change with excitation power, thus reflecting a genuine feature of few-particle states. Our theoretical model calculations show good agreement with these experimental results. When a prepulse is used to generate a population inversion in the quantum dots, we also observed the effects of nondegenerate biexcitonic correlations in differential transmission. [ABSTRACT FROM AUTHOR]

This research extends and tests principles to establish good practice and overcome practical barriers in the strategic management of data quality. The research explores the issues that define and control data quality in national health data collections and the mechanisms and frameworks that can be developed to achieve and sustain good data quality. The aim is to make the strategic management of data quality, and the prevention of persistent errors, everyday, ;institutionalized' activities. Using action research methodology and a combination of interpretive and positivist data collection and analysis methods, this research provides the health informatics community with an understanding of the issues related to developing and implementing programmes to improve data quality. Healthcare is a complex system that is highly political and culturally diverse, and applied health informatics research is essential to improve outcomes and performance. [ABSTRACT FROM AUTHOR]

Ageing populations and unhealthy lifestyles have led to some chronic conditions such as diabetes and heart disease reaching epidemic proportions in many developed nations. This paper explores the potential of mobile technologies to improve this situation. The pervasive nature of these technologies can contribute holistically across the whole spectrum of chronic care ranging from public information access and awareness, through monitoring and treatment of chronic disease, to support for patient carers. A related study to determine the perceptions of healthcare providers to m-health confirmed the view that attitudes were likely to be more important barriers to progress than technology. A key finding concerned the importance of seamless and integrated m-health processes across the spectrum of chronic disease management. [ABSTRACT FROM AUTHOR]

Members of the rhodophytan order Cyanidiales are unique among phototrophs in their ability to live in extreme environments that combine low pH levels (∼0.2 to 4.0) and moderately high temperatures of 40 to 56°C. These unicellular algae occur in far-flung volcanic areas throughout the earth. Three genera (Cyanidium, Galdieria, and Cyanidioschyzon) are recognized. The phylogenetic diversity of culture isolates of the Cyanidiales from habitats throughout Yellowstone National Park (YNP), three areas in Japan, and seven regions in New Zealand was examined by using the chloroplast RuBisCO large subunit gene (rbcL) and the 18S rRNA gene. Based on the nucleotide sequences of both genes, the YNP isolates fall into two groups, one with high identity to Galdieria sulphuraria (type II) and another that is by far the most common and extensively distributed Yellowstone type (type IA). The latter is a spherical, walled cell that reproduces by internal divisions, with a subsequent release of smaller daughter cells. This type, nevertheless, shows a 99 to 100% identity to Cyanidioschyzon merolae (type IB), which lacks a wall, divides by "fission"-like cytokinesis into two daughter cells, and has less than 5% of the cell volume of type IA. The evolutionary and taxonomic ramifications of this disparity are discussed. Although the 18S rRNA and rbcL genes did not reveal diversity among the numerous isolates of type IA, chloroplast short sequence repeats did show some variation by location within YNP. In contrast, Japanese and New Zealand strains showed considerable diversity when we examined only the sequences of 18S and rbcL genes. Most exhibited identities closer to Galdieria maxima than to other strains, but these identities were commonly as low as 91 to 93%. Some of these Japanese and New Zealand strains probably represent undescribed species that diverged after long-term geographic isolation. [ABSTRACT FROM AUTHOR]

