Multi-channel absolute distance measurement system with sub ppm-accuracy and 20 m range using frequency scanning interferometry and gas absorption cells.

We present an implementation of an absolute distance measurement system which uses frequency scanning interferometry (FSI). The technique, referred to as dynamic FSI, uses two frequency scanning lasers, a gas absorption cell and a reference interferometer to determine the unknown optical path length difference (OPD) of one or many measurement interferometers. The gas absorption cell is the length reference for the measurement system and is traceable to international standards through knowledge of the frequencies of its absorption features. The OPD of the measurement interferometers can vary during the measurement and the variation is measured at the sampling rate of the system (2.77 MHz in the system described here). The system is shown to measure distances from 0.2 m to 20 m with a combined relative uncertainty of 0.41 × 10⁻6 at the two sigma level (k = 2). It will be shown that within a scan the change in OPD of the measurement interferometer can be determined to a resolution of 40 nm.

Loss-of-function of activity-dependent neuroprotective protein (ADNP) by a splice-acceptor site mutation causes Helsmoortel-Van der Aa syndrome.

Mutations in ADNP result in Helsmoortel-Van der Aa syndrome. Here, we describe the first de novo intronic deletion, affecting the splice-acceptor site of the first coding ADNP exon in a five-year-old girl with developmental delay and autism. Whereas exome sequencing failed to detect the non-coding deletion, genome-wide CpG methylation analysis revealed an episignature suggestive of a Helsmoortel-Van der Aa syndrome diagnosis. This diagnosis was further supported by PhenoScore, a novel facial recognition software package. Subsequent whole-genome sequencing resolved the three-base pair ADNP deletion c.[-5-1_-4del] with transcriptome sequencing showing this deletion leads to skipping of exon 4. An N-terminal truncated protein could not be detected in transfection experiments with a mutant expression vector in HEK293T cells, strongly suggesting this is a first confirmed diagnosis exclusively due to haploinsufficiency of the ADNP gene. Pathway analysis of the methylome indicated differentially methylated genes involved in brain development, the cytoskeleton, locomotion, behavior, and muscle development. Along the same line, transcriptome analysis identified most of the differentially expressed genes as upregulated, in line with the hypomethylated CpG episignature and confirmed the involvement of the cytoskeleton and muscle development pathways that are also affected in patient cell lines and animal models. In conclusion, this novel mutation for the first time demonstrates that Helsmoortel-Van der Aa syndrome can be caused by a loss-of-function mutation. Moreover, our study elegantly illustrates the use of EpiSignatures, WGS and Phenoscore as novel complementary diagnostic tools in case a of negative WES result.

Women's experiences of pregnancy, childbirth, and the postnatal period in The Gambia: a qualitative study.

OBJECTIVE: In sub-Saharan African countries, there are unique cultural factors and adverse physical conditions that contribute to women's experiences of pregnancy and birth. The objective of this study was to qualitatively explore women's experiences of pregnancy, childbirth, the postnatal period, and maternal psychological distress in The Gambia. DESIGN AND METHODS: Semi-structured interviews were carried out with 55 women who had given birth within the previous year. RESULTS: Thematic analysis identified five themes: (1) transition to adulthood, (2) physical difficulties, (3) value of children in relation to others, (4) children as a strain, and (5) going through it alone. The results suggest that having a child is a defining point in women's lives associated with happiness and joy. However, women also described situations which could lead to unhappiness and distress in the perinatal period. A child conceived out of wedlock or a baby girl can be sources of distress because of negative cultural perceptions. The strain of having a child, particularly the additional financial burden, and minimal support from men were also a concern for women. Finally, women recognized the danger associated with delivery and expressed recurrent worries of complications during childbirth which could result in the death of them or the baby. CONCLUSIONS: Further research is needed to identify women vulnerable to psychological distress so that health services and target interventions can be developed accordingly.