A compact-rigid multi-analyser for energy and angle filtering of high-resolution X-ray experiments. Part 2. Efficiency of a single-crystal-comb.

Diffraction instruments using filtering by one or several analyser crystals exist since the 1980s and 1990s at synchrotron radiation sources, but, due to its low efficiency, this filtering is little used on laboratory sources. In order to overcome this limitation, the efficiency of a small diffraction filtering multi-analyzer block (MAD block) realized with a `single-crystal-comb' curved on a rigid support is demonstrated here. The geometry of this curved surface is logarithmic spiral and is optimized to allow multi-filtering over a relatively important diffraction angular range and to be also applicable over an X-ray spectral range. The efficiency of such a small rigid-compact MAD block consisting of this single-crystal-comb generating 20-50 Si(111) single-crystal blades, associated with a block of Soller collimators, is demonstrated. The angle between each crystal is 0.1°, so the measurement range of the comb is 2-5°. The geometry of this system has been optimized for operation with a synchrotron X-ray source over an energy range of 22 keV to 46 keV and could be used with laboratory X-ray sources (Ag Kα1, 22.1 keV). This MAD block complements and exploits the qualities of the `photon-counting' detectors which have very low intrinsic noise. Their joint efficacy is supported by powder pattern measurements of a LaB6 reference sample and of several heterogeneous samples of cultural heritage materials, carried out at 22 keV on the D2AM beamline at the ESRF. Their signal-to-noise ratio is excellent (1000/1) and allows the detection thresholds of the measurements (from 3-1% to 0.1%) to detect minor phases in the studies of `real' heterogeneous materials to be drastically improved.

New tools for calibrating diffraction setups.

New calibration tools in the pyFAI suite for processing scattering experiments acquired with area detectors are presented. These include a new graphical user interface for calibrating the detector position in a scattering experiment performed with a fixed large area detector, as well as a library to be used in Jupyter notebooks for calibrating the motion of a detector on a goniometer arm (or any other moving table) to perform diffraction experiments.

The In situ growth of Nanostructures on Surfaces (INS) endstation of the ESRF BM32 beamline: a combined UHV-CVD and MBE reactor for in situ X-ray scattering investigations of growing nanoparticles and semiconductor nanowires.

This paper presents the upgraded `In situ growth of Nanoscructures on Surfaces' (INS) endstation of the InterFace beamline IF-BM32 at the European Synchrotron Radiation Facility (ESRF). This instrument, originally designed to investigate the structure of clean surfaces/interfaces/thin-films by surface X-ray diffraction, has been further developed to investigate the formation and evolution of nanostructures by combining small- and wide-angle X-ray scattering methodologies, i.e. grazing-incidence small-angle X-ray scattering (GISAXS) and grazing-incidence X-ray diffraction (GIXD). It consists of a UHV chamber mounted on a z-axis type goniometer, equipped with residual gas analysis, reflection high-energy electron diffraction (RHEED) and Auger electron spectroscopy (AES) to complete the X-ray scattering investigations. The chamber has been developed so as up to eight sources of molecular beam epitaxy (MBE) can be simultaneously mounted to elaborate the nanostructures. A chemical vapor deposition (CVD) set-up has been added to expand the range of growing possibilities, in particular to investigate in situ the growth of semiconductor nanowires. This setup is presented in some detail, as well as the first in situ X-ray scattering measurements during the growth of silicon nanowires.

High-density electrode array for imaging in vitro electrophysiological activity.

The development of a high-density active microelectrode array for in vitro electrophysiology is reported. Based on the Active Pixel Sensor (APS) concept, the array integrates 4096 gold microelectrodes (electrode separation 20 microm) on a surface of 2.5 mmx2.5 mm as well as a high-speed random addressing logic allowing the sequential selection of the measuring pixels. Following the electrical characterization in a phosphate solution, the functional evaluation has been carried out by recording the spontaneous electrical activity of neonatal rat cardiomyocytes. Signals with amplitudes from 130 microVp-p to 300 microVp-p could be recorded from different pixels. The results demonstrate the suitability of the APS concept for developing a new generation of high-resolution extracellular recording devices for in vitro electrophysiology.

