Different transport regimes in a spatially-extended recirculating background

Passive scalar transport in a spatially-extended background of roll convection is considered in the time-periodic regime. The latter arises due to the even oscillatory instability of the cell lateral boundary, here accounted for by sinusoidal oscillations of frequency $\omega$. By varying the latter parameter, the strength of anticorrelated regions of the velocity field can be controled and the conditions under which either an enhancement or a reduction of transport takes place can be created. Such two ubiquitous regimes are triggered by a small-scale(random) velocity field superimposed to the recirculating background. The crucial point is played by the dependence of Lagrangian trajectories on the statistical properties of the small-scale velocity field, e.g. its correlation time or its energy.Comment: 9 pages Latex; 5 figure

Transport in finite size systems: an exit time approach

In the framework of chaotic scattering we analyze passive tracer transport in finite systems. In particular, we study models with open streamlines and a finite number of recirculation zones. In the non trivial case with a small number of recirculation zones a description by mean of asymptotic quantities (such as the eddy diffusivity) is not appropriate. The non asymptotic properties of dispersion are characterized by means of the exit time statistics, which shows strong sensitivity on initial conditions. This yields a probability distribution function with long tails, making impossible a characterization in terms of a unique typical exit time.Comment: 16 RevTeX pages + 6 eps-figures include

Efficiency in Saving Infant Lives: the Influence of Water and Sanitation Coverage

In this paper, we aim to assess the relationship between water and sanitation coverage and saved infant lives. Our hypothesis is that extended coverage implies measurable results in terms of reduced infant mortality. Moreover, we suspect that with the same resources, ceteris paribus, different countries can achieve better or worst results depending on the efficiency which the resources are used. We explore the policy consequences, simulating the effects that improvements in efficiency can yield in terms of the reduction in child mortality. Our approach is first to explore with a database of Latin American countries the "production function" of survivor infants on 1,000 births. Once we identify the causal relationship with an econometric model, we estimate a production frontier with Data Envelopment Analysis in order to determine the best performers: countries which can do better with the same "inputs". Finally, we simulate the consequence of catching up to the frontier in each country. The impressive quantitative results are interesting for policy concerns, since efficiency is reconciled with equity (in the sense that the winners of the coverage increases and the health improvements are the poorer).water; sanitation; health

Interference phenomena in scalar transport induced by a noise finite correlation time

The role played on the scalar transport by a finite, not small, correlation time, $\tau_u$, for the noise velocity is investigated, both analytically and numerically. For small $\tau_u$'s a mechanism leading to enhancement of transport has recently been identified and shown to be dominating for any type of flow. For finite non-vanishing $\tau_u$'s we recognize the existence of a further mechanism associated with regions of anticorrelation of the Lagrangian advecting velocity. Depending on the extension of the anticorrelated regions, either an enhancement (corresponding to constructive interference) or a depletion (corresponding to destructive interference) in the turbulent transport now takes place.Comment: 8 pages, 3 figure

Simple stochastic models showing strong anomalous diffusion

We show that {\it strong} anomalous diffusion, i.e. \mean{|x(t)|^q} \sim t^{q \nu(q)} where $q \nu(q)$ is a nonlinear function of $q$, is a generic phenomenon within a class of generalized continuous-time random walks. For such class of systems it is possible to compute analytically nu(2n) where n is an integer number. The presence of strong anomalous diffusion implies that the data collapse of the probability density function P(x,t)=t^{-nu}F(x/t^nu) cannot hold, a part (sometimes) in the limit of very small x/t^\nu, now nu=lim_{q to 0} nu(q). Moreover the comparison with previous numerical results shows that the shape of F(x/t^nu) is not universal, i.e., one can have systems with the same nu but different F.Comment: Final versio

TOWARDS FULLY AUTOMATED DIGITAL ALIBIS WITH SOCIAL INTERACTION

Digital traces found on local hard drives as a result of online activities have become very valuable in reconstructing events in digital forensic investigations. This paper demonstrates that forged alibis can be created for online activities and social interactions. In particular, a novel, automated framework is presented that uses social interactions to create false digital alibis. The framework simulates user activity and supports communications via email as well as instant messaging using a chatbot. The framework is evaluated by extracting forensic artifacts and comparing them with the results obtained from a human user study

New treatments for breast cancer: Breakthroughs for patient care or just steps in the right direction?

