Frequency tunable continuous THz wave generation in a periodically poled fiber

An all-fiber approach to terahertz generation using a periodically poled optical fiber is proposed and experimentally demonstrated. In the proposed approach, a continuous-wave THz wave is generated at a periodically poled fiber by beating two optical wavelengths from two laser sources with the wavelength spacing corresponding to the frequency of the THz wave. The key component in the system is the periodically poled fiber, which is made by a twin-hole fiber with the fiber core residing between two holes. The twin-hole fiber is then thermally poled at a temperature of similar to 260 degrees C with a voltage of 3.3 kV applied to the silver electrodes inside the two holes to introduce second-order nonlinearity. The quasi phase matching (QPM) condition is achieved by periodically erasing the thermal poling induced second-order nonlinearity with an ultraviolet laser, which enhances the energy conversion efficiency. The proposed approach is validated by an experiment. The emission of a THz wave centered at 3.8 THz with an output power of 0.5 mu W is observed. The frequency tunability between 2.2 and 3.8 THz is also experimentally demonstrated.

Effects of protein supplementation frequency on physiological responses associated with reproduction in beef cows

The objective of this experiment was to determine if frequency of protein supplementation impacts physiological responses associated with reproduction in beef cows. Fourteen nonpregnant, nonlactating beef cows were ranked by age and BW and allocated to 3 groups. Groups were assigned to a 3 x 3 Latin square design, containing 3 periods of 21 d and the following treatments: 1) soybean meal supplementation daily (D), 2) soybean meal supplementation 3 times/week (3WK), and 3) soybean meal supplementation once/week (1WK). Within each period, cows were assigned to an estrus synchronization protocol: 100 mu g of GnRH + controlled internal drug release device (CIDR) containing 1.38 g of progesterone (P-4) on d 1, 25 mg of PGF(2 alpha) on d 8, and CIDR removal + 100 mu g of GnRH on d 11. Grass-seed straw was offered for ad libitum consumption. Soybean meal was individually supplemented at a daily rate of 1 kg/cow (as-fed basis). Moreover, 3WK was supplemented on d 0, 2, 4, 7, 9, 11, 14, 16, and 18 whereas 1WK was supplemented on d 4, 11, and 18. Blood samples were collected from 0 (before) to 72 h after supplementation on d 11 and 18 and analyzed for plasma urea-N (PUN). Samples collected from 0 to 12 h were also analyzed for plasma glucose, insulin, and P-4 (d 18 only). Uterine flushing fluid was collected concurrently with blood sampling at 28 h for pH evaluation. Liver biopsies were performed concurrently with blood sampling at 0, 4, and 28 h and analyzed for mRNA expression of carbamoyl phosphate synthetase I (CPS-I; h 28) and CYP2C19 and CYP3A4 (h 0 and 4 on d 18). Plasma urea-N concentrations were greater (P < 0.01) for 1WK vs. 3WK from 20 to 72 h and greater (P < 0.01) for 1WK vs. D from 16 to 48 h and at 72 h after supplementation (treatment x hour interaction, P < 0.01). Moreover, PUN concentrations peaked at 28 h after supplementation for 3WK and 1WK (P < 0.01) and were greater (P < 0.01) at this time for 1WK vs. 3WK and D and for 3WK vs. D. Expression of CPS-I was greater (P < 0.01) for 1WK vs. D and 3WK. Uterine flushing pH tended (P <= 0.10) to be greater for 1WK vs. 3WK and D. No treatment effects were detected (P >= 0.15) on expression of CYP2C19 and CYP3A4, plasma glucose, and P-4 concentrations, whereas plasma insulin concentrations were greater (P <= 0.03) in D and 3WK vs. 1WK. Hence, decreasing frequency of protein supplementation did not reduce uterine flushing pH or plasma P-4 concentrations, which are known to impact reproduction in beef cows.

Effects of supplementation frequency on the ruminal fermentation and enteric methane production of beef cattle grazing in tropical pastures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A virtual experiment for the detection of specific features in the frequency response of a coupled nonlinear and linear oscillator

This paper presents an investigation into some practical issues that may be present in a real experiment, when trying to validate the theoretical frequency response curve of a two degree-of-freedom nonlinear system consisting of coupled linear and nonlinear oscillators. Some specific features, such as detached resonance curves, have been theoretically predicted in multi degree-of-freedom nonlinear oscillators, when subject to harmonic excitation, and the system parameters have been shown to be fundamental in achieving such features. When based on a simplified model, approximate analytical expression for the frequency response curves may be derived, which may be validated by the numerical solutions. In a real experiment, however, the practical achievability of such features was previously shown to be greatly affected by small disturbances induced by gravity and inertia, which led to some solutions becoming unstable which had been predicted to be stable. In this work a practical system configuration is proposed where such effects are reduced so that the previous limitations are overcome. A virtual experiment is carried out where a detailed multi-body model of the oscillator is assembled and the effects on the system response are investigated.

Active power reserve for frequency control provided by distributed generators in distribution networks

In a smart grid environment, attention should be paid not only to the power supplied to satisfy loads and system losses but also to the services necessary to provide security and stability to the system: the so-called ancillary services. As they are well known the benefits that distributed generation can bring to electrical systems and to the environment, in this work the possibility that active power reserve for frequency control could be provided by distributed generators (DGs) in an efficient and economical way is explored. The proposed methodology was tested using the IEEE 34-bus distribution test system. The results show improvements in the capacity of the system for this ancillary service and decrease in system losses and payments of the distribution system operator to the DGs.

Laser frequency measurements and spectroscopic assignments of optically pumped 13CH3OH

A three-laser heterodyne system was used to measure the frequencies of twelve optically pumped laser emissions from 13CH3OH in the far-infrared (FIR) region. These emissions, ranging from 54 to 142 μm, are reported with fractional uncertainties up to ±2 × 10-7 along with their polarization relative to the CO2 pump. Using the 9P32 and 10R14 CO2 lines, complete spectroscopic assignments for two laser systems were confirmed.

Dielectric properties of Sr0.75Ba0.25Nb 2O6 thin films: Bias field, frequency and temperature dependence

Ferroelectric strontium barium niobate solid solutions had received great attention due to their excellent pyroelectric, electrooptic and photorefractive properties. Furthermore, they usually also present very interesting phase transition characteristics. In this work, polycrystalline single phase Sr 0.75 Ba 0.25 Nb 2 O 6 thin films were prepared by a hybrid chemical method and deposited on Pt/Ti/SiO 2 /Si substrates. The temperature dependence of dielectric constant was measured at different frequencies and bias field levels. The presence of two dielectric dispersion regions with relaxor characteristics was observed at distinct temperature ranges, corresponding to the ferro-paraelectric and to a structural phase transition at low temperatures, respectively. A specific dielectric dispersion region, associated with an incommensurate superstructure frequently observed in bulk samples, was not observed in this films probably due to their small grain sizes. © 2002 Taylor & Francis.

Frequency upconversion involving triads and quartets of ions in a Pr3+/Nd3+ codoped fluoroindate glass

Frequency upconversion (UC) processes involving energy transfer (ET) among Nd 3+ and Pr 3+ ions in a fluoroindate glass are reported. In a first experiment, the excitation of Pr 3+ [transition 3H 4→ 1D 2] and of Nd 3+ [transition 4I 9/2→( 2G 7/2+ 4G 5/2)] was achieved with a dye laser operating in the 575-590 nm range. In a second experiment, the Nd 3+ ions were excited with the second harmonic of a Nd: YAG laser at 532 nm. The ET processes leading to UC in both experiments were studied by monitoring the blue fluorescence decay at 480 nm due to the transition 3P 0→ 3H 4 in Pr 3+. In the more relevant UC process, quartets of ions (Nd-Nd-Pr-Pr) are excited due to absorption of three laser photons by two Nd 3+ ions which transfer their energy to two Pr 3+ ions. Each Pr 3+ ion promoted to the 3P 0 level decays to the ground state emitting one photon in the blue region. This conclusion was achieved investigating the dependence of the UC fluorescence intensity as a function of laser intensity, samples concentrations, and temporal behavior of the UC signal. Other UC processes involving nonisoionic groups of three ions are also reported. © 2002 American Institute of Physics.

Analysis of linearity and frequency response of a novel piezoelectric flextensional actuator using a homodyne interferometer and the J(1)-J(4) method

Piezoelectric transducers are widely used in high-resolution positioning systems. This paper reports the experimental analysis of a novel piezoelectric flextensional actuator (PFA), which is designed by using the topology-optimization method through a low-cost homodyne Michelson interferometer. By applying the J(1) - J(4) method for signal demodulation, which provides a linear and direct measurement of dynamic optical phase shift independent of fading, the nanometric displacements of the PFA were determined. Linearity and frequency response of the PFA were evaluated up to 50 kHz. PFA calibration factor and amplification rate were determined for the PFA operating in the quasi-static regime. To confirm the observed frequencies of resonance, an impedance analyzer is also utilized to measure the magnitude and phase of the PFA admittance.

Does radioiodine therapy in patients with differentiated thyroid cancer increase the frequency of another malignant neoplasm?

Objectives. To compare the frequency of another primary malignancy in patients with differentiated thyroid carcinoma (DTC) who received radioiodine therapy or not ((131)I). Material and Methods. 168 cases of DTC patients were retrospectively evaluated as to the frequency of another neoplasia by comparing patients with and without it, taking into account clinical, laboratory, and therapeutic parameters. Results. Another primary malignancy occurred in 8.9% of patients. Of these, 53.3% showed the malignancy before (131)I and 46.7% after it. By comparing both groups, the age at the moment of diagnosis of another neoplasia was 46.1 ± 20.2 years for the group before (131)I therapy and of 69.4 ± 11.4 years for the group after it (P = 0.02). Of the 148 patients treated with (131)I, 4.7% developed another malignancy. The latter were older (61 ± 17 years) than those who did not show another cancer type (44.1 ± 14.2 years) (P < 0.05). Conclusion. The frequency of another neoplasia found after (131)I was similar to that found before (131)I.

Effect of himatanthus sucuuba in maternal reproductive outcome and fetal anomaly frequency in rats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Clinical study on survival rate of short implants placed in the posterior mandibular region: resonance frequency analysis

Short implants are increasingly used, but there is doubt about their performance being similar to that of regular implants. The aim of this study was to compare the mechanical stability of short implants vs. regular implants placed in the edentulous posterior mandible. Twenty-three patients received a total of 48 short implants (5 × 5.5 mm and 5 × 7 mm) and 42 regular implants (4 × 10 mm and 4 × 11.5 mm) in the posterior mandible. Patients who received short implants had <10 mm of bone height measured from the bone crest to the outer wall of the mandibular canal. Resonance frequency analysis (RFA) was performed at time intervals T0 (immediately after implant placement), T1 (after 15 days), T2 (after 30 days), T3 (after 60 days), and T4 (after 90 days). The survival rate after 90 days was 87.5% for the short implants and 100% for regular implants (P < 0.05). There was no significant difference between the implants in time intervals T1, T2, T3, and T4. In T0, the RFA values of 5 × 5.5 implants were higher than values of 5 × 7 and 4 × 11.5 implants (P < 0.05). A total of six short implants that were placed in four patients were lost (three of 5 × 5.5 mm and three of 5 × 7 mm). Three lost implants started with high ISQ values, which progressively decreased. The other three lost implants started with a slightly lower ISQ value, which rose and then began to fall. Survival rate of short implants after 90 days was lower than that of regular implants. However, short implants may be considered a reasonable alternative for rehabilitation of severely resorbed mandibles with reduced height, to avoid performing bone reconstruction before implant placement. Patients need to be aware of the reduced survival rate compared with regular implants before implant placement to avoid disappointments.

Low frequency of Y anomaly detected in Australian Brahman cow-herds

Indicine cattle have lower reproductive performance in comparison to taurine. A chromosomal anomaly characterized by the presence Y markers in females was reported and associated with infertility in cattle. The aim of this study was to investigate the occurrence of the anomaly in Brahman cows. Brahman cows (n = 929) were genotyped for a Y chromosome specific region using real time-PCR. Only six out of 929 cows had the anomaly (0.6%). The anomaly frequency was much lower in Brahman cows than in the crossbred population, in which it was first detected. It also seems that the anomaly doesn't affect pregnancy in the population. Due to the low frequency, association analyses couldn't be executed. Further, SNP signal of the pseudoautosomal boundary region of the Y chromosome was investigated using HD SNP chip. Pooled DNA of non-pregnant and pregnant cows were compared and no difference in SNP allele frequency was observed. Results suggest that the anomaly had a very low frequency in this Australian Brahman population and had no effect on reproduction. Further studies comparing pregnant cows and cows that failed to conceive should be executed after better assembly and annotation of the Y chromosome in cattle.

Breakfast frequency, adiposity, and cardiovascular risk factors as markers in adolescents

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparison of frequency and time domain electromyography parameters in women with patellofemoral pain

Despite its high incidence, patellofemoral pain etiology remains unclear. No prior study has compared surface electromyography frequency domain parameters and surface electromyography time domain variables, which have been used as a classic analysis of patellofemoral pain. Thirty one women with patellofemoral pain and twenty eight pain-free women were recruited. Each participant was asked to descend a seven step staircase and data from five successful trials were collected. During the task, the vastus medialis and vastus lateralis muscle activities were monitored by surface electromyography. The data were processed and analyzed in four variables of the frequency domain (median frequency, low, medium and high frequency bands) and three time domain variables (Automatic, Cross-correlation and Visual Onset between the vastus medialis and vastus lateralis muscles). Reliability, Receiver Operating Characteristic curves and regression models were performed. The medium frequency band was the most reliable variable and different between the groups for both muscles, also demonstrated the best values of sensitivity and sensibility, 72% and 69% for the vastus medialis and 68% and 62% for the vastus lateralis, respectively. The frequency variables predicted the pain of individuals with patellofemoral pain, 26% for the vastus medialis and 20% for the vastus lateralis, being better than the time variables, which achieved only 7%. The frequency domain parameters presented greater reliability, diagnostic accuracy and capacity to predict pain than the time domain variables during stair descent and might be a useful tool to diagnose individuals with patellofemoral pain.