Ångstrom-Depth Resolution with Chemical Specificity at the Liquid-Vapor Interface.

The determination of depth profiles across interfaces is of primary importance in many scientific and technological areas. Photoemission spectroscopy is in principle well suited for this purpose, yet a quantitative implementation for investigations of liquid-vapor interfaces is hindered by the lack of understanding of electron-scattering processes in liquids. Previous studies have shown, however, that core-level photoelectron angular distributions (PADs) are altered by depth-dependent elastic electron scattering and can, thus, reveal information on the depth distribution of species across the interface. Here, we explore this concept further and show that the experimental anisotropy parameter characterizing the PAD scales linearly with the average distance of atoms along the surface normal obtained by molecular dynamics simulations. This behavior can be accounted for in the low-collision-number regime. We also show that results for different atomic species can be compared on the same length scale. We demonstrate that atoms separated by about 1 Å along the surface normal can be clearly distinguished with this method, achieving excellent depth resolution.

First (e,e) coincidence measurements on solvated sodium benzoate in water using a magnetic bottle time-of-flight spectrometer.

Understanding the mechanisms of X-ray radiation damage in biological systems is of prime interest in medicine (radioprotection, X-ray therapy…). Study of low-energy rays, such as soft-X rays and light ions, points to attribute their lethal effect to clusters of energy deposition by low-energy electrons. The first step, at the atomic or molecular level, is often the ionization of inner-shell electrons followed by Auger decay in an aqueous environment. We have developed an experimental set-up to perform electron coincidence spectroscopy on molecules in a water micro-jet. We present here the first results obtained on sodium benzoate solutions, irradiated at the oxygen and carbon K-edges.

X-Ray induced desorption and photochemistry in CO ice.

We report an investigation of X-ray induced desorption of neutrals, cations and anions from CO ice. The desorption of neutral CO, by far the most abundant, is quantified and discussed within the context of its application to astrochemistry. The desorption of many different cations, including large cations up to the mass limit of the spectrometer, is observed. In contrast, the only desorbing anions detected are O- and C-. The desorption mechanisms of all these species are discussed with the aid of their photodesorption spectrum. The evolution of the X-ray absorption spectrum shows significant chemical modifications of the ice upon irradiation, which along with the desorption of large cations gives a new insight into X-ray induced photochemistry in CO ice.

Mechanism of Indirect Photon-Induced Desorption at the Water Ice Surface.

Electronic excitations near the surface of water ice lead to the desorption of adsorbed molecules, through a so far debated mechanism. A systematic study of photon-induced indirect desorption, revealed by the spectral dependence of the desorption (7-13 eV), is conducted for Ar, Kr, N_{2}, and CO adsorbed on H_{2}O or D_{2}O amorphous ices. The mass and isotopic dependence and the increase of intrinsic desorption efficiency with photon energy all point to a mechanism of desorption induced by collisions between adsorbates and energetic H/D atoms, produced by photodissociation of water. This constitutes a direct and unambiguous experimental demonstration of the mechanism of indirect desorption of weakly adsorbed species on water ice, and sheds new light on the possibility of this mechanism in other systems. It also has implications for the description of photon-induced desorption in astrochemical models.

Desorption of neutrals, cations, and anions from core-excited amorphous solid water.

Core-excitation of water ice releases many different molecules and ions in the gas phase. Studying these desorbed species and the underlying desorption mechanisms can provide useful information on the effects of x-ray irradiation in ice. We report a detailed study of the x-ray induced desorption of a number of neutral, cationic, and anionic species from amorphous solid water. We discuss the desorption mechanisms and the relative contributions of Auger and secondary electrons (x-ray induced electron stimulated desorption) and initial excitation (direct desorption) as well as the role of photochemistry. Anions are shown to desorb not just through processes linked with secondary electrons but also through direct dissociation of the core-excited molecule. The desorption spectra of oxygen ions (O+, OH+, H2O+, O-, and OH-) give a new perspective on their previously reported very low desorption yields for most types of irradiations of water, showing that they mostly originate from the dissociation of photoproducts such as H2O2.

beta(2)-Microglobulin amyloidosis caused spinal cord compression in a long-term haemodialysis patient.

