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The Centre for Isotope Research (CIO) at the University of Groningen has operated a radiocarbon (14C) dating laboratory for almost 70 years. In 2017, the CIO received a major upgrade, which involved the relocation of the laboratory to new purpose-built premises, and the installation of a MICADAS accelerator mass spectrometer. This period of transition provides an opportunity to update the laboratory’s routine procedures. This article addresses all of the processes and quality checks the CIO has in place for registering, tracking and pretreating samples for radiocarbon dating. Complementary updates relating to radioisotope measurement and uncertainty propagation will be provided in other forthcoming publications. Here, the intention is to relay all the practical information regarding the chemical preparation of samples, and to provide a concise explanation as to why each step is deemed necessary.
Texture (of a polycrystalline sample) means the orientation distribution of the many crystallites in the sample with respect to a coordinate system on the sample, for example the rolling direction. Texture is responsible for many macroscopic properties of materials, for example in metals and alloys in the process of rolling or hot-pressing. It carries importance in many everyday production processes. Also in areas of geological science the texture of the sample, e.g. of the rocks should be known in order to explain geological processes.
Position-sensitive detectors (PSD's) are commonly available for X-ray diffraction, where they are used in the angle dispersive mode at fixed wavelength λ. They are sensitive to the scattering angle 2Θ. The resolution of such instruments is determined by the physical properties of the detector, and, of course, the distance from the sample. Using continuous radiation solid state detectors (Ge, Ge(Li), Si(Li)) are sensitive to energy (equivalent to λ) at fixed scattering angle 2Θo, They are being used for X-rays, especially with synchrotron radiation. Because X-rays travel with the speed of light, those two techniques cannot be combined. Thermal neutrons, on the other hand, are comparatively slowly traveling particles (2200 m/s at 300 K) and consequently time-of-flight (TOF) instruments with choppers at continuous neutron beams are known for a long time; they are being used as well for diff-actomet! y as for inelastic scattering.
Two strategies are at present commonly used in studying and refining crystal structures from powder diffraction data: the total pattern refinement proposed by Rietveid (1969) and the two-step method originally proposed and applied by Will (Will et al., 1965). The latter one works by separating-the intensity determination of the individual peaks from the actual structure refinement, structure analysis or any structural calculation (tor example based on line broadening). Both methods have their merits, and their drawbacks.
Blood pressure (BP) tracks from childhood to adulthood, and early BP trajectories predict cardiovascular disease risk later in life. Excess postnatal weight gain is associated with vascular changes early in life. However, to what extent it is associated with children’s BP is largely unknown. In 853 healthy 5-year-old children of the Wheezing-Illnesses-Study-Leidsche-Rijn (WHISTLER) birth cohort, systolic (SBP) and diastolic BP (DBP) were measured, and z scores of individual weight gain rates adjusted for length gain rates were calculated using at least two weight and length measurements from birth until 3 months of age. Linear regression analyses were conducted to investigate the association between weight gain rates adjusted for length gain rates and BP adjusted for sex and ethnicity. Each standard deviation increase in weight gain rates adjusted for length gain rates was associated with 0.9 mmHg (95% CI 0.3, 1.5) higher sitting SBP after adjustment for confounders. Particularly in children in the lowest birth size decile, high excess weight gain was associated with higher sitting SBP values compared to children with low weight gain rates adjusted for length gain rates. BMI and visceral adipose tissue partly explained the association between excess weight gain and sitting SBP (β 0.5 mmHg, 95% CI −0.3, 1.3). Weight gain rates adjusted for length gain rates were not associated with supine SBP or DBP. Children with excess weight gain, properly adjusted for length gain, in the first three months of life, particularly those with a small birth size, showed higher sitting systolic BP at the age of 5 years.
The ability to predict upper respiratory infections (URI), lower respiratory infections (LRI), and gastrointestinal tract infections (GI) in independently living older persons would greatly benefit population and individual health. Social network parameters have so far not been included in prediction models. Data were obtained from The Maastricht Study, a population-based cohort study (N = 3074, mean age (±s.d.) 59.8 ± 8.3, 48.8% women). We used multivariable logistic regression analysis to develop prediction models for self-reported symptomatic URI, LRI, and GI (past 2 months). We determined performance of the models by quantifying measures of discriminative ability and calibration. Overall, 953 individuals (31.0%) reported URI, 349 (11.4%) LRI, and 380 (12.4%) GI. The area under the curve was 64.7% (95% confidence interval (CI) 62.6–66.8%) for URI, 71.1% (95% CI 68.4–73.8) for LRI, and 64.2% (95% CI 61.3–67.1%) for GI. All models had good calibration (based on visual inspection of calibration plot, and Hosmer–Lemeshow goodness-of-fit test). Social network parameters were strong predictors for URI, LRI, and GI. Using social network parameters in prediction models for URI, LRI, and GI seems highly promising. Such parameters may be used as potential determinants that can be addressed in a practical intervention in older persons, or in a predictive tool to compute an individual's probability of infections.
