Let $A$ be a local noetherian ring and $N$ be a locally sheaf on the projective space $P^3_A$ : one proves easily that there exists a family $C$ of (smooth connected) curves contained in $P^3_A$, flat over $A$, and an integer $h$ such that the ideal sheaf $J$ of $C$ has a resolution $0\to P\to N\to J\to 0$ where $P$ is a direct sum of invertible sheaves $O_P(-n_i)$. In this paper we determine, for a given sheaf $N$, all the families of curves with such a resolution, especially the minimal ones (corresponding to the minimum value of $h$). It gives a description of the biliaison class related to $N$, and a tool for constructing families of space curves.

Let $A$ be a noetherian ring and $R_A$ be the graded ring $A[X,Y,Z,T]$. In this article we introduce the notion of a triad, which is a generalization to families of curves in ${\bf P}^3_A$ of the notion of Rao module. A triad is a complex of graded $R_A$-modules $(L_1 \to L_0 \to L_{-1})$ with certain finiteness hypotheses on its cohomology modules. A pseudo-isomorphism between two triads is a morphism of complexes which induces an isomorphism on the functors $ h_0 (L\otimes .)$ and a monomorphism on the functors $h_{-1} (L\otimes .)$. One says that two triads are pseudo-isomorphic if they are connected by a chain of pseudo-isomorphisms. We show that to each family of curves is associated a triad, unique up to pseudo-isomorphism, and we show that the map $\{\hbox{families of curves}\}\to \{\hbox{triads}\}$ has almost all the good properties of the map $\{\hbox{curves}\}\to \{\hbox{Rao modules}\}$. In a section of examples, we show how to construct triads and families of curves systematically starting from a graded module and a sub-quotient (that is a submodule of a quotient module), and we apply these results to show the connectedness of $H_{4,0}$.

The aim of this paper is to prove a generalization of a theorem of Rao for families of space curves, which caracterizes the biliaison classes of curves. First we introduce the concept of pseudo-isomorphism of coherent sheaves, which generalizes the concept of stable isomorphism. An N-type resolution for a family of curves $C$ over the local ring $A$, defined by an ideal $J$, is an exact sequence $0\to P\to N\to J\to 0$ where $N$ is a locally free sheaf on $P^3_A$ and $P$ is a direct sum of invertible sheaves $O_P(-n_i)$. We prove the two following results, when the residual field of $A$ is infinite : 1. Let $C$ and $C'$ be two flat families of space curves over the local ring $A$. Then $C$ and $C'$ are in the same biliaison class if and only if their ideals $J$ and $J'$ are pseudo-isomorphic, up to a shift. 2. Let $C$ and $C'$ be two flat families of space curves over the local ring $A$, with N-type resolutions, involving sheaves $N$ and $N'$. Then $C$ and $C'$ are in the same biliaison class if and only if $N$ and $N'$ are pseudo-isomorphic, up to a shift.

The perception of degraded speech input is essential in everyday life and is a major challenge in a variety of clinicalsettings, including for cochlear implant users. We investigated English speakers perception of noisy speech via an audio-visual lexical decision paradigm that modulated cross-modal integration, adaptive modulation of task difficulty, and ex-plicit feedback on response accuracy. We then tested whether proficiency with this task transferred to the perception ofnoisy audio stimuli in a post test. Although we observed a processing advantage for bimodal stimuli during training,particularly in the adaptive training condition, we did not observe any benefit from these conditions in the post test, nor abenefit associated with providing explicit feedback. These results are discussed in relation to other studies of audio-visualintegration and learning to perceive noisy speech, which may have observed different results due to more extensive trainingand different baseline proficiency levels.

