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The Arcminute Cosmology Bolometer Array Receiver (Acbar) is a multifrequency millimeter-wave receiver optimized for observations of the Cosmic Microwave Background (CMB) and the Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies. Acbar was installed on the 2.1 m Viper telescope at the South Pole in January 2001 and the results presented here incorporate data through July 2002. The power spectrum of the CMB at 150 GHz over the range ℓ = 150 — 3000 measured by Acbar is presented along with estimates for the values of the cosmological parameters within the context of ΛCDM models. The inclusion of ΩΛ greatly improves the fit to the power spectrum. Three-frequency images of the SZ decrement/increment are also presented for the galaxy cluster 1E0657–67.

We report the first measurements of anisotropy in the cosmic microwave background (CMB) radiation with the Arcminute Cosmology Bolometer Array Receiver (ACBAR). The instrument was installed on the 2.1m Viper telescope at the South Pole in January 2001; the data presented here are the product of observations up to and including July 2002. The two deep fields presented here, have had offsets removed by subtracting lead and trail observations and cover approximately 24 deg^2 of sky selected for low dust contrast. These results represent the highest signal to noise observations of CMB anisotropy to date; in the deepest 150GHz band map, we reached an RMS of 8.0\mu K per 5' beam. The 3 degree extent of the maps, and small beamsize of the experiment allow the measurement of the CMB anisotropy power spectrum over the range \ell = 150-3000 with resolution of \Delta \ell=150. The contributions of galactic dust and radio sources to the observed anisotropy are negligible and are removed in the analysis. The resulting power spectrum is found to be consistent with the primary anisotropy expected in a concordance \Lambda CDM Universe.

We report an investigation of cosmological parameters based on the measurements of anisotropy in the cosmic microwave background radiation (CMB) made by ACBAR. We use the ACBAR data in concert with other recent CMB measurements to derive Bayesian estimates of parameters in inflation-motivated adiabatic cold dark matter models. We apply a series of additional cosmological constraints on the shape and amplitude of the density power spectrum, the Hubble parameter and from supernovae to further refine our parameter estimates. Previous estimates of parameters are confirmed, with sensitive measurements of the power spectrum now ranging from \ell \sim 3 to 2800. Comparing individual best model fits, we find that the addition of \Omega_\Lambda as a parameter dramatically improves the fits. We also use the high-\ell data of ACBAR, along with similar data from CBI and BIMA, to investigate potential secondary anisotropies from the Sunyaev-Zeldovich effect. We show that the results from the three experiments are consistent under this interpretation, and use the data, combined and individually, to estimate \sigma_8 from the Sunyaev-Zeldovich component.

We present new submillimeter polarimetric observations of the Galactic center region, made using the SPARO polarimeter that operates at the South Pole. Compared with previous submillimeter polarimetry of this region, our measurements cover much more sky area, and they imply that the molecular gas in the central few hundred pc is threaded by a large scale toroidal magnetic field. We consider this result together with radio observations that show evidence for poloidal fields in the Galactic center, and with Faraday rotation observations. We compare all of these observations with a magnetodynamic model for the Galactic center.

We have observed the linear polarization of 450 micron continuum emission from the Galactic center, using a new polarimetric detector system that is operated on a 2 m telescope at the South Pole. The resulting polarization map extends ~ 170 pc along the Galactic plane and ~ 30 pc in Galactic latitude, and thus covers a significant fraction of the central molecular zone. Our map shows that this region is permeated by large-scale toroidal magnetic fields. We consider our results together with radio observations that show evidence for poloidal fields in the Galactic center, and with Faraday rotation observations. We compare all of these observations with the predictions of a magnetodynamic model for the Galactic center that was proposed in order to explain the Galactic Center Radio Lobe as a magnetically driven gas outflow. We conclude that the observations are basically consistent with the model.

