Bremsstrahlung enhancement in electron probe microanalysis for homogeneous samples using Monte Carlo simulation.

Fluorescence enhancement in samples irradiated in a scanning electron microscope or an electron microprobe should be appropriately assessed in order not to distort quantitative analyses. Several models have been proposed to take into account this effect and current quantification routines are based on them, many of which have been developed under the assumption that bremsstrahlung fluorescence correction is negligible when compared to characteristic enhancement; however, no concluding arguments have been provided in order to support this assumption. As detectors are unable to discriminate primary from secondary characteristic X-rays, Monte Carlo simulation of radiation transport becomes a determinant tool in the study of this fluorescence enhancement. In this work, bremsstrahlung fluorescence enhancement in electron probe microanalysis has been studied by using the interaction forcing routine offered by penelope 2008 as a variance reduction alternative. The developed software allowed us to show that bremsstrahlung and characteristic fluorescence corrections are in fact comparable in the studied cases. As an extra result, the interaction forcing approach appears as a most efficient method, not only in the computation of the continuum enhancement but also for the assessment of the characteristic fluorescence correction.

Intestinal gas content and distribution in health and in patients with functional gut symptoms.

BACKGROUND: The precise relation of intestinal gas to symptoms, particularly abdominal bloating and distension remains incompletely elucidated. Our aim was to define the normal values of intestinal gas volume and distribution and to identify abnormalities in relation to functional-type symptoms. METHODS: Abdominal computed tomography scans were evaluated in healthy subjects (n = 37) and in patients in three conditions: basal (when they were feeling well; n = 88), during an episode of abdominal distension (n = 82) and after a challenge diet (n = 24). Intestinal gas content and distribution were measured by an original analysis program. Identification of patients outside the normal range was performed by machine learning techniques (one-class classifier). Results are expressed as median (IQR) or mean ± SE, as appropriate. KEY RESULTS: In healthy subjects the gut contained 95 (71, 141) mL gas distributed along the entire lumen. No differences were detected between patients studied under asymptomatic basal conditions and healthy subjects. However, either during a spontaneous bloating episode or once challenged with a flatulogenic diet, luminal gas was found to be increased and/or abnormally distributed in about one-fourth of the patients. These patients detected outside the normal range by the classifier exhibited a significantly greater number of abnormal features than those within the normal range (3.7 ± 0.4 vs 0.4 ± 0.1; p < 0.001). CONCLUSIONS & INFERENCES: The analysis of a large cohort of subjects using original techniques provides unique and heretofore unavailable information on the volume and distribution of intestinal gas in normal conditions and in relation to functional gastrointestinal symptoms.

Functional gut disorders or disordered gut function? Small bowel dysmotility evidenced by an original technique.

BACKGROUND: This study aimed to determine the proportion of cases with abnormal intestinal motility among patients with functional bowel disorders. To this end, we applied an original method, previously developed in our laboratory, for analysis of endoluminal images obtained by capsule endoscopy. This novel technology is based on computer vision and machine learning techniques. METHODS: The endoscopic capsule (Pillcam SB1; Given Imaging, Yokneam, Israel) was administered to 80 patients with functional bowel disorders and 70 healthy subjects. Endoluminal image analysis was performed with a computer vision program developed for the evaluation of contractile events (luminal occlusions and radial wrinkles), non-contractile patterns (open tunnel and smooth wall patterns), type of content (secretions, chyme) and motion of wall and contents. Normality range and discrimination of abnormal cases were established by a machine learning technique. Specifically, an iterative classifier (one-class support vector machine) was applied in a random population of 50 healthy subjects as a training set and the remaining subjects (20 healthy subjects and 80 patients) as a test set. KEY RESULTS: The classifier identified as abnormal 29% of patients with functional diseases of the bowel (23 of 80), and as normal 97% of healthy subjects (68 of 70) (P < 0.05 by chi-squared test). Patients identified as abnormal clustered in two groups, which exhibited either a hyper- or a hypodynamic motility pattern. The motor behavior was unrelated to clinical features. CONCLUSIONS & INFERENCES: With appropriate methodology, abnormal intestinal motility can be demonstrated in a significant proportion of patients with functional bowel disorders, implying a pathologic disturbance of gut physiology.

