678 research outputs found
design and Multiphysics simulation of new XZ accelerometer
No full textLAUREA MAGISTRALEI sistemi microelettromeccanici (MEMS) sono dispositivi che consistono in una componente meccanica che è l'elemento mobile e una componente elettronica che è responsabile della conversione della risposta meccanica in una risposta elettrica. I dispositivi MEMS hanno componenti dell'ordine dei micrometri, ad esempio molto più piccoli di un capello umano. Questa tesi si concentra sugli accelerometri, sensori di movimento in grado di misurare accelerazioni esterne. Viene descritta e analizzata una geometria innovativa di un accelerometro asse XZ, precedentemente proposta dal Dipartimento di Ingegneria Civile e Ambientale (DICA) del Politecnico di Milano e STMicroelectronicsTM. Considerando quindi il risultato ottenuto su questo dispositivo, viene progettato un nuovo accelerometro asse XZ con l'obiettivo di migliorarne le prestazioni specialmente in termini di deriva dell'offset e non linearità. Gli accelerometri proposti sono fabbricati attraverso il nuovo processo di fabbricazione ThELMA-Double (Thick Epitaxial Layer for Micro-gyroscopes and Accelerometers – Double) sviluppato da STMicroelectronics. Il risultato mostra che la non linearità del nuovo accelerometro XZ è ridotta, garantendo così una migliore stabilità delle prestazioni rispetto alle tensioni residue.Micro-electro-mechanical systems (MEMS) are devices that consist of a mechanical component that is the mobile element and an electronic component that is responsible for converting the mechanical response into an electrical response. MEMS devices have components in the order of micrometers, e.g. much smaller than a human hair. This thesis focuses on accelerometers, sensors of motion able to measure external accelerations. An innovative geometry of a XZ-axis accelerometer, previously proposed by the Department of Civil and Environmental Engineering (DICA) of Politecnico di Milano and STMicroelectronicsTM, is described and analyzed. Considering then the result obtained on this device, a new XZ-axis accelerometer is designed with the aim to improve its performances especially in terms of offset drift and nonlinearities. The proposed accelerometers are fabricated through the new fabrication process ThELMA-Double (Thick Epitaxial Layer for Micro-gyroscopes and Accelerometers – Double) developed by STMicroelectronics. The result shows that the non-linearity of the new XZ accelerometer is reduced, thus guaranteeing a better stability of the performance with respect to residual stresses
Synthesising 30 years of mathematical modelling of Echinococcus Transmission
No full textBackground: Echinococcosis is a complex zoonosis that has domestic and sylvatic lifecycles, and a range of different intermediate and definitive host species. The complexities of its transmission and the sparse evidence on the effectiveness of control strategies in diverse settings provide significant challenges for the design of effective public health policy against this disease. Mathematical modelling is a useful tool for simulating control packages under locally specific transmission conditions to inform optimal timing and frequency of phased interventions for cost-effective control of echinococcosis. The aims of this review of 30 years of Echinococcus modelling were to discern the epidemiological mechanisms underpinning models of Echinococcus granulosus and E. multilocularis transmission and to establish the need to include a human transmission component in such models
Norm inequalities for cartesian decompositions
No full textAbstractLet the Cartesian decomposition of a complexn × n matrixT beT = A + iB withA, B Hermitian. Letαj andβj be the eigenvalues ofA andB respectively ordered so that|α1|⩾ … ⩾ |αn|and|β1|⩾ … ⩾ |βn|. We prove that∥diag(α1+iβ1,…αn+iβn)∥⩽2∥T∥ for every unitarily invariant norm this settles affirmatively a conjecture of Ando and Bhatia (T. Ando, R. Bhatia, Eigenvalue inequalities associated with the cartesian decomposition, Linear and Multilinear Algebra 22 (1987) 133)
A mathematical model of Chikungunya dynamics and control: the major epidemic on Reunion Island
No full textChikungunya is a re-emerging arboviral disease transmitted by Aedes spp. mosquitoes. Although principally endemic to Africa and Asia, recent outbreaks have occurred in Europe following introductions by returning travellers. A particularly large outbreak occurred on Réunion Island in 2006, the published data from which forms the basis of the current study. A simple, deterministic mathematical model of the transmission of the virus between humans and mosquitoes was constructed and parameterised with the up-to-date literature on infection biology. The model is fitted to the large Réunion epidemic, resulting in an estimate of 4.1 for the type reproduction number of chikungunya. Although simplistic, the model provided a close approximation of both the peak incidence of the outbreak and the final epidemic size. Sensitivity analysis using Monte Carlo simulation demonstrated the strong influence that both the latent period of infection in humans and the pre-patent period have on these two epidemiological outcomes. We show why separating these variables, which are epidemiologically distinct in chikungunya infections, is not only necessary for accurate model fitting but also important in informing control