We use data from the White Dish experiment to set limits on cosmic microwave background radiation anisotropies in open and spatially-flat-Lambda cold dark matter cosmogonies. We account for the White Dish calibration uncertainty, and marginalize over the offset and gradient removed from the data. Our 2-sigma upper limits are larger than those derived previously. These upper limits are consistent with those derived from the $COBE$-DMR data for all models tested., Comment: 17 pages of latex. Uses aasms4.sty. 4 figures included. Submitted to ApJS

The third year of observations with the Python microwave background experiment densely sample a $5.5^o\times 22^o$ region of sky that includes the fields measured during the first two years of observations with this instrument. The sky is sampled in two multipole bands centered at $l \approx 92$ and $l \approx 177$. These two data sets are analyzed to place limits on fluctuations in the microwave sky at 90 GHz. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background we find flat band power estimates of $\delta T_l\equiv \sqrt{l(l+1)C_l/2\pi }% =54_{-12}^{+14}\mu K$ at $l=92_{-24}^{+37}$ and $\delta T_l=58_{-13}^{+15}\mu K$ at $l=177_{-58}^{+66}$. Combining the entire three year set of Python observations, we find that the angular power spectrum of fluctuations has a spectral index $m=.02_{-.16}^{+.18}$ and an amplitude $% \delta T_{l_e}=53_{-11}^{+13}\mu K$ at $l_e=145_{-74}^{+59}$ for the functional form $\delta T_l=\delta T_{l_e}(l/l_e)^m$. The stated uncertainties in the amplitudes and spectral index represent 1$\sigma $ confidence intervals in the likelihood added in quadrature with a 20\% calibration uncertainty and an estimate of the effects introduced due to imperfect overlap of the beams on the sky. The limits of $l$ are determined from the full width at half maximum of the window functions.

We present the first in-depth analysis of the massive cluster AS1063. This is one of the hottest X-ray clusters discovered to date and is undergoing a major merging event. The average temperature of the hot intracluster medium has been measured, using Chandra/ACIS-I, and found to be >11.5 keV. Optical spectroscopy, from GMOS-S, has provided a mean redshift of 0.3461 and a large velocity dispersion of 1840^(+230)_(–150) km s^(–1). Both the large velocity dispersion and high X-ray temperature suggest a very massive cluster (M_(200) > 2.5 × 10^(15) M_☉) and/or a merger system. The merger model is supported by a small offset between the galaxy density and the peak of the X-ray emission, the presence of offset and twisted X-ray isophotes, and a non-Gaussian galaxy velocity distribution. We also report that the velocity distribution is better represented by the velocity dispersion produced during a merger than by the velocity distribution of a relaxed cluster. Moreover, we find that two non-concentric beta models are a better description for the distribution of the cluster gas than a single beta model. Therefore, we propose that a recent merger event close to the plane of the sky is responsible for the observed properties of the cluster. In addition, optical imaging, from SuSI2 on the New Technology Telescope and GMOS-S at Gemini, has also uncovered the presence of several gravitational arcs that have been used to further constrain the mass and dynamics of the cluster.

The design and performance of an instrument to measure cosmic microwave background (CMB) anisotropy on angular scales from 10’ to 30’ is reported. The instrument utilizes a single‐mode waveguide bolometer cooled by an adiabatic demagnetization refrigerator. This is the first time a 100 mK bolometer has been used in a CMB experiment. Observations of the CMB were made using this radiometer from the South Pole during the 1991–1992 season and, with minor modifications, during the 1992–1993 season. The radiometer is used with a fully steerable altitude‐azimuth Cassegrain telescope built for this observation, also described here.

Nitrogenase activity of washed Azotobacter vinelandii cells was enhanced by the addition of Ca2+ and Mg2+, and the enhancement increased with the O2 concentration. In assays provided with a level of O2 that was initially supraoptimal and inhibitory to nitrogenase activity, the addition of Ca2+ or Mg2+ affected both the maximum respiration rate (Vmax) of the cells and the apparent affinity [KS(O2)] of cell respiration for O2. Changes in these parameters correlated with changes in nitrogenase activity. Aeration-dependent increases in Vmax and KS(O2) were inhibited by rifampin and chloramphenicol and were also observed in ammonium-grown cultures.

In this paper, we present results from the complete set of cosmic microwave background (CMB) radiation temperature anisotropy observations made with the Arcminute Cosmology Bolometer Array Receiver (ACBAR) operating at 150 GHz. We include new data from the final 2005 observing season, expanding the number of detector-hours by 210% and the sky coverage by 490% over that used for the previous ACBAR release. As a result, the band-power uncertainties have been reduced by more than a factor of two on angular scales encompassing the third to fifth acoustic peaks as well as the damping tail of the CMB power spectrum. The calibration uncertainty has been reduced from 6% to 2.1% in temperature through a direct comparison of the CMB anisotropy measured by ACBAR with that of the dipole-calibrated WMAP5 experiment. The measured power spectrum is consistent with a spatially flat, LambdaCDM cosmological model. We include the effects of weak lensing in the power spectrum model computations and find that this significantly improves the fits of the models to the combined ACBAR+WMAP5 power spectrum. The preferred strength of the lensing is consistent with theoretical expectations. On fine angular scales, there is weak evidence (1.1 sigma) for excess power above the level expected from primary anisotropies. We expect any excess power to be dominated by the combination of emission from dusty protogalaxies and the Sunyaev-Zel'dovich effect (SZE). However, the excess observed by ACBAR is significantly smaller than the excess power at ell > 2000 reported by the CBI experiment operating at 30 GHz. Therefore, while it is unlikely that the CBI excess has a primordial origin; the combined ACBAR and CBI results are consistent with the source of the CBI excess being either the SZE or radio source contamination., Submitted to ApJ; Changed to apply a WMAP5-based calibration. The cosmological parameter estimation has been updated to include WMAP5

