Pliensbachian magnetostratigraphy: new data from Paris Basin (France)

Sampling of an industrial drill string from the northeastern Paris Basin (Montcornet, France) provides early Jurassic magnetostratigraphic data coupled with biochronological control. About 375 paleomagnetic samples were obtained from a 145 m thick series of Pliensbachian rocks. A composite demagnetization thermal up to 300 C and an alternating field up to 80 mT were used to separate the magnetic components. A low unblocking temperature component (<250degreesC) with an inclination of about 64 is interpreted as a present-day field overprint. The characteristic remanent component with both normal and reversed antipodal directions was isolated between 5 and 50 mT. Twenty-nine polarity intervals were recognized. Correlation of these new results from the Paris Basin with data from the Breggia Gorge section (Ticino, southern Alps, Switzerland), which is generally considered as the reference section for Pliensbachian magnetostratigraphy, reveals almost identical patterns of magnetic polarity reversals. However, the correlation implies significant paleontological age discrepancies. Revised age assignments of biostratigraphic data of Breggia as well as an objective evaluation of the uncertainties on zonal boundaries in both Breggia and Moncornet resolve the initial discrepancies between magnetostratigraphic correlations and biostratigraphic ages. Hence, the sequence of magnetic reversals is significantly strengthened and the age calibration is notably improved for the Pliensbachian, a stage for which sections combining adequate magnetic signal and biostratigraphic constraints are still very few. (C) 2002 Elsevier Science B.V. All rights reserved.

Detecting nanoscale vibrations as signature of life.

The existence of life in extreme conditions, in particular in extraterrestrial environments, is certainly one of the most intriguing scientific questions of our time. In this report, we demonstrate the use of an innovative nanoscale motion sensor in life-searching experiments in Earth-bound and interplanetary missions. This technique exploits the sensitivity of nanomechanical oscillators to transduce the small fluctuations that characterize living systems. The intensity of such movements is an indication of the viability of living specimens and conveys information related to their metabolic activity. Here, we show that the nanomotion detector can assess the viability of a vast range of biological specimens and that it could be the perfect complement to conventional chemical life-detection assays. Indeed, by combining chemical and dynamical measurements, we could achieve an unprecedented depth in the characterization of life in extreme and extraterrestrial environments.

La maladie des vibrations [The vibration syndrome].

The vibration syndrome is an often unrecognized occupational neurovascular disease with a prevalence of more than 70% in certain high-risk occupations. Early recognition is crucial because continued exposure to vibration can lead to irreversible ischemic injury and loss of digits. Digital ischemia due to the vibration syndrome may be due to a vasospastic phenomenon, an organic microangiopathy or arterial thrombosis. Demyelinating neuropathy and carpal tunnel syndrome are often associated. Many pathophysiological mechanisms are implicated: hyperactivity of the central sympathetic nervous system, release of plasma endothelin-1 and loss of calcitonin-gene-related-peptide vasoregulation. Investigation tests, treatment and the European Community Directive for the protection of workers are also presented.

Whole-body vibration training: metabolic cost of synchronous, side-alternating or no vibrations.

Whole-body vibration training improves strength and can increase maximal oxygen consumption ([·V]O(2max)). No study has compared the metabolic demand of synchronous and side-alternating whole-body vibration. We measured [·V]O₂ and heart rate during a typical synchronous or side-alternating whole-body vibration session in 10 young female sedentary participants. The 20-min session consisted of three sets of six 45-s exercises, with 15 s recovery between exercises. Three conditions were randomly tested on separate days: synchronous at 35 Hz and 4 mm amplitude, side-alternating at 26 Hz and 7.5 mm amplitude (peak acceleration matched at 20 g in both vibration conditions), and no vibrations. Mean [·V]O₂ (expressed as %[·V]O(2max)) did not differ between conditions: 29.7 ± 4.2%, 32.4 ± 6.5%, and 28.7 ± 6.7% for synchronous, side-alternating, and no vibrations respectively (P = 0.103). Mean heart rate (% maximal heart rate) was 65.6 ± 7.3%, 69.8 ± 7.9%, and 64.7 ± 5.6% for synchronous, side-alternating, and no vibrations respectively, with the side-alternating vibrations being significantly higher (P = 0.019). When analysing changes over exercise sessions, mean [·V]O₂ was higher for side-alternating (P < 0.001) than for synchronous and no vibrations. In conclusion, side-alternating whole-body vibration elicits higher heart rate responses than synchronous or no vibrations, and could elevate [·V]O₂, provided the session lasts more than 20 min.

