De epidemie voorbij: rekenmodellen voor infectieziektebestrijding

Oratie uitgesproken door Prof.dr. Jacco Wallinga bij de aanvaarding van het ambt van bijzonder hoogleraar op het gebied van Mathematische Modellering van Infectieziekten aan de Universiteit Leiden vanwege het Rijksinstituut voor Volksgezondheid en Milieu op vrijdag 21 oktober 2016Oratie uitgesproken door Prof.dr. Jacco Wallinga bij de aanvaarding van het ambt van bijzonder hoogleraar op het gebied van Mathematische Modellering van Infectieziekten aan de Universiteit Leiden vanwege het Rijksinstituut voor Volksgezondheid en Milieu op vrijdag 21 oktober 201

A self-aligned gate definition process with submicron gaps

A self-aligned gate definition process is proposed. Spacings between adjacent gates of 0.5 µm and smaller are fabricated. The spacing is realized by an edge-etch technique, combined with anisotropic plasma etching of the single poly-silicon layer. Straight gaps with minor width variation are fabricated. Minority carrier life-time and breakdown voltage are not affected

Low hydrogen content silicon nitride films deposited at room temperature with a multipolar ECR plasma source

Silicon nitride layers with very low hydrogen content (less than 1 atomic percent) were deposited at near room temperature, from N2 and SiH4, with a multipolar electron cyclotron resonance plasma. The influences of pressure and nitrogen flow rate on physical and electrical properties were studied in order to minimize the hydrogen and oxygen content in the layers. The optimized layers were characterized by a refractive index of 1.98, a dielectric constant of 7.2, and Si/N ratio values of 0.78. The layers exhibited very good dielectric strength, which was confirmed by large breakdown fields of 12 MV/cm, very high resistivities of 1016 Omega cm, and maximum charges to breakdown values of 90 C/cm2. Increasing the deposition pressure and decreasing the N2 flow improved the SiN/Si interface, due to increased oxygen incorporation. The dominant conduction mechanism in the layers was the Poole-Frenkel effect. The critical field and the trap energy had similar dependencies on deposition pressure. Fowler-Nordheim tunneling occurred at high gate biases, for the layers deposited at the highest pressure of about 22 mTorr

Visible light emission from reverse-biased silicon nanometer-scale diode-antifuses

Silicon nanometer-scale diodes have been fabricated to emit light in the visible range at low power consumption. Such structures are candidates for emitter elements in Si-based optical interconnect schemes. Spectral measurements of Electroluminescence (EL) on the reverse-biased nanometer-scale diodes brought into breakdown have been carried out over the photon energy range of 1.4-2.8 eV. Previously proposed mechanisms for avalanche emission from conventional silicon p-n junctions are discussed in order to understand the origin of the emission. Also the stability of the diodes has been tested. Results indicate that our nanometer-scale diodes are basically high quality devices. Furthermore due to the nanometer-scale dimensions, very high electrical fields and current densities are possible at low power consumption. This makes these diodes an excellent candidate to be utilized as a light source in Si-based sensors and actuator application

Dynamics of weed populations : spatial pattern formation and implications for control

Modelling studies were carried out to analyse spatio-temporal dynamics of annual weed populations and to identify the key factors that determine the long-term herbicide use of weed control programmes. Three different weed control programmes were studied.In the first weed control programme, herbicides are applied to the whole field only if the weed density exceeds a threshold value, otherwise there is no control at all. The dynamics of a weed population subjected to such a 'threshold control programme' is characterized by aperiodic (quasi-periodic or chaotic) cycles, whereas the long-term herbicide use does not depend on the threshold value.In the second weed control programme, the optimum herbicide dosage is determined and applied to the whole field. In this case the density of the weed population will approach a low equilibrium value. The herbicide use of such an 'optimum dose control programme' is determined by the herbicide dose required to keep the weed population at a low density.In the third weed control programme, the spatial scale of weed control decision making is reduced such that only weed patches are sprayed. The herbicide use of such a 'patch control programme' is determined by the spatial pattern of weeds as well as the spatial resolution of the patch sprayer. The patch control programme is only of interest if weeds are heterogeneously distributed over space. It is shown that invading annual weed populations are capable of generating patches, even in an otherwise homogeneous habitat, if the forward tail of the projected seed dispersal curve declines slower than exponential. It is shown that annual weed populations are also capable of generating patches in an otherwise homogeneous habitat if they are held at a constant low density. In the latter case, the weed patch formation is a self-organized critical phenomenon.</p

A high-energy ion implanted BICMOS process with compatible EPROM structures

A 1.5µm high-energy ion implanted BiCMOS process is proposed. This process offers NMOS, PMOS, vertical npn transistors and VIPMOS-EPROM devices. The process structure is modular in order to achieve CMOS and bipolar transistors in uncompromised forms. Consequently, the N-well and collector regions are defined separately. Conflicting requirements for the collector doping profile have been optimized towards practical electrical device characteristics

Use of Otolith Strontium:Calcium Ratios for Hindcasting Larval Cod Gadus Morhua Distributions Relative to Water Masses on Georges Bank

The concentration ratios of strontium to calcium in laboratory-reared larval cod otoliths are shown to be related to the water temperature (T) at the time of otolith precipitation. This relationship is curvilinear, and is best described by a simple exponential equation of the form (Sr/Ca x 1000 = a exp(-T/b). We show that when Sr/Ca elemental analyses are related to the daily growth increments in the larval otoliths, relative temperature histories of individual field-caught larvae can be reconstructed from the egg stage to the time of capture. We present preliminary examples of how such reconstructed temperature histories of Atlantic cod Gadus morhua larvae, collected on Georges Bank during April and May 1993, may be interpreted in relation to the broad-scale larval distributions and the hydrography of the Bank

Коментарі Валерія Шевчука в літописі Самійла Величка як позатекстова інтерпретація давньоукраїнської пам'ятки

У статті розглядаються різновиди коментарів як позатекстової інтерпретації Валерієм Шевчуком барокової пам’ятки – Літопису Самійла Величка.The article deals with Valery Shevchuk’s way of varieties of the commentaries as out-of-text interpretation of Baroque remembrance of Chronicle of Samiylo Velitchko