Some Remarks on Real and Complex Output Feedback

We provide some new necessary and sufficient conditions which guarantee arbitrary pole placement of a particular linear system over the complex numbers. We exhibit a non-trivial real linear system which is not controllable by real static output feedback and discuss a conjecture from algebraic geometry concerning the existence of real linear systems for which all static feedback laws are real

Selecting the rank of truncated SVD by Maximum Approximation Capacity

Truncated Singular Value Decomposition (SVD) calculates the closest rank-$k$ approximation of a given input matrix. Selecting the appropriate rank $k$ defines a critical model order choice in most applications of SVD. To obtain a principled cut-off criterion for the spectrum, we convert the underlying optimization problem into a noisy channel coding problem. The optimal approximation capacity of this channel controls the appropriate strength of regularization to suppress noise. In simulation experiments, this information theoretic method to determine the optimal rank competes with state-of-the art model selection techniques.Comment: 7 pages, 5 figures; Will be presented at the IEEE International Symposium on Information Theory (ISIT) 2011. The conference version has only 5 pages. This version has an extended appendi

Impurity-induced step interactions: a kinetic Monte-Carlo study

A one-dimensional continuum description of growth on vicinal surfaces in the presence of immobile impurities predicts that the impurities can induce step bunching when they suppress the diffusion of adatoms on the surface. In the present communication we verify this prediction by kinetic Monte-Carlo simulations of a two-dimensional solid-on-solid model. We identify the conditions where quasi one-dimensional step flow is stable against island formation or step meandering, and analyse in detail the statistics of the impurity concentration profile. The sign and strength of the impurity-induced step interactions is determined by monitoring the motion of pairs of steps. Assemblies containing up to 20 steps turn out to be unstable towards the emission of single steps. This behavior is traced back to the small value of the effective, impurity-induced attachment asymmetry for adatoms. An analytic estimate for the critical number of steps needed to stabilize a bunch is derived and confirmed by simulations of a one-dimensional model.Comment: 9 pages, 8 figure

Euroland: Recovery will slow down

The economic recovery in the euro area has accelerated in the course of 2004. During the first two quarters, real GDP rose at an annual rate of slightly over 2 percent, after about 1½ percent in the second half of 2003. For the first time since 2001, overall capacity utilization increased. Exports were driven by the boom in the world economy so that the dampening effects of the previous appreciation of the euro were more than compensated. Internal demand picked up somewhat; especially private consumption recovered whereas investment of firms was rather sluggish. As a consequence of the upswing, the situation on the labor market stopped deteriorating. Inflation also picked up because of the surge in oil prices. During the summer, the HICP rose by more than 2 percent. The sharp increase in oil prices will dampen domestic demand in the near future. In addition, the boom in the world economy has probably already passed its peak. Consequently, the economic expansion in the euro area is likely to slow down somewhat in the rest of this year. This forecast is supported by various leading indicators. For 2004 as a whole, we expect real GDP to increase by 1.9 percent. The unemployment rate will average 9 percent and will thus be slightly higher than last year. Also because of higher oil prices, inflation will be higher than the target rate of the ECB. In 2005, the expansion of domestic demand will slow down further. Especially consumers will be cautious given the weak prospects for income in the medium term. External demand will also lose momentum so that real GDP growth will be moderate in the course of next year. The rate will average 1.9 percent. Inflation is expected to be slightly below 2 percent. All in all, the recovery will be very modest when compared to previous cycles. One reason is that the growth of potential output is lower than before. Our estimate for the current year amounts to 1 percent. The slowdown in recent years is mainly due to the slower growth of productivity. In contrast, the number of total hours worked has increased. Apparently gains of employment can only be achieved at the expense of productivity growth. This is a pessimistic diagnosis given the goal of the EU to become the most dynamic economic region of the world. In spite of the economic recovery, the situation of public finances has deteriorated further. The aggregated budget deficit will probably increase to 2.8 percent of GDP, compared to 2.7 percent last year. The deficits will also be higher than reported in most national Stability Programmes. In addition to Germany, France, the Netherlands, and Greece, the deficit ratio will also exceed the 3 percent margin in Italy and Portugal. The current proposals for a reform of the Pact are mainly concerned with a more generous interpretation of the 3 percent ceiling. However, the main target of the Stability and Growth Pact (SGP) is that government budgets should be balanced or in surplus over the medium term. This target has not been achieved in many countries in recent years; it is not even planned in the Stability Programmes for France and Germany until 2007. This failure cannot be attributed at all to the weakness of the economy in recent years. In fact, the cyclically adjusted deficits of these two countries are higher today than at the end of the 1990s. In other words, there has not been a consolidation of the budget at all. If the SGP loses its strength or if there were no binding rules for fiscal policy, the consequences would be severe for various reasons. First of all, it would be a disadvantage for the countries themselves. Given the likely demographic changes, it would be wise to start saving now; the fact is, however, that the debt burden continues to increase making fiscal policy less sustainable. Second, those countries which intend to join the monetary union in the near future hardly have any incentive to stick to the targets of the Pact if other members ignore or stretch the rules. The criteria for entry would therefore be softened which would be in stark contrast to the fundamentals of the European Monetary Union. The ECB has left key interest rates at a very low level for more than a year. Meanwhile, the euro area economy has recovered as expected by the central bank. The high oil prices are a risk factor for the future path of economic activity. However, this will probably not lead to a cut of interest rates especially because inflation has remained stubbornly high. The next step is likely to be a tightening of monetary policy. Given our forecast of a moderate upturn, we expect that monetary policy will be tightened only moderately; a raise of 25 basis points is likely around the turn of the year. Such a move is also in line with the reactions of the ECB in the past, which can be described by an empirical Taylor rule. --