Aim. This study explored the opinions of nurses and doctors working in emergency departments towards the development of the Acute Care Nurse Practitioner service in the United Kingdom. Background. Studies carried out in the United States and Canada suggest that the Acute Care Nurse Practitioner can have a positive impact on the critically ill or injured patients' experiences in the emergency department. This role is well developed in the United States and Canada, but is still in its infancy in the United Kingdom. Design and methods. A descriptive, exploratory design incorporating questionnaires (n = 98) and semi-structured interviews (n = 6) was employed. The sample included nurses and doctors from seven emergency departments and minor injury units. Results. Respondents felt it was important for the Acute Care Nurse Practitioner to have obtained a specialist nurse practitioner qualification and that the Acute Care Nurse Practitioner should retain a clinical remit. While participants seemed comfortable with nurses undertaking traditional advanced skills such as suturing, reluctance was displayed with other advanced skills such as needle thoracocentesis. Three main themes were identified from the interviews: inter-professional conflict, autonomy and the need for the Acute Care Nurse Practitioner. Discussions. Doctors were reluctant to allow nurses to practise certain additional advanced skills and difficulties appear to be centred on the autonomy and other associated inter-professional conflicts with the role of the Acute Care Nurse Practitioner. Conclusion. Nurses and doctors identified a need for the Acute Care Nurse Practitioner, but the blurring of boundaries between doctors and nurses can result in inter-professional conflict unless this is addressed prior to the introduction of such advanced practitioners. Relevance to clinical practice. As the role of the emergency nurse diversifies and expands, this study re-affirms the importance of inter-professional collaboration when seeking approval for role expansions in nursing. [ABSTRACT FROM AUTHOR]

We examined karyotypes of the endemic New Zealand reptile genus Sphenodon (tuatara) from five populations, finding a karyotype unchanged for at least one million years. Animals karyotyped were from five geographically distinct populations, representing three groups, namely S. guntheri, S. punctatus (Cook Strait group), and S. punctatus (northeastern North Island group). All five populations have a diploid chromosome number of 2n = 36, consisting of 14 pairs of macrochromosomes and four pairs of microchromosomes. Chromosomal differences were not found between the five populations nor between female and male animals, except for one animal with a structural heteromorphism. Similarity between Sphenodon and Testudine karyotypes suggests an ancestral karyotype with a macrochromosome complement of 14 pairs and the ability to accumulate variable numbers of microchromosome pairs. Our research supports molecular phylogenies of the Reptilia. Copyright © 2003 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

We demonstrate coded excitation of broadband terahertz for imaging applications. The encoded transmitter uses optical rectification of femtosecond laser pulses in poled lithium niobate patterned with a 53-bit binary phase code. The terahertz wave forms are detected by electro-optic sampling in zinc telluride. A digital pulse compression filter decodes the binary wave forms, producing broadband pulses at 1.0 THz. A two-dimensional imaging experiment shows comparable performance between the encoded transmitter and a zinc telluride emitter. [ABSTRACT FROM AUTHOR]

We demonstrate three-dimensional imaging using single-cycle terahertz electromagnetic pulses. Reflection-mode imaging is performed with a photoconductive transmitter and receiver and a reconstruction algorithm based on time reversal. A two-dimensional array is synthesized from ten concentric ring annular arrays with numerical apertures ranging from 0.27 to 0.43. The system clearly distinguishes image planes separated by 1.5 mm and achieves a -6 dB lateral resolution of 1.1 mm. In terms of the illuminating terahertz power spectrum, the lateral resolution is 38% and 81% of the peak and mean wavelengths, respectively. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the chromosomes from the New Zealand skinks, genus Oligosoma. Identification of common karyotypes in Oligosoma and Leiolopisma; Derivation of Cyclodina from Oligosoma; Absence of sex-related heteromorphisms in the species.

Using femtosecond three-pulse pump-probe spectroscopy, we investigated the transparency condition for the ground and first excited states in self-organized In[sub 0.4]Ga[sub 0.6]As quantum dots at different temperatures and wavelengths. The temperature-dependent behavior of the transparency condition is consistent with calculations using a multilevel model with a large density of states in the quantum-well reservoir. The twofold spatial degeneracy of the first excited state and the temperature dependence of the thermal equilibrium processes were experimentally observed. [ABSTRACT FROM AUTHOR]