K-edge imaging with the XPAD3 hybrid pixel detector, direct comparison of CdTe and Si sensors.

We investigate the improvement from the use of high-Z CdTe sensors for pre-clinical K-edge imaging with the hybrid pixel detectors XPAD3. We compare XPAD3 chips bump bonded to Si or CdTe sensors in identical experimental conditions. Image performance for narrow energy bin acquisitions and contrast-to-noise ratios of K-edge images are presented and compared. CdTe sensors achieve signal-to-noise ratios at least three times higher than Si sensors within narrow energy bins, thanks to their much higher detection efficiency. Nevertheless Si sensors provide better contrast-to-noise ratios in K-edge imaging when working at equivalent counting statistics, due to their better estimation of the attenuation coefficient of the contrast agent. Results are compared to simulated data in the case of the XPAD3/Si detector. Good agreement is observed when including charge sharing between pixels, which have a strong impact on contrast-to-noise ratios in K-edge images.

A method for early detection of graft failure in pancreas transplantation.

Pancreatic transplantation is intended to normalize carbohydrate metabolism in insulin-dependent diabetics by restoring endogenous insulin release, and it is usually performed together with kidney transplantation in patients with end-stage renal failure. A major problem in these patients is the daily control of the grafted pancreas because traditional measurements do not appear to be adequate to evaluate pancreatic function. Aiming at early detection of graft failure, we have analyzed in 8 such patients and in 20 nondiabetic kidney-grafted patients (a control group) the following variables: 24-hr glycosuria (absolute values, or values after natural logarithmic transformation) and 24-hr urinary C-peptide excretion (corrected for 24-hr urinary creatinine). These measurements, considered alone, did not detect pancreatic graft failure; for instance, glycosuria can depend on immunosuppressive steroid treatment, and it was often found even in the control group. On the contrary, the ratio Ln 24-hr glycosuria: 24-hr urinary C-peptide varied from 0.00 to 0.18 in the control group and in normally working pancreatic grafts; when the pancreatic grafts failed, however, as confirmed by arteriographic evidence, histologic findings, or dynamic endocrine tests, this ratio rose far higher than 0.18, reaching values as high as 12.2. Use of this ratio provides a simple technique for daily evaluation of pancreatic graft function and for early detection of graft failure.

The cell in absence of aggregation artifacts.

Eduard Kellenberger understood that the conventional resin-embedding, he helped to develop (Ryter, A., Kellenberger, E., 1958. L'inclusion au polyester pour l'ultramicrotomie. J. Ultrastruct. Res. , 2, 200-214), was prone to aggregation artifacts (Kellenberger, E., 1987. The response to biological macromolecules and supramolecular structures to the physics of specimen cryo-preparation. In: Steinbrecht, R.A., Zierold, K. (Eds.), Cryo-techniques in Biological Electron Microscopy, Springer, Berlin, pp. 35-63). He was instrumental in developing various methods to overcome this limitation, for instance, by using low temperature-embedding and partially hydrophilic resins (Carlemalm, E., Garavito, R.M., Villiger, W., 1982. Resin development for electron microscopy and an analysis of embedding at low temperature. J. Microstruct., 126, 123-143; Villiger,W., 1993. Low temperature-embedding with Lowicryl resins. In: Robards, A.W., Wilson, A.J. (Eds.), Procedures in electron microscopy, Wiley, Chichester, UK, pp. 16:7.3-16:7.6). In principle, cryo-electron microscopy of vitreous sections is free of any aggregation artifact since the material remains fully hydrated and is free of chemical fixation or staining. The method is technically difficult still, but recent progress has made it amenable to routine practical applications. We compare here electron microscopical aspects of Zea mays meristem cells prepared by: (1) conventional resin-embedding and sectioning; (2) low temperature-embedding and sectioning of freeze substituted samples; and (3) cryo-sections of vitrified samples. The appearance of the extra-cellular space, the cytoplasm and the nucleoplasm are very different in conditions (1) and (3). They appear as compact, irregular and well delineated structures in conventional resin sections, whereas they are more diffuse and homogeneous in the vitreous sections. In the resin sections, the material seems to form a complex matrix, whereas it looks more like a thick soup in the vitreous sample. Low temperature-embedding (condition 2) shows an intermediate appearance. We suggest that regardless of the difference due to staining and different sectioning conditions, the other image differences are the consequence of aggregation artifacts in the resin-embedded specimens.

