Modification by focused ultrasound pulses of electrically evoked responses from an in vitro hippocampal preparation.

The application of short pulses of focused ultrasound was studied as a method of modifying electrically evoked responses in the mammalian brain. The in vitro hippocampal preparation was employed to facilitate delivery and dosimetry of ultrasound, and assessment of mechanisms of ultrasound effects. Cellular and dendritic field potential responses evoked by electrical stimulation of the Schaffer/Commissural afferents were examined before, during and after exposure of a portion of the CA1 region to focused ultrasound pulses for periods ranging from 2 to 15 min. Focused ultrasound with a repetition rate of 150 kHz was delivered in pulses comparable in duration to an electrical pulse that could initiate activity in the nervous system. The pulses had a center frequency of 750 kHz, durations of about 6 microseconds, and spatial-peak-temporal-averaged intensities of about 80 W/cm2. These parameters are markedly different from those employed in conventional diagnostic ultrasound. Temperatures in the bath and tissue were monitored. Extracellular field potentials reflecting the presynaptic fiber volley, dendritic response and cellular discharge were significantly reduced by exposure to ultrasound. Recovery occurred to varying degrees, and in one experiment was complete. Average temperature changes observed were less than 1 degree C. The present study demonstrates that the electrically evoked response in mammalian brain can be altered by ultrasound in a non-thermal, non-cavitational mode, and that such effects are potentially reversible.

Sex differences in verbal IQ-performance IQ discrepancies among patients with schizophrenia and normal volunteers.

Substantial verbal IQ (VIQ)-performance IQ (PIQ) discrepancies may reflect brain dysfunction. The authors examined 159 patients with schizophrenia (115 men and 44 women) or schizoaffective disorder (25 men and 19 women) and 79 normal participants (33 men and 46 women), calculated mean VIQ-PIQ discrepancy scores by sex and diagnosis, and identified persons with large VIQ-PIQ discrepancies (15-point difference in either direction). Schizophrenic/schizoaffective men had a larger mean VIQ-PIQ discrepancy than did other groups. The proportion of all patients with either VIQ > PIQ or PIQ > VIQ (17.8%) was not significantly different from that of normal participants (22.8%). However, significantly more men than women with schizophrenia exhibited a VIQ > PIQ pattern (20% vs. 3.2%). No unusual discrepancy patterns were noted among normal participants. Results were interpreted in light of theories of hemisphere dysfunction in schizophrenia.

Focused ultrasound modifications of neural circuit activity in a mammalian brain.

The application of focused, pulsed ultrasound was studied as a method of modifying the activity of a local neural circuit of the mammalian brain. An in vitro hippocampal preparation was used to facilitate delivery, dosimetry and assessment of mechanisms of ultrasound effects. Extracellular evoked potentials were recorded from cell and dendritic layers of the rat hippocampal dentate gyrus. Focused pulses of ultrasound with center frequency of 500 kHz and repetition rate of 200 kHz were studied and found both to enhance and to depress electrically evoked field potentials. The fiber volley and cell population potentials were depressed, whereas the dendritic potential was enhanced. Results suggest a simultaneous mechanical and thermal mechanism of ultrasound in modifying evoked field potentials of dentate local circuits.

Confirmatory factor analysis of a test used for certification in sport scuba diving.

The purpose of this study was to confirm the underlying factor structure of the entry-level scuba diving certification test published by the National Association of Underwater Instructors (NAUI). The test measures knowledge mastery across 6 content areas. A sample of 400 female and male entry-level scuba diving students aged from 18 to 47 years participated in the study. A rigorous structural equation modeling approach was used to confirm the factor structure of the test. The results verify that two latent factors or constructs accurately represent knowledge mastery for entry-level scuba diving students. Also, cross-validation procedures were used to examine the accuracy of measurement model replication. Collectively, these findings support the construct validity of the test.

Effects of voltages on cows over a complete lactation. 1. Milk yield and composition.