We measured the transient temperature-dependent carrier population in the confined states of self-assembled In[sub 0.4]Ga[sub 0.6]As quantum dots as well as those of the surrounding wetting layer and barrier region using differential transmission spectroscopy. Results show directly that thermal reemission and nonradiative recombination contribute significantly to the dynamics above 100 K. We offer results of an ensemble Monte Carlo simulation to explain the contribution of these thermally activated processes. [ABSTRACT FROM AUTHOR]

We demonstrate coherent control of the cavity-polariton modes of a quantum-well semiconductor microcavity in a two-color scheme. The cavity enhancement of the excitonic nonlinearity gives rise to a large signal; modulating the relative phase of the excitation pulses between zero and π produces a differential reflectivity (ΔR/R) of up to 20%. The maximum nonlinear signal is obtained for cocircular pump and probe polarization. Excitation-induced dephasing is responsible for the incoherent nonlinear response, and limits the contrast ratio of the optical switching. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have performed time-resolved photoluminescence on GaAs/AlxGa1-xAs single quantum well structures with an electric field applied perpendicular to the well plane. The quantum wells are coupled to the GaAs continuum through a thin barrier; the escape time of the electrons in the well was measured by time-resolved photoluminescence. The dependence of the decay time on applied bias was found to agree very well with a simple semiclassical model. [ABSTRACT FROM AUTHOR]

Identifying causal factors to intervene on to delay age‐related declines in cognitive function is urgently needed. We examined associations between non‐exercise testing cardiorespiratory fitness (NETCRF; estimated using sex, age, body mass index, resting heart rate, and physical activity) at 45 years and cognitive function outcomes (immediate and delayed verbal memory; verbal fluency; visual processing speed) at 50 years in 8130 participants from the 1958 British birth cohort. In unadjusted models, higher NETCRF was associated with better cognitive function across all outcomes. When adjusted for confounding factors, associations disappeared. In this cohort, associations between 45 years NETCRF and 50 years cognitive function likely result from confounding factors. [ABSTRACT FROM AUTHOR]

A correction to the article "Biogeographic and Phylogenetic Diversity of Thermoacidophilic Cyanidiales in Yellowstone National Park, Japan, and New Zealand" that was published in the previous issue is presented.

Uterine serous carcinoma (USC) is an aggressive subtype of endometrial cancer with high rates of relapse and death. As adjuvant therapy might be beneficial in early-stage disease, the impact of standard complete surgical staging is questioned. Therefore, we wanted to explore the optimal treatment strategy for women diagnosed with USC. A retrospective multicentre study of women diagnosed with primary USC in the UK and the Netherlands. Treatment strategy in relation to overall survival and progression-free survival was recorded and evaluated with Kaplan–Meier and Cox regression analysis. Furthermore, primary surgical staging and/or adjuvant treatment in relation to patterns of recurrence were evaluated. In total, 272 women with a median age of 70 years were included. Most patients presented with International Federation of Gynecology and Obstetrics (FIGO) stage I disease (44%). Overall, 48% of patients developed recurrent disease, most (58%) with a distant component. Women treated with chemotherapy showed significantly better overall survival (hazard ratio 0.50, 95% confidence interval 0.31–0.81; P = 0.005) and progression-free survival (hazard ratio 0.48, 95% confidence interval 0.28–0.80; P = 0.04) in multivariable analysis. Furthermore, even in surgically staged women with FIGO stage IA disease, a high recurrence rate of 42% was seen. Women with USC who received adjuvant chemotherapy showed better survival rates compared with those who received other or no adjuvant treatment. The benefit of adjuvant chemotherapy was observed across all tumour stages, including surgically staged FIGO stage IA. These data question the role of surgical staging in the absence of macroscopic disease in USC. • Majority of women with recurrent USC present with distant disease. • Women with USC, regardless of stage, benefit from adjuvant chemotherapy. • Adjuvant chemotherapy seems superior to other adjuvant therapy in women with USC. [ABSTRACT FROM AUTHOR]