Femtosecond laser ablation-ICP-mass spectrometry analysis of a heavy metallic matrix : determination of platinum group metals and gold in lead fire-assay buttons as a case study

Owing to the shorter time interval during which energy is delivered to the sample material, femtosecond (fs) laser ablation is preferable over nanosecond laser ablation for metallic samples. In this project, the influence of various laser parameters-beam diameter, repetition rate and laser fluence-on the ablation of Pb as a heavy metallic matrix using an infrared (lambda = 795 nm) fs-LA system (150 fs pulse duration) was studied. The merits of Ar and He as carrier gases were compared and as He did not provide a substantial improvement in the limits of detection, while deposition of sample material on the window of the ablation chamber was more pronounced, Ar was selected for all further measurements. The effect on the ICP caused by the introduction of various amounts of sample aerosol was studied by monitoring the signal intensity for Ar-38(+). It was shown that maximizing the amount of sample ablated and thus, the amount of sample aerosol introduced into the ICP, did not result in maximum sensitivity, which was rather obtained under 'compromise' conditions. Subsequently, femtosecond LA-quadrupole-based ICP-mass spectrometry (ICP-MS) was used for the determination of traces of the platinum group metals (PGMs) Rh, Pd, Ru, Ir and Pt and of Au in Pb buttons obtained by fire assay of platiniferous ore reference materials. The signal of Pb-204(+) was used as an internal reference, correcting for variations in the laser ablation and transport efficiencies and in the instrument's sensitivity. The spectral interferences established for some of the target nuclides due to the occurrence of Pb2+ ions were successfully overcome by pressurizing the reaction cell with NH3. Quantification versus a calibration curve constructed on the basis of the results obtained for matrix-matched standards (>99% Pb) provided excellent accuracy, superior to those obtained using nanosecond LA-ICP-MS. Also the limits of detection were improved by a factor ranging between 3 and 10 and are <0.010 mu g g(-1) for the most important PGMs (Rh, Pd, Pt) and Au. Several measures, such as the use of a large ablation cell and housing up to 10 Pb buttons, were taken to increase the sample throughput. In the same context, day-to-day reproducibility of the calibration curve was also examined. When recording a 'fresh' calibration curve every day, the average bias between the experimental results and the corresponding reference values was established to be <2.5% for every target element. When using one calibration curve during three consecutive days, the bias still remains <10%, while the sample throughput is increased and analysis of several tens of buttons per day is feasible (10-15 min total analysis time per sample)

New Products of Defense Secretion in South East Asian Whip Scorpions (Arachnida: Uropygi: Thelyphonida)

Secretion products from the opisthosomal defense gland of south east Asian whip scorpions were identified for the first time by gas-chromatography and mass-spectrometry. Specimens of the genera Hypoctonus, Typopeltis and Ginosigma were tested. While some ingredients are present in large concentrations, others are possibly only side products and may be synthesized more incidentally. For this reason no important functional role is attributed to them. There are considerable individual differences concerning the concentrations of various ingredients. While the secretion products of most species of the genus Typopeltis - similar to Mastigoproctus - are characterized by acetic and octanoic acid in large concentrations, the secretion product of Hypoctonus siamensis provides octanoic acid only in a very low concentration but it is characterized by hexyl acetate

Engineered DNA modifying enzymes: Components of a future strategy to cure HIV/AIDS

AbstractDespite phenomenal advances in AIDS therapy transforming the disease into a chronic illness for most patients, a routine cure for HIV infections remains a distant goal. However, a recent example of HIV eradication in a patient who had received CCR5-negative bone marrow cells after full-body irradiation has fuelled new hopes for a cure for AIDS. Here, we review new HIV treatment strategies that use sophisticated genome engineering to target HIV infections. These approaches offer new ways to tackle the infection, and alone or in conjunction with already established treatments, promise to transform HIV into a curable disease

Dominant two-loop electroweak corrections to the hadroproduction of a pseudoscalar Higgs boson and its photonic decay

We present the dominant two-loop electroweak corrections to the partial decay widths to gluon jets and prompt photons of the neutral CP-odd Higgs boson A^0, with mass M_{A^0} < 2 M_W, in the two-Higgs-doublet model for low to intermediate values of the ratio tan(beta) = v_2/v_1 of the vacuum expectation values. They apply as they stand to the production cross sections in hadronic and two-photon collisions, at the Tevatron, the LHC, and a future photon collider. The appearance of three gamma_5 matrices in closed fermion loops requires special care in the dimensional regularization of ultraviolet divergences. The corrections are negative and amount to several percent, so that they fully compensate or partly screen the enhancement due to QCD corrections.Comment: 9 pages, 3 figure