Infantile spasms and Menkes disease.

Epileptic seizures are a common feature in Menkes disease, an X-linked genetic disorder of copper metabolism. Details of type of seizures are rarely reported. We report the evolution of infantile spasms in two patients with Menkes disease and the relation with subcutaneous administration of copper-histidine.

[Factors associated with childhood diabetes manifesting as ketoacidosis and its severity]. / Facteurs associés à l'acidocétose révélatrice du diabète de l'enfant et à sa sévérité

INTRODUCTION: Type 1 diabetes in children in France is frequently diagnosed at the stage of ketoacidosis (DKA). PATIENTS AND METHODS: A prospective study was performed in a group of 72 children (mean age = 9.4 years) at onset of diabetes, in order to determine which factors were associated to DKA and to the severity of DKA (pH < 7.10) at diagnosis. RESULTS: Younger age was related to DKA (p = 0.03), but not to its severity. A lesser frequency of DKA was found in children with a family history of insulin-treated diabetes ( p = 0.04). Misdiagnosis was more frequently observed in children with DKA than in children without DKA (p = 0.02) and in case of severe DKA at admission by comparison with non severe cases (76 vs 23%; p = 0.002). Children in low economic intake families exhibited more frequently a severe DKA (77 vs 23%; p = 0.002) and were more frequently misdiagnosed before admission (48% vs 10%; p < 0.01). Urine strips for glucose and ketone determinations were underused for diagnosis before admission (15% only). CONCLUSION: Those results underline the need to both inform physicians and ameliorate the access to health care for low social class families, in order to take up the challenge of reducing the incidence of DKA at diagnosis in diabetic children in our country.

[Severe ketoacidosis because of delayed diagnosis of diabetes in children. 4 cases to alert physicians]. / Acidocétose sévère par retard au diagnostic de diabète chez l'enfant. Quatre observations pour alerter les médecins.

BACKGROUND: In France, 48% of children with insulin-dependent diabetes mellitus (IDDM) are seen for the first time at the stage of keto-acidosis (DKA), a figure far higher than in other countries. The four consecutive cases reported in this paper suggest that severity at presentation is directly related to the delay of diagnosis. CASE REPORTS: All children, aged 6 to 11, presented with severe clinical and metabolic conditions: coma, hemodynamic failure, severe dehydration and acidosis (pH = 6.86 to 7.06). However, clinical symptoms were a present from 2 to 4 months, parents did not worry about them. Family practitioners visited 2-21 days before admission failed to immediately make the diagnosis of IDDM. True DKA was however present in all cases 48 hours prior to admission. CONCLUSIONS: Earlier diagnosis of IDDM in children is necessary to reduce morbidity and mortality of DKA. General practitioners, pediatricians and emergency care practitioners must be made fully aware to consider diabetes in children and to use more extensively glucose-tests based on urine and blood strips.

Prenatal isolated mild ventriculomegaly: outcome in 167 cases.