We have surveyed the current state of telehealth in New Zealand. The survey found 22 telehealth projects active in 2003, compared with 12 identified in a previous survey in 2000. Many projects were small, localized and led by enthusiasts. Sustainability was a problem and many projects had failed to enter routine operation. Teleradiology and telepsychiatry services focused on acute hospitals were the most frequent clinical applications. The majority of projects (9 of the 22) were on the North Island, concentrated around Auckland. Telehealth appears to have special potential for rural communities and for the remote treatment (telecare) of chronic disease. However, the provision of telehealth in New Zealand is patchy and meets the same barriers to success as have been identified elsewhere, which make it difficult to move telehealth into routine operation. The obstacles constitute not so much a failure of individual projects as a lack of a driving force to take advantage of the opportunities. It is to be hoped that a suggested strategic framework can help to harness the opportunities. [ABSTRACT FROM AUTHOR]

Ultrafast differential transmission spectroscopy with a resonant pump reveals evidence of electronic tunneling among the excited levels of vertically aligned In[sub 0.4]Ga[sub 0.6]As self-organized quantum dots. This evidence of tunneling is observed as a rapid spectral redistribution of electrons within a few hundred femtoseconds of optical excitation. Measurements show that this spectral spread is independent of carrier density and, therefore, indicate that carrier-carrier scattering is not the main mechanism for carrier redistribution. Instead, electronic tunneling is responsible for the interdot coupling; tunneling rate calculations agree reasonably with the experiment, supporting this conclusion. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have measured the attenuation of longitudinal acoustic waves in a series of amorphous and nanocrystalline silicon films using picosecond ultrasonics. The films were grown using a modified very high frequency glow discharge method on steel substrates. The deposition conditions were similar to that used in the fabrication of high-efficiency solar cells. The film thicknesses were varied so we could distinguish between interface losses and intrinsic losses within the silicon films. We determine the attenuation of amorphous Si to be 780 ± 160 cm-1 at 100 GHz and 340 ± 120 cm-1 at 50 GHz, values that are lower than those predicted by theories based on anharmonic interactions of the sound wave with localized phonons or extended resonant modes. We determine the attenuation of nanocrystalline Si at 50 GHz to be nearly an order of magnitude higher than amorphous Si (2600 ± 660 cm-1) and compare that value to a simple Rayleigh scattering prediction. [ABSTRACT FROM AUTHOR]

Using a femtosecond three-pulse pump-probe technique, we investigated spectral hole-burning and gain recovery dynamics in self-organized In(Ga)As quantum dots. The spectral hole dynamics are qualitatively different from those observed in quantum wells, and allow us to distinguish unambiguously the gain recovery due to intradot relaxation and that due to carrier capture. The gain recovery due to carrier-carrier scattering-dominated intradot relaxation is very fast (∼130 fs), indicating that this is not the factor limiting the bandwidth of directly modulated quantum dot lasers. [ABSTRACT FROM AUTHOR]