Human reticulocyte 15-lipoxygenase (15-hLO-1) and epithelial 15-lipoxygenase (15-hLO-2) have been implicated in a number of human diseases, with differences in their substrate specificity potentially playing a central role. In this paper, we present a novel method for accurately measuring the substrate specificity of the two 15-hLO isozymes and demonstrate that both cholate and specific LO products affect substrate specificity. The linoleic acid (LA) product, 13-hydroperoxyoctadienoic acid (13-HPODE), changes the ( k cat/ K m) (AA)/( k cat/ K m) (LA) ratio more than 5-fold for 15-hLO-1 and 3-fold for 15-hLO-2, while the arachidonic acid (AA) product, 12-( S)-hydroperoxyeicosatetraenoic acid (12-HPETE), affects only the ratio of 15-hLO-1 (more than 5-fold). In addition, the reduced products, 13-( S)-hydroxyoctadecadienoic acid (13-HODE) and 12-( S)-hydroxyeicosatetraenoic acid (12-HETE), also affect substrate specificity, indicating that iron oxidation is not responsible for the change in the ( k cat/ K m) (AA)/( k cat/ K m) (LA) ratio. These results, coupled with the dependence of the 15-hLO-1 k cat/ K m kinetic isotope effect ( (D) k cat/ K m) on the presence of 12-HPETE and 12-HETE, indicate that the allosteric site, previously identified in 15-hLO-1 [Mogul, R., Johansen, E., and Holman, T. R. (1999) Biochemistry 39, 4801-4807], is responsible for the change in substrate specificity. The ability of LO products to regulate substrate specificity may be relevant with respect to cancer progression and warrants further investigation into the role of this product-feedback loop in the cell.

In contrast to the classic view of static DNA double-strand breaks (DSBs) being repaired at the site of damage, we hypothesize that DSBs move and merge with each other over large distances (m). As X-ray dose increases, the probability of having DSB clusters increases as does the probability of misrepair and cell death. Experimental work characterizing the X-ray dose dependence of radiation-induced foci (RIF) in nonmalignant human mammary epithelial cells (MCF10A) is used here to validate a DSB clustering model. We then use the principles of the local effect model (LEM) to predict the yield of DSBs at the submicron level. Two mechanisms for DSB clustering, namely random coalescence of DSBs versus active movement of DSBs into repair domains are compared and tested. Simulations that best predicted both RIF dose dependence and cell survival after X-ray irradiation favored the repair domain hypothesis, suggesting the nucleus is divided into an array of regularly spaced repair domains of ~;1.55 m sides. Applying the same approach to high-linear energy transfer (LET) ion tracks, we are able to predict experimental RIF/m along tracks with an overall relative error of 12percent, for LET ranging between 30 350 keV/m and for three different ions. Finally, cell death was predicted by assuming an exponential dependence on the total number of DSBs and of all possible combinations of paired DSBs within each simulated RIF. Relative biological effectiveness (RBE) predictions for cell survival of MCF10A exposed to high-LET showed an LET dependence that matches previous experimental results for similar cell types. Overall, this work suggests that microdosimetric properties of ion tracks at the submicron level are sufficient to explain both RIF data and survival curves for any LET, similarly to the LEM assumption. Conversely, high-LET death mechanism does not have to infer linear-quadratic dose formalism as done in the LEM. In addition, the size of repair domains derived in our model are based on experimental RIF and are three times larger than the hypothetical LEM voxel used to fit survival curves. Our model is therefore an alternative to previous approaches that provides a testable biological mechanism (i.e., RIF). In addition, we propose that DSB pairing will help develop more accurate alternatives to the linear cancer risk model (LNT) currently used for regulating exposure to very low levels of ionizing radiation.

An increase in fluid pressure in faults can trigger seismicity and large aseismic motions. Understanding how fluid and faults interact is an essential goal for seismic hazard and reservoir monitoring, but this key relation remains unclear. We developed an in situ experiment of fluid injections at a 10 meter scale. Water was injected at high pressure in different geological structures inside a fault damaged zone, in limestone at 280 m depth in the Low Noise Underground Laboratory (France). Induced seismicity, as well as strains, pressure, and flow rate, was continuously monitored during the injections. Although nonreversible deformations related to fracture reactivations were observed for all injections, only a few tests generated seismicity. Events are characterized by a 0.5-to-4 kHz content and a small magnitude (approximately −3.5). They are located within 1.5 m accuracy between 1 and 12 m from the injections. Comparing strain measurements and seismicity shows that more than 96% of the deformation is aseismic. The seismic moment is also small compared to the one expected from the injected volume. Moreover, a dual seismic behavior is observed as (1) the spatiotemporal distribution of some cluster of events is clearly independent from the fluid diffusion (2) while a diffusion-type pattern can be observed for some others clusters. The seismicity might therefore appear as an indirect effect to the fluid pressure, driven by aseismic motion and related stress perturbation transferred through failure.