The effect of mountain bike suspensions on vibrations and off-road uphill performance.

AIM: This study evaluates the effect of front suspension (FS) and dual suspension (DS) mountain-bike on performance and vibrations during off-road uphill riding. METHODS: Thirteen male cyclists (27+/-5 years, 70+/-6 kg, VO(2max)59+/-6 mL.kg(-1).min(-1), mean+/-SD) performed, in a random sequence, at their lactate threshold, an off-road uphill course (1.69 km, 212 m elevation gain) with both type of bicycles. Variable measured: a) VO(2) consumption (K4b2 analyzer, Cosmed), b) power output (SRM) c) gain in altitude and d) 3-D accelerations under the saddle and at the wheel (Physilog, EPFL, Switzerland). Power spectral analy- sis (Fourier) was performed from the vertical acceleration data. RESULTS: Respectively for the FS and DS mountain bike: speed amounted to 7.5+/-0.7 km.h(-1) and 7.4+/-0.8 km.h(-1), (NS), energy expenditure 1.39+/-0.16 kW and 1.38+/-0.18, (NS), gross efficiency 0.161+/-0.013 and 0.159+/-0.013, (NS), peak frequency of vibration under the saddle 4.78+/-2.85 Hz and 2.27+/-0.2 Hz (P<0.01) and median-frequency of vertical displacements of the saddle 9.41+/-1.47 Hz and 5.78+/-2.27 Hz (P<0.01). CONCLUSION: Vibrations at the saddle level of the DS bike are of low frequencies whereas those of the FS bike are mostly of high frequencies. In the DS bike, the torque produced by the cyclist at the pedal level may generate low frequency vibrations. We conclude that the DS bike absorbs more high frequency vibrations, is more comfortable and performs as well as the FS bicycle.

Wound infection following stoma takedown: primary skin closure versus subcuticular purse-string suture.

Abstract: Background Stoma closure has been associated with a high rate of surgical site infection (SSI) and the ideal stoma-site skin closure technique is still debated. The aim of this study was to compare the rate of SSI following primary skin closure (PC) versus a skin-approximating, subcuticular purse-string closure (APS). Methods All consecutive patients undergoing stoma closure between 2002 and 2007 by two surgeons at a single tertiary-care institution were retrospectively assessed. Patients who had a new stoma created at the same site or those without wound closure were excluded. The end point was SSI, determined according to current CDC guidelines, at the stoma closure site and/or the midline laparotomy incision. Results There were 61 patients in the PC group (surgeon A: 58 of 61) and 17 in the APS group (surgeon B: 16 of 17). The two groups were similar in baseline and intraoperative characteristics, except that patients in the PC group were more often diagnosed with benign disease (p = 0.0156) and more often had a stapled anastomosis (p = 0.002). The overall SSI rate was 14 of 78 (18%). All SSIs occurred in the PC group (14 of 61 vs. 0 of 17, p = 0.03). Conclusions Our study suggests that a skin-approximating closure with a subcuticular purse-string of the stoma site leads to less SSI than a primary closure. Randomized studies are needed to confirm our findings and assess additional end points such as healing time, cost, and patient satisfaction.

Plunging when drilling: effect of using blunt drill bits.