We describe a technique for generating tunable narrow-band terahertz radiation via optical rectification in periodically-poled lithium niobate. Frequency tuning is accomplished by spatially chirping the domain width laterally to the beam propagation direction, and adjusting the temperature of the sample. We demonstrate tuning over a continuous range from 0.8 to 2.5 THz. The bandwidth of the terahertz waveforms is as narrow as 0.02 THz. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Objective: To assess a comprehensive package of ultrasound quality control in the Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project, a large multicenter study of fetal growth.Methods: Quality control (QC) measures were performed for 20 313 ultrasound scan images obtained prospectively from 4321 fetuses at 14-41 weeks' gestation in eight geographical locations. At the time of each ultrasound examination, three fetal biometric variables (head circumference (HC), abdominal circumference (AC) and femur length (FL)) were measured in triplicate on separately generated images. All measurements were taken in a blinded fashion. QC had two elements: (1) qualitative QC: visual assessment by sonographers at each study site of their images based on specific criteria, with 10% of images being re-assessed at the Oxford-based Ultrasound Quality Unit (compared using an adjusted kappa statistic); and (2) quantitative QC: assessment of measurement data by comparing the first, second and third measurements (intraobserver variability), remeasurement of caliper replacement in 10% (interobserver variability), both by Bland-Altman plots and plotting frequency histograms of the SD of triplicate measurements and assessing how many were above or below 2 SD of the expected distribution. The system allowed the sonographers' performances to be monitored regularly.Results: A high level of agreement between self- and external scoring was demonstrated for all measurements (κ = 0.99 (95% CI, 0.98-0.99) for HC, 0.98 (95% CI, 0.97-0.99) for AC and 0.96 (95% CI, 0.95-0.98) for FL). Intraobserver 95% limits of agreement (LoA) of ultrasound measures for HC, AC and FL were ± 3.3%, ± 5.6% and ± 6.2%, respectively; the corresponding values for interobserver LoA were ± 4.4%, ± 6.0% and ± 5.6%. The SD distribution of triplicate measurements for all biometric variables showed excessive variability for three of 31 sonographers, allowing prompt identification and retraining.Conclusions: Qualitative and quantitative QC monitoring was feasible and highly reproducible in a large multicenter research study, which facilitated the production of high-quality ultrasound images. We recommend that the QC system we developed is implemented in future research studies and clinical practice. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Objective: To compare the standard methods for ultrasound measurement of fetal head circumference (HC) and biparietal diameter (BPD) (outer-to-outer (BPDoo) vs outer-to-inner (BPDoi) caliper placement), and compare acquisition of these measurements in transthalamic (TT) vs transventricular (TV) planes.Methods: This study utilized ultrasound images acquired from women participating in the Oxford arm of the INTERGROWTH-21(st) Project. In the first phase of the study, BPDoo and BPDoi were measured on stored images. In the second phase, real-time measurements of BPD, occipitofrontal diameter (OFD) and HC in TT and TV planes were obtained by pairs of sonographers. Reproducibility of measurements made by the same (intraobserver) and by different (interobserver) sonographers, as well as the reproducibility of caliper placement and measurements obtained in different planes, was assessed using Bland-Altman plots.Results: In Phase I, we analyzed ultrasound images of 108 singleton fetuses. The mean intraobserver and interobserver differences were < 2% (1.34 mm) and the 95% limits of agreement were < 5% (3 mm) for both BPDoo and BPDoi. Neither method for measuring BPD showed consistently better reproducibility. In Phase II, we analyzed ultrasound images of 100 different singleton fetuses. The mean intraobserver and interobserver differences were < 1% (2.26 mm) and the 95% limits of agreement were < 8% (14.45 mm) for all fetal head measurements obtained in TV and TT planes. Neither plane for measuring fetal head showed consistently better reproducibility. Measurement of HC using the ellipse facility was as reproducible as HC calculated from BPD and OFD. OFD by itself was the least reproducible of all fetal head measurements.Conclusions: Measurements of BPDoi and BPDoo are equally reproducible; however, we believe BPDoo should be used in clinical practice as it allows fetal HC to be measured and compared with neonatal HC. For all head measurements, TV and TT planes provide equally reproducible values at any gestational age, and HC values are similar in both planes. Fetal head measurement in the TT plane is preferable as international standards in this plane are available; however, measurements in the TV plane can be plotted on the same standards. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

We investigate the response of multi-layer epitaxial graphene and chemical vapor deposition (CVD)-grown single-layer graphene to strong terahertz (THz) fields. Contrary to theoretical predictions of strong nonlinear response, the transmitted fields exhibit no harmonic generation, indicating that the nonlinear response is limited by fast electron thermalization due to carrier-carrier scattering. The fast electron heating gives rise to large THz transmission enhancement (>15%) in single-layer CVD graphene at high THz fields (ETHz > 10 kV cm-1). The nonlinear effects exhibit non-Drude behavior in the THz conductivity, where THz fields induce extreme non-equilibrium electron distributions. [ABSTRACT FROM AUTHOR]

