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We have measured the terahertz spectrum of pure l-tyrosine at nineteen temperatures in the range 6K to 300K using a synchrotron as the source of radiation. By fitting the temperature dependence of the observed modes with a Bose-Einstein model, we determine unequivocal low-frequency modes of l-tyrosine at absolute zero temperature occur at 1.02 ± 0.01, 1.61 ± 0.01, 1.97 ± 0.01, and 2.19 ± 0.01THz. This determination is consistent with the more reliable of the earlier measurements. We conclude that many of the recently reported features in the terahertz spectrum of l-tyrosine are experimental artefacts.

The concept of a pharmacophore has been very useful in the field of drug design, to explain the structure–activity of a series of ligands, and to search for new or alternative chemotypes. We start by placing pharmacophores in their biological context, to discuss the best situations for their use. The next section deals with the fundamentals of pharmacophore elucidation, dealing with feature definition and the role of protonation and tautomer states. Methods for aligning the feature model and for scoring the alignment are then presented. The final sections deal with the use of pharmacophores and the issues that can arise in their application.

Several CIDP patients need long-term corticosteroids or intravenous immunoglobulin (IVIG), with IVIG being associated with improved safety profile. SCIG is an alternative option for immunoglobulin delivery but it was not investigated in large-scale trials in CIDP. PATH was a randomized, double-blind trial investigating 0.2 and 0.4 g/kg weekly doses of SCIG IgPro20 (Hizentra®, CSL Behring) versus placebo for maintenance treatment in 172 CIDP patients. IVIG-dependent adults with definite or probable CIDP were eligible. The primary outcome was the percentage of subjects with a CIDP relapse (1-point deterioration on adjusted INCAT disability score) or who were withdrawn for any reason during the 24-week SCIg-treatment. Multiple secondary endpoints were assessed. Overall, 33% of patients on high-dose SCIG, 39% of those on low-dose SCIG and 63% of placebo recipients experienced CIDP relapse or were withdrawn from treatment (p

Albinism is a group of inherited conditions in which affected individuals have less than normal pigment in the eyes, skin, and hair compared to others of the same race and ethnic background. The prevalence of all types of albinism in the United States is estimated at 1 in 20,000, based on poor epidemiological data. X-linked Nettleship-Falls ocular albinism (XLOA, OA1) affects approximately 1/150,000 males in the population. XLOA effects reduce visual acuity and nystagmus, result in a mild skin and hair phenotype, and occur mostly in XY males. Female carriers of XLOA have normal visual acuity, but often show iris punctate transillumination and a classic pattern of mosaic retinal pigmentation, coarse and grainy in the macula and becoming increasingly reticular into the periphery of the retinal pigment epithelium. Studies of OA1 have shown linkage of a single gene to markers at Xp22.3-p22.2. About 48% of the reported mutations in the OA1 gene are intragenic deletions and about 43% are point mutations. We present a hierarchical strategy for mutation screening for diagnostic testing for OA1 that comprises two tiers: first, multiplex PCR to detect intragenic deletions in the OA1 gene with denaturing high-performance liquid chromatography (dHPLC), and, second, heteroduplex analysis with dHPLC to scan for mutations, with subsequent sequencing of variants to confirm putative mutations in the OA1 gene. Prenatal diagnosis can be provided for families when the mutation has been firmly identified. We have validated this procedure with positive controls that were identified in patients by Southern blot, single-stranded conformation polymorphism (SSCP), and sequencing. In this hierarchical strategy, these procedures have an analytical sensitivity of99%.

The study of CPT invariance with the highest achievable precision in all particle sectors is of fundamental importance for physics. Equally important is the question of the gravitational acceleration of antimatter. In recent years, impressive progress has been achieved at the Low Energy Antiproton Ring (LEAR) at CERN in capturing antiprotons in specially designed Penning traps, in cooling them to energies of a few milli-electron volts, and in storing them for hours in a small volume of space. Positrons have been accumulated in large numbers in similar traps, and low energy positron or positronium beams have been generated. Finally, steady progress has been made in trapping and cooling neutral atoms. Thus the ingredients to form antihydrogen at rest are at hand. We propose to investigate the different methods to form antihydrogen at low energy, and to utilize the best of these methods to capture a number of antihydrogen atoms sufficient for spectroscopic studies in a magnetostatic trap. Once antihydrogen atoms have been captured at low energy, spectroscopic methods can be applied to interrogate their atomic structure with extremely high precision and compare it to its normal matter counterpart, the hydrogen atom. Especially the 1S-2S transition, with a lifetime of the excited state of 122 ms and thereby a natural linewidth of 5 parts in 1016, offers in principle the possibility to directly compare matter and antimatter properties at a level of 1 part in 1018. Additionally, comparison of the gravitational masses of hydrogen and antihydrogen, using either ballistic or spectroscopic methods, can provide direct experimental tests of the Weak Equivalence Principle for antimatter at a high precision.

The time-varying gravitational field produced by a Weber bar is used to explore mathematical features of the linearized Einstein equation. We present a self-contained formal framework for the treatment of the linear field, which is applicable to several situations where the standard quadrupolar formulas are not adequate. The expressions for retarded integrals reveal a singularity associated with boundary conditions. Results from the transverse traceless subgauge are compared with the radiation calculated from retarded integrals. Lienard-Wiechert potentials are used in a treatment of the Weber bar as a collection of point particles and further possible applications are outlined. The Riemann tensor clarifies the transition from near-field geodesic forces to tidal forces in the far field., 27 pages, 5 figures. Submitted to J. Math. Phys

Osmotic swelling of fish erythrocytes activates a broad-specificity permeation pathway that mediates the volume-regulatory efflux of taurine and other intracellular osmolytes. This pathway is blocked by inhibitors of the erythrocyte band 3 anion exchanger, raising the possibility that band 3 is involved in the volume-regulatory response. In this study of eel erythrocytes, a quantitative comparison of the pharmacology of swelling-activated taurine transport with that of band 3-mediated SO4(2-) transport showed there to be significant differences between them. N-ethylmaleimide and quinine were effective inhibitors of swelling-activated taurine transport but caused little, if any, inhibition of band 3. Conversely, DIDS was a more potent inhibitor of band 3-mediated SO4(2-) flux than of swelling-activated taurine transport. In cells in isotonic medium, pretreated then co-incubated with 0.1 mM DIDS, the band 3-mediated transport of SO4(2-) and Cl- was reduced to a low level. Exposure of these cells to a hypotonic medium containing 0.1 mM DIDS was followed by the activation of a Cl- permeation pathway showing the same inhibitor sensitivity as swelling-activated taurine transport. The data are consistent with swelling-activated transport of taurine and Cl- being via a common pathway. A comparison of the swelling-activated transport rates for taurine and Cl- with those for several other solutes was consistent with the hypothesis that this pathway is an anion-selective channel, similar to those that mediate the volume-regulatory efflux of Cl- and organic osmolytes from mammalian cells.

We have magnetically driven a tapered-thickness spherical aluminum shell implosion with a 12.5 MA axial discharge. The initially 4 cm radius, 0.1 to 0.2 cm thick, [plus minus]45[sup [degree]] latitude shell was imploded along conical electrodes. The implosion time was approximately 15 [mu]sec. Radiography indicated substantial agreement with 2D-MHD calculations. Such [ital calculations] for this experiment [ital predict] final inner-surface implosion velocity of 2.5 to 3 cm/[mu]sec, peak pressure of 56 Mbar, and peak density of 16.8 g/cm[sup 3] ([gt]6 times solid density). The principal experimental result is a demonstration of the feasibility of electromagnetic-driven spherical liner implosions in the cm/[mu]sec regime.

Six design options for a scintillating fiber inner tracker for the SDC detector operating at the Superconducting Super Collider (SSC) are simulated. Concentric cylindrical configurations of axial fiber superlayers, ranging from four to six in number, are considered. Tracks from events generated by Pythia 4.8 at rates up to ten times design luminosity are swum through the tracker. Algorithms for reconstructing tracks of physics interest with p T > 10 GeV/ c among a background of low p T tracks are described. The optimum configuration found permits level 1 triggering up to η = 2.3 at ten times design luminosity. Inclusion of additional stereo fibers in this configuration permits level 2 stereo reconstruction up to eight times design luminosity.

Trackers based on scintillating-fiber technology are being considered by the Solenoidal Detector Collaboration at SSC and the DO collaboration at Fermilab. Some 600 fibers in the Fermilab Tevatron CO area were irradiated, thereby obtaining a hadronic irradiation at realistic rates. Four-meter-long samples of ten Bicron polystyrene-based fibre types, maintained in air, dry nitrogen, argon, and vacuum atmospheres within stainless-steel tubes, were irradiated for seven weeks at various distances from the accelerator beam pipes. Maximum doses, measured by thermoluminescence detectors, were about 80 krad. Fiber properties, particularly light yield and attenuation length, were measured over a one-year period. A description of the work together with the results is presented. At the doses achieved, corresponding to a few years of actual fiber-tracking detector operation, little degradation was observed. Recovery after several days' exposure to air was noted. Properties of unirradiated samples kept in darkness show no changes after one year. >

We present measurements of the 2π0 mass spectrum in proton—antiproton annihilations. The f2 (1520) resonance is strongly produced in the 3π0 channel. Its production along with an η is observed, but strongly suppressed. Other features are seen in the data, including the f2 (1270) and structures at 2000 MeV/c2 and above.

A test facility to study the light-transmission properties of scintillating fiber waveguides for tracking applications in high-energy physics is being developed. A light-tight box 2 m in length has been built, and data acquisition hardware and software is in place for testing various aspects of scintillating fibers and waveguides. Scintillating fibers have been excited with radioactive sources, ultraviolet light sources, and light-emitting diodes. Various photodetectors such as photomultiplier tubes, photodiodes, charge-coupled devices and solid-state photomultipliers have been utilized to detect the transmitted light. Studies of attenuation length and transmission through splices are presented. >

During a balloon flight in July 1987 of the MIFRASO hard X-ray telescope, a single drift-scan observation was performed to survey a region of the sky containing the galactic black hole candidate Cyg X−1. In about 900 seconds of on-source useful data, Cyg X−1 was detected in the energy range 15–300 keV with a high degree of statistical significance. The photon spectrum is well described by either a single power law with a photon index of α = 1.9 ± 0.07 or a Comptonized model characterized by an electron temperature of kT = 56 ± 9 keV and an optical depth of τ = 2.3 ± 0.3. The measured flux values suggest that during the MIFRASO observation the source was in the so called ‘superlow’ state.

High energy observation of the Coma Cluster of Galaxies was obtained during a balloon flight on July 15, 1987 with the MIFRASO telescope over the photon energy range 18 + 130 keV. The data have been obtained from the scintillation detector array and two proportional counters. The source excesses detected correspond to a statistical significance of 5.0 σ and 5.1 σ respectively. The present data are compared with previous observations of Coma Cluster and interpreted in terms of the Inverse Compton (IC) emission model. The existence of active galaxies associated with the Cluster as possible origin of the detected hard X-ray emission is also discussed.

Terahertz emission from (100) p-type InAs illuminated by ultrafast near-infrared pulses is investigated. A two-fold rotational symmetry was observed when rotated about the surface normal. A quadratic relationship was found for the emission dependence on optical pump power. These suggest the presence of photocarrier transport and optical rectification mechanisms. The InAs emission was found to exceed that of a blackbody radiator for frequencies below 1 THz for nominal input power levels. The generated power was found to be roughly two orders of magnitude greater than a 1mm ZnTe emitter.

This paper describes an investigation into millimetric antennas for future telematic applications. System studies have been performed on the basis of current transponder technology at 63 GHz and have shown that for adequate communications to roadside beacons and other vehicles two or three antennas will be needed. The required antenna gain and efficiency can be met with microstrip antenna types. Patch or microstrip rampart line arrays have been examined. A novel beam shaping method for the rampart array has been developed. Active integrated antennas also show potential for vehicle systems at 63 GHz and some initial results are presented. These could be useful for the low gain antennas integrated with the millimetric front-end. A study of mounting options shows that in-bumper or behind the number plate location is preferred.

Modern phased array radar applications require large radiating apertures that are protected from the environment by an RF-transparent radome. Radome design requires many compromises between RF loss, mechanical strength, environmental effects, ease of manufacture and cost. Phased arrays in naval applications are mounted high on the topside structure in order to maximise system performance, including radar range, so that radome weight must also be minimised in order to limit adverse effects on the stability/turning moment of the ship. Together, these factors make design and manufacture of radomes a challenging task. Manufacture of radomes utilises a number of established techniques and materials. In manufacture it is important to identify realistic tolerances and practical manufacturing methods in order to identify a radome design that is practical and economic to build, rather than trying to pursue an unattainable or expensive design that is over-toleranced. This paper describes the design of an S-band radome for a naval radar application; calculation of the radome performance; and the use of a quasi-optical focused beam range and reflectivity arch to verify the performance predictions.

Scintillating fiber tracking detectors are being developed for the SDC experiment at Superconducting Super Collider (SSC) and the upgrade of the D0 detector at the Fermilab Tevatron. The many attractive features of a fiber tracker include good position resolution, low occupancy, low mass in the active volume, and excellent resistance to radiation damage. An additional important feature, especially at the SSC, is the intrinsically prompt response time of a scintillating fiber. The photodetector of choice is the visible light phonon counter (VLPC), a device which combines high rate capability with high quantum efficiency at visible wavelengths. To realize the high rate capability of the VLPC requires the implementation of a suitable, fast preamplifier. Until recently, studies of fibers and VLPCs with radioactive sources and cosmic rays have been performed under low rate conditions using transimpedance amplifiers (TIAs). The authors report on the response characteristics of a fiber-VLPC system coupled to a variety of fast preamplifiers, including QPA02, VTX, and TVC devices. Their performance is compared with that of a transimpedance amplifier. >

The parasitic capacitances, self-, and mutual-inductances of the Power Electronic Building Block (PEBB-1) module are extracted using a 3-D field solver. The elements are included in a circuit simulation of the Auxiliary Resonantly Commutated Pole (ARCP) converter topology. Comparisons of the performance with and without the parasitic elements is provided. Alternate control schemes are evaluated to compensate for the increased package losses.

The switching characteristics of 4H-SiC asymmetric GTO thyristors are studied and compared to Si-based IGBTs, MCTs and MOSFETs. Forward current density, turn-off time and forward blocking voltage parameters are matched for the various switching devices. From the measurements, the necessary parameters were extracted to develop a simple PSPICE circuit model for the SiC GTO. The simulated response of the model is compared to the experimental response of the device.

Linearly polarised Vivaldi radiating elements were introduced by Gibson (1979) and have received wide attention due to their broad bandwidths and relative ease of manufacture. Development of Vivaldi elements with a dual-polar capability is more complex because of the non-planar antenna geometry and feed configuration. Also, in array applications, the element design must take account of the complex mutual coupling environment at the array aperture. Prediction of the coupling environment, and in particular the variation of the antenna match with array scan angle, requires use of full-wave electromagnetic modelling techniques. In this paper, we describe the design and evaluation of dual-polar Vivaldi elements optimised for operation in the array environment with frequency bandwidths of up to 3:1 and scan angles of up to 60/spl deg/. The wide-angle scan performance of elements immersed within infinite arrays has been modelled using FDTD techniques. Comparison of FDTD predictions with the measured performance of isolated elements is presented. The wide scan range and bandwidth requirements required the use of customised "blind-mate" connectors.

The requirements for antennas for future telematic systems at 63 GHz have been considered. Making reasonable assumptions about other terms in link budget calculations leads to an antenna directivity requirement of -2ldBi for communication with roadside beacons. However, communication with near by vehicles requires null-free coverage at wide angles. Additional requirements are that the antenna should be low cost, unobtrusive on the vehicle and tolerant to a range of climatic conditions. Two antenna options have been considered in detail. A single aperture antenna, consisting of a mechanically scanned shaped reflector, has been successfully designed and built. This antenna has demonstrated the successful application of shaped reflector synthesis software, originally written for the design of satellite antennas, to antennas with wide-angle coverage for automotive applications. (6 pages)

A shaped beam reflector antenna suitable for future telematic systems has been successfully demonstrated at 63 GHz. This has shown that reflector profile synthesis based on an aperture plane approach can be applied to highly shaped beams extending over wide angular regions. The antenna performance can be significantly modified by scattering from the feed and surrounding structures. These effects can be predicted by use of the FDTD method of analysis in place of a more conventional physical optics approach which neglects nearby dielectric bodies. This allows the investigation of antenna performance when installed in a wide range of locations on motor vehicles. Potential low cost manufacturing techniques have been identified and it is believed that a millimetre-wave reflector antenna could be economically viable for the consumer automotive market.

This paper describes an X-band antenna for use in an experimental airborne radar system. The antenna is designed to radiate either linear or circular (CP) polarisation and generates monopulse sum (/spl Sigma/) and difference (/spl Delta/) beams in azimuth. The antenna has two interchangeable gain modes of operation. Achieving the exacting antenna performance required a close interaction between electrical and mechanical design. Low cross-polar and sidelobe levels have been achieved through precision manufacturing of the antenna components. High performance is achieved from within a compact (470 mm high) radome by using CAD techniques to ensure efficient use of the swept volume. The mass and moments of inertia have been minimised, in order to be compatible with a 360/spl deg/ rotating scanner platform, by extensive use of CAD and stress-analysis tools.

We report on a search for metastable positively and negatively charged states of strange quark matter in Au+Pb reactions at 11.6 A GeV/c in experiment E864. We have sampled approximately six billion 10% most central Au+Pb interactions and have observed no strangelet states (baryon number A < 100 droplets of strange quark matter). We thus set upper limits on the production of these exotic states at the level of 1-6 x 10^{-8} per central collision. These limits are the best and most model independent for this colliding system. We discuss the implications of our results on strangelet production mechanisms, and also on the stability question of strange quark matter., 21 pages, 9 figures, to be published in Nuclear Physics A (Carl Dover memorial edition)

A 96-channel, 3-superlayer, scintillating-fiber tracking system has been tested in a 5 GeV/ cπ − beam. The scintillating fibers were 830 μm in diameter, spaced 850 μm apart, and 4.3 m in length. They were coupled to 6 m long, clear fiber waveguides and finally to visible light photon counters. A spatial resolution of ∼ 150 μm for a double-layered ribbon was achieved with this tracking system. This first prototype of a charged-particle tracking system configured for the Solenoidal Detector Collaboration at the Superconducting Super Collider is a benchmark in verifying the expected number of photoelectrons from the fibers.

Cyclotron resonance has been employed to explore the effects of substrate orientation and carrier concentration on the valence band structure of strained InxGa1−xSb/GaSb quantum wells. The in-plane masses are much reduced by the strain decoupling of the heavy-hole and light-hole levels. We find that the in-plane mass is lower for [1 1 1] growth than for [0 0 1] growth, which we relate to the fact that γ3>γ2 (Luttinger parameters). [1 1 1] samples were grown with high carrier concentrations (∼5×1011 cm−2) by exploiting the modifications to the band profile induced by the piezoelectric field. For filling factors v M J =± 3 2 . The results show that the first M J =± 3 2 levels are more strongly coupled to the light-hole states than the first M J =- 3 2 levels. This behaviour is verified by k·p theory calculations of the Landau levels.

We present the first high-statistics study of the ηη system over the mass range 1000–3000 MeV/c2. The experiment was performed at the Fermilab Antiproton Accumulator, and the data sample consists of six-photon final states produced in antiproton-proton annihilations at s in the range 2950–3620 MeV. We find evidence for three states with masses 1488 ± 10 MeV/c2, 1748 ± 10 MeV/c2 and 2104 ± 20 MeV/c2 respectively.

The Fiber Tracking Group (FTG) of the Solenoidal Detector Collaboration (SDC) is developing a high rate tracking subsystem appropriate for the SDC detector based on scintillating fiber (SciFi) technology. In the past two years a major upgrade in the design was conceived, which reduces the material and cost of the tracker and improves the effectiveness of the tracking system as a trigger element. The results of simulations of the performance of the tracker at Penn State have been very important in keeping the SciFi technology as an attractive option for a tracking system for the SDC collaboration. In the past year an array of scintillating fiber elements has been evaluated in a test beam at Brookhaven. Past experience of Penn State personnel at Brookhaven proved valuable in making the test beam runs a success.

The Fiber Tracking Group (FTG) of the Solenoidal Detector Collaboration (SDC) is developing a high rate tracking subsystem appropriate for the SDC detector based on scintillating fiber (SciFi) technology. In the past two years a major upgrade in the design was conceived, which reduces the material and cost of the tracker and improves the effectiveness of the tracking system as a trigger element. The results of simulations of the performance of the tracker at Penn State have been very important in keeping the SciFi technology as an attractive option for a tracking system for the SDC collaboration. In the past year an array of scintillating fiber elements has been evaluated in a test beam at Brookhaven. Past experience of Penn State personnel at Brookhaven proved valuable in making the test beam runs a success.

This report discusses the following topics on the Soleoidal Detector Collaboration: Summary and overview of the detector; physics and detector requirements; central tracking system; superconducting magnet; calorimetry; muon system; electronics; online computing; offline computing; safety; experimental facilities; installation; test and calibration beam plan; and cost and schedule summary.

The object of this paper is to describe a novel approach for designing molecules by computer. The goal is to provide an interactive system that will use the forces of molecular recognition and expert input from an organic chemist to design lead compounds that are synthetically and biologically viable. When the binding site of a receptor is known through pharmacophoric mapping or x-ray crystallography, rational computer-aided design of novel lead compounds offers the hope of avoiding the shortcomings associated with the present methods of discovery by chance or mass-screening, as well as using any knowledge of mechanism that might be available.

Ulcerative colitis is one of the few diseases in which smoking appears to confer some benefit (1). We report a patient whose ulcerative colitis deteriorated on several occasions on stopping cigarettes, and improved on restarting smoking. As a result, she continued smoking despite developing airflow limitation and severe emphysema. She was subsequently found to have α 1 anti-trypsin deficiency. She later noticed that she could get a similar benefit in her colitis with nicotine chewing gum as she had with cigarettes. For patients with smoking-responsive ulcerative colitis, non-tobacco forms of nicotine delivery such as gum or transdermal patches should be considered to avoid the hazards of cigarette smoke.

The pp annihilation cross section has been measured with good resolution (∼ 2 MeV RMS) in the mass range 1900–1960 MeV. No narrow structures are seen, the 90% confidence level upper limit being 8–12 mb MeV for the integrated area of a resonance in this mass range. However, we do not rule out a very narrow bump-dip structure seen in an earlier experiment in the 1935–1941 MeV mass interval. The data also do not support the existence of a broad structure previously reported at 1937 MeV.

We report on the data analysis and techniques used to determine particle identification from the relativistic rise in ionization as detected by CRISIS, a 1 × 1 × 3 m 3 , 192 cell, ionization-sampling drift chamber containing an 80% argon/20% carbon dioxide gas mixture. For 100 GeV/ c protons/antiprotons (pions) we obtain an ionization FWHM of 7.6% (7.9%), which compares well with the design value of 7.8%. The separation between the mean ionization values for the protons and pions was determined to be 7.9%. We also present the analysis of particle identification for secondary particles produced by interactions in the bubble chamber. A statistical method for correcting for the overlapping ionization curves from secondary protons/antiprotons and pions is discussed.

Aminozolamide (6-amino-2-benzothiazolesulfonamide) is a carbonic anhydrase inhibitor derived from ethoxzolamide that has been shown in gel formulation to lower IOP in rabbits, primates and humans. This study was designed to determine whether aminozolamide in suspension was also effective in lowering IOP. In separate single dose and multiple dose studies, patients with ocular hypertension were tested over 24 hours. No statistically significant drop in intraocular pressure was noted between the treated and control eye. In addition, conjunctival injection was noted in three of eleven subjects after multiple dosing. These studies suggest that retention of aminozolamide at the active site is inadequate when delivered in a suspension vehicle. In the past 10 years, efforts to develop an effective topical carbonic anhydrase inhibitor have been vigorously pursued. This has been aided by advancements in drug delivery and chemical synthesis involving molecular modification of existing carbonic anhydrase inhibitors. Various compounds have been developed that retain carbonic anhydrase inhibitory activity, penetrate the cornea and optimize the other important pharmacokinetic properties to lower intraocular pressure. One such compound, aminozolamide (6-amino-2-benzothiazolesulfonamide) is derived from ethoxzolamide. In suspension, it has been shown to lower IOP in rabbits and primates. It also has been shown to lower IOP in patients with ocular hypertension when delivered in a gel vehicle. The carbomer gel vehicle, a drug delivery system also used with pilocarpine (Pilopine HS), is used to prolong ocular contact and enhance penetration. The importance of the role of the vehicle in a topical carbonic anhydrase inhibitor has not been assessed.(ABSTRACT TRUNCATED AT 250 WORDS)

The problem of sudden and unexpected death after the parenteral administration of a therapeutic dose of choloroquine in fibrile patients was investigated using rabbits. Hyperthermia was produced in both conscious and anaesthetized rabbits using a Megatherm Junior diathermy machine. Lead II of the electrocardiogram, respiration and blood pressure were monitored during slow i.v. injection of chloroquine. In hyperthermic rabbits, striking cardiac arrhythmias, circulatory collapse and death occured at a dose level 13 as great as in normal rabbits. Animals that had been heated and allowed to cool before the injection, tolerated 23 of the lethal dose for normal rabbits, and twice as much as the hyperthermic rabbits.