Influence of mechanical stresses on the hydrolytic aging of standard and low styrene unsaturated polyester composites

Standard and low styrene emission glass fiber‐reinforced unsaturated polyester (FRP) composites were aged by immersion under flexural and tension loads, to evaluate modifications to the mechanical properties as a function of exposure time under stress. The application of a mechanical load does not modify either the quantity of the absorbed water or the diffusion coefficients significantly. For an applied stress of less than 10% of the fiber strength, the influence on aging is small, but for larger applied stresses, the rate of reduction in the mechanical properties is accelerated and, in some cases, premature rupture is observed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2185–2195, 2002     

ACNUC--a portable retrieval system for nucleic acid sequence databases: logical and physical designs and usage

ACNUC is a database structure and retrieval software for use with either the GenBank or EMBL nucleic acid sequence data collections. The nucleotide and textual data furnished by both collections are each restructured into a database that allows sequence retrieval on a multi-criterion basis. The main selection criteria are: species (or higher order taxon), keyword, reference, journal, author, and organelle; all logical combinations of these criteria can be used. Direct access to sequence regions that code for a specific product (protein, tRNA or rRNA) is provided. A versatile extraction procedure copies selected sequences, or fragments of them, from the database to user files suitable to be analysed by user-supplied application programs. A detailed help mechanism is provided to aid the user at any time during the retrieval session. All software has been written in FORTRAN 77 which guarantees a high degree of transportability to minicomputers or mainframes.     

A new analytical model for the GaAs MESFET in the saturation region

A model that provides the static characteristics and the elements of the equivalent electrical scheme is presented. It is based on an approximate quadratic form for the depleted region under the gate when the electron velocity reaches the saturation velocity. The potential in the channel is calculated using Poisson's equation and taking into account the variation of the electron density inside it. The main physical phenomena such as edge effects, overshoot velocity, and carrier injection in the buffer layer are also taken into account. Theoretical and experimental results for the I-V characteristics, transconductance, output conductance, gate-source capacitance, and gate-drain capacitance are presented for a submicrometer-gate MESFET. The results calculated using this model agree well with experimental data     

Compositional design of isochronous systems

The synchronous modeling paradigm provides strong correctness guarantees for embedded system design while requiring minimal environmental assumptions. In most related frameworks, global execution correctness is achieved by ensuring the insensitivity of (logical) time in the program from (real) time in the environment. This property, called endochrony or patience, can be statically checked, making it fast to ensure design correctness. Unfortunately, it is not preserved by composition, which makes it difficult to exploit with component-based design concepts in mind. Compositionality can be achieved by weakening this objective, but at the cost of an exhaustive state-space exploration. This raises a trade-off between performance and precision. Our aim is to balance it by proposing a formal design methodology that adheres to a weakened global design objective: the non-blocking composition of weakly endochronous processes, while preserving local design objectives for synchronous modules. This yields an effective and cost-efficient approach to compositional synchronous modeling.     

Exploring system architectures in AADL via Polychrony and SynDEx

Architecture analysis & design language (AADL) has been increasingly adopted in the design of embedded systems, and corresponding scheduling and formal verification have been well studied. However, little work takes code distribution and architecture exploration into account, particularly considering clock constraints, for distributed multi-processor systems. In this paper, we present an overview of our approach to handle these concerns, together with the associated toolchain, AADL-Polychrony-SynDEx. First, in order to avoid semantic ambiguities of AADL, the polychronous/multiclock semantics of AADL, based on a polychronous model of computation, is considered. Clock synthesis is then carried out in Polychrony, which bridges the gap between the polychronous semantics and the synchronous semantics of SynDEx. The same timing semantics is always preserved in order to ensure the correctness of the transformations between different formalisms. Code distribution and corresponding scheduling is carried out on the obtained SynDEx model in the last step, which enables the exploration of architectures originally specified in AADL. Our contribution provides a fast yet efficient architecture exploration approach for the design of distributed real-time and embedded systems. An avionic case study is used here to illustrate our approach.     

Fluorescent Polymer Nanoparticles for Cell Barcoding In Vitro and In Vivo

Fluorescent polymer nanoparticles for long‐term labeling and tracking of living cells with any desired color code are developed. They are built from biodegradable poly(lactic‐co‐glycolic acid) polymer loaded with cyanine dyes (DiO, DiI, and DiD) with the help of bulky fluorinated counterions, which minimize aggregation‐caused quenching. At the single particle level, these particles are ≈20‐fold brighter than quantum dots of similar color. Due to their identical 40 nm size and surface properties, these nanoparticles are endocytosed equally well by living cells. Mixing nanoparticles of three colors in different proportions generates a homogeneous RGB (red, green, and blue) barcode in cells, which is transmitted through many cell generations. Cell barcoding is validated on 7 cell lines (HeLa, KB, embryonic kidney (293T), Chinese hamster ovary, rat basophilic leucemia, U97, and D2A1), 13 color codes, and it enables simultaneous tracking of co‐cultured barcoded cell populations for >2 weeks. It is also applied to studying competition among drug‐treated cell populations. This technology enabled six‐color imaging in vivo for (1) tracking xenografted cancer cells and (2) monitoring morphogenesis after microinjection in zebrafish embryos. In addition to a robust method of multicolor cell labeling and tracking, this work suggests that multiple functions can be co‐localized inside cells by combining structurally close nanoparticles carrying different functions.     

