Direct microcontact printing of oligonucleotides for biochip applications

BACKGROUND: A critical step in the fabrication of biochips is the controlled placement of probes molecules on solid surfaces. This is currently performed by sequential deposition of probes on a target surface with split or solid pins. In this article, we present a cost-effective procedure namely microcontact printing using stamps, for a parallel deposition of probes applicable for manufacturing biochips. RESULTS: Contrary to a previous work, we showed that the stamps tailored with an elastomeric poly(dimethylsiloxane) material did not require any surface modification to be able to adsorb oligonucleotides or PCR products. The adsorbed DNA molecules are subsequently printed efficiently on a target surface with high sub-micron resolution. Secondly, we showed that successive stamping is characterized by an exponential decay of the amount of transferred DNA molecules to the surface up the 4(th )print, then followed by a second regime of transfer that was dependent on the contact time and which resulted in reduced quality of the features. Thus, while consecutive stamping was possible, this procedure turned out to be less reproducible and more time consuming than simply re-inking the stamps between each print. Thirdly, we showed that the hybridization signals on arrays made by microcontact printing were 5 to 10-times higher than those made by conventional spotting methods. Finally, we demonstrated the validity of this microcontact printing method in manufacturing oligonucleotides arrays for mutations recognition in a yeast gene. CONCLUSION: The microcontact printing can be considered as a new potential technology platform to pattern DNA microarrays that may have significant advantages over the conventional spotting technologies as it is easy to implement, it uses low cost material to make the stamp, and the arrays made by this technology are 10-times more sensitive in term of hybridization signals than those manufactured by conventional spotting technology

Observations sur des cas de myiase canine à <em>Cordylobia anthropophaga</em> Blanchard à Bobo-Dioulasso, République de Haute-Volta

Un cas de myiase à Cordylobia anthropophaga chez un chien adulte et trois cas chez des chiots sont décrits. Après avoir étudié la symptomatologie et indiqué la thérapeutique mise en oeuvre, les auteurs relatent le processus de contamination et son importance épidémiologique pour l'homme notamment. La durée du cycle larvaire dans les cas rapportés est d'environ un mois. Des essais d'élevage à partir de larves transplantées sur rats blancs et de larves extraites à leur maturité ont abouti à la constitution d'une colonie adulte qui n'a pu avoir de descendanc

Du chaos deterministe au bruit dans des systèmes optiques avec retard

An optical device with a variational structure driven by a delayed feedback, F(x(t — d)) = sinAx(t — d) is shown to display high dimensional chaos with dimension increasing linearly with two parameters, the delay d and the feedback frequency A . For large delay d and large frequency A, the system is shown to display Gaussian-Markovian statistics like a system driven b y a white noise. Decreasing the frequency A leads to effects very similar to those of a colored noise, and decreasing the dela y leads to quite special phenomena like phase transitions, giving rise to new peaks in the probability distribution . An analytica l description using the tools of stochastic equations agrees with the numerical results .Un système optique possédant une structure variationnelle, et forcé par une rétro-injection retardée, F(x(t - d)) = sin Ax(t- d), émet un signal lumineux chaotique dont la dimension croit linéairement avec deux paramètres, le retard d et la fréquence A. Pour de grandes valeurs du retard et de la fréquence, le signal émis a une statistique Gaussienne et Markovienne, comme la solution d'une équation de Langevin forcée par un bruit blanc. Lorsqu'on diminue la valeur du paramètre A, la statistique est modifiée comme celle d'une équation de Langevin forcée par un bruit coloré. Lorsqu'on diminue le retard, de nouveaux pics apparaissent dans la distribution de probabilité, comme dans les transitions de phase induites par du bruit coloré. Une description analytique utilisant les méthodes des signaux aléatoires permet d'interpréter les résultats numériques

Synthesis, stability and zeolitic behavior of δ­ALn3F10,xH2O and γ­ThLn2F10,H2O phases (Ln = lanthanide)

Two series of hydrated fluorides have been prepared by a “chimie douce” process. For the first family, more than twenty five compounds of δ-ALn3F10,xH2O (A+ = alkaline ions, NH4+, H3O+ and Ln = lanthanide) have been prepared. They crystallize in the Fd [[3 with combining macron]] m space group (a ≈ 15.4 Å and Z = 16) and are isotypic with δ-(H3O)Yb3F10,xH2O (x = 1). The diamond-type structure of these phases (diamond stacking of octahedral units of antiprisms, called UOA[8]), creates cavities and tunnels where the water molecules can move. The second family, γ-ThLn2F10,H2O (Ln3+ = Er3+, Dy3+ and Yb3+) results from the substitution of Ln3+ and A+ by a tetravalent cation. The new compound γ-ThEr2F10,H2O (Fm [[3 with combining macron]] m space group, a = 10.739(1) Å and Z = 8) is isotypic with γ-KYb3F10. Water molecules are located inside the tunnels (8c sites) of a CCP stacking of UOA[8] through which they can move. For both series, the thermal stability and the zeolitic behaviour, studied by DTA/TGA and X-ray thermodiffractometry, are reported and a low zeolitic water capacity, around 2–4% in mass, is observed

Mitotic Rounding Alters Cell Geometry to Ensure Efficient Bipolar Spindle Formation

Accurate animal cell division requires precise coordination of changes in the structure of the microtubule-based spindle and the actin-based cell cortex. Here, we use a series of perturbation experiments to dissect the relative roles of actin, cortical mechanics, and cell shape in spindle formation. We find that, whereas the actin cortex is largely dispensable for rounding and timely mitotic progression in isolated cells, it is needed to drive rounding to enable unperturbed spindle morphogenesis under conditions of confinement. Using different methods to limit mitotic cell height, we show that a failure to round up causes defects in spindle assembly, pole splitting, and a delay in mitotic progression. These defects can be rescued by increasing microtubule lengths and therefore appear to be a direct consequence of the limited reach of mitotic centrosome-nucleated microtubules. These findings help to explain why most animal cells round up as they enter mitosis

Quorum-sensing activity and related virulence factor expression in clinically pathogenic isolates of Pseudomonas aeruginosa

AbstractRespiratory isolates of Pseudomonas aeruginosa were collected from 58 critically-ill patients with ventilator-associated pneumonia. Expression of elastase and pyocyanin was assessed semi-quantitatively, while quorum-sensing activity was assessed by quantifying the levels of the autoinducers N-3-oxododecanoyl-L-homoserine lactone (C12-HSL) and N-butanoyl-L-homoserine lactone (C4-HSL). Correlations were sought between quorum-sensing activity and the expression of these two virulence factors, and all results were compared to those obtained with the laboratory reference strains PA103, a strain defective in quorum-sensing, and PAO1, a functional quorum-sensing strain. More than two-thirds of clinically pathogenic isolates had increased levels of elastase and/or pyocyanin, and high quorum-sensing activity, as assessed by autoinducer levels. However, a strong correlation between quorum-sensing activity and virulence factor production was revealed only for elastase and not for pyocyanin (C12-HSL/elastase, r = 0.7, p 2 × 10−9; C4-HSL/elastase, r = 0.7, p 2 × 10−9). These data suggest that the pathogenicity of P. aeruginosa isolates from critically-ill patients with ventilator-associated pneumonia is caused, at least in part, by an increase in elastase production regulated by quorum-sensing, while increased pyocyanin production in these isolates may be regulated predominantly by mechanisms other than quorum-sensing

Treatment Motivation Differences between Minnesota and Methadone Program Patients with Substance Use Disorder in Latvia

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Experimental observation of spatial antibunching of photons

We report an interference experiment that shows transverse spatial antibunching of photons. Using collinear parametric down-conversion in a Young-type fourth-order interference setup we show interference patterns that violate the classical Schwarz inequality and should not exist at all in a classical description.Comment: 4 pages, 7 figure

Tarmo: A Framework for Parallelized Bounded Model Checking

This paper investigates approaches to parallelizing Bounded Model Checking (BMC) for shared memory environments as well as for clusters of workstations. We present a generic framework for parallelized BMC named Tarmo. Our framework can be used with any incremental SAT encoding for BMC but for the results in this paper we use only the current state-of-the-art encoding for full PLTL. Using this encoding allows us to check both safety and liveness properties, contrary to an earlier work on distributing BMC that is limited to safety properties only. Despite our focus on BMC after it has been translated to SAT, existing distributed SAT solvers are not well suited for our application. This is because solving a BMC problem is not solving a set of independent SAT instances but rather involves solving multiple related SAT instances, encoded incrementally, where the satisfiability of each instance corresponds to the existence of a counterexample of a specific length. Our framework includes a generic architecture for a shared clause database that allows easy clause sharing between SAT solver threads solving various such instances. We present extensive experimental results obtained with multiple variants of our Tarmo implementation. Our shared memory variants have a significantly better performance than conventional single threaded approaches, which is a result that many users can benefit from as multi-core and multi-processor technology is widely available. Furthermore we demonstrate that our framework can be deployed in a typical cluster of workstations, where several multi-core machines are connected by a network