The effect of long-term voltage exposure on milk yield and composition was assessed. Forty cows in second to fifth lactation were used. Four groups of 10 Holstein cows were exposed to either 0, 1, 2, or 4 V throughout an entire lactation. Each group was housed in a free-stall environment with bunk feed and water provided for ad libitum intake. Voltages (AC, 60 Hz) were applied between waterers and a metal grid. Cows could not drink without placing their front hooves on the metal grid. Individual records were maintained for milk weights, milk fat, protein, and somatic cell counts. Average actual (7312, 8527, 6938, and 7725 kg for groups exposed to 0, 1, 2, or 4 V, respectively) and mature equivalent (7802, 9281, 7308, and 8911 kg for groups exposed to 0, 1, 2, or 4 V, respectively) milk weights for 305 d showed no significant differences between groups exposed or unexposed to voltage. Average actual milk yields for 305 d in the previous lactations were 8016, 8163, 7679, and 7876 kg for groups exposed to 0, 1, 2, or 4 V, respectively. Somatic cell counts, milk fat, and protein showed no significant differences between groups exposed or unexposed to voltage. Feed and water intakes were not affected by voltage.

Effects of voltages on cows over a complete lactation. 2. Health and reproduction.

For the effects of voltages on health and reproduction, 40 cows in second to fifth lactation were divided into four groups of 10. These included a control group that was not subjected to voltages and three treatment groups that were given either 1, 2, or 4 V at the water bowl. Cows in the treatment groups were exposed during the entire lactation to voltage whenever they drank. Voltages did not sufficiently affect milk yield. General health parameters studied were mastitis, hoof problems, and changes in body weight. Reproductive and calving parameters examined were days to first breeding, days open, services per conception, response to PGF2 alpha, calving intervals, visible abortion, and calves born dead. Voltages did not significantly influence cow health or reproductive performance.

Cow sensitivity to electricity during milking.

Alternating currents were delivered to lactating cattle through the milk during milking. Electrodes were placed at the top of each short milk tube and jointed for one electrical contact. A metal grid on which the cows' rear hooves stood during milking was the second contact. Constant voltages (0 to 16 V) applied to contacts showed first lactation cows to be more sensitive than multiple lactation cows. First lactation cows kicked milking machines at 8 V (currents greater than 5 mA), and multiple lactation cows kicked at 16 V (currents greater than 8 mA). At lower voltages, there were no consistent significant differences in milking duration, milk yield, or composition for primary or residual milk. Application of constant currents of 5 mA for first lactation cows and 8 mA for multiple lactation cows produced no undesired behaviors but did result in some differences in production variables. Milking duration decreased during application of constant current to first lactation cows. Blood cortisol monitored in the multiple lactation cows during trial 2 showed a significant increase during milking but was equivalent or less during application of current. This study demonstrates that currents of 5 mA or less, delivered through the milk line, did not produce any direct economic effect. To produce this current, voltages on the milk pipe line would have to be in excess of 125 V (obvious human safety hazard) or in excess of 5 V on the claw of the milking cluster.

Tau neutrinos favored over sterile neutrinos in atmospheric muon neutrino oscillations.

The previously published atmospheric neutrino data did not distinguish whether muon neutrinos were oscillating into tau neutrinos or sterile neutrinos, as both hypotheses fit the data. Using data recorded in 1100 live days of the Super-Kamiokande detector, we use three complementary data samples to study the difference in zenith angle distribution due to neutral currents and matter effects. We find no evidence favoring sterile neutrinos, and reject the hypothesis at the 99% confidence level. On the other hand, we find that oscillation between muon and tau neutrinos suffices to explain all the results in hand.

Solar 8B and hep neutrino measurements from 1258 days of Super-Kamiokande data.

Solar neutrino measurements from 1258 days of data from the Super-Kamiokande detector are presented. The measurements are based on recoil electrons in the energy range 5.0-20.0 MeV. The measured solar neutrino flux is 2.32+/-0.03(stat)+0.08-0.07(syst)x10(6) cm(-2) x s(-1), which is 45.1+/-0.5(stat)+1.6-1.4(syst)% of that predicted by the BP2000 SSM. The day vs night flux asymmetry (Phi(n)-Phi(d))/Phi(average) is 0.033+/-0.022(stat)+0.013-0.012(syst). The recoil electron energy spectrum is consistent with no spectral distortion. For the hep neutrino flux, we set a 90% C.L. upper limit of 40x10(3) cm(-2) x s(-1), which is 4.3 times the BP2000 SSM prediction.

Constraints on neutrino oscillations using 1258 days of Super-Kamiokande solar neutrino data.

We report the result of a search for neutrino oscillations using precise measurements of the recoil electron energy spectrum and zenith angle variations of the solar neutrino flux from 1258 days of neutrino-electron scattering data in Super-Kamiokande. The absence of significant zenith angle variation and spectrum distortion places strong constraints on neutrino mixing and mass difference in a flux-independent way. Using the Super-Kamiokande flux measurement in addition, two allowed regions at large mixing are found.