Dynamic study of tissue circulation in the cervix uteri and the prognosis of the newborn infant

A new machine has been developed to measure heat dissipated in the tissues especially by convection linked to the blood flow. Its use is simple and without any danger as far as application to the pregnant cervix goes. New discoveries are presented. A new concept of the micro-circulation is considered together with the consequences. The practitioner may be able to draw conclusions as to the prognosis, as to whether a small-for-dates fetus together with or without premature labour is likely. This depends on the tracings obtained which register the intrinsic activity of the periarteriolar muscles.     

Electromagnetic behavior of a FIR waveguide laser

We consider the electromagnetic behaviorof a FIR (far infrared) waveguide laser. In a first step, we deal with the different modes which can propagate in the waveguide. Then, we compute the reflection and transmission coefficients of the coupling holes. Finally, we determine the oscillation conditions for each mode.     

Comportement electrochimique des oxydes mixtes MexCo1 − x Mn2O4 (Me = Ni,Cu; 0,75 ⩾ x ⩾ 0,25)

It is demonstrated through the electrochemical reduction of cobalt manganese spinels that it is possible to increase the cathodic reactivity by replacement of cobalt ions by nickel and copper cations. The reduction reaction occurs on active sites formed by Mn⁴⁺ ions associated, in octahedral sites, with Mn³⁺ ions, for the Ni_xCo_{1 ? x} Mn₂O₄ compounds. For the copper manganites oxides, Cu_xCo_{1 ? x}Mn₂O₄, the electrochemical reaction is likely to occur by the redox on solid state between Mn³⁺ and Cu²⁺ cations.     

In vitro influence of apatite-granule-specific area on human growth hormone loading and release

PURPOSE: The study was conducted to evaluate risk factors, natural history, and clinical consequences of a periprosthetic leak after endovascular repair of an abdominal aortic aneurysm. METHODS: We reviewed the initial and follow-up data, including angiograms, contrast-enhanced computed tomography (CT) scans, abdominal duplex scans, and plain abdominal films for all patients undergoing tube graft repair using the endovascular graft system (early prototype) between February 10, 1993, and January 24, 1995. RESULTS: Sixty-eight patients underwent placement or attempted placement of a tube graft implant in 13 centers in the United States. Nine patients required conversion to open repair, leaving 59 patients with functioning grafts for evaluation. The mean follow-up time was 27 +/- 8 months (range, 2 to 48 months). Twenty-eight (47%) of 59 patients had initial periprosthetic leaks (6 proximal, 14 distal, 3 proximal and distal, 5 indeterminate) on their first postoperative CT scans. Fourteen (50%) of the initial 28 leaks sealed spontaneously. Two other patients had their leaks sealed by endovascular means, leaving 12 patients with persistent leaks for follow-up evaluation. Four patients developed late leaks between 18 and 24 months of follow-up: one who had a spontaneously sealed initial leak, one with a second leak, and two who developed late leaks. Of the 16 patients with sealed leaks, 10 had aneurysm size reduction during follow-up. Three aneurysm sacs enlarged before spontaneous sealing but have not had sufficient follow-up time to document the size change since the seal. One patient died of respiratory failure 5 months after graft implantation. One patient whose leak was sealed by intervention has not yet had a CT scan for evaluation. In one patient with a sealed leak and whose aneurysm had initially shrunk, the area reopened and progressed to a nonfatal rupture that was surgically corrected. There were two late deaths from unrelated causes. Twelve patients in the sealed group are alive and well. Of the 12 patients with persistent leaks, five underwent open surgical repair without complication, and one underwent successful endovascular repair with a second graft. Six patients continue to live with their initial grafts and have an average aneurysm sac enlargement of 0.1 cm per year. CONCLUSIONS: Although initial periprosthetic leaks were common with the use of this early prototype, 50% spontaneously sealed. The subsequent clinical course of patients with persistently sealed leaks was no different from that of patients who had no leaks. However, continued CT surveillance is warranted, because in one patient with an initially sealed leak, the area reopened and progressed to nonfatal rupture. Another two patients without initial leaks developed late leaks. In a small group of selected patients with continued leaks, their aneurysms appeared to enlarge at a rate considerably slower than would have been expected in patients with untreated aneurysm, suggesting that even a person after endovascular repair with a persistent leak may have had some beneficial hemodynamic modification.