Transmission Oscillator Ultrasonic Spectrometer (TOUS): A new research instrument

TOUS is capable for measuring very small changes in acoustic attenuation and phase velocity. Its high sensitivity to small changes in ultrasonic absorption results in part from operation under marginal conditions. In spite of high sensitivity, TOUS system is relatively simple, inexpensive, and compact

Neural networks in geophysical applications

Neural networks are increasingly popular in geophysics. Because they are universal approximators, these tools can approximate any continuous function with an arbitrary precision. Hence, they may yield important contributions to finding solutions to a variety of geophysical applications. However, knowledge of many methods and techniques recently developed to increase the performance and to facilitate the use of neural networks does not seem to be widespread in the geophysical community. Therefore, the power of these tools has not yet been explored to their full extent. In this paper, techniques are described for faster training, better overall performance, i.e., generalization,and the automatic estimation of network size and architecture

A Local One-Zone Model of MHD Turbulence in Dwarf Nova Disks

The evolution of the magnetorotational instability (MRI) during the transition from outburst to quiescence in a dwarf nova disk is investigated using three-dimensional MHD simulations. The shearing box approximation is adopted for the analysis, so that the efficiency of angular momentum transport is studied in a small local patch of the disk: this is usually referred as to a one-zone model. To take account of the low ionization fraction of the disk, the induction equation includes both ohmic dissipation and the Hall effect. We induce a transition from outburst to quiescence by an instantaneous decrease of the temperature. The evolution of the MRI during the transition is found to be very sensitive to the temperature of the quiescent disk. As long as the temperature is higher than a critical value of about 2000 K, MHD turbulence and angular momentum transport is sustained by the MRI. However, MHD turbulence dies away within an orbital time if the temperature falls below this critical value. In this case, the stress drops off by more than 2 orders of magnitude, and is dominated by the Reynolds stress associated with the remnant motions from the outburst. The critical temperature depends slightly on the distance from the central star and the local density of the disk.Comment: 20 pages, 2 tables, 6 figures, accepted for publication in Ap

Dissipation in Compressible MHD Turbulence

We report results of a three dimensional, high resolution (up to 512^3) numerical investigation of supersonic compressible magnetohydrodynamic turbulence. We consider both forced and decaying turbulence. The model parameters are appropriate to conditions found in Galactic molecular clouds. We find that the dissipation time of turbulence is of order the flow crossing time or smaller, even in the presence of strong magnetic fields. About half the dissipation occurs in shocks. Weak magnetic fields are amplified and tangled by the turbulence, while strong fields remain well ordered.Comment: 5 pages, 3 Postscript figures, LaTeX, accepted by Ap.J.Let

Cover crops as affecting soil chemical and physical properties and development of upland rice and soybean cultivated in rotation.

Cover crops can provide changes in soil chemical and physical properties, which could allow a sustainable development of soybean and upland rice rotation in Brazilian Cerrado. The objective of this study was to determine the effects of cover crops (cultivated in the offseason) in the soybean-upland rice rotation (cultivated in the summer season) on the soil chemical and physical properties, yield components and grain yield of the cash crops. The experimental design was a randomized block design in factorial scheme 4 × 2 with six replications. Treatments were composed by four cover crops: fallow, millet (Pennisetum glaucum) + Crotalaria ochroleuca, millet + pigeon pea (Cajanus cajans), and millet + pigeon pea + Urochola ruziziensis in the offseason with one or two cycles of cover crops, with rice (Oryza sativa) or soybean (Glycine max) in the summer season. Cover crops alone provided no changes in soil chemical properties. However, the rotation cover crops / cash crops / cover crops / cash crops reduced pH, Al and H + Al and increased Ca, Mg, K and Fe contents in the soil. The cover crops millet + pigeon pea and millet + pigeon pea + U. ruziziensis improved soil physical properties in relation to fallow, especially in the 0?0.10 m soil layer. In spite of the improvement of the soil physical properties after two years of rotation with cover crops and cash crops, the soil physical quality was still below the recommended level, showing values of macroporosity, S index and soil aeration capacity lower than 0.10 m3/m3, 0.035 and 0.34, respectively. Upland rice production was higher under mixtures of cover crops than under fallow, mainly because of soil physical changes done by these mixtures of cover crops. Soybean grain yield was similar under all cover crops tested, but was higher after the rotation cover crops / upland rice / cover crops than after only one cycle of cover crops

The impact of a ward pharmacist in a surgical ward of a private hospital in the Eastern Cape