Summary We demonstrate adaptive aberration correction for depth-induced spherical aberration in a multiphoton scanning microscope with a micromachined deformable mirror. Correction was made using a genetic learning algorithm with two-photon fluorescence intensity feedback to determine the desired shape for an adaptive mirror. For a 40×/0.6 NA long working distance objective, the axial scanning range was increased from 150 mm to 600 mm. [ABSTRACT FROM AUTHOR]

Examines the dynamics of injected carriers and the conditions for intersubband gain and inversion in semiconductor indium gallium arsenine-gallium arsenide self-organized quantum dots using direct femtosecond pump-probe spectroscopy. Electron relaxation time between excited and ground states; Analysis of carrier relaxation and phonon bottleneck.

We employ two different methods to generate controllable elliptical polarization of teraherz (THz) pulses. First, THz pulses are generated via optical rectification in nonlinear crystals using a pair of temporally separated and perpendicularly polarized optical pulses. The THz ellipticity is controlled by adjusting the relative time delay and polarization of the two optical pulses. We generate mixed polarization states of single-cycle THz pulses using ZnTe, and elliptically polarized multicycle THz pulses in periodically poled lithium niobate crystals. Second, we generate elliptically polarized THz pulses by making a THz “wave plate” using a combination of a wire-grid THz polarizer and a mirror to transform linearly polarized multicycle THz pulses into elliptical polarization. [ABSTRACT FROM AUTHOR]

Ultrafast laser pulses are used to generate single-cycle picosecond acoustic pulses in thin metal films on silicon. For small initial excitation spot sizes, propagation of the acoustic pulses across a 485-μm Si crystal leads to significant diffraction effects. The temporal reshaping of the acoustic wave form due to diffraction is investigated, and we demonstrate that the acoustic far field can be reached. [ABSTRACT FROM AUTHOR]

An abstract of the article "Ultrasound reproducibility for fetal biometry measurements: results from the INTERGROWTH-21st Project" by A. Cavallaro and colleagues is presented.

An abstract of the article "Reproducibility of fetal head biometry measurements acquired in the transthalamic and the transventricular plane," by V. Donadono and colleagues is presented.

An abstract of the article "Quality control of ultrasound biometry in a large-scale study: results from the INTERGROWTH-21st Project," by A. Cavallaro and colleagues is presented.

An abstract of the article "Reproducibility of fetal brain measurements using 3D ultrasound" by R. Napolitano and others, is presented.

An abstract of the research paper "Which Is Best for Fetal Head Biometry: The Transthalamic or Transventricular Plane," by R. Napolitano and colleagues is presented.

We demonstrate a nondestructive probing technique to investigate the inner crystal domain structure of ferroelectric crystals by analyzing the terahertz wave forms generated by optical rectification. Quantitative analysis of the domain structure has been performed for the domain width in periodically poled lithium niobate. Simulation results show that the terahertz wave form analysis reproduces root-mean-square domain width fluctuations. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Femtosecond optical pulses are used to generate narrow-band terahertz wave forms via optical rectification in a periodically poled lithium niobate crystal. By cooling the crystal to reduce losses due to phonon absorption, we are able to obtain bandwidths as narrow as 18 GHz at a carrier frequency of 1.8 THz. Temperature-dependent measurements show insignificant bandwidth broadening between 10 and 120 K, although the terahertz power substantially decreases as the temperature increases. Absolute power measurements indicate a conversion efficiency of at least 10[sup -5]. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We demonstrate a promising technique for generating narrow-band terahertz electromagnetic radiation. Femtosecond optical pulses are propagated through a periodically poled lithium-niobate crystal, where the domain length is matched to the walk-off length between the optical and THz pulses. The bandwidth of the THz wave forms is 0.11 at 1.7 THz. Optical rectification gives rise to a THz wave form which corresponds to the domain structure of the periodically poled lithium niobate. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]