Very little is known about the distribution of hepatitis C virus (HCV) within South America. To assess the exposure of the general population to this virus, a number of sera obtained from three distinct geographical and racial groups were screened using a combination of immunoassays. Initial screening was undertaken with an inhouse immunoassay (core-ELISA) using synthetic peptides based on the N-terminus of the HCV core protein. Sera which were repeatedly positive by core-ELISA were also assessed using a commercial third-generation assay. The highest prevalence rate (2.3%) was seen in sera taken from the Tumaco region of Colombia. Lower rates were found in sera taken from La T, Ecuador (0.7%) and Las Majadas, Venezuela (0.7%). This indicates significantly different prevalence in different racial and geographical groups within the region.

In the spectrogram made on the third day, the lines observed for the fresh solution had disappeared and three new lines slightly above 1000 cm.-1 had appeared. In addition, the solution which originally had been odorless had acquired the odor of ammonia. Observance of NH»"1" lines was impossible because of the strong continuous background in that region. DiscussionGoubeau4 found a weak line at 857, a very weak, questionable line at 970 and a line of medium intensity at 2192 cm.-1 in the Raman spectrum of solid potassium cyanate. In aqueous solution, he found 852, very weak, and 2185, weak. Pal and Sen Gupta5 also reported frequencies at 838 and 2183, and in addition listed frequencies at 1229 and 1314, not found by Goubeau. These two frequencies were found also in the present investigation.As Williams points out, these lines cannot be attributed to vibrations of the linear 0-C=Ngroup. The fact that Goubeau found lines at 1204 (weak) and 1307 (strong) for cyanic acid suggests the possibility that there may be some of this acid in the potassium cyanate solution.Another possibility is that mercury cyanate or silver cyanate may have been present as an impurity. Goubeau found lines at 1232 (weak) and 1302 (medium) for the former and at 1233 (weak) and 1297 (medium) for the latter. He attributed these frequencies to the doublet vi, 2 vt (analogous to the resonance doublet in carbon dioxide) of the linear 0=C=Ngroup.Aqueous solutions of potassium carbonate and potassium bicarbonate have Raman frequencies at 1069 and 1035 cm.-1, respectively.6 Measurements of the Raman spectra of aqueous solutions of ammonium carbonate and ammonium bicar-

To quantitatively understand laser ablation of kidney stones by near-infrared (NIR) lasers, accurate measurements of physical properties related to heating and mechanical failure are needed. While light scattering varies among individual stones, absorption coefficients for the materials that form the bulk of each kidney stone are measurable when scattering is controlled. We developed methods to grow single crystals with lengths and widths >20 μm for the minerals that form kidney stones: calcium oxalate monohydrate, calcium oxalate dihydrate, calcium hydrogen phosphate dihydrate, hydroxyapatite, anhydrous uric acid, and magnesium ammonium phosphate hexahydrate. These single crystals were used with an infrared microscope to measure their NIR absorption coefficients from 1.67 to 2.5 μm. The strong correlation between single crystal NIR spectra and diffuse reflectance NIR spectra indicates little anisotropy in absorption. Most minerals absorbed more strongly at 1.94 μm than 2.12 μm, the wavelengths of thulium fiber and holmium:YAG surgical lasers, respectively. For water bearing minerals, we attribute absorption mainly to water combination modes and assign NIR absorption peaks to specific water molecules and the OH bonds thereof where possible. Reported absorption coefficients can be used to quantitatively compare both laboratory investigations of ablation and surgical experience to physical properties for the first time.

In this circuit for determining the fundamental frequency of •i monophonic tone synthesizer, the closing of one playing-key switch grounds the 6ontrol terminals of two different electronic gates. One of these gates is in the conventional voltage divider circuit which supplies a potential of magnitude corresponding to the position of the selected key within a chromatic octave. The other gate is responsive to any key switch within a given octave, and its output supplies a potential corresponding to that octave. The combination of the two potentials controls the frequency of the voltage controlled oscillator. -DWM 4,108,038 43.75. Tv TIME SHARED TONE KEYING SYSTEM IN ELECTRONIC MUSICAL INSTRUMENT Eiichiro Aoki, assignor to Nippon Gakki 22 August 1978 (Class 84/1.03); filed in Japan 4 April 1975This is another time-division multiplexing system for connecting the keyswitches of an electronic musical instrument to the tone-producing circuits, using a greatly reduced number of electrical conductors and input terminals to the tone-producing circuits. "The keying sequence pulses are obtained by sequentially scanning all the keys in the keyboard in one sequence, or maybe equivalently obtained by scanning the same keys in different octaves simultaneously and ANDgating with octave representing pulses .... The system is suitable for digitalization and for production in IC configuration."-DWM 4,109,208 43.75. Tv WAVEFORM PRODUCING SYSTEM Norio Tomisawa, Takehisa Amano, Yasuji Uchiyama and Takatoshi Okumura, assignors to Nippon Gakki 22 August 1978 (Class 328/13); filed 28 July 1972 This patent has 50 figures and illustrations. Perhaps the most efficient system shown uses a single octave of individual clock oscilla-12 OSClL-Jl2 • LATORS •1 0CTAV1 ; IxEaO,, tots 53 connected to an entire keyboard 51 of keyswitches 52 in the manner shown. The outputs of the selected keyswitches are routed to different input points 56 in an n-stage, successive pulse, generator composed of cascaded flip-flops 57, constituting a much more compact frequency divider circuit than the conventional divider chains associated with each top-octave oscillator. The outputs of the flipflops operate a decoder 58 which scans (samples) waveform memories 55 providing, at output terminals 59, musical waveforms to which memorized envelope control signals are subsequently applied.-DWM 4,114,495 43.75. Tv CHANNEL PROCESSOR Norio Tomisawa, assignor to Nippon Gakki 19 September 1978 (Class 84/1.01); filed in Japan 20 August 1975In contrast to many other recent digital organ patents using time division multiplexing methods for relating keys played to tones produced, this channel processor immediately assigns a key code to an available memory circuit. The release of a playing key is detected by clearing a memory storing the assigned channels by means of a start code generated by the key coder and subsequently ffmding that a channel among the cleared channels is not stored in the memory again. "This arrangement is very convenient for an electronic musical instrument becaus...

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