Medication errors are becoming problematic in both hospital and outpatient settings worldwide. Inappropriate use of medication can cause harm to the patient and maintaining high levels of quality patient care is essential to protect all patients. Clinical pharmacy practice contributes to improved patient care by optimising medication therapy; and promoting health, wellness and disease prevention. The involvement of a pharmacist at a ward level has been shown to improve patient care; reduce mortality and morbidity rates; decrease healthcare costs; minimise medication errors; and improve outcomes of drug therapy. However, clinical pharmacy is a fairly new practice in South Africa and there are limited studies available. This study aimed to evaluate the perceived benefits of a ward-based pharmacist on the provision of pharmaceutical care to patients in a hospital setting and to consequently implement a ward-based pharmacy service. The objectives of the study were: (1) to assess, via a questionnaire, the perceptions and attitudes of medical practitioners and nurses to ward-based pharmacy prior to and after implementation of a ward-based pharmacy service, (2) to implement a ward-based pharmacy service in a selected hospital ward; (3) to document and analyse the nature of the work and activities that a ward pharmacist undertakes, and (4) to document and analyse the frequency and nature of ward pharmacist interventions. The study was conducted in a surgical ward of a private hospital in the Eastern Cape. The study design was an intervention study, using a mixed-methods design, with a convergent approach. A convenience sample of 106 patients was obtained over the eight week study period. Participation was voluntary and confidentiality was maintained at all times. Four data collection tools were used during the study and a pilot study was conducted to ensure their validity and reliability. The quantitative data was analysed statistically while the qualitative questions were analysed through coding the various responses. The results of the study showed that medical practitioners and nurses of a surgical ward had a positive attitude towards ward pharmacy both prior to and after the implementation of a ward pharmacy service. There were ward pharmacist interventions made in 50% (n=106) of the patients who participated in the study. A large percentage (57%; 50; n=87) of the ward pharmacist interventions were pharmacist-initiated interventions to optimise patient care while prescribing errors (51%; 19; n=37) were the most commonly occurring medication error. The majority of the medication items involved in the interventions (34%; 34; n=101) were related to the anti-microbial medication class. Overall, there was a 73% (36; n=49) acceptance rate of the ward pharmacist interventions that were made to both the medical practitioners and nurses. There were a number of factors that had a significant relationship with a ward pharmacist intervention being required which included: (1) number of medication items (p=0.001; Chi² test; p<0.0005 Student’s t-test), (2) length of hospital stay (p<0.0005; Chi² test), (3) presence of one or more chronic disease states (p=0.003; Chi² test) and (4) presence of one or more allergies (p=0.028; Chi² test). The ward pharmacist interventions were shown to be of clinical significance and to have a positive impact on the patients concerned. It can be concluded that the ward pharmacy service was beneficial to the patients, medical practitioners and nursing staff

Tunable fibre-coupled multiphoton microscopy with a negative curvature fibre

Negative curvature fibre (NCF) guides light in its core by inhibiting the coupling of core and cladding modes. In this work, an NCF was designed and fabricated to transmit ultrashort optical pulses for multiphoton microscopy with low group velocity dispersion (GVD) at 800 nm. Its attenuation was measured to be <0.3 dB m(-1) over the range 600-850 nm and the GVD was -180 ± 70 fs(2)  m(-1) at 800 nm. Using an average fibre output power of ∼20 mW and pulse repetition rate of 80 MHz, the NCF enabled pulses with a duration of <200 fs to be transmitted through a length of 1.5 m of fibre over a tuning range of 180 nm without the need for dispersion compensation. In a 4 m fibre, temporal and spectral pulse widths were maintained to within 10% of low power values up to the maximum fibre output power achievable with the laser system used of 278 mW at 700 nm, 808 mW at 800 nm and 420 mW at 860 nm. When coupled to a multiphoton microscope, it enabled imaging of ex vivo tissue using excitation wavelengths from 740 nm to 860 nm without any need for adjustments to the set-up

Confirmation of Parity Violation in the Gamma Decay of 180Hfm^{180}Hf^{m}

This paper reports measurements using the technique of On Line Nuclear Orientation (OLNO) which reexamine the gamma decay of isomeric $^{\rm 180}$Hf$^{\rm m}$ and specifically the 501 keV 8$^{\rm -}$ -- 6$^{\rm +}$ transition. The irregular admixture of E2 to M2/E3 multipolarity in this transition, deduced from the forward-backward asymmetry of its angular distribution, has for decades stood as the prime evidence for parity mixing in nuclear states. The experiment, based on ion implantation of the newly developed mass-separated $^{\rm 180}$Hf$^{\rm m}$ beam at ISOLDE, CERN into an iron foil maintained at millikelvin temperatures, produces higher degrees of polarization than were achieved in previous studies of this system. The value found for the E2/M2 mixing ratio, $\epsilon$ = -0.0324(16)(17), is in close agreement with the previous published average value $\epsilon$ = - 0.030(2), in full confirmation of the presence of the irregular E2 admixture in the 501 keV transition. The temperature dependence of the forward-backward asymmetry has been measured over a more extended range of nuclear polarization than previously possible, giving further evidence for parity mixing of the 8$^{\rm -}$ and 8$^{\rm +}$ levels and the deduced E2/M2 mixing ratio.Comment: 28 pages, 9 figures, accepted for publication in Physical Review

Uso do tanque classe A no controle da irrigação do arroz de terras altas cultivado sob plantio direto.

É difícil quantificar com exatidão o volume total de água necessário para irrigação quando se utiliza irrigação suplementar, uma vez que este volume depende da quantidade e distribuição das chuvas. A necessidade total de água para o cultivo do arroz de terras altas varia de 600 a 700 mm. Considerando apenas a irrigação suplementar, as lâminas de água aplicadas podem variar de mais de 500 mm, no Rio Grande do Sul, a valores inferiores a 200 mm por ciclo, nas Regiões Sudeste e Centro-Oeste, dependendo do regime de chuvas. O requerimento de água do arroz irrigado por aspersão, entretanto, pode ser estimado a partir de tanques evaporimétricos, com base na relação existente entre a evaporação da água medida no tanque USWB Classe A (ECA) e a evapotranspiração da cultura (ETc). A relação é obtida utilizando-se coeficientes do tanque (Kp) e de cultura (Kc).bitstream/CNPAF/22243/1/circ_63.pd