OBJECTIVE: : Plunging when drilling can be a detrimental factor in patient care. There is, although, a general lack of information regarding the surgeon's performance in this skill. The aim of this study was to determine the effect that using sharp or blunt instruments had on the drill bit's soft tissue penetration, using a simulator. MATERIALS AND METHODS: : Surgeons taking part in an International Trauma Course were invited to participate. Two groups were defined: experienced and inexperienced surgeons. Twelve holes were drilled in the following order: 3 holes with a sharp drill bit in normal bone (SNB), 3 holes with a sharp drill bit in osteoporotic bone (SOB), 3 holes with a blunt drill bit in normal bone, and 3 holes with a blunt drill bit in osteoporotic bone. Mean values and Student t tests were used for statistical analysis. RESULTS: : Thirty-seven surgeons participated, 20 experienced and 17 inexperienced surgeons. Mean plunging depths for SNB, SOB, blunt drill bit in normal bone, and blunt drill bit in osteoporotic bone were, respectively, 5.1, 5.4, 21.1, and 13.9 mm for experienced surgeons and 7.6, 7.7, 22, and 15.9 mm for inexperienced surgeons. Drilling with SNB and with SOB was statistically different, with inexperienced surgeons plunging 2.5 mm (P = 0.31) and 2.6 mm (P = 0.042) deeper, respectively. There was a difference (P < 0.001) between sharp and blunt drill bits in all drilling conditions for both the groups. CONCLUSIONS: : Our study showed a significant difference in plunging depth when sharp or bunt drill bit was being used. Surgeons, regardless of their experience level, penetrate over 20 mm in normal bone and over 10 mm in osteoporotic bone.

Transferring control demands across incidental learning tasks - Stronger sequence usage in serial reaction task after shortcut option in letter string checking

After incidentally learning about a hidden regularity, participants can either continue to solve the task as instructed or, alternatively, apply a shortcut. Past research suggests that the amount of conflict implied by adopting a shortcut seems to bias the decision for vs. against continuing instruction-coherent task processing. We explored whether this decision might transfer from one incidental learning task to the next. Theories that conceptualize strategy change in incidental learning as a learning-plus-decision phenomenon suggest that high demands to adhere to instruction-coherent task processing in Task 1 will impede shortcut usage in Task 2, whereas low control demands will foster it. We sequentially applied two established incidental learning tasks differing in stimuli, responses and hidden regularity (the alphabet verification task followed by the serial reaction task, SRT). While some participants experienced a complete redundancy in the task material of the alphabet verification task (low demands to adhere to instructions), for others the redundancy was only partial. Thus, shortcut application would have led to errors (high demands to follow instructions). The low control demand condition showed the strongest usage of the fixed and repeating sequence of responses in the SRT. The transfer results are in line with the learning-plus-decision view of strategy change in incidental learning, rather than with resource theories of self-control.

New methods for detecting antibiotic resistant bacteria and preventing their spread