[Proton pump inhibitors: impact of professional practice evaluation on prescriptions pertinence]. / Inhibiteurs de la pompe à protons : impact d'une évaluation des pratiques professionnelles sur la pertinence des prescriptions.

OBJECTIVE: To improve the quality of proton pump inhibitors (PPI) prescription in an orthopaedic department. STUDY DESIGN: Prospective professional practice evaluation study. PATIENTS AND METHODS: A specific protocol concerning the best practice for using PPI in the perioperative period was established by anaesthesiologists and validated by all prescribers, according to recent recommendations published by French Afssaps. PPI prescription pertinence, mainly using the oral route, was based upon the presence of clearly identified risk factors. PPI mensual consumption and severe gastric complications were analyzed and compared with those obtained from the previous year. Ten months after the beginning of the protocol, the pertinence of PPI prescription was analyzed in 20 randomly selected medical records. Data are expressed in defined daily dose (DDD). RESULTS: After one year, a 35.5% decrease in oral PPI consumption was noted (901 ± 211 before vs 581 ± 235 DDD, after, P<0.05). A similar trend to a decrease in intravenous PPI consumption was observed (40 ± 23 vs 22 ± 26, P=0.06). During the same period, the overall incidence of severe gastric complication remained stable. The PPI prescription was pertinent in 85% of selected medical records. CONCLUSION: This study confirmed the interest of professional practice evaluation protocols to improve PPI prescription. A strong implication of all medical staff members is mandatory to maintain such benefits over time.

Stem cell differentiation by functionalized micro- and nanostructured surfaces.

New fabrication technologies and, in particular, new nanotechnologies have provided biomaterial and biomedical scientists with enormous possibilities when designing customized supports and scaffolds with controlled nanoscale topography and chemistry. The main issue now is how to effectively design these components and choose the appropriate combination of structure and chemistry to tailor towards applications as challenging and complex as stem cell differentiation. Occasionally, an incomplete knowledge of the fundamentals of biological differentiation processes has hampered this issue. However, the recent technological advances in creating controlled cellular microenvironments can be seen as a powerful tool for furthering fundamental biology studies. This article reviews the main strategies followed to achieve solutions to this challenge, particularly emphasizing the working hypothesis followed by the authors to elucidate the mechanisms behind the observed effects of structured surfaces on cell behavior.

[Value and limitations of puncture guided by x-ray computed tomography in hematology]. / Intérêt et limites de la ponction guidée par tomodensitométrie en hématologie.

Interpretable cytologic data were obtained in 63% of a series of 68 punctures, for biopsy of hematologic affections, guided by CT scanning. The frequency of puncture of post-therapy residual masses (44 cases) explains the high incidence of non-significant examination results after lymph node puncture. The technique was most effective (78% of punctures exploitable) when used for thoracic masses and visceral localizations. The method is very safe: lack of serious incidents and minor reactions, mainly during thoracic puncture, in only 4.4%. The method is simple in use and should be employed, within certain limits that should be recognized, very widely in hematologic diseases.

Dynamic CT features of hepatic abscesses.

Forty hepatic abscesses were examined with dynamic computed tomography (CT). A "double target sign," consisting of a hypodense central area surrounded by first a hyperdense ring and then a hypodense zone, seems to be highly suggestive of abscess formation. In 12 cases, the hepatic parenchyma surrounding the lesion demonstrated transient hyperdensity after contrast injection, possibly due to localized hepatic venous obstruction secondary to acute hepatic inflammation. This is similar to the appearance of an arterioportal fistula.

[External retromalleolar lymphography of the superficial and deep lymphatics of the lower limb (author's transl)]. / Voies lymphatiques superficielles et profondes du membre inférieur explorées par la lymphographie rétro-malléolaire externe.

External retromalleolar lymphography was employed to explore lower limb lymphatics in 39 patients. Though this type of approach enables deep lymph vessels of the thigh to be studied--at the price of a more difficult catheterization than when the classical approach is used--it is ineffective for demonstrating deep lower leg lymph vessels, filling occurring only in the superficial network. Its indications are therefore limited to cases following unsuccessful attempts with the classical approach.