Role of preferential weak hybridization between the surface-state of a metal and the oxygen atom in the chemical adsorption mechanism
No full textWe report on the chemical adsorption mechanism of atomic oxygen on the Pt(111) surface using angle-resolved-photoemission spectroscopy (ARPES) and density functional calculations. The detailed band structure of Pt(111) from ARPES reveals that most of the bands near the Fermi level are surface-states. By comparing band maps of Pt and O/Pt, we identify that d(xz) (d(yz)) and d(z)2 orbitals are strongly correlated in the surface-states around the symmetry point M and K, respectively. Additionally, we demonstrate that the s- or p-orbital of oxygen atoms hybridizes preferentially with the d(xz) (d(yz)) orbital near the M symmetry point. This weak hybridization occurs with minimal charge transfer.1321sciescopu
Electrochemical behaviour of gold, silver, platinum and palladium on the glassy carbon electrode modified by chitosan and its application
No full textThe chitosan-modified glassy carbon electrode can be used as a working electrode for the determination of precious metal elements: Au, Ag, Pt, Pd. In low pH medium, the complex anions of these precious elements combine with the protonated group -NH3+ in the chitosan molecule in the form of an ion-association complex. These metal ions were selectively enriched and we got sensitive anodic stripping current. These elements content in ore, welding material have been determined by this method. The results were consistent with those from standard sample and ICP atomic emission spectrometry method. The possible mechanism of electrochemical reaction has been proposed by the study of CV, UV and FT-Raman spectrometry. (C) 1998 Elsevier Science B.V. All rights reserved.Chemistry, AnalyticalSCI(E)PubMed42ARTICLE51099-11064
Identification of Plasmodium falciparum var1CSA and var2CSA domains that bind IgM natural antibodies
No full textMalaria in pregnancy is responsible for maternal anaemia, low-birth-weight babies and infant deaths. Plasmodium falciparum infected erythrocytes are thought to cause placental pathology by adhering to host receptors such as chondroitin sulphate A (CSA). CSA binding infected erythrocytes also bind IgM natural antibodies from normal human serum, a process that may facilitate placental adhesion or promote immune evasion. The parasite ligands that mediate placental adhesion are thought to be members of the variant erythrocyte surface antigen family P. falciparum erythrocyte membrane protein 1 (PfEMP1), encoded by the var genes. Two var gene sub-families, var1CSA and var2CSA, have been identified as parasite CSA binding ligands and are leading candidates for a vaccine to prevent pregnancy-associated malaria. We investigated whether these two var gene subfamilies implicated in CSA binding are also the molecules responsible for IgM natural antibody binding. By heterologous expression of domains in COS-7 cells, we found that both var1CSA and var2CSA PfEMP1 variants bound IgM, and in both cases the binding region was a DBL epsilon domain occurring proximal to the membrane. None of the domains from a control non-IgM-binding parasite (R29) bound IgM when expressed in COS-7 cells. These results show that PfEMP1 is a parasite ligand for non-immune IgM and are the first demonstration of a specific adhesive function for PfEMP1 epsilon type domains
Investigation on damage to structures under the Wenchuan Earthquake and the implications of seismic resistant design
No full textMalaria transmission after artemether-lumefantrine and dihydroartemisinin-piperaquine: a randomized trial.
No full textBACKGROUND: Artemisinin-based combination therapy (ACT) reduces the potential for malaria transmission, compared with non-ACTs. It is unclear whether this effect differs between ACTs. METHODS: A total of 298 children (age, 6 months to 10 years) with uncomplicated falciparum malaria were randomized to artemether-lumefantrine (AL; n = 153) or dihydroartemisinin-piperaquine (DP; n = 145) in Mbita, a community in western Kenya. Gametocyte carriage was determined by molecular methods on days 0, 1, 2, 3, 7, 14, 28, and 42 after treatment initiation. The gametocyte infectiousness to mosquitoes was determined by mosquito-feeding assays on day 7 after beginning therapy. RESULTS: The cumulative risk of recurrent parasitemia on day 42 after initiation of treatment, unadjusted by polymerase chain reaction findings, was 20.7% (95% confidence interval [CI], 14.4-28.2) for AL, compared with 3.7% (95% CI, 1.2-8.5) for DP (P < .001). The mean duration of gametocyte carriage was 5.5 days (95% CI, 3.6-8.5) for AL and 15.3 days (95% CI, 9.7-24.2) for DP (P = .001). The proportion of mosquitoes that became infected after feeding on blood from AL-treated children was 1.88% (43 of 2293), compared with 3.50% (83 of 2371) for those that fed on blood from DP-treated children (P = .06); the oocyst burden among mosquitoes was lower among those that fed on blood from AL-treated children (P = .005) CONCLUSIONS: While DP was associated with a longer prophylactic time after treatment, gametocyte carriage and malaria transmission to mosquitoes was lower after AL treatment. CLINICAL TRIALS REGISTRATION: NCT00868465
Decolorization and biodegradability of dyeing wastewater treated by a TiO?-sensitized photo-oxidation process
No full textAuthor name used in this publication: X. Z. LiAccepted ManuscriptPublishedGreen (AAM
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