Design of a Broadband Amplifier for High Speed Applications

This paper provides comprehensive insight into the design approach followed for an amplifier dedicated to high speed base band signals. To demonstrate the methodology, an amplifier consisting of nine PHEMT cascode cells within a distributed amplifier topology was designed. The resulting frequency response is 40 GHz at the 3-dB point, and the output voltage for a 43 Gbps eye diagram is 7.3 Vpp at the chip terminal

Weyl geometry, anti-De Sitter space, and Φ4\Phi^4-theory

We study the Gaussian approximation to the quantum fluctuations of the metric of the four dimensional anti-De Sitter spacetime. The associated massless scalar field has a quartic self interaction, for which we construct the generating functional of the $n$-point correlation functions. The concomitant infrared divergence is cured by a mass renormalization provided by the cosmological constant, which is also responsible for the renormalization of the coupling constant of the field theory.Comment: 9 pages, 1 figur

Vacuum fluctuations of a scalar field near a reflecting boundary and their effects on the motion of a test particle

The contribution from quantum vacuum fluctuations of a real massless scalar field to the motion of a test particle that interacts with the field in the presence of a perfectly reflecting flat boundary is here investigated. There is no quantum induced dispersions on the motion of the particle when it is alone in the empty space. However, when a reflecting wall is introduced, dispersions occur with magnitude dependent on how fast the system evolves between the two scenarios. A possible way of implementing this process would be by means of an idealized sudden switching, for which the transition occurs instantaneously. Although the sudden process is a simple and mathematically convenient idealization it brings some divergences to the results, particularly at a time corresponding to a round trip of a light signal between the particle and the wall. It is shown that the use of smooth switching functions, besides regularizing such divergences, enables us to better understand the behavior of the quantum dispersions induced on the motion of the particle. Furthermore, the action of modifying the vacuum state of the system leads to a change in the particle energy that depends on how fast the transition between these states is implemented. Possible implications of these results to the similar case of an electric charge near a perfectly conducting wall are discussed.Comment: 17 pages, 8 figure

Workshop on Tropical Cyclones and Climate, March 27-29, 2006

In March 2006, the International Research Institute for Climate and Society (IRI) hosted a two and a half day workshop on "Tropical Cyclones and Climate". The centerpiece of the workshop was a set of invited lectures, with a modest number of contributed oral presentations and a small poster session. Relatively lengthy discussion periods were built into the schedule, allowing in-depth discussion of the presentations and related issues

Characteristics of Western North Pacific Model Tropical Cyclogenesis

"Tropical cyclogenesis" in a low-resolution Atmospheric General Circulation model is studied, focusing on the Western North Pacific region during the June-October typhoon season. Time-dependent composites of the cyclones are formed and analyzed, with a focus on the temporal evolution of quantities averaged in space around the storm centers. Day zero of each composite corresponds to the time at which the cyclone passes the criteria for detection. Some variables whose magnitude is related to cyclone intensity (such as low-level vorticity and surface wind speed) show similar temporal evolution, with a slight decrease up to a few days before day zero, a weak local minimum at that point, and a strong increase after that for a week or more. The relative humidity at low levels has its minimum somewhat later, at about day zero. The mean composite environmental vertical wind shear lacks a minimum and increases monotonically through the entire genesis period until a week after day zero. This variation is mostly due to the mean cyclone track's moving through regions of different climatological shear, which varies monotonically from easterly to westerly, crossing zero shortly after day zero, and would be consistent with a controlling role of the shear on model cyclogenesis. A signal in the skewness of the lower-level relative humidity distribution over the ensemble suggests that a dry lower troposphere can prevent development of a model cyclone. The local minimum in many variables' time series suggests the presence of an initial disturbance that is suddenly enhanced, becoming a model tropical cyclone, as has been noted in observations

Q-curvature and Path Integral Complexity

We discuss the interpretation of path integral optimization as a uniformization problem in even dimensions. This perspective allows for a systematical construction of the higher-dimensional path integral complexity in holographic conformal field theories in terms of Q-curvature actions. We explore the properties and consequences of these actions from the perspective of the optimization programme, tensor networks and penalty factors. Moreover, in the context of recently proposed holographic path integral optimization, we consider higher curvature contributions on the Hartle-Hawking bulk slice and study their impact on the optimization as well as their relation to Q-curvature actions and finite cut-off holography

Immunological Response To Cell-free Antigens Of Paracoccidioides Brasiliensis: Relationship With Clinical Forms Of Paracoccidioidomycosis.

Sera from patients with the acute (AF) and chronic (CF) forms of paracoccidioidomycosis (PCM) were tested against Paracoccidioides brasiliensis cell-free antigens by Western blot (immunoblot). The CFA preparation contained components ranging in molecular mass from 18 to 102 kDa. The immunoglobulin G (IgG) reactivity profiles were similar for patients with both forms of the disease, and the 43-kDa component was recognized by 100% of the sera. IgM antibodies from the AF- and the CF-PCM sera recognized 21 and 20 components, respectively, the AF-PCM sera reacting preferentially with components with molecular masses above 50 kDa. None of the AF-PCM sera (IgM) reacted with the 43-kDa component, and only 10% of the CF-PCM sera recognized this molecule. The IgA response was more significant in the CF-PCM group than in the AF-PCM group, and the 43- and 74-kDa components were the most reactive ones (about 40% each). Our results showed that the cell-free antigen preparation is very appropriate for the immunoblotting analysis of PCM sera, and they also showed that the detection of IgG anti-gp43 is the best marker for the diagnosis and the following up of patients with the acute or the chronic form of the disease.31671-

Western North Pacific Tropical Cyclone Intensity and ENSO

The influence of the El Niño–Southern Oscillation (ENSO) on tropical cyclone intensity in the western North Pacific basin is examined. Accumulated cyclone energy (ACE), constructed from the best-track dataset for the region for the period 1950–2002, and other related variables are analyzed. ACE is positively correlated with ENSO indices. This and other statistics of the interannually varying tropical cyclone distribution are used to show that there is a tendency in El Niño years toward tropical cyclones that are both more intense and longer-lived than in La Niña years. ACE leads ENSO indices: during the peak season (northern summer and fall), ACE is correlated approximately as strongly with ENSO indices up to six months later (northern winter), as well as simultaneously. It appears that not all of this lead–lag relationship is easily explained by the autocorrelation of the ENSO indices, though much of it is. Interannual variations in the annual mean lifetime, intensity, and number of tropical cyclones all contribute to the ENSO signal in ACE, though the lifetime effect appears to be the most important of the three