The synthesis of boron carbide filaments final report

Synthesis, strength, crystal structure, and composite material formation of boron carbide whisker

Sintered silicon nitrode recuperator fabrication

The preliminary design and a demonstration of the feasibility of fabricating submodules of an automotive Stirling engine recuperator for waste heat recovery at 370 C are described. Sinterable silicon nitride (Sialon) tubing and plates were fabricated by extrusion and hydrostatic pressing, respectively, suitable for demonstrating a potential method of constructing ceramic recuperator-type heat exchangers. These components were fired in nitrogen atmosphere to 1800 C without significant scale formation so that they can be used in the as-fired condition. A refractory glass composition (Al2O3 x 4.5 CaO.MgO x 11SiO2) was used to join and seal component parts by a brazing technique which formed strong recuperator submodules capable of withstanding repeated thermal cycling to 1370 C. The corrosion resistance of these materials to Na2SO4 + NaCl carbon mixtures was also assessed in atmospheres of air, hydrogen and CO2-N2-H2O mixtures at both 870 C and 1370 C for times to 1000 hours. No significant reaction was observed under any of these test conditions

Orbital periods of the binary sdB stars PG0940+068 and PG1247+554

We have used the radial velocity variations of two sdB stars previously reported to be binaries to establish their orbital periods. They are PG0940+068, (P=8.33d) and PG1247+554 (P=0.599d). The minimum masses of the unseen companions, assuming a mass of 0.5 solar masses for the sdB stars, are 0.090 +/- 0.003 solar masses for PG1247+554 and 0.63 +/- 0.02 solar masses for PG0940+068. The nature of the companions is not constrained further by our data.Comment: 5 pages, 2 figure

Taranto’s Long Shadow? Cancer Mortality Is Higher for People Living Closer to One of the Most Polluted City of Italy

A national-scale study in Italy showed an incidence of cancer higher in the territories indicated as highly polluted compared to the regional average. One of them, the city of Taranto in Apulia (Italy), which is considered one of the most polluted cities in Europe, has numerous industrial activities that impact population health. We studied the epidemiological effects of a high level of pollution produced by the industrial area of Taranto in increasing the mortality rate for some specific cancer types in the city and towns of the two provinces located downwind. We analysed 10-year mortality rates for 15 major types of tumours reported among the residents of Taranto, of eight surrounding towns, randomly placed within an imaginary cone in the main wind direction from the vertex of the industrial zone of Taranto, and of the two related provinces (Bari and Taranto’s metropolitan areas). Our results confirm our hypothesis that the mortality rate for some specific types of cancer is higher than the norm in the municipality of Taranto. We also found strong evidence that, for 12 out of 15 tumour types, mortality decreases with the distance of the other towns from Taranto’s industrial site. However, we have reasons to believe that other local causes may be implicated in the excess of mortality in some specific municipalities besides the potential dispersal of pollutants from the industrial area of Taranto. The proximity to Taranto cannot, in fact, explain all the anomalies detected in some populations. It is likely that other site-specific sources of heavy pollution are playing a role in worsening the death toll of these towns and this must be taken into serious consideration by environmental policymakers and local authorities

Detection of sub-shot-noise spatial correlation in high-gain parametric down-conversion

Using a 1GW-1ps pump laser pulse in high gain parametric down-conversion allows us to detect sub-shot-noise spatial quantum correlation with up to one hundred photoelectrons per mode, by means of a high efficiency CCD. The statistics is performed in single-shot over independent spatial replica of the system. The paper highlights the evidence of quantum correlation between symmetrical signal and idler spatial areas in the far field, in the high gain regime. In accordance with the predictions of numerical calculations the observed transition from the quantum to the classical regime is interpreted as a consequence of the narrowing of the down-converted beams in the very high gain regime.Comment: 4,2 pages, 4 figure

