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N Michel

Publications and source records attributed to N Michel.

14 recordsLinked to original sources
PubMed2006

Density matrix renormalization group approach for many-body open quantum systems.

The density matrix renormalization group (DMRG) approach is extended to complex-symmetric density matrices characteristic of many-body open quantum systems. Within the continuum shell model, we investigate the interplay between many-body configuration interaction and coupling to open channels in case of the unbound nucleus (7)He. It is shown that the extended DMRG procedure provides a highly accurate treatment of the coupling to the nonresonant scattering continuum.

Journal Article↗
PubMed2005

Distribution of Streptococcus pneumoniae serotypes responsible for penicillin resistance and the potential role of new conjugate vaccines in New Caledonia.

Invasive pneumococcal disease is a significant cause of morbidity and mortality worldwide. The aim of this study was to establish the serotypes responsible for pneumococcal disease and the serotypes responsible for penicillin resistance in Noumea, New Caledonia. Isolates of Streptococcus pneumoniae from all body sites referred to the Microbiology Department of the Pasteur Institute in New Caledonia between May 1999 and May 2001 had serotyping and susceptibility testing performed. Basic demographic data on patients were also collected. A total of 298 isolates were included in the study. The most common serotypes were types 1 (20%), 23F (10%), 12F (8%), 19F (8%), and 6B (5%). The serotype distribution differed significantly with age, site of collection, and ethnicity. Overall, 280 of 298 (94%) of the isolates had serogroups that are included in the 23-valent vaccine. However, only 14 of 20 (70%) of the isolates associated with invasive disease from children younger than 5 years of age and 26 of 113 (23%) of invasive isolates from patients more than 5 years of age were included in the new 7-valent conjugate vaccine. Overall, reduced susceptibility to penicillin was found in 43 of 298 (14.4%) of the isolates, with 13% falling into the intermediate resistance category and only 5 (2%) being high-level resistant. A higher prevalence of penicillin resistance occurred in younger age groups and in European patients and involved specifically certain serotypes. The 7-valent conjugate pneumococcal vaccine has potential benefit for the New Caledonian population under 5 years of age and should be considered for future vaccines schedules.

Adult↗
PubMed2003

CBED and LACBED: characterization of antiphase boundaries.

Convergent-beam electron diffraction (CBED) and large-angle convergent-beam electron diffraction (LACBED) techniques are well adapted to the characterization of several types of crystal defects. In fact, dislocations, grain boundaries and stacking faults have already been successfully characterized with these methods. In the present paper, we describe the CBED and LACBED characterization of another type of crystal defect showing a special interest in materials science: antiphase boundaries (APBs). The first part of the paper is devoted to the determination of the effects of antiphase boundaries on CBED and LACBED patterns that could be expected from a theoretical point of view. It indicates that the superlattice excess lines present on these patterns are split into two lines with equal intensity when the incident beam is located on an APB. In the second part, we experimentally test these theoretical predictions on a specimen showing two different known types of antiphase boundaries. In a third part we indicate how these methods could be used to identify unknown APBs in a specimen. Finally, the advantages and disadvantages of both methods for the characterization of antiphase boundaries are discussed.

Journal Article↗
PubMed2002

Gamow shell model description of neutron-rich nuclei.

This work presents the first continuum shell-model study of weakly bound neutron-rich nuclei involving multiconfiguration mixing. For the single-particle basis, the complex-energy Berggren ensemble representing the bound single-particle states, narrow resonances, and the nonresonant continuum background is taken. Our shell-model Hamiltonian consists of a one-body finite potential and a zero-range residual two-body interaction. It is demonstrated that the residual interaction coupling to the particle continuum is important; in some cases, it can give rise to the binding of a nucleus.

Journal Article↗
PubMed2001

A DNA vaccine based on a shuffled E7 oncogene of the human papillomavirus type 16 (HPV 16) induces E7-specific cytotoxic T cells but lacks transforming activity.

Vaccination with oncogene-derived DNA for anti-cancer treatment carries a risk of de-novo tumor induction triggered by the persisting recombinant DNA. We hypothesized that an oncoprotein whose primary sequence has been rearranged ('shuffled') to maintain all possible T cell epitopes still induces cytotoxic T cells against the authentic protein but is devoid of transforming properties. As a model antigen, we used the E7 oncoprotein of the human papillomavirus (HPV) type 16, the major cause of cervical cancer. We have generated an artificial E7 molecule in which four domains were rearranged and, in order to maintain all possible T cell epitopes, certain sequences were duplicated. Upon transfection of this shuffled E7 gene (E7SH) into RMA cells, presentation of an E7 Db-restricted T cell epitope was shown by an E7-specific CTL line in vitro. Immunization of C57BL/6 mice with E7SH DNA induced E7-specific CTL and also conveyed protection against E7-positive syngeneic tumor cells. No transforming activity of E7SH DNA in NIH3T3 cells was detected, as determined by focus formation, induction of S-phase under conditions of serum deprivation and degradation of endogenous pRB. Our results suggest that DNA shuffling may become a promising concept for DNA-based anti-cancer vaccines.