A high-frequency combination probe was used to measure dynamic flow quality in the test section of the NASA Langley 0.3-m Transonic Cryogenic Tunnel. The probe measures fluctuating stagnation (total) temperature and pressure, static pressure, and flow angles in two orthogonal planes. Simultaneous measurements of unsteady total temperature and pressure were also made in the settling chamber of the tunnel. The data show that the stagnation temperature fluctuations remain constant, and the stagnation pressure fluctuations increase by a factor of two, as the flow accelerates from the settling chamber to the test section. In the test section, the maximum rms value of the normalized fluctuating velocity is 0.7 percent. Correlation coefficients failed to show vorticity, entropy, or sound as the dominant mode of turbulence in the tunnel.

We report improved measurements of temperature anisotropies in the cosmic microwave background (CMB) radiation made with the Arcminute Cosmology Bolometer Array Receiver (ACBAR). In this paper, we use a new analysis technique and include 30% more data from the 2001 and 2002 observing seasons than the first release to derive a new set of band-power measurements with significantly smaller uncertainties. The planet-based calibration used previously has been replaced by comparing the flux of RCW38 as measured by ACBAR and BOOMERANG to transfer the WMAP-based BOOMERANG calibration to ACBAR. The resulting power spectrum is consistent with the theoretical predictions for a spatially flat, dark energy dominated LCDM cosmology including the effects of gravitational lensing. Despite the exponential damping on small angular scales, the primary CMB fluctuations are detected with a signal-to-noise ratio of greater than 4 up to multipoles of l=2000. This increase in the precision of the fine-scale CMB power spectrum leads to only a modest decrease in the uncertainties on the parameters of the standard cosmological model. At high angular resolution, secondary anisotropies are predicted to be a significant contribution to the measured anisotropy. A joint analysis of the ACBAR results at 150 GHz and the CBI results at 30 GHz in the multipole range 2000 < l < 3000 shows that the power, reported by CBI in excess of the predicted primary anisotropy, has a frequency spectrum consistent with the thermal Sunyaev-Zel'dovich effect and inconsistent with primary CMB. The results reported here are derived from a subset of the total ACBAR data set; the final ACBAR power spectrum at 150 GHz will include 3.7 times more effective integration time and 6.5 times more sky coverage than is used here., 19 pages, 9 figures, ApJ

We present the design of a novel bolometer intended for measurement of radiation within a waveguide. The thermal link in the bolometer is a low-thermal conductance micromachined beam. Power is coupled from an antenna to a resistive termination at the center of the beam. The optimization of the design for an astronomical measurement leads to an operating temperature of 0.48 K, accessible with a He3 refrigerator. Measurements on the antenna absorber in a waveguide show an average absorption of 94% from 33 to 50 GHz.

We present detections of the Sunyaev-Zeldovich Effect (SZE) at 150GHz and 275GHz for the X-ray luminous z=0.299 cluster 1E0657-67. These observations were obtained as part of an X-ray, weak lensing, and SZE survey of nearby X-ray bright clusters. The SZE maps were made with the ACBAR (150, 210, 275 GHz) bolometer array installed at the Viper telescope located at the South Pole. We also present preliminary results from a blind SZE cluster survey., 6 pages, 1 color figure, proceedings from the Symposium: "Plasmas in the Laboratory and in the Universe: new insights and new challenges", September 16-19, 2003, Como, Italy

We review the first science results from the Arcminute Cosmology Bolometer Array Receiver (ACBAR); a multifrequency millimeter-wave receiver optimized for observations of the Cosmic Microwave Background (CMB) and the Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies. ACBAR was installed on the 2 m Viper telescope at the South Pole in January 2001 and the results presented here incorporate data through July 2002. We present the power spectrum of the CMB at 150 GHz over the range \ell = 150 - 3000 measured by ACBAR as well as estimates for the values of the cosmological parameters within the context of Lambda-CDM models. We find that the inclusion of Omega_Lambda greatly improves the fit to the power spectrum. We also observe a slight excess of small-scale anisotropy at 150 GHz; if interpreted as power from the SZ effect of unresolved clusters, the measured signal is consistent with CBI and BIMA within the context of the SZ power spectrum models tested., To be published in the proceedings of "The Cosmic Microwave Background and its Polarization", New Astronomy Reviews, (eds. S. Hanany and K.A. Olive). 10 pages, 2 figures

We describe the Arcminute Cosmology Bolometer Array Receiver (ACBAR); a multifrequency millimeter-wave receiver designed for observations of the Cosmic Microwave Background (CMB) and the Sunyaev-Zel'dovich effect in clusters of galaxies. The ACBAR focal plane consists of a 16-pixel, background-limited, 240 mK bolometer array that can be configured to observe simultaneously at 150, 220, 280, and 350 GHz. With 4-5' FWHM Gaussian beam sizes and a 3 degree azimuth chop, ACBAR is sensitive to a wide range of angular scales. ACBAR was installed on the 2 m Viper telescope at the South Pole in January 2001. We describe the design of the instrument and its performance during the 2001 and 2002 observing seasons., Comment: 59 pages, 16 figures -- updated to reflect version published in ApJS

The summit of Mauna Kea in Hawaii, the area near Cerro Chajnantor in Chile, and the South Pole are sites of large millimeter or submillimeter wavelength telescopes. We have placed 860 GHz sky brightness monitors at all three sites and present a comparative study of the measured submillimeter brightness due to atmospheric thermal emission. We report the stability of that quantity at each site., 6 figures

By mapping the cosmic microwave background (CMB) with an angular resolution of 4 arcminutes, the ACBAR receiver on the Viper telescope can be used to study dark matter in two ways — through measurement of the CMB anisotropy power spectrum and through a search for high redshift galaxy clusters.

The present study investigated cardiac response to acute alcohol challenge along the blood alcohol concentration (BAC) curve in two groups of young adult nonalcoholic men with (MFH) and without (FH-) multigenerational family histories of alcoholism, matched for drinking history. BACs and resting heart rate measurements were recorded every 10 min for 3 hr after ingestion of a 1.0 ml/kg dose of 95% USP alcohol at two different rates: one of 20 min (slow drinking) and the other of 5 min (fast drinking). Several analyses of variance were performed for each of the dependent measures [BAC and heart rate change from baseline (HRCH)]. A significant risk x BAC phase interaction emerged from the HRCH analysis, indicating that the MFH group was characterized by a significantly greater increase in resting heart rate along the ascending limb of the BAC curve. A significant risk x BAC phase x rate interaction indicated that, when alcohol was consumed at a faster rate, men with multigenerational family histories of alcoholism demonstrated a greater HRCH, which persisted throughout the BAC curve.

Individuals use and misuse alcohol (and other drugs) because of the pharmacologically mediated effects these substances have on the operation of 4 psychobiological systems, mediating response to motivationally relevant unconditioned and conditioned stimuli. These 4 systems have unique neuroanatomical structure, biochemical modes of operation, association with affect, behavior and cognition, and responsiveness to drugs of abuse. Individual variation in the operation of these systems determines individual susceptibility to initiation and maintenance of drug use and abuse. Sources of such variation differ, in a vitally important fashion, in various specific populations of individuals at heightened risk for drug abuse. Nonalcoholic sons of male alcoholics, with multigenerational family histories of male alcoholism, appear to be at heightened risk for the development of alcohol abuse because alcohol eliminates their heightened response to threat, and because they are hypersensitive to ethanol's psychomotor stimulant effects. Anxiety-sensitive individuals also appear attracted to alcohol for its anxiolytic properties. Many other important sources of idiosyncratic variability exist. Detailed analysis of such sources may lead to the development of more effective prevention and treatment programs.

This study investigated the relationships between provocation, acute alcohol intoxication, impaired frontal-lobe function, and aggressive behavior. The authors ranked 114 men according to their performance on two neuropsychological tests associated with frontal-lobe function. Forty-eight men (24 with scores in the upper and 24 with scores in the lower performance quartiles) participated in the full study. Half completed and aggression task while intoxicated, the remainder while sober. Aggression was defined as shock intensity delivered to a sham opponent. Shock intensity significantly increased as a main effect of provocation, alcohol intoxication, and lower cognitive performance. Furthermore, provocation interacted significantly with test performance such that individuals in the lower cognitive performance quartile responded to increased provocation with heightened aggression.

The existence of a relationship between cardiovascular reactivity to signalled shock and alcohol consumption can be inferred from studies of males at increased familial risk for alcoholism. The present study examined two groups of nonalcoholic men--those with multigenerational histories (MGH) of alcoholism and family--history negative (FH-) controls-to determine whether reactivity was related to voluntary ethanol consumption in the context of a beverage taste test. High reactors, a significant majority of whom were MGH males, drank significantly more vodka and orange juice, rum and coke, and orange juice when asked to rate the flavor of three alcoholic and two nonalcoholic drinks. High reactors also consumed more alcohol on a weekly basis according to their self-report.

Numerous studies have demonstrated the existence of an association between alcoholism and antisocial personality (ASP). The present study tested two hypotheses: First, that nonalcoholic men with a multigenerational familial history (MGH) of alcoholism would play more cards on a card task that has been shown previously to differentiate antisocial populations from normals and, second, that MGH subjects would display more evidence of ASP on two personality questionnaires: The Self-Report Psychopathy scale and the Socialization scale of the California Psychological Inventory. A total of 28 subjects (14 MGH and 14 family history negative for alcoholism [FH-]) were employed in this study. MGH subjects played significantly more cards during the card task than did FH- subjects. However, the two groups did not differ on the ASP questionnaires. The possibility that a subtle frontal-lobe deficit, rather than ASP per se, underlies the poorer performance of the MGH males is discussed.

Sons of male alcoholics are at increased risk for the development of alcoholism, and are characterized as well by other traits, that may serve as markers for the alcoholic predisposition. These other traits include mild cognitive abnormalities, cardiac hyper-reactivity to signalled electric shock, susceptibility to alcohol-intoxication elimination of that hyper-reactivity, and increased baseline heart-rate while drinking.

After a brief review of fluid mechanics scaling, the rationale for testing in the National Transonic Facility (NTF) for ship hydromechanics purposes is discussed. Some pertinent details of the “1986 Body of Revolution Experiment” are presented along with possibilities for a “Future Body of Revolution Experiment” and a “Future Rat Plate Experiment”. Finally NTF testing is considered from the “hydrodynamic” users point of view and a brief comparison is made between the NTF and the Conceptual Helium Tunnel (CHT), which is of major interest to this Conference.

Recent measurements of the diffuse background at millimeter wavelengths indicate no departure from a Planck spectrum near the peak of the blackbody curve. Anisotropy measurements indicate no structure, at the 2% level, in the recently detected submillimeter excess.

We have observed sharp resonances in the absorption of microwave radiation (30 to 50 GHz) in the vortex state of Bi 2 Sr 2 CaCu 2 O 8+δ . The unusual dispersion and temperature dependence suggest the excitation of an electronic mode strongly coupled to the vortex lattice.

With a bolometric technique, we have measured, in intense fields, the low temperature microwave surface resistance of 90-K and 60-K YBCO single crystals. From the viscosity inferred from the field dependence of surface resistance, the quasiparticle scattering rate 1/τ in the vortex core of YBCO is found to be strongly suppressed. The long relaxation times of quasiparticle place YBCO in the “superclean regime” where the lifetime broadening of the core energy levels is much less than the energy spacing.

Observations of a low-background region of sky at high Galactic latitude in a frequency band centered at nu = 90 GHz reveal highly significant detections of anisotropy on intermediate (aprroximately 1 deg) angular scales. The instrument is a 2 x 2 array of bolometric detectors operating at 50 mK, coupled to a 0.75 m off-axis parabolic telescope by single-mode corrugated feedhorns. The FWHM beamwidth of the instrument is 0.75 deg, with a beamswitch of +/- 2.75 deg on the sky. Interpreting the detected fluctuations as due to anisotropy in the cosmic microwave background, a likelihood analysis assuming a Gaussian correlation function in the temperature fluctuations yields most likely values of (delta T)/T of 3.1(sub -0.9)(sup +2.5) x 10(exp -5) and 3.8(sub -1.2)(sup +2.9) x 10(exp -5) at a coherence angle of 1.0 deg, for the left- and right-hand detectors, respectively. The stated errors are 95% confidence limits. Confirmation at other frequencies is required to rule out the possibility of foreground contamination.

We report the preliminary result of a search for cosmic microwave background (CMB) anisotropy. We made observations using a specially designed radiometer and on-axis Cassegrain telescope. The beam size was 12' at a frequency of 90 GHz. Observations were made during 1993 January from the South Pole. We observed five regions of sky near declination -75°, and set a 95% confidence level upper limit of ΔT< 2.3×10 -5 T CMB on Gaussian-correlated CMB anisotropy at an angular scale of O°. 15. This is the lowest upper limit to date on CMB anisotropy at this angular scale

The consequence of the existence, when a lens is present, of two propagation paths from a source to the observer is investigated. Attention is focused on quasars as background sources; however, the results received are general and apply to pulsars and stellar sources as well. 12 refs.

Measured position angles of 149 galaxies that lie in a sheet near the void in Corona Borealis are presented. The distribution of positions and position angles is tested for alignment; none is detected. 17 refs.

The brightness temperature of the sky is measured in five bands from 1 to 3 mm using apparatus related to that of Woody and Richards (1981) and Peterson et al. (1985). Examination of the data reveals the presence of two previously unknown systematic effects which limit the accuracy of the measurements. Similar systematic effects are most likely present in the data obtained previously with this apparatus. Upper limits to the temperature of the cosmic background radiation are set in four bands; the most stringent is T(CBR) less than 2.88 K at 1.1 mm (95 percent CL).

We have calculated and measured the reflectance of a variety of absorbers for cryogenic waveguide bolometers. The best absorber has

An overview of the actual technical status and achievements of different types of cryogenic detectors is given. Typical applications in several fields are discussed with emphasis put on appropriate nuclear experiments for the planned Princeton facility. The possibility of implementation in low temperature nuclear orientation experiments will be explored.

Tn5 was introduced into Alcaligenes eutrophus strain H1 by a suicide vector pSUP1011. Physical characterization of mutants obtained after Tn5 mutagenesis revealed a relatively high frequency of plasmid curing, or deletion of a 50 kb plasmid DNA segment. Results of Southern hybridization and chromosomal walking indicate that the same continuous stretch of plasmid DNA (designated as D region of plasmid) is deleted in four independent isolates. Moreover, the same deletion of plasmid DNA is also observed in a mitomycin C-generated mutant strain H1-4.

The present cryogenic blackbody reference, or 'cold load', for mm-wavelength radiation has an emissivity of more than 0.99 over a two-octave wavelength range and can be used as a calibrating standard for sensitive IR photometers. The transmittance spectrum obtained indicates that wave impedance and index do not vary significantly over the 80-360 GHz range.

The spectrum of the cosmic background radiation in five frequency bands extending from 2.3 to 11.0 cm with a balloon-borne liquid-helium-cooled photometer. The photometer compares the flux from the sky to the flux from an internal blackbody at 3.2 K. All five measurements are consistent with temperatures in the range 2.78 + or = 0.11 K, which is in good agreement with tempratures measured at lower frequencies. No significant deviation from a thermal spectrum was found.

Immobilization of Paramecium followed the binding of antibodies to the major proteins of the ciliary membrane (the immobilization antigens, i-antigens, approximately 250,000 mol wt). Immunoelectron microscopy showed this binding to be serotype-specific and to occur over the entire cell surface. Antibody binding also reduced the current through the Ca-channel of the excitable ciliary membrane as monitored using a voltage-clamp. The residual Ca-current appeared normal in its voltage sensitivity and kinetics. As a secondary consequence of antibody binding, the Ca-induced K-current was also reduced. The resting membrane characteristics and other activatable currents, however, were not significantly altered by the antibody treatment. Since monovalent fragments of the antibodies also reduced the current but did not immobilize the cell, the electrophysiological effects were not the secondary consequences of immobilization. Antibodies against the second most abundant family of proteins (42,000-45,000 mol wt) had similar electrophysiological effects as revealed by experiments in which the Paramecia and the serum were heterologous with respect to the i-antigen but homologous with respect to the 42,000-45,000-mol-wt proteins. Protease treatment, shown to remove the surface antigen, also caused a reduction of the Ca-inward current. The loss of the inward Ca-current does not seem to be due to a drop in the driving force for Ca++ entry since increasing the external Ca++ or reducing the internal Ca++ (through EGTA injection) did not restore the current. Here we discuss the possibilities that (a) the major proteins define the functional environment of the Ca-channel and that (b) the Ca-channel is more susceptible to certain general changes in the membrane.