Clarifying the smokescreen of Russian protected areas

Although in strictly protected areas no forest management and logging activities should be evident, a preliminary study detected that, even in the 200 areas with the highest protection of Russia, more than 2 Mha of trees have been lost between 2001 and 2018. Nonetheless, a relevant percentage of the actual drivers of tree loss in Russian strictly protected areas was surrounded by uncertainties due to several factors. Here, in an attempt to “clarify the smokescreen of Russian protected areas”, by validating previous remotely sensed data with new high-resolution satellite imagery and aerial images of land-use change, we shed more light on what has happened during the last 20 years. We used the same layer of tree loss from 2001 to 2020 but, instead of intersecting it with the MODIS data that could have been a source of underestimation of burned surfaces, we overlapped it to the layer of tree cover loss by dominant driver. We analysed the main drivers of tree loss in almost 200 strictly protected areas of Russia. We found that although fire is responsible for 75% of the loss in all strictly protected areas, forestry activities still account for 16%, and 9% is due to undefined causes. Therefore, uncontrolled wildfires (including those started before or after logging) and forestry activities are the main causes of 91% of the total tree loss. The combination of wildfires (often started intentionally) and forestry activities (illegally or barely legally put in place) caused a loss of an astonishing 3 million hectares. The fact that ≈10% of Russian tree cover was lost in two decades since 2001 only in strictly protected areas requires high attention by policymakers and important conservation actions to avoid losing other fundamental habitats and species during the next years when climate change and population growth can represent an additional trigger of an already dramatic situation. We call for an urgent response by national and local authorities that should start actively fighting wildfires, arsonists, and loggers even in inhabited remote areas and particularly in those included in strictly protected areas

Spatial correlations in hexagons generated via a Kerr nonlinearity

We consider the hexagonal pattern forming in the cross-section of an optical beam produced by a Kerr cavity, and we study the quantum correlations characterizing this structure. By using arguments related to the symmetry broken by the pattern formation, we identify a complete scenario of six-mode entanglement. Five independent phase quadratures combinations, connecting the hexagonal modes, are shown to exhibit sub-shot-noise fluctuations. By means of a non-linear quantum calculation technique, quantum correlations among the mode photon numbers are demonstrated and calculated.Comment: ReVTeX file, 20 pages, 7 eps figure

Polarization quantum properties in type-II Optical Parametric Oscillator below threshold

We study the far field spatial distribution of the quantum fluctuations in the transverse profile of the output light beam generated by a type II Optical Parametric Oscillator below threshold, including the effects of transverse walk-off. We study how quadrature field correlations depend on the polarization. We find spatial EPR entanglement in quadrature-polarization components: For the far field points not affected by walk-off there is almost complete noise suppression in the proper quadratures difference of any orthogonal polarization components. We show the entanglement of the state of symmetric intense, or macroscopic, spatial light modes. We also investigate nonclassical polarization properties in terms of the Stokes operators. We find perfect correlations in all Stokes parameters measured in opposite far field points in the direction orthogonal to the walk-off, while locally the field is unpolarized and we find no polarization squeezing.Comment: 16 pages, 18 figure

Investigation of the preparation of materials in space. Task 4 - Field management for weightless containerless processing Quarterly progress report, 22 Aug. - 31 Oct. 1969

Weightless containerless processing for space, electromagnetic position control, force measurements and techniques, and hydrodynamic

Translaminar dynamic fracture toughness of a hybrid fiber-metal laminate devised to high-temperature applications

A tenacidade à fratura translaminar dinâmica do laminado híbrido metal-fibra titânio-grafite com matriz termoplástica foi determinada sob as velocidades de impacto de 2,25 e 5,52 m/s, no intervalo de temperaturas de -196 a +180 °C, e comparada à de laminados compósitos convencionais de fibras de carbono e resina epóxi. Constatou-se que o laminado híbrido exibe uma tenacidade à iniciação da fratura inferior à dos compósitos tradicionais com fibras na forma de fita unidirecional, porém superior à dos laminados convencionais com fibras na forma de tecido bidirecional. Os ensaios de impacto revelaram que, comparativamente ao desempenho mecânico dos laminados carbono-epóxi, o emprego do laminado híbrido metal-fibra se justifica mais pela sua resistência à propagação do que à iniciação da fratura dinâmica.The translaminar dynamic fracture toughness of titanium-graphite hybrid fiber-metal laminate with thermoplastic matrix has been determined at the impact velocities of 2.25 and 5.52 m/s, within the temperature range from -196 to +180 ºC, and compared to that of conventional carbon-epoxy composite laminates. The hybrid laminate exhibits lower initiation fracture toughness than traditional unidirectional tape composites though it is tougher than conventional woven fabric laminates. Impact tests revealed that, if compared to the mechanical performance of conventional carbon-epoxy laminates, the fiber-metal laminate application must rely on its resistance to dynamic fracture propagation rather than on fracture initiation.Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES