Inversion of spinning sound fields

A method is presented for the reconstruction of rotating monopole source distributions using acoustic pressures measured on a sideline parallel to the source axis. The method requires no \textit{a priori} assumptions about the source other than that its strength at the frequency of interest vary sinusoidally in azimuth on the source disc so that the radiated acoustic field is composed of a single circumferential mode. When multiple azimuthal modes are present, the acoustic field can be decomposed into azimuthal modes and the method applied to each mode in sequence. The method proceeds in two stages, first finding an intermediate line source derived from the source distribution and then inverting this line source to find the radial variation of source strength. A far-field form of the radiation integrals is derived, showing that the far field pressure is a band-limited Fourier transform of the line source, establishing a limit on the quality of source reconstruction which can be achieved using far-field measurements. The method is applied to simulated data representing wind-tunnel testing of a ducted rotor system (tip Mach number~0.74) and to control of noise from an automotive cooling fan (tip Mach number~0.14), studies which have appeared in the literature of source identification.Comment: Revised version of paper submitted to JASA; five more figures; expanded content with more discussion of error behaviour and relation to Nearfield Acoustical Holograph

Spin-glass phase transition and behavior of nonlinear susceptibility in the Sherrington-Kirkpatrick model with random fields

The behavior of the nonlinear susceptibility $\chi_3$ and its relation to the spin-glass transition temperature $T_f$, in the presence of random fields, are investigated. To accomplish this task, the Sherrington-Kirkpatrick model is studied through the replica formalism, within a one-step replica-symmetry-breaking procedure. In addition, the dependence of the Almeida-Thouless eigenvalue $\lambda_{\rm AT}$ (replicon) on the random fields is analyzed. Particularly, in absence of random fields, the temperature $T_f$ can be traced by a divergence in the spin-glass susceptibility $\chi_{\rm SG}$, which presents a term inversely proportional to the replicon $\lambda_{\rm AT}$. As a result of a relation between $\chi_{\rm SG}$ and $\chi_3$, the latter also presents a divergence at $T_f$, which comes as a direct consequence of $\lambda_{\rm AT}=0$ at $T_f$. However, our results show that, in the presence of random fields, $\chi_3$ presents a rounded maximum at a temperature $T^{*}$, which does not coincide with the spin-glass transition temperature $T_f$ (i.e., $T^* > T_f$ for a given applied random field). Thus, the maximum value of $\chi_3$ at $T^*$ reflects the effects of the random fields in the paramagnetic phase, instead of the non-trivial ergodicity breaking associated with the spin-glass phase transition. It is also shown that $\chi_3$ still maintains a dependence on the replicon $\lambda_{\rm AT}$, although in a more complicated way, as compared with the case without random fields. These results are discussed in view of recent observations in the LiHo$_x$Y$_{1-x}$F$_4$ compound.Comment: accepted for publication in PR

Acumulação de polihidroxialcanoatos por culturas microbianas mistas do tratamento do efluente urbano