Accurately measuring and monitoring the thickness distribution of thin ice is crucial for accurate estimation of ocean–atmosphere heat fluxes and rates of ice production and salt flux in ice-affected oceans. Here we present results from helicopter-borne brightness temperature (TB) measurements in the Southern Ocean in October 2012 and in the Sea of Okhotsk in February 2009 carried out with a portable passive microwave (PMW) radiometer operating at a frequency of 36 GHz. The goal of these measurements is to aid evaluation of a satellite thin-ice thickness algorithm which uses data from the spaceborne Advanced Microwave Scanning Radiometer–Earth Observing System AMSR-E) or the Advanced Microwave Scanning Radiometer-II (AMSR-II). AMSR-E and AMSR-II TB agree with the spatially collocated mean TB from the helicopter-borne measurements within the radiometers’ precision. In the Sea of Okhotsk in February 2009, the AMSR-E 36GHz TB values are closer to the mean than the modal TB values measured by the helicopter-borne radiometer. In an Antarctic coastal polynya in October 2012, the polarization ratio of 36GHz vertical and horizontal TB is estimated to be 0.137 on average. Our measurements of the TB at 36 GHz over an iceberg tongue suggest a way to discriminate it from sea ice by its unique PMW signature.
Two nonlinear dynamos have been analyzed by numerical means: 3D-simulation of the magneto-hydrodynamic equations and qualitative analysis of a simplified low-dimensional mean field model. It turns out that both are capable of deterministic chaos in a certain parameter range. As the basic tool the calculation of Lyapunov exponents has been used.
Applying modern techniques of time series analysis, there are serious indications that the dynamics of the global solar activity is a low dimensional chaos. A simple non-linear dynamo model is qualitatively studied exhibiting a rich dynamical behaviour from steady state via some bifurcation to a chaotic regime.
Does excluding food and energy prices from the Consumer Price Index (CPI) produce a measure that better captures permanent price changes? To examine this question, we decompose CPI inflation and “core” inflation into their permanent and transitory components, using a correlated unobserved-components model. The stationarity of inflation may be time-varying, so we examine the performance of the core measure of inflation separately for periods in which inflation is I(1) and I(0). For a period in which inflation appears to be I(1), we find that core inflation and the permanent component of overall inflation are closely related, but there are some caveats. For a period in which inflation appears to be I(0), we decompose the core and overall price levels and find that the permanent component of the core CPI is much more volatile than the actual core series and that the core excludes volatile permanent shocks to the overall price level.
A problematic and disturbing behavior which can develop in people with dementia, is vocally disruptive behavior (VDB). To date, the study of VDB is underdeveloped and with only a limited knowledge base. Medications commonly used in VDB have limited benefits and specific risks in patients with dementia. This report details the case of a patient with frontotemporal dementia with VDB, which responded very well by providing a lollipop. Subsequently, we pose theory-based hypotheses in order to try to explain the beneficial effect of this intervention. This may contribute to a better understanding of VDB and possible treatment strategies.
Antipsychotic drugs (APD) are widely prescribed for people with dementia residing in long term care facilities (LTCFs). Concern has been expressed that such prescribing is largely inappropriate. The objective of this study is to examine if differences in facility-level prevalence of APD use in a sample of LTCFs for patients with dementia can be explained by patient and facility-related characteristics.
A point prevalence study was conducted using data from the VU University Resident Assessment Instrument (VURAI) database from nursing homes and residential care facilities in the Netherlands. Patients were selected who had a diagnosis of dementia. LTCF and patient characteristics were extracted from the VURAI; facility-level resident satisfaction surveys were provided by the National Institute for Public Health.
In total, 20 LTCFs providing care for 1,090 patients with dementia were investigated. Overall, 31% of patients used an APD. In facilities with a high prevalence of APD use behavioral symptoms were present in 62% of their patients. In facilities with medium APD use behavioral problems remained frequent (57%), and in facilities with low prevalence of APD use 54% of the patients had behavioral symptoms. Facilities with a high prevalence of APD use were often large, situated in urban communities, and scored below average on staffing, personal care, and recreational activities.
There was considerable variation between the participating LTCFs in the prevalence of APD use. Variability was related to LTCF characteristics and patient satisfaction. This indicates potential inappropriate prescribing because of differences in institutional prescribing culture.