Methicillin resistant Staphylococcus aureus (MRSA) bacteria have emerged in the early 1980's in numerous health care institutions around the world. The main transmission mechanism within hospitals and healthcare facilities is through the hands of health care workers. Resistant to several antibiotics, the MRSA is one of the most feared pathogens in the hospital setting since it is very difficult to eradicate with the standard treatments. There are still a limited number of anti-MRSA antibiotics but the first cases of resistance to these compounds have already been reported and their frequency is likely to increase in the coming years. Every year, the MRSA infections result in major human and financial costs, due to the high associated mortality and expenses related to the required care. Measures towards a faster detection of resistant bacteria and establishment of appropriate antibiotic treatment parameters are fundamental. Also as part as infection prevention, diminution of bacteria present on the commonly touched surfaces could also limit the spread and selection of antibiotic resistant bacteria. During my thesis, projects were developed around MRSA and antibiotic resistance investigation using innovative technologies. The thesis was subdivided in three main parts with the use of atomic force microscopy AFM for antibiotic resistance detection in part 1, the importance of the bacterial inoculum size in the selection of antibiotic resistance in part 2 and the testing of antimicrobial surfaces creating by sputtering copper onto polyester in part 3. In part 1 the AFM was used two different ways, first for the measurement of stiffness (elasticity) of bacteria and second as a nanosensor for antibiotic susceptibility testing. The stiffness of MRSA with different susceptibility profiles to vancomycin was investigated using the stiffness tomography mode of the AFM and results have demonstrated and increased stiffness in the vancomycin resistant strains that also paralleled with increased thickness of the bacterial cell wall. Parts of the AFM were also used to build a new antibiotic susceptibility-testing device. This nano sensor was able to measure vibrations emitted from living bacteria that ceased definitively upon antibiotic exposure to which they were susceptible but restarted after antibiotic removal to which they were resistant, allowing in a matter of minute the assessment of antibiotic susceptibility determination. In part 2 the inoculum effect (IE) of vancomycin, daptomycin and linezolid and its importance in antibiotic resistance selection was investigated with MRSA during a 15 days of cycling experiment. Results indicated that a high bacterial inoculum and a prolonged antibiotic exposure were two key factors in the in vitro antibiotic resistance selection in MRSA and should be taken into consideration when choosing the drug treatment. Finally in part 3 bactericidal textile surfaces were investigated against MRSA. Polyesters coated after 160 seconds of copper sputtering have demonstrated a high bactericidal activity reducing the bacterial load of at least 3 logio after one hour of contact. -- Au cours des dernières décennies, des bactéries multirésistantes aux antibiotiques (BMR) ont émergé dans les hôpitaux du monde entier. Depuis lors, le nombre de BMR et la prévalence des infections liées aux soins (IAS) continuent de croître et sont associés à une augmentation des taux de morbidité et de mortalité ainsi qu'à des coûts élevés. De plus, le nombre de résistance à différentes classes d'antibiotiques a également augmenté parmi les BMR, limitant ainsi les options thérapeutiques disponibles lorsqu'elles ont liées a des infections. Des mesures visant une détection plus rapide des bactéries résistantes ainsi que l'établissement des paramètres de traitement antibiotiques adéquats sont primordiales lors d'infections déjà présentes. Dans une optique de prévention, la diminution des bactéries présentes sur les surfaces communément touchées pourrait aussi freiner la dissémination et l'évolution des bactéries résistantes. Durant ma thèse, différents projets incluant des nouvelles technologies et évoluant autour de la résistance antibiotique ont été traités. Des nouvelles technologies telles que le microscope à force atomique (AFM) et la pulvérisation cathodique de cuivre (PCC) ont été utilisées, et le Staphylococcus aureus résistant à la méticilline (SARM) a été la principale BMR étudiée. Deux grandes lignes de recherche ont été développées; la première visant à détecter la résistance antibiotique plus rapidement avec l'AFM et la seconde visant à prévenir la dissémination des BMR avec des surfaces crées grâce à la PCC. L'AFM a tout d'abord été utilisé en tant que microscope à sonde locale afin d'investiguer la résistance à la vancomycine chez les SARMs. Les résultats ont démontré que la rigidité de la paroi augmentait avec la résistance à la vancomycine et que celle-ci corrélait aussi avec une augmentation de l'épaisseur des parois, vérifiée grâce à la microscopie électronique. Des parties d'un AFM ont été ensuite utilisées afin de créer un nouveau dispositif de test de sensibilité aux antibiotiques, un nanocapteur. Ce nanocapteur mesure des vibrations produites par les bactéries vivantes. Après l'ajout d'antibiotique, les vibrations cessent définitivement chez les bactéries sensibles à l'antibiotique. En revanche pour les bactéries résistantes, les vibrations reprennent après le retrait de l'antibiotique dans le milieu permettant ainsi, en l'espace de minutes de détecter la sensibilité de la bactérie à un antibiotique. La PCC a été utilisée afin de créer des surfaces bactéricides pour la prévention de la viabilité des BMR sur des surfaces inertes. Des polyesters finement recouverts de cuivre (Cu), connu pour ses propriétés bactéricides, ont été produits et testés contre des SARMs. Une méthode de détection de viabilité des bactéries sur ces surfaces a été mise au point, et les polyesters obtenus après 160 secondes de pulvérisation au Cu ont démontré une excellente activité bactéricide, diminuant la charge bactérienne d'au moins 3 logio après une heure de contact. En conclusion, l'utilisation de nouvelles technologies nous a permis d'évoluer vers de méthodes de détection de la résistance antibiotique plus rapides ainsi que vers le développement d'un nouveau type de surface bactéricide, dans le but d'améliorer le diagnostic et la gestion des BMR.