3T3 Cells↗
PubMed1990

[Development of maternal milk flora during continuous enteral feeding of premature infants].

Unheated breast milk constitutes the main element in the premature infant's nutrition. However, it contains bacterial flora which is possibly responsible for infant pathologies. The authors find a considerable increase in the bacterial population during continuous drip-feeding of the premature infant. Aerobic flora present in the syringe are increased by 2.2 and coliforms by 28.5, sometimes resulting in highly contaminated milk at the end of the continuous drip-feeding period. To ensure bacteriological security a reduction in microbial count at the beginning of continuous enteral nutrition is necessary, without affecting the nutritive and immunological properties of breast milk.

Enteral Nutrition↗
PubMed1987

Study of neuromotor reaction times under the influence of thyrotropin-releasing hormone.

Neuromotor reaction times (simple, choice, and decision) were measured when Thyrotropin-releasing hormone (TRH) was administered intravenously to nine healthy men in a double-blind study. Measurements were made of simple reaction time, choice reaction time, and decision time for each subject at various intervals over a 54-hr. period. Given the observed inherent interaction of the drug with the long time used (54 hr.), most analyses were conducted across separate time epochs. Injected subjects showed inhibition in the normal improvement of simple reaction time (which occurs with practice), and they reduced the time required to make a decision. Choice reaction time, however, remained unchanged across the drug-nondrug experimental conditions.

Adult↗
PubMed1986

Effect of directional response variables on eye-hand reaction times and decision time.

To determine if direction of response affects reaction time, we measured the time for hand response to a visual stimulus, using a sensitive, microprocessor-based testing device to determine simple reaction time (RT), choice RT, and decision time. Mean simple RT was 207 +/- 3.7 msec. (mean +/- SEM); mean choice RT was 268 +/- 4.2 msec; and mean decision time was 61 msec. No differences were noted for leftward versus rightward movements, or midline versus lateral movements. Choice RT increased by 1.49 msec./yr. of age. Simple RT increased significantly with age for the nondominant hand, but not for the dominant hand. Right-handed subjects were more rapid with the dominant hand for choice RT. We conclude that dominance of hand tested and test initiation mechanism have major effects, but direction of movement in the lateral plane has little effect on reaction time.

Adult↗
PubMed1981

Laser flow cytofluorometric analysis of HTC cells synchronized with hydroxyurea, nocodazole and aphidicolin.

The technique of laser flow cytofluorometry has been used to monitor the arrival in G1 and the subsequent progression through the cell cycle of HTC cells accumulated in metaphase with colcemid alone or after treatment with hydroxyurea and Nocodazole. Under the experimental conditions used in this study, the latter procedure gives much better results, avoiding in particular the extensive formation of micronucleated cells. Aphidicolin, an inhibitor of DNA polymerase, in combination with Nocodazole, provides a useful method to tightly synchronize these cells at the G1/S border.

Animals↗
PubMed1976

Vaccinia virus: the possibilities of its oncogenicity in humans.

Contrary to the earlier generally accepted view that vaccinia virus replicates in the cytoplasm only of suitable target cells, steadily accumulating data show that the viral genome spends a limited period of time in the nucleus. This, together with the many cases where a close association has been suspected or established between skin cancer and vaccination, suggests that vaccinia virus may, under certain yet undefined physiological conditions, act as an oncogenic virus in humans.

Cell Nucleus↗
PubMedDate not supplied

Design of a computerized device to measure simple reaction time/decision time.

The construction and validation of a computerized device to test simple reaction time and decision-making time is discussed. The device is required to demonstrate repeatability (consistency of response times from human subjects) across replications of the same experimental condition. A second requirement of the device is that it must separately and independently measure simple reaction time and the time it takes to process one bit of information. The concepts behind the construction of the box are discussed, as well as the design of its internal circuits to achieve these specifications.

Adult↗
PubMedDate not supplied

Experimental study on a large animal model of a new thermoablation technique.

BACKGROUND: A novel technique of thermoablation, using a microtube to deliver pulses of hot water vapour, was tested on a large animal model in order to evaluate its efficacy and potential adverse effects. MATERIALS AND METHODS: The medical device consisted of a microtube extension connected to a hydropneumatic pump. Pulses of pure water were injected though the microtube where they were heated and delivered as vapour into the target zone. The method was tested on the liver of 12 healthy pigs, either during open surgery or percutaneously under ultrasounds. RESULTS: The technique was efficient and well-tolerated by the animals. Large volumes of necrotic tissue were created in a significantly short time compared to concurrent thermoablative techniques. CONCLUSION: Anticipating human application, this experimental study demonstrated a safe and efficient innovative thermoablation technique. The first human applications have been successfully performed and will be reported soon.

Animals↗