Three areas of clinical research in breast cancer treatment led to news breaking presentations at the American Society of Clinical Oncology (ASCO) meeting, 1998, in Los Angeles. All three subjects represent important advances in cancer medicine. Prevention: Two related drugs, tamoxifen and raloxifene, were found in placebo controlled trials to significantly reduce the incidence of breast cancer for women at increased risk of developing the disease. Patterns of relapse showed that the reduced rate of breast cancer was exclusively observed for tumors expressing estrogen receptors, while the rate of tumors classified as estrogen-receptor negative was similar for the treatment and the control groups. This may indicate that the observed reduction in breast cancer incidence is due to a treatment effect on occult disease rather than its prevention. We certainly have no adequate information on mortality prevention. Adjuvant therapies: Taxol given every three weeks for four courses following an adjuvant treatment with four courses of doxorubicin and cyclophosphamide (AC) combination was found to be superior to not adding treatment after the four courses of AC in a trial involving 3170 patients. At 22 months of median follow-up, the quoted P-values were P = 0.0077 for disease-free survival and P = 0.039 for overall survival, but these did not cross the prospectively defined interim analysis boundaries for statistical significance at the 0.05 level. The difference was observed early during follow-up, and was exclusively seen in the 40% of patients who had ER-negative primaries and, therefore, did not receive tamoxifen following chemotherapy. One may thus argue that the early difference observed was primarily due to differences in the duration of the treatment regimens in the two groups and the early entry into the trial of patients with particularly aggressive neoplasia (e.g., ER-negative primaries) who would have benefited from a longer duration treatment. Treatment of advanced disease: The use of monoclonal antibodies to c-erb-B2 was found to induce responses in metastatic breast cancer. Patients with tumors expressing c-erb-B2 responded to weekly infusions of this biological agent. It was particularly impressive that the response rate for patients receiving infusion of the monoclonal antibodies together with the cytotoxics was superior to that with chemotherapy alone in a randomized trial. It is important to note that only patients with tumors overexpressing c-erbB-2 (the overall incidence is about 20%) were tested. It must still be demonstrated that the effect of these monoclonal antibodies is indeed confined to cells overexpressing c-erbB-2. Treatment related cardiac tox-icity remains a problem, and the effects of treatment in various subsets of patients need to be defined before starting investigations in the adjuvant setting, which is a clear further objective of this specific research. The significant findings from clinical research opened several new questions, which must be answered before allowing them to be employed in routine patient car

Interaction of Cisplatin with a CCHC Zinc Finger Motif

The interaction between cisplatin and an 18-residue CCHC zinc finger motif derived from a retroviral nucleocapsid protein (PyrZf18) has been studied using UV–visible, CD and 1H NMR spectroscopies and ESI-MS spectrometry. Cisplatin irreversibly blocks the cysteine zinc binding groups in the free peptide and is able to slowly eject zinc from the zinc–peptide complex. The observed end product of the reaction with cisplatin is a complex in which only one ammonia molecule is coordinated to platinum. After an initial binding with two cysteine residues and the formation of the (PyrZf18)– platinum–(NH3)2 complex, a release of one ammonia molecule occurs because of trans-labilization, and the third cysteine is coordinated, leading to a mixture of isomers and/or conformers of the (PyrZf18)–platinum–NH3 complex. The results are discussed with respect to the potential antiretroviral activity of platinum(II) compounds and to the possible interaction of cisplatin with the cellular nucleic acid binding proteins

Flow networks: A characterization of geophysical fluid transport

We represent transport between different regions of a fluid domain by flow networks, constructed from the discrete representation of the Perron-Frobenius or transfer operator associated to the fluid advection dynamics. The procedure is useful to analyze fluid dynamics in geophysical contexts, as illustrated by the construction of a flow network associated to the surface circulation in the Mediterranean sea. We use network-theory tools to analyze the flow network and gain insights into transport processes. In particular we quantitatively relate dispersion and mixing characteristics, classically quantified by Lyapunov exponents, to the degree of the network nodes. A family of network entropies is defined from the network adjacency matrix, and related to the statistics of stretching in the fluid, in particular to the Lyapunov exponent field. Finally we use a network community detection algorithm, Infomap, to partition the Mediterranean network into coherent regions, i.e. areas internally well mixed, but with little fluid interchange between them.Comment: 16 pages, 15 figures. v2: published versio