The Hodge ring of Kaehler manifolds

We determine the structure of the Hodge ring, a natural object encoding the Hodge numbers of all compact Kaehler manifolds. As a consequence of this structure, there are no unexpected relations among the Hodge numbers, and no essential differences between the Hodge numbers of smooth complex projective varieties and those of arbitrary Kaehler manifolds. The consideration of certain natural ideals in the Hodge ring allows us to determine exactly which linear combinations of Hodge numbers are birationally invariant, and which are topological invariants. Combining the Hodge and unitary bordism rings, we are also able to treat linear combinations of Hodge and Chern numbers. In particular, this leads to a complete solution of a classical problem of Hirzebruch's.Comment: Dedicated to the memory of F. Hirzebruch. To appear in Compositio Mat

«Нова система землеробства» І.Є. Овсинського: наукові ідеї в історичному вимірі

У статті на основі історико-наукового аналізу показано значення ідей І.Є. Овсинського про безвідвальний обробіток ґрунту, а також їх складний шлях утвердження до сьогодення. Його учні та послідовники продовжили і розвинули це вчення, значно доповнили та удосконалили. Ще наприкінці ХІХ ст. І.Є. Овсинський далекоглядно запропонував не просто нову систему обробітку ґрунту, а систему землеробства, яку сьогодні б назвали самовідновлюваним органічним землеробством. Ці ідеї так чи інакше зустрічаються у системах обробітку ґрунту по всьому світу.В статье на основании историко-научного анализа показано бессмертное значение идей И.Е. Овсинского о безотвальной обработке почвы, а также их сложный путь утверждения до сегодняшнего дня. Его ученики и последователи продолжили и развили это учение, значительно его дополнив и усовершенствовав. Еще в конце ХІХ в. И.Е. Овсинский предложил не просто новую систему обработки почвы, а систему земледеия, которую сегодня бы назвали самовосстанавливающимся органическим земледелием. Эти идеи так или иначе встречаются в системах обработки почвы по всему миру.In the article on the basis of historical and scientific analysis shows immortal value of ideas I.E. Ovsinsky of moldboard tillage, and their difficult path to approval today. His learned and followers continued and developed this theory, it is much updated and improved. In the late nineteenth century. I.E. Ovsinsky offered not just a new system of tillage, and the system of agriculture, which today would be called a resettable organic farming. These ideas are somehow found in soil treatment systems in the whole world

Seasonal variations of concentrations and optical properties of water soluble HULIS collected in urban environments

Major contributors to the organic aerosol include water-soluble macromolecular compounds (e.g. HULIS<sub>WS</sub>: Water Soluble Humic LIke Substances). The nature and sources of HULIS<sub>WS</sub> are still largely unknown. This work is based on a monitoring in six different French cities performed during summer and winter seasons. HULIS<sub>WS</sub> analysis was performed with a selective method of extraction complemented by carbon quantification. UV spectroscopy was also applied for their chemical characterisation. HULIS<sub>WS</sub> carbon represent an important contribution to the organic aerosol mass in summer and winter, as it accounts for 12–22% of Organic Carbon and 34–40% of Water Soluble Organic Carbon. We found strong differences in the optical properties (specific absorbance at 250, 272, 280 nm and E2/E3 ratio) and therefore in the chemical structure between HULIS<sub>WS</sub> from samples of summer- and wintertime. These differences highlight different processes responsible for emissions and formation of HULIS<sub>WS</sub> according to the season, namely biomass burning in winter, and secondary processes in summer. Specific absorbance can also be considered as a rapid and useful indicator of the origin of HULIS<sub>WS</sub> in urban environment

When stereotype threat does not impair performance, self-affirmation can be harmful

International audienc

Ability of the e-TellTale sensor to detect flow features over wind turbine blades: flow separation/reattachment dynamics

Monitoring the flow features over wind turbine blades is a challenging task that has become more and more crucial. This paper is devoted to demonstrate the ability of the e-TellTale sensor to detect the flow separation/reattachment dynamics over wind turbine blades. This sensor is made of a strip with a strain gauge sensor at its base. The velocity field was acquired using TR- PIV measurements over an oscillating thick blade section equipped with an e-TellTale sensor. PIV images were post-processed to detect movements of the strip, which was compared to movements of flow. Results show good agreement between the measured velocity field and movements of the strip regarding the separation/reattachment dynamics

Electron spin quantum beats in positively charged quantum dots: nuclear field effects

We have studied the electron spin coherence in an ensemble of positively charged InAs/GaAs quantum dots. In a transverse magnetic field, we show that two main contributions must be taken into account to explain the damping of the circular polarization oscillations. The first one is due to the nuclear field fluctuations from dot to dot experienced by the electron spin. The second one is due to the dispersion of the transverse electron Lande g-factor, due to the inherent inhomogeneity of the system, and leads to a field dependent contribution to the damping. We have developed a model taking into account both contributions, which is in good agreement with the experimental data. This enables us to extract the pure contribution to dephasing due to the nuclei.Comment: 10 pages, 6 figure

Nondissipative Addressing for Time-Division SQUID Multiplexing

International audienceRecent and future astronomical instruments are based on a focal plane mapped by a large array of superconducting bolometers. Cryogenic analog multiplexing readout techniques, based on superconducting quantum interference devices (SQUIDs), are currently developed to achieve the readout of large arrays of this kind of low noise background-limited detectors. To effectively reduce the number of cryogenic wires (particularly, SQUID biasing), line/column addressing is currently used in time-division multiplexing, i.e., same biasing is applied to a few SQUIDs (on a line) of different columns. This technique should dramatically increase power consumption if parallel biasing is applied via resistors to isolate each column; the power budget is particularly limited on this kind of front-end cryogenic readout. A design with one transformer per SQUID is also used to read out SQUID biased in series with no excess of consumption and crosstalk. We propose here a new biasing technique using simple surface-mounted capacitors, which is easier to implement. These capacitors are used to parallel bias SQUIDs without additional Joule effect while minimizing crosstalk. However, capacitors do not allow dc biasing and need a current mean value equal to zero to avoid biasing source saturation. We have then tested square current biasing through capacitors on a commercial SQUID. This measurement shows that capacitors are able to proper bias SQUID and then to perform a nondissipative addressing for time-division SQUID multiplexing

Giant optical anisotropy in a single InAs quantum dot in a very dilute quantum-dot ensemble

We present the experimental evidence of giant optical anisotropy in single InAs quantum dots. Polarization-resolved photoluminescence spectroscopy reveals a linear polarization ratio with huge fluctuations, from one quantum dot to another, in sign and in magnitude with absolute values up to 82%. Systematic measurements on hundreds of quantum dots coming from two different laboratories demonstrate that the giant optical anisotropy is an intrinsic feature of dilute quantum-dot arrays.Comment: submitted to Applied Physics Letter