OBJECTIVE: To define the contribution of prenatal investigation and evaluate the prognosis of isolated mild ventriculomegaly (IMV). DESIGN: Retrospective study. SETTING: University hospital between January 1992 and December 2002. POPULATION: One hundred and sixty-seven cases of prenatal unilateral or bilateral IMV without any associated anomaly at the time of initial diagnosis. METHODS: Complementary investigations were performed: amniocentesis with karyotyping, screening for viruses and acetylcholinesterase electrophoresis, magnetic resonance imaging (MRI), and ultrasonography every 3-4 weeks. MAIN OUTCOME MEASURES: Results of prenatal investigations, pregnancy outcome, and postnatal psychomotor development. RESULTS: IMV was diagnosed around 26.5 weeks. Amniocentesis revealed four chromosomal anomalies and two cytomegalovirus infections. MRI diagnosed brain-associated anomalies in 15 cases and ultrasonographic monitoring highlighted malformations not initially diagnosed in 28 cases. Termination of pregnancy (TOP) was considered in 21 pregnancies (12.6%). Indications were aneuploidy, fetal infectious disease or associated malformations. In women for whom a TOP was considered, consanguinity, fetus of female sex and frontal horn enlargement were statistically more frequent, ventriculomegaly was more often bilateral and asymmetrical, atrial width, and the rate of progressive ventricular enlargement were significantly higher. One hundred and one children with prenatal IMV were assessed between 19 and 127 months (mean age 54.68 +/- 2.87 months). Twelve children had neurological disease or psychomotor delay and 89 children had a normal psychomotor development. Poor neurological outcome was more often associated with atrial width greater than or equal to 12 mm, asymmetrical bilateral enlargement, and progression of the ventriculomegaly. CONCLUSION: The detection of IMV raises the question of the child's psychomotor development and justifies meticulous prenatal investigation. In addition to associated anomalies, three criteria are often associated with an unfavourable outcome: atrial width greater than 12 mm, progression of the enlargement, and asymmetrical and bilateral ventriculomegaly.

Electron beam-induced changes in vitreous sections of biological samples.

Nonpretreated high pressure frozen samples of Zea mays, cartilage and human erythrocytes were cryosectioned and observed at 110K in a cryoelectron microscope. Changes induced by medium doses of electron irradiation (< 10 ke nm-2) are described. After some ke nm-2, the most conspicuous cutting artefacts are erased to a large extent and the visibility of the cell organelles is improved. The sections, compressed in the cutting direction by the sectioning process, shrink once more, in the same direction, when irradiated. This shrinkage depends on the section support and on how the section is adsorbed to it. Shrinkage is not uniform: it is most pronounced in mitochondria, condensed chromatin and nucleolus. This differential shrinkage improves the visibility of major structures on the section and, as a result, 'nicer' images are recorded. However, this apparent improvement is a beam-induced artefact that must be paired with a loss of high resolution information.

DNA in human and stallion spermatozoa forms local hexagonal packing with twist and many defects.

In human and other mammal sperm nuclei, DNA is packed in a highly condensed state, the structure of which remains unsolved. Cryoelectron microscopy of vitrified sections provides a first direct view of the local arrangement of the nucleoprotamine filament. DNA aligns in parallel in layers and its orientation rotates along a single-twist direction as in a cholesteric liquid crystal. The structure contains numerous defects, which introduce locally double-twist configurations. Destruction of the SS bonds with dithiotrehitol relaxes the twist and favors the extension of the hexagonal close packing of the filaments, though keeping constant their interfilament distance.

[Rejections and cytomegalovirus infections after renal transplantation]. / Rejets et infections a cytomégalovirus après transplantation rénale

Immunosuppressed patients are known to be susceptible to infectious agents. Association of allograft rejection and herpes virus infection (high incidence of cytomegalovirus) was yet reported after renal transplantation. Authors studied 19 rejection episodes on 24 renal transplantation performed for 17 months, cytomegalovirus infection being associated in 7. Because of the therapeutic difficulties observed in these cases, a preventive attitude is necessary.