Genes and markers on the same chromosome have a linear arrangement, which can be described by a (linear) map. Genes and markers on different, non-homologous chromosomes are inherited independently and therefore there is no linear arrangement between them. This is the reason why genetic linkage maps are estimated separately for each chromosome. Determining which genes and markers belong to the same chromosome is therefore a necessary preparation for map construction. Sets of linked loci are called linkage groups. Ideally, the number of linkage groups is the same as the haploid number of chromosomes. In practice, this is not always the case. Sometimes, the set of loci studied does not cover the entire genome or is not distributed evenly across the genome. On other occasions, spurious linkage causes loci from separate chromosomes to end up in a single linkage group, which is a more common problem to solve.
Why determine linkage groups and how?
Chromosomes are very large linear molecules. Genes and genetic markers are, or represent, tiny parts of the chromosomes. They are referred to as loci. Their linear arrangement on the chromosomes can be described with mutual distance measures, for instance in base pairs or in recombination units. A linkage map is such a description. Because a linear arrangement exists only for loci of the same chromosome, determining which loci reside on the same chromosome is the first step in the construction of a linkage map. Loci on the same chromosome are physically linked, whereas those on different (non-homologous) chromosomes are physically unlinked. Genetic linkage is the phenomenon whereby traits have a tendency to be inherited together. Due to independent assortment of the chromosomes in meiosis, genetic linkage is the result of physical linkage. Determining whether two loci are genetically linked is the starting point of lumping loci into groups. It is preferable to identify such groups of linked genes and markers as linkage groups rather than as chromosomes, as long as the physical relationship between the loci and the chromosomes is not established (e.g. through cytogenetics). This is even more relevant if there are more groups than homologous chromosome pairs. Such situations often occur in experiments where the genome is not covered completely with markers.
The central idea of linkage analysis is that the rate of recombination between two loci is a reflection of their mutual distance on the chromosomes. Combining recombination frequencies between multiple loci on the same chromosome allows determination of the relative positions of these loci on the chromosome, thus creating a linkage map. A linkage map is defined by the order of its loci and by their mutual distances. This chapter is about obtaining the map distances for a given order.
Recombination frequencies and distances
One of the functions of a linkage map is to allow easy calculation of recombination frequencies between loci from their positions on the map. The linearity of a linkage map implies that distances can be added or subtracted. The question is whether recombination frequencies can be used as map distances. This problem was initially met by Sturtevant (1913), who was the first person to produce a genetic linkage map. At the time, it was becoming clear that genetic factors were located on the chromosomes. Sturtevant realized that it should be possible to determine the spatial arrangement of the genetic factors on the linear structure of a chromosome using recombination frequencies between factors as measures of their mutual distances. However, he found a discrepancy between the sum of adjacent distances and the direct measurement of the overall distance. He claimed that shorter distances were measured more accurately. He attributed the discrepancy to double recombinations and to a phenomenon now known as crossover interference. The essence of the problem is that recombination frequencies are not additive. The problem was solved by Haldane (1919), who derived a function that translates recombination frequencies into additive distances.
Around 1900, scientists tried to understand the relationship between the inheritance of simple traits and observations of meiotic cell division under a microscope. It was the time that Mendel's laws on the inheritance of traits (Mendel, 1865) were rediscovered. Mendel did not have any idea of the biological mechanisms underlying his laws. However, some 35 years later, after studying Boveri's 1902 paper, Sutton (1902) realized that chromosomes and their behaviour in meiotic cell division could very well explain Mendel's results. However, in the many experimental crosses carried out to study the simultaneous inheritance of two traits, occasionally large deviations from Mendel's Law of Independent Assortment were observed. Bateson et al. (1905) described these deviations in terms of coupling of the heritable factors determining the traits. In subsequent work by Morgan and others, it became clear that heritable factors could be grouped with respect to the law of independent assortment: if two factors belonged to the same group, then their inheritance showed some interdependence; otherwise, the law would hold. In other words, they started realizing that these groups corresponded with chromosomes. By 1911, Morgan showed the possibility of recombination between factors lying on the same chromosome (Morgan, 1911a). Morgan assumed that this was due to an interchange (as he called the crossing over) between homologous chromosomes during meiosis. This corresponded very well with the detailed cytological observations of Janssens (1909). Later, Morgan (1911b) suggested that the heritable factors should be located in a linear fashion on the chromosomes and that the degree of coupling between traits would depend on the distance between the factors on the chromosomes. Sturtevant (1913), a student of Morgan, tested the hypothesis that the proportion of crossovers (as he called the recombinants) could be used as an index of the distance between two factors. He argued that, after determining distances from A to B and from B to C, it should be possible to predict the distance from A to C and to determine the order of the factors on the chromosome. Sturtevant successfully analysed six factors located on the sex chromosome of Drosophila and thus became the first ever person producing a genetic map. With his work, the chromosome theory of inheritance became really established.