Os microrganismos podem acumular intracelularmente inclusões de polihidroxialcanoatos (PHAs) durante o tratamento de águas residuais, utilizando o efluente urbano como fonte de carbono. Estes polímeros biodegradáveis surgem como alternativa aos plásticos convencionais, permitindo reduzir a quantidade de lamas enviadas para tratamento posterior. A monitorização da acumulação de PHAs nos microrganismos das lamas ativadas da ETAR de Penices foi efetuada durante 30 dias, recorrendo ao método de Cromatografia Gasosa (CG) e à técnica de coloração de Negro Sudão B (NSB). Os resultados obtidos por CG revelaram uma acumulação máxima, em fração mássica, de PHAs igual a 5.3 % nas lamas ativadas, relativamente ao teor de biomassa liofilizada e uma concentração máxima de 127 mg L-1. Os resultados obtidos por NSB corroboraram estes valores, pelo que esta técnica poderá ser uma alternativa viável para a quantificação de PHAs, sendo mais fácil de operar e menos dispendiosa. Concluiu-se ainda que a produção de PHAs com culturas mistas à escala industrial para este caso de estudo não é viável, dadas as baixas quantidades obtidas de polímero e o elevado investimento em unidades de extração e purificação do mesmo.The microorganisms can accumulate intracellularly inclusions of polyhydroxyalkanoates (PHAs) during wastewater treatment, using the urban efluent as carbon source. These biodegradable polymers appear to emerge as an alternative to conventional plastics, allowing to reduce the amount of activated sludge sent to posterior treatment. The monitoring of the PHAs accumulation in the activated sludge microorganisms of the Penices wastewater treatment facility was performed for 30 days, using gas chromatography (GC) and Sudan Black B (SBB) staining. GC results revealed a maximum accumulation of PHAs mass fraction of 5.3 % in the activated sludge, in relation to the liophilized biomass content, and a maximum concentration of 127 mg L -1 . The SBB results corroborated these values, and therefor this technique can be a viable alternative to the PHAs quantification, being easier to operate and less costly. Still, it was possible to conclude that the PHAs production with mixed cultures at the industrial scale is not viable in this case, given the obtained low quantities of polymer and the high investment in extraction and purification units

An Ultra-Stable Referenced Interrogation System in the Deep Ultraviolet for a Mercury Optical Lattice Clock

We have developed an ultra-stable source in the deep ultraviolet, suitable to fulfill the interrogation requirements of a future fully-operational lattice clock based on neutral mercury. At the core of the system is a Fabry-P\'erot cavity which is highly impervious to temperature and vibrational perturbations. The mirror substrate is made of fused silica in order to exploit the comparatively low thermal noise limits associated with this material. By stabilizing the frequency of a 1062.6 nm Yb-doped fiber laser to the cavity, and including an additional link to LNE-SYRTE's fountain primary frequency standards via an optical frequency comb, we produce a signal which is both stable at the 1E-15 level in fractional terms and referenced to primary frequency standards. The signal is subsequently amplified and frequency-doubled twice to produce several milliwatts of interrogation signal at 265.6 nm in the deep ultraviolet.Comment: 7 pages, 6 figure

Método de substituição de seiva para preservação de mourões.

bitstream/CNPF-2009-09/35558/1/com_tec97.pd

Teaching Laminar-flow reactors: From experimentation to CFD simulation

An integrated chemical engineering lab experiment is described in this paper. It makes use of a laminar-flow tubular reactor (LFTR) through consecutive lab sessions. In a first session (not described here), the pseudo first-order kinetic constant for the reaction between crystal violet and sodium hydroxide is determined at different temperatures in a batch reactor. Then a tracer experiment is used to characterize the flow, pattern in the LFTR, and finally the steady-state conversion of crystal violet in the reactor is measured. For computing the theoretical reactor conversion, students must use the previously collected kinetic and tracer data, in a concept-integration exercise. A computational fluid dynamics (CFD) code (Fluent) is also used to simulate both the tracer and the isothermal reaction experiments performed in the LFTR. A very good agreement is obtained between experimental and simulated results and both only differ slightly from the theoretical predictions. The use of the CFD program is particularly noteworthy. For instance, transient simulations allow a very nice visualization of the tracer concentration front evolution, while the steady-state profiles along the axial position provide a good perspective of how reactant concentration varies within the reactor

Metastatic Testicular Germ Cell Tumor or a Chemoresponsive Liver Hemangioma?

Testicular germ cell tumors are the most common solid organ malignancy in young adult men. The presence of non-pulmonary visceral metastasis is an independent factor that places such patients into the higher risk group. Hepatic hemangiomas are the most common tumors of the liver and are entirely benign. Overlap between these entities may occur, particularly when metastases are hypervascular. We describe a case of a 27-year-old man with a testicular germ cell tumor and a nodule in the right hepatic lobe suggestive of hemangioma. After three cycles of chemotherapy, a size reduction in the hepatic nodule was confirmed, and this lesion was removed. Pathology revealed a fibrosing hemangioma. In this case report, the authors discuss the possible mechanisms for the hemangioma chemotherapy response