STUDY DESIGN: A case report of cervical myelopathy caused by epidural beta (2)-microglobulin (beta2m) amyloid deposits in a 50-year-old woman with haemodialysis treatment. OBJECTIVE: Long-term haemodialysis in patients with end-stage renal disease leads to several complications based on beta2m deposits, which can affect, in the cervical spine, the intervertebral disk, and in rare cases, they may compress the spinal cord and nerves. The objective of this report is to describe the clinical and radiological follow-up preceding the indispensable surgical excision of an amyloid mass in a 50-year-old woman with haemodialysis treatment. Long-term postoperative cervicalgia owing to subcondylian bone cyst-associated atlanto-occipital instability is also described and discussed. SETTING: Department of Neurosurgery A, Hop Pellegrin, Bordeaux, France. CASE REPORT: We present a clinical case of a patient with spinal cord compression. The patient was treated by surgical excision of an amyloid mass subsequent to a C2-C3 laminectomy. The patient experienced clinical improvement with a regression of all of her neurological symptoms. Histological findings confirm the diagnosis of beta2m amyloid deposition. However, 5 years after surgery the subcondylian bone cysts were still observed and atlanto-occipital instability required her to wear a minerva. CONCLUSION: Our case report confirms that surgical excision of beta2m epidural deposits is necessary and relevant when neurological prognosis is discussed, and that pain is still the major symptom of disease evolution. The use of high-flux synthetic membranes could decrease the beta2m blood level and early renal graft is the only method to prevent such complications.

Giant cell arteritis involving the lower limbs.

Giant cell arteritis is an inflammatory disease that can affect the arteries anywhere in the body. Two cases are reported in which the arteries of the lower limbs were involved. Intermittent claudication with a walking distance of only 30 m was the inaugural manifestation in both cases. A biopsy of the superficial femoral artery provided the diagnosis in the first case. Ergotamine toxicity was considered initially in the second case. Acute ischemia and gangrene requiring amputation can complicate giant cell arteritis of the lower limbs and consequently corticosteroid therapy in an effective dose should be given as soon as the diagnosis is made. The inflammatory arterial lesions improve under therapy, but irreversible fibrosis with stenosis can develop if treatment is initiated late.

Bioelectrical impedance analysis in small- and appropriate-for-gestational-age newborn infants.

OBJECTIVE: To determine the reliability of bioelectrical impedance analysis, and to compare and contrast the anthropometric and BIA status of newborns. DESIGN: BIA and anthropometric parameters were compared in the few days after birth and at about 3 weeks of age. SETTING: At the maternity hospital or in a paediatric care unit. SUBJECTS: Small- or appropriate-for-gestational-age newborns, with birth weight below or above the 10th percentile of the reference value, respectively. Measurements were performed on 36 and 47 newborns at birth, and for a subgroup (21 and 11) again about 3 weeks later, respectively. RESULTS: At birth, length2/resistance was 4.3 +/- 0.6 and 6.1 +/- 1.2 cm2/omega (P = 10(-7)), and at 3 weeks of age length2/resistance was 5.0 +/- 0.6 and 5.7 +/- 0.8 cm2/omega (P = 0.11), for small- and appropriate-for-gestational-age newborns, respectively. Percentage reliability was 2.2% and 2.6% for intra- and inter-observer measurements of resistance. Importance of a correct placement of the sensor electrode was demonstrated. CONCLUSIONS: Ease of measurement and reliability of BIA in neonates were shown. Evolution of BIA values is in agreement with the known increase in total body water linked to regrowth of cell mass in small-for-gestational-age infants. Additional study is required before BIA should be used in usual clinical setting in newborns due to the lack of prediction equation.

Evidence that liver microsomes of human neonates desaturate essential fatty acids.

delta 6- and delta 5-Desaturation of essential fatty acids of n-6 and n-3 series are required for the biosynthesis of polyunsaturated fatty acids (PUFAs), which are precursors of eicosanoids and constituents of membrane phospholipids. This pathway could be of special importance during the perinatal period, when PUFAs accretion in the central nervous system is very active. However, experimental evidence of delta 6- and delta 5-desaturase activities in man is very scarce, and no data are available for newborns. We report the delta 6- and delta 5-desaturase activities detected in human liver microsomes from three neonates who died from associated malformations. Radiochemical assays of delta 6- and delta 5-desaturase activities performed with reverse phase HPLC analysis of the products in the n-6 series ranged from 4.8-13.6 to 3.2-16.4 pmol substrate converted.min-1.mg-1 microsomal proteins, respectively. In the n-3 series delta 6-desaturase activity ranged from 5.3 to 12.8 pmol.min-1.mg-1. The relationships between enzyme activities and substrate concentrations suggest excess substrate inhibition for n-6 and not for n-3 fatty acids. These results demonstrate significant delta 6- and delta 5-desaturase activities in human liver of neonates, but this activity was lower than previously reported in adult humans and in mammals, especially rodents.

Brainstem conduction time abnormalities in small for gestational age infants.

Brainstem auditory evoked responses (BAER) were recorded in 89 neonates born between 32 and 40 weeks, in order to analyze the consequences of intrauterine growth retardation on brainstem conduction time. The I-V interval was measured in 28 appropriate for gestational age (AGA) infants (control group), in 24 small for gestational age (SGA) infants with maternal hypertensive disease (MHD) and in 37 SGA infants without MHD. At any gestational age, SGA infants with MHD always presented an acceleration of their brainstem conduction time as compared to the other SGA infants. For the SGA full-term twins without MHD, the brainstem conduction time was delayed. These results reflect the specific consequences on brainstem development of the various factors responsible for intrauterine growth retardation (IURG).

[Results of medical treatment of gastroduodenal ulcers with disordered gastric emptying]. / Résultats du traitement médical des ulcères gastro-duodénaux avec gêne à l'évacuation gastrique

The efficacy of medical treatment was studied in 53 patients with a peptic ulcer responsible for disturbed gastric emptying. An improvement in gastric emptying was noted in 38 cases and persistence of the disorder in 15 cases. These results were not related to the dose of anticholinergic drug, nor to the degree of disturbance in gastric emptying. Only one improvement was noted out of 7 cases of pyloric ulcer. A relapse of disturbed gastric emptying, occurred in 17 out of 38 patients who were initially improved. 25 patients out of 53 were finally operated on, 15 owing to persistence of the gastric emptying disturbance under treatment and 10 owing to a relapse. Out of 18 gastrectomy specimens, the ulcer was found to be healed in 7 cases. It seems that disturbed gastric emptying may be due to fixed deformities of the pylorus which are little changed by medical treatment, and minor disturbances of emptying regress well under treatment. Disturbed gastric emptying due tp pyloric ulcer is the most difficult to treat medically.

[Clinical study and course of 102 cases of chronic pancreatitis]. / Etude clinique et évolutive de 102 cas de pancréatite chronique

Symptomatology, signs and clinical course were studied in 102 cases of chronic pancreatics (CP), confirmed on the basis of strict criteria. Calcifications were present in 72 cases and chronic alcoholism in 81 cases. In seven patients acute pancreatitis, confirmed at surgery, appeared to have preceeded the development of CP. The only clinical difference between calcifying and non-calcifying forms was a higher incidence of steatorrhea in the first group. Cholelithiasis was present in 17 p.cent, alcoholic cirrhosis in 17 p.cent and a peptic ulcer in 24 p.cent of the whole series. Seventy two patients underwent surgery either for a complication in their course (attack of acute pancreatitis, pancreatic pseudo-cyst, cholestatic jaundice, segmental portal hypertension or antro-pyloroduodenal stenosis) or for cholelithiasis. Course assessed in 70 patients studied for more than 2 years was regressive in almost 60 p.cent of cases. There was no difference in the frequency of regression in those patients undergoing surgery and those treated medically only. In all cases, abstention from alcohol is an essential factor to a favourable result.